“最近发展区”在物理概念教学中的应用

阐述了如何利用"最近发展区"理论指导物理概念教学,新课的概念教学不要一步到位,往往要搭建一个平台,使得学生能够顺着台阶掌握新概念,学习新知识.     

SiCp/Al复合材料切削仿真及实验研究

对SiCp/Al复合材料的颗粒和基体分别进行定义建立有限元仿真模型,使用ABAQUS有限元软件从微观角度分析了不同切削速度和切削深度对切削力的影响以及应力场分布情况,研究切屑的形成过程、基体和颗粒的内部应力分布、刀具和颗粒之间的相互作用以及简要分析了材料表面缺陷的成因,通过车削实验进行验证.研究表明:微观仿真模型中由于高硬度SiC颗粒的存在会产生大量的微裂纹以及单一小空洞和不连续空洞,形成表面缺陷,且剪切区域微裂纹的扩展是产生切屑的重要因素;通过对比,实验获得的切削力变化及其波动和形成机制与仿真结果一致.     

Fabrication of mixed perovskite organic cation thin films via controllable cation exchange

Here in this paper, we demonstrate a facile technique for creating the mixed formamidinium(HN = CHNH_3~+, FA~+)and methylammonium(CH_3NH_3~+, MA~+) cations in the lead iodide perovskite. This technique entails a facile drop-casting of formamidinium iodide(FAI) solutions on as-prepared MAPbI_3 perovskite thin films under the controlled conditions,which leads to controllable displacement of the MA~+ cations by FA~+ cations in the perovskite structure at room temperature. Uniform and controllable mixed organic cation perovskite thin films without a "bi-layered" or graded structure are achieved. By applying this approach to photovoltaic devices, we are able to improve the performances of devices through extending their optical-absorption onset further into the infrared region to enhance solar-light harvesting. Additionally,this work provides a simple and efficient technique to tune the structural, electrical, and optoelectronic properties of the light-harvesting materials for high-performance perovskite solar cells.