Zr掺杂对MgB2超导微观结构和超导电性的影响

将Mg粉、Zr粉和B粉按比例混合获得Mg1-xZrxB2(x=5%10%和20%),压制成型后,在流通氩气的条件下于800℃烧结2h.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)分析烧结后样品的显微结构和化学组成,采用差热分析(DTA)观察Zr掺杂对MgB2分解温度的影响,并用物性测试仪(PPMS)测试样品的超...     

Electron-phonon coupling in cuprate and iron-based superconductors revealed by Raman scattering

Electron-phonon coupling （EPC） in cuprate and iron-based superconducting systems, as revealed by Raman scat- tering, is briefly reviewed. We introduce how to extract the coupling information through phonon lineshape. Then we discuss the strength of EPC in different high-temperature superconductor （HTSC） systems and possible factors affecting the strength. A comparative study between Raman phonon theories and experiments allows us to gain insight into some crucial electronic properties, especially superconductivity. Finally, we summarize and compare EPC in the two existing HTSC systems, and discuss what role it may play in the HTSC.     

雷达武器装备联合试验技术研究进展综述

针对雷达武器装备联合试验需求,详细梳理了国外雷达武器装备联合试验理论方法以及联合试验体系架构的发展历程.在此基础上,分析了国内在雷达武器装备联合试验理论方法以及体系架构方面的研究现状.并通过对比美军分布式联合试验体系架构平台TENA与国内典型联合试验支撑平台JoSim,总结了国内联合试验平台在中间件、对象模型以及资源库...     

Raman scattering studies on the collapsed phase of CaCo_2As_2

In this work,Raman scattering measurements have been performed on the collapsed phase CaCo_2As_2 crystals.At least 8 Raman modes were observed at room temperature though CaCo_2As_2 is structurally similar to other 122 compounds like BaFe_2As_2.Two Raman modes are assigned to the intrinsic A_(1g)and B_(1g)of this material system respectively.The other ones are considered to originate from the local vibrations relevant to cobalt vacancies.Careful polarized measurements allow us to clearly resolve the four-fold symmetry of the B_(1g)mode,which put strong constraints on possible point group symmetries of the system with Co vacancies.The temperature-dependent measurements demonstrate that the anomalies in both frequency and width of the B_(1g)mode occur around Neel temperature T_N.The anomalies are considered to be related to the gap opening near the magnetic transition.The study may shed light on the structural and magnetic changes and their correlations with superconductivity in 122 systems.     

Strain-modulated excitonic gaps in mono-and bi-layer MoSe_2

Photoluminescence(PL) and Raman spectra under uniaxial strain were measured in mono- and bi-layer MoSe_2 to comparatively investigate the evolution of excitonic gaps and Raman phonons with strain. We observed that the strain dependence of excitonic gaps shows a nearly linear behavior in both flakes. One percent of strain increase gives a reduction of ~42 meV(~35 me V) in A-exciton gap in monolayer(bilayer) MoSe_2. The PL width remains little changed in monolayer MoSe_2 while it increases rapidly with strain in the bilayer case. We have made detailed discussions on the observed strain-modulated results and compared the difference between monolayer and bilayer cases. The hybridization between 4d orbits of Mo and 4p orbits of Se, which is controlled by the Se–Mo–Se bond angle under strain, can be employed to consistently explain the observations. The study may shed light into exciton physics in few-layer MoSe_2 and provides a basis for their applications.     

块体MgB_2中Zr元素对其致密性和微观结构的影响

将Mg粉、Zr粉和B粉按比例混合获得MgxZr1-xB2(x=5%、10%和20%),压制成型后,在流通氩气的条件下于800℃烧结2h。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)分析显微结构和化学组成,并且对烧结后的样品进行差热分析DSC。结果表明,适量的Zr掺杂使得MgB2的平均晶粒尺寸变小,晶界面积增加和晶粒连接性改善,从而获得致密性较高的MgB2超导体。     

关联电子体系中电子和磁的拉曼散射

周期结构的晶格振动和分子的振动或转动谱,可以看作材料的特征指纹,拉曼散射正是探测这些振动的非常灵敏和有效的技术,因此它已经被广泛地应用到基础研究和工业生产的各个方面.而原则上,通过固体中的自由载流子或自旋与光的非弹性散射过程,人们也可以获得关于电子和磁激发的重要信息.文章对电子和磁的拉曼散射基本概念作了简要介绍,并对一些关联电子体系中的拉曼实验作了简要综述.特别是在非常规超导中,拉曼散射在确定超导能隙的大小和各向异性以及配对对称性等方面发挥了独特的作用.     

基于北斗卫星导航系统的高精度授时技术与海事服务结合的探讨

北斗卫星导航系统是我国自行研发的卫星导航系统,其卫星授时服务精度可达20ns,处于世界领先技术水平。在海事服务中引入北斗技术可有效提高公共服务能力和质量,优化海事服务整体效率,进一步提升海事服务水平。本文从北斗系统授时原理入手,探讨其与海事服务中航标管理和安全搜救业务结合的可行性。     

Raman scattering under extreme conditions

Raman scattering is a versatile and powerful technique and has been widely used in modern scientific research and vast industrial applications. It is one of the fundamental experimental techniques in condensed matter physics, since it can sensitively probe the basic elementary excitations in solids like electron, phonon, magnon, etc. The application of extreme conditions(low temperature, high magnetic field, high pressure, etc.) to Raman scattering, will push its capability up to an unprecedented level, because this enables us to look into new quantum phases driven by extreme conditions, trace the evolution of the excitations and their coupling, and hence uncover the underlying physics. This review contains two topics.In the first part, we will introduce the Raman facility under extreme conditions, belonging to the optical spectroscopy station of Synergetic Extreme Condition User Facilities(SECUF), with emphasis on the system design and the capability the facility can provide. Then in the second part we will focus on the applications of Raman scattering under extreme conditions to a variety of condensed matter systems such as superconductors, correlated electron systems, charge density waves(CDW) materials, etc. Finally, as a rapidly developing technique, time-resolved Raman scattering will be highlighted here.     

测量噪声相关线性系统异类传感器航迹融合

研究了异类传感器航迹融合问题。在测量噪声相关的条件下,利用线性无偏最小方差估计的基本理论,通过对异类传感器的状态估计采用顺序滤波的方法,得到了相关测量噪声线性系统异类传感器测量融合算法和状态矢量融合算法。计算机数字仿真结果表明,由于考虑了测量噪声之间的相关性,该算法比噪声不相关融合算法具有更好的跟踪性能,航迹跟踪的精度得到了改善。