• Title/Summary/Keyword: Chemical condition

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Reaction Condition Dependency of Propagating Behavior in the Polymerization Reaction by Thermal Front

  • Huh, Do-Sung;Choe, Sang-Joon;Lee, Burm-Jong
    • Bulletin of the Korean Chemical Society
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    • v.23 no.2
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    • pp.325-329
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    • 2002
  • In this study, the dependency of the behavior of propagating front on the reaction condition in frontal polymerization reaction has been studied. We have used some multifunctional acrylates as a monomer and ammonium persulfate as an initiator for the polymerization reactions. In frontal polymerization, a method of producing polymeric materials via a thermal front that propagates through the unreacted monomer/initiator solution, the behavior of self propagating front shows various dynamic patterns depending on the reaction condition. We have obtained some spin modes of propagating front in the number of 'hot spots' or 'spin heads' by changing the reaction condition. The effect of the reactor tube diameter on the mode of propagating front has also been studied by using some reactor tubes with different size of tube diameter and it has been examined in some detail by adopting an experimental method of two-tubes system.

The thermal cycle degration of MEA in PEMFC under cold start condition (냉시동 환경에서 thermal cycle이 FEMFC의 MEA 열화에 미치는 영향)

  • Rhee, Jun-Kee;Seo, Dong-Ho;Jeon, Yu-Kwon;Shul, Yong-Gun
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.412-414
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    • 2009
  • In recent times, starting up polymer electrolyte membrane fuel cells(PEMFC) in sub-zero condition is a great challenge of fuel cell electric vehicle(FCEV). The water produced in a cathode during PEMFCs operate. The water changes into the form of solid/ice in sub-zero temperatures and this makes trouble in PEMFC cells. Voltage of PEMFC drops and cold startup is failed. This paper describes an experimental study on the effect of thermal cycle to degradation of MEA in PEMFC.

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Physical and Rheological Properties of Thermoplasticized Crosslinked-Polyethylene Foam in Supercritical Methanol

  • Cho, Hang-Kyu;Hong, Soon-Man;Baek, Kyung-Yeol;Koo, Chong-Min;Lee, Hong-Shik;Lee, Youn-Woo
    • Macromolecular Research
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    • v.17 no.12
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    • pp.950-955
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    • 2009
  • The physical and rheological properties of thermoplasticized irradiation-crosslinked polyethylene foam using supercritical methanol treatment were investigated by GPC, FTIR, DSC, WAXS, DMTA and UDS. The polyethylene foam was selectively decrosslinked into thermoplasticized polyethylene in an appropriate supercritical methanol condition without any undesirable side reactions such as oxidation and disproportionation. The thermoplasticization was promoted with increasing reaction temperature to reach completion above $380^{\circ}C$. The supercritical reaction condition affected the crystallization behavior, and mechanical and rheological properties of the decrosslinked polyethylene foam, but not its crystallographic structure or crystallinity.

Influence of Drought Stress on Chemical Composition of Sesame Seed

  • Kim, Kwan-Su;Ryu, Su-Noh;Chung, Hae-Gon
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.51 no.1
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    • pp.73-80
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    • 2006
  • Sesame (Sesamum indicum L.) seeds contain abundant oil and antioxidative lignans related to the seed quality. To evaluate the potential effects of drought stress on the chemical composition of sesame seeds, eighteen cultivars were imposed water-deficit condition by withholding irrigation during 15 days at podding and maturing stage, compared with well-watered plants as control in seed yield and chemical composition. Drought treatments showed great decrease of seed yield with not affecting seed weight. The contents of sesamin and sesamolin decreased while lignan glycosides inversely increased in response to drought stress. Oil content was not significantly changed by drought treatment in spite of its slight decrease. In case of fatty acid composition, there were significant differences in increase of oleic acid while inverse decrease of linoleic acid under drought stress condition. These results demonstrate that the chemical composition of sesame seed may be modified with drought stress. In particular, the increase of sesaminol glucosides with strong antioxidative activity was observed.

A study on Chemical Cleaning of Copper Corrosion Product in cooling system (냉각계통의 구리 부식 생성물의 화학세정에 관한 연구)

  • Lee, Han-Chul;Lee, Chang-Woo;Hyun, Seong-Ho
    • Journal of Korean Society of Water and Wastewater
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    • v.13 no.1
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    • pp.140-145
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    • 1999
  • This study was carried out a investigate the effect of chemical cleaning of corrosion product in cooling system made of copper and copper alloy as basic material and used cooling water as pure water. We studied chemical cleaning condition that minimizes the influence on basic material by means of EDTA solution so as to eliminate the slurry in cooling system. As a result, we found that the main components of sludge in cooling system produced by corrosion of copper were $Cu_2O$, CuO, Cu, and Fe. The optimum condition of chemical cleaning was 400 ppm EDTA solution at $60^{\circ}C$.

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Robust tuning of quadratic criterion-based iterative learning control for linear batch system

  • Kim, Won-Cheol;Lee, Kwang-Soon
    • 제어로봇시스템학회:학술대회논문집
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    • 1996.10a
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    • pp.303-306
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    • 1996
  • We propose a robust tuning method of the quadratic criterion based iterative learning control(Q-ILC) algorithm for discrete-time linear batch system. First, we establish the frequency domain representation for batch systems. Next, a robust convergence condition is derived in the frequency domain. Based on this condition, we propose to optimize the weighting matrices such that the upper bound of the robustness measure is minimized. Through numerical simulation, it is shown that the designed learning filter restores robustness under significant model uncertainty.

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The Theory of Significant Structure of Liquids : A New Method of Fixing Parameters (액체의 구조에 관하여 -새로운 Parameter 결정법-)

  • Hyungsuk Park;Seihun Chang
    • Journal of the Korean Chemical Society
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    • v.7 no.2
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    • pp.174-178
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    • 1963
  • The new method to determine the parameters in the liquid partition function of H. Eyring and co-workers is proposed, in which method the equilibrium condition of the three phases and the boundary condition of the liquid partition function at the triple point are used. The calculated thermodynamic properties using the new determined parameters are agreed well with the observed values.

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TMEDA Catalyzed Henry (Nitroaldol) Reaction under Metal and Solvent-free Conditions

  • Majhi, Anjoy;Kadam, Santosh T.;Kim, Sung-Soo
    • Bulletin of the Korean Chemical Society
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    • v.30 no.8
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    • pp.1767-1770
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    • 2009
  • The Henry (nitroaldol) reaction proceeds under mild conditions with catalytic amount of tetramethylethylenediamine (TMEDA) to afford $\beta$-nitro alkanol in considerably excellent yield. Structurally diverse aldehydes react with nitromethane in presence of 0.3 equiv of TMEDA under solvent-free condition at rt. The low catalytic loading and mild reaction condition are the key features of the catalytic method.

TMEDA: Efficient and Mild Catalyst for the Acylation of Alcohols, Phenols and Thiols under Solvent-free Condition

  • Kadam, Santosh T.;Lee, Han-Bin;Kim, Sung-Soo
    • Bulletin of the Korean Chemical Society
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    • v.30 no.5
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    • pp.1071-1076
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    • 2009
  • N,N,N′,N′-tetramethylethylenediamine (TMEDA) acts as a simple, mild and efficient catalyst for the acylation of alcohols, phenols and thiols at room temperature under solvent-free condition. Acylation reaction with acetic anhydride and benzoic anhydride proceeds with good to excellent yield in the presence of TMEDA as the catalyst.