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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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Journal DOI :
Korean Society for Atmospheric Environment
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Volume & Issues
Volume 17, Issue 5 - Oct 2001
Volume 17, Issue 4 - Aug 2001
Volume 17, Issue E1 - Apr 2001
Volume 17, Issue 3 - Mar 2001
Volume 17, Issue 2 - Feb 2001
Volume 17, Issue 6 - Jan 2001
Volume 17, Issue 1 - Jan 2001
Volume 7, Issue 6 - 00 2001
Volume 7, Issue 5 - 00 2001
Volume 7, Issue 4 - 00 2001
Volume 17, Issue E4 - 00 2001
Volume 17, Issue E3 - 00 2001
Volume 17, Issue E2 - 00 2001
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Lubricants in Future Data Storage Technology
Myung S. Jhon ; 최형진 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 263~263
Experimentation and theory for the dynamic behavior of thin perfluoropolyther (PFPE) films, as well as PFPE application to the hard disk drive system, are reviewed. A method for extracting spreading dynamics from the scanning microellipsometry (SME) for various PFPE/solid durface pairs, and the rheological characterization of bulk PFPEs, are extensively reviewed. Furthermore, the interrelationship among SME measurements, surface energy, rheology, and tribology, is discussed. Phenomenological microscale mass transfer thory and Monte Carlo simulation techniques are adopted to model the dynamic behavior of thin film lubricants in a unified manner. The fractal dimension is also introduced for potential use in a fingerprint analysis of lubricant/surface pairs. Applications to replenishment and solvent effects on media noise will also be discussed. Integrated modeling with air bearing/lubricant coupling and its applications are also examined.
Removal Process for Octamethylcyclotetrasiloxane form Biogas in Sewage Treatment Plant
이성호 ; 조원일 ; 송태영 ; 김호연 ; 이우진 ; 이영철 ; 백영순 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 276~276
As concern continues to increase over "greenhouse" gases, such as methane and carbon dioxide, many sewage treatment plants have collected and utilized their biogas mixture as a fuel for producing energy. In the case study of sewage treatment plant, biogas has been used as fuel for the gas boilers for the digesters. However, during the several months, unknown white powder is deposited inside the boiler after combustion. It caused severe problems and raised the maintenance cost. We analyzed the deposited mineral and biogas by ICP-MS and GC-MS. As a result, the main deposited component was oxidized silicon, and the biogas sample contained octamethylcyclotetrasiloxane (D4, 20 ppm). Accordingly, a removal process for D4 from the biogas fuel was investigated for the smooth operation of wastewater treatment plants. Through an experiment of the adsorption and detection, it was found that alumina exhibited a more adsorptivity than other materials. The analytical methodology of D4 in the biogas is established in the study.
Electrorheological Behavior of Chitosan Adipicate Suspension as Anhydrous ER fluid
최웅수 ; 박영성 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 281~281
The electrorheological(ER) behavior of a chitosan adipicate suspension in silicone oil was investigated by varying the electric fields, volume fractions of particles, and shear rates, respectively. The chitosan adipicate suspension showed a typical ER response caused by the polarizability of an amide polar group and shear yield stress due to the formation of multiple chains upon application of an electric field. The shear stress for the suspension exhibited a linear dependence on the volume fraction of particles and an electric field power of 1.88. On the basis of the results, the newly synthesized chitosan adipicate suspension was identified as an anhydrous ER fluid.
Effect of Activator on Hydrogen Peroxide Bleaching of White Lidger
안병준 ; Ryuichiro Kondo ; Kokki Sakai ; 박기현 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 285~285
The effectiveness of novel activators in the hydrogen peroxide bleaching of white ledger was investigated. With the addition of 1% sodium persulfate, 4% Prestogen EB, and thiourea(molar ratio to residual hydrogen peroxide=1/2) to hydrogen peroxide bleaching, the brightness of the bleached pulps increased by up to 2~3 points when compared to hydrogen peroxide bleaching with conventional activators. The effectiveness of the activators in enhancing the brightness was in the order of Prestogen EB, thioruea, sodium persulfate and silicates. The strengths of the pulps bleached by hydrogen peroxide with the novel activators were slightly lower or similar to those of the pulps bleached by conventional hydrogen peroxide. In particular, the addition of sodium persulfate produced a more maked decrease in the tensile index of the bleached pulp. Accordingly, sequential oxidative and reductive bleaching with the addition of thiourea to the residual hydrogen peroxide was found to be most effective in view of the bleaching chemical cost, brightness gains, and strength of the bleached pulps.
