• Title/Summary/Keyword: Reliability

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Application of Industrial Reliability Technology to Nation Defense Field (민간 신뢰성기술의 국방분야 활용방안)

  • Song, Byeong-Suk;Cho, Jai-Rip
    • Journal of Applied Reliability
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    • v.8 no.2
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    • pp.61-73
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    • 2008
  • Reliability program in one of the most efficient tools for cost saving during the acquisition process including alternatives for design configurations, operation concepts, maintenance concepts. Industrial reliability centers have already equipped with infrastructure such as reliability standards, reliability apparatus. In this study revitalizing plans are proposed to apply industrial reliability technology to national defense technology.

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A Heuristic Algorithm for the Reliability Optimization of a Distributed Communication Network

  • Hung, Chih-Young;Yang, Jia-Ren;Park, Dong-Ho;Liu, Yi-Hsin
    • International Journal of Reliability and Applications
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    • v.9 no.1
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    • pp.1-5
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    • 2008
  • A heuristic algorithm for reliability optimization of a distributed network system is developed so that the reliability of a large system can be determined efficiently. This heuristic bases on the determination of maximal reliability set of maximum node capacity, maximal link reliability and maximal node degree.

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Reliability Equivalence Factors of a Series - Parallel System in Weibull Distribution

  • El-Damcese, M.A.;Khalifa, M.M.
    • International Journal of Reliability and Applications
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    • v.9 no.2
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    • pp.153-165
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    • 2008
  • This paper discusses the reliability equivalences of a series-parallel system. The system components are assumed to be independent and identical. The failure rates of the system components are functions of time and follow Weibull distribution. Three different methods are used to improve the given system reliability. The reliability equivalence factor is obtained using the reliability function. The fractiles of the original and improved systems are also obtained. Numerical example is presented to interpret how to utilize the obtained results.

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Reliability Evaluation of Power System Operations Considering Time-Varying Features of Components

  • Hu, Bo;Zheng, Ying;Yang, Hejun;Xia, Yun
    • Journal of Electrical Engineering and Technology
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    • v.10 no.4
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    • pp.1422-1431
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    • 2015
  • The reliability of power system components can be affected by a numbers of factors such as the health level of components, external environment and operation environment of power systems. These factors also affect the electrical parameters of power system components for example the thermal capacity of a transmission element. The relationship of component reliability and power system is, therefore, a complex nonlinear function related to the above-mentioned factors. Traditional approaches for reliability assessment of power systems do not take the influence of these factors into account. The assessment results could not, therefore, reflect the short-term trend of the system reliability performance considering the influence of the key factors and provide the system dispatchers with enough information to make decent operational decisions. This paper discusses some of these important operational issues from the perspective of power system reliability. The discussions include operational reliability of power systems, reliability influence models for main performance parameters of components, time-varying reliability models of components, and a reliability assessment algorithm for power system operations considering the time-varying characteristic of various parameters. The significance of these discussions and applications of the proposed techniques are illustrated by case study results using the IEEE-RTS.

Unified Reliability and Its Cost Evaluation in Power Distribution Systems Considering the Voltage Magnitude Quality and Demand Varying Load Model (전압 크기의 품질 및 전력수요 변동모델을 고려한 배전계통의 통합적인 신뢰도 및 비용 평가)

  • Yun, Sang-Yun
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.52 no.12
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    • pp.705-712
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    • 2003
  • In this paper, we propose new unified methodologies of reliability and its cost evaluation in power distribution systems. The unified method means that the proposed reliability approaches consider both conventional evaluation factor, i.e. sustained interruptions and additional ones, i.e. momentary interruptions and voltage sags. Because the three voltage quality phenomena generally originate from the outages on distribution systems, the basic and additional reliability indices are summarized considering the fault clearing mechanism. The proposed unified method is divided into the reliability evaluation for calculating the reliability indices and reliability cost evaluation for assessing the damage of customer. The analytic and probabilistic methodologies are presented for each unified reliability and its cost evaluation. The time sequential Monte Carlo technique is used for the probabilistic method. The proposed DVL(Demand Varying Load) model is added to the reliability cost evaluation substituting the average load model. The proposed methods are tested using the modified RBTS(Roy Billinton Test System) form and historical reliability data of KEPCO(Korea Electric Power Corporation) system. The daily load profile of the each customer type in domestic are gathered for the DVL model. Through the case studies, it is verified that the proposed methods can be effectively applied to the distribution systems for more detail reliability assessment than conventional approaches.

