Analysis of the small-angle X-ray scattering of linear polyethylene by a paracrystalline lattice model

Three paracrystalline lattice models for the interpretation of the small angle scattering of polyethylene are discussed: The “lattice model”, the “stapel model” (often referred to as the lamellar stack model) and the “proportional model”. While the applicability of the first model is restricted, the latter models differ in the statistical assumptions of lamellar and interlamellar thickness distributions. The principal advantage of the proportional model over the stapel model is its applicability through the adjustment of only three parameters: long period, crystallinity and one statistical parameter. Small angle X-ray curves of linear polyethylene are interpreted by the proportional model. The results are in good agreement with stapel model calculations.     

聚合动力学研究方法进展

从构造聚合动力学模型所采用的数学方法出发 ,对聚合动力学模型———概率统计模型、机理模型及基于MonteCarlo模拟模型等的进展进行了综述。     

分子动力学模拟苯和萘在超临界二氧化碳中的无限稀释扩散系数

采用球型模型和点位-点位模型对超临界二氧化碳的自扩散系数及苯或萘在超临界二氧化碳中的无限稀释扩散系数进行了分子动力学模拟。结果表明,球型模型及点位-点位模型均可较准确地预测二氧化碳的自扩散系数,球型模型因形式简单,准确度相对较差;点位-点位模型准确度虽高,但需较长的模拟机时。两种位能模型所获得的准确度相当,但点位-点位模型可以更精细地反映体系的微观结构。     

Model for the prediction of separation profile of oil-in-water emulsion

This paper proposed a model that explains the separation mechanism of oil-in-water emulsion taking into account both creaming and coalescence processes. Oil-in-water emulsion separation experiments were performed in a batch separator using kerosene and distilled water. The predictions of the proposed model agreed well with the experimental results as well as previously published experimental data. The comparison between the proposed model and the previously published model showed that the proposed model has higher accuracy in predicting the separation profile of oil-in-water emulsion, with an accuracy of within 10%. Thus the proposed model gives better representation of the oil-in-water emulsion separation process.     

Modelling of kinetics of microbial degradation of simulated leachate from tobacco dust waste

This paper presents a kinetic analysis of the biodegradation of organic pollutants in a batch bioreactor and investigates the kinetic properties of activated sludge using different mathematical models. The treatment was conducted for different initial concentrations of leachate from 500 mg dm^?3 to 5000 mg dm^?3 and initial concentrations of activated sludge from 1.84 g dm^?3 to 6.62 g dm^?3 over 48 h. Four different kinetic models were applied to the data. The kinetic analysis was performed with the traditional Monod model, the modified Monod model with endogenous metabolism, the Haldane model, and the Haldane model extended to include endogenous metabolic consumption and known as the Endo-Haldane model. Kinetic parameters for each model were determined using differential analysis and the Nelder-Mead method of non-linear regression. The lowest deviations and very good matches with the experimental data were achieved using the Endo-Haldane model. This indicated that this model best described the process of biodegradation of leachate from tobacco waste composting. This is due to this model incorporating the effects both of inhibition and endogenous metabolism.     

Energetics of the neighbor exclusion model of intercalation

The nearest-neighbor exclusion model for intercalation was studied using an energetical approach. It was shown that creation of the intercalation site in the exclusion model corresponds to the same energetical destabilization of the structure as in the standard model of intercalation. The stability of the intercalation complex formed in the case of the exclusion model is lower by 68 kcal/mol as compared with the standard model, but geometrical structures of both complexes are very similar. The electrostatic molecular potential method was also used to further characterize the intercalation site formed within both models of intercalation.     

正癸烷燃烧机理及航空煤油点火延时动力学模拟

以单一正癸烷作为国产航空煤油的单组分替代模型, 应用自有的碳氢燃料反应机理生成程序ReaxGen-Combustion构建了燃烧反应的详细机理. 以国产煤油在加热型激波管上的燃烧实验为参考, 对比研究了文献报道的3组分替代模型(模型Ⅰ)、2组分替代模型(模型Ⅱ)以及本文的单组分替代燃烧反应机理(模型Ⅲ)在预测我国航空煤油点火延时特性方面的实用性. 结果表明, 温度在1052~1538 K时, 模型Ⅰ预测的点火延时与实验值相差较大; 模型Ⅲ在温度高于1176 K时的预测值与实验值符合较好, 在1052~1176 K之间时则相差较大; 模型Ⅱ与模型Ⅲ预测值符合很好, 由于前者考虑了低温反应机理, 因而对1052~1176 K区间的预测精度与模型Ⅲ相比有所改善. 计算还发现, 模型Ⅱ中添加的20%(质量分数)1,2,4-三甲基苯对高温段点火延时未产生明显影响.     

