• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.1
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• pp.57-65
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• 2010

Two types of microbial fuel cells(MFC) were continuously operated using synthetic wastewater. One was conventional two-chambered MFC using proton exchange membrane(PEM-MFC), the other was upflow type membraneless MFC(ML-MFC). Graphite felt was used as a anode in PEM-MFC. In membraneless MFC, two MFCs were operated using porous RVC(reticulated vitreous carbon) as a anode. Graphite felt was used as a cathode in all experiments. In experiment of PEM-MFC, the COD removal rate based on the surface area of anode was about $3.0g/m^2{\cdot}d$ regardless of organic loading rate. And the coulombic efficiency amounted to 22.4~23.4%. The acetic acid used as a fuel was transferred through PEM from the anodic chamber to cathodic chamber. The COD removal rate in ML-MFC were $9.3{\sim}10.1g/m^2{\cdot}d$, which indicated the characteristics of anode had no significant effects on COD removal. Coulombic efficiency were 3.6~3.7 % in both cases of ML-MFC experiments, which were relatively small. It was also observed that the microbial growth in cathodic chamber had an adverse effects on the electricity generation in membraneless MFC.

• Microbiology and Biotechnology Letters
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• v.10 no.1
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• pp.15-26
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• 1982

A potential fungal lipid producer from starch, which was identified as Muror plumbeus, was isolated from natural sources and its optimum cultivation condition for lipid production was investigated. The Mucor plumbeus FRI 0007 showed the highest felt weight and lipid content which were 2.09 $\pm$ 0.24g per 50$m\ell$ of medium and 37.43% on dry weight basis respectively after 20 days incubation on the medium containing 21% of starch as a carbon source. The urea was the best nitrogen source as compared with sodium nitrate, potassium nitrate, magnesium nitrate, ammonium nitrate and ammonium acetate and its optimum concentration was 2.14g/$\ell$, showing 2.39 $\pm$ 0.07 g felt/50$m\ell$ of medium and 50.73% lipid content on dry weight basis after 25 days incubation. Besides the starch as a carbon source and urea as a nitrogen source, the Mucor plumbeus FRI 0007 utilized ZnSO$_4$, MgSO$_4$, NaH$_2$PO$_4$, $K_2$SO$_4$and FeCl$_3$as mineral sources. However, it did not require ail the above 5 minerals in group in-dispensably for its growth and lipid accumulation. The lipid and economic coefficient of Mucor plumbeus FRI 0007 grown on the medium containing 0.44g $K_2$SO$_4$or 5.00g MgSO$_4$/$\ell$solely were 14.96 and 15.37 and 31.12 and 26.10 which was higher than those on the medium containing the above 5 minerals.

• Clean Technology
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• v.23 no.3
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• pp.308-313
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• 2017

In this study, we investigated the electrocatalytic effects of the N and O co-doping of Graphite Felt (GF) electrode for the vanadium redox flow battery (VRFB) at the cathode and the anode reaction, respectively. The electrodes were prepared by chemical vapor deposition (CVD) with $NH_3-O_2$ at 773 K, and its effects were compared with an electrode prepared by an O doping treatment. The surface morphology and chemical composition of the electrodes were characterized by scanning electron microscopy (SEM) and photoelectron spectroscopy (XPS). The electrocatalytic properties of these electrodes were characterized in a VRFB single cell comparing the efficiencies and performance of the electrodes at the cathode, anode, and single cell level. The results exhibited about 2% higher voltage and energy efficiencies on the N-O-GF than the O-GF electrode. It was found that the N and O co-doping was particularly effective in the enhancement of the reduction-oxidation reaction at the anode.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.4
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• pp.324-330
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• 2015

