Terrain-based propagation model for rural area-an integral equationapproach

A terrain-based propagation model for vertically polarized radio waves is described, based on the field integral equation for a smooth surface. The model is simplified from a 3D integral equation model to a one-dimensional integral equation by assuming that the surface is magnetically perfectly conducting (a soft surface) with no transverse variations. By assuming no back scattering, the integral equation is turned into a simple integral. The method is tested numerically with known solutions. The integral equation model is also applied to actual terrain profiles at four frequencies (144, 435, 970, 1900 MHz), and the results are compared with results from the Hata model and measurements. The standard deviation (STD) of the error is a growing function of frequency, from 3 to 9 dB     

Comparison of fast integral mesh truncation schemes for hybridFE-BI systems

By virtue of their low operation count, the application of fast integral methods such as the fast multipole (FMM) and adaptive integral methods (AIM) result in a substantial quickening of the boundary integral portion of the hybrid finite element-boundary integral (FE-BI) method, independent of the shape of the BI contour. Recently, various versions of the FMM have been proposed, each introducing a different approximation to the implementation of the boundary integral. The main goal of this Letter is to provide a comparison of the effect of these fast integral algorithms on the boundary integral when used in conjunction with the traditional FE-BI method     

Exact Closed-Form Expression of a Sommerfeld Integral for the Impedance Plane Problem

A Sommerfeld integral for an impedance half-plane is one of the classical problems in electromagnetic theory. In this paper, the integral is evaluated into two series representations, which are expressed in terms of the exponential integral and the Lommel function, respectively. It is shown that the series expansions absolutely converge for any parameters, such as distance or surface impedance. Then based on the Lommel function expansion, an exact closed-form expression of the integral is formulated. This expression is written in terms of incomplete Weber integrals, which are directly related to incomplete cylindrical functions such as incomplete Lipschitz–Hankel integrals. Additionally, a complete asymptotic series of the integral is obtained based on the exponential integral expansion. With conventional methods such as steepest descent method, it is cumbersome to derive the divergent series. The validity of all the formulations derived in this paper is demonstrated through a comparison with a numerical integration of the integral for various situations.     

复变量菲涅尔积分的一种新计算方法

本文利用将复变量的菲涅尔积分转换成实变量的菲涅尔积分，进行数值计算的方法，成功地求得了复变量的菲涅尔积分，这对有耗媒质的绕射问题以及复射线的绕射问题的求解有非常重要的参考价值。     

Computational Implementation of Asymmetric Integral Imaging by Use of Two Crossed Lenticular Sheets

We propose an asymmetric integral imaging method to adjust the resolution and depth of a three‐dimensional image. Our method is obtained by use of two lenticular sheets with different pitches fabricated under the same F/#. The asymmetric integral imaging is the generalized version of integral imaging, including both conventional integral imaging and one‐dimensional integral imaging. We present experimental results to test and verify the performance of our method computationally.     

基于CPLD的CIS积分时间软调节

传统图像传感器修改积分时间的过程比较麻烦,为了能实现积分时间的在线调节,设计一种能通过SPI口在线实时改变积分时间的图像传感器系统。该系统是在1片可编程逻辑器件CPLD里集成图像传感器的驱动电路和积分时间调节电路,单片微机通过SPI同步串口和CPLD交换数据。仿真结果表明该系统可以实现在线修改积分时间。     

A survey of the near-field far-field inverse scattering inverse source integral equation

The Kirchhoff direct integration of the scalar wave equation is reviewed, and some properties of the Kirchhoff surface integral are discussed, from the perspective of the inverse scattering inverse source problem. A modified Kirchhoff surface integral is introduced, leading to a Fredholm integral equation of the first kind for the unknown sources (induced by the incident field) inside a volume in terms of the (scattered) fields on the surface enclosing this volume. The properties and physical meaning of this integral equation are discussed. A generalization of this integral equation for the vector electromagnetic wave equations is presented.     

