• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.21 no.4
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• pp.245-275
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• 2017

The present investigation deals, Dufour and heat source effects on radiative MHD slip flow of a viscous fluid in a parallel porous plate channel in presence of chemical reaction. The non-linear coupled partial differential equations are solved by using two term perturbation technique subject to physically appropriate boundary conditions. The numerical values of the fluid velocity, temperature and concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. By increasing the slip parameter at the cold wall the velocity increases whereas the effect is totally reversed in the case of shear stress at the cold wall. It is observed that the effect of Dufour and heat source parameters decreases the velocity and temperature profiles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.9
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• pp.681-685
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• 2012

We investigated the dry etching characteristics of TiN in $TiN/Al_2O_3$ gate stack using a inductively coupled plasma system. TiN thin film is etched by BCl3/He plasma. The etching parameters are the gas mixing ratio, the RF power, the DC-bias voltages and process pressures. The highest etch rate is in $BCl_3/He$ (25%:75%) plasma. The selectivity of TiN thin film to $Al_2O_3$ is pretty similar with $BCl_3/He$ plasma. The chemical reactions of the etched TiN thin films are investigated by X-ray photoelectron spectroscopy. The intensities of the Ti 2p and the N 1s peaks are modified by $BCl_3$ plasma. Intensity and binding energy of Ti and N could be changed due to a chemical reaction on the surface of TiN thin films. Also we investigated that the non-volatile byproducts such as $TiCl_x$ formed by chemical reaction with Cl radicals on the surface of TiN thin films.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.1085-1090
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• 1991

Chemical heat pump is a system to upgrade the low level energy such as industrial waste heat and solar energy by using coupled endothermic and exothermic chemical reactions. Dehydrogenation of 2-propanol can absorb heat near 80.deg. C and is transformed into acetone and hydrogen. Hydrogenation of acetone can liberate heat near 200.deg. C. Dehydrogenation of 2-propanol is difficult around 80.deg. C because .DELTA.G has positive value, but dehydrogenation reaction in liquid phase can overcome this problem because vaporized acetone and hydrogen can be rapidly eliminated. In this work, dehydrogenation of 2-propanol was investigated in liquid phase with Raney nickel catalyst. The energy efficiency of the chemical heat pump was estimated by computer simulation.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1136-1144
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• 1999

The collision-induced reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on a silicon (001)-(2×1) surface is studied by use of the classical trajectory approach. The model is based on reaction zone atoms interacting with a finite number of primary system silicon atoms, which then are coupled to the heat bath, i.e., the bulk solid phase. The potential energy of the Hads‥Hgas interaction is the primary driver of the reaction, and in all reactive collisions, there is an efficient flow of energy from this interaction to the Hads-Si bond. All reactive events occur on a subpicosecond scale, following the Eley-Rideal mechanism. These events occur in a localized region around the adatom site on the surface. The reaction probability shows the maximum near 700K as the gas temperature increases, but it is nearly independent of the surface temperature up to 700 K. Over the surface temperature range of 0-700 K and gas temperature range of 300 to 2500 K, the reaction probability lies at about 0.1. The reaction energy available for the product states is small, and most of this energy is carried away by the desorbing H2 in its translational and vibrational motions. The Langevin equation is used to consider energy exchange between the reaction zone and the bulk solid phase.

• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1508-1512
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• 2004

A gas chromatography/mass spectrometric (GC/MS) method has been developed for the determination of trace mono-n-butyltin (MBT), di-n-butyltin (DBT), and tri-n-butyltin (TBT) compounds in sediments. Samples were extracted by 10% acetic acid in methanol containing 0.03% tropolone and were then derivatized for GC/MS analysis. Ethylation by sodium tetraethylborate and phenylation by sodium tetraphenylborate were evaluated as a derivatization reaction of the organotins in sample extract. n-Hexane was added into reaction media in the beginning of the reaction for the continuous extraction of derivatized organotins. Ethylation requires less than 2 hours to get proper derivatization yields for MBT, DBT, and TBT altogether and produces relatively low amounts of side reaction products. Compared to ethylation, phenylation requires much longer time but provides relatively lower yield and produces considerable amounts of side reaction products. Therefore, the ethylation reaction was applied for the analysis of organotin compounds in sediment. An isotope dilution mass spectrometric (IDMS) method based on GC/MS has been applied to the accurate determination of DBT compounds in the sediments. The IDMS results from the analyses of sediment samples showed a reasonable repeatability and a good agreement with the values obtained by IDMS based on liquid chromatography/induced coupled plasma/mass spectrometry.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.384-388
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• 2010

