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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 7, Issue 3 - Dec 1991
Volume 7, Issue 2 - Oct 1991
Volume 7, Issue 1 - May 1991
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Mechanical Properties and Atomic Force Microscopic Cross Sectional Analysis of Injection Molded Poly(ethylene terephthalate-co-4,4'-bibenzoate)
D. A. Schiraldi ; Joshua J. Lee ; S. A. C. Gould ; M. L. Occelli ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 67~67
A series of poly(ethylene terephthalate-co-4,4'-bibenzoate), PETBB, copolymers were prepared using isomeric 2,4'-, 3,4'-, and 4,4'-bibenzoate monomers. Only the 4,4'-bibenzoate copolymers produced the desired, high temperature, semicrystalline materials. As a result, a PETBB copolymer containing 55 mole% 4,4'-bibenzoate was scaled up and injection molded, along with poly(ethylere terephthalate), PET, and poly(butylene terephthalate), PET, homopolymers. The PETBB copolymer was demonstrated to give shorter injection molding cycle times than PET (known for its short cycle times), and exhibited better thermal properties than either homopolymer. The PETBB copolymer exhibited 40-50% higher tensile and modulus properties when compared to PBT injection molding resin. An examination of cross-sections of the PETBB molded bars by atomic force microscopy showed these bars to be morphologically homogeneous, with no discernable surface skin effects. Details of the PETBB morphology are shown in the AFM images presented.
Physicochemical and Thermal Properties of Viscose Rayon Borate Felt
Ko, Y. G. ; Choi, U. S. ; Ahn, D. J. ; Kim, J. S. ; Kim, T. Y. ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 72~72
Berate, as a multifunctional material that is a flame retardant, smoke suppressant, afterglow suppressant and electrically resistant, was synthesized on viscose rayon felt using surface modification reactions. In addition viscose rayon phosphate was also synthesized for a comparison test. All reactions were confirmed by ATR FT-IR and TOF-SIMS. The thermal properties of the synthesized viscose rayon berates were investigated using a thermogravimetric analysis and calculated activation energy using the Freeman and Carroll method. The optimal reaction temperature of the synthesized viscose rayon berate was found to be 350 ℃. Oxygen index and volumetric resistance rate tests of viscose rayon berate were conducted for flame retardency and electrical resistance, and compared with viscose rayon phosphate, The synthesized viscose rayon berate showed excellent physicochemical and thermal properties, and was found to be a highly effective flame retardant and electrically resistant.
Preparation and Dental Properties of Novel Functional Polymeric Restorative Materials
김오영 ; 이태정 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 78~78
The preparation of novel polymeric dental restorative materials (PDRM) was carried out using hybrid-filler, which was consisted of fumed silica microfiller and barium glass macrofiller, resulting in the improvement of mechanical properties of PDRM. In order to enhance the miscibility of inorganic hybrid-filler with organic resin matrix in PDRM and to conduct the homogeneity of filler, its surface was hydrophobically treated with γ-methacryloxypropyl trimethoxysilane and freeze-drying method was adopted to remove the solvents. Diametral tensile strength, flexural strength, Knoop hardness, polymerization shrinkage, and abrasion resistance of PDRM prepared were investigated comparing with those of commercial PDRM products. The PDRM produced in this work showed excellent mechanical properties as well as superior polymerization shrinkage values. It was also discovered that PDRM prepared by using hybrid-filler resulted in better surface characteristics.
Effect of Coating Cycle on Ferroelectric Properties of PZT Thin Films Prepared by Sol-Gel Processing
서경원 ; 조성현 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 87~87
Ferroelectric PZT thin films on Pt/Ti/SiO2/Si(100) substrates with a thickness of 0.14 to 0.42 mum were prepared by sol-gel processing with one to seven spin coatings of a 0.4 M starting solution (Pb/Zr/Ti=1.1/0.52/0.48). After the fifth coating cycle, a dominant of the PZT (110) phase appeared, which was sufficient to achieve a proper intensity of perovskite PZT thin film. The relative dielectric constant (epsilon (r)) of the films increased as the number of coating cycles increased, while the dissipation factor hardly changed. The remnant polarization (P-r) also increased slightly, whereas the coercive field (E-c) significantly decreased. The electrical properties of the thin film coated five times (0.3 mum) were shown to be suitable for dielectric devices.
