Effect of solution extrusion rate on morphology and performance of polyvinylidene fluoride hollow fiber membranes using polyvinyl pyrrolidone as an additive

<正>Polyvinylidene fluoride(PVDF) hollow fiber membranes prepared from spinning solutions with different polyvinyl pyrrolidone(PVP) contents(1%and 5%) at different extrusion rates were obtained by wet/dry phase process keeping all other spinning parameters constant.In spinning these PVDF hollow fibers,dimethylacetamide(DMAc) and PVP were used as a solvent and an additive,respectively.Water was used as the inner coagulant.Dimethylformamide(DMF) and water(30/70) were used as the external coagulant.The performances of membranes were characterized in terms of water flux,solute rejection for the wet membranes.The structure and morphology of PVDF hollow fiber were examined by BET adsorption,dry/wet weight method and scanning electron microscopy(SEM).It is found that the increase in PVP content and extrusion rate of spinning solution can result in the increase of water flux and decrease of solute rejection.The improvements of interconnected porous structure and pore size are induced by shear-thinning behavior of spinning solution at high extrusion rates,which could result in the increase of water flux of hollow fiber membranes.The increase of extrusion rate also leads to the increase of membrane thickness due to the recovery effect of elastic property of polymer chains.     

利用光谱图线表估计含量

通过光谱试验,证实了借助C.K.加里宁等著的《光谱图线表》在Q24型摄谱仪上进行全定性与含量估计分析是可行的,从而使该分析更加简便。     

沙霍捕虫的启示──谈体校中专物理教材的改革

沙霍捕虫的启示──谈体校中专物理教材的改革陈文清（安徽省体育运动学校合肥２３０００１）新版的美国基础物理教材，有一个明显的特点：在每一章之前，都有一幅提问式的图片，叫章首图．其中有一幅沙霍捕捉甲壳虫的章首图，这幅章首围内容为：沙漠里的沙霍为什么能准确...     

中专物理教材弹性问题的探讨

教材的弹性问题,是近年研究的热点课题之一。加强教材弹性建设是当前教材改革的重点工程。根据普通中专的性质、任务以及中专生身心发展的特点,增加教材弹性更具有特殊意义。因此,对于将要改编和其它正在编写的     

中专物理教材评价的探索

要搞好教学,教师必须有驾驭教材的本领。本文就中专物理教材评价的要素以及对体校物理教材的评价,作一探讨。 1 评价的原则 1.1 体现“三主”原则。要看教材是否体现以学生为主体、发挥教师的主导作用、以培养能力和方法为主线的原则。     

充水粘弹性管道的频散曲线计算分析*

针对谱方法分析计算充水粘弹性管道的广义特征值问题,根据Chebyshev多项式及微分矩阵、位移和应力连续条件,将波动方程离散为相应的线性方程。利用MATLAB数值编程计算充水弹性和粘弹性管道对应频率下的轴对称纵向导波频散曲线和衰减曲线。分析表明,波传播在粘弹性管道中不仅具有衰减特性,而且由于水和粘弹性壳体交叉耦合作用,在一定频率范围内产生两种截断模态。     

Daphnezomines A和B的四环核心骨架合成（英文）

在虎皮楠生物碱家族中, daphnezomine A型生物碱仅包含三位成员:daphnezomine A (1), daphnezomine B (2)以及dapholdhamineB.这些生物碱含有独特的氮杂金刚烷骨架,9个连续的手性立体中心,因此呈现出巨大的合成挑战性.报道了分子1和2的四环核心骨架的合成.关键步骤包括一个黄氏酰胺活化增环反应和一个Hutchins-Kabalka还原重排反应.