• Title, Summary, Keyword: Kinetics

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Polymorphism of Sulpiride and its Pharmaceutical Applications(II) Transformation Kinetics of Sulpiride Polymorphs (Sulpiride의 Polymorphism 및 그 약제학적 연구(II) Polymorph 상호간의 Transformation Kinetics)

  • 김길수;이민화
    • YAKHAK HOEJI
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    • v.26 no.4
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    • pp.231-237
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    • 1982
  • The transformation kinetics between polymorphs of sulpiride and the effect of additives on the transformation kinetics were studied. The results could be summarized as follows. 1. Transformation kinetics of the polymorph form I to form II in water suspenion was first order type and transformation rate constant at $25^{\circ}C$ is $2.61{\times}10^{-2}min^{-1}$, the half life of form I was about 27 minutes and the activation energy for transformation was 21.35 Kcal/mole. 2. Glycerine and coloring agents increased the rate of transformation., In the case of polysorbate 80, the rate constant increased in proportion to the concentration of polyserbate 80. Simple syrup showed no effect 3n transformation kinetics.

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Accumulation and Decay of Macroscopic Correlations in Elementary Reactions Kinetics

  • Doktorov, Alexander B.;Kipriyanov, Alexander A.;Kipriyanov, Alexey A.
    • Bulletin of the Korean Chemical Society
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    • v.33 no.3
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    • pp.941-952
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    • 2012
  • In the present contribution the Encounter Theory (ET) (the prototype of the classical Collision Theory in rarefied gases) concepts for widely occurring diffusion assisted irreversible bulk reactions A + A ${\rightarrow}$ C and A + B ${\rightarrow}$ C in liquid solutions examined by the authors in the literature are analyzed and compared with each other for these different types of reactions. It is shown that for a particular case of equal initial concentrations $[A]_0=[B]_0$ in the reaction A + B ${\rightarrow}$ C, when the kinetics of both reactions A + A ${\rightarrow}$ C and A + B ${\rightarrow}$ C in the framework of formal chemical kinetics and ET are the same, the accumulation of macroscopic correlations breaking the concepts of independent encounters and leading to the Generalized Encounter Theory (GET) are drastically different. The influence of the force interaction and the decay of nonstable reactants on the time behavior the macroscopic correlations is also briefly discussed.

Application of Coupled Reactor Kinetics Method to a CANDU Reactor Kinetics Problem.

  • Kim, Hyun-Dae-;Yeom, Choong-Sub;Park, Kyung-Seok-
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • pp.141-145
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    • 1994
  • A computer code for solving the 3-D time-dependent multigroup neutron diffusion equation by a coupled reactor kinetics method recently developed has been developed and for evaluating its applicability in CANDU transient analysis applied to a 3-D kinetics benchmark problem which reveals non-uniform loss of coolant accident followed by an asymmetric insertion of shutdown devices. The performance of the method and code has been compared with the CANDU design code, CERBERUS, employing a finite difference improved quasistatic method.

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Hydrolysis of Oils by Using Immobilized Lipase Enzyme : A Review

  • Murty, V.Ramachanda;Bhat, Jayadev;Muniswaran, P.K.A.
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.7 no.2
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    • pp.57-66
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    • 2002
  • This review focuses on the use of immobilized lipase technology for the hydrolysis of oils. The importance of lipase catalyzed fat splitting process, the various immobilization procedures, kinetics, deactivation kinetics, New immobilized lipases for chiral resolution, reactor configurations, and process considerations are all reviewed and discussed.

Investigation on the Prediction Performance of the Chemical Kinetics for the Numerical Simulation of MILD Combustion (마일드 연소장 수치계산을 위한 화학반응기구의 예측성능 검토)

  • Kim, Yu Jeong;Oh, Chang Bo
    • 한국연소학회:학술대회논문집
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    • pp.341-344
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    • 2012
  • The prediction performance of the chemical kinetics for the numerical simulation of MILD combustion was investigated. A wall-confined turbulent methane jet combustor was adopted as a configuration. Four chemical kinetics, such as a global 3-step, WD4, Skeletal, and DRM-19, were investigated, The air stream of the wall-confined MILD jet combustor was diluted with combustion products. It was found that the DRM-19 was optimal for the numerical simulation of the MILD combustion.

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Reaction Kinetics for the Synthesis of Oligomeric Poly (lactic acid)

  • Yoo Dong Keun;Kim Dukjoon;Lee Doo Sung
    • Macromolecular Research
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    • v.13 no.1
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    • pp.68-72
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    • 2005
  • A low-molecular-weight poly(lactic acid) was synthesized through the condensation reaction of L-lactic acid. The effects that the catalyst and temperature have on the reaction rate were studied to determine the optimum reaction conditions. The reaction kinetics increased with temperature up to $210^{\circ}C$, but no further increase was observed above this temperature. Among a few selective catalysts, sulfuric acid was the most effective because it maximized the polymerization reaction rate. Reduction of the pressure was another important factor that enhanced this reactions kinetics.