Human microsomal prostaglandin E synthase-1 (mPGES-1) catalyzes the conversion of prostaglandin $H_2$ ($PGH_2$) into prostaglandin $E_2$ ($PGE_2$). To establish a stable and efficient method to assess the activity of mPGES-1, a coupled enzyme assay system using mPGES-1, 15-hydroxyprostaglandin dehydrogenase (15-PGDH) and phosphomolybdic acid (PMA) was developed. In this assay system, $PGH_2$ was converted to $PGE_2$ by mPGES-1, and then $PGE_2$ was further transformed to the 15-keto-$PGE_2$ by 15-PGDH accompanying the production of NADH, which was easily detected by fluorescence spectrometry in a multi-well plate format. During the reaction, spontaneous oxidation of $PGH_2$ was prevented by PMA. Using this novel assay, the $K_m$ value of mPGES-1 for $PGH_2$ and the $IC_{50}$ value of the previously characterized inhibitor, MK-886, were determined to be 0.150 mM and $2.8\;{\mu}M$, respectively, which were consistent with the previously reported values. In addition, low backgrounds were observed in the multi-wall plate screening of chemical compounds.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.833-838
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• 2014

The energy- and time-dependent branching to the competing dissociation paths are studied by theory for coupled unimolecular dissociations of the o-, m-, and p-chlorotoluene radical cations to $C_7{H_7}^+$ (benzylium and tropylium). There are four different paths to $C_7{H_7}^+$, three to the benzylium ion and one to the tropylium ion, and all of them are coupled together. The branching to the multiple paths leads to the multiexponential decay of reactant with the branching ratio depending on both internal energy and time. To gain insights into the multipath branching, we study the detailed kinetics as a function of time and internal energy on the basis of ab inito/RRKM calculations. The number of reaction steps to $C_7{H_7}^+$ is counted for each path. Of the three isomers, the meta mostly goes through the coupling, whereas the para proceeds with little or no coupling. In the beginning, some reactants with high internal energy decay fast to the benzylium ion without any coupling and others rearrange to the other isomers. Later on all three isomers dissociate to the products via long-lived intermediates. Thus, the reactant shows a multiexponential decay and the branching ratio varies with time as the average internal energy decreases with time. The reciprocal of the effective lifetime is taken as the rate constant. The resulting rate-energy curves are in line with experiments. The present results suggest that the coupling between the stable isomers is thermodynamically controlled, whereas the branching to the product is kinetically controlled.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2743-2748
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• 2014

Novel 4'-trifluoromethyl-5'-norcarbocyclic purine phosphonic acid analogs were efficiently synthesized from commercially available 1,3-dihydroxy cyclopentane (5). Trifluoromethylation was successfully performed by using the Ruppert-Prakash reaction. The purine nucleosidic bases were efficiently coupled by using the Mitsunobu reaction. The synthesized adenosine phosphonic acids analogs 13 and 16 were screened for antiviral activity against human immunodeficiency virus-1 (HIV-1). Adenine derivative 13 exhibited significant anti-HIV-1 activity.

• Transactions on Electrical and Electronic Materials
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• v.18 no.2
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• pp.74-77
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• 2017

In this work, we investigated the etching characteristics of TaNO thin films and the selectivity of TaNO to $SiO_2$ in an $O_2$/CF4/Ar inductively coupled plasma (ICP) system. The maximum etch rate of TaNO thin film was 297.1 nm/min at a gas mixing ratio of O2/CF4/Ar (6:16:4 sccm). At the same time, the etch rate was measured as a function of the etching parameters, such as the RF power, DC-bias voltage, and process pressure. X-ray photoelectron spectroscopy analysis showed the efficient destruction of the oxide bonds by the ion bombardment, as well as the accumulation of low volatile reaction products on the etched surface. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the $CF_4$-containing plasmas.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.211-219
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• 1998

Propellants pressurized and fed into the combustion chamber undergoes the mechanical, chemical combustion processes. Along with their distinctive physical characteristics, propellant combustion is typically divided into the processes; injection, atomization, mixing, vaporization and chemical reaction. These processes assumed to happen in a serial manner are strongly coupled, thereby involves formidable physical complexities. In this study a numerical experiment is attempted to simulate the burning sprays due to OFO, FOF triplet / FOOF split doublet injectors. Based on Eulerian-Lagrangian frame, Navier-Stokes equation system for compressible flows is preconditioned with low Reynolds number $k-{\varepsilon}$ turbulent model and time-integrated by LU-SGS, and the sprays are described by DSF model with the characteristics initialized by experimentally determined spray characteristics. Simplified single global reaction model approximates heptane-air reaction. It was observed that FOOF split doublet injector shows better atmization with shortest residence and the FOF triplet injector produces better combustion performance.