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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korean Society for Atmospheric Environment
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Korean Society for Atmospheric Environment
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Volume & Issues
Volume 13, Issue 6 - Dec 1997
Volume 13, Issue 5 - Oct 1997
Volume 13, Issue 4 - Aug 1997
Volume 13, Issue 3 - Jun 1997
Volume 13, Issue 2 - Apr 1997
Volume 13, Issue 1 - Feb 1997
Volume 3, Issue 4 - 00 1997
Volume 3, Issue 3 - 00 1997
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Facilitated Transport of Oxygen in Poly(dimethylsiloxane-co-styrene-co-4-vinyl pyridine) Terpolymer Membrane Containing Cobalt Schiff Base Carrier
홍재민 ; 이상욱 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 165~165
A facilitated transport membrane was prepared by incorporating a cobalt Schiff base, Co(salen), as an oxygen carrier into a terpolymer membrane of poly(dimethylsiloxane-co-styrene-co-4-vinyl pyridine) A reversible oxygen binding of the carrier was investigated with UV-visible spectroscopy. The terpolymer membrane with carrier showed that the permeability of oxygen was increased from 275 to 405 barrer due to a facilitation action of Co(salen) carriers. Upon incorporating Co(salen) into the membrane, the free volume is expected to be increased due to the bulkiness of Co(salen). The increased free volume resulted in the enhanced permeabilities of both oxygen and nitrogen. Therefore, the oxygen selectivity over nitrogen through the terpolymer membrane with Co(salen) was only marginally increased. The effects of the temperature and carrier concentration on the diffusivity and solubility were also investigated.
Effects of Additive on Electrical Tree Behavior in Epoxy Resin
조영신 ; 이홍기 ; 심미자 ; 김상욱 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 171~171
The electrical tree behaviors in the cured DGEBA(diglycidyl ether of bisphenol A)-MDA(4,4'-methylene dianiline) epoxy resin system according to the addition of SN(succinonitrile) were studied. The effects of temperature and electrode separation on the dielectric breakdown strength were measured. The discolored region detected around the needle electrode under high electric field corresponded to the rearrangement of unreacted functional groups and post-curing reaction by electro-chemical reaction. With the increase of SN content, the dielectric breakdown strength reduced and saturated to 25 kV/mm. As the temperature and electrode gap increased, the dielectric breakdown strength decreased. The shape of the tree in this system was dendrite type.
Photoluminescent Properties of Zinc Gallate doped with Tm, Ce, Dy and Mn
유호진 ; 박희동 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 177~177
The luminescent properties of the Tm, Ce, Dy and Mn-doped synthesized with solid state reaction method were studied. Under 254 nm excitation, zinc gallate exhibited a broad-band emission extending from 330 nm to 510 nm, peaking at 450 nm. The emission intensity of 0.015 mole % Tm-doped zinc gallate is allmost twice as much as that of undoped zinc gallate On the otller hand, Mn-doped zinc gallate showed a new strong narrow-band emission, peaking at 504 nm, and the maximum intensity at the doping concentration of 0.006 mole % Mn
Lipase-supported Preparation of Optically Active 2-Amino Alcohols of Biological Interest
진명종 ; 김상한 ; 정성택 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 182~182
Transesterification of racemic N-acetylated 2-amino alcohols with vinyl acetate was investigated in the presence of inexpensive commercial porcine pancreatic lipase. The enzymatic kinetic resolution occurred with high reactivity and enantioselectivity to give optically pure N,O-diacetylate and N-monoacetylate. This result clearly indicates that the biocatalytic route can be efficiently used in the preparation of enantiopure 2-amino alcohol.
Synthesis of Na-P1 Zeolite from Coal Fly Ash
김완복 ; 정승훈 ; 안병준 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 185~185
Na-P1 zeolite was synthesized from coal fly ash with a 2-3 M NaOH solution at 100-150℃. Other than these conditions, four kinds of zeolites were also found along with Na-P1. Faujasite, hydroxy sodalite, analcime, and cancrinite phases were identified under various conditions. Na-P1 zeolite exhibited high CEC of 215 meq/100 g and strong affinity for Pb and Sr metal ions. These results give the application for the removal of heavy metal ions from the conversion of waste fly ash to Na-P1 zeolite.
