• International Journal of Reliability and Applications
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• 제11권1호
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• pp.55-67
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• 2010

There has been a recent upsurge in demand for the improvement of car reliability in the Northern American which is the primary market of South Korea automobile industry. It has been required that the warranty for transmission control unit for passenger cars directly related to passenger safety or security should be extended for 10 years and 160,000 km. In this paper, the test method for reliability and evaluation criteria is presented to evaluate the reliability on the automatic transmission controller. Reliability certification test can be roughly divided into two types: a quality test and life assessment test and a quality test can be subdivided into a basic performance test and environmental resistance test. There are 3 types of tests on the performance test for automatic transmission controller and environmental resistance test is composed of 14 items. Life test is performed with only the product passed this quality test. In this study, operation limit test at the high-temperatures, accelerated life test under specific temperature and accelerated life test for 2 or 3 stress levels are shown as a way for life test.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제60권3호
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• pp.465-470
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• 2011

Recently fault currents are increasing in a network. It is caused by increase in electric demand and high penetration of distributed generation with renewable energy sources. Moreover, distribution network has become more and more complex as mesh network to improve the distribution system reliability and increase the flexibility and agility of network operation. Accordingly, the fault current will exceed capacity of circuit breakers soon and all the various rational solutions to solve this problem are taken into account. Under these circumstances, superconducting fault current limiter(SFCL) is a new alternative in the viewpoint of technical and economic aspects. This study presents operation processes for a resistive-type of SFCL, and it proposes reliability model for the SFCL. When a SFCL is installed into a network, the contribution of decreased fault currents to failure for distribution equipments can be quantified. As a result, it is expected that a SFCL makes the reliability of adjacent equipments on existing network improve and these changes are analyzed. We propose a methodology to evaluate the reliability in the distribution network where a SFCL is installed considering a reliability model for resistive-type of SFCL and reliability changes for adjacent equipments which are proposed in this paper.

• Journal of Korean Physical Therapy Science
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• 제19권1호
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• pp.17-25
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• 2012

Purpose : The aim of this study was from data collection to item development in the first study before developing a valid and reliable instrument reflecting Korean's own language expression and culture. Methods : The fist survey was 140 osteoarthritis(OA) patients in 2 Cites was studied from November to December 2009. Open-ended questionnaire was decided 39 items from the first open survey. Questionnaire on the Korean Osteoarthritis Impact Measurement Scale(KAIMS) was recruited 2 professors and 5 physical therapists. Second survey was applied to 133 OA patients. Results : OA patients's average age${\pm}$standard deviation was $66.08{\pm}11.10$ years. The internal consistency reliability of 3 items. As estimated by Cronbach's alpha coefficient(${\alpha}$), was high(range, 0.86~0.96). 0.43~0.91 ${\alpha}$ coefficient for the internal consistency reliability of item-each scale was also high. However, item-discriminant validity on 3 items was low(${\alpha}$, 0.92~0.97). The construct validity by factor analysis was a little low. Conclusion : This study revealed that we confirmed a generation for 39 items on KAIMS reflecting Korean's own language expression and culture. Also, those of reliability were a little high. And, we will have to study the last instrument development (3rd study) by more subjects in the future.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제19권2호
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• pp.146-154
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• 2009

Dynamic response of a hull mounted sonar(HMS) to shocks transmitted through hull structures is analyzed and then the structural reliability of the sonars is evaluated. Finite element model of the hull mounted sonar is established and the transient responses to the shock is calculated using MSC.NASTRAN. According to BV043, the maximum allowable accelerations at the foundation of the sonar are converted from the shock spectra allowable for HMS. They are applied vertically and horizontally, respectively, using the large mass method. The structural reliability is evaluated by comparing the von-Mises stresses with the material yield stress. The drum for sensors shows a high reliability owing to mounts by which the shock waves from the base structure are well protected. However, the mounts between the base structure and the drum to mount sensors show a high stress intensity. The base structure also reveals a high stress intensity at the connection points to the hull.

• Journal of the Korean Society for Railway
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• 제8권4호
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• pp.348-353
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• 2005

In designing the structures of railway rolling stocks, deterministic methods associated with the concept of a safety factor have been traditionally used. The deterministic approaches based on the mean values of applied loads and material properties have been used as safety verification for the design of rolling-stock car body structures. The uncertainties in the applied loading for the high speed train and the strength of new materials in the rolling stocks require the application of probabilistic approaches to ensure fatigue safety in the desired system. Pressure loadings acting on the car body when the train passes through tunnels show reflected pressure waves for high-speed trains and they may cause a fatigue failure in vehicle bodies. Use of new material technology as body structures also introduces uncertainties in the material strength. A probabilistic approach is more adaptable in designing reliable structures when the pressure waves from the tunnels pounds and new material technology is adopted. In this paper, it is proposed that a fatigue design and assessment method based on a reliability which deals with the loading variations on a railway vehicle due to the pressure reflected in tunnels and the strength variations of material. Equation for the fatigue reliability index has been formulated to calculate the reliability assessment of a vehicle body under fluctuating pressure loadings in a tunnel. Considered in this formulation are the pressure distribution characteristics, the fatigue strength distribution characteristics, and the concept of stress-transfer functions due to the pressure loading.