Chemical of Conveersion of Paper Sluge Incineration Ash into Synthetic Zeolite
문성필 ; 안병준 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 292~292
Paper sludge incineration ash (PSIA) is mainly composed of aluminosilicate glass with metal impirities, such as Fe, Ca, Mg, K, P, Ti and Since the glass is a readily available source of Si and Al for zeolite synthesis, PSIA can be used as a raw material for zeolite. In this study, we investigated the optimum conditions of synthesizing zeolite from PSIA. The synthesized products were characterized using XRD, XRF, EDS, SEM, and FT-IR spectroscopy, mainly composed of Na-Pl zeolite, could be obtained from PSIA with 1-2 M NaOH solutions at a reflux temperature. Hydroxy sodalite was formed at higher NaOH concentration (i.e. 3.505.0 M). The synthesized zeolite exhibited a high cation exchange capacity (CEC) of 244 meq/100g.
Modification of Polysulfone Membranes and Their Application to Gas Separations
임지원 ; 김중란 ; 박유인 ; 이규호 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 299~299
The surface of polysulfone membranes has been modified using the fluorine chemicals, PFPA (pentafluoropropionic anhydride F.W.=310.05) and TFI (Trideca-fluoro-8-idoctane, F.W.=474.0), based on Friedel-Crafts reaction mechanism with varying reaction temperatures, reaction time, and catalysis types. The resulting membranes were characterized through the analysis of ESCA, contact angle measurement and pure water permeability. And the modified PS membranes were exposed to gases of O₂,N₂, and CO₂to measure the permeation rates and ideal separation factors. In addition, the diffusivities and solubilities of individual gases were measured.
EMI Shielding Properties of Carbon Nanofiber Filled Poly Vinylidene Fluoride Coating Materials
이방원 ; 우원준 ; 송희숙 ; 박홍수 ; 함현식 ; 우종부 ; 김명수 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 305~305
The effectiveness of electromagnetic interference (EMI) shielding was measured for poly vinylidene fluoride (PVDF) coating materials containing carbon nanofibers. When the thickness of carbon nanofibers filled PVDF coating materials varied from 25 to100 μm, the electrical conductivity of coating materials was almost constant around 2.0 S/cm except for the case of 25 μm. Although the electrical conductivity should not change with the thickness of coating, the lower value with the thinner thickness could be related to the lack of uniformity at the lower thickness range. The specific surface area and electrical conducitivity of filler were important factors for the shielding effectiveness (SE) of the coating materials. In order to apply carbon nanofibers as EMI shielding materials, large specific surface area and high electrical conductivity were desirable. The SE of the coating material showed a high value with the mild heat treatment at 1100℃ for 1 h and was proportional to the electrical conductivity of the coating materials.
Chemial Modification Poly(styrene-alt-maleic anhydride)with Antimicrobial 4-Aminobenzoic Acid and 4-Hydroxybenzoic Acid
정재훈 ; 봉용섭 ; 고석범 ; 이연식 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 310~310
Poly(styrene-alt-maleic anhydride)(SMA) is one of the most appropriate intermediate polymers that can be converted into bioactive polymers as its succinic anhydride units can react with any bioactive agents with low molecular weights containing amino and hydroxyl groups. In this study, SMA was reacted with antimicrobial 4-aminobenzoic acid and 4-hydroxybenzoic acid to obtain P-1 and P-2, respectively, with reasonably high yields. The glass transition temperatures of P-1 and P-2 were higher than that of SMA due to hydrogen-bonding interactions. The polymers became crosslinked on heating at about 300℃. The new polymers were found to exhibit excellent bacteriocidal activities even though their antifungal activites were not satisfactory.
