带重结点的H_m~T(θ)型求积公式

本文讨论了2π周期函数的正常积分带重结点的具有最大三角精度m-1的HTm(θ)型求积公式;当结点组取定后,得到了求积公式具体的型,并且构造出HTm(θ)型求积公式.     

带重结点的HTm(θ)型求积公式

本文讨论了2π周期函数的正常积分带重结点的具有最大三角精度m-1的HTm（θ）型求积公式;当结点组取定后，得到了求积公式具体的型，并且构造出HTm（θ）型求积公式.     

含Hilbert核的奇异积分带重结点的求积公式

本文讨论了Ｈｅｒｍｉｔｅ三角插值问题利用Ｈｅｒｍｉｔｅ三角插值建立２π周期函数正常积分带重结点的求积公式，用分离奇异点的方法建立了含Ｈｉｌｌｂｅｒｔ核的奇积分带重结点的求积公式。     

三角多项式类中的Birkhoff型三角插值

本文在三角多项式类中讨论了2π周期函数的一类Birkhoff型等距结点的三角插值问题,给出了此问题有解的充要条件,并构造出插值基.     

插值三角多项式在Orlicz空间逼近的渐进等式

对于具有等距分布插值结点的三角多项式,借助广义的Minkowski不等式在Orlicz空间内建立了由三角多项式逼近的渐近等式.并对于Orlicz空间内不同的函数类给出不同的结果.     

一类轴对称平面域上的求积公式

§1 引 言 设二维区域Ω,权函数p(x,y)0,(x,y)∈Ω。寻求以下的求积公式 y≈sum from j=1 to N(c_j(x_j,y_j)), (1.1)使其具有m次代数精度而结点数N为最小,其中c_j为权系数,(x_j,y_j)为结点,j=1,2,…N。我们称具有这种性质的求积公式为具有m次代数精度的最少结点求积公式,简称为最少结点求积公式。 研究各种求积公式中结点数下界,以及构造出各种区域上最少结点求积公式是很有意义的问题。由于求积公式的结点数下界对于固定的代数精度而言,是随积分区域而变化的。因此,只能对各种具体的区域来研究结点数下界的问题。例如和H.Moller     

不带微商的边界型求积公式

本文在不带微商项的条件下,对一些特殊区域构造了具有最高代数精确度的边界型求积公式。还对某些较广泛的区域解决了构造3次边界型或非边界型求积公式的“最少结点数”的问题。 首先,我们在立方体区域上将Sadowsky的42点5次边界型求积公式的结点个数减少到32点,并证明了要构造立方体区域上的5次边界型对称求积公式,结点个数不能少于32。文中还构造出n维双层球壳区域上具有最高(3次)代数精度和最少结点个数((2n+2)点)的边界型求积公式。因此,[5]中构造出的3维双层球壳区域上的8点3次边界型求积公式是“最少结点数”的求积公式。最后,证明了对于2维、3维轴对称区域(即关于所有坐标轴都对称的区域)构造3次求积公式,至少分别用到4个和6个结点。对于n维球域构造3次求积公式至少要用到2n个结点。 本文出现的求积公式都是不带微商项的。     

张量积型二元数值积分研究

基于张量积型的二元牛顿插值多项式,构造了矩形网格上的二元求积公式,其对一些二元多项式精确成立,数值算例说明了求积公式的可行性.     

Hilbert核奇异求积

该文用分离奇点的方法建立了含Hilbert核的奇异积分带重结点的求积公式,给出了求积公式余项的积分表示式。     

球域上的某种意义下的最佳求积公式

关于高维球域上的求积公式,美国的Stroud曾利用代数方法构造了“乘积型求积公式”(见[1])。所谓区域R_n上的求积公式为“乘积型公式”,意即它是由n次迭加一维求积公式所产生的公式。这种公式所用结点个数随着维数的增大而迅速增大,所以对于大维数的积分不宜去构造“乘积型求积公式”。本文应用[2]中给出的矩形域、立方域上的最佳边界型求积公式,给出构造球域上求积公式的一种方法。这种方法的优点是对n维球域的求积公式,只须用一个n-1维的边界型求积公式和一个一维求积公式     

Birkhoff型三角插值

1 引言 Birkhoff三角插值是近年来比较活跃的一个研究课题,涉及Birkhoff三角插值的研究文献也很多(如G.G.Lorentz~([1]),沈燮昌~([2])等综合性文章).     