A comparison of integral equations with unique solution in theresonance region for scattering by conducting bodies

A comparison of integral equations, for problems involving scattering by arbitrary-shape conducting bodies, having a unique solution in the resonance region is presented. The augmented electric and magnetic field integral equations and the combined field integral equation, in their exact and approximate versions, are considered. The integral equations and the basis and test functions used in the method of moments to solve them are reviewed. Their implementation in a computer code is analyzed, mainly the relation between the matrix properties and the CPU time and memory. Numerical results (condition number and backscattering cross section) are presented for the cube. It is shown that the combined field integral equation, and the approximate (symmetric) combined field integral equation, are the most efficient equations to use in the neighborhood of resonant frequencies, because the overdetermined augmented integral equations require an extra matrix multiplication     

微分算子与子波构造

将传统意义下的整数阶微分运算拓展到非整数阶微分情形,直接仿照整数阶微分在时域的极限定义形式是很困难的.本文从分析微分运算的频域形式着手,将微分算子分解成幅度算子和相位算子,并将其与子波变换特征进行比照研究,从而解决了非整数阶微分的拓展问题,同时也得到了微分运算与子波变换的内在联系,为非整数阶微分计算提供了一种逼近方式.文中提出了幅度算子、广义Hilbert变换等新概念并重点探讨了基于非整数阶微分运算的子波构造及其局域化特征等问题.     

减轮Simeck算法的积分攻击

该文对轻量级分组密码算法Simeck在积分攻击下的安全性进行了研究。通过向前解密扩展已有的积分区分器,构造了16轮Simeck48和20轮Simeck64算法的高阶积分区分器,并在新区分器的基础上,利用等价子密钥技术和部分和技术,结合中间相遇策略和密钥扩展算法的性质,实现了24轮Simeck48和29轮Simeck64算法的积分攻击。攻击24轮Simeck48的数据复杂度为246,时间复杂度为295,存储复杂度为282.52;攻击29轮Simeck64的数据复杂度为263,时间复杂度为2127.3,存储复杂度为2109.02。与Simeck算法已有积分攻击的结果相比,该文对Simeck48和Simeck64积分攻击的轮数分别提高了3轮和5轮。     

An exact line integral representation of the physical opticsscattered field: the case of a perfectly conducting polyhedral structureilluminated by electric Hertzian dipoles

An exact line integral representation of the electric physical optics scattered field is presented. This representation applies to scattering configurations with perfectly electrically conducting polyhedral structures illuminated by a finite number of electric Hertzian dipoles. The positions of the source and observation points can be almost arbitrary. The line integral representation yields the exact same result as the conventional surface radiation integral; however, it is potentially less time consuming and particularly useful when the physical optics field can be augmented by a fringe wave contribution as calculated from physical theory of diffraction equivalent edge currents. The final expression for the line integral representation is lengthy but involves only simple functions and is thus suited for numerical calculation. To illustrate the exactness of the line integral representation, comparisons of numerical results obtained from the surface and the line integral representations are performed     

Analytical simplification of the 2-D method of moments impedance integral

The elements of the two-dimensional (2-D), method of moments (MoM) impedance matrix are analytically reduced by way of an integral transform. The resulting impedance expression is a single integral with an analytic integrand for nearly arbitary shape and weight function sets. The reduced expression requires fewer computations, thereby reducing the matrix fill time. This moments via integral transform method (MITM) is based on an integral representation of the Green's function (Hankel function) and utilizes a special integral transform. The method is developed for 2-D perfectly electrically conducting bodies subjected to a transverse magnetic field. A comparison between brute force and MITM is presented for polynomial shape and weight functions.     

Analytical technique to evaluate the asymptotic part of theimpedance matrix of Sommerfeld-type integrals

The propagation of electromagnetic waves in a grounded dielectric slab has numerous applications in printed antenna technology and in the analysis of microwave- and millimeter-wave integrated circuits. For the accurate analysis of microstrip dipoles and circuits based on the moment of method (MoM), a crucial step is the precise evaluation of the impedance matrix elements which contain the integration of Sommerfeld-type integrals. The integral transform method with the asymptotic extraction technique is formulated for calculating a Sommerfeld-type integral problem. This formulation allows the infinite double integral of the asymptotic part of the impedance matrix to be transformed into a finite one-dimensional (1-D) integral. This finite 1-D integral contains a spherical Legendre function and can be easily evaluated numerically after the singular part of the integral is performed analytically. It is shown that the proposed method dramatically reduces the computation time and improves the accuracy over the conventional method to evaluate the asymptotic part of impedance matrix     

