• Journal of the Korean GEO-environmental Society
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• v.23 no.3
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• pp.23-29
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• 2022

In this study, we investigated the ozone nanobubble process in which nanobubble and ultrasonic cavitation were applied simultaneously to improve the dissolution and self-decomposition of ozone. To confirm the organic decomposition efficiency of the process, a 200 mm × 200 mm × 300 mm scale reactor was designed and phenol decomposition experiments were conducted. The use of nanobubble was 2.07 times higher than the conventional ozone aeration in the 60 minutes reaction and effectively improved the dissolution efficiency of ozone. Ultrasonic irradiation increased phenol degradation by 36% with nanobubbles, and dissolved ozone concentration was lowered due to the promotion of ozone self-decomposition. The higher the ultrasonic power was, the higher the phenol degradation efficiency. The decomposition efficiency of phenol was the highest at 132 kHz. The ozone nanobubble process showed better decomposition efficiency at high pH like conventional ozone processes but achieved 100% decomposition of phenol after 60 minutes reaction even at neutral conditions. The effect by pH was less than that of the conventional ozone process because of self-decomposition promotion. To confirm the change in bubble properties by ultrasonic irradiation, a Zetasizer was used to measure the bubbles' size and zeta potential analysis. Ultrasonic irradiation reduced the average size of the bubbles by 11% and strengthened the negative charge of the bubble surface, positively affecting the gas transfer of the ozone nanobubble and the efficiency of the radical production.

• Clean Technology
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• v.16 no.1
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• pp.51-58
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• 2010

Methane was produced from the anaerobic digestion of marine macro-algae. Elemental analysis was first performed to estimate the theoretical methane production of three macro-algae (Undaria pinnatifida, Laminaria japonica, Hizikia fusiformis). Three algae were found to contain C 34 ~ 36%, H 5%, O 37 ~ 43%, N 2 ~ 4%, S 0.4 ~ 0.7%, and ash 14~21%, and the theoretical methane content was in the range of 56 ~ 60%, which can produce 442 ~ 568 mL $CH_4$ per g of volatile solid (VS). Using the biological methane potential (BMP) test, we found that L. japonica resulted in the highest yield of methane (52%). Moreover, various operational conditions, such as algae amount, pH, salinity, particle size, and pre-treatment, were investigated in order to find an optimal condition of anaerobic digestion. At pH 8.0, the autoclaved L. japonica (5g VS/200 mL), when used without washing salt, produced 268.5 mL/g VS which is 65% of the theoretical methane productions. Furthermore, using a CSTR (with the working volume of 7 L out of the total volume of 10 L), we have successfully operated the reactor for 65 days and obtained maximum methane production rate of 1.4 L/day with purity of 70%.

• Clean Technology
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• v.16 no.4
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• pp.258-264
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• 2010

This study estimated the possibility of phosphate removal characteristics to utilize EAF(electric arc furnace) slag as submarine cover material. The major phosphate removal mechanism was a certain formation of HAP precipitation occurred by the ionization reaction between $Ca^{2+}$ and $OH^-$, which were leached from the EAF Slag. Another phosphate removal mechanism was the adsortion of EAF slag surface. As a result of $PO_4{^-}-P$ removal characteristics using continuous column reactor, $PO_4{^-}-P$ concentration decreased rapidly after 3 days and 10 days later, it show under 0.5 ppm. The result as applied in real sea water, shows that the phosphate removal effects were 93~98% by the subaqueous sediment removal using the EAF slag. In conclusion, EAF slag is useful in $PO_4{^-}-P$ removal and control and it is possible to use without additional process like crush and selection.

