• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1996년도 경북지부 결성 및 추계학술발표회 논문집
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• pp.58-62
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• 1996

To check the variability of the effective diffusion coefficient in the unsaturated porous soil media. a Monte Carlo simulation was done for the equation suggested by Millington and Quirk(1961). The results shows that the probability density function of D$_{c}$/D$_{o}$ is positively skewed. It means the chance of having less effective diffusion coefficient values in the soil media than mean value is high. Also, the distribution types of D$_{c}$/D$_{o}$ are about same regardless of assumed distribution types of input parameters.ers.ers.

• 대한수학회논문집
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• 제12권2호
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• pp.419-425
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• 1997

Consider a d-dimensional domain D that has finite Lebesque measure and a Dirichlet form which has discontinuous coefficient. Then the stationary Markov process corresponding to the given Dirichlet form is a semimartingale under suitable condition for D and the coefficient.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2001년도 총회 및 춘계학술발표회
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• pp.89-92
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• 2001

This study aims at investigating the relationship between dispersion coefficient ratio to molecular diffusion coefficient (D$_{l}$ /D$_{m}$) and Peclet number (Pe) for multi-solute system in non-Darcian flow regime. Existing understanding on solute dispersion is primarily derived from one-solute system in Darcian flow regime. We found that solute dispersion in rock fractures can be characterized by the mechanism of both macrodispersion and Taylor dispersion, even for non-Darcian f]ow domain. For the Darcian flow regime even different solutes lead to the same D$_{l}$ /D$_{m}$ at same Pe. However, as the flow becomes non-Darcian, solute with a higher molecular diffusion coefficient result in higher D$_{l}$ /D$_{m}$ at tile same Pe than that with a lower diffusion coefficient.cient.

• International Journal of Concrete Structures and Materials
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• 제10권1호
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• pp.61-73
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• 2016

In predicating the probability distribution of chloride diffusion coefficient of recycled aggregate concrete ($D_{RAC}$), the morphological characteristics of three phases, i.e., the old attached mortar, the natural aggregate and the new mortar, should all be taken into account. The present paper attempts to develop a probability density evolution method (PDEM) to achieve this. After verifying the derived PDEM results with experimental results, the effects of old attached mortar to the $D_{RAC}$ are examined in a quantitative manner. It is found that (1) the variation of the attached mortar content is much sensitive to $D_{RAC}$; (2) given the probability distribution of the content and chloride diffusion coefficient of old mortar, the probability distribution of DRAC can be analysed based on the PDEM; and (3) the critical chloride diffusion coefficient at a certain assurance rate can be obtained by the PDEM. The analysis results of this investigation will be valuable to the durability design for RAC.

• 폴리머
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• 제24권2호
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• pp.194-200
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• 2000

폴리이미드/N-methyl-2-pyrrolidone(NMP)계에서 의 상호확산계수를 Vrentas-Duda의 hole free volume 이론을 이용하여 나타내었다. NMP와 폴리이미드의 기초 물성과 그룹기여이론을 이용하여 상호확산계수식 내의 여러 자유부피인자들을 결정할 수 있었으며 폴리이미드가 NMP에 팽윤되는 거동을 실험으로 측정함으로써 지수전확산계수인 D$_{0}$를 구할 수 있었다. 결정된 확산계수식을 이용한 이론적 팽윤거동이 온도에 따른 폴리이미드/NMP 계의 실험적 거동을 잘 묘사함을 알 수 있었다.다.

• Computers and Concrete
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• 제8권3호
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• pp.343-355
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• 2011

This paper presented the model to predict the chloride diffusion coefficient in tension zone of plain concrete under flexural cyclic load. The fictitious crack based analytical model was used together with the stress degradation law in cracked zone to predict crack growth of plain concrete beams under flexural cyclic load. Then, under cyclic load, the chloride diffusion, in the steady state and one dimensional regime, through the tension zone of the plain concrete beam, in which microcracks were formed by a large number of cycles, was simulated with assumptions of continuously straight crack and uniform-size crack. The numerical analysis in terms of the chloride diffusion coefficient, $D_{tot}$, normalized $D_{tot}$, crack width and crack length was issued as a function of the load cycle, N, and load level, SR. The nonlinear model as regarding with the chloride diffusion coefficient in tension zone and the load level was proposed. According to this model, the chloride diffusion increases with increasing load level. The predictions using model fit well with experimental data when we adopted suitable crack density and tortuosity parameter.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1997년도 총회 및 춘계 학술발표회 논문집
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• pp.79-82
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• 1997

