• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.500_502
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• 2009

한전의 분산전원 연계규정에 따르면 수전고객은 변압기 결선이 ${\triangle}-Yg$ 주로 사용되나 분산전원 연계선로는 변압기 결선이 $Yg-{\triangle}$ 형태로 연계되어 있다. 전원계통 고장시 ${\triangle}-Yg$ 결선 방식은 역조류가 발생되지 않으나, $Yg-{\triangle}$ 결선방식은 중성선을 통해 최대 2000[A]까지 역으로 고장전류를 공급한다[1]. 이때 보호계전기 오동작뿐만 아니라 연계용변압기, 케이블 등 설비보호를 위해서는 고장전류의 크기를 반드시 제한해야 된다. 본 논문은 연계용변압기에 의해서 공급되는 중성선의 과전류 현상을 해석하고, 이론적으로 해석된 결과를 PSCAD/EMTDC로 검증하였으며 고장전류의 크기를 저감하기 위해 NGR 저항 값을 조절하면서 고장전류의 크기를 시뮬레이션 하였다. 분산전원 연계선로에서 영상분 고장전류의 크기를 저감하는 방법으로 연계용 변압기($Yg-{\triangle}$) 1차 측에 중성선에 NGR(Neutral Grounding Reactor; 중성점 접지리액터)을 설치해야 하며 영상임피던스를 조절하는 방법을 제시하였다.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.42-48
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• 2013

The global warming of the Korean Peninsula proceeds most rapidly in the world and its abnormal climate is more deepening. In the result of the surged electricity consumption by intense heat of summer and severe cold of winter, electricity supply and demand status is in hard situation. Currently, the supply of natural gas is increased because natural gas has the lowest greenhouse-gas emissions among the existed fossil fuel. Natural gas cooling has a lot of advantage such as decreasing electricity peak, reducing construction expenses in additional power plant, operating natural gas storage facilities efficiently, and playing a role as distributed generations. Therefore, this study analyzes the economic feasibilities of gas cooling as an alternative for electric power load management.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.4
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• pp.428-434
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• 1997

The effect of genetic diversity in sub-populations on breeding efficiency was examined with prospect of potential crossbreeding. Simulation study of selection was performed for 20 generations with 20 replications each, comparing average breeding values and inbreeding coefficients between the two breeding systemes; single population scheme and two population scheme. The different genetic levels were assumed to be caused by different gene frequencies. Phenotypes of two traits generated polygenic effect with additive 36 loci and residuals distributed normally were selected by selection index procedure. High genetic gain with less inbreeding was clearly recognized in the single population scheme, independently of difference in genetic level, economic weight and genetic correlation. Genetic correlation after selection in the single population scheme was lower than the two population scheme. When crossbreeding between the sub-population was taken into account, superiority of the two population scheme was suggested under those restrictions; difference in genetic level is moderate, selection criterion for the two traits is not far from even economic weight, and genetic correlation is positive with low to moderate value. The use of complementarity increased the possibility of the two population scheme.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.4
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• pp.422-427
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• 1997

Breeding efficiency was investigated to reveal crucial factors for constructing effective breeding system with subdivided populations under equal genetic level. Simulation study of selection experiment was performed for 20 generations with 20 replications each, comparing average breeding values and inbreeding coefficients between the two breeding systems; single population scheme and two population scheme, each of which had the same genetic parameters. Genetic correlations (-0.5 to 0.5) were assumed to be caused only by pleiotropic effect of a gene. Phenotypes of the two traits generated by polygenic effect with additive 36 loci and residuals distributed normally were selected by two traits selection index procedure. Comparing between the single population scheme and the two population scheme, the single population scheme showed higher genetic gain with lower inbreeding coefficient. This result was confirmed particularly for the situation of high selection intensity, high heritability and high degree of unevenness for economic weight. Genetic correlations in the single population scheme were significantly lower than the two population scheme when initial genetic correlation was negative. When terminal crossbreeding for the two population scheme is taken into account, superiority of the two population scheme was suggested. The terminal crossbreeding was effective under the situation of long term selection, existence of moderate inbreeding depression and use of less extreme economic weight.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.240-241
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• 2006

Islanding operations of DG usually occur when power supply from the main utility is interrupted due to several reasons but the DG keeps supplying power into the distribution networks. These kinds of islanding conditions cause negative impacts on protection, operation, and management of distribution systems. Therefore, it is necessary to effectively detect the islanding conditions and swiftly disconnect DG from distribution network. This paper proposes the islanding detection algorithm for DG using the change of the voltage unbalance and the output power of DG. The proposed method effectively combines the conventional parameters for detecting the islanding conditions. The proposed methods were verified using the radial distribution network of IEEE 34 bus.

