The persistent current in an Aharonov－Bohm ring with a side-coupled quantum dot

We have investigated the persistent current in a mesoscopic ring with a side-coupled quantum dot. The problems are probed by using the one-impurity Anderson Hamiltonian and are treated with the slave boson mean field theory. It is shown that the persistent current in this system has the spin fluctuations, and the charge transfers between the two subsystems are suppressed in the limit of Δ/T_K^0《1. The minimum value of the persistent current for ξ_K/L=5 of the odd parity system provides an opportunity to detect the Kondo screening cloud.     

电子回旋共振放电电离特性的PIC/MCC模拟

A theoretical and computational model is presented to study the ionization of the argon electron cyclotron resonance(ECR)microwave discharge using a quasi-three-dimensional electromagnetic particle-in- cell plus Monte Carlo collision method.The interaction between the charged particles and microwave fields are described by the electromagnetic mode of particle-in-cell method.The collision processes are treated with Monte Carlo method.The simulation code is the original work.The results of the particle simulation for the ECR discharge of argon gas which include the microscopic features of charged particles and the electromagnetic characteristics of the ECR discharge plasma,and also the transient phenomena have been presented.     

A three-dimensional coupled-mode model for the acoustic field in a two-dimensional waveguide with perfectly reflecting boundaries

This paper presents a three-dimensional(3D) coupled-mode model using the direct-global-matrix technique as well as Fourier synthesis. This model is a full wave, two-way three-dimensional model, and is therefore capable of providing accurate acoustic field solutions. Because the problem of sound propagation excited by a point source in an ideal wedge with perfectly reflecting boundaries is one of a few three-dimensional problems with analytical solutions, the ideal wedge problem is chosen in this work to validate the presented three-dimensional model. Numerical results show that the field results by analytical solutions and those by the presented model are in excellent agreement, indicating that the presented model can serve as a benchmark model for three-dimensional sound propagation problems involving a planar two-dimensional geometry as well as a point source.     

YBa_2Cu_3O_(7-δ)/BaHfO_3/YBa_2Cu_3O_(7-δ)复合多层涂层导体的织构外延及临界电流特性北大核心CSCD

通过脉冲激光沉积技术(PLD),在氧化物缓冲层合金基底上外延生长一系列具有相同厚度,不同BaHfO3插层数(N=0、1、2、3)的YBa_2Cu_3O_(7-δ)/BaHfO_3/YBa_2Cu_3O_(7-δ)复合多层膜.X光衍射分析表明:所有样品都是c轴取向,随着层数的增加,薄膜的面内和面外织构有一定的退化.拉曼光谱图也可以看出除了N=3的样品有微弱的a轴峰,其它样品都只有c轴峰.通过扫描电镜观察发现,BaHfO_3插层的引入没有对YBa_2Cu_3O_(7-δ)超导薄膜表面产生明显的影响,薄膜表面光滑无裂痕.通过原子力显微镜发现YBa_2Cu_3O_(7-δ)超导薄膜的粗糙度在引入单层BaHfO3插层时最大,之后随着插层数的增加而减小.感应法测试表明,BaHfO3插层数为N=1时,YBa_2Cu_3O_(7-δ)超导薄膜的临界电流密度Jc(77K,自场)达到2.86 MA/cm2.在场临界电流表明,引入较少BaHfO_3插层(N=1、2)表现相对好的磁场依赖关系.     

宽带大功率螺旋线行波管返波振荡研究

在一维场论注-波互作用理论的基础上,引入磁场对角向速度的影响,建立了二维非线性返波注-波互作用理论,模拟返波振荡.对不同空间电荷参量下起振长度的变化进行了小信号分析比较,结果与等效线路模型比较接近;对某8—18GHz行波管进行了实测比较,结果也比较一致.同时还研究了影响返波振荡起振长度的因素,提出了该管的抑制返波振荡方案.     

走进新课程理念下的高中物理课堂

去年秋，江苏省普通高中开始新课程改革，新理念、新教材催生了新课堂．通过大量的课堂观察，笔者发现各学校尽管课时进度不一，但在课堂创新的方式上都做了有益的尝试，存有共性．现总结出来，以便与广大一线物理教师共同探讨．     

激光脉冲水中传输时域展宽特性的分析计算

推导出不同距离、水质和探测参量情况下激光脉冲在水中传输的时域展宽表达式，并提出光波门选通法来代替传统的脉宽检测方法，计算结果与实际相符，对水下激光探测应用有重要的实际意义。     

高压下稳态六方Ge2Sb2Te5结构、电子和光学性质的第一性原理研究

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质.计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好.基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性.从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17 GPa和34 GPa出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合.同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20 eV内的变化情况.     

课堂笔记是牢固掌握知识的重要方法

课堂笔记是牢固掌握知识的重要方法裴晓林（石家庄铁路工程学校０５００４３）中国有句俗语叫作“好记性不如烂笔头”，其大意是说，再好的记忆力，也不如把该记录的内容写成文字，以便将来的复查．为帮助学生能更快更牢地掌握所学过的知识，本文结合自己的教学实践，主要...     

MgO晶须的物相组成和微观形貌多样性

采用适当MgO-Al比例物料,压制成型后放入气氛炉中于1500℃烧制6h,最终在样块表面得到 MgO晶须.晶须的物相组成为方镁石,显微结构研究表明多数呈细长的柱状,顶端尖锐,长约600～800μm ,长径比100～200;晶须发育的纹理特征有多种,晶须的横截面有扁六边形、正六边形、菱形和正四边形以及不规则形状等多种,能谱分析表明晶须的形貌与化学组成有关.