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B-Spline Solution and the Chaotic Dynamics of Troesch's Problem

100%
Caglar H., Caglar N., Ozer M.
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vol. 125
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issue 2
554-560
EN
A B-spline method is presented for solving the Troesch problem. The numerical approximations to the solution are calculated and then their behavior is studied and commenced. The chaotic dynamics exhibited by the solutions of Troesch's problem as they were derived by the decomposition method approximation are examined and an approximate critical value for the parameter λ is introduced also in this study. For the parameter value slightly less than λ ≈ 2.2, the solutions begin to show successive bifurcations, finally entering chaotic regimes at higher λ values. The effectiveness and accuracy of the B-spline method is verified for different values of the parameter, below its critical value, where the first bifurcation occurs.
2
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The Numerical Solution of Fractional Diffusion Equation by Using Local Polynomial Regression

100%
Caglar H., Caglar N., Ozer M.
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vol. 125
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issue 2
551-553
EN
In this paper, we apply the local polynomial regression for the solution of the one-dimensional fractional diffusion equation. The Caputo fractional derivative is used for the formulation. A numerical example is given to show the application of the present method. The effect of the fractional order (α) of the equation is illustrated by changing α from 1.01 to 1.99.
3
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B-Spline Solution for a Convection-Diffusion Equation

100%
Caglar H., Caglar N., Ozer M.
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vol. 125
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issue 2
548-550
EN
This paper is concerned with the numerical solution of the convection diffusion problems. A family of B-spline methods has been considered for the numerical solution of the problems. The results showed that the present method is an applicable technique and approximates the exact solution.
4
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Characterization of Viscoelastic Materials Using Free-Layered and Sandwiched Samples: Assessment and Recommendations

100%
Ozer M., Koruk H., Sanliturk K.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1251-1254
EN
Viscoelastic materials are widely used in many applications in practice. However, determination of the elastic and damping properties of these materials is quite difficult in the sense that the identified results may contain high degree of uncertainty. The characterization of viscoelastic materials using the Oberst beam method, based on non-contact excitation and response measurements, is revisited in this paper. The effects of signal processing parameters such as frequency resolution in Frequency Response Function (FRF) measurements, as well as the effects of various single-degree-of-freedom modal analysis methods, including circle-fit, half-power and line-fit are investigated first. Then, the modal loss factors, Young's modulus and shear modulus of some sample viscoelastic materials are identified using both the free-layered and sandwiched samples. The results obtained from different tests are compared, discussed and some recommendations are made so as to identify the damping and elastic properties of typical viscoelastic materials with better accuracy. Analyses of a large number of FRF measurements show that the selection of the appropriate signal processing parameters and the use of appropriate modal analysis method can be very significant during the identification of viscoelastic materials. By following the approach presented in this paper, the damping and elastic properties of viscoelastic materials can be identified with better accuracy using either free-layered or sandwiched samples. The material properties obtained by this approach can be used for developing valid structural models and/or for damping optimization purposes.
5
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Sintering Behaviour of ZnO:Cu Ceramics Fabricated by Sol-Gel Derived Powders

88%
Bahşi Z., Oral A., Aslan M., Kayahan E., Ozer M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
271-273
EN
Doped zinc(II) oxide (ZnO:Cu) ceramics were prepared from sol-gel derived nanocrystalline powders. Powders were prepared by dissolving zinc and copper acetates in isopropyl alcohol. Ethanolamine was used to enhance the solubility of acetates. Powders were produced by the calcination of the dried gels at 750°C. The crystal size of the undoped powders were uniform and around 50 nm while grain size of Cu doped powders varied between 0.3 and 2 μm. X-ray mapping of the powders showed that Cu was not homogeneously distributed and some particles had higher Cu content. After pressing of the powders, both doped and undoped ceramics were sintered at 1200C for 2 h. Microstructure of the Cu doped ceramics showed that Cu atoms partially dissolved in ZnO matrix and the rest formed a second phase in the grain boundaries. Average grain size of the ZnO:Cu ceramics was around 30 μm. Relative densities of the ceramics increased from 0.695 to 0.857 by Cu doping.
6
Content available remote

The Concept of Unidirectionally Coupled Nonlinear Circuits via a Memristor

76%
Volos C., Kyprianidis I., Stouboulos I., Stavrinides S., Anagnostopoulos A., Ozer M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
268-270
EN
Confirmation of the existence of memristor by researchers at 2008 attracts much interest on this newly found circuit element. This is due to the fact that memristor opens up new functionalities in electronics and it has led to the interpretation of phenomena regarding not only electronics but also biological systems. In this work, we have studied the simulated dynamic behavior of two unidirectionally coupled nonlinear circuits via a memristor. This confirms the transition from chaotic desynchronization to complete chaotic synchronization through a regime of intermittent synchronization between the unidirectionally coupled circuits.
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