• Journal of Navigation and Port Research
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• v.32 no.3
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• pp.167-172
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• 2008

The aim of this paper is to determine the replacement time of containerships in economical viewpoint. Especially, there was a lot of vagueness to the cost data for calculation of an economical life in a containership. For this, a fuzzy number used to express the vague nature about a cost data. This paper developed the fuzzy cost model using fuzzy numbers, and to analyze more practically than the existing cost model. And the proposal model used to decide the economical life about various kinds of containerships.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.241-242
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• 2007

This paper aims to determination of container ship's economical replacement policy by Fuzzy Annual Equivalent Cost Method Especially, though there was much vagueness to expense for calculation of container ship's economical life, this paper expressed such vague nature with a fuzzy number. And this paper developed the fuzzy expense model with a fuzzy number, and to analyze more practically than an expense model, was decided economical life-age with an application in a containership of various volumes.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.525-535
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• 2009

In this paper a heuristic method for identifying individual pipes in water pipe networks to determine specific sections of the pipes that need to be replaced due to deterioration. An appropriate minimum pipe length is determined by selecting the pipe length that has the greatest variance of the average cumulative break number slopes among the various pipe lengths used. As a result, the minimum pipe length for the case study water network is determined as 4 m and a total of 39 individual pipe IDs are obtained. The economically optimal replacement times of the individual pipe IDs are estimated by using the threshold break rate of an individual pipe ID and the pipe break trends models for which the General Pipe Break Prediction Model(Park and Loganathan, 2002) that can incorporate the linear, exponential, and in-between of the linear and exponetial failure trends and the ROCOFs based on the modified time scale(Park et al., 2007) are used. The maximum log-likelihoods of the log-linear ROCOF and Weibull ROCOF estimated for the break data of a pipe are compared and the ROCOF that has a greater likelihood is selected for the pipe of interest. The effects of the social costs of a pipe break on the optimal replacement time are also discussed.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.10a
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• pp.32-37
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• 2003

2002년 말 현재 약 232,000대의 엘리베이터가 설치되어 있고 승객용이 전체의 85%를 차지하고 있으며, 매년 약 15,000∼20,000대씩 증가하고 있다. 엘리베이터 사고는 대부분 사망으로 연결되는 중대사고이며 사회적 물의를 일으키게 된다. 와이어로프는 엘리베이터의 안전운행을 위해 중요한 요소중의 하나이므로 파단사고를 막기 위하여 보수업체 등 관리주체에서는 손상정도에 관계없이 일정기간마다 무조건 교체함으로써 자원의 낭비와, 경제적, 환경적 손실을 가져오게 된다.(중략)

• Proceedings of the Korean Reliability Society Conference
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• 2000.11a
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• pp.257-267
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• 2000

Mostly, the economic analyses for replacement of major components of nuclear power Plants(NPPs) have been performed in deterministic ways. However, the analysis results are more or less affected by the uncertainties associated with input variables. Therefore, it is desirable to use a probabilistic economic analysis method to properly consider uncertainty of real problem. In this paper, the probabilistic economic analysis method and decision analysis technique are briefly described. The probabilistic economy analysis method using decision analysis will provide efficient and accurate way of economic analysis for the repair and/or replace mai or components of NPPs.

• Informatization Policy
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• v.19 no.2
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• pp.85-105
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• 2012

So far, the importance of informatization, as well as investment into it, has been growing steadily. Due to the uncertainties and risks in adopting information technologies, systematic decision-making is definitely needed in investing in a large scale information system. Based on the existing theories about the economic life span of information systems and in consideration of the actual cost involved in the adoption and operation of the systems by the financial institutions in Korea, this study presents the optimal economic life span for all types of information systems in terms of the economic cost and generalizes the optimal life span. The ultimate purpose of this study is to develop a model that could be used in anticipating the timing of economic replacement of the information system of the same type and making decisions on IT investment.

