• Title/Summary/Keyword: Lifetime Analysis

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Lifetime Assessment Criteria and Failure Analysis for the Clutch Coil in an Automotive Air Conditioner (자동차용 에어컨 클러치 코일의 수명평가 기준과 고장해석)

  • Choi, Man-Yeop;Wei, Shin-Hwan;Kim, Jung-Sik;Jeong, Hai-Sung
    • Journal of Applied Reliability
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    • v.11 no.2
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    • pp.111-126
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    • 2011
  • The clutch coil mounted on the automotive air conditioner is an important part which actuates the clutch to connect or disconnect the pulley and the compressor according to the climate control condition in an automobile. Here, it is generally required that the clutch coil should ensure the long term durability requirement, such as a warranty for the 10 years of field operation or 160,000 km driving, especially in a brand new item, and so forth. However, some difficulties have arisen in restoring its credibility, since domestic specifications for the part have not been yet unified. In order to ensure the reliability, test methods and assessment criteria should be standardized. Moreover, assessed lifetime under specific conditions and potential failure analysis would be important. In this study, lifetime test specifications for the clutch coil have been reviewed and methodological suggestions are provided to ensure reliability, utilizing a quality function deployment through the potential failure mode effect analysis.

Lifetime Assessment for Oil-Paper Insulation using Thermal and Electrical Multiple Degradation

  • Kim, Jeongtae;Kim, Woobin;Park, Hung-Sok;Kang, Ji-Won
    • Journal of Electrical Engineering and Technology
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    • v.12 no.2
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    • pp.840-845
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    • 2017
  • In this paper, in order to investigate the lifetime of oil-paper insulation, specimens were artificially aged with thermal and electrical multiple stresses. Accelerated ageing factors and equivalent operating years for each aging temperatures were derived from results of tensile strengths for the aged paper specimens. Also, the evaluation for the multi-stress aged specimens were carried out through the measurement of impulse breakdown voltage at high temperature of $85^{\circ}C$. The lifetimes of the oil-paper insulations were calculated with the value of 66.7 for 1.0 mm thickness specimens and 69.7 for 1.25 mm thickness specimens throughout the analysis of impulse BD voltages using equivalent operating years, which means that dielectric strengths would not be severely decreased until the mechanical lifetime limit. Therefore, for the lifetime evaluation of the oil-paper insulation, thermal aging would be considered as a dominant factor whereas electrical degradation would be less effective.

Statistical Analysis for Fatigue Lifetime of Ceramics (세라믹스의 피로수명에 대한 통계적 분석)

  • 박성은;김성욱;이홍림
    • Journal of the Korean Ceramic Society
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    • v.34 no.9
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    • pp.927-934
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    • 1997
  • Static and cyclic fatigue tests were carried out for alumina specimen to study the statistical analyses (normal, lognormal and Weibull distribution) of fatigue lifetime data and nominal initial crack length data. Fatigue lifetime data followed Weibull distribution better than normal or lognormal distribution, for the shape parameter of the notched specimen was larger than that of the unnotched specimen. The nominal initial crack length data obtained from fatigue lifetime followed the lognormal and Weibull distribution better than normal distribution, for the coefficient of variation of the unnotched specimen was larger than that of the notched specimen, and shape parameter of unnotched specimen was smaller than that of the notched specimen.

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Lifetime estimation of a covered overhead line conductor

  • Leskinen, Tapio;Kantola, Kari
    • Wind and Structures
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    • v.6 no.4
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    • pp.307-324
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    • 2003
  • The paper presents results of studies concerning wind-induced aeolian vibration and fatigue of a 110 kV covered conductor overhead line. Self-damping measurement techniques are discussed: power method is found to be the most reliable technique. A method for compensating tension variations during the self-damping test is presented. Generally used empirical self-damping power models are enhanced and the different models are compared with each other. The Energy Balance Analysis (EBR) is used to calculate the aeolian vibration amplitudes, which thereafter are converted to bending stress for the calculation of conductor lifetime estimate. The results of EBA are compared with field measurements, Results indicate that adequate lifetime estimates are produced by EBA as well as field measurements. Generally the EBA gives more conservative lifetime expectancy. This is believed to result from the additional damping existing in true suspension structures not taken into account by EBA. Finally, the correctness of the line design is verified using Cigre's safe design tension approach.

Effects of Constituents in CNT Pastes on the Field Emission Characteristics of Carbon Nanotubes

  • Kim, Suk-Hwan;Lee, Dong-Gu
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.3
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    • pp.245-249
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    • 2011
  • Carbon nanotubes (CNTs) have been significantly used for the field emitters for display applications. However, the lifetime of CNT emitters which are formed by screen printing technique is not guaranteed yet, because the constituents in CNT paste affect the lifetime of CNTs. The CNT pastes for screen printing are normally composed of organic vehicles (nitro cellulose, ethyl cellulose, etc) and additives (glass frits, indium tin oxide (ITO), etc) with CNTs. In this study, the effects of constituents in CNT pastes on the lifetime and emission characteristics of CNTs were investigated by thermal and electrical analysis. Use of glass frits worsened the lifetime and electron emission of CNTs. However, an addition of ITO to CNT paste rather improved the lifetime of CNTs. Degradation of CNTs was small when nitro cellulose was used in CNT paste as an organic vehicle.

