• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.63.1-63.1
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• 2011

To analyze the phenomenon of corrosion in the PV module, we experimented damp heat test at $85^{\circ}C$/85% relative humidity(RH) and $65^{\circ}C$/85% RH for 2,000 hours, respectively. We used 30 mini-modules designed of 6inch one cell. Despite of 2,000 hours test, measured $P_{max}$ is not reached failure which is defined less than 80% compared to initial $P_{max}$. Therefore, we calculate proper curve fitting over 2,000 hours. Data less than 80% $P_{max}$ is found and B10 lifetime is calculated by the number of failure specimens and weibull distribution. Using B10 lifetime that the point of failure rate 10% and Peck's model, the predictable equation of lifetime was derived under temperature and humidity condition.

• 반도체디스플레이기술학회지
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• 제19권4호
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• pp.126-129
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• 2020

We introduce a lifetime assessment technique using deep learning algorithm with complex electrical parameters such as resistivity, permittivity, impedance parameters as integrated indicators for predicting the degradation of the organic molecules. The evaluation system consists of fully automated in-situ measurement system and multiple layer perceptron learning system with five hidden layers and 1011 perceptra in each layer. Prediction accuracies are calculated and compared depending on the physical feature, learning hyperparameters. 62.5% of full time-series data are used for training and its prediction accuracy is estimated as r-square value of 0.99. Remaining 37.5% of the data are used for testing with prediction accuracy of 0.95. With k-fold cross-validation, the stability to the instantaneous changes in the measured data is also improved.

• 사물인터넷융복합논문지
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• 제7권4호
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• pp.9-14
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• 2021

고신뢰성을 요구하는 컴퓨팅 시스템에서 저장장치의 수명예측방법은 데이터 보호뿐만 아니라 활용성을 극대화 할 수 있기 때문에 시스템 관리하기 위한 중요한 요소 중 한 가지이다. 최근 여러 저장시스템에서 저장장치로 사용되고 있는 SSD(Solid State Drive)의 수명은 이를 구성하고 있는 낸드 플래시 메모리의 수명이 실질적인 수명과 연결된다. 따라서 SSD를 이용하여 구성한 저장시스템에서는 낸드 플래시 메모리의 수명을 정확하고 효율적으로 예측하는 방법이 필요하다. 본 논문에서는 낸드 플래시 메모리 불량 발생빈도를 이용하여 플래시 메모리 기반 저장장치의 수명 예측을 최적화할수 있는 방법을 제안한다. 이를 위해 DWPD(Drive Writes Per Day) 단위로 데이터를 처리할 때 발생하는 불량 발생빈도를 수집하기 위한 비용 매트릭스(Cost Metrix)를 설계한다. 그리고 경사하강법(Gradient Descent)을 이용하여 수명의 마감이 발생하는 경사도까지 남은 비용을 예측하는 방법을 제안한다. 마지막으로 시뮬레이션을 통해 임의의 불량이 발생했을 때 제안하는 방법을 통한 수명예측의 우수성을 증명했다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.1945-1947
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• 2005

This study considers find out best accelerated life testing and lifetime prediction of electrolytic capacitors. We proved about relation between failure and deterioration mechanism from last thesis. Beside we performed test that temperature and voltage press higher than allowance specification. Failure distribution acquired from those test. And wiebull function and Minitab program applied to accelerated constant and lifetime by means of calculation. At the result, goodness of fit affect to weibull function and acceleration factor therefore fitting is important factor in reliability testing.

• 한국강구조학회 논문집
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• 제14권2호
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• pp.365-373
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• 2002

이 논문에서는 교량의 수명을 예측하기 위한 시스템 신뢰성 이론이 설명되고, 생애 분포 함수를 이용하여 현존하는 교량의 잔존 수명을 예측하는 방법이 설명된다. 시스템 이론과 생애함수 (survivor functions) 를 이용하여 LIFETIME 이라는 프로그램을 개발하였다. Survivor functions은 주어진 시간 t에 대해 신뢰성을 산출한다. 이 프로그램을 이용하여 콜로라도주에 있는 교량의 수명을 예측하였다. 이 교량은 직렬과 병렬로 구성된 시스템으로 컴퓨터 모델링 되었으며 이 모델을 이용하여 시스템 파괴 확률을 시간에 대해 계산하였다.

