• Journal of the Microelectronics and Packaging Society
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• v.14 no.2 s.43
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• pp.1-8
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• 2007

A flat fluorescent lamp (FFL) was developed as a light source for LCD TV Backlight. The channels of FFL were realized by forming the flat glass at high temperature. The performance of the backlight with FFL was shown to improve by optimizing the FFL channel profile that has elliptical shape, 4.4 mm height and 1.4 mm sealing distance. In this paper, the brightness uniformity of LCD TV backlights was investigated by optical simulation of FFL channel profiles. The brightness of LCD TV using FFL with the optimized channel profile was shown to be $576\;cd/m^2$.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.422.2-422.2
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• 2014

가스장 이온원(GFIS: Gas Field Ionization Source)은 전자현미경보다 분해능이 향상된 이온현미경의 광원으로 사용하기 위하여 연구되고 있고, 큰 각전류 밀도, 작은 크기의 가상 이온원 그리고 좁은 에너지 퍼짐을 특징으로 한다. 여러 가지 장점을 가지고 있는 GFIS을 개발하기 위해서는 GFIS에서 발생된 이온빔의 형상을 관찰 것이 매우 중요하며, 이러한 관찰을 위한 시스템에는 주로 마이크로 채널 플레이트 (MCP: Micro Channel Plate)가 사용된다. MCP는 채널내부에 입사한 입자의 에너지에 의해서 생성된 이차전자를 수 천 배에서 수 백 만 배 이상 증폭시켜 형광판에 조사하고 발광시키는 방법으로 작은 신호를 영상으로 관찰 할 수 있도록 한다. MCP의 큰 증폭비는 작은 크기의 신호를 큰 신호로 증폭하여 관찰하는데 용이하여, GFIS 방법으로 생성된 이온빔(이온빔 전류 값은 pA 수준)을 관찰하기에 적합하다. 그러나 MCP를 이용하여도 증폭된 이온빔의 세기가 매우 작기때문에 생성된 이온빔 형상을 정확하게 관찰하기 위해서는 MCP의 형광판을 촬영하는 카메라 노출시간을 길게하여 데이터 수집 시간을 늘려야 하는 문제가 있다. 본 발표에서는 이온빔 형상 관찰에 소요되는 시간을 단축하기 위하여 MCP의 잡음이 GFIS의 이온빔 이미지 관찰에 미치는 영향을 분석하고 이를 제거 방법을 소개한다. 본 연구에서는 GFIS 방출 이온빔의 이미지에 포함된 MCP 잡음 특성을 장(전계)이온현미경 (Field Ion Microscope)실험을 통하여 분석하였고, 디지털 이미지 처리 방법을 이용하여 방출 이온빔 이미지에서 MCP 잡음을 제거하여 방출 이온빔 이미지만 추출할 수 있었다. 본 연구에서 제안한 방법을 GFIS 방출 이온빔 관찰시스템에 적용함으로써 기존 방법에 비해 노출시간을 단축하여 방출 이온빔을 관찰 할 수 있었으며, 노이즈 제거 효과로 향상된 이온빔 형상을 얻을 수 있었다. 본 연구결과의 관찰시간 단축과 향상된 이온빔 형상 획득은 이온현미경 개발에 필수적인 단원자 이온빔을 보다 효율적으로 개발할 수 있으며 디지털 이미지 처리로 GFIS 이온빔 생성을 자동화하는데 응용할 수 있다. 더불어 기존방법에 비해 이미지 획득을 위한 MCP의 노출시간을 단축할 수 있으므로 실험장비 수명 단축 방지 및 관리에 큰 장점이 있다.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1894-1899
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• 2007

This paper presents the thermal characteristics for micro heat exchanger with different micro-channel shapes. The shapes of micro-channel has been manufactured sheet metal by chemical etching for the I shape of straight channel and V and W shapes of chevron feature and fabricated micro plated heat exchangers using the vacuum brazing of bonding technology. The experimental study has been performed on heat transfer and pressure drop characteristics with various Reynolds number for water to water at the counter flows. The average heat transfer rate of V and W shapes has been showed about 1.5${\sim}$1.6 times large than those of I shape. For the comparison of Nusselt number, it is known that the convective heat transfer of V and W shapes represent more effect than I shape. The pressure drops of V and W shapes are about 1.2${\sim}$1.7 times lager than those of I shape.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.8
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• pp.75-83
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• 2005

