• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.214-217
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• 2004

The cure kinetics of blends of epoxy(tetraglycidyl-4,4'-diaminodiphenylmethane ; TGDDM)/curing agent(diaminodiphenyl sulfone ; DDS) resin with amine terminated polyetherimide-CTBN-amine terminated polyetherimide triblock copolymer(ABA) were studied using differential scanning calorimetry under isothermal conditions to determine the reaction parameters such as activation energy and reaction constants. By increasing the amount of ABA in the blends, the final cure conversion was decreased. Lower values of the final cure conversions in the epoxy/ABA blends indicated that ABA hinders the cure reaction between the epoxy and curing agents. 1be value of the reaction order, m, for the initial autocatlytic reaction was not affected by blending ABA with epoxy resin, and the value was approximately 1.0. The value of n for the nth order component in the autocatalytic analysis was increased by increasing the amount of ABA in the blends, and the value increased from 2.0-3.4. A diffusion controlled reaction was observed as the cure conversion increased and the rate equation was successfully analyzed by incorporating the diffusion control term for the epoxy/DDS/ABA blends.

• Bulletin of the Korean Chemical Society
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• 제20권1호
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• pp.35-41
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• 1999

Stability characteristics of hyperbolic reaction-diffusion equations with a reversible Brusselator model are investigated as an extension of the previous work. Intensive stability analysis is performed for three important parameters, Nrd, β and Dx, where Nrd is the reaction-diffusion number which is a measure of hyperbolicity, β is a measure of reversibility of autocatalytic reaction and Dx is a diffusion coefficient of intermediate X. Especially, the dependence on Nrd of stability exhibits some interesting features, such as hyperbolicity in the small Nrd region and parabolicity in the large Nrd region. The hyperbolic reaction-diffusion equations are solved numerically by a spectral method which is modified and adjusted to hyperbolic partial differential equations. The numerical method gives good accuracy and efficiency even in a stiff region in the case of small Nrd, and it can be extended to a two-dimensional system. Four types of solution, spatially homogeneous, spatially oscillatory, spatio-temporally oscillatory and chaotic can be obtained. Entropy productions for reaction are also calculated to get some crucial information related to the bifurcation of the system. At the bifurcation point, entropy production changes discontinuously and it shows that different structures of the system have different modes in the dissipative process required to maintain the structure of the system. But it appears that magnitude of entropy production in each structure give no important information related for states of system itself.

• 한국재료학회지
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• 제26권5호
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• pp.235-240
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• 2016

Appropriate thermo-mechanical properties of nickel-based superalloys are achieved by heat treatment, which induces precipitation and solid solution hardening; thus, information on the temperature ranges of precipitation and dissolution of the precipitates is essential for the determination of the heat treatment condition. In this study, thermal analyses of nickel-based superalloys were performed by differential scanning calorimetry method under conditions of various heating rates of 5, 10, 20, or 40K/min in a temperature range of 298~1573K. Precipitation and dissolution temperatures were determined by measuring peak temperatures, constructing trend lines, and extrapolating those lines to the zero heating rate to find the exact temperature under isothermal condition. Determined temperatures for the precipitation reactions were 813, 952, and 1062K. Determined onset, peak, and offset temperatures of the first dissolution reaction were 1302, 1388, and 1406K, respectively, and those values of the second dissolution reaction were 1405, 1414, and 1462K. Determined solvus temperature was 1462K. The study showed that it was possible to use a simple method to obtain accurate phase transition temperatures under isothermal condition.

• Molecular & Cellular Toxicology
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• 제2권4호
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• pp.251-256
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• 2006

The exploration of genes which expressions are changed by exposure to ecotoxicants or pollutants can provide the important information about the reaction mechanisms in the body as well as adaptation to exterior stimulus or environmental changes. Also they can be developed as biomarkers for the detection of environmental pollution. Differential display polymerase chain reaction (DD-PCR) technique has been usefully used to hunt the clones which expressions are up-regulated or down-regulated by exterior changes and this study aimed to search for those clones in diesel oil-exposed rockfish (Sebastes schlegeli) using DD-PCR. The RNA isolated from liver of 20 ppb diesel oil-exposed rockfish was used for screening of the differentially displayed genes and total 44 differentially expressed genes (DEG) are detected then their nucleotide sequences were analyzed. The present data provided the general information about the effect of diesel oil contamination on marine organism and further more the primary step in development of new biomarkers for marine environmental pollution or ecotoxicological stresses.

• 대한화학회지
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• 제35권2호
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• pp.165-171
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• 1991

6,6-dibromopenicillanic acid 1,1-oxide(DBPA)의 6위치 dibromo기의 전기화학적 환원을 direct current, differential pulse polarography, cyclic voltammetry, 조절전위 전기량법으로 연구하였다. DBPA 환원과정은 2단계-0.48, -1.62 volts)에서 모두 완전비가역으로 2전자씩 이동하는 EC, EC 반응기구로 진행하였다. 조절전위 전기분해를 이용하여 6-bromo-PA와 6,6-dihydro-PA를 단계적으로 합성하였으며, pH 변화에 다른 폴라로그램의 해석과 생성물 분석의 결과를 바탕으로 전기화학적 반응기구도 제안하였다.

