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image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Approximation Theory...arrow_drop_down
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Approximation Theory and Its Applications
Article . 1992 . Peer-reviewed
License: Springer Nature TDM
Data sources: Crossref
image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
zbMATH Open
Article . 1992
Data sources: zbMATH Open
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A note on Bernstein type operators

Authors: Zhou, Dingxuan;

A note on Bernstein type operators

Abstract

For Bernstein operators \(B_ n\) one has the direct theorem \[ \| B_ n f-f\|_ \infty\leq C\left\{ w^ 2_ \varphi\left(f,{1\over\sqrt n}\right)_ \infty +{1\over n} \| f\|_ \infty\right\},\quad n\in\mathbb{N}, \] where \(C\) is independent of \(n\) and \(w^ 2_ \varphi(f,\cdot)_ \infty\) denotes the second order Ditzian-Totik modulus of smoothness with respect to the sup-norm and here with the special stepweight \(\varphi(x)=\sqrt{x(1-x)}\). Neither for Bernstein- Kantorovich operators \(K_ n\) nor for Bernstein-Durrmeyer operators \(M_ n\) on \(C[0,1]\) an estimate with the same upper bound does hold. The latter shows a counterexample in the present paper. Writing \(L_ n\) for either \(K_ n\) or \(M_ n\) the authors prove the following direct theorem on \(C[0,1]\): \[ \| L_ n f-f\|_ \infty\leq C\left\{w^ 2_ \varphi\left(f,{1\over\sqrt n}\right)_ \infty+w\left(f,{1\over n}\right)_ \infty+{1\over n}\| f\|_ \infty\right\},\quad n\in \mathbb{N}, \] where \(C\) is again independent of \(n\) and \(w(f,\cdot)_ \infty\) denotes the classical first order modulus of continuity, \(\varphi(x)=\sqrt{x(x-1)}\). Reviewer's remark'' For \(L_ n=M_ n\) and simultaneous approximation \textit{H. H. Gonska} and \textit{X. L. Zhou} have obtained already in 1990 the same upper bound [c.f. J. Approximation Theory 67, No. 3, 284-302 (1991; Zbl 0756.41027)].

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Keywords

Approximation by positive operators, Ditzian-Totik modulus of smoothness, Bernstein- Kantorovich operators, Bernstein-Durrmeyer operators, Bernstein operators

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popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
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influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
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