https://hdl.handle.net/20.500.12294/193 Matematik-Bilgisayar Bölümüne ait koleksiyonlar bu alt bölümde listelenir. 2026-04-14T14:28:48Z https://hdl.handle.net/20.500.12294/3855 Data-Driven Surrogate-Assisted Optimization of Metamaterial-Based Filtenna Using Deep Learning Mahouti, Peyman; Belen, Aysu; Tarı, Özlem; Belen, Mehmet Ali; Karahan, Serdal; Koziel, Slawomir In this work, a computationally efficient method based on data-driven surrogate models is proposed for the design optimization procedure of a Frequency Selective Surface (FSS)-based filtering antenna (Filtenna). A Filtenna acts as a module that simultaneously pre-filters unwanted signals, and enhances the desired signals at the operating frequency. However, due to a typically large number of design variables of FSS unit elements, and their complex interrelations affecting the scattering response, FSS optimization is a challenging task. Herein, a deep-learning-based algorithm, Modified-Multi-Layer-Perceptron (M2LP), is developed to render an accurate behavioral model of the unit cell. Subsequently, the M2LP model is applied to optimize FSS elements being parts of the Filtenna under design. The exemplary device operates at 5 GHz to 7 GHz band. The numerical results demonstrate that the presented approach allows for an almost 90% reduction of the computational cost of the optimization process as compared to direct EM-driven design. At the same time, physical measurements of the fabricated Filtenna prototype corroborate the relevance of the proposed methodology. One of the important advantages of our technique is that the unit cell model can be re-used to design FSS and Filtenna operating various operating bands without incurring any extra computational expenses. 2023-01-01T00:00:00Z https://hdl.handle.net/20.500.12294/3155 Approximation by Generalized Integral Favard-Szasz Type Operators Involving Sheffer Polynomials Karateke, Seda; Atakut, Cigdem; Buyukyazici, Ibrahim This article deals with the approximation properties of a generalization of an integral type operator in the sense of Favard-Szász type operators including Sheffer polynomials with graphics plotted using Maple.We investigate the order of convergence, in terms of the first and the second order modulus of continuity, Peetre’s K-functional and give theorems on convergence in weighted spaces of functions by means of weighted Korovkin type theorem. At the end of the work, we give some numerical examples. © 2019, University of Nis. All rights reserved. 2019-01-01T00:00:00Z https://hdl.handle.net/20.500.12294/2913 Magnetic Transitions in Two Novel Mixed-Valence Iron(Ii)–Iron(Iii) Metal Formate Frameworks : Two Sublattice Model Yurtseven, Hasan Hamit; Tarı, Özlem We study the two-sublattice model in the mean field theory by expanding the Gibbs free energy in terms of the magnetizations M1 (Mup) and M2 (Mdown) with the quadratic coupling M12M22 (quadrupolar interactions) for the order–disorder transition in the two mixed-valence iron (II)-iron (III) metal formate frameworks, C2H5NH3FeIIFeIIIHCOO6 and C2H52NH2FeIIFeIIIHCOO6. Expressions derived from the Gibbs free energy for the temperature dependence of the magnetizations M1 and M2, are fitted to the observed data (H=100Oe) from the literature for the two mixed-valence iron (II) – iron (III) system. The inverse susceptibilities (χ1-1 and χ2-1) are predicted as a function of temperature (H=100Oe) from the two-sublattice model. Additionally, the field dependence of the total magnetization (M=M1+M2) is analyzed using the literature data for the compounds studied. We find that the two-sublattice model with the quadrupolar interactions, is satisfactory to describe the order–disorder transition in the two mixed-valence iron (II) – iron (III) metal formate frameworks as studied here. It indicates that the two-sublattice model can also be applied to some other multiferroic mixed materials. 2022-01-01T00:00:00Z https://hdl.handle.net/20.500.12294/2886 Calculation of the Liquid-Solid Phase Diagram and the Thermodynamic Quantities of the Binary System of Tetradecane and Hexadecane Using the Mean Field Theory Yurtseven, H.; Emirosmanoğlu, T.; Tarı, Özlem The T - x phase diagram of a binary system of tetradecane + hexadecane is calculated using the Landau phenomenological model. Expressions derived for the phase lines are fitted to experimental data from the literature and the fitted parameters are determined for the transitions of liquid-solid I, liquid-solid II and solid I-solid II in this binary system. The temperature dependence of the thermodynamic quantities, including the order parameter, susceptibility, enthalpy, entropy, heat capacity, thermal expansion and the isothermal compressibility are predicted for this solid-liquid equilibrium system of tetradecane + hexadecane. It is found that the mean field model developed here describes satisfactorily the observed behavior of the first order transition in the tetradecane + hexadecane system. 2021-01-01T00:00:00Z