• Science of Emotion and Sensibility
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• v.11 no.1
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• pp.105-112
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• 2008

This study investigated the effect of 40% oxygen administration on the addition task performance in three levels of difficulties and physiological signals. Ten male and female college students were selected as the subjects for this study. The experiment consisted of two runs: one was a addition task, with normal air (21% oxygen) administered and the other was with hyperoxic air (40% oxygen) administered. The experimental sequence in each run consisted of Rest1 (3 min), Task1 (1 min, one digit addition task), Task2 (1 min, two digit addition task), Task3 (1 min, three digit addition task), and Rest2 (4 min). Blood oxygen saturation and heart rate were measured throughout the five phases. The accuracy rates of the addition task were enhanced with 40% oxygen administration compared to 21% oxygen. Difference in the accuracy rates grew higher with the rise of difficulty. When 40% concentration oxygen is supplied, blood oxygen saturation increased and heart rate was decreased comparing to 21%. This study showed that the supply of high concentration oxygen increases blood oxygen saturation, which in turns accelerates brain activation resulting from cognitive process and enhances arithmetic abilities. Particularly when difficulty is high, demand for oxygen increases and, as a result, the effect of high concentration oxygen becomes more significant.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.71-71
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• 2012

Chemically modified graphene has been great interest for the application of printed electronics using solution prossesable technique. Here, we demonstrate a large area graphene exfoliation method with fewer defects on the basal plane by application of shear stress in solution to obtain high quality reduced graphene oxide (RGO). Moreover, we introduce a novel route to preparing highly concentrated and conductive RGO in various solvents by monovalent cation-${\pi}$ interaction. Noncovalent binding forces can be induced between a monopole (cation) and a quadrupole (aromatic ${\pi}$ system). The stability of this RGO dispersion was more sensitive to the strength of the cation-${\pi}$ interactions than to the cation-oxygen functional group interactions. The RGO film prepared without a post-annealing process displayed superior electrical conductivity of 97,500 S/m. Our strategy can facilitate the development of large scalable production methods for preparing printed electronics made from high-quality RGO nanosheets.

• YAKHAK HOEJI
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• v.29 no.3
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• pp.144-151
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• 1985

Cathodic stripping voltammetric determination of traces of selenium in plant samples was studied. Stripping peak of selenium (IV) from Cu-Se intermettalic deposit in acidic media containing copper (II) ion is specific, highly sensitive and well defined, is successfully used for the quantitative determination of selenuin down to the level of 1ng/ml. Sample is burnt in a calorimeter bomb under the oxygen pressure of 40atm. and the selenium is absorbed in 0.1M NaOH. After the solution is filtrated, concentrated and acidified with HCl, then passed through a column of cation exchange resin in the $H^{+}$ form(Dowex 50X-8). The column eluate is analyzed for selenium by differential pulse cathodic stripping voltammetric method. Analytical results of selenium for NBS SMR is well agreement with the certified values. Results are given for a series of plant materials.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.134-139
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• 2006

Partial nitirification and denitrification process has been reported to be technically feasible and economically favorable, especially for wastewater treatment with high ammonium concentration or low Carbon/Nitrogen ratio. This research was performed to survey nitrite accumulation by nitritation in treating ADEPT effluent of piggery wastewater, which contains highly concentrated ammonia. To estimate the possibility of nitrite accumulation, DO concentration and SRT were investigated as key operational parameters. This result proved that nitritation to nitrite was steadily obtained under short sludge retention time. Oxygen limitation was proved to be just a subsidiary parameter. Energy efficiency of nitritation-denitritation process was higher than complete nitrification-denitrification because external carbon requirement for denitritation could be saved. Though the influent contained significant nonbiodegradable organic substrate, total nitrogen removal efficiency was more than 51% in nitritation-denitritation system.

• Journal of Sensor Science and Technology
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• v.15 no.2
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• pp.84-89
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• 2006

Highly concentrated p-type ZnO thin films can be obtained by doping of N, P and As elements. In this study, undoped ZnO buffer layers were prepared on a (0001) sapphire substrate by a ultra high vaccum pulsed laser deposition(UHV-PLD) method. ZnO buffer layers were deposited with various deposition temperature($400{\sim}700^{\circ}C$) at 350 mtorr of oxygen working pressure. Arsenic doped(1 wt%) ZnO thin films were deposited on the ZnO buffer layers by UHV-PLD. Crystallinity of the samples were evaluated by X-ray diffractometer and scanning electron microscopy. Optical, electrical properties of the ZnO thin films were estimated by photoluminescence(PL) and Hall measurements. The optimal condition of the undoped ZnO buffer layer for the deposition of As-doped ZnO thin films was at $600^{\circ}C$ of deposition temperature.

