• Title/Summary/Keyword: Chemical kinetic modeling

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Modeling of Piston Crevice Hydrocarbon Oxidation in SI Engines (전기점화 기관 간극 체적 내 미연탄화수소의 산화 모델링)

  • Choi, Hoi-Myung;Kim, Se-Jun;Min, Kyung-Doug
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.884-889
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    • 2001
  • Combustion chamber crevices in SI engines are identified as the largest contributor to the engine-out hydrocarbon emissions. The largest of crevice region is the piston ring pack crevice. To predict and understand the oxidation process of piston crevice hydrocarbons, a 3-dimensional numerical simulation method was developed. A engine shaped computational mesh with moving grid for piston and valve motions was constructed. And a 4-step oxidation model involving 7 species was used and the 16 coefficients in the rate expressions were optimized based on the results from a detailed chemical kinetic mechanism for the oxidation condition of engine combustion chamber. Propane was used as a fuel in order to eliminate oil layer absorption and liquid fuel effect.

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Simulating Bioremediation of Uranium-Contaminated Aquifers

  • ;Peter R. Jaffe
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2002.09a
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    • pp.161-166
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    • 2002
  • Bioremediation of trace metals in groundwater may require the manipulation of redox conditions via the injection of a carbon source. To simulate the numerous biogeochemical processes that will occur during the bioremediation of trace-metal-contaminated aquifers, a reactive transport model has been developed. The model consists of a set of coupled mass balance equations, accounting for advection, hydrodynamic dispersion, and a kinetic formulation of the biological or chemical transformations affecting an organic substrate, electron acceptors, corresponding reduced species, and trace metal contaminants of interest, uranium in this study. The redox conditions of the domain are characterized by estimating the pE, based on the concentrations of the dominant terminal electron acceptor and its corresponding reduced specie. This pE and the concentrations of relevant species we then used by a modified version of MINTEQA2, which calculates the speciation/sorption and precipitation/dissolution of the species of interest under equilibrium conditions. Kinetics of precipitation/dissolution processes are described as being proportional to the difference between the actual and calculated equilibrium concentration.

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Shock Tube and Modeling Study of Ethanol Ignition (에탄올 점화 과정에 관한 충격관 실험 및 모델 연구)

  • Shin, Kuan-Soo;Park, Ki-Soo;Gwon, Eun-Sook
    • Journal of the Korean Chemical Society
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    • v.48 no.1
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    • pp.12-16
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    • 2004
  • The ignition of ethanol-oxygen-argon mixture was studied in reflected shock waves over the temperature range of 1281-1625 K and the pressure range of 0.69-1.06 bar. The ignition delay time was measured by the sudden increase of pressure profile and the radiation emitted by OH radicals. The relationship between the ignition delay time and the concentrations of ethanol and oxygen was determined in the form of mass-action expressions with an Arrhenius temperature dependence. In contrast to the behavior observed in methanol, ethanol acts to inhibit rather than accelerate its own ignition. Several kinetic mechanisms proposed for ethanol oxidation at high temperatures have been tested by the computer simulation.

Computational Modeling of Cyclic Voltammetry on Multi-electron Electrode Reaction using Diffusion Model (확산모델을 이용한 다중전자 전극반응에 대한 순환전위법의 전산모델링)

  • Cho, Ha-Na;Yoon, Do-Young
    • Journal of the Korean Electrochemical Society
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    • v.15 no.3
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    • pp.165-171
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    • 2012
  • Here is implemented MATLAB program to analyze the characteristic curves of cyclic voltammetry which involves the multi-electron electrode reaction considered as key processes in electrochemical systems. For the electrochemical mass-transfer system, Fick's concentration equation subject to semi-infinite diffusion model for the boundary condition was discretized and solved by the explicit finite difference method. The resulting concentration values were converted into currents at each node by using Butler-Volmer equation. Based on the good agreement between the present numerical solution and the existing experimental results, effects of kinetic constants and CV scan rates on the reaction mechanism in multi-electron transfer processes were investigated effectively.

