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Article An Elaboration of the Cai-Xu Result on (p, q)-integers(Springer Heidelberg, 2020) Ostrovska, SofiyaThe investigation of the (p, q)-Bernstein operators put forth the problem of finding the conditions when a sequence of (p, q)-integers tends to infinity. This is crucial for justifying the convergence results pertaining to the (p, q)-operators. Recently, Cai and Xu found a necessary and sufficient condition on sequences {p(n)} and {q(n)}, where 0 < q(n) < p(n) <= 1, to guarantee that a sequence of (p(n), q(n))-integers tends to infinity. This article presents an elaborated version of their result.Article ON THE IMAGES OF ENTIRE FUNCTIONS UNDER THE LIMIT q-BERNSTEIN OPERATOR(indian Nat Sci Acad, 2017) Ostrovska, SofiyaThe limit q-Bernstein operator B-q comes out naturally as the limit for the sequence of q-Bernstein operators in the case 0 < q < 1 : Alternatively, it can be viewed as a modification of the Szasz-Mirakyan operator related to the Euler distribution. In this paper, a necessary and sufficient condition for a function g to be an image of an entire function under B-q is presented.Article Citation - WoS: 11Citation - Scopus: 15The q-versions of the Bernstein Operator: From Mere Analogies To Further Developments(Springer Basel Ag, 2016) Ostrovska, SofiyaThe article exhibits a review of results on two popular q-versions of the Bernstein polynomials, namely, the LupaAY q-analogue and the q-Bernstein polynomials. Their similarities and distinctions are discussed.Article Citation - WoS: 1Citation - Scopus: 1Geometric Properties of the Lupas q-transform(Tusi Mathematical Research Group, 2014) Ostrovska, SofiyaThe Lupas q-transform emerges in the study of the limit q-Lupas operator. This transform is closely connected to the theory of positive linear operators of approximation theory, the q-boson operator calculus, the methods of summation of divergent series, and other areas. Given q is an element of (0, 1), f is an element of C[0, 1], the Lupas q-transform of f is defined by: [GRAPHICS] where [GRAPHICS] The analytical and approximation properties of A(q) have already been examined. In this paper, some properties of the Lupas q-transform related to continuous linear operators in normed linear spaces are investigated.Article Norming Subspaces Isomorphic to l1(Springer Heidelberg, 2015) Ostrovska, SofiyaNorming subspaces are studied widely in the duality theory of Banach spaces. These subspaces are applied to the Borel and Baire classifications of the inverse operators. The main result of this article asserts that the dual of a Banach space X contains a norming subspace isomorphic to l(1) provided that the following two conditions are satisfied: (1) X* contains a subspace isomorphic to l(1); and (2) X* contains a separable norming subspace.Article The Inversion Results for the Limit q-bernstein Operator(Springer Basel Ag, 2018) Ostrovska, SofiyaThe limit q-Bernstein operator B-q appears as a limit for a sequence of the q-Bernstein or for a sequence of the q-Meyer-Konig and Zeller operators in the case 0 < q < 1. Lately, various features of this operator have been investigated from several angles. It has been proved that the smoothness of f is an element of C[0, 1] affects the possibility for an analytic continuation of its image B-q f. This work aims to investigate the reciprocal: to what extent the smoothness of f can be retrieved from the analytical properties of B-q f.Article Citation - WoS: 2Citation - Scopus: 2On the q-bernstein Polynomials of the Logarithmic Function in the Case q > 1(Walter de Gruyter Gmbh, 2016) Ostrovska, SofiyaThe q-Bernstein basis used to construct the q-Bernstein polynomials is an extension of the Bernstein basis related to the q-binomial probability distribution. This distribution plays a profound role in the q-boson operator calculus. In the case q > 1, q-Bernstein basic polynomials on [0, 1] combine the fast increase in magnitude with sign oscillations. This seriously complicates the study of q-Bernstein polynomials in the case of q > 1. The aim of this paper is to present new results related to the q-Bernstein polynomials B-n,B- q of discontinuous functions in the case q > 1. The behavior of polynomials B-n,B- q(f; x) for functions f possessing a logarithmic singularity at 0 has been examined. (C) 2016 Mathematical Institute Slovak Academy of SciencesArticle Citation - WoS: 3Citation - Scopus: 3Sup and Max Properties for the Numerical Radius of Operators in Banach Spaces(Taylor & Francis inc, 2016) Ostrovska, SofiyaThe article deals with the following problem: given a bounded linear operator A in a Banach space X, how can multiplication of A by an operator of norm one (contraction) affect the numerical radius of A? The approach used in this work is close to that employed by Vieira and Kubrusly in 2007 for their study concerning spectral radius. It turns out that this study is closely related to the study of V-operators conducted in 2005 by Khatskevich, Ostrovskii, and Shulman; the results of this article demonstrate that in certain cases the obtained property of an operator implies that it is a V-operator, while in some other cases the converse is true.Article Citation - WoS: 1Citation - Scopus: 2On the Powers of Polynomial Logistic Distributions(Brazilian Statistical Association, 2016) Ostrovska, SofiyaLet P(x) be a polynomial monotone increasing on (-infinity, +infinity). The probability distribution possessing the distribution function F(x) = 1/1 + exp{-P(x)} is called the polynomial logistic distribution associated with polynomial P and denoted by PL(P). It has recently been introduced, as a generalization of the logistic distribution, by V. M. Koutras, K. Drakos, and M. V. Koutras who have also demonstrated the importance of this distribution in modeling financial data. In the present paper, for a random variable X similar to PL(P), the analytical properties of its characteristic function are examined, the moment-(in)determinacy for the powers X-m, m is an element of N and vertical bar X vertical bar(p), p is an element of (0, +infinity) depending on the values of m and p is investigated, and exemplary Stieltjes classes for the moment-indeterminate powers of X are constructed.
