用于高速摄影变象管的软X射线光电阴极

光阴极由衬底(包括介质阴极的导电基底)和光电发射膜构成。采用了聚丙烯、Formvar和Paylene三种有机薄膜作阴极衬底。建立了这些薄膜的制备技术。用一台自制的软X射线单色仪在277—7469ev光子能量范围内测量了这些薄膜的透过率。 研究了CsI、CsBr、Au和MgF₂四种光电阴极的光电发射特性和光电发射与阴极厚度的关系,找出了最佳阴极厚度。用软X射线单色仪在277—7469ev光子能量范围内测量了最佳厚度阴极的绝对量子效率,四种阴极最大值分别为4.50、2.90、0.25和0.12。我们还在同一阴极衬底上分区制备了四种阴极,在变象管荧光屏上比较其亮度,结果和测量的一致。 用LAB5型表面分析仪对CsI和Au阴极的光电子初能量分布作了测量,CsI阴极光电子初能量分布半高宽远小于Au。因此CsI是适用于高速摄影变象管比较理想的软X射线光电阴极。     

A.第十九届国际高速摄影和光子学会议概况

本文对第19届国际高速摄影与光子学会议做了简介,主要谈到了光机式相机、高速视频技术、全息和干涉计量。     

Interactive vortex shedding from a pair of circular cylinders in a transverse arrangement

Interactive vortex shedding in the multiply connected domain formed by a pair of circular cylinders is analysed by the FEM–FDM blending technique. The vorticity–streamfunction formulation is used to solve the incompressible Navier–Stokes equations at Re = 100, with the time-dependent wall streamfunctions determined from the pressure constraint condition and the far-field streamfunctions from the integral series formula developed earlier by the authors. The standard Galerkin finite element method is used in the relatively small FEM subdomain and the finite difference method based on the general co-ordinate system in the rest of the flow domain. Symmetric, antisymmetric and asymmetric wake patterns are obtained confirming the earlier experimental findings. The bistable nature of the asymmetric vortex shedding as well as the intermittent drifting from one status to the other between symmetric and antisymmetric wake patterns are reported.     

A Synthesis of Thalidomide

A synthesis of racemic thalidomide ( 1 ) was described and the important formal [3+3] cycloaddition strategy was a keystep. The total yield of thalidomide ( 1 ) was 18% in five steps from known 3 .     

Fluid forces on a square cylinder in oscillating flows with non‐zero‐mean velocities

The unsteady forces on a square cylinder in sinusoidally oscillating flows with non‐zero‐mean velocities are investigated numerically by using a weakly compressible‐flow method with three‐dimensional large eddy simulations. The major parameters in the analysis are Keulegan–Carpenter number (KC) and the ratio between the amplitude and the mean velocities of the approaching flow (A_R). By varying the values of KC and A_R the resulting drag and lift of the cylinders are analyzed systematically at two selected approaching‐flow attack angles (0 and 22.5^°). In the case of the non‐zero attack angle, results show that both the drag and lift histories can be adequately described by Morison equations. However, Morison equations fail to correctly describing the lift history as the attack angle is zero. In addition, when the ratio of A_R/KC is near the Strouhal number of the bluff‐body flow, the resulting drag is promoted due to the occurrence of resonance. Based on the results of systematic analyses, finally, the mean and inertia force coefficients at the two selected attack angles are presented as functions of KC and A_R based on the Morison relationships. Copyright © 2008 John Wiley & Sons, Ltd.     

Simple Method in Diagnosing Cancer Cells by a Novel Fluorescence Probe BMVC

Different cellular accumulations with distinct fluorescence properties of BMVC in cancer cells from normal cells allow us to establish a simple and economic method for the diagnosis of cancer cells. With using a light emitting diode to excite the BMVC molecule, microarray fluorescence analysis of a cell‐based glass chip provides an easy method towards the detection of a limited number of cancer cells.     

一种新型面阵CCD航天立体摄影测量光学系统

采用一台大面阵CCD和广角摄影物镜的组合，研制成功一种新型的单面阵CCD航天立体摄影测量系统.该系统焦距为23.3 mm;视场角为40°;在空间分辨率为36 lp/mm时，MTF均值达到0.8以上;光谱适应范围为0.5 μm~0.75 μm.和国内外常用的三线阵CCD遥感立体测量相机相比，本系统结构更简单、体积更小，重量更轻，更加适用于航天遥感应用环境.     

The effects of melt annealing and counterpart's molecular weight on the thermal properties and phase morphology of poly(L‐lactide)‐based blends

The thermal properties and phase morphology of poly(L ‐lactide) (PLLA)‐based blends have been studied. Two poly(ethylene glycol)s (PEGs) with molecular weight (MW) of about 1,500 (1.5k) g/mol and 2,000,000 (2M) g/mol, respectively, were used as counterparts. The blends were annealed at a preselected temperature of 200 °C for either 2 min or 30 min before the characterizations. Both PEGs were determined to enhance the crystallizability of PLLA. After a 2‐min process of annealing, the PEG(1.5k)'s crystallization efficiency on PLLA has been noted to increase with the increase of its content. Conversely, PEG(2M)'s crystallization efficiency declined with the increase of its content. Extending the annealing time has evidently changed the PEGs' crystallization effect on PLLA. Moreover, the PEG(1.5k) has, to a greater extent, brought about the depression of PLLA's melting temperature by increasing its content, and this depression increased with the annealing time. The blends exhibited lower thermal stability than those of the parent components, particularly for the PEG(1.5k)‐included system with a higher PEG content. Regardless of the annealing time, the PEG(1.5k)‐included blends have shown homogeneous melt morphology under light microscope, whereas the PEG(2M)‐included blends have displayed phase‐separated melt morphology. In addition to the composition, PEG's MW and annealing time influence the crystalline morphology of the blends. The ringed PLLA spherulites have appeared mostly in the 2‐min annealed PEG(1.5k)‐included blends. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1497–1510, 2009