旋波媒质中谱域电并矢Green函数的分解

介绍了一种推导无耗、互易和无界旋波媒质中谱域并矢Green函数表达式的新方法·　这种方法以Hemholtz定理以及并矢Diracδ函数的无散和无旋分解为基础,首先将电矢量的并矢Green函数方程分解成无散电矢量的并矢Green函数方程和无旋电矢量的并矢Green函数方程,然后经Fourier变换导出了旋波媒质中谱域电并矢Green函数的无散分解表达式和无旋分解表达式·　用这种方法推导旋波媒质中并矢Green函数就可以避免必须用波场的分解法和并矢Green函数的本征函数展开法·     

用横场伊辛模型研究应力对铁电薄膜的热力学性质的影响

用横场伊辛模型研究了铁电薄膜的热力学性质.在体系的哈密顿量中引入一个两维的在平面内的应力，并假设应力从基底材料和薄膜材料之间的界面层到薄膜的表面层是呈指数形式衰减的.结果显示：压应力有利于极化，使居里温度向高温区移动，而张应力对极化和居里温度的影响正好相反.扩散长度对铁电薄膜的热力学性质有很大的影响. 关键词： 铁电薄膜 应力 横场伊辛模型     

The multielectron dissociative ionization dynamics of N2 molecule in intense femtosecond laser fields with arbitrary polarization

The field-ionization Coulomb explosion model is extended to investigate the multielectron dissociative ionization process of N₂ molecule irradiated by an intense femtosecond laser field with an arbitrary polarization. The ionization process of N₂ molecule is found to be optimal at the critical internuclear distance R_c=7a.u., which is independent of the laser polarization state, the molecular explosion channel and the angle between the molecular axis and the direction of laser electric field. The kinetic energies of the ion fragments are identical in the cases of linear and circular polarizations at the same incident laser intensity. However,the probability of electron ionization is very sensitive to the above three parameters. At the critical distance R_c=7a.u. the angular dependence of the threshold intensity for the over-the-barrier ionization leads to the geometric alignment of molecules in the case of linear polarization. The threshold intensity in the case of circular polarization is apparently higher than that in the case of linear polarization, which can well explain the significant decrease of ionization in the case of circular polarization. The numerical calculations are compared with the experimental measurements.     

区间上单峰扩张自映射周期轨道的超旋转对

设f是区间I=[0,1]上的单峰扩张自映射, k ∈N,m≥2,λm,k是方程x(k-1)m(xm- 1)Q(x,m 1) (x(k-1)m-1)Q(x,m)=0在(1, ∞)上的唯一实根,其中Q(x,m)=(xm- 2xm-1 1).本文证明:若f的扩张常数λ≥λm,k,则f有超旋转对为(k,km 1)的周期轨道. 此外,还指出,当1<λ<λm,k时,在区间上存在单峰扩张自映射具有扩张常数λ却无超旋转对为(k,km 1)的周期轨道.     

Variational analysis of the disc-loaded waveguide slow-wave structures

The variational method is applied to calculate the dispersion characteristics of disc-loaded waveguide slow-wave structures. The parameters describing the waveguide discontinuities in disc-loaded waveguide are calculated by the variational method. Then the dispersion characteristics of slow-wave structures are obtained using lossless microwave quadrupole theory. Good agreement was observed between results of the variational method and those of field matching method and high frequency structure simulator. In the case of broad band, results of the variational method are better than those of field matching method.     

利用Λ型原子与双模腔场的相互作用进行量子信息处理

利用Λ型三能级原子与一个两模腔场在两光子共振和单光子大失谐条件下的相互作用模型，给出了制备两个和三个远距离的腔场的纠缠态和如何实现一个量子比特的原子态的远距离转移、纠缠态的转移的方案；同时找到了一种不用进行Bell基测量而实现纠缠交换的方法；构造了实现量子交换门的操作.最后对实验的可行性进行了分析. 关键词： 量子信息处理 Λ型原子 双模腔场 相互作用     

多面体对称性的探索

如果一个多面体关于某个平面对称，我们就称它具有对称性．正棱柱、正棱锥这些基本的几何体都具有对称性．利用对称来研究多面体，是一个容易被大家忽视的重要方法．从近几年的高考来看，立体几何题所给出的多面体很多都具有对称性．利用对称性质解题，所体现的思维过程更加完美．所以，我们要加强对多面体对称性的研究．     

Focusing of Surface Acoustic Wave on a Piezoelectric Crystal

We investigate the focusing phenomena of a surface acoustic wave （SAW） field generated by a circular-arc interdigital transducer （IDT） on a piezoelectric crystal. A rigorous vector field theory of surface excitation on the crystal we developed previously is used to evaluate the convergent SAW field instead of the prevalent scalar angular spectrum used in optics. The theoretical results show that the anisotropy of a medium has great impact on the focusing properties of the acoustic beams, such as focal length and symmetrical distributions near the focus. A dark field method is used in experiment to observe the focusing of the SAW tield optically. Although the convergent phenomena of SAW field on the anisotropic media or piezoelectric crystals are very complicated, the experimental data are in agreement with those from the rigorous theory.     

高速粒子场同轴Fraunhofer全息数据处理系统研究

介绍了用同轴Fraunhofer全息测量强动载下材料表面微喷射粒子场的数据处理方法.在全息像重建过程中，将再现的三维粒子场由计算机控制分成许多小薄层采集.在数据处理过程中根据图像中粒子边缘，决定在整幅图或局部采用边缘检测的方法提取大粒子，根据图像的灰度分布将图像分成很多小区域，在每个小区域采用不同的阈值分割图像.在处理结果的校正中根据粒子场的特点，去除过大、过小和重复统计粒子.采用该方法得到了粒子的空间分布图像及粒子大小的统计结果.     

谈概念转变教学之策略

 概念转变新一轮的课程改革注重学生的发展,关注物理同生活、同社会的联系,注重学生已有的知识、经验在以后学习中的作用。这些在物理学习之前形成的对现象、事实的感知理解,其中一些与科学概念相一致,为进一步学习科学知识打下基础,而另一些则与科学知识相矛盾,即存在错误的前概念。建构主义者认为,学生总是在自己原有经验和认知能力的基础上,建构他对新知识的理解,所以物理学习中学生头脑中的前概念是必然存在的。前概念对于学生来说,那是他们的精神财富,曾经“成功地”解释某些现象,是认识特殊现象的宝贵工具,例如,物体不推不动,运动方向受力等等。