Isentropic Analysis for the Long Range Trajectories of Yellow Sands
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 89~95
Yellow sands often occur in Korea during April and May each year, and they are believed to come from the Mongolian Gobi desert as the snow starts to melt in Spring time. Since the analysis of aerosol particulates can hardly distinguish the origin of particulates, the isentropic analysis of meteorological data is often used for the trajectories of the long range transport of yellows sand or air pollutants. The yellow sand case of April 9 $\sim$ 15, 1988, in Korea is analyzed for the identification of long range transport of yellow sands and their trajectories in East Asia, using isentropic analyses. We have tranformed the ECMWF grid data, analyzed in pressure coordinates, into the isentropic coordinates and then have traced the 286 K and 290 K air mass which started Gobi desert. The result shows the transport of yellow sands from the Gobi desert to the Korean peninsula.
Application of Small-Angle Laser Light Scattering Technique to Study Amorphous Iron Hydroxide Flocs
정석조 ; Rose Amal ; 조영민 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 92~92
The validity of the small angle laser light scattering(SALLS) technique for analyzing the structure of aggregated particles was examined based on an evaluation of fractal dimension. Hydrolyzing metal salts were used for the coagulation and the pH was adjusted by addition of a sodium hydroxide solution. The effect of agitation was also observed and a Malvern Mastersizer was used as the light scattering instrument. It was found that the SALLS method was useful in evaluating the fractal dimension of micron-sized flocs in real time, plus the mechanical shear rate had no affect on the flee break-up or restructuring.
The Meteorological Factors Governing
Concentrations During the Wintertime in Seoul Area
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 96~104
An investigation is carried out for the roles of the synoptic meteorology in governing $SO_2$ concentrations in Seoul during the wintertime. This study has used the daily records of wind and temperature measured at the Korea Meteorological Administration in Seoul. A one-dimensional diffusion model has been used for investigating the influence of the mixing height on the diurnal variation of concentration. The day to day variations of the concentration are well correlated with those of wind and temperature. The diurnal variation of the concentration is dictated by the variation of mixing height. It is also found that mesoscale wind field is required to explain the mesoscale distribution of the concentration.
A Photocatalytic Degradation of Phenol Over TiO2 Prepared by Sol-Gel Method
홍성수 ; 주창식 ; 임창규 ; 안병현 ; 임권택 ; 이건대 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 99~99
Photocatalytic degradation of phenol has been carried out over various titanium dioxides. Titanium dioxides were prepared by sol-gel method from titanium iso-propoxide at different R ratio (H2O/titanium isopropoxide) and calcination temperature. All titanium dioxides were characterized by XRD, BET surface area analyzer and UV-DRS. The effect of reaction conditions, such as initial concentration of reactants, reaction temperature and concentration of oxidants on the photocatalytic activity has been studied. Titanium dioxides prepared by sol-gel method show higher activity than commercial TiO2 catalysts on the photocatalytic degradation of phenol. The crystallization of titanium dioxide increases as increasing calcination temperature and rutile-type structure appears when it is calcined at 600 ℃. Titanium dioxide prepared at R ratio=75 and calcined at 400 ℃ shows the highest activity on the photocatalytic degradation of phenol. The photocatalytic degradation of phenol shows pseudo-first order reaction and the degradation rate increases with decreasing initial phenol concentration.
