• 센서학회지
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• 제5권3호
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• pp.87-92
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• 1996

Pb과잉인 PLT 타겟을 이용하여 MgO(100) 단결정 기판위에 고주파 마그네트론 스펏터링법으로 PLT박막을 제조하였으며, c-축 배향에 따른 물리적 및 전기적 특성을 조사하였다. PLT박막의 c-축 배향성은 제조조건에 따라 변화하며, 본 연구에서의 제조조건은 기판온도가 $640^{\circ}C$, 분위기압이 10 mTorr, $Ar/O_{2}$비가 10 및 고주파 전력밀도가 $1.7 W/cm^{2}$이었다. 이러한 조건에서 제조된 PLT 박막은 표면에서의 Pb/Ti 비가 1/2, 저항률이 $8{\times}10^{11}{\Omega}{\cdot}cm$ 및 비유전률이 110 이었다. PLT박막을 이용하여 초전형 적외선 센서를 제조하였으며, 제조된 적외선 센서의 피크 대 피크 전압은 450 mV, 신호대 잡음비는 7.2 였다.

• 대한전자공학회논문지SD
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• 제44권8호
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• pp.65-73
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• 2007

본 논문에서는 UMTS용 수신기를 위한 저 전력 CMOS 연속-시간 시그마-델타 모듈레이터에 대해 논한다. 저 전력 동작수행을 위한 연속 시간 모듈레이터의 루프 필터는 선형성이 우수하고, 튜닝 회로가 비교적 간단한 active-RC 필터로 구성하였다. 본 모듈레이터의 구조는 전력 효율을 높이기 위해 24의 OSR (Oversampling Ratio)의 3차 4비트 단일 루프로 구성하였고, 초과 루프 지연 시간에 의한 성능 저하를 방지하기 위해 반주기 지연 제환 경로를 추가하였다. 제작한 회로의 SNR, SNDR, Dynamic range는 각각 71dB, 65dB, 74dB로 측정되었다. 설계한 연속-시간 시그마-델타 모듈레이터는 0.18-um CMOS 표준공정으로 제작하였고, 1.8V의 단일 전원 전압에서 15mW의 전력을 소모한다.

• 조명전기설비학회논문지
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• 제26권4호
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• pp.41-47
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• 2012

This paper deals with the electrical characteristics related to power loss, equivalent resistance, and leakage currents flowing through new and deteriorated zinc oxide(ZnO) arrester elements subjected to the mixed DC and 60[Hz] AC voltages. The test specimens were deteriorated by 8/20[${\mu}s$] impulse current of 2.5[kA]. The leakage current-applied voltage($I-V$) characteristic curves of ZnO surge arrester elements were measured as a parameter of the ratio of the peak of 60[Hz] AC voltage to the peak of total voltage. As a consequence of test results, in case of the same applied voltage, the leakage currents flowing through the deteriorated ZnO arrester elements were higher than those flowing through the new ZnO surge arrester elements. The cross-over phenomenon in $I-V$ curves of ZnO surge arrester elements measured as a parameter of the mixed ratio of DC and AC voltages was observed at the low current domain. The effect of DC voltage on the leakage current flowing through ZnO surge arrester elements is pronounced at the same magnitude of test voltages. In addition, the larger the applied number of 8/20[${\mu}s$] impulse current of 2.5[kA] is, the greater the power loss is, in particular, the more severe the power loss increases at higher applied voltages.

• KSBB Journal
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• 제14권2호
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• pp.225-229
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• 1999

본 연구에서는 광학적으로 순수한 S-(+)-ketoprofen을 얻기 위한 효소적 분할공정을 개발하는 것을 그 내용으로 하고 있다. 결과에 의하면 Candida rugosa 유래의 lipase는 음이온 교환수지에 의해 두 가지 형태의 효소로 분리되었으며 특히 첫 번째 peak의 lipaserk (S)-enantiomer에 대해 선택성이 매우 높은 것으로 나타났다. 온도 pH, 첨가제의 영향에 대해서 조사한 결과 높은 활성을 유지하면서 광학적으로 순수한 (S)-ketoprofen을 얻는 조건을 찾지는 못하였으나, $37^{\circ}C$의 온도에서 선택성이 높았으며 ethylen glyco과 같은 polyalcohol 종류가 첨가될 경우 선택성이 증가한다는 결과를 얻을 수 있었다.

• 한국재료학회지
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• 제29권7호
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• pp.456-462
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• 2019

ZnO thin-films are grown on a p-Si(111) substrate by RF sputtering. The effects of growth temperature and $O_2$ mixture ratio on the ZnO films are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and room-temperature photoluminescence (PL) measurements. All the grown ZnO thin films show a strong preferred orientation along the c-axis, with an intense ultraviolet emission centered at 377 nm. However, when $O_2$ is mixed with the sputtering gas, the half width at half maximum (FWHM) of the XRD peak increases and the deep-level defect-related emission PL band becomes pronounced. In addition, an n-ZnO/p-Si heterojunction diode is fabricated by photolithographic processes and characterized using its current-voltage (I-V) characteristic curve and photoresponsivity. The fabricated n-ZnO/p-Si heterojunction diode exhibits typical rectifying I-V characteristics, with turn-on voltage of about 1.1 V and ideality factor of 1.7. The ratio of current density at ${\pm}3V$ of the reverse and forward bias voltage is about $5.8{\times}10^3$, which demonstrates the switching performance of the fabricated diode. The photoresponse of the diode under illumination of chopped with 40 Hz white light source shows fast response time and recovery time of 0.5 msec and 0.4 msec, respectively.

