• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.297-300
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• 2001

The SMZ half-bridge converter uses the resonance between the inductance of transformer and the resonant capacitances to transfer the input power to the load. In addition to this kind of characteristic of the converter, there are some features such as the capability of soft switching operation, a lower switching loss, and a higher power density in the converter. However in the low-voltage and high-output current applications of the converter, the extremely increased output ripple voltage prevents the converter from normal operation. In order to overcome the drawback of the converter, adding the output filter inductor to the converter, the converter shows the completely different resonant characteristics. In this paper, We analyzed the resonant characteristics of the SMZ converter with the output filter inductor and investigated what the analyzed results affect the converter operation. The experiment of a I50W prototype SMZ converter with 5V output and 310V input is carried out to verity the validity of the analyzed results.

• 한국전기전자재료학회논문지
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• 제22권5호
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• pp.419-424
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• 2009

ZnO films doped with different contents of indium ($0.1{\sim}10$ at.%) were deposited on Si (111) substrate by Pulsed Laser Deposition (PLD). The structural, electrical and optical properties of the films were investigated using XRD, AFM, Hall and PL measurement. Results showed that un-doped ZnO film had (002) plane as the c-axis orientated growth, whereas indium doped ZnO films exhibited the peak of (002) and the weak (101) plane. In addition, in the indium doped ZnO films, the electron concentration is ten times higher than that of un-doped ZnO film, while the resistivity is ten times lower than that of un-doped ZnO film. The indium doped ZnO films have UV emission about 380 nm and show a red shift with increasing contents of indium. The I-V curve of the fabricated diode show the typical diode characteristics and have the turn on voltage of about 2 V.

• 한국실내디자인학회논문집
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• 제16권4호
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• pp.89-98
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• 2007

This paper studied the spatial factors activating the personal interaction based on case studies of $M\'{e}diath\'{e}ques$ in France. The spatial factors are analyzed into material factors and dematerial factors. The material factors have physical features in space and directly or indirectly activate the personal interaction. They consist of 8 elements including pocket space, balcony, atrium, stairs, elevators, windows, conference rooms and furnitures. The dematerial factors consist of 6 elements including polycentrism, continuance, mixture, interpenetration, dematerialization, transparency. They are compounded of material factors and explain them conceptually. But dematerial factors are abstract concepts. To provide reliability I confirm the relationship with dematerial factors by using a connections, topology, a phased depth of the Depthmap as the framework of the visual recognition of the space syntax covering the characteristic of dematerial factors. The result of the quantitative analysis human-behavior in $V\'{e}nissieux$ $M\'{e}diath\'{e}que$ and the result of applying the spatial factors of $M\'{e}diath\'{e}ques$ as the community center to the $V\'{e}nissieux$ $M\'{e}diath\'{e}que$ proved that the spatial factors are significant factors of the $M\'{e}diath\'{e}ques$ as the community center.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권5호
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• pp.379-384
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• 1999

Langmuir-Blodgett(LB) films which have high ordered orientation and ordering structure are fabricated by LB method which deposit the ultra-thin films of organic materials at a molecular level. The electrical characteristics of stearic acid LB ultra-thin films for the horizontal direction were investigated to develop the gas sensor using LB ultra-thin films. The optimal deposition condition to deposit the LB ultra-thin films was obtained from $\pi-A$ isotherms and the deposition status of stearic acid LB ultra-thin films was verified by the measurement of deposition ratio, UV-absorbance, and electrical properties for LB ultra-thin films. The conductivity of stearic acid LB ultra-thin films for horizontal direction was about $10_{-8}[S/cm]$. The activation energy for LB ultra-thin films with respect to variation of temperature was about 1.0[eV], which was correspond to semiconductor material. The response characteristics for organic gas were confirmed by measuring the response time, recovery time, and reproducibility of the LB ultra-thin to each organic gas. Also, the penetration and adsorption behavior of gas molecule were confirmed through the organic gas response characteristics of LB ultra-thin films with respect to temperature.

