White-light emission from porous-silicon-aluminum Schottky junctions

Summary Porous-silicon-based white-light-emitting devices are presented. The fabrication process on different substrates is described. The peculiarities of technological steps for device fabrication (porous-silicon formation and aluminum treatment) are underlined. Doping profile of the porous layer, current-voltage characteristics, time response, lifetime tests and electroluminescence emission spectrum of the device are presented. A model for electrical behaviour of Al/porous silicon Schottky junction is presented. Electroluminescence spectrum of the presented devices showed strong similarities with white emission from crystalline silicon junctions in the breakdown region. Paper presented at the III INSEL (Incontro Nazionale sul Silicio Emettitore di Luce), Torino, 12–13 October 1995.     

对声波和弹性波传播模拟的Hamilton系统方法

建立了离散化网格上的准粒子体系，引入此体系的Hamilton系统描述，用来模拟声波和弹性波的传播.介绍了准粒子间相互作用的九点模型并给出互作用系数.证明了Hamilton系统方法 和声波、弹性波方程的关系，并给出两个方法中所使用物理量的关系.使用辛算法对给定的 介质模型进行数值模拟. 关键词： Hamilton系统方法 九点互作用模型 声波方程 弹性波方程 辛算法     

Thermoluminescence of Cosmic matter

Summary A simplified model of thermoluminescence in silicates is presented and the astronomical applications of the phenomenon are shown. Finally our experimental apparatus and preliminary tests are presented and compared with those in the literature. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Supersymmetry with isospin

Super-invariant generalizations of the Casimir operators of the Poincaré and isospin algebras are presented. Superfields are discussed, in particular, the simplest irreducible superfields are constructed explicitly, and free and interaction Lagrangians involving them are presented.     

基于抛物方程的海陆环境信号时延与到达角估计

针对复杂海陆环境中的无线信号传播预测问题,研究了适用于抛物方程的信号时延与到达角估计方法。将自由空间中抛物方程轴向波前信号视为本地副本信号,然后利用信号的自相关特性,将接收信号与副本信号进行互相关运算,最后通过相关函数的峰值检索,得到脉冲信号在复杂环境中传播的附加时延。采用数值算例,验证了该方法的正确性和有效性。此外,采用多重信号分类算法,由抛物方程构建接收阵列的协方差矩阵,并对其进行特征值分解,然后利用信号子空间和噪声子空间的正交性,实现复杂环境中的信号到达角估计。仿真结果表明,相比于传统的平面波谱方法,该方法具有更高的多径分辨率。基于上述方法,并结合数字地图,在典型的海陆环境中进行了仿真实验,分析了蒸发波导对脉冲信号传播时延和到达角的影响。     

Eigenvalue analysis of Timoshenko beams and axisymmetric Mindlin plates by the pseudospectral method

A study of the free vibration of Timoshenko beams and axisymmetric Mindlin plates is presented. The analysis is based on the Chebyshev pseudospectral method, which has been widely used in the solution of fluid mechanics problems. Clamped, simply supported, free and sliding boundary conditions of Timoshenko beams are treated, and numerical results are presented for different thickness-to-length ratios. Eigenvalues of the axisymmetric vibration of Mindlin plates with clamped, simply supported and free boundary conditions are presented for various thickness-to-radius ratios.     

X‐ray fluorescence analysis with a pyroelectric x‐ray generator

Several types of handy x‐ray fluorescence spectrometers are presented. The results obtained with a Niton spectrometer are presented as a goal to develop a laboratory‐made spectrometer using an Amptek Cool‐X pyroelectric x‐ray generator. A small and cheap charge‐up x‐ray emitting device and its spectrum are also presented. Handy x‐ray spectrometers are now progressing rapidly and the detection limits are in the range of a few ppm for certain elements. Copyright © 2005 John Wiley & Sons, Ltd.     

混沌同步的充分条件及应用

对两大类常用连续混沌系统，给出了同步的充分条件，以及状态变量的演化范围，对其作了证明，从理论上分析了这些充分条件一定可实现. 作为应用，证明了时变参数混沌同步的实现充分条件，并用Chua系统仿真实现. 时变参数混沌同步通信具有强抗破译性，也给出其抗破译的仿真. 关键词： 条件Lyapunov指数(CLE) Chua电路 参数同步     

PHOTOCHROME DYE TRACING IN WATER FLOWS

The properties and uses of photochromic dyes are presented, and the history of the use of various photochromic dyes in fluid flow experiments is discussed. The mechanisms and theory of the changes in properties of various types of photochromic dyes are presented. In response to the need for a water-soluble photochromic dye, a tri-arylmethane dye, Acid Violet 19, was selected for use in two-phase air-water experiments. Its optical and chemical properties are given, and the dependence of its rate constant on various parameters is studied. Details of the use of Acid Violet 19 in fluid flow experiments are presented.     