The Reliability of Balance, Gait, and Muscle Strength Test for the Elderly with Dementia: A Systematic Review

  • Lee, Han-Suk;Park, Sun-Wook
    • Journal of the Korean Society of Physical Medicine
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    • v.12 no.3
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    • pp.49-58
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    • 2017
  • PURPOSE: To summarize the evaluation tools of balance [Berg Balance Scale (BBS), timed up and Go (TUG), forward reaching test (FRT)], gait [6 m walking Test (6MWT)], and strength [Chair Stand Test (CST)] for patients with dementia. METHODS: The following databases were searched: Pub MED, Cochrane, Sciences Direct, and Web of Sciences. The inclusion criteria were as follows: 1) repeated measurement design, 2) subjects with dementia, 3) use of testing tools such as the BBS, TUG, FRT, 6MWT, and CST, 4) report the reliability. One reviewer performed the quality assessment of diagnostic accuracy study and two evaluators performed data extraction independently. RESULTS: Six articles and one letter were included. The interrater reliability of 6MWT, TUG, and CST, were acceptable (ICC>.90). However, FRT had unacceptable reliability. In test-retest reliability, only BBS has acceptable reliability (ICC>.90). Others had various reliabilities. The risk of interrater reliability bias was low in all studies. However, the risk of bias of intrarater reliability was low in five studies and moderate in two studies. CONCLUSION: The interrater reliability of the 6MWT, TUG, and CST were acceptable. However, in test-retest reliability, only BBS has acceptable reliability. Therefore, we suggest the use of BBS to test the balance of dementia patients. In addition, the study of tool reliability according to the subtype of dementia is needed in the future.

A Study on the Improvement of Reliability Prediction Model for Guided Missile (유도탄의 신뢰도 예측 모델 개선에 관한 연구)

  • Seo, Yang Woo;Yoon, Jung Hwan;Kim, Hee Wook;Kim, Jung Tae
    • Journal of the Korean Society of Systems Engineering
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    • v.16 no.1
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    • pp.9-17
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    • 2020
  • Currently, Storage Reliability is analyzed when predicting the reliability of guided missile. However, Mission Reliability and Logistics Reliability should be analyzed according to the definition of reliability in MIL-STD-785B. Therefore, it is necessary to accurately predict the reliability of guided missile based on the definition of reliability. In this paper, we proposed improved the reliability procedure and model for guided missile based on which the definition of reliability considering the mission profile. The proposed model can calculate the final failure rate by applying the ratio of the dormant and storage according to the mission profile. The proposed model has been confirmed to be more accurate than the existing model compared to the actual failure rate value. The results of this study can be useful for applying the reliability prediction to any guided missile.

Joint reliability importance of series-parallel systems

  • Dewan, I.;Jain, K.
    • International Journal of Reliability and Applications
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    • v.12 no.2
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    • pp.103-116
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    • 2011
  • A series-parallel system with independent but non-identical components is considered. The expressions have been derived for the joint reliability importance (JRI) of m (${\geq}2$) components, chosen from a series-parallel system. JRIs of components of two different series-parallel systems are studied analytically and graphically.

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Set Covering Problem and Reliability of the Covers

  • Liu, Y.-H.;Tzeng, G.-H.;Park, Dong-Ho
    • International Journal of Reliability and Applications
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    • v.5 no.4
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    • pp.147-154
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    • 2004
  • This work developed and algorithm for a set covering model when the reliability of covers is a concern. This model extended the usage of the set covering model.

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