Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor

Fluidized-bed reactor is a candidate for dimethyl ether （DME） synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller （BET）, X-ray powder diffraction （XRD） and temperature programmed reduction （TPR）.     

利率理论研究的演进历程综述——从“真实分析”到“货币分析”

利率是货币经济学的核心范畴和重要的宏观经济变量。该文将利率理论区分为微观利率理论和宏观利率理论,前者研究利率的产生和本质,后者研究利率对宏观经济的影响。通过梳理利率理论研究内容和方法的演进历程,为利率理论的未来研究提供帮助。     

政治价值与政治活动的追求——探析政治概念的二元结构

政治作为一种生活实践活动,本身就内含着政治价值与政治活动的统一,由此决定了政治活动应是经验性与规范性之间的一种张力。站在这种立场上审视政治概念在西方的发展史,不难发现,古代人的政治观念与近代人的政治观念分别走向了追求政治活动与追求政治理性的两个极端,而唯有马克思主义才使得政治回归到了其现实生活的根基之中。     

几种环境条件对唾液淀粉酶活性的影响

讨论了不同条件下唾液淀粉酶活性的差异。实验结果表明,影响唾液淀粉酶活性的因素很多,必须在各种条件适宜的情况下,才能发挥其最佳的催化作用;淀粉酶具有高度专一性,其活性受温度、pH值、激活剂及抑制剂、酶浓度以及作用时间等多种因素影响;每个人产生唾液淀粉酶的量不同,活性强弱也有差异。     

综合实践活动课程论教学探索

高师小学教育专业的培养目标是培养实践型与研究型的小学教师,在课程结构设计中,应该关注综合实践活动师资短缺与素质缺失等教育现实,开设综合实践活动课程论,培养适合基础教育新课改需求的、综合能力较强的小学教育师资。     

美国图书馆“快照日”活动及其启示

全球金融危机对美国图书馆发展产生了巨大冲击,由美国新泽西州图书馆协会和新泽西州立图书馆于2009年首倡的图书馆快照日活动在减少消极影响方面取得了良好的社会效果。美国图书馆快照日活动具有项目内容多样化、项目策划模式化、宣传方式多样化等特点。我国图书馆开展读者活动时．应充分借鉴美国图书馆快照日活动的成功经验,改变以本位思想形成的推广思路,重视读者活动效果评估及评估结果,注重与社区、学校、文化机构、新闻媒体等团体间的合作,形成整体合力和规模效应,以更好地服务于读者。     

知识活动中的知识单元与知识计量研究

人类社会的知识活动根据其特征可以分为知识创造活动、知识管理活动和知识利用活动三类。知识计量贯穿知识活动全过程,但知识创造、知识管理和知识利用过程中对知识进行计量采用的知识单元不同。知识单元的构建是突破知识计量研究瓶颈的关键。参考文献16。     

Physical fitness of primary school children in relation to overweight prevalence and physical activity habits

Abstract

A cross-sectional study was carried out to analyse, through a limited number of fitness tests, the main conditioning and coordinative abilities in children aged 8–9 years, and their relationship with gender, anthropometric variables and physical activity habits. The height and weight of 256 boys and 241 girls were measured and information about physical activity habits was collected using a self-administered questionnaire. Physical performance was assessed by means of a few standardised tests: ‘sit & reach’, medicine-ball forward throw, standing long jump, 20 m running speed, and forward roll test. In both boys and girls, body weight and Body Mass Index (BMI) were positively correlated with the medicine-ball throw performances and negatively correlated for the standing long jump and speed tests, while no association was found with tests measuring back flexibility and total body coordination. Daily physical activity and participation in sport were not significantly correlated with body weight and BMI, but were positively associated with children's motor performance. The standardised fitness tests selected in the current study have been found to be suitable to identify fitness levels of primary school children. Thanks to their limited number and ease of measurement, they can be used in any school context to classify children and for monitoring the effects of targeted interventions promoting physical activity.     

"体育"本体论(三)——体育的本体和哲学矛盾

体育的生命力取决于是否有人去做,去实践,其本质很难用文字表达。这种体育的实践性与文字性表达的高度矛盾,正是体育在人类文明中具有的特殊之处。“体育的本体就是身体运动,即体育以身体运动本身为目的。”这样表达体育的本质既可以在操作性上排除被动运动、生活自理和工作等非体育,又可以在价值层上净化体育思想、保持体育的纯粹性。在哲学上,我们应处理好体育的两对矛盾:一、人的身体或意志谁是第一性的问题。二、“人”与“物”谁是第一性的问题。只有通过反复思考,我们才能从当今的体育现实中汲取一种智慧。     

我国居住水平的长期和短期影响因素实证分析

本文利用协整检验和面板数据分析我国居住水平的长期和短期影响因素。发现利率、收入房价比与居住水平存在长期协整关系,说明利率的提高长期会降低居住水平,限价、限开发房屋种类的政策是短期行为,提供低息房贷和发展中低档商品房的同时提高居民收入的方法才是长效的。面板数据分析发现提高人均收入和维持房地产市场稳定对提高居住水平有重要的作用。东西部房地产市场存在地区差异,东部对利率较敏感,中西部对收入和物价的变化较敏感,针对差异可选择不同的政策。