• 공업화학
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• 제10권4호
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• pp.548-556
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• 1999

질소 분위기에서 폴리에틸렌 열분해의 속도론적 연구를 $10^{\circ}C/min$와 $50^{\circ}C/min$ 사이의 여러 가지 가열속도에서 비등온 질량감소 기술을 이용하여 수행하였다. 속도 상수들에 대한 정보를 얻기 위하여 질량감소 곡선 및 그 미분값을 Kissinger, Freeman-Carroll, Flynn-Wall, Coats-Redfern, Chatterjee-Conrad, Friedman, Horowitz-Metzger 및 Ozawa 방법과 Denq 방법을 이용하여 해석하였다. 연구에 사용된 수학적인 방법에 따라 속도 상수의 결과값에 많은 차이가 있음을 알 수 있었으며, 따라서 열분해의 속도 상수 결정에 있어서는 각 방법의 장 단점에 대한 비교 분석 연구가 선행되어야 할 것으로 판단되었다. 본 연구로부터 HDPE의 겉보기 활성화 에너지의 값이 LDPE의 값보다 크게 나타냄을 확인할 수 있었다.

• 한국미생물·생명공학회지
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• 제19권2호
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• pp.186-192
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• 1991

It is very important to have a good kinetic model which considers the effects of both ammonium and glucose for the control and optimization of the poly-${\beta}$-hydroxybutyrate (PHB) fermentation. A kinetic model for the growth of Alcaligenes eutrophus and the biosynthesis of PHB under both ammonium and glucose limitation was proposed. Growth rate of residual biomass was expressed as a function of concentrations of residual biomass, glucose and ammonium having glucose inhibition. PHB production rate was expressed as a function of concentrations of residual biomass, glucose, ammonium and PHB content having ammonium and product inhibitions. Novel approaches were made to estimate the parameters in the model equations which considered two limiting substrates. Model parameters were evaluated by graphical and simplex methods. The proposed kinetic model fitted the data very well.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2989-2994
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• 2013

The solvolysis rate constants of 3,4- (1) and 3,5-dimethoxybenzoyl (2) chlorides were measured in various pure and binary solvents at $25.0^{\circ}C$, and studied by application of the extended Grunwald-Winstein (G-W) equation, kinetic solvent isotope effect in methanolysis and activation parameters. The solvolysis of 1 was interpreted as the unimolecular pathway due to a predominant resonance effect from para-methoxy substituent like 4-methoxybenzoyl chloride (3), while that of 2 was evaluated as the dual mechanism, with unimolecular or bimolecular reaction pathway according to the character of solvent systems (high electrophilic/nucleophilic) chosen, caused by the inductive effect by two meta-methoxy substituents, no resonance one. In the solvolyses of 1 and 2 with two $-OCH_3$ groups, the resonance effect of para-methoxy substituent is more important to decide the mechanism than the inductive effect with other corresponding evidences.

• Nuclear Medicine and Molecular Imaging
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• 제41권2호
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• pp.78-84
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• 2007

Quantitative analysis of dynamic brain PET data using a tracer kinetic modeling has played important roles in the investigation of functional and molecular basis of various brain diseases. Parametric imaging of the kinetic parameters (voxel-wise representation of the estimated parameters) has several advantages over the conventional approaches using region of interest (ROI). Therefore, several strategies have been suggested to generate the parametric images with a minimal bias and variability in the parameter estimation. In this paper, we will review the several approaches for parametric imaging with linearized methods which include graphical analysis and mulilinear regression analysis.

• 상하수도학회지
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• 제13권3호
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• pp.42-55
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• 1999

A mathematical model for biological nutrient removal in a sequencing batch reactor process, which is based on the IAWQ Activated Sludge Model No. 2 with a few modifications, has been developed. Twenty water quality components and twenty three kinetic equations are incorporated in the model. The model is structured in the matrix form based on the law of mass conservation using stoichiometry and kinetic equations. Stoichiometric coefficients and kinetic parameters included in the model equations are chosen from the literature. A multistep predictor-corrector algorithm of variable step-size is adopted for solving the vector nonlinear ordinary differential equations. The simulation for experimental results is conducted to evaluate the validity of the model and to calibrate coefficients and parameters. The simulation using the model well represents the experimental results from laboratory. The mathematical model developed in this study may be utilized for the design and operation of a sequencing batch reactor process under the steady and unsteady-state at various environmental conditions.

• Bulletin of the Korean Chemical Society
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• 제25권5호
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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.

