• 대한전자공학회논문지SD
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• 제41권6호
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• pp.1-7
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• 2004

본 논문에서는 2차원 양자 역학적 모델링 및 시뮬레이션(quantum mechanical modeling and simulation)으로써, 자기정렬 이중게이츠 구조(self-aligned double-gate structure)인 FinFET에 관하여 결합된 푸아송-슈뢰딩거 방정식(coupled Poisson and Schrodinger equations)를 셀프-컨시스턴트(self-consistent)한 방법으로 해석하는 수치적 모델을 제안한다. 시뮬레이션은 게이트 길이(Lg)를 10에서 80nm까지, 실리콘 핀 두께($T_{fin}$)를 10에서 40nm까지 변화시켜가며 시행되었다. 시뮬레이션의 검증을 위한 전류-전압 특성을 실험 결과값과 비교하였으며, 문턱 전압 이하 기울기(subthreshold swing), 문턱 전압 롤-오프(thresholdvoltage roll-off), 그리고 드레인 유기 장벽 감소(drain induced barrier lowering, DIBL)과 같은 파라미터를 추출함으로써 단채널 효과를 줄이기 위한 소자 최적화를 시행하였다. 또한, 고전적 방법과 양자 역학적 방법의 시뮬레이션 결과를 비교함으로써,양자 역학적 해석의 필요성을 확인하였다. 본 연구를 통해서, FinFET과 같은 구조가 단채널 효과를 줄이는데 이상적이며, 나노-스케일 소자 구조를 해석함에 있어 양자 역학적 시뮬레이션이 필수적임을 알 수 있었다.

• 설비공학논문집
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• 제7권2호
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• pp.298-309
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• 1995

Low-fin tubes are widely used to enhance condensation heat transfer. In this study, condensation heat transfer experiment was conducted on the low-fin tube using R-11. Three different fin densities-787 fpm (fins per meter), 1102 fpm. 1378 fpm-were tested. The results show that low-fin tube enhances the condensation heat transfer considerablely. The enhancement increases as the fin density increases. It was also found that the fin shape and height have a significant effect on the condensation heat transfer coefficient. Slender or high fins showed a higher condensing heat transfer coefficient compared with fat, low fins. For the tube with 1378 fpm, however, excessive fin height decreased the condensing heat transfer coefficient. The reason may be attributed to the increasing condensate retention angle as the fin density increases. The experimental data are compared with existing prediction models. Results show that Webb's surface tension model predicted the data best (within ${\pm}20%$), which confirms that surface tension plays the major role in low-fin tube condensation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2390-2395
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• 2007

The present research was experimentally performed to analyze the effect of delta-wing vortex generators(DWVG) on the heat transfer of fin surface of the plate fin-oval tube. The local heat transfer coefficient of the fin surface for four kinds of DWVG's arrangement was measured by the naphthalene sublimation technique for Reynolds numbers ranging from 2000 to 3200. The results showed that the heat transfer of the plate fin-oval tube can be significantly enhanced by DWVG for relatively low Reynolds numbers.

• 설비공학논문집
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• 제14권6호
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• pp.485-492
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• 2002

Heat transfer and pressure drop on the air side of a plate-louvered fin heat exchanger with new shape of louver fin have been investigated experimentally. Water is employed inside the flat tube to transfer heat with air for convenience. This problem is of particular interest in the design of a plate-louvered heat exchanger. The effect of air flow rate, water flow rate and water temperature on pressure drop as well as heat transfer in air side are studied in detail. The present results showed a good agreement qualitatively with the previous results in general. Based on the experimental data, f-factor and j -factor correlations of the present louvered-fin are suggested. It is also found that heat transfer could be enhanced with new shape of louver fin, compared with the conventional louvered-fin, while the f-factor remains unchanged.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.627-632
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• 2006

An experimental study is conducted to investigate the effect of the tube row and fin spacing on the air-side heat transfer and friction characteristics of fin-tube heat exchangers with slit fin pattern. A total of twelve samples of fin-tube heat exchangers with the nominal tube diameter of 7 mm, transverse tube pitch of 19 mm and longitudinal tube pitch of 12.5 mm are tested. The thermal fluid measurements are made using a psychometric calorimeter. The raw data are reduced to the desired heat transfer coefficient in terms of j-factor and friction factor of f for various frontal air velocities, fin pitches and number of tube rows.

