• 제목/요약/키워드: film coefficient

검색결과 1,070건 처리시간 0.02초

Optical Constants and Dispersion Parameters of CdS Thin Film Prepared by Chemical Bath Deposition

  • Park, Wug-Dong
    • Transactions on Electrical and Electronic Materials
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    • 제13권4호
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    • pp.196-199
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    • 2012
  • CdS thin film was prepared on glass substrate by chemical bath deposition in an alkaline solution. The optical properties of CdS thin film were investigated using spectroscopic ellipsometry. The real (${\varepsilon}_1$) and imaginary (${\varepsilon}_2$) parts of the complex dielectric function ${\varepsilon}(E)={\varepsilon}_1(E)+i{\varepsilon}_2(E)$, the refractive index n(E), and the extinction coefficient k(E) of CdS thin film were obtained from spectroscopic ellipsometry. The normal-incidence reflectivity R(E) and absorption coefficient ${\alpha}(E)$ of CdS thin film were obtained using the refractive index and extinction coefficient. The critical points $E_0$ and $E_1$ of CdS thin film were shown in spectra of the dielectric function and optical constants of refractive index, extinction coefficient, normal-incidence reflectivity, and absorption coefficient. The dispersion of refractive index was analyzed by the Wemple-DiDomenico single-oscillator model.

Feature Scale Simulation of Selective Chemical Vapor Deposition Process

  • Yun, Jong-Ho
    • 한국진공학회지
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    • 제4권S1호
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    • pp.190-195
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    • 1995
  • The feature scale model for selective chemical vapor deopsition process was proposed and the simulation was performed to study the selectivity and uniformity of deposited thin film using Monte Carlo method and string algorithm. The effect of model parameters such as sticking coefficient, aspect ratio, and surface diffusion coefficient on the deposited thin film pattern was improved for lower sticking coefficient and higher aspect ratio. It was revealed that the selectivity loss ascrives to the surface diffusion. Different values of sticking coefficients on Si and on SiO2 surface greatly influenced the deopsited thin film profile. In addition, as the lateral wall angle decreased, the selectively deposited film had improved uniformity except the vicinity of trench wall. The optimum eondition for the most flat selective film deposition pattern is the case with low sticking coefficient and slightly increased surface diffusion coefficient.

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Film-Cooling Hole의 유출계수에 관한 수치해석적 연구 (A Computational Study for the Discharge Coefficient of a Film-Cooling Hole)

  • 김재형;김희동;박경암
    • 한국추진공학회지
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    • 제7권2호
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    • pp.15-22
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    • 2003
  • 본 연구에서는 2차원 압축성 Navier-Stokes 방정식을 사용하여 $30^{\cire}$ 경사진 터빈익의 냉각구를 통한 유출계수를 예측하였다. 내/외부 유동이 유출계수에 미치는 영향을 알아보기 위하여 외부유동만 존재하는 경우, 내부유동만 존재하는 경우 그리고 내/외부 유동이 없는 3가지 경우에 대하여 수치해석을 수행하였으며. 실험결과와 비교하였다. 본 연구의 수치해석결과는 유출계수를 잘 예측하였으며, 외부유동은 유출계수를 감소시키고, 내부유동은 냉각구내에서의 전압손실과 경계층의 영향을 감소시켜 특정 구간에서 유출계수를 증가시킨다는 것을 알았다.

