• Title, Summary, Keyword: reliability index

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Lifetime Performance Index for Weibull Distribution: Estimation and Applications (와이블 분포를 따를 때 수명성능지수의 추정과 활용)

  • Seo, Sun-Keun
    • Journal of Applied Reliability
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    • v.13 no.3
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    • pp.191-206
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    • 2013
  • Application areas for Lifetime Performance Index(LPI), a kind of process capability index to be frequently used as a means of measuring process performance are illustrated with examples. Statistical properties for maximum likelihood and unbiased estimators of LPI are evaluated and discussed under Weibull distribution with known shape parameter. Furthermore, guidelines for selecting an estimator of LPI are also presented.

Probability of Failure on Sliding of Monolithic Vertical Caisson of Composite Breakwaters (혼성제 직립 케이슨의 활동에 대한 파괴확률)

  • 이철응
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.14 no.2
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    • pp.95-107
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    • 2002
  • A reliability analysis on sliding of monolithic vertical caisson of composite breakwaters is extensively carried out in order to make the basis for the applicability of reliability-based design method. The required width of caisson of composite breakwaters is determined by the deterministic design method including the effect of impulsive breaking waves as a function of water depth, also studied interactively with the results of reliability analyses. It is found that the safety factor applied in current design may be a little over-weighted magnitude for the sliding of caisson. The reliability index/failure probability is also seen to slowly decrease as the water depth increases for a given wave condition and a safety factor. In addition, optimal safety factor can roughly be evaluated by using the concept of target reliability index for several incident waves. The variations of optimal safety factor may be resulted from the different wave conditions. Finally, it may be concluded from the sensitivity studies that the reliability index may be more depended on the incident wave angles and the wave periodsrather than on the bottom slopes and the thickness of rubble mound.

A Study on Reliability Evaluation and Improvement Process of Aerospace Electronic Equipments using Operational Reliability-Cost Matrix (신뢰성-비용 매트릭스를 이용한 항공전자장비의 신뢰성 평가 및 개선 프로세스 연구)

  • Jo, In-Tak;Lee, Sang-Cheon;Park, Jong-Hun;Bae, Sung-Moon
    • Journal of the Korean Society for Quality Management
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    • v.42 no.4
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    • pp.633-646
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    • 2014
  • Purpose: The conventional predicted MFTBF by military standard has a wide discrepancy to that of real-world operation, which leads to overstock and increase operation cost. This paper introduces a analyzing frame using operational reliability and cost data to overcome the discrepancy, and provides reliability improvement process employing the analyzing frame. Methods: This paper suggests Reliability-Cost Matrix (R-C Matrix) and Operational Reliability & Cost Index (ORCI) as a tool for reliability evaluation. Results: KOREIP(KAI's Operational Reliability Evaluation and Improvement Process) is developed employing Reliability-Cost Matrix and Operational Reliability & Cost Index. Conclusion: KOREIP provides a process and its activities based on Reliability-Cost Matrix frame. The process and activities leads reliability improvement of aerospace electronic equipments by means of categorizing and follow-up action based on the concept of frame.

A Study of Reliability of Predictive Models for Permanent Deformation and Fatigue Failure Related to Flexible Pavement Design (연성포장설계의 소성변형과 피로파괴 예측모델에 대한 신뢰성 연구)

