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Approximation Results for Hadamard-Type Exponential Sampling Kantorovich Series

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The present paper deals with construction of a new family of exponential sampling Kantorovich operators based on a suitable fractional-type integral operators. We study convergence properties of newly constructed operators and give a quantitative form of the rate of convergence thanks to logarithmic modulus of continuity. To obtain an asymptotic formula in the sense of Voronovskaja, we consider locally regular functions. The rest of the paper devoted to approximations of newly constructed operators in logarithmic weighted space of functions. By utilizing a suitable weighted logarithmic modulus of continuity, we obtain a rate of convergence and give a quantitative form of Voronovskaja-type theorem via remainder of Mellin–Taylor’s formula. Furthermore, some examples of kernels which satisfy certain assumptions are presented and the results are examined by illustrative numerical tables and graphical representations.
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Mediterr. J. Math. (2023) 20:263
https://doi.org/10.1007/s00009-023-02459-2
1660-5446/23/050001-21
published online July 10, 2023
c
The Author(s), under exclusive licence to Springer
Nature Switzerland AG 2023
Approximation Results for Hadamard-Type
Exponential Sampling Kantorovich Series
Sadettin Kursun, Ali Aral and Tuncer Acar
Abstract. The present paper deals with construction of a new
family of exponential sampling Kantorovich operators based on a suit-
able fractional-type integral operators. We study convergence properties
of newly constructed operators and give a quantitative form of the rate
of convergence thanks to logarithmic modulus of continuity. To obtain
an asymptotic formula in the sense of Voronovskaja, we consider locally
regular functions. The rest of the paper devoted to approximations of
newly constructed operators in logarithmic weighted space of functions.
By utilizing a suitable weighted logarithmic modulus of continuity, we
obtain a rate of convergence and give a quantitative form of Voronovskaja-
type theorem via remainder of Mellin–Taylor’s formula. Furthermore,
some examples of kernels which satisfy certain assumptions are pre-
sented and the results are examined by illustrative numerical tables and
graphical representations.
Mathematics Subject Classification. 41A35, 30D10, 94A20, 41A25, 26A33,
44A15.
Keywords. Exponential sampling Kantorovich series, Hadamard-type
fractional integral operators, rate of convergence, modulus of continuity,
logarithmic weighted space of functions, Voronovskaja-type formulae.
1. Introduction
The generalized sampling-type operators were developed by E. T. Whittaker
[58], V. A. Kotel’nikov [49] and C. E. Shannon [56]. The theory and applica-
tions of sampling-type operators are among the most challenging areas in the
field of approximation theory, especially in the domains of image and signal
processing (see [13,27]). The family of operators is given by
Ssinc
wgx):=
kZ
gk
wsinc (w˜xk),˜xR,w > 0,(1.1)
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... Agrawal and Baxhaku (Agrawal & Baxhaku,2025) (Butzer, 1983). This includes work on Kantorovich-type modifications (Kumar et al., 2022), (Coroianu et al., 2021) (Costarelli & Vinti, 2014), (Kursun et al., 2023), (Kursun et al., 2024a) and the exponential sampling formula (Ostrowski et al. (Ostrowsky et al., 1981), Bertero and Pike (Bertero & Pike, 1991), and Gori (Gori, 1993)), which is particularly relevant for applications involving exponentially-spaced data, such as those found in optical physics and engineering. Butzer and Jansche (Butzer & Jansche, 1998) further explored the exponential sampling formula using Mellin analysis, highlighting its suitability for handling sampling and approximation problems involving exponentially-spaced data (Butzer & Jansche, 1997). ...
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With much material not previously found in book form, this book fills a gap by discussing the equivalence of signal functions with their sets of values taken at discreet points comprehensively and on a firm mathematical ground. The wide variety of topics begins with an introduction to the main ideas and background material on Fourier analysis and Hilbert spaces and their bases. Other chapters discuss sampling of Bernstein and Paley-Wiener spaces; Kramer's Lemma and its application to eigenvalue problems; contour integral methods including a proof of the equivalence of the sampling theory; the Poisson summation formula and Cauchy's integral formula; optimal regular, irregular, multi-channel, multi-band and multi-dimensional sampling; and Campbell's generalized sampling theorem. Mathematicians, physicists, and communications engineers will welcome the scope of information found here.