• Nuclear Engineering and Technology
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• v.41 no.10
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• pp.1347-1360
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• 2009

A multi-dimensional component for the thermal-hydraulic system analysis code, MARS, was developed for a more realistic three-dimensional analysis of nuclear systems. A three-dimensional and two-fluid model for a two-phase flow in Cartesian and cylindrical coordinates was employed. The governing equations and physical constitutive relationships were extended from those of a one-dimensional version. The numerical solution method adopted a semi-implicit and finite-difference method based on a staggered-grid mesh and a donor-cell scheme. The relevant length scale was very coarse compared to commercial computational fluid dynamics tools. Thus a simple Prandtl's mixing length turbulence model was applied to interpret the turbulent induced momentum and energy diffusivity. Non drag interfacial forces were not considered as in the general nuclear system codes. Several conceptual cases with analytic solutions were chosen and analyzed to assess the fundamental terms. RPI air-water and UPTF 7 tests were simulated and compared to the experimental data. The simulation results for the RPI air-water two-phase flow experiment showed good agreement with the measured void fraction. The simulation results for the UPTF downcomer test 7 were compared to the experiment data and the results from other multi-dimensional system codes for the ECC delivery flow.

• Biotechnology and Bioprocess Engineering:BBE
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• v.3 no.2
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• pp.103-108
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• 1998

A hydrophobic substrate triolein was hydrolyzed by lipase in a mono-phase reaction system containing cyclodextrin(CD) as emulsifier. The triolein was transformation to an emulsion-like state in the CD containing reaction system in contrast to the oil-droplet like state without CD due to the formation of an inclusion complex between the lipids and CDs. The hydyrolysis reaction increased substantially in the CD containing reaction system, and the optimum reaction conditions including the amount of lipase, ${\beta}$-CD concentration, and mixing ratio of triolein and ${\beta}$-CD, were determined. The performance of the enzyme reaction in a mono-phase reaction system was compared with that of a two-phase reaction system which used water immiscible hexane as the organic solvent. The role of a CD in the mono-phase reaction system was elucidated by comparing the degree of the inclusion complex formation with triolein and oleic acid, Km and Vmax values, and product inhibition by oleic aicd in aqueous and CD containing reaction systems. The resulting enhanced reaction seems to be caused by two phenomena; the increased accessibility of lipase to triolein and reduced product inhibition by oleic acid through the formation of an inclusion complex.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.3
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• pp.158-166
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• 2010

The purification of two liquid phases ($H_2SO_4$ phase and HIx phase) formed from a Bunsen reaction in Sulfur-Iodine (SI) hydrogen production process was investigated in order to operate SI process efficiently. The each synthetic solution for two liquid phases contained impurities was prepared on the basis of a proper composition obtained from Bunsen reaction. The purification of each solution was performed by counter-current flow using a packed column at different temperatures and $N_2$ flow rates. As the results of purification, impurities existed in each phase were decreased with increasing the temperature and the $N_2$ flow rate. In particular, the increase of the $N_2$ flow rate at the lower temperatures was effective to remove impurities by a reverse Bunsen reaction without side reactions. On the whole, it may be concluded that the purification of each phase is accomplished by mixing effects of the stripping, the evaporation, and the reverse Bunsen reaction.

• Journal of Powder Materials
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• v.6 no.4
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• pp.314-319
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• 1999

The solid state reaction by mechanical alloying(MA) generally proceeds by lowering the free energy as the result of a chemical reaction at the interface between the two adjacent layers. However, Lee et $al.^{1-5)}$ reported that a mixture of Cu and Ta, the combination of which is characterized by a positive heat of mixing of +2kJ/mol, could be amorphized by mechanical alloying. This implies that there exists an up-hill process to raise the free energy of a mixture of pure Cu and la to that of an amorphous phase. It is our aim to investigate to what extent the MA is capable of producing a non-equilibrium phase with increasing the heat of mixing. The system chosen was the ternary $Cu_{30}Ta_{ 70-x}Mo_ x$ (x=35, 10). The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-K $\alpha$ radiation, thermal analysis, electron diffraction and TEM micrographs. In the case of x=35, where pure Cu powders were mixed with equal amount of pure Ta and Mo powders, we revealed the formation of bcc solid solution after 150 h milling but its gradual decomposition by releasing fcc-Cu when milling time exceeded 200 h. However, an amorphous phase was clearly formed when the Mo content was lowered to x=10. It is believed that the amorphization of ternary $Cu_{30}Ta_{60}Mo_{10}$ powders is essentially identical to the solid state amorphization process in binary $Cu_{30}Ta_{70}$ powders.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.11-19
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• 2005

