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asghari-shivaee--hossein
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Advanced isoconversional kinetics of nanocrystallization in Fe73.5Si13.5B9Nb3Cu 1 alloy
, Article Thermochimica Acta ; Volume 494, Issue 1-2 , 2009 , Pages 80-85 ; 00406031 (ISSN) ; Madaah Hosseini, H. R ; Sharif University of Technology
2009
Abstract
Nanocrystallization kinetics of amorphous Finemet alloy was studied using Vyazovkin advanced isoconversional method under non-isothermal condition. Well known Kissinger model-fitting method and four isoconversional methods of Kissinger-Akahira-Sunose (KSA), Flynn-Wall-Ozawa (FWO), Tang, and Starink were also used for the determination of activation energy. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) patterns were used for thermal and structural analyses, respectively. According to Vyazovkin and other isoconversional methods, the mean value of variable activation energy, as a function of conversion, was obtained as 350 kJ mol-1. While, according to Kissinger method,...
The dependency of optical properties on density for hot pressed MgF2
, Article Infrared Physics and Technology ; Volume 51, Issue 6 , 2008 , Pages 546-549 ; 13504495 (ISSN) ; Madaah Hosseini, H. R ; Asghari Shivaee, H ; Sharif University of Technology
2008
Abstract
The effects of the most important parameters of hot pressing, including temperature, time and pressure on densification, microstructure and infrared transparency of MgF2 ceramics are discussed. The results show that the absorption or scattering of incident radiation is strongly dependent on the amount of porosity. By increasing the temperature or the pressure, transparency at infrared wavelengths has been increased due to the rise in density. For the longer hot pressing times, a continuous increase in density and infrared transparency has been seen as well. Cold pressing before hot press has minor effects on the density and infrared transparency of MgF2. © 2008 Elsevier B.V. All rights...
Structural and magnetic study of active screen plasma nitrided Fe 73.5Si13.5B9Nb3Cu1and Fe77Si11B9Nb2.4Cu0.6 ribbons
, Article Scientia Iranica ; Volume 17, Issue 1 F , 2010 , Pages 12-22 ; 10263098 (ISSN) ; Madaah Hosseini, H.R ; Asghari Shivaee, H ; Roostaie, S ; Sharif University of Technology
2010
Abstract
The comparative study of Active Screen Plasma Nitriding (ASPN) treatment of two Finemet-type alloys with the compositions of Fe73.5Si 13.5B9Nb3Cu1 and Fe 77Si11B9Nb2.4Cu0.6 was investigated in different temperatures ranging from 410°C to 56°C. Differential Scanning Calorimetry (DSC), X-Ray Diffractometery (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), electrical resistivity, microhardness measurements and magnetic characterization by a Vibrating Sample Magnetometer (VSM) were utilized to characterize the treated samples. The comparison of the DSC data for the alloys suggested that the smaller amount of Nb as a growth inhibitor shifted the crystallization...
Influence of annealing on the electrochemical behavior of finemet amorphous and nanocrystalline alloy
, Article Journal of Materials Science ; Volume 45, Issue 2 , 2010 , Pages 546-551 ; 00222461 (ISSN) ; Nozad Golikand, A ; Madaah Hosseini, H. R ; Asgari, M ; Sharif University of Technology
2010
Abstract
The electrochemical corrosion behavior of finemet alloy at various heat treatment temperatures was investigated. Thermal behavior and structural changes were studied using differential scanning calorimetry and X-ray diffractometry, respectively. The electrochemical corrosion of amorphous and annealed samples was investigated in 0.10 M NaOH solution using electrochemical impedance spectroscopy and linear sweep voltammetery. Changes in morphology of the samples before and after corrosion were characterized using optical microscope. The results showed that structural relaxation and nanocrystallization during the heat treatment improved corrosion behavior of the alloy. The heat-treated alloy at...
The Study of Eliminating Gender Gap in Iran Labor Market on Participation Rate of Married Urban Women
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Joshaghani, Hossein (Supervisor)
Abstract
The low female labor force participation rate in the Iranian labor market relative to the global average and even to countries that do not differ significantly from the socio-economic characteristics of our country is one of the important questions of the Iranian labor market. In this study, we seek to answer the question of whether the economic participation rate of married women will increase if the gender gaps in wages, job findings and job losses among women and men are eliminated in the Iranian labor market. To answer this question using household expenditure and income data and labor force data, we show that between the two categories of occupations, in terms of the share of women's...