• 한국전기전자재료학회논문지
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• 제14권7호
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• pp.572-577
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• 2001

The electrical properties of Pr$_{6}$ O$_{11}$ -based ZnO varistors consisting of ZnO-Pr$_{6}$ O$_{11}$ -CoO-Cr$_2$O$_3$-Er$_2$O$_3$ ceramics were investigated with sintering temperature in the range of 1325~f1345$^{\circ}C$. As sintering temperature is raised., the nonlinear exponent was increased up to 1335$^{\circ}C$, reaching a maximum 70.53, whereas raising sintering temperature further caused it to decrease, reaching a minimum 50.18 and the leakage current was in the range of 1.92~4.12 $\mu$A. The best electrical properties was obtained from the varistors sintered at 1335$^{\circ}C$, exhibiting a maximum (70.53) in the nonlinear exponent and a minimum (1.92 $\mu$A) in the leakage current, and a minimum (0.035) in the dissipation factor. On the other hand, the donor concentration was in the range of (0.90~1.14)x10$^{18}$ cm$^{-3}$ , the density of interface states was in the range of (2.69~3.60)x10$^{12}$ cm$^{-2}$ , and the barrier height was in the range of 0.77~1.21 eV with sintering temperature. With raising sintering temperature, the variation of C-V characteristic parameters exhibited a mountain type, reaching maximum at 134$0^{\circ}C$. Conclusively, it was found that the V-I, C-V, and dielectric characteristics of Pr$_{6}$ O$_{11}$ -based ZnO varistors are affected greatly by sintering temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1352-1354
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• 1998

$LiNbO_3$ transistor showed relatively stable characteristic, low interface trap density, and large remanent polarization. This paper reports ferroelectric $LiNbO_3$ thin films grown directly on p-type Si(100) substrates by 13.56 MHz rf magnetron sputtering system for FRAM applications. To take advantage of low temperature requirement for growing films, we deposited $LiNbO_3$ films lower than $300 ^{\circ}C$. RTA(Rapid Thermal Anneal) treatment was performed for as-deposited films in an oxygen atmosphere at $600^{\circ}C$ for 60 sec. We learned from X-ray diffraction that the RTA annealed films were changed from amorphous to poly-crystalline $LiNbO_3$ which exhibited (012), (015), and (022) orientations. The I-V characteristics of $LiNbO_3$ films before and after anneal treatment showed that RTA improved the leakage current of films. The leakage current density of films decreased from $10^{-5}$ to $10^{-7} A/cm^2$ at room temperature measurement. Breakdown electric field of the films exhibited higher than 500 kV/cm. The C-V curves showed the clockwise hysteresis represents ferroelectric switching characteristics. From C-V curves, we calculated dielectric constant of thin film $LiNbO_3$ as 27.5 which is close to that of bulk value.

• 에너지공학
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• 제2권2호
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• pp.200-207
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• 1993

본 논문은 5.9kW급 인산형 연료전지 발전시스템의 운전에 필요한 메탄올 연료개질기의 설계와 이의 운전 특성에 관한 것이다. 연료개질장치는 메탄올을 연소용 및 개질용연료로 사용하며, 개 질 반응 촉매는 CuO-ZnO계를 사용하고, 개질 반응기는 단일 환형 반응기 형태로 설계하였다. 개질 장치의 일산화탄소 생성 특성은 전체적으로 이론적인 평형값에는 도달하지 못하였으나, 반응온도가 증가할수록 농도가 증가하였으며, 개질 연료의 물/메탄올 몰비가 증가하면 감소하였다. 정격운전에서 촉매반응기의 축방향 온도분포는 이론적인 값과 잘 일치하였으며, 운전 개시후 50분 훈에 정상 운전이 가능하였다. 개질 시스템의 효율은 정격운전에서는 72.3%, 1/4 부하에서는 77%로 부하가 증가할수록 효율은 감소하였다. 개질기를 연료전지 본체와 연계운전시 개질기에 개질용 메탄올 및 연소용 메탄올의 공급유량이 각각 88.1 mol/h, 50.0mol/h 인 경우 정격전압인 37.6V의 전안에서 안정적인 5.5 kWh의 전력을 생산 할 수 있었다.

