• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.252-257
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• 1998

Two-stage power factor correction (PFC) converter with a single PWM controller for universal input voltage (90-264V) is proposed. It consists of a power factor pre-regulator cascaded by a DC/DC converter as in a conventional two-stage approach. However, a single PWM controller is used as in a single-stage, single-switch PFC approach. The switch in the PFC part is synchronized with the switch in the DC/DC converter with a fixed switching frequency. Employing an adaptive delay scheme the switch in the PFC part is controlled to limit the energy storage capacitor voltage within a designed range for the optimum efficiency, and to reduce input current harmonic distortion. The experimental results obtained on a 200W (5V/40A) prototype PFC converter are given to verify the effectiveness of the proposed control method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8234-8242
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• 2015

This study aims to explore ways to provide a high quality work environment services to social workers to analyze the relevance of relationships and exhaustion of the organizational environment, and the working environment and clients with disabilities living facility workers Gwangju and Jeonnam 252 people were targeting professionals working with people with disabilities living facility located on the main results are as follows. Organizational environment, work environment, organizational environment results by setting the relationship with the client as independent variables conducted a regression analysis to investigate the factors that influence independent of exhaustion (${\beta}$=-.200, p=.001) and Job environment (${\beta}$=-.460, p<.001) was a significant independent explanatory factor was 31.0%. However, relationships with clients (${\beta}$=-.059, p=0.258) were not significant factors in exhaustion. Consequently, practitioners must always have the confidence to actively work with pride and facilities are needed to improve the organizational environment and the working environment.

• Journal of the Korean Society of Earth Science Education
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• v.6 no.3
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• pp.252-260
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• 2013

The purpose of this study is find out the correlation of level of knowledge of pre-service elementary teacher with space perception ability on 'Earth and Space' of elementary science. During the second semester of 2013, for 15 weeks, the classes were conducted for 3 hours per week and we find out knowledge Understanding degree and select terms offered by 5th grade science courses 'The solar system and the stars', 'Earth and Moon', 'change of seasons' section and measured space perception ability degree of pre-service elementary school teacher with a questionnaire. We analyzed the correlation of understanding level of knowledge in the field of astronomy of pre-service elementary school teacher with space perception ability. The results of the study are presented as follows. First, pre-service elementary school teacher showed a low level of knowledge understanding as it goes the upper grades about upper concept in 'The solar system and the stars', 'Earth and Moon', 'change of seasons' section' of astronomy area of elementary science 'Earth and space sector'. The pre-service elementary school teachers needs to acquire knowledge of astronomy area in elementary school curriculum. Second, pre-service elementary school teacher showed that there are differences individually in 'finding solid body' of sub-element of space perception ability. This shows that 'finding solid body' factor is associated with space perception ability. Third, in the section of 'The earth and the Universe' for elementary education, 'Reflection' and 'Finding solid body' which are low-level components of space perception ability were verified that have a corelationship with general grades in the astronomy conception test.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.252-257
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• 2010

The availability of the thermal energy has been deeply recognized recently to encourage the cascade usage of thermal energy from combustion. Within the frame work, a 1 kW class Stirling engine based cogeneration system has been proposed for a unit of a distributed energy system. The capacity has been designed to be adequate for the domestic usage, which requires high compactness as well as low emission and noised. To develop a highly efficient system with satisfying these requirements, a premixed slot flame burner has been proposed and a series of numerical simulation has been performed to establish a design tool for the combustion chamber. The thermal radiation model has been found to highly affect the computational results and a proper resolution to analyze the heat transfer characteristics of the high temperature heat exchanger. Finally, the combustion characteristics of the premixed flame with the metal fiber type burner has been studied.

• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.252-264
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• 2002

In this study, the experimental apparatus for boiling point and melting point in science textbooks of various curriculums were analyzed. Science teachers' views on the difference between the experimental value and the value written in textbooks were inquired, too. Their views on the experimental apparatus, nd results of freezing point,melting point, boiling point, fractional distillation, and thermometer calibration were also investigated. The results of this study showed that the types of experimental apparatus for boiling point and melting point were somewhat dif-ferent with science textbooks and curriculum. The teachers' views were also various according to their background. In the experiment of the fractional distillat ion, a large number of teachers recognized mismatch between the exper-imental value and the value written in textbooks as mistake of textbook contents or problem of experiment itself. The teachers of chemistry background take higher recognition of the requirement of thermometer calibration than those of non-chemistry background in middle school.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.613-624
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• 2013

The purpose of this study is to identify the priorities with respect to the characteristics of tourism resources development plan between the South and the North Korea. Through a preliminary investigation 287 lists of questions were distributed from May 14, 2012 to December 5, 2012 and from among them 252 lists were used. Expert Choice 11.5 was used to do pairwise comparisons and priorities assessment. Based upon the results of empirical analysis, the priority order sets of the domain of tourism resources development plan should be related to the development contents, the development objects, the development patterns, and the development subjects in the South Korea. Those should be related to the development subjects, the development objects, the development contents, and the development patterns in the North Korea.

• Journal of the Korean Society of Earth Science Education
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• v.12 no.3
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• pp.252-260
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• 2019

The purpose of this study is to assist school science class by investigating effective Earth's rotation experiments of districts by school level. The researcher investigated or developed nine experiments for learning Earth's rotation, and conducted and discussed these experiments with 26 elementary school teachers. Each teachers chose an effective Earth's rotation experiment for the district and wrote the reason. As a result, elementary school teachers chose the experiment that is easy to prepare and to do. And elementary school students are interested in the experiments by conducting them on their own. Middle and high school teachers chose more difficult experiments that could be connected with other concepts. University teachers chose effective experiments based on application of knowledge, active exploration, computer literacy, and difficulty.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.4
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• pp.331-335
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• 2012

On January 13th 2012 Italian flag Costa Concordia was partly sunk. The ship was carrying 4,252 passengers and crew; in the next few days the bodies of 30 people were found. Two are still missing. Two South Korean passengers and an Italian crew member was rescued from the ship on January 15th, more than 24 hours after the accident. As of June 18th 2012 (The date of presentation) around 32 people had not been accounted for. In this paper, it is viewed and pointed out the cause, problem, and implication for the future. As a result, intelligent innovative evacuation system for the VLPS (Very Large Passenger Ship) should be set up in terms of international maritime safety.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6044-6052
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• 2015

This study was conducted to identify the level of empathy and clinical practice stress and the relationship between empathy and clinical practice stress in nursing students. Data were collected from 252 nursing students between 1st September and 31st December 2013. 249 questionnaires were analyzed using descriptive statistics, t-test, ANOVA, and Pearson's correlation coefficient. The mean scores of empathy level in the subcategories for perspective taking 3.57, fantasy 3.59, empathic concern 3.72 and personal distress 3.15 were above median and the mean score for clinical practice stress 3.03 was above median. Clinical practice stress positively correlated with personal distress on empathy. These findings indicate that there is a need to manage personal distress on empathy for nursing students with high level of personal distress to lessen stress in clinical practice of nursing students.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.213-220
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• 2016

This study surveyed 252 senior citizens in the Chungnam and Chungbuk regions to review the effects that information use has on quality of life. Participants were divided into two sub-groups based on household types. Data was analyzed using PASW Statistics 18.0. Major findings are as follows: First, information use, mental and psychological health, as well a&s social relationships found in study subjects were significantly higher among seniors not living alone. Second, factors that influence the quality of life were found to be same for each group, but significantly different for their influence of each group. Factors that influence the quality of life were found to be economic status, information use, and education level. Factors that influence the quality of life in elderly living alone were found to be economic status, education level, information use. Based on these findings, the study presents practical and integrated measures to help the original objective of this research to be achieved.