• Journal of the Korea Safety Management & Science
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• v.7 no.2
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• pp.73-83
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• 2005

This paper is to propose tolerance intervals for expected time at the given reliability and confidence level for continuous and discrete reliability model. We consider guaranteed - coverage tolerance intervals, that is, reliability - confidence level tolerance intervals. These proposed methodologies can be applied to any industrial application where the customer's operating specification require a high level of reliability.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.141-145
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• 2005

Nowadays, most industries take $B_{6\sigma}$ quality level as a goal of the ultimate quality level of their products. On the other hand, $B_{10}$ to life indicates the time that $10\%$ of products are failed. There is no relation between the $B_{6\sigma}$ quality level and the $B_{10}$ to life. Therefore, some industries perform their quality control activities and reliability engineering activities separately. So I propose one measure which can express quality and reliability level simultaneously for the products to pursue quality and reliability activities together in the industry.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.262-266
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• 2014

In this paper, we consider the problem of determining the confidence level in zero-failure reliability sampling plans when the life distribution is Weibull distribution with a shape parameter m and a scale parameter ${\eta}$. We introduce zero-failure reliability sampling plans for Weibull distribution and investigate some characteristics of zero-failure reliability sampling plans. Finally, We propose new guideline for determining the confidence level in zero-failure reliability sampling plans for assuring $B_x-life$.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.149-156
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• 2008

A reliability model of Level II AFDA is developed to analyze the stability of armor units on the sloped coastal structures. Additionally, the partial safety factors of random variables related to armor units can be straightforwardly evaluated by applying the inverse-reliability method in which influence coefficients and uncertainties of random variables, and target probability of failure are combined directly. In particular, a design equation for armor units is derived in terms of the same criteria as deterministic design method in order to apply the reliability-based design method of Level I without some understanding to the reliability analysis. Finally, it is confirmed that several results redesigned by the reliability-based design method of Level I have satisfactorily agreement with results of CEM as well as those of Level II AFDA.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.4
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• pp.355-362
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• 2008

A reliability model of Level II AFDA is proposed to analyze the wave run-up occurring by the interaction of incident waves and sloped coastal structures. The reliability model may be satisfactorily calibrated by Level III Monte-Carlo simulation. Additionally, the partial safety factors of random variables related to wave run-up can be straightforwardly evaluated by the inverse-reliability method that use influence coefficients and uncertainties of random variables, and target probability of failure. In particular, a design equation for wave run-up is derived in the same form as that of deterministic design method so that the reliability-based design method of Level I may be applied easily. Finally, it is confirmed that results redesigned by the reliability-based design method of Level I with partial safety factors suggested in this paper are satisfactorily compared with results of CEM(2006) as well as those of Level II AFDA.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.204-206
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• 2001

This paper presents methodology to evaluate interruption cost for determination of optimal reliability level. Recently, the power interruption cost is considered one of the useful index to determine optimal reliability level. Accordingly, in this paper reports estimation results of customer interruption cost to determine optimal reliability level by the economic macro method based on the 5 years from 1995 to 1999 and various kinds of customers in Korea.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.8-19
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• 1997

In this study an adequate type of offshore structure at the Sakhalin region as cold region is proposed and its structural design results are presented based on the reliability analysis. Structural safety assessment has been carried out for the proposed offshore structure at the Sakhalin area as designed by the reliability method. And a rational design procedure is presented based on the reliability analysis. Followings are drawn through the present study : - Four colum TLP structure is proposed as an adequate offshore structure type at the cold region like the Sakhalin region and the reliability-based structural design results are presented. It is seen that the proposed type is a more adequate and economic than the fixed type. - Safety assessment of the proposed structure applying the extended incremental load method is performed. - Referring the allowable safety level for offshore structures it has been found present TLP structure has sufficient structural safety at the system level as well as at the component level.

• International Journal of Reliability and Applications
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• v.17 no.1
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• pp.51-63
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• 2016

Stress function of ball bearing is function of multiple stochastic factors and this system is so complex that analytical expression for reliability is difficult to obtain. To address this pressing problem, in this article, we have made an attempt to approximate system reliability of this important item based on reliability bounds under the stress strength setup. This article also provides level of error of this item. Numerical analysis has been adopted to show the closeness between the upper and lower bounds of this item.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.365-369
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• 2006

It is concentrated on a methodology to establish a scheme of investment on power distribution systems of components. This paper provides a methodology to estimate the scheme as using a customer interruption cost regarding reliability indices in power distribution systems. The proposed method basically uses the failure rate depending on time for explaining the deterioration of a component. Therefore, the theory of the sensitivity is used for deciding the precedence of the investment to consider an effect of each component's failure rate on the system reliability. After Estimating the sensitivity on component investment cost making incremental reliability level is produced by component's investment cost accumulated according to the precedence of the sensitivity. After that, the failure rate corresponding with reliability level on the curve of investment cost is used as producing the curve of customer interruption cost. Two curves have the crossing point that is proposed to acceptable reliability level for customer and utility. In this paper, the acceptable reliability level for customer with the utility is assessed to analyze customer interruption cost and sensitivity of reliability indices. In conclusion the result of investment based on this method is shown to the reliability level with two cost.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.535-540
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• 2022

DC-link capacitors are reliability-critical components in a photovoltaic (PV) inverter. Typically, the lifetime of a DC-link capacitor is evaluated by considering the voltage and hot-spot temperature of the capacitor under the specific operating condition of the PV inverter. However, the output of the PV inverter is determined by solar irradiation and ambient temperature, which vary with the seasons; accordingly, the hot-spot temperature of the capacitor also changes. Therefore, the mission profile of the PV system should be considered to effectively evaluate the reliability of the DC-link capacitor. In this study, the reliability of the DC-link capacitor of a three-level NPC inverter is comparatively analyzed with and without considering the mission profiles of the PV system, where two mission profiles recorded in Arizona and Iza are considered. The accumulated damage of the DC-link capacitor is calculated based on the lifetime model by analyzing its thermal loading. Afterward, a reliability evaluation of the DC-link capacitor is performed at the component level and then at the system level by considering all capacitors by means of Monte Carlo analysis. Results reveal the importance of performing a mission-profile-based reliability evaluation during the design of high-reliability PV inverters to achieve the target reliability performance.