学具的选择与使用有效性的思考     

唐彩彩 《小学教学参考》2008,(36)

众所周知,学具具有直观形象,可以化抽象为具体,能充分调动学生的积极性,帮助学生建立概念、理解算理,培养学生的动手能力、创新能力等等数不清的优势。正因如此,学具以其不可替代的手段经常在课堂中高调亮相。  相似文献   

《升和毫升》教学设计——北师大版五年级下册     

林钦 《福建教育》2007,(2):43-44

[设计片段一]感受升1．教师演示，把1分米’的正方体容器装满水，再将水倒进容积是1升的容器中，刚好倒满，说明“1升=1分米…’。2．参照1升水的体积，估一估大瓶橙汁的体积。3．参照1升水的体积和橙汁的体积，估一估红色塑料桶的容积。  相似文献   

Unperturbed dimensions of atactic poly（dibenzyl itaconate）s     

MA Hai-zhu YE Gao-xiang 《浙江大学学报(A卷英文版)》2007,8(7):991-998

The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, deduced by the pseudo-stereochemical equilibrium approach, may be used to investigate the configurational-conformational properties of atactic polymers with large side groups [poly(itaconates) for instance]. The calculated results showed that poly(itaconates) have larger dimension of the molecule than other vinyl polymers. Comparison of the dimension between considering and without considering side groups showed that the effect of large side groups on the unperturbed dimension for short-chain polymers is more obvious than that of long-chain polymers and, if the dimension of side groups increases, the effect also increases. The dimension differences of PDBzI between short-chain and long-chain polymers are investigated by the relation of characteristic ratios and temperature coefficients with temperature. Moreover, the dependence between the temperature coefficients and the tacticity of chains shows that the temperature characters of the isotactic, syndiotactic and atactic PDBzI chains have remarkable difference.  相似文献   

在明辨中深度理解概念——“体积与容积”的教学思考与实践     

《小学教学参考》2019,(35)

教师应该围绕概念内涵的核心来组织和开展教学活动。以"体积与容积"一课的教学思考与实践为例,谈在具体教学中,如何通过深刻分析概念本质及其蕴含的数学思想,来设计有利于学生慎思、明辨的学习活动,促进学生深度学习,真正把知识内化为能力。  相似文献   

Investigation of oil-air two-phase mass flow rate measurement using Venturi and void fraction sensor   总被引：6，自引：0，他引：6  

张宏建  岳伟挺  黄志尧 《浙江大学学报(A卷英文版)》2005,6(6):601-606

INTRODUCTION Accurate measurement of multiphase fluids flow rates in the petroleum industry is of great importance. The most reliable measurement technique for multi-phase flow is separating the mixture and using con-ventional devices for measuring single-phase flow. However, in many cases the separation is not practical from both technical and economical points of view. An alternative solution is the multiphase flow me-tering system, usually consisting of a combination of devices for ph…  相似文献   

Preparation and characterization of TiO₂/expanded graphite     

赖奇  朱世富  刘国钦  邹敏  李玉峰  罗学萍 《天津大学学报(英文版)》2010,16(2):156-159

In order to obtain anatase TiO2/expanded graphite with high expansion volume, titania gel was introduced to expandable graphite surface by sol-gel process, and then the composite was expanded and calcined at high temperature. The samples were analysed by using scanning electron microscope (SEM), X-ray diffraction(XRD), energy disperse spectroscopy(EDS), and differential scanning calorimetry(DSC). The optimal conditions for preparation are as follows: the molar ratio of tetrabutyl orthotitanate to triethanolamine is 1∶0.4, and the calcination and expansion temperature is in the range of 650-750 °C. Under such conditions, the expansion volume of composites could reach 98 mL/g, and the mass loss ratio is less than 5%. The analysis shows that lower temperature and smaller particle size of graphite are helpful to the formation of anatase-type of TiO2, but larger particle size will lead to lower mass loss ratio, and higher temperature and larger particle size will lead to higher expansion volume.  相似文献   

《容积和容积单位》教学设计与分析     

马顺红 《数学大世界(高中辅导)》2010,(7):31-31,47

教学目标：1．知道容积的含义,理解体积和容积之间的联系与区别。2．认识常用的容积单位升与毫升,初步建立升与毫升的容积观念。3．培养观察、独立思考和应用几何基础知识解决实际问题的能力。教学重、难点：知道容积的含义,掌握容积单位间的进率;量（升、毫升）感的培养。  相似文献   

白酒生产废水中溶解氧的测定     

张玉柱  张嘉鑫 《黑龙江科技信息》2013,(23):29-29

介绍了碘量法测定白酒生产废水中溶解氧的具体方法,包括需要的仪器与试剂、具体操作方法及计算。  相似文献   

基于面部图像的非接触式婴儿心率监测     

许桢杰  高国琴  方志明 《教育技术导刊》2019,18(10):12-18

为实现便捷、可靠的日常婴儿心率实时监测,提出一种基于面部图像的非接触式婴儿心率实时监测方法。首先引入欧拉视频放大技术,对一定时间间隔内视频的每一帧图像进行颜色增强处理,从而改善婴儿面部颜色变化微弱、所含心率信息不明显的问题;然后,通过Adaboost算法从每一视频帧中识别出婴儿面部,并从婴儿面部选取脸颊区域作为敏感区域以提取脉搏波信号,以此为基础提出一种改进的反射光强模型,抑制日间因环境光变化引起的干扰以及运动噪声干扰,提高脉搏波信号信噪比;此外采用摄像头的红外自主光源,通过一种基于相空间重构的单通道独立成分分析法分离夜间脉搏波信号的运动噪声,解决因夜间光照条件差引起的婴儿心率监测困难的问题;最后开发整个系统上位机应用程序,并通过实验验证该方法正确性和有效性。  相似文献   

变式教学的一次成功尝试     

张慧 《高中数学教与学》2012,(6):22-24

<正>变式教学是目前课堂教学中经常采用的一种教学手段,它可以调动学生的学习积极性,锻炼其解题能力,深化对知识内容的理解.在以往的教学过程中往往是教师变,学生练.笔者通过"导数在实际生活中的应用"这一节课,尝试了一次教师适当引导,学生自己  相似文献