• Journal of Periodontal and Implant Science
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• v.26 no.1
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• pp.143-160
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• 1996

The purpose of this study was to evaluate the response in aspect of attachment and growth rate of osteoblasts and growth rate of osteoblasts and human gingival fibroblasts to the commercially pure titanium(CP titanium)and titanium alloy(Ti-6AI-4V) that are used widely as implant materials, and to obtain the basic information to ideal implant materials. In the studly, commercially pure titanium in first test group, titanium alloy(Ti-6AI-4V) in second test group, cobalt-chrome-molybdenum alloy(Co-Cr-Mo alloy) in positive control group, and tissue culture polystyrene plate in negative control group were used. The results of this study were as follows. 1. Bone marrow cells cultured on CP titanium and Ti-6Al-4V showed significantly greater attachment and growth rate(p(0.05) compared to Co-Cr-Mo alloy in each time. 2. There were no significant differences(p>0.05) in attachment and growth rate of bone marrow cells cultured on CP titanium and Ti-6AI-4V or tissue culture plate. 3. Most bone marrow cells cultured on CP titanium, Ti-6Al-4V and tissue culture plate were attached well to each substratum in first 2days, and then, grew at higher growth rate. On the other hand, some cells cultured on Co-Cr-Mo alloy failed to attach in first 2 days, and then, attached cells grew at lower growth rate than other groups. 4. Attachment and growth rates of gingival fibroblasts cultured on CP titanium and Ti-6Al-4V showed no significant differences(p>0.05) compared to Co-Cr-Mo alloy in 2 days, but significantly greater increase(p<0.05) in 5 and 9 days. 5. There were no significantly differences(p>0.05) between growth rates on gingival fibroblasts cultured on CP titanium, Ti-6Al-4V and tissue culture plate in 2 and 5days, but a significant lower growth rate(p<0.05) on CP titanium and Ti-6Al-4V versus tissue culture plate. 6. Some gingival fibroblasts cultured on all specimen groups failed to attach, but attached cells grew well, especially on CP titanium, Ti-GAl-4V and tissue culture plate. 7. There were no significant differences(P>0.05) between growth rates of both bone marrow cells and gingival fibroblasts cultured on CP titanium and Ti-6AI-4V. As a result of this study, both commercially pure titanium and Ti-6AI-4V showed excellent biocompatibility and there was no significant difference in the cellular response to the both metals. Bone marrow cells cultured on each substratum showed significantly greater growth rate and responded sensitively to cytotoxic effects of metal surfaces compared to gingival fibroblasts. Considering cell response to the substrate, it was likely that the composition itself of titanium metals have no significant effect on the biocompatibility. Further study need to be done to evaluate the influence of surface characteristics on cellular responses.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.5
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• pp.655-662
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• 2004

An adsorption process to recover the pure $CH_4\;and\;CO_2$ from its mixture was examined. In this study, activated carbon fibers were used as a selective adsorbent. The activated carbon fibers has 78~94% micropore volume and 10.5~20.3${\AA}$ narrow pore size, and showed high adsorption rate and the good selectivity for $CO_2$ under the ambient pressure. The ACF with high surface area showed short mass transfer zone and long breakthrough time and, its adsorption capacity depended on the microporosity. Compared with single component adsorption, the amount adsorbed $CO_2$ on ACF increased by the roll-up of $CH_4$ in mixed gases. The adsorption selectivity increased as now rate and $CO_2$ concentration of mixed gases increased, showing 5.2 selectivity for 75% $CO_2$ concentration.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.4
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• pp.474-480
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• 2011

Hydrocarbon is required to be converted to pure hydrogen without carbon monooxide (CO) for polymer exchange membran fuel cell (PEMFC) applications. In this paper, CO cleaning processes as the downstream of Dimethyl ehter (DME) autothermal reforming process were performed in micro-reactors. Our study suggested two kinds of water gas shift (WGS) reaction process: High Temperature shift (HTS) - Low Temperature shift (LTS), Middle temperature shift (MTS). Firstly, using perovskite catalyst for MTS was decreased effieiciency since methanation. Using HTS-LTS the CO concentration was decreased about 2% ($N_2$ & $H_2O$ free) with the reaction temperature of $420^{\circ}C$ and $235^{\circ}C$ for HTS and LTS, respectively. As the final stage of CO cleaning process, preferential oxidation (PROX) was applied. The amount of additional oxygen need 2 times of stoichiometric at $65^{\circ}C$. The total conversion reforming efficiency of 75% was gained.

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.82-86
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• 2006

Propylene Carbonate (PC) has the interesting properties of being able to dissolve and dissociate lithium salts, thus leading to highly conducting electrolytes even at low temperatures. Moreover, electrolytes that contain PC are stable against oxidation at voltages up to ~5 V. However, it is known that, when lithium is intercalated into graphite in pure PC based electrolytes, solvent co-intercalation occurs, leading to the destruction of the graphite structure. (i.e., exfoliation). The objective of this study was to suppress PC decomposition and prevent exfoliation of the graphite anode by co-intercalation. Electrochemical characteristics were studied using Kawasaki mesophase fine carbon (KMFC) in different 1 M $LiPF_6$/PC-based electrolytes. Electrochemical experiments were completed using chronopotentiometry, cyclic voltammetry, impedance spectroscopy, X-ray diffraction, and scanning electron microscopy. From the observed results, we conclude that the MA and $Li_2CO_3$ additive suppressed co-intercalation of the PC electrolyte into the graphite anode. The use of additives, for reducing the extent of solvent decomposition before exfoliation of the graphite anode, could therefore enhance the stability of a KMFC electrode.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.88-93
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• 2002

