• 제목/요약/키워드: Out-diffusion

검색결과 1,226건 처리시간 0.032초

폴리에틸렌글리콜의 분자량에 따른 셀룰로스에서의 확산 거동 (The Effect of the Molecular Weight of Poly(ethylene glycol) on Diffusion through Cellulose)

  • 윤기종;우종형;서영삼
    • 한국염색가공학회지
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    • 제16권1호
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    • pp.48-52
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    • 2004
  • Diffusion/penetration rates of finishing agents are not a major criterion in the design of low molecular weight finishing agents. However, in the case of polymeric finishing agents, high molecular weights result in large hydrodynamic volumes and diffusion/penetration of the finishing agent into the substrate may become a critical factor in the design of textile finishing agents. Thus the effect of the molecular weight of a model compound, polyethylene glycol, on its diffusion through a cellulose membrane or cotton fabric is studied. Diffusion experiments of polyethylene glycol of molecular weight 400, 1000, 2000, 4600, 8000, and 10000 through cellulose membrane or fabric was carried out in a glass U-tube diffusion apparatus and the half penetration times and the penetration coefficients were determined. Both the half penetration times and the penetration coefficients exhibited a significant change between molecular weight 2000 and 2500 as the molecular weight of polyethylene glycol increased, suggesting that there is a critical molecular weight above which diffusion/penetration becomes difficult. Based on this study on a model compound, it is suggested that polymeric textile finishing agents can be expected to exhibit similar behavior.

활성탄 흡착모델과 칼럼실험을 통한 Volatile Organic Compounds의 막확산계수와 표면확산계수의 도출 (Calculation of Film Diffusion Coefficients and Surface Diffusion Coefficients of Volatile Organic Compounds Using Activated Carbon Adsorption Model and Small Column Test)

  • 이병호;이준희
    • 상하수도학회지
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    • 제13권1호
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    • pp.72-80
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    • 1999
  • Separation of VOCs(Volatile Organic Compounds) in Water Using Activated Carbon is known to be effective. Activated Carbon has been and will be employed in many water treatment plants. Simplified plug flow homogeneous surface diffusion model(PFHSDM) has been used to predict adsorption of organic matter. Finite Element Method(FEM) was used to analyze the model. Out of water quality control substances, benzene, toluene and tetrachloroethylene were used in the small column test. Film diffusion coefficients and surface diffusion coefficients were obtained from the column test, and were compared with the modeling results. Mc Cune, Williamson, William and Kataoka model, were compared with film diffusion coefficients obtained in the test. McCune model was fitted best for those VOCs used in this experiment. Film diffusion coefficients of VOCs obtained were benzene 0.265 cm/min, toluene 0.348 cm/min and tetrachloroethylene 0.298 cm/min. Surface diffusion coefficients of VOCs obtained were benzene $6.36{\times}10^{-8}cm^2/min$, toluene $3.20{\times}10-8cm2/min$, and tetrachloruethylene $4.94{\times}10^{-8}cm^2/min$.

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Modeling of diffusion-reaction behavior of sulfate ion in concrete under sulfate environments

  • Zuo, Xiao-Bao;Sun, Wei;Li, Hua;Zhao, Yu-Kui
    • Computers and Concrete
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    • 제10권1호
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    • pp.79-93
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    • 2012
  • This paper estimates theoretically the diffusion-reaction behaviour of sulfate ion in concrete caused by environmental sulfate attack. Based on Fick's second law and chemical reaction kinetics, a nonlinear and nonsteady diffusion-reaction equation of sulfate ion in concrete, in which the variable diffusion coefficient and the chemical reactions depleting sulfate ion concentration in concrete are considered, is proposed. The finite difference method is utilized to solve the diffusion-reaction equation of sulfate ion in concrete, and then it is used to simulate the diffusion-reaction process and the concentration distribution of sulfate ion in concrete. Afterwards, the experiments for measuring the sulfate ion concentration in concrete are carried out by using EDTA method to verify the proposal model, and results show that the proposed model is basically in agreement with the experimental results. Finally, Numerical example has been completed to investigate the diffusion-reaction behavior of sulfate ion in the concrete plate specimen immersed into sulfate solution.