Comparative Study of Effects of Rubbing Parameters on Polyimide Alignment Layers and Liquid Crystal Alignment
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 316~316
The effects of both rubbing force and rubbing density on polymide alignment layers (ALs) and liquid crystal (LC) alignment were investigated, applying a wide range of pile impression and the number of rubbings. Weak rubbing creates inhomogeneous, partial modification of the AL, and in the region of weak rubbing reorientation of functional groups at the polymide surface, orientation of the polyimide backbone along the rubbing direction, uniformity of LC alignment, pretilt angle, and azimuthal anchoring energy all increase with either pile impression (rubbing force) or the number of rubbings (rubbing density), showing a correlation between them. In the regime of strong rubbing where the AL gets sufficiently modified and the defect-free uniform alignment is thus achieved, the effects of rubbing force on these features are quite different from those of rubbing density, suggesting that the force and the density should be independently treated for the better characterization of the rubbing process. High-force rubbing further increases the modified surface area and surface polarity of the AL and consequently causes a decrease in pretilt angle and enhancement of both anchoring energy and thermal stability of pretilt angle, which doesn't occur for a greater number of low-force rubbings.
Through the Adsorption-Desorption Cycle Assisted by Microwave Irradiation
류현석 ; 박용기 ; 박상은 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 326~326
Microwave energy was employed for the removal of
by repetitive adsorption-desorption cycle over
(LSC)/H-ZSM-5 adsorbent having dual functions of
adsorption and microwave absorption. The desired desorption temperature in the range from room temperature to 1000℃ was achieved successfully within 3 min by the control of LSC loading and microwave input power. The 25% LSC/H-ZSM-5 showed the highest sorption capacity of
(0.130 mmol/g). It was found that the adsorption-desorption cycles were reversible and no deactivation was observed even after 10 repeated cycles. When the microwave is applied in the desorption step of
, the desorption rate is 5 times faster than that of conventional thermal swing, which resulted in the enriched desorption of
in percentage order. The desorption rate was further improved by the presence of water and ten times faster rate was obtained over the water adsorbed LSC/H-ZSM-5.
Synthesis and Catalytic Properties of Niobium Carbides
최정길 ; 김정식 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 332~332
The carburization of Nb₂
(99.99%, Aldrich Chemical Co. Ltd.) was carried out using pure methane in a temperature-programmed manner. The variation in BET surface areas and oxygen uptakes of the niobium carbides was observed with different heating rates and molar hourly space velocity, suggesting that the sorption properties of these materials were strong functions of these preparative conditions used in this study. It was observed that these materials were active for ammonia decomposition reaction. While the oxygen uptake increased with increasing the BET surface area, the conversion of ammonia decomposition decreased. These results suggest that NH₃decomposition over these materials is structure-sensitive. As in the case of other transition metal carbides (V, Ta, and Mo), this structure-sensitivity was considered to be ascribed to the variations of surface composition with surface area. The conversion of ammonia decomposition for the materials prepared in the current study was observed to be comparable to that determined for the commercial niobium carbides.
Arylation of Styrene Catalyzed by Palladium Nitrate-Phosphine Complex
신정애 ; 황영애 ; 박용성 ; 우재완 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 337~337
The reactions of styrene with benzene to activate the aromatic C-H bond have been carried out using Pd(NO₃)₂ and phosphines (PR₃, R=
) as the catalytic system. The reaction conditions in this work using Pd(OAc)₂and phosphines to compare the effect of nitrate with acetate. The yield of the product, trans-stilbene, increases as the electron donating ability of the substituents on the phosphine increases and decreases as the steric hindrance increases; P(
F)₃. On the other hand, the migratory aptitude of the subsituent in phosphine to the palladium metal is reinforced as the electronegativity of the substituent increases. Generally, the yield of the product is lower for the less basic nitrate system than for the acetate one, which shows a parallel result with the above substituent effect.
Reconstruction of Particle Concentration Distribution in Annular Couette Flow using Electrical Impedance Tomography
김민찬 ; 김신 ; 김경윤 ; 이정훈 ; 이윤준 ;
Journal of Korean Society for Atmospheric Environment, volume 7, issue 5, 2001, Pages 341~341
An inverse problem is solved to obtain the particle concentration profile in a suspension under an annular Couette flow using electrical impedance tomography (EIT). The finite element method (FEM) is employed for the forward problem and the regularized Newton-Raphson iterative method is used for the inverse problem. The continuous conductivity distribution is approximated as a piecewise constant function. To evaluate the robustness of the reconstruction algorithm, several test cases are considered. Accordingly, it was confirmed that the proposed algorithm can be used to reconstruct the particle concentration in a suspension.