• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.503-503
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• 2007

본 논문에서는 지중배전(22.9kV) 선로에 사용되는 지상변압기를 대상으로 수행한 방열해석 및 개선과 변압기수명연장에 관한 검토 결과를 수록하였다. 변압기의 열화메커니즘에 대한 문헌 조사를 통해 변압기 온도와 수명간의 관계를 작도하였는바, 수명 평가를 위한 핵심 인자로 열에 의한 절연지의 열화에 초점을 맞추었다. 기존 외함에 설치된 방열구중 상부 위치를 상부판에도 변경하는 경우 약25%의 통풍량 증가 효과를 기대할 수 있을 것으로 평가 되었으며 상부판과 내함 사이에 형성되던 고온 영역에서의 온도를 약$15^{\circ}C$정도 낮출 수 있는 것으로 나타났다. 절연지의 인장강도 변화로 평가한 수명예측 곡선에 따르면 약$10^{\circ}C$의 은도 저감은 약10배의 수명 연장 효과를 가져오는 것으로 나타난바, 본 연구에서 확인한 방열구의 위치 변경에 따른 지상기기 내부의 온도 저하는 변압기 수명을 연장하는데 일조할 것으로 기대된다. 기존 지상변압기에서의 방열구조를 통해 변압기 온도와 수명간의 관계를 작도하였는바, 수명 평가를 위한 핵심인자로 효과적으로 방열할 수 있는 새로운 외함의 구조 및 디자인을 제시하고 시뮬레이션을 통해 개선효과를 예측하였다. 또한, 개선된 모델을 가지고 실제 변압기를 제작한 후 부하를 인가하여 개선전과 후에 대한 방열효과를 실증시험을 통해 확인하였다.

• The Korean Journal of Applied Statistics
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• v.31 no.1
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• pp.41-65
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• 2018

In Korea, as the mortality rate improves in a shorter period of time than in developed countries, it is important to consider the selection of the time series as well as the model selection in the mortality projection. Therefore, this study proposed a method using the multiple regression model in respect to the selection of the time series period. In addition, we investigate the problems that arise when various time series are used based on the Lee-Carter (LC) model, the kinds of LC model along with Lee-Miller (LM) and Booth-Maindonald-Smith (BMS), and the non-parametric model such as functional data model (FDM) and Coherent FDM, and examine differences in the age-specific mortality rate and life expectancy projection. Based on the analysis results, the age-specific mortality rate and predicted life expectancy of men and women are calculated for the year 2030 for each model. We also compare the mortality rate and life expectancy of the next generation provided by Korean Statistical Information Service (KOSIS).

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.30-36
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• 2013

This paper presents a method to estimate a storage life for loss of stabilizer content as storage periods using accelerated life test data. The estimate of storage life based on deterministic accelerated life test and degradation data cannot describe a condition distribution and storage life distribution. Previously, the method to show the condition distribution and storage life distribution by using gamma process has been studied. But it has limitation because it is impossible to collect the deterioration data at initial production phase. The estimated storage life presented by this study shows the similar value to previous studies and the method can describe the condition distribution and storage life distribution. So, the estimation method studied in this paper can be used for a life cycle management about deterioration of propellant for propulsion unit or components of missile, too.

• The Korean Journal of Applied Statistics
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• v.9 no.1
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• pp.53-73
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• 1996

This paper compares two accelerated life for Weibull distribution. One is the optimum constant stress accelerated life test which minimizes the asymptotic variance of maximum likelihood estimator of a specified quantile at design stress, and the other is corresponding simple step stress test. The models and optimum designs of constant stress and step stress tests are reviewed. Behaviors of asymptotic variances, effects of design parameters to optimum tests, and expected numbers of failures and expected test times of the two tests are investigated. The efficiency of step stress test relative to constant stress test is studied in terms of variance ratio, and robustness to preestimates of design parameters are investigated.

• The Korean Journal of Applied Statistics
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• v.9 no.2
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• pp.119-134
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• 1996

Accelerated life testing (ALT) of a system is commonly used to reduce time and cost. ALT is achieved by subjecting the test systems to more severe conditions than the normal ones to obtain estimates of life distribution under normal condition. The major interest of this research is to use a model of incorporating the common environmental effect on the components serially linked into a system-so called frailty model for the system life time distribution under each stress and to discuss the related data analysis and comparison of the model with the generally used one. The profile likelihood is used to get an initial values required to compute maximum likelihood estimates and simulation is carried for comparison.

• Nuclear industry
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• v.35 no.4
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• pp.65-70
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• 2015

통합된 형상 관리 정보 시스템은 원전의 허가에서부터 설계, 조달, 건설, 시험 가동, 운영, 유지보수와 원자로의 폐기까지 원전 수명의 전 과정을 아우르는 모든 데이터와 정보들을 총괄하여 관리하는 것이다. 최신 형상 정보 관리 시스템을 도입하면 원전 수명의 전 단계에 걸쳐 운영상의 이점과 경제적인 수익을 기대할 수 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.568-574
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• 2021

According to the Framework Act on Sustainable Infrastructure Management, which has been enforced since 2020, reservoirs should be managed to minimize life cycle costs caused by aging through preemptive management such as systematic maintenance and performance improvement. For maintenance in consideration of the life cycle, it is essential to derive the end of life due to continuous performance degradation as the common period increases. For this purpose, it is necessary to develop a performance-predicting model for reservoirs. In this study, a reservoir was divided into main complex facilities to develop a model for the maintenance of the life cycle. A model was developed for each facility. For model development, maintenance information data were collected under management by the Rural Community Corporation. The data available for model development were selected by analyzing the collected data. The developed model was used to predict the expected life expectancy of the reservoir in the current maintenance system and the expected life expectancy in the case of no action. By using the developed model, it is expected that it will be possible to support decision making in operation management and maintenance while considering the life cycle of the reservoir.

• Journal of Korean Society for Quality Management
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• v.8 no.2
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• pp.23-28
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• 1980

Life of a system involves hazards from various sources which, it is believed, can be assessed by means of quite simple expressions. By a suitable combination of these expressions to provide for the relevance of each of the hazards, it is held that a realistic appraisal of the sensitivity of each type failure can be adequately monitored. This paper accordingly presents the mathematical concepts in relation to each of the hazards and then proceeds to indicate the general relationship which these have to some experiences in life monitoring.

• Journal of Information Technology and Architecture
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• v.10 no.3
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• pp.323-334
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• 2013

There are many studies on the project planning, project management and quality management. The cost of the new project takes only 20% of system's lifetime resource and the costs of the maintenance and infrastructure take more than 80%, so the study on the maintenance is much more important than the study on the new project. There has been many studies on the economic life cycle of the system using it's maintenance cost, but no studies on it's infrastructure cost. This paper provides how we can adapt infrastructure cost, which takes more than 40% of system's life cycle cost, to the economic life cycle of the system and its effects on the system's economic life cycle.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.816-818
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• 2016

The Industry 4.0 should decide work operation of manufacture facilities by itself. But small and medium sized enterprises(SMEs) still not prepared these work operations. In this paper, we had research that work operation manufacture facilities of a management system of mold life-cycle based on CPS. The management system of mold manages life-cycle using by shot, this information offers users by cloud system. This system will help SMEs products quality improve and business operation more efficiency.