Matematik Bölümü
http://hdl.handle.net/20.500.12485/23
Department of Mathematics2023-06-06T13:01:04ZUnpredictable oscillations of SICNNs with delay
http://hdl.handle.net/20.500.12485/945
Unpredictable oscillations of SICNNs with delay
Fen, Mehmet Onur; Fen, Fatma Tokmak
We rigorously prove that unpredictable oscillations take place in the dynamics of shunting inhibitory cellular neural networks (SICNNs) with delay when rectangular input currents generated by an unpredictable sequence are utilized. The existence, uniqueness, and exponential stability of such oscillations are discussed. The contraction mapping principle is applied to achieve the theoretical results. Numerical simulations supporting the presence of unpredictable oscillations are provided, and the transfer of unpredictable behavior between SICNNs under unidirectional coupling is demonstrated. It is also shown by means of the delayed feedback control method that the obtained unpredictable behavior is controllable. Moreover, an application to secure communication is discussed. (C) 2021 Elsevier B.V. All rights reserved.
2021-11-13T00:00:00ZImpact of power law fluid and magnetic field on double diffusive mixed convection in staggered porous cavity considering Dufour and Soret effects
http://hdl.handle.net/20.500.12485/922
Impact of power law fluid and magnetic field on double diffusive mixed convection in staggered porous cavity considering Dufour and Soret effects
Geridönmez, B. Pekmen; Jamal, Muhammad; Hussain, Shafqat
This study deals the influence of power law fluid and inclined magnetic field on a porous medium in staggered cavity. The effect of Soret and Dufour parameters are also given attention. A two dimensional system of partial differential equations has been discretized by employing Galerkin finite element method. A finite element method involving the cubic polynomials (P-3) has been implemented to compute for velocity, temperature and concentration fields while the pressure is approximated by quadratic (P-2) finite element space of functions. The system of discretized equations is simplified using the adaptive Newton's method. Simulations are performed for various ranges of pertinent parameters such as power law index (between 0.6 and 1.8), Hartmann number (between 0 and 100), Lewis number (between 1 and 10), Dufour/Soret numbers (between -3 and 3), Darcy number (between 10(-5) and 10(-2)), magnetic field inclination (between 0 degrees and 90 degrees) and buoyancy ratio (between 0 and 10). It is inferred that the retarding effect of the rising Lorentz force is pronounced on fluid flow. The convective heat transfer is enhanced with the change of Dufour number from negative to positive. The suppression on convection at the inclination angle gamma = 90 degrees is much more than gamma = 0 degrees. The increment in Dufour and Soret numbers has an improving influence on both the average Nusselt and Sherwood numbers, and thus the convective heat and mass transfer at buoyancy ratio N = 10.
2021-02-01T00:00:00ZEffects of partial magnetic field in a vented square cavity with aiding and opposing of MWCNT-water nanofluid flows
http://hdl.handle.net/20.500.12485/912
Effects of partial magnetic field in a vented square cavity with aiding and opposing of MWCNT-water nanofluid flows
Geridönmez, B. Pekmen; Öztop, Hakan F.
A numerical investigation for examining the effect of a uniform partial magnetic field on fluid flow and heat transfer of Multi Walled Carbon Nano Tube (MWCNT)-water nanofluid is done in a vented square cavity considering aiding and opposing flows without changing temperature boundary conditions. Modified Maron-Pierce equation for dynamic viscosity and Xue equation for thermal conductivity of nanofluid are achieved. The radial basis function (Rbf) based pseudo spectral method with cubic polyharmonic spline Rbf and nonuniform Gauss-Chebyshev-Lobatto (GCL) nodes are performed to solve the problem governed by stream function-vorticity formulation. The considered parameters are Richardson number (0.1 <= Ri <= 100), the center of the partial magnetic field (0.25 <= lbc <= 0.75), Hartmann number (0 <= Ha <= 100), Reynolds number (100 <= Re <= 400) and concentration of nanoparticles (0 <= phi <= 0.05). The results show that the partial magnetic field centered in the middle of the left wall has more reducing effect on convective heat transfer than the bottom and top centered one in both cases of flows. Convective heat transfer increases with the rise in solid volume fraction up to 0.02, but then a decrease is remarkably noticed.
2021-12-01T00:00:00ZScattering properties of impulsive difference Dirac equations
http://hdl.handle.net/20.500.12485/855
Scattering properties of impulsive difference Dirac equations
Solmaz, Şeyda; Bairamov, Elgiz
: In this paper, we explore the Jost solutions and the scattering matrix of the impulsive difference Dirac systems
(IDDS) on the whole axis and study their analytic and asymptotic properties. Furthermore, characteristic properties of
the scattering matrix of the IDDS have been examined.
2021-07-01T00:00:00Z