大口径光束波前采样器(孔栅)的研制

应用平面波角谱理论，分析了采样器对光波场采样和分光的基本原理以及对空间采样频率的选择规则，描述了实际研制的大口径采样器的结构设计，并通过数值方法和高能激光大气传输实验研究了高能激光经采样器前／后的远场光斑分布关系。结果表明：利用光束波前采样器能高保真地实现对高能激光束的分光。     

用电磁打点计时器进行受迫振动实验--介绍我校的一个自学物理实验

介绍一种用简单的方法进行的受迫振动实验。     

一种软X射线多层膜界面粗糙度的计算方法

提出一个利用多层膜小角X射线衍射谱衍射峰积分强度计算多层膜界面粗糙度的公式。用磁控溅射技术制备Mo／Si多层膜，用波长为0．154nm的硬X射线测量样品在小掠入射角区的衍射曲线，分别用本文公式和反射率曲线拟合方法计算了样品的界面粗糙度。实验结果表明：由本文公式获得的界面粗糙度近似于拟合方法获得的界面粗糙度，它们略等于多层膜界面实际粗糙度。     

Analytical solution for an anomalous hollow beam in a fractional Fourier transforming optical system with a hard aperture

Based on the fact that a hard aperture function can be expanded into a finite sum of complex Gaussian functions, the approximate analytical expressions for the output field distribution of an anomalous hollow beam (AHB) passing through an apertured fractional Fourier transform (FRT) system are derived. By using the approximate analytical formulae and diffraction integral formulae, the propagation properties of an AHB in circular and rectangular apertured FRT system are studied numerically. The results show that this method provides a convenient tool for studying the propagation properties of an AHB passing through apertured FRT system, and the apertured FRT system can be applied to laser beam shaping conveniently.     

Temperature measurement of nonsteady arcs

The temporal change of the radial temperature profile of a free burning argon arc at power frequency and a flashover arc near the surface of a polluted plate is experimentally determined with the help of a spectroscopic system, the detail of which is described in this paper. The image of the arc is scanned by a rotating 30-facet mirror drum over the entrance slit of a grating spectrometer. The intensity of up to four spectral lines can be simultaneously measured. The temperature results for the argon arc are derived by employing the absolute intensity method and the relative intensity method. This preliminary experimental investigation shows that the system is capable of measuring and monitoring the temperature development of nonsteady arcs which may be randomly moving in a known space     

Bernoulli方程的演示设计

Bernoulli方程是流体力学的一个基本方程。本将介绍几种简单、有趣而又十分有效的Bernoulli方程演示设计。     

Annealing effects on structure and laser-induced damage threshold of Ta2O5/SiO2 dielectric mirrors

The effects of annealing on structure and laser-induced damage threshold (LIDT) of Ta₂O₅/SiO₂ dielectric mirrors were investigated. Ta₂O₅/SiO₂ multilayer was prepared by ion beam sputtering (IBS), then annealed in air under the temperature from 100 to 400 °C. Microstructure of the samples was characterized by X-ray diffraction (XRD). Absorption of the multilayer was measured by surface thermal lensing (STL) technique. The laser-induced damage threshold was assessed using 1064 nm free pulsed laser at a pulse length of 220 μs.

It was found that the center wavelength shifted to long wavelength gradually as the annealing temperature increased, and kept its non-crystalline structure even after annealing. The absorbance of the reflectors decreased after annealing. A remarkable increase of the laser-induced damage threshold was found when the annealing temperature was above 250 °C.     

On locating low altitude moving targets using a planar acoustic sensor array

It is of engineering importance to locate low altitude moving targets with acoustic methods due to the blindness of the traditional radar detecting. In this paper, an algorithm for locating low altitude moving targets is put forward based on a five-element planar acoustic sensor array. The method is realized through estimations of the sensor-to-sensor time delays of the source signal generated by the low altitude moving target. The angle and range estimation performance of the proposed method are analyzed, respectively, both in theoretical and numerical sense.     

Dynamical properties of two-band superlattices with strong interband coupling in real space under the action of ac and dc－ac fields

Within a two-band tight-binding model driven by ac and dc－ac electric fields, using numerical methods, we investigate the dynamics of electrons and the quasi-energy spectrum of the system with strong interband coupling in real space. We find that when the bandwidth is suppressed to a value much smaller than the field frequency, the dynamical localization can exist in the system. The corresponding regions are found for the occurrence of dynamical localization in the parameter space.     

Investigation on transition crystal of ordinary rutile TiO2 powder and its sonocatalytic activity

The transition crystal TiO(2) sonocatalyst was prepared utilizing the method of ultrasonic irradiation in hydrogen peroxide solution. The sonocatalytic activity of the transition crystal TiO(2) powder was validated through the degradation of methyl orange in aqueous solution by ultrasonic irradiation. The results show that the sonocatalytic activity of the transition crystal TiO(2) powder is obviously higher than that of pure rutile and anatase TiO(2) powders as well as mixed rutile and anatase TiO(2) powders according to the proportion of corresponding transition crystal TiO(2) catalyst. The degradation ratio of methyl orange in the presence of the transition crystal TiO(2) catalyst surpasses 75% within 80 min ultrasonic irradiation, while the degradation ratios are 55.93%, 51.68% and 40.88%, respectively, for rutile, mixed and anatase TiO(2) powders.