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Article Citation - WoS: 12Citation - Scopus: 13BIFURCATIONS AND HYPERCHAOS FROM A DC DRIVEN NONIDENTICAL JOSEPHSON JUNCTION SYSTEM(World Scientific Publ Co Pte Ltd, 2010) Kurt, Erol; Canturk, MehmetThe 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 R-cp 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 R-cp 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 I-i and R-cp.Article Citation - WoS: 1Citation - Scopus: 1Structural and Optical Properties of Thermally Evaporated Ga-In Thin Films(World Scientific Publ Co Pte Ltd, 2014) Isik, Mehmet; Gullu, Hasan HuseyinIn this paper, structural and optical properties of Ga-In-Se (GIS) thin films deposited by thermal evaporation technique have been investigated. The effect of annealing was also studied for samples annealed at temperatures between 300 degrees C and 500 degrees C. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy have been used for structural characterization. It was reported that increase of annealing temperature results with better crystallization and chemical composition of the films were almost same. Optical properties of the films were studied by transmission measurements in the wavelength range of 320-1100 nm. The direct bandgap transitions with energies in the range of 1.52 eV and 1.65 eV were revealed for the investigated GIS films. Photon energy dependence of absorption coefficient showed that there exist three distinct transition regions for films annealed at 400 degrees C and 500 degrees C. The quasicubic model was applied for these transitions to calculate crystal-field splitting and spin-orbit splitting energy values.Article A Density Functional Theory Study on the Structural and Electronic Properties of Pbx< (x Plus y Plus z=2, 3) Clusters(World Scientific Publ Co Pte Ltd, 2018) Pekoz, Rengin; Erkoc, SakirThe structural and electronic properties of neutral ternary PbxSbySez clusters (x y + z = 2, 3) in their ground states have been explored by means of density functional theory calculations. The geometric structures and binding energies are systematically explored and for the most stable configurations of each cluster type vibrational frequencies, charges on atoms, energy difference between highest occupied and lowest unoccupied molecular orbitals, and the possible dissociations channels have been analyzed. Depending on being binary or ternary cluster and composition, the most energetic structures have singlet, doublet or triplet ground states, and trimers prefer to form isosceles, equilateral or scalene triangle structure.Article Structural and Electronic Properties of the Dppc Molecule(World Scientific Publ Co Pte Ltd, 2006) Erkoc, Sakir; Korkmaz, FilizThe structural and electronic properties of the DPPC molecule have been investigated theoretically by performing semi-empirical self-consistent-field molecular-orbital theory calculations at the PM3 level in its ground state.Review Citation - WoS: 8Citation - Scopus: 10Group 12 Elements and Their Small Clusters: Electric Dipole Polarizability of Zn, Cd and Hg, Zn2 Dimer and Higher Znn< Microclusters and Neutral, Cationic and Anionic Zinc Oxide Molecules (zno, Zno+ and Zno-)(World Scientific Publ Co Pte Ltd, 2012) Oymak, Huseyin; Erkoc, SakirThis review is in general about group 12 elements and their small microclusters. In this part, after presenting an extensive literature survey of the electric dipole polarizability studies of the Zn, Cd and Hg atoms, we specifically target zinc-containing small clusters, beginning with the Zn-2 dimer, the Zn-3 trimer, higher Zn-n clusters and the neutral, cationic and anionic zinc oxide clusters: ZnO, ZnO+ and ZnO-. We tabulated experimental and theoretical results for the spectroscopic constants (dissociation energy D-e or D-0, bond length r(e), fundamental frequency w(e), anharmonicity constant w(e)x(e) and dipole moment mu(e)) of the diatomic clusters and the first and second ionization potentials IP1 and IP2 and electron affinity EA of the species reviewed.Article Minimum-Energy Distribution of Point Charges Confined To a Square(World Scientific Publ Co Pte Ltd, 2019) Oymak, Huseyin; Alkuwafi, AbdulwahhabThe minimum-energy configurations of N(2 <= N <= 160) identical classical point charges confined within a square under the effect of a Coulombic 1/r potential have been determined by performing steepest-descent simulations. The energies of the final optimized configurations are given, along with their corresponding structural charge distributions. When all systems evolve in time to reach a minimum-energy configuration, local or global, they are all seen to be in quest of symmetry.Article Citation - WoS: 4Citation - Scopus: 4Optical Characterization of Ga2ses Layered Crystals by Transmission, Reflection and Ellipsometry(World Scientific Publ Co Pte Ltd, 2015) Isik, Mehmet; Gasanly, NizamiOptical properties of Ga2SeS crystals grown by Bridgman method were investigated by transmission, reflection and ellipsometry measurements. Analysis of the transmission and reflection measurements performed in the wavelength range of 400-1100 nm at room temperature indicated the presence of indirect and direct transitions with 2.28 eV and 2.38 eV band gap energies. Ellipsometry measurements were carried out in the 1.2-6.0 eV spectral region to get information about optical constants, real and imaginary parts of the pseudodielectric function. Moreover, the critical point (CP) analysis of the second derivative spectra of the pseudodielectric constant in the above band gap region was accomplished. The analysis revealed the presence of five CPs with energies of 3.87, 4.16, 4.41, 4.67 and 5.34 eV.