• Journal of Families and Better Life
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• v.24 no.4 s.82
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• pp.75-92
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• 2006

This study examines the psychological independence in the family system of unmarried women to see how well they become psychologically independent within the relationships with family. A total of 452 subjects of the study were sampled from 20 to 30 unmarried women living in Seoul, Incheon and Gyeonggi-do. The results of the study are as follows: First, the scores of unmarried women's perception of family system were normal category. The scores of family system of unmarried women showed to be distributed to high scores among the overall ranges of scores which means they recognized their family system in general in a healthy way. Second, the level of the subjects' psychological independence from their fathers was shown to be higher than that from their mothers. The result means unmarried women were more dependent on their mothers than fathers. Third, the family system of unmarried women affected the level of psychological independence from their parents. The sub-factors of the family system significantly affected the level of psychological independence. Particularly, enmeshed and disengaged boundary and cooperative factors between spouses and generations affected the level of psychological independence. Fourth, the family system affected each sub-factor of psychological independence of unmarried women. Even though family system were different depending on each sub-factor of psychological independence, they affected the level of psychological independence.

• Human Ecology Research
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• v.54 no.5
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• pp.475-485
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• 2016

This study explored mothers' and grandmothers' perception regarding child rearing practices as overprotective behaviors for first to third grade levels of elementary school. The study was conducted on 202 mothers and grandmothers of first to third grade elementary school students. Questionnaires were made with 40 questions on overprotection behaviors selected from the existing questions for preschooler, high grade elementary students, and youth. The questionnaires were distributed to target subjects to answer how they would perceive when each of question is applied to their lower grade elementary students. Based on the collected responses and the factor analysis, it was found out that the overprotective behaviors were classified into four factors such as "reduction in independence," "over-sensitiveness to safety," "interference in daily life," and "health anxiety." There were significant differences in the perception of the overprotective behavior by the subjects depending on the generations, features of children and mothers. This study focused on the lower grade elementary school students who have been removed from studies due to the lack of intervention measures. It has the implication in that the findings of the study can give the basic data for the development of the scale on overprotective behaviors in lower grade elementary school students.

• World Technopolis Review
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• v.6 no.1
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• pp.2.1-2.9
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• 2017

Humanity is experiencing a very fast-paced technological evolution. As technological systems evolve exponentially, societies are becoming more global and are starting to have impacts beyond their geographic demarcations. This implies that, the actions of a person who is across the ocean from where we live could have significant impacts on our everyday lives. This article explores the complexity of globalization, identifies a number of global issues, and looks at the University and the Science and Technology Parks as potential sources of human capital to tackle current and forthcoming global challenges, ranging from new energy sources to potable water distributions. The article focuses on current efforts that are taking place across universities and science and technology parks around the world. We propose a new methodology whereby interdisciplinary work can inform the development of multidisciplinary approaches to solve some of the most complex global issues such as cyber security and educating the next generations of global leaders, providing them them with the necessary skills to be successful in a globally distributed workforce.

• The Journal of Korean Association of Computer Education
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• v.17 no.6
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• pp.115-122
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• 2014

One of the problems with current youth generations is increasing rate of violence and suicide in their school lives, and this study aims at the design of a sentiment analysis system to prevent suicide by uising big data process. The main issues of the design are economical implementation, easy and fast processing for the users, so, the open source Hadoop system with MapReduce algorithm is used on the HDFS(Hadoop Distributed File System) for the experimentation. This study uses word count method to do the sentiment analysis with informal data on some sns communications concerning a kinds of violent words, in terms of text mining to avoid some expensive and complex statistical analysis methods.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.484-485
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• 2008

A micro-grid (MG) is a new concept to aggregate distributed generations (DGs) and loads in a small area. The difference between MG and DG is that MG can supply power to loads even in islanding conditions. The magnitude of the fault current depending on interconnection between the MG and utility and the number of DGs in the MG. Therefore, the setting value of the OCR must be changed depending on operating conditions of the MG. This paper proposes the over-current relay considering operating conditions of the MG. In the proposed algorithm, the supervisory control and data acquisition decides the operating conditions of the MG and sends the proper setting values to each OCR. The performance of the algorithm was investigated in the case of the various operating conditions.