Reaction Kinetics of Oxygen for Microporous Carbons with High Surface Area
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 191~191
The reaction of oxygen with microporous carbons with high surface area at temperatures up to approximately 1000 K is studied using combined thermogravimetric analyzer and mass spectrometer. The study will place an emphasis on the role of the carbon-oxygen surface complex. The surface complex is the primary intermediate in carbon gasification, yet its role in the reaction is not well understood. Below 900 K, for example, the complex is stable and remains on the surface as the reaction proceeds. Above this temperature, though, the complex desorbs readily, and adsorption is presumably the rate controlling step.
An Infrared Spectroscopic Study of Acetylacetone Adsorbed on Layer Silicates Containing Various Interlayer Cations
손종락 ; 이상일 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 198~198
The adsorption of acetylacetone on layer silicates containing various cations has been studied by means of infrared spectroscopy, X-ray and thermal analyzer. An analysis of several split bands in the region of 1740-1520 cm-1 was made. The split bands were attributed to the interaction of carbonyl with surface hydroxyl and cationic hydroxyl groups, and were responsible for the formation of acetylacetonate complexes between enolic or anionic acetylactone and metal cation in silicate layer.
Preparation of 1,1,1-trifluoroethane by Catalytic Fluorination of 1,1,1-trichloroethane and 1-fluoro-1,1-dichloroethane
김홍곤 ; 김훈식 ; 이병권 ; 권영수 ; 박근유 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 203~203
Preparation of 1,1,1-trifluoroethane by catalytic gas phase fluorination of 1,1,1-trichloroethane and 1-fluoro-1,1-dichloroethane was studied. Mixtures of chromium fluoride and magnesium fluoride were found to be active fluorinating catalysts for preparing 1,1,1-trifluoroethane. Molar ratio of chromiunl to magnesium in the active catalysts was determined to be in the range of 0.2/ to 4/1. Optimal conditions of reaction temperature, contact time and feed composition as well as the extent of the catalyst temperature increase by the exothermic reactions were also studied. Two stage fluorination reaction was proposed for producing a high yield of 1,1,1-trifluoroethane and for lengthening the catalyst lifetime : 1,1,1-trichloroethane to 1-fluoro-1,1-dichloroethane at a low temperature first and 1-fluoro-1,1-dichloroethane to 1,1,1-trifluoroethane at a high temperature later.
Effect of Hysteresis Behavior on Two-phase Vertical Downward Flow Through Tubes
Shim W. Jaewoo ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 210~210
This study reports an experimental investigation of hysteresis behavior in two-phase, air-water, downward flow through a vertical test section that included two turbine flow meters. Void fractions were measured at the inlet and outlet of the test section by two gamma densitometers. The turbine flow meter response was correlated for a calibration model to measure the flow rates of each phase in a two-phase downward flow mixture. The correlation was found to depend only on the actual volumetric flow rate of the gas and liquid at the location of each flow meter. For liquid flow rates less than 13.6 actual cubic meter per hour (acmh) the correlation or the calibration model becomes more non-linear and the void fraction exhibits hysteresis which is more pronounced at the lower liquid flow rates. For a constant liquid flow rate less than 13.6 acmh, the void fraction measured for increasing gas flow lies below the values measured for decreasing gas flow. These differences can be very large, yet the turbine flow meter responses are practically unaffected by these changes.
Preparation and Performance of the Briquette Type Activated Carbon Based on Bituminous Coal
김상철 ; 홍인권 ; 박경애 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 218~218
Bituminous coal-based activated carbon was prepared in a rotary kiln type furnace and the effect of pretreatment on the preparation of activated carbon was investigated. A manufacturing process using steam as the activation agent was employed. The flow rate of the activation agent(steam) was found to have significant influence on the development of the porous network of the briquette type activated carbon. Furthermore, activation temperature affected on the properties of activated carbon. The adsorption capacity, or iodine value(I2) was increased in the activation temperature range of 800 to 900℃, yet decreased at higher temperatures than 900℃. Then, the activation effect was analyzed by the definition of the activated carbon(AC) yield. It was found that the optimum activation time and steam amount were 240 minutes, and 1g steam/g coal·hr, respectively.
