فهرست مطالب

  • Volume:3 Issue:1, 2009
  • تاریخ انتشار: 1388/02/11
  • تعداد عناوین: 8
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  • Takook Page 1
  • Khojier, Savaloni Page 9
    Titanium films of 37.6 nm thickness were deposited on stainless steel type 304, and they were post-annealed under flow of oxygen at different temperatures. The structure of the films was analysed using RBS, XRD and AFM. The results showed an initial reduction of the grain size and surface roughness at 473 K annealing temperature, but grainsize and surface roughness increased at higher temperatures. It is observed that the crystallographic structure of the film goes through a sudden change at 943 K annealing temperature and three phases of titanium oxide (i.e., rutile, anatase and brokite) are formed. The RBS spectra showed that oxygen density and penetration depth in the sample increased with annealing temperature.
  • Khoramabadi, Ghomi Page 14
    The Bohm sheath criterion in a collisional plasma sheath under finite ion temperature is examined with a two fluid model. It is shown that by considering the neutral-ion collision in the sheath, there will be an upper as well as lower limit for the sheath velocity criterion, but the finite ion temperature only affects the lower limit.
  • Khalaj, Taheri, Nasiri Laheghi, Alizadeh Eslami Page 19
    Diamond nano crystals and nano crystalline diamond films have been synthesized on an Aluminium substrate by Hot Filament Chemical Vapor Deposition (HFCVD) system in a CH4/H2 gas mixture. This study focuses on the effect of etching gasses, N2, NH3, and, H2 on diamond growth on Al substrate. The optimal conditions were found tobe: gas flow rate = 330 sccm, substrate temperature Ts = 500 °C, and reaction pressure = 30 Torr. Good quality diamond nano crystals with (111) crystallite were grown on the Al substrate by H2 as the etching gas. In terms of morphology, the analyses were carried out by Scanning Electron Microscopy (SEM). The crystallinity of the Diamond nano crystal films and nano crystalline diamonds were analyzed by X-Ray Diffraction (XRD) analysis.
  • Kouhi, Rezvani Jalal Page 23
    The temporal evolution of the plane interface between two ideal semi-infinite plasmas is considered by means of one-dimensional Riemann solver for the MHD equations. Using two-dimensional Riemann solver for the MHD equations, the time evolution of the rectangular perturbed interface is investigated. It is shown that in the presence of magnetic field, the perturbation vanishes gradually but in the absence of magnetic field the perturbation grows similar to a mushroom instability such as Rayliegh-Taylor and Richtmyer-Meshkov instabilities in fluids.
  • Ghahramany, Moujie Page 28
    Neutral pion photo-production on the proton is studied using a unitary isobar model. The model contains Born terms, contributions from vector meson exchanges and nucleon resonances. This model (MAID 2007) is implemented as a part of the MAID program (the MAID program can be accessed from the web page: http://www.kph.uni-mainz.de). We have compared the results obtained from this model with the BONN-ELSA-CBexperimental data for differential and total cross section. Comparison is carried out for photon energy range of 0.3 - 1.6 Gev. We also have investigated the role of different nucleon resonances in differential cross section in thismodel.
  • Khoda, Bakhsh, Behnia, Jahanbakhsh Page 36
    Stability monitoring of nuclear reactors has been extensively investigated in the last few decades. However, the identification methods and proposed intelligent control systems are not appropriate for real cases [1]. In this study stability analyses of nuclear reactors have been done by using a dynamical system approach. We elaborated therelation between nuclear fission and spatial chaos. The relation among neutron effective multiplication coefficient k, concentration rate of uranium and chemical shim, indicates that the nuclear self-sustaining chain fission and nuclear fusion have literally spatial nonlinear dynamical behavior. Stability boundaries are obtained in several three andtwo-dimensional parameter spaces. We have found the absolutely stable area of nuclear reactor, which is markedly different from the formerly mentioned areas.
  • Ilkhani, Abolhassani, Aslaninejad Page 41
    Electric field gradients (EFG) at In and Ce sites, electronic specific heat and the magnetic moments at Ce site have been calculated for CeIn3.The calculations were performed by increasing pressure gradually from -5 to +22 GPa, within the density functional theory (DFT) and using the augmented plane waves plus local orbital (APW+lo) method. The so-called PBE-GGA+U and WC-GGA+U schemes have been employed. Results show that the calculated EFG’s at the In site grow smoothly by imposing pressure. We have compared the EFG’s at zero pressure with theoretical and experimental results. It is shown that our simulation results for EFG’s are close to the results of the other study and in good agreement with experimental data at the ambient pressure. We show that with increasing the pressure, the electronic density of states at Fermi level decreases and causes an increase in EFG. Results also indicate that by increasing the pressure, both f density of states at Fermi level and the magnetic moment of Ce decrease. An almost linear increase of magnetic moment versus Ce-4f density of states at Fermi level is observed for the certain range of parameters.