Computational Aspect for Function-Valued Padé-Type Approximation

The computational problems of two special determinants are investigated. Those tion for computing Fredholm integral equation of the second kind. The main tool to be used in this paper is the well-known Schur complement theorem.     

Padé and Padé-Type Approximation for 2π-Periodic Lp Functions

The numerical evaluation of a 2-periodic L ^p function by its Fourier series expansion may become a difficult task whenever only a few coefficients of this series are known or it converges too slowly. In this paper we propose a general method to evaluate such any function, by means of composed Padé-type approximants. The definition, the main ideas, and the properties of the approximants will be given. After having done this successfully, we will consider several concrete examples and a theoretical application to the convergence acceleration problem of functional sequences.     

Computational Aspect For Function-Valued Padé-Type Approximation

The computational problems of two special determinants are investigated. Those determinants appear in the construction of the function-valued Pade-type approximation for computing Fredholm integral equation of the second kind. The main tool to be used in this paper is the well-known Schur complement theorem.     

Generalized Padé-Type Approximation and Integral Representations

In several complex variables, the multivariate Padé-type approximation theory is based on the polynomial interpolation of the multidimensional Cauchy kernel and leads to complicated computations. In this paper, we replace the multidimensional Cauchy kernel by the Bergman kernel function K (z,x) into an open bounded subset of C ⁿ and, by using interpolating generalized polynomials for K (z,x), we define generalized Padé-type approximants to any f in the space OL ²() of all analytic functions on which are of class L ². The characteristic property of such an approximant is that its Fourier series representation with respect to an orthonormal basis for OL ²() matches the Fourier series expansion of f as far as possible. After studying the error formula and the convergence problem, we show that the generalized Padé-type approximants have integral representations which give rise to the consideration of an integral operator – the so-called generalized Padé-type operator – which maps every f OL ²() to a generalized Padé-type approximant to f. By the continuity of this operator, we obtain some convergence results about series of analytic functions of class L ². Our study concludes with the extension of these ideas into every functional Hilbert space H and also with the definition and properties of the generalized Padé-type approximants to a linear operator of H into itself. As an application we prove a Painlevé-type theorem in C ⁿ and we give two examples making use of generalized Padé-type approximants.     

A New Vector-Valued Padé-Type Approximation in the Inner Space

1 Introducton There are various definitions for vector Pad′e approximants. In [10], Wynn was led to use the McLeod isomorphism between vectors and some matrices (Cli?ord numbers) for establishing results for the Pad′e approximants. This theory was devel…     

On the existence of nonlinear Padé-Chebyshev approximations for analytic functions

Mathematical Notes - We present examples of two functions that are analytic on the interval [?1, 1] and satisfy the condition that, for any n = 2, 3, …, the first of them does not have...     

On the Order of Best Approximation by Polynomials in H_q~p Spaces

ＯｎｔｈｅＯｒｄｅｒｏｆＢｅｓｔＡｐｐｒｏｘｉｍａｔｉｏｎｂｙＰｏｌｙｎｏｍｉａｌｓｉｎＨ■ＳｐａｃｅｓＸｉｎｇＦｕｃｈｏｎｇ（邢富冲）（ＣｅｎｔｒａｌＵｎｉｖｅｒｓｉｔｙｆｏｒＮａｔｉｏｎａｌｉｔｉｅｓ，Ｂｅｉｊｉｎｇ，１０００８１）Ｃｏｍｍｕｎｉ...     

On the Best Approximation in Non-Archimedean Normed Linear Spaces

ＯｎｔｈｅＢｅｓｔＡｐｐｒｏｘｉｍａｔｉｏｎｉｎＮｏｎ－ＡｒｃｈｉｍｅｄｅａｎＮｏｒｍｅｄＬｉｎｅａｒＳｐａｃｅｓｏｎＷｅｉｄｕｎ（邱维敦）（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，ＬｏｎｇｙｏｎＮｏｒｍａｌＣｏｌｌｅｇｅ，Ｆｕｊｉａｎ，３６...     

Multipoint Padé Approximation of the Psi Function

Mathematical Notes - The Newton interpretation of the psi function by rational functions with free poles is studied. A discrete formula for the Rodrigues determinants is obtained and the limit...     

Asymptotics of the Best Polynomial Approximation of?|x|p and?of?the Best Laurent Polynomial Approximation of sgn(x) on Two Symmetric Intervals

We present a new method that allows us to get a direct proof of the classical Bernstein asymptotics for the error of the best uniform polynomial approximation of |x| ^p on two symmetric intervals. Note that, in addition, we get asymptotics for the polynomials themselves under a certain renormalization. Also, we solve a problem on asymptotics of the best approximation of sgn(x) on [−1,−a]∪[a,1] by Laurent polynomials.      