• Applied Chemistry for Engineering
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• v.34 no.2
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• pp.126-130
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• 2023

In response to environmental demands, pyrolysis is one of the practical methods for obtaining reusable oils from waste plastics. However, the waste plastic pyrolysis oils (WPPO) are consumed as low-grade fuel oil due to their impurities. Thus, this study focused on the upgrading method to obtain naphtha catalytic cracking feedstocks from WPPO by the hydroprocessing, including hydrotreating and hydrocracking reaction. Especially, various transition metal sulfides supported catalysts were investigated as hydrotreating and hydrocracking catalysts. The catalytic performance was evaluated with a 250 ml-batch reactor at 370~400 ℃ and 6.0 MPa H₂. Sulfur-, nitrogen-, and chlorine-compounds in WPPO were well eliminated with nickel-molybdenum/alumina catalysts. The NiMo/ZSM-5 catalyst has the highest naphtha yield.

• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.175-188
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• 2023

Global interest in hydrogen energy is increasing as an eco-friendly future energy that can replace fossil fuels. Accordingly, a next-generation hydrogen production technology using microorganisms, nuclear power, etc. is being developed, while a lot of time and effort are still required to overcome the cost of hydrogen production based on fossil fuels. As a way to minimize greenhouse gas emissions in the hydrocarbon-based hydrogen production process, methane direct decomposition technology has recently attracted attention. In order to improve the economic feasibility of the process, the simultaneous production of value-added carbon materials with hydrogen can be one of the most essential aspects. For that purpose, various studies on catalysis related to the quality and yield of high-value carbon materials such as carbon nanotubes (CNTs). In terms of process technology, a number of the research and development of fluidized-bed reactors capable of continuous production and improved gas-solid contact efficiency has been attempted. Recently, methane direct decomposition technology using a fluidized bed has been developed to the extent that it can produce 270 kg/day of hydrogen and 1000 kg/day of carbon. Plus, with the development of catalyst regeneration, separation and recirculation technologies, the process efficiency can be further improved. This review paper investigates the recent development of catalysts and fluidized bed reactor for methane direct pyrolysis to identify the key challenges and opportunities.

• Nuclear Engineering and Technology
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• v.27 no.6
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• pp.877-887
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• 1995

YGN 3 is the first nuclear power plant to use the Core Protection Calculator (CPC) as the core protection system and the Core Operating Limit Supervisory System (COLSS) as the core monitor-ing system in Korea. The CPC is designed to provide on-line calculations of Departure from Nucleate Boiling Ratio (DNBR) and Local Power Density (LPD) and to initiate reactor trip if the core conditions exceed the DNBR or LPD design limit. The COLSS is designed to assist the operator in implementing the Limiting Conditions for Operation (LCOs) in Technical Specifications for DNBR/Linear Heat Rate (LHR) margin, azimuthal tilt, and axial shape index and to provide alarm when the LCOs are reached. During YGN 3 initial startup testing, extensive CPC/COLSS related tests ore peformed to ver-ify the CPC/COLSS performance and to obtain optimum CPC/COLSS calibration constants at var, -ious core conditions. Most of test results met their specific acceptance criteria. In the case of missing the acceptance criteria, the test results ore analyzed, evaluated, and justified. Through the analysis and evaluation of each of the CPC/COLSS related test results, it can be concluded that the CPC/COLSS are successfully Implemented as designed at YGN 3.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.140-148
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• 1994

A qualification test was performed for the iron removal chemical cleaning of the secondary side of nuclear steam generators at the selected temperature, 1$25^{\circ}C$, higher than the standard application temperature, 93$^{\circ}C$. The field cleaning condition for a nuclear unit was tested in a bench scale test loop including a SUS 316 stainless steel autoclave with one gallon capacity as a test vessel. The kinetics of sludge dissolution, corrosion of the secondary side materials and change of solvent chemistry were monitored. Test results indicated that more thorough cleaning was accomplished in less than half of the cleaning time required at 93$^{\circ}C$. And the total corrosions of the secondary side materials were found to be less than the values at 93$^{\circ}C$. While the solvent is recirculated and heated by an external chemical cleaning equipment for the conventional 93$^{\circ}C$ process, the secondary side is heated by the lateral heat of the primary coolant without the recirculation of the cleaning solution, and the solvent is mixed by vigorous boiling induced by periodic ventilation for the high temperature process. The requirement that the reactor coolant pumps should be running during the cleaning operation is the major disadvantage of the high temperature process which also should be considered when chemical cleaning is planned for steam generators under operation.

• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.484-492
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• 1994

Microstructures of Nb$_2$O$_{5}$-doped UO$_2$ pellets have been investigated during sintering under H$_2$ and $CO_2$ atmospheres. Pellets are sintered at 1$700^{\circ}C$ in H$_2$ atmosphere and at 130$0^{\circ}C$ in $CO_2$ atmosphere for 1 to 41 hr. The addison of Nb$_2$O$_{5}$ causes the formation of large pores, which shrink to some extent in H$_2$ atmosphere but very little in $CO_2$. Fine pores in the Nb$_2$O$_{5}$-doped UO$_2$ pellet are almost annihilated when sintered under H$_2$ atmosphere but little changed under $CO_2$ atmosphere. The increase in grain size due to Nb$_2$O$_{5}$ addition is much larger in H$_2$ atmosphere than in $CO_2$. Thus the enhancement of uranium diffusion in UO$_2$ due to the Nb$_2$O$_{5}$ addition is thought to be more significant in H$_2$ atmosphere. Microstructures of Nb$_2$O$_{5}$-doped UO$_2$ pellets sintered in H$_2$ atmosphere are discussed from the viewpoint of in-reactor performance. Possible defects formation due to Nb$_2$O$_{5}$ addition is discussed to explain the enhancement of uranium diffusion in H$_2$ and $CO_2$ atmospheres.> atmospheres.

• Journal of Life Science
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• v.32 no.3
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• pp.232-240
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• 2022

Various methods are known for preparing liposomes, the simplest being the Bangham method which has been widely used. Although it is possible to produce liposomes effectively on a small experimental level with this approach, large-scale production cannot be easily performed due to difficulties in removing the organic solvent and the size of the reactor required to form the lipid film. On the other hand, emulsion can mass produce tons of liposomes with uniform particles but has the disadvantage of a significantly low capture rate. This study therefore developed an optimal liposome processing method using heat with improved capture rate and stability, and bio-absorption experiments were performed by oral administration to SD rat alongside capture rate, particle size, and zeta potential. Through the heating method, a small and uniform liposome of about 214 nm was formed and the capture rate was 38.67%, confirming that the liposome prepared by heating has a higher capture rate than the 26.46% achieved through emulsion. Comparing blood concentrations, it showed a 1.5 to 2 fold increase in all groups, gradually decreasing until 4-12 hr. The highest blood concentration of ascorbic acid powder was about 12.017 ㎍/ml, the emulsion liposome 13.871 ㎍/ml, and the heating liposome 16.322 ㎍/ml, thereby showing an improved absorption rate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.497-502
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• 2009

The wastewater treatment by photocatalyst decomposes pollutants directly in water, and it is easy to decompose indecomposable organics and inorganic. and Especially, it has an advantage that there is no secondary production of pollutants. However, there will be many problems which are generated depending on the type of photocatalyst. The type of rotating photocatalyst minimizes previous problems, and advanced oxidation processes is possible by the application of rotating disc method. The consideration of the characteristics about various designs and operation factors is needed for the application of rotating photocatalyst system. In this study, rotating photocatalyst was manufactured for rotating disc method by fixing of $TiO_2$. The operation factors were derived for the wastewater treatment by the reaction of rotating photocatalyst. The contained quantity of $TiO_2$ was limited about 70%. The more the contained quantity of $TiO_2$ was increased, the more the treatment rate was continually increased. The optimum rotating photocatalyst was R4, and the contained quantity of $TiO_2$ was 36.8%. The more the exposed amount of UV is increased, the more the decomposition effect of TCODcr was continually increased. However, the adequate strength of light source must be determined by the consideration of economical efficiency. The more the speed of rotating photocatalyst is increased, the more treatment efficiency was increased. When UV lamp was not submerged in reactor, the wastewater treatment was efficient in the order of the depth of water 50%, 30%, 10%, 70%, 100%. This study is a basic research for the development of a system which treats organics in solar light.