  • Kim, Dowan;Han, Beomsoo;Kim, Yeonjoo;Mun, Sungho
    • International Journal of Highway Engineering
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    • v.16 no.6
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    • pp.105-113
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    • 2014
  • PURPOSES: The objective of this paper is to select the confidential intervals by utilizing the second moment reliability index(Hasofer and Lind; 1974) related to the number of load applications to failure which explains the fatigue failure and rut depth that it indicates the permanent deformation. By using Finite Element Method (FEM) Program, we can easily confirm the rut depth and number of load repetitions without Pavement Design Procedures for generally designing pavement depths. METHODS : In this study, the predictive models for the rut depth and the number of load repetitions to fatigue failure were used for determining the second moment reliability index (${\beta}$). From the case study results using KICTPAVE, the results of the rut depth and the number of load repetitions to fatigue failure were deducted by calculating the empirical predictive equations. Also, the confidential intervals for rut depth and number of load repetitions were selected from the results of the predictive models. To determine the second moment reliability index, the spreadsheet method using Excel's Solver was used. RESULTS : From the case studies about pavement conditions, the results of stress, displacement and strain were different with depth conditions of layers and layer properties. In the clay soil conditions, the values of strain and stresses in the directly loaded sections are relatively greater than other conditions. It indicates that the second moment reliability index is small and confidential intervals for rut depth and the number of load applications are narrow when we apply the clay soil conditions comparing to the applications of other soil conditions. CONCLUSIONS : According to the results of the second moment reliability index and the confidential intervals, the minimum and maximum values of reliability index indicate approximately 1.79 at Case 9 and 2.19 at Case 22. The broadest widths of confidential intervals for rut depth and the number of load repetitions are respectively occurred in Case 9 and Case 7.

Validity and Reliability of the Arabic Version of the Copenhagen Neck Functional Disability Scale in Neck Pain Patients

  • Elbeltagy, Ahmed Mohammed;El Sayed, Wadida Hassan;Allah, Soheir Shehata Rezk
    • Asian Spine Journal
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    • v.12 no.5
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    • pp.817-822
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    • 2018
  • Study Design: Prospective observational study. Purpose: To test the face validity, content validity, feasibility, internal consistency, reliability, and test-retest reliability of the Arabic version of the Copenhagen Neck Functional Disability Scale (CNFDS). Overview of Literature: CNFDS is a clinical evaluation tool that accurately reflects the patient's perception regarding his/her functionality with existing cervical pain. This study aimed to investigate the validity and reliability of the Arabic version of the CNFDS in measuring the disability level in chronic neck pain patients. Method: Seventy-four patients with neck pain were recruited, and 135 sheets (test and retest sheets) were completed by patients; two expert panels (each comprising ten experts) participated in this study. Arabic translation (forward translation), development of the preliminary translated version, English translation (backward translation), development of the prefinal version, and testing of the prefinal version was performed by experts; thereafter, the final version was tested on patients. Index of clarity, expert proportion of clearance, index of content validity (CVI), expert proportion of relevance, descriptive statistics, missed item index, Cronbach's alpha, and Spearman's rank correlation coefficient were used for statistical analyses. Results: The study revealed that the scale index of clarity was 86.84%, scale CVI was 99.33%, scale-level content validity index (universal agreement method) was 99.33%, 99.15% of the scale items were filled in all sheets, the scale was answered in less than 3 minutes in about 75% cases, Cronbach's alpha was 0.856 (0.796, 0.905), and all Spearman's correlations between the test and retest results were statistically significant. Conclusions: The Arabic version of the CNFDS has adequate validity and reliability for the measurement of the disability level in chronic neck pain patients.

A reliability analysis method for rock slope controlled by weak structural surface

  • Zhou, Jia-wen;Jiao, Ming-yuan;Xing, Hui-ge;Yang, Xing-guo;Yang, Yu-chuan
    • Geosciences Journal
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    • v.21 no.3
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    • pp.453-467
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    • 2017
  • Catastrophic landslides maybe occur in rock slope due to the effect of strong earthquakes or heavy rainfall. The stability of rock slope is usually controlled by different scales of weak structural surfaces, which are uncertain and randomly exist in the rock slope. According to the geological characteristics of rock slope, two typical failure modes - plane and wedge are possible. A second-order second-moment (SOSM) method is presented to calculate the reliability index and the failure probability of rock slope, which is an improvement over the first-order second-moment (FOSM) method, and performance functions are built up with the classic limit equilibrium method. The presented method is applied to analyze the failure probability of two rock slopes at the Jinping I Hydropower Station and is compared with the Monte Carlo method and the FOSM method. The computed results show that for plane failure, the reliability index and the failure probability determined by the presented method are 0.563 and 28.7%, respectively, and the reliability index and the failure probability determined by Monte Carlo method are 0.677 and 24.9%, respectively. However, for the FOSM method, the reliability index and failure probability are -0.025 and 51.0%, respectively. For both plane failure and wedge failure, the difference between the presented method and the Monte Carlo method is very small, but the failure probability of plane failure determined by FOSM method is larger than that of the other two methods. The presented method can provide a useful tool to evaluate the failure probability of rock slope.

