• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.279-290
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• 2013

Due to the continuous space development by mankind, the number of space objects including space debris in orbits around the Earth has increased, and accordingly, difficulties of space development and activities are expected in the near future. In this study, among the stages for space debris removal, the implementation of a vision-based approach technique for approaching space debris from a far-range rendezvous state to a proximity state, and the ground test performance results were described. For the vision-based object tracking, the CAM-shift algorithm with high speed and strong performance, and the Kalman filter were combined and utilized. For measuring the distance to a tracking object, a stereo camera was used. For the construction of a low-cost space environment simulation test bed, a sun simulator was used, and in the case of the platform for approaching, a two-dimensional mobile robot was used. The tracking status was examined while changing the position of the sun simulator, and the results indicated that the CAM-shift showed a tracking rate of about 87% and the relative distance could be measured down to 0.9 m. In addition, considerations for future space environment simulation tests were proposed.

• Korean Journal of Materials Research
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• v.16 no.2
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• pp.75-79
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• 2006

The effect of ozone and/or ultrasound treatments on the efficiency of slurry removal in post sliced cleaning (PSC) of silicon ingot was studied. Efficiency of slurry removal was evaluated as functions of time, temperature and surfactant with DOE (Design of Experiment) method. Residual slurries were observed on the wafer surface in case of cleaning by ozone or ultrasound separately. However, a clean wafer surface was appeared when cleaned with ozone and ultrasound simultaneously. It has found that cleaning time was the main effect among temperature, time and surfactant. Elevated temperature, addition of surfactant and high ozone concentration helped to accelerate efficient removal of slurry. The improvement of removal efficiency seems to be related to the formation of more active OH radicals. The highly cleaned surface was achieved at 10 wt% ozone, 1 min and 10 vol% surfactant with ultrasound. Application of ozone and ultrasound might be a useful method for PSC process in wafer cleaning.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.654-664
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• 2019

The geometrical and electromagnetic variables of a rectangular-type magnetohydrodynamic (MHD) circulation system are optimized to solve MHD equations for the active decay heat removal system of a prototype Gen-IV sodium fast reactor. Decay heat must be actively removed from the reactor coolant to prevent the reactor system from exceeding its temperature limit. A rectangular-type MHD circulation system is adopted to remove this heat via an active system that produces developed pressure through the Lorentz force of the circulating sodium. Thus, the rectangular-type MHD circulation system for a circulating loop is modeled with the following specifications: a developed pressure of 2 kPa and flow rate of $0.02m^3/s$ at a temperature of 499 K. The MHD equations, which consist of momentum and Maxwell's equations, are solved to find the minimum input current satisfying the nominal developed pressure and flow rate according to the change of variables including the magnetic flux density and geometrical variables. The optimization shows that the rectangular-type MHD circulation system requires a current of 3976 A and a magnetic flux density of 0.037 T under the conditions of the active decay heat removal system.

• Microbiology and Biotechnology Letters
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• v.50 no.1
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• pp.71-80
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• 2022

Lipases (triacylglycerol acylhydrolases [EC 3.1.1.3]) are water-soluble enzymes. They catalyze the hydrolysis of fats and oils. A cold-active lipase from marine Bacillus cereus HSS, isolated from the Mediterranean Sea, Alexandria, Egypt, was purified and characterized. The total purification depending on lipase activity was 438.9 fold purification recording 632 U/mg protein. The molecular weight of the purified lipase was estimated to be 65 kDa using sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The optimum substrate concentration, enzyme concentration, pH, and temperature were 1.5 mM, 100 µl, pH 6 and 10℃, respectively. The lipase was tolerant to NaCl concentrations ranging from 1.5 to 4.5%. The lipase was affected by the tested metal ions, and its activity was inhibited by 16% in the presence of 0.05 M SDS. The application of the cold-active lipase for the removal of an oil stain from a white cotton cloth showed that it is a promising biological agent for the treatment of oily wastes and other related applications. To the best of our knowledge, this is the first report of the purification and characterization of a lipase from marine B. cereus HSS isolated from the Mediterranean Sea.

• Journal of Soil and Groundwater Environment
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• v.27 no.3
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• pp.41-49
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• 2022

This study utilized citric acid as a floating agent in biological denitrification process and assessed its role under different carbon supplying conditions. Several microcosm tests including citric acid active (CAA), precipitating tablet release active (PTRA) and floating tablet release active (FTRA) were conducted to evaluate nitrate denitrification efficacy. In CAA reactors, nitrate removal was accompanied by the formation of denitrification by-products such as nitrite and nitrous oxide, with the extent of nitrate removal being proportional to citric acid concentration. These results suggest that citric acid induced heterotrophic biological denitrification. PTRA reactor that incorporated CAA and the same electron donor showed a similar denitrification efficiency to CAA reactor. FTRA reactor, which contained the same amount of fumarate as PTRA, enhanced denitrification by 7% as compared to the PTRA reactor. The overall results of this work indicate that surplus citric acid can be efficiently utilized in heterotrophic denitrification.

