内增强变象管相机中的干扰研究

本文讨论了带快门的内增强变象管相机的快门电路及其对扫描电路的干扰,干扰信号对相机性能指标的影响及解决方法。     

高空核爆炸碎片云早期扩展规律研究

利用磁流体力学理论建立了描述碎片云运动的壳层模型,采用该模型模拟了美国Starfish高空核爆炸试验碎片云的运动参数,通过与文献模拟结果的比对,验证了所建模型的正确性.针对典型大当量和小当量核爆的不同,重点模拟了千吨级利百万吨级核武器在100,400和1500 km高度爆炸时碎片云运动扩展情况,分析了当量的差异引起的扩展规律的不同.结果表明:高空核爆炸时不同爆炸条件和大气环境对碎片云的扩展规律有着显著的影响,不同方向上碎片云的环境参数差异明显.     

Magnetically tunable silicon-ferrite photonic crystals for terahertz circulator

The gyromagnetic properties of ferrite materials and the nonreciprocal property of a silicon-ferrite photonic crystal cavity are investigated in the terahertz region. Through the structure optimization and analysis of defect mode coupling, we design a magnetically tunable circulator, of which central operating frequency can be tuned from 180 to 205 GHz and the maximum isolation is 65.2 dB. Moreover, the further study shows that the gyrotropy, dispersion, and ferromagnetic loss of ferrite materials under the different external magnetic fields greatly affect the transmission and isolation property of this device. This circulator is flexible to realize functions of controllable splitting, routing, filtering and isolation by changing the external magnetic field for the THz applications.     

Preparation, magnetic and electromagnetic properties of polyaniline/strontium ferrite/multiwalled carbon nanotubes composite

Strontium ferrite particles were firstly prepared by sol-gel method and self-propagating synthesis, and then the polyaniline/strontium ferrite/multiwalled carbon nanotubes composites were synthesized through in situ polymerization approach. Structure, morphology and properties of the composite were characterized by various instruments. XRD analysis shows that the output of PANI increases with the increase of the content of MWCNTs, due to the large surface area of MWCNTs. Because of the coating of PANI, the outer diameter of MWCNTs increases from 10 nm to 20-40 nm. The electrical conductivity of the composites increases with the amount increase of MWCNTs and reaches 7.2196 S/cm in the presence of 2 g MWCNTs. The coercive force of the composites prepared with 2 g MWCNTs is 7457.17 Oe, which is much bigger than that of SrFe₁₂O₁₉ particles 6145.6 Oe, however, both the saturation magnetization and the remanent magnetization of the composite become much smaller than those of SrFe₁₂O₁₉ particles. The electromagnetic properties of the composite are excellent in the frequency range of 2-18 GHz, which mainly depend on the dielectric loss in the range of 2-9 GHz, and mainly on the magnetic loss in the range of 9-18 GHz.     

Ar adsorptions on Al （111） and Ir （111） surfaces： a first-principles study

We investigate the adsorptions of Ar on Al (111) and Ir (111) surfaces at the four high symmetry sites,i.e.,top,bridge,fcc-and hcp-hollow sites at the coverage of 0.25 monolayer (ML) using the density functional theory within the generalized gradient approximation of Perdew,Burke and Ernzerhof functions.The geometric structures,the binding energies,the electronic properties of argon atoms adsorbed on Al (111) and Ir (111) surfaces,the difference in electron density between on the Al (111) surface and on the Ir (111) surface and the total density of states are calculated.Our studies indicate that the most stable adsorption site of Ar on the Al (111) surface is found to be the fcc-hollow site for the (2 × 2) structure.The corresponding binding energy of an argon atom at this site is 0.538 eV/Ar atom at a coverage of 0.25 ML.For the Ar adsorption on Ir (111) surface at the same coverage,the most favourable site is the hcp-hollow site,with a corresponding binding energy of 0.493 eV.The total density of states (TDOS) is analysed for Ar adsorption on Al (111) surface and it is concluded that the adsorption behaviour is dominated by the interaction between 3s,3p orbits of Ar atom and the 3p orbit of the base Al metal and the formation of sp hybrid orbital.For Ar adsorption on Ir (111) surface,the conclusion is that the main interaction in the process of Ar adsorption on Ir (111) surface comes from the 3s and 3p orbits of argon atom and 5d orbit of Ir atom.     

