Closed-form Representations for Errors of Cubic Spline Approximations on Equally Spaced Knots

This paper considers estimating errors in the approximationof an arbitrary linear functional on C⁴[0, L] by use of cubicsplines on equally spaced knots. Using explicit formulas derivedfor the cubic spline approximations of f_k(x) = cos (kx/L), formulasare found for the cosine expansion of the Peano Kernel for theremainder functional.     

Lebesgue Constant of Local Cubic Splines with Equally Spaced Nodes

It is proved that the uniform Lebesgue constant (the norm of a linear operator from C to C) of local cubic splines with equally spaced nodes, which preserve cubic polynomials, is equal to 11/9.     

A Posteriori Corrections for Non-periodic Cubic and Quintic Interpolating Splines at Equally Spaced Knots

The method proposed recently by Lucas [13], for the a posterioricorrection of odd-degree interpolating periodic splines is extendedto non-periodic cubic and quintic splines.     

作为一元等距结点样条推广的多元样条

作者们在[4]中已经指出了给定剖分下多元B-样条存在的必要条件(1).它表明,并不是对所有的剖分都有多元B-样条存在的。人们也许以为,如同一元情况一样,只要多元B-样条存在,则它们一定组成多元样条空间的支集(即多元样条空间是所有多元B-样条所支架起来的空间)。本文以标准的三角剖分(2-单纯形)下,多元样条空间S²:=S₄²为例指出这种认识是错误的。事实上,本文定理2,3和4对这个问题已给出了明确的结论。 以上结论说明多元B-样条并不是基本的     

The Distribution of the Rational Points on the Unit Circle

In the paper, the explicit form of distribution function for the lengths of arcs connecting neighbouring rational points on the unit circle whose denominators do not exceed given value, is given.     

Stability of Discrete Approximations and Necessary Optimality Conditions for Delay-Differential Inclusions

This paper is devoted to the study of optimization problems for dynamical systems governed by constrained delay-differential inclusions with generally nonsmooth and nonconvex data. We provide a variational analysis of the dynamic optimization problems based on their data perturbations that involve finite-difference approximations of time-derivatives matched with the corresponding perturbations of endpoint constraints. The key issue of such an analysis is the justification of an appropriate strong stability of optimal solutions under finite-dimensional discrete approximations. We establish the required pointwise convergence of optimal solutions and obtain necessary optimality conditions for delay-differential inclusions in intrinsic Euler–Lagrange and Hamiltonian forms involving nonconvex-valued subdifferentials and coderivatives of the initial data.     

Self-Similarity of Some Sequences of Points on a Circle

The self-similarity and periodicity properties are proved for the derivatives d^mO₀ of the sequences O₀, which are obtained by shifting the unit circle by the arc . Bibliogrhaphy: 5 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 302, 2003, pp. 81–95.     

Mass Points of Measures and Orthogonal Polynomials on the Unit Circle

Orthogonal polynomials on the unit circle are completely determined by their reflection coefficients through the Szeg recurrences. We assume that the reflection coefficients tend to some complex number a with 0<a<1. The orthogonality measure μ then lives essentially on the arc {e^it :αt2π−α} where sin with α(0,π). Under the certain rate of convergence it was proved in (Golinskii et al. (J. Approx. Theory96 (1999), 1–32)) that μ has no mass points inside this arc. We show that this result is sharp in a sense. We also examine the case of the whole unit circle and some examples of singular continuous measures given by their reflection coefficients.     

单位圆内拟亚纯映射的奇异点

本文通过一般化Tsuji的一个结果,证明了单位圆内零级K-拟亚纯映射涉及重值的一类奇异点的存在性.     

稳定随机游动重点集的离散豪斯道夫维数

设是ｄ维格子点上的严格α－稳定的随机游动，称为的Ｐ重点集（Ｐ１），本文讨论了的离散豪斯道夫维数，并对，（ａ＜ｄ），证明了Ｐ重点集的维数都等于ａ，即     

Reconstruction of the Linear Ordinary Differential System Based on Discrete Points

In this paper, we discuss an inverse problem, i.e., the reconstruction of a linear differential dynamic system from the given discrete data of the solution. We propose a model and a corresponding algorithm to recover the coefficient matrix of the differential system based on the normal vectors from the given discrete points, in order to avoid the problem of parameterization in curve fitting and approximation. We also give some theoretical analysis on our algorithm. When the data points are taken from the solution curve and the set composed of these data points is not degenerate, the coefficient matrix $A$ reconstructed by our algorithm is unique from the given discrete and noisefree data. We discuss the error bounds for the approximate coefficient matrix and the solution which are reconstructed by our algorithm. Numerical examples demonstrate the effectiveness of the algorithm.     

On the No-Gap Second-Order Optimality Conditions for a Discrete Optimal Control Problem with Mixed Constraints

Motivated by our recent works on optimality conditions in discrete optimal control problems under a nonconvex cost function, in this paper, we study second-order necessary and sufficient optimality conditions for a discrete optimal control problem with a nonconvex cost function and state-control constraints. By establishing an abstract result on second-order optimality conditions for a mathematical programming problem, we derive second-order necessary and sufficient optimality conditions for a discrete optimal control problem. Using a common critical cone for both the second-order necessary and sufficient optimality conditions, we obtain “no-gap” between second-order optimality conditions.     

Fitting a Set of Points by a Circle

Given a set of points S={p ₁ ,. . ., p _n } in Euclidean d -dimensional space, we address the problem of computing the d -dimensional annulus of smallest width containing the set. We give a complete characterization of the centers of annuli which are locally minimal in arbitrary dimension and we show that, for d=2 , a locally minimal annulus has two points on the inner circle and two points on the outer circle that interlace anglewise as seen from the center of the annulus. Using this characterization, we show that, given a circular order of the points, there is at most one locally minimal annulus consistent with that order and it can be computed in time O(n log n) using a simple algorithm. Furthermore, when points are in convex position, the problem can be solved in optimal Θ(n) time. Received June 25, 1997, and in revised form March 5, 1998.     

单位圆内拟亚纯映射的Borel点

研究了单位圆内的拟亚纯映射,建立了角域内的基本不等式,从而证明了拟亚纯映射的Borel点的存在性。     

单位圆内拟亚纯映射的Nevanlinna点

该文定义了单位圆内拟亚纯映射的Nevanlinna点与Borel点，并证明了单位圆内满足条件~lim_{r→1}{T(r)/{log1/(1-r)}}=∞的拟亚纯映射的Nevanlinna点与Borel点的存在性。