Electron paramagnetic resonance studies on manganite Pr0.5Sr0.5Mn1−x Ga x O3 (x=0 and 0.05)

In this paper, we present the investigations of electron paramagnetic resonance on perovskite manganite Pr_0.5Sr_0.5MnO₃ and Ga-doped Pr_0.5Sr_0.5Mn_0.95Ga_0.05O₃. The temperature dependent paramagnetic resonance spectra parameters (effective g-factor, peak-to-peak linewidth ΔH _pp and double integrated intensities) have been used to study the paramagnetic spin correlations and spin dynamics. The gradual increase of effective g-factor is attributed to the presence of orbital ordering above T _C. The model fittings of temperature dependent double integrated intensities reveal Arrhenius law is appropriate for describing Pr_0.5Sr_0.5Mn_0.95Ga_0.05O₃ instead of Pr_0.5Sr_0.5MnO₃ system. As for Pr_0.5Sr_0.5MnO₃, the broadening of linewidth with the temperature increase origins from the contribution of small polaron hopping in the PM regime. However, as for Pr_0.5Sr_0.5Mn_0.95Ga_0.05O₃, the broadening of EPR linewidth can be understood with the spin-lattice relaxation mechanism.     

New formulas for normalizing photon-added（-subtracted） two-mode squeezed thermal states

For the first time,we derive the compact forms of normalization factors for photon-added(-subtracted) two-mode squeezed thermal states by using the P-representation and the integration within an ordered product of operators(IWOP) technique.It is found that these two factors are related to the Jacobi polynomials.In addition,some new relationships for Jacobi polynomials are presented.     

A new method for removing impulse noise based on noise space characteristic

This paper proposes a new method for eliminating impulse noise. Based on the space characteristic of object and noise, three kinds of basic noise patterns are introduced to describe noise and detect noise candidates. Correspondingly, noise removal operators are presented to remove the impulse noise. Extensive experiment results have shown that the proposed method is better than some of the state-of-the-art methods.     

Surface-enhanced Raman scattering effect of gold nanoparticle arrays: The influence of annealing temperature,excitation power and array thickness

Gold nanoparticle arrays are fabricated for surface-enhanced Raman scattering (SERS) and the effect of the annealing temperature, the thickness of nanoparticle array and the exciting power on the SERS signals are investigated. The particle distribution and particle size are dense and uniform on the glass substrate when the 10 nm gold film was annealed at 250 °C and strong SERS signals for Rhodamine 6G were achieved via a 532 nm excitation with a 10 mW power. The SERS signal at 1650 cm⁻¹ is enhanced more than 10 times as compared to that of the gold film without annealing. The strong SERS behavior of gold nanoparticle arrays may broaden the SERS applications in biomedical and analytical chemistry.     

第一性原理研究硫化镉高压相变及其电子结构与弹性性质

采用第一性原理研究了CdS的六方纤锌矿(WZ), 立方闪锌矿(ZB) 和岩盐矿(RS)相在高压条件下的相稳定性、 相变点、电子结构以及弹性性能.WZ相与RS 相可以在相应的压强范围内稳定存在, 而ZB相不能稳定存在.压强大于2.18 GPa时, WZ相向RS相发生金属化相变.WZ相中S原子电负性大于Cd, 且电负性差值小于1.7, CdS的WZ相为共价晶体.高压作用下, S原子半径被强烈压缩, 有效核电荷增加, 对层外电子吸引能力提高, 电负性急剧增大, 导致S与Cd的电负性差值大于1.7, CdS的RS相以离子晶体存在. WZ相的C₄₄随压强增加呈下降趋势, 导致WZ相力学不稳定, 并向RS相转变.当压强大于2.18 GPa时, RS相C₁₁, C₁₂随压强增加而增大, 并且C₄₄保持稳定, 说明RS相具有良好的高压稳定性与力学性能. 关键词： 第一性原理 相变 电子结构 弹性性质     

基于符号分析的极大联合熵延迟时间求取方法

本文通过符号分析法求取联合熵的极大值点, 进而得到相空间重构的最佳延迟时间, 通过对几个典型的混沌系统进行数值仿真试验, 结果表明, 该方法简化了计算, 提高了效率, 能够准确快速地获得最佳延迟时间, 从而有效地重构原系统的相空间, 为混沌信号识别提供一种快速有效的途径. 关键词： 相空间重构 延迟时间 联合熵 符号分析     

超导器件在军事和工程化方面的研究及应用进展综述(上)

对超导器件在国内外军事领域上的研究和应用进展进行了综述,分析了目前我国超导器件研制以及在武器装备上应用所面临的主要问题,提出了解决的办法,并重点介绍了中国电子科技集团公司第16所以及中电集团低温电子技术研发中心的研究成果,并提出了加快我国超导器件在武器装备上应用的建议。     

Effects of microstructure on the temperature dependence of relative initial permeability of NiCuZn ferrites

In the present work, ferrites with compositions of (Ni_0.27Zn_0.64Cu_x)Fe_1.98O₄ (x=0.1, 0.2) were prepared by conventional ceramic methods. The relationship between the microstructure and the temperature dependence of relative initial permeability was investigated. It was found that intergranular pores in the ferrites generate large demagnetizing fields, reducing the temperature dependence of the effective anisotropy field H_eff, and decreasing the temperature dependence of the relative initial permeability accordingly. However, intragranular pores pin the movement of domain walls. Compared with the permeability induced by domain wall motion, the permeability that resulted from the spin rotation is more sensitive to temperature. As a result, the relative initial permeability of ferrites becomes more sensitive to temperature with increasing micropores within grains.     

平行共轴线圈的磁场特征研究与实验设计

通过计算机及相关的传感器和数据采集接口辅助,研究了平行共轴双线圈间距分别为0.5R,R,1.5R时,轴线方向磁场强度的分布规律及特征.从平行共轴双线圈间距为R的亥姆霍兹线圈所形成的均匀磁场出发,结合理论推导,自己设计并组装了三线圈实验装置,实现了平行共轴三线圈均匀磁场区域扩大、强度增强的实验设计,在一定程度上弥补了传统亥姆霍兹线圈磁场测量的不足并有助于对其深入的理解和研究.     

纵向带状裂隙形貌的逆时偏移超声成像

传统的工业超声成像方法通常只能确定缺陷的位置与横向尺寸,无法获得缺陷的形貌信息.一些特殊的缺陷,如纵向裂纹,是典型的例子.基于多阵元技术,开展了固体介质缺陷逆时偏移超声成像方法的数值与实验研究.针对铝块平底纵裂纹及内部纵裂纹两种传统方法无法有效成像的缺陷,首先开展了单分量逆时偏移成像方法研究,给出了基于数值仿真的逆时偏移成像结果以及基于多阵元超声成像实验系统实验测试的逆时偏移成像结果.进一步开展了基于多分量位移检测与转换横波分离的逆时偏移成像方法研究,并提出了基于新型多分量激光干涉仪进行检测的思路.数值仿真结果证实了多分量逆时偏移图像重建结果可以克服单分量方式的缺点,得到明显优于单分量检测时的图像.