• Journal of Microbiology and Biotechnology
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• v.21 no.9
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• pp.988-994
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• 2011

A significant amount of nitrous oxide ($N_2O$), which is one of the serious greenhouse gases, is emitted from nitrification and denitrification of wastewater. Batch wastewater nitrifications with enriched nitrifiers were carried out under oxygen-limited condition with synthetic (without organic carbon) and real wastewater (with organic carbon) in order to find out the effect of ammonium concentration on $N_2O$ emission. Cumulated $N_2O$-N emission reached 3.0, 5.7, 6.2, and 13.5 mg from 0.4 l of the synthetic wastewater with 50, 100, 200, and 500 mg/l ${NH_4}^+$-N, respectively, and 1.0 mg from the real wastewater with 125 mg/l ${NH_4}^+$-N. The results indicate that $N_2O$ emission increased with ammonium concentration and the load. The ammonium removal rate and nitrite concentration also increased $N_2O$ emission. Comparative analysis of $N_2O$ emission from synthetic and real wastewaters revealed that wastewater nitrification under oxygen-limited condition emitted more $N_2O$ than that of heterotrophic denitrification. Summarizing the results, it can be concluded that denitrification by autotrophic nitrifiers contributes significantly to the $N_2O$ emission from wastewater nitrification.

• Journal of Magnetics
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• v.10 no.4
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• pp.137-141
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• 2005

We confirmed that the improvement in properties of magnetic tunnel junctions prepared by radical oxidation after thermal treatment was mostly resulted from the redistribution of oxygen at the $AIOx/Co_{90}Fe_{10}$ interface. The as-deposited Al oxide barrier was oxygen-deficient but most of it re-oxidized into $Al_2O_3$, the thermodynamically stable stoichiometric phase, through thermal treatment. As a result, the effective barrier height was increased from 1.52 eV to 2.27 eV. On the other hand, the effective barrier width was decreased from 8.2 ${\AA}$ to 7.5 ${\AA}$. X-ray absorption spectra of Fe and Co clearly showed that the oxygen in the CoFe layer diffused back into the Al barrier and thereby enriched the barrier to close to a stoichiometirc $Al_2O_3$ phase. The oxygen bonded with Co and Fe diffused back by 6.8 ${\AA}$ and 4.5 ${\AA}$ after thermal treatment, respectively. Our results confirm that controlling the chemical structures of the interface is important to improve the properties of magnetic tunnel junctions.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.11a
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• pp.195-200
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• 2002

산업체 열 설비 및 동력장치는 대부분이 화석연료를 연소과정을 통한 열에너지로 변환하여 사용하는 구조로 되어있으며, 화석연료의 연소는 필연적으로 온실가스인 $CO_2$, 및 대기 오염 물질인 NOx, SOx, 등을 배출한다. 이에 화석연료의 연소에 의한 환경 및 인체에 미치는 오염물질의 저감과 열에너지의 손실을 줄이기 위해 활발한 연구가 수행되고있으며, 최근에는 연소용 공기 중에 산소를 첨가하여 연소하는 산소부화 연소, 순산소 만으로 연소시키는 방법에 대한 연구가 진행 중에 있다.(중략)

• Proceedings of the Membrane Society of Korea Conference
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• 1994.10a
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• pp.38-41
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• 1994

막분리(membrane separation)법은 막 전후의 압력차, 농도차 등을 추진력(driving foroe)으로 하여 분리대상물질에 대한 막의 선택투과성 차이를 이용, 분리를 행하는 것이다. 이 분리법은 기존의 분리공정인 심냉법(cryogenic separation)과는 달리 상변환 공정이 필요없어 에너지가 적게 들고 또한 PSA(pressure swing adsorption)법에서와 같은 cycle 운전이 필요없어 연속적으로 분리가 가능하며 시스템도 간단하다. 최근 기체 막분리의 경우 수소 및 탄산가스의 회수정제, 공기중의 산소와 질소의 분리 등에 실용화되고 있다. 여기서는 공기중의 산소를 분리하여 30-40% 산소부화공기(oxygen enriched air)를 간편하게 제조할 수 있는 산소부화막장치와 연소장치에의 응용기술 및 연구결과에 대해 간략히 소개하고자 한다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.93-97
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• 2000

This study was carried out to investigate the effect of rotifer fed the different diets in high density culture on larval flounder Paralichthys olivaceus. Potifer was enriched with enrichment supplements, Marine ${\alpha}\;and\;{\omega}-yeast$ for 6 hours after being cultured with freshwater Chlorella for 18 hours during high density culture before it was fed to larval flounder. And rotifer was culutured with marine Chlorella and freshwater Chlorella for 24 hours during semi-continuous high density culture before it was fed to larval flounder. Culture tanks(21 working volum) set for rotifer culture in a water bath($28{\circ}C$) were continuously supplied with oxygen gas. The content of n-3 HUFA to fatty acids in rotifer(dry weight ${\%}$) enriched with Marine ${\alpha}$ for 6 hours and cultures with marine Chlorella for 24 hours were higher than that in rotifer enriched with ${\omega}-yeast$ for 6 hours or cultured with freshwater Chlorella for 24 hours. The growth and survival rates of larval flounder fed on rotifer enriched with Marine ${\alpha}$ for 6 hours and cultured with marine Chlorella for 24 hours were higher than those of larval flounder fed on rotifer enriched with ${\omega}-yeast$ for 6 hours or cultured with freshwater Chlorella for 24 hours. And the content of n-3 HUFA of larval flounder fed on rotifer enriched with Marine ${\alpha}$ for 6 hours was higher than that of larval flounder fed on other rotifers, The results from this study indicated that rotifer culture with marine Chiorelia would be suitable for the high density culture and effective diet for the growth of larval flounder.

