• 한국자동차공학회논문집
• /
• 제11권3호
• /
• pp.13-19
• /
• 2003

Mathematically simplified reaction scheme that simulates autoignitions of the end gases in spark ignition engines has been studied computationally. The five equation model is described, to predict the essential features of hydrocarbon oxidation. This scheme has been calibrated against autoignition delay times measured in rapid compression machines. The rate constants, activation temperatures, Ta, Arrhenius preexponential constants, A, and heats of reaction for stoichiometric n-heptane/air, iso-octane/air, and their mixtures have all been optimised. The optimisation has been guided by Morley's correlation of the ratio of chain branching to linear termination rates with octane number. Comparisons between computed and experimental autoignition delay times have validated the Present simplified reaction scheme and the influences of octane number upon autoignition delay times have been computationally investigated. It has been found that both cool flame and high temperature direct reactions can have an effect on autoignition delay times.

• 대한화학회지
• /
• 제13권4호
• /
• pp.241-247
• /
• 1969

The catalytic reaction between carbon monoxide and oxygen was investigated with the various nickel oxide catalysts at different partial pressures of carbon monoxide and oxygen and at reaction temperatures in the region of 120$^{circ}$to 250$^{circ}C$. The reaction has the highest rate with the nickel oxide catalyst which is sintered at low temperature. A reaction mechanism to explain the data is derived. From the Arrhenius equation, the activation energies in the region of experimental temperatures are found to be from 5.49 to 9.15 kcal/mole. The concentration of excess oxygen in the nickel oxide seems to vary according to the sintering temperatures and periods and is the controlling factor in determining the type of kinetics followed by the catalytic reaction.

• 공업화학
• /
• 제5권3호
• /
• pp.517-523
• /
• 1994

DGEBA(diglycidyl ether of bisphenol A)/MDA(4,4'-methylene dianiline)/SN(succinonitrile)/HQ(hydroquinone)계의 경화반응 속도론 및 메카니즘을 연구하였다. SN과 HQ는 반응성 첨가제와 촉매로 도입하였다. 경화반응 속도론은 DSC 분석에 의해 Kissinger equation과 fractional-life법을 이용하여 연구하였다. DGEBA/MDA/SN 계의 활성화에너지와 반응차수는 SN의 함량에 관계없이 거의 일정하였고, 촉매로써 HQ가 첨가됨으로 인해 활성화 에너지와 반응시작온도가 낮아졌다. 이들 계의 반응 메카니즘을 고찰하기위하여 SN의 함량에 따라 FT-IR을 측정하였다. 그리고, SN:HQ의 혼합비는 4:1이었다. Diamine으로 경화되는 에폭시 수지의 경화반응 메카니즘은 primary amine-epoxy 반응, secondary amine-epoxy 반응, epoxy-hydroxyl 반응이 일어나는 것으로 알려져 있다. DGEBA/MDA/SN/HQ 계에서는 HQ의 hydroxyl 기가 epoxy 및 amine과 결합하여 전이상태를 형성하여 epoxide ring을 빠르게 개환시켜줌으로써 amine-epoxy반응이 쉽게 일어남을 알았다.

• 대한수학회지
• /
• 제50권1호
• /
• pp.81-93
• /
• 2013

We consider a distributed optimal flux control problem: finding the potential of which gradient approximates the target vector field under an elliptic constraint. Introducing the Lagrange multiplier and a change of variables the Euler-Lagrange equation turns into a coupled equation of an elliptic equation and a reaction diffusion equation. The change of variables reduces iteration steps dramatically when the Gauss-Seidel iteration is considered as a solution method. For the elliptic equation solver we consider the Cell Boundary Element (CBE) method, which is the finite element type flux preserving methods.

• 지질공학
• /
• 제24권4호
• /
• pp.575-581
• /
• 2014

The reliable measurement of geotechnical properties in cold regions should account for their fluctuations with temperature. The objective of this paper is to introduce a chemical model based on the Arrhenius equation that can predict the properties of materials as their temperature changes. The model can monitor phases and reaction rates as they change with temperature. It has been already applied in the fields of geology, construction, chemistry, materials engineering, and food science. The application of the Arrhenius equation requires a reliable estimate of the activation energy. Therefore, this study also demonstrates several methods for evaluating activation energy in different contexts through summaries and reviews of previous research related to the Arrhenius equation. This paper may be of wide use in obtaining temperature-dependent parameters in geotechnical engineering.

