• Advances in environmental research
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• 제7권2호
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• pp.139-159
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• 2018

Green Leaf Volatiles (GLVs) is a class of biogenically emitted oxygenated hydrocarbons that have been identified as a potential source of Secondary Organic Aerosols (SOA) via aqueous oxidation. The physico-chemical properties of GLVs are vital to understanding their fate and transport in the atmosphere via fog processing, but few experimental data are available. We studied the aqueous solubility, 1-octanol/water partition coefficient, and Henry's law constant ($K_H$) of five GLVs at $25^{\circ}C$: methyl jasmonate, methyl salicylate, 2-methyl-3-buten-2-ol, cis-3-hexen-1-ol, and cis-3-hexenyl acetate. Henry's law constant was also measured at temperatures and ionic strengths typical of fog. Experimental values are compared to scarcely-available literature values, as well as estimations using group and bond contribution methods, property-specific correlations and molecular dynamics simulations. From these values, the partition coefficients to the air-water interface were also calculated. The large Henry's law constant of methyl jasmonate ($8091{\pm}1121M{\cdot}atm^{-1}$) made it the most significant GLV for aqueous phase photochemistry. The HENRYWIN program's bond contribution method from the Estimation Programs Interface Suite (EPI Suite) produced the best estimate of the Henry's constant for GLVs. Estimations of 1-octanol/water partition coefficient and solubility are best when correlating an experimental value of one to find the other. Finally, the scavenging efficiency was calculated for each GLV indicating aqueous phase processing will be most important for methyl jasmonate.

• 대한화학회지
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• 제36권4호
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• pp.477-484
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• 1992

Y123 초전도체 및 Y124 초전도체 결정 구조에서 사슬과 층에 존재하는 구리의 화학결합 및 전자 성질을 반경험적 분자 궤도론인 ASED-MO로 계산하여 VEP(valence electron population), DOS(density of state) 및 COOP(crystal orbital overlap population)로써 고찰하였다. 또한 구리 원자의 환경 효과를 알아보기 위하여 하전 덩어리 모델에 수소의 점전하가 있는 경우와 점전하가 없는 경우를 도입하였다. ASED-MO 계산 결과로 부터, Y123 초전도체 및 Y124 초전도체의 사슬에 존재하는 구리 원자는 전자 받게 역할을 하며, 층에 존재하는 구리 원자는 전자 주게 역할을 한다는 것을 알 수 있었다. 점전하가 없는 Y123 초전도체 및 Y124 초전도체의 사슬에 존재하는 구리의 산화 상태는 층에 존재하는 구리의 산화 상태보다도 더 크다. Y123 초전도체의 층에 존재하는 구리 원자의 산화 상태는 Y124 초전도체의 층에 존재하는 구리 원자의 산화 상태보다도 더 크다. 그리고 Y123 초전도체의 사슬과 층에 존재하는 구리 원자는 주위 환경에 크게 영향을 받지 않으며, Y124 초전도체의 사슬과 층에 존재하는 구리 원자의 경우 Y123 초전도체와 다르게 주위 환경에 크게 영향을 받는다는 것을 알 수 있었다. 또한 Cu1-O4, Cu2-O4의 전자분포와 결합성은 Y123 초전도체와 Y124 초전도체가 다르게 나타났다.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2002년도 연료전지심포지움 2002논문집
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• pp.211-218
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• 2002

