• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1069-1070
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• 2008

At the coupling area linking high speed line and conventional line, according to distance between trains due to speed limit of conventional line, the power load of substation supplying to this conventional line increase. At the coupling area between Kimcheon SS and Kyoungsan SS, train operation have problems caused by instantaneous voltage drop. So, this paper propose evaluation method of maximum load capacity at current normal feeding condition.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.177-182
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• 2002

This paper presents the loss analysis of Three Level Converter. Three Level DC/DC Converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. This converter reduces the voltage stress across the main switch to half of input voltage. This paper analyses the loss of each component and the various losses in the circuit assessed. The result of the analysis are verified using 2.5kW prototype.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.1
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• pp.21-23
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• 2002

Compared visual acuity that is measured in a artificial myopia with the numerical calculation. Calculation included image's height as well as blur circle that is formed to retina. The blur circle calculated in geometrical optics model, and height of retinal image calculated by refractive power and visual acuity that is measured in a artificial myopia. Define this result as "blur ratio" about blur circle and height of retinal image, and investigated blur ratio relationship about visual acuity in a artificial myopia.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1998.11a
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• pp.121-126
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• 1998

인간이 쾌적하다고 느끼게 되는 것에는 인간과 환경간의 상호작용이 포함되어 있다. 쾌적한 환경을 만든다고 할 때에는 인간과 환경을 하나의 시스템으로 두고 관련되는 여러 요소들이 계속적으로 피이드백 되는 것으로 생각하여야 한다. 쾌적감이란 여러 가지 감성 요소가 복합적으로 조합되어 하나의 이미지와 합치되는 것으로 표현되는 고도의 심리적인 체험감이다. 그러므로 쾌적환경에 대하여 인간의 특성을 중심으로 설계하려고 하면 인간이 쾌적환경을 인지하는 과정이 어떤 과정을 거치게 되는가를 알고 그 특성을 고려하여야 한다. 본 연구는 쾌적감을 구성하고 있는 요소이미지가 어떻게 구성되어 있으며, 환경요소에 대한 감각이미지와는 어떤 구조로서 이루어져 있는 지를 실험적으로 알아보고 퍼지 추론을 이용하여 표현하였다.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.324-328
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• 2001

This paper presents parallel operation and control loop design of ZVT(Zero Voltage Transition) Full Bridge DC/DC Converter. At parallel operation of ZVT Full Bridge Converter, dynamic current shared inductor devides the same current of unit converter and ZVT circuit and aids to high efficiency in the system. Base on the modeling of ZVT. Full Bridge Converter, the control loop is designed using a simple two-pole, one-zero compensation circuit. To show the validity of the design procedures, the small signal analysis of the closed loop system and open loop system is carried out and the superiority of the dynamic characteristics is verified through the experiment with a 2kW, 50kHz prototype converter.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2521-2524
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• 2002

In this paper, We propose an Image processing algorithm for a paper-cup inner defect inspection. First, we devide a cup image to four sections considering the characteristic of a cup and filter noises limit by using the flood-fill algorithm and median filter. Second, to obtain the clearer inspection result of the edge point inner cup, We apply the sharpening convolution filer to the objected inspect the edge points by using the LOG edge detector. Third, executing sub-pixel operation with the orignal image, we find the defect parts in the cup. Finally, denoting the inspected defect parts as rectangular, we recompose the images of the defected ones.

• Journal of the Korean Ceramic Society
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• v.24 no.2
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• pp.147-154
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• 1987

Silicon nitride powders were prepared by the simultaneous reduction and nitridation from powder mixtures of Kim cheon quartzite and carbon (graphite or carbon black) at1400$^{\circ}C$ for 10 hours in nitrogen atmosphere. The effects of the reaction variables on the yield of products and on the ${\alpha}$/${\beta}$ ratio were examined. The average particle size, density, and the ${\alpha}$/${\beta}$ ratio of the obtained si3N4 were 1.0$\mu\textrm{m}$, 3.10g/㎤ and 90/10, respectively. It was found that the Si3N4 powders obtained in this work were comparable to the foreign commercial products.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1168-1170
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• 2000

A half bridge time sharing type high frequency resonant inverter to give VVVF function in the inverter used as power source of induction heating at high frequency is presented in this paper, this paper also realize the output control of independence irrespective of the switching frequency using Phase-Shift. The analysis of the proposed circuit is generally described by using the normalized parameters. Also, the principle of basic operation and the its characteristics are estimated by the parameters, such as switching frequency, the variation of phase angle(${\varphi}$) of Phase-Shift. It is certain that the proposed circuit will be used and expanded in the high frequency power supplies like induction heating systems.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.402-408
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• 1989

$\beta$-Sialon powder was synthesized by the simultaneous reduction and nitridation of the mixed powder of Hadong kaolin and Kimcheon quartzite, using graphite as a reducing agent. The synthesized $\beta$-Sialon powder (Z=1) was hot-pressed at 175$0^{\circ}C$, for 90min under 30MPa in N2 atmosphere, after Yttria and YAG composition material were added as sintering agents. The effects of grain-boundary crystallization on high-temperature mechanical properties of $\beta$-Sialon ceramics were investigated. Strength degradation was observed at above 1,00$0^{\circ}C$ for the $\beta$-Sialon (Z=1)-8wt% Y2O3 composition, but it was not observed up to 1,20$0^{\circ}C$ for the $\beta$-Sialon-8wt% YAG composition which was annealed at 1,40$0^{\circ}C$ for 4 hours in N2 atmosphere. After the $\beta$-Sialon-8wt% YAG composition was annealed, the decrease of fracture toughness was observed.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.368-371
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• 2000

Two-stage power factor correction (PFC) converter with a single PWM controller is proposed. It consists of a power factor pre-regulator cascaded by an isolated DC/DC converter as in a conventional two-stage approach. However, a single PWM controller is used as in a single-stage, single-switch PFC approach. This converter gives the goof power factor correction, low line current harmonic distortions, and tight output voltage regulations. This converter also has a high efficiency by employing an soft switching method. The proposed approach has advantages such as high performance over the single-stage approach and low cost over two-stage approach. The experimental results obtained on a 300W (30V/10A) prototype PFC converter are given to verify the effectiveness of the proposed control method.