• 제목/요약/키워드: photochemical

검색결과 828건 처리시간 0.029초

도시 대기중에서 반응성 대기오염물질의 농도변화 상관성에 관한 연구 (A Study on the Relationship among the Concentration of Reacting Air Pollutants in Urban Atmosphere)

  • 이화운;김유근;장은숙
    • 한국환경과학회지
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    • 제6권4호
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    • pp.351-357
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    • 1997
  • In the Atmosphere under the various physical and chemical condition different chemical reactions occur and there are a number of air pollutants which are generated by photochemical reaction by absorbing solar energy. Therefor various testing simulation was done as foundation work to develop the numerical model for the prediction of concentration of air pollutants. It was shown change of msjor air pollutants concentration In according to variation of photodissociation speed constant, Kl and Initial condition of air pollutants concentration which plays major role In photochemical reaction. The photochemical reaction model which was used In this study Is found to be useful for understanding relationship among the concentration of reacting air pollutants and the prediction of concentration of air pollutants in urban atmosphere.

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특허분석에 의한 광화학적 수소제조 기술동향 (Technology Trend for Photochemical Hydrogen Production by the Patent Analysis)

  • 문상진;강경석;한혜정;백진욱;김종욱
    • 한국수소및신에너지학회논문집
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    • 제18권2호
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    • pp.197-206
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    • 2007
  • There are several methods for the hydrogen production such as steam reforming of natural gas, photochemical method, biological method, electrolysis and thermochemical method, etc. Many researches have been widely performed for the hydrogen production method having low production cost and high efficiency. In this paper, the patents concerning the photochemical hydrogen production method were gathered and analyzed. The search range was limited in the open patents of USA(US), European Union(EP), Japan(JP), and Korea(KR) from 1996 to 2005. Patents were gathered by using key-words searching and filtered by filtering criteria. The patent application trend was analyzed by the years, countries, companies, and technologies.

2004년 여름 서울에서 발생한 고농도 오존 사례의 광화학적 분석 (Photochemical Analysis of Ozone Episodes in the Metropolitan Area of Seoul During the Summer 2004)

  • 손장호
    • 한국대기환경학회지
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    • 제22권3호
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    • pp.361-371
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    • 2006
  • This study examines ozone episodes occurred during the intensive sampling periods (Jun. 1-30, 2004) in the air of Seoul metropolitan area. During that period, there were 8 events (or days) in which 1 hr averaged ozone concentrations were greater than 100 ppbv. The photochemical analysis of ozone chemistry (i.e., budget and formation and destruction strengths of ozone) was carried out using a photochemical box model. Peaks in diurnal ozone variations during ozone episode periods occurred were concurrent with the sudden change of the slope of $NO_{2}/NO$ ratio, suggesting significant correlation with photochemical reactivity. In addition, the ozone peaks were concurrent with high concentrations of ozone precursors, peroxy radicals of $HO_{2},\;CH_{3}O_{2},\;and\;RO_{2}$. High ozone levels during the ozone episodes are likely to be affected by ozone destruction rate.

The Mechanisms for Thermal and Photochemical Isomerizations of N-Substituted 2-Halopyrroles: Syntheses of N-Substituted 3-Halopyrroles

  • Park, Sung-Hyun;Ha, Hong-Joo;Lim, Chul-Taek;Lim, Dong-Kwon;Lee, Kwang-Hee;Park, Yong-Tae
    • Bulletin of the Korean Chemical Society
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    • 제26권8호
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    • pp.1190-1196
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    • 2005
  • Halopyrroles, N-substituted 2-halopyrroles were prepared by halogenation of N-substituted pyrroles with NBS, NCS, or surfuryl chloride. N-Substituted 3-halopyrroles were synthesized by acid-catalyzed thermal and photochemical isomerization reactions of N-substituted 2-halopyrroles. Both the thermal and photochemical reactions were acid-catalyzed. For the acid-catalyzed isomerization, a mechanism of [1,3] bromine shift followed by deprotonation is operated. For the acid-catalyzed photoisomerization, an excited triplet state of 2-protonated N-benzyl-2-halopyrrole produces an intermediate N-substituted pyrrole complex with halonium ion which is equilibrated with N-substituted pyrrole plus halonium ion, and then the halonium ion newly adds to 3-position of N-substituted pyrrole followed by deprotonation to afford N-benzyl-3-halopyrrole.

