• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1660-1669
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• 2014

Partial discharge (PD) detection plays a major role in the life time assessment of liquid insulation in power transformers. Many research works are being carried out to replace conventional mineral oil insulation in transformers by vegetable oils. It is necessary to understand the PD characteristics of vegetable oils before recommending them as an alternate for mineral oil. In this paper, the breakdown strength and PD characteristics of palm and corn oil were investigated in both unaged and thermally aged conditions. Laboratory experiments were performed as per IEC test procedures. PD signals were measured using wide band detection system. Phase resolved PD pattern of vegetable oils and mineral oil were compared. Effect of increase in voltage stress on the PD pattern of palm and corn oil were studied. Time and frequency domain analysis of PD pulses at needle-plane electrode configuration was carried out. Statistical analysis of PD pattern i.e. skewness and shape parameter variations with respect to applied thermal stress were also carried out. From the results, it is observed that palm and corn oils have better breakdown strength and PD characteristics even under long-term thermal stress and hence they can be used for power transformer applications.

• 전기학회논문지
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• 제66권11호
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• pp.1605-1611
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• 2017

In this study, the characteristic lifetime of power facilities such as power transformers and GIS were investigated as the basis of power facility asset management. It is difficult to obtain the operation and failure data of the facilities in Korea. Therefore, the number of failures of the electric power facilities was calculated from the operation data and hazard rate shown in the overseas literatures, and the statistical analysis was performed using the Weibull distribution function. As a result of extracting and analyzing the data of the UK National Grid for power transformers, the characteristic lifetime (scale parameter) of 116.45 years was considered to be a very appropriate value for power transformer management and can be used as a comparative data of the analysis of the domestic transformers. As for the GIS, based on the Bays and Bay-Years data and the hazard rate according to the operation years of the 123kV GIS in Germany, it is found out that the characteristic lifetime of GIS is not so meaningful. It is necessary to decide a maintenance strategy and lifetime expectancy considering the characteristics of the design, materials and manufacturing process of GIS.

• 가족자원경영과 정책
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• 제20권3호
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• pp.25-43
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• 2016

This study focused on the time use of a dual-earner working group with preschool children on working and nonworking days using 2014 time-use survey data provided by Statistics Korea(KOSTAT). We collected the time-use data recorded in a 2,158 time diary. We divided the time use into 4 parts ; paid work, household labor work (including caring work), leisure and living essentials. For the statistical analysis, we used SPSS 18.0 packages, i.e., descriptive statistics, T-test, Anova with Duncan test and regression for the impact off the independent factors. The results verified gender differences in time use and recognized the usefulness of the time-allocation analysis for the diagnosis of Work and Life Balance(WLB). In the conclusion, we suggest increasing men's time allocation for household labor as a crucial solution to the WLB of dual-earner working groups. And the follow-up study should include the various factors that affect the time allocation of dual-earner groups, such as type of labor and job and children's ages.

• 가정과삶의질연구
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• 제31권4호
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• pp.97-111
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• 2013

The purpose of this study was to explore the typology of child care, investigate the characteristics of child care types, and analyze the differences in time deficit as well as time satisfaction by the types of child care for dual-earner couples with preschool children. The data source for this research was the 2009 Time Use Survey conducted by the Korea National Statistical Office. Dual-earners aged 20 to 59 years completed 1,568 time diaries, which were analyzed using chi-square, cluster analysis, and ANOVA analysis. Child care time was classified into three types in the three categories of child care, household work sharing and leisure sharing for both males and females respectively. Three types for husbands were named "vulnerable", "household work child care predominant" and "leisure predominant". The three types for wives were named "vulnerable", "household work child care oriented" and "household work child care". The characteristics of each type depended on age, education, weekly working hours, gender role of husbands and age, weekly working hours of wives. The vulnerable type of wives showed the highest level of time deficit. Based on the results, implications for Public policy on child care and various types of education as well as programs were suggested.

• 산업공학
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• 제12권3호
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• pp.448-457
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• 1999

Accelerated degradation is concerned with models and data analyses for degradation of product performance over time at overstress and design conditions. Although there have been numerous studies with accelerated degradation theory in reliability, very few actually apply to parametric statistical analyses. This paper shows how to analyze degradation data, provides tests for how well the assumptions hold. Reel sensors, a sort of photointerrupters in home VCR, hive been tested, and least-square analyses are used to illustrate our approach. Tests for linearity of the performance-time relationship, dependence of the lognormal distribution, and the standard deviation on time are performed. The mean life of tested sensors is assessed at about 414,000 hours, and the Arrhenius activation energy of this reaction is concluded to be 0.39 eV as results.

• 전자공학회논문지T
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• 제35T권1호
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• pp.1-6
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• 1998

본 연구는 부분방전 시스템을 이용하여 열화진단을 실시하였다. 열화 분석 방법으로는 위상각 부분방전 펄스진폭 열화시간과 위상각 부분방전 펄스수 열화시간의 양상을 왜도와 첨쇄도로 3차원 분석하여 열화의 정보로 이용하였다. 두번째로는 C (경도), G (무게중심)의 통계적 파라메터를 이용하여 방전의 군소화가 발생하는 시간을 구하여 그 지점으로부터 수명 4예측을 하였다.

