共查询到20条相似文献,搜索用时 31 毫秒
1.
K. A. Kopotun 《分析论及其应用》1995,11(2):41-58
Some estimates for unconstrained and convex polynomial approximation in the uniform metric are obtained. These results are
given in terms of the Ditzian-Totik moduli of smoothness
, ≤1 with
. The construction of the approximating polynomials does not depend on λ. 相似文献
2.
A. Horwitz 《分析论及其应用》1993,9(2):71-80
Let
and let
, where P
c
n
denoles the Taylor polynomial to f at c of order n, where n is even. TA and TM are reach generalizations of the Trapezoidal
rule and the midpoint rule, respectively, and are each exact for all polynomials of degree ≤n+1. We let L(f)=αTM(f)+(1−α)TA(f),
where
, to obtain a numerical integration rule L which is exact for all polynomials of degree≤n+3 (see Theorem 1). The case n=0
is just the classical Simpson's rule. We analyze in some detail the case n=2, where our formulae appear to be new. By replacing
P
(a+b)
2/n+1
(x) by the Hermite cubic interpolant at a and b, we obtain some known formulae by a different approach (see [1] and [2]).
Finally we discuss some nonlinear numerical integration rules obtained by taking piecewise polynomials of odd degree, each
piece being the Taylor polynomial of f at a and b, respectively. Of course all of our formulae can be compounded over subintervals
of [a,b]. 相似文献
3.
WangJianli ZhouSongping 《分析论及其应用》2003,19(3):280-288
The present paper deals with best onesided approximation rate in Lp spaces ^~En(f)Lp of f∈C2π.Although it is clear that the estimate ^~E(f)Lp≤C‖f‖Lp cannot be correct for all f∈L^p2π in case p<∞, the question whether ~En(f)Lp≤Cω(f,n^-l)Lp or ^~En(f)Lp≤CEn(f)Lp holds for f∈ C2π remains totally untouched.Therefore it forms a basic problem to justify onesided approximation. The present paper will provide an answer to settle down the basis. 相似文献
4.
Let {zk=xk+iyk} be a sequence on upper half plane
and {si} be the number of appearence of zk in {z1,z2,...,zk}. Suppose sup si<+∞. Let ω(x) be a weight belonging to A∞ and
. We Consider the weighted Hardy space
and operator Tp mapping f(z)∈H
+w
p
into a sequence defined by
, 0<p≤+∞, j=1,2,.... Then Tp(H
+w
p
)=lp if and only if {zk} is uniformly separated. Besides the effective solution for interpolation is obtained.
Supported by National Science Foundation of China and Shanghai Youth Science Foundation 相似文献
5.
For arbitrary given positive term series
and
, the present paper provides an interesting necessary and sufficient condition for
.
In Memory of Professor M. T. Cheng
The Research Project of the Mathematical Institute, Ningbo University.
Supported in part by Zhejiang Provincial Natural Science Foundation, and by State Key Laboratory of Southwest Institute of
Petroleum. 相似文献
6.
V. L. Oleînik 《Journal of Mathematical Sciences》2000,101(3):3133-3138
Let {
}, where {
} is the open unit disk on the complex plane {
}. In G, we consider analytic solutions u(t, z) ({
}, {
}) of the heat equation 2ut=uzz with initial data f(z)=u(0, z) belonging to the Fock space F, i.e., to the space of entire functions square summable with
the weight e−|z|2.Conditions on a nonnegative measure μ on G are described under which for all f ∈ F we have {
} Bibliography: 17 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 247, 1997, pp. 146–155.
Translated by S. V. Kislyakov. 相似文献
7.
8.
Let
and
be adjoint nilpotent orbits in a real semisimple Lie algebra. Write
≥
if
is contained in the closure of
. This defines a partial order on the set of such orbits, known as the closure ordering. We determine this order for the split
real form of the simple complex Lie algebra, E
8. The proof is based on the fact that the Kostant-Sekiguchi correspondence preserves the closure ordering. We also present
a comprehensive list of simple representatives of these orbits, and list the irreeducible components of the boundaries
and of the intersections
. 相似文献
9.
