• 전기학회논문지P
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• 제63권4호
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• pp.317-321
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• 2014

This paper describes the information for quantitative simulation of weakly ionized plasma. We must grasp the meaning of the plasma state condition to utilize engineering application and to understand materials of plasma state. Using quantitative simulations of weakly ionized plasma, we can analyze gas characteristic. In this paper, the electron Ionization and diffusion Coefficients in $CH_4$ has been analysed over the E/N range 0.1~300[Td], at the 300[$^{\circ}K$] by the two term approximation Boltzmann equation method and Monte Carlo Simulation. Boltzmann equation method has also been used to predict swarm parameter using the same cross sections as input. The behavior of electron has been calculated to give swarm parameter for the electron energy distribution function has been analysed in $CH_4$ at E/N=10, 100 for a case of the equilibrium region in the mean energy. A set of electron collision cross section has been assembled and used in Monte Carlo simulation to predict values of swarm parameters. The result of Boltzmann equation and Monte Carlo Simulation has been compared with experimental data by Ohmori, Lucas and Carter. The swarm parameter from the swarm study are expected to sever as a critical test of current theories of low energy scattering by atoms and molecules.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1336-1340
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• 2011

Molecular dynamics simulations have been performed to investigate the transport properties of self-diffusion coefficients in the penetrable-sphere model system. The resulting simulation data for the product of the packing fraction and the self-diffusion coefficient exhibit a transition from an increasing function of density in lower repulsive systems, where the soft-type collisions are dominant, to a decreasing function in higher repulsive systems, where most particle collisions are the hard-type reflections due to the low-penetrability effects. A modified Enskog-like equation implemented by the effective packing fraction with the mean-field energy correction is also proposed, and this heuristic approximation yields a reasonably good result even in systems of high densities and high repulsive energy barriers.

• Advances in environmental research
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• 제4권3호
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• pp.183-196
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• 2015

Migration of leachate generated through embankment of construction waste soil (CWS) in low-lying areas was studied through physical and chemical analysis. A leachate solution containing soluble cations from CWS was found to have a pH above 9.0. To determine the distribution coefficients in the alkali solution, column and migration tests were conducted in the laboratory. The physical and chemical properties of CWS satisfied environmental soil criteria; however, the pH was high. The effective diffusion coefficients for CWS ions fell within the range of $0.725-3.3{\times}10^{-6}cm^2/s$. Properties of pore water and the amount of undissolved gas in pore water influenced advection-diffusion behavior. Contaminants migrating from CWS exhibited time-dependent concentration profiles and an advective component of transport. Thus, the transport equations for CWS contaminant concentrations satisfied the differential equations in accordance with Fick's 2nd law. Therefore, the migration of the contaminant plume when the landfilling CWS reaches water table can be predicted based on pH using the effective diffusion coefficient determined in a laboratory test.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.281-284
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• 2003

When concrete structures are exposed under marine condition for a long time, the steel in concrete is corroded due to the ingression of chlorides in the sea water. Because the damages of corrosion resulting from the chloride ion are very serious, many research have been performed. In this study, it was experimentally investigated that the mechanical and diffusion characteristics of concrete substituted with ordinary portland cement, silica fume and blast furnace slag to investigate the chloride ingress characteristics with concrete quality. Chloride diffusion coefficients in concrete shows increasing tendency as w/c ratio increase. Also test results indicate that blend of admixture become lower chloride diffusion coefficients in concrete as compared with normal concrete.

• Nuclear Engineering and Technology
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• 제47권5호
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• pp.588-595
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• 2015

This study presents an effective method for additional recovery of residual actinides in liquid electrodes after the electrowinning process of pyroprocessing. The major distinctive feature of this method is a reactor with multiple reaction cells separated by partition walls in order to improve the recovery yield, thereby using the interelement difference in diffusion coefficients within the liquid electrode and controlling the selectivity and purity of element recovery. Through an example of numerical simulation of the diffusion scenarios of individual elements, we verified that the proposed method could effectively separate the actinides (U and Pu) and rare-earth elements contained in liquid cadmium. We performed a five-step consecutive recovery process using a simplified conceptual reaction cell and recovered 58% of the initial amount of actinides (U + Pu) in high purity (${\geq}99%$).

