• Journal of Electrical Engineering and Technology
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• 제4권1호
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• pp.123-130
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• 2009

The partial discharge (PD) measurement is a very effective method to assess the winding insulation condition of high-voltage machines, since most of the insulation failure processes are directly or indirectly caused by PD. On-line PD measurements, which can detect insulation defects of winding in the early stages on rotating machines in operation, have been accepted as the most important technique. The epoxy mica capacitive coupler is currently and extensively used for on-line detection of PD pulses of high-voltage rotating machines. To evaluate the feasibility of developing a capacitive coupler that is easier to manufacture at a lower cost compared to epoxy mica couplers, a 100pF capacitive coupler made of ceramic material is designed, fabricated and tested for on-line PD measurements of 23 kV electrical machines. A series of electrical tests and accelerated aging tests are performed on the ceramic coupler to evaluate the performance requirements, long-term reliability and thermal stability for in field application. The test results show that the newly developed ceramic coupler provides equal and improved performance at a lower cost compared to epoxy mica couplers, and estimated voltage life is anticipated to surpass 100 years.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1337-1345
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• 2018

The reliability of power transmission and distribution depends up on the consistency of insulation in the high voltage power transformer. In recent times, considering the drawbacks of conventional mineral oils such as poor biodegradability and poor fire safety level, several research works are being carried out on natural ester based nanofluids. Earlier research works show that sunflower oil has similar dielectric characteristics compared with mineral oil. BIOTEMP oil which is now commercially available in the market for transformers is based on sunflower oil. Addition of nanofillers in the base oil improves the dielectric characteristics of liquid insulation. Only few results are available in the literature about the insulation characteristics of nano modified natural esters. Hence understanding the influence of addition of nanofillers in the dielectric properties of sunflower oil and collecting the database is important. Considering these facts, present work contributes to investigate the important characteristics such as partial discharge, lightning impulse, breakdown strength, tandelta, volume resistivity, viscosity and thermal characteristics of $SiO_2$ nano modified sunflower oil with different wt% concentration of nano filler material varied from 0.01wt% to 0.1wt%. From the obtained results, nano modified sunflower oil shows better performance than virgin sunflower oil and hence it may be a suitable candidate for power transformer applications.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2019년도 제60차 하계학술대회논문집 27권2호
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• pp.401-402
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• 2019

The purpose of this study is to find specific service quality factors of enterprises that can maximize the perception of banks' services to users of commercial banks in China, and to establish empirically how these quality factors affect the bank's image. They also want to verify the impact of the positive image of the bank on the user's satisfaction and the willingness to use the bank's services. For empirical verification of this study, questionnaires will be used to customers who have used the services of each of the four commercial banks in China, and the survey was conducted. The collected data were analyzed using the SPSS using statistical techniques such as Cronbach' ${\alpha}$, Investigative Factor Analysis, Reliability Analysis, Correlation Analysis, Regression and Difference Verification. The results of the verification were summarized below. First, the quality of service of commercial banks has a partial positive effect on the bank's image. Second, the image of a commercial bank has a positive effect on customer satisfaction. Third, the image of a commercial bank has a positive effect on the purpose of use. Fourth, the image of commercial banks has a partial mediated effect between service quality and customer satisfaction. Fifth, the image of a commercial bank has a partial mediated effect between the quality of service and its intended use.

• International Journal of Advanced Culture Technology
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• 제11권2호
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• pp.256-266
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• 2023

The purpose of this study is to investigate the relationship between stress and school life adaptation according to the degree of participation in physical education class and perception of middle school students. In order to achieve this research objective, the subjects of this study were sampled using cluster random sampling from male and female students attending middle schools in Gwangju Metropolitan City and Jeollanam-do in 2020. 150 males and 150 females, a total of 300 people were sampled. The statistical analysis used for data analysis was frequency analysis, exploratory factor analysis, reliability analysis, and multiple regression analysis using SPSS Windows 21.0 Version. The conclusions obtained in this study through data analysis by such methods and procedures are as follows. First, it was found that middle school students' participation in physical education classes and perceptions had a partial effect on stress. Second, it was found that the degree of participation and awareness of middle school students' physical education class had a partial effect on their adaptation to school life. Third, middle school students' stress was found to have a partial effect on school life adaptation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1969-1971
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• 2004

