• Title, Summary, Keyword: diffusion coefficient

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Evaluation of Diffusion Property of Latex Modified Concrete (LMC(Latex Modified Concrete)의 염소이온 확산 특성)

  • Park, Sung-Ki;Won, Jong-Pil;Park, Chan-Gi
    • Journal of The Korean Society of Agricultural Engineers
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    • v.50 no.4
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    • pp.27-37
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    • 2008
  • It is most serious problem which is various occurs from the agricultural concrete structure and off shore concrete structure the problem which it comes to think is deterioration of the concrete which is caused with the corrosion of the reinforcing steel which is caused by with permeation of the water and the sea water. Specially the off shore concrete structure has been deteriorated by the steel reinforcement corrosion. The latex modified concrete(LMC) was adds latex in the plain concrete as the latex has increase the durability of concrete. This study were accomplished to the estimate the diffusion coefficient of LMC, and the time dependent constants of diffusion. The average chloride diffusion coefficient was estimated. Also, the average chloride diffusion coefficient was compared with diffusion coefficient test results of 28 curing days. The test results indicated that the average chloride diffusion coefficient could closely estimate the test results of the diffusion coefficient test results of 28 curing days.

Diffusion of Progesterone in Polyacrylamide Gel (Polyacrylamide gel에서 Progesterone의 확산 거동)

  • 김명희;김말남;민병례
    • Korean Journal of Microbiology
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    • v.28 no.3
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    • pp.278-282
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    • 1990
  • Diffusion and partition of progesterone into the polyacrylamide gel was examined. Diffusion coefficient of progesterone decreased down to an asymptotic value as the concentration of the organic solvents in the diffusing medium increased. However the partition coefficient diminished steadily. Crosslinking density in the gel didn't affected the diffusion coefficient considerably but lowered the partition coefficient due to the contraction of pore volume of the gel. Progesterone showed higher diffusion coefficient as well as partition coefficient in the polyurethane than in the polyacrylamide gel, which seems to be ascribed to the difference in hydrophobicity, pore volume and pore size of the polymer matrix.

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Effective Diffusion Coefficient in the Porous Media (다공성 미디아에 있어서 유효확산계수)

  • Jeehyeong Khim
    • Journal of Korea Soil Environment Society
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    • v.1 no.2
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    • pp.83-90
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    • 1996
  • A diffusion process is often the main mechanism of soil gas/vapor movement in the vadose zone. The diffusion coefficients in the porous soil media are different from those in the free air phase by the reduction of available area for diffusion, tortuous diffusion path and variable cross section area along the diffusion path. To take account those effects of the diffusion process in the porous media, usually the terms of effective diffusion coefficient and tortuosity are have been used. However, as there are many differents definitions for the tortuosity, when the term of tortuosity is used, it is necessary to examine it throughly. Moreover, there are many different equations for the effective diffusion coefficient according to the investigators and the differences in the values of effective diffusion coefficients between the equations are not insignificant, the selection of the equation should be done with caution. In this paper, the different definitions of effective diffusion coefficient are examined and discussed. As well as definitions, the lots of availabe models for the diffusion coefficient in terms of porosities are compared. Also, the constrictiviy which explains the effect of cross sectional area change over the diffusion path was discussed.

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Prediction of Lithium Diffusion Coefficient and Rate Performance by using the Discharge Curves of LiFePO4 Materials

  • Yu, Seung-Ho;Park, Chang-Kyoo;Jang, Ho;Shin, Chee-Burm;Cho, Won-Il
    • Bulletin of the Korean Chemical Society
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    • v.32 no.3
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    • pp.852-856
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    • 2011
  • The lithium ion diffusion coefficients of bare, carbon-coated and Cr-doped $LiFePO_4$ were obtained by fitting the discharge curves of each half cell with Li metal anode. Diffusion losses at discharge curves were acquired with experiment data and fitted to equations. Theoretically fitted equations showed good agreement with experimental results. Moreover, theoretical equations are able to predict lithium diffusion coefficient and discharge curves at various discharge rates. The obtained diffusion coefficients were similar to the true diffusion coefficient of phase transformation electrodes. Lithium ion diffusion is one of main factors that determine voltage drop in a half cell with $LiFePO_4$ cathode and Li metal anode. The high diffusion coefficient of carbon-coated and Cr-doped $LiFePO_4$ resulted in better performance at the discharge process. The performance at high discharge rate was improved much as diffusion coefficient increased.