• 한국세라믹학회지
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• 제20권2호
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• pp.129-134
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• 1983

MgO.$Al_2O_3$ polycrstalline spinel powder was subjected to vaporization over the temperature range of 1150-130$0^{\circ}C$ under H2 atmosphere. Diffusion coefficient of oxygen ion through the spinel were calculated using the measure vaporization rates as follows : D=28.4 exp(-901500/RT) Reference data of the vaporization rates of MgO.$8Al_2O_3$ single crystal spinel were applied to the vaporiza-tion model proposed in this study and were calculated to give the oxygen ion diffusion coefficients over the tempera-ture 1700-195$0^{\circ}C$. The obtained diffusion coefficients are as follows: $D=3.20{\times}106$ exp(-155600/RT)

• Korean Chemical Engineering Research
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• 제57권3호
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• pp.358-367
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• 2019

본 연구에서는 활성탄과 제올라이트 13X에 대한 벤젠, 톨루엔 및 자일렌 증기의 기체 흡착평형과 입자내부의 확산 특성을 조사하였다. 압력 범위 0.01~0.07 bar 사이에서 흡착온도를 각각 293.15 K, 303.15 K, 313.15 K로 변화시키면서 정적흡착실험을 수행하였다. 흡착평형은 Langmuir, Freundlich 및 Toth 흡착등온식을 적용하여 해석하였다. 그 결과 표준편차는 Langmuir 식과 Toth 식에서 낮았으며, Freundlich 식에서 표준편차가 가장 컸다. Langmuir 상수를 Arrhenius 식의 형태로 표현하여 구한 흡착에너지는 5.26~31.0 kJ/mol 정도로 물리흡착의 특성을 나타냈다. 흡착제에 따른 흡착질의 최대 흡착량은 활성탄의 경우 벤젠, 톨루엔, 자일렌으로 갈수록 최대 흡착량이 감소했으며, 제올라이트 13X의 경우 활성탄과는 반대로 최대 흡착량이 자일렌에서 가장 크고 벤젠에서 가장 작게 나타났다. 벤젠, 톨루엔 및 자일렌 증기의 유효확산계수는 약 $10^{-5}{\sim}10^{-4}cm^2/s$ 정도로 나타났으며, 압력이 증가함에 따라 값이 작아지고 온도가 증가함에 따라 값이 커지는 경향을 보였다. 온도와 압력의 변화에 따른 유효확산계수의 변화는 활성탄보다 제올라이트 13X에서 민감하게 나타났다. 따라서 압력 변동이 급격하게 발생하는 흡착공정에서 제올라이트 13X를 사용할 경우 정밀한 동적거동 예측을 위해서는 확산계수를 압력에 대한 함수로 표현하는 것이 필요하다.

• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.2158-2160
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• 2009

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.775-778
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• 1999

Accelerated chloride diffusion tests were carried out to estimate the chloride diffusion coefficient of concrete using ordinary portland cement, low heat belite-rich portland cement, and sulphate resistant portland cement. Concrete using low heat belite-rich portland cement showed a high diffusion coefficient due to delayed hydration of low heat belite rich portland cement, while the diffusion coefficients of concrete using sulphate resistant portland cement and ordinary portland cement were low.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.669-674
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• 2003

The purpose of this study is to identify the diffusion coefficients of carbon dioxide for various concrete mixtures. The test results indicate that the diffusion coefficient increases with the increase of water-cement ratio. The diffusion coefficient decreases with the increase of relative humidity at the same water-cement ratio. The diffusion of carbon dioxide reached the steady-state within about five hours after exposure. It was found that the diffusion coefficient of cement paste is larger then that of concrete or mortar. The quantitative values of diffusivity of carbon dioxide in this study will allow more realistic assessment of carbonation depth in concrete structures.