The Influence of Topography on
Concentration is Seoul Area
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 105~113
An investigation is carried out for the role of topography in governign the mesoscale distribution of $SO_2$ concentration in Seoul. The three dimensional wind fields computed for a given synoptic meteorological condition by an atmospheric mesoscale model in the terrain following coordinate have been employed to compute the three dimensional mesoscale distributions of $SO_2$ concentration by the diffusion model in Seoul area. Terrain may affect the mesoscale distributions of $SO_2$ concentration through its influence on the mesoscale wind fields. This study discusses only the terrain effect on the concentration through its modification of the wind. This effect is to produce higher concentration in lower area according to the structure of divergence fields derived from and atmospheric mesoscale model.
Improved Decomposition Efficiency of Nitrogen Oxides using Superposing SPCP and Corona Discharges
우인성 ; 강현춘 ; 조정국 ; 황명환 ; 강안수 ; M. Yamaguma ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 105~105
The superposing effect of an SPCP(Surface discharge-induced Plasma Chemical Process) and corona discharge were studied for the removal of NOx from industrial flue gases. The NOx removal rates caused by an SPCP, corona discharge, and superposing discharge were monitored and compared. The parameters included the concentration, flow rate of gas, frequency, and type of discharge. The experimental results showed that the NOx removal rate with a superposing discharge was 10 similar to 30% higher than that with the other two modes. The maximum obtainable NOx removal rate with only a SPCP (18 W) on a corona discharge (7 W) was 85% and 12%, respectively. However, the combination of the two modes, produced a 95% NOx removal rate with a discharge power of 18 W with a lower frequency (450 Hz). A higher NOx removal rate was observed with a lower frequency in the upper electrode in the combined reactor and a higher frequency in the lower electrode. Accordingly, corona discharge (below 600 Hz) in the current study, a combined with an SPCP electrode (at a lower power) appeared to be the best method to remove NOx.
Methane Combustion over Lanthanoid Perovskite Catalysts
김규성 ; 김상범 ; 최우진 ; 김태옥 ; 함현식 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 110~110
Methane combustion over perovskite catalysts was investigated using a fixed-bed reactor at 1 bar. Co, Mn, Fe, and Ni were used as the B-site of the perovskite catalysts (ABO(3)) and La was used as the A-site. The effect of the calcination temperature on methane combustion and the structure of the perovskite were also investigated. Using XRD, surface area measurements, and O2-TPD, the effects of the perovskite structure, oxygen species adsorbed, and surface area on methane combustion were all examined. The formation of a perovskite structure was affected by the calcination temperature. A catalyst desorbing oxygen at a lower temperature was better for methane combustion, whereas an oxygen species desorbing at a lower temperature was found to be responsible for methane combustion.
PIXE Analysis of Aerosol Particles - Preparation of Standard Samples and Calibration Test -
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 114~118
Particle Induce X-Ray Emission (PIXE) analysis is one of the most useful methods which can determine the elemental concentration of aerosol particles in nano-gram range. The main purpose of this paper is to establish the measurement system and the procedure of PIXE analysis. The standard samples were prepared to calibrate the PIXE analysis by three different techniques. The linear relationships between the peak counts from PIXE spectra and the mass density from RBS spectra were obtained for each standardized element under the applied measurment geometry and conditions. The sensitivity curves for PIXE analysis were determined from these relationships.
Catalytic Recombination of Hydrogen and Oxygen in Air Stream
김광락 ; 백승우 ; 최희주 ; 정홍석 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 116~116
This paper presents the results of a study aimed at determining the feasibility of using catalytic oxidation to scavenge hydrogen from air. A series of experiments were conducted to assess the catalytic recombination characteristics of hydrogen in an air stream using 0.5% Pd/alumina catalysts. The H2 to H2O fractional conversion was determined at various inlet air temperatures (25∼150 ℃) and flow rates (5∼15 L/min.). The catalyst produced remarkable fractional conversion values up to 0.9 when operated at 150 ℃ with an apparent activation energy of about 3.17 kcal/mol within a temperature range of 50∼150 ℃. The results show that the catalyst had a relatively low activated energy and possessed satisfactory characteristics for catalytic oxidation.
