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Dehno Khalaji A.,Golestan University
Journal of Cluster Science | Year: 2013

Nickel(II) complex, Ni(Brsalph)(NO3) was synthesized and characterized by elemental analyses and Fourier-transformed infrared (FT-IR) spectroscopy. Heating of Ni(Brsalph)(NO3) at 550 °C for 3. 5 h have resulted NiO nanoparticles. Fourier-transformed infrared spectrum confirmed the composition of products. The crystalline structures and morphology of NiO nanoparticles were studied by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. © 2012 Springer Science+Business Media New York.

This study focuses on the preparation and characterization of nickel oxide nanoparticles from nickel(II) Schiff base complexes as new precursors. At first nickel(II) complexes [Ni(salophen)] and [Ni(Me-salophen)] were synthesized and characterized by elemental analyses and FT-IR spectroscopy. Then NiO nanoparticles were prepared by solid-state thermal decomposition at 550 oC for 3. 5 h. The FT-IR spectrum confirmed the composition of products. The crystalline structures and morphology of products were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD results revealed that the obtained products were nickel oxide. SEM and TEM images demonstrated that the NiO nanoparticles have uniform shape with size between 35 and 70 nm. © 2012 Springer Science+Business Media New York.

Javan M.B.,Golestan University
Applied Physics A: Materials Science and Processing | Year: 2013

The structural, electronic and optical properties of SinC n (n = 12,16,20,30,35 and 60) nanocages were studied using different approximations of density functional theory, i.e. local density approximation (LDA), generalized gradient approximation (GGA) and density functional theory based tight binding approximation (DFTB). The highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) energy gaps were calculated for all nanocages. Time-dependent density functional theory (TD-DFT) was also applied for estimating of the optical excitation and exciton binding energies of the nanocages and the results compared with pure DFT calculations. © Springer-Verlag Berlin Heidelberg 2013.

Khajenabi F.,Golestan University
Astrophysical Journal | Year: 2016

We investigate the orbital motion of cold clouds in the broad-line region of active galactic nuclei subject to the gravity of a black hole, a force due to a non-isotropic central source, and a drag force proportional to the velocity square. The intercloud is described using the standard solutions for the advection-dominated accretion flows. The orbit of a cloud decays because of the drag force, but the typical timescale of clouds falling onto the central black hole is shorter compared to the linear drag case. This timescale is calculated when a cloud moves through a static or rotating intercloud. We show that when the drag force is a quadratic function of the velocity, irrespective of the initial conditions and other input parameters, clouds will generally fall onto the central region much faster than the age of whole system, and since cold clouds present in most of the broad-line regions, we suggest that mechanisms for the continuous creation of the clouds must operate in these systems. © 2016. The American Astronomical Society. All rights reserved.

Khabaz R.,Golestan University
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

A mathematical simulation approach based on the general purpose Monte Carlo N-particle transport code MCNP was developed to calculate the departure in reading of the neutron spectrometer instrument from that expected according to the inverse square law. The calculations were performed to evaluate the effects of beam divergence on the response of a 10 in. spherical device equipped with a long BF3 counter irradiated by 11 mono-energy neutron beams. The necessary geometry correction factor, because of non-uniform illumination, for the calibration of seven polyethylene spheres with several radionuclide neutron sources, i.e. Ra-Be, 241Am-Be, 241Am-B and Po-Be sources was also determined. In all calculations, the displacement of effective center from the geometric center of moderating spheres, when used as an instrument for neutron fluence measurement, was quantified. © 2013 Elsevier B.V.

