Specific interactions in blends containing Chitosan and functionalized polymers. Molecular dynamics simulations

Chitosan (CS)/poly(vinyl alcohol) (PVA) and Chitosan/poly(2-hydroxyethyl methacrylate) (P2HEM) blends have been studied through molecular dynamic simulations. In a previous work it was found miscibility between these polymers and it was attributed to hydrogen bonding formation. However, the experimental information obtained was not enough to know which of the interacting groups of Chitosan, i.e. -CH₂OH or -NH₂, are responsible of the interaction. Therefore, we have performed molecular dynamics simulation runs of 1 ns in order to calculate radial distribution functions (RDF) for the groups tentatively involved in the interaction. The results are correlated with our previous experimental data. This way, we have obtained a more precise conclusive information about the interactions involved as function of the blends composition. For low compositions of PVA and P2HEM the interaction is predominantly with the hydroxymethyl groups of CS while as the composition of PVA and P2HEM increases, the interaction with the amine groups increases.     

Fluctuations and waves in fluidized bed systems: The influence of the air-supply system

A general model of the response of a fluidized bed to disturbances is formulated, and the information provided by the model with respect to the dynamics of the bed, the bed plus the air-plenum and the bed plus the entire air-supply system, is investigated. Expressions given in literature on the fundamental frequency of the bed-plenum system are analyzed, and it is shown that they are a special case of the general model. In order to simulate various types of interaction between the bed and the rest of the system, experiments were performed in a cold fluidized bed unit operated under both non-circulating and circulating conditions. At low velocity, three regimes were identified: the multiple bubble regime with almost no interaction between bed and air-plenum, the single bubble regime with the interaction between bed and air-plenum only, and a regime with numerous irregular bubbles, where the bed interacted with the entire air-supply system. At high fluidization velocity, the exploding bubble regime was identified, with the same dominant frequency as that of the single bubble regime (the interaction with the air-supply system remains at that frequency). The models investigated correctly reproduce the dynamics when the bed is independent of the other parts of the system, or when the bed interacts only with the air-plenum. However, the models are only partially applicable when the bed interacts with the entire air-supply system. The reasons for this are investigated. In the case of system interaction, pressure waves, generated in the bed, interact with pressure pulsations from the air-supply system. This results in a coupled system, which is not covered by the models. Pressure waves resulting from events in the bed, are recognized as the coherent part of the cross power spectra of pressure fluctuations measured in the bed and the air-plenum.     

基于Protel DXP的电路仿真设计

Protel DXP是集所有设计工具于一身的电子设计自动化(EDA)软件.文中运用其内嵌的仿真器叙述了分压式偏置电路放大器的仿真设计过程,设计过程简单、方便.在电子线路理论教学过程中引入电路设计仿真环节在不同情况下对电路进行实时分析,不仅可以提高学生的学习兴趣,而且能够在较短时间内加深学生对理论知识的理解;在工程设计过程中利用仿真工具对电路进行即时测试,可以缩短设计周期,提高设计效率.     

基于MAPINFO和VB的自来水管网信息系统的建立

介绍基于MapInfo平台，利用VB语言进行二次开发，建立自来水管网地理信息系统的关键技术及其注意的问题。     

建筑电气设计中AutoCAD二次开发的研究

基于AutoCAD的二次开发环境下,建立幻灯片库,在AutoCAD本身所包含的程序帮助下,将已建好的幻灯片库嵌入到AutoCAD用户专用下拉菜单中.给设计者创造属于自己的开发环境,使AutoCAD在建筑电气设计中的使用更加灵活,极大的提高设计效率.     

一部特具匠心的精品教材——评张仲谋《宋词欣赏教程》

张仲谋教授的新著《宋词欣赏教程》，是南京大学出版社出版的“江苏省高等学校精品教材系列”中的一种。该书共8章，既构成一个严谨的教学体系，又多有创新出彩之处；对于词的艺术个性有深刻的把握和精当的阐发；又善于引导学生，循循善诱。该书既是教材，亦具有学术专著的品格。     

论我国大学不良竞争的形成及控制

大学在办学资源、办学过程、办学质量、办学形象的竞争中出现大量的不良倾向。大学的不良竞争是由于政府主导资源配置、资源和制度供给不足、大学系统重构等因素导致。必须通过控制主体、控制手段的转变和控制对象的发展形成新的控制机制，以保证大学竞争的秩序化和规范化。     

Matlab语言与线性电路的符号仿真

目前的电路仿真软件通常是在电路中所有元件值都是给定的情况下得到一些数值结果，而非解析结果。该文利用Matlab的符号运算功能编程，通过节点列表法，实现了任意线性电路的自动解析求解，为电路分析提供了一个有效的辅助工具。     

天津独流减河工程监控系统现地通信单元设计

提出一种配电网电容电流测量的新方法，在零序电压互感器的开口三角侧串联一个可调电感，通过注入一个变频恒流信号寻找配电网的谐振频率，改变可调电感的数值后寻找另一谐振频率，联立2个谐振方程求解电容电流，该方法消除了电压互感器漏抗对测量的影响。开发了配电网电容电流测量仪，经模拟试验和现场测试表明，该方法具有安全、快捷、准确等特点，适用于中性点不接地或经随调式消弧线圈接地配电网。