弦论小史（三）

我在《超弦史话》一开始就描述了弦论第二次革命开始的情形,多年后的现在回顾起来,也还是充满刺激。弦论第二次革命发端于1994年中的两篇文章：威滕和塞伯格（Nathan Seiberg）关于超对称规范理论的文章,以及胡尔（Christopher Hull）和汤森（Paul Townsend）关于弦论中的所谓U对偶的文章。在美国,第一篇影响的效应是即时的,甚至纽约时报都在第一时间报道了这个进展。一时之间,网上的物理文库充满了关于超对称场论的文章。与威滕和塞伯格工作的遭遇相反,起初没有太多人重视胡尔和汤森的工作。     

超强超短脉冲激光诱发大尺度氘团簇聚变

 利用低温脉冲气阀获得了平均含有3×103氘原子的氘团簇。在飞秒激光装置上实现了氘团簇聚变,每发中子产额为1×10³。中子产额对激光功率密度敏感,保持激光能量不变,随着激光焦斑的变大,DD聚变中子产额逐渐增加,最大值出现在激光焦斑为470 mm时;继续增大激光焦斑,没有观察到中子信号。实验结果还表明激光氘团簇聚变发生的区域主要是激光辐照的等离子体热区,此区域内邻近氘团簇库仑爆炸发射的高能氘离子碰撞引发聚变反应。     

培养学生立体思维能力的实践

人们在认识客观世界,反映外界事物时,总是通过一定的思维方式来进行的.通常所说的思维方式,主要是指逻辑思维和辩证思维.我们也知道,创造力是人类得以生存发展的不竭的动力.创造力是主体在创造活动中表现出来、发展起来的各种能力的总和;它主要指能产生新设想的创新思维能力和产生新成果的创造性技能.     

A Four-Dimensional Measurement Scheme for Single Photon Time-Polarization

We propose an experimental scheme to realize the four-dimensional projective measurements tor a single photon. The photon polarization and time-energy provide the four-dimensional Hilbert space. Based on this scheme, we suggest an experiment to test the violation of Bell inequalities of four-dimensional systems. In addition, by virtue of a maximally entangled biphoton state, we also show that it is possible to construct a quantum key distribution channel that can provide two-bit key with one pair of entangled photons.     

Interesting Features of n2D Rydberg Series Fine-Structure Splittings along the Sodium-Like Isoelectronic Sequence

Using a simplified multi-configuration Dirac-Fock （SMCDF） scheme based on the multi-configuration Dirac-Fock （MCDF） theory, we study the systematic variations of the fine-structure splittings of n^2 D3/2,5/2 Rydberg series along the sodium-like isoelectronic sequence, i.e. the fine-structure orderings vary with increasing atomic number Z. The competition between the spin-orbit interactions and the exchange interactions due to relativistic effects of the nd orbital wavefunctions well explain such variations. Furthermore, the effect of Breit interactions which plays the secondary role is studied.     

化学教学论课程中学生活动的设计与研究

“化学教学论”的教学实践中,坚持围绕每个内容专题,设计和组织学生活动,开展了汇报、讨论、辩论、设计、评价、学期论文汇报和答辩等多种形式的系列学生活动,取得了很好的教学效果。介绍了设计和研究化学教学论课程中学生活动的模型,详细和系统的学生活动设计框架,具体的活动组织与实施方案,并结合本校化学教育专业的实际进行了实践研究,运用活动后即时访谈、跟踪性访谈和调查问卷等方法调查分析了实践效果,结果表明,实施效果良好。     

A note on ＂Block H-matrices and spectrum of block matrices＂

In this paper, we make further discussions and improvements on the results presented in the previously published work ＂Block H-matrices and spectrum of block matrices＂. Furthermore, a new bound for eigenvalues of block matrices is given with examples to show advantages of the new result.     

撞击荷载作用下单层椭圆抛物面网壳的动力稳定分析

利用ANSYS/LS-DYNA 有限元程序,考虑几何非线性和材料非线性效应,开展单层椭圆抛物面网壳结构在撞击荷载作用下的动力稳定性研究.分析了该类网壳在以一定高度的自由落体撞击作用下的撞击力响应(撞击力、节点位移、杆件轴力和能量)及网壳失稳模态,进一步根据产生的动力响应对其在撞击作用下的弹塑性动力稳定问题进行了判定.结果表明:网壳结构在撞击作用下失稳时,撞击力时程曲线形状基本上呈陡峭的三角形脉冲荷载形式,其最大峰值和脉宽与撞击冲量及网壳所处变形阶段的刚度性能相关;特征节点的位移响应突然增大,失稳部位杆件的轴力大幅减小,结构的变形能和总能量也突然增大,整个结构变形形状发生突变;节点的残余位移、撞击力和持时等特征参数都产生一致性突变.     

Nonlinear coupled dynamics of liquid-filled spherical container in microgravity

Nonlinear coupled dynamics of a liquid-filled spherical container in microgravity are investigated. The governing equations of the low-gravity liquid sloshing in a convex axisymmetrical container subjected to lateral excitation is obtained by the variational principle and solved with a modal analysis method. The variational formulas are transformed into a frequency equation in the form of a standard eigenvalue problem by the Galerkin method, in which admissible functions for the velocity potential and the liquid flee surface displacement are determined analytically in terms of the Gaussian hypergeometric series. The coupled dynamic equations of the liquid-filled container are derived using the Lagrange＇s method and are numerically solved. The time histories of the modal solutions are obtained in numerical simulations.