• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.13 no.1
• /
• pp.94-101
• /
• 1999

In this paper the problems associated with the switching surge of PWM inverter devices were analysed. As the application of ASD for efficient speed control of AC rmtors is increased, so is the rrntor and ASD-related failure increased. In the industrial rmtor awlications, the introduction of PWM drives can sometmes cause insulation breakdown between the phase windings due to high transient voltage peak. The motor cable length combined with the high switching frequency becomes more sensitive issue for proper drive operation. Effects of the cable length and high switching frequency influence both on rmtor and inverter. When the insulation level of rmtor winding is low, the failure probability caused by high peak voltage and fast voltage rise times(dv/dt) is high. Voltage refloctions are simulated far rmtor capacities, ASD and rise times and are presented graphically. The filtering techniques are discussed to reduce the rmtor terminal overvoltage and dv/dt in inverter fed AC rrntor drive systems. We confirmed that the lower motar capacity and rmtar insulation level, the shorter switching time and cable length and the higrer the probability of insulation breakdown .kdown .

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.8
• /
• pp.38-44
• /
• 2008

Internet Data Centers (IDCs), which are resulted by the rapid progress of Information Technology industry, consist of high-density digital loads with internet server systems. Introduction of DC distribution system may simplify the conventional electric power conversion system, and may result in the improvement of electric power efficiency. However, this conjecture has never been tested under Korean IDC environment. In this study, electric power efficiency of DC distribution system from KT Namsuwon IDC is contrasted with that of conventional AC distribution system from KT Bundang IDC. DC 48[V] based distribution system showed 13.2[%] higher efficiency than the conventional AC based distribution system. The further analysis with the assumption of DC 380[V] suggests efficiency improvement over 25[%] can be achieved.

• Applied Chemistry for Engineering
• /
• v.9 no.5
• /
• pp.667-673
• /
• 1998

Rebar corrosion in a simulated pore solution (SPS) with chloride ion was analyzed by Tafel and AC impedance method and corrosion effects of surface roughness and iron oxide layer were also investigated. Corrosion estimation of rebar by electrochemical impedance spectroscopy is very useful, and the measured value can be adapted to proposed electrochemical equivalent circuit model. Corrosion potential increased to the cathodic direction as the concentration of chloride ions increased and corrosion current had the same tendency as above. Surface films were analyzed with scanning electron microscope and Auger electron spectroscopy. Thermally oxidized layer by torch flame for 15 sec was very poor at anti-corrosive property. The corrosion rate of rebar increased as the surface roughness increased. Also, higher temperatures above RT of SPS in initial stage caused a rebar to be corroded faster.

• Journal of the International Relations & Interdisciplinary Education
• /
• v.1 no.2
• /
• pp.68-79
• /
• 2021

This study tried to analyze the case of character education class using reading for pre-primary early childhood teachers. To this end, the criteria for character education were established based on literature research, and a list of books appropriate for it was selected, and then applied to practice. The goal of character education class using reading for pre-school teachers is to cultivate the character that an early childhood teacher should have and to develop the ability to apply character education program through reading to young children. This study selected books based on the contents of personality virtues after taking a course on the concept and theory of personality contents for college students who are taking the 'personality and emotional reading' course in their major. Therefore, this study is meaningful in that it presents contents that can be practiced in connection with the family as a personality education program that can be applied not only to pre-primary teachers, but also to early childhood teachers and young children.

• Journal of the Korea Convergence Society
• /
• v.10 no.2
• /
• pp.277-284
• /
• 2019

This study is positive research to figure out enculturation types and to analysis influence of enculturation types on life's satisfaction of the marriage immigrant women. By precedent study, enculturation types was classified by integration factor, separation factor, assimilation factor and marginalization factor. To achieve objectives of study, we carried out sampling, survey and statistical analysis. According to result of study, integration factor and assimilation factor were appeared positive influence and separation factor was appeared negative influence statistically on quality of life of them. Therefore for quality of life of the marriage immigrant women, it need to develop interact system with native persons, support opportunity to associate with koreans, and promote fair treatment and interaction of koreans for them. And government have to execute multiculturalism policy more than assimilation policy. this study have that was samples's regional limitation, few variables limitation, and cross-sectional research's limitation. Therefor it needs more wide and depth research than this for future.