Numerical simulation of diffusion in the stratified flow

  • Mizumoto N.;Kawamura T.
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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    • pp.255-256
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    • 2003
  • Simulations of atmospheric diffusion process under stable and unstable conditions were carried out using both numerical and experimental methods. Results from the previous study show that numerical simulation using 3-dimensional incompressible Navier-Stokes equation and density deviation are in good agreement with typical plume pattern. In this study, we use experimental data of temperature and wind profile obtained from a thermally stratified wind tunnel as initial conditions for numerical simulation and compare the results.

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BIFURCATION ANALYSIS OF A DELAYED EPIDEMIC MODEL WITH DIFFUSION

  • Xu, Changjin;Liao, Maoxin
    • 대한수학회논문집
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    • 제26권2호
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    • pp.321-338
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    • 2011
  • In this paper, a class of delayed epidemic model with diffusion is investigated. By analyzing the associated characteristic transcendental equation, its linear stability is investigated and Hopf bifurcation is demonstrated. Some explicit formulae determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using the normal form theory and center manifold theory. Some numerical simulation are also carried out to support our analytical findings. Finally, biological explanations and main conclusions are given.

SiGe/Si/SiGe Channel을 이용한 JFET의 전기적 특성 (Electrical Properties of JFET using SiGe/Si/SiGe Channel Structure)

  • 박병관;양현덕;최철종;김재연;심규환
    • 한국전기전자재료학회논문지
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    • 제22권11호
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    • pp.905-909
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    • 2009
  • The new Junction Field Effect Transistors (JFETs) with Silicon-germanium (SiGe) layers is investigated. This structure uses SiGe layer to prevent out diffusion of boron in the channel region. In this paper, we report electrical properties of SiGe JFET measured under various design parameters influencing the performance of the device. Simulation results show that out diffusion of boron is reduced by the insertion SiGe layers. Because the SiGe layer acts as a barrier to prevent the spread of boron. This proposed JFET, regardless of changes in fabrication processes, accurate and stable cutoff voltage can be controlled. It is easy to maintain certain electrical characteristics to improve the yield of JFET devices.

FEM해석을 통한 콘크리트내 수분침투 및 확산 예측 (Prediction of Water Penetration and Diffusion in Concrete Through FEM Analysis)

  • 유조형;이한승
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
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    • pp.87-88
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    • 2010
  • A permeability of concrete is a very important factors evaluating durability. So, we are carrying out a lot of relational data bases and experiment regarding a permeability. In order to evaluate a permeability of concrete, we are proceeding study on the water penetration and diffusion in concrete by water pressure. Because a way to evaluate a permeability of concrete has a limit. We will present a good method of evaluating durability of concrete using the water penetration depth of concrete by water pressure. To carry this out, we executed experiment with penetration depth of concrete by water pressure and verified it though FEM analysis.

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Effect of Metal Barrier Layer for Flexible Solar Cell Devices on Tainless Steel Substrates

  • Kim, Kyoung-Bo
    • Applied Science and Convergence Technology
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    • 제26권1호
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    • pp.16-19
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    • 2017
  • A thin metal layer of molybdenum is placed between the conventional barrier layer and the stainless steel substrate for investigating the diffusion property of iron (Fe) atoms. In this study, the protection probability was confirmed by measuring the concentration of out-diffused Fe using a SIMS depth profile. The Fe concentration of chromium (Cr) barrier layer with 10 nm molybdenum (Mo) layer is 5 times lower than that of Cr barrier without the thin Mo layer. The insertion of a thin Mo metal layer between the barrier layer and the stainless steel substrate effectively protects the out-diffusion of Fe atoms.

SPLINE DIFFERENCE SCHEME FOR TWO-PARAMETER SINGULARLY PERTURBED PARTIAL DIFFERENTIAL EQUATIONS

  • Zahra, W.K.;El-Azab, M.S.;Mhlawy, Ashraf M. El
    • Journal of applied mathematics & informatics
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    • 제32권1_2호
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    • pp.185-201
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    • 2014
  • In this paper, we construct a numerical method to solve singularly perturbed one-dimensional parabolic convection-diffusion problems. We use Euler method with uniform step size for temporal discretization and exponential-spline scheme on spatial uniform mesh of Shishkin type for full discretization. We show that the resulting method is uniformly convergent with respect to diffusion parameter. An extensive amount of analysis has been carried out to prove the uniform convergence with respect to the singular perturbation parameter. The obtained numerical results show that the method is efficient, stable and reliable for solving convection-diffusion problem accurately even involving diffusion parameter.