• Elastomers and Composites
• /
• 제50권2호
• /
• pp.92-97
• /
• 2015

A study on reaction kinetics for a PTMG/TDI prepolymer with 2,2'-dichloro-4,4'-methylenedianiline (MOCA), of which formulations may be generally used for fabricating high performance polyurethane elastomers, was peformed using non-isothermal differential scanning calorimetry (DSC). A number of thermograms were obtained at several constant heating rates, and analysed using Flynn-Wall-Ozawa (FWO) isoconversional method for activation energy, $E_a$ and extended-Avrami equation for reaction order, n. Urea formation reaction of the present system was observed to occur through the simple exothermic reaction process in the temperature range of $100{\sim}130^{\circ}C$ for the heating rate of $3{\sim}7^{\circ}C/min$. and could be well-fitted with generalized sigmoid function. Though activation energy was nearly constant as $53.0{\pm}0.5kJ/mol$, it tended to increase a little at initial stage, but it decreases at later stage by the transformation into diffusion-controlled reaction due to the increased viscosity. Reaction order was evaluated as about 2.8, which was somewhat higher than the generally well-known $2^{nd}$ order values for the various urea reactions. Both the reaction order and reaction rate explicitly increased with temperature, which was considered as the indication of occurring the side reactions such as allophanate or biuret formation.

• Carbon letters
• /
• 제4권4호
• /
• pp.185-191
• /
• 2003

Two types of carbon fiber based high modulus- and isotropic-pitch were exposed to isothermal oxidation in air and $CO_2$ gas and the weight change was measured by TGA apparatus. The kinetic equation was introduced $f=1-{\exp}(-at^b)$ and the constant b was obtained in the range of 1.02~1.68 for the isotropic fiber and obtained 0.91~1.93 for the high modulus fiber respectively. In considering the effect of the atmosphere for isothermal oxidation, the value of the constant b obtained in the carbon dioxide was higher than that obtained in the air. Therefore, it was found that the pitch based carbon fiber shows sigmoidal characteristic when it is oxidized in the carbon dioxide. In addition, it was also found that $k_f = 0.5$, which was reaction constant at f = 0.5, was a very useful parameter for evaluation of the oxidation reactivity of pitch based carbon fibers. According to the consideration, it is suggested that the conversion-time curves of the pitch based carbon fibers are correlated by normalized equation $f=1-{\exp}(-A{\tau}^B)$, where ${\tau}=t/t_f= 0.5$.

• 한국환경과학회지
• /
• 제24권4호
• /
• pp.461-470
• /
• 2015

As hydrogeologic parameters such as hydraulic conductivity and specific yield are estimated by aquifer test, these are dependent on specific points at which field test was conducted. To overcome these site-specific limitations, a method of estimating transmissivity of aquifer using distribution features for parameters in Water table fluctuation model is newly suggested. Distribution features in reaction factor, specific yield and transmissivity having the function of pore space in aquifer are used to derive empirical equation for estimating transmissivity. From the result for applying the equation for 10 groundwater stations in Northeast Jeju Island, this equation is available for estimating transmissivity compared to the value estimated by existing equations. The estimated transmissivity ranged from 14.2 to $3,716.9m^2/day$, and its average was $821.8m^2/day$.

• 산업기술연구
• /
• 제17권
• /
• pp.241-247
• /
• 1997

A numerical model has been proposed for a diffusion flame reactor to manufacture ultrafine $TiO_2$ powders. The model equations such as mass balance equation, the 0th, 1st, and 2nd moment equations of aerosols were considered. The phenomena such as $TiCl_4$ reaction rate, $TiO_2$ nucleation rate and the coagulation of $TiO_2$ powders were included in the aerosol dynamic equation. It is found that the $TiO_2$ particle concentration becomes higher, as the inlet $TiCl_4$ concentration and the total gas flow rate increase, and also as the flame temperature decreases. The $TiO_2$ particle size increases, as the flame temperature and the inlet $TiCl_4$ concentration increase and the total gas flow rate decreases.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제52권2호
• /
• pp.85-90
• /
• 2003

In this work $Cd_{4}GeSe_{6}$ and $Cd_{4}GeSe_{6}$ : $Co^{2+}$ single crystals were grown by the chemical transport reaction method and the structure of $Cd_{4}GeSe_{6}$ and $Cd_{4}GeSe_{6}$ : $Co^{2+}$ single crystals were monoclinic structure. The temperature dependence of optical energy 9ap was fitted well to Varshni equation. Also, the entropy, enthalpy and heat capacity were deduced from the temperature dependence of optical energy gap.