Induction Parameter Modeling of Hydrocarbon Fuel/Oxidizer for Detonation Wave Analysis (데토네이션 파 해석을 위한 탄화수소 연료/산화제의 Induction Parameter Modeling)

  • Choi, Jeong-Yeol;Yang, Vigor
    • 한국연소학회:학술대회논문집
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    • pp.57-62
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    • 2003
  • A general procedure of obtaining reliable one-step kinetics model for hydrocarbon mixture from the fully detailed chemistry is described iin this study. One-step theoretical formulation of the induction parameter model IPM uses a theoretical reconstruction of the induction time database obtained from a detailed kinetics library. Non-dimensional induction time calculations is compared with that of detailed kinetics. The IPM was latter implemented to fluid dynamics code and applied for the numerical simulation of detonation wave propagation. The numerical results including the numerical smoked-foil record show the all the details of the detonation wave propagation characteristics at the cost around 1/100 of the detailed kinetics calculation.

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FURTHER EVALUATION OF A STOCHASTIC MODEL APPLIED TO MONOENERGETIC SPACE-TIME NUCLEAR REACTOR KINETICS

  • Ha, Pham Nhu Viet;Kim, Jong-Kyung
    • Nuclear Engineering and Technology
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    • v.43 no.6
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    • pp.523-530
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    • 2011
  • In a previous study, the stochastic space-dependent kinetics model (SSKM) based on the forward stochastic model in stochastic kinetics theory and the Ito stochastic differential equations was proposed for treating monoenergetic space-time nuclear reactor kinetics in one dimension. The SSKM was tested against analog Monte Carlo calculations, however, for exemplary cases of homogeneous slab reactors with only one delayed-neutron precursor group. In this paper, the SSKM is improved and evaluated with more realistic and complicated cases regarding several delayed-neutron precursor groups and heterogeneous slab reactors in which the extraneous source or reactivity can be introduced locally. Furthermore, the source level and the initial conditions will also be adjusted to investigate the trends in the variances of the neutron population and fission product levels across the reactor. The results indicate that the improved SSKM is in good agreement with the Monte Carlo method and show how the variances in population dynamics can be controlled.

Theoretical and Experimental Studies on the Kinetics of Cation Redistribution Processes in Complex Oxides

  • Shi, Jianmin;Becker, Klaus-Dieter
    • Journal of the Korean Ceramic Society
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    • v.47 no.1
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    • pp.39-46
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    • 2010
  • The kinetics of cation reequilibration have been studied theoretically and experimentally in complex oxides after an external perturbation of equilibrium by temperature jumps. A general kinetic model for cation redistribution amongst non-equivalent sites in complex oxides is derived based on a local homogeneous point defect mechanism involving cation vacancies. Temperature-jump optical relaxation spectroscopy has been established to investigate cation kinetic processes in spinels and olivines. The kinetic model satisfactorily describes the experimental absorbance relaxation kinetics in cobalt containing olivines and in nickel containing spinels. It is found that the kinetics of cation redistribution in complex oxides shows a strong temperature- and composition-dependence. Activation energies for cation redistribution in Co-Mg olivines are found to range between 200 and 220 kJ/mol whereas an energy barrier of about 230 kJ/mol is observed in the case of nickel gallate spinel.

Effect of Ga, Nb Addition on Disproportionation Kinetics of Nd-Fe-B Alloy

  • Kwon, H.W.;Yu, J.H.
    • Journal of Magnetics
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    • v.14 no.4
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    • pp.150-154
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    • 2009
  • The effect of Ga and, Nb addition on the kinetics and mechanism of the disproportionation of a Nd-Fe-B alloy were investigated by isothermal thermopiezic analysis (TPA) using $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ (x=0 and 0.3, y= 0 and 0.2) alloys. The addition of Ga and Nb retarded the disproportionation kinetics of the Nd-Fe-B alloy significantly, and increased the activation energy of the disproportionation reaction. The disproportionation kinetics of the $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ alloys measured under an initial hydrogen pressure of 0.02 MPa were fitted to a parabolic rate law. This suggested that during the disproportionation of $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ alloys with an initial hydrogen pressure of 0.02 MPa, a continuous disproportionation product is formed and the overall reaction rate is limited by the diffusion of hydrogen atoms (or ions).