• Journal of the Korean Institute of Gas
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• v.25 no.2
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• pp.1-12
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• 2021

MILD(Moderate or Intense Low-oxygen Dilution) combustion has attracted attention as the clean thermal energy technology due to the lower emissions of unburnt carbon and NO_x. MILD combustion aims to enlarge the combustion reaction zone using the spontaneous ignition phenomenon of the reactants. In this study, the ignition delay time of CH₄ according to the initial temperature of reactants and the addition of CO, H₂ was investigated using a numerical approach. Ignition delay time became shorter as the increases of initial temperature and H₂ addition. But, CO addition to the fuel increase the ignition delay time. In case of H₂ addition to the fuel, the ignition delay time decreased because the higher fraction of HO₂ promotes the decomposition of methyl radical(CH₃) and produce OH radical. However, in case of CO addition to the fuel, ignition delay time inceased because a high proportion of HCO consumes H radical. There was no significant effect of HCO on the reduction of ignition delay time. Also, the increase rates of NO emissions by the addition of CO and H₂ were approximately 7% and 1%, respectively. A high proportion of NCO affects the increase in NO production rate.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2008.11a
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• pp.482-487
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• 2008

성능이 우수한 다성분계 전극을 개발하기 위하여 Ru를 주 전극성분으로 Pt, Sn, Sb 및 Gd를 보조 전극성분으로 하여 3, 4성분계 전극의 성능과 산화제 생성량 및 전극 표면 분석을 행하여 다음의 결과를 얻었다. 1. 2분 동안 단위 W당 제거된 RhB 농토는 Ru:Sn:Sb=9:1:1 > Ru:Pt:Gd=5:5:1 > Ru:Sn=9:1 > Ru:Sn:Gd=9:1:1 > Ru:Sb:Gd=9:1:1로 나타났다. Ru:Sn:Sb=9:1.1 전극에서 발생하는 free Cl, ClO$_2$ 및 H$_2$O$_2$농도가 다른 전극보다 높은 것으로 나타나 산화제 생성경향과 RhB 분해율과는 상관관계가 있는 것으로 사료되었다. 4성분계 전극 중에서 Ru:Sn:Sb:Gd 전극의 성능이 가장 우수한 것으로 나타났으나 3성분계 전극인 Ru:Sn:Sb=9:1.1 전극보다 성능이 떨어지는 것으로 나타났다. Ru:Sn:Sb=9:1:1 전극에서 생성되는 산화제 농도가 다른 두 종류의 산화제 농도보다 높은 것으로 나타났고 4성분 전극의 경우 Ru:Sn:Sb:Gd 전극의 산화제 농도가 Ru:Sn:Sb:Gd 전극이 높거나 유사한 경우로 나타나 산화제 생성 경향과 RhB분해 능과는 상관관계가 있는 것으로 나타났다. 초기 RhB 분해 속도가 높은 전극의 COD 제거율도 높은 것으로 나타났다. OH 라디칼은 발생하지 않지만 염소계 산화제 농도가 높고 RhB제거율이 높아 Ru를 주 성분으로 한 전극의 RhB분해는 주로 간접 산화작용에 의한 것이며, 개발된 3, 4성분계 산화물 전극은 간접 산화용 전극임을 알 수 있었다. 에칭을 하기 전의 Ti판은 표면이 매끄러운 것으로 나타났으며, 35% 염산으로 에칭한 후의 Ti메쉬는 매우 거친 표면조직을 가지는 것을 관찰할 수 있었다. Ru:Sn:Sb=9:1:1 전극과 Ru:Sn:Sb:Gd 전극의 SEM 사진을 관찰한 결과 두 전극 모두 전극 물질이 균일하게 도포되어 있었으며, 두 전극 모두 열소성을 통해 전극 성분을 코팅할 때 발생하는 "mud crack"이 발생한 것이 관찰되었다 EDX 분석에서 Cl이 관찰되었는데, 전극 성분의 불완전 산화로 인한 비양론적 산화물 때문이며 이는 RhB 분해성능과 관련 있는 것으로 사료되었다.