• Computers and Concrete
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• 제20권4호
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• pp.369-380
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• 2017

The effects of the vertical component of a ground motion on the earthquake performances of semi-ductile high-rise R/C structures were investigated in the present study. Linear and non-linear time-history analyses were conducted on an existing in-service R/C building for the loading scenarios including and excluding the vertical component of the ground motion. The ratio of the vertical peak acceleration to the horizontal peak acceleration (V/H) of the ground motion was adopted as the main parameter of the study. Three different near-source earthquake records with varying V/H ratio were used in the analyses. The linear time-history analyses indicated that the incorporation of the vertical component of a ground motion into analyses greatly influences the vertical deflections of a structure and the overturning moments at its base. The lateral deflections, the angles of rotation and the base shear forces were influenced to a lesser extent. Considering the key indicators of vertical deflection and overturning moments determined from the linear time-history analysis, the non-linear analyses revealed that the changes in the forces and deformations of the structure with the inclusion of the vertical ground motion are resisted by the shear-walls. The performances and damage states of the beams were not affected by the vertical ground motion. The vertical ground motion component of earthquakes is markedly concluded to be considered for design and damage estimation of the vertical load-bearing elements of the shear-walls and columns.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.447-448
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• 2008

The goal of this study is to find flame dynamic behavior using a transverse fuel injection in a model combustor, and is to investigate main causes of unstable combustion in a liquid-fueled combustor. For transverse fuel injection into air cross flow, spray result shows similar tendency with Wu et al.[1998] until spray arrives at flame-holder. However, passing through flame-holder, fuel inflow into recirculation region of flameholder is not sufficient so it makes large difference between shear flame and recirculation flame behind flameholder. In combustion tests, the stable flame shows a kind of shear flames and low peaks of dynamic pressure frequencies. On the other hand, unstable flame shows periodic detached flame in recirculation zone and a strong peak of dynamic pressure frequency. The instability frequency is highly affected by influx air velocity, air temperature, equivalence ratio and wake or vortex shedding frequency behind the flameholder.

• 한국진공학회지
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• 제15권4호
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• pp.374-379
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• 2006

본 연구에서는 전계 방출소자로 사용하기 위한 탄소나노튜브의 합성 방법으로, pin to plate type의 대기압 플라즈마 소스를 사용한 AP-PECVD(Atmosphere pressure plasma enhanced chemical vapor deposition)를 이용하였으며, 이를 통하여 대기압에서 성장된 탄소나노튜브의 구조적 및 전기적 특성을 연구하였다. 유리 / 크롬 / 니켈을 기판으로 사용하여 $400{\sim}500^{\circ}C$ 변화 영역에서 탄소나노튜브를 성장시킨 결과 다중벽 탄소나노튜브가 얻어짐을 알 수 있었다. $500^{\circ}C$에서 성장시킨 탄소나노튜브의 경우 FT-Raman을 이용한 분석 결과 $I_D / I_G$ ratio 가 0.772 임을 관찰하였으며 TEM으로 분석결과, 내부의 그래파이트층은 15 - 20 층, 내부 직경은 10-15nm, 외부 직경은 30 - 40nm 이고, 각 층간의 간격은 0.3nm 임을 알 수 있었다. 또한 전계 방출 문턱전압은 $2.92V/{\mu}m$ 이고, FED 에서 요구되는 $1mA/cm^2$의 방출전류밀도는 $5.325V /{\mu}m$의 문턱전압 값을 가지는 것을 관찰하였다.

• Journal of Power Electronics
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• 제15권6호
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• pp.1446-1455
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• 2015

This paper illustrates resonant tank design considerations and the implementation of a LLC resonant converter with a wide battery voltage range based on the fundamental harmonic approximation (FHA) analysis. Unlike the conventional design at zero load, the parameter K (the ratio of the transformer magnetizing inductor L_m to the resonant inductor L_r) of the LLC converter in this paper is designed with two charging points, (V_{o_min}, I_{o_max1}) and (V_{o_max}, I_{o_max2}), according to the battery charging strategy. A 2.9kW prototype with an output voltage range of 36V to 72V dc is built to verify the design. It achieves a peak efficiency of 96%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1456-1458
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• 1996

In resonant tunneling diodes with the quantum well structure showing the negative differential resistance (NDR), it is essential to increase both the peak-to-valley current ratio (PVCR) and the peak current density ($J_p$) for the accurate switching operation and the high output of the device. In this work, a resonant interband tunneling diode (RITD) with single quantum well structure, which is composed of $In_{0.53}Ga_{0.47}As/ln_{0.52}Al_{0.48}As$ heterojunction on the InP substrate, is suggested to improve the PVCR and $J_p$ through the narrowed tunnel barriers. As the result, the measured I-V curves showed the PVCR over 60.