• The Journal of the Korean dental association
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• v.20 no.3 s.154
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• pp.233-237
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• 1982

A review of the literature was presented, illustrating the effect that gingivally retained orthodontic elastic bands have on the periodontal tissues. A case report was presented for treatment of mobile maxillary central incisors secondary to a subgingival elastic band. Following surgical removal of elastic band and periodontal debridement, the teeth were successfully retained with active orthodontic appliances. Until a harmless radiopaque medium can be safely incorporated into elastic bands, extreme caution in their use should be observed. Not only should all attempts be made to anchor the elastic bands to the clinical crown, but the patient should receive through instructions in their placement and removal.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.218-224
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• 2008

Coal-, coconut- and wood-based activated carbons and anthracite were tested to evaluate adsorption and biodegradation performances of chloral hydrate. In the early stage of the operation, the adsorption was the main mechanism for the removal of chloral hydrate, however as increasing populations of attached bacteria, the bacteria played a major role in removing chloral hydrate in the activated carbon and anthracite biofilter. It was also investigated that chloral hydrate was readily subjected to biodegrade. The coal- and coconut-based activated carbons were found to be most effective adsorbents in adsorption of chloral hydrate. Highest populations and activity of attached bacteria were shown in the coal-based activated carbon. The populations and activity of attached bacteria decreased in the order: coconut-based activated carbon > wood-based activated carbon > anthracite. The attached bacteria was inhibited in the removal of chloral hydrate at temperatures below 10$^{\circ}C$. It was more active at higher water temperatures(20$^{\circ}C$ <) but less active at lower water temperature(10$^{\circ}C$>). The removal efficiencies of chloral hydrate obtained by using four different adsorbents were directly related to the water temperatures. Water temperature was the most important factor for removal of chloral hydrate in the anthracite biofilter because the removal of chloral hydrate depended mainly on biodegradation. Therefore, the main removal mechanism of chloral hydrate by applying activated carbon was both adsorption and biodegradation by the attached bacteria. The observation suggests that the application of coalbased activated carbon to the water treatment should be the best for the removal of chloral hydrate.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.308-311
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• 2011

The reaction mechanism of selective catalytic reduction of NOx over sewage sludge char impregnated with MnOx using $NH_3$ as the reducing agent was investigated. The active Mn phase was shown to be $Mn_3O_4$ from the XRD analysis. Adsorption was the dominant NOx removal mechanism at low temperatures below $150^{\circ}C$ although reduction reaction also contributed partly to the NOx removal at $100{\sim}150^{\circ}C$. The reaction rate constants of NOx removal over non-impregnated and MnOx-impregnated active chars were compared based on experimental results. The MnOx-impregnated char was shown to have a higher reaction rate constant and a higher NOx removal efficiency due to a higher collision coefficient and a lower activation energy. The activation energy for both chars was shown to be relatively low (10~12 kJ/mol) under the experimental conditions of this study.

• Journal of the Korean Chemical Society
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• v.57 no.3
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• pp.316-321
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• 2013

Electrocoagulation (EC) technique is applied for the treatment of wastewater containing heavy metals ions such as nickle (Ni), lead (Pb) and cadmium (Cd) by using sacrificial anodes corrode to release active coagulant flocs usually aluminium or iron cations into the solution. During electrolytic reactions hydrogen gas evolve at the cathode. All the experiments were carried out in Batch mode. The tank was filled with synthetic wastewater containing heavy metals and efficiency of electro-coagulation in combination with aluminum and iron electrodes were investigated for removal of such metals. Several parameters, such as contact time, pH, electro-coagulant concentration, and current density were optimized to achieve maximum removal efficiency (%). The concentrations of heavy metals were determined by using Atomic Absorption Spectroscopy (AAS). It is found that the electro-coagulation process has potential to be utilized for the cost-effective removal of heavy metals from wastewater specially using iron electrodes in terms of high removal efficiencies and operating cost.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.48-56
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• 2018

A potassium copper hexacyanoferrate (KCuHCF) embedded magnetic hydrogel bead (HCF-Mbead) was synthesized via a facile double crosslinking methods of $Fe^{3+}$ ionic binding and freeze-thaw for effective $Cs^+$ removal. The HCF-Mbead had a hierarchical porous structure facilitating fast access of $Cs^+$ ions to embedded active sites. The adsorbent showed enhanced $Cs^+$ removal properties in terms of capacity (69.2 mg/g), selectivity ($K_d=4{\times}10^4mL/g$, 1 ppm $Cs^+$ in seawater) and stability (>99.5% removal in pH 3~11) with rapid magnetic separation. This study further opens the possibility to develop an efficient material that links the integration of adsorption and recovery.