• Title/Summary/Keyword: precursors

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Production of Photodynamic Herbicide by Photosynthetic Bacteria (광합성균주에 의한 제초활성 물질의 생산)

  • Choi, Kyung-Min;Lee, Sung-Taik
    • Journal of the Korea Organic Resources Recycling Association
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    • v.5 no.1
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    • pp.25-32
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    • 1997

  • The effect of levulinic acid (LA) and biosynthetic precursors of ${\delta}$-aminolevulinic acid (ALA) on the production of extracellular ALA was examined for the cells of soil derived Rhodospirillum rubrum N-1 belonged to the genus Rhodospirillaceae. The extracellular yield of ALA was increased to 23 fold (45 mg/l) from the basal condition (Lascelles' medium without L-glutamate) by successive addition of LA at initial (10 mM) and mid-log stage (30 mM) of cell cultivation. In addition to initial/mid-log mutual supplementations of LA (10 mM/30 mM) and glutamate (30/30 mM), respectively, by means of alternative feeding 10 mM $C_4$-precursors at mid-log phase of culture the extracellular ALA content was reached to 75 mg/l (40 fold).

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Polymerization and Thermal Characteristics of Acrylonitrile/Dicyclohexylammonium 2-Cyanoacrylate Copolymers for Carbon Fiber Precursors

  • Kim, Ki-Young;Park, Woo-Lee;Chung, Yong-Sik;Shin, Dong-Geun;Han, Jin-Wook
    • Carbon letters
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    • v.12 no.1
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    • pp.31-38
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    • 2011

  • This study experimentally investigated dicyclohexylammonium 2-cyanoacrylate (CA) as a potential comonomer for polyacrylonitrile (PAN) based carbon fiber precursors. The P(AN-CA) copolymers with different CA contents (0.19-0.78 mol% in the feed) were polymerized using solution polymerization with 2,2-azobis(isobutyronitrile) as an initiator. The chemical structure and composition of P(AN-CA) copolymers were determined by proton nuclear magnetic resonance and elemental analysis, and the copolymer composition was similar to the feeding ratio of the monomers. The effects of CA comonomer on the thermal properties of its copolymers were characterized differential scanning calorimetry (DSC) in nitrogen and air atmospheres. The DSC curves of P(AN-CA) under nitrogen atmosphere indicated that the initiation temperature for cyclization of nitrile groups was reduced to around $235^{\circ}C$. The heat release and the activation energy for cyclization reactions were decreased in comparison with those of PAN homopolymers. On the other hand, under air atmosphere, the P(AN-CA) with 0.78 mol% CA content showed that the initiation temperature of cyclization was significantly lowered to $160.1^{\circ}C$. The activation energy value showed 116 kJ/mol, that was smaller than that of the copolymers with 0.82 mol% of itaconic acids. The thermal stability of P(AN-CA), evidenced by thermogravimetric analyses in air atmosphere, was found higher than PAN homopolymer and similar to P(AN-IA) copolymers. Therefore, this study successfully demonstrated the great potential of P(AN-CA) copolymers as carbon fiber precursors, taking advantages of the temperature-lowering effects of CA comonomers and higher thermal stability of the CA copolymers for the stabilizing processes.

  • https://doi.org/10.5714/CL.2011.12.1.031 인용 PDF KSCI

Development of a Short-term Model for Ozone Using OPI (오존최대농도지표를 이용한 오존단기예측모형 개발)

  • 전의찬;김정욱
    • Journal of Korean Society for Atmospheric Environment
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    • v.15 no.5
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    • pp.545-554
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    • 1999

  • We would like to develop a short-term model to predict the time-related concentration of ozone whose reaction mechanism is complex. The paper targets Seoul where an ozone alert system has recently been employed. In order to develop a short-term prediction model for ozone, we suggested the Ozone Peak Indicator(OPI), an equivalent of the potential daily maximum ozone concentration, with precursors being the only limiting factor, and we calculated the Ozone Peak Indicarot as OPI={$ rac{(O_3)_{max}cdot(H_{eH})_{max}(Rad)_{max}$ to preclude the influence of mixing height and solar radiation on the daily maximum ozone concentration. The OPI on the day of the prediction is to be calcultated by using the relation between OPI and the initial value of precursors. The basic prediction formula for time-related ozone concentration was established as $O_3(1)={(OPI)cdot Rad(t-2)H_{eH}}$, using the OPI, solar radiation two hours before prediction and mixing height. We developed, along with the basic formula for predicting photochemical oxidants, "SEOM"(Seoul Empirical Oxidants Model), a Fortran program that helps predict solar radiation and mixing height needed in the prediction of ozone pollution. When this model was applied to Seoul and an analysis of the correlation between the observed and the predicted ozone concentrations was made through SEOM, there appeared a very high correlation, with a coefficient of 0.815. SEOM can be described as a short-term prediction model for ozone concentration in large cities that takes into account the initial values of precursors, and changes in solar radiation and mixing height. SEOM can reflect the local characteristics of a particular and region can yield relatively good prediction results by a simple data input process.t process.

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