• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.724-727
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• 2008

Studies on binary adder have been variously developed. According to those studies of critical worst delay and mean delay time of asynchronous binary adders, carry select adders (CSA) based on hybrid structure showed 17% better performance than ripple carry adders (RCA) in 32 bit asynchronous processors, and 23% better than in 64 bit microprocessor implemented. In the complicated signal processing systems such as RSA, it is essential to optimize the performance of binary adders which play fundamental roles. The researches which have been studied so far were subject mostly to addition algorithms or adder structures. In this study, we analyzed and designed adders in an asp;ect of synthesis method. We divided the ways of implementing adders into groups, each of which was synthesized with different synthesis options. Also, we analyzed the variously implemented adders to evaluate the performance and area so that we can propose a different approach of designing optimal binary adders.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.117-123
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• 1999

This work was focused on the synthesis and their catalytic performance on microporous materials having various pore types and dimensions in structures, such as the SAPO-34 and the SAPO-44 with CHA type, the SAPO-17 with ERI type of three dimensional structures, and the ZSM-23 with MTT type of one dimensional structure. Synthesized materials exhibited various acidities and the selectivities to olefin in methanol conversion. As a result, the order of their acid strength was as follows; SAPO-44>SAPO-34>SAPO-17>ZSM-5. On the other hand, the CHA type materials, such as SAPO-34 and SAPO-44, had high selectivity to light olefins(ethylene or propylene), and ZSM-23 with MTT typ of one dimensional structure showed high selectivity to paraffins over $\textrm{C}_{5}$~. This result is a proof that the structure in material had strong influence on catalytic performance. In addition, a surprising result is that the catalytic selectivity to ethylene enhanced on Ni-corporated materials compared with the non-corporated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.5
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• pp.906-912
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• 2017

In this paper, we studied a design method for a broadband 3-element quasi-Yagi antenna (QYA) for indoor digital television (DTV) reception. The proposed QYA employs a novel balun between a microstrip (MS) line and a coplanar strip (CPS) line feeding the driver dipole. The proposed balun is constructed by connecting the end of MS line to CPS line through a shorting pin, and the CPS and ground reflector are connected through a circular ring-type conductor. An antenna, as an design example for the proposed antenna, is designed for the operation in the frequency band of 470-806 MHz for terrestrial DTV. The antenna fabricated on an FR4 substrate with a size of $270mm{\times}150mm$ showed a good performance such as a frequency band of 470-820 MHz for a voltage standing wave ratio < 2, a gain > 4.0 dBi, and a front-to-back ratio > 8.4 dB over the DTV frequency band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6B
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• pp.423-432
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• 2012

We design a control circuit that can switch input power between a rechargeable battery and a sensor communication device (mote) depending on the operating state of a solar cell as well as the active and sleep mode of a sensor MAC protocol. A mote that simply combines a solarcell and a rechargeable battery may die if there is not sunlight long. A battery is recharged if sunlight is sufficient and a device is in a sleep mode, and it supplies power if sunlight is low and the mote is in an active mode. A mote can switch its input power between solar cell and battery depending on the output level of a solar cell. During this switching, a mote may lose its state information due to the reset of a microprocessor by the transient power-off. A capacitor is used to cope with this phenomenon and also supplies power to a mote during a sleep mode. Experimental results show that the solar cell based mote operates in a very stable manner against the lack of sunlight long.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.923-930
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• 2009

In this paper, we introduce a satellite conceptual design software which can be used for outlining a new satellite as well as for educational purpose. This software consists of three commercial tools: MATLAB, STK(Satellite Tool Kit), and Excel. The management of the design software is done by MATLAB which provides basic calculations, GUI(Graphical User Interface), Excel data base management, and STK control. STK, an orbital simulation software developed by AGI, takes a part of obtaining accurate orbital information of a satellite. Excel, a product of Microsoft, is used for the data base of previous satellites and for the saving place of temporary and final results of the software. The conceptual design of a satellite is to roughly estimate power system and mass. In the power system design, the sizes of solar array and battery are determined. Based on the database of existing satellites, we can estimate the subsystems's mass fraction of a target satellite. Design examples for Kompsat 1 and 2 are suggested for verification of the developed software.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.387-387
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• 2011

