从点电荷到场的升华——大学物理中关于电磁学教学的思考

电磁学是工科大学物理课程的重要内容之一,其中如麦克斯韦方程组等诸多抽象公式对于初学大学物理的一年级新生有一定的难度.本文围绕“场”这一核心内容,通过“实验规律→场的性质→场与物质的相互作用”这条线索将整个电磁学的内容贯穿起来,讨论如何实现从点电荷到场的升华,最终得到关于场的统一理论.并以变速运动点电荷为例,说明场描述下的麦克斯韦方程组的解如何超越静电场的高斯定理,以问题为导向,引导学生在探究和思考中深入理解电磁学的核心内容.     

Eigenstate Distribution Fluctuation of a Quenched Disordered Bose–Hubbard System in Thermal-to-Localized Transitions

We study the thermalization of a quenched disordered Bose–Hubbard system. By considering the eigenstate distribution fluctuation, we show that the thermal to many-body localized transition is always connected to a minimum of this distribution fluctuation. We also observe a Mott-localized regime, where the system fails to thermalize due to the strong on-site repulsion. Lastly, we show how to detect this eigenstate distribution fluctuation in a cold atom system, which is equivalent to measure the Loschmidt echo of the system. Our work suggests a way to measure the thermal-to-localized transitions in experiments, especially for a large system.     

Synthesis, Crystal Structure and Luminescent Properties of [Zn（bipy）_2（H_2O）_4]·L·3H_2O

A novel coordination complex [Zn(bipy)2(H2O)4]·L·3H2O (1, bipy = 4,4'-bipyridine, LHNa = aniline-2,5-disulfonic acid monosodium salt) has been synthesized from LHNa by using hydrothermal method and structurally characterized. The result indicates that complex 1 belongs to the monoclinic system, space group P21/c with a = 20.392(3), b = 7.4052(12), c = 23.843(3) , β = 116.253(10)°, V = 3.2291(8) 3, Z = 4, Dc = 1.553 g·cm-3, μ = 0.962 mm-1, F(000) = 1568, and the final R = 0.0497 and wR = 0.1290. The complex 1 has a 0-D discrete structure, and generates an infinite 3-D network with the aid of O–H…O hydrogen bonds and π-π interactions.     

Syntheses and Characterization of Two New Alkaline Earth Metal-organic Topological Frameworks with 3-Amino-1H-1,2,4-triazole-5-carboxylate

Two new alkaline earth metal coordination polymers constructed from the deriva-tive of 1,2,4-triazole are presented herein,namely,{[Sr(AmTAZAc)2(H2O)]}(1) and {[Ba(AmTAZAc)2(H2O)]}(2)(AmTAZAc = 3-amino-1H-1,2,4-triazole-5-carboxylate),which have been synthesized by using the layering method and structurally characterized by elemental analysis,IR,and single-crystal X-ray diffraction.Complexes 1 and 2 are isostructural,and both crystallize in the orthorhombic system,space group Fdd2.X-ray structural analysis shows that 1 or 2 has an intriguing 3-D infinite network of(318.438.510) topology based on a 2-D sheet structure of(4,4) net.The result shows that noncovalent interactions play an important role in strengthening the whole structures of the compounds.     

时效温度和Ag对Al-Zn-Mg合金力学性能与微观结构的影响

本文研究了在不同时效温度条件下Ag对Al-Zn-Mg铝合金力学性能与微观结构的影响。结果表明，随着时效温度的提升，Ag对合金硬度的影响增大，合金晶界无析出带宽度明显减小。时效温度为120℃时，含Ag和不含Ag的Al-Zn-Mg铝合金均以η系列相析出为主，但含Ag合金的晶内析出相分布更为细小弥散，尺寸减小的同时径厚比增大。当时效温度升高至160℃和180℃,Ag对合金峰值硬度的提升作用显著增加。此时，Al-Zn-Mg合金主要强化相由η系列相转变为T系列相，同时尺寸明显增大，而含Ag合金中主要强化相类型与120℃时相同，仍然为η系列相，且尺寸并未明显增大。