• Korean Journal of Plant Resources
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• v.24 no.2
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• pp.130-138
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• 2011

In this study, we evaluated the protective effects of the hot water extract from red bean (Phaseolus angularis) against oxidative DNA and cell damage induced by hydroxyl radical. The antioxidant activities were evaluated by hydroxyl radical and hydrogen peroxide scavenging assay, and $Fe^{2+}$-chelating assay. Although the extract with hot water didn't scavenge the hydroxyl radical, it removed and chelated hydrogen peroxide and ferrous iron necessary for the induction of hydroxyl radical by 71% and 64% at 200 ${\mu}g/ml$, respectively. Its protective effect on oxidative DNA damage was carried using ${\Psi}$X-174 RF I plasmid DNA comparing the conversion level of supercoiled form of the plasmid DNA into open-circular form and linear form and the expression level of phospho-H2AX in NIH 3T3 cells. In ${\Psi}$X-174 RF I plasmid DNA cleavage assay, it inhibited oxidative DNA damage by 96% at 200 ${\mu}g/ml$. Also, it decreased the expression of phospho-H2AX by 50.1% at 200 ${\mu}g/ml$. Its protective effect against oxidative cell damage was measured by MTT assay and the expression level of p21 protein in NIH 3T3 cells. In MTT assay for the protective effect against the oxidative cell damage, it inhibited the oxidative cell death and the abnormal cell growth induced by hydroxyl radical. Also, it inhibited p21 protein expression by 98% at 200 ${\mu}g/ml$. In conclusion, the results of the present studies indicate that hot water extract from red bean exhibits antioxidant properties and inhibit oxidative DNA damage and the cell death caused by hydroxyl radical.

• Journal of the Korean Applied Science and Technology
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• v.38 no.5
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• pp.1302-1313
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• 2021

In this study, Gami-Sumiwon (GS; Cynanchi wilfordii R., Angelica gigantis R., Lycium chinense M., Betula platyphylla S., Cryptotympana atrata F. and Carthamus tinctorius L.) and/or Sinomenium acutum R. (SC) was extracted with 70% ethanol or water. And We investigated the antioxidant activity effect of GS±SC. The following experimental techniques were used to evaluate the antioxidant efficacy of GS±SC. HPLC chromatogram, heavy metal content, ABTS/DPPH radical scavenging analysis, SOD-like activity assay, FACS, and NO assay. As a result of the experiment, the sinomenine content was found to be higher in DW extracts, and decursin was found to be higher in 80% ethanol extracts. And, the amount of heavy metals in all extracts was below the standard value. ABTS, and DPPH radical scavenging activity was identified that GS±SC(EtOH) was found to have a higher scavenging activity than GS±SC(DW). But, SOD showed the opposite result. No cytotoxicity of GS was observed on Raw 264.7 cells at concentration of 1~100 ㎍/㎖. The ROS production was significantly decreased that GS±SC(DW) was found to have a higher scavenging activity than GS±SC(EtOH). However, NO production showed the opposite result. Looking at the results of SOD and ROS analysis, SC does not seem to have a function of prevention. SC is thought to have an effect on the removal of free radicals generated after oxidative stress. This result objectively confirmed the antioxidant effect of GS±SCs. We will continue to conduct in-depth research. Therefore, it is believed that the possibility of using GS±SCs as a functional material can be established. The more diverse the objectives, the higher the value of GS utilization is thought to be.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.2 s.51
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• pp.197-206
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• 2005

In the present study, the Chuncheon buckwheat extracts prepared from its seed coats, seeds and stems were used to determine anti-oxidative effects, the content of rutin and phytic acid, and the protective role against cadmium at the cellular level. futhermore, it was evaluated whether the buckwheat, mainly known as a healthy food source, might be applicable to functional cosmetics. Up to $100 {\mu}g/mL$ of the extract was not toxic in HaCaT and B16F10 cell lines using MTT assay. The anti-oxidative capacity of superoxide radicals was shown in seed coats extracts > stem extracts=seed extracts. Although its content of rutin, known as one of effective anti-oxidants, mainly exists in the stem, any extract did not eliminate hydroxyl radicals. Phytic acid, known as a heavy metal-chelate agent, was highly concentrated in the stem. The Chuncheon buckwheat extract had $10\%$ protective effect against the treatment of $50{\mu}M$ cadmium at which $50\%$ of HaCaT cells survived. Confocal laser scanning microscope revealed the intracellular generation of reactive oxygen species (ROS) by cadmium treatment. Finally, we identified that the stem extract had the most protective effect on the elimination of ROS.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.4 s.48
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• pp.499-502
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• 2004

DPPH radical-generating system was used to evaluate the antioxidant properties of the Rosaceae. The inhibitory effects of ethanolic extracts from Rosaceae plants were investigated on melanin biosynthesis which is closely related to hyperpigmentation. Of the Rosaceae extracts, Prunus sargentii, Rubus coreanus, Chaenomeles sinensis, Photinia glabra and Pyrus pyrifolia showed a potent inhibition of tyrosinase, the enzyme which converts 3-(3,4-dihydroxyphenyl) alanine (dopa) to dopachrome in the melanin biosynthetic process. Furthermore, MMT assay was used to check the cytotoxicity of extracts on the human foreskin fibroblast cell line, Hs68. Among the Rosaceae, bark of Prunus sargentii, bark wood of Photinia glabra and all parts or Chaenomeles sinensis showed more than $50\%$ inhibition of mushroom tyrosinase activity at 100 ug/mL and more than $80\%$ of strong DPPH radical-scavenging activity at 10 ug/mL. In audition to, they had no cytotoxic activity on Hs68. These results suggest that these extracts might be except a controler in pigmentation.

