• Korean Membrane Journal
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• v.4 no.1
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• pp.20-24
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• 2002

The surface of polysulfone membranes has been modified using the fluorine chemicals, ITFE (2-iodo-1,1,1-trifluoro-ethane F.W.=209.94) and PFPI (1H,1H-pentafluoro-n-propyl iodide F.W.=259.95), and PFI (1H,1H,2H,2H-perfluorohexyl iodide, F.W.=373.99) based on Friedel-Crafts reaction mechanism with varying reaction temperatures, reaction time, and catalysis types. The resulting membranes were characterized through mainly the contact angle measurement and pure water permeability. The smaller reactant shows the larger contact angles. FeBr$_3$ catalyst is more effective than AlCl$_3$. Typically, the PS film treated with ITFE at $25^{\circ}C$ under FeBr$_3$ catalyst showed the contact angle 78.5$^{\circ}C$ which indicated 10% over the value of unreacted PS films. More than 50% of pure water flux 8.0 g/$m^2$hr, reduced at reaction time 10 min relative to the original flux, 3.49 g/$m^2$hr.

• Bulletin of the Korean Chemical Society
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• v.12 no.3
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• pp.276-281
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• 1991

Electrochemical behaviors of optically active sparteine-Cu(II) dihalide complexes were investigated by polarography and cyclic voltammetry (CV). These Cu(II) complexes are rather easier to be reduced to Cu(I) states when comparison is made with other nonplaner copper complexes, We have assigned the CV peaks and polarographic waves related to the redox processes for these complexes. We could also observe the exchange reaction of Cu(II) ion in the complex with mercury metal in the cell having mercury pool. The redox mechanism of these complelxes is as follows; The 1st wave appeared at +0.47 V/+0.65 V corresponds to the reaction of $SpCuX_2+ e{\rightleftarrow}SpCuX_{2^-}$ and the 2nd one at +0.26 V/+0.21 V does the reaction of $SpCuX_{2 ^-} +e{\rightleftarrow}SpCuX_2^{2-}$. The 3rd one at -0.35 V/-0.27 V is dueto the reduction of mercury complex formed via exchange reaction. Where, X is chloride ion.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.35-35
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• 2010

Understanding the mechanistic details of heterogeneous catalytic reactions will provide a way to tune the selectivity between various competing reaction channels. In this regard, catalytic decomposition of alcohols over the rutile $TiO_2$(110) surface as a model oxide catalyst has been studied to understand the reaction mechanism employing the temperature-programmed desorption (TPD) technique. The $TiO_2$(110) model catalyst is found to be active toward alcohol dehydration. We find that the active sites are bridge-bonded oxygen vacancies where RO-H heterolytically dissociates and binds to the vacancy to produce alkoxy (RO-) and hydroxyl (HO-). Two protons adsorbed onto the bridge-bonded oxygen atoms (-OH) readily react with each other to form a water molecule at ~500 K and desorb from the surface. The alkoxy (RO-) undergoes decomposition at higher temperatures into the corresponding alkene. Here, the overall desorption kinetics is limited by a first-order decomposition of intermediate alkoxy (RO-) species bound to the vacancy. We show that detailed analysis on the yield and the desorption temperatures as a function of the alkyl substituents provides valuable insights into the reaction mechanism. After the catalytic role of the oxygen vacancies has been established, we employed x-ray photoelectron spectroscopy to further study the surface electronic structure related to the catalytically active defective sites. The defect-related state in valence band has been related to the chemically reduced $Ti^{3+}$ defects near the surface region and are found to be closely related to the catalytic activity of the $TiO_2$(110) surface.

• Journal of the Korean Society of Combustion
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• v.9 no.2
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• pp.10-17
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• 2004

A two-dimensional direct numerical simulation is performed to investigate the flame structure of $CH_4/N_2-Air$ counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman#s detailed reaction mechanism are adopted in this calculation. To quantify the strain on flame induced by a vortex, a scalar dissipation rate (SDR) is introduced. The results show that fuel-side and air-side vortex cause an unsteady extinction. In this case, the flame interacting with a vortex is extinguished at much larger SDR than steady flame. It is also found that air-side vortex extinguishes a flame more rapidly than fuel-side vortex. The unsteady effect induced by flame-vortex interaction does not lead to a transient OH overshoot of the maximum steady concentration observed in experiment, while $HO_2$ radical increases more than the maximum steady concentration with increasing SDR. In addition, it is seen that NO and $NO_2$ are not sensitive to the unsteady variation of SDR.

• Journal of the Korean Ceramic Society
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• v.18 no.1
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• pp.35-40
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• 1981

The kinetics of the dehydration of Ha-dong kaolin was studied isothermally at various temperatures. Dehydration rate was measured by thermogravimetry method in the temperature range of 440~50$0^{\circ}C$ and the particle size range of 170~325mesh. The general equation f($\alpha$)=kt, where $\alpha$ is the fraction reacted in the time and the function f($\alpha$) depends on the reaction mechanism, was applied to this reaction. The function, f($\alpha$) was obtained by application of reduced-time plot and plot of lnln (1-$\alpha$) vs. ln (time), and expressed as (1-$\alpha$) ln (1-$\alpha$)+$\alpha$=kt. The dehydration followed the diffusion-controlled reaction model and gave activation energy of 30Kcal/mole.

