• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.973-976
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• 2008

Recently, it is increasingly reported that the deterioration of concrete structure under marine environments is due to diffusion and penetration of chloride ions. It is very important to estimate the diffusion coefficient of chloride ion in concrete. Estimation methods of chloride diffusivity by concentration difference is time-consuming. Therefore, chloride diffusivity of concrete is mainly conducted by electrically accelerated method, which is accelerating the movement of chloride ion by potential difference. However, there has not been any proper method for field quality control to closely determine the diffusion coefficient of chloride ion through accelerated tests using potential difference. In this paper, the various test methods for determination of chloride diffusion coefficient in concrete were investigated through comparison accelerated tests. From the results of estimated diffusion coefficient of chloride ion, relationship between the ponding test and acceleration test was examined.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.409-412
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• 2008

This study were evaluated the corrosion threshold reached at steel reinforcement in latex modified concrete(LMC). Accelerated testing was accomplished to the evalate the diffusion coefficient of LMC mix, and the time dependent constants of diffusion. Also, average chloride diffusion coefficient was estimated. From the average chloride ion diffusion coefficient, the time which critical chloride contents at depth of reinforcement steel was estimated. Test results indicated that the corrosion threshold reached at reinforcement in LMC are effected on the mix proportion factor including latex content, and water-cement ratio.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.780-785
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• 2005

To investigate the microcrack healing behavior of $Si_3N_4-20wt\%SiC-8wt\%Y_2O_3$ composite ceramics(SNCY8), we observe the crack length evolution a! the time of 20, 40, 60 minutes with in-situ optical microscopy by varying healing temperature of $800\~1200^{\circ}C$. Crack healing obviously occurred as heating temperature and time increased. We proposed a simple model of effective diffusion based on the crack length evolution with healing condition, and determined the effective diffusion coefficient as Our result implies that we may predict the healing ability quantitatively with temperature and time in structural ceramics through the effective diffusion coefficient model.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.469-472
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• 2012

Intensity modulated photocurrent spectroscopy and intensity modulated photovoltage spectroscopy were investigated to measure the dynamic response of charge transfer and recombination in the standard, $TiCl_4$-treated and the combined scattering layer electrode dye-sensitized solar cells (DSSCs). IMPS and IMVS provided transit time ($\tau_n$), lifetime ($\tau_r$), diffusion coefficient ($D_n$) and effective diffusion length ($L_n$). These expressions are derived that generation, collection, and recombination of electrons in a thin layer nanocrystalline DSSC under conditions of steady illumination and with a superimposed small amplitude modulation. In this experimental, IMPS/IMVS showed that the main effect of $TiCl_4$ treatment is to suppress the recombination of photogenerated electrons, thereby extending their lifetime. And the Diffusion coefficient of combined scattering layer electrode is $6.10{\times}10^{-6}$ higher than that of the others, resulting in longer diffusion length.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.557-562
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• 2004

We discuss diffusion of particles in turbulent flows. In hydrodynamic turbulence, it is well known that distance between two particles imbedded in a turbulent flow exhibits a random walk behavior. The corresponding diffusion coefficient is ${\~}$ ${\upsilon}_{inj}{\iota}_{turb}$, where ${\upsilon}_{inj}$ is the amplitude of the turbulent velocity and ${\iota}_{turb}$ is the scale of the turbulent motions. It Is not clear whether or not we can use a similar expression for magnetohydrodynamic turbulence. However, numerical simulations show that mixing motions perpendicular to the local magnetic field are, up to high degree, hydrodynamical. This suggests that turbulent heat transport in magnetized turbulent fluid should be similar to that in non-magnetized one, which should have a diffusion coefficient ${\upsilon}_{inj}{\iota}_{turb}$. We review numerical simulations that support this conclusion. The application of this idea to thermal conductivity in clusters of galaxies shows that this mechanism may dominate the diffusion of heat and may be efficient enough to prevent cooling flow formation when turbulence is vigorous.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.187-190
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• 1991

The analytical model to investigate the effects of the drift and diffusion carrier transport upon the Hall effect is presented and applied to the general PN junction structure. The diffusion current effect on the Hall coefficient can not be considered in the conventional model, which produces the conversion of the direction of the induced Hall field between measured and calculated values. The proposed analytical model which considers the diffusion current effect provides the coincident results with the previous experimental results.

• Advances in Traditional Medicine
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• v.7 no.1
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• pp.79-84
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• 2007

Urease was immobilized with calcium alginate by entrapment method in the form of spherical beads and stored in Tris/acetate buffer (pH 7.3) at $4^{\circ}C$. Urease immobilized at different concentration of alginate beads (3%, 4% and 5%) showed higher apparent $K_{m}$ values than the soluble urease. Furthermore, $K_{m}$ has been shown to be corelated with effective diffusion coefficient (De) at different concentration of alginate gel. The present study showed that diffusion and reaction contribute to control the overall rate.

• Journal of Ginseng Research
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• v.9 no.2
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• pp.248-255
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• 1985

In order to investigate the optimal drying condition of white ginseng by using bulk air drier(130 x 62 x 65cm), drying curves, diffusion coefficient at various drying temperature, the energy of activation, variation of color intensity and chemical components during drying of white ginseng were studied. Fick's second low of diffusion for diffusion out of spheres was successfully applied to describe the drying of white ginseng. It was found that the diffusion coefficient of water was 2.2x107, 9.0x107 cm2/sec at drying temperature 4$0^{\circ}C$, 55$^{\circ}C$, respectively. An Arrhenius type temperature dependency of moisture diffusivity was found, the energy of activation being 18.8 Kcal/g mol. Color intensity of white ginseng dried at various drying temperature was increased with an increase in drying temperature. The contents of crude protein, reducing sugar and crude saponin during drying of white ginseng were gradually decreased as increasing of drying time. And with the sensory evaluation by multiple comparison difference analysis, the optimal drying temperature of white ginseng was between 45$^{\circ}C$ and 5$0^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.20 no.2
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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)

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.532-540
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• 2019

PET microfibers with various diameters (0.5, 0.2, 0.06, and 0.01 dpf) were dyed with a dispersed dye (C.I. Disperse Blue 56) at various temperatures. The dyeing process was conducted under infinite dyebath conditions at constant temperatures. The effects of the dyeing temperature and diameter on the partition coefficient, affinity, and diffusion coefficient of disperse dyes were studied. The curve of isotherms was fitted well to Nernst-type model in a large range of initial dye concentrations. At the same temperature, the partition coefficient and affinity decreased with increasing sample diameter due to the increase in surface area. At all deniers, the partition coefficient and affinity decreased with increasing temperature because the dyeing process is an exothermic reaction. In addition, the decrease in radius of the sample gives rise to a decrease in the heat of dyeing. The fine diameter of the sample resulted in an increased surface area but decreased space between the microfibers. Consequently, decreasing the diameter of the microfibers leads to a decrease in the diffusion coefficient. At the same diameter, the diffusion coefficient increased with increasing temperature because of rapid dye movement and the large free volume of the sample inside. In addition, thermal dependence of the diffusion coefficient increased when the diameter of the sample increased.