• 한국생물정보학회:학술대회논문집
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• 한국생물정보시스템생물학회 2005년도 BIOINFO 2005
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• pp.272-277
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• 2005

We introduce a new approach to optimize the parameters in biological kinetic models by quantifier elimination (QE), in combination with numerical simulation methods. The optimization method was applied to a model for the inhibition kinetics of HIV proteinase with ten parameters and nine variables, and attained the goodness of fit to 300 points of observed data with the same magnitude as that obtained by the previous optimization methods, remarkably by using only one or two points of data. Furthermore, the utilization of QE demonstrated the feasibility of the present method for elucidating the behavior of the parameters in the analyzed model. The present symbolic-numeric method is therefore a powerful approach to reveal the fundamental mechanisms of kinetic models, in addition to being a computational engine.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3218-3222
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• 2013

The aminolyses, anilinolysis and pyridinolysis, of bis(2-oxo-3-oxazolidinyl) phosphinic chloride (1) have been kinetically investigated in acetonitrile at 55.0 and $35.0^{\circ}C$, respectively. For the reactions of 1 with substituted anilines and deuterated anilines, a concerted SN2 mechanism is proposed based on the selectivity parameters and activation parameters. The deuterium kinetic isotope effects ($k_H/k_D$) invariably increase from secondary inverse to primary normal as the aniline becomes more basic, rationalized by the transition state variation from a backside to a frontside attack. For the pyridinolysis of 1, the authors propose a stepwise mechanism with a rate-limiting step change from bond breaking for more basic pyridines to bond formation for less basic pyridines based on the selectivity parameters and activation parameters. Biphasic concave upward free energy relationship with X is ascribed to a change in the attacking direction of the nucleophile from a frontside attack with more basic pyridines to a backside attack with less basic pyridines.

• Elastomers and Composites
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• 제21권1호
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• pp.13-19
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• 1986

최근(最近)에 와서는 황(黃)에 의(依)한 고무의 가황반응(加黃反應)이 발열반응(發熱反應)이라는데 주안점(主眼點)을 두어 근래(近來) 고분자화학(高分子化學) 분야(分野)에서 그 활용도(活用度)가 높은 열분석기(熱分析機) (특(特)히 DSC, DTA)가 가황발열현상연구(加黃發熱現象硏究)에 많이 이용(利用)되고 있다. 그러나 고무의 가황반응(加黃反應)을 속도론적(速度論的)으로 연구하여 이론적(理論的) 기초(基礎)를 확립(確立)하여 두는 것이 필요(必要)하다는 것은 여러 학자(學者)들이 전(前)부터 느껴왔으나 고무탄성체(彈性體)는 한번 가황(加黃)되면 일반적(一般的)인 용매(溶媒)에 의(依)한 용해(溶解)가 어렵기 때문에 반응물(反應物)(황, 가황촉진제(黃, 加黃促進劑))이나 생성물(生成物)의 농도측정(濃度測定)에 의(依)한 가황반응(加黃反應)의 속도론적(速度論的) 연구(硏究)가 어려웠다. 그래서 본(本) 연구(硏究)에서는 DSC(Differential Scanning Calorimetry)를 이용(利用)하여 얻은 천연(天然)고무의 가황발열(加黃發熱) thermogram을 Borchardt-Daniel이 제안한 방법으로 분석(分析)하여 kinetic data(즉, rate constant k, frequency factor ko, Activation Energy Ea)를 얻었다. 또한 이 kinetic data가 가황촉진제의 종류(種類)에 따라 어떻게 달라지는지, 실제공정(實際工程)에서 적정가황시간(適正加黃時間), 온도(溫度), 가황촉진제(加黃促進劑)의 종류(種類), 배합량(配合量) 결정(決定)에 활용(活用)할 수 있는 방안(方案)에 대(對)해서도 관심을 두고 검토(檢討)하였다. 한편 DSC에 의(依)한 방법(方法)의 신뢰도를 검토하기 위하여 DSC용(用)으로 쓰여진 것과 동일(同一)한 시료를 사용하여 Oscillating Disk Rheometer에 의한 Cure Curve를 얻고 이 Cure Curve를 분석(分析)하여 얻은 kinetic data를 앞서 구한 data와 비교검토(比較檢討)하였다.

• Carbon letters
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• 제22권
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• pp.14-24
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• 2017

Carboxylated multi-wall carbon nanotubes (MWCNTs-COOH) have been used as efficient adsorbents for the removal of picric acid from aqueous solutions under stirring and ultrasound conditions. Batch experiments were conducted to study the influence of the different parameters such as pH, amount of adsorbents, contact time and concentration of picric acid on the adsorption process. The kinetic data were fitted with pseudo-first order, pseudo-second-order, Elovich and intra-particle diffusion models. The kinetic studies were well described by the pseudo-second-order kinetic model for both methods. In addition, the adsorption isotherms of picric acid from aqueous solutions on the MWCNTs were investigated using six two-parameter models (Langmuir, Freundlich, Tempkin, Halsey, Harkins-Jura, Fowler-Guggenheim), four three-parameter models (Redlich-Peterson, Khan, Radke-Prausnitz, and Toth), two four-parameter equations (Fritz-Schlunder and Baudu) and one five-parameter equation (Fritz-Schlunder). Three error analysis methods, correlation coefficient, chi-square test and average relative errors, were applied to determine the best fit isotherm. The error analysis showed that the models with more than two parameters better described the picric acid sorption data compared to the two-parameter models. In particular, the Baudu equation provided the best model for the picric acid sorption data for both methods.