• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.9 no.1
• /
• pp.33-40
• /
• 2011

In the compacted bentonite containing $Ag_2O$, the transport of iodide ion was investigated by Through-diffusion method. It is confirmed that Iodide ion is transported by diffusion process in the compacted bentonite containing $Ag_2O$ as well as in the compacted bentonite without $Ag_2O$. However, the lag-time of iodide ion in the compacted bentonite containing $Ag_2O$ is larger than that in the compacted bentonite without $Ag_2O$. The increase of the lag-time was observed in pure iodide ion solution and also in 0.1M NaCl-iodide ion solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing $Ag_2O$ has lower value than that in the compacted bentonite without $Ag_2O$. The effect of $Ag_2O$ on the effective diffusion coefficient was not clearly investigated in the compacted bentonite containing $Ag_2O$ while the values of effective diffusion coefficient of iodide ion in the compacted bentonite without $Ag_2O$ obtained in this study were similar to those in the compacted bentonite reported in the literature.

• Computers and Concrete
• /
• v.3 no.2_3
• /
• pp.103-122
• /
• 2006

Drying shrinkage of concrete occurs due to the loss of moisture and thus, it is controlled by moisture diffusion process. On the other hand, the shrinkage causes cracking of concrete and affects its moisture diffusion properties. Therefore, moisture diffusion and drying shrinkage are two coupled processes and their interactive effect is important for the durability of concrete structures. In this paper, the two material parameters in the moisture diffusion equation, i.e., the moisture capacity and humidity diffusivity, are modified by two different methods to include the effect of drying shrinkage on the moisture diffusion. The effect of drying shrinkage on the humidity diffusivity is introduced by the scalar damage parameter. The effect of drying shrinkage on the moisture capacity is evaluated by an analytical model based on non-equilibrium thermodynamics and minimum potential energy principle for a two-phase composite. The mechanical part of drying shrinkage is modeled as an elastoplastic damage problem. The coupled problem of moisture diffusion and drying shrinkage is solved using a finite element method. The present model can predict that the drying shrinkage accelerates the moisture diffusion in concrete, and in turn, the accelerated drying process increases the shrinkage strain. The coupling effects are demonstrated by a numerical example.

• Asian Journal of Atmospheric Environment
• /
• v.2 no.1
• /
• pp.1-13
• /
• 2008

A numerical simulation method has been developed to predict atmospheric flow and stack gas diffusion using a calculation domain of several km around a stack under complex terrain conditions containing buildings. The turbulence closure technique using a modified k-$\varepsilon$-type model under a non hydrostatic assumption was used for the flow calculation, and some of the calculation grids near the ground were treated as buildings using a terrain-following coordinate system. Stack gas diffusion was predicted using the Lagrangian particle model, that is, the stack gas was represented by the trajectories of released particles. The numerical model was applied separately to the flow and stack gas diffusion around a cubical building and to a two-dimensional ridge in this study, before being applied to an actual terrain containing buildings in our next study. The calculated flow and stack gas diffusion results were compared with those obtained by wind tunnel experiments, and the features of flow and stack gas diffusion, such as the increase in turbulent kinetic energy and the plume spreads of the stack gas behind the building and ridge, were reproduced by both calculations and wind tunnel experiments. Furthermore, the calculated profiles of the mean velocity, turbulent kinetic energy and concentration of the stack gas around the cubical building and the ridge showed good agreement with those of wind tunnel experiments.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.816-819
• /
• 1992

Binary compound semiconductor InSb crystal which has direct-transition energy gap (0.17 ev) grown by vertical Bridgman method, then the electric-magnetic and optical properties of InSb crystal were surveyed. The growth rate of the crystals was 1mm/hr and the lattice constant $a_\circ$ of the grown crystal was 6.4863$\AA$. The electrical properties were examined by the Hall effect measurement with the van der Pauw method in the temperature range of 70$\sim$300K, magnetic field range of 500$\sim$10000 gauss. The undoped InSb crystal was n-type, the concentration and the electron mobility were 2$\sim$6 ${\times}$ $10^{16}$$\textrm{cm}^{-3}$ and carrier mobility was 6$\sim$2${\times}$$10^{4}$$cm^{2}$/v.sec at 300K, respectively. The carrier mobility was decreased with $T^{-1/2}$ due to the lattice scattering above 100K, and decreased by impurity scattering below100K. The magnetoresistance was increased 190% at 9000 gauss as compared with non-appliced magnetic field and the magnetoresistance was increased with increasing the magnetic field. Also, the Hall voltage was increased with increasing the magnetic field and decreasing the thickness of sample. The optical energy band gap of InSb at room temperature determined using the IR spectrometer was 0.167eV. The diffusion depth of Zn into InSb proportionally increased with the square root of diffusion time and the activation energy for Zn diffusion was 0.67eV. The temperature dependence of diffusion coefficient was $D=4.25{\times}10^{-3}$exp (-0.67/$K_BT$).