On the Rabbinical Approximation of π

We discuss the Rabbinical tradition of geometry concerning circular shapes, as it appears in the Babylonian Talmud and in later commentaries. Three explanations of the difference between π and the Rabbinical value for it, so far not widely known among the scientific community, are given.Copyright 1998 Academic Press.Nous discutons ici la tradition rabbinique en géométrie à propos des figures circulaires, telle qu'elle apparaı̂t dans le Talmud babylonien et dans des commentaires ulterieurs. Trois explications sont proposées pour la différence entre π et la valeur donnée dans la littérature rabbinique. Ces explications semblent peu connues dans la communauté scientifique.Copyright 1998 Academic Press.Wir diskutieren die rabbinische Tradition der Geometrie der kreisförmigen Formen, wie sie im babylonischen Talmud und in späteren Kommentaren erscheint. Wir geben drei Erklärungen für den Unterschied zwischen π und seinem rabbinischen Wert, die unter Wissenschaftlern noch nicht weit bekannt sind.Copyright 1998 Academic Press.MSC 1991 subject classifications: 01A35, 01A17     

On the Nontriviality of the Polynomial Invariant of Two-Component Link

ＯｎｔｈｅＮｏｎｔｒｉｖｉａｌｉｔｙｏｆｔｈｅＰｏｌｙｎｏｍｉａｌＩｎｖａｒｉａｎｔｏｆＴｗｏ－ＣｏｍｐｏｎｅｎｔＬｉｎｋ￥ＷａｎｇＸｉｎｇｙｕ；ＺｈａｏＧｕａｎｇｆｅｎｇ（ＨｅｎａｎＵｎｉｖｅｒｓｉｔｙ，Ｋａｉｆｅｎｇ，Ｈｅｎａｎ，４７５００１）（...     

On the Best Degree of Approximation by Euler (E,q)-Means

Let f(x)∈L_(2π) and its Fourier series by f(x)～α_0/2+sum from n=1 to ∞(α_ncosnx+b_nsinx)≡sum from n=0 to ∞(A_n(x)). Denote by S_n (f,x) its partial sums and by E_n~q(f,x) its Euler (E, q)-means, i. e. E_n~q(f,x)=1/(1+q)~π sum from m=0 to n((?)q~(n-m)S_m(f,x)), with q≥0 (E_n~0≡S_n). In [1] Holland and Sahney proved the following theorem. THEOREM A Ifω(f,t) is the modulus of continuity of f∈C_(2π), then the degree of approximation of f by the (E,q)-means of f is givens by##特殊公式未编改     

On Copositive Approximation in Spaces of Continuous Functions Ⅱ:The Uniqueness of Best Copositive Approximation

This paper is part Ⅱ of "On Copositive Approximation in Spaces of Continuous Functions". In this paper, the author shows that if Q is any compact subset of real numbers, and M is any finite dimensional strict Chebyshev subspace of C(Q), then for any admissible function f ∈C(Q)\M, the best copositive approximation to f from M is unique.     

On the Approximation of Combination of Linear Operators

Let f(x)∈C_(2π).For Valle-Poussin integrals V_n(f,x)=(2n)!! 1(2n-1)!! 2πintegral grom -πto π(f(x 1)cos~(2n)t/2 dt), Z.Ditzian and G.Freud considered the approximation of their combination writingV_(n,1)(f,x)=2V_(2n-1)(f,x)-V_(n-1)(f,x),V_(n,2)(f,x)=8/3V_(4n-1)(f,x)-2V_(2n-1)(f,x) 1/3V_(n-1)(f,x), they proved that V_(n,1)(f,x)-f(x)=O(ω_4(f,1/n~(1/2))), V_(n,2)(f,x)-f(x)=O(ω_6(f,1/n(1/2))) In this paper, using the asymptotic expansions of linear operators with many terms,we generalize the above result to the case of eombination of m terms, where mis an arbtirary positive integer.     

On the Non-Existence of the Closed Orbit for a Liénard System

A sufficient condition for a Liénard system to have no non-trivial closed orbits is given by transforming the system into another system called the Bogdanov—Takens system. The result here (Theorem 2) is a partial improvement of that of Wang and Yu [2].AMS Subject Classification (2000), 34C07, 34C25, 34C26, 34D20     

On the Order of Affine Wavelet Approximation

Suppose h∈L~2(R), α_0>1, b_0>0 and h_(mn) (x) =α_0~(-m/2)h(α_0~(-m)x - nb_0),m,n∈Zand suppose that {h_(mn)} is a frame with frame bounds A,B>0,where <·,·> is the standard inner product on L~2(R) and ||·|| is the L~2 norm on R .Wecall {h_(mn)} the affine frame. Denote its dual frame by {h_(mn)} .It is well known that forany f ∈L~2 (R),