Chemical Equilbrium Analysis of the $30\;ton_f$ - class KARI LRE Nozzle Flow (KARI 30톤급 액체 로켓 엔진 노즐 유동 화학 평형 해석)

  • Lee, Dae-Sung;Kang, Ki-Ha;Cho, D.R.;Choi, Jeong-Yeol;Choi, H.S.
    • Journal of the Korean Society of Propulsion Engineers
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    • v.12 no.3
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    • pp.9-15
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    • 2008
  • Nozzle flow analyses of $30\;ton_f$-class KARI liquid rocket engine for high altitude propulsion are carried out using a chemically frozen and equilibrium flow analysis code developed previously. It is considered that the combined frozen- and shifting- equilibrium analysis is cost-effective regarding the convergence characteristics and modeling uncertainties, though the non-equilibrium analysis is most reliable approach. A dependable performance prediction could be attainable through the present analyses that account for the recombination process and thermal and kinetic energy recovery during the expansion process with viscous effects.

Kinetic Modeling of Submerged Culture of A. blazei with Mixed Carbon Sources of Glucose and Dextrin

  • Na Jeong-Geol;Kim Hyun-Han;Chang Yong-Keun;Lee Sang-Jong
    • Journal of Microbiology and Biotechnology
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    • v.16 no.9
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    • pp.1331-1337
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    • 2006
  • A mathematical model has been proposed for the batch culture of Agaricus blazei with mixed carbon sources of glucose and dextrin. In the proposed model, the metabolism of A. blazei was divided into three parts: cell growth, exopolysaccharides (EPS) production, and another EPS production pathway activated by dextrin hydrolysis. Each pathway was described mathematically and incorporated into the mechanistic model structure. Batch cultures were carried out with six different carbon source compositions. Although parameters were estimated by using the experimental data from the two extreme cases such as glucose only and dextrin only, the model represented well the profiles of glucose, cell mass, and EPS concentrations for all the six different carbon source mixtures, showing a good interpolation capability. Of note, the lag in EPS production could be quite precisely predicted by assuming that the glucose-to-cell mass ratio was the governing factor for EPS production.

Synthesis, Characterization, DFT Modeling and Antimicrobial Studies on the Ti(IV), Y(III) and Ce(IV) Ofloxacin Solid Complexes

  • Sadeek, Sadeek A.;Zordok, Wael A.;El-Shwiniy, Walaa H.
    • Journal of the Korean Chemical Society
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    • v.57 no.5
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    • pp.574-590
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    • 2013
  • A new solid complexes of Ti(IV), Y(III) and Ce(IV) have been synthesized with ofloxacin. The formulae and structure of the complexes have been proposed in the light of analytical, spectral ($^1H$ NMR, IR and UV-Visible), magnetic, molar conductivities and thermal studies. The complexes are soluble in DMSO-$d_6$ and DMF. The measured molar conductance values indicate that, the three complexes are electrolyte in nature. The results support the formation of the complexes and indicated that ofloxacin reacts as a bidentate ligand chelate to the metal ion through the pyridone oxygen and one carboxylato oxygen. The kinetic parameters of thermogravimetric and its differential have been evaluated by using Coats Redfern (CR) and Horowitz-Metzeger (HM) methods. The thermodynamic data reflect the thermal stability for all complexes. The metal- ligand binding of the Ti(IV), Y(III) and Ce(IV) complexes is predicted using density funcational theory at the B3LYP-CEP-31G level of theory and total energy, dipole moment estimation of different Ti(IV), Y(III) and Ce(IV) ofloxacin structures. The biological activities of the ofloxacin, inorganic salts and their metal complexes were assayed against different bacterial species.