반대방향의 방향각을 갖는 2열 분사구조의 막냉각 특성(II) -분사비의 영향- (Film Cooling from Two Rows of Holes with Opposite Orientation Angles(II) -Blowing Ratio Effect-)

  • 안준;정인성;이준식
    • 대한기계학회논문집B
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    • 제25권8호
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    • pp.1131-1139
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    • 2001
  • Experimental results are presented, which describe the effect of blowing ratio on film cooling from two rows of holes with opposite orientation angles. The inclination angle is fixed at 35°, and the orientation angles are set to be 45°for the downstream row, and -45°for the upstream row. The studied blowing ratios are 0.5, 1.0 and 2.0. The boundary layer temperature distributions are measured using thermocouple at two downstream locations. Detailed adiabatic film cooling effectiveness and heat transfer coefficient distributions are measured with TLC(Thermochromic Liquid Crystal). The adiabatic film cooling effectiveness and heat transfer coefficient distributions are discussed in connection with the injectant behaviors inferred from the boundary layer temperature distributions. Film cooling performance, represented by heat flux is evaluated from the adiabatic film cooling effectiveness and heat transfer coefficient data. The results show that the investigated geometry provides improved film cooling performance at the high blowing ratios of 1.0 and 2.0.

수직관 내 순수 증기의 층류 액막 응축 모델 (Laminar Film Condensation Model of Pure Steam in a Vertical Tube)

  • 김동억
    • 한국유체기계학회 논문집
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    • 제17권3호
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    • pp.33-40
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    • 2014
  • In this study, a new model for calculating the liquid film thickness and condensation heat transfer coefficient in a vertical condenser tube is proposed by considering the effects of gravity, liquid viscosity, and vapor flow in the core region of the flow. In order to introduce the radial velocity profile in the liquid film, the liquid film flow was regarded to be in Couette flow dragged by the interfacial velocity at the liquid-vapor interface. For the calculation of the interfacial velocity, an empirical power-law velocity profile had been introduced. The resulting liquid film thickness and heat transfer coefficient obtained from the proposed model were compared with the experimental data from other experimental study and the results obtained from the other condensation models. In conclusion, the proposed model physically explained the liquid film thinning effect by the vapor shear flow and predicted the condensation heat transfer coefficient from experiments reasonably well.

일반 측방 두부규격 방사선사진과 측방 추부규격 전산화 방사선사진에서의 계측점의 신뢰도에 대한 비교 연구 (A COMPARATIVE STUDY OF COMPUTED RADIOGRAPHIC CEPHALOMETRY AND CONVENTIONAL CEPHALOMETRY IN RELIABILITY OF HEAD FILM MEASUREMENTS (LANDMARKS IDENTIFICATION))

  • 김형돈;김기덕;박창성
    • 치과방사선
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    • 제27권1호
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    • pp.99-106
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    • 1997
  • The purpose of this study was to compare & to find out the variability of head film measurements (and marks identification) between Fuji computed radiographic cephalometry and conventional cephalometry. 28 Korean adults were selected. Lateral cephalometric FCR film and conventional cephalometric film of each subject was taken. Four investigators identified 24 cephalometric landmarks on lateral cephalometric FCR film and conventional cephalometric film. The comparable measurements between lateral cephalometric FCR film and conventional cephalometric film were statistically analysed. The results were as follows : 1. In FCR film & conventional film, coefficient of variation (C.V.) of 24 landmarks was taken horizonta1ly & vertically. There is no significant difference of rank order of landmarks in C.V. between two films. 2. In comparison of significant differences of landmarks variability between FCR film & conventional film, horizontal value of coefficient of variation, showed significant differences in four landmarks among twenty-four landmarks, but vertical value of coefficient of variation showed significant differences in sixteen landmarks among twenty-four landmarks. FCR film showed significantly less variability than conventional film in 17 subjects among 20(4+16) subjects that showed significant difference.

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반대방향의 방향각을 갖는 2열 분사구조의 막냉각 특성 : 분사비의 영향 (Film Cooling from Two Rows of Holes with Opposite Orientation Angles: Blowing Ratio Effects)

