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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 18, Issue 6 - Dec 2002
Volume 18, Issue 5 - Oct 2002
Volume 18, Issue 4 - Aug 2002
Volume 18, Issue 3 - Jun 2002
Volume 18, Issue 2 - Apr 2002
Volume 18, Issue 1 - Feb 2002
Volume 8, Issue 6 - 00 2002
Volume 8, Issue 5 - 00 2002
Volume 8, Issue 2 - 00 2002
Volume 18, Issue E4 - 00 2002
Volume 18, Issue E3 - 00 2002
Volume 18, Issue E2 - 00 2002
Volume 18, Issue E1 - 00 2002
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Bed-Shrinking Flow-Through Reactor in Dilute Acid Hydrolysis of Cane Bagasse Cellulose
김준석 ; 홍인석 ; Lee, Yoon Y. ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 10~432
The kinetics of cellulose hydrolysis under dilute acid conditions (1.0, 2.0, and 3.0 wt.%), including extremely low acid (ELA) conditions (0.07 wt.%) and a temperature range of 180-220 ℃ were investigated using batch reactors and bed-shrinking flow-through (BSFT) reactors. The maximum yield of glucose obtained from the batch reactor experiments is about 30% from sugarcane bagasee which occurred at 200 and 210 ℃. The maximum glucose yields from pre-treated bagasse feedstocks based on a BSFT reaction increased to 55%. With sugarcane bagasse feedstocks, a large amount of glucose is unaccounted for in the latter phase of batch reactions. Therefore, to improve the BSFT reactor performance, a two-stage BSFT reaction was applied using hydrogen peroxide. It appears that a half amount of K. lignin was released during the first-stage reaction, while the maximum glucose yield increased through the second-stage BSFT reaction. The maximum yield of glucan hydrolysis using the two-stage BSFT reaction under ELA conditions at a high reaction temperature was much higher than that from the batch and BSFT reactions. In the experiments using a two-stage BSFT reaction, a glucose yield of 63% was obtained for sugarcane bagasse feedstocks at respective temperatures of 210 and 220 ℃ under ELA conditions.
Correlation between Band-gap and the Number of Defects in Titanium Silicide Thin Film
모만진 ; 정일현 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 11~437
Ti-Si thin films for application in an infrared-ray sensor were manufactured using the rf-plasma CVD method. The growth mechanism which increased the internal diffusion of the titanium atoms was found to be associated with the reciprocal reaction of the dangling bonds generated by the desorption of hydrogen in the hydrogenated amorphous films. However, the morphology of the Ti-Si thin films became homogeneous with an increase in the annealing time. The grain boundary of the Ti-Si crystals was decomposed with the annealing of Ti/a-Si:H/Si(100) thin films fabricated by dilute gas (H2). Titanium silicide exhibited a lattice structure of C54(311). In particular, the process showed a linear correlation between the number of defects and the band-gap. The ideal band-gap, which is possible to design the essential property, could be inferred from the linear relationship. Accordingly, it is possible to design the conditions for an optimum process to produce a specific number of defects in order to manufacture films with a specific band-gap.
Preparation of Functional Anion-Exchange Resin and Its Selective Adsorption of Palladium in Nitric Acid Medium
김광락 ; 이민수 ; 안도희 ; 임성팔 ; 정홍석 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 12~472
Separation of palladium metals is possible with the use of synthetic adsorbent resins. Two types of adsorbents based on a macroporous styrene-divinylbenzene copolymer were prepared by amination with phenylenediamine and impregnation with benzimidazole solution. A higher Pd(II) adsorption capacity on the aminated resin derivative was obtained in nitric acid solution than that on the conventional anion-exchange resins, such as Dowex 1x8-400 and IRN-78. The functional impregnated resin was found to have a superior distribution coefficient value of Pd(II) with about 14000 mL/g while the aminated resin had only about 700 mL/g. From this preliminary study, functional impregnated resin was shown to have good potential applicability for precious metal recovery as adsorption media from the spent fuel.