Determination of the Jump of a Function of Generalized Bounded Variation by the Derivatives of a Trigonometric Interpolation Polynomial

We obtain formulas expressing the value of the jump of a bounded periodic function of harmonic bounded variation in a neighborhood of the point under consideration via the derivatives of odd order of the Lagrange trigonometric interpolation polynomial with equidistant nodes and via the derivatives of even order of the conjugate polynomial.     

Gauss Harmonic Interpolation Formulas for Circular Regions

This paper developes a procedure for computing and tabulatingweights and nodes for a Gauss harmonic interpolation formulawhich allows one to approximate a harmonic function of two variablesat a given interior point of an arbitrary circular region withgiven prescribed values on the boundary. The nodes can be calculatedby finding the Zeros of simple, well-behaved trigonometric polynomial,and each individual weight can be calculated directly by usingexactness properties. Examples are given demonstrating the easeof computation and the accuracy of the formulas.     

求解混合三角多项式方程组的直接GBQ方法

许多科学与工程领域,我们经常需要求混合三角多项式方程组的全部解.一般来说,混合三角多项式方程组可以通过变量替换及增加二次多项式转化为多项式方程组,进而利用数值方法进行求解,但这种转化会增大问题的规模从而增加计算量.在本文中,我们不将问题转化,考虑利用直接同伦方法求解,并给出基于GBQ方法构造的初始方程组及同伦定理的证明.数值实验结果表明我们构造的直接同伦方法较已有的直接同伦方法更加有效.     

Algorithms for solving Hermite interpolation problems using the Fast Fourier Transform

We present a method for computing the Hermite interpolation polynomial based on equally spaced nodes on the unit circle with an arbitrary number of derivatives in the case of algebraic and Laurent polynomials. It is an adaptation of the method of the Fast Fourier Transform (FFT) for this type of problems with the following characteristics: easy computation, small number of operations and easy implementation.In the second part of the paper we adapt the algorithm for computing the Hermite interpolation polynomial based on the nodes of the Tchebycheff polynomials and we also study Hermite trigonometric interpolation problems.     

Fourier and barycentric formulae for equidistant Hermite trigonometric interpolation

We consider the Hermite trigonometric interpolation problem of order 1 for equidistant nodes, i.e., the problem of finding a trigonometric polynomial t that interpolates the values of a function and of its derivative at equidistant points. We give a formula for the Fourier coefficients of t in terms of those of the two classical trigonometric polynomials interpolating the values and those of the derivative separately. This formula yields the coefficients with a single FFT. It also gives an aliasing formula for the error in the coefficients which, on its turn, yields error bounds and convergence results for differentiable as well as analytic functions. We then consider the Lagrangian formula and eliminate the unstable factor by switching to the barycentric formula. We also give simplified formulae for even and odd functions, as well as consequent formulae for Hermite interpolation between Chebyshev points.     

二元Lagrange三角插值多项式在Orlicz空间内的逼近

研究了二元函数用一种组合型的三角插值多项式算子逼近的问题.借助连续模这一工具,给出了这类三角插值多项式在Orlicz空间内的逼近定理.     

Pointwise error estimates for trigonometric interpolation and conjugation

An estimate due to Gaier [2] for the error committed in replacing a periodic function f by an interpolating trigonometric polynomial is sharpened in such a way that the estimate makes evident the interpolating property of the polynomial. A similar improvement is given for Gaier's estimate of the difference between the conjugate of f and the conjugate trigonometric polynomial.     

Lattice Paths and Positive Trigonometric Sums

A trigonometric polynomial generalization to the positivity of an alternating sum of binomial coefficients is given. The proof uses lattice paths, and identifies the trigonometric sum as a polynomial with positive integer coefficients. Some special cases of the q -analogue conjectured by Bressoud are established, and new conjectures are given. January 22, 1997. Date revised: July 9, 1997.     

Comparison of two orthogonal series methods of estimating a density and its derivatives on an interval

We compare the merits of two orthogonal series methods of estimating a density and its derivatives on a compact interval—those based on Legendre polynomials, and on trigonometric functions. By examining the rates of convergence of their mean square errors we show that the Legendre polynomial estimators are superior in many respects. However, Legendre polynomial series can be more difficult to construct than trigonometric series, and to overcome this difficulty we show how to modify trigonometric series estimators to make them more competitive.