• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.419-427
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• 1992

The performance of homemade thermal field-flow fractionation (ThFFF) and the optimization for separation are investigated in terms of retention parameters and selectivity using polystyrene standards. The ribbonlike channel was constructed by sandwiching two Mylar spacers between two highly polished copper bars which serve as channel walls. The hot bar was heated by two electrical cartridge heaters and the cold bar had holes through the entire length, allowing tap water as coolant to enter. It has been observed that the retention of polystyrenes increases as the temperature gradient increases. And the retention decreases as the cold wall temperature increases from 20 to $45^{\circ}C$. In comparison with size exclusion chromatography, ThFFF is more selective but has relatively low efficiency. It has been found that the plate height is proportional to the flow velocity and good estimates of polydispersities can be made directly from the ThFFF data.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1182-1190
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• 2014

$Cd_{1-x}Zn_xS$-sensitized $K_4Nb_6O_{17}$ composite photocatalysts (designated $Cd_{1-x}Zn_xS/K_4Nb_6O_{17}$) were prepared via a simple deposition-precipitation method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), $N_2$ sorption, ultraviolet-visible light diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence measurements (PL), and X-ray photoelectron spectroscopy (XPS). The $Cd_{0.8}Zn_{0.2}S$ particles were scattered on the surface of $K_4Nb_6O_{17}$, and had a relatively uniform size distribution around 50 nm. The absorption edge of $K_4Nb_6O_{17}$ was shifted to the visible light region and the recombination of photo-generated electrons and holes suppressed after $Cd_{0.8}Zn_{0.2}S$ loading. The $Cd_{0.8}Zn_{0.2}S$(25 wt %)/$K_4Nb_6O_{17}$ composite possessed the highest photocatalytic activity for hydrogen production under visible light irradiation, evolving 8.278 mmol/g in 3 h. Recyclability tests were performed, and the composite photocatalysts were found to be fairly stable. The mechanism of charge separation between the photogenerated electrons and holes at the $Cd_{0.8}Zn_{0.2}S/K_4Nb_6O_{17}$ composite was discussed.

• BMB Reports
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• v.29 no.6
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• pp.569-573
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• 1996

Clinical strains of Mycobacterium tuberculosis, M. terrae complex, M. gordonae, M. avium-intracellulae complex, and M. fortuitum from Korean patients were isolated and analyzed by comparing large restriction fragment (LRF) patterns produced by digestion of genomic DNA with infrequent-cutting endonucleases like AsnI and XbaI. and pulsed-field gel electrophoresis (PFGE). Three M. tuberculosis, two M. terrae complex, two M. gordonae, two M. avium-intracellulae complex, and two M. fortuitum strains were compared by using AsnI and XbaI. and this allowed easy visual separation of all epidemiologically unrelated strains. PFGE exhibits different DNA restriction patterns which are easy to compare. Genome size of the strains roughly ranged from 3020 to 3335 kb. The LRF patterns are useful for epidemiologic studies of tuberculosis with regard to drug resistance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.10
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• pp.893-899
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• 2010

A previous study showed that hemodynamics is correlated with stenosis in the coronary artery. The flow characteristics and the distributions of the hemodynamic wall parameters in the coronary artery are investigated under physiological flow condition. The present study also aims to establish the mechanism of the generation of atherosclerosis by analyzing the hemodynamic variables in the coronary artery where atherosclerosis frequently occurs. The stenosis phenomena due to atherosclerosis are related to not only the biochemical reaction between blood and blood vessels but also the hemodynamic factors sush as flow separation and oscillatory wall shear stress. As the bifurcated angle increases, the size of the recirculation area that appears in the cross section increases and disturbed flow is observed in this area. We speculate that this area is the starting point of atherosclerosis in the coronary artery.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.71-78
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• 2001

This paper presents the results of an experimental investigation on the combustion of single droplets arrays of Ethyl alcohol and kerosene fuel droplets in atmospheric pressure. The initial droplet diameters, d$_{0}$, were nominally 1.3~1.8mm, and inter-droplet separation distance l(l/do=1.31~2.60). experimental results indicate that burning rate constants(K) of ethyl alcohol and kerosene droplets were independent of initial droplet size as 0.0083, 0.0095 $\textrm{cm}^2$/sec. For 1-D droplet array's kerosene fuel droplet, burning rate constants(K) decreases with decreasing normalized inter-droplet distance. Normalized inter-droplet distance has stronger effect on 2nd fuel droplet than 3rd fuel droplet. When normalized inter-droplet distance is larger than 2.60, the effect of droplet spacing on droplet life is very small.

• Polymer(Korea)
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• v.27 no.1
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• pp.3-8
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• 2003

Polysiloxanes with methacrylate groups at both terminals were synthesized by a hydrosilylation reaction between allyl methacrylate and hydride-terminated polysiloxanes. The polysiloxane methacrylates with high molecular weights could be prepared through the reaction of polysiloxane methacrylates and octamethylcyclotetrasiloxane with an acid catalyst. The structures of the prepared polysiloxane methacrylates were verified by $^1$H- and $^{29}Si-NMR.$ The polysiloxane methacrylates were freely miscible with silicone oils. Polysiloxane films with microphase-separated liquid silicone oil were prepared by photo-crosslinking the mixture of polysiloxane methacrylates and silicone oil. Scanning electron microscopy (SEM) of the films showed that the size of silicone oil droplets became smaller with a lower loading of silicone oil, lower molecular weight of polysiloxane methacrylate, and lower molecular weight of silicone oil.