토양내에서 오염유기물질이 불포화토양내에 유입될 때의 dispersion coefficient를 adsorption과 desorption과정에 대해 알아보았다. apparent dispersion coefficient를 측정하기 위해 일상적인 상대습도(46%)조건에서 parametric analysis를 행하였다. 실험에 사용된 토양은 fine sand와 silt-clay혼합시료였고, 흐름방향은 상향과 하향으로 하였다. 그리고, Freon gas를adsorbing solute로 사용하였다. 오염물질로는 DCM, TCE, DCB를 사용하였다. 분석을 위해서 linear와 probability scale의 breakthrough curve를 사용하였다. 공기에서의 diffusion coefficient의 예측을 위하여 Graham's law를 계산에 사용하였고, DCM diffusion coefficient는 0.098$\textrm{cm}^2$/s로 계산되었다. 연구결과, adsorption과 desorption의 속도는 차이가 있는 것으로 나타났으며, diffusion이 flow regime을 좌우하는 것으로 나타났다. 그리고, desorption에서의 D$^{a}$ D$^{o}$ 는 1보다 클수도 있다. 또한, dispersion은 silt-clay혼합시료에서의 속도와 함께 증가한다. dispersion은 Freon의 sorption방향에 크게 의존한다.

• 한국운동역학회지
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• 제17권2호
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• pp.83-91
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• 2007

This experiment studied the change in a human's control of his or her static posture by analyzing the stabilogram diffusion and, by using the said study, evaluated the control ability of different groups with different experiences. The postures had a rising requirement of heel-rise according to three conditions: heel-toe, ball, toe; the groups were divided into dance major student and non-dance majors. The results of the critical points according to posture did not show a direct relation with the change in postures that had a rising requirement of heel-rise. The diffusion coefficient(D) had greater stochastic activity for short-term regions that utilize open-loop controls without feedback than for long-term regions that used closed-loop controls with feedback to maintain balance. The directional results of the body undergoing disturbance showed that A/P direction's diffusion coefficient (D) was larger than that of M/L direction. Both feet's planar diffusion coefficients were a linear combination of the diffusion coefficients calculated for the x and y axis. In studying the different abilities to control posture between a dance major student and a non-dance majors, a comparison of open-loop control's diffusion coefficient(D) was effective, and dance major student had superior control ability to that of non-dance majors.

• International Journal of Railway
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• 제4권4호
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• pp.86-92
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• 2011

Chloride ion diffusion at the corner of rectangular-shaped concrete structures is presented. At the corner of rectangular-shaped concrete, chloride ion diffusion is in two-dimensional process. Chloride ions accumulate from two orthogonal directions, so that corrosion-free life of concrete structures is significantly reduced. A numerical procedure based on finite element method is used to solve the two-dimensional diffusion process. Orthotropic property of diffusion coefficient of concrete is considered and chloride ion profile obtained from numerical analysis is used to produce transformed diffusion coefficient. Comparisons of experimental data are also carried out to show the reliability of proposed numerical analysis. As a result of two-dimensional chloride diffusion, corrosion-free life of concrete structure for railway is estimated using probability of corrosion initiation. In addition, monographs that produces transformed diffusion coefficient and corrosion-free life of concrete structure are made for maintenance purpose.

• Applied Science and Convergence Technology
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• 제23권6호
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• pp.371-375
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• 2014

Diffusion coefficient of Fe in polycrystalline host ZnSe as a mid-IR gain medium has been measured in the annealing temperature ranges of 850 to $950^{\circ}C$. The synthesis of the samples was carried out in quartz ampoule in which the Fe thin film deposited by physical vapor evaporation method on the ZnSe. One can realize that the diffusion coefficient strongly depends on the surface active surfactants through the cleaning process and the substrate temperature during the thin film deposition leading to $2.04{\times}10^{-9}cm^2/s$ for $Fe^{2+}:ZnSe$. The Annealing temperature dependence of the Fe ions diffusion in ZnSe was used to evaluate the activation energy, $E_a$=1.39 eV for diffusion and the pre-exponential factor $D_0$ of $13.5cm^2/s$.