In this study, Pt/Pd (1.1), PtPd (2:1) and PtPd (3:1) binary catalysts and Pt/Ru/Pd (5:4:1) ternary catalyst were designed. The catalysts were synthesized by impregnation method using $NaBH_4$ as a reducing agent. A good catalyst for methanol oxidation requires low on-set potential, stable durability and low activation energy. In order to investigate the catalytic activity for the methanol oxidation, electrochemical measurements such as cyclic voltammetry and chronoamperometry were peformed in sulfuric acid with/without methanol solution. In order to calculate the activation energy of the reaction, electrochemical measurements were also tested at different temperatures. For investigation of the structural analysis such as particle size and alloying, X-ray diffraction and transmission electron microscopy analysis were used. In order to identify the role of the Pd and to determine the composition of the surface of the Pt/Pd nanoparticles, X-ray photoelectron spectroscopy (XPS) analysis was investigated. The XPS spectra of Pd showed that Pd appears only as a metallic state in the binary catalysts. The chemical states of Pt in PtPd catalysts are both metallic and oxidative. Polarization curves and power density data were obtained by testing the DMFC unit cell performance of PtPd and PtRuPd catalysts. These data showed that Pt/Pd (2:1) and Pt/Ru/Pd (5:4:1) have better performance than Pt and Pt/Ru, respectively.

• 한국환경과학회지
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• 제16권8호
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• pp.995-999
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• 2007

This study assessed the characteristics of emission and cell toxicology of Methylethylketone(MEK) in ambient air of industrial area. MEK is produced by the oxidation of sec-butyl alcohol and used as the solvent for making ink, printing, coating of film, bonding material and drug extraction. The MEK concentrations in the ambient-air of industrial area in Gimhae City was detected in the range of $25.4{\sim}1,580{\mu}g/m^3$ with an average $297.4{\mu}g/m^3$. The concentration of MEK showed a descending tendency from April to August followed by its increased tendency since then. The effects of MEK on the human lung cancer A549 cells was examined by the generation of Reactive Oxygen Species(ROS) and cytotoxicity. The range of MEK concentration detected in the area induced ROS generation affecting the oxidation state with a little effects on the viability of the cells.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.829-831
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• 1992

Ultrathin metal-oxide-semiconductor(MOS) gate dielectrics have been fabricated by conventional thermal oxidation in $N_2O$ ambient. Compared to oxides grown in $O_2$, $N_2O$ oxides exhibit significantly low flatband voltage and small shift in flatband voltage. $N_2O$ oxidation induces a slight decrease in mobile ionic charge density($N_m$), fixed charge density($N_f$) and surface state charge density($N_{ss}$). This study establishes that $N_2O$ oxides may have a great impact on future MOS ULSI technology in which ultrathin gate dielectrics are required.

• 공업화학
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• 제5권6호
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• pp.1056-1061
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• 1994

$80^{\circ}C$에서 열처리하거나, $80^{\circ}C$와 상대습도 85%인 습도 조건에서 처리한 황동이 피복된 강선 코드의 표면 상태와 고무와 접착 성질을 조사하였다. 열처리로 황동의 산화가 진행되었으며, 습윤처리 후에는 더 심하게 산화되었다. 처리기간이 길어질수록 전처리한 코드의 접착 성질이 나빠졌으며, 고무부착 정도가 심하게 저하되었다. 황동 피복층의 산화로 인한 코드의 접착 성질 저하를 산화아연층의 과도한 성장과 연계지어 설명하였다.

• E2M - 전기 전자와 첨단 소재
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• 제7권2호
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• pp.145-151
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• 1994

The multi-dielectric layer SiOz/Si3N4/SiO2(ONO) is used to scale down the memory device. In this paper, the change of composition in ONO layer due to the process condition and the conduction mechanism are observed. The composition of the oxide film grown through the oxidation of nitride film is analyzed using auger electron spectroscopy(AES). AES results show that oxygen concentration increases at the interface between oxide and nitride layers as the thickness -of the top oxide layer increases. Results of I-V measurement show that the insulating properties improve as the thickness of the top oxide layer increases. But when the thickness of the nitride layer decreases below 63.angs, insulating peoperties of film 28.angs. of top oxide and film 35.angs. turn over showing that insulating property of film 28.angs. of top oxide is better than that of film 35.angs. of top oxide. This phenomenon of turn over is thought as the result of generation of surface state due to oxygen flow into nitride during oxidation process. As the thickness of the top oxide and nitride increases, the electrical breakdown field increases, but when the thickness of top oxide reaches 35.angs, the same phenomenon of turn over occurs. Optimum film thickness for scaled multi-layer dielectric of memory device SONOS is estimated to be 63.angs. of nitride layer and 28.angs. of top oxide layer. In this case, maximum electrical breakdown field and leakage current are 18.5[MV/cm] and $8{\times}{10^-12}$[A], respectively.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.2
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• pp.257-263
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• 2006