Kinetic modeling of industrial steam cracker

A comprehensive mathematical model is a very useful tool for the selection of feedstock, optimized cracker product mix, downstream production planning, and optimized plant performance. As a part of achieving this prime objective, a mathematical model has been developed for the simulation of the radiation section of a steam cracker unit. The model involves solving differential component, energy, and momentum balance equations numerically to generate temperature, concentration, and pressure profiles along the length of the reactor tube. The model has been developed in FORTRAN using the lSODE solver. The model considers 19 free radicals and 35 molecules connected over 433 reactions. The model was used to simulate the performance of propane and ethane cracking. The model predicted propane conversion is 95.55 against the plant data of 95% at a coil outlet temperature of 845 ​°C and the corresponding predicted ethylene and propylene yield is 34.49 and 11.53% respectively. The model has been validated for ethane cracking performance. The model predicted ethylene yield is in good agreement with that of plant values for ethane cracking. The model provides a basis for the optimization of process parameters for the given geometry. The model is useful to answer what-if questions and to investigate operational strategies.     

半连续乳液聚合动力学模型

介绍半连续乳液聚合动力学模型的研究进展及建模方法，归结出３种形式模型，基础模型，具体模型与通用模型，指出通常从一些假定出发，根据质量平衡，能量平衡反应机理建立模型方程，通过模型参数估计，已有模型参数的利用及模型变量的求取，使用数值方法求解模型。     

Study on phenomenological curing model of epoxy resin for prediction of degree of cure

Curing course of Huntsman 1564/3486 epoxy resin system was studied under dynamic and isothermal curing conditions by differential scanning calorimetry technique. The autocatalytic cure kinetic model was established to describe the curing behaviour. A new modified phenomenological curing model based on the Olivier??s model was proposed to predict the relationship between the degree of cure and the couple of time and temperature. Then, the degree of cure was calculated by both the kinetic model and the modified Olivier??s model. A comparison of the results calculated with the experimental data show that the modified Olivier??s model is more accurate in the later stage of the curing course, especially at high temperatures. The modified Olivier??s model is simple and easy to use, could be applied to predict the degree of cure at isothermal temperatures well in engineering.     

Correlation of mean ionic activity coefficient using a two-parameters model

In this study, a two-parameters model is presented based on the solvation phenomena. Using this model, the mean ionic activity coefficients of 146 salts and activity coefficients of individual ions of some 1 : 1 and 1 : 2 salts have been correlated successfully. The results of the present model have been compared with the Khoshkbarchi–Vera model and three-characteristic parameter correlation model of Lin and Lee model. These comparisons show that the present model predicts the mean ionic activity coefficient better than others.     

Modeling of the salt effects on hydrophobic adsorption equilibrium of protein

A two-state protein model is proposed to describe the salt effects on protein adsorption equilibrium on hydrophobic media. This model assumes that protein molecules exist in two equilibrium states in a salt solution, that is, hydrated and dehydrated states, and only the dehydrated-state protein can bind to hydrophobic ligands. In terms of the two-state protein hypothesis and the steric mass-action theory, protein adsorption equilibrium on hydrophobic media is formulated by a five-parameter equation. The model is demonstrated with the adsorption of bovine serum albumin to Phenyl Sepharose gels as a model system. The effects of salt type (sodium chloride, sodium sulfate and ammonium sulfate) on the model parameters are discussed. Then, the model formulism is simplified in terms of the small magnitude of the protein dehydration equilibrium constant in the model. This simplification has returned the model derived on the basis of the two-state protein hypothesis to its original mechanism of salt effects on the hydrophobic adsorption of protein. This simplified model also creates satisfactory prediction of protein adsorption isotherms.     

Comparison of various models describing the adsorption of surfactant molecules capable of interfacial reorientation

The thermodynamic model for describing the adsorption of surfactant molecules in different adsorption states, the reorientation model, is reconsidered on a more rigorous level. The resulting model equations are used to describe experimental surface pressure data published in the literature. The new model proposed contains three physical parameters and describes the experimental dependencies Pi(c) for oxethylated alcohols very accurately.     

