Ostrovska, Sofiya
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Ostrovska, Sofıya
Ostrovska,S.
Ostrovska, Sofia
S., Ostrovska
S.,Ostrovska
O., Sofiya
Ostrovska, S
Sofiya, Ostrovska
Ostrovska, S.
Ostrovska, Sofiya
Ostrovska S.
O.,Sofiya
Ostrovska,S.
Ostrovska, Sofia
S., Ostrovska
S.,Ostrovska
O., Sofiya
Ostrovska, S
Sofiya, Ostrovska
Ostrovska, S.
Ostrovska, Sofiya
Ostrovska S.
O.,Sofiya
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Profesor Doktor
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sofia.ostrovska@atilim.edu.tr
Main Affiliation
Mathematics
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Sustainable Development Goals
3
GOOD HEALTH AND WELL-BEING
1
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5
GENDER EQUALITY
1
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17
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1
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Documents
102
Citations
931
h-index
14
Documents
88
Citations
823
Scholarly Output
108
Articles
101
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309/2284
Supervised MSc Theses
2
Supervised PhD Theses
0
WoS Citation Count
832
Scopus Citation Count
934
WoS h-index
13
Scopus h-index
14
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0
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0
WoS Citations per Publication
7.70
Scopus Citations per Publication
8.65
Open Access Source
43
Supervised Theses
2
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| Journal | Count |
|---|---|
| Journal of Mathematical Analysis and Applications | 8 |
| Statistics & Probability Letters | 4 |
| Journal of Approximation Theory | 3 |
| Abstract and Applied Analysis | 3 |
| Mediterranean Journal of Mathematics | 3 |
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108 results
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Now showing 1 - 10 of 108
Article Citation - WoS: 7On the Approximation of Analytic Functions by the q-bernstein Polynomials in the Case q > 1(Kent State University, 2010) Ostrovska, SofiyaSince for q > 1, the q-Bernstein polynomials B(n,q) are not positive linear operators on C[0, 1], the investigation of their convergence properties turns out to be much more difficult than that in the case 0 < q < 1. In this paper, new results on the approximation of continuous functions by the q-Bernstein polynomials in the case q > 1 are presented. It is shown that if f is an element of C[0, 1] and admits an analytic continuation f(z) into {z : |z| < a}, then B(n,q) (f; z) -> f (z) as n -> infinity, uniformly on any compact set in {z : |z| < a}.Article Citation - WoS: 1Citation - Scopus: 2Functions Whose Smoothness Is Not Improved Under the Limit q-bernstein Operator(Springer, 2012) Ostrovska, SofiyaThe limit q-Bernstein operator B-q emerges naturally as a modification of the Szasz-Mirakyan operator related to the Euler probability distribution. At the same time, this operator serves as the limit for a sequence of the q-Bernstein polynomials with 0 < q < 1. Over the past years, the limit q-Bernstein operator has been studied widely from different perspectives. Its approximation, spectral, and functional-analytic properties, probabilistic interpretation, the behavior of iterates, and the impact on the analytic characteristics of functions have been examined. It has been proved that under a certain regularity condition, B-q improves the smoothness of a function which does not satisfy the Holder condition. The purpose of this paper is to exhibit 'exceptional' functions whose smoothness is not improved under the limit q-Bernstein operator. MSC: 26A15; 26A16; 41A36Article Citation - WoS: 1Citation - Scopus: 1On the q-moment Determinacy of Probability Distributions(Malaysian Mathematical Sciences Soc, 2020) Ostrovska, Sofiya; Turan, MehmetGiven 0Article Citation - WoS: 9Citation - Scopus: 9The Approximation of Logarithmic Function by q-bernstein Polynomials in the Case q > 1(Springer, 2007) Ostrovska, SofiyaSince in the case q > 1, q-Bernstein polynomials are not positive linear operators on C[ 0, 1], the study of their approximation properties is essentially more difficult than that for 0 < q < 1. Despite the intensive research conducted in the area lately, the problem of describing the class of functions in C[ 0, 1] uniformly approximated by their q-Bernstein polynomials ( q > 1) remains open. It is known that the approximation occurs for functions admitting an analytic continuation into a disc {z : | z| < R}, R > 1. For functions without such an assumption, no general results on approximation are available. In this paper, it is shown that the function f ( x) = ln( x + a), a > 0, is uniformly approximated by its q-Bernstein polynomials ( q > 1) on the interval [ 0, 1] if and only if a >= 1.