Bessel functions and buckling of the uniform column under combined action due to its own weight and an axial load

If one considers the set of vertical and horizontal loads applied to the column with constant inertia, the classical homogeneous Euler differential equation of the third-order expressing the behavior of the column under its own weight uniformly distributed along the vertical axis is transformed into a non-homogeneous equation by the concept of fictitious length. A new operator attached to Bessel functions is introduced, and the general solution to the non- homogeneous equation is obtained, leading to a formula expressing the critical load of the bar. New formulae are also proposed for the critical load of the bar under its own weight acting alone, and under different support conditions.     

基于小波分析的Bessel声场预处理

采用Fourier-Bessel方法对环型换能器的声场进行数值计算,并对仿真声场进行了深入讨论.通过对换能器轴向声压分布的分析,针对声近场明显的扰动,提出一种新的方法对声场进行预处理,即利用小波多分辨率分析降噪,去除近场杂频率成分,提高声压幅度.研究结果表明,小波分析技术能提高Bessel声场的基波成像质量,对于小波变换在Bessel超声成像中的应用提供了很好的依据.     

Truncation error for the generalized Bessel type sampling series

Numerous upper bounds for the truncation error of the Shannon sampling expansion associated with the Fourier transforms are available in the literature. In this paper we derive an upper bound for the truncation error of the generalized sampling expansion associated with the Hankel (Bessel) transform. A clear example of the application of such series is in the analysis of optical systems with circular symmetry. A lower bound for the Bessel function J_m(j_?,N+iy), which agrees with the known asymptotic one and is necessary to this analysis, is derived. The method, which employs complex contour integration, can be applied to other generalized sampling expansions.     

一个求多项式零点的并行迭代及其收敛的初始条件

首先构造了一个求多项式零点的并行迭代,然后对它的收敛性进行了分析,得出其收敛的两种类型的初始条件     

基于高阶贝塞尔函数预测的路由空洞填补算法

提出一种基于高阶贝塞尔函数预测控制的路由空洞填补算法,进行移动网络电磁波通信路由协议设计,设计高阶贝塞尔函数特性及预测控制技术,采用高阶贝塞尔函数预测控制技术,通过移动网络电磁波通信网进行信息传输,产生不同的层次分类属性,实现对空洞填补算法改进。实验结果表明,算法能使路由空洞空间支路减少,边缘空间增益得到有效控制,降低误码率,提高移动网络电磁波通信系统的通信性能。     

Block-pulse functions method of the inverse laplace transform for irrational and transcendental transfer functions

A new direct method of the block-pulse functions technique of the inverse Laplace transform for irrational and transcendental transfer functions is presented. It is shown that the existing indirect method can be used equivalently with the new one. Two illustrative examples are given.     

Transfer functions of networks with switches

Of concern here are properties of linear networks that contain switches. It is shown that transfer functions can be identified with these networks through the use of a mathematical device called the advance operator. The operator which is based on the Laplace transform technique absorbs the discontinuities engendered by the switches.     

Special functions of circuits and systems

The polynomial solutions of the equation fy″ + gy′ + λy = 0 are obtained and classified for f, g, and λ certain second-degree, first-degree, and zero-degree polynomials, respectively. Applications are given illustrating the use of these polynomials in the construction of amplitude functions and system functions and in tree counting. In particular, all-pole and rational filter functions are considered which include as special cases the Chebyshev, Butterworth, elliptic, Bessel, and various transitional filter functions.     

Realization Theory of Ladder Networks in Terms of the Poles and Zeros of Reflection Coefficient and its Application to a Bandpass Matching Problem

Necessary and sufficient conditions for the realization of lossless, lowpass, ladder networks terminated by a resistance are presented, in terms of the poles and zeros of the reflection coefficient. These conditions yield explicit expressions for the element values. They are then extended to highpass networks. These results are next used in solving a bandpass matching problem and the limitations on the performance of matching networks due to constraints imposed by the load are discussed. A suitable example is worked out to illustrate the problem.     

Powers of SPR functions and preservation properties

Basic properties of a new class of strictly positive real (SPR) functions are stated. Four problems are studied. The first deals with SPR preservation of transfer functions, obtained under the composition of polynomials with SPR0 functions. The second deals with Hurwitz stability preservation of the numerator of transfer functions, obtained under the composition of polynomials with SPR0 functions. The third deals with making a Hurwitz closed-loop plant, an SPR0 function by substituting s by SPR0 functions. The four deals with the synthesis of simultaneous SPR feedback plants. For the new class of SPR0 functions, a characterization is presented. For the first and second problems, sufficient conditions are presented using the new class of SPR0 functions. For the third and four problems, two examples are presented, the first being for simultaneous SPR closed-loop systems via constant controllers. The second is for simultaneous stabilization via universal feedback adaptive control.     

浅谈广告的市场定位及其作用

广告的市场定位是企业为自己的产品所设定的范围和目标,从而满足一部分人需要的方法。因为无论任何企业的任何产品,都无法满足所有顾客的整体要求,因此选择了广告的市场定位才能够准确地把握目标市场。     

Topological formulation of general linear network functions

This paper first discusses the corrections of the errors which Jong and Zobrist made in Ref. (1) and next describes the sign determination suitable forthese topological formulas. The technique for sign determination is based on the node partitioning algorithm which is also presented.     

Ladder realizations of multivariable positive real functions

Necessary and sufficient conditions are obtained for the realization of an m-variable positive real function (PRF) as the impedence function of a resistively-terminated ladder network of m lossless two-ports connected in cascade. Each two-port is a single-variable lossless ladder with all of its transmission zeros either at the origin or at finity. Conditions are also obtained when each of the two-ports is a Fujisawa-type lowpass ladder.     

试论科学普及的社会功能

本文认为科学普及的社会功能应包括以下四个方面 :首先是提高国民科技素质的重要手段 ;其次有助于健全社会科技意识 ;对学校教育而言 ,科普工作是一个重要的配合与补充 ;对科学自身的进步和发展也同样具有十分重要的意义。