• 농업과학연구
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• 제11권2호
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• pp.315-321
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• 1984

0.1M tetraethylammoniumperchlorate (TEAP)를 지지전해질로 한 acetonitrile속에서 direct current (DC), differential pulse (DP) polarography 및 cyclo voltammetry (CV) 방법에 의한 Sumithion의 전기화학적 환원반응은 -1.0~-2.50volt vs. Ag-AgCl 범위에서, 제1단계로 P-Oph 결합의 분열에 의하여 dimethylthiophosphonyl radical과 p-nitro-m-cresol이 생성되는 1전자 유사가역반응이 일어나고, 제2단계는 전형적인 1전자 비가역 반응으로 dimethylthiophosphonyl radical이 dimethylthiophosphonate가 되며, 제3단계 반응은 2.7volt vs. Ag-AgCl의 높은 음전위에서 p-nitro-m-cresol은 4전자 비가역반응에 의한 nitro group의 환원으로 p-hydroxy-amino-m-cresol이 생성되는 총 3단계의 비가역적인 electron-transfer chemical reaction (EC) 메카니즘으로 전극반응이 진행됨을 알았다.

• Journal of applied mathematics & informatics
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• 제35권3_4호
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• pp.277-302
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• 2017

In this paper, we have proposed a numerical method for Singularly Perturbed Boundary Value Problems (SPBVPs) of reaction-diffusion type of third order Ordinary Differential Equations (ODEs). The SPBVP is reduced into a weakly coupled system of one first order and one second order ODEs, one without the parameter and the other with the parameter ${\varepsilon}$ multiplying the highest derivative subject to suitable initial and boundary conditions, respectively. The numerical method combines boundary value technique, asymptotic expansion approximation, shooting method and finite difference scheme. The weakly coupled system is decoupled by replacing one of the unknowns by its zero-order asymptotic expansion. Finally the present numerical method is applied to the decoupled system. In order to get a numerical solution for the derivative of the solution, the domain is divided into three regions namely two inner regions and one outer region. The Shooting method is applied to two inner regions whereas for the outer region, standard finite difference (FD) scheme is applied. Necessary error estimates are derived for the method. Computational efficiency and accuracy are verified through numerical examples. The method is easy to implement and suitable for parallel computing. The main advantage of this method is that due to decoupling the system, the computation time is very much reduced.

• 대한화학회지
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• 제32권3호
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• pp.195-202
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• 1988

Acetonitrile 용액중에서 3-phenyl-4-nitrosydnone의 전기화학전 환원을 direct current, differential pulse polarography, cyclic voltammetry 그리고 controlled potential coulometry 방법으로 연구하였다. Phenyl-N 단일 결합의 분리 이전에 nitro 기능기의 비가역적 전자 전달-화학반응(EC)기구의 진행으로 다전자 이동에 의한 amino(또한 hydroxylamino)기를 형성하고, 높은 음 전위 영역에서 2,3 비가역성 환원파의 일전자전달-화학반응에 의한 phenyl hydrazine을 생성하였다. 음극 반파 전위들은 cetyltrimethyl ammonium bromide의 억제 효과에 의해 음의 값으로 이동하였고 한편, sodium lauryl sulfate micelle은 높은 음전위 영역에서 제 2,3 환원파의 가역성산화 peaks를 보였다.

• 한국안전학회지
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• 제16권2호
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• pp.75-79
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• 2001

For handling and storage of reactive chemicals, the hazard evaluations have been extremely important. In the chemical industry, the most concerns are focused on the thermal harzards such as runaway reactions and thermal decompositions, which are mostly governed by thermodynamics and reaction kinetics or these reactive chemical in the system. This study no investigated the thermal decomposition characteristics of nitrophenylhydrazine isomers by using differential scanning calorimeter(DSC) and accelerating rate calorimeter(ARC). Experimental results showed that exothermic onset-temperatures in nitrophenylhydrazine(NPH) isomers were about 160-$210^{\circ}C$ by DSC and 100-$150^{\circ}C$ by ARC. The decomposition temperature acquired by ARC was about 50-$60^{\circ}C$ lower than that by DSC. Reaction heats were about 40-100cal/g by DSC and 330-750ca1/g by ARC. While ortho isomer of NPH show two distinct exothermic peaks, para isomer shows a single peak in DSC curves. The first exothermic peak for 2-NPH is mainly due to intramolecular dehydration forming 1-hydroxybenzotriazole(HOBT) and the second exothermic peak is mainly due to the decomposition of HOBT formed in the first step of decomposition. The exothermin peak in the DSC curve for 4-NPH is mainly due to dissociation of hydrazino and nitro groups.

• 한국안전학회지
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• 제24권4호
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• pp.40-46
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• 2009

The early identification of thermal hazards associated with a process such as the heats of reaction, exothermic decompositions, and the understanding of thermodynamics before any large scale operations are undertaken. The evaluation of reaction factors and thermal behavior on esterification process in manufacture of concrete mixture agents are described in the present paper. The experiments were performed in the differential scanning calorimetry(DSC), C 80 calorimeter, and thermal screening unit($TS^u$). The aim of the study was to evaluate the thermal stability of single material and mixture in esterification process. We provided the thermal data of chemical materials to present safe operating conditions through this study.