For evaluation of partial discharge performances of electrical power appratus such as Insulator, circuit breaker and transformer and so on, Partial discharge measuring system(ERA) consisted of PD detector including amplifier, coupling capacitor, PD calibrator and voltage divider are used PD measuring system is very important factor which affect the test result and show reliability of test result in test laboratory, In this paper, we describe tracebility and uncertainty of PD measuring system in test laboratory based on IEC 60270.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.110-115
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• 2004

The hybrid fault diagnosis method based on a combination of the signed digraph (SDG) and the partial least-squares (PLS) has the advantage of improving the diagnosis resolution, accuracy and reliability, compared to those of previous qualitative methods, and of enhancing the ability to diagnose multiple fault. In this study, the method is applied for the multiple fault diagnosis of the Tennessee Eastman challenge process, which is a realistic industrial process for evaluating process contol and monitoring methods. The process is decomposed using the local qualitative relationships of each measured variable. Dynamic PLS (DPLS) model is built to estimate each measured variable, which is then compared with the estimated value in order to diagnose the fault. Through case studies of 15 single faults and 44 double faults, the proposed method demonstrated a good diagnosis capability compared with previous statistical methods.

• 한국해양공학회지
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• 제17권6호
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• pp.23-31
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• 2003

As there are so many uncertainties associated with using the determinism analysis method in the design of rubble mound breakwater, it is impossible for a designed construction to provide ultimate stability. First of all, due to the uncertainty of Load and Resistance, a safety level concerning the destruction mode of construction must be given. Then, the optimization design should be processed. After all, we can say that it is a more reasonable design method than the design used by the stability rate. In this study, an established design process is accomplished using Hudson's equation and an economic analysis with the breakwater's section is also conducted. Hudson's equation is compared to Van der Meer's equation. These results are utilized to drop a damage rate, increase the stability of construction, and determine the optimization section of the breakwater.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1765-1772
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• 2015

The integrity of the gas insulated switchgear (GIS) is vital to the safety of an entire power grid. However, there are some limitations on the techniques of detecting and diagnosing partial discharge (PD) induced by insulation defects in GIS. This paper proposes a joint electro-chemical detection method to resolve the problems of incomplete PD data source and also investigates a new unique fault diagnosis method to enhance the reliability of data processing. By employing ultra-high frequency method for online monitoring and the chemical method for detecting SF6 decomposition offline, the acquired data can form a more complete interpretation of PD signals. By utilizing DS evidence theory, the diagnostic results with tests on the four typical defects show the validity of the new fault diagnosis system. With higher accuracy and lower computation cost, the present research provides a promising way to make a more accurate decision in practical application.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 춘계학술대회 논문집 전기설비전문위원
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• pp.96-99
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• 2008

On-line condition monitoring is a useful tool for maintaining and extending the longevity of power transformers. An intelligent diagnostic system is desirable for operational safety and reliability. Bringing these concepts together results in a powerful support tool for engineers, reducing the volume of data to deal with, and making the data more meaningful. This paper describes how a multi-agent system for diagnosing the cause of transformer partial discharge activity was coupled with a method of UHF partial discharge monitoring, creating an on-line condition monitoring system. The challenges presented by the on-site environment are discussed, along with the implications for the complete system.

• 한국생활과학회지
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• 제14권1호
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• pp.69-79
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• 2005

The purpose of this study is to investigate child rare teachers' job satisfaction in relation to their burnout and differences in their job satisfaction by demographic variables. Subjects of this study were 285 child care teachers in Chungnam province. They responded to 'Teachers' Work Satisfaction Scale' and 'Teachers' Burnout Scale.' The collected data were analyzed by one-way ANOVA, Pearson's partial correlation, stepwise multiple regression, $Scheff{\acute{e}}$ test for post hoc test, and Cronbach's a for reliability with SPSS PC program(10.0 version). The results are as follows: First, total job satisfaction was high in teachers with high school diploma and those married. Also, burnout level was high in teachers with high school diploma, those with more than 5 year, those married, and those over 40 years old. Second, the partial correlation coefficient of teachers' job satisfaction in relation to their burnout was -.52. Finally, teachers' burnout and demographic variables explained approximately 31% for total score of job satisfaction and $13{\sim}33%$ for subscales of it.