The electrolyte flow rates of vanadium redox flow battery play very important role in terms of ion transfer to electrolyte, kinetics and pump efficiency in system. In this paper a vanadium redox flow battery single cell was tested to suggest the optimization criteria of electrolyte flow rates on the efficiencies. The compared electrolyte circulation flow rates in this experimental work were 15, 30 and 45 mL/min. The charge/discharge characteristics of the flow rate of 30 mL/min was the best out of all flow rates in terms of charging and discharging time. The current efficiencies, voltage efficiencies and energy efficiencies at the flow rate of 30 mL/min were the best. The IR losses obtained at thd current density of $40mA/cm^2$, at the flow rates of 15, 30 and 45 mL/min were 0.085 V, 0.042 V and 0.115 V, respectively. The charge efficiencies at the current density of $40mA/cm^2$ were 96.42%, 96.45% and 96.29% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. The voltge efficiencies at the current density of $40mA/cm^2$ were 77.34%, 80.62% and 76.10% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. Finally, the energy efficiencies at the current density of $40mA/cm^2$ were 74.57%, 77.76% and 73.27% for the electrolyte flow rates of 15, 30 and 45 mL/min, respectively. The optimum flow rates of electrolytes were 20 mL/min in most of operating variables of vanadium redox flow battery.

• Journal of the Korean Institute of Educational Facilities
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• v.25 no.2
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• pp.3-9
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• 2018

This study is designed to measure the indoor environment and research on the environmental situation in the lecture room where the lecture is conducted during the winter time in order to understand the level of environment in the lecture room and then suggest the method of improving the environment in the lecture room in the future. The findings are as follows. First, the number of ventilation measured at Lecture Room 1 was 1.2 times/hour while that at Lecture Room 2 was 2.2 times/hour. Second, the lighting at Lecture Room 1 and 2 was 650~700 lux while the noise at Lecture Room 1 and 2 was not more than 60dB. Third, Group 1 and Group 2 felt in the same way that the air quality in the lecture room was not good when the air quality was measured in 30 minutes after the start of lecture. Fourth, both Group 1 and Group 2 showed the lowered concentration on the class in 30 minutes after the start of the class when the room was heated. But Group 1 got less drop in the concentration when they was put in the non-heated room. Fifth, As for the change in the carbon dioxide volume during lecture, the carbon dioxide volume in the room where the windows was closed rose 1,000~1,400ppm from that at the time of start, thus showing that the indoor air quality got worsened. In addition, it is hard to control the indoor temperature due to the heating and non-heating. Accordingly, it is necessary to get the heating system which can make the ventilation in order to keep the environmental level in the lecture room to a certain level and keep the proper indoor temperature.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.2
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• pp.200-205
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• 2017

The three electrodes (carbon felt) were tested in all-vanadium redox flow battery (VRFB) to confirm the its usefulness. The electrode property was measured by the CV (cyclic voltammetry) method. The current ratio of maximum peak(IPA/IPC) in GF040BH5 and GF051BH3 had almost the same value compared to that in XF30A. The performances of VRFB using the each electrode were measured during 5 cycles of charge-discharge at the current density of $60mA/cm^2$. An average energy efficiency of the VRFB was 77.8%, 77.3%, and 79.2% for XF30A, GF040BH5 and GF051BH3, respectively. It was confirmed from the data that GF040BH5 and GF051BH3 is well suited for use in a VRFB as a electrode, like XF30A.

• Journal of Korean Elementary Science Education
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• v.21 no.1
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• pp.127-134
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• 2002

Although the reward based on group accomplishment in cooperative learning has a merit to emphasize interdependency, it may have some undesirable side effects such as free rider effect and sucker effect. For the purpose of reducing these side effects, this study examined how the adjustment of the reward structure affected the scholastic achievement, the perception of learning environments, and the attitude toward science class by adding individual reward to group reward. We selected 2 classes of sixth grade in an elementary school, and taught on oxygen and carbon dioxide for 13 class hours in cooperative learning strategies. Group reward was applied to one class, and both group and individual rewards were applied to the other class. Analysis of the results indicated that the achievement scores of the students under the group and individual rewards were significantly higher than those under the group reward. In addition, they had more difficulty in science class and felt less satisfied. The upper level students under the group and individual rewards were also found to exhibit more competition. Educational implications were discussed.