Two-pion interferometry for granular sources

A review on the two-pion Hanbury-Brown—Twiss (HBT) interferometry in the granular source model of quark-gluon plasma droplets is presented. The characteristic quantities of the granular source extracted by imaging analysis are presented and compared with the HBT radii obtained by the usual Gaussian formula fit. The signals of granular sources are presented.     

基于正弦灰度变换的X光图像增强

介绍了灰度变换法的几种形式 ,提出了一种正弦非线性变换法 ,对三幅数字X光医学图像进行了处理 ,获得了令人满意的对比度增强效果 ,证明该方法有效而实用     

Interpretation of measured spectral line shapes using a square-well potential: The absorption lines of cesium broadened by rare gases

A simple square-well potential is used as an aid in understanding the complicated evolution of the absorption lines and their associated satellites for cesium perturbed by the rare gases. New experimental halfwidth data for cesium perturved by Xe, Ar, and He are presented. In the case of Xe, data for the second, third and fourth members are presented to 30, 7, 1 rd (relative density), respectively. For Ar, data are presented for the third through the ninth member. The pressure range for the third and fourth members is from 0 to 20 rd. For the other members, it ranges to 8 rd for the fifth and to 2 rd for the ninth. Third and fourth member helium data are presented to about 20 and 8 rd, respectively. Several theoretical computer profiles are used to illustrate the evolution of the line and satellites with foreign gas pressure and these are compared with the experimental data.     

The radiation impedance of a rectangular piston

The radiation impedance of a rectangular piston is expressed as the Fourier transform of its impulse response, which is obtained from the recent work of Lindermann [1]. The analytical evaluation of the transform is performed and new integral expressions are presented for both the radiation resistance and reactance. The integrals are readily evaluated in terms of elementary functions at both the low and high frequency limits. The integrals are also expressed as series of Bessel functions which are valid for all frequencies and aspect ratios. Numerical results are presented to illustrate the behavior of the radiation resistance and reactance as a function of the aspect ratio of the piston and a normalized frequency parameter. Additional numerical results are then presented to illustrate the accuracy of the analytical expressions for the radiation resistance and reactance at low and high frequencies. Finally, numerical results are presented to illustrate the application and accuracy of using standard FFT algorithms to evaluate the radiation resistance and reactance directly from the impulse responses.     

Hysteresis characteristics of an analytical vector hysteron

The analytical way to describe uniaxial single-domain particles, using new symmetry considerations on the magnetic anisotropy, as a vector hysteresis unit (vector hysteron), is presented. The main characteristics of the vector hysteron such as the longitudinal hysteresis loops, transversal hysteresis loops and rotational hysteresis loops are presented. An extension of the vector hysteron and a vector hysteron that can be applied to the ferroelectric hysteresis are also presented.     

High-Order Lump-Type Solutions and Their Interaction Solutions to a (3+1)-Dimensional Nonlinear Evolution Equation *

By means of the Hirota bilinear method and symbolic computation, high-order lump-type solutions and a kind of interaction solutions are presented for a (3+1)-dimensional nonlinear evolution equation. The high-order lump-type solutions of the associated Hirota bilinear equation are presented, which is a kind of positive quartic-quadratic-function solution. At the same time, the interaction solutions can also be obtained, which are linear combination solutions of quartic-quadratic-functions and hyperbolic cosine functions. Physical properties and dynamical structures of two classes of the presented solutions are demonstrated in detail by their graphs.      

Defects in metals

Recent study of defects in metals using Mössbauer spectroscopy is presented. Vacancy and interstitial atoms are focussed as defects in metals. General remarks for the study of defects are presented first and then, as examples of the study,¹¹⁹Sb and⁵⁷Co Mössbauer measurements to monitor the trapping and detrapping process of quenched-in vacancies in Au are discussed with the aid of the complementary techniques which are resistivity measurement, computer simulation and positron lifetime measurement. Detailed results from these complementary techniques are described. Recent theoretical calculations for defect-associated states are also presented briefly.     

Gas flow in domain with cubic package of spheres

Viscous gas flow in the domain with a cubic package of spheres is considered. The problem formulation and the solution method are briefly presented. The integral parameters are presented, and the flow character is identified.     

干涉技术的新发展——光电相位测量技术

本文介绍了干涉测量中近年发展起来的光电相位测量技术的基本原理,比较了各种方法的特点,给出了通用数学模型,并介绍了部分应用实例。     

视觉测量中的相机标定问题

回顾了计算机视觉中相机标定的问题,在分析并比较多种相机标定方法的基础上对其进行了分类,提出了现有理论和方法在实际工程应用中存在的问题以及未来的发展动态。     

谈高校基础实验室仪器设备配置的几个问题

本文提出高校物理实验室，仪器设备购置中应注意的几条原则。并提出一套估算办法。