空心微球结构Au/Ag合金泡沫块体的制备

将平均晶粒尺寸为4.6 nm的金粒子通过静电作用粘附于聚苯乙烯（PS）微球表面用于化学镀,化学镀金后PS表面的金沉积层几乎达到完全包覆,厚度70~90 nm;在Au/PS表面进行化学镀银,沉积的银颗粒堆积紧密,颗粒大小较先前沉积的金颗粒大,镀覆层厚度增厚至200~400 nm;模板去除后,获得了完全自支撑的Au40Ag60空心微球结构的圆柱状泡沫材料。制备的金银合金泡沫由直径约10 m的空心球壳组成,圆柱体直径约5 mm,密度约1.2 g/cm3。     

1064 nm激光对中性密度滤光片的损伤机理研究

中性密度滤光片的典型结构是在K9玻璃上镀金属膜,来实现对激光的有效吸收.由于损伤阈值较低,严重限制了其在高能激光系统中的应用.实验研究了较高激光能量密度下滤光片的损伤形貌和损伤机理.损伤形貌的变化特征是:随着激光能量密度的增加,滤光片先出现损伤点,后以损伤点为中心产生裂纹,且裂纹长度逐渐变长,最终连接成线状和块状,导致大面积的薄膜脱落.建立了缺陷吸收激光能量升温致中性密度滤光片表面薄膜损伤的模型,计算了薄膜表面的温度和应力分布,讨论了薄膜表面不均匀温升造成的径向、环向和轴向热应力分布.理论分析显示:环向应力是造成薄膜沿径向产生裂纹的主要原因.当激光能量密度大于约2.2 J/cm²,杂质粒子半径大于140 nm且相邻杂质粒子之间的距离小于10 μ m时,裂纹才能大量连接起来引起薄膜的大面积脱落.     

爆炸电子发射初期阴极表面电场的研究

为了研究二极管爆炸电子发射初始阶段阴极表面复杂的物理现象及规律, 建立了由场致电子发射阴极构成的一维平板真空二极管物理模型,通过自行编程数值求解泊松方程, 考虑了发射出的电子对阴极表面电场的非线性影响,自洽模拟得到了阴极表面电场随时间的变化情况. 模拟结果表明,爆炸电子发射初期,阴极表面电场随时间的增加而呈现出不断振荡的规律, 且振荡幅度越来越小,最终到达一个稳态的值,二极管两极板之间的外加电场越大, 阴极表面稳态电场的绝对值越大;电场增强系数越大,阴极表面稳态电场的绝对值越大. 在整个时间演变过程中,阴极表面的实际电场强度决定着阴极发射的电流密度大小, 反过来阴极发射的电流密度又会影响到阴极表面的电场.     

纳米分辨相干反斯托克斯拉曼散射显微成像

采用附加探测光声子耗尽法来实现超衍射极限相干反斯托克斯拉曼散射显微成像. 此方法引入一束环形分布的附加探测光来消耗点扩展函数周边的相干声子, 实现点扩展函数的改造, 从而达到超越衍射极限的空间分辨率. 为了获得更高的空间分辨率和更佳的相位匹配条件, 通常需采用高数值孔径物镜对抽运光、斯托克斯光和探测光进行聚焦, 此时标量衍射理论不再成立. 基于矢量衍射理论, 分析了线偏振光、圆偏振光先后经过螺旋相位片和高数值孔径物镜后的光强分布, 结果表明: 圆偏振光在高数值孔径物镜后焦平面的光强分布呈中心对称状, 较线偏振环形光更适合作为附加探测光. 此外, 采用全量子理论分析了附加探测光声子耗尽法. 结果表明: 当附加探测光与探测光强度比为80时, 成像系统的横向空间分辨率可以达到45 nm; 继续提高附加探测光强度, 空间分辨将进一步提高.