• KEPCO Journal on Electric Power and Energy
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• 제3권2호
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• pp.107-111
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• 2017

The reliability on high cycle fatigue damage mechanism for new blades manufactured by reverse-engineering is demonstrated by success-run test. Turbine blades always experience various dynamic loads in turbine operation, as well as being in resonance condition and forced by fluid-induced vibrations mostly during run-up/down, which may accumulate high cycle damage to the blades. The accidents caused by blade failure especially incur not only a lot of troubles to the machinery but also huge financial losses. Therefore it is necessary to verify the reliability of blades in advance for the safe use. The success run test for the reliability demonstration is designed and performed for the new blades using the technique known as resonant high cycle fatigue testing.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제32권12C호
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• pp.1135-1141
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• 2007

In this paper, an adaptive bit-reliability mapping is proposed for the bit-level Chase combining in LDPC-coded high-order modulation systems. Contrary to the previously known bit-reliability mapping that assigns the information (or parity) bits to more (or less) reliable bit positions, the proposed mapping adaptively assigns codeword bits to the bit positions of various reliabilities by considering the characteristics of code and protection levels of bits in high-order modulation symbol. Compared with the symbol-level Chase combining and the constellation rearrangement bit mapping, the proposed mapping gives $0.7{\sim}1.3$ dB and $0.1{\sim}1.0$ dB performance gain at $FER=10^{-3}$ with no additional complexity, respectively. Adaptive bit-reliability mappings are derived for various environments and the validity of them is confirmed through simulation.

• Journal of Industrial Convergence
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• 제18권3호
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• pp.19-25
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• 2020

In the software development process, software reliability evaluation is a very important issue. In particular, finding the optimal development model that satisfies high reliability is the more important task for software developers. For this, in this study, Pareto and Erlang life distributions were applied to the finite failure NHPP model to evaluate the reliability attributes. For this purpose, parametric estimation is applied to the maximum likelihood estimation method, and nonlinear equations are calculated using the bisection method. As a result, the Erlang model showed better performance than the Pareto model in the evaluation of the strength function and the mean value function. Also, as a result of inputting future mission time and evaluating reliability, the Erlang model showed an effectively high trend together with the Pareto model, while the Goel-Okumoto basic model showed a decreasing trend. In conclusion, the Erlang model is the best model among the proposed models. Through this study, it is expected that software developers will be able to use it as a basic guideline for exploring and evaluating the optimal software reliability model.

• The Journal of Korean Physical Therapy
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• 제27권5호
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• pp.311-314
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• 2015

Purpose: This study attempted to determine intra-rater reliability and inter-rater reliability for measurement of foot form using the FPI-6 (Foot Posture Index) in patients with hemiplegia caused by stroke. Methods: Twenty two stroke patients were recruited into the research and their foot posture was evaluated using the FPI. Two raters assessed 6 items sequentially in accordance with the FPI-6 manual. This procedure involved asking the subject to take several steps in-place, prior to settling into a comfortable stance position with double limb support. Subjects were instructed to stand still with their arms by their sides and look straight ahead. FPI-6 values ranged from -2 to +2 for each of the six criteria and from -12 to +12 for the total score, indicating a position for each foot either along the supinated (negative score) to pronated (more than +6) continuum of foot posture. Results: The results showed that intra-rater reliability and inter-rater reliability for a total FPI-6 score was high: 0.807-0.888. An almost perfect agreement between the two raters was identified in the foot's morphological classification (Somer's D=0.712; p<0.05). Intra-percentage agreement was high (88.6%). Conclusion: The FPI-6 is a quick, simple, and reliable clinical tool with demonstrated good to excellent intra-rater reliability and good inter-rater reliability when used in assessment of the stroke patient's foot.

• Journal of the Korean Society of Physical Medicine
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• 제8권1호
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• pp.137-145
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• 2013

PURPOSE: The purpose of this study is to examine assessment of test-retest reliability for 13 items of pediatric balance scales, then the intrarater reliability among the raters. METHODS: Study participants included 6 children with spastic cerebral palsy who could walk. Raters were consist of seventy-four, 2nd year physical therapy major students. The children's ability to achieve physical balance was wideotaped for PBS items. The raters watched the tapes and evlauated each child twice. Test-retest reliability was analyzed using the Spearman correlation, and interrater reliability was analyzed using the Kendall's coefficient of concordance for ranks. RESULTS: The total PBS scores averaged 49.22 and 50.06 for first and second tests. Test-retest reliability of PBS individual items were between low and high. The low itmes were 3 items, and high were 4 itmes. Interrater reliability were low agreement. CONCLUSION: Based on the study, the pediatric balance scale is an effective evaluating tool for measuring functional balance of school age child. However, the agreement of students or beginner's interpretation is necessary in conjunction to this study results. On top of that, it is important to provide detailed explanation and repetitive training, which improves the analysis reliability. Also, each category subscores level for the pediatric balance scale must be examined carefully in conjunction to performing test, only after improving match quality via preceding practice.