Papers by alireza hojabri
We present a novel slanted faces of thin-disk composite Yb:YAG \ YAG laser which is side-pumped b... more We present a novel slanted faces of thin-disk composite Yb:YAG \ YAG laser which is side-pumped by four non-symmetric hollowducts. The pump light distribution in the disk is modeled by using Monte-Carlo ray tracing method. The temperature distribution inside the crystal is calculated by taking into account either the concentration of Yb ion or the different transmission of laser output coupler. By using Finite Element Analysis (FEA) method, we calculated the absorption efficiency through the disk. The resonator is simulated by self consistently method. The resulting of optical efficiency and the output power of our laser have been modeled.
This book is persian language. This book is for M.Sc. Students of Nuclear Physics and Nuclear Eng... more This book is persian language. This book is for M.Sc. Students of Nuclear Physics and Nuclear Eng. Also, lecturers can use this book for the last year of B.Sc. Students of Nuclear Physics and Nuclear Eng.
Nuclear Engineering and Design, 2007
Critical heat flux (CHF) is an important parameter for the design of nuclear reactors. Although m... more Critical heat flux (CHF) is an important parameter for the design of nuclear reactors. Although many experimental and theoretical researches have been performed, there is not a single correlation to predict CHF because it is influenced by many parameters. These parameters are based on fixed inlet, local and fixed outlet conditions. Artificial neural networks (ANNs) have been applied to a wide variety of different areas such as prediction, approximation, modeling and classification. In this study, two types of neural networks, radial basis function (RBF) and multilayer perceptron (MLP), are trained with the experimental CHF data and their performances are compared. RBF predicts CHF with root mean square (RMS) errors of 0.24%, 7.9%, 0.16% and MLP predicts CHF with RMS errors of 1.29%, 8.31% and 2.71%, in fixed inlet conditions, local conditions and fixed outlet conditions, respectively. The results show that neural networks with RBF structure have superior performance in CHF data prediction over MLP neural networks. The parametric trends of CHF obtained by the trained ANNs are also evaluated and results reported.
Arxiv preprint physics/0409090, 2004
Arxiv preprint physics/0410032, 2004
Quarterly Journal of Applied Chemical Research, 2015
In the present work, cupric oxide (CuO) films were obtained through thermal annealing of the copp... more In the present work, cupric oxide (CuO) films were obtained through thermal annealing of the copper (Cu) films deposited on quartz substrates by DC magnetron sputtering method. The annealing was performed in air atmosphere for different times ranging from 60-240 min at temperature of 400 oC. The influence of annealing times on structural and morphological properties of the films was investigated by different analyses. The XRD results showed that the as-deposited film was Cu, while those annealed at different times were composed of CuO. By increasing annealing times up to 180 min, the intensity of CuO diffraction peaks increased and further enhancement of annealing times led to decrease of the crystallinity. Also, the AFM images of the films conformed the dependence of surface morphology to annealing times.
Inorganic and Nano-Metal Chemistry, 2020
Abstract Nanocrystalline MoO3 films were synthesized using thermal oxidation of molybdenum films ... more Abstract Nanocrystalline MoO3 films were synthesized using thermal oxidation of molybdenum films deposited on quartz substrates by DC magnetron sputtering at different sputtering powers and times. The structural, morphological and optical properties of MoO3 films were studied by XRD, AFM, FESEM, RBS, and spectrophotometry. XRD patterns showed that, upon thermal oxidation the amorphous Mo films transformed to polycrystalline α-MoO3. The average crystallite size varied between 23 and 49 nm. AFM and FESEM images exhibited that the surface morphology of the films effectively influenced by sputtering parameters. The variation of transmittance and optical band gap with the deposition parameters were also discussed.
Journal of Fusion Energy, 2006
... Fusion, 28, 881 (1988) 3. FC Schuller, Plasma Phys. Control Fusion, 37, A135 (1995) 4. M. Gho... more ... Fusion, 28, 881 (1988) 3. FC Schuller, Plasma Phys. Control Fusion, 37, A135 (1995) 4. M. Ghoranneviss, A. Hojabri, et al., Nucl. Fusion, 43, 210215 (2003) 5. R. Valencia, et al., J. Nucl. Mater, 228, 254256 (1996) 6. WN-C. Sy, J. Phys. A: Math. ...
