• The Korean Journal of Ceramics
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• 제5권3호
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• pp.217-223
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• 1999

Proten-conductive $SrZr_{0.95} Y_{0.05} O_{2.975}$ powder was prepared by citrate gel method its characteristics and sinterability were investigated. Amorphous gel could be obtained from a citric acid solution that $SrCO_3$ and metal nitrates were dissolved. The initial decomposition of the gel proceeded up to $250^{\circ}C$, followed by combustion of its decomposition products in the temperature range from $250^{\circ}C$ to $500^{\circ}C$. A well-crystallized perovskite phase with a stoichiometric composition after calcination at $1000^{\circ}C$. Sintering green compacts of this powder for 6 h showed a considerable densification to start at $1200^{\circ}C$ and resulted in 86.8% and 96.5% relative densities at $1400^{\circ}C$ and $1600^{\circ}C$, respectively. Whereas, the powder compacts prepared by solid state reaction had much lower relative densities, 73% at $1400^{\circ}C$ and 92% at $1600^{\circ}C$.

• 전기전자학회논문지
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• 제22권2호
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• pp.344-349
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• 2018

AlGaN/GaN HEMT를 제작하여 상온에서 $-178^{\circ}C$의 저온에 이르기까지 트랜지스터의 전기적인 특성 변화를 연구하였다. 상온에서 264 mA/mm를 나타내던 게이트 길이 $2{\mu}m$인 HEMT의 드레인 전류는 온도의 감소에 따라 변화하여 $-108^{\circ}C$의 온도에서 388 mA/mm로 47%의 증가를 나타냈으며 최대 트랜스컨덕턴스는 121 mS/mm로 부터 183 mS/mm로 증가하였다. 또한 $-178^{\circ}C$의 온도에 이르기까지 -0.39 V의 문턱전압 변화를 보였다. 이러한 변화는 주로 상온에서부터 $-108^{\circ}C$의 온도에서 나타나고 있으며 온도감소에 따른 $720{\Omega}/sq.$ 로부터 $300{\Omega}/sq.$로 감소하는 면저항의 변화와 함께하고 있다.

• 한국전기전자재료학회논문지
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• 제22권4호
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• pp.303-306
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• 2009

This paper describes the characteristics of polycrystalline 3C-SiC doubly clamped beam micro resonators. The polycrystalline 3C-SiC doubly clamped beam resonators with $60{\sim}100{\mu}m$ lengths, $10{\mu}m$ width, and $0.4{\mu}m$ thickness were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonant frequency was measured by a laser vibrometer in vacuum at room temperature. For the $60{\sim}100{\mu}m$ long cantilevers, the fundamental frequency appeared at $373.4{\sim}908.1\;kHz$. The resonant frequencies of doubly clamped beam with lengths were higher than simulated results because of tensile stress. Therefore, polycrystalline 3C-SiC doubly clamped beam micro resonators are suitable for RF MEMS devices and bio/chemical sensor applications.

• 한국기계가공학회지
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• 제11권4호
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• pp.1-6
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• 2012

This paper addresses the issue of Renewable Energy for Electricity Storage device is one of the NAS (Sodium-Sulfur) battery will be about the module. For safety reasons, not the actual battery cells using a dummy cell in the module's operating temperature setting to examine the characteristics of the insulation vacuum of the wall temperature and external temperature changes measured over time. Upper and lower boundaries of the wall vacuum insulation characteristics cotton C intervals over time, average $5^{\circ}C$, but the temperature is rising, 4C section with little temperature change did not occur. On the other hand, about $3^{\circ}C$ in section 4D, and it was confirmed that the temperature rises. Wall vacuum insulation characteristics over time to look at the experiments and measurements are described.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.131-131
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• 2009

This paper describes the fabrication and characteristics of polycrystalline (poly) 3C-SiC microresonators with $3{\times}10^{17}{\sim}1{\times}10^{19}cm^{-3}$ in-situ N-doping concentrations. In this work, the crystallinity, carrier concentration and surface morphology of the grown thin films were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The 1.2 ${\mu}m$ thick cantilvers and the 0.4 ${\mu}m$ thick doubly-clamped beam microresonators with various lengths were implemented using in-situ doping poly 3C-SiC thin films. The characteristics of the poly 3C-SiC microresonators were evaluated using quartz and a laser vibrometer under vacuum at room temperature. The resonant frequencies of the SiC microresonators decreased with doping concentrations owing to the reduction of the Young's modulus of the poly 3C-SiC thin films. It was confirmed that the resonant frequencies of the poly 3C-SiC microresonators are controllable by adjusting the doping concentrations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.1973-1978
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• 2008