This paper examines the physico-chemical properties and structural features of thio lignin and alcohol lignin preparations extracted from fast-growing poplar wood. The lignin preparations were characterized using UV, IR and alkaline nitrobenzene oxidation methods. The yield was higher in thiolignin due to its preparation from wood under drastic alkaline conditions and almost the total amount of alkaline degraded lignin was precipitated except acid soluble lignin. In case of ethanol lignin, structural modifications were comparatively less and form a cream colored lignin more or less similar to its original natural color. The methoxyl values were higher due to syringyl unit present in hard wood lignin in addition to guaicyl unit present in soft wood. The higher values of methoxyl content of isolated lignin revealed that it was built up of high syringyl units. The elementary analysis, methoxyl group and hydroxyl groups were presented by $C_{9}$ formula indicated that it was made up of phenyl propane monomers. Nitrobenzene oxidation of thio lignin and ethanol lignin yield more or less the chromatograms of similar pattern, except difference in relative percentage. The ultra violet spectra of lignins were quite similar, irrespective of the source and method of isolation. Infrared spectroscopy studies of poplar deltoides, thio and ethanol lignin shown different absorption bands which have been utilized for structural investigations.

• Food Science and Biotechnology
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• 제18권2호
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• pp.413-418
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• 2009

Effects of chlorophyll and visible light exposure on the volatile formations and headspace oxygen content were studied in lard model systems at $55^{\circ}C$. Samples with or without addition of chlorophyll under light underwent photosensization or photooxidation, respectively. Total volatiles (TI) in lard with 5 ppm chlorophyll photosensization were 19 times higher than those in visible light photooxidized samples for 48 hr while TI in lard with chlorophyll in the dark were not significantly different from those in photooxidized samples (p>0.05). Headspace oxygen content in photosensitized lard decreased from 21 to 15% for 48 hr but that in photooxidized lard or that in lard with chlorophyll in the dark did not change significantly (p>0.05), which indicates that lard system used in this study is a photosensitizer-free model system and the presence of chlorophyll accelerated the lipid oxidation only under visible light. Oxidation mechanisms of photooxidation with or without presence of photosensitizers under visible light were not the same based on the difference of oxidized volatile profiles and headspace oxygen depletion.

• 한국세라믹학회지
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• 제31권9호
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• pp.1060-1068
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• 1994

Stable zirconia sol was prepared from zirconium butoxide Zr(OC4O9)4 as a precursor and ethylacetoacetate(EAcAc) or diethylene glycol(DEG) as a chelating agent under ambient agent under ambient atmosphere by Sol-Gel process. The sythesized sol was coated on 304 stainless steel substrate by dip coating, thereafter zirconia film could be obtained by heat-treatment at $600^{\circ}C$. The characteristics of coating film were determined by FT-IR, XRD, and ellipsometion peak represented Zr-O-Zr bonding of tetragonal phase was shown at 470cm-1. Crystallization of zirconia gel and film from amorphous state to tetragonal phase started at 40$0^{\circ}C$, and then transformed into monoclinic phase around $700^{\circ}C$. Zirconia film coated on 304 stainless steel substrate showed relatively low porosity of 16% when it was coated with 0.4M zirconia sol and thereafter heat-treated at 80$0^{\circ}C$ and the film was densified continuously up to 90$0^{\circ}C$. The zirconia film of 10 nm thick acted as a protective layer against oxidation up to $700^{\circ}C$.