A Preliminary Study on Index Development for the Certificate Systems of Family-Friendly Corporations (가족친화기업 인증제 도입을 위한 지표개발 연구)

  • Yoo, Gye-Sook;Jun, Hey-Jung
    • Journal of the Korean Home Economics Association
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    • v.45 no.9
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    • pp.113-130
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    • 2007
  • The purpose of this research was to develop an index for the certificate systems of family-friendly corporations. To be specific, first of all this research reviewed indexes which were developed in foreign countries. Second, it examined the domestic indexes related to the evaluation of family-friendly corporations. Third, it derived characteristics of family-friendly corporations through an in-depth interview with recruiters from those corporations in Korea and developed the index for the certificate systems of family-friendly corporations. And fourth, it tested the validity and reliability of the developed index. Based on the characteristics of family-friendly corporations which were revealed through the qualitative analysis on the data from the in-depth interview with recruiters from 30 family-friendly corporations, we developed 10 indexes for the certificate systems of family-friendly corporations. Also the analysis of the validity and reliability of the developed index indicated that it has high validity and reliability. Finally this research proposed how to apply this developed index to policies related to the certificate systems of family-friendly corporations.

Application of Management Reliability Index for Water Distribution System Assessment

  • Choi, Taeho;Lee, Sewan;Kim, Dooil;Kim, Mincheol;Koo, Jayong
    • Environmental Engineering Research
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    • v.19 no.2
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    • pp.117-122
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    • 2014
  • Indexes of safety, restoration, damage impact, and management reliability were developed to assess reliability of drinking water distribution networks (DWDNs) management. The developed indexes were applied to evaluate the reliability of the pipeline management stage during unexpected mechanical and hydraulic accidents of components. The results were used to support the decision-making process in effective management and maintenance by enhancing the administrator's system understanding and by helping to create appropriate maintenance and management policies. The results of this study indicated that application of a management reliability index to assess DWDNs reliability may help create a more effective plan for establishing DWDNs management and maintenance.

A Study on Reliability Characteristic Curve of Transmission & Substation System considering Device Fault's Uncertainty (설비고장의 불확실성을 고려한 송변전계통의 공급신뢰도 특성곡선에 관한 연구)

  • Jeon, Dong-Hoon;Kim, Kern-Joong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.9
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    • pp.1500-1506
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    • 2008
  • In this paper, we proposed new reliability characteristic curve, which-can clearly show reliability property of transmission and substation system considering uncertainty such as frequency and duration of device fault. It express the relationship of duration of load curtailments, demand not supplied, and energy not served as “ y = $ax^{-1}$ " curve. and we proposed the method, which can objectively assess reliability of transmission and substation system using proposed characteristic curve as new reliability index. In this method, we used energy index of reliability(EIR) as a criterion of assessment. Finally, we performed a variety of case study for KEPCO system in order to verify usefulness of proposed method.

Reliability-Based Topology Optimization Using Single-Loop Single-Vector Approach (단일루프 단일벡터 방법을 이용한 신뢰성기반 위상최적설계)

  • Bang Seung-Hyun;Min Seung-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.8
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    • pp.889-896
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    • 2006
  • The concept of reliability has been applied to the topology optimization based on a reliability index approach or a performance measure approach. Since these approaches, called double-loop single vector approach, require the nested optimization problem to obtain the most probable point in the probabilistic design domain, the time for the entire process makes the practical use infeasible. In this work, new reliability-based topology optimization method is proposed by utilizing single-loop single-vector approach, which approximates searching the most probable point analytically, to reduce the time cost. The results of design examples show that the proposed method provides efficiency curtailing the time for the optimization process and accuracy satisfying the specified reliability.