• Title/Summary/Keyword: 미세대류

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MOCVD 반응기의 온도분포가 필름 성장율에 미치는 영향에 대한 연구

  • 김병호;임익태;김광선
    • Proceedings of the Korean Society Of Semiconductor Equipment Technology
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    • 2004.05a
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    • pp.147-153
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    • 2004
  • 본 연구에서는 MOCVD 반응기의 온도분포가 필름 성장률에 미치는 영향에 대해 분석하였다. 온도해석에는 반응기 벽면의 전도열전달과 기체의 대류열전달이 포함되었다. 또 서셉터와 실험에 사용된 그래파이트 평판 사이의 웨이퍼 미세 간극을 해석에 포함하여 반응기 내부의 온도를 예측하였다. 정밀한 온도해석을 통해 얻은 반응기의 온도 분포를 이용하여 GaAs와 InP의 필름성장률을 해석하였으며 그 결과 미세 틈새가 GaAs의 필름 성장률에 영향을 미치는 것을 확인하였다.

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Marangoni Convection Instability of a Liquid Floating Zone in a Simulated Microgravity (모사된 미세중력장내 액체부유대에서의 Marangoni대류의 불안정성)

  • 이진호;이동진;전창덕
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.2
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    • pp.456-466
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    • 1994
  • Experimental investigation was made to study the mechanism of fluid and thermal oscillation phenomena of surface-tension driven flow in a cylindrical liquid column heated from above which is the low-gravity floating zone simulated on earth. Hexadecane, octadecane, silicon oil (10cs), FC-40 and water are used as the test liquids. The onset of the oscillatory thermocapillary convection appears when Marangoni number exceeds its criteria value and is found to be due to the coupling among velocity and temperature field with the free surface deformation. The frequency of temperature oscillation decreases with increasing aspect ratio for a given diameter and Marangoni number and the oscillation level increases with Marangoni number. The flow pattern in the liquid column appears either as symmetric or asymmetric 3-D flow due to the oscillatory flow in the azimuthal direction. The free surface deformation also occurs either as symmetric or asymmetric mode and its frequency is consistent with those of flow and temperature oscillations. The amplitude of surface deformation also increases with Marangoni number.

Spray Characteristics of Superheated Swirl Spray Vertically Introduced into Convective Cross-flow (대류유동으로 수직 분사된 과열 와류분무의 분무특성)

  • Lee, Hae-Cheon;Yoon, Woong-Sup
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.11a
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    • pp.395-398
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    • 2010
  • 감압비등에 의한 미립화는 더 미세한 직경의 액적을 얻을 수 있고, 분무각이 증가하며, 더 좋은 혼합특성을 갖는 다는 점에서 단순 압력식 미립화와 차이가 난다. 감압비등이란 과열된 액체를 포화 압력 이하의 대기 중으로 분사하여 급격한 비등에 의해 이루어지는 미립화이다. 본 연구는 금속 연료를 이용한 추진기관의 산화제인 물 공급기술에 감압비등과정을 이용한 와류분무를 적용시키기 위해 수행됐다. 분열길이와 같은 거시적 특성은 Charge-Couple Device(CCD) 카메라를 이용해 측정하였고, Sauter Mean Diameter(SMD)와 SMD분포와 같은 미시적 특성은 Global Sizing Velocimetry(GSV) 시스템을 이용해 측정했다. 실험은 압력과 온도, 대류 속도를 변화시키며 진행했다.

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A Study on the Prediction of Residual Probability of Fine Dust in Complex Urban Area (복잡한 도심에서의 유입된 미세먼지 잔류 가능성 예보 연구)

  • Park, Sung Ju;Seo, You Jin;Kim, Dong Wook;Choi, Hyun Jeong
    • Journal of the Korean earth science society
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    • v.41 no.2
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    • pp.111-128
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    • 2020
  • This study presents a possibility of intensification of fine dust mass concentration due to the complex urban structure using data mining technique and clustering analysis. The data mining technique showed no significant correlation between fine dust concentration and regional-use public urban data over Seoul. However, clustering analysis based on nationwide-use public data showed that building heights (floors) have a strong correlation particularly with PM10. The modeling analyses using the single canopy model and the micro-atmospheric modeling program (ENVI-Met. 4) conducted that the controlled atmospheric convection in urban area leaded to the congested flow pattern depending on the building along the distribution and height. The complex structure of urban building controls convective activity resulted in stagnation condition and fine dust increase near the surface. Consequently, the residual effect through the changes in the thermal environment caused by the shape and structure of the urban buildings must be considered in the fine dust distribution. It is notable that the atmospheric congestion may be misidentified as an important implications for providing information about the residual probability of fine dust mass concentration in the complex urban area.

