Mn^（κ）（αn,f,x）在Lp[0,1]中的逼近

本文引进了推广的Bernstein-Kantorvich多项式Mn^(κ)(αn,f,x)并且估计了它在空间Lp[0,1]中的逼近阶。     

某些广义插值在L_p ~(2π)和L_p(R)空间的逼近(英文)

给出了两种插值算子，并研究了它们在和L~(2π)_p和Lp（R）L空间上的逼近阶．用实数α阶的积分模给出逼近度．     

L_[0,1]~p(1

梅雪峰  周颂平 《数学进展》2005,(6)

推广的Kantorovich多项式算子在Lp[0,1](1≤p)中的一个整体逆定理

本文对推广的Ｋａｎｔｏｒｏｖｉｃｈ多项式算子,在满足一定条件下,得出了算子逼近过程中的一个整体逆定理,从而推广了文献（１）中Ｚ‘Ｄｉｔｚｉａｎ的结果。     

Lp[0,1]空间Müntz有理逼近的Jackson型估计

设Λ={λn}n∞=1为正的实数数列,且当n→∞时,有λn↘0.本文给出了当λn≤Mn-1/2,n=1,2,…,(其中M＞0为一正常数)时Müntz系统{xλn}的有理函数在Lp[0,1]空间的逼近速度,主要结论为Rn(f,Λ) Lp≤CMω(f,n-1/2)Lp,1≤p≤∞.     

推广的Grunwald插值在LBaM,ω空间中的逼近

本文研究了推广的Grunwald插值算子在LBaM,ω空间中的逼近.利用Orlicz空间范数和LBaM空间范数关系的不等式,以第一类Chebyshev多项式的零点为结点时,获得了两类推广的Grunwald插值算子在加权的LBaM,ω空间中的逼近阶.     

关于Bernstein-Kantorovi多项式在L_P[0,1]空间中的逼近阶

§1.引 言 对于1≤p<∞,以L_p[a,b]表示适合||f||L_p[a,b]={ |f(x)|~pdx}~(1/p)<∞的f全体。记L_∞[a,b]≡C[a,b],||f||L_∞[a,b]=max|f(x)|. 若a=0.b=1,简记||f||L_p[0,1]=||f||L_p·又设 B_p={g:g(x),g’(x),x(1一x)g’(x)∈L_p[0、1]; x(1-x)g’(x)|x=0,1=0},     

推广的Kantorovich多项式算子在Lp[0,1](1≤P)中的一个局部逆定理

本文在引进了推广的Ｋａｎｔｏｒｏｖｉｃｈ多项式算子的条件下,假设（ａｎ）有界得到了该算子在逼近过程中的局部逆定理,从而推广了文献「１」中Ｚ－Ｄｉｔｚｉａｎ的结果。     

Hp(Ωn)(0＜p＜1)上临界阶Riesz平均强求和的逼近

本文讨论了球面上Hardy空间Hp(0＜p＜1)中Riesz平均的强求和在临界阶δ=n/p-n+1/2的有界性,并且建立了它和最佳逼近之间的关系.     

EXPLICIT TWO-STEP HIGH-ACCURACY METHODS FOR y" = f(x,y)

In this paper, an almost P-stable two-step sixth-order Hybrid method with phase-lag of order infinity and a class explicit eighth-order Obreckoff methods with phase-lag of order 10-24 are developed for the numerical integration of the special second-order periodic initial-value problems. These methods have the advantage of higher algebraic order and considerably smaller phase-tag compared with some methods in [1-6]. Numerical examples indicate that these new methods are more accurate than methods developed by [1-6].     

Неравенство Для Алгебраических Многоченов и зависимостб Между Наилучщими СтепеннЫми приближениями $$E(f)_{L_p } E(f)_{L_q } $$ Фуhкций $$f(x)\varepsilon L_p $$

Acta Mathematica Hungarica -     

The Jackson Inequality for the Best L2-Approximation of Functions on [0, 1] with the Weight x

Let L^2（[0, 1], x） be the space of the real valued, measurable, square summable functions on [0, 1] with weight x, and let n be the subspace of L2（[0, 1], x） defined by a linear combination of Jo（μkX）, where Jo is the Bessel function of order 0 and {μk} is the strictly increasing sequence of all positive zeros of Jo. For f ∈ L^2（[0, 1], x）, let E（f, n） be the error of the best L2（[0, 1], x）, i.e., approximation of f by elements of n. The shift operator off at point x ∈[0, 1] with step t ∈[0, 1] is defined by T（t）f（x）=1/π∫0^π f（√x^2 ＋t^2-2xtcosO）dθ The differences （I- T（t））^r/2f = ∑j=0^∞（-1）^j（j^r/2）T^j（t）f of order r ∈ （0, ∞） and the L^2（[0, 1],x）- modulus of continuity ωr（f,τ） = sup{｜｜（I- T（t））^r/2f｜｜：0≤ t ≤τ] of order r are defined in the standard way, where T^0（t） = I is the identity operator. In this paper, we establish the sharp Jackson inequality between E（f, n） and ωr（f, τ） for some cases of r and τ. More precisely, we will find the smallest constant n（τ, r） which depends only on n, r, and % such that the inequality E（f, n）≤ n（τ, r）ωr（f, τ） is valid.     

关于函数y=f(x)与y=|f(x)|

本文对函数 y=f ( x)与 y=|f ( x) |的部分性质进行了比较和分析 ,指出了它们性质上的区别与联系 .     

Solution générale de l'équation fonctionnellef[x +yf(x)]=f(x)f(y)

Sans résuméDédié à A. M. Ostrowski à l'occasion de son 75^e anniversaire     

Approximation of 1/x by exponential sums in [1, {infty})

^** Email: braess{at}num.rub.de^*** Email: wh{at}mis.mpg.de Approximations of 1/x by sums of exponentials are well studiedfor finite intervals. Here the error decreases like (exp(–ck))with the order k of the exponential sum. In this paper we investigateapproximations of 1/x in the interval [1, ). We prove estimatesof the error by and confirm this asymptotic estimate by numerical results. Numericalresults lead to the conjecture that the constant in the exponentequals .     

The growth of solutions of f″+ e-zf′+ Q(z)f - 0 where the order (Q)＝ I

This paper investigates the growth of solutions of the equation f" + e-zf′ + Q(z)f＝ 0 wherethe order (Q)＝ 1. When Q(z) ＝ h(z)ebz, h(z) is nonzero polynomial, b ≠ -1 is a complex constant, every solution of the above equation has infinite order and the hyper-order 1. We improve the results of M. Frei, M.Ozawa, G. Gundersen and J. K. Langley.