• Proceedings of the KSME Conference
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• 2008.11a
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• pp.250-255
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• 2008

This study utilized a high speed lap-shear test to evaluate the mechanical behavior of Sn-37Pb/Cu and Sn-37Pb/Electroless Nickel immersion Gold under bump metallization solder joints under high speed loading and hence the drop reliability. The samples were aged for 120 h at different temperatures ($120^{\circ}C,\;150^{\circ}C,\;170^{\circ}C$) and afterward tested at different displacement rates (0.01 mm/s to 500 mm/s) to examine the effects of aging on the drop life reliability. The combination of the stress-strain graphs captured from the shear tests and identifying a fracture mode dominant in the samples for different strain rates leads us to conclude that the drop reliability of solder joints degrades as the aging temperature increases, possibly due to the role of the IMC layer. This study successfully demonstrates that the analysis based on a high speed lap-shear test could be critically used to evaluate the drop reliability of solder joints.

• Journal of Applied Reliability
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• v.7 no.1
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• pp.31-43
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• 2007

The function of O-ring seals is to prevent leakage during the service life of the components in which they are installed. The life prediction of O-ring is very important at various industry fields. Generally, to evaluated the long-term performance of O-ring in severe environments has applied a life prediction technique based on accelerated life test (ALT). In this work, Accelerated thermal aging test(l20, 130, 140, $150^{\circ}C$) of O-ring was applied for life prediction of O-ring. The property changes after thermal aging test was measured using TGA, DSC, FT - IR, Video Microscope and SEM. Shape parameter and life prediction were obtained using MINITAB program.

• Journal of Applied Reliability
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• v.11 no.3
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• pp.235-244
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• 2011

Hydraulic hose assemblies deliver a fluid power in various oil pressure equipment such as construction machinery, automobile, aircraft, industrial machinery, machine tools and machinery for ships. Also, they are widely used as pipes in oil pressure circuit. When we estimate their lifetime, it is essential to conduct an accelerated life test by choosing the factor that suits the usage condition of the test object since traditional test method for estimating lifetime under the influence of various external factors incurs hardship in terms of time and expenses. The objective of this study is to propose an acceleration model that takes both temperature and pressure without flexing condition into consideration. The lifetime is estimated by applying the proposed temperature-nonthermal acceleration model to the test data. And we compare the proposed temperature-nonthermal acceleration model and the accelerated life equation suggested by John(1994).

• Proceedings of the Korean Reliability Society Conference
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• 2006.05a
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• pp.116-125
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• 2006

Piston assemblies, which are key components of hydraulic high pressure pumps & motors, are major failure products operating at high pressure and high speed, and the main failure mode is wearout of the shoe surface. To predict the actual life of piston assemblies. we require to find out the most sensitive parameters and establish related empirical formula. In this study, we analyzed the life of piston and shoe assemblies in accordance with variation of speed, pressure, and temperature to reduce the life test time, then analyzed the result of combined accelerated life test which is applied by high speed, speed pressure, and high temperature simultaneously, and finally developed combined accelerated life test model.

• Journal of Drive and Control
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• v.21 no.1
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• pp.16-21
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• 2024

The yaw gearbox is a key device in a wind power generator that improves power generation efficiency by rotating hundreds of tons (400 to 600 tons) of nacelle so that the blade reaches 90 degrees in the wind direction. Recently, installation sites have been advancing from land to sea as they have become super-large at (8-12) MW to increase the economic feasibility of wind power generators and utilize excellent wind resources, and the target life of large wind power generators is 25 to 30 years. The yaw gearbox of 6 to 12 sets is installed in a very complex place inside the nacelle on the tower with parallels, and it is important to secure the reliability of the yaw gearbox because if a failure occurs after installation, it costs tens to hundreds of times the price of a new product to restore. In this study, equivalent loads were calculated by analyzing failure mode and field data, accelerated life test conditions were established, and a test device was constructed to perform the accelerated life tests and performance tests to ensure the reliability of the gearbox.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1305-1311
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• 2015

A butterfly valve is a type of flow-control device typically used to regulate a fluid flow. This paper presents an estimation of the shape parameter of the Weibull distribution, characteristic life, and $B_{10}$ life for a concentric butterfly valve based on a statistical analysis of the reliability test data taken before and after the valve improvement. The difference in the shape and scale parameters between the existing and improved valves is reviewed using a statistical hypothesis test. The test results indicate that the shape parameter of the improved valve is similar to that of the existing valve, and that the scale parameter of the improved valve is found to have increased. These analysis results are particularly useful for a reliability qualification test and the determination of the service life cycles.