• Proceedings of the Military Operations Research Society of Korea Conference
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• 2005.10d
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• pp.1-34
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• 2005

함정은 수많은 장비 및 무기체계로 구성된 복합무기체계로서 장비유지비용이 타 무기체계에 비해 크며, 운용 및 교체시 막대한 국방예산이 소요된다. 본 연구의 목적인 함정교체를 위한 도태시기, 즉 함정수명 결정시 고려요소로서는 첫째, 전략, 전술상의 요소 둘째, 장비의 성능 요소 셋째, 운영유지비의 비용 요소 넷째, 군수지원상의 문제 다섯째, 예산상의 문제 등이 고려된다. 그러나 본 연구는 함정이란 복합무기체계의 수명을 결정하는 요소 중 정책적인 고려사항 등은 제외하고, 경제성 측면을 고려한 함정의 수명을 추정, 제시한다. 연구 절차는 무기체계 획득단계에서 경제성 평가를 수행하기 위한 방법으로 앞으로 도입될 장비에 대한 수명주기비용을 추정하고, 그 결과를 활용하여 장비의 경제수명을 결정할 수 있는 방법을 제시하였다. 즉, 현재 국방 분야에서 비용추정을 위해 널리 사용되고 있는 PRICE 전산모델을 이용하여 운영유지비용을 포함한 수명주기 전반에 대한 항목별 비용을 추정하는 방법을 제시하고, 이 자료를 바탕으로 경제수명 결정 모형 중 적합하다고 판단된 등가 연간 비용방법을 적용하여 등가 유지비용과 자본회수비가 최소가 되는 시점을 장비의 경제수명으로 결정한 것이다. 제시된 절차를 이지스 구축함(KDX-III)에 적용하여 경제수명을 결정한다. 본 연구에서 제시된 방법을 통해 보다 과학적이고 경제적으로 함정의 도태시기를 결정하는데 사용함으로써 국방예산 절감에 기여하게 될 것으로 판단된다.

• Electric Engineers Magazine
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• v.185 no.1
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• pp.22-30
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• 1998

전력계통 가운데 중요한 역할을 담당하고 있는 대용량 전력용변압기는 효율이 높고 그 특성이 매우 안정되어 있는 설비이나 절연유의 여과와 같은 보수작업에도 불구하고 점진적인 열화과정이 누적진행되며 결국에는 교체를 필요로 하게 된다. 이러한 교첵 적절한 시기에 이루어지지 않는 경우 불시의 고장현상 또는 사고가 발생하게 되어 전력계통뿐 아니라 사회적 경제적으로도 큰 문제를 야기한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.493-502
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• 2019

Recently, the installation of renewable energy including PV systems in distribution systems has increased energetically to cope with climate change and energy shortages according to the government's policy of renewable energy 3020. On the other hand, the electrical performance and lifespan of PV modules installed outdoors can be decreased considerably due to a range of deterioration phenomena depending on the ambient environmental factors. To overcome these problems, replacement of degraded PV modules with new ones is increased before the lifespan guaranteed by the makers of PV modules. Therefore, this paper proposes a disposal diagnosis algorithm to evaluate the time interval of the optimal replacement for PV modules according to performance degradation rate of PV modules. In addition, this study modeled an economic evaluation, which is composed of the cost and benefit of PV systems. From the simulation results based on the proposed modeling and algorithm to consider the performance degradation rate specifically, the replacement approach was found to have the best B/C ratio in 10th year with a 3[%] degradation rate and the disposal diagnosis algorithm of PV modules are useful and practical tools for economic evaluations of the replacement of PV modules.

• Journal of Korea Water Resources Association
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• v.42 no.6
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• pp.457-464
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• 2009

This paper proposes methodologies for analyzing the accuracy of the proportional hazards model in predicting consecutive break times of water mains and estimating the time interval for economical water main replacement. By using the survival functions that are based on the proportional hazards models a criterion for the prediction of the consecutive pipe breaks is determined so that the prediction errors are minimized. The criterion to predict pipe break times are determined as the survival probability of 0.70 and only the models for the third through the seventh break are analyzed to be reliable for predicting break times for the case study pipes. Subsequently, the criterion and the estimated lower and upper bound survival functions of consecutive breaks are used in predicting the lower and upper bounds of the 95% confidence interval of future break times of an example water main. Two General Pipe Break Prediction Models(GPBMs) are estimated for an example pipe using the two series of recorded and predicted lower and upper bound break times. The threshold break rate is coupled with the two GPBMs and solved for time to obtain the economical replacement time interval.