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... Remark 5.5. The convergence results established in the present paper extend for the nonlinear sampling Kantorovich operators (and also for the linear ones, see Remark 3.1) the convergence results proved in [24]. More precisely, in [24] the convergence has been proved for the usual weighted sup-norm, while here we can deduce the convergence with respect to the weighted L p -norm, 1 ≤ p < +∞. ...
... The convergence results established in the present paper extend for the nonlinear sampling Kantorovich operators (and also for the linear ones, see Remark 3.1) the convergence results proved in [24]. More precisely, in [24] the convergence has been proved for the usual weighted sup-norm, while here we can deduce the convergence with respect to the weighted L p -norm, 1 ≤ p < +∞. ...
Article
In the present paper, convergence in modular spaces is investigated for a class of nonlinear discrete operators, namely the nonlinear multivariate sampling Kantorovich operators. The convergence results in the Musielak-Orlicz spaces, in the weighted Orlicz spaces, and in the Orlicz spaces follow as particular cases. Even more, spaces of functions equipped by modulars without an integral representation are presented and discussed.
... Then, they investigated essential convergence results of them. The family of operators (2) has been studied by considering its different forms: Kantorovich forms in [7], Durrmeyer forms in [14], bivariate forms in [9], multivariate forms in [4,30]. Another recent study on exponential sampling series is due to Aral et al. [8] in which authors constructed a new family of operators by generalizing Kantorovich type of exponential sampling series by replacing integral means over exponentially spaced intervals with its more general analogue, Mellin Gauss Weierstrass singular integrals. ...
... In order to determine the rate of convergence, a new modulus of continuity, called "weighted logarithmic modulus of continuity" was introduced. Here we mention that weighted approximation of sampling type operators are very recent and active research area, for most recent paper on weighted approximation of classical sampling operators, we refer the readers to [1,2,5,6]. However, rate of pointwise convergence and an upper estimate for pointwise convergence were not presented for the operators (3). ...
... For other publications in the literature on this subject, see also [3,4,9,17,18,29-34, 36, 45]. Furthermore, for the approximation properties of generalized sampling operators and their different forms in weighted spaces of continuous functions (see, [1,2,8,10,43]). ...
Preprint
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.
... The proofs of these theorems are omitted here. For further details, readers are referred to the original sources (see [1,2]). ...
Article
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In this paper, we collect some recent results on the approximation properties of generalized sampling operators and Kantorovich operators, focusing on pointwise and uniform convergence, rate of convergence, and Voronovskaya-type theorems in weighted spaces of functions. In the second part of the paper, we introduce a new generalization of sampling Durrmeyer operators including a special function ρ\rho which satisfies certain assumptions. For the family of newly constructed operators, we obtain pointwise convergence, uniform convergence and rate of convergence for functions belonging to weighted spaces of functions.
... numerical analysis, and optimization problems (see [3][4][5][6][7][8][9] and [10]). The classical Bernstein operators are a widely-used tool for approximating functions in the continuous function space on the interval [0, 1] (see [2,[11][12][13][14][15] and [16]). ...
Article
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In this article, we introduce a modified class of Bernstein–Kantorovich operators depending on an integrable function ψαψα {\psi}_{\alpha } and investigate their approximation properties. By choosing an appropriate function ψαψα {\psi}_{\alpha } , the order of approximation of our operators to a function f f is at least as good as the classical Bernstein–Kantorovich operators on the interval [0,1][0,1] \left[0,1\right] . We compared the operators defined in this study not only with Bernstein–Kantorovich operators but also with some other Bernstein–Kantorovich type operators. In this paper, we also study the results on the uniform convergence and rate of convergence of these operators in terms of the first‐ and second‐order moduli of continuity, and we prove that our operators have shape‐preserving properties. Finally, some numerical examples which support the results obtained in this paper are provided.
... Acar and Draganov [31] established a strong converse inequality for the rate of convergence of generalized sampling operators with the aid of moduli of smoothness. Acar et al. [32] derived the quantitative estimates for the rate of approximation of sampling Kantorovich operators in terms of weighted modulus of continuity for continuous functions belonging to weighted spaces and also established Voronovskaja type theorems in quantitative form. Recently, Acar and Draganov [33] presented a strong converse inequality for the rate of the simultaneous approximation by generalized sampling operators in the L p -norm, 1 ≤ p ≤ ∞. ...
