• 전기전자학회논문지
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• 제17권1호
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• pp.71-76
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• 2013

본 연구에서는 AlGaN/GaN HEMT (High electron mobility transistor)를 제작하고 채널폭의 감소에 따른 특성의 변화를 고찰하였다. AlGaN/GaN 이종접합구조 기반의 기판 위에 채널의 길이는 $1{\mu}m$, 채널 폭은 각각 $0.5{\sim}9{\mu}m$가 되도록 전자선 리소그라피 방법으로 트랜지스터를 제작하였다. 게이트를 형성하지 않은 상태에서 채널의 면저항을 측정한 결과 sub-${\mu}m$ 크기로 채널폭이 작아짐에 따라 채널의 면저항이 급격히 증가하였으며, 트랜지스터의 문턱전압은 $1.6{\mu}m$와 $9{\mu}m$의 채널폭에서 -2.85 V 이었으며 $0.9{\mu}m$의 채널폭에서 50 mV의 변화, $0.5{\mu}m$에서는 350 mV로 더욱 큰 변화를 보였다. 트랜스컨덕턴스는 250 mS/mm 내외의 값으로부터 sub-${\mu}m$ 채널에서 150 mS/mm로 채널폭에 따라 감소하였다. 또한, 게이트의 역방향 누설전류는 채널폭에 따라 감소하였으나 sub-${\mu}m$ 크기에서는 감소가 둔화되었는데 채널폭이 작아짐에 따라 나타는 이와 같은 일련의 현상들은 AlGaN 층의 strain 감소로 인한 압전분극 감소가 원인이 되는 것으로 사료된다.

• 대한기계학회논문집B
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• 제27권8호
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• pp.1158-1164
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• 2003

Steady-state structure and acoustic-pressure responses of $H_2$/Air counterflow diffusion flames are studied numerically with a detailed chemistry in view of acoustic instability. The Rayleigh criterion is adopted to judge acoustic amplification or attenuation from flame responses. Steady-state flame structures are first investigated and flame responses to various acoustic-pressure oscillations are numerically calculated in near-equilibrium and near-extinction regimes. The acoustic responses of $H_2$/Air flame show that the responses in near-extinction regime always contribute to acoustic amplification regardless of acoustic-oscillation frequency Flames near extinction condition are sensitive to pressure perturbation and thereby peculiar nonlinear responses occur, which could be a possible mechanism in generating the threshold phenomena observed in combustion chamber of propulsion systems.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.198-201
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• 2004

We have developed a multi-domain vertically aligned liquid crystal display (MVA-LCD) that produces natural gray-scale images even at high viewing angles. We divided each pixel into two areas and set different threshold voltages for each sub-area. A transparent electrode in a sub-area is not connected directly to the source electrodes but via the capacitance of the SiN layer. In particular, light-orange skin color appears very natural, even at a high inclination angle. The contrast ratio is over 500 in the normal direction and over 10 from any viewing angle.

• JSTS:Journal of Semiconductor Technology and Science
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• 제8권2호
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• pp.134-138
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• 2008

We present a power gating turn-on mechanism that digitally suppresses ground-bounce noise in ultra-deep submicron technology. Initially, a portion of the sleep transistors are switched on in a pseudo-random manner and then they are all turned on fully when VVDD is above a certain reference voltage. Experimental results from a realistic test circuit designed in 65nm bulk CMOS technology show the potential of our approach.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권4호
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• pp.840-855
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• 2011

In the context of additive noise steganography model, we propose a method to detect least significant bit (LSB) matching steganography in grayscale images. Images are decomposed into detail sub-bands with local linear transform (LLT) masks which are sensitive to embedding. Novel normalized characteristic function features weighted by a bank of band-pass filters are extracted from the detail sub-bands. A suboptimal feature set is searched by using a threshold selection algorithm. Extensive experiments are performed on four diverse uncompressed image databases. In comparison with other well-known feature sets, the proposed feature set performs the best under most circumstances.

• Ocean Systems Engineering
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• 제2권1호
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• pp.17-31
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• 2012

This study investigated the behavior of a non-isothermal $CO_2$ bubble formed through a leak process from a high-pressure source in a deep sea. Isenthalpic interpretation was employed to predict the state of the bubble just after the leak. Three modes of mass loss from the rising bubble were demonstrated: dissolution induced by mass transfer, condensation by heat transfer and phase separation by pressure decrease. A graphical interpretation of the last mode was provided in the pressure-enthalpy diagram. A threshold pressure (17.12 bar) was identified below which the last mode was no longer present. The second mode was as effective as the first for a bubble formed in deep water, leading to faster mass loss. To the contrary, only the first mode was active for a bubble formed in a shallow region. The third mode was insignificant for all cases.

• Ocean Systems Engineering
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• 제2권1호
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• pp.33-47
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• 2012

This study revealed the behavior of droplets formed through leak process in deep water. There was a threshold depth named the universal attraction depth (UAD). Droplets rose upward in the zone below the UAD called the rising zone, and settled down in the zone above the UAD called the settling zone. Three mass loss modes were identified and formulated: dissolution induced by mass transfer, condensation by heat transfer and phase separation by pressure decrease. The first two were active for the settling zone, and all the three were effective for the rising zone. In consequence, the life time of the droplets in the rising zone was far shorter than that of the droplets in the settling zone.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.94-100
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• 2017

Stress drain bias dependent current model is proposed for sub-70-nm p-channel metal-oxide semiconductor field-effect transistors (pMOSFETs) under drain-avalanche-hot-carrier (DAHC-) mechanism. The proposed model describes the both on-current and off-current degradation by using two device parameters: channel length variation (${\Delta}L_{ch}$) and threshold voltage shift (${\Delta}V_{th}$). Also, it is a simple and effective model of predicting reliable circuit operation and standby power consumption.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.614-620
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• 2020

In a previous study, delayed hydride cracking (DHC) assessment of pressurized water reactor (PWR) spent fuel during dry storage using the threshold stress intensity factor (K_IH) was performed. However, there were a few limitations in the analysis of the cladding properties, such as oxide thickness and mechanical properties. In this study, those models were modified to include test data for irradiated materials, and the cladding creep model was introduced to improve the reliability of the DHC assessment. In this study, DHC susceptibility of PWR spent fuel during dry storage depending on the axial elevation was evaluated with the improved assessment methodology. In addition, the sensitivity of affecting parameters such as fuel burnup, hydride thickness, and crack aspect ratio are presented.

• JSTS:Journal of Semiconductor Technology and Science
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• 제5권2호
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• pp.136-147
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• 2005

A theoretical design evaluation based on a hydrodynamic transport simulation of strained Si-SiGe on insulator (SSOI) type nMOSFETs is reported. Although, the net performance improvement is quite limited by the short channel effects, simulation results clearly show that the strained Si-SiGe type nMOSFETs are well-suited for gate lengths down to 20 nm. Simulation results show that the improvement in the transconductance with decreasing gate length is limited by the long-range Coulomb scattering. An influence of lateral and vertical diffusion of shallow dopants in the source/drain extension regions on the device performance (i.e., threshold voltage shift, subthreshold slope, current drivability and transconductance) is quantitatively assessed. An optimum layer thickness ($t_{si}$ of 5 and $t_{sg}$ of 10 nm) with shallow Junction depth (5-10 nm) and controlled lateral diffusion with steep doping gradient is needed to realize the sub-50 nm gate strained Si-SiGe type nMOSFETs.