• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.2
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• pp.99-108
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• 2018

This paper presents a design study of a solid state power oscillator to replace the conventional magnetron. The operational conditions of a single-stage 300 W LDMOS power amplifier were fully characterized. The power module consisted of two amplifiers connected in parallel. A delay-line feedback loop was designed for self-oscillation. A phase shifter was inserted in the delay-line feedback loop for adjusting the round-trip phase. Experiments performed using the power oscillator showed an output power of 800 W and a DC-RF conversion efficiency of 58 % at 2.327 GHz. The measured results were in good agreement with those predicted by numerical simulations.

• Annual Conference of KIPS
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• 2002.11a
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• pp.273-276
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• 2002

사이버 공간은 개방성, 익명성, 탈중심성의 특성을 갖는다. 이러한 특성으로 인하여 긍정적인 측면과 부정적 측면이 동시에 나타나고 있다. 청소년들의 사이버 공간에서의 활동은 제공되는 정보를 단순하게 탐색하는 수동적 역할에 그치지 않는다. 청소년들은 자신의 의견을 제시하거나 정보를 제공하는 역할도 동시에 하고 있다. 이 과정에서 스스로 유해한 정보를 생산하거나 게시판에서 타인에게 해를 끼치는 행위가 발생하고 있다. 본 논문은 청소년들의 적극적인 정보제공 활동 시점에 발생하고 있는 정보화 역기능 현상을 해결하는 방안으로 인터넷 게시판에서 유해단어 필터링에 의한 정보윤리 교육 기법을 제안한다. 인터넷 게시판에서 유해단어 필터링 기법은 초 중등학교 홈페이지 게시판에서 나타나는 부적절한 행동과 상대방에 대한 성적 모욕, 욕설의 사용, 상대방 비하 등에 관련된 유해단어를 추출하여 유해단어 사전을 구축하고 필터링하는 방법이다. 필터링 된 결과에 따라 글 쓰는 시점에서 정보윤리 컨텐츠를 제공한다. 이 기법을 학교 홈페이지 게시판에 적용한 결과 그렇지 않은 경우에 비하여 학생들의 글쓰기 자세와 글 내용이 바른 것으로 나타났다.

• Journal of Korea Foundry Society
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• v.29 no.3
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• pp.144-149
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• 2009

In this study, we investigated optimum condition of cooling plate method to obtain semi-solid AM100A Mg alloy with fine and globular morphology. AM100A Mg alloy were hot extruded at $380^{\circ}C$ extrusion temperature under extrusion ratio of 25 : 1 and ram speed of 2.4 mm/sec. Vickers hardness test, optical microscopy, scanning electron microscopy, and image analyzer were performed to identify the optimum conditions of cooling plate method. Optimum conditions of cooling plate method to fabricate semi-solid AM100A Mg alloy with fine and globular microstructures were achieved at a pouring temperature of $602^{\circ}C$ and the angle of cooling plate of 60 degree.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.1
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• pp.103-108
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• 2002

The metal-oxide-semiconductor field-effect transistor(MOSFET) has undergone many changes in the last decade In response to the constant demand for increased speed, decreased power, and increased packing density. The state -of-the-art simulation programs are developed by engineers and scientists. This paper has compared commercial programs of Micro-tec and ISE-TCAD in device simulation. This paper investigates LDD MOSFET using two simulators. Bias condition is applied to the devices with gate lengths(Lg) 180㎚. We have presented MOSFET's characteristics such as I-V characteristic and electric field, and compared Micro-tec with ISE TCAD.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.635-637
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• 2017

The perception that programming is difficult is spread among learners. Indeed, in college education, the dropout rate of programming classes is higher than in other courses. Therefore, it is necessary to analyze the cognitive aspects of why learners think programming is difficult and then to propose appropriate teaching strategies for them. Recently, studies are under way to understand how the brain learns and is most effective in what situations, based on the development of brain science. This is the study of brain-compatible learning. The purpose of this study is to propose an instructional design on programming lessons based on brain-compatible learning principles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.191-194
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• 1999

