• Communications for Statistical Applications and Methods
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• v.18 no.6
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• pp.687-696
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• 2011

Customer Lifetime or Customer Lifetime Value is a essential metric of differentiated CRM marketing and differentiated marketing strategy as a company core competency. However, customer lifetime used in companies is easily obtained from a confined simple customer attrition rate at some specific time point regardless of customer characteristics. In this study, in order to overcome the constraints of previous simple methods and to make practical use of it in industries, we suggest a method that estimates a customer lifetime using a customer segment based survival analysis with the censored data of customers; in addition, we apply this method to A mobile telecom company data. A method using customer segment based survival analysis is suggested in this study 1) includes all customers having different subscription dates, 2) reduces individual error, 3) can reflect trends after the observed time point and is more realistic.

• Journal of Digital Contents Society
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• v.15 no.1
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• pp.19-27
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• 2014

In order to estimate the life of 2,5 inch HDD which is adopted by PC environment, make the test plan which reflect the failure mode of market, make the test model of accelerated life test which reflect the stress of temperature. after an analysis of the environment of PC using, test procedure was decided that operation was write 50 % and read 50 %, and then access method was sequential 50 % and random 50%. The acceleration life test was executed on condition that temperature was $50^{\circ}C$ and $60^{\circ}C$, performance was 95 % in max performance, test time was 1000 hours. by the test of goodness of fit of anderson-darling of the failure data during test, it was confirmed that the distribution of failure fellow weibull. test for shape and scale was equal, and shape parameter was 0.7177, characteristic life was 429434 hours at normal user condition($30^{\circ}C$) by the analysis of weibull-arrhenius modeling. It made no difference about the statistics when equality test was executed. The activation energy was 0.2775eV. In analyzing between the failure samples of acceleration test and the samples of market return even though there is detail difference about the share of failure mode, the rank of share was almost same. This study suggest the test procedure of acceleration test of 2.5 inch HDD in PC using environment, and help the life estimation at manufacture and user.

• Proceedings of the KIEE Conference
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• 2007.04b
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• pp.28-30
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• 2007

본 논문은 변압기의 과부하 상태를 모의하고 내부 절연물의 잔존수명을 평가하기 위한 방법으로 열적 스트레스를 인가한 가속 수명 시험을 수행하여 광유 함침 절연지의 전기적 기계적 열화 특성을 분석하였다. 시험에 사용된 절연 재료는 변압기의 주 절연물로 널리 사용하고 있는 셀룰로스계 크래프트 절연지와 광유계 절연유를 사용하였다. 가속 열열화 시험은 IEEE/ANSI Standard C59.91-1981의 수명 예측 곡선에 의거하여 국내 배전환경에 부합하도록 $55^{\circ}C$ 절연시스템을 기준으로 하였으며, $150^{\circ}C$에서 약 1,000시간 동안 열 스트레스를 인가함으로써 변압기의 수명이 다하도록 모의하였다.

• Journal of the Korea Concrete Institute
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• v.15 no.4
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• pp.529-540
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• 2003

Recently, the researches on the durability design of concrete structures have been studied. As the examples, models to evaluate the service life prediction of the structure have been developed. The purpose of this article is to develop the model for predicting remaining service life. The final aim is to provide the user time for repairing the concrete structures. In addition, it makes possible to maintain the concrete structure economically. 70 reservoirs out of the inland concrete structures were selected and concrete structures of their components were surveyed. Two methods were used for measuring carbonation; TG/DTA method and Phenolphtalein indicator and, the value of pH was measured by the pH meter, After deriving correlations of calcium carbonate and used year, duration from completion year to 2002, pH value, and concrete cover depth the model was developed for predicting remaining service life by measuring data as small as possible. The conventional models had been developed on the basis of experiment data obtained from the restricted lab environment like as carbon gas exposure. On the other hand this model was developed on the basis of measuring data obtained from the real field that the complex deterioration actions are occurred such as freezing and thawing, carbonation, steel corrosion, and so on. The reliability of the developed model will be evaluated high in this point and this model can help to maintain concrete structures economically by providing the manager time to repair the deteriorated concrete structures in site of facility management.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1445-1451
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• 2011

Pneumatic valves are widely used parts that have the ability to control the air supplied to automation systems. However, if failure occurs in a pneumatic valve, it may affect the entire system and could lead to huge losses, depending on the characteristics of the system at the time of failure. Because of this significant risk and the level of consumer demand for reliability, there has been much study on ensuring the reliability of products by predicting valve lifetime distributions and degradation characteristics. In this paper, in order to determine the main factors useful for predicting the lifetime of a pneumatic valve, the scale parameter and $B_{10}$ life time value of the widely used plug-in-type pneumatic manifold valves were measured using complete observational data on the valve lifetimes. And also the property of life distribution has been distribution-suitabilityreviewed by correlation coefficients, the degradation characteristics of valve has been presented by the result of analysis through dynamic response time test and leakage test.

• 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.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1718-1720
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• 2010

저 전력 무선 센서 네트워크와 마이크로 센서를 결합하여 환경이나 상황을 인지하고 모니터링을 통해 수집된 정보를 사람에게 전하는 WSN(Wireless Sensor Network) 기술에 대한 많은 연구가 진행되고 있다. 본 논문은 바이너리 모델을 사용하여 단순 탐지 확률을 표현하는 기존 시뮬레이터들의 Coverage 표현의 한계를 극복하기 위해 Heat-map을 이용한 시뮬레이터를 개발했다. 이 시스템은 기존 바이너리 모델을 확장하고, GIS를 사용하여 지형정보를 함께 가시화함으로써 서비스 지형에 대한 센서 네트워크 구성뿐만 아니라 수명예측 메커니즘을 이용한 에너지 소모에 따른 노드의 수명을 가시화 한다.

• Journal of Energy Engineering
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• v.22 no.4
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• pp.338-346
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• 2013

The conventional lead acid battery is optimized for cranking performance of engine. Recently electric devices and fuel economy technologies of battery have influenced more deep cycle of dynamic behavior of battery. I also causes to reduce battery life-time. This study proposed that aging battery model is focused for increasing of battery durability. The stress factors of battery aging consist of discharge rate, charging time, full charging time and temperature. This paper considers the electrochemical kinetics, the ionic species conservation, and electrode porosity. For prediction of battery life cycle we consider battery model containing strong impacts, corrosion of positive grid and shedding. Finally, we validated that modeling results were compared with the accelerated thermal measurement data.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1503-1512
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• 1992

The strength evaluation and life prediction on the corrosion part of structure is one of the most important subjects, as a viewpoint of reducing economic loss by regular inspection, maintenance, repair and replace. For this purpose, it has been difficult to obtain the available data on growth of pit depth or growth rate of each pit which depends on time. In this paper, the life prediction and strength evaluation method was suggested for the structure with irregular stress concentration part by surface corrosion. The statistical distribution pattern of corrosion depth and the degree of fatigue strength decline were confirmed according to corrosion period by artificial corrosion of SS41 steel. The life prediction and the fatigue strength evaluation of materials with consideration of the corrosion period on the extreme value statistic analysis by the data of maximum depth of corrosion and on random variable was studied.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.75-86
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• 1996

A fatigue life prediction program for multiple planar surface cracks in finite plates and T-fillet joints, based on linear elastic fracture mechanics was developed. This prediction technique include the crack coalescence, mutual interation and the stress intensity concentration effect in welded joints. Total of 44 cases were compared with lida's and Vosikovsky's experimental results and it was found that the present method was a reasonable tool for the predictioin of fatigue life.