• 한국유체기계학회 논문집
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• 제20권1호
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• pp.29-34
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• 2017

An analysis on pressure drop in vortex amplifier has been performed. Based on theoretical approach with flow physics on well-known firm ground from previous studies, two dimensional flow model, which is very useful to calculate pressure drop of vortex amplifier, is proposed. Parametric studies on inlet and outlet boundary conditions also have been performed so that it found the most influential parameter is the inlet swirl velocity condition. Finally, a simple formulation is given to calculate total pressure drop.

• 한국분말재료학회지
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• 제15권1호
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• pp.46-52
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• 2008

The restrictor, which is a fluid channel from a reservoir to a chamber inside a thermal micro actuator, has been fabricated using ArF and KrF excimer lasers, Diode-Pumped Solid State Lasers (DPSSL) and femtosecond lasers for a feasibility study. A numerical model of fluid dynamics for the actuator chamber and restrictor is presented. The model includes bubble formation and growth, droplet ejection through nozzle, and dynamics of fluid refill through the restrictor from a reservoir. Since an optimized and well-fabricated restrictor is important for a high frequency actuator, some special beam delivery setups and post processing techniques have been researched and developed. The effects of variations of the restrictor length, diameter, and tapered shapes are simulated and the results are analyzed to determine the optimal design. The numerical results of droplet velocity and volume are compared with the experimental results of a cylindrical-shaped actuator. It is found that the micro actuators having tapered restrictors show better high frequency characteristics than those having a cylindrical shape without any notable decrease of droplet volume. The laser-fabricated restrictors demonstrate initial feasibility for the laser direct ablation technique although more development is required.

• 한국결정성장학회지
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• 제23권3호
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• pp.129-134
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• 2013

사파이어($Al_2O_3$) 단결정 웨이퍼는 청색 LED(light emitting diode) 제작을 위한 핵심 소재로 사용되고 있으며, 사파이어 단결정의 품질에 따라 LED의 성능이 크게 좌우하게 된다. 여러 가지 사파이어 단결정 제조방법 중 키로플러스(Kyropoulos)법은 도가니 직경에 근접한 크기로 잉곳 생산이 가능하며, 내부 전위밀도가 낮아 고품질의 대구경 사파이어 잉곳 제작이 가능하다. 키로플러스법 공정에서 용융 알루미나의 유동은 seed의 성장 형태, 도가니 및 단열재의 형상에 영향을 받으며, 유동양상에 따라 단결정 사파이어 잉곳의 품질이 좌우된다. 특히 온도구배는 hot-zone 내부의 히터 구조와 밀접한 관련이 있으므로 본 연구에서는 도가니 단위표면적당 하부와 측면 히터의 발열비율에 따른 CFD(computational fluid dynamics) 해석을 실시하고, 해석결과를 토대로 각각 용융 알루미나의 유동 및 remelting 현상에 대해 분석하였으며, 이상적인 히터 발열비율을 도출하였다.

• 한국태양에너지학회 논문집
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• 제28권1호
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• pp.9-17
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• 2008

An experimental investigation has been carried out to study the effects of different working fluids on the behavior and thermal performance of a hi-directional thermodiode. The thermodiode was made up of two rectangular loops mounted between a collector plate and a radiator plate. Rotatable joints between the horizontal and inclined segments of the loops enable easy alteration of the direction of heat transfer. The loops and the tank were filled with a working fluid for effective heat transfer when the thermodiode was forwarded biased. Six different working fluids were tested with thermal conductivity values ranging from 0.1 to $0.56W/m-^{\circ}C$, thermal expansion coefficient values ranging from $1.8\;{\times}10^{-4}$ to $1.3\;{\times}\;10^{-3}\;K^{-1}$, and kinematic viscosity values ranging from $0.65\;{\times}\;10^{-6}$ to $100\;{\times}\;10^{-6}\;m^2/s$. Especially, mixtures of $Al_2O_3$ (30nm Particle) in deionized water have been tested for the volumetric ratios of 0.01, 0.02, 0.03, 0.1, 0.2%. Each experiment was carried out after the loop was filled with a working fluid for effective heat transfer and the thermodiode was forwarded biased. The solar thermodiode was heated by a radiant heater consisting of 20 halogen lamps that generated a heat flux of about $1000\;W/m^2$ on the collector surface. Results are given in terms of temperature development in different parts of the loop as heat is delivered from its hot end to the surrounding atmosphere by the radiator made of copper plates.

• 한국광학회지
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• 제27권6호
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• pp.218-222
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• 2016

레이저 다이오드 TO 패키지 내부의 주요 부분과 히트싱크 구조의 열전달 특성을 전산모사를 통해 분석하고, 개선구조의 효율적 적용방안을 제안하였다. 열 병목 현상을 개선하기 위해, 레이저 다이오드 상부에 열 우회를 도모할 수 있는 방열구조물을 설치하는 것을 제안하였고, 열저항 단순모델 기대치와 비교하여 그 우회 효율 개선 정도를 더욱 향상시키는 적용 범위를 파악하였다. 열 병목을 감안하여 방열 도움 구조물을 적절히 추가함에 따라, 통상적인 기대 수준보다 더욱 향상된 열 우회 효율을 얻을 수 있었음을 보고한다.