Photochemical Reaction of Nalidixic Acid in Methanol

  • Park, Hyoung-Ryun;Park, Ok-Hyun;Lee, Hong-Yune;Seo Jung-Ja;Bark, Ki-Min
    • Bulletin of the Korean Chemical Society
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    • 제24권11호
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    • pp.1618-1622
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    • 2003
  • The photochemical reactions of methanolic nalidixic acid (NAL) solution in the absence and in the presence of air have been investigated using 300 nm UV light. From the reactions, 1-ethyl-7-methyl-4-oxo-4-hydro-1,8-naphthyridine (EMDN),formic acid, and formaldehyde are produced. In the presence of air, hydrogen peroxide is also detected along with the products listed above. The presence of oxygen during the irradiation of methanolic NAL solution effects on the product yield. The initial quantum yields of the products and of the NAL decomposition are determined. Possible reaction pathways for the photochemical reaction are suggested on the basis of the products analysis.

Effects of Oxygen on the Photochemical Behaviors of Methacrylic Homopolymer Containing Anthracene Groups

  • Kim, Yong-Woon;Chae, Kyu-Ho
    • Journal of Photoscience
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    • 제9권3호
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    • pp.57-63
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    • 2002
  • A homopolymer containing anthracene groups, poly[6-(9-anthryloxy)hexyl methacrylate] (PAn) was prepared and the effect of oxygen on its photochemical reaction was studied by UV and IR absorption spectroscopy in order to understand its photochemical behavior. Photochemical reaction of the PAn in THF solution under an atmosphere of air resulted in the formation of endoperoxide at the beginning stage of reaction followed by photodimerization reaction after all the oxygen was consumed, whereas photodimerization and endoperoxide formation took place concomitantly in the film state. The photoreversible reaction of the anthracene photodimer groups in the polymer by photolysis with 254 nm UV light was not efficient. The IR absorption spectral changes of the PAn film upon irradiation indicate that various photooxidation products were produced in the atmosphere of air.

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전기장 광화학 증착법에 의한 직접패턴 비정질 FeOx 박막의 제조 및 저항변화 특성 (Electric-field Assisted Photochemical Metal Organic Deposition for Forming-less Resistive Switching Device)

  • 김수민;이홍섭
    • 마이크로전자및패키징학회지
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    • 제27권4호
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    • pp.77-81
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    • 2020
  • Resistive RAM (ReRAM)은 전이금속 산화물의 저항변화 특성을 이용하는 차세대 비휘발 메모리로 전이금속산화물 내의 산소공공의 재분포를 통한 저항변화 특성을 이용한다. 따라서 저항변화 특성을 위해 전이금속산화물 내에는 일정량 이상의 산소공공이 요구되며 이를 위해서는 박막 형성 공정에서 산화 수를 조절할 수 있는 공정이 필요하다. 본 연구에서는 직접패턴이 가능한 photochemical metal organic deposition (PMOD) 공정을 사용하여 UV 노출에 의해 photochemical metal organic precursor의 ligand가 분해되는 과정에서 전기장을 인가하여 박막내의 산화 수를 조절하는 실험을 진행하였다. Electric field assisted PMOD (EFAPMOD) 법을 이용하여 FeOx 박막의 산화 수 조절이 가능함을 x-ray photoelectron spectroscopy (XPS) 분석과 I-V 측정을 통하여 확인하였으며, EFAPMOD 공정 중 인가하는 전압의 크기를 조절하여 박막의 산화 수를 조절할 수 있음을 확인하였다. 따라서 EFAPMOD 공정 중 인가전압의 크기를 이용하여 저항변화 특성에 적합한 적정한 산화수를 가지는 금속산화물 박막을 얻고 그 저항변화 특성을 조정할 수 있음을 확인하였다.

산소 존재하에서 UVB에 의한 페플록사신의 광화학적 반응의 특성 (Characteristics of Photochemical Reaction of Pefloxacin Irradiated by UVB in an Aerobic Condition)

  • 최윤수;이경선
    • 약학회지
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    • 제44권1호
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    • pp.36-40
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    • 2000
  • The photodegradation of pefloxacin, photolabile fluoroquinolone antibacterial agent, was studied. In the presence of $N_2$, photodegradation of pefloxacin was suppressed. The singlet oxygen and free radical generated in the reaction media proceeded photochemical reaction. The photodegradation of peflxacin was sensitized by benzophenone, a triplet state sensitizer.

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The Link Between Stereoselectivity and Spin Selectivity in Intermolecular and Intramolecular Photochemical Reactions

  • Griesbeck, Axel G.
    • Journal of Photoscience
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    • 제10권1호
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    • pp.49-60
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    • 2003
  • How stereo selectivity in singlet and triplet photocycloaddition and photocyclization reactions, respectively, is linked to spin selectivity and how this link affects our understanding of photochemical reaction mechanisms, is described in this review. As illustrative examples, the Paterno-Buchi reaction and the Norrish-Yang cyclization are described with emphasis on triplet biradical structure and dynamics.

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