• 전자공학회논문지A
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• 제33A권6호
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• pp.136-143
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• 1996

A simple analytic model for the planar junctions with multiple foating field limiting rings(FLR) is presented which yields analytic expressions for the breakdown voltage and optimum ring spacings. the normalized potential of each ring is derived as a function of the normalized depletion width and the ring spacing. Based on the assumption that the breakdwon occurs simulataneously at cylindrical junctions of FLR structure where the peak sruface electric fields are equal, the optimum ring spacings are determined. The resutls are in good agreement with the simulations obtained from two dimensional device simulation program MEDICI and with the experimental data reported. The normalized experessions allow a calculation of breakdown voltage and optimum spacing over a broad range of junction depth and background doping levels.

• 소음진동
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• 제5권2호
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• pp.197-206
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• 1995

Microphone array is designed to measure the equivalent source height of vehicle noise. The equivalent source position is defined for an arbirary distribution of acoustic sources above a perfectly reflecting plane and a microphone array for its measurement is developed. The normalized errors of the measured equivalent source heights are defined including the effects of background noise, the geometric near field, and source size. Normalized errors of the measured source heights obtained by a nemerical simulation for each parameter lead to optimization of the microphone spacing and to the design of an array which gives the equivalent source height as a function of frequency. The performance of the designed array is verified using the stationary loudspeaker experiments.

• 한국토양비료학회지
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• 제51권2호
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• pp.79-89
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• 2018

Subsurface drip irrigation (SDI) system is considered one of the most effective methods for water application. A 2-year field study was conducted to investigate the effect of SDI systems with various dripline spacing (0.7 or 1.4 m) and position (under furrow or ridge) on soybean (Glycine max L.) production at a sandy-loam soil in Miryang, South Korea. For 2016-2017, average grain yield in SDI irrigated plots, $3.16Mg\;ha^{-1}$, was statistically greater than rainfed irrigated plot ($2.63Mg\;ha^{-1}$). Soybean grain yield averaged $3.25Mg\;ha^{-1}$ for the 0.7 m dripline spacing and $3.07Mg\;ha^{-1}$ for the 1.4 m spacing for the two-year period compared to a rainfed irrigated average of $2.63Mg\;ha^{-1}$ for the same period. Soybean treated with SDI system had significantly greater values of normalized difference vegetation index and stomatal conductance, indicating that soybean plants in SDI plots had greater photosynthetic and stomatal activity due to the higher water availability in soil. Irrigation water use efficiency (IWUE) was greatest in the plot of 0.7 m spacing installed under ridge position than any other plot across growing season. Average soil water content in plots with 0.7 m dripline spacing was $0.21m^3\;m^{-3}$ at 5 cm depth layer, which was 45% greater compared to the plots with 1.4 m spacing, even though the gross irrigation amounts were greater in 1.4 m spacing plots. It is concluded that wide dripline spacing (1.4 m) is probably the more economical installation design for SDI system compared to 0.7 m spacing in this study soil because the initial cost for dripline may be reduced with wide spacing design, even though the IWUE is greater in the plot of 0.7 m dripline spacing.

• 한국음향학회지
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• 제29권8호
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• pp.491-496
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• 2010

Rijke관에 놓인 나선형 가열기에 의하여 생성되는 열음향 파워를 수치해로 구하였다. 음장의 각진동수와 공기의 열확산계수에 의하여 무차원화한 가열선의 지름 d, 간격 P-d 및 유속 $U_0$가 음향 파워 생성에 미치는 영향을 구하고 고찰하였다. 가열선 간격이 충분히 클 때 무차원 유속이 $U_0{\approx}0.8$, 무차원 지름이 d.4일 때 가장 큰 열음향파워가 생성된다. 그러나 가열선 사이의 간격이 가까워지면 음향 파워 생성이 크게 증가하며 $d{\approx}2$, $P-d{\approx}3$에서 최대로 되며, 간격이 충분히 먼 경우의 최대값의 5배 이상이 될 수 있다. 최대 음향파워를 생성하는 유속은 가열선 간격에 관계없이 $U_0{\approx}0.8$일 때이다.

• 대한전자공학회논문지SD
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• 제38권9호
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• pp.624-633
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• 2001

회절격자 반주기 길이의 랜덤 변이가 QWS-DFB 레이저의 특성을 나타내는 척도인 xL 값에 미치는 영향을 알아보았다. QWS-DFB 레이저의 양 거울면은 무반사면으로 하였고, 회절격자 랜덤 변이는 평균이 0이고 분산이 1인 상관되어 있는 두 Gaussian 랜덤 변수로 나타내었다. 회절격자 반주기의 랜덤 변이가 있으면 동일 위상성분의 되먹임이 적어져 유효 xL 값이 감소하고 모드 간격이 줄어든다. 그런데, 회절격자 주기의 랜덤 변이가 있을 때 곁모드 간격에서 구한 결합계수 xL/sub SM/값과 주모드 거울면 손실에서 구한 xL/sub SM/는 일치하지 않으며, 랜덤 변이가 없을 때의 xL값보다 작다. 이 결과는 곁모드 간격 또는 spontaneous emission spectrum을 사용하여 측정한 xL/sub SM/ 값을 실제로 되먹임되는 정도를 나타내는 xL/sub eff/로 해석하여서는 안된다는 사실을 보여준다.