• Journal of Veterinary Science
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• 제19권6호
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• pp.835-839
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• 2018

Auditory tube diverticula, also known as guttural pouches, are naturally occurring dilations of the auditory tube in horses that communicate with the nasopharynx through a small ostium. Infection and select other conditions can result in inflammation and narrowing of the nasopharyngeal ostium, which prevents drainage of fluid or egress of air and can lead to persistent infection or guttural pouch tympany. Auditory tube diverticulotomy allows continuous egress from the auditory tube diverticula and is a feature of disease treatment in horses, in which medical treatment alone is not successful. Transpharyngeal endoscopic auditory tube diverticulotomy was performed using a diode laser either at a single dorsal pharyngeal recess location or bilaterally caudal to the nasopharyngeal ostium in 10 horse head specimens. Both methods resulted in clear communication between the nasopharynx and auditory tube diverticula. Diverticulotomy performed in the dorsal pharyngeal recess required less laser energy and activation time and had a shorter surgical duration than diverticulotomy performed caudal to the nasopharyngeal ostium. Further study related to the clinical application of both techniques is warranted.

• 대한의용생체공학회:의공학회지
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• 제19권4호
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• pp.369-377
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• 1998

본 논문에서는 레이저 다이오드의 자기혼합 효과를 이용한 레이저 도플러 혈류계를 위한 신호처리 알고리즘들에 대한 in vitro적인 실험결과를 비교하였다. 단순하고 유연성있는 레이저 도플러 시스템을 구성함으로써 디지털 신호해석 방법에 의하여 여러 가지 신호처리 알고리즘들을 비교할 수 있도록 하였다. 이 시스템은 다양한 알고리즘을 퍼스널 컴퓨터를 사용하여 소프트웨어로 제어하므로써 다양한 알고리즘을 선택하여 비교 연구할 수 있도록 하였다. 또한, 유체 흐름의 재현성과 조직의 혈류 흐름을 모의하기 위하여 두 개의 실험적인 혈류모델을 제작하여 적용하였다. 광원은 파장 780nm의 레이저 다이오드를 사용하였으며, 3 종류의 입자 농도와 속도를 갖는 액체를 두 개의 실험모델에 흘리면서 측정된 결과들을 비교하였다. 그 결과 주파수로 가중되지 않은 알고리즘(0차 모멘트)이 속도와 농도변화를 잘 나타내는 반면에 주파수로 가중된 알고리즘들(1차와 2차 모멘트, 0차 모멘트와의 비)은 농도보다는 속도 변화를 잘 나타내었다.

• 반도체디스플레이기술학회지
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• 제18권1호
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• pp.92-96
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• 2019

In the presence of ${\mu}-tip$ embedded in a slot-die head for stripe coatings, there arises the capillary flow that limits an increase of the stripe density, which is required for the potential applications in organic light-emitting diode displays. With an attempt to suppress it, we have employed a computational fluid dynamics software and performed simulations by varying the ${\mu}-tip$ length and the contact angles of the head lip and ${\mu}-tip$. We have first demonstrated that such a capillary flow phenomenon (a spread of solution along the head lip) observed experimentally can be reproduced by the computational fluid dynamics software. Through simulations, we have found that stronger capillary flow is observed in the hydrophilic head lip with a smaller contact angle and it is suppressed effectively as the contact angle increases. When the contact angle of the head lip increases from $16^{\circ}$ to $130^{\circ}$, the distance a solution can reach decreases sharply from $256{\mu}m$ to $44{\mu}m$. With increasing contact angle of the ${\mu}-tip$, however, the solution flow along the ${\mu}-tip$ is disturbed and thus the capillary flow phenomenon becomes more severe. If the ${\mu}-tip$ is long, the capillary flow also appears strong due to an increase of flow resistance (electronic-hydraulic analogy). It can be suppressed by reducing the ${\mu}-tip$ length, but not as effectively as reducing the contact angle of the head lip.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.443-444
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• 2006

The influence of the heat sources on LED junction temperature are Engine room air, Back plate, Electric power device, and so on. LED lamp cooling system is considered to be an important subject fur high light efficiency. Because LED Chip will be problem When LED junction temperature be over $135^{\circ}C$, In this Study, The Looped Heat Pipe System is considered to prevent LED Chip fall. The LHPS is consist of evaporator part, condenser part, heat pipe part. The working fluid of LHPS is HCFC-123. In this study, to prevent LED Chipfall, we study thermal characteristics for Looped Heat Pipe System with LED lamp.

• Journal of Biosystems Engineering
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• 제30권2호
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• pp.114-120
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• 2005

In this study, a biological reaction and measurement control system was developed to rapidly measure the insecticide imidacloprid residues in agricultural products. The biological reaction part of the system was designed to include micro-pumps and valves for fluid transport, and a polystyrene covet as a reaction chamber. The measurement control part of the system consisted of a photodiode with a light-emitting diode for optical density measurement, and a control microcomputer to implement assay. Signal output was read as the rate of change in optical density at 645 nm. The sensitivity of the system was 2.2 ng/mL ($IC_50$). The system could execute a measurement cycle in about 19 minutes. Research will be continued to develop an automatic sampler fur imidacloprid residues from agricultural products.