• Journal of Mechanical Science and Technology
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• 제16권1호
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• pp.109-115
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• 2002

Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin -circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of finn-flat tube heat exchanger without vertex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger At the same time, pressure losses for four types of heat exchanger is measured and compared.

• 한국군사과학기술학회지
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• 제18권3호
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• pp.220-225
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• 2015

In this study, the effect of stationary fin and buoyancy devices on dynamic pithing of the tracked vehicle was investigated. For this work, the stationary fin and buoyancy devices were installed in front of body and then pitching variation was measured when rapidly reducing the vehicle speed in water operation. According to the results of measuring the freeboard at each case, when only fin was installed, the effect on freeboard of tracked vehicle in water was negligible. However, when buoyancy devices were installed, front freeboard was approximately increased by about 20~25 mm and rear freeboard was decreased by about 10~15 mm per each addition of 100 kg buoyancy device. Based on the calculation result of pitching decrease rates, it was found that the pitching variation was decreased approximately 12.3 % by fin installation and approximately 2 % by installation of each 100 kg of buoyancy device. The case in which only fin installation was made showed the best efficiency in decreasing pitching variation of the tracked vehicle in water compared to the other cases.

• 한국전산유체공학회지
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• 제3권1호
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• pp.82-88
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• 1998

As a par of a project related to the development of the design algorithm of a compact heat exchanger for the application of the electronic home appliances, the effect of the discreteness of the airflow boundary generated on the cooling fin surface on the heat transfer and pressure drop characteristics of the heat exchanger was studied numerically. In general, there are two critical design parameters seriously considered in the design of the heat exchanger; heat transfer rate(Q) and pressure drop coefficient(C/sub p/). Even though the higher heat transfer rate with lower pressure drop characteristics is required in a design of the heat exchanger, it is not an easy job to satisfy both conditions at the same time because these two parameters are phenomenally inversely proportional. To control the boundary layer thickness and its length along the streamline, the surface of the flat fin was modified to accelerate the heat transfer rate on the fin surface. To understand the effect of the discreted fin size(S/sub w/) and its location(S/sub h/) on the performance of the heat exchanger in the airflow field, the flat fin was modified as shown in Fig. 1. From this study, it was found that the smaller and more number of slits on the fin surface showed the higher energy diffusion rate. It means that the discreteness of the boundary layer is quite important on the heat transfer rate of the heat exchanger. On the other hand, if the fin surface configuration is very complex than needed, higher static pressure drop occurs than required in a system and it may be a reason of the induced aerodynamic noise in the heat exchanger.

• Journal of information and communication convergence engineering
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• 제8권1호
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• pp.107-111
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• 2010

This paper has presented the dependence of the threshold voltage on back gate bias and drain voltage for FinFET. The FinFET has three gates such as the front gate, side and back gate. Threshold voltage is defined as the front gate bias when drain current is 1 micro ampere as the onset of the turn-on condition. In this paper threshold voltage is investigated into the analytical potential model derived from three dimensional Poisson's equation with the variation of the back gate bias and drain voltage. The threshold voltage of a transistor is one of the key parameters in the design of CMOS circuits. The threshold voltage, which described the degree of short channel effects, has been extensively investigated. As known from the down scaling rules, the threshold voltage has been presented in the case that drain voltage is the 1.0V above, which is set as the maximum supply voltage, and the drain induced barrier lowing(DIBL), drain bias dependent threshold voltage, is obtained using this model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.219-221
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• 2006

The recently developed autopilot controller can make the input-output (I/O) dynamic characteristics of the nonlinear missile dynamics linear and independent of flight conditions. However, significant fin actuator dynamics can degenerate the I/O dynamic performance of the overall system. In this paper, we propose a singular perturbation-like method to compensate the effect of significant fin actuator dynamics in nonlinear missile control. The proposed compensation method does not require the time derivatives of fin angles but can maintain the linear I/O dynamic characteristics provided by the recently developed autopilot controller.