기류방출형 정전기제거장치의 개발에 관한 연구

  • 이동훈;박훈규
    • Proceedings of the Korean Institute of Industrial Safety Conference
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    • 2003.05a
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    • pp.167-172
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    • 2003
  • 액정판넬(LCD) 및 반도체 제조공정에 있어서 정전기 발생으로 인하여 미세한 먼지가 LCD 및 반도체 웨이퍼에 부착되거나, 정전기 방전에 의해 반도체소자 및 LCD 유리기판상의 패헌의 파괴를 야기하여 제품의 수율을 저하시키고 제조원가를 상승시키는 주요한 요인이 된다. 현재 이러한 제조공정에서 정전기를 위한 대책으로 코로나방전에 의한 이온바(Ion Bar) 및 이온브로어(Ion Blower)를 제전설비로 사용하고 있으나, 이 장치는 코로나 방전에 의한 이온을 발생시키고 이온화된 공기를 불어 내기 위하여 팬을 사용하여 공기를 대류 시킨다.(중략)

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Optical Properties of Asian Dust with LIDAR System (LIDAR 시스템을 이용한 황사의 광학적 특성 연구)

  • 최성철;차형기;김덕현;김영상
    • Proceedings of the Korea Air Pollution Research Association Conference
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    • 2002.04a
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    • pp.213-214
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    • 2002
  • 황사는 몽골이나 중국 북부의 황토지대에서 강한 바람에 의하여 고공으로 올라간 많은 미세한 모래먼지가 대기 중에 넓게 퍼져 하늘 전체를 덮고 떠다니다가 상층의 편서풍에 의해서 운반되어 서서히 하강하는 현상 또는 하강하는 모래먼지로 알려져 있다 최근 몇몇 연구가들에 의해 황사기간 중 대류권 내에서 편광소멸도를 측정하고 있다(Sakai 2000, Kobayashi 1985). 이들은 황사기간 중 편광소멸도는 0.2이상으로 높게 나타난다고 하였다. (중략)

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Effects of Double-diffusive Convection on the Mass Transport of Copper Ions in a Horizontal Porous Layer (수평 다공성유체층에서 이온의 물질전달에 대한 이중확산대류 효과)

  • Yoon Do-Young;Kim Min Chan;Choi Chang Kyun
    • Journal of the Korean Electrochemical Society
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    • v.2 no.2
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    • pp.98-105
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    • 1999
  • In the present study, buoyant force and its stabilizing effects in an electrostatic field were examined systematically in order to reduce the effect of natural convection with thermal stratification in a horizontal fluid-saturated porous layer. The correlation of ionic mass transport induced by double-diffusive convection in a horizontal porous layer has been derived theoretically. And the theoretical model was examined by electrochemical experiments. The theoretical correlation for mass transport which is satisfying Forchheimer's flow equation and based on the micro-turbulence model is derived as a function of soltual Darcy-Rayleigh number, thermal Darcy-Rayleigh number and Lewis number. In the experiment, the mass transport of copper ions in $CuSO_4-H_2SO_4$ solution is measured by electrochemical technique. By assembling theoretical correlation and experimental results, the mass transport correlation induced by double-diffusive convection is proposed as $$Sh=\frac{0.03054(Rs_D-LeRa_D)^{1/2}}{1-3.8788(Rs_D-LeRa_D)^{-1/10}}$$ The present correlation looks flirty reasonable with comparing experimental results, and very promising for the applications of its prototype into various systems involving heat transfer as well as mass transfer, in order to control the effects of natural convection effectively.

Measurement of the Shear Rate-Dependent Thermal Conductivity for Suspension with Microparticles (미립자를 포함한 현탁액의 전단율에 의존적인 열전도율 측정)

  • Lee, Sung-Hyuk;Shin, Sehyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.8
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    • pp.1141-1151
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    • 1998
  • An effective thermal conductivity measurement for suspensions of microparticles in oil mixture is conducted in order to evaluate the shear rate-dependence of the thermal conductivity of suspensions. Measurements are made for rotating Couette flows between two concentric cylinders. The rotating outer cylinder is immersed into a constant temperature water bath while the stationary inner cylinder is subject to a uniform heat fluff. Test fluids are made to be homogeneous suspensions, in which neutrally buoyant microparticles ($d=25{\sim}300{\mu}m$) are uniformly dispersed. The present measurements show strong shear-rate dependent thermal conductivities for the suspensions, which are higher than those at zero shear rate. The shear rate dependent thermal conductivity increases with the particle size and volume concentration.4 new model for shear rate-dependent thermal conductivity of microparticle suspensions is proposed; the correlation covers from zero shear rate value to asymptotic plateau value at moderately high shear rates.

Thermal Stresses Near the Crystal-Melt Interface During the Floating-Zone Growth of CdTe Under Microgravity Environment (미세중력장 CdTe 흘로우팅존 생성에서 결정체-용융액 계면주위의 열응력)

  • Lee Kyu-Jung
    • Journal of computational fluids engineering
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    • v.3 no.1
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    • pp.100-107
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    • 1998
  • A numerical analysis of thermal stress over temperature variations near the crystal-melt interface is carried out for a floating-zone growth of Cadmium Telluride (CdTe). Thermocapillary convection determines crystal-melt interfacial shape and signature of temperature in the crystal. Large temperature gradients near the crystal-melt interface yield excessive thermal stresses in a crystal, which affect the dislocations of the crystal. Based on the assumption that the crystal is elastic and isotropic, thermal stresses in a crystal are computed and the effects of operating conditions are investigated. The results show that the extreme thermal stresses are concentrated near the interface of a crystal and the radial and the tangential stresses are the dominant ones. Concentrated heating profile increases the stresses within the crystal, otherwise, the pulling rate decreases the stresses.

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