基于雷达方程修正的目标探测距离评估方法

针对现有的雷达方程在评估对海雷达最大探测距离上与实际不符的问题,提出了在一般方程的基础上,利用实测数据来修正方程的方法。分析了一般雷达方程应用的局限性,根据试验中海杂波对目标探测的影响,简化一般方程为信杂比方程。利用X波段对海探测雷达的试验数据,对信杂比方程进行修正,克服了方程在实际应用的不足,使方程能够满足该类型雷达对目标的最大探测距离的计算。计算结果表明,修正后方程计算的结果与雷达显示的结果基本相同。     

Nonlinear conductance-volume relationship for murine conductance catheter measurement system

The conductance catheter system is a tool to determine instantaneous left ventricular volume in vivo by converting measured conductance to volume. The currently adopted conductance-to-volume conversion equation was proposed by Baan, and the accuracy of this equation is limited by the assumption of a linear conductance-volume relationship. The electric field generated by a conductance catheter is nonuniform, which results in a nonlinear relationship between conductance and volume. This paper investigates this nonlinear relationship and proposes a new nonlinear conductance-to-volume conversion equation. The proposed nonlinear equation uses a single empirically determined calibration coefficient, derived from independently measured stroke volume. In vitro experiments and numerical model simulations were performed to verify and validate the proposed equation.     

均匀随机媒质中传播的波——有不同波数的m-n阶矩方程的解

在研究随机媒质中传播的波的一些有关问题时,常常需要求解波的矩方程。具有不同波数的m-n阶矩方程是一个抛物近似的偏微分波动方程。本文应用格林函数方法将偏微分方程变为积分方程,并用迭代法求得了该积分方程的解。同时,又应用接连散射的方法求解了具有不同波数的m-n阶矩方程,两种方法所得的结果完全相同。文中对解的物理含义作了说明,并讨论了用于波传播研究中的一些问题。     

Pulse response analysis of a complementary MOSFET inverter by the hyperbolic functional description

The characteristic equation of a MOSFET which up to the present has been expressed by two equations is given by a single equation using a hyperbolic function. The pulse response analysis of a complementary MOSFET inverter is carried out with the use of this new characteristic equation, and the results that have been shown by several equations are represented by a single equation.     

The electron beam in a cathode-ray tube

The beam in a cathode-ray tube is described by a "paraxial" Liouville equation. This equation takes into account the thermal spread of the electrons as well as the influence of the space charge of the beam. The solution of this equation is given. An ordinary differential equation is derived for the beam radius. The equation has been solved in the field-free region outside the gun. The result is presented in graphs which can be applied to the determination of the spot size on the screen of a cathode-ray tube.     

A note on the method of analytical regularization

Many problems of electromagnetics are governed by singular integral equations of the first kind. As discussed by Nosich (1999), it is often possible to obtain a different equation describing the problem by applying the method of analytical regularization, and analytically inverting part of the original equation. The transformed equation is of the second kind. Therefore, as a rule, it is usually preferable to apply a numerical method to the transformed equation than to the original one. What appears to be an exception to that rule is discussed in the present paper: under proper conditions, and for a particular numerical method, results obtained by application to the transformed equation are shown to be identical to those obtained by application to the original equation. Some consequences of this equivalence are discussed     

均匀随机媒质中传播的波有不同波数的m-n阶矩方程的解

在研究随机媒质中传播的波的一些有关问题时,常常需要求解波的矩方程。具有不同波数的m-n阶矩方程是一个抛物近似的偏微分波动方程。本文应用格林函数方法将偏微分方程变为积分方程,并用迭代法求得了该积分方程的解。同时,又应用接连散射的方法求解了具有不同波数的m-n阶矩方程,两种方法所得的结果完全相同。文中对解的物理含义作了说明,并讨论了用于波传播研究中的一些问题。     

The Convergence of the Eigen Equation for Dielectric Waveguide Array

The eigen equation for Dielectric Waveguide Array (DWA) established by [1] was discussed. The convergence of the eigen equation was also analyzed in detail. Numerical results for a particular rectangular DWA was presented. Compared with those obtained by previous different ways, faster convergence for the eigen equation was reached easily. The characteristics of the eigen equation for DWA was particularly useful in computer propramming and engineering.     

