促进初中数学课堂教学有效生成的几种途径

1问题提出随着课程改革的不断深入,课堂教学更加注重学生的主体地位,强调师生的互动和合作.而在这个互动的过程中意味着更多的不确定性和生成性,因此预设和生成就构成了新课程教学的一对基本矛盾,共同存在于课堂教学之中.课堂教学需要预设,更需要生成.     

Heterogeneous growth of KDP/KT crystal

The growth of heterogeneous crystal has aroused a great deal of interest in recent years. In this study, KH_2PO_4(KDP)/KTaO_3(KT) heterogeneous crystal is acquired based on the KT substrate. Here, we report the observation of the oriented layer-by-layer structure in KDP/KT composite crystal by scanning electron microscopy(SEM). The structure of KDP/KT composite crystal is accurately identified by transmission electron microscopy(TEM) for the first time and we find that the KT crystals dope into KDP crystal in the growth process with the mode of doping. It can be obtained from the analysis of crystal structure that the structure difference leads to the doping growth mode. Our research demonstrates a facile method to fabricate a composite nonlinear optical crystal based on KDP/KT heterostructure, and might shed light on potential applications of the composite nonlinear optical crystal.