利用固体物理LED发光原理测量普朗克常数

普朗克常数是物理学中一个重要的常数,利用二极管的量子特性探讨运用发光二极管来测量普朗克常数。通过测量二极管的伏安曲线,确定其阈值电压,根据相关量子理论,间接得出普朗克常数,通过与光电效应法测量普朗克常数的测量结果相比较,结果表明此误差略大,但作为一种新型的实验方法探索,对于开拓学生的综合素养还是非常有益的。     

超声粒子图像测速技术及应用

心血管疾病的产生与动脉血流的流动状况密切相关。然而,目前普遍应用的超声多普勒成像技术不能精确测量复杂血流流场信息。本文提出了一种基于超声造影微泡的超声全流场粒子图像测速技术,能够获得多维流速速度信息,且不依赖于声束与速度向量之间的夹角。本文首先着重阐述了超声全流场粒子测速技术的基本原理以及系统组成,并对直管流和旋转流场流体动力学特性进行了实验测试研究,实验结果表明本技术能够测量全流场速度,并可作为表征复杂血流流场的有力手段。      

First-principles calculation of magnetism of icosahedral Fe clusters

Icosahedral iron clusters are synthesized and characterized in our group by using experimental methods.But the measurements of magnetic properties still face difficulties:the sizes of the clusters and the amount of product.Therefore theoretical methods are employed to study these issues.In this paper,icosahedral iron clusters containing 13,55,147,309 atoms are calculated by ab initio techniques.After the structural relaxation,the magnetism of the clusters is found to be similar to that of face centred cubic(FCC) iron with stronger ferromagnetism on the surface.But the central atom of each cluster is exceptional,which has a smaller magnetic moment.We also study the electronic structural properties in the clusters for a better explanation of the magnetism.It is suggested that in small clusters,the magnetic properties still depend on the local structural arrangement.