• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.350-350
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• 2010

Silicon carbide (SiC), one of the well known wide band gap semiconductors, shows high thermal conductivities, chemical inertness and breakdown energies. The design of normally-off 4H-SiC VJFETs [1] has been reported and 4H-SiC VJFETs with different lateral JFET channel opening dimensions have been studied [2]. In this work, 4H-SiC based VJFETs has been designed using the device simulator (ATLAS, Silvaco Data System, Inc). We varied the n-epi layer thickness (from $6\;{\mu}m$ to $10\;{\mu}m$) and the channel width (from $0.9\;{\mu}m$ to $1.2\;{\mu}m$), and investigated the static characteristics as blocking voltages, threshold voltages, on-resistances. We have shown that silicon carbide JFET structures of highly intensified blocking voltages with optimized figures of merit can thus be achieved by adjusting the epi layer thickness and channel width.

• 한국해양공학회지
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• 제34권6호
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• pp.442-453
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• 2020

Underwater color images suffer from low visibility and color cast effects caused by light attenuation by water and floating particles. This study applied single image enhancement techniques to enhance the quality of underwater images and compared their performance with real underwater images taken in Korean waters. Dark channel prior (DCP), gradient transform, image fusion, and generative adversarial networks (GAN), such as cycleGAN and underwater GAN (UGAN), were considered for single image enhancement. Their performance was evaluated in terms of underwater image quality measure, underwater color image quality evaluation, gray-world assumption, and blur metric. The DCP saturated the underwater images to a specific greenish or bluish color tone and reduced the brightness of the background signal. The gradient transform method with two transmission maps were sensitive to the light source and highlighted the region exposed to light. Although image fusion enabled reasonable color correction, the object details were lost due to the last fusion step. CycleGAN corrected overall color tone relatively well but generated artifacts in the background. UGAN showed good visual quality and obtained the highest scores against all figures of merit (FOMs) by compensating for the colors and visibility compared to the other single enhancement methods.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3754-3767
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• 2023

Turbulent jet discharges in subcooled water pools are essential for safety systems in nuclear power plants, specifically in the pressure suppression pool of boiling water reactors and In-containment Refueling Water Storage Tank of advanced pressurized water reactors. The gas and liquid flow in these systems is investigated using multiphase flow analysis. This field has been extensively examined using a combination of experiments, theoretical models, and Computational Fluid Dynamics (CFD) simulations. ANSYS CFX offers two approaches to model multiphase flow behavior. The non-homogeneous Eulerian-Eulerian Model has been used in this work; it computes global information and is more convenient to study interpenetrated fluids. This study utilized the Large Eddy Simulation Model as the turbulence model, as it is better suited for non-stationary and buoyant flows. The CFD results of this study were validated with experimental data and theoretical results previously obtained. The figures of merit dimensionless penetration length and the dimensionless buoyancy length show good agreement with the experimental measurements. Correlations for these variables were obtained as a function of dimensionless numbers to give generality using only initial boundary conditions. CFD numerical model developed in this research has the capability to simulate the behavior of non-condensable gases discharged in water.

• 한국정보처리학회논문지
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• 제5권6호
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• pp.1639-1651
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• 1998

본 논문에서는 RESO(REcomputation with Shifted Operands)와 같은 시간 결함허용 기법을 이용한 단일칩 컴퓨터의 결함허용성을 평가하기 위한 분석 및 시뮬레이션 모델을 제안한다. 단일칩으로 들어오는 모든 작업은 이중화 처리된다고 가정하고 1차 작업과 2차 작업의 효율적인 처리를 위한 세가지 스케쥴링 방법들을 제안하고 분석한다. 고안된 스케쥴링 방법들은 결함과 결함허용으로 인한 응답시간 지연이 시스템의 비용에 미치는 영향을 단일칩의 부하와 결함발생율에 따라서 평가한다. 제안된 모델을 사용하면 비용, 단일칩의 부하 및 결함발생율과 같은 실험 파라미터에 기초한 최적 지연($\kappa$)를 가지는 결함허용 스케쥴을 구할 수 있다.