Statistical Optimization of Medium Components for the Improved Production of Cystocin by Streptomyces sp. GCA0001
Madan Kumar Kharel ; 이희찬 ; 송재경 ; 류광경 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 12~427
Different medium components were screened to improve the productivity of the novel bioactive compound, cystocin from the Streptomyces sp. GC0001. Plackett and Burman statistical design was employed to screen the effective components. Finally, response surface methodology based on three factors Box-Behnken design was applied to optimize the limiting variables such as soytone, glucose and magnesium sulfate concentration. The antibiotic yield was increased accordingly with the concentration of soytone and glucose. Magnesium sulfate has vital role in productivity besides the other carbon and nitrogen sources. Pharmamedia retained the strongest negative effect for the production of antibiotic and the effect due to sucrose and calcium carbonate was minor. The optimal concentrations of medium components for the cystocin production are determined as; soytone (50 g/L), glucose (40 g/L) and magnesium sulfate (30 g/L).
The Role of Ionic Groups of Latices in Coating Process
이용규 ; 김창근 ; Fumihiko Onabe ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 12~443
The styrene-butadiene based anionic and amphoteric latices were prepared and then the flow and electrokinetic behavior of these latices were evaluated. The interaction of these latices with pigment particles and base paper were also determined. The interaction of three component system consisting of amphoteric latex, anionic latex and clay particles was also examined. The effect of the difference of anionic and amphoteric groups on the coating color properties, coating layer structure and the printability are presented. Based on a variety of component systems having ionic latices, the role of ionic groups of latices in a variety of phenomena in coating process, such as the control of binder migration using amphoteric latex-based was color discussed in detail.
Theoretical Study for the Separation of Polyelectrolytes by Electrophoresis in the Chromatography
Park, Young G. ; Lim, Hwa E. ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 13~419
Electrophoretic separation was theoretically performed for large polyelectrolytes in the column packed with polymeric gel particles. This paper dealed with the computer simulation based on the Langevin equation of motion and the governing equation for the mass transfer in the presence of an electric field, the theoretical calculation of migration of polyelectrolyte in gel contributed to the understandings of mass transfer in the column. Theoretical studies were investigated in order to establish a relationship providing intraparticle convection effects as a function of an electric field, since a polyelectrolyte quickly orients through the pores of gel in the field direction. Dimensionless transient equations were derived considering mobility for the separation of polyelectrolytes and they were studied by two different dimensionless numbers in the fluid and solid phases in the column, showing how the concentration profiles of polyelectrolyte inside a particle varied in the column according to values of dimensionless number of individual polyelectrolyte. Langevin and governing equations were solved using the numerical method and an operator theory.
Electrochemical Deposition of Spherical Shaped Cu₂O Cluster on Aluminum Electrode
이재영 ; 노태근 ; 탁용석 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 14~454
The spherical shaped cuprous oxide (Cu2O) cluster was synthesized on metal aluminum by the galvanostatic method. The adsorption of hydroxide ion from dissolved oxygen and nitrate ion increased the local surface pH and resulted in the formation of aluminum (hydro) oxide. Irregular dissolution of aluminum (hydro) oxide due to non-uniform pH distribution was observed. Then, the spherical Cu2O cluster was deposited on conducting aluminum surface. This result was clearly characterized by means of scanning electron microscope, energydispersive X-ray analysis, and X-ray diffraction measurement.
A Study on the Feasibility of Silicon Nitride Thin Film as Diffusion Barriers over IC Chip Packaging
조명찬 ; 노병일 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 14~458
The feasibility of using Plasma-Enhanced Chemical Vapor Deposited (PECVD) silicon nitride thin films as diffusion barriers over metal bondpads, bonds, and bondwires in microelectronic packagings was investigated. Films between 550 to 5000 Å were almost impervious to salt solution over 36 h. Film over a micron cracked spontaneously from internal stresses. Film thickness measurement under a 1 mil bondwire over a flat silicon substrate by a stylus profilometer showed that the film began to get significantly thinner starting over four wire diameters away from the center of the bond. Salt immersion test indicated that the failure mechanism was corrosion of bondpad metallization starting under the stitch bond due to incomplete coverage of the silicon nitride film. Thermal shock cracked the films and caused severe corrosion on the metal bonding areas as evidenced by hydrogen evolution during salt immersion testing. The results showed that PECVD silicon nitride thin film can be potential protective films over metal areas in microelectronic assemblies, by optimizing the deposition conditions for more conformal coating in the occluded cavity under the stitch bond and increased resistance to thermal stress-induced cracking.
