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Approximation Properties of Mellin-Steklov Type Exponential Sampling Series

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Abstract

In this paper, we introduce Mellin-Steklov exponential samplingoperators of order r,rNr,r\in\mathbb{N}, by considering appropriate Mellin-Steklov integrals. We investigate the approximation properties of these operators in continuousbounded spaces and Lp,1p<L^p, 1 \leq p < \infty spaces on R+.\mathbb{R}_+. By using the suitablemodulus of smoothness, it is given high order of approximation. Further, we present a quantitative Voronovskaja type theorem and we study the convergence results of newly constructed operators in logarithmic weighted spaces offunctions. Finally, the paper provides some examples of kernels that support the our results.

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Communications in the presence of noise
  • C E Shannon
C. E. Shannon, Communications in the presence of noise, Proceedings of the IRE, 37 1949, 10-21.