• YAKHAK HOEJI
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• v.49 no.5
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• pp.386-391
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• 2005

The discovery of drugs for the treatment of mast cell-mediated allergic disease is a very important subject in human health. The Amomum xanthiodes (Zingiberaceae) has been used for centuries as a traditional medicine in Korea and is known to have an anti-inflammatory effect. However, its specific mechanism of action is still unknown. In this report, we investigated the effect of hot water extract from Amomum xanthiodes (EAX) on the mast cell-mediated allergic reaction and studied its possible mechanisms of action. EAX inhibited compound 48/80-induced systemic anaphylaxis and serum his­tamine release in mice. EAX decreased the passive cutaneous anaphylaxis reaction activated by anti-dinitrophenyl (DNP) IgE antibody. EAX dose-dependently reduced histamine release from rat peritoneal mast cells activated by compound 48/80 or anti-DNP IgE. EAX increased cAMP and decreased compound 48/80-induced intracellular $Ca^{2+}$ levels. Our findings provide evidence that EAX inhibits mast cell-derived allergic reactions, and also demonstrate the involvement of cAMP and intracellular $Ca^{2+}$ in these effects.

• Korean Journal of Materials Research
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• v.16 no.1
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• pp.50-57
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• 2006

Phase mixtures of Titanium boride, nitride, and carbide powder were produced by the reduction of a mixture of titanium and boron oxides with carbon via a gas-solid phase reaction. Boron oxides produce a vapour phase or decompose to a metal sub-oxide gaseous species when reduced at elevated temperature. The mechanism of BO sub-oxide gas formation from $B_2O_3$ and its subsequent reduction to titanium diboride for the production of uniform size hexagonal platelets is explained. These gaseous phases are critical for the formation of boride, nitride and carbide ceramics. For the production of ceramic phase composite microstructures, the nitrogen partial pressure was the most critical factor. Some calculated equilibrium phase fields has been verified experimentally. The theoretical approach therefore identifies conditions for the formation of phase mixtures. The thermodynamic and kinetic factors that govern the phase constituents are also discussed.

• Food Science and Biotechnology
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• v.14 no.1
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• pp.16-20
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• 2005

Additions of ground garlic, chili and ginseng powder did not affect the breaking force and strain of directly heated gel of Alaska pollack surimi. In comparison, these additives reduced the setting effect achieved by incubation of the salted surimi at $25^{\circ}C$, and resulted in a decreased breaking force and strain for the two step heated gel. Garlic almost completely inhibited the myosin cross-linking reaction, an important reaction for improving the gel properties occurring in the setting process. However, chili and ginseng powder minimally inhibited the cross-linking reaction. Thus, this study proposes that the mechanism for the suppression of the setting effect by chili and ginseng is different from that of garlic.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.11a
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• pp.83-83
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• 2000

Alkylketene dimer was known as a cellulose reactive or alkaline size because it does not require to fix to the fiber as do the traditional rosin sizes. A proposed sizing mechanism of AKD was the formation of P -ketoester bond between AKD and cellulose which provides the permanent attachment and the orientation of the hydrophobic alkylchains outward. However, some questions about the reaction had arisen and thus, the sizing mechanism of AKD has been a subject of controversy for several decades. The major concern of the controversy is that AKD is really reactive with cellulose or not in the papermaking conditions. In this study, reaction between AKD and pulp fiber was investigated, in order to find out whether AKD forms P-ketoester with pulp fiber during aging under no catalyzed neutral condition with obvious spectroscopic evidence. In addition, effect of aging treatment on the sizing development was studied. It has been disclosed that, in absence of water, AKD reacted with cellulose to form P -ketoester linkage under no catalyzed neutral condition, while, in presence of water, most of AKD was hydrolyzed to a dialkyl ketone or P -ketoacid. In addition, during the aging treatment of AKD-sized paper, its typical IR spectra bands gradually were reduced, completely disappeared after 6hr aging, and formed new absorption bands at 1707cm-' and shoulder peak at 1700cm-' which refer to the typical dialkylketone absorption bands. Therefore, the formation of P -ketoester between AKD and pulp fiber is impossible in the practical papermaking process. It could be suggested that the sizing development of AKD-sized paper is obtained by next two mechanism: 1) formation of a thin-layer of AKD on the fiber surface through melting and spreading of AKD emulsion particles by heat and 2) the hydrolysis of AKD to dialkyl ketone which has higher melting point, during drying and storage of AKD sized papers.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.1
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• pp.71-78
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• 2002

In this study, the influence of the presence of discontinuity planes on the load transfer mechanism and the pattern of loosening zone was studied based on the laboratory test. The trap-door and the reaction plates are installed as the bottom plane of the model box. The vertical discontinuity plane is installed in the dry sand. Various overburden heights and locations of discontinuity planes are applied as major factors in this study. The results show that at higher overburden heights over about 1.5 times the excavation width, the ratio of the transferred stress to the insitu stress converges to a certain value even if the overburden height increases further. The results also show that the discontinuity plane gives relatively larger influence on the load transfer mechanism, that produces the unsymmetrical load concentration, when the discontinuity plane locates within the tunnel width. When the discontinuity plane locates outside the tunnel width, the unsymmetrical load concentration is reduced considerably.