• Nuclear Engineering and Technology
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• v.19 no.2
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• pp.122-129
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• 1987

Experiments and numerical analysis have been performed to investigate the effect of preoxidation by oxidizing Zircaloy-4 specimens at a higher temperature after a period of exposure at a lower temperature. The oxidation experiments were performed between $700^{\circ}C$ and 85$0^{\circ}C$ after Preoxidation at $650^{\circ}C$ in a steam and water mixture for 600 seconds and 1,800 seconds. As the thickness of preoxidized layer increased, the oxidation rate of preoxidized specimens at higher temperature became lower than that of as-received claddings. A transition region of oxidation rate exist in the preoxidized specimens, and the region disappeared rapidly as the oxidation temperature increased. This effect appeared more clearly at lower temperatures. According to the results of numerical analysis performed in this study, the growth rate of oxide layer thickness and weight gains were similarly affected by the thickness of preoxidized layer.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.103-111
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• 2000

Ozonation and advanced oxidation($H_2O_2/O_3$) process were investigated under various experimental conditions to improve the efficiency of biological filter used for the treatment of recycled wastewater from aquaculture. Ammonia removal followed the first-order reaction whose reaction rate constant(k) was $2.0{\times}10^{-2}min^{-1}$ in ozonation. The ammonia removal rate increased according as the bicarbonate alkalinity is increased. About 46% $NH_3$ was oxidized by ozone at 200 mg/L as $CaCO_3$. When alkalinity existed in wastewater, ammonia removal rate by advanced oxidation was very low due to the inhibition effect of bicarbonate. However, when initial pH was adjusted to about 8.2 by 0.1 N KOH, ammonia removal rate was improved higher than that by ozonation. Especially. ammonia removal rate was the highest at $H_2O_2/O_3$ of 0.25 and about 90% of ammonia was removed in 30 min at this ratio as pH was maintained over 9. In the case of wastewater containing ammonia and organic constituents, ammonia removal efficiency by both ozonation and advanced oxidation decreased seriously because organic constituents consumed the oxidant faster than ammonia. In addition the optimal $H_2O_2/O_3$ ratio was changed. Like ammonia removal, DOC(dissolved organic carbon) increased for first 10 min and then decreased slowly because the particulate organic constituents were oxidized rapidly and then produce DOC. Even when the ammonia concentration by twice, oxidation of DOC was not retarded.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.3
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• pp.245-252
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• 2010

For the purpose of evaluating to remove elemental mercury using SCR (Selective Catalytic Reduction) catalysts, the result of the concentration variation of elemental mercury in lab experiment and field measurement was compared. The effect of the elemental mercury oxidation on commercial catalysts was studied in simulated gas. Three species of SCR catalyst, $V_2O_5-TiO_2$ type, were selected. The elemental mercury reduced 30% without HCl gas in SCR operating condition. But the width of reduction increased 60% at 20 ppm HCl gas. According to the result of field measurement, reduction rate of elemental mercury at SCR outlet showed 60%. The total mercury concentration decreased about 20%. The results were similar to the lab test. The results of chemical analysis of test sample showed increase of mercury concentration but surface change was not observed.

• Journal of environmental and Sanitary engineering
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• v.18 no.4
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• pp.45-51
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• 2003

This study was conducted to remove the color in dyeing wastewater by ozone oxidation process, and the results were summarized as follows ; The 18.3％ of BOD and 56.3％ TOC were removed as decreasing with pH 1 in dyeing wastewater, containing the polyester reducing process. It showed that terephthalic acid was precipitated at low pH. The color of dyeing wastewater was removed by the first order reaction, and the reaction rate constants at pH 3, 7, 12 were investigated $0.234{\;}min^{-1},{\;}0.215{\;}min^{-1}{\;}and{\;}0.201{\;}min^{-1}$ respectively. It showed that color was more effectively removed with direct reaction of ozone than radical reaction(non-direct reaction). As increasing of the water temperature, the reaction rate constants were increased slightly. It indicated that activity of ozone was improved at high water temperature.

• Journal of environmental and Sanitary engineering
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• v.11 no.2
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• pp.59-63
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• 1996

To treat certain wastewater that has alcohol and phenol, we performed the ozone electrolysis by using the titanium electrode. In this experiment, we examined decomposition voltage of organics, time for electrolysis, and removal efficiency of organics. In addition we compared the ozone oxidation electrolysis. The followings are results; 1. When it comes to the alcohol treatment in wastewater, ozone electrolysis showed higher removal efficiency than ozone oxidation or electrolysis. 2. After comparing the decomposition rate of methylalcohol, ethylalcohol, and prophylalcohol in ozone electrolysis, we knew the fact that increasing carbon number made the decomposition rate slow. 3. According to the treatment of alcohol by ozone electrolysis, decomposition voltage was 50V, time for electrolysis was three hours, and treatment acidity was neutral (pH 6.5 - 8.1). 4. Ozone electrolysis was effective to the phenol treatment. When we treated phenol by using ozone electrolysis for three hours, TOC treatment efficiency was 95%. However, ozone oxidation just showed 45% treatment efficiency.

