• Title, Summary, Keyword: reliability index

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Intrarater and Interrater Reliability of the Dynamic Gait Index in Persons With Parkinson's Disease

  • Hwang, Su-Jin;Woo, Young-Keun
    • Physical Therapy Korea
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    • v.17 no.4
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    • pp.55-60
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    • 2010
  • Clinical measures that Quantify falling risk factors are needed for the accurate evaluation of patients and to plan an intervention strategy. The purpose of this study was to examine the test-retest and interrater reliability of the dynamic gait index (DGI) for persons with Parkinson's disease (PD). A total of 22 idiopathic PD patients were recruited from rehabilitation hospital, Korea in this study. The DGI was assessed in two sessions that were, three days apart. We also measured Berg balance test (BBT) and geriatric depression scale (GDS) for concurrent validity with DGI. Intrarater and interrater reliability (.96 and .98 respectively) for DGI were high. indicating good agreement. The DGI was showed a good positive correlation with the BBS (r=.852). but not GDS (r=-.462). Intrarater and interrater reliability of DGI were high in people with PD. The DGI could be a reliable measure to evaluate functional postural control during gait activities in the PD population, and the ability of DGI to detect real change is acceptable in research and clinical settings.

Reliability-Based Shape Optimization Under the Stress Constraints (응력 제한조건하의 신뢰성 기반 형상 최적설계)

  • Oh, Young-Kyu;Park, Jae-Yong;Im, Min-Gyu;Park, Jae-Yong;Han, Seog-Young
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.19 no.4
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    • pp.469-475
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    • 2010
  • The objective of this study is to integrate reliability analysis into shape optimization problem using the evolutionary structural optimization (ESO) in the application example. Reliability-based shape optimization is formulated as volume minimization problem with probabilistic stress constraint under minimization max. von Mises stress and allow stress. Young's modulus, external load and thickness are considered as uncertain variables. In order to compute reliability index, four methods, i.e., reliability index approach (RIA), performance measure approach (PMA), single-loop singlevector (SLSV) and adaptive-loop (ADL), are used. Reliability-based shape optimization design process is conducted to obtain optimal shape satisfying max. von Mises stress and reliability index constraints with the above four methods, and then each result is compared with respect to numerical stability and computing time.

Reliability analysis for design of shield tunnel segment lining under earthquake load (쉴드 터널 세그먼트 라이닝의 내진설계를 위한 신뢰성해석)

  • Park, Young-Bin;Kim, Do;Byun, Yosep;Lee, Gyu-Phil
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.22 no.3
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    • pp.249-259
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    • 2020
  • Design criteria for limit state design of underground structures have already been published overseas, and research has been conducted to revise the design method in Korea. In order to estimate the probability of failure under seismic load, the probability variable should be considered in the reliability analysis. In this study, the failure probability of the existing shield tunnel segment lining design was calculated by applying the coefficient of variation (COV) for the earth pressure and the seismic load effect in consideration of the statistical characteristics of the domestic ground properties. Based on the results of calculating the reliability index (β) from the calculated probability of failure and analyzing the reliability index according to the change in the load factor and the results of domestic and foreign research, the target reliability index (βT) during earthquakes of shield tunnel segment lining is analyzed to be "2.3", it was proposed as the target reliability index for the design of the limit state under seismic load.

Reliability Evaluation of a Microgrid Considering Its Operating Condition

  • Xu, Xufeng;Mitra, Joydeep;Wang, Tingting;Mu, Longhua
    • Journal of Electrical Engineering and Technology
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    • v.11 no.1
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    • pp.47-54
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    • 2016
  • Microgrids offer several reliability benefits, such as the improvement of load-point reliability and the opportunity for reliability-differentiated services. The primary goal of this work is to investigate the impacts of operating condition on the reliability index for microgrid system. It relies on a component failure rate model which quantifies the relationship between component failure rate and state variables. Some parameters involved are characterized by subjective uncertainty. Thus, fuzzy numbers are introduced to represent such parameters, and an optimization model based on Fuzzy Chance Constrained Programming (FCCP) is established for reliability index calculation. In addition, we present a hybrid algorithm which combines scenario enumeration and fuzzy simulation as a solution tool. The simulations in a microgrid test system show that reliability indices without considering operating condition can often prove to be optimistic. We also investigate two groups of situations, which include the different penetration levels of microsource and different confidence levels. The results support the necessity of considering operating condition for achieving accurate reliability evaluation.

Reliability and Validity of the Neck Disability Index in Neck Pain Patients (경통 환자 평가를 위한 Neck Disability Index의 신뢰도와 타당도)

  • Lee, Eun-Woo;Shin, Won-Seob;Jung, Kyoung-Sim;Chung, Yi-Jung
    • Physical Therapy Korea
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    • v.14 no.3
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    • pp.97-106
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    • 2007
  • The purpose of this study was to determine reliability and validity of the Neck Disability Index (NDI) now in use for the first time in neck pain patients of Korea. Fifty subjects (26 males and24 female) with neck pain enrolled in the study. They completed a standardized self-administered questionnaire that include pain intensity, personal care, lifting, reading, headaches, concentration, work, driving, sleeping and recreation. Reliability was determined by intra-class correlation coefficient (ICC) and Cronbach's alpha by internal consistency. Validity was examined by correlating the NDI scores to the Visual Analog Scale (VAS) score. The Test-retest reliability of the translated versions of the NDI was good ICC (2,1) = .90 (95%CI .85 .95). Cronbach's alpha value for NDI was found to be .95 and this was statistically significant (p<.05). The criterion-related validity coefficients was .72 (p<.01). We conclude that the Korean version of NDI has shown to be a reliable and valid instrument for the assessment of neck pain.

