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刘颖范 《高等学校计算数学学报》1996,18(4):300-310
自Korovkin的文[1]问世以来,有关线性正算子逼近的各种工作一直是颇受逼近论界关注的研究课题,如[2]~[4]等分别考虑了连续函数,L~p空间及随机函数的正算子逼近.然而在一元逼近中,由积分核引出的卷积与形式卷积型算子却占有极为重要的地位,这不仅因为已经有较多具体的积分核能方便地用于误差估计;特别,还有一些如Timan定理那样 相似文献
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有理逼近的一些最新进展 总被引:6,自引:1,他引:5
作为非线性逼近的一个重要特殊情形,有理函数逼近(即有理逼近)无论在实践中还是在应用中有都有重要的意义,有理逼近日益成为逼近论的一个重要和具有很强生命力的课题。近年来,在这一方面的研究成果不断涌现,其中许多都是非常有意义的。本文将对此作一个总结,特别对其中涉及我们自己的工作作一个回顾。 相似文献
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N. Hussain 《分析论及其应用》2006,22(1):72-80
We extend the concept of R-subcommuting maps due to Shahzad[17,18] to the case of non-starshaped domain and obtain a common fixed point result for this class of maps on non-starshaped domain in the setup of p-normed spaces. As applications, we establish noncommutative versions of various best approximation results for generalized I-nonexpansive maps on non-starshaped domain. Our results unify and extend that of Al-Thagafi, Dotson, Habiniak,Jungck and Sessa, Latif, Sahab, Khan and Sessa and Shahzad. 相似文献
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关于苏联科学院数学研究所在函数逼近论方面的工作(下)CA.捷里亚可夫斯基(原苏联科学院数学研究所)6多元函数逼近多元函数逼近的正逆定理最早是由D.Jackson[4]和S.N.Bernstein[5]与一元函数的定理同时给出的,对多元函数的系统研究要... 相似文献
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本给出了一个逼近显示圆的新算法,该算法是通过相交多形而不是内接多边形逼近圆,由于构造构交多连形时其面积等于圆面积,因此新算法的最优逼近,同时还推广到椭圆。 相似文献
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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
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[1]中讨论了无界区域上轴对称Stokes绕流的无限元方法,我们利用转移矩阵X以及组合刚度矩阵K_z将问题归结为一个有限阶代数方程组。[1]又给出了两种计算K_z的迭代方法,并证明了迭代方法的收敛性。最后证明了无限元解收敛于精确解,估计了误差的阶。这个方法的优点是:无穷远边界条件自然,计算规模小,边界形状不受限制,程序通用,并且理论基础比较完整。 本文是[1]的继续。我们将迭代格式作了一些简化,使之更便于计算;并且利用这种 相似文献
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本文求出用Jackson算子Jn(f;x)逼近C2n中的函数f(x)时的准确逼近常数:对?n≥1,有|Jn(f;x)-f(x)|≤(4-6/π)ω(f;1/n)及用阶数不超过n的三角多项式对函数f(x)的最佳逼近常数的上界估计:?n≤1,有Kn(f)e≤(7-(21)/(2π))ω(f;1/n) 相似文献
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ON SYMMETRIC SCALAR CURVATURE ON 总被引:1,自引:0,他引:1
JI Min 《数学年刊B辑(英文版)》1999,20(3):325-330
1.IntroductionGivenacontinuousfunctionRonthestandardsphereS',itisaninterestingproblemwhetherRcanbethescalarcurvatureofsomemetricgwhichispointwiseconformaltothestandardmetricgoonS2.Ifwesetg~e"go,whereuisafunctiononS',theproblemisequivalenttothesolvabilityofthefollowingPDE:--A..u 2--Re"=0,onS2.(l'1)KazdanandWarner[9]pointedoutthatitmaybeinsolvable.Inthelastfewyears,alotofworkhasbeendonetosolveproblem(l.l),especiallywhenRpossessessomekindsofsymmetries.AfterthepioneerworkduetoMoser[lo]forthe… 相似文献
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D. VENDRUSCOLO 《数学年刊B辑(英文版)》2005,26(2):315-322
§ 1 . IntroductionQuestions about bounds for indices ?rst appeared in the ?xed point context. The ?rstresults appeared in studies of surface homeomorphisms (see [13, 18, 19]). In [12, 14] and[15] some results about bounds for Nielsen ?xed point class ind… 相似文献
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本文研究了一类曲面的无穷小Ⅰ(Ⅲ)—等距,得到了两个整体定理,并由此证明了在适当的边界条件下,特殊Weingarten曲面M的无穷小Ⅰ(Ⅲ)—等距Φ是关于M的无穷小刚体运动。 相似文献
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《Quaestiones Mathematicae》2013,36(4):339-350
Abstract In this note we prove an extension of B. de Pagter's theorem (positive, compact, irreducible operators on Banach lattices are not quasi-nilpotent) for positive, band irreducible operators on Banach lattices satisfying some additional conditions. 相似文献
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本文讨论G逆半群上的同余,文中给出刻划p^k,pk,p^T,pT的方法,并用来讨论半格同余,纯幂同余,群同余及幂等元分离同余。 相似文献
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This article considers a class of bottleneck capacity expansion problems. Such problems aim to enhance bottleneck capacity to a certain level with minimum cost. Given a network G(V, A, C) consisting of a set of nodes V= {v1,v2,…,vn},a set of arcs A ■ {(vi, vj) | i=1,2,…, n;j=1,2,…,n} and a capacity vector C. The component cij of C is the capacity of arc (vi ,vj). Define the capacity of a subset A' of A as the minimum capacity of the arcs in A, the capacity of a family F of subsets of A is the maximum capacity of its members. There are two types of expanding models. In the arc-expanding model, the unit cost to increase the capacity of arc (vi, vj) is wij. In the node-expanding model, it is assumed that the capacities of all arcs (vi,vj) which start at the same node vi should be increased by the same amount and that the unit cost to make such expansion is wi. This article considers three kinds of bottleneck capacity expansion problems (path, spanning arborescence and maximum flow) in both expanding models. For each kind of expansion problems, this article discusses the characteristics of the problems and presents several results on the complexity of the problems. 相似文献