• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04a
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• pp.201-203
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• 2000

To improve characteristics of optical devices that used be WDM system optimally, we investigated characteristics of two types structures that consisted of non-uniform thickness Quantum well. They have high characteristic temperature and 3dB bandwidth of spontaneous emission are 57nm, 50nm respectively, which are 1.4times, 1.3times wider than conventional structure.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.295-300
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• 1990

This paper describes a new method to increase the fundamental output of PWM inverter by adding all triplen-harmonics to sinusoidal reference wave. As a result, the amplitude of the fundamental component is increased upto 21 percent compared with the conventional SPWM method, and hence the conversion efficiency of dc link is higher. Also as the commutation number of the inverter is decreased to two-thirds, the heating of the switch devices is reduced. In addition random carrier modulation is adopted to lower the acoustic noise at given frequency modulation index.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.163-166
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• 2005

Colors are in the inseparable relation ia the all parts of human life. The color influences not only our psychological and physiological aspects, but also our way of behavior. The purpose of this study was to investigate the color preference and the personal color of 100 university students. As results of researching current university students color preference when we compare it with pre-studied results, it shows some differences. In pre-studied, the blue and black marked high degree, but for recent students, it has appeared that warm color is highly preferred. Also warm color has shown as the personal color. There were significant differences in the relation between the blood type and color preference. It appears that the blood type A and B were preferred to cold color while the blood type of B and AB were preferred to warm color.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2065_2066
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• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.328-333
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• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.395-400
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• 2011

Scanning Probe Lithography is a method to localized oxidation on single crystal silicon wafer surface. This study demonstrates nanometer scale non contact lithography process on (100) silicon (p-type) wafer surface using AFM(Atomic force microscope) apparatuses and pulse controlling methods. AFM-based experimental apparatuses are connected the DC pulse generator that supplies ultra short pulses between conductive tip and single crystal silicon wafer surface maintaining constant humidity during processes. Then ultra short pulse durations are controlled according to various experimental conditions. Non contact lithography of using ultra short pulse induces electrochemical reaction between micro-scale tip and silicon wafer surface. Various growths of oxides can be created by ultra short pulse non contact lithography modification according to various pulse durations and applied constant humidity environment.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.10-13
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• 2007

System requirements (SRs), which describe the technical attributes to be satisfied by a desired system, serve as a fundamental guideline for system development. Standard methods and processes to define SRs are suggested in systems engineering literature. But in practice, we encounter many difficulties in defining and managing SRs since there are few experiences on development of complex systems in accordance with systems engineering processes of development. In this paper, to expanding SRs management experiences in a working-level, we reviewed problems occured in SRs defining process in 'Urban MAGLEV Train Project', and analyzed our activities to adjust and solve the problems.

• Proceedings of the KIEE Conference
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• 2007.11c
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• pp.128-130
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• 2007

외과수술용 핸드피스는 현재 국내 외 병원에서 사용되고 있는 수술 장비 중 필수 보유 장비이다. 선진 수술 기법인 인공관절 대체 수술 시 뼈(Bone)절단, 다듬질 구멍 등, 초 섬세 가공을 목적으로 하는 기기이다. 기존의 공압식(Air Type)은 수술 시 많은 양의 질소(N2 Gas)가 소모됨으로써 질소탱크 보관에 많은 공간이 필요하고 잦은 교체를 필요로 한다. 또한 기계소음과 공압식 호스의 이동으로 시술자와 환자사이에 불편함이 발생하고 감염의 위험성이 있으므로 최근에는 충전식을 선호하고 있다. 이러한 이유로 기존의 공압식을 대체할 배터리형 외과수술용 핸드피스를 연구하게 되었다.

• Proceedings of the KIEE Conference
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• 2007.11c
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• pp.70-73
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• 2007

Many methods have been developed to overcome the PAPR(peak-to-average power ratio) problem. Selective mapping(SLM) partial transmit sequence(PTS), subblock phase weighting(SPW) and gradient descent(GD) are used widely to reduce the PAPR. In this paper, we present a effective PAPR reduction method, decrease the calculation through Radix-2 DIF IFFT procedure and GD method. and can transmit selecting data sequence that satisfy threshold value as one part of proposed method, in case satisfy fixed threshold value, or transmit selecting data sequence with the lower papr operating remained part for performance improvement.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.18-29
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• 2011

Light emitting diode(LED) technology has been increasingly developed and larger color gamut by LED illuminations can be reproduced; therefore more efficient LED lighting design can be accomplished under a consideration of color emotion. Fifty-two LED colors which are uniformly distributed on the uniform chromaticity space are evaluated in terms of fatigueness and preference and their relation to three color-appearance attributes(lightness, chroma and hue) are investigated. As a result, 23 human observers likely to prefer and feel comfortable, when lightness of a given LED color stimulus increases as well as its chroma decreases. The highest fatigueness score is observed in red color series and the most preferred LED color is found in green color series. In addition, fatigueness and preference show a strong negative linear relation and their Pearson correlation is higher than -0.8.