连续可导函数类的最优拉格朗日插值

在构造拉格朗日插值算法时,插值结点的选择是十分重要的.给定一个足够光滑的函数,如果结点选择的不好,当插值结点个数趋于无穷时,插值函数不收敛于函数本身.例如龙格现象:对于龙格函数f(x)=1/1+25x^2,如果拉格朗日插值的结点取[-1,1]上的等距结点,那么逼近的误差会随着结点个数增多而趋于无穷大⑴,由此可知插值结点的选择尤为重要.     

具Jacobi节点的Hermite-Fejr插值算子的渐近估计(Ⅱ)

在[2]中我们建立了以第一、二类Chebyshev多项式的零点作为结点的Hermite-Fejer插值算子以及以第二类Chebyshev多项式的零点和端点±1作为结点的拟Hermite-Fejer插值算子对二次可微函数的渐近估计.本文将建立另两个插值算子对二次可微函数的渐     

关于球面上的Lagrange插值

1引 言 单位球面上的插值问题一直是三元插值问题中比较受关注的部分.近年来,球面上的 Lagrange插值问题已经得到了很好地解决.例如[1]中给出了构造单位球面上的Lagrange 插值适定结点组的一种方法：添加圆周法.[2]和[3]中研究了单位球面上的多项式插值问题,给出了构造单位球面上的插值适定结点组的另外两种方法.     

一个无限可微函数类的最优Lagrange 插值

本文研究\,$[-1,1]$上的一个无限可微函数类$F_\infty$在空间$L_\infty[-1,1]$及加权空间$L_{p,\omega}[-1,1]$, $1\le p< \infty$ ($\omega$是$(-1,1)$上的非负连续可积函数)的最优Lagrange插值.我们证明了基于首项系数为1且于$L_{p,\omega}[-1,1]$上有最小范数的多项式零点的Lagrange插值对$1\le p< \infty$是最优的. 同时我们给出了当结点组包含端点时的最优结点组.     

Lagrange插值在最大框架下的逼近误差

<正>1引言代数多项式插值理论是函数逼近理论和计算数学的重要研究内容.在函数逼近理论研究中,传统研究内容是对个体函数讨论插值多项式依赖于连续模或多项式最佳逼近的误差估计问题,其系列研究结果可见专著[7]或综述文章[8],近期研究结果可见[1,5]及     

关于三次样条插值的逼近阶

对于三次周期样条插值,我们得到插值样条逼近阶和被插函数光滑性之间的关系,本文继续讨论非周期边界条件的情形。 对[0,1]的n等分分划,用L_n~Ⅰ(f,x)、L_n~Ⅱ(f,x)分别表示满足下列条件的以[0,1]的n等分点为结点的三次样条函数     

二次样条插值的收敛性

<正> 本文讨论一类插值结点与样条结点不重合的二次样条插值.[6]讨论了这类插值的存在性、唯一性和某种变分性质.[1—3],[5]讨论了它的特殊情形——中点插值的收敛性和误差界,本文在一般情况下得出了类似的结果.[4]在一般情况下讨论了收敛性,其条件是 f(x)∈Lipα(0<α≤1).本文给出了当 f(x)∈C~0[a,b]时的收敛性及 f(x)∈C~l[a,b](l=1,2,3)时的余项估计.     

二次样条插值及其变分性质

<正> 关于二次样条插值已有不少讨论,例如[1]讨论了样条结点与插值结点重合的二次     

定义域曲面上光滑插值方法

1　引　　言限制在光滑曲面的函数插值是计算几何中一个较新研究方向 ,有广泛的应用前景 .如飞机机翼上压力估算 ;人体表面的温度分布 ;分析地球上的降雨量以及大气层的“温室效应”,包括臭氧层的估计等 .目前 ,已有一些解决它的方法 ,其中大部分方法是构造球面上插值函数[1 ,2 ,3 ] ,主要思想是用大圆弧代替直线段 ,从而将欧氏空间中已有的插值方法推广到球面上构造插值函数 ,这种方法最大的缺陷是难以推广到一般的曲面上 ,因一般曲面上两点间测地线不易求出 .还有一些方法 [4,5,6] 是基于曲面的三角或四面体划分 ,有相对多得多的插值函数…     

Grunwald插值算子的Lp收敛速度

讨论了以第二类Tchebycheff多项式的零点为插值结点组的Grünwald插值于Lp下的收敛性.当1≤p＜2时,给出了收敛速度的一个精确估计;当p≥2时,说明了其Lp下不是收敛算子列.给出了一种以第二类Tchebycheff多项式的零点为插值结点组的修改的Grünwald插值,证明了其于Lp(1≤p＜∞)下是收敛的.     

INTERPOLATION WITH RESTRICTED ARC LENGTH

AbstractFor given data (t_i,y_i),i=0, 1,…,n,0=t_0相似文献   

О наилучшем выборе уз лов при интерполиров ании функций эрмитовыми с плайнами

The problem of optimal choice of knots is considered for the functions belonging to the classW ^2m+1 V, concerning interpolation by means of Hermite splines. The problem of asymptotically best choice of the knots for interpolation of a fixed functionf(x) (f^(2m+2)(x)>0, 0x1) by Hermite splines is also treated.     

