• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.5-11
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• 2004

Characteristics of advective-diffusive transport of inorganic chemicals in clayey soils as well as in two hardened barrier materials of silica and lime are analyzed from the laboratory column test and compared with those of pure diffusive column test. The results show that the average dispersion coefficients of three materials are $4.39\times l0^{-10}\textrm{m}^2 /s,\; 1.98\times l0^{-10}\textrm{m}^2 /s,\; 1.99\times l0^{-10}\textrm{m}^2 /s$, respectively, and the value of clay is higher than that of hardened barrier materials. There was no significant difference between the dispersion coefficients of advective-diffusive column tests and the effective diffusion coefficients from the pure diffusive column tests, if advective velocity was lower than l0$^{-7}$$m^2$/s. The range of dispersion coefficients of advective-diffusive column tests was narrower than that of diffusion coefficients of pure diffusion tests.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.9
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• pp.8-13
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• 2008

Noise in homogeneous extrinsic semiconductor samples is calculated due to distributed diffusion noise sources. As the length of the device shrinks at a fixed bias voltage, the ac-wise short-circuit noise current shows excess noise as well as thermal noise spectra. This excess noise behaves like a full shot noise when the channel length becomes very small compared with the extrinsic Debye length. For the first time, the analytic formula of the excess noise in extrinsic semiconductors from velocity-fluctuation noise sources is given for finite frequencies. This formula shows the interplay between transit time, dielectric relaxation time, and velocity relaxation time in determining the terminal noise current as well as the carrier density fluctuation. As frequency increases, the power spectral density of the excess noise rolls off. This formula sheds light on noise in nanoscale MOSFETs where quasi-ballistic transport plays an important role in carrier transport and noise.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.579-582
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• 2012

Removing residual water in a fuel cell is a critical operational process for managing its performance and controlling its lifetime. Understanding the mechanism of water transport in fuel cells is essential for the design of the water removal process. In this study, an experimental method for measuring the water evaporation rate through a gas diffusion layer, which is a porous medium, under steady-state conditions was developed. Experimental bench tests were conducted to apply the developed method. Then, the effects of various parameters of the drying gas and the gas diffusion layer were experimentally measured. The water evaporation rate increased as the humidity of the drying gas decreased and the flow rate of the drying gas increased. In addition, a thinner gas diffusion layer yielded a higher water evaporation rate.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.5
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• pp.775-781
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• 2002

The T-type amino acid transporter 1 (TATI) is a Na$^{+}$-independent amino acid transporter which selectively trans- ports aromatic amino acids subserving the amino acid transport system T. To understand the transport properties of aromatic amino acids by human TAT1 (hTATl ), we have examined the hTATl -mediated aromatic amino acid transports using a Xenopus laeuis oocyte expression system. When expressed in Xenopin laeuis oocytes, hTATl induced L- [$^{14}$ C]tryptophan transport which was not dependent on Na$^{+}$ or Cl$^{[-10]}$ in the medium. Uptake was time-dependent and exhibited a linear dependence on incubation time up to 30 min. The L- ($^{14}$ C)tryptophan uptake was highly inhibited by L-isomers of tryptophan, tyrosine and phenylalanine, whereas other L-amino acids did not inhibit hTATl -mediated L- ($^{14}$ C)tryptophan uptake. The hTATl induced the relatively low-affinity transport of aromatic amino acids such as L- ($^{14}$ C)tryptophan, L- ($^{14}$ C)tyrosine and L- ($^{14}$ C)phenylalanine (Km values: 450～750 $\mu$M), consistent with the properties of classical amino acid transport system T. The L- ($^{14}$ C)tryptophan uptake did not show any remarkable pH dependence within the pH range of 5.5 to 8.5. The time-dependent efflux of L- ($^{14}$ C)tryptophan was detected from the oocytes expressing hTATl, which was not affected by the presence or absence of L-tryptophan in the extracellular medium, indicating that hTATl-mediated transport is due to the facilitated diffusion. Expression of hTATl in Xenopu laevis oocytes induced the transport of tryptophan, tyrosine and phenylalanine, indicating that hTATl is a transporter subserving system T These results suggest that hTATl has essential roles in the absorption of aromatic amino acids from epithelial cells to the blood stream. Hecause hTATl is proposed to be crucial to the efficient absorption of aromatic amino acids from intestine and kidney, its defect such as blue diaper syndrome could be involved in the disruption of aromatic amino acid transport.ort.

• Journal of the Korean Electrochemical Society
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• v.23 no.4
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• pp.81-89
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• 2020

To understand the performance of the electrochemical device, the analysis of the mechanism of ionic conduction is important. However, due to the ionic interaction in the electrolyte and the complexity of the electrolyte structure, a clear analysis method of the ion conduction mechanism has not been proposed. Instead, a variety of mathematical models have been devised to explain the mechanism of ion conduction, and this review introduces the Arrhenius and Vogel-Tammann-Fulcher (VTF) model. In general, the above two mathematical models are used to describe the temperature dependence of the transport properties of electrolytes such as ionic conductivity, diffusion coefficient, and viscosity, and a suitable model can be determined through the linearity of the graph consisting of the logarithm of the moving property and the reciprocal of the temperature. Currently, many electrolyte studies are evaluating the suitability of the above two models for electrolytes by varying the composition and temperature range, and the ion conduction mechanism analysis and activation energy calculation are in progress. However, since there are no models that can accurately describe the transport properties of electrolytes, new models and improvement of existing models are needed.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.1 no.1
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• pp.19-33
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• 1997