First, methods of numerical analysis of gas-particle flows is classified into micro, meso and macro scale approaches based on the concept of multi-scale mechanics. Next, the explanation moves on to discrete particle simulation where motion of individual particles is calculated numerically using the Newtonian equations of motion. The author focuses on the cases where particle-to-particle interaction has significant effects on the phenomena. Concerning the particle-to-particle interaction, two cases are considered: the one is collision-dominated flows and the other is the contact-dominated flows. To treat this interaction mathematically, techniques named DEM(Distinct Element Method) or DSMC (Direct Simulation Monte Carlo) have been developed DEM, which has been developed in the field of soil mechanics, is useful for the contact -dominated flows and DSMC method, developed in molecular gas flows, is for the collision-dominated flows. Combining DEM or DSMC with CFD (computer fluid dynamics), the discrete particle simulation becomes a more practical tool for industrial flows because not only the particle-particle interaction but particle-fluid interaction can be handled. As examples of simulations, various results are shown, such as hopper flows, particle segregation phenomena, particle mixing in a rotating drum, dense phase pneumatic conveying, spouted bed, dense phase fluidized bed, fast circulating fluidized bed and so on.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.2
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• pp.306-307
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• 2011

Two phases of experiment were conducted to produce compost using sewage sludge and sawdust as mixing materials to determine their chemical properties and the performance of selected test crops. The first phase was done to produce compost as potting media and the second phase was done to test the efficacy of the produced compost. With regard to some chemical properties of the compost, pH was moderately acidic (5.11 to 5.58) while the OM, N, P, and K contents of the compost were 23.8-35.9, 1.12-1.56, 254.9-555.7, and 40.4-62.6, respectively.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2037-2042
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• 2003

The purpose of this research is to develop the model of turbulence modulation due to the presence of particles in various types of particle-laden flows. Available experimental data were surveyed and the dependence of turbulence modulation of carrier-phase on particle size, concentration and particle Reynolds number were examined. This study takes into account the effect of wake produced by particle, the drag between phases and the velocity gradient in the wake to estimate the production of turbulence. The model of turbulence modulation using the mixing length theory under the assumption of equilibrium flow is proposed. Numerical results show that the model is successful in predicting the characteristics of the particle-laden flow in various conditions both qualitatively and quantitatively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.813-820
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• 2003

The purpose of this research is to develop the model of turbulence modulation due to the presence of particles in various types of particle-laden flows Available experimental data are surveyed and the dependence of turbulence modulation of carrier-phase on particle size, concentration and. particle Reynolds number are examined. This study takes into account the effect of wake produced by particle, the drag between phases and the velocity gradient in the wake to estimate the production of turbulence. The model of turbulence modulation using the mixing length theory under the assumption of equilibrium flow is proposed. Numerical results show that the model is successful in predicting the characteristics of the particle-laden in various flow conditions both qualitatively and quantitatively.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.50-58
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• 2001

The purpose of this research is to obtain the information of the development process of a vaporizing GDI spray using exciplex fluorecence method. Fluorobenzene/DEMA system was used as the exciplex-forming dopants. The 2-D spray images of liquid and vapor phases were acquired, and the behavior of both phases was analyzed by the image processing. The experiment was performed at the three different ambient perssures and the ambient temperature of 273K and 473K. As the result of this work, it was found that the development characteristics of GDI spray have stronger effect on the ambient pressure than on the ambient temperature. With an increase of ambient pressure, the distribution of vapor phase was decreased and the concentration of that was denser. Two regions, namely cone and mixing regions could be identified from those resulrs.

• Proceedings of the Korean Fiber Society Conference
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• 1987.06b
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• pp.12-12
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• 1987

To improve the fibrillation phenomenon and processibili to of poly(p-phenyleneterephthalamide) (PPD-T) , a P/E copolyamide was prepared by introducing 4,4'-ethylene dianiline (EDA) into rigid chain backbone. The effects of semi-flexible segment on the liquid crystalline properties were investigated. The EDA, used as a comonomer, was prepared by catalylitic reduction of p,p'-dinitrophenyl , obtained by oxidative coupling of p,p'-dinitrotoluene. Various high molecular weight PIE copolyamides were prepared by low temperature solution polycondensation of terephthaloyl chloride (TPC) with various mixtures of p-phenylene diamine (PPD) and EOA. The PfE copolyamides were completely dissolved in 100% svlfuric acid, and the phase transition of P/E copolyamide-sulfuric acid systems was examined in teams of concentration and temperature. Over the chemical compositions, PIE=911, 812, and 713, solutions of anisotropic single phase were acquired. In particular, the two mixing ratios, 911 and 812, gave a good anisotropic spinning dope.