• 한국재료학회지
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• 제5권2호
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• pp.251-258
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• 1995

$Bi_{2}Te_{3}$와 PbTe의 혼합물에서 $Bi_{2}Te_{3}-PbBi_{4}Te_{7}$의 공정조직이 형성됨을 이용, 제2상의 미세조직 제어로 열전도도의 감소에 따른 성능지수 향상을 목적하여 여러 조건에서 제조된 n-type(Bi, Pb)-Te계 공정조성 일방향 응고재의 열전특성을 조사하였다. 일방향응고시 공정상 PbBi_{4}Te_{7}$이 $Bi_{2}Te_{3}$의 벽개면(0001)을 따라 lamellar 형태로 성장하였으며, 성장속도가 1.4 \times 10^{-4}$cm/sec에서 $8.3 \times 10^{-4}$cm/sec로 증가됨에 따라 4PbBi_[4]Te_{7}$의 상간격은 10.4 $\mu \textrm{m}$에서 3.2$\mu \textrm{m}$로 감소되었다. Seeback계수는 성장방향 및 성장속도와 온도구배에는 관계없이 약 $\mid$$\alpha$$\mid$=29 $\mu$ V/K일정하였다. 전기전도도는 성장속도에 따라 약간 감소하는 경향을 보였고 성장방향에 평행한 경우가 수직한 경우보다 약 3배 정도 컸다. 성능지수는 성장방향과 성장속도 및 온도구배에 따라 약간씩 변화를 보였다. 수직한 경우가 평행한 경우에 비해 상대적으로 증가하는 경향을 나타내었는데 이는 lamellar 간격이 줄어듦에 따른 열전도도의 감속에서 비롯된 것으로 분석되었다.

• 한국철학논집
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• 제32호
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• pp.43-78
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• 2011

조선중기 북인의 모집단을 형성하는데 주축이 되었던 학파는 남명학파와 화담학파였다. 경의(敬義)의 실천을 강조한 남명의 사상은 임진왜란 때 다수의 의병장을 배출하였고, 광해군대 정인홍이 북인의 영수로 활약하면서 그 사상이 이어졌다. 이외에 성리학을 절충적으로 이해하고 개방적 성향을 보인 화담의 사상이 북인 학파에 큰 영향을 미쳤다. 광해군대에 북인이 정국을 운영할 때 실천적인 성향이 강해지고, 성리학에 대해 상대적으로 자유스런 분위기가 조성된 것에는 남명이나 화담의 사상적 영향력이 크다고 판단된다. 대북(大北)의 정인홍과 허균, 소북(小北)의 김신국, 남이공 등은 북인의 사상과 현실인식을 적극적으로 피력한 인물이었다. 1623년의 인조반정이후 사상계가 퇴계학파나 율곡학파가 주축이 된 주자성리학 흐름으로 정착되면서 북인(北人)의 사상은 시대의 주류적 흐름에서 밀려나게 된다. 정치사상에도 자파(自派)만이 군자당(君子黨)이라 확신하고 타 정파에 배타적인 입장을 취한 점 또한 몰락의 원인이 되었다. 17세기 중반 인조반정과 호란을 거치면서 조선사상계가 주자성리학 중심으로 재편되면서 북인(北人)의 사상은 역사의 전면에서 밀려나 저류적인 흐름으로서 그 역사적 기능을 수행하게 된다. 북인(北人)의 사상은 17세기 중, 후반 근기남인 학자들이나 18세기의 실학자 이익(李瀷)에게 일정한 영향을 미치면서 그 흐름이 일부 이어졌다. 북인은 조선중기 서인, 남인과 함께 정치, 사상을 이끌어간 대표적인 정파이자 학파였다. 최근 북인의 뿌리가 되는 조식과 서경덕에 대한 연구를 비롯하여, 북인 정치사상의 계승에 대한 연구가 체계적으로 수행되고 있다. 이러한 연구는 조선중기 이후 정치사와 사상사 연구의 폭을 보다 확대 줄 것이다.

• 농업과학연구
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• 제46권1호
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• pp.183-194
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• 2019

Adulteration of argan oil with some other cheaper oils with similar chemical compositions has resulted in increasing demands for authenticity assurance and quality control. Fast and simple analytical techniques are thus needed for authenticity analysis of high-priced argan oil. Raman spectroscopy is a potent technique and has been extensively used for quality control and safety determination for food products In this study, Raman spectroscopy in combination with a net analyte signal (NAS)-based methodology, i.e., hybrid linear analysis method developed by Goicoechea and Olivieri in 1999 (HLA/GO), was used to predict the different concentrations of olive oil (0 - 20%) added to argan oil. Raman spectra of 90 samples were collected in a spectral range of $400-400cm^{-1}$, and calibration and validation sets were designed to evaluate the performance of the multivariate method. The results revealed a high coefficient of determination ($R^2$) value of 0.98 and a low root-mean-square error (RMSE) value of 0.41% for the calibration set, and an $R^2$ of 0.97 and RMSE of 0.36% for the validation set. Additionally, the figures of merit such as sensitivity, selectivity, limit of detection, and limit of quantification were used for further validation. The high $R^2$ and low RMSE values validate the detection ability and accuracy of the developed method and demonstrate its potential for quantitative determination of oil adulteration.

