• International Journal of Precision Engineering and Manufacturing
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• v.8 no.3
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• pp.50-53
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• 2007

Improving the reliability or long-term dependability of a system requires a different approach from the previous emphasis on short-term concerns. The purpose of this paper is to present a reliability evaluation method for an oil cooler intended for high-precision machining centers. The oil cooler system in question is a cooling device that minimizes the deformation caused from the heat generated by driving devices. This system is used for machine tools and semiconductor equipment. We predicted the reliability of the system based on the failure rate database and conducted the reliability test using a test-bed to evaluate the life of the oil cooler. The results provided an indication of the reliability of the system in terms of the failure rate and the MTBF of the oil cooler system and its components, as well as a distribution of the failure mode. These results will help increase the reliability of oil cooler systems. The evaluation method can also be used to determine the reliability of other machinery products.

• Journal of Korean Society for Quality Management
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• v.10 no.2
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• pp.2-9
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• 1982

In principle the methods of increasing the reliability of complex system can be classified into the following four basic methods: (1) using the stand-by redundancy; (2) decreasing the failure rate of the system; (3) decreasing the time of continuous operation; (4) decreasing the mean repair time. Among the above four methods, it is generally known that the method of stand-by redundancy is the most effective general, to increase the reliability of systems. Therefor this paper aims to compare the gain in reliability which is achieved by applying stand-by redundancy with other methods, and to show the characteristics of each method From the comparison of the methods of increasing reliability, the following important facts are found: When the method of stand-by redundancy is used to increase the reliability of complex systems intended for long-term operation, a hight multiplicity of stand-by redundancy is required. Thus an increase of the reliability of complex system by applying stand-by redandancy is realized at the expense of characteristics such as weight, size, cost, increased complexity of operation conditions. And this property restricts its use in systems which are critical with respect to weight, size, cost or operation conditions. The method of stand-by redundancy is the most effective when this method is used to increase the reliability of complex systems intended for short-term operation, and the method of decreasing failure rate is the most effective when it is used to increase the reliability of systems intended for long-term use. The methods of increasing reliability discussed in this paper make it possible to make highly reliable systems. But it is not possible to make a highly reliable system using a single method of increasing reliability, even if it is the most effective one. Therefore it is recommended to use all or a majority of the above four methods by choosing it in accordance with the properties of the system under construction.

• 한국노년학
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• v.30 no.1
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• pp.81-91
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• 2010

The purpose of this study was to test a validity and reliability of Cognitive Performance Scale(CPS), a cognitive measure generated from 5 items(comatose status, decision making, short-term memory, making self understood, and eating). Method: 393 patients in 2 hospitals for the elderly with dementia were measured with CPS by two nurses independently. The inter-rater agreement was tested by comparing two scores. The CPS score was compared with GDS, which was measured by doctors and nurses, and MMSE score which was drawn from the claim data of Health Insurance Review & Assessment Service. Result: The correlation coefficient between CPS and GDS was 0.742(p<0.0001), CPS and MMSE was -0.794(p<0.0001). The Cronbach's coefficient alpha of CPS was 0.742, Kappa value was 0.772~1.000. The CPS showed high validity and reliability in long term care hospitals of Korea.

• Journal of Environmental Science International
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• v.22 no.10
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• pp.1305-1316
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• 2013

A long-term wind resource map was made to provide the key design data for the 2.5 GW Korean West-South Offshore Wind Project, and its reliability was validated. A one-way dynamic downscaling of the MERRA reanalysis meteorological data of the Yeongwang-Gochang offshore was carried out using WindSim, a Computational Fluid Dynamics based wind resource mapping software, to establish a 33-year time series wind resource map of 100 m x 100 m spatial resolution and 1-hour interval temporal resolution from 1979 to 2012. The simulated wind resource map was validated by comparison with wind measurement data from the HeMOSU offshore meteorological tower, the Wangdeungdo Island meteorological tower, and the Gochang transmission tower on the nearby coastline, and the uncertainty due to long-term variability was analyzed. The long-term variability of the wind power was investigated in inter-annual, monthly, and daily units while the short-term variability was examined as the pattern of the coefficient of variation in hourly units. The results showed that the inter-annual variability had a maximum wind index variance of 22.3% while the short-term variability, i.e., the annual standard deviation of the hourly average wind power, was $0.041{\pm}0.001$, indicating steady variability.

