• Journal of the Korean Chemical Society
• /
• v.53 no.6
• /
• pp.635-639
• /
• 2009

Experimental work was carried out to study the combustion kinetics of the Indian coal-char in the varying mixture of carbon dioxide-oxygen ($CO_2-O_2$). The coal sample was pulverized and sieved to less than 58 microns and charred using volatile furnace by passing the nitrogen gas. The experiments were carried out using the Thermo Gravimetric Analyzer (TGA-50) at CPRI, Bangalore, different proportions of ($CO_2-O_2$) gas was allowed in to the TGA-50 (80-20, 60-40, 40-60, 20-80) mole basis were used to study the combustion kinetics of coal Isothermally, kinetic parameters like Activation energy (E) and the pre-exponential factors (A) are calculated using the unification approach and modified Arrhenius equation.

• Journal of Hydrogen and New Energy
• /
• v.25 no.4
• /
• pp.425-435
• /
• 2014

Simulation studies on catalytic methanation reaction in externally cooled tubular reactor filled with monolithic catalysts were carried out using a general purpose modelling tool $gPROMS^{(R)}$. We investigated the effects of operating parameters such as gas space velocity, temperature and pressure of feeding gas on temperature distribution inside the reactor, overall CO conversion, and chemical composition of product gas. In general, performance of methanation reaction is favored under low temperature and high pressure for a wide range of their values. However, methane production becomes negligible at temperatures below 573K when the reactor temperature is not high enough to ignite methanation reaction. Capacity enhancement of the reactor by increasing gas space velocity and/or gas inlet pressure resulted no significant reduction in reactor performance and heat transfer property of catalyst.

• Analytical Science and Technology
• /
• v.20 no.3
• /
• pp.251-254
• /
• 2007

In this study, a convenient, fast and accurate inductively coupled plasma atomic emission spectrometry (ICP-AES) method has been optimized for the determination of osmium in aqueous solutions. The method makes use of the reaction of sulfurous acid with osmium to quantitative conversion of volatile Os(VIII) to non-volatile Os(IV) in the pH range 2-10. The response was found to be stabilized immediately after sulfurous acid reacted with osmium. The precision was calculated to be 0.5-4.5 % (RSD) under various ICP-AES conditions. The detection limit was 2.5-57.7 ng/g based on $3{\sigma}$ of the blank response (n=3) using a concentric flow nebulization.

• Applied Chemistry for Engineering
• /
• v.10 no.5
• /
• pp.701-706
• /
• 1999

The effect of siloxane oligomer content on thermal stability and internal stress of DGEBA epoxy resin was investigated. Siloxane-epoxy polymers having terminal epoxy group were prepared by reaction of siloxane-DDM prepolymer with DGEBA epoxy resin. Thermal stability was studied in terms of the initial decomposition temperature(IDT), temperature of maximum rate of weight loss($T_{max}$), integral procedural decomposition temperature(IPDT), and decomposition activation energy($E_t$) using TGA data. The thermal stability increased with increasing the siloxane oligomer content and showed a maximum value in the case of 5 wt% siloxane oligomer content in the blend system. While, the coefficient of thermal expansion(${\alpha}_r$) and the flexural modulus($E_r$) allowed us to study internal stress of the blend system. As the content of siloxane oligomer increases, the internal stress systematically decreases as decreasing both ${\alpha}_r$ and $E_r$.

• Journal of the Korean Ceramic Society
• /
• v.39 no.6
• /
• pp.540-549
• /
• 2002

In this work, the hydration behaviour of portland cement pastes containing fly ash, blast-furnace slag and silica fume is investigated by Impedance Spectroscopy(IS). As fly ash or blast-furnace slag was added to portland cement, the values of R$_{t(s+1)}$ and R$_{t(s+1)}$ were decreased in the early hydration period. It showed that hydration of cement containing blending components was slower than it of the reference cement paste with the same W/C ratio. However, the cement paste containing silica fume had a large value of R$_{t(s+1)}$ and R$_{t(int)}$due to very rapid pozzolanic reactivity of silica fume in the hydration time. In OPC-fly ash system, a characteristic plateau region appeared between straight-line and semicircle. The plateau region continued to grow in range with the content of fly ash and the hydration time.