Application of on-surface MEI method on wire antennas

The formulas of the on-surface measured equation of invariance (OSMEI) for wire antennas are derived. The unknowns of each node on the antenna surface are expressed by the vector potential function and surface current density. The unknowns in the vicinity of each node are coupled in a linear equation and the coefficients of the linear equation are determined by the measured equation of invariance (MEI) method. The final impedance matrix obtained by the OSMEI is a highly sparse matrix. It demonstrates that the currents on thin wire antennas may also be solved by a differential equation-based formulation in addition to the conventional integral equations     

波导系统中电子注辐射过程的能量守恒关系

本文应用电磁场的算子理论求出了在任意截面的波导系统内,由电子注电流所激励的电磁场的公式。在这一公式中由单位功率流下的场代替了一般并矢格林函数中的归一化本征常数;这样,不但可以证明激励过程中的能量守恒关系,还可以比较方便地应用到各种实际的电子器件的互作用理论中去。     

Propagation of soliton waves in nonlinear dielectric slab waveguides of parabolic index of refraction

The pulse propagation in a non-linear slab waveguide of parabolic index of refraction is treated by using differential equation techniques. A graded index dielectric slab waveguide free of material dispersion with a cubic order non-linearity is considered. The electromagnetic wave inside the waveguide is described in terms of a non-linear equation. Slowly varying envelope function representation is employed to develop a non-linear partial differential equation for the unknown envelope function of the electric field. An averaging method over the transverse direction is applied to reduce the unknown envelope function non-linear differential equation into a form resembling the well known non-linear Schrödinger differential equation. This equation is solved by applying the Inverse Scattering Method. The N-soliton solution is developed and presented explicitly for the practical case of the single mode dielectric slab waveguide. Numerical results presenting single and double soliton propagation are also given.     

Efficient numerical techniques for solving Pocklington's equation and their relationships to other methods

It is shown that testing Pocklington's equation with piecewise sinusoidal functions yields an integro-difference equation whose numerical solution is identical to that of the point-matched Hallen's equation when a common set of basis functions is used with each. For any choice of basis functions, the integro-difference equation has the simple kernel, the fast convergence, the simplicity of point-matching, and the adequate treatment of rapidly varying incident fields, but none of the additional unknowns normally associated with Hallen's equation. Furthermore, for the special choice of piecewise sinusoids as the basis functions, the method reduces to Richmond's piecewise sinusoidal reaction matching technique, or Galerkin's method. It is also shown that testing with piecewise linear (triangle) functions yields an integro-difference equation whose solution converges asymptotically at the same rate as that of Hallen's equation. The resulting equation is essentially that obtained by approximating the second derivative in Pocklington's equation by its finite difference equivalent. The authors suggest a simple and highly efficient method for solving Pocklington's equation. This approach is contrasted to the point-matched solution of Pocklington's equation and the reasons for the poor convergence of the latter are examined.     

Pulse propagation in a nonlinear dielectric slab waveguide

The evolution of an optical pulse in a single-mode, step index dielectric slab waveguide which is characterized by an intensity dependent dielectric function in the core and cladding regions is treated by means of differential equation techniques. A cubic order non-linearity is considered. The electromagnetic field distribution in the slab waveguide region satisfies a non-linear wave equation. This field can be represented in terms of even TE guided modes with a slowly varying envelope amplitude function. Then using the well known approximation, based on the slowly varying character of the amplitude function, a non linear partial differential equation is obtained for the amplitude function. As the coefficients of this equation depend on the distance across the transverse direction X, an averaging technique over x is applied to reduce the nonlinear partial differential equation into a form that is easily transformed to the so-called non-linear Scroedinger differential equation. This equation is then attacked by means of the well known Inverse Scattering method in the case of reflection less potentials. The single and double soliton solutions are obtained explicitly for a single-mode slab waveguide. Finally numerical results are presented in the time domain.     

