• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.2
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• pp.101-106
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• 2009

The disjoining pressure is an important physical property in modeling the small-scale transport phenomena on thin film. It is a very useful definition in characterizing the non-continuum effects that are not negligible in heat and mass transport of the film thinner than submicro-scales. We present the calculated values of disjoining pressure of He, Kr and Xe thin films absorbed on graphite substrate using Molecular Dynamics Simulation (MD). The disjoining pressure is accurately calculated in the resolution of a molecular scale of the film thickness. The characteristics of the pressure are discussed regarding the molecular nature of the fluid system such as molecular diameter and intermolecular interaction parameters. The MD results are also compared with those based on the continuum approximation of the slab-like density profile and the results on other novel gases in the previous study. The discrepancies of the continuum model with MD results are shown in all three configurations and discussed in the view point of molecular features.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.6
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• pp.362-366
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• 2002

A mathematical model has been developed for describing the oxygen concentration during the exponential growth of microorganisms, in a static solid substrate bed supported on a tray fermentor. The model equations comprise of one partial differential equation for mass transfer and an ordinary differential equation of growth. After nondimensionlisation, analytical solution tn the model has been obtained by the method of Laplace transforms. An expression for critical thickness of bed is deduced from the model equation. The significance of the model in the design of tray fermentors is discussed. The validity of the discussion is verified by taking an illustration from the literature.

• Bulletin of the Korean Chemical Society
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• v.6 no.3
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• pp.128-131
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• 1985

A series of copolymer membranes of 2-hydroxyethylmethacrylate (HEMA) with selected hydrophobic monomers were prepared without crosslinking agents. The equilibrium water content, the partition coefficient, and the permeability of the solutes such as urea, methylurea, 1,3-di-methylurea, and acetamide via these membranes were measured. The partition coefficient data show that as the hydrophobicity of solutes increased, the partition of solutes were dictated by hydrophobic interaction between solute and polymer matrix. Diffusion coefficients obtained in these experiments decrease as the water content of polymer membrane decreases. This decrease is blunt as the excess heat capacities, ${\phi}C^0_p$ (excess) in aqueous solution at infinite dilution of solute increases. To investigate the relationship between water content and diffusion coefficient, the results of the diffusion experiments were examined in light of a free-volume model of diffusive transport. The remarkable increase of urea mobility in the polymer network containing relatively larger bulk water can be considered as water structure breaking effect.

• Journal of Radiation Industry
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• v.4 no.4
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• pp.391-395
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• 2010

The characteristics for pollutant transport in tidal influenced area was investigated using tidal wave hydraulic scale model. Hydraulic scale model was composed of the tidal generator, attenuation area and channel. Also, wave height, current meter and conductivity meter were used with the measured instruments in hydraulic scale model. NaCl with a tracer was used to evaluate the advection phenomena under the different velocity profiles. The arrival time of the maximum concentration in the condition of the relatively fast velocity was measured about 30 seconds faster than ones in the conditions of low velocity. The measured concentrations of the tracer were shown in the detection points of the flow direction consecutively.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.666-672
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• 2003

Vacuolar degeneration of the gastric epithelial cells is a characteristic feature of the derangement of mucosa where Helicobacter pylori colonizes, and H. pylori vacuolating cytotoxin (VacA) has been suggested to playa key role in it. To elucidate the VacA-involved degenerative mechanism, VacA was purified, and its impact on degeneration of HeLa cells was determined. In the presence of ammonium chloride, cell vacuolation by VacA was dose-and time-dependent, however, no detectable degeneration of the cells was observed with the VacA concentration tested. A further increase of vacuolation was shown in cells pre-treated with diethyl pyrocarbonate (DEPC) , and this resulted in a change of the cell morphology to become spherical. Similar phenomena were also observed when HeLa cells were co-cultivated with intact H. pylori cells. It was remarkable to note that the degree of growth inhibition was proportional to the increase in vacuole formation, suggesting that the vacuolation rate would be critical for cell degeneration. Surprisingly, although VacA was itself inhibited by DEPC, its uptake was markedly increased by this agent, similar to that found in cells with Nabutyrate. These data indicate that the cell's tolerance of VacA transport may be critical for vacuolar degeneration and may be changeable during H. pylori inhabitation.

