人甲状腺旁素1型受体的结构特征

人甲状腺旁素1 型受体(PTH1R)是骨形成相关的B类G蛋白偶联受体, 其底物甲状腺旁腺素(PTH)及类似物具有抗骨质疏松作用. 由于此类受体的三维结构难以进行实验测定, 本文采用同源模建的方法, 完整构建了胞外区、跨膜区及其它相关区域, 并通过对接研究, 阐明复合物的氢键、疏水性相互作用及其与底物的相互作用关系和关键位点. 为进一步设计和发展此类药物提供理论依据.     

Social influence, agent heterogeneity and the emergence of the urban informal sector

We develop an agent-based computational model in which the urban informal sector acts as a buffer where rural migrants can earn some income while queuing for higher paying modern-sector jobs. In the model, the informal sector emerges as a result of rural-urban migration decisions of heterogeneous agents subject to social influence in the form of neighboring effects of varying strengths. Besides using a multinomial logit choice model that allows for agent idiosyncrasy, explicit agent heterogeneity is introduced in the form of socio-demographic characteristics preferred by modern-sector employers. We find that different combinations of the strength of social influence and the socio-economic composition of the workforce lead to very different urbanization and urban informal sector shares. In particular, moderate levels of social influence and a large proportion of rural inhabitants with preferred socio-demographic characteristics are conducive to a higher urbanization rate and a larger informal sector.     

THEME‐SEER: a multidimensional exploratory technique to analyze a structural model using an extended covariance criterion

In this work, we present a new approach to path modeling based on an extended multiple covariance criterion: system extended multiple covariance (SEMC). SEMC is suitable to measure the quality of any structural equations system. We show why SEMC may be preferred to criteria based on usual covariance of components and also to criteria based on residual sums of squares. We give a pursuit algorithm ensuring that SEMC increases and converges. When one wishes to extract more than one component per variable group, a problem arises of component hierarchy. To solve it, we define a local nesting principle of component models that makes the role of each component statistically clear. We then embed the pursuit algorithm in a more general algorithm that extracts sequences of locally nested models. We finally provide a component backward selection strategy. The technique is applied to cigarette data to model the generation of chemical compounds in smoke through tobacco combustion. Copyright © 2012 John Wiley & Sons, Ltd.     

蒸汽压缩制冷系统的稳态和瞬态建模分析

针对蒸汽压缩制冷系统工作过程的分析,建立了蒸汽压缩系统的瞬态和稳态数学模型,对整个蒸汽制冷系统的内部结构开展了深入的研究,并对其组成结构中的相关单元模块进行了建模与分析,在此基础上给出了制冷系统详细的瞬态和稳态的数学模型描述形式,通过对模型的仿真与测试给出了制冷系统工作过程中主要参数的变化情况,尤其是仿真结果与实际系统的工作过程进行对比,验证后表明本文所建立的工作模型,其COP性能与实测的结果误差不超过5%。     

基于新物性库的低温回热器REGEN模拟

REGEN程序是用于回热式低温制冷机中回热器部分的仿真模拟软件。在仅内嵌有氦元素工质的基础上,工作新增了包含N2、H2、Ne、Ar和甲烷等13种低温工质的物性库,介绍了其适用温度、压力区间及计算精度等情况。在保留原有氦-4(4He)的基础上补充了当前最新的4He状态方程的研究成果,以此验证了新物性库与原物性库的衔接性和复现性。使用基于新物性库的REGEN3.3a程序对He、H2和Ne为工质的斯特林型脉管制冷机,进行了模拟优化计算并比较了采用不同工质时制冷机的制冷系数。     

Copolymerization of VDF and HFP in Supercritical Carbon Dioxide: A Robust Approach for Modeling Precipitation and Dispersion Kinetics

A kinetic model is developed for the heterogeneous free‐radical copolymerization of vinylidene fluoride and hexafluoropropylene in supercritical CO₂. The model accounts for polymerization in both the dispersed (polymer‐rich) phase and in the continuous (polymer‐free) supercritical phase, for radical interphase transport, diffusion limitations, and chain‐length‐dependent termination in the polymer‐rich phase. A parameter evaluation strategy is developed and detailed to estimate most of the kinetic parameters a priori while minimizing their evaluation by direct fitting. The resulting model predictions compare favorably with the experimental results of conversion and MWD at varying monomer feed composition, monomer concentration, interphase area, and pressure of the system.

     

A modeling approach for the non‐isothermal antisolvent crystallization of a solute with weak temperature dependent solubility

Antisolvent crystallization is a crystallization technique, which is normally operated isothermally. However, non‐isothermal operation is on occasions performed for solutes that have temperature dependent solubility. This paper shows that it is beneficial to operate antisolvent crystallizers non‐isothermally even for solutes whose solubility is weakly dependent on temperature. In this context, it demonstrates the joint control of particle mean size and size distribution coefficient of variation. A non‐isothermal crystallization model‐based framework is developed for the sodium chloride‐ethanol‐water system and validated for both isothermal and non‐isothermal operations. This framework was used to systematically determine both the optimal antisolvent feed rate and temperature profiles that minimize the coefficient of variation while producing a specified mean crystal size. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)