光滑Jordan.曲线上一类极值多项式的逼近性质

关于Bieberbach多项式的逼近性质已有许多精彩结果,然而Jordan曲线上极值多项式的逼近性质却很少被考察.本文得到了C^1+α光滑Jordan曲线上一类极值多项式的一些逼近结果.     

Uniform Convergence of the Generalized Bieberbach Polynomials in Regions with Zero Angles

Let C be the extended complex plane; G C a finite Jordan with 0 G; w= (z) the conformal mapping of G onto the disk normalized by . Let us set , and let be the generalized Bieberbach polynomial of degree n for the pair (G,0), which minimizes the integral in the class of all polynomials of degree not exceeding n with . In this paper we study the uniform convergence of the generalized Bieberbach polynomials with interior and exterior zero angles and determine its dependence on the properties of boundary arcs and the degree of their tangency.     

Jacobi Polynomials,Weighted Sobolev Spaces and Approximation Results of Some Singularities

In this paper, we give some polynomial approximation results in a class of weighted Sobolev spaces, which are related to the Jacobi operator. We further give some embeddings of those weighted Sobolev spaces into usual ones and into spaces of continuous functions, in order to use the above approximation results in the p‐version (or the spectral method) of some finite or boundary element methods. Finally, two typical examples of the polynomial approximation of some singularities of boundary value problems in polygonal or polyhedral domains are presented.     

WKB Approximation and Krall-Type Orthogonal Polynomials

We give a unified approach to the Krall-type polynomials orthogonal withrespect to a positive measure consisting of an absolutely continuous oneperturbed by the addition of one or more Dirac deltafunctions. Some examples studied by different authors are considered from aunique point of view. Also some properties of the Krall-type polynomials arestudied. The three-term recurrence relation is calculated explicitly, aswell as some asymptotic formulas. With special emphasis will be consideredthe second order differential equations that such polynomials satisfy. Theyallow us to obtain the central moments and the WKB approximation of thedistribution of zeros. Some examples coming from quadratic polynomialmappings and tridiagonal periodic matrices are also studied.     

Some Geometric Properties of Julia Sets and filled-in Julia Sets of Polynomials

In this paper, some geometric properties of connected Julia sets and filled-in Julia sets of polynomials are given.     

Approximation by rational functions in Smirnov-Orlicz classes

Let G be a doubly-connected domain bounded by Dini-smooth curves. In this work, the approximation properties of the Faber-Laurent rational series expansions in Smirnov-Orlicz classes EM(G) are studied.     

Approximation by Algebraic Polynomials on Rectangles

A direct theorem for approximation by algebraic polynomials in two variables with different degrees in each variable in L_p-metric (1 p ) on rectangles is proved, and the dependence of the constants on various parameters is studied.     

Asymptotic Properties of Zeros of Hypergeometric Polynomials

In a paper by K. Driver and P. Duren (1999, Numer. Algorithms21, 147–156) a theorem of Borwein and Chen was used to show that for each k the zeros of the hypergeometric polynomials F(−n, kn+1; kn+2; z) cluster on the loop of the lemniscate {z: |z^k(1−z)|=k^k/(k+1)^k+1}, with Re{z}>k/(k+1) as n→∞. We now supply a direct proof which generalizes this result to arbitrary k>0, while showing that every point of the curve is a cluster point of zeros. Examples generated by computer graphics suggest some finer asymptotic properties of the zeros.     

多元Bernstein多项式加权逼近的Steckin-Marchaud型不等式

引进一种新的光滑模,建立多元Ｂｅｒｎｓｔｅｉｎ多项式加权逼近的Ｓｔｅｃｋｉｎ Ｍａｒｃｈａｕｄ型不等式．     

Carathéodory’s Theorem and moduli of local connectivity

We give a quantitative proof of the Carathéodory Theorem by means of the concept of a modulus of local connectivity and the extremal distance of the separating curves of an annulus.     

单位根上重Hermite插值多项式的逼近阶

设ｆ（ｚ）在｜ｚ｜≤１解析，在｜ｚ｜≤１连续．本文得到了基于单位根的扩充Ｈｅｒｍｉｔｅ插值多项式在｜ｚ｜≤１上一致收敛于ｆ（ｚ）的逼近阶和在｜ｚ｜＝１上平均收敛于ｆ（ｚ）的逼近阶，且一般说来，阶还是精确的．进而说明，重数不同的插值多项式的逼近阶不同于重数相同的插值多项式的逼近阶．     

单纯形上的Stancu多项式与最佳多项式逼近

作为Bernstein多项式的推广,本文定义单纯形上的多元Stancu多项式.以最佳多项式逼近为度量,建立Stancu多项式对连续函数的逼近定理与逼近阶估计,给出Stancu多项式的一个逼近逆定理,从而用最佳多项式逼近刻划Stancu多项式的逼近特征.     

Dynamics of 2D fluid in bounded domain via conformal variables

In the present work, we compute numerical solutions of an integro-differential equation for traveling waves on the boundary of a 2D blob of an ideal fluid in the presence of surface tension. We find that solutions with multiple lobes tend to approach Crapper capillary waves in the limit of many lobes. Solutions with a few lobes become elongated as they become more nonlinear. It is unclear whether there is a limiting solution for small number of lobes, and what are its properties. Solutions are found from solving a nonlinear pseudodifferential equation by means of the Newton conjugate-residual method. We use Fourier basis to approximate the solution with the number of Fourier modes up to $$.     

Meromorphic functions with bounded boundary rotation

In this article, we generalize the class of meromorphic functions with bounded boundary rotation and related classes. Characterizations and some properties of these classes of functions are given.     

Orlicz空间中三角多项式倒数对周期可微函数的逼近定理

利用Orlicz空间内有关不等式技巧在Orlicz空间内研究了用三角多项式的倒数逼近周期可微函数的问题.得到了一个逼近定理及其推论.     

MEROMORPHIC FUNCTIONS WITH BOUNDED BOUNDARY ROTATION

In this article, we generalize the class of meromorphic functions with bounded boundary rotation and related classes. Characterizations and some properties of these classes of functions are given.     

Pointwise Approximation Theorems for Combinations and Derivatives of Bernstein Polynomials

We establish the pointwise approximation theorems for the combinations of Bernstein polynomials by the rth Ditzian-Totik modulus of smoothness wФ^r（f, t） where Ф is an admissible step-weight function. An equivalence relation between the derivatives of these polynomials and the smoothness of functions is also obtained.     

On a generalization of the class of functions with bounded Mocanu variation

The object of this paper is to generalise the well-known class of functions analytic in the unit disc having bounded Mocanu variation. Certain properties of this more general class are investigated using convolution techniques.     

Zero Distribution of Composite Polynomials and Polynomials Biorthogonal to Exponentials

We analyze polynomials P _n that are biorthogonal to exponentials , in the sense that

Julia集的逼近

提出了一个逼近 Julia集的算法 ,并与反函数迭代算法及逃逸时间算法进行了分析比较 .该算法具有较好的通用性 ,可用于绘制许多有理映照动力系统的 Julia集 ,包括用现有算法无法绘制的某些 Julia集的计算机图