• International Journal of Air-Conditioning and Refrigeration
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• 제15권2호
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• pp.78-83
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• 2007

An experimental study has been carried out to analyze the thermal stability and to estimate the lifetime of refrigerating lubricants. PAG and POE oil are considered as test oils in this study. The viscosity of PAG and POE oil was measured by the vibration type viscometer while temperature is varied periodically in the range of $0^{\circ}C{\sim}100^{\circ}C$. In order to estimate lifetime of PAG and POE oil with temperature, the viscosity was measured while the test temperature of oils was maintained continuously at $180,\;200\;and\;220^{\circ}C$. The lifetime of oils is estimated as the decrease in viscosity change by 15%. The results indicate that the reduction rates of viscosity of PAG and POE oil are less than 5% after 510 temperature variation cycles. However, when the oils are kept at high temperature, it is found that the lifetimes of PAG oil is seen to be 244, 177 and 89 hours at the test temperature of $180,\;200\;and\;220^{\circ}C$, respectively, where as the lifetimes of POE oil are estimated to be 1,744, 1,007 and 334 hours at the temperature of $180,\;200\;and\;220^{\circ}C$, respectively. Thus, the lifetime of POE oil is found to be much longer than that of PAG oil. The lifetime correlations of PAG and POE oil are also obtained by Arrhenius's equation method in this paper.

• 대한기계학회논문집A
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• 제40권3호
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• pp.259-265
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• 2016

최근에 온도변화 환경에서 칩저항 실장용 유 무연 솔더의 수명예측모델이 개발되었다. 개발된 수명예측모델에 의하면 가속조건에서는 칩저항 실장 무연솔더가 유연솔더보다 수명이 적은 것으로 나타나지만, 실제조건에서는 무연솔더의 신뢰성이 유연솔더보다 우수하다. 본 연구에서는 개발된 수명예측모델의 검증 연구를 수행한다. 수명예측모델을 다른 칩저항 실장 유 무연 솔더 시험 결과에 적용하고 비교하기 위해서, 유한요소모델을 개발하고 시험 온도사이클 조건을 적용한다. 변형율 에너지 밀도를 계산하고 수명을 예측한다. 마지막으로 유 무연 솔더에 대해서 예측결과를 시험결과와 비교한다. 검증 결과는 개발된 수명예측모델이 사용 가능한 범위에서 수명을 예측할 수 있음을 보인다.

• Carbon letters
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• 제28권
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• pp.9-15
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• 2018

In the aerospace field, Carbon/Cork composites have been used for rocket propulsion systems as a light weight structural component with a high bending stiffness and high thermal insulation properties. For the fabrication of a carbon composite with a heat insulation cork part, the bonding properties between them are very important to determine the service life of the Carbon/Cork composite structure. In this study, the changes in the interfacial adhesion and mechanical properties of Carbon/Cork composites under accelerated aging conditions were investigated. The accelerated aging experiments were performed with different temperatures and humidity conditions. The properties of the aged Carbon/Cork composites were evaluated mainly with the interfacial strength. Finally, the lifetime prediction of the Carbon/Cork composites was performed with the long-term property data under accelerated conditions.

• Journal of Astronomy and Space Sciences
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• 제32권4호
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• pp.367-377
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• 2015

Atmospheric drag force is an important source of perturbation of Low Earth Orbit (LEO) orbit satellites, and solar activity is a major factor for changes in atmospheric density. In particular, the orbital lifetime of a satellite varies with changes in solar activity, so care must be taken in predicting the remaining orbital lifetime during preparation for post-mission disposal. In this paper, the System Tool Kit (STK$^{(R)}$) Long-term Orbit Propagator is used to analyze the changes in orbital lifetime predictions with respect to solar activity. In addition, the STK$^{(R)}$ Lifetime tool is used to analyze the change in orbital lifetime with respect to solar flux data generation, which is needed for the orbital lifetime calculation, and its control on the drag coefficient control. Analysis showed that the application of the most recent solar flux file within the Lifetime tool gives a predicted trend that is closest to the actual orbit. We also examine the effect of the drag coefficient, by performing a comparative analysis between varying and constant coefficients in terms of solar activity intensities.

• Smart Structures and Systems
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• 제22권2호
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• pp.167-174
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• 2018

Digital input and output modules are widely used to connect digital sensors and actuators to automation systems. Digital I/O modules provide flexible connectivity extension to numerous sensors and actuators and protect systems from high voltages and currents by isolation. Components in digital I/O modules are inevitably affected by operating and environmental conditions, such as high voltage, high current, high temperature, and temperature cycling. Because digital I/O modules transfer signals or isolate the systems from unexpected voltage and current transients, their failures may result in signal transmission failures and damages to sensitive circuitry leading to system malfunction and system shutdown. In this study, the lifetime of optocouplers, one of the critical components in digital I/O modules, was predicted using Bayesian tracking approaches. Accelerated degradation tests were conducted for collecting the critical performance parameter of optocouplers, current transfer ratio (CTR), during their lifetime. Bayesian tracking approaches, including extended Kalman filter and particle filter, were applied to predict the failure. The performance of each prognostic algorithm was then compared using accuracy and robustness-based performance metrics.