Prompt neutron lifetime calculations for the NIRR-1 reactor

  • Ibrahim, Yakubu V.;Adeleye, Micheal O.;Njinga, Raymond L.;Odoi, Henry C.;Jonah, Sunday A.
    • Advances in Energy Research
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    • v.3 no.2
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    • pp.125-131
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    • 2015
  • Prompt neutron lifetime calculations have been performed for the NIRR-1 reactor HEU and LEU cores using the 1/v insertion and the Adjoint flux weighing methods. Results of calculations obtained for the HEU and LEU cores are respectively $57.3{\pm}0.8$ and $47.5{\pm}0.7$ for the 1/v insertion and $56.9{\pm}0.3$ and $46.3{\pm}0.5$ for the Adjoint flux. There is a good agreement seen between the two methods for both cores. The prompt neutron lifetime was observed to be shorter in the LEU than for the HEU as expected. However, the Adjoint flux weighing method seemed to be the easiest method in calculating the prompt neutron lifetime for NIRR-1.

Lifetime Extension Method for Non-Volatile Memory based Deep Learning System by analyzing Data Write Pattern (데이터 쓰기 패턴 분석을 통한 비휘발성 메모리 기반 딥러닝 시스템의 수명 연장 기법)

  • Choi, Juhee
    • Journal of the Semiconductor & Display Technology
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    • v.21 no.3
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    • pp.1-6
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    • 2022
  • Modern computer systems usually have special hardware for operations used in deep learning workload even edge computing environment. Non-volatile memories (NVMs) have been considered for alternative memory storage because they consume little static energy and occupy small area. However, there is a problem for NVMs to be directly adopted. An NVM cell has limited write endurance, so that the lifetime of NVM-based memory system is much shorter than that of conventional memory system. To overcome this problem for the deep learning system, this paper proposes a novel method to extend the lifetime based on the analysis of the deep learning workloads. If an incoming block has more than a predefined number of frequently used values, the cacheline is defined as write friendly block. During the victim selection, the cacheline has lower possibility to be chosen as victim. The experimental results show that the lifetime is increased by about 50% and energy consumption is decreased by 3% with a little performance hurt.

Life Testing of Failure Rate Increasing Items for Reliability Analysis (신뢰도(信賴度) 분석(分析)을 위한 고장률(故障率) 증가품목(增加品目)에 대한 수명검정(壽命檢定))

  • Seo, Nam-Su
    • Journal of Korean Institute of Industrial Engineers
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    • v.12 no.1
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    • pp.139-146
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    • 1986
  • This study is concerned with the development of statistical life test plans for the mean lifetime of an item whose underlying lifetime distribution is a two parameter Weibull, which is perhaps the most widely used lifetime model. For this purpose, I used the likelihood ratio test method, and I verified the developed test plans and determined the sampling size and censoring number by computer similation.

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The Study on the Lifetime Estimation using Fault Tree Analysis in Design Process of LNG Compressor (천연가스 압축기 설계 단계에서 FTA를 이용한 수명 예측 연구)

  • Han, Yongshik;Do, Kyu Hyung;Kim, Taehoon;Kim, Myungbae;Choi, Byungil
    • Transactions of the Korean hydrogen and new energy society
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    • v.26 no.2
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    • pp.192-198
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    • 2015
  • Fault Tree Analysis to predict the lifetime in the design process of LNG compressor is considered. Fault Trees for P & ID of the compressor are created. Individual components that comprise the compressor are configured with the basic event. The failure rates in the PDS and OREDA are applied. As results, the system failure rate and the reliability over time are obtained. Further, the power transmission and the shaft seal system is confirmed to confidentially importantly contribute to the overall lifetime of the system. These techniques will help to improve the reliability of design of large scale machinery such as a plant.

Internalizing Symptoms as Mediators of Lifetime Incidence of Trauma and Quality of Life among Out-of-School Youths

  • Lee, Yeon Jung;Lee, So Hee;Han, Woori;Lee, Moon-Soo;Um, Dae Hyun;Chung, Eun Hee;Eom, Jeong Min
    • Journal of the Korean Academy of Child and Adolescent Psychiatry
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    • v.29 no.3
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    • pp.137-143
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    • 2018
  • Objectives: The present study aimed to investigate the relationships among the lifetime incidence of trauma, internalizing symptoms, and quality of life (QoL) in out-of-school youths (OSYs). Methods: We recruited 50 OSYs in South Korea. Participants completed the following surveys: completed Lifetime Incidence of Traumatic Events for children, Youth Self Report, and The KIDSCREEN-27 QoL measure for children and adolescents. Mediation analysis was conducted to test the research hypotheses. Results: The mean lifetime incidence of traumatic events among OSYs was 3.27 (standard deviation, 2.41). Internalizing symptoms significantly mediated the lifetime incidence of trauma and QoL. OSYs with fewer internalizing symptoms exhibited a better QoL in the domain of psychological well-being, although their lifetime incidence of trauma was higher. Conclusion: The results of current study suggest that assessment and therapeutic intervention with regard to internalizing symptoms are needed to increase the QoL of OSYs.