A Viscoelastic Study of Glass Transition and Degradation Processes of Phenolic Resin/Carbon Fiber Composites (페놀수지/탄소섬유 열경화성 복합재료의 유리전이와 고온 분해과정에서 관찰되는 점탄성 특성 연구)

  • ;J. C. Seferis
    • The Korean Journal of Rheology
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    • v.11 no.1
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    • pp.9-17
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    • 1999
  • Viscoelastic characteristics of cured phenolic resin/carbon fiber composite materials were investigated through glass transition and degradation reaction processes in the high temperature region up to $400^{\circ}C$. A typical glass transition of the cross-linked thermoset polymer was followed by irreversible degradation reactions, which were exhibited by the increasing storage modulus and loss modulus peak. A degradation master curve was constructed by using the vertical and horizontal shift factors, both of which complied well with the Arrhenius equation in light of the kinetic expression of degradation rate constants. Using an analogy to the Havriliak-Negami equation in dielectric relaxation phenomena, a viscoelastic modeling methodology was developed to characterize the frequency- and temperature-dependent complex moduli of the degrading thermoset polymer composite systems. The temperature-dependent relaxation time of the degrading composites was determined in a continuous fashion and showed a minimum relaxation time between the glass transition and degradation reaction regions. The capability of the developed modeling methodology was demonstrated by describing the complex behavior of the viscoelastic complex moduli of reacting phenolic resin composite systems.

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Rigorous Modeling and Simulation of Multi-tubular Reactor for Water Gas Shift Reaction (Water Gas Shift Reaction을 위한 Multi-tubular Reactor 모델링 및 모사)

  • Park, Junyong;Choi, Youngjae;Kim, Kihyun;Oh, Min
    • Korean Chemical Engineering Research
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    • v.46 no.5
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    • pp.931-937
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    • 2008
  • Rigorous multiscale modelling and simulation of the MTR for WGSR was carried out to accurately predict the behavior of process variables and the reactor performance. The MTR consists of 4 fixed bed tube reactors packed with heterogeneous catalysts, as well as surrounding shell part for the cooling purpose. Considering that fluid flow field and reaction kinetics give a great influence on the reactor performance, employing multiscale methodology encompassing Computational Fluid Dynamics (CFD) and process modeling was natural and, in a sense, inevitable conclusion. Inlet and outlet temperature of the reactant fluid at the tube side was $345^{\circ}C$ and $390^{\circ}C$, respectively and the CO conversion at the exit of the tube side with these conditions approached to about 0.89. At the shell side, the inlet and outlet temperature of the cooling fluid, which flows counter-currently to tube flow, was $190^{\circ}C$ and $240^{\circ}C$. From this heat exchange, the energy saving was achieved for the flow at shell side and temperature of the tube side was properly controlled to obtain high CO conversion. The simulation results from this research were accurately comparable to the experimental data from various papers.

Minimal systems analysis of mitochondria-dependent apoptosis induced by cisplatin

  • Hong, Ji-Young;Hara, Kenjirou;Kim, Jun-Woo;Sato, Eisuke F.;Shim, Eun Bo;Cho, Kwang-Hyun
    • The Korean Journal of Physiology and Pharmacology
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    • v.20 no.4
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    • pp.367-378
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    • 2016
  • Recently, it was reported that the role of mitochondria-reactive oxygen species (ROS) generating pathway in cisplatin-induced apoptosis is remarkable. Since a variety of molecules are involved in the pathway, a comprehensive approach to delineate the biological interactions of the molecules is required. However, quantitative modeling of the mitochondria-ROS generating pathway based on experiment and systemic analysis using the model have not been attempted so far. Thus, we conducted experiments to measure the concentration changes of critical molecules associated with mitochondrial apoptosis in both human mesothelioma H2052 and their ${\rho}^0$ cells lacking mitochondrial DNA (mtDNA). Based on the experiments, a novel mathematical model that can represent the essential dynamics of the mitochondrial apoptotic pathway induced by cisplatin was developed. The kinetic parameter values of the mathematical model were estimated from the experimental data. Then, we have investigated the dynamical properties of this model and predicted the apoptosis levels for various concentrations of cisplatin beyond the range of experiments. From parametric perturbation analysis, we further found that apoptosis will reach its saturation level beyond a certain critical cisplatin concentration.