Silicon Carbide Fibers from Copolymers of Commercial Polycarbosilane and Silazane
Choi, Guang J. ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 223~223
A new approach to prepare silicon carbide fibers by a non-oxidative chemical crosslinking of a commercial, low molecular weight polycarbosilane via copolymerization with vinyl silazane monomer was investigated. Dicumyl peroxide was used as an initiator for copolymerization reactions. SiC fibers were Produced by pyrolyzing the spun Polymer fibers at 1000℃ without any additional curing Process. The ceramic yield upon pyrolysis was 65-70%. According to neutron activation analysis, the oxygen content of our copolymer- derived SiC fibers was less than 3 wt%. The tensile strength of our SiC fibers increased slightly after 1400℃ heat-treatment while it dropped greatly after 1500 ℃ treatment.
Charge-Transfer Effect in Solid Phase Peptide Synthesis : Kinetic Studies in Peptide Bond Formation between Nitrobenzophenone Oxime Resin Esters and Amino Acid Esters
박병덕 ; 김의덕 ; 이윤식 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 229~229
The effects of charge-transfer complex formation on the rate of peptide bond formation in solid-phase peptide synthesis (SPPS) were examined. 4-Nitro and 3-nitrobenzophenone oxime resins which can act as electron acceptors were prepared. Amino acid 4-(methylthio)phenyl [MTP] esters and 4-methoxyphenyl [PMP] esters which can act as electron donors were prepared. Amino acid pheny[Ph] esters were also prepared for comparison. The aminolysis reactions of the oxime resin esters with amino acid MTP, PMP, and Ph esters were compared in dipeptide formation reactions. The reactions were followed by reverse phase HPLC and their pseudo first-order rate constants were calculated. The results showed that the charge transfer interactions largely depended on the steric hindrance between the electron donors and acceptors. When there is little steric hindrance like Gly esters, MTP and PMP esters revealed fast reactions due to charge-transfer interactions. But, in case of other amino acid esters, the aminolysis reactions were influenced by other factors, such as nucleophilicity, orientation, and bulkiness of the nucleophiles.
Characterization of Supported Cobalt Catalysts by TPR and TPD
최정길 ; 최형기 ; 정문기 ; 오현균 ; 최종오 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 235~235
The surface of cobalt catalysts supported on Al2O3, SiO2, and TiO2 were investigated using temperature-programmed reduction and desorption. Effects of different supports, metal loading, and preparation condition on cobalt catalyst properties were also evaluated. The activation energy of reduction increased in the following order : Co/TiO22O32. For different metal loadings, the catalyst with the lower loading was less readily reducible than that with the higher metal loading. This was confirmed using the results from measurements of particle size, amount of CO desorbed and catalytic activity. While carbon monoxide adsorption at room temperature produced four carbon monoxide desorption peaks for Al2O3-supported cobalt catalyst, one carbon monoxide desorption peak was observed for cobalt catalysts supported on SiO2 and TiO2. Based on the results on the amount of carbon monoxide desorbed, it was considered that multiple desorption peaks on Co/Al2O3 catalyst might be due to the morphological changes between cobalt oxide and alumina support, and the stabilization of Co2+by SiO2 support and the concept of SMSI (strong metal-support interaction) were suggested to explain the results for Co/SiO2 and Co/TiO2 catalysts, respectively.
Luminescence Properties of Zinc Gallate Affected by Mg and Rare-earth Elements
유호진 ; 박희동 ;
Journal of Korean Society for Atmospheric Environment, volume 3, issue 3, 1997, Pages 247~247
Zinc gallate (ZnGa2O4,) phosphor shows promising low voltage properties. Phosphor powders of zinc gallate added with Mg and rare-earth elements were prepared with solid state-reaction method to improve blue luminescent properties. Tm (or Dy), Mg-added zinc gallate phosphor exhibited a strong blue band emission, peaking at about 420 nm, the maximum intensity at the concentration of 0.005 mol% Tm and 0.2 mol% Mg. It was possible to control luminescent characteristics of zinc gallate by adding various elements.