Class size and achievement in introductory economics: Evidence from the TUCE III data

Does class size affect achievement in introductory economics? This paper addresses this question using a national economic education data base (TUCE III), consolidating these data so that each observation represents a single class rather than a single student, thereby alleviating several estimation problems that plague empirical work in this area. Our results indicate that class size does not affect student achievement, and further, that class characteristics over which instructors or department chairs have control also do not influence achievement. These results are remarkably robust to different specifications, so long as students' Scholastic Aptitude Test (SAT) scores are used to control for ability and account is taken of whether the TUCE test result counted toward the students' final grade.     

二氧化钛负载磷钨杂多酸催化合成环己酮1,2-丙二醇缩酮

以H3PW12O40／TiO2为催化剂催化合成了环己酮1，2-丙二醇缩酮，探讨了H3PW12O40／TiO2对缩酮反应的催化活性，较系统地研究了酮醇物质的量比，催化剂用量，反应时间诸因素对产品收率的影响．实验表明：H3PW12O40／TiO2是合成环己酮1，2-丙二醇缩酮的良好催化剂，在n（环己酮）：n（1，2-丙二醇）=1：1．7，催化剂用量为反应物料总质量的0．5％，环己烷为带水剂，反应时间1．0h的优化条件下，环己酮1，2-丙二醇缩酮的收率可达83．7％．     

12阶群的特征标表

通过群的同构分类的观点,分析了12阶群的生成关系,再利用特征标的基本性质一一构造每个群的特征标表。     

时段式教室照明节能控制器的设计

介绍了一种可预设定时间的照明节能控制器的研发.该控制器硬件以AT98S52单片机为控制芯片,DS12C887时钟芯片为时钟计时,软件采用MCS-51单片机汇编语言,可在每天预定的3个时间段内对教室、车间等公共场合的照明灯进行集中控制,实现在该3个时段内当房间无人时关断照明,房间有人时开启照明并适时延长照明时间的节能控制.该控制器时钟运行不受市电停电影响,时钟年误差小于10 min.     

LY12硬铝合金表面离子注入层的性能及结构分析

用能量75keV、剂量1.0×10~(17)～7.0×10~(17)ions/cm~2的氮离子注入LYl2硬铝合金,研究了注入剂量对材料表面硬度行为的影响,实验发现存在一个剂量阈值D_(1b)=5.0×10~(17)N~+/cm~2,以该剂量的N~+注入可使LYl2硬铝合金的表面硬度得到最大程度的提高.用X-ray衍射仪探测到注入层出现AlN第二相,同时用TRIM算法计算了注入后的氮高子浓度分布和辐射损伤分布.实验和计算结果表明,弥散强化和缺陷强化是N~+注入LYl2硬铝合金的主要强化机制.     

我国现代学制百年演进历程与改革前瞻

学制作为国家教育制度体系中的重要构成,其改革事关国家教育发展的方向和未来。我国现代学制始创于1902年的壬寅学制,随后经癸卯学制、壬子癸丑学制的探索实践,至1922年颁布的壬戌学制最终确定了我国现代学制的基本框架,并延续使用百年。通过对现代学制百年演进史的梳理和审视,总结出学制改革应坚持科学性、系统性、弹性化、渐进性、合法性和集中性六原则。具体建议为：要依据学生身心发展变化确定学制改革思路;要与基础教育的整体改革相适应;要进行充分的实地调查与研究;要先试点先行,稳步推进;要完善学制的法律制度,于法有据、依法实施;要在政府统一领导下进行学制改革。     

固载杂多酸TiGeW12O40／TiO2的合成、表征及催化活性

报道了固载杂多酸TiGeW12O40/TiO2的制备方法，并用IR、XRD对其结构进行表征，研究了催化剂在酯化反应中的催化作用．     

Teacher blogs and education policy in a publicly private world: filling the gap between policy and practice

K-12 teachers who write about their daily work on blogs and other social media platforms share local knowledge and wisdom from the immediate view of the classroom. These first-hand retellings of everyday classroom life offer a unique critique of educational policy from the teachers’ perspective. Reporting on the analysis of 14 public-facing blogs written by New York City public school teachers, this paper highlights the possibilities held in these digital narratives by painting a picture of how teachers respond to the implementation of new educational policies.     

Electrochemical properties of CoFe<Subscript>3</Subscript>Sb<Subscript>12</Subscript> as potential anode material for lithium-ion batteries

A skutterudite-related antimonide, CoFe₃Sb₁₂, was prepared with vacuum melting. XRD analysis showed the material contained Sb, FeSb₂, CoSb₂ and CoSb₃ phases. The electrochemical properties of the ball-milled CoFe₃Sb₁₂−10 wt% graphite composite were studied using pure lithium as the reference electrode. A maximal lithium inserting capacity of about 860 mAh/g was obtained in the first cycle. The reversible capacity of the material was about 560 mAh/g in the first cycle and decreased toca. 320 mAh/g and 250 mAh/g after 10 and 20 cycles respectively.Ex-situ XRD analyses showed that the antimonides in the pristine material were decomposed after the first discharge and that antimony was the active element for lithium to insert into the host material. Project supported by the National Natural Foundation of China (No. 59771032) and the RFDP of the Education Ministry of China (No. 20010335045)