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Reliability and Validity on Oswestry Low Back Pain Disability Index(OLBPDI) in Patients with Low Back Pain (일부 요통환자를 대상으로 한 OLBPDI의 신뢰도 및 타당도)

  • Yi, Seung-Ju;Kim, Jin-Seop
    • Journal of Korean Physical Therapy Science
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    • v.18 no.3
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    • pp.53-61
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    • 2011
  • Purpose : his study was to analyze the reliability and validity on Oswestry Low Back Pain Disability Index (OLBPDI) in patients with low back pain. Methods : The sample consisted of 211 patients who had received treatments at the physical therapy units of 3 medical institutions from February to December 2008 in Andong city. Questionnaires on the OLBPDI were recruited by 6 physical therapists. The internal structure and reliability of the scales were evaluated by means of item-internal consistency(Cronbach's alpha coefficient:${\alpha}$), item-discriminant validity, Pearson's relation coefficient. Results : An average of patients's age was 41.1 years. The range of OLBPDI subscales were .93~.94 in Cronbach's ${\alpha}$. The internal consistency reliability of total item-each item were also internally consistent with Cronbach's ${\alpha}$ range of .94~.95(Pearson's correlation coefficient range: .62~.89). However, high correlation were obtained among 10 items(.67~.83), therefore the item-discriminant validity was a little low. Conclusion: In conclusion, the results reported here confirm the reliability of the OLBPDI scales in patients with low back pain. The collection of information on the level of disability due to low back pain using this instrument was acceptable to patients. A further prospective multi-center study will be necessary to prove the reliability and validity.

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An Improved Investment Priority Decision Mettled for the Electrical Facilities Considering the Reliability of Distribution Networks (배전계통 신뢰도를 고려한 전기설비투자 우선순위 결정 기법)

  • Park Chang-Ho;Chae Woo-Kyu;Jang Sung-Il;Kim Kwang-Ho;Kim Jae-Chul;Park Jong-Keun;Choi Jung-Hwan
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.54 no.4
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    • pp.177-184
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    • 2005
  • This paper proposes a improved investment priority decision method of the facilities considering the reliability of distribution networks. The proposed method decides a investment order of the facilities combining, by fuzzy rules, the investment priority decision of KEPCO and the priority decision considering reliability evaluation indices. Where reliability evaluation indices are SAIFI(System Average Interruption Frequency Index) and SAIDI(System Average Interruption Duration Index), as referred to evaluation index for sustained interruption. The reliability analysis method of distribution networks applied in this paper utilizes analytic method, where the used reliability data is historical data of KEPCO. Particularly, we assumed that the failure rate increased as the equipment ages. To verify the performance of the proposed method, we applied it with the planned projects to reinforce the weak facility electrical facilities in KEPCO in 2004. The evaluation result showed that, under a limited budget, the reliability of the KEPCO in the Busan region using the proposed method can be enhanced than using the conventional KEPCO's method. Therefore, the results verify the proposed method can be efficiently used in the actual priorities method for investing the electrical facilities.

Reliability Based Design of Caisson type Quay Wall Using Partial Safety Factors (부분안전계수를 이용한 케이슨식안벽의 신뢰성설계법)

  • Kim, Dong-Hyawn;Yoon, Gil-Lim
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.21 no.3
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    • pp.224-229
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    • 2009
  • Partial safety factors(PSFs) for Level I reliability based design of caisson type quay walls were calculated. First order reliability method(FORM) based PSFs are the functions of sensitivities of limit state function with respect to design random variables, target reliability index, characteristic values and first moment of random variables. Modified PSFs for water level and resilient water level are newly defined to keep consistency with the current design code. In the numerical example, PSFs were calculated by using a target reliability index. Seismic coefficient is defined to show extreme distribution. It was found that PSFs for seismic coefficient becomes smaller as the return period for design seismic coefficient grows longer.

Reliability-Based Optimization using Sensitivity Analysis of Reliability Index (신뢰성 지수의 민감도 해석을 이용한 신뢰성에 기초한 최적설계)

  • 조효남;민대홍;권우성
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.101-108
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    • 2000
  • An optimum design algorithm using efficient reanalysis is proposed for reliability-based optimization problems formulated as the minimization of initial cost and expected failure cost with reliability constraints. The reliability-based optimization is high cost to evaluate objective function and constraints needed reliability analysis. Therefore the sensitivity analysis of reliability index for approximated reanalysis is necessary. In this paper, three solution approaches are suggested and tested. The approaches include : (1) sensitivity analysis using finite difference; (2) sensitivity analysis using automatic differentiation (AD); and (3) sensitivity analysis with respect to intermediate variables using AD. Numerical example is optimized to show the reliability and effectiveness of the new algorithm.

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Reliability Based Real-time Slope Stability Assessment

  • Lee, Seung-Rae;Choi, Jung-Chan;Kim, Yun-Ki
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.427-435
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    • 2008
  • A reliability based slope stability assessment method is proposed and examined considering the variation of matric suction which is measured by a real time slope monitoring system. Mean value first order reliability method and advanced first order reliability method are used to calculate reliability indices of a slope. The applicability of methods is compared by applying them to the range of matric suctions measured by the real-time monitoring system. Sensitivity analysis is also performed to examine the contribution of random variables to the reliability index of slope. Finally, the proposed method is applied to a model slope. The results show that the reliability index of slope can be used for efficient slope management by quantifying the risk of slope in real time.

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