탄소 나노튜브(Carbon nanotubes, CNTs)는 육각형 모양의 구조로서 오직 탄소만으로 이루어진 소재이다. CNT는 열전도율이 다이아몬드보다 약 2배 우수하고, 전기 전도는 구리에 비해 1,000배 높으며, 강도는 강철보다 100배나 뛰어나다. CNT의 이러한 특성을 이용한 트랜지스터, 태양전지, 가스 검출을 위한 고감도 센서, 나노 섬유, 고분자-탄소나노튜브 고기능 복합체 등 많은 분야에서 연구가 활발히 진행되고 있다. 또한 수직으로 성장된 탄소 나노튜브는 일반적인 재료에서는 보기 드물게 힘들게 직경이 나노 크기인 반면 길이는 수 mm까지 합성 되기 때문에 앞서 언급한 분야로의 활용이 더욱 유리하며, 그 중에서도 나노 섬유, 나노 복합체로서의 활용에 극히 유용하다. 이러한 이유로 수직 배열된 CNT 합성에 많은 연구가 집중 되고 있다. 여러 합성 방법 중 성장 변수를 비교적 용이하게 조절 가능한 열 화학 기상 증착법(Thermal chemical vapor deposition, TCVD)을 이용하여 수직 배열된 수 mm의 CNT를 합성한 연구 결과들이 보고된 바 있다. 그러나 앞선 연구결과들은 CNT의 성장속도가 느릴 뿐만 아니라 합성 시간이 길어질수록 성장 속도가 감소하는 경향을 보였다. 반면, 마이크로웨이브 플라즈마 화학 기상 증착법(Microwave plasma CVD, MPCVD)은 기존의 다른 TCVD에 비해 낮은 온도에서 CNT를 합성할 수 있는 장점을 가지며, 고출력(~600 W 이상)의 플라즈마를 사용하기 때문에 성장률이 높고 고밀도의 CNT 합성이 가능하다. 본 연구에서는 철을 촉매금속으로 사용하고 MPCVD을 이용하여 얇은 다중벽 CNT를 합성하였다. 철은 직류 마그네트론 스퍼터(D.C magnetron sputter)를 사용하여 증착하였다. 합성시 가스는 탄소 공급원인 메탄($CH_4$)과 함께 플라즈마 공급원인 수소($H_2$)를 사용하였다. 또한 산소($O_2$)의 주입 여부에 따른 CNT의 성장 속도와 성장 길이를 비교하였다. 산소를 주입하였을 때, CNT의 성장 속도와 길이 모두 크게 향상됨을 확인 할 수 있었다. 이는 촉매금속 표면의 비정질 탄소의 흡착으로 인해 활성화된 촉매금속의 반응시간을 증가시키기 때문이다. 성장된 CNT는 주사전자 현미경(Scanning Electron Microscopy, SEM)과 라만 분광법(Raman spectroscopy)을 통해 표면형상과 결정성을 분석하였다.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1142-1147
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• 2008

Nano-structured porous carbon fiber(PCF) for the catalyst supports of the direct methanol fuel cell (DMFC) were prepared from the mesophase pitch by using the nano-MgO powders. Specific surface area of the PCFs was $8{\sim}58m^2/g$ and surface pore structures had almost meso pore diameter of 10~20 nm which were depending on the amount of MgO spheres. Aqueous reduction method was used to load 60 wt% PtRu on the prepared PCF supports. The electro-oxidation activity and single cell performance of the 60 wt% Pt-Ru catalysts were measured by cyclic voltammetry and unit cell test. The performances of these catalysts increased by 5~10% compared with one of commercial catalyst.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.694-700
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• 1999

In this paper, we studied the design of power divider using the slow-wave effect of Photonic Bandgap structure, which is etched on the ground plane. The proposed PBG structure can provides the changing of the characteristic impedance of the transmission line and the group delay velocity characteristic. Therefore we can make wider width than the width of conventional transmission line and decrease the length of transmission line. We presented the application for power divider using the characteristic impedance and electrical length extracted from scattering parameter. As adding proposed defect units, the effect of defect is studied. The experimental results show good agreements with the simulated results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.14-19
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• 2016

In this paper, a wideband slot antenna with corrugated structure antenna is proposed. The proposed antenna consists of a ground plane with corrugated slot and microstrip feed-line. Even with a limited dimension of $70{\times}70{\times}1.6mm$, the proposed antenna has wide bandwidth due to the longer current path formed by the corrugated slot structure. Measured bandwidth(10 dB return loss) and fractional bandwidth of the proposed antenna are 2,180 MHz(2.5~4.68 GHz) and 60.7 % at the center frequency of 3.59 GHz. The proposed antenna has an omni-directional radiation pattern and measured gains and average efficiency were 3.48~5.83 and dBi, 81.55 %, respectively.

• Clean Technology
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• v.18 no.3
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• pp.295-300
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• 2012

Synthesis of well-defined particle with tunable size, shape, and functionalities is strongly emphasized for various applications such as chemistry, biology, material science, chemical engineering, medicine, and biotechnology. This study presents micromolding method for the fabrication of anisotropic particles with elegant control of curvature of covex roof. For the demostration of rapid fabrication of the particles, we have applied polydimethylsiloxane (PDMS) micromold as structure guiding template and wetting fluid to control curvature of roof of the particles. Based on this approach, we can control the radius of curvature from $20{\mu}m$ to $70{\mu}m$ with different aspect ratio of mold. In addition, wetting fluids with different wetting properties can also modulate the height and radius of curvature of the particles. We envision that this methodology is promising tool for precise control of particle shape in 3-dimensional space and new synthetic route for anisotropic particles with cost effective, simple, easy, and fast procedure.