We construct functions Mα which are piecewise homogeneous polynomials on the (d+1)-dimensional torus Ud+1. These functions possess complete symmetry with respect to the independent variables. The symmetry and homogeneous relations
for these functions are exploited to obtain a recurrence relation and explicit representations. Furthermore, we show that
, where ω=e12x/k, 0≤jt≤k−1, are linearly independent. By restricting Mα to Ud, we obtain the complex analogue of polynomial box splines on a (d+1)-direction mesh on Ud, which is a multivariate analogue of B-splines on the circle studied by I.J. Schoenberg[8]. 相似文献
10.
Mitsuru Uchiyama 《Integral Equations and Operator Theory》2000,37(1):95-105
LetA, B be bounded selfadjoint operators on a Hilbert space. We will give a formula to get the maximum subspace
such that
is invariant forA andB, and
. We will use this to show strong monotonicity or strong convexity of operator functions. We will see that when 0≤A≤B, andB−A is of finite rank,A
t
≤B
t
for somet>1 if and only if the null space ofB−A is invariant forA. 相似文献
11.
In studying local harmonic analysis on the sphere Sn, R.S. Strichartz introduced certain zonal functions ϕ2(d(x, y)) which satisfy the equation
, where Δz is the Laplace operator and δ−y the Dirac measure. The explicit expression of the constant a (λ) is given by R.S. Strichartz in the case that n is odd. Appyling
the Apéry identity, we show in this paper that
for n even, where wn-1 is the surface area of Sn-1,
.
The author's research was supported by a grant from NSFC. 相似文献
12.
Yasunori Fujikoshi Yoshimichi Ochi 《Annals of the Institute of Statistical Mathematics》1984,36(1):119-128
Summary In this paper we obtain an asymptotic expansion of the distribution of the maximum likelihood estimate (MLE)
based onT observations from the first order Gaussian process up to the term of orderT
−1. The expansion is used to compare
with a generalized estimate
including the least square estimate (LSE)
, based on the asymptotic probabilities around the true value of the estimates up to the terms of orderT
−1. It is shown that
(or the modified MLE
) is better than
(or the modified estimate
). Further, we note that
does not attain the bound for third order asymptotic median unbiased estimates. 相似文献
13.
P. Pych-Taberska 《分析论及其应用》1994,10(4):25-36
For measurable functions f of two real variables there are considered the Boolean sums
of parametric extensions of certain univariate Durmeyer-type operators
and
. The weighted mixed moduli of continuity of
are estimated and the degrees of approximation of f by
in some weighted norms are investigated. 相似文献
14.
XuSenlin DengQintao ChenDongmei 《分析论及其应用》2004,20(3):288-293
Let M be a compact minimal hypersurface of sphere Sn 1(1). Let (M) be H (r)-torus of sphere Sn 1 (1).Assume they have the same constant mean curvature H, the result in [1] is that ifSpec0(M, g) =Spec0((M), g),then for 3≤ n ≤ 6, r2≤n-1/n or n ≥ 6, r2 ≥ n-1, then M is isometric to (M). We improved the result and prove that: if Spec0(M,g) =Spec0((M),g), then M is isometric to (M). Generally, if Specp(M,g) =Specp((M),g), here p is fixed and satisfies that n(n - 1) ≠ 6p(n - p), then M is isometric to (M). 相似文献
15.
We theoretically investigate the asymptotical stability, local bifurcations and chaos of discrete-time recurrent neural networks
with the form of
, where the input-output function is defined as a generalized sigmoid function, such asv
i
=2/π arctan(π/2μiμi),
and
, etc. Numerical simulations are also provided to demonstrate the theoretical results. 相似文献
16.
Cao Jiading 《分析论及其应用》1989,5(2):99-109
Let an≥0 and F(u)∈C [0,1], Sikkema constructed polynomials:
, ifα
n
≡0, then Bn (0, F, x) are Bernstein polynomials.
Let
, we constructe new polynomials in this paper:
Q
n
(k)
(α
n
,f(t))=d
k
/dx
k
B
n+k
(α
n
,F
k
(u),x), which are called Sikkema-Kantorovic polynomials of order k. Ifα
n
≡0, k=1, then Qn
(1) (0, f(t), x) are Kantorovič polynomials Pn(f). Ifα
n
=0, k=2, then Qn
(2), (0, f(t), x) are Kantorovič polynomials of second order (see Nagel). The main result is:
Theorem 2. Let 1≤p≤∞, in order that for every f∈LP [0, 1],
, it is sufficient and necessary that
,
§ 1. Let f(t) de a continuous function on [a, b], i. e., f∈C [a, b], we define[1–2],[8–10]:
.
