共查询到20条相似文献,搜索用时 0 毫秒
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A method is developed for constructing a convenient basis ofrational wedge functions for collocation on convex polygon boundaries. 相似文献
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针对极大值函数的一类光滑逼近——凝聚函数,对其作进一步研究.指出凝聚函数的一阶导数对光滑参数取极限时恰好得到极大值函数的一个次梯度,从而凝聚函数不仅可以一致逼近极大值函数,而且该函数富含极大值函数的一阶信息,可很好的刻画极大值函数的一阶特征.进一步,对光滑逼近函数的光滑参数做简单分析,得到的结果揭示了光滑参数的变动对凝聚函数的影响.并分别以正值函数及绝对值函数为例,对所得到的结果给出几何说明. 相似文献
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Two approaches for the efficient rational approximation of the Fermi-Dirac function are discussed: one uses the contour integral representation and conformal real〉 ping, and the other is based on a version of the multipole representation of the Fermi-Dirac function that uses only simple poles. Both representations have logarithmic computational complexity. They are of great interest for electronic structure calculations. 相似文献
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We repair numerical difficulties in applying saddlepoint tail probability approximations when the ordinate at which the approximation is evaluated is near the mean of the distribution approximated. These modifications apply to double saddlepoint approximations to conditional distributions as well. 相似文献
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For k an algebraic closure of the finite field , ℓ prime distinct from p and X a surface over k, we prove that the field of rational functions k(X) can be recovered from the maximal pro-ℓ-quotient of its absolute Galois group – in fact already from the second central descending series quotient of .
Submitted: July 2004, Revision: October 2005, Final revision: February 2008, Accepted: February 2008 相似文献
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In this note, the author discusses the problem of best simultaneous approximation by function pairs. The existence and characterization theorems of the best simultaneous approximation in L1 and L∞ norms are obtained respectively, and some rezults of [ 1 ] are the special case of the theorems of the paper. 相似文献
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António M. Caetano 《Journal of Approximation Theory》1998,94(3):383-395
Sharp estimates for the approximation numbers of embeddings between the function spacesBspqandFspqon domains are given in a case not thoroughly studied by Edmunds and Triebel. Corresponding sharp estimates are also obtained for the counterparts of that case in the weighted function space setting. 相似文献
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Using the method of construction,with the help of inequalities,we research the Muntz rational approximation of two kinds of special function classes,and give the corresponding estimates of approximation rates of these classes under widely conditions.Because of the Orlicz Spaces is bigger than continuous function space and the Lp space,so the results of this paper has a certain expansion significance. 相似文献
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Shi Yingguang 《数学年刊B辑(英文版)》1982,3(5):639-644
This paper discusses the minimization problem: For a Given n-dimensional subspace K and a function f of C(X), find a function pair (p_1,p_2)\in K x K, p_1 \geq f \geq p_2 such that $||p_1-p_2||=[\mathop {\mathop {\inf }\limits_{({q_1},{q_2}) \in K \times K} }\limits_{{p_1} \ge f \ge {q_2}} ||{q_1} - {q_2}||\]$
We call such a pair(p_1, p_2) (if any) a best approximation pair to f from K.
This paper has proved a characterization theorem for best L_1 approximation pairs which says that (p_1,p_2) is a best L_1 approximation pair if and only if p_1 and p_2 are respectively an upper sided and a lower sided best L_1 approximation to f.
With the provisos that K is a Haar subspace and thet 1\in K it turns out that the above conclusion of the characterization theorem for best L_\infty approximation pairs is also true. However we have further established, without the provisos at all, a “complete” characterization theorem for best L_\infty approximation pairs.
Furthermore, sufficient conditions for uniqueness of best L_\infty approximation pairs are also given. 相似文献
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关于二元函数的三角插值逼近 总被引:2,自引:0,他引:2
本文以两组不同的节点构造了一个组合型的二元三角插值多项式算子Lmn(f;x,y),并且研究了二元连续周期函数对这个算子的收敛性及收敛阶的估计等问题。 相似文献
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Geometric arguments provide a basis for piecewise rational approximationover collections of regions of the type used in finite-elementstudies. The approximation is continous over the collectionof regions and the rational basis functions provide a basisfor linear functions over each element. Conic sides are analysed,and an alternative to isoparametric co-ordinates is described. 相似文献
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A.M. Shvetsova 《Analysis Mathematica》2001,27(3):201-222
Continuing investigations of S. A. Telyakovskii, S. B. Stechkin, A. I. Stepanets and R. M. Trigub, the author studies two questions about approximation of the class of periodic functions with a bounded -derivative by polynomials in the spaces C and L.First, the asymptotics of approximation by partial sums of Fourier series has been found without limitations for the decreasing order of . Second, the exact decreasing order of the best approximation of the class has been found. New examples are also given. 相似文献
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We expand upon the known results on sharp linear Fourier methods of approximation where the approximation is the best in terms of both rate and constant among all polynomial procedures of approximation. So far these results have been studied due to their mathematical beauty rather than their practical importance. In this paper we show that they are the core mathematics underlying best statistical methods of solving noisy ill-posed problems. In particular, we suggest a procedure for recovery of noisy blurred signals based on samples of small sizes where a traditional statistics concludes that the complexity of such a setting makes the problem not worthy of a further study. Thus, we present a problem where a combination of the classical approximation theory and statistics leads to interesting practical results. 相似文献