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 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 Citation - WoS: 4Citation - Scopus: 4On the Powers of the Kummer Distribution(Academic Publication Council, 2017) Ostrovska, Sofiya; Turan, Mehmet; MathematicsThe Kummer distribution is a probability distribution, whose density is given by f (x) = cx (alpha-1)(1 + delta x)(-gamma) e(-beta x), X > 0, where alpha, beta, delta > 0, gamma is an element of R and C is a normalizing constant. In this paper, the distributions of random variable X-P, p > 0, where X has the Kummer distribution, are considered with the conditions being IFR/DFR, some properties of moments depending on the parameters and the moment-(in) determinacy. In the case of moment-indeterminacy, exemplary Stieltjes classes are constructed.Article Citation - WoS: 1Citation - Scopus: 1The Distance Between Two Limit q-bernstein Operators(Rocky Mt Math Consortium, 2020) Ostrovska, Sofiya; Turan, MehmetFor q is an element of (0, 1), let B-q denote the limit q-Bernstein operator. The distance between B-q and B-r for distinct q and r in the operator norm on C[0, 1] is estimated, and it is proved that 1 <= parallel to B-q - B-r parallel to <= 2, where both of the equalities can be attained. Furthermore, the distance depends on whether or not r and q are rational powers of each other. For example, if r(j) not equal q(m) for all j, m is an element of N, then parallel to B-q - B-r parallel to = 2, and if r = q(m) for some m is an element of N, then parallel to B-q - B-r parallel to = 2(m - 1)/m.Article Citation - WoS: 2Citation - Scopus: 2On the Properties of the Limit q-bernstein Operator(Akademiai Kiado Zrt, 2011) Ostrovska, SofiyaThe limit q-Bernstein operator B-q = B-infinity,B-q : C [0, 1]. C [0, 1] emerges naturally as a q-version of the Szasz-Mirakyan operator related to the q-deformed Poisson distribution. The latter is used in the q-boson theory to describe the energy distribution in a q-analogue of the coherent state. The limit q-Bernstein operator has been widely studied lately. It has been shown that B-q is a positive shape-preserving linear operator on Cinverted right perpendicular0, 1inverted left perpendicular with. parallel to B-q parallel to = 1. Its approximation properties, probabilistic interpretation, behavior of iterates, and the impact on the smoothness have been examined. In this paper, it is shown that the possibility of an analytic continuation of B(q)f into {z : vertical bar z vertical bar < R}, R > 1, implies the smoothness of f at 1, which is stronger when R is greater. If B(q)f can be extended to an entire function, then f is infinitely differentiable at 1, and a sufficiently slow growth of B(q)f implies analyticity of f in {z : vertical bar z-1 vertical bar < delta}, where delta is greater when the growth is slower. Finally, there is a bound for the growth of B(q)f which implies f to be an entire function.Article Citation - WoS: 13Citation - Scopus: 15Induced Scattering Limits on Fast Radio Bursts From Stellar Coronae(Iop Publishing Ltd, 2016) Lyubarsky, Yuri; Ostrovska, SofiyaThe origin of fast radio bursts remains a puzzle. Suggestions have been made that they are produced within the Earth's atmosphere, in stellar coronae, in other galaxies, or at cosmological distances. If they are extraterrestrial, the implied brightness temperature is very high, and therefore the induced scattering places constraints on possible models. In this paper, constraints are obtained on flares from coronae of nearby stars. It is shown that the radio pulses with the observed power could not be generated if the plasma density within and in the nearest vicinity of the source is as high as is necessary to provide the observed dispersion measure. However, one cannot exclude the possibility that the pulses are generated within a bubble with a very low density and pass through the dense plasma only in the outer corona.
