Browsing by Author "Yavuz E."

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    Molybdenum oxide/platinum modified glassy carbon electrode: A novel electrocatalytic platform for the monitoring of electrochemical reduction of oxygen and its biosensing applications
    (2013) Çakar I.; Özdokur K.V.; Demir B.; Yavuz E.; Demirkol D.O.; Koçak S.; Timur S.; Ertaş F.N.
    The reduction of oxygen to water is one of the most important reactions in electrochemistry with regards to the wide range of applications in electrocatalysis, metal corrosion, and fuel cell and mostly in biosensor studies. Present study describes the use of a glassy carbon electrode modified with platinum and molybdenum oxide (Pt-MoOx) in strongly acidic solutions for electrocatalytic reduction of oxygen dissolved in buffer solution for the first time. The dispersion of Pt nanoparticles on MoOx provides larger surface area and better electrocatalytic activity for oxygen reduction and the best response toward dissolved oxygen was obtained with a mole ratio of 1:90 Pt:Mo in deposition solution. The modified surface was then used as a biosensing platform for the monitoring of oxygen consumption due to the bio-catalytic action of glucose oxidase (GOx) as the model enzyme. After optimization of the operational conditions, analytical characterization and application of the glucose oxidase GOx biosensor to flow injection analysis mode have been successfully performed. © 2013 Published by Elsevier B.V. All rights reserved.
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    Electrochemical preparation, characterization of molybdenum-oxide/platinum binary catalysts and its application to oxygen reduction reaction in weakly acidic medium
    (Elsevier Ltd, 2015) Yavuz E.; Özdokur K.V.; Çakar I.; Koҫak S.; Ertaş F.N.
    This study reports a detailed analysis of an electrode material containing molybdenum oxide and platinum nanoparticles which shows superior catalytic effect towards to oxygen reduction in weakly acid medium. The material is sequentially electrodeposited on a glassy carbon electrode from aqueous solutions of MoO 4 2- and PtCl 4 2- either by cycling the potential or by applying pulsed potential technique. Chemical and morphological characterization of the electrode surface was made by X-ray photoelectron spectroscopy, scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The electrode performance towards oxygen reduction reaction was investigated in pH 5.0 acetate buffer solution saturated with oxygen and parameters such as the cell content and electrodeposition conditions were optimized. The performance of the electrode was compared with Pt disk, bare glassy carbon, platinum modified glassy carbon electrodes along with the electrode modified in a single step and named as Pt-MoO x /GCE. Overall results indicated that sequentially deposited molybdenum oxide and platinum modified glassy carbon electrode designated as Pt/MoO x /GCE has shown higher catalytic activity considering the peak location and current intensities. This was consisted with the pulsed electrodeposition process and even higher catalytic activity was obtained than the electrode modified by cycling voltammetry. © 2014 Elsevier Ltd. All rights reserved.
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    Tauberian theorems for Abel summability of sequences of fuzzy numbers
    (American Institute of Physics Inc., 2015) Yavuz E.; Çoşkun H.
    We give some conditions under which Abel summable sequences of fuzzy numbers are convergent. As corollaries we obtain the results given in [E. Yavuz, Ö. Talo, Abel summability of sequences of fuzzy numbers, Soft computing 2014, doi: 10.1007/s00500-014-1563-7]. © 2015 AIP Publishing LLC.
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    On the Borel summability method of sequences of fuzzy numbers
    (IOS Press, 2016) Yavuz E.; Çoşkun H.
    In the current paper, we define Borel summability of sequences of fuzzy numbers and investigate Tauberian conditions under which Borel summable sequences of fuzzy numbers are convergent. Also, we give analogous Tauberian results for Borel summability method of series of fuzzy numbers. © 2016 -IOS Press and the authors. All rights reserved.
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    Abel summability of sequences of fuzzy numbers
    (Springer Verlag, 2016) Yavuz E.; Talo Ö.