The NOx emission characteristics of DME in counterflow nonpremixed flames were investigated numerically, and brief experiments were carried out to compare the flame shapes and NOx emissions with those of $C_3H_8$ and $C_2H_6$. The DME flames were calculated using Kaiser's mechanism, while the $C_2H_6$ flames were calculated using the $C_3$ mechanism. These mechanisms were combined with the modified Miller-Bowman mechanism for the analysis of NOx. Experimental results show that DME flame has the characteristics of partial premixed flame and the flame length becomes very shorter compared with general hydrocarbon fuels and then, the NOx emission of DME is low as much as 60% of $C_3H_8$. In the calculated results of counterflow nonpremixed flames, the EINO of DME nonpremixed flame is low as much as 50% of the $C_2H_6$ nonpremixed flame. The cause of $EI_{NO}$ reduction is attributed mainly to the characteristics of partial premixed flame due to the existence of O atom in DME and partly to the O-C bond in DME, instead of C-C bond in hydrocarbon fuels.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.957-959
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• 2005

A noise reduction equipment in power systems was device combined in a passive element such as the form of L, R and C. A analysis of frequency characteristics for the transformer models shall be considered the additional capacitance between the windings($C_{ps}$), terminals($C_s$), and winding-ground($C_g$). A noise in transformer is modeled by take account into the different frequency. In case of the high frequency, transformer windings with stray capacitance have lower impedance. Therefore a noise is transferred from primary winding to secondary winding. Noise Cut Transformer(NCT) was the noise reduction device and was normally single phase two-winding type transformer. We analyzed frequency characteristics using the nodal network analysis with the equivalent circuit and the simulation of the MATLAB.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.312-316
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• 1999

I-V characteristics of Praseodymium-based ZnO varistor doped with $Nd_2O_3$ in the range 0.0-2.0mol% sintered at 130$0^{\circ}C$ and 135$0^{\circ}C$ were investigated. In the all sides, ZnO varistors sintered at $1300^{\circ}C$ exhibited much better varistor characteristics than that at 135$0^{\circ}C$. All ZnO varistors doped with $Nd_2O_3$ sintered at $1300^{\circ}C$ exhibited good varistor characteristics but particularly ZnO varistor doped with l.Omol% $Nd_2O_3$ exhibited the best characteristics, which the nonlinear is 65.2 and the leakage current is 4.5pA. It is estimated that ZnO varistor doped with l.Omol% $Nd_2O_3$ will begin to be sufficiently used as basic composition to fabricate a good varistor.

• 대한전기학회논문지
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• 제43권3호
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• pp.420-431
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• 1994

The HgCdTe material, which is II-VI compound semiconductor, is important materials for the fabrication of the infrared detectros. To suggest the model of accurate MIS C-V calculation for narrow band gap semiconductors such as HgCdTe, non-parabolicity from k.p theory and degeneracy effect are considered. And partially ionized effect and compensation effect which are material's properties are also considerd. Especially, degenerated material C-V characteristics from Fermi-Dirac statistics and exact charge theory are presented to get more accurate analysis of the experimental results. Also the comparison with calculation results between the general MIS theory from Boltzmann appoximation method and this model which is considered the narrow band gap semiconductor properties, show that this model is more useful theory to determination of accurate low and high frequency C-V characteristics.

• 한국통신학회논문지
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• 제29권5A호
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• pp.484-491
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• 2004

L-band EDFA는 작은 평균밀도 반전율에서 동작하기 때문에 C-b란d에서 상대적으로 높은 흡수율로 인해 펌프 효과를 가지게 된다. 본 논문에서는 980nm의 펌프 입력 광 파워, C-band 펌프 파장 및 입력 광 파워에 따라 펌프 효과에 대해 논하고자 한다. 즉, C-band 펌프광의 흡수 또는 후방 자연방출광의 흡수라는 두 가지 다른 메카니즘을 통해 펌프 효과를 야기 시키게 된다. 또한 동일한 소 신호 이득 조건 하에서 L-band 신호 입력 광에 의한 포화 특성 (포화 광출력, 잡음지수에 있어서 장파장의 C-band 펌프가 양호한 것으로 나타난다. 전광 고정이득 L-band EDFA에서 C-band발진의 효과를 검토한 결과 L-band발진에 비해서 개선된 특성은 없는 것으로 나타난다.