• Korean Journal of Crystallography
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• v.10 no.1
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• pp.20-27
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• 1999

CaF2 단결정을 흑연도가니를 사용하여 He 분위기 하에서 탄만법으로 성장시켰다. 수화방지를 위해 PbF2를 출발물질에 도포하였다. 열구배에 따른 계면의 움직임인 성장속도는 배플판에 의해 성공적으로 조절되었다. 결정성장의 최적조건은 온도구배가 37℃/cm, 냉각속도가 10℃/hr 및 2.5tw% PbF2를 사용한 경우로, 성장속도는 약 3.2 mm/hr이었으며, 위로 볼록한 고액계면을 갖는 단결정이 성장되었다. IR분석 결과, 1500∼4000 cm-1(6.7∼2.5 ㎛)영역에서 약 96%의 투과도를 보였다. 결함밀도를 측정하기 위해, 성장축에 수직 및 수평으로 절단한 면을 농축 H2SO4에서 약 30분간 에칭하여 간섭현미경으로 관찰한 결과, 각각 3.4×104/cm2였다. 이러한 결과는 수화에 따른 성장된 단결정의 투명도의 경향과 일치하였다. 결정에 대한 XRD분석 결과 우선성장 방향은 <311>이었다.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1918-1920
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• 2001

초소형 히트파이프는 고집적 반도체 소자에서 발생되는 열을 효과적으로 소산하기 위한 열교환 장치이다. 초소형 히트파이프는 작동유체가 상 변화 잠열을 이용한 칩 레벨의 냉각 장치이다. 작동유체는 진공으로 밀봉된 공간내에서 외부 동력 없이 모세관력에 의하여 이동한다. 본 논문에서는 실리콘보다 열전도도가 우수하여 발생되는 열을 더욱 빠르게 소산시킬 수 있는 구리 모재의 초소형 히트파이프를 제작한다. 특히, 모세관력은 히트파이프의 성능을 좌우하는 요소이다. 모세관력 향상을 위해서 구리 전기도금으로 이용하여 홈(groove)부분을 제작한다. 윅(wick) 제작, 구리판 접합, 작동유체 충전등으로 초소형 히트파이프를 제작한 후, 성능 실험한 결과를 보여준다.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1566-1571
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• 2003

The cold plate used for a CEU(Control Electronics Unit) of an EV(Electric Vehicle) is extremely important since the dissipation of the heat generated from power devices like IGBT(Insulated Gate Bipolar Transistor) and diode has a significant effect on the performance as well as the durability of the CED. The cold plate consists of seven power devices, and coolant flows through the passage bonded to a groove of the cold plate. In order to find out heat transfer and pressure drop characteristics, series of numerical analyses for the cold plate with enhanced coolant passages were conducted. Based on results of the numerical analyses, an improved model of the cold plate has been proposed. The experiments under the various conditions have been conducted to compare the performance of the proposed cold plate to the present one. As a result of the numerical analyses together with the experiments, the ideal design of the cold plate could be offered.

• Journal of Korea Foundry Society
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• v.39 no.5
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• pp.94-101
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• 2019

This study investigated the microstructure properties of A356 and AC8A alloys with a rheocasting mold using an inclined cooling plate. In addition, a formability evaluation was performed according to the solid fraction. Regardless of the position, the overall microstructure was shown to be uniform and a finer crystal structure was obtained as the solid fraction increased. The study confirmed that the molding pattern changed according to the solid fraction and that the spherical α-Al and eutectic α were identified. The results of the formability according to the solid fraction of A356 and AC8A alloys were similar to the simulation results.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.268-273
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• 1997

사용후핵연료는 장기간 강한 방사선과 붕괴열이 방출된다. 따라서 사용후핵연료를 안전하게 운반하기 위하여 수송용기는 방사선차폐의 건전성, 격납경계의 유지 및 내부 붕괴열의 적절한 제거 등의 설계기준을 만족하도록 설계되어야 한다. 본 연구에서는 28개의 PWR 사용후핵연료집합체를 운반할 수 있는 KSC-28 수송용기의 적절한 열전달 특성을 갖는 copper 냉각핀 및 aluminum 전열판을 설정하였다. 또한, 정상수송조건 및 화재사고조건에 대한 열전달해석을 수행하여 수송용기의 열적 건전성을 평가하였고 여기에서 얻어진 온도를 열하중으로 고려하여 열응력해석을 수행함으로써 수송용기의 온도변화에 따른 구조적 건전성을 평가하였다.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.9
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• pp.130-137
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• 1996

