• 한국수소및신에너지학회논문집
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• 제18권1호
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• pp.32-39
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• 2007

CO oxidation and selective CO oxidation of $La_xCe_{1-x}Co_yCu_{1-y}O_{3-{\alpha}}$ perovskite(x=1, 0.9, 0.7. 0.5; y=1, 0.9, 0.7, 0.5) were investigated. For CO oxidation, catalytic activities were studied according to different preparation conditions such as pH and calcination temperature. The influence of the change of the $O_2$ concentration for selective CO oxidation was studied, too. The substitution of Ce for La improved the catalytic activity for CO oxidation and selective CO oxidation and best activity was observed for $La_{0.7}Ce_{0.3}CoO_3$ prepared at pH 11 and calcined at $600^{\circ}C$. The temperature of 90% CO conversion for CO oxidation using $La_{0.7}Ce_{0.3}CoO_3$ was $230^{\circ}C$. In contrast to the enhancement effect by Ce substitution, the partial substitution of Cu for Co in $LaCo_yCu_{1-y}O_{3-{\alpha}}$ decreased catalytic activities for CO oxidation reaction compared to that using $LaCoO_3$. For selective CO oxidation, the best CO conversion was 66% at $230^{\circ}C$ for $La_{0.7}Ce_{0.3}CoO_3$. The CO conversion of $La_{0.7}Ce_{0.3}CoO_3$ was greatly increased from 66% to 91% as increasing $O_2$ concentration from 1% to 2%.

• 한국분말재료학회지
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• 제11권2호
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• pp.111-117
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• 2004

The oxidation behavior of 91 WC-9Co hardmetal in weight percentage has been studied in the present work as a part of the development of recycling process. The morphological and compositional changes of the WC-Co hardmetal with oxidation time at 90$0^{\circ}C$ were analyzed by using surface observation and X-ray diffraction. respective]y. As the oxidation time increased, the WC-Co hardmetal was continuously expanded to form porous oxide mixtures of $CoWO_4$ and $WO_3$. The morphology of porous oxide mixture was basically dependent on initial shape of the WC-Co hardmetal. From thermo-gravimetric (TG) analysis, it was found that the oxidation rate was increased with increasing oxidation temperature and oxygen content in the flowing atmospheric gas. The fraction of oxidation versus time curves showed S-curve relationship at a given of oxidation temperature. These oxidation behaviors of the WC-Co hardmetal were discussed in terms of previously proposed kinetic models.

• 한국식품영양과학회지
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• 제24권2호
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• pp.202-207
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• 1995

The effects of lipoxygenase, linoleic acid, tocopherol and pH on the co-oxidation of $\beta$-carotene in the aqueous system were studied. It showed that the co-oxidation of $\beta$-carotene was noticeable at both pH 7.4 and 9.0. As the concentraitons of linoleic acid and $\beta$-carotene increased, the rate of oxidation of $\beta$-carotene tended to be increased. However, $\alpha$- and $\delta$-tocopherol retarded the co-oxidation of $\beta$-carotene. As the concentrations of tocopherols increased, $\beta$-carotene was more stabilized, generally. But low concentration of $\alpha$-tocopherol(10-4M) acted more effective antioxidant than high concentration of it(10-3M) at pH 7.4. The antioxidant effect of tocopherol greatly depended on pH ; it was outstanding at pH 7.4.

• Environmental Engineering Research
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• 제20권2호
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• pp.191-197
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• 2015

The first objective of this study was to discuss the applicability of the $CO_2/CH_4$ ratio method in order to assess $CH_4$ oxidation efficiency. To achieve this objective, a comparison between $CO_2/CH_4$ ratios and the mass balance method was conducted. The second objective of this study was to estimate the $CH_4$ oxidation efficiency in an interim landfill soil cover and assess how a $CH_4$ influx influences the $CH_4$ oxidation efficiency. The results showed that despite the $CO_2$ problems brought by respiration, the $CH_4$ oxidation efficiencies obtained by the $CO_2/CH_4$ ratio method led to similar results compared to the mass balance method. In this respect, the $CO_2/CH_4$ ratio method can be an indicator of the $CH_4$ oxidation efficiencies for landfill cover soils. The $CH_4$ oxidation efficiencies derived in this study through the $CO_2/CH_4$ ratio method ranged between 46% and 64%, and between 41% and 62% through the mass balance method. The results imply that the Intergovernmental Panel on Climate Change's (IPCC) default value of 10% for the $CH_4$ oxidation efficiency is an underestimation for landfill cover soils. $CH_4$ oxidation efficiency tends to be negatively correlated with $CH_4$ influx. Therefore, $CH_4$ influx reaching a landfill cover should be limited in order to increase the $CH_4$ oxidation efficiency.

