镜面微尘散射光干涉的实验

观察光的干涉现象,常需特殊的仪器及细心的调节。而散射光的干涉却不需要这些。生活用的镜面上,如果封有尘埃,在暗室里,距镜面一米左右,用手电简垂直照射镜面,在光源反射象的周围可以观察到彩色的环形条纹,犹如日华(见图1)。这个有趣的现象曾引起包括牛顿在内的许多著名科学家的研究。但是目前用的光学教材中几乎不讨论这种现象,所以鲜为人知。实际上这种现象在教学和科研中均有一定的价值。本世纪五十年代Burch基于散射光干涉的原理提出一种新型的干涉仪——散射板干涉仪,由于其独特的优点正引起人们的重视。     

一种干涉现象的初步研究

本文报道一种干涉现象,并描述了观察这种现象的几种装置,阐明了干涉机理,推导了程差公式。将计算结果和实验结果作了比较,两者基本相符。对这种干涉现象的特点和应用也作了初步探讨。     

劈尖干涉现象的计算机仿真

在《光的干涉》课堂教学中,由于其原理比较抽象,学生难以理解和掌握该部分知识。本文以劈尖干涉为例,借助计算机仿真手段再现劈尖干涉现象,并讨论了入射光波长、劈尖中介质的折射率、劈尖倾角等因素对干涉现象的影响,通过形象直观的图形演示加深学生对劈尖干涉现象的理解。     

工程测量中光波干涉必须满足的几个条件

讨论了两列光波发生干涉现象的理想化条件和在实验中能否观察到干涉现象发生的操作性条件，推导了各种情况下的理论公式。从工程应用的角度出发，研究了检测仪器的响应时间T和光强分辨能力对观察光的干涉现象的影响，提出了观察光的干涉现象的第四个必要条件，对在各种情况下应用光的干涉现象有一定的指导作用。     

静电场边值问题的矩量法解

本文采用修正格林函数积分方程的矩量法数值解技术求解静电场边值问题。这种方法具有较边界积分法积分域小的特点,不仅有高的计算效率和精度,尤其适用于有无限延伸导体边界的边值问题。本文着重讨论与传输线问题等效的边值问题,这是典型的二维静电场问题,对高频和微波技术有重要的实用价值。本文方法也适用于三维静电场问题和交变电磁场问题。     

从运动镜面的反射谈起

用运动界面的边值关系推导运动镜面的反射定律，引出电磁波边值关系的协变性，对积分形式的Maxwell方程的协定性进行了讨论。     

发生薄膜干涉的厚度要求

人教社全日制普通高级中学教科书《物理·必修加选修》第三册第二十章第一节是"光的干涉".教材在讲到薄膜干涉的应用时有这样一段话:"光的干涉现象在技术中有重要应用.例如,在磨制各种镜面或其他精密的光学平面时,可以用干涉法检查平面的平整程度.如图1(a)所示,在被测平面上放一     

中子自旋干涉和地球引力的影响

本文分析了极化中子束通过突变磁场后, 在中子旋量分量之间发生的干涉, 即自旋干涉; 计算了地球引力的影响, 指出这种引力干涉现象不违背"弱等效原理"与COW实验的结果有显著区别.     

偏振光干涉的琼斯矩阵分析

根据琼斯矢量对偏振光的适用性,应用琼斯矩阵推导出了偏振光干涉的表达式,讨论了几例常见的偏振光干涉现象.     

光源空间相干性的测量

时间相干性及空间相干性都是从发光本质来考虑产生干涉的条件对光源的要求.它们是光干涉现象中的重要概念.本文以典型的杨氏干涉实验讨论空间相干性的测量,以加深对空间相干性的理解.     

A moving Kriging interpolation-based boundary node method for two-dimensional potential problems

In this paper,a meshfree boundary integral equation(BIE) method,called the moving Kriging interpolationbased boundary node method(MKIBNM),is developed for solving two-dimensional potential problems.This study combines the BIE method with the moving Kriging interpolation to present a boundary-type meshfree method,and the corresponding formulae of the MKIBNM are derived.In the present method,the moving Kriging interpolation is applied instead of the traditional moving least-square approximation to overcome Kronecker’s delta property,then the boundary conditions can be imposed directly and easily.To verify the accuracy and stability of the present formulation,three selected numerical examples are presented to demonstrate the efficiency of MKIBNM numerically.     

Boundary element-free method for elastodynamics

The moving least-square approximation is discussed first. Sometimes the method can form an ill-conditioned equation system, and thus the solution cannot be obtained correctly. A Hilbert space is presented on which an orthogonal function system mixed a weight function is defined. Next the improved moving least-square approximation is discussed in detail. The improved method has higher computational efficiency and precision than the old method, and cannot form an ill-conditioned equation system. A boundary element-free method (BEFM) for elastodynamics problems is presented by combining the boundary integral equation method for elastodynamics and the improved moving least-square approximation. The boundary element-free method is a meshless method of boundary integral equation and is a direct numerical method compared with others, in which the basic unknowns are the real solutions of the nodal variables and the boundary conditions can be applied easily. The boundary element-free method has a higher computational efficiency and precision. In addition, the numerical procedure of the boundary element-free method for elastodynamics problems is presented in this paper. Finally, some numerical examples are given.     

