• 제목/요약/키워드: Solution diffusion

검색결과 1,035건 처리시간 0.024초

GLOBAL EXISTENCE OF SOLUTIONS TO THE PREY-PREDATOR SYSTEM WITH A SINGLE CROSS-DIFFUSION

  • Shim, Seong-A
    • 대한수학회보
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    • 제43권2호
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    • pp.443-459
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    • 2006
  • The prey-predator system with a single cross-diffusion pressure is known to possess a local solution with the maximal existence time $T\;{\leq}\;{\infty}$. By obtaining the bounds of $W\array_2^1$-norms of the local solution independent of T we establish the global existence of the solution. And the long-time behaviors of the global solution are analyzed when the diffusion rates $d_1\;and\;d_2$ are sufficiently large.

전기화학적 촉진법에 의한 콘크리트의 염화물이온 확산계수 평가에 관한 실험적 연구 (An Experimental Study on Evaluation of Coefficient of Chloride Diffusion by Electrochemical Accelerated Test in Concrete)

  • 조봉석;김갑수;김재환;김용로;권영진;김무한
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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    • pp.705-710
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    • 2003
  • In this study, to confirm the diffusion coefficient of chloride ion is affected by the concentration of NaCl solution, capacity of voltage, time of an electric current, the diffusion coefficient of chloride ion in concrete was investigated through an electrochemical accelerated test. and the results of these test were compared with the diffusion coefficient of chloride ion by test of sodium chloride solution digestion. As the results of this study, the diffusion coefficient of chloride ion wasn't affected by the concentration of NaCl solution, capacity of voltage, time of an electric current within the range of this study and was similar to the diffusion coefficient of chloride ion by test of sodium chloride solution digestion.

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고분자막내에서 용매 확산 모델 (Solvent diffusion model in polymer membrane)

  • 김종수;이광래
    • 한국막학회:학술대회논문집
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    • 한국막학회 1998년도 추계 총회 및 학술발표회
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    • pp.59-62
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    • 1998
  • 1. 서론 : 막내부에서 물질전달을 설명하는 이론으로 현재 solution-diffusion model과 pore-flow model 두 가지가 있다. 이 중에서 흡착, 확산, 탈착의 3과정을 거치는 solution-diffusion model이 주로 사용되고 있다. 본 연구에서는 solution-diffusion model 에서 상호확산계수를 구하기 위해서 Vrentas-Duda식을 이용하여 자기확산계수를 구하고 Bearman식으로부터 상호확산계수를 구하는 과정을 UNIFAC-FV와 modified UNIFAC-FV을 이용하여 계산하였으며 Flory-Huggins식을 이용한 기존방법과 비교하였다.(생략)

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적응성 유한체적법을 적용한 다차원 확산공정 모델링 (Thermal Diffusion Process Modeling with Adaptive Finite Volume Method)

  • 이준하;이흥주
    • 반도체디스플레이기술학회지
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    • 제3권3호
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    • pp.19-21
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    • 2004
  • This paper presents a 3-dimensional diffusion simulation with adaptive solution strategy. The developed diffusion simulator VLSIDIF-3 was designed to re-refine areas. Refine scheme was calculated by the difference of doping concentration between any of two nodes. Each element is greater than tolerance and redo diffusion process until error is tolerable. Numerical experiment in low doping diffusion problem showed that this adaptive solution strategy is very efficient in both memory and time, and expected this scheme would be more powerful in complex diffusion model.

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염분환경하 콘크리트 경화체의 내구성에 미치는 혼합재의 영향 (I) 시멘트 경화체중에서의 Cl-이온의 확산 (Effect of Blending Materials on the Durability of Concrete (I) Diffusion of Cl-ions through Hardened Cement Paste)

  • 김남중;최상흘;정재동;한기성
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1991년도 가을 학술발표회 논문집
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    • pp.11-14
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    • 1991
  • Apparent diffusion coefficients of Cl-ions through hardened cement paste(HCP), which were partly substituted blending materials, were determined. Also, pore solution was extracted from HCP which were immersed in NaCl solution, and Cl- concentration of the solution were analyzed. Partly substitution of pozzolanic materials considerably reduced the diffusion rate for Cl-ions and Cl- concentration of pore solution. Binding capacity of Cl- is related to the content of Al2O3 and pozzolanic reactivity.