• Textile Coloration and Finishing
• /
• v.12 no.1
• /
• pp.52-60
• /
• 2000

In the prior studies, we reported that the dye uptakes of C. I. Disperse Violet 1 on polyester fiber in hexane and cyclohexane were higher than those in the other solvents, as the number of carbon atoms of alkanes decreased, the dye uptake increased, and the logarithmic plot of the dye uptakes vs. the solubilities of the dye showed that the dye uptakes are inversely proportional to the solubilities. In this study, for Interpretation of dyeing behavior of C. I. Disperse Violet 1 on polyester in alkanes, the thremodynamic parameters of dyeing, such as standard affnity, heat of dyeing(enthalpy change), entropy change, diffusion coefficient, and activation energy of diffusion, were obtained from isotherms and dyeing rates at different temperature. As the number of carbon atoms of alkanes increased, the standard affinity decreased, but the heat of dyeing(enthalpy change) and the entropy change showed larger negative values. These results mean that as the number of carbon atoms of alkanes increases, the dye uptake decreases, but both the fraction of the dye molecules dyed at relatively highly aligned or compact region of polyester fiber and the regularity of dye aggregates in the fiber become increased. As the number of carbon atoms of alkanes increased, the diffusion coefficient decreased, but the activation energy of diffusion increased. In the alkane of larger number of carbon atoms, because the solubility of the dye is higher, the desorption rate of the dye is faster and the diffusion coefficient is smaller than those in the smaller alkanes. But the energy required to separate the dye molecules from the alkane molecules is much higher because the interaction between the alkane molecule and the dye molecule become strong with the number of carbon atoms.

• Current Photovoltaic Research
• /
• v.9 no.3
• /
• pp.96-105
• /
• 2021

Even though above 22% efficiencies have been reported in Cd-free Cu(In,Ga)Se₂ (CIGS) solar cell with Zn-containing buffers, the efficiencies with Zn-containing buffers, in general, are well below 20%. One of the reasons is Zn diffusion from the Zn-containing buffer layer to CIGS film during buffer growth. To avoid the degradation, it is necessary to prevent the diffusion of Zn atoms from Zn-containing buffer to CIGS film. For the purpose, we characterized an In₂Se₃ film as a possible diffusion barrier layer because In₂Se₃ has no Zn component. It was found that an In₂Se₃ layer grown at 300℃ was very effective in preventing Zn diffusion from a Zn-containing buffer. Also, the In₂Se₃ had a large potential barrier in the valence band at the In₂Se₃/CIGS interface. Therefore, In₂Se₃ passivation has the potential to achieve a super-high efficiency in CIGS solar cells that employ Cd-free ALD processed buffers containing Zn.

• Journal of the Korean Ceramic Society
• /
• v.25 no.4
• /
• pp.390-398
• /
• 1988

Effects of atmospheres and adidtives on the grain growth of TiO2 ceramics were investigated. In the range of 1300~140$0^{\circ}C$, grain growth was increased in CO2 as compared with O2 atmosphere and the grain boundary migration activation energy was lower than the diffusion activation energy of oxygen ion in TiO2. Also, in the case of addition of oxides, the grain growth was increased by oxides acting as a acceptor andinhibited by oxides acting as a donor. From the above results, when the oxygen vacancy concentration was increased, the intrinsic grain boundary mobility was increased and the pore drag force was decreased due to the rapid densification. Also it seems that the pore was migrated by the surface diffusion rather than lattice diffusion.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.379-381
• /
• 2009

The simulation model for metal-supported Solid Oxide Fuel Cell(SOFC) is developed in this study. Open circuit voltage is calculated using Nernst equation and Gibbs free energy is required by thermodynamic. The exchange current densities are compared with experimental results since exchange current density is most effective factor for the activation loss. Liu's study is used for the exchange current density of cathode, BSCF, and Koide's result is applied for the exchange current density of anode, Ni/YSZ. For the ohmic loss, ionic conductivity of YSZ is described from Kilner's mode and the data are compared with Wanzenberg's experimental data. Diffusivity is an important factor for the mass transfer through the porous medium. Both binary diffusion and Knudsen diffusion are considered as the diffusion mechanism. For validation, simulation results at this work are compared with our experimental results.

• Journal of Electrochemical Science and Technology
• /
• v.9 no.2
• /
• pp.99-108
• /
• 2018

Proton exchange membrane (PEM) water electrolysis systems offer several advantages over traditional technologies including higher energy efficiency, higher production rates, and more compact design. In this study, all the experiments were performed with a self-designed PEM electrolyser operated at 1 atm and $25^{\circ}C$. Two types of electrolyte were used: (i) potassium hydroxide (KOH), and (ii) sulfuric acid ($H_2SO_4$). In the experiments, the voltage, current, and time were measured. The concentration of the electrolyte significantly affected the electrolyser performance. Overall the best case was with 15 wt% $H_2SO_4$ at the anode channel and 20 wt% at the cathode channel with. In addition, increasing the difference in concentration of the sulfuric acid had an effect on the diffusion. The diffusion flux became larger when the difference in concentration became larger, increasing electrolyser efficiency without the addition of extra energy.

• Korean Journal of Hydrosciences
• /
• v.8
• /
• pp.111-123
• /
• 1997

A one-dimensional eddy diffusion model and a mixed-layer model are developed and applied to simulate the vertical temperature profiles in lakes. Also the running result of each method are compared and analyzed. In an eddy diffusion model, molecular diffusivity is neglected and eddy diffusivity which does not need lake-specific fitting parameter and constant lake's level are applied. The heat exchanges at the water surface and the bottom are formulated by the energy balance and zero energy gradient, respectively. In a mixed-layer model, two layers approach which has a constant thickness is adopted. The application of these models which use explicit finite difference and Runge-Kutta methods respectively demonstrates that the models simulate water temperatures efficiently.