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Study of Sintering Behaviour and Electrical Conductivity of Cr-Zn-Fe-O System

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Journal of materials Science & Technology 1999年第1期15卷 79-82页

作者： Hanna, A.A. Khalil, m.sh. Saleh, H.I. Ali, A.F. Inorganic Chemistry Department National Research Centre Dokki Cairo Egypt

A series of chemical composition based on Cr, Fe and O with Zn as a partially substituting ion has been prepared in the general formula Zn//xCr//1// minus //xFe//2O by coprecipitation method using NH//4OH as the precipitating agent at pH equals 10.3. The prepared samples were identified by both thermal analysis (DTA and TGA) and X-ray diffraction. It was found that no single phase is obtained for any of the studied compositions but a mixture of different phases is observed, depending on the molar percentage of zinc ion substitution as well as on the sintering temperature. The temperature dependence of the electrical conductivity, sigma , of the prepared samples is plotted between 25 and 680 degree C. It was observed that the electrical conductivity increases with temperature for both samples with x equals 0.00 and 0.80 Zn ion content while it is nearly temperature independent for samples with intermediate Zn concentration x equals 0.2 and 0.5 mol fraction. The activation energy, E//a, calculated from the linear relation, lg sigma -1000/T for the final mixtures (sintered at 1300 degree C) was calculated. (Edited author abstract) 16 Refs.

关键词： Chromium compounds

Influences of substrate temperature on microstructure and corrosion behavior of APS Ni_(50)Ti_(25)Al_(25) inter-metallic coating

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Chinese Physics B 2018年第2期27卷 607-612页

作者： sh Khandanjou m Ghoranneviss sh Saviz m Reza Afshar Plasma Physics Research Center Science and Research Branch Islamic Azad University Department of materials Engineering Science and Research Branch Islamic Azad University

In the present investigation, Ni_（50）Ti_（25）Al_（25）（at.%） mechanically alloyed powder is deposited on carbon steel *** the coating process, the substrate is heated to temperature ranging from room temperature to 400℃. The microstructure, porosity, microhardness, adhesion strength, and corrosion behavior of the coating are investigated at different substrate temperatures. Results show that coating porosity is lower on high temperature surface. microhardness and adhesion strength of the deposition layer on the substrate without preheating have lower values than with preheating. The polarization test result shows that corrosion performance of the coating is dependent on micro cracks and porosities and the increasing of substrate temperature can improve the quality of coating and corrosion performance.

关键词： Ni50Ti25Al25 coating air plasma spray planetary ball milling inter-metallic compounds corrosion resistance

Solving two-dimensional Volterra-Fredholm integral equations of the second kind by using Bernstein polynomials

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Applied mathematics(A Journal of Chinese Universities) 2017年第1期32卷 68-78页

作者： m.sh.Dahaghin sh.Eskandari Department of mathematics Shahrekord University Shahrekord Iran

In this paper, we present a numerical method for solving two-dimensional VolterraFredholm integral equations of the second kind（2DV-FK2）. Our method is based on approximating unknown function with Bernstein polynomials. We obtain an error bound for this method and employ the method on some numerical tests to show the efficiency of the method.

关键词： Volterra approximating approximate variational proof iterative uniformly exact wavelet inequality

Kerosene-alumina nanofluid flow and heat transfer for cooling application

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Journal of Central South University 2016年第4期23卷 983-990页

作者： m.mahmoodi sh.Kandelousi Department of Aerospace Engineering Malek-Ashtar University of Technology Department of mechanical Engineering Babol University of Technology

Kerosene-alumina nanofluid flow and heat transfer in the presence of magnetic field are studied. The basic partial differential equations are reduced to ordinary differential equations which are solved semi analytically using differential transformation method. Velocity and temperature profiles as well as the skin friction coefficient and the Nusselt number are determined analytically. The influence of pertinent parameters such as magnetic parameter, nanofluid volume fraction, viscosity parameter and Eckert number on the flow and heat transfer characteristics is discussed. Results indicate that skin friction coefficient decreases with increase of magnetic parameter, nanofluid volume fraction and viscosity parameter. Nusselt number increases with increase of magnetic parameter and nanofluid volume fraction while it decreases with increase of Eckert number and viscosity parameter.

关键词： magnetic field nanofluid heat transfer differential transformation method

Discontinuous Sturm-Liouville Problems Containing Eigenparameter in the Boundary Conditions

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Acta mathematica Sinica,English Series 2006年第5期22卷 1519-1528页

作者： m.KADAKAL O.sh.mUKHTAROV Ondokuz mayis University Science and Arts Faculty Department of MathematicsKurupelit 55139 Samsun Turkey Gaziosmanpasa University Science and Arts Faculty Department of MathematicsTokat 60000 Turkey

In this paper, discontinuous Sturm-Liouville problems, which contain eigenvalue parameters both in the equation and in one of the boundary conditions, are investigated. By using an operatortheoretic interpretation we extend some classic results for regular Sturm-Liouville problems and obtain asymptotic approximate formulae for eigenvalues and normalized eigenfunctions. We modify some techniques of [Fulton, C. T., Proc. Roy. Soc. Edin. 77 （A）, 293-308 （1977）], [Walter, J., math. Z., 133, 301-312 （1973）] and [Titchmarsh, E. C., Eigenfunctions Expansion Associated with Second Order Differential Equations I, 2nd edn., Oxford Univ. Pres, London, 1962], then by using these techniques we obtain asymptotic formulae for eigenelement norms and normalized eigenfunctions.