The uniqueness of a solution to the time-domain integral equation for the nonstationary diffraction problem

Diffraction of a nonstationary electromagnetic field by a conducting body is studied with the use of the method of integral equations. It is shown that the presence of resonances of the interior domain does not violate the uniqueness of a solution to the time-domain integral equation, unlike the frequency-domain integral equation.     

Integral equation for the fields inside a dielectric cylinder immersed in an incidentE-wave

The scattering of a time-harmonicE-wave by a dielectric cylinder is solved by a single integral equation. Two alternatives are investigated to derive such a single integral equation. Interest is focused on the fields inside the dielectric. In this case the integral equation has only the incident electric field as its source term.     

Simplification of integral imaging system by using a lenticular lens array

Integral imaging is a 3D display technology without any additional equipment. A new system is proposed in this paper, which uses a lenticular lens array to replace the lens array in the conventional integral imaging system. The lenticular integral imaging system reduces the complexity and the price of integral imaging system. The positive characteristics of conventional integral imaging system, such as full parallax and quasi-continuous view points, are still kept on the proposed system in horizontal direction. Optical results show that the time for calculating the elemental images is reduced by 25% compared with the conventional one. The resolution of integrated image in vertical direction is 4 times higher than that of conventional system. This proposed system opens a new way on application of integral imaging.     

基于非均匀棱镜阵列的三维集成成像视角增强方法

针对传统集成成像系统视角受限于单元透镜尺寸及其焦长的问题,提出了一种基于非均匀棱镜阵列的三维集成成像视角增强方法。以传统集成成像重构显示原理为基础,借助于非均匀棱镜阵列对重构光线的偏转作用,设计了显示透镜阵列和非均匀棱镜阵列组合的立体显示模式。依据集成成像的三维重构显示原理,利用光线追迹理论,导出了非均匀棱镜阵列的结构参数和集成成像系统视角之间的关系模型。仿真实验表明,基于非均匀棱镜阵列的集成成像系统视角比传统集成成像系统有了显著提高。     

Linear inverse problems in wave motion: nonsymmetric first-kindintegral equations

We present a general framework to study the solution of first-kind integral equations. The integral operator is assumed to be compact and nonself-adjoint and the integral equation can possess a nonempty null space. An approach is presented for adding contributions from the null space to the minimum-energy solution of the integral equation through the introduction of weighted Hilbert spaces. Stability, accuracy, and nonuniqueness of the solution are discussed through the use of model resolution, data fit, and model covariance operators. The application of this study is to inverse problems that exhibit nonuniqueness     

遍历积分的计算与推广

遍历理论研究的是群在可测空间上作用的定性理论.这里主要分析遍历积分的计算公式,将[0,1]区间上的遍历积分公式推广到实数区间上,分别用A、B两类积分来表示有理区间和无理区间,并给出积分公式,可以看到[0,1]区间上的遍历积分公式是提出A类遍历积分的特例.还给出遍历积分中变量在定义域内做遍历运动的几何表述.     

Current induced by TE excitation on a conducting cylinder located near the planar interface between two semi-infinite half-spaces

An analysis is presented for determining the current induced by a known transverse electric excitation on a perfectly conducting cylinder located near the planar interface separating two semi-infinite, homogeneous half-spaces of different electromagnetic properties. The conducting cylinder of general cross section is of infinite extent and the excitation is transverse electric to the cylinder axis. Two types of integral equations, the magnetic field integral equation and the electric field integral equation, are formulated, and the Green's functions for the integral equations are derived in an appendix. Numerical solution methods for solving the integral and integrodifferential equations are presented. For a strip parallel or perpendicular to the interface, a circular cylinder, and a rectangular cylinder, data are presented and discussed for selected parameters, including the case of a cylinder resting on the interface.