Thermal Treatment of Crude Terephthalic Acid Recovered from Alkali Weight-Reduction Wastewater
이동구 ; 장태선 ; 신채호 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 17~405
A study has been made of the thermal treatment of crude terephthalic acid (CTA) at 280 ℃ to improve above specifications of polymer-grade. CTA was recovered from alkali wastewater, which was discharged from the alkali weight-reduction processing stage of polyester textile. The trace impurities contained in the recovered CTA could be classified into inorganics such as Si, Mg, Ca, Al, Fe, Mn, Ti, Cr and K, and organics such as ketones and acid derivatives. The removal of the trace impurities by using the thermal treatment method resulted in the oxidation of organics to volatile materials, and of inorganics to the oxides. The purified terephthalic acid (PTA) obtained by way of the thermal treatment could be enhanced up to the commercial polymer-grade specifications such as ash content, colorimetric value, and transmittance.
Decomposition of Chlorofluorocarbon by Non-thermal Plasma
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 17~488
Decomposition of chlorofluorocarbon (CFC) was carried out using a Surface discharge induced Plasma Chemical Process (SPCP) reactor, and the effect of process variables such as decomposition efficiency, power consumption and applied voltage were investigated. The decomposition efficiency of CFC-12 with various electric frequencies (5~50 kHz), flow rates (100~1000 mL/min), initial concentrations (100~10000 ppm), electrode materials (W, Cu, Al), and electrode thicknesses (1, 2, 3 mm) was measured and the products were analyzed by FT-IR. The experimental results showed that a frequency of 10 kHz produced the highest decomposition efficiency of 92.7% for CFC-12 at the power consumption of 29.6 W and that the decomposition efficiency decreased when increasing the frequency above 20 kHz. As such, the decomposition efficiency per unit power was 3.13%/W for CFC-12. The decomposition efficiency increased when increasing the residence time and decreasing the initial concentration of pollutants. The decomposition efficiency also increased when increasing the thickness of the discharge electrode, and the highest decomposition efficiency was obtained with an electrode diameter of 3 mm. As regards the electrode material, the decomposition efficiency was in the order of tungsten (W), copper (Cu), and aluminum (Al). The optimum power for the maximum decomposition efficiency was 25.3 W for CFC.
Effect of Flow Velocity and Inhibitor on Formation of Methane Hydrates in High Pressure Pipeline
이정환 ; 백영순 ; 성원모 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 17~493
Hydrate blockages can occur in natural gas pipelines operated under high pressure and moderately low temperature conditions. Accordingly, the current study was carried out to understand the mechanism of hydrate plugging and examine inhibitors so as to prevent hydrate plugging in natural gas pipelines. The experiments were performed using a flow loop apparatus consisting of a 1.575 cm inside diameter and 400 cm long tube with a 20 cm long transparent view pipe. Most experiments were conducted at 4.90 MPa, 5.90 MPa, and 6.87 MPa with various flow velocities ranging from 0.28 through 0.78 m/s. The temperature in the loop was decreased at a rate of 2.2 K/h from initial temperature of 290.15 K until the pipe was plugged by hydrates. The hydrate equilibrium conditions under various flowing conditions with the methane were measured. And, the hydrate forming phenomena were observed when adding methanol as an inhibitor. The results of both the plugging tendency and the effect of the methanol concentration are presented. Consequently, the current study provides methods for predicting hydrate plugging phenomena and hydrate control techniques using an inhibitor for use in sub-sea pipeline systems as well as PNG (pipelined natural gas) transmission systems.
Fluorination of Metals and Metal Oxides by Gas-Solid Reaction
권상운 ; 김응호 ; 안병길 ; 유재형 ; 안호근 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 18~477
The technology on the transmutation of nuclear waste has been developed to reduce the risks during the long-term storage of the long-lived radioactive nuclides. The fluorination of metals and metal oxides was studied to investigate the preparation of the fuel for a transmutation reactor. The solid reactants reacted with diluted hydrogen fluoride gas to produce fluorides in a monel tubular reactor. CeO2, Nd2O3, and SrO were successfully fluorinated by the gas-solid reaction method. Noble metals did not react with hydrogen fluoride gas and could be separated from other elements during the dissolution step. Among the various gas-solid reaction models, the phase boundary controlled (reaction controlled) model was suitable for the fluorination of CeO2, whereas the nucleation and growth model was suitable for Nd2O3 and SrO. Reaction time required for the complete conversion could be predicted from the models.
