Is the Near-Earth Current Sheet Prior to Reconnection Unstable to Tearing Mode？

The tearing mode instability plays a key role in the triggering process of reconnection. The triggering collisionless tearing mode instability has been theoretically and numerically analyzed by many researchers. However, due to the difficulty in obtaining the observational wave number, it is still unknown whether the tearing mode instability can be excited in an actual plasma sheet prior to reconnection onset. Using the data from four Cluster satellites prior to a magnetospheric reconnection event on 13 September 2002, we utilized the wave telescope technique to obtain the wave number which corresponds to the peak of power spectral density. The wavelength is about 18RE and is consistent with previous theoretic and numerical results. After substituting the wave vector and other necessary parameters of the observed current sheet into the triggering condition of tearing mode instability, we find that the near-Earth current sheet prior to reconnection is unstable to tearing mode.     

Morlet小波在确定局部周期中的应用

本文通过引入改进的Morlet小波变换核函数,得到了等幅值的Morlet小波变换(MMWT)和功率谱(MMPS).理论及实验均表明,MMPS不但能够准确的确定信号的局部周期,而且使相同振幅(强度)的谐波产生了相同大小的MMPS,弥补了MPS的不足.对于MMWT还给出了相应的Morlet小波变换尺度与频率转化公式.     

γ激光——未来新一代的激光器

 激光技术是二十世纪六十年代最重要的科学技术成就之一.它的诞生使人们深化了对于光的认识,并使光学同其它技术学科发生了联系,开拓了光学应用极其广阔的前景.历史的回顾早在五十年代初期美国物理学家汤斯(C.Tcw-nes)构思了利用二能态分子制造激光器的想法,拟出了设计方案,并在哥伦比亚大学辐射实验室的报告会上作了介绍,但没能引起反响.直到1954年第一台微波激射器研制成功后,才受到人们的重视.     

对于自共振激光加速器中轴向场问题的讨论

从洛仑兹力方程的旋量形式出发，讨论了电磁场中电荷运动的轴向电场和轴向磁场问题以及平面波的脉冲和Larmor功率。这些问题是研究自共振激光加速器的基础。From the spinorial form of the Lorentz force equation, the problems about axial electric field and axial magnetic field of charge motion in electromagnetic fields, as well as plane wave pulse and Larmor power have been discussed in this paper. These problems are the foundation of studying the autoresonance laser accelerator (ALA).     

Constructive characterizations of （γp, γ）- and （γp, γpr）-trees

Let G =(V,E) be a graph without isolated vertices.A set S  V is a domination set of G if every vertex in V -S is adjacent to a vertex in S,that is N[S] = V .The domination number of G,denoted by γ(G),is the minimum cardinality of a domination set of G.A set S  V is a paired-domination set of G if S is a domination set of G and the induced subgraph G[S]has a perfect matching.The paired-domination number,denoted by γpr(G),is defined to be the minimum cardinality of a paired-domination set S in G.A subset S  V is a power domination set of G if all vertices of V can be observed recursively by the following rules:(i) all vertices in N[S] are observed initially,and(ii) if an observed vertex u has all neighbors observed except one neighbor v,then v is observed(by u).The power domination number,denoted by γp(G),is the minimum cardinality of a power domination set of G.In this paper,the constructive characterizations for trees with γp = γ and γpr = γp are provided respectively.     

用Zn/F离子先后注入和热退火法实现ZnO量子点的可控生长

将Zn/F离子先后注入到非晶二氧化硅中并分别在400,600,700 ℃下进行了退火.用光学吸收谱、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)对退火的样品进行分析,发现在600 ℃退火后ZnO量子点已经形成.二次离子质谱仪(SIMS)测试发现在溅射时间为2 s时Si,Zn元素同时出现,说明没有在衬底的表面形成ZnO薄膜.从原子力显微镜(AFM)图像看到有少量的颗粒被蒸发到衬底的表面,说明在衬底的内部形成了ZnO量子点.F离子注入的作用为在衬底的内部形成ZnO量子点提供了O2分子.