A Study on Chloride ion Diffusion in Cracked Concrete (균열이 발생한 콘크리트에서의 염화물 이온 확산에 관한 연구)

  • 배상운;박상순;변근주;송하원
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.677-682
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    • 2001
  • In this study, a method to evaluate diffusion coefficient of chloride ion in cracked concrete is proposed. For cracked concrete having either anisotropic or isotropic crack network, each crack of saturated concrete is considered as a V shape crack, and an effective diffusion coefficient is expressed with diffusion coefficients of cracked part and noncracked part and a so-called crack spacing factor. A comparison with experimental results shows that the diffusion coefficient for cracked concrete is accurately predicted by the effective diffusion coefficient. Prediction results also show that the cracks in concrete markedly change the diffusion properties and accelerate penetration of drifting species. The method in this paper can be effectively used to consider the effect of cracks on concrete diffusion coefficient of cracked concrete.

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Experimental Study on the Relationship between Time-Dependent Chloride Diffusion Coefficient and Compressive Strength (시간의존성 염화물 확산계수와 압축강도 상관성에 대한 실험적 연구)

  • Lee, Seung-Hoon;Kwon, Seung-Jun
    • Journal of the Korea Concrete Institute
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    • v.24 no.6
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    • pp.715-726
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    • 2012
  • Since strength and diffusion coefficient of concrete, representative concrete properties that in change with age, the time effect must be considered in the analysis of chloride penetration. In this study, an evaluation of correlation between accelerated diffusion coefficient, apparent diffusion coefficient, and compressive strength in high performance concrete with various mineral admixtures such as ground granulated blast furnace slag, fly ash, and silica fume was performed. For this work, thirty mix proportions were prepared. Accelerated diffusion coefficients at the age of 28, 91, 180, and 270 days were evaluated. For apparent diffusion coefficient, submerging test for 6 months was performed. For evaluation of compressive strength with ages, the compressive strength test was carried out at an age of 7, 28, 91, 180 days. The results of accelerated diffusion coefficient, apparent diffusion coefficient, and strength were compared, and the correlation was analyzed considering time dependency. From this study, linear relationship between accelerated diffusion and apparent diffusion coefficient were obtained regardless of concrete age. The linear relations were also observed in strength-accelerated diffusion coefficient and strength-apparent diffusion coefficient regardless of concrete age.

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

  • 조봉석;김갑수;김재환;김용로;권영진;김무한
    • Proceedings of the Korea Concrete Institute Conference
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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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Comparison Study on Electric Acceleration Test Method for Estimation of Chloride Diffusion Coefficient (염화물 확산 평가를 위한 전기적 실험법의 비교 연구)

  • Choi, Yoon-Suk;Choi, Sung-Ha;Kim, Myung-Yu;Yang, Eun-Ik;Yi, Seong-Tae
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.257-260
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    • 2005
  • A general electric acceleration testing method for estimation of chloride diffusion coefficient is RCPT and CTH. Also, this testing methods have merit that reduce the testing time. In this paper, an experimental study is executed to investigate the effect of testing method on coefficient of chloride diffusion and it is compared with RCPT and CTH. According to this experiment results, W/C ratio and testing method influence chloride diffusion coefficient of concrete. As W/C ratio is increased, diffusion coefficient in concrete is also increased. Diffusion coefficient obtained by each testing method show the different values. However, there is no remarkable difference between the two testing method.

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Enhanced vertical diffusion coefficient at upper layer of suspended sediment concentration profile

  • Kim, Hyoseob;Jang, Changhwan;Lhm, Namjae
    • Ocean Systems Engineering
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    • v.2 no.4
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    • pp.289-295
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    • 2012
  • Assume fluid eddy viscosity in the vertical direction is parabolic. Sediment particles diffuse with the given fluid eddy viscosity. However, when the vertical diffusion coefficient profile is computed from the suspended sediment concentration profile, the coefficient shows lager values than the fluid mixing coefficient values. This trend was explained by using two sizes of sediment particles. When fine sediment particles like wash load are added in water column the sediment mixing coefficient looks much larger than the fluid mixing coefficient.

An innovative method for determining the diffusion coefficient of product nuclide

  • Chen, Chih-Lung;Wang, Tsing-Hai
    • Nuclear Engineering and Technology
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    • v.49 no.5
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    • pp.1019-1030
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    • 2017
  • Diffusion is a crucial mechanism that regulates the migration of radioactive nuclides. In this study, an innovative numerical method was developed to simultaneously calculate the diffusion coefficient of both parent and, afterward, series daughter nuclides in a sequentially reactive through-diffusion model. Two constructed scenarios, a serial reaction (RN_1 ${\rightarrow}$ RN_2 ${\rightarrow}$ RN_3) and a parallel reaction (RN_1 ${\rightarrow}$ RN_2A + RN_2B), were proposed and calculated for verification. First, the accuracy of the proposed three-member reaction equations was validated using several default numerical experiments. Second, by applying the validated numerical experimental concentration variation data, the as-determined diffusion coefficient of the product nuclide was observed to be identical to the default data. The results demonstrate the validity of the proposed method. The significance of the proposed numerical method will be particularly powerful in determining the diffusion coefficients of systems with extremely thin specimens, long periods of diffusion time, and parent nuclides with fast decay constants.