A steady transonic dilute premixed combustion in a diverging channel is investigated by using asymptotic analysis. This model explores the nonlinear interactions between the near-sonic speed of the flow, the small changes in geometry from a straight channel, and the small heat release due to the one-step first-order Arrhenius chemical reaction. The reactive flow is described by a nonhomogeneous transonic small-disturbance (TSD) equation coupled with an ordinary differential equation for the calculation of the reactant mass fraction in the combustible gas. Also the asymptotic analysis reveals the similarity parameters that govern the reacting flow problem. The results show the complicated nonlinear interaction between the convection, reaction, and geometry effects and its effect on the flow behavior.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.332-332
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• 2012

프로그래밍 단자와 채널 단자가 게이트 산화 막으로 절연되는 플래시 스위치 및 SRAM 스위치와는 달리 상변화 스위치에서는 채널 단자를 통해 흐르는 전기신호가 프로그래밍 단자를 통해 그대로 누설되는 문제점이 발생한다. 이러한 문제점을 해결하기 위해서 지난 연구에서는 칼코겐화물로 구성되는 다층구조를 제안하고 $Ge_2Sb_2Te_5$의 특성을 보고하였다. 본 연구에서는 스퍼터링 방식을 이용하여 조성비가 다른 GeSbTe 박막을 증착하고 온도변화에 따른 면 저항 및 표면 형상 변화를 관찰한 후 이를 통해 다층구조에 적용하기에 적합한 조성비를 얻고자 하였다. GeSbTe 박막의 조성비에 따라 면 저항 및 표면형상이 크게 변화 하는 것을 확인 하였으며 이러한 결과로부터 프로그래머블 스위치에 적용되는 칼코겐화물 합금의 조성비는 스위치의 성능 좌우하는 중요한 파라미터임을 확인하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.92-98
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• 2020

In this study, an injection mold with conformal cooling channels was designed and manufactured for use in the production of a thick plastic cosmetic container that required high gloss surfaces. A cooling analysis verified the design of the conformal cooling channel for the cosmetic container, and also showed that the cooling efficiency was superior to that of the straight cooling channel. Slide cores designed with the conformal cooling channel were manufactured using the Layers Parting method and vacuum diffusion bonding. Subsequent test injection and quality inspection showed no problem in the appearance and dimensional accuracy of the produced product. The cycle time for product production was about 110 seconds, sufficient for mass production.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1436-1441
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• 2004

The internal cooling passage of a gas turbine blade can be modeled as a ribbed channel. Most studies have considered square ribs. However, the ribs can be rounded due to improper manufacturing or wear during the operation. Hence, we have studied two different rib geometries in this study, i.e. square and semicircle ribs. We have performed large eddy simulations (LES) and experiments to validate the results from the simulations. LES predicts the detailed flow and thermal features, which have not been captured by simulations using turbulence models. By investigating the instantaneous flow and thermal fields, we propose the mechanisms for the local heat transfer distribution between ribs. For both the geometries, heat transfer is enhanced by the entrainment of the cold fluid by the vortical motions and impingement of the entrained cold fluid on the ribs.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.370-373
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• 2008

It is known that the temperatures of die, punch, holder and punch pad need to be kept different to get better formability in Mg sheet forming processes. Heating and cooling channels are usually equipped in each tool to assign different temperature. This study focused on the optimal design of the heating and cooling channels for a cross-shaped deep drawing die set. While the die and blankholder were heated to and kept at $250^{\circ}C$ by using heat cartridges, the punch and punch pad were kept at much lower temperature than that of the die and blankholder by water circulating through cooling channels. All the approaches were done by numerical analyses, aiming to maximize the cup height and to minimize the punch corner radius without any failure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1383-1389
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• 2011

The current study focuses on the consistent analysis of heat transfer in multichannel volumetric solar receivers used for concentrating solar power. Changes in the properties of the absorbing material and channel dimensions are considered in an optical model based on the Monte Carlo ray-tracing method and in a one-dimensional heat transfer model that includes conduction, convection, and radiation. The optical model results show that most of the solar radiation energy is absorbed within a very small channel length of around 15 mm because of the large length-to-radius ratio. Classification of radiation losses reveals that at low absorptivity, increased reflection losses cause reduction of the receiver efficiency, notwithstanding the decrease in the emission loss. As the average temperature increases because of the large channel radius or small mass flow rate, both emission and reflection losses increase but the effect of emission losses prevails.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.7-12
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• 2016

This paper deals with a parametric study on cooling channel configurations to enhance the cooling effect. As a cooling effect has been increased, the exhaust gas by the plant from a manufacture is becoming deceased. To solve this problem, the design of a efficient cooling system is needed. In this paper, the cooling channel was analyzed to improve the cooling performance. The heat transfer rates depending on the number of baffle and the heiht of fin were obtained by using numerical simulation method. Three-dimensional Reynolds-averaged Naiver-Stokes equations were used to estimate flow and heat transfer in cooling channel, and the $k-{\varepsilon}$ model for turbulence closure was employed.