• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.1-9
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• 2016

The co-culture system of microalgae and bacteria enables simultaneous removal of BOD and nutrients in a single reactor if the pair of microorganisms is symbiotic. In this case, nutrients are converted to biomass constituents of microalgae. This review highlights the importance and recent researches using symbiotic co-culture system of microalgae and bacteria in wastewater treatment, focusing on the removal of nitrogen and phosphorus. During wastewater treatment, the microalgae produces molecular oxygen through photosynthesis, which can be used as an electron acceptor by aerobic bacteria to degrade organic pollutants. The released $CO_2$ during the bacterial mineralization can then be consumed by microalgae as a carbon source in photosynthesis. Microalgae and bacteria in the co-culture system could cooperate or compete each other for resources. In the context of wastewater treatment, positive relationships are prerequisite to accomplish the sustainable removal of nutrients. Therefore, the selection of compatible species is very important if the co-culture has to be utilized in wastewater treatment.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.612-621
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• 2018

In this study, $TiO_2$ nanotube plate and metal electrodes(Copper, Nickel, Stainless Steel, Aluminum, Tin, Titanium) were compared on cathodic reduction of nitrate ($NO_3{^-}-N$) during electrolysis. The electrochemical characteristics were compared based on electrochemical impedance spectroscopy (EIS). The surface morphology was obtained using scanning electron microscopy (SEM) method. Brunauer-Emmett-Teller (BET) method was implemented for the specific surface area analysis of the cathodes. To study kinetics, 90 minute batch electrolysis of nitrate solution was performed for each cathodes. In conclusion, under the condition of relatively low ($0.04 A\;cm^{-2}$) current density, $TiO_2$ nanotube plate showed no surface corrosion during the electrolysis, and the reaction rate was measured the highest in the kinetic analysis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.2
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• pp.166-172
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• 1994

To evalulate the antioxidant effect of flavonoid(+)-catechin on n-3 polyunsaturated fatty acids in vivo, rats were fed with diets containing $5\%$ corn oil(CO), $5\%$ corn oil and $15\%$ purified fresh fish oil(FO) or peroxidized fish oil(PFO) for 10 days. To accerelate lipid peroxidation, all of them were injected with 60mg phenobarbital(a day per kg body weight), and treated with phorone(diisopropylidene acetone) before the rats were killed. Contents of triglyceride, phospholipid, cholesterol and lipid peroxide and the activities of GOT, GPT in serum and total lipid and cholesterol content in liver of PFO group rats were significantly higher than those of the FO one. Contrary to our expectations, the activities of superoxide dismutase (SOD), catalase and glutathione peroxidase(GSH-Px) in liver of the FO group were ]ewer than those of the PFO group. These results might be explained as the results of homeostasis. Even though the hepatic glutathione were depleted, catechin and a-tocopherol inhibited production of lipid peroxide effectively. These results suggested that catechin be considered an antioxidative and hepatoprotective agent.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.502-509
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• 1997

Aromatic pollutants(benzene, toluene, ethylbenzene and xylenes) were photodegraded by using a UV oxidation and the rates of degradation were investigated under various reaction conditions. Each of the solution containing 50 ppm benzene, 150 ppm ethylbenzene and 250 ppm xylenes was found UV-photodegraded over 90% in 1 hour of reaction time, wheras the only was 43 % degradation was obtained with 350 ppm toluene solution. A single component solution was more degradable than a mixed component solution and benzene was almost photodegraded at a pH 4.0, 6.4 and 10.0 after reaction time is 1 hr, ehtylbenzene was photodegraded about 92%(pH 4.0), 90%(pH 6.4) and 91%(pH 10.0), xylenes was photodegraded about 95%(pH 4.0), 90%(pH 6.4) and 92%(pH 10.0), but toluene was photodegraded about 80%(pH 4.0), 43%(pH 6.4) and 70%(pH 10.0), respectively. Kinetics studies show that the rate of decay in TOC(total organic carbon) were pseudo first-order rate except ethylbenzene, and then we could evaluate mineralization rate constants(k) of aromatics.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.41-47
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• 2010

This study was conducted to assess the applicability of pilot scale system and to evaluate the treatment efficiency on operational parameters such as humic acid concentration, initial pH and air flow rate on the ozone/peroxyl radical reaction system. The decolorization of ozone/peroxyl radical system was higher than that of only process. Removal efficiency of ozone/peroxyl radical system was generally increased with the increase of intial concentration of humic acid but decreased over the range of 30mg/L. Treatment efficiency of HA at acid pH was smaller compared to that of neutral or basic pH and increased with increasing the air flow rate from 1L/min to 3L/min. In pilot-scale test, average removal of TOC and $COD_{Cr}$ was about 70% and 60%, respectively and ozone/peroxyl radical reaction system was indicated a potential in water treatment application.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.11
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• pp.2643-2648
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• 2015

This paper analyzes the phenomenon of drain induced barrier lowering(DIBL) for doping profiles in channel of asymmetric double gate(DG) MOSFET. The DIBL, the important short channel effect, is described as lowering of source barrier height by drain voltage. The analytical potential distribution is derived from Poisson's equation to analyze the DIBL, and the DIBL is observed according to the change of doping profile to influence on potential distribution. As a results, the DIBL is significantly influenced by projected range and standard projected deviation, the variables of channel doping profiles. The change of DIBL shows greatly in the range of high doping concentration such as $10^{18}/cm^3$. The DIBL increases with decrease of channel length and increase of channel thickness, and with increase of bottom gate voltage and top/bottom gate oxide film thickness.

