• 열병합발전
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• 통권27호
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• pp.5-9
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• 2002

High pressure steam pipe in power plants is subjected to service conditions under which creep processes take place limiting the component's lifetime. To ensure a safe and economic operation it is necessary to get accurate information about the lifetime situation of single components as well as of the whole system. Careful evaluation is combined with FEM analysis, NDT, microstructure evaluation. Especially, 14MoV63 steel is used as material for main steam pipe for 30 years old power plants. In service inspections have shown an increasing number of cracks and creep cavities beside stress concentration parts. A detailed analysis came to the conclusion that lifetime has been consumed to a high degree, 80%level.

• 항공우주기술
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• 제13권1호
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• pp.184-192
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• 2014

본 논문에서는 JSpOC에서 제공하는 TLE 데이터를 이용하여 지구 저궤도 상에 존재하는 인공적인 우주물체의 궤도수명을 예측하였다. 이를 위해 1957년부터 현재까지 우주파편 개체수의 변화를 관찰하여 우주파편 생성의 요인과 현재 남아있는 물체들의 현황을 파악하였으며, 현재 지구 저궤도 상에 존재하는 총 11,792개의 물체에 대해 2050년까지 궤도전파를 수행하여 궤도수명을 분석하였다. 효율적인 계산을 위해 STK/Lifetime Tool을 사용하였으며, 재진입 시 지상에 낙하할 가능성이 있는 폐위성이나 로켓동체와 같이 질량 대비 단면적이 큰 물체에 대해 연간 재진입 빈도를 분석하였다. 분석 결과 2050년까지 매해 위성과 로켓동체는 약 9개가 재진입하며, 지상에 피해를 줄 수 있는 규모는 약 2-3개로 나타났고, 전체 분석 대상의 약 40%이상은 200년 이상의 궤도수명을 가지는 것으로 나타났다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.161-164
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• 2008

We proposed 2-phase regression of power function inside exponential for PDP lifetime data analysis. In introducing our method we discussed the reason why PDP degradation behavior is described by exponential function basically. By applying our method to 50HD and 50FHD PDP lifetime experiment data, we obtained more than 100,000Hr lifetime. From these results, we claim that PDP lifetime is more than 100,000Hr.

• 응용통계연구
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• 제21권4호
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• pp.631-638
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• 2008

가속수명시험은 실제 사용조건보다 열악한 수준으로 시험하여 빠른 기간 내에 제품의 고장자료를 얻고, 실제 사용조건에서의 수명관련 품질 특성치를 추정하는 방법이다. 본 논문에서는 가속수명 자료를 이용하여 분위수 회귀추정 방법을 통해 정상 조건에서의 수명을 추정하는 방법을 제안한다. 대표적인 가속 스트레스인 온도와 전압을 갖는 실제 자료에 분위수 회귀 모형을 적용하여 수명을 추정하였다.

• 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.

• Asian Pacific Journal of Cancer Prevention
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• 제17권8호
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• pp.4083-4088
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• 2016

Background: Physical inactivity has been identified as the fourth leading risk factor for global mortality and is associated with increased breast cancer diagnosis and recurrence. Purpose: To examine the association between adult lifetime physical activity and breast cancer risk in a case-control analysis. Materials and Methods: This study involved 122 cases of breast cancer and 121 controls in the state of Kelantan in Malaysia. A comprehensive measure of lifetime physical activity was used to assess occupational, household, and recreational/sports activity. For every type of activity, a metabolic equivalent (MET) score was assigned using the compendium of physical activities. MET-hours/week per year for all types of activities at different levels of intensities for different age groups were calculated. Logistic regression analysis was used to estimate odds ratios between various measures of physical activity and breast cancer risk. Conclusions: The mean MET-hours/week per year for all activities were 120.0 and 132.9 of MET-hours/week per year for cases and controls respectively. Household activities accounted for about 70% of the total lifetime physical activities. Only about 2.5% of the total lifetime physical activities were in the form of recreational/sports. This study found no association between lifetime occupational and recreational/sports physical activities with breast cancer risk among Kelantanese women. However, higher intensity lifetime household activities seemed to significantly reduce risk of breast cancer.

• 드라이브 ㆍ 컨트롤
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• 제12권1호
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• pp.21-27
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• 2015

Pneumatic cylinders are classified into rod-type pneumatic cylinders and rodless pneumatic cylinders depending on the presence of the rod. Rodless cylinders have a constant area and have no deflection. Rodless cylinders are widely used in automatic systems requiring high-speed performance and high-precision transportation. However, the research of the pneumatic cylinder has been focused on the structure and life characteristics. In this research, aging characteristics and shape parameter analysis which are related to the lifetime were investigated. By conducting the lifetime tests with two different materials for the transfer plate, the failure mode and lifetime characteristics were analyzed. By the Anderson-Darling (A-D) verification based on the complete data set, the analysis results of lifetime distribution, shape parameter, and scale parameter were provided.

• 기술사
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• 제43권2호
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• pp.60-63
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• 2010

This analysis introduces a lube oil circulation system for a big reducer in the chemical process industries. We have been operating the system and found out that the system greatly helped us save the maintenance cost by increasing the lifetime of the reducer.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제28회 KOSCO SYMPOSIUM 논문집
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• pp.183-191
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• 2004

The burning characteristics of interacting droplets with internal circulation in a convective flow are numerically investigated at various Reynolds numbers. The transient combustion of 2-dimensionally arranged droplets, both the fixed droplet distances of 5 radii to 40 radii horizontally and 4 radii to 24 radii vertically, is studied. The results obtained from the present numerical analysis reveal that the transient flame configuration and retardation of droplet internal motion with the horizontal or vertical droplet spacing substantially influence lifetime of interacting droplets. At a low Reynolds number, lifetime of the two droplets with decreasing horizontal droplet spacing increases monotonically, whereas their lifetime with decreasing vertical droplet spacing decreases due to flow acceleration. This flow acceleration effect is reversed when the vertical droplet spacing is smaller than 5 radii in which decreasing flame penetration depth causes the reduction of heat transfer from flame to droplets. At a high Reynolds number, however, lifetime of the first droplet is hardly affected by either the horizontal droplet spacing or flow acceleration effect. Lifetime with decreasing vertical droplet spacing increases due to reduction of flame penetration depth. Lifetime of interacting droplets exhibits a strong dependence on Reynolds number, the horizontal droplet spacing and the vertical droplet spacing and can be con-elated well with these conditions to that of single burning droplet.

• 품질경영학회지
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• 제41권1호
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• pp.135-148
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• 2013

Purpose: This paper presents a method to evaluate the stockpile reliability of propelling charge for performance and storage safety with storage time. Methods: We consider a performance failure level is the amount of muzzle velocity drop which is the maximum allowed standard deviation multiplied by 6. The lifetime for performance is estimated by non-linear regression analysis. The state failure level is assumed that the content of stabilizer is below 0.2%. Because the degradation of stabilizer with storage time has both distribution of state and distribution of lifetime, it must be evaluated by stochastic process method such as gamma process. Results: It is estimated that the lifetime for performance is 59 years. The state distribution at each storage time can be shown from probability density function of degradation. It is estimated that the average lifetime as $B_{50}$ life is 33 years from cumulative failure distribution function curve. Conclusion: The lifetime for storage safety is shorter than for performance and we must consider both the lifetime for storage safety and the lifetime performance because of variation of degradation rate.