Article
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In the present article, we introduce a Kantorovich variant of the neural network interpolation operators activated by smooth ramp functions proposed by Qian and Yu (2022). We discuss the convergence of these operators in the spaces, C([c,d])C([c,d]) C\left(\left[c,d\right]\right) and Lp([c,d]),1≤p<∞Lp([c,d]),1p< {\mathtt{L}}^{\mathtt{p}}\left(\left[c,d\right]\right),1\le \mathtt{p}<\infty , and establish some direct approximation theorems. Further, we derive the converse results by means of Berens–Lorentz lemma and Peetre's K‐functional. We present a multivariate version of the aforementioned Kantorovich neural network interpolation operators and investigate the direct and converse results in the continuous and Lp,1≤p<∞Lp,1p< {\mathtt{L}}^{\mathtt{p}},1\le \mathtt{p}<\infty , spaces.
... where is an locally integrable function defined on R such that the series is absolutely convergent for every x ∈ R; see [5]. For the rest of the works in classical sampling and its Kantorovich forms, for example, see [6][7][8][9][10][11][12][13][14][15][16][17][18][19] and references therein. Freud [20] examined the widely recognized Hermite-Fejer interpolation process, H n , applied at the zeros of general orthogonal polynomials and provided criteria to guarantee that lim n→∞ H n (x) = (x). ...
Article
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In the present paper, we analyze the behavior of the exponential‐type generalized sampling Kantorovich operators Kωφ,GKωφ,G {K}_{\omega}^{\varphi, \mathcal{G}} when discontinuous signals are considered. We present a proposition for the series Kωφ,GKωφ,G {K}_{\omega}^{\varphi, \mathcal{G}} , and we prove using this proposition certain approximation theorems for discontinuous functions. Furthermore, we give several examples of kernels satisfying the assumptions of the present theory. Finally, some numerical computations are performed to verify the approximation of discontinuous functions f f by Kωφ,GfKωφ,Gf {K}_{\omega}^{\varphi, \mathcal{G}}f .
... In recent years, Kantorovich-type generalizations have been a popular area of research both in the sense of defining new operators as well as in respect of exponential sampling series. For further investigation, one can see, [2][3][4][5]7,8,16,[18][19][20][21]30] and the reference cited therein. ...
Article
In the present paper, we introduce a new sequence of α\alpha -Bernstein-Kantorovich type operators, which fix constant and preserve Korovkin’s other test functions in a limiting sense. We extend the natural Korovkin and Voronovskaja type results into a sequence of probability measure spaces. Then, we establish the convergence properties of these operators using the Ditzian-Totik modulus of smoothness for Lipschitz-type space and functions with derivatives of bounded variations.
... For the rest of the sampling theory, see [45,59]. In the field of classical sampling theory, numerous results have been published in the papers [1][2][3][4][10][11][12]20,[40][41][42]57]. ...
Article
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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.
... Subsequently, some preservation properties of the Baskakov-Kantorovich operator were studiedly Zhang in [54]. For recent developments in this direction, we refer to [1], [4], [5], [6], [13], [22], [24] and [36]. ...
... One can think to extend such results to more general families of operators and the more general context of weighted spaces presented in the papers [15,16]. A significant direction of research in the Approximation Theory by positive linear operators is concerned with the complete asymptotic expansion of such operators (see [17][18][19][20][21]). ...
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In a series of papers, most of them authored or co-authored by H. Gonska, several authors investigated problems concerning the composition and decomposition of positive linear operators defined on spaces of functions. For example, given two operators with known properties, A and B, we can find the properties of the composed operator A∘B, such as the eigenstructure, the inverse, the Voronovskaja formula, and the second-order central moments. One motivation for studying composed operators is the possibility to obtain better rates of approximation and better Voronovskaja formulas. Our paper will address such problems involving compositions of some classical positive linear operators. We present general results as well as numerical experiments.
