Erol Kurt

Ionization effects and linear stability in a coaxial plasma device

AbstractA 2-D computer simulation of a coaxial plasma device depending on the conservation equations of electrons, ions and excited atoms together with the Poisson equation for a plasma gun is carried out. Some characteristics of the plasma focus device (PF) such as critical wave numbers ac and voltages Uc in the cases of various pressures Pare estimated in order to satisfy the necessary conditions of traveling particle densities (i.e. plasma patterns) via a linear analysis. Oscillatory solutions are characterized by a nonzero imaginary part of the growth rate

BIFURCATIONS AND HYPERCHAOS FROM A DC DRIVEN NONIDENTICAL JOSEPHSON JUNCTION SYSTEM

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Phase-dependent characteristics of a superconducting junction by using the Schrödinger wave function

(σ) for all cases. The model also predicts the minimal voltage ranges of the system for certain pressure intervals.

An analysis of the image homogeneity in an ionization-type infrared image converter using the fractal dimension

A numerical study is carried out on the dynamics of a non-autonomous chaotic circuit. The parametrical dependencies and features of a time-dependent circuit are explored. A novel feature of the present circuit model is that it contains a new non-autonomous nonlinear sub-circuit, namely, a non-autonomous Chuas diode (NCD), which indicates nonlinear resistor behaviour and enhances the complexity of the standard Chuas diode. Periodic cases are observed as functions of voltage f, driving frequency ω and the frequency of NCD . Chaos occurs for appropriate system parameters.

Alternative numerical modeling of a superconducting charge qubit as an eigenvalue problem

The dynamics of a resistively coupled system of nonidentical Josephson junctions (JJ) with dc feedings is explored theoretically. The effects of system parameters on the dynamic features are defined and equilibrium features of the system of equations are explored in such a nonidentical JJ system for the first time. By using center manifold reduction, the inverse of coupling resistance Rcp is considered as the main bifurcation parameter. The bifurcation at the vicinity of the equilibrium point is found to be transcritical, stable and unstable regimes are also indicated analytically. It is observed that the amplitudes of the output voltages on the coupling resistance Rcp are changeable and mostly uncorrelated for two parts of superconducting junction system. Such a system exhibits very rich dynamics from periodic to chaotic behavior for certain parameter sets. While the regular characteristics are observed for moderate and lower feeding currents, chaotic and highly-complex patterns are obtained for relatively higher values of them. Besides, a wider hyperchaotic region is found for wide ranges of parameters after the determination of phase diagrams compared to the earlier studies. The nonidentical nature of JJs governs the complicated dynamics on the phase space. The present circuitry can be utilized for various purposes such as stable, chaotic or hyperchaotic behavior depending on the parameters Ii and Rcp.

Preliminary plasma focus studies at ODAK-3K device using track detectors

Patterns are theoretically formed in the frame of a hydromagnetic convection induced by radial buoyancy in an electrically conducting fluid contained by a rotating cylindrical annulus with a homogeneous magnetic field ( B) in the azimuthal direction. The annulus is assumed to rotate with an angular frequency, Ω under the small gap approximation with rigid cylindrical boundaries. The onset of convection is found in the form of axial, axisymmetric or oblique rolls with a broken symmetry. The roll angle Ψ depends on the ratio between the Chandrasekhar number, Q ~ B 2, and the Coriolis number, τ ~ Ω. In addition to fully three-dimensional (3D) numerical simulations, weakly nonlinear and Galerkin analyses for roll patterns are performed for Prandtl number P = 0.1. At finite amplitudes, secondary instabilities are encountered in the form of longwave and shortwave.

Power characteristics of a new contactless piezoelectric harvester

As a macroscopic quantum system, superconducting junction devices are considered both analytically and numerically with the help of the Schrodinger wave equation. Considering the Cooper pair wave function ψ in a time-dependent nature, the Hamiltonian of the system is constructed. The phase difference θ is assumed to be a unique independent variable of the superconducting junction in order to evaluate the characteristics of the system. The probability ρ(θ) and super current j(θ) densities are determined for different applied voltages V. It is observed that both the amplitude and the period of the wave function ψ(θ) have indicated different behaviors as functions of θ for various cases of V. Similarly, ρ and j reflect drastic changes. It is shown that numerical results are in good agreement with the analytic results. Our results indicate consistency with some earlier experimental studies for different superconducting devices.

Experimental and Theoretical Explorations on the Buckling Piezoelectric Layer Under Magnetic Excitation

Abstract This paper analyses the image homogeneity realized by recording the spatial distribution of the gas discharge light emission in an ionization-type infrared (IR) image converter with a gallium arsenide semiconductor photodetector. The image of the photodetector material which contains the internal inhomogeneities is studied thoroughly at the optimum converter condition in order to image the large-diameter photodetector plates (100 mm) for nondestructive analysis. The analysis of the image homogeneity is determined by the fractal dimension of the gas discharge light emission when a current is passed through a converter cell. The images are analysed using both the profile and spatial distribution light emission intensity data showing the internal inhomogeneity in the photodetector plate. Thus, by using the fractal concept, the image quality of the high-resistivity photodetector plate can be assessed exactly and the size and location of the internal inhomogeneities in the photodetector plate can be ascertained.