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     

咪唑类氮氧自由基的ESR波谱的酸度相关性-pH自旋探针应用研究之一

根据咪唑类氮氧自由基的结构特性合成了一系列的pH自旅探针,其ESR波谱参数均在一定范围内与介质的酸性呈明显的相关性.可望为较精确地测量化学胶束、细胞等微观体系的pH值开辟一个新的途径.本文研究了灵敏变化的pH范围与取代基的关系,得到了5种自旅探针的ESR参数-pH曲线、pKa值以及Hanmmett相关图,分析了如何通过改变取代基合成出不同pH变化范围并适用于不同生物和化学体系的pH自旅探针,最终达到付诸应用的目的.     

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.     

水合乙酸锌脱水反应的动力学

用等温热重法和非等温热重法研究了Zn(CH3COO) 2·2H2 O的脱水反应 .在 61.1、62 .8、66.2、69.9℃下的等温热重数据 ,由等转化率下的lnt=E/RT +ln[g(α) /A]进行拟合 ,确定了活化能的大小 ;升温速率为 10℃ /min的非等温热重曲线显示 ,Zn(CH3COO) 2·2H2 O的脱水反应发生在 71～ 10 2℃间 ,其数据通过Doyle Zsako法进行拟合 ,以线性相关系数为判据 ,并结合等温热分析拟合结果 ,得到该脱水反应的积分动力学模式函数g(α) =[-ln( 1-α) ]2 / 3、活化能E =10 0 .8kJ/mol、指前因子ln(A/s-1) =3 6.0 9、动力学补偿效应方程为lnA =0 .3 3 3 9E + 2 .0 10 .     

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.     

Valley density profile for highly efficient x-ray lasers with good beam quality

A plasma with a valley density profile at the required electron density for high-gain operation of an x-ray laser could be obtained using a normally incident 300 ps laser pulse followed by a grazing-incident 300 ps laser pulse. Sudden heating of the valley plasma region by another grazing-incident 300 fs laser pulse would then yield a highly efficient x-ray laser beam with a deflecting angle of 2 mrad and a divergence angle of 4 mrad. Saturation operation of the x-ray laser beam at 32.6 nm could be achieved with a total pump energy of less than 100 mJ.