... Estimates of the rate of approximation of general sampling operators (1.1) in spaces of continuous functions associated with the weight ρ 2,2 have been recently obtained in [1]. Similar results for integral modifications of the general sampling operator were established in [2,3]. Also, such results were proved for an integral form of general exponential sampling operators in function spaces equipped with a logarithmic weight in [4,Section 5]. ...
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We construct a sampling operator with the property that the smoother a function is, the faster its approximation is. We establish a direct estimate and a weak converse estimate of its rate of approximation in the uniform norm by means of a modulus of smoothness and a K-functional. The case of weighted approximation is also considered. The weights are positive and power-type with non-positive exponents at infinity. This sampling operator preserves every algebraic polynomial.
... Similar considerations for generalized sampling Kantorovich series and generalized exponential sampling series were studied in refs. [17] and [18], respectively. ...
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The present article deals with local and global approximation behaviors of sampling Durrmeyer operators for functions belonging to weighted spaces of continuous functions. After giving some fundamental notations of sampling type approximation methods and presenting well definiteness of the operators on weighted spaces of functions, we examine pointwise and uniform convergence of the family of operators and determine the rate of convergence via weighted modulus of continuity. A quantitative Voronovskaja theorem is also proved in order to obtain rate of pointwise convergence and upper estimate for this convergence. The last section is devoted to some numerical evaluations of sampling Durrmeyer operators with suitable kernels.
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This work discusses two periods of transformation of the Proto-Kartvelian population: the first (L–XXV centuries BC) when the entire population spoke one Proto-Kartvelian language and lived in a relatively large area; the second period – (XXV–X centuries BC), when the population divided into three parts: Proto-Svan; speaking the Colchian-Georgian language and the third part was scattered on the European continent. The second period is described by two different mathematical models: a part of the Proto-Kartvelian speaking population went to Europe and slowly began the process of their assimilation on the European continent. The unknown function that determines the number of Proto-Kartvelian speaking people in Europe at the time is described by a Pearl - Verhulst-type mathematical model with variable coefficients that also take the assimilation process into account. The analytical solution of the Cauchy problem is found in quadratures. The population that remained primarily in former Asia and the Caucasus region was gradually divided into two groups: those who spoke the Proto-Svan and those who spoke Colchian-Georgian languages. To describe their interference and development, a mathematical model is used, which is described by a nonlinear dynamic system with nonlinear terms of self-limitation and takes into account the unnatural reduction of the Colchian-Georgian population as a result of hostilities with neighboring peoples. For a dynamic system without nonlinear terms of self-constraint, in the case of certain relationships between variable coefficients, the first integral was found, by means of which the Bernoulli equation with variable coefficients was obtained for one of the unknown functions. In the case of constant coefficients of the dynamic system, for certain dependences between the coefficients, the dynamic system follows the system of Lotka–Volterra equations, with corresponding periodic solutions. For the general mathematical model (nonlinear terms of self-limitation and unnatural reduction of the Colchian-Georgian population due to hostilities with neighboring peoples) in two cases of certain interdependencies between constant coefficients, it is shown that the divergence of an unknown vector-function in the physically meaningful first quarter of the phase plane changes the sign when passing through some half-direct one. Taking into account the principle (theorem) of Bendixson, theorems have been proved, on the variability of the divergence of the vector field and the existence of closed trajectories in some singly connected domain of the point located on this half-direct (starting point of the trajectory). Thus, for the general dynamic system, with some dependencies between constant coefficients, it is shown that there is no assimilation of the Proto-Svan population by the Colchian-Georgian population and these two populations (Colchian-Georgian and Proto-Svan) coexist peacefully in virtually the same region due to the transformation of the Proto-Kartvelian population.