As usual, for the space Lp [a,b](1≤p<∞), we have
and L[a, b]=l1[a, b].
Letα
n
⩾0and F(u)∈C[0,1],Sikkema-Bernstein polynomials
[3] [4].
The author expresses his thanks to Professor M. W. Müller of Dortmund University at West Germany for his supports. 相似文献
17.
A. G. Babenko 《Mathematical Notes》1996,60(3):248-263
In this paper we prove the Jackson-Stechkin inequalityE
n−1(f)<ω
n
(f, 2τ
n
,λ),n≥1,m≥5,r≥1, f ∈L2(
),f ≢ const, which is sharp for eachn=2, 3, ...; hereE
n−1
(f) is the best approximation of a functionf by spherical polynomials of degree ≤n−1, ω
n
(f, τ) is theτth modulus of continuity off based on the translations
,t ∈ ℝ,x ∈
,
,
is the measure of the unit Euclidean sphere
,
, andτ
n
,λ is the first positive zero of the Gegenbauer cosine polynomial
(cost).
Translated fromMatematicheskie Zametki, Vol. 60, No. 3, pp. 333–355, September, 1996.
The present paper was discussed at Ural State University in a seminar headed by Professor Arestov. The author is grateful
to Professor Arestov and Associate Professor Popov for useful conversations.
This research was supported by the State Commission for Higher Education of the Russian Federation under grant No. 2-16-5-31
and by the Russian Foundation for Basic Research under grant No. 93-011-196. 相似文献
18.
S. Pirzada Merajuddin T. A. Naikoo 《分析论及其应用》2007,23(4):363-374
Let D(U, V, W) be an oriented 3-partite graph with |U|=p, |V|=q and |W|= r. For any vertex x in D(U, V, W), let d x and d-x be the outdegree and indegree of x respectively. Define aui (or simply ai) = q r d ui - d-ui, bvj(or simply bj) = p r d vj - d-vj and Cwk (or simply ck) = p q d wk - d-wk as the scores of ui in U, vj in V and wk in Wrespectively. The set A of distinct scores of the vertices of D(U, V, W) is called its score set. In this paper, we prove that if a1 is a non-negative integer, ai(2≤i≤n - 1) are even positive integers and an is any positive integer, then for n≥3, there exists an oriented 3-partite graph with the score set A = {a1,2∑i=1 ai,…,n∑i=1 ai}, except when A = {0,2,3}. Some more results for score sets in oriented 3-partite graphs are obtained. 相似文献
19.
Deh-phone Kung Hsing 《Annali di Matematica Pura ed Applicata》1976,109(1):235-245
Summary We consider the system(L):
, t ⩾ p, y(t)=f(t), t⩽0, where y is an n-vector and each Ai, B(t) are n × n matrices. System(L) generates a semigroup by means of Ttf(s)=y (t+s, f), f(s) ∈ BCl(− ∞, 0]. Under some hypotheses concerning the roots ofdet
where
is the Laplace transform of B(t), the asymptotic behavior of y(t) is discussed. Two typical results are: Theorem 3.1: suppose
∥B(t)∥ ɛ L1[0, ∞),
thendet
forRe λ>0 iff for every ɛ>0 there is an Mɛ>0 such that ∥Ttf∥l ⩽ ⩽ Mɛ
exp [ɛt]∥f∥l for t ⩾ 0. Corollary 3.1.1: suppose
exp [at]B(t) ∈ ∈ L1[0, ∞) for some a>0 anddet
forRe λ>−a. Then the solution of(L) is exponentially asymptotically stable.
Entrata in Redazione il 21 marzo 1975.
The author is grateful to ProfessorC. Corduneanu for suggesting this problem and for many helpful discussions during the preparation of the paper. 相似文献
20.
Given H≥0 and bounded convex curves α1, ...,⇌n, α in the plane z=0 bounding domains D1, …, Dn, D, respectively, with
if i ∈ j and with Di ⊂ D, we obtain several results proving the existence of a constanth depending only on H and on the geometry of the curves
αi, α such that the Dirichlet problem for the constant mean curvature H equation:
where
may accept or not a solution. 相似文献