Interpolation by periodic splines with Birkhoff knots

Summary We give a complete characterization of the Hermite interpolation problem by periodic splines with Birkhoff knots. As a dual result we derive the characterization of the Birkhoff interpolation by periodic splines with multiple knots.Sponsored by the Bulgarian Ministry of Education and Science under Contract No. MM-15     

Interpolation and Approximation by Splines on [0, ∞ )

We investigate interpolation and approximation problems by splines, which possess a countable set of knots on the positive axis. In particular, we characterize those sets of points, which admit unique Lagrange interpolation and give some sufficient and some necessary conditions for best approximations. Moreover, we show that the classical results of spline-approximation theory are not available for splines with a countable set of knots.     

Two-scale symbol and autocorrelation symbol for B-splines with multiple knots

The Fourier transforms of B-splines with multiple integer knots are shown to satisfy a simple recursion relation. This recursion formula is applied to derive a generalized two-scale relation for B-splines with multiple knots. Furthermore, the structure of the corresponding autocorrelation symbol is investigated. In particular, it can be observed that the solvability of the cardinal Hermite spline interpolation problem for spline functions of degree 2m+1 and defectr, first considered by Lipow and Schoenberg [9], is equivalent to the Riesz basis property of our B-splines with degreem and defectr. In this way we obtain a new, simple proof for the assertion that the cardinal Hermite spline interpolation problem in [9] has a unique solution.     

Two-scale symbol and autocorrelation symbol for B-splines with multiple knots

The Fourier transforms of B-splines with multiple integer knots are shown to satisfy a simple recursion relation. This recursion formula is applied to derive a generalized two-scale relation for B-splines with multiple knots. Furthermore, the structure of the corresponding autocorrelation symbol is investigated. In particular, it can be observed that the solvability of the cardinal Hermite spline interpolation problem for spline functions of degree 2m+1 and defectr, first considered by Lipow and Schoenberg [9], is equivalent to the Riesz basis property of our B-splines with degreem and defectr. In this way we obtain a new, simple proof for the assertion that the cardinal Hermite spline interpolation problem in [9] has a unique solution.     

An always successful method in univariate convex C^2 interpolation

Summary. We consider convex interpolation with cubic splines on grids built by adding two knots in each subinterval of neighbouring data sites. The additional knots have to be variable in order to get a chance to always retain convexity. By means of the staircase algorithm we provide computable intervals for the added knots such that all knots from these intervals allow convexity preserving spline interpolation of continuity. Received May 31, 1994 / Revised version received December 22, 1994     

Hermite Interpolation of Data Sets by Minimal Spline Spaces

Hermite interpolation of 2n + k data by spline spaces of order k with n variable knots counting multiplicities is studied. A characterization of the minimal spline spaces which admit a solution of the interpolation problem is obtained. A sufficient condition on uniqueness of interpolating spline functions is given.     

Nonnegative splines, in particular of degree five

Summary. We investigate splines from a variational point of view, which have the following properties: (a) they interpolate given data, (b) they stay nonnegative, when the data are positive, (c) for a given integer they minimize the functional for all nonnegative, interpolating . We extend known results for to larger , in particular to and we find general necessary conditions for solutions of this restricted minimization problem. These conditions imply that solutions are splines in an augmented grid. In addition, we find that the solutions are in and consist of piecewise polynomials in with respect to the augmented grid. We find that for general, odd there will be no boundary arcs which means (nontrivial) subintervals in which the spline is identically zero. We show also that the occurrence of a boundary arc in an interval between two neighboring knots prohibits the existence of any further knot in that interval. For we show that between given neighboring interpolation knots, the augmented grid has at most two additional grid points. In the case of two interpolation knots (the local problem) we develop polynomial equations for the additional grid points which can be used directly for numerical computation. For the general (global) problem we propose an algorithm which is based on a Newton iteration for the additional grid points and which uses the local spline data as an initial guess. There are extensions to other types of constraints such as two-sided restrictions, also ones which vary from interval to interval. As an illustration several numerical examples including graphs of splines manufactured by MATLAB- and FORTRAN-programs are given. Received November 16, 1995 / Revised version received February 24, 1997     

Convex interval interpolation using a three-term staircase algorithm

Motivated by earlier considerations of interval interpolation problems as well as a particular application to the reconstruction of railway bridges, we deal with the problem of univariate convexity preserving interval interpolation. To allow convex interpolation, the given data intervals have to be in (strictly) convex position. This property is checked by applying an abstract three-term staircase algorithm, which is presented in this paper. Additionally, the algorithm provides strictly convex ordinates belonging to the data intervals. Therefore, the known methods in convex Lagrange interpolation can be used to obtain interval interpolants. In particular, we refer to methods based on polynomial splines defined on grids with additional knots. Received September 22, 1997 / Revised version received May 26, 1998