• International Journal of Naval Architecture and Ocean Engineering
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• 제5권1호
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• pp.101-115
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• 2013

This paper examines the application of structural reliability analysis to submarine pressure hulls to clarify the merits of probabilistic approach in respect thereof. Ultimate strength prediction methods which take the inelastic behavior of ring-stiffened cylindrical shells and hemi-spherical shells into account are reviewed. The modeling uncertainties in terms of bias and coefficient of variation for failure prediction methods in current design guidelines are defined by evaluating the compiled experimental data. A simple ultimate strength formulation for ring-stiffened cylinders taking into account the interaction between local and global failure modes and an ultimate strength formula for hemispherical shells which have better accuracy and reliability than current design codes are taken as basis for reliability analysis. The effects of randomness of geometrical and material properties on failure are assessed by a prelimnary study on reference models. By evaluation of sensitivity factors important variables are determined and comparesons are made with conclusions of previous reliability studies.

• International Journal of Precision Engineering and Manufacturing
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• 제8권3호
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• pp.50-53
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• 2007

Improving the reliability or long-term dependability of a system requires a different approach from the previous emphasis on short-term concerns. The purpose of this paper is to present a reliability evaluation method for an oil cooler intended for high-precision machining centers. The oil cooler system in question is a cooling device that minimizes the deformation caused from the heat generated by driving devices. This system is used for machine tools and semiconductor equipment. We predicted the reliability of the system based on the failure rate database and conducted the reliability test using a test-bed to evaluate the life of the oil cooler. The results provided an indication of the reliability of the system in terms of the failure rate and the MTBF of the oil cooler system and its components, as well as a distribution of the failure mode. These results will help increase the reliability of oil cooler systems. The evaluation method can also be used to determine the reliability of other machinery products.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 2006년도 추계 학술대회
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• pp.333-338
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• 2006

A simple but practical approach to evaluate the reliability of electronic ballasts for the low wattage fluorescent lamp has been presented in this study. We briefly reviewed the basic concepts of the electronic ballast. We then proposed a simple model and evaluated the reliability of the ballast using computer simulation.

• 품질경영학회지
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• 제39권4호
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• pp.507-515
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• 2011

MIL-HDBK-217 has played a pivotal role in reliability prediction of electronic equipments for more than 30 years. Recently, RIAC developed a new methodology $217Plus^{TM}$which officially replaces MIL-HDBK-217. Sensitivity analysis of the 217Plus component models to various parameters has been performed and meaningful observations have been drawn in this study. We first briefly reviewed the $217Plus^{TM}$ methodolog and compared it with the conventional model, MIL-HDBK-217. We then performed sensitivity analysis $217Plus^{TM}$ component models to various parameters. Based on the six parameters and an orthogonal array selected, we have performed indepth analyses concerning parameter effects on the model. Our result indicates that, among various parameters, operating temperature and temperature rise during operation have the most significant impacts on the life of a component, and thus a design robust to high temperature is the most importantly required. Next, year of manufacture, duty cycle, and voltage stress are weaker but may be significant when they are in heavy load conditions. Although our study is restricted to a specific type of diodes, the results are still valid to other cases. The results in this study not only figure out the behavior of the predicted failure rate as a function of parameters but provide meaningful guidelines for practical applications.

• 한국신뢰성학회지:신뢰성응용연구
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• 제6권2호
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• pp.135-150
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• 2006

Rubber material properties and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. This paper discusses the failure mechanism and material tests were carried out to predict the useful lifetime of NBR and EPDM for compression motor, which is used in refrigerator component. The heat-aging process leads not only to mechanical properties change but also to chemical structure change so called degradation. In order to investigate the aging effects on the material properties, the accelerated test were carried out. The stress-strain curves were plotted from the results of the tensile test for virgin and heat-aged rubber specimens. The rubber specimens were heat-aged in an oven at the temperature ranging from $70^{\circ}C\;to\;100^{\circ}C$ for a period ranging from 1 to 180 days. Compression set results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the compression set test, several useful lifetime prediction equations for rubber material were proposed.

• 한국컴퓨터정보학회논문지
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• 제19권5호
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• pp.61-69
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• 2014