Primary Effects of Ozone on MUsca domestica L.
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 119~126
Air pollution is directly and indirectly associated with the toxicology through the increase of mortality, the decrease of oviposition rate, and the decline of insect population, as well as the disruption of equilibria with higher or lower trophic levels. To investigate intrinsic decrease rates, oviposition period, and emerging rates of pupae of house fly under air pollution stresses, healthy individuals of Musca domestica L. were collected in the field, cultured in the laboratory for 2 $\sim$ 3 generations, and artificially exposed to $O_3 (4 ppm) in automatically controlled air pollutant fumigation chambers. Results from this study are summarized as follows: 1. Survivorship curves of both control group and exposed groups of healthy house fly to 4 ppm $O_3$ have linearly or stair-like decreasing trends of revers S-shape. 2. For cohorts exposed to 4 ppm of $O_3$, intrinsic decrease rate of cohort exposed for 2 hours significantly increases compared to that of control group, slight increases were observed for those exposed for 4 hours and 8 hours, which shows no distinct relationships between exposure period and intrinsic decrease rate. 3. While the numbers of pupae of exposed cohorts increase with the increase of exposure period, emerging rate shows a distinct decrease. 4. The relationships between emerging rate (E) of pupae and the exposure period (T) for cohorts exposed to 4 ppm of $O_3$ are expressed with the equation, E (%)=21.027 - 7.942 ln (T).
Synthesis and Characterization of Organic-Free MFI Type Zeolite
장옹일 ; 이종훈 ; 김미영 ; 안병준 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 121~121
The crystallization of MFI type zeolite was studied in the absence of organic templates to elucidate the process of the MFI - to-Quartz transformation. The crystallization products were characterized using XRD, EDX, FT-Raman, SEM, and Si-29 MAS NMR. The first splitting of the MFI crystal seemed to occur mostly at aluminum-rich sites, which are thermodynamically unstable and highly reactive in the presence of an OH(-) ion. Accordingly, it is suggested that MFI does not transform to the α-quartz phase via an amorphous solution based on the complete disintegration of the MFI crystal, but rather transforms via a bundle of sheet-like intermediates.
A Stochastic Model for Air Pollutant Concentration
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 127~136
This paper is concerned with the development and application of a stochastic model for daily sulphur dioxide $(SO_2)$ concentrations in urban area (Seoul). For this, the characteristics of the regression trend, periodicity and dependence of the daily $SO_2$ concentration are investigated by a statistisical analysis of the daily average $SO_2$ values measured in Seoul area during 1989 $\sim$ 1990. Based on these, nonlinear regression time series model for the prediction of daily $SO_2$ concentrations is derived. A statistical procedure for using the model to predict the concentration level is also proposed.
Determination of Iron, Copper, and Zinc in Rainwater by Ion Chromatography
Journal of Korean Society for Atmospheric Environment, volume 7, issue 2, 1991, Pages 137~142
A method is developed for the simultaneous determination of dissolved iron, copper, and zinc in rainwater. The method involves 25-fold evaporative concentration, ion chromatographic separation and subsequent spectrophotometric detection after post-column reaction with 4-(2-pyridylazo) resorcinol. Analytical sensitivities, being defined by the slopes of calibration curves, are 0.93, 0.54, and 0.11 Abs/ $\mu$g/ml for iron, copper, zinc, respectively. Detection limits render around a few tenth of one ng/ml. Precisions evaluated by replicate analysis of real sample are better than 10% RSD. Due to the lack of certified standards for rainwater, the accuracy of the method could not be assessed directly. However, the results of this method agree well with those by inductively coupled plasma mass spectrometry. Analytical results for a suite of Seoul rainwaters are presented herein.