Boundary element-free method for elastodynamics

1 Introduction In recent years, more and more attention has been paid to researches on the meshless (or meshfree) method, which makes it a hot direction of computational mechanics[1,2]. The meshless method is the approximation based on nodes, then the large deformation and crack growth problems can be simulated with the method without the re-meshing technique. And the meshless method has some advantages over the traditional computa- tional methods, such as finite element method (FEM) and boun…     

Two methods to solve a fractional single phase moving boundary problem

A moving boundary problem of a melting problem is considered in this study. A mathematical model using the Caputo fractional derivative heat equation is proposed in the paper. Since moving boundary problems are difficult to solve for the exact solution, two methods are presented to approximate the evolution of the temperature. To simplify the computation, a similarity variable is adopted in order to reduce the partial differential equations to ordinary ones.     

Shear wave speed recovery using moving interference patterns obtained in sonoelastography experiments

Two new experiments were created to characterize the elasticity of soft tissue using sonoelastography. In both experiments the spectral variance image displayed on a GE LOGIC 700 ultrasound machine shows a moving interference pattern that travels at a very small fraction of the shear wave speed. The goal of this paper is to devise and test algorithms to calculate the speed of the moving interference pattern using the arrival times of these same patterns. A geometric optics expansion is used to obtain Eikonal equations relating the moving interference pattern arrival times to the moving interference pattern speed and then to the shear wave speed. A cross-correlation procedure is employed to find the arrival times; and an inverse Eikonal solver called the level curve method computes the speed of the interference pattern. The algorithm is tested on data from a phantom experiment performed at the University of Rochester Center for Biomedical Ultrasound.     

Prediction capabilities of classical and shear deformable beam models excited by a moving mass

In this paper, a comprehensive assessment of design parameters for various beam theories subjected to a moving mass is investigated under different boundary conditions. The design parameters are adopted as the maximum dynamic deflection and bending moment of the beam. To this end, discrete equations of motion for classical Euler-Bernoulli, Timoshenko and higher-order beams under a moving mass are derived based on Hamilton's principle. The reproducing kernel particle method (RKPM) and extended Newmark-β method are utilized for spatial and time discretization of the problem, correspondingly. The design parameter spectra in terms of the beam slenderness, mass weight and velocity of the moving mass are introduced for the mentioned beam theories as well as various boundary conditions. The results indicate the existence of a critical beam slenderness mostly as a function of beam boundary condition, in which, for slenderness lower than this so-called critical one, the application of Euler-Bernoulli or even Timoshenko beam theories would underestimate the real dynamic response of the system. Moreover, there would be a roughly linear relation between the weight of the moving mass and the design parameters for a certain value of the moving mass velocity in most cases of boundary conditions.     

A geometrical quantum phase in Newtonian gravity

The quantum mechanical behaviour of a particle moving in a Newtonian potential is investigated. It is found that the scalar potential can give rise to interference effects for simply connected regions in which the gravitational force on the particle vanishes. A matter wave interferometry experiment is proposed to verify the existence of a geometrical quantum phase, which can be used to explicitly test the Dirichlet boundary conditions in Newtonian gravity.     

Heat transfer of non-Newtonian liquid flows in convergent-divergent channels with fourth-kind thermal boundary conditions

In the present paper, we consider the heat transfer of non-Newtonian liquid flows moving in convergent- divergent channels with common boundary. The case of flows moving in opposite directions was addressed. At the common boundary, continuity conditions for temperature and heat flow were adopted. A mathematical model, a calculation algorithm, and simulation data are reported. Plots of numerical data characterizing the channel flows are presented. A comparative analysis of heat transfer in smooth and convergent-divergent channels is given.     

运动目标辐射声场干涉结构映射域特征研究

浅海低频声场呈稳定而显著的干涉特征,并蕴含声源状态和波导特性等信息.本文研究运动目标辐射声场干涉结构的简化映射以及映射域能量分布对目标运动状态的指示特征.理论分析了声压场和矢量声场空(时)频干涉谱图的二维傅里叶变换映射特征,推导了匀速运动目标时频干涉谱图映射域能量脊斜率与波导不变量以及距变率、航向角的关系式,证明了映射域脊斜率符号、脊斜率绝对值变化等对目标来袭或远离以及目标威胁程度的指示,并进行了数值仿真和海上试验研究.实测结果与理论、仿真分析有较好的一致性.研究结果表明:二维傅里叶变换可将声压场和矢量场时(空)频谱图干涉结构简化,匀速运动目标辐射声场干涉结构映射域的能谱脊斜率、距变率、航向角与波导不变量有解析关系式,声强谱、动能密度谱、声强流谱等声场干涉结构经映射后更为一致,映射域脊能简明的指示目标运动状态和威胁程度.     

An efficient moving mesh spectral method for the phase-field model of two-phase flows

We develop in this paper a moving mesh spectral method for the phase-field model of two-phase flows with non-periodic boundary conditions. The method is based on a variational moving mesh PDE for the phase function, coupled with efficient semi-implicit treatments for advancing the mesh function, the phase function and the velocity and pressure in a decoupled manner. Ample numerical results are presented to demonstrate the accuracy and effectiveness of the moving mesh spectral method.