• Korean Journal of Radiology
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• 제23권4호
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• pp.402-412
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• 2022

Objective: To evaluate the image quality and lesion detectability of lower-dose CT (LDCT) of the abdomen and pelvis obtained using a deep learning image reconstruction (DLIR) algorithm compared with those of standard-dose CT (SDCT) images. Materials and Methods: This retrospective study included 123 patients (mean age ± standard deviation, 63 ± 11 years; male:female, 70:53) who underwent contrast-enhanced abdominopelvic LDCT between May and August 2020 and had prior SDCT obtained using the same CT scanner within a year. LDCT images were reconstructed with hybrid iterative reconstruction (h-IR) and DLIR at medium and high strengths (DLIR-M and DLIR-H), while SDCT images were reconstructed with h-IR. For quantitative image quality analysis, image noise, signal-to-noise ratio, and contrast-to-noise ratio were measured in the liver, muscle, and aorta. Among the three different LDCT reconstruction algorithms, the one showing the smallest difference in quantitative parameters from those of SDCT images was selected for qualitative image quality analysis and lesion detectability evaluation. For qualitative analysis, overall image quality, image noise, image sharpness, image texture, and lesion conspicuity were graded using a 5-point scale by two radiologists. Observer performance in focal liver lesion detection was evaluated by comparing the jackknife free-response receiver operating characteristic figures-of-merit (FOM). Results: LDCT (35.1% dose reduction compared with SDCT) images obtained using DLIR-M showed similar quantitative measures to those of SDCT with h-IR images. All qualitative parameters of LDCT with DLIR-M images but image texture were similar to or significantly better than those of SDCT with h-IR images. The lesion detectability on LDCT with DLIR-M images was not significantly different from that of SDCT with h-IR images (reader-averaged FOM, 0.887 vs. 0.874, respectively; p = 0.581). Conclusion: Overall image quality and detectability of focal liver lesions is preserved in contrast-enhanced abdominopelvic LDCT obtained with DLIR-M relative to those in SDCT with h-IR.

• Current Optics and Photonics
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• 제6권5호
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• pp.497-505
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• 2022

Topological photonic nanocavities are considered to possess outstanding optical performance, and provide new platforms for realizing strong interaction between light and matter, due to their robustness to impurities and defects. Here hybrid plasmonic topological photonic nanocavities are proposed, by embedding various plasmon nanoantennas such as gold nanospheres, cylinders, and rectangles in a topological photonic crystal corner-state nanocavity. The maximum quality factor Q and minimum effective mode volume V_eff of these hybrid nanocavities can reach the order of 10⁴ and 10^-4 (𝜆/n)³ respectively, and the high figures of merit Q/V_eff for all of these hybrid nanocavites are stable and on the order of 10⁵ (𝜆/n)^-3. The relative positions of the plasmon nanoantennas will influence the coupling strength between the plasmon structures and the topological nanocavity. The hybrid nanocavity with gold nanospheres possesses much higher Q, but relatively large V_eff. The presence of a gold rectangular structure can confine more electromagnetic energy within a smaller space, since its V_eff is smallest, although Q is lowest among these structures. This work provides an outstanding platform for cavity quantum electrodynamics and has a wide range of applications in topological quantum light sources, such as single-photon sources and nanolasers.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권6호
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• pp.760-770
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• 2016

A 12-bit 750 kS/s Dual-Sampling Successive Approximation Register Analog-to-Digital Converter (SAR ADC) technique with reduced Capacitive DAC (CDAC) is presented in this paper. By adopting the Adaptive Power Control (APC) technique for the two-stage latched type comparator and using bootstrap switch, power consumption can be reduced and overall system efficiency can be optimized. Bootstrapped switches also are used to enhance the sampling linearity at a high input frequency. The proposed SAR ADC reduces the average switching energy compared with conventional SAR ADC by adopting reduced the Most Significant Bit (MSB) cycling step with Dual-Sampling of the analog signal. This technique holds the signal at both comparator input asymmetrically in sample mode. Therefore, the MSB can be calculated without consuming any switching energy. The prototype SAR ADC was implemented in $0.18-{\mu}m$ CMOS technology and occupies $0.728mm^2$. The measurement results show the proposed ADC achieves an Effective Number-of-Bits (ENOB) of 10.73 at a sampling frequency of 750 kS/s and clock frequency of 25 MHz. It consumes only 0.13 mW from a 5.0-V supply and achieves the INL and DNL of +2.78/-2.45 LSB and +0.36/-0.73 LSB respectively, SINAD of 66.35 dB, and a Figures-of-Merit (FoM) of a 102 fJ/conversion-step.