In the present paper, an attempt is made to explain the behavior of the magneto-hydro-dynamic (MH... more In the present paper, an attempt is made to explain the behavior of the magneto-hydro-dynamic (MHD) instabilities observed at low values of the edge safety factor on the basis of experimental results obtained on the Iran Tokamak I (IR-TI). The major disruption studied here consist of three phases: l) thermal instability, 2) growth of the magnetic island, 3) trigger mechanism. Estimates are given for the rateofislandgrowthandthecharacteristicgrowthtimeofthem=2/n=Imode,c'andthe experimentally and theoretically deduced values are found to be in reasonable agreement with each other. Keywords: IR-TI Tokamak, low edge safety factor, poloidal magnetic-field fluctuations, rate of island growth.
Journal of Theoretical and Applied Physics, 2012
Effects of low power direct current nitrogen plasma on linear and nonlinear optical properties of... more Effects of low power direct current nitrogen plasma on linear and nonlinear optical properties of red BS dye-doped poly(methyl methacrylate) (PMMA) film are studied employing different optical techniques. From spectrometry data, it is shown that applying plasma in such a low range of power does not affect the linear absorption coefficient, linear refractive index, and optical bandgap of this dye-doped polymer; however, nonlinear parameters are changed. Experiments are performed using the second harmonic of a continuous Nd-Yag laser beam at a 532-nm wavelength and 20-mW power. The effect of nonlinear refractive index of red BS dye-doped PMMA film in broadening the laser beam is observed. The optical bleaching behavior is investigated by measurement of the intensity of laser beam through the sample. Its third-order nonlinearity is measured using close and open Z-scan data. Nonlinear absorption coefficient and refractive index, as well as real and imaginary parts of the third-order nonlinear optical susceptibility χ 3 , are changed significantly due to plasma treatment.
Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 2011
The effect of heat treatment on the carbide particles size in Fe-Cr-W-V-C alloy was investigated.... more The effect of heat treatment on the carbide particles size in Fe-Cr-W-V-C alloy was investigated. The microstructural analysis of the specimens after heat treatment was carried out by optical microscopy (OM) and scanning electron microscopy (SEM). Geometric shape, size distribution, lattice parameter, and the type of the nanometric carbides were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD) and selected area electron diffraction (SAED). Also, the hardness of specimens was determined. The results revealed that the average length of particles was 80 and 163 nm and the average thickness value was 43 and 83 nm, after tempering at 600 and 700 • C, respectively. M 23 C 6 and M 7 C 3 were also identified by XRD and SAED.
Metal Science and Heat Treatment, 2011
... Therefore, SEM and TEM analyses are necessary for further investigations. 206 A. Novinroozet ... more ... Therefore, SEM and TEM analyses are necessary for further investigations. 206 A. Novinroozet al. 50 m μ Fig. 1. Alloy microstructure after treatment for solid solution at 1000°C, 30 min. 50 m μ 50 m μ à b Fig. ... 208 A. Novinrooz et al. MC 23 6 MC 7 3 (511) (501) (601) (421) ...
Journal of Materials Engineering and Performance, 2011
The microstructural features of nanocarbide particles formed in Fe-Cr-W-V alloy were studied. A F... more The microstructural features of nanocarbide particles formed in Fe-Cr-W-V alloy were studied. A Fe-Cr-W-V alloy was first heat treated under different conditions. In this study, optical microscopy, scanning and transmission electron microscopy, x-ray diffraction, and hardness tester were used. The shape, size distribution, type, and lattice parameters of the extracted particles were investigated. The identified carbides were MC, M 7 C 3 , and M 23 C 6. The particle size measurements showed that the mean length of carbide particles during 0.5, 5, and 20 h was about 103, 128, and 142 nm, respectively. Also, the mean thickness of carbide particles during 0.5, 5, and 20 h was about 54, 67, and 74 nm, respectively.
Japanese Journal of Applied Physics, 2010
We report that Fe sheathed LaFeAsO 0.9 F 0.1 wires with Ti as a buffer were fabricated by the pow... more We report that Fe sheathed LaFeAsO 0.9 F 0.1 wires with Ti as a buffer were fabricated by the powder-in-tube (PIT) method for the first time. Compared to the common two-step vacuum quartz tube synthesis method, the PIT method is more convenient and safe for synthesizing the novel iron-based layered superconductors. Structural analysis by means of x-ray diffraction shows that LaFeAsO 0.9 F 0.1 is the main phase in wires produced by this synthesis method. The transition temperature of the LaFeAsO 0.9 F 0.1 wire is around 25 K. The micrograph shows a homogeneous microstructure with a grain size of 1-3 µm. The results suggest that the PIT process is promising for preparing iron-based layered superconductors.