• Proceedings of the Safety Management and Science Conference
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• 2004.05a
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• pp.145-151
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• 2004

Reliability assurance problem is an important issue in advanced company with good R&D capacity. In Korea, long-term and large-scale project for reliability improvement and certification have been conducted from 2000, 4 years ago. Generally, assurance is composed of system assurance and lot assurance. For reliability lot assurance. it is prerequisite to development reliability sampling plan with time-saving and minimum cost. In this paper, we aim to investigate previous study on reliability lot assurance focused on reliability sampling plans and propose some suggestions for the future study.

• The Korean Journal of Health Service Management
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• v.5 no.1
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• pp.45-60
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• 2011

The purpose of this study is ultimately to contribute to enhancing quality of patients' life, by grasping quality level of care-giving service that is recognized by inpatients of long-term care hospital, and by pursuing a plan for improving quality of care-giving service based on this. For this, targeting 500 patients who entered 40 long-term care hospitals in Daejeon Metropolitan City, the quality of service was multi-dimensionally grasped by using SERVQUAL scale. As a result of research, the quality of care-giving service, which is recognized by patients as survey subjects, tended to be relatively high with about 4 points as a whole out of 5-point perfection. By item, reliability was indicated to be the highest with 4.56 points. The next was surveyed to be in order of tangibility, empathy, responsiveness, and assurance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.129-130
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• 2005

The electrical stress has a major effect on the long-term reliability of the thyristor. Therefore, it is needed to analyze the relationship between reliability and stress. In this paper, we investigate the device failure mechanism which induced by the stress. And also investigate the effect of the thermal stress on the device failure and relationship between electrical and thermal stress. Two-dimensional process simulator ATHENA and device simulator ATLAS are used to analyze the failure mechanism of the device.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.361-364
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• 2002

The paper presents a basic study on reliability evaluation using METRIS for long term expansion planning of transmission system. The main frame of methodelogy of the reliability evaluation of a transmission system in the METRIS is based on evaluation philosophy that the reliability level of a transmission system is equal to difference between the reliability level of HLII and that of HLI. While basic general theory of probabilistic reliability evaluation of transmission system has been presented, the GUI characteristics of input/out data system of METRIS have been demonstrated by the RBTS case study on METRIS.

• Journal of Korean Academy of Nursing
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• v.44 no.4
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• pp.398-406
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• 2014

Purpose: This study was done to develop and test the validity and reliability of the Korean version of the Pain Assessment Checklist for Seniors with Limited Ability to Communicate (PACSLAC-K) in assessing pain of elders with dementia living in long-term care facilities. Methods: The PACSLAC-K was developed through forward-backward translation techniques. Survey data were collected from 307 elders with dementia living in 5 long-term care facilities in Korea. Data were analyzed using descriptive statistics, Pearson correlation, Spearman's rho, paired t-test, ROC (receiver operation characteristic) curve with the SPSS/WIN (20.0) program. Results: The PACSLAC-K showed high internal consistency (.90), interrater reliability (.86), intrarater reliability (.93), and high concurrent validity (.74) in paired t-test with PAINAD. Discriminant validity also showed a significant difference compared with no pain. The PACSLAC-K showed a sensitivity of .93, specificity of .88, and Area Under the Curve of .95 in the ROC curve. Conclusion: The findings of this study demonstrate that PACSLAC-K is useful in assessing pain for elders with dementia living in long-term care facilities.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1749-1753
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• 2007

The reliability, that is Long-Term Quality, require an approaching different from Short-Term Quality which is used before. As the electronic components are able to be easily normalized on the reliability testing, various testing standards are used. In this study, we proposed two reliability simulator that is PoF(Physics of Failure)-based and failure rate models-based. PoF-based simulator is introduced based on CalceEP program that is created by University of Maryland. This simulator can be modified by user interface of properties and PoF models and operated on stand alone system. Failure rate models-based simulator introduced according to analyzing reliability prediction documents. Also, unified database including failure data models is built from existing MIL-HDBK-217F N2, PRISM, and Bellcore, and web-based simulator is developed. The developed reliability simulator will service of the PoF model, properties, failure rate model accumulated and its data by web and internet.