In the present paper the effect of various process conditions on the final weight of injection molded rectangular plates has been investigated in detail. The main parameters involved in the simulations were melt temperature, mold temperature, injection speed and packing pressure. The dimensions of the plate used were 100mm long, 2mm of width and polystyrene was used as a molding material. The shear viscosity of the polymeric material was treated as a function of shear rate, temperature and pressure through the whole processes including packing and cooling stages. By increasing a packing pressure the final weight of sample increased linearly. Furthermore, as the melt temperature, the mold temperature and the injection speed increased, the final weight of the injection molded plate decreased within the molding window.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1754-1759
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• 2008

To produce plastic parts that have fine pattern through conventional injection molding, a lot of difficulties follow. Therefore, rapid heating and cooling methods are good candidates for manufacturing injection-molded parts with micro/nano patterns. In this study, we adopted the E-Mold patent technology. The mold for E-Mold technology has a separate heated core with micro heaters. It is very important to optimize the lay-out of the heaters in heated core because it influences both control and distribution of mold temperature. We developed a optimization method of heating line lay-out by using commercial softwares and compared the output with the experimental results. We used Pro-Engineer Wildfire 2.0 for the mold design, ICEMCFD for mesh generation, and FLUENT for heat transfer simulation. The simulation results showed the temperature profile from $60^{\circ}C$ to $120^{\circ}C$ or $180^{\circ}C$ during heating and cooling process which were compared with the injection molding experiments. We concluded that the simulation could well explain the experimental results. It was shown that the E-Mold optimization design for heater lay-out could be available through the simulation.

• Korean Journal of Optics and Photonics
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• v.31 no.1
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• pp.7-12
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• 2020

In this paper, we experimentally investigate the fiber fuse in single-mode 2-kW-class high-power fiber amplifiers, depending on the cooling method at the splicing point. We measured the temperature of the splicing point between the pump-signal combiner and gain fiber as a function of laser output power. The temperature of the splicing point increased from 20 to 32℃ with a slope of 0.01℃/W, up to 1.2 kW of laser output power. At higher powers the temperature of the splicing point increased dramatically, with a slope of 0.08℃/W. After that, the fiber amplifier was destroyed during operation at 1.96 kW of output power by fiber fuse. The bullet shape, a common feature of fiber fuse, was observed in the damaged passive fiber core of the pump-signal combiner. Later, we adopted an improved water-cooled cold plate to increase the cooling efficiency at the splicing point, and investigated the laser output power. The temperature at the splicing point was 35.8℃ with a temperature-rise slope of 0.007℃/W at the maximum output power of 2.05 kW. The beam quality M² was measured to be less than 1.3, and the output beam's profile was a stable Gaussian shape. Finally, neither fiber fuse nor mode instability was observed in the fiber amplifier at the maximum output power of 2.05 kW.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.301-316
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• 1995

experimental and computational studies ore carried out to investigate the natural convection of the single phase flow in a tank with a heated horizontal plate facing downward. This is a simplified model for investigations of the influence of a core melt at the bottom of a reactor vessel on the thermal hydraulic behavior in a oater filled cavity surrounding the vessel. In this case the vessel is simulated by a hexahedron insulated box with a heated plate Horizontally mounted at the bottom of the box. The box with the heated plate is installed in a water filled hexahedron tank. Coolers are immersed in the U-type water volume between the box and the tank. Although the multicomponent flows exist more probably below the heated plate in reality, present study concentrates on the single phase flow in a first step prior to investigating the complicated multicomponent thermal hydraulic phenomena. In the present study, in order to get a better understanding for the natural convection characteristics below the heated plate, the velocity and temperature are measured by LDA(Laser Doppler Anemometry) and thermocouples, respectively. And How fields are visualized by taking pictures of the How region with suspended particles. The results show the occurrence of a very effective circulation of the fluid in the whole How area as the heater and coolers are put into operation. In the remote region below the heated plate the new is nearly stagnant, and a remarkable temperature stratification can be observed with very thin thermal boundary. Analytical predictions using the FLUTAN code show a reasonable matching of the measured velocity fields.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.1-7
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• 2017

When implementing butt joint welding of two plates, it is useful to attach end-tabs made of a metal with high heat conductivity (e.g., copper) at the front and back sides of the welded plates to prevent the bead from rolling down and prevent defects that may occur at the tips of the weld zone. In this study, the fin shape, which is known to have good heat discharging characteristics by natural convection, has been applied to enhance the cooling performance of the end-tab. From both experiment and numerical analysis, it was confirmed that end-tabs with fin-shaped holes have better heat discharging performance than end-tabs without holes. Through thermal and fluid flow analysis, the cooling rates of end-tabs with different hole shapes were estimated in order to figure out characteristics of shape factor that are important for the heat discharging performance. As a result, we found that the structure including vertical fins with optimal fin gap was the best-performing shape.