• Journal of the Korean Society of Urban Environment
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• v.18 no.4
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• pp.391-399
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• 2018

In this study, Diazinon which is the most widely used organophosphorus pesticides (OPPs) among pesticides was removed by ozone/hydrogen peroxide advanced oxidation process (Peroxone AOP). Diazinon is mainly found in groundwater, drinking water, rivers and ponds that are near agricultural areas using the pesticide. Accumulation of Diazinon on the body in the form of metabolites causes neurotoxicity, confusion, dizziness and vomiting. Diazinon is not easily removed by conventional water treatment processes. This study investigated the Diazinon removal characteristics with OH radicals with strong oxidizing power generated by using ozone and hydrogen peroxide. We determined optimal hydrogen peroxide/ozone injection molar ratio and confirmed the elimination reaction to initial Diazinon concentration, pH and DOC concentration, which are factors influencing the removal efficiency. Domestic researches on pesticide removal in the environment are much less than the cases of overseas. This study is expected to provide a basis for the process design for pesticide removal.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.5
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• pp.325-332
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• 2022

The vertical take-off and vertical landing (VTVL) function is essential to carry out exploration missions on the moon or Mars. For this, the engine of the exploration vehicle must have appropriate thrust control accuracy and response time. The hybrid rocket engine (HRE) is known to have a high level of thrust control capability that can satisfy these conditions. This study aims to first verify whether the thrust control performance of the developed HRE is suitable for VTVL. To this end, an oxidizer supply system that does not use a pressurization device was adopted, aiming for a mission time of about 10 seconds. In this study, the thrust control characteristics appearing under various supply pressure decreasing conditions were identified through experiments. Appropriate tank and charging conditions were set from the experimental results. In addition, the results of previous studies and current study's test were compared to confirm whether the developed HRE had adequate control performance for VTVL, and finally, the thrust control performance was verified through altitude control simulation.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.421-421
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• 2021

도시화, 산업화로 인해 하수처리장 유입하수 내 질소 농도가 증가하면서 그에 따른 부영양화 발생, 수생태계에 독성을 미치는 등의 악영향 또한 증가하게 되었다. 하수 내 고농도 질소를 처리하기 위해 1990년 초 연구가 시작되어 현재 보편적으로 사용되고 있는 생물학적 질소 제거 공정은 산소공급과 외부탄소원 보충 과정에서 상당한 비용이 소요된다. 이와 같은 문제점이 대두됨에 따라 고도의 질소 제거 공정이 요구되면서, 경제적으로 개선이 이루어져 기존의 질산화·탈질 공정보다 효율적인 혐기성 암모늄 산화 공정(ANaerobic AMMonium OXidation, ANAMMOX)이 제안되었다. ANAMMOX 공정은 혐기성 조건 아래 전자공여체와 전자수용체로써 암모니아성 질소와 아질산성 질소를 이용해 질소가스 형태로 질소를 제거하는 공정이다. 질산화·탈질 공정과 비교했을 때, 폭기과정에서의 산소요구량 감소, 외부탄소원 불필요, 질소 제거 과정 단축 등의 장점을 가진다. 본 연구는 수처리공정에서의 ANAMMOX 공정의 적용 가능성을 확인하고, 암모니아성 질소대비 아질산성 질소 비율에 따른 Mainstream ANAMMOX 공정의 효율 비교를 통해 공정의 안정성과 높은 제거효율을 확보할 수 있는 NH₄⁺ 대비 NO₂^- 비율을 도출하는데 목적이 있다. 실험실 규모의 Mainstream ANAMMOX 반응조에 적용한 비율은 선행연구를 비롯한 화학양론식에서 제시된 비율을 바탕으로 산정하였다. 1.00부터 1.30의 전체적인 비율을 Initial과 Advanced 2개의 구간으로 나누어 운전한 결과, 각 구간의 NH₄⁺ 제거효율은 각각 58~86%, 94~99%였다. NH₄⁺ 대비 NO₂^- 비율이 증가함에 따라 공정의 안정성이 확보되고, NH₄⁺ 및 총질소(TN) 제거효율이 증가하는 경향이 나타났다. 본 연구의 결과는 수처리공정에서의 안정적인 ANAMMOX 공정 적용을 유도하고, ANAMMOX 공정의 성능개선을 도모하는 연구의 기초로 활용될 수 있다.

• Membrane Journal
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• v.22 no.2
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• pp.95-103
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• 2012

To treat nitrate and non-biodegradable organics effectively in sewage, industrial wastewater and livestock wastewater, the activated sludge process integrated by a membrane separation and a porous electrode- electrolysis was proposed and its efficiency was investigated. The proposed system was consisted of 3 processes; activated sludge, membrane filtration and electrolysis. In the study, the membrane filtration played a role in reducing the load of the electrolysis to operate the proposed process stably. The electrolysis consisted of a porous electrode to increase the efficiency due to the extension of the specific surface area. Additionally, redox reaction in the electrolysis was induced by decomposing influent water as current was applied. As a result, hydrogen free radicals and oxygen radicals as intermediates were produced and they acted as oxidants to play a role in decomposing non-degradable organics. It was environmentally-friendly process because intermediates produced by porous electrode were used to treat waste matters without supplying external reagent. Experimental data showed that the proposed process was more excellent than activated sludge process. SS removal efficiencies of the proposed process, membrane filtration and activated sludge process were about 100%, about 100% and about 90%, respectively. COD removal efficiencies of the proposed system, membrane filtration and activated sludge process were about 92%, about 84% and about 78%, respectively. T-N removal efficiencies of the proposed system, membrane filtration and activated sludge process were about 88%, about 67%, and about 58%, respectively. The SS data showed that SS was efficiently removed in the single of the membrane filtration. The COD/T-N data showed that COD/T-N of membrane hybrid process was treated by removing a little soluble organics and SS, and that COD/T-N of electrolysis hybrid process was treated by oxidize organics with high removal rate.