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Babamoradi M.,Sharif University of Technology | Heidari Saani M.,Maleke Ashtar University of Technology | Ranjbar A.,Tohoku University | Vesaghi M.A.,Sharif University of Technology | Kawazoe Y.,Tohoku University
European Physical Journal B | Year: 2011

Using a generalized Hubbard Hamiltonian, many-electron wavefunctions of negatively charged (NV -) and neutral nitrogen-vacancy (NV 0) centers in diamond were calculated. We report the effect of symmetric relaxation of surrounding atoms on the spin density, calculated from the many electron wavefunctions in the ground and excited states. We evaluated the error, that, arises in estimation of spin density when lattice relaxation effect is neglected in Electron Paramagnetic Resonance experiment and showed that the ground state spin density distribution is accessible in outward relaxations. The computed oscillator strengths give a higher efficiency for the 1.945 eV photoluminescence (PL) line of NV - with respect to 2.156 eV PL line of NV 0 which agrees well with experiment. This result is explained based on the largest the ground state spin among available values for the NV - with respect to NV 0. The transition probability between degenerate ground and excited states slightly depends on the S z value. Finally, we report on the electronic configurations which contribute to the ground and excited states and discuss the population variation of electronic configurations with relaxation. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg. Source

Moonesun M.,Maleke Ashtar University of Technology | Korol Y.M.,National University of Shipbuilding | Brazhko A.,National University of Shipbuilding
Journal of Taiwan Society of Naval Architects and Marine Engineers | Year: 2015

This paper discusses about an optimum hydrodynamic shape of stern of submarine in minimum resistance point of view. Submarines have two major categories for hydrodynamic shape: tear drop shape and cylindrical middle body shape. Here, submarine with parallel (cylindrical) middle body are studied because, the most of naval submarines and ROVs have cylindrical middle body shape. Every hull shape, have three parts: bow, cylinder and stern. This paper wants to propose an optimum stern shape by CFD method and Flow Vision software. Major parameter in hydrodynamic design of stern is wake field (variation of fluid velocity) and resistance. The focus of this paper is on the resistance at fully submerge mode without free surface effects. Firstly, all available equations for the stern shape of submarine are presented. Secondly, for all equations of shapes, CFD analysis has been done. In all models, the velocity, dimensions of domain, diameter, bow shape and the total length (bow, middle and stem length) are constant. Source

Ranjbar A.,Tohoku University | Babamoradi M.,Sharif University of Technology | Heidari Saani M.,Maleke Ashtar University of Technology | Vesaghi M.A.,Sharif University of Technology | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Using a generalized Hubbard Hamiltonian, many-electron calculations of energy levels and corresponding wave functions of negatively charged and neutral nitrogen-vacancy centers in diamond were reported. The energies, orbital, and spin symmetries of the ground and excited states are in good quantitative agreement with available optical and electron paramagnetic resonance measurements. The many-electron wave functions were employed to predict the spin density on the N and C atoms in the ground and excited states. The present model explains the recent, experimentally observed definite nonzero spin density on N atom for the 4A2 excited state of the neutral charge state of NV (NV0) based on the multiple electronic configuration of the corresponding many-electron wave function. © 2011 American Physical Society. Source

Hajizadeh-Oghaz M.,Maleke Ashtar University of Technology | Razavi R.S.,Maleke Ashtar University of Technology | Estarki M.L.,Isfahan University of Technology
Bulletin of Materials Science | Year: 2014

Yttria-stabilized zirconia nanopowders were synthesized on a relatively large scale using Pechini method. In the present paper, nearly spherical yttria-stabilized zirconia nanopowders with tetragonal structure were synthesized by Pechini process from zirconium oxynitrate hexahydrate, yttrium nitrate, citric acid and ethylene glycol. The phase and structural analyses were accomplished by X-ray diffraction; morphological analysis was carried out by field emission scanning electron microscopy and transmission electron microscopy. The results revealed nearly spherical yttria-stabilized zirconia powder with tetragonal crystal structure and chemical purity of 99.1% by inductively coupled plasma optical emission spectroscopy on a large scale. © 2014 Indian Academy of Sciences. Source

Pouretedal H.R.,Maleke Ashtar University of Technology | Ebadpour R.,Maleke Ashtar University of Technology
International Journal of Thermophysics | Year: 2014

The non-isothermal thermogravimetric method was used to study the thermal decomposition of KClO4, KNO3, and NaNO3 at heating rates of (5, 10, 15, and 20) K·min-1. The activation energy of thermal decomposition reactions was computed by isoconversional methods of Ozawa-Flynn-Wall, Kissinger-Akahiro-Sunose, and Friedman equations. Also, the kinetic triplet of the thermal decomposition of salts was determined by the model-fitting method of the modified Coats-Redfern equation. The activation energies of KClO4, KNO3, and NaNO3 of (293 to 307, 160 to 209, and 192 to 245) kJ·mol-1, respectively, are obtained by non-isothermal isoconversional methods. The modified Coats and Redfern method showed that the most probable mechanism functions g (α) of [-ln (1-α)]1/3 (model A3: Arami-Erofeev equation) and (1-α)- 1 -1 (model F2: second order) can be used to predict the decomposition mechanisms of KClO4, KNO 3, and NaNO3, respectively. © 2014 Springer Science+Business Media New York. Source

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