The high oxidants, which occur the daily maximum concentrations in the afternoon, are transported into the other region via long range transport mechanisms or trapped within the shallow mixing boundary layer and then removed physically (deposition, transport by mountain wind, etc.) and chemically (reaction with local sources). Therefore, modeling formation of photochemical oxidants requires a complex description of both chemical and meteorological processes. In this study, as a part of air quality studies, we reviewed various aspects of photochemical modeling on the basis of currently available literature. The result of the review shows that the model is based on a set of coupled continuity equations describing advection, diffusion, transport, deposition, chemistry, emission. Also photochemical oxidant models require a large amount of input data concerned with all aspects of the ozone life cycle. First, emission inventories of hydrocarbon and nitrogen oxides, with appropriate spatial and temporal resolution. Second, chemical and photochemical data allowing the quantitative description of the formation of ozone and other photochemically-generated secondary pollutants. Third, dry deposition mechanisms particularly for ozone, PAN and hydrogen peroxide to account for their removal by absorption on the ground, crops, natural vegetation, man-made and water surfaces. Finally, meteorological data describing the transport of primary pollutants away from their sources and of secondary pollutants towards the sensitive receptors where environmental damage may occur. In order to improve our present study, shortcomings and limitation of existing models are pointed out and verification process through observation is emphasized.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.6
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• pp.256-263
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• 2007

For $P_B=50Torr,\;P_T=5401Torr,\;T_S=450^{\circ}C,\;{\Delta}T=20K$, Ar=5, Pr=3.34, Le=0.01, Pe=4.16, Cv=1.05, adiabatic and linear thermal profiles at walls, the intensity of solutal convection (solutal Grashof number $Grs=7.86{\times}10^6$) is greater than that of thermal convection (thermal Grashof number $Grt=4.83{\times}10^5$) by one order of magnitude, which is based on the solutally buoyancy-driven convection due to the disparity in the molecular weights of the component A ($Hg_2Cl_2$) and B (He). With increasing the partial pressure of component B from 20 up to 800 Torr, the rate is decreased exponentially. It is also interesting that as the partial pressure of component B is increased by a factor of 2, the rate is approximately reduced by a half. For systems under consideration, the rate increases linearly and directly with the dimensionless Peclet number which reflects the intensity of condensation and sublimation at the crystal and source region. The convective transport decreases with lower g level and is changed to the diffusive mode at $0.1g_0$. In other words, for regions in which the g level is $0.1g_0$ or less, the diffusion-driven convection results in a parabolic velocity profile and a recirculating cell is not likely to occur. Therefore a gravitational acceleration level of less than $0.1g_0$ can be adequate to ensure purely diffusive transport.

• Journal of the Korean GEO-environmental Society
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• v.7 no.3
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• pp.43-54
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• 2006

In this paper, the uniaxial, triaxial compression tests and consolidation tests on the clay sample substituted initial pore water for pollutant were performed to evaluate the change in geotechnical properties of the contaminated clay. The contaminant transport analysis on embankment type landfill using the MT3D model was also performed to evaluate the extent of transport and diffusion. There was tendency that strength, compressibility and permeability has increased with the increase in the concentration of NaCl solution. The increase in the strength and compressibility of sample saturated with leachate was higher than samples saturated with NaCl solution, but in the permeability coefficient was lower. As the result of contaminant transport analysis, the predicted concentration was in high with the increase in the initial concentration of $Cl^-$ ion and increased in a non-linear form. The transportation distance calculated with use of regression equation between the distance from contaminant source and the concentration of $Cl^-$ ion was increased with the increase in the initial concentration.

• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.539-546
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• 2016

It is over 12 years since the launch of Korea Train eXpress (KTX) services. Demand for the KTX has been on the increase continuously but few studies have been produced related to this phenomenon. KTX passenger demand has been constantly increasing due to influencing factors such as the expansion of network, rise of oil prices, etc. In this study, our main focus is to verify that there are other types of elements that are causing an increase in KTX demand; our approach looks at changes in social and psychological aspect that have occurred due to the reduction of travel time and cost, as well as the imposition of a five-day workweek. In other words, we considered diffusion theory in the marketing area, which affects product selection and purchasing attitudes, as a key factor that is causing passenger demand to increase. That is to say that it is hypothesized that the demand for travel on the KTX has increased due to the train's utility, which is spread by the diffusion effect Therefore, the Bass diffusion model was applied to explain the dramatic increase in KTX passenger demand. Based on this foundation, it was also discussed how certain marketing strategies that incorporate the diffusion effect should be considered variously for sustainable management of rail transportation, while considering a steady passenger demand.

• Bulletin of the Korean Chemical Society
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• v.5 no.3
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• pp.104-108
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• 1984

The self-diffusion experiment of THO was performed across a series of copolymer hydrogel membranes at different temperatures. Copolymer hydrogel membranes were prepared by copolymerizing 2-hydroxyethyl methacrylate (HEMA) and 2-aminoethyl methacrylate (AEMA) in the presence of the solvent and the crosslinker, ethylene glycol dimethacrylate (EGDMA). By changing the crosslinker content and the ratio of HEMA and AEMA monomer, two series of copolymer hydrogel membranes were synthesized. The tagging material was THO and efflux of THO was counted on a Liquid Sc-intillation Counter. The experimental data show that the permeability decreases as the amount of EGDMA and the mole fraction of HEMA increase, and the permeability is proportional to the temperature. The partition coefficient shows a parallel trend with permeability. Using the relationship between viscosity and diffusivity, the viscosity of water within the membrane was obtained. According to the result, the viscosity of watler within the membrane has the same value with those of supercooling water. And we obtained the activation energy of THO for transport in the membrane by using Arrhenius plotting.