• Food Science and Biotechnology
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• v.15 no.6
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• pp.937-941
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• 2006

Chitosan has a wide range of applications in biomedical materials as well as in dietary supplements. Chitosan oligosaccharide with free-amine group (COFa) is an improvement over traditional chitosan that lacks the usual impurities and materials detrimental to the body. Based on a previous study of water soluble chitosan (WSC, chitosan lactate), we investigated the molecular weight (Mw) - dependent absorption phenomena of COFa in vitro and in vivo with various Mws. The absorption of CO Fa was significantly influenced by its molecular weight. As Mw increases, the absorption decreases. The absorption profiles for 5 K COFa (Mw=5 kDa) were observed to be more than 10 times higher than those of high molecular weight chitosan (100 K HWSC Mw=100 kDa) in both in vitro and in vivo transport experiments. Furthermore, the in vitro transport experiment suggested that transcellular transport of the COFa (Mw <10 kDa) through Caco-2 cell layer could occur with a negligible cytotoxic effect. The COFas showed a cytotoxic effect on Caco-2 cells that was dependent on dose and Mw. COFa could be transported transcellularly through the Caco-2 cell layer.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.166-170
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• 2014

In this paper, we investigate the electric and magnetic properties of the engine oil, and estimate its changing time in transport truck. The four diesel trucks are selected, and the capacitance and inductance are investigated with parallel capacitor and induction coil, respectively. The measured capacitance gradually increases up to 10,000~14,000 km due to the activation of antioxidant, and then decreasing phenomena happen. The inductance decreases and the saturation began in 10,000~14,000 km range. Although the behavior of inductance is different from that of capacitance, but changing points are similar. From those results, we can estimate the changing time of engine oil is around 10,000~14,000 km and the inductance can be used for monitoring of engine oil in transport trucks.

• Journal of Korean Society of Water and Wastewater
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• v.7 no.2
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• pp.9-23
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• 1993

Emission of hazardous and volatile organic chemicals from solid waste landfill site was become to important issue because of environmental pollution and health risk by such chemicals. Laboratory batch and continuous experiments were conducted respectively to elucidate isothermal sorption behaviors and transport phenomena(by gas through unsaturated solid waste layer) in wet solid waste-gas system. Source separated and size reduced refuse(bulky waste) and incinerated ash were used after controlling water content, and trichloroethylene(TCE) was chosen among many such chemicals because of it's generality among those man-created pollutants. Isothermal TCE sorption equilibria wet solid waste-gas system can be described in linear equation and partition coefficient in this system can be estimated approximately by the simple equation derived from schematic structure of the system. Transport equation modified by instantaneous equilibrium sorption fraction and kinetic sorption rate(overall mass transfer capacity coefficient) simulated well the column experiment results.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.243-256
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• 2011

This paper considers the concept of analog computing based on a cellular neural network (CNN) paradigm to simulate nuclear reactor dynamics using a time-dependent second order form of the neutron transport equation. Instead of solving nuclear reactor dynamic equations numerically, which is time-consuming and suffers from such weaknesses as vulnerability to transient phenomena, accumulation of round-off errors and floating-point overflows, use is made of a new method based on a cellular neural network. The state-of-the-art shows the CNN as being an alternative solution to the conventional numerical computation method. Indeed CNN is an analog computing paradigm that performs ultra-fast calculations and provides accurate results. In this study use is made of the CNN model to simulate the space-time response of scalar flux distribution in steady state and transient conditions. The CNN model also is used to simulate step perturbation in the core. The accuracy and capability of the CNN model are examined in 2D Cartesian geometry for two fixed source problems, a mini-BWR assembly, and a TWIGL Seed/Blanket problem. We also use the CNN model concurrently for a typical small PWR assembly to simulate the effect of temperature feedback, poisons, and control rods on the scalar flux distribution.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.3-17
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• 2007

This paper provides an introduction to life-span simulation and numerical approach to support the performance design processes of reinforced concrete structures. An integrated computational system is proposed for life-span simulation of reinforced concrete. Conservation of moisture, carbon dioxide, oxygen, chloride, calcium and momentum is solved with hydration, carbonation, corrosion, ion dissolution. damage evolution and their thermodynamic/mechanical equilibrium. Coupled analysis of mass transport and damage mechanics associated with steel corrosion is presented for structural performance assessment of reinforced concrete. Multi-scale modeling of micro-pore formation and transport phenomena of moisture and ions are mutually linked for predicting the corrosion of reinforcement and volumetric changes. The interaction of crack propagation with corroded gel migration can also be simulated. Two finite element codes. multi-chemo physical simulation code (DuCOM) and nonlinear dynamic code of structural reinforced concrete (COM3) were combined together to form the integrated simulation system. This computational system was verified by the laboratory scale and large scale experiments of damaged reinforced concrete members under static loads, and has been applied to safety and serviceability assessment of existing structures. Based on the damage details predicted by the nonlinear finite element analytical system, the life-span-cost of RC structures including the original construction costs and the repairing costs for possible damage during the service life can be evaluated for design purpose.