• 운동영양학회지
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• 제16권1호
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• pp.1-9
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• 2012

Long chain fatty acids (LCFAs) are transported into cells via plasma transporters, are activated to fatty acyl-CoA by fatty acyl-CoA synthase (ACS), and enter mitochondria via the carnitine system (CPT1/CACT/CPT2). The mitochondrial carnitine system plays an obligatory role in β-oxidation of LCFAs by catalyzing their transport into the mitochondrial matrix. Fatty acyl-CoAs are oxidized via the β-oxidation pathway, which results in the production of acetyl-CoA. The acetyl-CoA can be imported into the tricarboxylic acid (TCA) cycle for oxidation in the mitochondrial matrix or can be used for malonyl-CoA synthesis by acetyl-CoA carboxylase 2 (ACC2) in the cytoplasm. In skeletal muscle, ACC2 catalyzes the carboxylation of acetyl-CoA to form malonyl-CoA, which is a potent endogenous inhibitor of carnitine palmitoyltransferase 1 (CPT1). Thus, ACC2 indirectly inhibits the influx of fatty acids into the mitochondria. Fatty acid metabolism can also be regulated by malonyl-CoA-mediated inhibition of CPT1.

• 생명과학회지
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• 제2권2호
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• pp.91-96
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• 1992

효소에 의한 carotenoid의 co-oxidationgus상은 lipoxygenasechrao하에서 지방산인 linoleic acid가 산화되어 이때 만들어진 free radical에 의해 carotenoid가 쉽게 산화되기 때문에 일어나는 현상이다. 이화같이 carotenoid의 co-oxidation에서 lipoxygenase는 free radical을 만들면서 반응속도를 빠르게 하는 촉매제의 역할을 다음과 같이 담당하고 있다고 할 수 있다. Lipoxygenase에 의한 carotenoid의 co-oxidation 현상을 처음 발견한 것은 대두가루를 밀가루와 혼합하여 사용할 때였다. 대두가루 속에 다량 함유된 lipoxygenase에 의해 밀가루의 carotenoid 색소가 표백되는 것을 보고 이 현상은 lipoxygenase에 의해 기질은 지방산이 산화되는 동안 caroenoid가 쉽게 co-oxidation되기 때문이라는 것을 알아내었다. 즉, carotenoid는 지질이 존재하는 반응시스템에서 항산화제로서 혹은 secondary substrate로서 작용한다고 할 수 있다.

• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1199-1203
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• 2012

Catalytic filters consisting of Ni nanoparticle and carbon fiber with different oxidation states of Ni (either metallic or oxidic) were prepared using a chemical vapor deposition process and various post-annealing steps. CO oxidation reactivity of each sample was evaluated using a batch type quartz reactor with a gas mixture of CO (500 mtorr) and $O_2$ (3 torr) at $300^{\circ}C$. Metallic and oxidic Ni showed almost the same CO oxidation reactivity. Moreover, the CO oxidation reactivity of metallic sample remained unchanged in the subsequently performed second reaction experiment. We suggested that metallic Ni transformed into oxidic state at the initial stage of the exposure to the reactant gas mixture, and Ni-oxide was catalytically active species. In addition, we found that CO oxidation reactivity of Ni-oxide surface was enhanced by increase in the $H_2O$ impurity in the reactor.

• 공업화학
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• 제32권4호
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• pp.385-392
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• 2021

본 연구에서는 Co/CeO₂ 촉매 제조 시 코발트의 첨가 함량 및 세리아의 소성온도에 따른 물리·화학적 특성 및 일산화질소 산화 성능을 비교하였다. Co/CeO₂ 촉매의 구조적 특성은 XRD, BET 분석을 통하여 확인하였으며, 코발트 표면밀도에 따른 표면 결정 상태를 제안하였다. 또한, Raman, XPS 분석을 통하여 촉매의 산화가 및 산소 결합 상태를 확인하였으며, 일산화질소 산화 성능과의 관계를 제안하였다. H₂-TPR 분석을 통하여 촉매의 특성 변화에 따른 산소전달특성을 확인하였으며, 일산화질소 산화를 위한 촉매의 활성점(Co³⁺)을 제안하였다.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3660-3665
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• 2011

CO-tolerant PtMo/C alloy electrocatalyst was prepared by a colloidal method, and its electrocatalytic activity toward CO oxidation was investigated. Electrochemical study revealed that the alloy catalyst significantly enhanced catalytic activity toward the electro-oxidation of CO compared to Pt/C counterpart. Cyclic voltammetry suggested that Mo plays an important role in promoting CO electro-oxidation by facilitating the formation of active oxygen species. The effect of Mo on the electronic structure of Pt was investigated using X-ray absorption spectroscopy to elucidate the synergetic effect of alloying. Our in-depth spectroscopic analysis revealed that CO is less strongly adsorbed on PtMo/C catalyst than on Pt/C catalyst due to the modulation of the electronic structure of Pt d-band. Our investigation shows that the enhanced CO electrooxidation in PtMo alloy electrocatalyst is originated from two factors; one comes from the facile formation of active oxygen species, and the other from the weak interaction between Pt and CO.

• E2M - 전기 전자와 첨단 소재
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• 제7권6호
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• pp.511-519
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• 1994

The effect of the deposition conditions, such as the base pressure, working pressure, sputtering power, pre-sputtering, and deposition thickness in facing targets sputtering system(FTS), on the oxidation of the TbFeCo thin films was studied by investigating the magneto-optical properties as well as oxygen analysis by the AES depth profiles. The results showed that the base pressure did not affect the magnetic properties so much, probably due to the short flight distance of the sputtered particles. At the higher sputtering power and lower working pressure with pre-sputtering the oxidation of TbFeCo thin films was decreased. As the film thickness increased the TbFeCo thin films showed the perpendicular anisotropy from in-plane anisotropy overcoming the oxidation effect at the beginning of the sputtering.