$Zn_{0.5}Cd_{0.5}Al_{2}Se_{4}$ and $Zn_{0.5}Cd_{0.5}Al_{2}Se_{4}:Co^{2+}$ + single crystals were grown by CTR method. The grown single crystals have defect chalcopyrite structure with lattice constant a= 5.5966A. c= 10.8042${{\AA}}$ for the pure. a= 5.6543${{\AA}}$. c= 10.8205${{\AA}}$ for the Co-doped single crystal. respectively. The optical energy band gap was given as indirect band gap. The optical energy band gap was decreased according to add of Co-impurity. Temperature dependence of optical energy band gap was fitted well to the Varshni equation. From this relation. we can deduced the entropy. enthalpy and heat capacity. Also. we can observed the Co-impurity optical absorption peaks assigned to the $Co^{2+}$ ion sited at the $T_d$ symmetry lattice and we consider that they were attributed to the electron transitions between energy levels of ions.

• Bulletin of the Korean Chemical Society
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• v.18 no.10
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• pp.1090-1093
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• 1997

The solvent effects on the isotropic NMR shifts in conformationally rigid ligands such as quinuclidine, pyridine, and 4-aminopyridine coordinated to the paramagnetic polyoxometalate, [SiW11CoⅡO39]6- (SiW11Co), are reported. For these complexes the ligand exchange is slow on the NMR time scale and pure 1H NMR signals have been observed at room temperature. The signals for the SiW11Co complexes are shifted upfield whe dimethyl sulfoxide-d6 (DMSO) is added to a D2O solution. The isotropic shifts are separated into contact and pseudocontact contributions by assuming that the contact shifts are proportional to the isotropic shifts of the same ligands coordinated to [SiW11NiⅡO39]6-. It is shown that both the contact and pseudocontact shifts decrease (the absolute values of the pseudocontact shifts increase), when D2O is replaced by DMSO. It is suggested that D2O, a strong hydrogen bond donor, withdraws electron density from [SiW11CoⅡO39]6-, increasing the acidity of the cobalt ion toward the axial ligand. When D2O is replaced by DMSO, the acidity of the cobalt ion in SiW11Co decreases, weakening the Co-N bond. Then both the contact and pseudocontact shifts are expected to decrease in agreement with the observed solvent effects.

• Journal of Korea Foundry Society
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• v.14 no.6
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• pp.558-565
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• 1994

The horizontal continuous casting process with the heated mold was applied to obtain the unidirectionally solidified rods($4{\sim}8mm$ dia.) of pure copper with good surface quality. The results could be summarized as follows. 1. The unidirectional solidification of pure copper rods with good surface(mirror surface) quality could be obtained by placing the S/L interface inside the heated mold cavity even though the cast copper rods were covered with thin copper oxide layer. 2. The casting speed for 4mm dia. rods with mirror surfaces was affected significantly by the mold-cooler distance rather than the cooling flow rate when other casting conditions were fixed. 3. The casting speed was the main factor affecting the oxidation of copper during the continuous casting and the thickness of copper oxide layer decreased almost linearly as the casting speed increased.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1957-1962
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• 2003

In order to design the phantom of heart, we have developed the multi-dipole current source system. Such a one be clue to the various motion of heart. The magnetocardiograph (MCG) system for diagnosing the disease of the heart due to an analysis of the heart signal. The multidipole current source system be built by microprocessor. We use the shield room to obtain a good experimental result. Then the signal acquired is mixed with a background noise, through a filtering extracts a pure signal. The pure signal such a heart phantom is analyzed by an electromagnetic map.

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.103-113
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• 1998

By using a gas-tight electrochemical cell, we can perform high-temperature coulometric titration and measure electronic transport properties to determine the elecronic defect structure of metal oxides. This technique reduces the time and expense required for conventional thermogravimetric measurements. The components of the gas-tight coulometric titration cell are an oxygen sensor, Pt/yttria stabilitized zirconia(YSZ)/Pt, and an encapsulated metal oxide sample. Based on cell design, both transport and thermodynamic measurements can be performed over a wide range of oxygen partial pressure ($pO_2=10^{-35}$ to 1 atm). This paper describes the high-temperature gas-tight electrochemical cells used to determine electronic defect structures and transport properties for pure and doped-oxide systems, such as YSZ, doped and pure ceria $(Ca-CeO_2 \;and\; CeO_2)$, copper oxides and copper-oxide-based ceramic superconductors, transition metal oxides, $SrFeCo_{0.5}O_x,\; and \;BaTiO_2$.

• Carbon letters
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• v.15 no.1
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• pp.50-56
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• 2014

We prepared ethylene vinyl alcohol (EVOH)/graphene oxide (GO) membranes by solution casting method. X-ray diffraction analysis showed that GOs were fully exfoliated in the EVOH/GO membrane. The glass transition temperatures of EVOH were increased by adding GOs into EVOH. The melting temperatures of EVOH/GO composites were decreased by adding GOs into EVOH, indicating that GOs may inhibit the crystallization of EVOH during non-isothermal crystallization. However, the equilibrium melting temperatures of EVOH were not changed by adding GOs into EVOH. The oxygen permeability of the EVOH/GO (0.3 wt%) film was reduced to 63% of that of pure EVOH film, with 84% light transmittance at 550 nm. The EVOH/GO membranes exhibited 100 times better (water vapor)/(oxygen) selectivity performance than pure EVOH membrane.