• 가족자원경영과 정책
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• 제20권3호
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• pp.45-65
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• 2016

The purpose of this study is to investigate the participation in social activities by full-time housewives with infants and preschool children. The data in this study comes from a 1 percent free sample of the 2010 Population and Housing Census collected by Statistics Korea. The statistical methods for this study were percentage, chi-square test, and logistic regression analysis. The findings are as follows. First, there are differences in participation in social activities according to number of infants, number of preschool children, and number of elementary schoolchildren. Second, there was the difference in participation in social activities between full-time housewives and full-time wives' husbands. Third, factors like full-time housewives' age, educational level, number of preschool children and elementary schoolchildren, number of rooms, and occupancy status affected participation in social activities by full-time housewives. These results show that full-time housewives were under pressure in relation to participation in social activities because of their caregiving labor but participated in religious and educational activities actively.

• 대한지역사회영양학회지
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• 제7권5호
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• pp.705-714
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• 2002

The purpose of this study was to examine the relative importance of everyday life stress, obesity stress, and social support on the BMIs of junior. high school students. Subjects in this study consisted of 229 adolescents from two junior high schools in Iksan-city and Hamyul-eup. For data analyses, the frequencies, percentages, means, 1-tests, Chi-squares, one-way ANOVAS, Pearson's correlation coefficients and regressions were conducted using SPSS WIN program. The mean BMI of the subjects was 20.18, and the ratio of students'BMIs less than 20 was 56.8%, that of students'BMIs greater than or equal to 25 was 8.3%. There were no statistical differences in BMIs by grade and sex. Statistically significant differences in the obesity of the junior high school students were detected according to demographic characteristics such as economic levels, areas of residence, TV watching time, and fathers'physiques. There were significant differences in everyday life stresses, obesity stresses, and social support by sex, but not by grade. Girls showed higher stress levels than boys, specially in family-related life stresses, social relationships, and self-related stresses. Also girls showed higher stress level related to obesity than boys. Girls got more support from their mothers, siblings and friends than boys. With respect to the type of social support, girls perceived more financial, informational, emotional, and judgemental support than boys. These results suggest that girls became more stressed, although on the other hand, they received more social support than boys. The higher the economic level, the longer the TV watching time, and the higher the stresses from everyday life and obesity, the higher the BHIs of the junior high school students were. In conclusion, everyday life stress and obesity stress were the important factors in relation to the junior high school students'obesity.

• Journal of Korean Neurosurgical Society
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• 제56권6호
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• pp.482-487
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• 2014

Objective : We assessed the life-time prevalence (LTP) of chronic low back pain (LBP) in young Korean males. We also evaluated the relationship between lumbar spinal lesions and their health related quality-of-life (HRQOL). Methods : A cross-sectional, self-reported survey was conducted in Korean males (aged 19-year-old) who underwent physical examinations for the conscript. We examined 3331 examinees in November 2014. We included 2411 subjects, who accepted to participate this study without any comorbidities. We interviewed using simple binary questions for their LBP experience and chronicity. HRQOL was assessed by Short-Form Health-Survey-36 (SF-36) in chronic LBP and healthy control groups. Radiological assessment was performed in chronic LBP group to determine whether there were any pathological causes of their symptoms. Results : The LTP of chronic LBP was 13.4%. Most (71.7%) of them didn't have any lumbar spinal lesions (i.e., non-specific chronic LBP). The SF-36 subscale and summary scores were significantly lower in subjects with chronic LBP. Between specific and non-specific chronic LBP group, all physical and mental subscale scores were significantly lower in specific chronic LBP group, except mental health (MH) subscale score. In MH subscale and mental component summary score, statistical significant differences didn't appear between two groups (p=0.154, 0.126). Conclusion : In Korean males 19 years of age, the LTP of chronic LBP was 13.4%, and more than two-thirds were non-specific chronic LBP. Chronic LBP had a significant impact on HRQOL. The presence of lumbar spinal pathoanatomical lesions affected mainly on the physical aspect of HRQOL. It influenced little on the mental health.

• Journal of Microbiology and Biotechnology
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• 제16권12호
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• pp.1940-1946
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• 2006

The influence of environmental conditions on the ganoderic acid (GA) content in the fungus Ganoderma lucidum was investigated using a one-factor-at-a-time design and orthogonal design. Among the various medium components examined, sucrose, soybean powder or peptone, ferrous sulfate, and pH 6.0 were the most suitable carbon source (factor A), nitrogen source (factor B), mineral source (factor C), and initial pH (factor D), respectively, for the GA content in the one-factor-at-a-time design. According to the orthogonal design, the order of effect for the four factors on the GA content was A>C>D>B. The best level of factor A was $A_2$ (sucrose) with a value of +0.34 mg/100 mg DW. The optimal treatment combination was $A_2B_1C_3D_1$ with which the GA content reached up to 2.63$\pm$0.011 mg/100 mg DW. The interactions between the mineral ion and the nitrogen source, and the mineral ion and the pH were both highly significant (P<0.01). The highest interaction effect was ($B_2{\times}D_2$) with a value of +0.19 mg/100 mg DW, which was higher than the level effect value for $B_2$ (peptone) and D$_2$ (pH 5.0). Therefore, the results proved that interactions between factors cannot be ignored. The results also indicated the importance of the interactions between the factors, which may help to understand the metabolic pathway leading to triterpene biosynthesis and the expression and regulation of the key enzymes involved.