• Title/Summary/Keyword: Chemical mechanism

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Prediction of Ignition Delay for HSDI Diesel Engine (고속 직분식 디젤 엔진에서의 점화지연시기 예측)

  • Lim, Jae-Man;Kim, Yong-Rae;Ohn, Hyung-Suk;Min, Kyoung-Doug
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1704-1709
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    • 2004

  • New reduced chemical kinetic mechanism for prediction of autoignition process of HSDI diesel engine was investigated. For precise prediction of the ignition characteristics of diesel fuel, mechanism coefficients were fitted by the experimental results of ignition delay of diesel spray in a constant volume vessel. Ignition delay of diesel engine on various operation condition was calculated based on the new reduced chemical mechanism. The calculation results agreed well with experimental data.

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The Cofactors Role on Chemical Mechanism of Recombinant Acetohydroxy Acid Synthase from Tobacco

  • Kim, Joung-Mok;Kim, Jung-Rim;Kim, Young-Tae;Choi, Jung-Do;Yoon, Moon-Young
    • Bulletin of the Korean Chemical Society
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    • v.25 no.5
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    • pp.721-725
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    • 2004

  • Acetohydroxy acid synthase (AHAS) is one of several enzymes that require thiamine diphosphate and a divalent cation as essential cofactors. The active site contains several conserved ionizable groups and all of these appear to be important as judged by the fact that mutation diminishes or abolishes catalytic activity. Recently, we have shown [Yoon, M.-Y., Hwang, J.-H., Choi, M.-K., Baek, D.-K., Kim, J., Kim, Y.-T., Choi, J.-D. FEBS Letters 555 (2003), 185-191] that the activity is pH-dependent due to changes in $V_{max}$ and V/$K_m$. Data were consistent with a mechanism in which substrate was selectively catalyzed by the enzyme with an unprotonated base having a pK 6.48, and a protonated group having a pK of 8.25 for catalysis. Here, we have in detail studied the pH dependence of the kinetic parameters of the cofactors (ThDP, FAD, $Mg^{2+}$) in order to obtain information about the chemical mechanism in the active site. The $V_{max}$ of kinetic parameters for all cofactors was pH-dependent on the basic side. The pK of ThDP, FAD and $Mg^{2+}$ was 9.5, 9.3 and 10.1, respectively. The V/$K_m$ of kinetic parameters for all cofactors was pH-dependent on the acidic and on the basic side. The pK of ThDP, FAD and $Mg^{2+}$ was 6.2-6.4 on the acidic side and 9.0-9.1 on the basic side. The well-conserved histidine mutant (H392) did not affect the pH-dependence of the kinetic parameters. The data are discussed in terms of the acid-base chemical mechanism.

  • https://doi.org/10.5012/bkcs.2004.25.5.721 인용 PDF KSCI

Generation of a skeletal mechanism of coal combustion based on the chemical pathway analysis

  • Ahn, Seongyool;Watanabe, Hiroaki;Shoji, Tetsuya;Umemoto, Satoshi;Tnno, Kenji
    • 한국연소학회:학술대회논문집
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    • 2014.11a
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    • pp.5-7
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    • 2014

  • A skeletal mechanism of coal combustion was derived from a detailed coal combustion kinetic mechanism through an importance analysis of chemical pathways. The reduction process consists of roughly two parts. The first process is performed based on a connectivity analysis between species. In this process, DRGEPSA is chosen for reduction process. Strongly connected species and related reactions from the important species set as start species by the operator are sorted into the reduced mechanism. About 70% of species and reactions can be removed with a limited accuracy loss. Subsequently the second reduction process, CSP, is performed. This method focuses on an importance of each reaction and can reduce a volume of mechanism appropriately. Through these analyses, a skeletal mechanism is generated that is including 65 species and 150 reactions. The generated skeletal mechanism is verified through a comparison with the detailed mechanism in the homogeneous reactor model of CHEMKIN-PRO under wide range of conditions. The generated mechanism can give an advantage in the analysis of coal combustion characteristics in detail in large scale simulations such as LES and DNS.

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Electro-chemical Mechanical Deposition for Planarization of Cu Interconnect (Cu 배선의 평탄화를 위한 ECMD에 관한 연구)

  • Jeong, Sukhoon;Seo, Heondeok;Park, Boumyoung;Park, Jaehong;Park, Seungmin;Jeong, Moonki;Jeong, Haedo;Kim, Hyoungjae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.18 no.9
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    • pp.793-797
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    • 2005

  • This study introduces Electro-chemical Mechanical Deposition(ECMD) lot making Cu interconnect. ECMD is a novel technique that has ability to deposit planar conductive films on non-planar substrate surfaces. Technique involves electrochemical deposition(ECD) and mechanical sweeping of the substrate surface Preferential deposition into the cavities on the substrate surface nay be achieved through two difference mechanisms. The first mechanism is more chemical and essential. It involves enhancing deposition into the cavities where mechanical sweeping does not reach. The second mechanism involves reducing deposition onto surface that is swept. In this study, we demonstrate ECMD process and characteristic. We proceeded this experiment by changing of distribution of current density on divided water area zones and use different pad types.

  • https://doi.org/10.4313/JKEM.2005.18.9.793 인용 PDF KSCI