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In 1903 Fredholm published his famous paper on integral equations. Since then linear integral operators have become an important tool in many areas, including the theory of Fourier series and Fourier integrals, approximation theory and summability theory, and the theory of integral and differential equations. As regards the latter, applications were soon extended beyond linear operators. In approximation theory, however, applications were limited to linear operators mainly by the fact that the notion of singularity of an integral operator was closely connected with its linearity. This book represents the first attempt at a comprehensive treatment of approximation theory by means of nonlinear integral operators in function spaces. In particular, the fundamental notions of approximate identity for kernels of nonlinear operators and a general concept of modulus of continuity are developed in order to obtain consistent approximation results. Applications to nonlinear summability, nonlinear integral equations and nonlinear sampling theory are given. In particular, the study of nonlinear sampling operators is important since the results permit the reconstruction of several classes of signals. In a wider context, the material of this book represents a starting point for new areas of research in nonlinear analysis. For this reason the text is written in a style accessible not only to researchers but to advanced students as well. Contents 1. Kernel functionals and modular spaces 2. Absolutely continuous modulars and moduli of continuity 3. Approximation by convolution type operators 4. Urysohn integral operators with homogeneous kernel functions. Applications to nonlinear Mellin-type convolution operators 5. Summability methods by convolution-type operators 6. Nonlinear integral operators in the space BV[subscript [actual symbol not reproducible]] 7. Application to nonlinear integral equations 8. Uniform approximation by sampling type operators. Applications in signal analysis 9. Modular approximation by sampling type operators.
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In this paper, the behavior of the sampling Kantorovich operators has been studied, when discontinuous functions (signals) are considered in the above sampling series. Moreover, the rate of approximation for the family of the above operators is estimated, when uniformly continuous and bounded signals are considered. Finally, several examples of (duration-limited) kernels which satisfy the assumptions of the present theory have been provided, and also the problem of the linear prediction by sampling values from the past is analyzed.
Chapter
If a signal f is band-limited to [—πW, πW] for some W > 0, then f can be completely reconstructed for all values of t ∈ R from its sampled values f (k/W), k ∈ Z, taken just at the nodes k/W, equally spaced apart on the whole R, in terms of \begin{array}{*{20}{c}} {f(t) = \sum\limits_{{k = - \infty }}^{\infty } {f\left( {\frac{k}{W}} \right)\frac{{\sin \pi (Wt - k)}}{{\pi (Wt - k)}}} } & {(t \in R).} \\ \end{array} (5.1.1) KeywordsBounded Linear OperatorLinear PredictionPolynomial SplinePast SampleNyquist RateThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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The Voronovskaya theorem which is one of the most important pointwise convergence results in the theory of approximation by linear positive operators (l.p.o) is considered in quantitative form. Most of the results presented in this paper mainly depend on the Taylor’s formula for the functions belonging to weighted spaces. We first obtain an estimate for the remainder of Taylor’s formula and by this estimate we give the Voronovskaya theorem in quantitative form for a class of sequences of l.p.o. The Grüss type approximation theorem and the Grüss-Voronovskaya-type theorem in quantitative form are obtained as well. We also give the Voronovskaya type results for the difference of l.p.o acting on weighted spaces. All results are also given for well-known operators, Szasz-Mirakyan and Baskakov operators as illustrative examples. Our results being Voronovskaya-type either describe the rate of pointwise convergence or present the error of approximation simultaneously.
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Here we give some pointwise convergence theorems and asymptotic formulae of Voronovskaja type for a general class of Kantorovich discrete operators. Applications to the Kantorovich version of some discrete operators are given.
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In this paper we consider some generalized Shannon sampling operators, which are defined by band-limited kernels. In particular, we use dilated an averaged versions of some previously known kernels. We give also some examples of using sampling operators in imaging applications.
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In this paper an asymptotic formula of Voronovskaja type for a multivariate extension of the Kantorovich generalized sampling series is given. Moreover a quantitative version in terms of some moduli of smoothness is established. Finally some particular examples of kernels are discussed, as the Bochner-Riesz kernel and the multivariate splines. © 2011 Institute of Mathematics, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Chinese Mathematical Society and Springer-Verlag Berlin Heidelberg.
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On approximation properties of sampling operators by dilated kernels
  • A Kivinukk
  • G Tamberg
Kivinukk A, Tamberg G. On approximation properties of sampling operators by dilated kernels. In: 8th International Conference on Sampling Theory and Applications (SAMPTA'09); Marseille, France; 2009.
On approximation properties of generalized Kantorovich-type sampling operators
  • O Orlova
  • G Tamberg
Orlova O, Tamberg G. On approximation properties of generalized Kantorovich-type sampling operators. Journal of Approximation Theory 2016; 201: 73-86. doi: 10.1016/j.jat.2015.10.001