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Novel MgCl2-supported Ziegler-Natta (Z-N) catalysts prepared using a new one-pot ball milling method caneffectively control the amounts of Ti-loading in the catalysts. Complex GPC data on polypropylene synthesized by thesenovel catalysts were analyzed using the method of fitting the molecular weight distribution (MWD) curves with a multipleFlory-Schulz function. It was found that multiple active centers exist in these novel catalysts. Detailed study of the effects ofthe Ti-loadings in the catalysts on the distribution of the active centers showed that the Ti-loadings in the novelMgCl2-supported Z-N catalysts might affect the proportion of each type of active centers; and might be the main factorresponsible for the effect of the Ti-loadings on the microstructure, the molecular weight and molecular weight distributionwidth of the resultant polymer, the catalytic activity and polymerization kinetics. 相似文献
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<正> 一、快速跑教材的生化、生理特点中学体育教学大纲规定,快速跑初中一、二年级的跑距为40—60米,从初三到高二跑距略有延长。这一教材,从能量代谢的角度来看,属于高能磷酸盐分解释放能量的无氧代谢。高能磷酸盐主要是三磷酸线苷(ATP)和磷酸肌酸(CP)。生 相似文献
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天体运动是每年高考的重点和热点之一,考查的本质是牛顿第二定律在匀速圆周运动中的应用,多以选择题的形式出现．要正确解答天体运动问题,除了掌握万有引力提供向心力外还要明确天体运动的7个关键点． 相似文献
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INTRODUCTION Polypropylene is one of very important syn-thetic resins. In general, people pay more attentionsto the development of catalysts with high isotacticspecificity for propylene polymerization (Wang etal., 1995; Soga and Shiono, 1997). However, withthe development of the various use of polypropyl-ene (Jiang and Wu, 1999; Tiemblo et al., 1999),such as use of atactic polypropylene as an additivefor building top grade highway recently, peoplebegan to make efforts to synthesize… 相似文献
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油价上涨总会牵动某些车主朋友的神经,其实如果养成了好的驾驶习惯,油价上涨的那部分是完全可以用节省来抵消的。笔者所理解的节油驾驶不是一种方法,而是一个长期的驾驶习惯,习惯与方法的不同点就在于习惯是长期性的。 相似文献
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<正> 力量素质,在各项身体素质中,占有极为重要的地位。它不仅是发展速度、弹跳等素质的基础,而且还直接影响着运动技术水平的提高。为了提高力量素质训练的效果,在安排训练计划时不仅要注意确定力量练习在全面身体训练中的比重,同时 相似文献
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精心设计激情引趣──谈向小学生进行爱国主义教育的做法西城区育民小学赵振荣主持人：关依兰学生是爱国主义教育的对象和主体，主体在教育过程中的主动参与性、积极实践性直接关系到教育成效的高低。我校从多年的德育实践中深刻地认识到：教育者必须对教育内容、教育形式... 相似文献
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