  • 안준;정인성;이준식
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 춘계학술대회논문집B
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    • pp.113-118
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    • 2000
  • Experimental results describing the effects of blowing ratio on film cooling from two rows of holes with opposite orientation angles are presented. The inclination angle was fixed at $35^{\circ}$ and the orientation angles were set to be $45^{\circ}$ for downstream row. and $-45^{\circ}$ for upsream row. The studied blowing ratios were 0.5, 1.0 and 2.0. The boundary layer temperature distributions were measured using thermocouple at two downstream loundary layer temperature distributions were measured using thermocouple at two downstream locations. Detailed adiabatic film cooling effectiveness and heat transfer coefficient distributions were measured with TLC(Thermochromic Liquid Crystal). The adiabatic film cooling effectiveness and heat transfer coefficient distributions are discussed in connection with the injectant behaviors inferred from the boundary layer temperature distributions. Film cooling performance, represented by heat flux was calculated with the adiabatic film cooling effectiveness and heat transfer coefficient data.

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구리와 은 박막의 열팽창계수에 미치는 결정립 크기와 박막 두께의 영향 (The Effect of Grain Size and Film Thickness on the Thermal Expansion Coefficient of Copper and Silver Thin Films)

  • 황슬기;김영만
    • 대한금속재료학회지
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    • 제48권12호
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    • pp.1064-1069
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    • 2010
  • Thin films have been used in a large variety of technological applications such as solar cells, optical memories, photolithographic masks, protective coatings, and electronic contacts. If thin films experience frequent temperature changes, thermal stresses are generated due to the difference in the coefficient of thermal expansion between the film and substrate. Thermal stresses may lead to damage or deformation in thin film used in electronic devices and micro-machined structures. Thus, knowledge of the thermomechanical properties of thin films, such as the coefficient of thermal expansion, is an important issue in determining the stability and reliability of the thin film devices. In this study, thermal cycling of Cu and Ag thin films with various microstructures was employed to assess the coefficient of thermal expansion of the films. The result revealed that the coefficient of thermal expansion (CTE) of the Cu and Ag thin films increased with an increasing grain size. However, the effect of film thickness on the CTE did not show a remarkable difference.

The Effect of Non-condensable Gas on Direct Contact Condensation of Steam/Air Mixture

  • Lee, Hanchoon;Kim, Moohwan;Park, Suki
    • Nuclear Engineering and Technology
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    • 제33권6호
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    • pp.585-595
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    • 2001
  • A series of experiments have been carried out to investigate the effects of non-condensable gas on the direct contact film condensation of vapor mixture under an adiabatic wall condition. The average heat transfer coefficient of the direct contact condensation was obtained at the atmospheric pressure with four main parameters ; air-mass fraction, mixture velocity, film Reynolds number, and the degree of water film subcooling having an influence on the condensation heat transfer coefficient. With the analysis of 88 experiments, a correlation of the average Nusselt number for direct contact film condensation of steam/air mixture at an adiabatic vertical wall was proposed as functions of film Reynolds number, mixture Reynolds number, air mass fraction, and Jacob number. The average heat transfer coefficient for steam/air mixture condensation decreased significantly while air mass fraction increased. The average heat transfer coefficients also decreased as the Jacob number increased, and were scarcely affected by the film Reynolds number below a mixture Reynolds number of about 245,000.

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LiBr 수용액의 수평관 유하액막 증발에 있어서의 열전달계수 특성 (The characteristics of heat transfer coefficient for falling-film evaporation on a horizontal tube with aqueous LiBr solution)

  • 지용해;김동관김무환
    • 대한기계학회논문집B
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    • 제21권2호
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    • pp.294-302
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    • 1997
  • Falling-film evaporation experiments for aqueous solution of lithium bromide (LiBr) were performed on a horizontal smooth 19.05-mm-dia copper tube. Average heat transfer coefficients were obtained with varied film Reynolds numbers, system pressures, LiBr concentrations and degrees of wall superheat. Heat transfer coefficients increase with increasing system pressure and decreasing concentration. For degrees of wall superheat, the heat transfer coefficient did not't show the distinct trend. For this experimental ranges, heat transfer coefficients showed maximum values at an optimal film Reynolds number. The results of this work were compared with pool boiling data reported previously, and it was shown that the heat transfer performance is superior to the pool boiling.