• Korean Journal of Agricultural Science
• /
• v.11 no.1
• /
• pp.176-181
• /
• 1984

Linear free energy relation ship(LFER) on the insecticidal activity of O,O-diethylphenylphosphate (A) and 3,5-dimethylphenyl-O,O-diethylphosphate (B) derivatives were studied by EHT MO calculation method and regression analysis method. LFER between varying substituent constants and $pI_{50}$ constants of phosphates, (A) & (B) were calculated with applying Hammett, Okamoto-Brown, Taft and Swain-Lupton's DSP equations;percent resonance effect(R) and field effect(F) of (A) were %R=33.5 & %F=66.5 and also that of (B) were %R=2 & %F=98, respectively. On the basis of above findings, the insecticidal activities were similar for both (A) and (B), but (B) have larger field and inductive contribution than (A), due to the 3,5-dimethyl group of (B).

• Applied Biological Chemistry
• /
• v.32 no.2
• /
• pp.170-177
• /
• 1989

In order to seek the molecular basis of higher insecticidal activity of the carbamates with two methyl groups, m-xylyl-N-methylcarbamate(MXNMC) than the corresponding unsubstituted phenyl N-methylcarbamate(PNMC), these two derivatives have been studied by molecular orbital(MO) theoretically using extended $H\ddot{u}ckel$ theory(EHT), and analysis of regression and linear free energy relationship(LFER). The most stable stereo structure(Z, Z) shows that the phenyl group occupies vertical(${\theta}=90^{\circ}$) position on the plane of the N-methylcarbamyl group. Regression analysis shows that especially good correlation exists between the $pI_{50}$ values and the calculated MO quantities when the hydrogen atomic charge of metaposition and of m-methyl groups, and LUMO energy are taken as variables. The LFER analysis on the carbamylation indicates that field(F) effect(60%) is slightly larger than resonance(R) effect(40%) in PNMC(E>R), whereas, in case of MXNMC, R effect(98.6%) is much larger than F effect(1.4%)($R{\gg}F$). From the basis on the findings, the enhancement of insecticidal activity of MXNMC may be the result of hyperconjugation by m-methyl groups.

• Korean Journal of Food Science and Technology
• /
• v.24 no.5
• /
• pp.456-462
• /
• 1992

This study was performed to rapid fermentation from sardine hydrolyzate by using column reactor. The column reactor was constructed from three glass columns $(30cm{\times}5cm)$ and each column was packed with colloidal silica and sodium alginate (1:5) on which Pediococcus halophilus R-22, Saccharomyces rouxii R-60 and Candida etchellsii H-50, respectively, was previously fixed. At that time, optimal conditions for rapid fermentation were found the pH of 5.2, temperature of $30^{\circ}C$ and 10% NaCl. For rapid fermentation, immobilized whole cells of P. halophilus R-22, S. ruoxii R-60 and C. etchellsii H-50 packed the each column reactor were produced 0.75% lactic acid, 2.5% ethylalcohol and 18 mg/l 4-ethylguaiacol under the optimal conditions.

• Journal of the Korean Chemical Society
• /
• v.39 no.9
• /
• pp.734-740
• /
• 1995

The primary and secondary structures of Xanthomonas palargonii 5S rRNA were determined. The higher order structure of the 5S rRNA was also analysed using several ribonucleases and chemical probes, such as ethylnitrourea, Pb2+, dimethylsulfate and diethyl pyrocarbonate. Ethylnitrourea was used for probing the phosphate groups involved in the tertiary interactions in the 5S rRNA. Nucleotides G72, A73, G75, A78, G98, G100 and A101 in unstable helical region d, nucleotides C36, C37, A39, and C41 in loop c, nucleotides A29 and G33 in stem C became resistant to ethylnitrourea modification in the presence of Mg2+. On the basis of findings from chemical and enzymatic studies, and also Pb2+-induced cleavages, it was concluded that region b-C and unstable helical region d may act as hinges in the folding of 5S rRNA.

• Parasites, Hosts and Diseases
• /
• v.36 no.1
• /
• pp.47-54
• /
• 1998

Small subunit ribosomal RNA (SSU rRNA) gene nucleotide sequences of bovine ReiLerin isolates from Korea (KLS and KCB) and japan (JHS) were determined. The genes from each isolate were amplified by the polymerase chain reaction and the approxi- mately 1.8 kb product cloned and sequenced by a modified dideoxynucleotide method. Overlapping gene segments produced with a series of primers were sequenced, resoRting in a complete DNA sequence for both forward and reverse strands of the SSU rRNA genes of each isolate. SSU rRNA gene sequences (termed Type A) were identical among the bovine ReiLeri,n isolates from Korea and the isolate from Japan. A GenBank data library homolo- gy search showed the sequence to be the same as that listed as leiLeyia buKeLi isolated from cattle in Marula, Kenya.