• Environmental Engineering Research
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• v.20 no.3
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• pp.277-284
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• 2015

Experiments for highly concentrated contaminants in pig waste slurry were carried out for the feasibility test of a pilot-scale innovative process scheme of engaging autothermal thermophilic aerobic digestion (ATAD) and expended granular sludge bed (EGSB) followed by sequencing batch reactor (SBR) system. Contaminants in pig waste slurry such as organic substance, total nitrogen (TN), ammonia nitrogen and total phosphorus (TP) contents were successfully reduced in the system. Total volatile solids (TVS) and chemical oxygen demands (COD) for organic matter in the feed were 32.92 g/L and 42.55 g/L respectively, and they were reduced by about 98.7% and 99.2%, respectively in the system. The overall removal efficiencies for TN and ammonium nitrogen were found to be 98.1 and 98.5%, respectively. The overall removal efficiency for total phosphorus was also found to be 92.5%. Faecal coliform density was reduced to <$1.2{\times}10^4CFU/g$ total solids. Biogas and $CH_4$ were produced in the range of 0.39-0.85 and $0.25-0.62m^3/kg$ [VS removed], respectively. The biogas produced in the system comprised of $295{\pm}26ppm$ (v/v) [$H_2S$].

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.5
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• pp.340-344
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• 2000

Microbial oxidation of D-sorbitol to L-sorbose by Acetobacter suboxydans is of commercial importance since it is the only biochemical process in vitamin C synthesis. The main bottleneck in the batch oxidation of sorbitol to sorbose is that the process is severely inhibited by sorbitol. Suitable fed-batch fermentation designs can eliminate the inherent substrate inhibition and improve sorbose productivity. Fed-batch sorbose fermentations were conducted by using two nutrient feeding strategies. For fed-batch fermentation with pulse feeding, highly concentrated sorbitor (600g/L) along with other nutrients were fed intermittently in four pulses of 0.5 liter in response to the increased DO signal. The fed-batch fermentation was over in 24h with a sorbose productivity of 13.40g/L/h and a final sorbose concentration of 320.48g/L. On the other hand, in fed-batch fermentation with multiple feeds, two pulse feeds of 0.5 liter nutrient medium containing 600g/L sorbitol was followed by the addition of 1.5 liter nutrient medium containing 600g/L sorbitol at a constant feed rate of 0.36L/h till the full working capacity of the reactor. The fermentation was completed in 24h with an enhanced sorbose productivity of 15.09g/L/h and a sorbose concentration of 332.60g/L. The sorbose concentration and productivity obtained by multiple feeding of nutrients was found to be higher than that obtained by pulse feeding and was therefore a better strategy for fed-batch sorbose fermentation.

• Journal of the Korean Chemical Society
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• v.58 no.1
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• pp.68-71
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• 2014

Petroleum refining unavoidably generates large volumes of oily wastewater. The environmentally acceptable disposal of oily wastewater is a current challenge to the petroleum industry. Nowadays, more attentions have been focused on the treatment techniques of oily wastewater. Oily wastewater contained highly concentrated and toxic organic compounds. Wet peroxide oxidation (WPO) and catalytic wet oxidation (CWO) were applied to eliminate pollutants to examine the feasibility of the WPO/CWO of oily wastewater. The results indicated that more than 80% chemical oxygen demand (COD) removal from oily wastewater was achieved with CWO. Homogenous catalyst, $NaHCO_3$ and $Na_2CO_3$ and NaOH showed effective removal for pollutants in oily wastewater. Greater than 90% COD removal was achieved with WPO. It was concluded that WPO was a far more effective process for oily wastewater.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.120-127
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• 2017

High temperature oxygen and water vapor was generated from catalytic decomposition of rocket grade highly concentrated hydrogen peroxide, and monopropellant thruster system was developed and applied into space propulsion system. In this research, background research and conceptual design of underwater propulsion system using catalytic decomposition of hydrogen peroxide was progressed. Two types of system was designed with different steam injection methods. Propulsion system that has ring-type steam injector was manufactured and performance estimation of system was performed with different nozzle exit area. Performance evaluation with central steam injection type jet engine will be progressed in the future.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.25-32
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• 2010

Contamination of soil and groundwater by the compounds of hydrocarbon petroleum has been widely accepted as the main cause that harms the environments and health. To remove those pollutants, absorbing clothes, activated carbons, or oil-water separation devices with the gravity method are employed for treatment. However, those materials and devices cannot remove the emulsion pollutants despite of their efficiency for removing free products. Therefore, we investigated the problems which occur during the groundwater treatment for the highly concentrated suspended solid particles, which can be resulted from excavation, and to propose methods to remove TPH(Total Petroleum Hydrocarbon). After coagulation experiment with high molecular polymers, the concentration of SS(Suspended Solids) and COD(Chemical Oxygen Demand) turned to satisfy the groundwater quality criteria within 5 minutes while the concentration of TPH failed to meet the water quality standard of effluent. Consequently, the water quality criteria for effluent could not be met by single DAF(Dissolved Air Flotation) process. However all water quality criteria could be satisfied after 20 minutes when coagulation reactions are carried out simultaneously in the DAF reactor.