• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.783-784
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• 2009

• 대한기계학회논문집A
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• 제33권10호
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• pp.991-1004
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• 2009

Operating experience of the various components in the nuclear power plants has shown that a variety of degradation mechanisms can occur during operation. Therefore, the accurate lifetime evaluation and systematic management are very important for the safe as well as the economical operation of the nuclear power plants. In this paper, the characteristics of a total of 17 degradation mechanisms were reviewed and the plausible degradation mechanisms such as stress corrosion cracking, fatigue, irradiation embrittlement, and so on, were identified. Also, the lifetime evaluation technologies which have been developed for the application to the domestic nuclear power plants are described. In addition, a total of 48 aging management programs which have been established for the safe operation of the various components are explained.

• 전력전자학회논문지
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• 제27권4호
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• pp.291-296
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• 2022

Capacitor is one of the reliability-critical components in power converters. The lifetime of the capacitor decreases as the operating temperature increases, and power losses caused by capacitor current are the main cause of the capacitor temperature increase. Therefore, various studies are being conducted to improve the lifetime of the capacitor by reducing the current of DC-link capacitors. In this study, pulse width modulation methods proposed for improving the lifetime of DC-link capacitors of the three-level NPC inverter are comparatively analyzed. The lifetime evaluation of the DC-link capacitor under different modulation methods is performed at component level first and then system level by considering all capacitors by applying Monte Carlo simulation. Furthermore, their effects on the efficiency and THD of the output current are also considered.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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• pp.155-159
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• 1997

We investigated the effect of mechanical backside damage in Czochralski silicon wafer. The intensity of mechanical damage were evaluated by minority carrier recombination lifetime by a laser excitation/microwave reflection photoconductance decay method, photo-acoustic displacement method, X-ray section topography, and wet oxidation/preferential etch methods. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and the photoacoustic displacement values are also increased proportionally.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.190-191
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• 2006

In this paper, a method to assess the reliability of an insulating spacer used in gas insulated switchgear by electrical accelerated lifetime test is represented. And a test plan to assure the expected lifetime with 90 % confidence level is also included.

• Journal of Advanced Marine Engineering and Technology
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• 제39권8호
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• pp.828-832
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• 2015

This study is conducted for the evaluation of corrosion and lifetime prediction of fire extinguishing pipelines in residential buildings. The fire extinguishing pipeline is made of carbon steel. Twenty-four samples were selected among all the fire extinguishing pipelines in a building; the selection was based on specimenspositions, pipeline diameters, and pipeline thickness. Analysis was conducted by using the results of visual inspection, electrochemical potentiodynamic anodic polarization test, pitting depth measurements, and extreme value statistics with the Gumbel distribution. The maximum pitting depth and remaining life were statistically predicted using extreme value statistics. During visual inspection, pitting corrosion was observed in several samples. In addition, extreme value statistics demonstrated that there were several pipelines that were very sensitive to pitting corrosion. However, the pitting corrosion was not critical in all the pipelines; thus, it was necessary to change only those pipelines that were severely corroded.

• Corrosion Science and Technology
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• 제3권4호
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• pp.161-165
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• 2004

Aluminum source in an Al-Fe coating reacts with molten carbonate and develops a protective $LiAlO_2$ layer on the coating surface during operation of molten carbonate fuel cells (MCFC). However, if aluminum content in an Al-Fe coating decreases to a critical level for some reasons during MCFC operation, a stable and continuous $LiAlO_2$ protective layer can no longer be maintained. The aluminum content in an Al-Fe coating can be depleted by two different processes; one is by corrosion reaction at the surface between the aluminum source in the coating and molten carbonate, and the other is inward-diffusion of aluminum atoms within the coating into a substrate. In these two respects, therefore, the decreasing rate of aluminum concentration in an Al-Fe coating was measured, and then the influences of these two aspects on the lifetime of Al-Fe coating were investigated, respectively.

• International Journal of Contents
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• 제7권1호
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• pp.8-13
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• 2011

For energy-efficiency in Wireless Sensor Networks (WSNs), when a sensor node detects events, the sensing period for collecting the detailed information is likely to be short. The lifetime of WSNs decreases because communication modules are used excessively on a specific sensor node. To solve this problem, the TARP decentralized network packets to neighbor nodes. It considered the average data transmission rate as well as the data distribution. However, since the existing scheme did not consider the energy consumption of a node in WSNs, its network lifetime is reduced. In this paper, we propose an energy awareness congestion control scheme based on genetic algorithms in WSNs. The proposed scheme considers the remaining amount of energy and the transmission rate on a single node in fitness evaluation. Since the proposed scheme performs an efficient congestion control, it extends the network lifetime. In order to show the superiority of the proposed scheme, we compare it with the existing scheme through performance evaluation. It is shown that the proposed scheme enhances the data fairness and improves the network lifetime by about 27% on average over the existing scheme.

• 드라이브 ㆍ 컨트롤
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• 제16권3호
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• pp.33-41
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• 2019

This study presents the development of a lifetime test bench for the strain wave reducer which is a precision gear reducer of the robot to realize fault diagnosis and failure prognostics. To this end, the lifetime test bench was designed to detect the vertical forward/reverse direction rotation load. Through the lifetime test bench, it is possible to apply the same load spectrum from robot working scenarios. We developed a data integration gateway for fault data collection. Through the development of dedicated software for fault diagnosis and failure prognostics, these data from vibration, noise and temperature sensors were collected and analyzed along with the operation of the lifetime evaluation.

• 마이크로전자및패키징학회지
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• 제15권2호
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• pp.55-61
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• 2008

본 논문은 블루투스 모듈의 구조 및 솔더접합부에 대한 신뢰성 평가에 국한된 기존의 방법을 확장하여 정량적인 신뢰성 평가를 수행한 결과를 나타낸다. Field 환경조건에서의 정량적인 신뢰성 평가를 위해, 온도 싸이클링(temperature/thermal cycling)에서의 온도차를 가속스트레스로 선정하여 가속수명시험을 실시하였다. 가속수명시험을 통해 구한 고장시간 데이터들을 이용하여 수명분포 매개변수들을 추정하고 코핀-만슨(Coffin-Manson) 모델을 이용하였다. 가속수명시험을 수행한 결과, 블루투스 모듈의 고장모드는 Open, 고장메커니즘은 크랙(Crack)과 박리(Delamination)였다. Field에서 수거한 고장품들의 고장모드와 고장메커니즘이 가속수명시험을 통해 재현되었다. 또한 본 논문에서 블루투스 모듈이 Field에서 받을 수 있는 온도 싸이클링에서의 다양한 온도차에 대한 정량적인 수명을 예측할 수 있는 방법이 제시되었다. 제안된 방법을 이용하여 온도차 $70^{\circ}C$를 받고 있는 블루투스 모듈의 $B_{10}$ 수명은 약 4년으로 추정되었다.