    In the present study, we have introduced the concept of Abel summability for sequences and series of fuzzy numbers. Also, some tauberian results in classical analysis have been generalized to fuzzy analysis. © 2014, Springer-Verlag Berlin Heidelberg.
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    Euler summability method of sequences of fuzzy numbers and a Tauberian theorem
    (IOS Press, 2017) Yavuz E.
    We introduce Euler summability method for sequences of fuzzy numbers and state a Tauberian theorem concerning Euler summability method, of which proof provides an alternative to that of K. Knoop[Über das Eulersche Summierungsverfahren II, Math. Z. 18 (1923)] when the sequence is of real numbers. As corollaries, we extend the obtained results to series of fuzzy numbers. © 2017 - IOS Press and the authors.
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    Tauberian theorems for Lambert and zeta summability methods in fuzzy number space
    (University of Nis, 2017) Yavuz E.
    We extend Lambert and zeta summability methods to space of fuzzy numbers and prove Tauberian theorems for Lambert and zeta summability methods of fuzzy numbers, the one for zeta summability method providing a new proof when the sequence is of real numbers. © 2017, University of Nis. All rights reserved.
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    On the logarithmic summability method for sequences of fuzzy numbers
    (Springer Verlag, 2017) Yavuz E.; Çoşkun H.
    We define logarithmic summability method for sequences of fuzzy numbers and prove theorems dealing with the convergence behavior of logarithmic summable sequences of fuzzy numbers. The study also reveals slowly decreasing and Landau one-sided type Tauberian results analogous to those given by Móricz (Stud Math 219:109–121, 2013). © 2016, Springer-Verlag Berlin Heidelberg.
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    Fuzzy trigonometric korovkin type approximation via power series methods of summability
    (Politechnica University of Bucharest, 2018) Yavuz E.
    We prove a fuzzy trigonometric Korovkin type approximation theorem via power series methods of summability and give a related approximation result for periodic fuzzy continuous functions by means of fuzzy modulus of continuity. An illustrative example concerning fuzzy Abel-Poisson convolution operator is also constructed. © 2018 UPB Scientific Bulletin, Series A: Applied Mathematics and Physics. All rights reserved.
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    Comparison theorems for summability methods of sequences of fuzzy numbers
    (IOS Press, 2018) Yavuz E.
    In this study we compare Cesàro and Euler weighted mean methods of summability of sequences of fuzzy numbers with Abel and Borel power series methods of summability of sequences of fuzzy numbers. Also, some results dealing with series of fuzzy numbers are obtained. © 2018 - IOS Press and the authors.
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    On the resummation of series of fuzzy numbers via generalized Dirichlet and generalized factorial series
    (IOS Press, 2019) Yavuz E.
    We introduce semicontinuous summation methods for series of fuzzy numbers and give Tauberian conditions under which summation of a series of fuzzy numbers via generalized Dirichlet series and via generalized factorial series implies its convergence. Besides, we define the concept of level Fourier series of fuzzy valued functions and obtain results concerning the summation of level Fourier series. © 2019 - IOS Press and the authors. All rights reserved.
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    Tauberian theorems for statistical summability methods of sequences of fuzzy numbers
    (Springer Verlag, 2019) Yavuz E.
    We give Tauberian conditions of slow decrease type under which statistical Cesàro summability and statistical logarithmic summability of sequences of fuzzy numbers imply convergence in fuzzy number space. Besides, we obtain a sufficient condition for statistically convergent sequences of fuzzy numbers to converge in the ordinary sense. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
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    Approximation of Continuous Periodic Functions of Two Variables via Power Series Methods of Summability
    (Springer, 2019) Yavuz E.; Talo Ö.
    We prove a Korovkin-type approximation theorem via power series methods of summability for continuous 2 π-periodic functions of two variables and verify the convergence of approximating double sequences of positive linear operators by using modulus of continuity. An example concerning double Fourier series is also constructed to illustrate the obtained results. © 2017, Malaysian Mathematical Sciences Society and Penerbit Universiti Sains Malaysia.