Photocatalytic Activity of Gamma-irradiated TiO₂
정흥호 ; 이면주 ; 정진호 ; 최상원 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 23~483
Anatase TiO2 powders were treated by gamma-irradiation. The change of catalysts and their effect on the production of hydroxyl radicals were characterized by electron paramagnetic resonance (EPR) spectroscopy. Anatase TiO2 showed four typical peaks at g=2.005, g=1.992, g=1.973, and g=1.951. The intensity of the peaks was increased by gamma-irradiation, and the increase was positively dependent on irradiation dose. The intensity of the peaks is deeply related to the efficiency of hydroxyl radical production by photocatalysis, and the efficiency was directly proportional to the difference of Ti(3+) (g=1.992) and O(-)(g=2.005) intensity. Moreover, the photooxidative decomposition of perchloroethylene (PCE) was linearly dependent on the efficiency of hydroxyl radical production.
Roles of Oxidation and Coagulation in Fenton Process for the Removal of Organics in Landfill Leachate
윤제용 ; 김윤기 ; 허진 ; 이윤호 ; 이동수 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 35~410
High potential of coagulation to remove organics has not been fully recognized in Fenton process and coagulation has been used as an auxiliary process removing iron in effluent. This study evaluates the relative role of oxidation and coagulation step of Fenton process in the removing of biologically treated leachate organics of Metropolitan Landfill in Korea. This study showed that to the maximum, 30% of DOC and 40% of COD removal efficiencies were achieved by the Fenton oxidation step alone, whereas, 60% of DOC and 75% of COD removal efficiencies were achieved by the combined Fenton oxidation and subsequent Fenton coagulation step, as the same Fenton's reagent condition ([Fe(2+)]0 = 1250 or 2500 mg/L, and [H2O2]0 = 0 ~ 3000 mg/L) was applied in laboratory experiments. In addition, it was observed that the rapid decomposition of H2O2 with time did not lead to the corresponding removal of leachate organics. This means that OH radical generated from the H2O2 decompostion is not effectively invoved in degrading the leachate organics, pointing out the possibility of uneconomical use of H2O2 and unwarranted retention time of Fenton oxidatiom chamber in Fenton leachate treatment plant. Furthermore, the investigation of field Fenton process confirmed the observation of laboratory scale study, revealing that the DOC and COD removal effciencies in the Fenton oxidation step were less than 10~20% prior to the Fenton coagulation step, and major removals of DOC and COD (60~70%) were achieved after the finial Fenton coagulation step. These findings demonstrate the significance of the coagulation in Fenton process and raise a need for individual assessments of both oxidation and coagulation for the optimal design and evaluation of a whole Fenton processes. The individual assessments, however, should be conducted in an integrative manner because the preceding process (oxidation) may affect the performance the next process (coagulation).
Methane Reforming Reactions over Stable Ni/θ-Al₂O₃ Catalysts
우현석 ; 준기원 ; Wen Sheng Dong ; 백성찬 ; 박상은 ;
Journal of Korean Society for Atmospheric Environment, volume 8, issue 5, 2002, Pages 36~464
NiO/θ-Al2O3 catalysts were prepared and investigated after reduction treatment in the methane conversion reactions, such as oxy-reforming, steam reforming and oxy-steam reforming. Among the catalysts with various Ni loading, 12% Ni loading exhibits not only the highest catalytic activity and selectivity but also remarkable stability. The TPR results reveal that strong interaction between Ni and support results in forming stable NiOx species. Reducibility of NiO and the population of NiOx compared with NiO and/or NiAl2O4 play very important roles in the catalytic activity and stability of Ni/θ-Al2O3. Metallic Ni sites formed from the reduction of both NiO weakly interacting with the support and NiOx, strongly interacting with the support are active sites for methane reforming reactions. Even though free NiO sites are prerequisite for high activity, the increase of NiO population in high Ni loading favorably promotes Ni sintering resulting in undesirable catalytic properties