• The Magazine of the IEIE
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• v.37 no.8
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• pp.31-40
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• 2010

1947년 트랜지스터의 발명을 시작으로 사이리스터, MOSFET 및 IGBT 등의 전력반도체 소자가 개발되면서 산업, 가전 및 통신 등의 다양한 분야에서 실리콘 기반의 전력반도체 소자가 활용되고 있다. 개발 당시에는 10A/수백V 정도의 전류통전능력 및 전압저지능력을 가지고 있었지만, 현재에는 8000A/12kV급의 대용량 소자까지 생산되고 있다. 이러한 전력반도제 소자는 다양한 응용분야에 서 높은 전압 저지능력, 큰 전류 통전 능력 및 빠른 스위칭 특성을 요구하고 있다. 특히 최근의 전력변환장치들은 고온동작특성 및 고효율화에 대한 요구가 더욱 강조되고 있다. 일반적인 실리콘 전력반도체소자는 물질적인 특성한계로 고온에 서의 동작 시 소자 특성이 떨어지는 특징을 보이고 있어 고온 환경에 적합한 전력반도체 소자의 필요성이 증가되어 실리콘에 비해 밴드�b이 넓은 SiC 및 GaN 등의 wide bandgap 반도체 물질의 연구가 활발히 진행되고 있다. 특히 SiC는 단결정 성장을 통한 웨이퍼화가 용이하고 소자 제작공정이 기존 실리콘공정과 유사하여 많은 연구가 진행되었으며 일부 소자에서 상용화가 진행되었다. 본고에서는 현재 활발히 진행되고 있는 탄화규소 전력반도체소자의 기술동향에 대해 소개하고자 한다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.535-538
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• 2002

Suspension effect has been studied by using superconductor of BiPbSrCaCuO ceramics containing $Ag_2()$. It has been clear that $Ag_2()$ acts as pinning center which plays an important role to the suspension effect. Magnetic repulsive force which affects a superconductor located in magnetic flux from toroidal magnet, has been investigated. It has been concluded that the suspension effect arises from the interaction between the pinning effect and the diamagnetic effect.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.4
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• pp.101-107
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• 1997

In order to detect and suppress chatter in turning process, a stability control methodology was studied through manipulation of spindle speeds regarding to chatter frequencies, The chatter frequency was identified by monitoring and signal processing of sound pressure during turing on a lathe. The stability control methodology can select stable spindle speeds without knowing a prior knowledge of machine compliances and cutting dynamics. Reliability of the developed stability control methodology was verified through turing experiments on an engine lathe. Experimental results show that a microphone is an excellent sensor for chatter detection and control .

• Journal of Korea Technology Innovation Society
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• v.6 no.1
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• pp.74-91
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• 2003

Science and Technology University(STU) will be established by twenty-two government institutes next year. STU has latent problems with geographical limitations caused by organizing the faculties and facilities of the government research institutes, which are located all over the country. This study tries to examine the Educational Administration(Opreation) Model of STU and analyse expected problems and further, proposes the introduction of cyber education system which will maximize efficiency of educational operation of the system and enhance learning. It also discusses the practical problems in the implementation of cyber education system.

• Journal of the Korea Computer Industry Society
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• v.5 no.4
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• pp.415-426
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• 2004

Distance teacher training is on the increase raplidly because of its merit. But distance teacher training's weak points with its quantitative increasement has been proposed. Especially many study said commonly that distance tearcher training has weak points for contents, teaching method, evaluation method. So in this study, we will develop the teaching method of distance teacher training to solve weak points of distance teacher training with microteaching, cognitive apprenticeship model, teacher evaluation method. We think this teaching method will improve a teacher's teaching ability.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.81-87
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• 2006

This paper deals with an empirical model for decoupling control to control the refrigeration system effectively. The conventional control schemes of the system are mainly focused on representative two control methods, superheat control and capacity control. The capacity control is basically conducted to respond partial loading conditions on the purpose of energy saving. The superheat control is mainly carried out to maintain maximum coefficient of performance (COP). In the variable speed refrigeration system, the capacity and the superheat are controlled by inverters and electronic expansion valves respectively for saving energy and improving cost performance. The capacity and superheat can not be controlled independently because of interfering loop when the compressor speed and opening angle electronic expansion valve is varied. Therefore, we suggest decoupling model to eliminate the interfering loop at first. Next, each transfer function in decoupling control model is obtained from number of experiments.

• Proceedings of the KOR-KST Conference
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• 1995.05b
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• pp.188-198
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• 1995

On the basis of deeply analysing the historical course of formation and national conditions as well as economic environment of the China various kinds and different characteristics cities in several large districts. thisthesis studies the present situation of China cities' outside transportation ways and their existing problems which are given a quantitative comparing analysis. For the purpose of promoting the economic development of these cities, this thesis proposes on perfecting direction and improving strength of the \China cities outside transportation ways.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2006.05a
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• pp.129-145
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• 2006

본 연구는 과학기술연합대학원대학교(UST)를 중심으로 한 과학기술계의 새로운 대학원모델을 평가하는 기법에 주안점을 두고 있다. UST와 일본의 SOKENDAI(The Graduate University for Advanced Studios)를 비교함으로써 새로운 대학원모델의 필요성을 말하고 있다. UST는 커리큘럼과 도제식 수업, 맞춤형 교육체계, 현장 중심형 인력양성체계들이 아직 높은 수준에 도달하지 못한 반면 교육목적과 비전이 상당 수준 만족스럽다는 결과를 얻고 있는 조사를 바탕으로 한 UST의 평가에 관해 다루고 있다. 본 연구에서는 대학평가체계의 네 가지 유형과 함께 토론회와 모든 평가에 부합되는 고급 평론을 통하여 UST에 방법론적으로 적용할 수 있는 평가방식을 제안한다. UST를 위한 새로운 평가방식은 대학원평가를 위한 특수성과 보편성으로 서로 동일하다. UST는 다 학제적이며 신생 융합기술분야에서 현장중심형인 리더십을 갖춘 인재양성을 위한 교육체계를 가지고 있으며 동시에 세계적인 특성을 가지고 있다. 두 요소는 특수성이 더욱 강조된 5:5, 6:4의 비율을 보이고 있다. 앞으로 후속적인 보완연구가 추가되면 더욱 활용성이 높아질 것으로 기대된다.

• Journal of the Korea Computer Industry Society
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• v.6 no.5
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• pp.791-800
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• 2005

In this work, we developed educational contents for ASP programming efficiency. These contents are applied to the cognitive apprentice model, one of the teaching-learning models based in constructivism. Specifically the functions of these contents are as follows: Learners can learn from the lecturing video made of multimedia, they have practical programming training according to the lecturing video showing illustration executed similar to a practical environment, and they grasp level of their understanding by themselves as doing the assigned tasks. Therefore we can anticipate for learning effects, because the contents that we developed can induce learners to learn by themselves and interest them in programming practice.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.115-118
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• 2001

High-temperature superconductor films of YBa$_2$Cu$_3$$O_{7-x}$ were fabricated by electrophoretic deposition (EPD) from alcohol-based suspension. Maximum stability is observed for the suspension containing iso-alcohol as the dispersion medium. However, for the formation of a dense and adherent coating of YBCO on a silver substrate by EPD, the best results were obtained in mix PrOH and BuOH suspension. The superconducting critical current density (J$_{c}$) was 1200 A/cm$^2$ for a films deposited in 30% iso-PrOH and 70 % iso-BuOH suspension.ion.