超二代微光像增强器Na2KSb(Cs)多碱光电阴极荧光谱研究

利用785 nm波长激光作为激发源,测量了超二代微光像增强器Na2KSb(Cs)多碱光电阴极的荧光谱.试验中发现该荧光谱不是一条光滑的高斯型曲线,而是一条在高斯型荧光谱上叠加了一定频率间隔小锯齿峰的曲线.经实验验证和理论分析证明该荧光谱上的小锯齿峰是一种干涉条纹,与超二代微光像增强器的结构有关.干涉条纹之间的间距与相邻两干涉峰波长的乘积成正比,与超二代微光像增强器的近贴聚焦距离成反比.干涉条纹调制度大小与Na2KSb(Cs)多碱光电阴极的厚度成反比.通过测量超二代微光像增强器Na2KSb(Cs)多碱光电阴极荧光谱上两相邻干涉条纹的间距和调制度,就可以测量或比较出不同超二代微光像增强器Na2KSb(Cs)多碱光电阴极的膜厚、近贴聚焦距离.研究结果对提高超二代微光像增强器阴极灵敏度和分辨力提供了一个有效的分析手段.     

中国城乡居民养老制度可持续性的精算研究

围绕我国城乡居民养老保险体系可持续化问题,从中国实际出发,分层次、多角度的分析了当前我国的养老保险制度.首先,针对中国养老保险基金问题,基于当前养老保险体制,分别从三个层次入手,建立中国城乡居民养老保险基金收支模型;其次,基于养老制度的可持续性,建立了养老金缺口模型,并对养老金缺口的未来趋势进行了合理预测;最后,对所建立的模型进行了评价及推广.     

空气ESD辐射电磁场和放电间隙区分布研究

在固定放电空气间隙条件,利用电流靶和半圆环天线对空气静电放电(ESD)的辐射电磁场进行了探测和记录,根据空气ESD辐射电磁场的特征研究了空气ESD的放电特性和放电间隙区分布规律。提出了空气ESD存在"增长间隙区"、"跌落间隙区"、"平坦间隙区"和"零放电间隙区"4个放电间隙区,放电间隙区的分布主要与放电电压的大小相关,且在高电压时各放电间隙区分布更明显;一定电极接近速度下的空气ESD与一定放电间隙区的空气ESD相对应。     

基于潜在语义分析和相关反馈的图像检索方法

为了解决传统的CBIR系统中存在的"语义鸿沟"问题,提出一种基于潜在语义索引技术(LSI)和相关反馈技术的图像检索方法.在进行图像检索时,先在HSV空间下提取颜色直方图作为底层视觉特征进行图像检索,然后引入潜在语义索引技术试图将底层特征赋予更高层次的语义含义;并且结合相关反馈技术,通过与用户交互进一步提高检索精度.实验...     

二维金属型光子晶体带隙研究

考虑金属的色散特性,运用时域有限差分方法计算了分别由Ag、Al两种金属构成的三角晶格二维金属型光子晶体的带隙结构,得出了带隙结构与填充率的关系曲线.以Ag填充率为0.6为例,三角晶格的第一带隙归一化频率的上限为0.90,第二带隙的范围为1.24～1.41;正方晶格第一带隙归一化频率的上限为0.70,第二带隙的范围为0....     

用于红外探测的短周期InAs/GaSb超晶格材料的生长

用金属有机物化学气相淀积法(MOCVD)在GaSb衬底上生长InAs/GaSb超晶格,探索了最佳的生长厚度,优化了各种生长参数,并且分析了源流量控制的重要性.得到的超晶格材料的光致发光(PL)谱、X射线双晶衍射图以及表面形貌图表明,生长的超晶格材料可以响应10μm的长波,且具有良好的表面形貌和外延层质量.     

康普顿散射对非磁化等离子体光子晶体禁带密度温度特性的影响

应用多光子非线性康普顿(Compton)散射模型和有限时域差分法,研究了多光子非线性Compton散射对非磁化等离子体光子晶体光子禁带密度和温度特性的影响,提出了将入射光、Compton散射光、等离子体的温度和密度作为调控光子禁带的新机制。研究结果表明,改变温度和等离子体密度分布可实现对等离子体光子晶体的光子禁带拓展,而Compton散射减小了这种拓展效应。Compton散射可使光子禁带向高频方向比散射前有较大的移动,能更好地实现等离子体光子晶体的高通滤波特性。     

Synthesis,Structure, and Property of a Three-dimensional Channel Quaternary Compound： Cs0.75（6）Er4.43（5）In3.32（6）S12

A new quaternary rare-earth sulfide, Cs0.75（6）Er443（5）In3.32（6）S12 （1）, is discovered by high temperature solid state reactions with a slight excess of CsCI flux. The structure is characterized by single-crystal X-ray diffraction data, while crystallizes in hexagonal space group P63/m （No. 176） with a = 12.0329（6）, c = 3.8693（5）A, V= 485.18（7） A3, Z = 1, Mr = 1606.57, Dc = 5.499 g/cm3,μ = 25.457 mm-1, F（000） = 752, the final R = 0.0337 and wR = 0.0904 for 328 observed reflections with I 〉 2σ（I）. Its structure features a three-dimensional framework with hexagonal channels that are centered by Cs cations. Such channels are formed by double chains of edge-sharing M（1）S6 （M（1） = Er（1）/In（1）） octahedra and single chains of Er（2）S6 triprism interconnected by corner-sharing. The syntheses, single-crystal analyses, optical band gap and magnetic property are reported.     

New Polymers for Optimizing Organic Photovoltaic Cell Performances

The performance of an organic solar cell critically depends on the materials used in the active layer. Desirable characteristics of active layer materials include an intense optical absorption covering broad range of the solar spectrum to maximize photon capture, the ability to effectively separate charges upon photo‐excitation, high charge mobility to allow efficient charge transport to the electrodes, and suitable HOMO and LUMO levels to ensure a high device voltage. In order to optimize these properties simultaneously, we have designed and synthesized conjugated polymers containing alternating electron‐donating and electron‐accepting units. Based on one of the low band gap polymers we designed and synthesized previously, poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)], we carried out both side chain and main chain modifications in order to improve performance even further. By incorporating fluorene repeating units into the main chain, it is possible to adjust the absorption characteristics of the polymers while maintaining a desirable HOMO level and good charge carrier mobility. The solubility profile of the polymer can be adjusted by modifying the side chains, and soluble polymer with mobility as high as 7×10^?2 cm²/Vs is realized when a combination of 2‐ethylhexy and hexyl groups are used as side chains. These polymers should be promising candidates for high performance solar cells according to a recently published model (3).