Copper deposits in the Kerman Cenozoic magmatic arc (KCMA) of Iran are genetically related to Miocene porphyries. The porphyries and their associated Cu deposits were intruded and emplaced into Eocene volcanic-sedimentary successions. Lead isotope compositions of the Eocene volcanic rocks exhibit homogeneous, non-radiogenic values (206Pb/204Pb=18.40 to 18.49, 207Pb/204Pb=15.41 to 15.48, and 208Pb/204Pb=38.15 to 38.36). In contrast, the Miocene ore-hosting porphyries and associated sulfide minerals also show a relatively radiogenic and homogenous Pb-isotopic values with orogen character (206Pb/204Pb=18.52 to18.60, 207Pb/204Pb=15.58 to 15.64, and 208Pb/204Pb=38.57 to 38.80). The shift in the Pb-isotopic composition of igneous rocks with time towards higher Pb-isotopic values precludes derivation of the ore-hosting porphyries from a reservoir of similar composition to those in the Eocene volcanic rocks. The non-radiogenic Pb-isotope signature of the Eocene volcanic rocks indicates an origin from subduction-related mantle-derived magmas, whereas the higher Pb-isotopic values of the Miocene ore-hosting porphyries suggest an increasing involvement of crustal materials (with lower U/Pb ratios than the upper crust) in the source region of these rocks.Combining the Pb-isotope data with petrogenetic considerations suggests derivation of the middle Miocene ore-hosting porphyries from a mixed reservoir with slightly radiogenic Pb values, such as a hybridized lower continental crustal source. This source probably formed because of the involvement of Cretaceous-Oligocene subduction-related mantle-derived mafic magmas at the base of arc crust. The contribution of the Miocene collision-related mantle-derived mafic magma in melting of the hybridized lower continental crust caused generation of the middle Miocene porphyries, hosting large copper deposits with the least 206Pb/204Pb ratios among other porphyries. The higher 206Pb/204Pb ratios of the late Miocene-Pliocene porphyries hosting small copper deposits, as well as barren porphyries, may reflect a decreasing involvement of collision-related mantle-derived mafic magma in the source of the late Miocene-Pliocene porphyries.The overall similarity in Pb-isotope values between sulfide minerals and ore-hosting porphyries suggests a magmatic source for most of the Pb and possibly other metals. The more radiogenic isotopic ratios of some late sulfide minerals suggest an insignificant metal contribution from an external source such as local country rocks during hydrothermal circulation. © 2010 Elsevier B.V.

ZnO nanoparticles were synthesized by a simple chemical precipitation method at 0 °C and annealed in air at temperatures of 200, 400 and 600 °C. Effect of annealing temperature on the optical properties were characterized by the UV-Vis and photoluminescence (PL) spectroscopy. The PL spectra of as prepared ZnO nanoparticles exhibits a narrow UV and a broad yellow emission peaks which are related to defect levels in the band gap. With the annealing temperature increasing, the intensity of yellow emission is strongly decreased, whereas the green emission is revealed. In addition, it was found that, there is a slight red shift in the UV absorption peak and a blue shift in the visible emission peak when the annealing temperature increases. © 2012 Elsevier B.V. All rights reserved.

Fasihi K.,Golestan University
Journal of Lightwave Technology | Year: 2014

We present a new high-contrast all-optical controllable switch and router, which is based on two cross-waveguide-based nonlinear photonic crystal switches and a T-branch waveguide. We show that by applying a proper state of control signals (a controlled switching mechanism), the input power can be routed to any of the two output ports. The operation of the proposed device is investigated through the use of analytical and numerical methods. © 1983-2012 IEEE.

Khabaz R.,Golestan University
Journal of Radioanalytical and Nuclear Chemistry | Year: 2014

In the present study, the Monte Carlo calculations were carried out to evaluate the effect of beam divergence on the response of a spherical thermal-neutron counter at the center of a spherical moderating assembly. A model of 3He detector surrounded with 10 in. diameter polyethylene sphere was utilized to calculate the point isotropic and plane-parallel beams responses of twelve different energies, and obtain the geometry factor and its parameters (a4 and a5) based on general formulations. Furthermore, for 2, 3, 5, 8, 10 and 15 in. spheres exposed to three different radionuclide neutron sources with various energy spectra, the parameters of geometry factor were quantified, as a function of moderator radius and neutron energy. Obtained results based on this method were compared with the experimental data for one specific source. Finally, by these parameters the obtained values of the geometry factor based on two formulations were compared to each other. © 2014 Akadémiai Kiadó.

Khabaz R.,Golestan University
Annals of Nuclear Energy | Year: 2012

This paper represents the evaluation of the gamma-ray spectrum associated with the 252Cf spontaneous fission source, based on Monte Carlo simulation. In this study, with the help of the fission yields and gamma-ray spectrum emitted from each of the products, the probability of gammas in 252Cf fission has been obtained. Furthermore, the probabilities of emitted gammas following the alpha decay from 252Cf have been computed, given that in this isotope 96.91% of decays are in the form of alpha. Finally, about 450 gammas with different energies and probabilities have been extracted and after regulating their normalization, they are given to the MCNP computer code as input. Some addition gammas due to (n, γ) interaction in the detector have also been considered. The obtained results are in relatively good agreement with experiment data. © 2012 Elsevier Ltd. All rights reserved.

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