• The Journal of Korean Physical Therapy
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• v.25 no.4
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• pp.210-216
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• 2013

Purpose: A cost effective tool for the clinical measurement of trunk reposition sense is clearly needed. This study was to analyze intrarater and interrater Reliability of trunk repositioning error (TRE) test which assesses trunk position sense using a portable digital inclinometer. Methods: Twenty four normal healthy subjects were recruited. TRE was measured using a portable digital inclinometer. A digital inclinometer (Acumar-ACU360; Lafayetter Instrument) with precision to $1^{\circ}$ was placed on skin over the spinous process from first to second thoracic vertebra (T1-T2) and secured with double-sided tape. TRE test during sitting forward and lateral flexion movement was assessed. When they reached a point approximately 50% of full trunk flexion range, the examiner instructed the subjects to stop and told them. This was the target position that they should try to reproduce exactly. Each subject performed six trials. Results: ICC (2,1) for intrarater reliability (with-day and between-day) of TRE test in sagittal and frontal plane of movement was 0.75 and 0.78 (excellent reliability). Interrater reliability was 0.66 in sagittal and 0.64, frontal plane (fair to good reliability). However, there were poor correlations between an average of TRE test in sagittal and frontal plane. Conclusion: TRE test using a portable digital inclinometer demonstrated good to excellent reliability. The device may be a cost effective clinical measurement for trunk reposition sense measurement.

• Physical Therapy Rehabilitation Science
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• v.6 no.1
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• pp.20-25
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• 2017

Objective: During the physical therapy education, if we can understand the student's attitude then we can make valuable suggestions with respect to the teaching in the universities and professional employment in the country. The aim of the current study is to develop a questionnaire to test the physical therapy students' attitudes towards their education and profession and to test its test-retest reliability and content validity. Design: Cross-sectional study. Methods: A total of 47 physical therapy students who were in their final year were randomly selected to participate in the study. After the making of the questionnaire, it was given to 6 professional experts teaching in the field of physical therapy to obtain their responses for each question with a 5-point Likert scale grading. Their answers were used in making the content validity of the questionnaire. Afterwards, the physical therapy students were asked to fill the questionnaire. Instrument reliability and test-retest reliability were also assessed by having the students complete the questionnaire after one month of taking the questionnaire. Results: The content validity index was 0.71 for the whole scale and values of individual subdivisions were ranging from 0.69 to 0.75. Instrument reliability measured by Cronbach's alpha coefficient was 0.86 for the whole scale and subdivision values were ranging from 0.32 to 0.86. Test-retest reliability was assessed by intraclass correlation coefficient, which was 0.71 for whole scales and subdivision values were ranging from 0.38 to 0.70. Conclusions: This questionnaire, which assesses the physical therapy student attitude towards their education and profession, has good content validity, instrument reliability, and test-retest reliability.

• Journal of Applied Reliability
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• v.16 no.3
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• pp.208-215
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• 2016

Purpose: ASRP for the domestic development guided missiles requires not only for the reliability evaluation of the products in storage but also for the life cycle management of the products including development prototypes and initial production items. Methods: For this purpose, it should be performed to build a performance database before and after the accelerated aging test with shelf life items including development prototypes and initial production items, based on which the lifetime prediction should also be carried out. In addition, HILS must be applied for the acceptance test with the initial and follow-up production items, and also for ASRP for the long-term storage products in order to secure systematic quality assurance. Results: The results for the life cycle reliability Improving of domestic development of guided missiles are DB building of prescription Item performance, active application of HILS, Management associated with guided missiles life cycle and to Secure technology data about the introduction of foreign guided missiles. Conclusion: Furthermore, it is demanded that DTaQ, the managing agency of ASRP, actively take part in the process to maintain reliability engagement consistency over the life cycle of guided missiles.

• Korean Journal of Adult Nursing
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• v.21 no.2
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• pp.235-244
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• 2009

Purpose: This research was carried out to evaluate the validity and reliability of the Korean version of the Summary of Diabetes Self-Care Activities Questionnaire (SDSCA) for Korean older adults with type 2 diabetes. Methods: Translation and back-translation were performed to develop the Korean version of the SDSCA. Then the Korean version SDSCA was applied to a sample of 112 older adults who had participated in diabetes self management education in Seoul. The internal consistency and the test-retest reliability were examined to test the reliability. Factor analysis was used to examine the construct validity. Results: The internal consistency measured with Cronbach's alpha was .77 and the total test-retest reliability was .68 with items ranging from .21 to 1.00. As the result of the factor analysis, six factors -foot care, diet, exercise, blood sugar test, medication, and smoking- were revealed as the original instrument subcategories. These six factors explained 81.17% of total variance. Conclusion: The reliability and validity of the Korean version SDSCA Questionnaire was supported for use in older patients with type 2 diabetes in Korea.