협업 필터링 추천은 사용자의 아이템에 대한 선호도를 기반으로 유사 아이템 집합 또는 유사 사용자 집합을 생성하고 이를 이용해 사용자의 특정 아이템에 대한 선호도를 예측한다. 따라서 선호도 행렬이 희박할 경우, 추천의 신뢰도는 급격히 낮아진다. 본 논문에서는 위 문제를 해결하기 위해 데이터 신뢰도 기반 가중치를 이용한 하이브리드 선호도 예측 기법을 제안한다. 선호도 예측은 유사 아이템 집합과 유사 사용자 집합을 모두 생성하고 각 집합을 통해 사용자의 선호도를 예측하며, 모델의 상황을 반영한 가중치를 이용해 각 예측치를 병합하여 수행된다. 이 기법은 사용자 선호도 예측 정확도를 높이며 선호도 행렬 희박도가 높은 상황에도 추천 서비스의 신뢰도를 유지할 수 있도록 한다. 이 기법을 바탕으로 추천 시스템을 구현하고 절대평균오차를 기준으로 서비스 신뢰도 향상을 측정하였다. 실험에서 본 기법은 Hao Ji가 제안한 기존의 기법에 비해 선호도 행렬 희박도가 84% 이상인 상황에서 평균 21.7%의 성능 향상을 보여 효과적으로 행렬 희박도 문제를 해소할 수 있음을 검증하였다.

• 한국항행학회논문지
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• 제27권6호
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• pp.755-762
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• 2023

우주방사선을 측정을 위해서는 측정장비의 신뢰성이 중요하다. 본연구는 이에 대한 실증으로 현재 우리나라에서 운영되고 있는 우주방사선 실측장비인 Liulin와 TEPC을 항공기에 탑재하여 인천과 로스엔젤레스 구간에서 측정하여 비교하였다. 또한 우주방사선량을 확인하기 위해서는 사전에 예측프로그램을 통한 분석이 필요하므로 FAA가 개발한 CARI-6M과 우리나라의 KREAM 프로그램을 사용하여 예측치를 도출하였다. 검증결과 2개의 장비는 허용수준인 20% 이내로 장비 신뢰도에 문제가 없었다. 또한, 예측프로그램도 각각의 차이가 매우 미세한 것으로 나타났다. 그러나 예측프로그램의 예측값과 실측치와는 큰 차이를 보이는 것으로 분석되었다. 따라서 이에 대한 보정이나 지속적인 연구를 통하여 예측치가 실측치와 유사하도록 프로그램을 보완하는 것이 요구된다.

• 한국항공우주학회지
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• 제46권5호
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• pp.393-401
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• 2018

고체 로켓 추진기관에서 우발점화를 방지하기 위해 사용하는 전자식 점화안전장치의 신뢰도 예측에 관하여 연구하였다. 신뢰도 예측을 위해 가장 먼저 점화안전장치의 주요 구성품(점화회로, 고전압 기폭관, 격벽착화기)을 정의하고, 각 구성품의 작동원리에 대해 시스템 분석을 수행하였다. 시스템 분석을 통해 선별된 입력 변수를 이용하여 각 부품의 성능 모델링을 수행하였으며, 복잡한 해석이 필요한 경우 반응표면기법을 이용하여 다항식으로 근사하였다. 마지막으로 만들어진 성능 모델링을 기반으로 몬테칼로 시뮬레이션을 적용하여 설계 신뢰도를 예측하였다.

• 대한안전경영과학회지
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• 제15권1호
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• pp.109-120
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• 2013

As information-oriented industry has been developed and electronic devices has come to be smaller, lighter, multifunctional, and high speed, the components used to the devices need to be much high density and should have find pattern due to high integration. Also, diverse reliability problems happen as user environment is getting harsher. For this reasons, establishing and securing products and components reliability comes to key factor in company's competitiveness. It makes accelerated test important to check product reliability in fast way. Out of fine pattern failure modes, failure of Electrochemical Migration(ECM) is kind of degradation of insulation resistance by electro-chemical reaction, which it comes to be accelerated by biased voltage in high temperature and high humidity environment. In this thesis, the accelerated life test for failure caused by ECM on fine pattern substrate, $20/20{\mu}m$ pattern width/space applied by Semi Additive Process, was performed, and through this test, the investigation of failure mechanism and the life-time prediction evaluation under actual user environment was implemented. The result of accelerated test has been compared and estimated with life distribution and life stress relatively by using Minitab software and its acceleration rate was also tested. Through estimated weibull distribution, B10 life has been estimated under 95% confidence level of failure data happened in each test conditions. And the life in actual usage environment has been predicted by using generalized Eyring model considering temperature and humidity by developing Arrhenius reaction rate theory, and acceleration factors by test conditions have been calculated.

• Bioinformatics and Biosystems
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• 제1권2호
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• pp.128-133
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• 2006

This paper compares domain combination based protein-protein interaction prediction method with domain based protein-protein interaction method. The prediction accuracy and reliability of the methods are compared using the same prediction technique and interaction data. According to the comparison, domain combination based prediction method has showed superior prediction accuracy to domain based prediction method for protein pairs with fully overlapped domains with protein pairs in learning sets. When we consider that domain combination based method has the effects of assigning a weight to each domain interaction, it implies that we can improve the prediction accuracies of currently available domain or domain combination based protein interaction prediction methods further by developing more advanced weight assignment techniques. Several significant facts revealed from the comparative studies are also described in this paper.