• Applied Chemistry for Engineering
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• v.3 no.2
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• pp.256-265
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• 1992

The kinetics for the oxidative coupling of methane over NaCl(30wt%)/ZnO(60wt%)/${\alpha}-Al_2O_3$ catalyst was investigated, and then the active oxygen species were discussed. The conversion rate of methane was measured at the atmospheric pressure with various combinations of partial pressure of methane and oxygen at temperature range of $650^{\circ}C{\sim}750^{\circ}C$, at conversions less than with 10%. These rate data were then used to verify the proposed Langmuir-Hinshelwood kinetic equation. The rate limiting step appeared to be the formation of the methyl radicals by the reactin of the adsorbed methane and the adsorbed oxygen, which were adsorbed on the different active sites of the catalyst. The activation energy of the methyl radical formation was estimated to be ca. 39 kcal/mol. From the kinetic studies, the oxygen species respolsible for the formation of methyl radicals was proposed to be diatomic oxygen such as $O{_2}{^{2-}}$ or $O_2{^-}$ on the surface.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.12
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• pp.142-149
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• 2008

This paper proposes an effective decomposition method of trichloroethylene using pellet packed-bed non-thermal plasma reactor and catalyst. For that, two types of reactors filled with manganese dioxide and alumina pellets are designed. When $MnO_2$ packed reactor is used, TCE decomposition rate is high due to the generation of oxygen atom radicals at the surface of catalyst during ozone decomposition. In addition, When $Al_2O_3$ packed reactor is used, TCE is oxidized into DCAC and it did not decomposed into small molecules such as COx and $Cl_2$. However, the plasma processed gas using $Al_2O_3$ packed reactor is passed through the $MnO_2$ catalyst reactor, which is placed at the downstream of plasma reactor, the decomposition rate increased as well due to oxygen atom radicals through ozone decomposition. Therefore, the adequate use of $MnO_2$ catalyst in the plasma process is very promising way to increase the decomposition efficiency.

• Journal of Soil and Groundwater Environment
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• v.7 no.2
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• pp.73-81
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• 2002

In normal Fenton's reagent, the reductive mechanism of carbon tetrachloride (CT) with superoxide radical (${O_2}^-$.) was observed and the rate of ${O_2}^-$. production was investigated as a function of $H_2O$$_2$ concentration and pH. As pH was increased, the rate of 1-hexanol degradation was rapidly decreased from 90% (at pH 3) to 5% (at pH 11). On the other hand, more degradation of carbon tetrachloride was observed at higher pH regimes indicating Fenton's reaction is an oxidant-reductant co-existing system at neutral pHs. The rate of $O_2^{-}$ . production was observed at different $H_2$$O_2$ concentrations and at different pHs. The rate increased from (45.3$\pm$7.8) x $10^{-6}$ M/s to (151.0$\pm$26.2) x $10^{-6}$ M/s ($294mM H_2$$O_2$) at pH 11: the rate 3150 increased from (22.1$\pm$3.8) x $10^{-6}$ M/s at pH 7 to (151.0$\pm$26.2) x $^10{-6}$ M/s at pH 11 with 294mM $H_2$$O_2$, These results showed that Fenton's reagent could be applied at wide pH regimes. Especially, carbon tetrachloride, which can not be easily adsorbed to soils and then can be dissolved into groundwater causing a cancer, could be efficiently treated by Fenton's reagent.reagent.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.440-445
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• 2014

The purpose of this study was to investigate anti-inflammatory and antioxidant effects of essential oil from seed of Zanthoxylum schinifolium on cultured RAW 264.7 cell line. Antioxidant activity of essential oil was evaluated by two different assays as 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and super oxide dismutase (SOD) like activities. This essential oil was tested for cell viability on RAW 264.7 cell line by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. The effects of anti-inflammatory on LPS-induced RAW 264.7 cell line was studied by the content of nitric oxide (NO) and prostagladin $E_2$ ($PGE_2$) in cells. The essential oil of seed from Zanthoxylum schinifolium obtained dose-dependently increased the scavenging activity on DPPH radical scavenging activity and SOD like activity. The essential oil showed low cytotoxicity as more than 98% cell viability in $40{\mu}g/mL^{-1}$ concentration. The essential oil of seed extracted from Zanthoxylum schinifolium presented obvious effect on inflammation. These results suggest that essential oil of seed from Zanthoxylum schinifolium may have value as the potential anti-inflammatory effects by decreasing the action of NO and $PGE_2$ and preventing the activation of oxidative.