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확산형 흡수식 냉장고에서 작동매체 충진조건이 증발온도에 미치는 영향 (Effects of Charging Conditions on Evaporating Temperature for Diffusion Absorption Refrigerator)

  • 김선창;김영률;백종현;박승상
    • 설비공학논문집
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    • 제15권10호
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    • pp.828-834
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    • 2003
  • A diffusion absorption refrigerator is a heat-generated refrigeration system. It uses a three-component working fluid consisting of the refrigerant (ammonia), the absorbent (water) and the auxiliary gas (hydrogen or helium). In this study, experimental investigations have been carried out to examine the effects of charging conditions of working fluids on the evaporating temperature for diffusion absorption refrigerator. Experimental parameters considered in the present experiments are charging concentration, solution charge and system pressure determined by auxiliary gas charged. As a result, in the charging condition of 35% of concentration and 20 kg$_{f}$cm$^2$ of system pressure, the system has the lowest evaporating temperature. It was found that there exists a minimum value of solution charge for the operation of diffusion absorption refrigerator.r.

Modeling of ion diffusion coefficient in saturated concrete

  • Zuo, Xiao-Bao;Sun, Wei;Yu, Cheng;Wan, Xu-Rong
    • Computers and Concrete
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    • 제7권5호
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    • pp.421-435
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    • 2010
  • This paper utilizes the modified Davis model and the mode coupling theory, as parts of the electrolyte solution theory, to investigate the diffusivity of the ion in concrete. Firstly, a computational model of the ion diffusion coefficient, which is associated with ion species, pore solution concentration, concrete mix parameters including water-cement ratio and cement volume fraction, and microstructure parameters such as the porosity and tortuosity, is proposed in the saturated concrete. Secondly, the experiments, on which the chloride diffusion coefficient is measured by the rapid chloride penetration test, have been carried out to investigate the validity of the proposed model. The results indicate that the chloride diffusion coefficient obtained by the proposed model is in agreement with the experimental result. Finally, numerical simulation has been completed to investigate the effects of the porosity, tortuosity, water-cement ratio, cement volume fraction and ion concentration in the pore solution on the ion diffusion coefficients. The results show that the ion diffusion coefficient in concrete increases with the porosity, water-cement ratio and cement volume fraction, while we see a decrease with the increasing of tortuosity. Meanwhile, the ion concentration produces more obvious effects on the diffusivity itself, but has almost no effects on the other ions.

적응성 유한체적법을 적용한 다차원 확산공정 모델링

  • 이준하;이흥주;변기량
    • 한국반도체및디스플레이장비학회:학술대회논문집
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    • 한국반도체및디스플레이장비학회 2004년도 춘계학술대회 발표 논문집
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    • pp.55-58
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    • 2004
  • This paper presents a 3-dimensional diffusion simulation with adaptive solution strategy. The developed diffusion simulator VLSIDIF-3 was designed to re-refine areas where difference of doping concentration between any of two nodes of each element is greater than tolerance and redo diffusion process until error is tolerable. Numerical experiment in low doping diffusion problem showed that this adaptive solution strategy is very efficient in both memory and time, and expected this scheme would be more powerful in complex diffusion model.

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DIFFUSION APPROXIMATION OF TIME DEPENDENT QUEUE SIZE DISTRIBUTION FOR $M^X$/$G^Y$/$_c$ SYSTEM$^1$

  • Choi, Bong-Dae;Shin, Yang-Woo
    • 대한수학회논문집
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    • 제10권2호
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    • pp.419-438
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    • 1995
  • We investigate a tansient diffusion approximation of queue size distribution in $M^{X}/G^{Y}/c$ system using the diffusion process with elementary return boundary. We choose an appropriate diffusion process which approxiamtes the queue size in the system and derive the transient solution of Kolmogorov forward equation of the diffusion process. We derive an approximation formula for the transient queue size distribution and mean queue size, and then obtain the stationary solution from the transient solution. Accuracy evalution is presented by comparing approximation results for the mean queue size with the exact results or simulation results numerically.

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AN APPROXIMATE ANALYTICAL SOLUTION OF A NONLINEAR HYDRO-THERMO COUPLED DIFFUSION EQUATION

  • Lee, Jeong-woo;Cho, Won-cheol
    • Water Engineering Research
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    • 제2권3호
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    • pp.187-196
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    • 2001
  • An approximate analytical solution of a nonlinear hydro-thermo coupled diffusion equation is derived using the dimensionless form of the equation and transformation method. To derive an analytical solution, it is drastically assumed that the product of first order derivatives in the non-dimensionalized governing equation has little influence on the solution of heat and moisture behavior problem. The validity of this drastic assumption is demonstrated. Some numerical simulation is performed to investigate the applicability of a derived approximate analytical solution. The results show a good agreement between analytical and numerical solutions. The proposed solution may provide a useful tool in the verification process of the numerical models. Also, the solution can be used for the analysis of one-dimensional coupled heat and moisture movements in unsaturated porous media.

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