• Journal of electromagnetic engineering and science
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• 제13권4호
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• pp.240-244
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• 2013

In this paper, we present an improvement of a closed-form formula for mutual impedance computation. Depending on the center-to-center spacing between two rectangular microstrip patch antennas, the mutual impedance formula is separated into two parts. The formula based on synthetic asymptote and variable separation is utilized for spacings of more than 0.5 ${\lambda}_0$. When the spacing is less than 0.5 ${\lambda}_0$, an approximate formula is proposed to improve the computation for closely spaced elements. Simulation results are compared to computational results of mutual impedances and mutual coupling coefficients as functions of normalized center-to-center spacing in both E- and H-plane coupling configurations. A good agreement between simulation and computation is achieved.

• 한국통신학회논문지
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• 제29권12C호
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• pp.1623-1632
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• 2004

본 논문에서는 전형적인 실내 무선 채널 환경에서 초광대역 (Ultra Wide Band; UWB) 신호의 고속 동기 획득을 위한 Single-Dwell 연속 통기 탐색 기반의 Linear 탐색 알고리즘 및 Bit Reversal 탐색 알고리즘에 대한 성능분석을 수행하였다. IEEE 802.15 Task Group 3a UWB 실내 무선 채널 환경에서 프레임 구간 및 탐색 단위 구간 등의 변화에 따른 모의실험 결과. Linear 탐색 알고리즘보다 Bit Reversal 탐색 알고리즘이 정규화된 평균 동기 획득 소요 시간에 대해 단연 우수함을 확인하였으며, 탐색 종료 구간의 범위 변화에 따른 정규화된 평균 동기 획득 소요 시간이 이상적인 경우와 거의 일치함을 확인하였다. 특히, Bit Reversal 탐색 알고리즘의 경우 탐색 단위 구간이 세밀할수록 동일한 소요 시간에 대해 더욱 정확한 동기 획득 성능을 얻음을 확인할 수 있었다.

• 대한기계학회논문집B
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• 제24권4호
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• pp.570-577
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• 2000

Local heat transfer characteristics inside a hard disk driver(HDD) are investigated in this study. The investigation is considered between disks co-rotating in a cylindrical enclosure. The gap spacing, rotating speed and head-arm positions are mainly considered to understand the flow and heat transfer in the co-rotating disks. The naphthalene sublimation technique is used to determine local heat/mass transfer coefficients on the rotating disk. Flow patterns inside the co-rotating disks are investigated using a Laser Doppler Anemometer (LDA) and also analyzed numerically. The results show that the heat transfer coefficients on the disk changed little with the gap spacing between disks. Heat transfer rates in the outer region increases with increasing rotating Renolds number, but the values normalized by that on a free rotating disk give a similar pattern for the tested cases. The head-arm inserted between the rotating disks destroys the inner region resulting in enhancement of heat transfer in that region.

• 전자공학회논문지A
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• 제31A권7호
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• pp.95-101
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• 1994

A novel concept for the analysis of planar devices with a field limiting ring(FLR) is presented which allows analytic expressions in a normalized form for the potential distributions of FLR structure. Based on the method of image charges the main and ring junctions with identical cylindrical edges are kept to be two different equipotential surfaces. The potential relations between main and ring junction of the FLR structure are compared with 2-dimensional device simulation program. MEDICI. A good accordance is found. Comparisions with experimental data reported for the optimum ring spacing and the relative improvement of the breakdowm voltages in the FLR sturcture show the validity of the concept. The normalized expressions allow a universal application regardless to the junction depths and background doping levels.

• 한국전자파학회논문지
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• 제15권12호
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• pp.1199-1206
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• 2004

본 논문에서는 나카가미-m 페이딩 채널에서 정규화된 부반송파의 간격에 따라 구분되는 직교 MC DS- CDMA 시스템과 오브래핑 되지 않는 MC DS-CDMA시스템을 분석하였다. 다중 반송파 시스템에서 발생하는 선택 경로수를 줄이기 위하여 Hybrid SC/MRC 방식이 적용되어 MRC 방식을 사용한 경우와 비교 분석하였다. 분석 결과, Hybrid SC/MRC 방식을 MRC 방식으로 대체할 수 있으며, 주어진 대역폭이 고정되어 있는 경우 부반송파의 수를 증가시키면 부반송파 간격이 증가하고 필요한 대역폭이 더 많이 필요함으로 부반송파의 수는 주어진 대역폭을 고려하여 선택하여야함을 확인하였다.