• Membrane Journal
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• v.11 no.3
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• pp.124-132
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• 2001

Silica membranes were prepared on a porous ${\alpha}$-alumina tube with pore size of 150nm by sol-gel and chemical vapor deposition(CVD) method for hydrogen separation at high temperatures. Silica and ${\gamma}$-lumina membranes formed by the sol-gel method possessed a large amount of mesopores of a Knudsen diffusion regime. In order to improve the $H_2$ selectivity, silica was deposited in the sol-gel derived silica/${\gamma}$-alumina layer by thermal decomposition of tetraethyl orthosilicate(TEOS) at $600^{\circ}C$. The CVD with forced cross flow through the porous wall of the support was very effective in plugging mesopores that were left unplugged in the membranes. The CVD modified silica/alumina composite membrane completely rejected nitrogen permeation and thus showed a high $H_2$ selectivity by molecular sieve effect. the permeation of hydrogen was explained by activated diffusion and the activation energy was 9.52kJ/mol.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.6
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• pp.402-409
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• 2001

Different bioligands carrying synthetic adsorbents have been reported in the literature for protein separation, We have developed a novel and new approach to obtain high protein ad-sorption capacity utilizing 2-methacrylamidohistidine(MAH) as a bioligand. MAH was synthe-sized by reacting methacrylocholride and histidine, Spherical beads with an average size of 150-200㎛ were obtained by the radical suspension polymerization of MAH and 2-hydrosyethyl-methacrylate(HEMA) conducted in an aqueous dispersion medium. p(HEMA-co-MAH) beads had a specific surface area of 17.6㎡/g . Synthesized MAH monomer was characterized by NMR. p(HEMA-co-MAH) beads were characterized by swelling test, FTIR and elemental analysis. Then Cu(II) ions were incorporated onto the beads and Cu(II) loading was found to be 0.96 mmol/g.These affinity beads with a swelling ration of 65% and containing, 1.6 mmol MAH/g were used in the adsorption/desorption of human serum albumin(HSA) from both aqueous solutions and hu-man serum. The adsorption of HSA onto p(HEM-co-MAH) was low(8.8 mg/g). Cu(II) chelation onto the beads significantly increased the HSA adsorption (56.3 mg/g). The maximum HSA ad-sorption ws observed at pH 8.0 Higher HSA adsorption was observed from human plasma(94.6 mgHSA/g) Adsorption of other serum proteins were obtained as 3.7 mg/g for fibrinogen and 8.5mg/g for γ-globulin. The total protein adsorption was determined as 107.1mg/g. Desorption of HSA was obtained using 0.1 M Tris/HCl buffer containing 0.5 M NaSCN, High desorption rations(up to 98% of the adsorbed HSA) were observed. It was possible to reuse Cu(II) chelated-p(HEMA-co-MAH) beads without significant decreases in the adsorption capacities.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.648-653
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• 2012

Hybridization of dense ceramic membranes for hydrogen separation with an electronically conductive metallic phase is normally utilized to enhance the hydrogen permeation flux and thereby to increase the production efficiency of hydrogen. In this study, we developed a nickel and proton conducting oxide ($BaCe_{0.9}Y_{0.1}O_{3-{\delta}}$: BCY) based cermet (ceramic-metal composites) membrane. Focused on the general criteria in that the hydrogen permeation properties of a cermet membrane depend on its microstructural features, such as the grain size and the homogeneity of the mix, we tried to optimize the microstructure of Ni-BCY cermets by controlling the fabrication condition. The Ni-BCY composite powder was synthesized via a solid-state reaction using $2NiCO_3{\cdot}3Ni(OH)_2{\cdot}4H_2O$, $BaCeO_3$, $CeO_2$ and $Y_2O_3$ as a starting material. To optimize the mixing scale and homogeneity of the composite powder, we employed a high-energy milling process. With this high-energy milled composite powder, we could fabricate a fine-grained dense membrane with an excellent level of mixing homogeneity. This controlled Ni-BCY cermet membrane showed higher hydrogen permeability compared to uncontrolled Ni-BCY cermets created with a conventionally ball-milled composite powder.

• Journal of the Korean Ceramic Society
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• v.50 no.4
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• pp.301-307
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• 2013

SiC hollow fiber was fabricated by curing, dissolution and sintering of Al-PCS fiber, which was melt spun the polyaluminocarbosilane. Al-PCS fiber was thermally oxidized and dissolved in toluene to remove the unoxidized area, the core of the cured fiber. The wall thickness ($t_{wall}$) of Al-PCS fiber was monotonically increased with an increasing oxidation curing time. The Al-PCS hollow fiber was heat-treated at the temperature between 1200 and $2000^{\circ}C$ to make a SiC hollow fibers having porous structure on the fiber wall. The pore size of the fiber wall was increased with the sintering temperature due to the decomposition of the amorphous $SiC_xO_y$ matrix and the growth of ${\beta}$-SiC in the matrix. At $1400^{\circ}C$, a nano porous wall with a high specific surface area was obtained. However, nano pores grew with the grain growth after the thermal decomposition of the amorphous matrix. This type of SiC hollow fibers are expected to be used as a substrate for a gas separation membrane.