Recently, with the rapid development and demand for compactness of portable communications, the requirement for compact and low-cost filter is increasing. One of the methods for reducing size and cost is to use high dielectric constant and low loss dielectric material in filter. The other is new monoblock dielectric band-pass filter (BPF) which has holes in a single dielectric body without additional coupling elements. This structure effectively reduces the size and cost of the filters. For previous conventional coaxial type dielectric BPF, dielectric substrates were used for coupling between adjacent resonators and additional input and output ports were needed. Coupling between adjacent resonators of monoblock BPF can be otained via electrode pairs. Capacitances of electrode pair structure for coupling are intensively investigated by 3-D FEM. The BPF for PCS has been designed to have a 30 MHz pass-bandwidth with center frequency of 1855 MHz and an attenuation pole at below the passband using a commercial 3-D structure simulator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.70-73
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• 2004

Two different $SnO_2$ nanomaterials(nanowires and nanobelts) were synthesized from the thermal evaporation of ball-milled $SnO_2$ powders at $1350^{\circ}C$ without the presence of any catalysts, and their structural properties are then investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. This investigation reveals that the $SnO_2$ nanowires are single-crystalline and their growth direction is parallel to the [100] direction, and that the $SnO_2$ nanobelts are single crystalline and their shape is zigzag. In addition, photoresponse of a single $SnO_2$ nanowire was performed with light above-gap energy, and different characteristics of photoresponse were obtained for the nanowire at ambient atmosphere and in vacuum.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.401-404
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• 2004

광학 현미경을 이용한 포토리소그래피 방법을 통해 단일 나노선에 선택적 전극을 형성하였다. $SiO_2$ 기판에 나노선을 도포하여 사용하였고 수 마이크로미터 길이의 단일 나노선에 2단자 전극을 형성하는데 충분한 resolution을 얻을 수 있었다. 리소그래피 노광 광원으로는 현미경에 내장된 할로겐 램프를 사용하였고, 동일 광원으로 관측하기 위해 광학 필터를 사용하였다. 실험 상황에 따라 금속, OHP 필름, 종이 등의 재질로 다양한 마스크를 제작하여 사용하였다. 대물렌즈의 교환을 통해 다양한 projection 배율을 구현하였다.

• Journal of Korean Society of Rural Planning
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• v.26 no.3
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• pp.79-89
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• 2020

Since the Republic of Korea had been registered as the 24th member of OECD DAC in 2009, recent trend of Korea's ODA has showed drastic increase including agriculture and rural development sector. Particularly, various rural development projects have been implemented adopting development experience and methodology of Saemaul Undong (SMU, New Village Movement). This study implemented statistical analysis between villagers' participation and achievement of rural community development project, based on practical data out of 'Saemaul Undong Project in Myanmar', to suggest meaningful implication in terms of participatory rural development. It emphasized the importance and necessity of villagers' participation in rural development through regression analysis that proved positive correlation between villagers' participation and rural development project. It proves that income-generation part has significantly greater influence than capacity-building and living environment part in terms of rural community development project: Based on the analysis, comparing impact of each independent variable, income generation has 1.88 and 1.68 times greater impact than capacity-building and living environment respectively. The result, on the other side, rather raise the importance of careful consideration for project design and implementation to harmonize those three parts altogether especially rural development for developing countries: capacity-building and living environment parts suggests essential foundation to make income generation successful that enables to secure project achievement and sustainability.

• Journal of Chest Surgery
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• v.40 no.6 s.275
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• pp.459-462
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• 2007

Pericardial cysts are uncommon benign congenital mediastinal lesions and they are most often found in either cardiophrenic angle. We present here one case of atypically located pericardial cyst that was located in the sub-pulmonary region. The clinicians should take into consideration this entity in the differential diagnosis of cystic lesion of the mediastinum. The diagnostic difficulties that are encountered and the utility of video-assisted thoracoscopy are described.