波形对数字信道化接收机测频性能影响分析

对于典型的数字信道化接收机之后级联相位差分法测频的处理架构,现有的测频精度表达式未考虑波形复包络对测量精度的影响。该文针对这一问题,推导了考虑波形复包络影响的新的测频精度表达式,并进行了仿真。仿真分析的结果与推导的精度表达式一致,表明改进的测频精度表达式能够有效反映信号波形对测频性能的影响。     

Solutions for Some Waveguide Discontinuities by the Method of Moments (Short Papers)

The electromagnetic boundary value problem of two waveguides coupled by an aperture or an aperture in a waveguide radiating into free space may be described by an integral equation. An analytical solution to this integral equation cannot be readily found due to the complexity of the kernel. However, extremely useful results may be obtained if the method of moments is employed to reduce the integral equation to a matrix equation which can be solved by known methods. In this short paper, series and shunt slots in a rectangular waveguide are analyzed using this technique.     

Known-Plaintext Attack to Two Cryptosystems Based on the BB Equation

Recently, Rama Murthy and Swamy proposed a symmetric cryptosystem based on the Brahmagupta-Bhaskara (BB) equation. The BB equation is the quadratic Diophantine equation nx ² + k = y ², where k is an integer and n is a positive integer such that radic(n) is irrational. For the particular case k=1, the equation is called the Pell equation. The proposed cryptosystem was modified later by the same authors in order to avoid the cryptanalysis given by Youssef. Below, a known-plaintext attack to both cryptosystems is presented.     

微机械槽板结构空气压膜阻尼的修正雷诺方程

推导出了一个适用于槽板结构压膜空气阻尼的微分方程.该方程与传统雷诺方程的区别是在雷诺方程的左边增加了一个用以表示气体从槽流出所引起的阻尼效应的修正项,并考虑了槽中有限气流通道长度的端头修正.在适当的边界条件下,利用此方程可以求解槽板压膜阻尼的压强分布、阻尼力和阻尼力系数.该槽板结构压膜空气阻尼的微分方程对槽板的厚度和横向尺度没有限制,为分析有限尺寸和有限厚度槽板的压膜空气阻尼提供了一个有用的方法.     

Transient excitation of a straight thin-wire segment: a new look atan old problem

The transient excitation of a straight thin-wire segment is analyzed with the aid of a one-dimensional integral equation for the current along the wire. An almost exact derivation of that equation, in which only the radial current on the end faces is approximated, is given. The integral equation obtained turns out to be identical to the reduced version of Pocklington's equation. On the basis of this derivation, existing and new numerical solution techniques are critically reviewed. Pocklington's equation and Hallen's equivalent form are solved directly by marching on in time as well as indirectly via a transformation to the frequency domain. For Pocklington's equation, a conventional moment-method discretization leads to a Toeplitz matrix that is inverted with Levinson's algorithm. For Hallen's equation, the Toeplitz structure is disturbed, and the frequency-domain constituents are determined with the aid of the conjugate-gradient-FFT method. Illustrative numerical results are presented and discussed     

Algorithm for solving the Welch-Berlekamp key-equation, with a simplified proof

An alternative technique due to Welch and Berlekamp (1983) for decoding Reed-Solomon codes has a key equation different in form from the key equation solved by the conventional Berlekamp-Massey algorithm or by the so-called Euclidean algorithm. The authors present an algorithm for solving the key equation which has a simple structure and which is readily shown to work.<>     

The wave propagation and mode coupling in warm ionosphere

The wave propagation in warm ionosphere is studied in both homogeneous and inhomogeneous ionosphere. When the temperature of electrons are taken into account, the plasma wave is a propagating wave. The dispersion relation of waves in warm ionosphere has been derived. It is an algebric equation which is analogue to the Appleton-Hartree equation, but in higher order. In a stratified warm ionosphere, the equation forq (Booker’sq) is an algebric equation. Both of these equations are used in study of the wave propagation in the ionosphere by means of ray tracing method. The wave mode linking in homogeneous ionosphere and mode coupling in stratified ionosphere are studied. The mode coupling between plasma wave and electromagnetic wave is discussed through the discussion of singularity of the wave equation. The wave fiold near the wave transformation region can be found out by solving the wave equation near the singularity. The justification of study mode conversion by ray tracing is explained. The results could be useful in the study of wavo absorption process and radio heating experiments in the ionospheres.