Entanglement in a two-spin (1/2,3/2) mixed-spin Heisenberg XX chain with an inhomogeneous external magnetic field

By using the concept of negativity, we investigate the thermal entanglement of a two-spin (1/2, 3/2) mixed-spin Heisenberg XX chain with an inhomogeneous external magnetic field. We obtain the analytical results of entanglement of this model. For the case of uniform magnetic field, we find that the critical temperature is higher than the results of the spin-1/2 chain and (1/2,1) mixed-spin chain. And by adjusting the nonuniform parameter b, one is able to obtain more entanglement at a higher temperature.     

S~5上仿Blaschke张量的特征值为常数的超曲面

设x:M→S~(n+1)是(n+1)-维单位球面上不含脐点的超曲面,在S~(n+1)的Moebius变换群下浸入x的四个基本不变量是:一个黎曼度量g称为Moebius度量;一个1-形式Φ称为Moebius形式;一个对称的(0,2)张量A称为Blaschke张量和一个对称的(0,2)张量B称为Moebius第二基本形式.对称的(0,2)张量D=A+λB也是Moebius不变量,其中λ是常数,D称为浸入x的仿Blaschke张量.李海中和王长平研究了满足条件:(i)Φ=0;(ii)A+λB+μg=0的超曲面,其中λ和μ都是函数,他们证明了λ和μ都是常数,并且给出了这类超曲面的分类,也就是在Φ=0的条件下D只有一个互异的特征值的超曲面的分类.本文对S~5上满足如下条件的超曲面进行了完全分类:(i)Φ=0,(ii)对某常数λ,D具有常数特征值.     

自相似集的质量分布原理与Hausdorff测度及其应用

本文提出了满足开集条件的自相似集的质量分布原理.作为应用,得到了计算一类满足开集条件的自相似集的Hausdorff测度的准确值的方法,并举例说明了此方法对于计算一类满足开集条件的自相似集的Hausdorff测度的准确值是行之有效的.     

Porous coordination polymers based on three planar rigid ligands

During the last two decades,porous coordination polymers(PCPs),usually called as metal-organic frameworks(MOFs),have been developed rapidly due to their versatile structural diversities and potential physical and chemical functions.This article provides a short review of recent advances in the design and constructions of porous coordination polymers based on three planar rigid ligands,including imidazole-4,5-dicarboxlate(H3IDC),1H-tetrazole(HTz),as well as 1H-tetrazole-5-carboxylate(H2Tzc).Their preparation...     

浆体管道内静止圆柱状型料的起动

在动量定理和能量定理的基础上,建立静止圆柱状型料在浆体管道内起动的动量方程和能量方程,并由此导出静止型料在浆体管道内的起动速度计算公式．经型料管道起动实验验证,该公式较好地描述了静止型料在浆体管道中开始起动的物理条件,能有效地推断和预测静止型料在浆体管道流中的起动速度．理论计算值和实验数据指出,静止型料在浆体管道内的起动速度,不仅和管道平均流速紧密相关,而且和浆体密度、型料形状比以及型料管道直径比紧密相关．