• Journal of Korean Society for Atmospheric Environment
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• v.18 no.3
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• pp.173-182
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• 2002

We investigated the effects of operating variables, such as electrical. reactor and gas parameters on toluene removal and discharge property in the dielectric barrier discharge (DBD) process. The toluene removal was initiated with the energy transfer to the reactor by loading of voltages higher than the discharge onset value. The energy transfer and toluene removal increased with the applied voltage. Higher removal rate was observed with smooth surface electrode despite of lower energy transfer compared with the coarse electrode, because more uniform discharge can be obtained on smooth surface state. The decrease of dielectric material thickness enhanced the removal efficiency by increasing the discharge potential. The toluene removal efficiency decreased with the increase of the inlet concentration. The increase of gas retention time enhanced the removal efficiency by the increase of energy density. The oxygen and humidity contents seem to exert significant influences on the toluene removal by dominating the generation of electrons, ions, and radicals which are key factors in the removal mechanism.

• Tribology and Lubricants
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• v.32 no.2
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• pp.67-71
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• 2016

This study investigates the characteristics of the sapphire wafer chemical mechanical polishing (CMP) process. The material removal rate is one of the most important factors since it has a significant impact on the production efficiency of a sapphire wafer. Some of the factors affecting the material removal rate include the pressure, platen speed and slurry. Among the factors affecting the CMP process, we analyzed the trends in the material removal rate and surface roughness, which are mechanical factors corresponding to both the pressure and platen speed, were analyzed. We also analyzed the increase in the material removal rate, which is proportional to the pressure and platen speed, using the Preston equation. In the experiment, after polishing a 4-inch sapphire wafer with increasing pressure and platen speed, we confirmed the material removal rate via thickness measurements. Further, surface roughness measurements of the sapphire wafer were performed using atomic force microscopy (AFM) equipment. Using the measurement results, we analyzed the trends in the surface roughness with the increase in material removal rate. In addition, the experimental results, confirmed that the material removal rate increases in proportion to the pressure and platen speed. However, the results showed no association between the material removal rate and surface roughness. The surface roughness after the CMP process showed a largely consistent trend. This study demonstrates the possibility to improve the production efficiency of sapphire wafer while maintaining stable quality via mechanical factors associated with the CMP process.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.5
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• pp.497-503
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• 2008

The Oxic-Settling-Anaerobic(OSA) process is a modified activated sludge processes for sludge reduction. It is evaluated that the sludge production in OSA process can decrease to 88% because of biomass decay and kinetic parameter($Y_H$ 0.237mgVSS/mgCOD, $b_H$ $0.195d^{-1}$) in anaerobic reactor, when compared with CAS process. However, it has problems caused by sludge reduction such as increase of nutrient loading. In case that the anoxic condition through the introduction of the intermittent aeration for the enhancement of nitrogen removal ability build up and enough rbCOD is suppled, maximum 88% of nitrogen is removed in the OSA process. If the OSA process optimizing the intermittent aeration cycle is applied to the separate sewage system with high rbCOD fraction, it can be converted to advanced process in terms of the sludge reduction and nitrogen removal, simultaneously.

• Journal of Environmental Health Sciences
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• v.34 no.6
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• pp.439-445
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• 2008

The feasibility study for the application of the removal and mineralization of Rhodamine B (RhB) was performed in a batch electrochemical reactor. The electro/UV process was consisted of DSA (dimensionally stable anode) electrode and UV-C or ozone lamp. The experimental results showed that RhB removal by the ozone lamp was higher than that of the UV-C lamp. Optimum current of the electro/UV process was 1 A. The electrochemical, UV and electro/UV process could completely degrade RhB, while a prolonged treatment was necessary to reach a high level RhB mineralization. It was observed that RhB removal in electro/UV process is similar to the sum of the UV and electrolytic decolorization. However, it was found that the COD of RhB could be degraded more efficiently by the electro/UV process (90.2 %) than the sum of the two individual oxidation processes [UV (19.7%) and electrolytic process (50.8%)]. A synergetic effect was demonstrated between the UV and electrolysis.

• Journal of Environmental Health Sciences
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• v.26 no.4
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• pp.15-20
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• 2000

The studies of swine wastewater treatment aim to development of process using soil microorganism. Removal rate of swine wastewater containing organic matter was 99 percent in case of high loading rate. Microorganism was devoted to improve the treatment efficiency of the process. According to the result obtained from biological treatment of high loading rate swine wastewater. Hydraulic retention time was 2.3 days in unit process of biological phosphorus removal. BO $D_{rm}$ / $P_{rm}$ ratio was 1122 in room temperature anaerobic process and 355.6 in mesophilic anaerobic process. And then phosphorus removal rate mesophilic anaerobic process was 3 time as much as than room temperature acaerobic process.