• BMB Reports
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• v.34 no.1
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• pp.39-42
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• 2001

Previous studies indicate that B. subtilis protoporphyrinogen oxidase is poorly inhibited by diphenyl ether herbicides. To better understand the basis of this insensitivity, the enzyme was overexpressed as a soluble protein in E. coli, purified and characterized. The mechanism of oxidation of B. subtilis protoporphyrinogen IX was studied and the enzyme kinetic parameters were determined for protoporpyrinogen IX; $K_m$, and $k_{cat}$ were $6.3\;{\mu}M$ and $0.028\;h-^1$, respectively. The enzyme required flavin adenine dinucleotide as a cofactor and its activity was enhanced by 1 mM n-octylglucopyranoside. The nonenzymatic oxidation rate was dependent on the concentration of protoporphyrinogen IX, suggesting that the reaction involves a pre-equilibrium step followed by a rate-limiting step.

• Journal of the Korean Applied Science and Technology
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• v.19 no.3
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• pp.206-212
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• 2002

The catalytic activities of several metalloporphyrin, wherein the porphyrins are TPP(5,lO,l5,20-Tetraphenyl-21H,23H-porphyrin) and (p-X)TPP (X =$CH_{3}O$, $CH_{3}$, F, Cl), are reported for the oxidation of styrene and it's derivatives. The electronic effects of substrates and porphyrins on the catalytic activity of metalloporphyrin containing the transition metal ion such as Mn(III) was discussed. Investigating the correlation between the Michaelis-Menten's rate parameters and the substituent constants, we are going to analyze the influences on the changes of catalytic activity or rate determining step during the processes of the formation and the dissociation of the M-oxo-olefin.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.63-64
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• 2000

The low-temperature Si oxidation kinetics by inductively coupled oxygen plasma has been studied. Linear rate constants had negative values when the oxide growth rate was described by linear-parabolic growth law. The analysis of transverse-optical mode frequencies and etch rates indicated that the density of surface oxide was lower than that of bulk oxide. The oxidation kinetics could be explained qualitatively by assuming a surface layer with larger diffusion coefficient and a bulk layer with smaller diffusion coefficient.

• Environmental Engineering Research
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• v.11 no.6
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• pp.318-324
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• 2006

The higher valence state of iron i.e., Fe(VI) was employed for the oxidation of one of an important toxic ion, cyanide in the aqueous medium. Cyanide was oxidized into cyanate, which is 1,000 times less toxic to cyanide and often accepted for its ultimate disposal. It was to be noted that Fe(VI) is a very powerful oxidizing agent and can oxidize most of the cyanide within few minutes i.e., ca 5 mins of contact. The data was obtained by the UV-Visible measurements for the Fe(VI) decomposition. The UV-Visible data was used to evaluate the overall rate constant for second order redox reaction between ferrate(VI) and cyanide. Also the pseudo first order rate constant was calculated as keeping the cyanide concentration in excess.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.6
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• pp.469-480
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• 2019

This study was conducted to evaluate the degradation and mineralization of PPCPs (Pharmaceuticals and Personal Care Products) using a CBD(Collimated Beam Device) of UV/H₂O₂ advanced oxidation process. The decomposition rate of each substance was regarded as the first reaction rate to the ultraviolet irradiation dose. The decomposition rate constants for PPCPs were determined by the concentration of hydrogen peroxide and ultraviolet irradiation intensity. If the decomposition rate constant is large, the PPCPs concentration decreases rapidly. According to the decomposition rate constant, chlortetracycline and sulfamethoxazole are expected to be sufficiently removed by UV irradiation only without the addition of hydrogen peroxide. In the case of carbamazepine, however, very high UV dose was required in the absence of hydrogen peroxide. Other PPCPs required an appropriate concentration of hydrogen peroxide and ultraviolet irradiation intensity. The UV dose required to remove 90% of each PPCPs using the degradation rate constant can be calculated according to the concentration of hydrogen peroxide in each sample. Using this reaction rate, the optimum UV dose and hydrogen peroxide concentration for achieving the target removal rate can be obtained by the target PPCPs and water properties. It can be a necessary data to establish design and operating conditions such as UV lamp type, quantity and hydrogen peroxide concentration depending on the residence time for the most economical operation.