• Journal of Microbiology and Biotechnology
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• v.19 no.8
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• pp.836-844
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• 2009

A denitrification bacterium was isolated from riverbed soil and identified as Ochrobactrum sp., whose specific enzymes for denitrification metabolism were biochemically assayed or confirmed with specific coding genes. The denitrification activity of strain G3-1 was proportional to glucose/nitrate balance, which was consistent with the theoretical balance (0.5). The modified graphite felt cathode with neutral red, which functions as a solid electron mediator, enhanced the electron transfer from electrode to bacterial cell. The porous carbon anode was coated with a ceramic membrane and cellulose acetate film in order to permit the penetration of water molecules from the catholyte to the outside through anode, which functions as an air anode. A non-compartmented electrochemical bioreactor (NCEB) comprised of a solid electron mediator and an air anode was employed for cultivation of G3-1 cells. The intact G3-1 cells were immobilized in the solid electron mediator, by which denitrification activity was greatly increased at the lower glucose/nitrate balance than the theoretical balance (0.5). Metabolic stability of the intact G3-1 cells immobilized in the solid electron mediator was extended to 20 days, even at a glucose/nitrate balance of 0.1.

• Journal of Microbiology and Biotechnology
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• v.19 no.7
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• pp.666-674
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• 2009

An electrochemical bioreactor (ECB) composed of a cathode compartment and an air anode was used in this study to characterize the ethanol fermentation of Zymomonas mobilis. The cathode and air anode were constructed of modified graphite felt with neutral red (NR) and a modified porous carbon plate with cellulose acetate and porous ceramic membrane, respectively. The air anode operates as a catalyst to generate protons and electrons from water. The growth and ethanol production of Z. mobilis were 50% higher in the ECB than were observed under anoxic nitrogen conditions. Ethanol production by growing cells and the crude enzyme of Z. mobilis were significantly lower under aerobic conditions than under other conditions. The growing cells and crude enzyme of Z. mobilis did not catalyze ethanol production from pyruvate and acetaldehyde. The membrane fraction of crude enzyme catalyzed ethanol production from glucose, but the soluble fraction did not. NADH was oxidized to $NAD^+$in association with $H_2O_2$reduction, via the catalysis of crude enzyme. Our results suggested that NADH/$NAD^+$balance may be a critical factor for ethanol production from glucose in the metabolism of Z. mobilis, and that the metabolic activity of both growing cells and crude enzyme for ethanol fermentation may be induced in the presence of glucose.

• Journal of Environmental Science International
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• v.19 no.8
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• pp.951-960
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• 2010

Sediment works as a resource for electric cells. This paper was designed in order to verify how sediment cells work with anodic material such as metal and carbon fiber. As known quite well, sediment under sea, rivers or streams provides a furbished environment for generating electrons via some electron transfer mechanism within specific microbial population or corrosive oxidation on the metal surfaces in the presence of oxygen or water molecules. We experimented with one type of sediment cell using different anodic material so as to attain prolonged, maximum electric power. Iron, Zinc, aluminum, copper, zinc/copper, and graphite felt were tested for anodes. Also, combined type of anodes-metal embedded in the graphite fiber matrix-was experimented for better performances. The results show that the combined type of anodes exhibited sustainable electricity production for ca. 600 h with max. $0.57\;W/m^2$ Al/Graphite. Meanwhile, graphite-only electrodes produced max. $0.11\;W/m^2$ along with quite stationary electric output, and for a zinc electrode, in which the electricity generated was not stable with time, therefore resulting in relatively sharp drop in that after 100 h or so, the maximum power density was $0.64\;W/m^2$. It was observed that the corrosive reaction rates in the metal electrodes might be varied, so that strength and stability in the electric performances(voltage and current density) could be affected by them. In addition to that, COD(chemical oxygen demand) of the sediment of the cell system was reduced by 17.5~36.7% in 600 h, which implied that the organic matter in the sediment would be partially converted into non-COD substances, that is, would suggest a way for decontamination of the aged, anaerobic sediment as well. The pH reduction for all electrodes could be a sign of organic acid production due to complicated chemical changes in the sediment.