• Journal of Environmental Health Sciences
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• v.27 no.3
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• pp.99-106
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• 2001

A laboratory experiment was performed to investigate phosphorus and nitrogen removal from synthetic wastewater by intermittently activated sludge process packed with aluminium plate. Three continuous experimental systems, I. e. an intermittently activated sludge process(Run A), an intermittently activated sludge process with an aluminium plate packed into the reactor(Run B), and a reactor post stage(Run C) were compared. In the batch experiments, the phosphorus removal time in the reactor packed with copper and aluminium plate simultaneously was faster than that of the reactor packed with only an aluminium plates. However, the reactor packed with only an aluminium plate could be used for phosphorus removal. Move phosphorus was removed with an increase of surface area of aluminium plate and electrolysis(NaCl) concentration. The efficiency of COD and nitrogen removal was not affected in Run B. However, the phosphrus removal efficiency decreased because of reaction products and activated sludge which gradually covered gradually the surface of the aluminium plate. The efficiency of phosphorus removal in Run C was 86.3% at the HRT of 3.2 hours. Especially, the efficiency of phosphorus removal in Run C was higher than that in Run B.

• Journal of Environmental Science International
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• v.8 no.6
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• pp.725-730
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• 1999

The advanced oxidation process (AOP) using ozone combined with hydrogen peroxide and ultraviolet treatment were evaluated for biodegradable dissolved organic carbon (EDOC) formation and dissolved organic carbon (DOC) removal. Oxidation treatment were conducted alone or combination with ozone, hydrogen peroxide and ultraviolet processes. Ozone dosage of ozone process was varied from $0.5mg/l{\ell}\cdot}min$ to $5mg/{\ell}{\cdot}min$. Ozone/hydrogen peroxide process was done using $20mg/{\ell}{\cdot}min$ of hydrogen peroxide concentration. Ozone/ultraviolet process was irradiated with $12mW/cm^2$ of density and 254nm. Ozone dosage was varied from $0.5mg/{\ell}{\cdot}min$ to $5mg/{\ell}{\cdot}min$ at the ozone/hydrogen peroxide and ozone/ultraviolet processes too. Contact time of all the process was 20 minutes. Oxidation treatment were performed on microfiltration effluent samples. BDOC formation was reached to an optimum at ozone dosage of $1.5mg/{\ell}{\cdot}min$ in the ozone/hydrogen peroxide process and $1mg/{\ell}{\cdot}min$ in ozone/ultraviolet process, after which BDOC formation was decreased at higher ozone dosages. But BDOC formation was increased with ozone dosages increasing in ozone process. The efficiency of DOC removal was higher AOPs than ozone process. Ozone/ultraviolet proces was the highest for DOC removal efficiency in each process. THMFP. removal efficiency by ozone/ultraviolet process was higher than that by each of ozone process and ozone/hydrogen peroxide process.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.1
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• pp.76-83
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• 2000

This research is about wastewater containing non-biodegradable TDI(Toluene Diisocyanate) that is treated by the activated carbon adsorption method. In the case of the Fenton oxidation process being applied to the existing process, optimal pH, reaction time, chemical dosing amount, removal rate, and cost were investigated. A pilot plant test was applied after finding optimal conditions with lab experiments. The optimal conditions were pH 3~5(COD removal rate 84~88%) and reaction time 30min~1hr. In higher $H_2O_2$ dosing amount, COD removal rate was a little higher. But there was little difference in the removal rate according to $FeSO_4{\cdot}7H_2O$ dosing amount. Treatment cost was economical in the case of the Fenton oxidation process being operated earlier than activated carbon adsorption system. But chemical dosing point, chemical mixing effect, chemical dosing amount, removal rate, and the cost of facility and others must be considered in practical process.

• Journal of Environmental Science International
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• v.4 no.5
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• pp.509-516
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• 1995

The treatment performances of anaerobic-aerobic activated sludge process were investigated under various operation conditions. The treatment system proposed in this study gave a relatively stable performance against hourly change of the flow rate and showed a satisfactory removal of nitrogen and phosphorus compounds under experimental conditions. The recycle ratio of mixed liquor from aerobic to anaerobic region and peak coefficient primarily controlled the extent of nitrogen removal. The recycle ratio had the optimum values which were determined by the microbial activities of nitrification and denitrification. The behavior of the treatment unit could be simulated by using the kinetic equations and reactor models which considered the treatment units as complete mixing tanks.

• Journal of Environmental Science International
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• v.4 no.5
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• pp.123-123
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• 1995

The treatment performances of anaerobic-aerobic activated sludge process were investigated under various operation conditions. The treatment system proposed in this study gave a relatively stable performance against hourly change of the flow rate and showed a satisfactory removal of nitrogen and phosphorus compounds under experimental conditions. The recycle ratio of mixed liquor from aerobic to anaerobic region and peak coefficient primarily controlled the extent of nitrogen removal. The recycle ratio had the optimum values which were determined by the microbial activities of nitrification and denitrification. The behavior of the treatment unit could be simulated by using the kinetic equations and reactor models which considered the treatment units as complete mixing tanks.