多层介质膜脉宽压缩光栅的严格矢量分析

用于展宽和压缩激光脉冲的多层膜脉宽压缩光栅是由多层介质高反膜和位于其顶层的浮雕光栅构成。以设计的高反射多层膜为基础,利用傅里叶模式理论分析了其衍射场分布,给出了TE波自准直角入射的使用条件下,多层介质膜脉宽压缩光栅衍射效率的表达式。以-1级衍射效率为评价函数,分别讨论了HfO2和SiO2为顶层材料时,多层膜脉宽压缩光栅-1级衍射效率高于0.95的光栅结构参量范围。结果表明,在该条件下,选择HfO2为顶层材料时,光栅结构参量有较大的取值范围。给出了优化的光栅结构参量,并分析了光栅制作误差及其使用条件的宽容度,对光栅制作工艺和使用具有一定的指导意义。     

五角棱镜光束转向波前误差的分析与检测

从分析五角棱镜的角度制造误差产生的光学平行差入手,建立起五角棱镜的光输出平面波前与运动误差和角度制造误差产生的扫描激光束转向的波前改变量之间的关系.采用渥拉斯顿棱镜型双频激光干涉仪实时测量五角棱镜的运动误差,即可计算出扫描激光束转向的波前误差,以便在大型望远系统波前测量时对此误差加以修正.     

Nonwetting of He and dilute He–He mixtures on Cs

For pure ⁴He on Cs a nonwet phase exists below ≈2 K but for dilute ³He–⁴He mixtures the wetting is reentrant. Measurements of the contact angle with dilute mixtures of liquid helium on Cs can be explained in detail in terms of ³He states together with ripplons at the Cs–He mixture interface, but it is impossible to account for the lower wetting temperatures or contact angles with only ³He states or ripplons. We discuss the influence of surface roughness of the Cs on the contribution of interface excitations to the free energy and suggest that the variety of contact angles found with different samples of Cs is due mainly to their degree of roughness.     

热变形谐振腔的激光模式理论分析

 应用微扰理论,对微热变形腔的激光模式进行了理论计算与分析;给出了激光模式之间的耦合以及等效光束发散角与镜面变形量之间的关系。结果表明：镜面中心处热变形量越大,模式之间的耦合越强,激光腔模式发生畸变就越严重;当镜面中心处热变形量为0.5λ时,基模TEM₀的中心光强将下降50%,其等效光束发散角将增大到镜面无变形时的2倍。     

昆虫自由飞行时翅膀攻角的光学测量

昆虫运动空气动力学研究需要测量昆虫运动的多种参数。其中 ,翅膀攻角是主要参数 ,是流体分析时主要的边界条件之一。由于昆虫的运动参数的测量同一般的测量相比具有一些特殊要求 ,它要求一定是非接触测量 ,因此成功的测量方法大都集中在光学测量方法上。本文以近年来有关昆虫自由飞行的实验为基础 ,着重介绍几种比较有特色的翅膀攻角的光学测量方法     

Artifact Halo Reduction in Phase Contrast Microscopy Using Apodization

A new phase contrast microscopy technique for halo reduction is proposed. This technique is based on an apodization method combined with the Zernike phase contrast method. Although it has been a difficult theoretical problem, the proposed technique achieves halo reduction by considering angles of diffraction and phase differences. The technique utilizes an apodized phase plate consisting of a quarter wave phase shift ring with a 25% transmittance, and a pair of adjacent rings, which have 50% transmittance. This element is placed at the back focal plane of the objective. The result is startling, halo reduced images of phase objects providing enhanced inner details.     

APPLICATION OF TIME-TEMPERATURE SUPERPOSITION PRINCIPLE TO EVALUATION OF SCATTERING INTENSITY EVOLUTION IN PHASE SEPARATION FOR PMMA/SAN BLENDS

Spinodal phase separation behavior of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile)(PMMA/SAN)blends was investigated by the time-resolved small angle light scattering (SALS) technique. It was found that the influence oftemperature on the scattering intensity evolution followed the time-temperature superposition principle. The relationshipbetween temperature and the relaxation time of scattering intensity I(t) can be well described by the Williams-Landel-Ferry(WLF) function.     

X-ray photoelectron spectroscopy as a tool for studies of the surface layer of microspheres. The case of polystyrene and poly(styrene–acrolein) microspheres with attached human serum albumin

The application of X-ray photoelectron spectroscopy (XPS) for studies of surface layers of objects with spherical shape was investigated using as examples polystyrene and poly(styrene–acrolein) microspheres with attached human serum albumin (HSA). The amounts of immobilized protein were determined by the standard biochemical Lowry method and by XPS, using the intensity of the N1s signals of HSA as a basis for evaluation. The XPS data were treated by taking into account the spherical shape of the particles analyzed (variable take-off angle of ejected electrons). The best agreement between the results of the biochemical and XPS determinations was found assuming that for the average particle the takeoff angle varies from 0° to 72.7°. This reflects the fact that in the multilayer arrangement of particles, placed onto the support of the XPS apparatus, the particles from the upper layer partially screen the edges of the particles in the layer below. Received: 23 November 1999 Accepted: 16 March 2000     

手性磺内酰胺双羟基衍生物的合成及晶体结构

N 己烯酰基手性三环磺内酰胺经不对称双羟基化获得二醇 4和 5 ,再进一步转变为对应的二甲基缩酮 6和 7(6 7∶33) ,总产率 81%。经晶体结构分析 ,6的构型为 (Sc(10 ) ,Rc(11) ) ,C =O与SO2 为反式构型 ,其S(1) N(1) C(9) O(3)的二面角为 175 .91°。 7为 (Rc(10 ) ,Sc(11) ) ,C =O与SO2 为顺式构型 ,其对应二面角为 4.6 9°     

光诱导聚合蒙脱土插层纳米复合材料的研究

用两种光聚合法研究了蒙脱土插层复合材料的制备.用小角X光衍射技术对产物内蒙脱土的结构进行表征,结果表明,蒙脱土经改性后能很好地使聚合单体及预聚物插入黏土层内并在光照下"就地”聚合生成光聚合复合材料.对光聚合法制备蒙脱土纳米复合材料的优缺点进行了初步讨论.