• Progress in Superconductivity
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• 제10권1호
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• pp.60-67
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• 2008

We present domestic efforts for superconducting fault current limiter (SFCL) application in the Korea Electric Power Corporation (KEPCO) grid and pending points at issue. KEPCO's decision to upgrade the 154 kV/22.9 kV main transformer from 60 MVA to 100 MVA cast a problem of high fault current in the 22.9 kV distribution lines. The grid planners supported adopting an SFCL to control the fault current. This environment friendly to SFCL application must be highly dependent upon the successful development of SFCL having specifications that domestic utility required. The required conditions are (1) small size of not greater than twice of 22.9 kV gas insulated switch-gear (GIS), (2) sustainability of current limitation without the line breaking by circuit breakers (CB) for maximum 1.5 seconds. Also, optionally, recommended is (3) the reclosing capability. Conventional resistive SFCLs do not meet (1) $\sim$ (3) all together. A hybrid SFCL is an excellent solution to meet the conditions. The hybrid SFCL consists of HTS SFCL components for fault detection and line commutation, a fast switch (FS) to break the primary path, and a limiter. This characteristic structure not only enables excellent current limiting performances and the reclosing capability, but also allows drastic reduction of HTS volume and small size of the cryostat, resulting in economic feasibility and compactness of the equipment. External current limiter also enables long term limitation since it is far less sensitive to heat generation than HTS. Semi-active operation is another advantage of the hybrid structure. We will discuss more pending points at issues such as maintenance-free long term operation, small size to accommodate the in-house substation, passive and active control, back-up plans, diagnosis, and so on.

• Journal of Electrochemical Science and Technology
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• 제13권4호
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• pp.497-503
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• 2022

Spinel ferrites (Ni_xFe_3-xO₄; x = 0.25, 0.5, 0.75 and 1.0) have been prepared at 550℃ by egg white auto-combustion route using egg white at 550℃ and characterized by physicochemical (TGA, IR, XRD, and SEM) and electrochemical (CV and Tafel polarization) techniques. The presence of characteristic vibration peaks in FT-IR and reflection planes in XRD spectra confirmed the formation of spinel ferrites. The prepared oxides were transformed into oxide film on glassy carbon electrodes by coating oxide powder ink using the nafion solution and investigated their electrocatalytic performance for OER in an alkaline solution. The cyclic voltammograms of the oxide electrode did not show any redox peaks in oxygen overpotential regions. The iR-free Tafel polarization curves exhibited two Tafel slopes (b₁ = 59-90 mV decade^-1 and b₂ = 92-124 mV decade^-1) in lower and higher over potential regions, respectively. Ni-substitution in oxide matrix significantly improved the electrocatalytic activity for oxygen evolution reaction. Based on the current density for OER, the 0.75 mol Ni-substituted oxide electrode was found to be the most active electrode among the prepared oxides and showed the highest value of apparent current density (~9 mA cm^-2 at 0.85 V) and lowest Tafel slope (59 mV decade^-1). The OER on oxide electrodes occurred via the formation of chemisorbed intermediate on the active sites of the oxide electrode and follow the second-order mechanism.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.494-497
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• 2004

본 연구는 방사선 영상센서 적용을 위한 $HgI_2$ 필름의 특성 평가에 관한 것으로서 X-선 조사조건별 인가전압에 따른 검출신호 특성을 조사하였다. 기존의 $HgI_2$ 검출기의 경우 신호량이 크다는 장점이 있으나 노이즈의 양이 크다. 이에 대한 해결책으로 보호층을 삽입하나 이 경우 X-선 조사에 따른 시간 응답 특성이 있어서 전하트랩현상(tailing effect)에 의한 영향이 크게 존재하였다. 따라서 본 논문에서는 이러한 문제점을 해결하고자 보호층으로써 a-Se 을 삽입하여 기존의 $HgI_2$ 검출기에서 사용되어지는 parlyene이 삽입된 검출기와 전기적 특성을 측정, 비교해보고자 한다. 제작방식으로는 대면적 제작이 용이한 스크린 프린팅 방식을 이용하여 두께 $140\;{\mu}m$와 $3\;cm\;{\times}\;2\;cm$ 면적으로 제조하였다. 측정결과, a-Se을 보호층으로 사용한 $HgI_2$ 필름이 민감도는 거의 비슷하나 누설전류가 안정화 되는데 걸리는 감소시간(decay time)이 parlyene을 사용한 구조에 비해 훨씬 낮았다. 또한 X선에 대한 민감도는 기존의 a-Se에 비해 월등히 높아 적은 방사선 조사량(radiation dose)에서도 신호검출이 가능하여 저선량이 요구되는 방사선 투시촬영(digital fluoroscopy) 적용에 유용할 것으로 기대된다.