• The Journal of the Convergence on Culture Technology
• /
• v.7 no.3
• /
• pp.311-320
• /
• 2021

The study looked at a cross section of inter-Korean sports through the lives of female north korean defector. The researcher was a north korean national team player in the early and mid-1990s and defected to the north and played for the national team in South Korea. After her retirement, she became a coach, but felt limited and left the sports world. After analyzing the informant's interviews, the prevailing idea was that she was always politically used, and there was a regret that he was spotlighted as a defector rather than an athletic skill. And she was not in a position to choose between South Korea and North Korea. It was also shown that inter-Korean sports exchanges could not be developed unless economic conditions were supported. As a stranger, the research participants felt alienated and adapted to South Korea. Her life is an example of experiencing inter-Korean sports at the same time, and it is believed that she can have personal, specific, and concrete characteristics while showing universality in the upcoming era of unification.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.5
• /
• pp.557-565
• /
• 2022

The effect of flow configuration in ammonia-fed solid oxide fuel cell are investigated by using a three-dimensional numerical model. Typical flow configurations including co-flow and counter-flow are considered. The ammonia is directly fed into the stack without any external reforming process, resulting in an internal decomposition of NH3 in the anode electrode of the stack. The result showed that temperature profile in the case of counter-flow is more uniform than the co-flow configuration. The counter-flow cell, the temperature is highest at the middle of the channel while in the case of co-flow, the temperature is continuously increased and reached maximum value at the outlet area. This leads to a higher averaged current density in counter-flow compared to that of co-flow, about 5%.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.15 no.4
• /
• pp.291-297
• /
• 2022

This Paper is about the study that design performance and reliability measurement circuits of the IPM which is an intelligent switching switch module included at an inverter circuits for driving of A.C. Servo motors in home appliance. IPM is a core device of motor driver and it's switching characteristics should be retained uniformly during the driving of a servo system. All of it's specification, the collector emitter switch on voltage Vce(on) spec. is very important. As the IPM are core part of inverters and producing from several brands and versions, for optimal performances of application systems a method and measurement & evaluation system to measure Vce(on) value, collector emitter switch on voltage, of the IPM IGBT switches with various brands are required. Especially, the proposed method can measure and evaluate Vce(on) values of IPM with load at mounting state on the motor driving circuits and proposed measurement & evaluation system can be important instrument systems for IPM user companies.

• Korean Journal of Culture and Social Issue
• /
• v.29 no.3
• /
• pp.341-359
• /
• 2023

This study investigated effects of college students' multicultural contacts on multicultural competency. This study also examined mediating effects of perspective taking and prejudice. Multicultural contacts were divided into quality of contacts and quantity of contacts. Effects of quality and quantity of contacts on multicultural competency through perspective taking and prejudice were separately analyzed using two models. For the purpose, 642 Korean college students completed the questionnaires including multicultural contacts, multicultural competency, perspective taking, prejudice and demographic information. The results indicate that both quality and quantity of contacts are associated with multicultural competency, but quality of contacts are more strongly associated with multicultural competency. Also, perspective taking and prejudice mediate the relationship between quality of contacts and multicultural competency while mediators did not mediate the relationship between quantity of contacts and multicultural competency. The results indicate that intimate and positive contacts with outgroup members help enhance college students' multicultural competency through increased perspective taking and prejudice reduction. Future multicultural education for undergraduate students should focus on increasing the quality of multicultural contacts and help them with perspective taking, and reducing prejudice.

• Korean Journal of Culture and Social Issue
• /
• v.19 no.3
• /
• pp.409-433
• /
• 2013

Despite leisure has been well-studied as an influence in coping with stress, psychological process of leisure experience have not examined. This study examined the effect of leisure experience on emotional exhaustion. Also, we attempted to find out whether psychological detachment from work has mediating effects on the relationship between leisure experience and emotional exhaustion. Data were collected from 215 workers employed in a variety of organizations. We divided leisure experience into perceived competence, social relation, nature relation, and control nature based on factor analysis. Results indicate that only perceived competence was negatively associated with emotional exhaustion. Further, psychological detachment partially mediated this relation. This result presented that perceived competence is most important factor in leisure experience for psychological recovery.