The European Physical Journal Applied Physics, 2010
Copper nitride films were prepared on glass and silicon substrates by reactive direct current mag... more Copper nitride films were prepared on glass and silicon substrates by reactive direct current magnetron sputtering at various N2-gas partial pressures at room temperature. The N2 partial pressure influenced the structural, electrical and optical properties of the deposited films. The X-ray diffraction measurement showed the phase change of the preferred orientation of Cu3N planes of samples from Cu-rich (111) planes
Journal of Applied Chemical Research, 2009
... Archive of SID www.SID.ir Page 2. A. Hojabri et al., J. Appl. Chem. Res., 10, 13-19 (2009) 14... more ... Archive of SID www.SID.ir Page 2. A. Hojabri et al., J. Appl. Chem. Res., 10, 13-19 (2009) 14 / ISSN : 2008-3815 ... Archive of SID www.SID.ir Page 3. A. Hojabri et al., J. Appl. Chem. Res., 10, 13-19 (2009) 15 ISSN : 2008-3815 / Instrument). ...
Acta Physica Polonica A, 2013
In this study, molybdenum (Mo) thin lms have been deposited on Si substrate by dc magnetron sputt... more In this study, molybdenum (Mo) thin lms have been deposited on Si substrate by dc magnetron sputtering. Then for preparation of MoO3 thin lms the thermal oxidation of Mo thin lms under the oxygen ow was employed in the electrical furnace. The inuence of the dierent thermal oxidation temperatures at 400, 600, 800 and 1000 • C on the structural and morphological properties of MoO3 thin lms were characterized by X-ray diraction and atomic force microscopy, respectively. The results show that the crystallinity and surface morphology of the lms are strongly dependent on the thermal oxidation temperatures.
Aluminum nitride (AlN) thin films have potential applications in microelectronic and optoelectron... more Aluminum nitride (AlN) thin films have potential applications in microelectronic and optoelectronic devices. In this study, AlN thin films with different thicknesses were deposited on silicon substrate by single ion beam sputtering method. The X-ray diffraction (XRD) spectra revealed that the structure of films with thickness of 50-150 nm was amorphous, while the polycrystalline hexagonal AlN with a rough surface was observed at a thickness of 300 nm. Also, the formation of AlN in amorphous films is identified by Fourier transform infrared (FTIR) spectroscopy. Atomic force microscopy (AFM) study confirms that the surface roughness and average grain size of films increased with film thickness.
Quarterly Journal of Applied Chemical Research, 2015
Molybdenum oxide (α-MoO)thin films were prepared on quartz and silicon substrates by thermal oxid... more Molybdenum oxide (α-MoO)thin films were prepared on quartz and silicon substrates by thermal oxidation of Mo thin films deposited using DC magnetron sputtering method. The influence of thermal oxidation times ranging from 60-240 min on the structural and morphological properties of the preparedfilms was investigated using X-ray diffraction, Atomic force microscopy and Fourier transform infrared spectroscopy. The XRD results revealed that the as deposited film was amorphous while those formed at thermal oxidation times between 60-180 min exhibited polycrystalline orthorhombic molybdenum oxides. The presence of (0k0) reflections in XRD patterns indicated the layered structure of α-MoO. Also the surface morphology of the films isdependent on the thermal oxidation times. The FTIR spectrum confirmed the formation of MoO3 and the peak at 992.53 cm-1 implythelayered structure of α-MoO3.
Chinese Journal of Chemical Physics, 2011
Density functional theory calculations are performed to study the structural, electronic and magn... more Density functional theory calculations are performed to study the structural, electronic and magnetic properties of hexagonal NiAs type and cubic zinc blende type MnSb structure and interface of zinc blende MnSb with GaSb(001). We used generalized gradiant approximation to calculate the exchange-correlation term in bulk and interface determination. The zinc blende structure of MnSb is found to be ferromagnetic half-metal
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Papers by alireza hojabri