基于近红外光谱技术的电子烟油烟碱含量快速检测研究

烟碱是电子烟烟油中的主要成分,其含量决定了电子烟油的风味口感及产品的安全性。为了提高电子烟油烟碱含量的测量效率,该文采用近红外光谱技术和极限学习机回归(ELMR)建立了电子烟油烟碱含量的定量预测模型。实验结果表明：相比于传统的主成分回归(PCR)和偏最小二乘回归(PLSR)模型,所建立的ELMR预测模型的决定系数R2为0.926 2,远高于PCR预测模型的0.859 0和PLSR预测模型的0.860 4;同时,使用ELMR模型的预测均方根误差(RMSEP)为0.026 8,小于PCR预测模型的0.043 1和PLSR预测模型的0.040 9。以上结果说明该文所建立的近红外光谱定量模型能够应用于烟碱含量的快速准确测量,为实现电子烟油烟碱含量的实时在线监测和其它质量参数的快速测量奠定了良好的基础。     

双酚A与碳酸二苯酯酯交换反应动力学研究进展

综述了双酚A与碳酸二苯酯熔融酯交换制备聚碳酸酯的反应动力学模型的研究进展,对官能团模型和分子碎片模型两种比较成功的动力学模型进行了详细的说明.介绍了一种新的四面体中间物模型,并对由不同模型导出的动力学方程式的计算结果与实验结果进行了讨论和比较.通过官能团模型可以得到反应级数,活化能,反应速率常数以及平衡常数,分子碎片模型最显著的优势是可以随时跟踪物质的浓度变化,进而得到物系的分子量分布和平均分子量,四面体中间物模型的计算结果与已有的实验数据符合良好,同时对动力学的进一步研究提出了改进方向.     

橡胶贮存寿命预测方法研究进展与思考建议

概述了用数学模型法预测橡胶贮存寿命的方法,包括阿伦尼斯模型,用ASTM D412评估橡胶拉伸性能,应力应变老化模型,压缩永久变形的预测方法,橡胶疲劳寿命损伤模型,用有限元法考核橡胶的裂纹长度与抗裂能之间的关系,基于叠加原理的寿命预测模型等,针对上述模型预测研究结果提出了相关思考建议。认为以老化动力学为基础预测材料寿命的数学模型法发展非常迅速,建议深入研究并拓宽应用;在透彻了解和掌握必需的分子结构参数的基础上,如果结合计算机技术模拟长期贮存或使用条件,对橡胶老化反应机理的研究可能是一个有前景的发展方向。     

On the Statistical Calibration of Physical Models

We introduce a novel statistical calibration framework for physical models, relying on probabilistic embedding of model discrepancy error within the model. For clarity of illustration, we take the measurement errors out of consideration, calibrating a chemical model of interest with respect to a more detailed model, considered as “truth” for the present purpose. We employ Bayesian statistical methods for such model‐to‐model calibration and demonstrate their capabilities on simple synthetic models, leading to a well‐defined parameter estimation problem that employs approximate Bayesian computation. The method is then demonstrated on two case studies for calibration of kinetic rate parameters for methane air chemistry, where ignition time information from a detailed elementary‐step kinetic model is used to estimate rate coefficients of a simple chemical mechanism. We show that the calibrated model predictions fit the data and that uncertainty in these predictions is consistent in a mean‐square sense with the discrepancy from the detailed model data.     

Influence of the chemorheology of toughened epoxy matrices on the processing behavior of high performance composites

The rheological and kinetic behavior of a new commercial toughened epoxy matrix is characterized through a complete experimental program. The kinetic behavior of the thermosetting resin is described by applying a new empirical model, accounting for autocatalytic and difussion control effects. The rheological model uses the kinetic information and describes the matrix viscosity as a function of temperature and degree of reaction using only three fitting parameters. The complete model is verified through calorimetric and rheological tests performed at different temperatures (isotherms) or heating rates (dynamic tests); or under more complex conditions simulating the processing conditions during autoclave lamination. Finally the chemo-rheological model is considered as a part of a master model describing the complete processing behavior of thermoset matrix composites. The use of the master model in control and optimization algorithms is also illustrated.