• Journal of the Korean Society of Safety
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• v.26 no.2
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• pp.42-47
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• 2011

Going underwater is supposed to begin with the history of human beings. At first it was confined to relatively shallow level, less than several meters by holding breath. Recently, deep level diving has been necessary for such purpose as construction, maritime salvage, military operations, research and sports by using SCUBA(self-contained underwater breathing apparatus) equipment. As one goes down into water, the pressure on the diver is increased due to water pressure with depth, usually 1 atm for each 10 m water level. In deep water, mixed gas or nitrox(EAN, enriched air nitrox) could be applied for the divers lest they should get disease due to high pressure. Of these, the former is usually composed of oxygen and inert gas like helium or hydrogen, the latter contains higher oxygen content than that in normal air in which the oxygen concentration is designated by the character "EAN" followed by vol. % of oxygen, for example, "EAN 40" contains 40% of oxygen. In this case, a victim was found at the 39 m below the sea surface breathing air and nitrox in cylinder wrongly marked as EAN 36, which was analyzed to contain 63% of oxygen by GC/TCD. The cause of death could not be exactly related with the oxygen content in the nitrox cylinder, because the accurate depth for the victim to dive was not known, even though the victim was just found at the depth of 39 m. However, the wrongly marked nitrox could be believed to be the main cause of the death at the depth unless there happened any other accident except that during diving.

• KSBB Journal
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• v.13 no.3
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• pp.223-230
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• 1998

Experiments for lignin peroxidase production have been conducted by aerobic fermentation of Phanerochaete chrysosporium under low shear rate and enriched oxygen environment. The result of flask cultures of white rot fungus indicated that high oxygen concentration and low shear force were essential for enhancement of lignin peroxidase production. Pentachlorophenol was readily degraded by lignin peroxidase produced in nutrient limited flask cultures. Polyurethane foam was fond to be an effective immobilization matrix of P. chrysosporium.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.10a
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• pp.65-66
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• 1997

1. 서론 : 현재의 막분리 기술로는 단 단계 분리공정(single-stage separation)으로 약 40%의 산소농축공기(oxygen-enriched air)를 얻을 수 밖에 없지만 심냉법(cryogenic techniques)보다는 에너지 소비율이 적으며, 공정이 비교적 간단하기 때문에 용도에 따라 순 산소를 꼭 필요로 하지 않는 제철소, 발전소 등의 연소분야, 호흡기 환자를 위한 의료분야, 생물공학이나 항공기 분야 등에 편리하게 이용될 수 있다. 이와 같이 용도가 다양한 산소를 분리막을 이용하여 보다 편리하고 값싸게 얻기 위해서는 산소와 질소의 막투과에 대한 새로운 지식을 얻고 막투과가 기체의 어떤 성질에 지배되고 있는가를 조사할 필요가 있다. 본 연구에서는 고무상 고분자막(rubbery polymer membrane)에 대한 산소/질소의 수착특성과 순수한 기체의 투과율(permeation rate)을 기초로 하여 혼합기체의 투과율, 분리인자(separation factor), 막분리 공정변수에 의한 중공사 분리막에서의 기체분리특성에 대하여 연구하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1625-1631
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• 2004

Investigation on Flue Gas Recirculation(FGR) flame and Fuel Injection Recirculation(FIR) flame was performed with numerical method. Quantitative Reaction Path Diagram(QRPD) is utilized to compare the different chemistry effects between FGR flame and FIR flame. In order to compare flamelets in various oxygen-enrichment conditions reasonably, the adiabatic flame temperature and Damkohler number were held fixed by modulating the amount of diluents to fuel and oxidizer stream and by varying global strain rate of flame respectively. Basic flame structures were compared and characteristics of CH$_4$ decomposition and NO formation were analyzed based on QRPD analysis between FGR flame and FIR flame.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.37-42
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• 2003

This research was carried on an 8100cc turbo-charged heavy duty diesel in the application of a cooled-EGR. Exhaust and intake manifold were modified and an electronically controlled EGR was installed in order to investigate engine performance and exhausted emission characteristics. High pressure route was designed in the compact form on the purpose of practicability in this cooled-EGR system, which constitutes a venturi tube to maintain pressure difference between exhaust manifold and compressor, an EGR cooler, an EGR valve and a solenoid valve.