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    On the Statistical Limits of Strongly Measurable Fuzzy Valued Functions
    (Prof. Dr. Mehmet Zeki SARIKAYA, 2020) Talo Ö.; Yavuz E.; Çoşkun H.
    We introduce the notions of statistical limit, statistical Cesàro summability of strongly measurable fuzzy valued functions and give slowly decreasing-slowly oscillating type Tauberian conditions under which statistical limits and statistical Cesàro summability of fuzzy valued functions imply ordinary limits in fuzzy number space. © 2020, Prof. Dr. Mehmet Zeki SARIKAYA. All rights reserved.
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    Cesàro summability of sequences in intuitionistic fuzzy normed spaces and related Tauberian theorems
    (Springer Science and Business Media Deutschland GmbH, 2021) Talo Ö.; Yavuz E.
    We define the concept of Cesàro summability method in intuitionistic fuzzy normed spaces and prove a related Tauberian theorem. Also, we define slowly oscillating sequences in intuitionistic fuzzy normed spaces, prove related theorems and show that Cesàro summability of slowly oscillating sequences implies ordinary convergence in intuitionistic fuzzy normed spaces. Finally, we give an analogue of classical two-sided Tauberian theorem due to Hardy by using the concept of q-boundedness. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
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    Basic trigonometric korovkin approximation for fuzzy valued functions of two variables
    (Academic Publishing House, 2021) Yavuz E.
    We prove the basic trigonometric Korovkin approximation theorem for fuzzy valued functions of two variables and verify the approximation by the help of fuzzy modulus of continuity. Also, we introduce double level Fourier series of fuzzy valued functions and investigate corresponding approximation through the use of Cesàro and Abel methods of summation of infinite series. © 2021 International Journal of Radiation Research. All rights reserved.
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    Tauberian theorems for statistical Cesàro and statistical logarithmic summability of sequences in intuitionistic fuzzy normed spaces
    (IOS Press BV, 2021) Yavuz E.
    We define statistical Cesàro and statistical logarithmic summability methods of sequences in intuitionistic fuzzy normed spaces(IFNS) and give slowly oscillating type and Hardy type Tauberian conditions under which statistical Cesàro summability and statistical logarithmic summability imply convergence in IFNS. Besides, we obtain analogous results for the higher order summability methods as corollaries. Also, two theorems concerning the convergence of statistically convergent sequences in IFNS are proved in the paper. © 2021 - IOS Press. All rights reserved.
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    On the convergence of sequences in ℝ+ through weighted geometric means via multiplicative calculus and application to intuitionistic fuzzy numbers
    (Taylor and Francis Ltd., 2022) Yavuz E.
    We define weighted geometric mean method of convergence for sequences in (Formula presented.) by using multiplicative calculus and obtain necessary and sufficient conditions under which convergence of sequences in (Formula presented.) follows from convergence of their weighted geometric means. We also obtain multiplicative analogues of Schmidt type slow oscillation condition and Landau type two-sided condition for the convergence in particular. Besides, we introduce the concepts of (Formula presented.) convergence, (Formula presented.) convergence, (Formula presented.) convergence, (Formula presented.) convergence for sequences of intuitionistic fuzzy numbers (IFNs) and apply the aforementioned conditions to achieve convergence in intuitionistic fuzzy number space. Examples of sequences are also given to illustrate the proposed methods of convergence. © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
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    A calculus for intuitionistic fuzzy values
    (TUBITAK, 2023) Yavuz E.
    We introduce ⊕ calculus and ⊗ calculus for intuitionistic fuzzy values and prove some basic theorems by using multiplicative calculus which has useful tools to represent the concepts of introduced calculi. Besides, we construct some isomorphic mappings to interpret the relationships between ⊕ calculus and ⊗ calculus. This paper reveals also new calculi for fuzzy sets in particular. © TÜBİTAK