关键词： Sturm-Liouville problem discontinuous boundary-value problem eigenvalue and eigenfunction eigenelement normalized eigenfunctions

Lower Bounds for Local Cohomology modules with Respect to a Pair of Ideals

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Algebra Colloquium 2016年第2期23卷 329-334页

作者： m. Lotfi Parsa sh. Payrovi Faculty of Science Sayyed Jamaleddin Asadabadi University Postal code: 65418-3-5583 Asadabad Iran Department of mathematics Imam Khomeini International University Postal code: 34149-1-6818 Qazvin Iran

Let R be a Noetherian ring, I and J two ideals of R, m an R-module and t an integer. Let S be a Serre subcategory of the category of R-modules satisfying the co ondition CI, and N be a finitely generated R-module with SuppRN= V（a） for some a ∈ W（I, J）. It is shown that if ExtR^J（N,HI^i,J（m）） ∈ S for all i 〈 t and all j 〈 t - i, then Ha^i（m） ∈ S for all i 〈 t. Let S be the class of all R-modules N with divmR N ≤ k, where k is an integer. It is proved that if Ha^i（m） ∈ S for all i 〈 t and all a ∈ W（I, J）, then HI^i,j（m） ∈ S for all i 〈 t. It follows that inf{i ： HI^i,j（m） S} = inf（inf{i ： Ha^i（m） S）： a ∈W（I,J）}.

关键词： extension functor local cohomology Serre subcategory

Interaction of a Two-Level Atom with the morse Potential in the Framework of Jaynes-Cummings model

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Chinese Physics Letters 2009年第9期26卷 169-172页

作者： m. R. Setare sh. Barzanjeh Department of Science Payame Noor University Bijar Iran Department of Physics Faculty of Science University of Isfahan Hezar Jerib Isfahan Iran

A theoretical study of the dynamical behaviors of the interaction between a two-level atom with a morse potential in the framework of the Jaynes Cummings model （JCm） is discussed. We show that this system is equivalent to an intensity-dependent coupling between the two-level atom and the non-deformed single-mode radiation field in the presence of an additional nonlinear interaction. We study the dynamical properties of the system such as, atomic population inversion, the probability distribution of cavity-field, the mandel parameter and atomic dipole squeezing. It is shown how the depth of the morse potential can be affected by non-classical properties of the system. moreover, the temporal evolution of the Husimi-distribution function is explored.

关键词： No English Keyword

Inverse Heat Transfer Problem of Thermal Contact Conductance Estimation in Periodically Contacting Surfaces

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Journal of Thermal Science 2009年第2期18卷 150-159页

作者： m.H.shojaeefard K.Goudarzi m.sh.mazidi Dept. of mechanical Engineering Iran University of Science and Technology

The problems involving periodic contacting surfaces have different practical applications. An inverse heat conductionproblem for estimating the periodic Thermal Contact Conductance (TCC) between one-dimensional, constantproperty contacting solids has been investigated with conjugate gradient method (CGm) of function *** method converges very rapidly and is not so sensitive to the measurement errors. The advantage of thepresent method is that no a priori information is needed on the variation of the unknown quantities, since the solutionautomatically determines the functional form over the specified domain. A simple, straight forward techniqueis utilized to solve the direct, sensitivity and adjoint problems, in order to overcome the difficulties associatedwith numerical methods. Two general classes of results, the results obtained by applying inexact simulatedmeasured data and the results obtained by using data taken from an actual experiment are presented. In addition,extrapolation method is applied to obtain actual results. Generally, the present method effectively improves theexact TCC when exact and inexact simulated measurements input to the analysis. Furthermore, the results obtainedwith CGm and the extrapolation results are in agreement and the little deviations can be negligible.

关键词： thermal contact inverse problem conjugates gradient method

Effect of the duty cycle of pulsed current on nanocomposite layers formed by pulsed electrodeposition

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Rare metals 2010年第2期29卷 209-213页

作者： m.Aliofkhazraei sh.Ahangarani A.Sabour Rouhaghdam Department of materials Engineering Faculty of Engineering Tarbiat Modares University Department of Advanced materials & Renewable Energies Iranian Research Organization for Science and Technology(IROST)

Nickel-tungsten/carbon nanotube nanocomposite layers with high content and uniform dispersion of carbon nanotubes were fabricated using pulsed electrodeposition *** layers were analyzed by scanning electron microscopy, atomic force microscopy, microhardness, and Tafel polarization *** effect of the duty cycle of pulsed current or concentration of carbon nanotubes in the metallic matrix on electrochemical and mechanical properties of obtained layers has been *** has been shown that both the electrochemical and mechanical properties of nanocomposite layers that formed by pulsed current were improved significantly with respect to un-composed Ni-W *** results were not only concerned by the concentration of carbon nanotubes in the layer but also influenced by the distribution of nanoparticulates in the metallic matrix.

关键词： nanocomposite corrosion nanostructure carbon nanotubes