Design and Analysis of Leader-based Framework For Resource Management in Mobile Clouds
, M.Sc. Thesis Sharif University of Technology ; Hossein Khalaj, Babak (Supervisor)
Abstract
Mobile Clouds are networks of devices with short-range communication capability, which at the same time can establish connection with the long-range cellular networks. Short-range communication links in mobile clouds provide the opportunity of resource sharing, which can result in new services for users. In this work, we study two key problems required to be addressed before the real implementation of resource sharing in mobile clouds; how to find the services offered in such clouds, and how to create incentive in users to share their resources for others.The goal of this work is to present a management framework for mobile clouds. Considering incentives in the form of price-based systems,...
Study of Nanocrystallization Kinetics, Microstructure and Magnetic Properties of Finemet-type Soft Magnetic Materials
, Ph.D. Dissertation Sharif University of Technology ; Madaah Hosseini, Hamid Reza (Supervisor) ; nozad, Ahmad (Supervisor) ; Beitollahi, Ali (Co-Advisor)
Abstract
Nanocrystallization kinetics of amorphous Finemet-type alloys was studied using Isokinetic and Isoconversional methods (Kissinger model-fitting method, Vyazovkin advance method, Kissinger–Akahira–Sunose(KSA),Flynn–Wall–Ozawa(FWO),Tang and Starink) under isothermal and non-isothermal conditions. Effects of chemical composition on the nanocrystallization kinetics, microstructure and magnetic properties of Fe73.5Si13.5B9Nb3Cu1 and Fe77Si11B9Nb2.4Cu0.6 alloys were also investigated. Kinetic triplet (activation energy, frequency factor and reaction model) were determined by these methods and compared for the alloys. According to isoconversional methods, the activation energy is variable as a...
Producing ultrafine-grained aluminum rods by cyclic forward-backward extrusion: Study the microstructures and mechanical properties
, Article Materials Letters ; Volume 74 , May , 2012 , Pages 147-150 ; 0167577X (ISSN) ; Zaeem, M. A ; Dehghani, K ; Shivaee, H. A ; Sharif University of Technology
2012
Abstract
A cyclic forward-backward extrusion (CFBE) process was used as a severe plastic deformation (SPD) technique to produce ultrafine-grained aluminum rods. Yield strength and tensile strength of the specimens increased by increasing the number of CFBE cycles, while elongation to break decreased due to an increase in the grain refinement and microhardness. According to transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) results, the average grain size was reduced from 120 μm to 315 nm after only 3 cycles of CFBE
Geometrically nonlinear micro-plate formulation based on the modified couple stress theory
, Article International Journal of Engineering Science ; Volume 51 , 2012 , Pages 292-309 ; 00207225 (ISSN) ; Sharif University of Technology
2012
Abstract
The couple stress theory is a non-classical continuum theory which is capable to capture size effects in small-scale structures. This property makes it appropriate for modeling the structures in micron and sub-micron scales. The purpose of this paper is the derivation of the governing motion equations and boundary conditions for the geometrically nonlinear micro-plates with arbitrary shapes based on the modified version of the couple stress theory. The consistent boundary conditions are provided at smooth parts of the plate periphery and also at the sharp corners of the periphery using variational approach
Basis free expressions for the stress rate of isotropic elastic materials in the cases of coalescent principal stretches
, Article International Journal of Solids and Structures ; Volume 47, Issue 5 , 2010 , Pages 611-613 ; 00207683 (ISSN) ; Sharif University of Technology
2010
Abstract
In this paper, some basis-free expressions for the material time derivative of Lagrangian stress tensors are presented which are generally valid in all cases of coalescent principal stretches. The material is assumed to be elastic and isotropic
Nanocrystallization kinetics and magnetic properties of the melt spun amorphous (Fe0.5Co0.5)77Si11B 9Cu0.6Nb2.4 alloy
, Article Thermochimica Acta ; Vol. 575, issue , 2014 , p. 64-69 ; Samadi, M ; Alihosseini, H ; Madaah Hosseini, H. R ; Sharif University of Technology
2014
Abstract
Kinetics of crystallization in an amorphous (Fe0.5Co 0.5)77Si11B9Cu0.6Nb 2.4 (at.%) alloy was investigated using differential scanning calorimetry (DSC). Transformed fraction as a function of temperature was obtained by accurate DSC measurement and the experimental data analyzed with Vyazovkin model-free kinetic method. Reconstructed form of the experimental kinetics model, g(α), clearly showed the crystallization mechanism do not belongs to a single model but almost follows the Avrami-Erofe'ev. Magnetic coercivity and hysteresis loss values of the annealed samples at 823 K were 7.5 A m-1 and 1.2 J m-3, compared to 17.1 A m-1 and 37.1 J m-3 for as spun samples. Magnetic measurements show the...
Study of nanocrystallization in FINEMET alloy by active screen plasma nitriding
, Article Journal of Alloys and Compounds ; Volume 491, Issue 1-2 , 2010 , Pages 487-494 ; 09258388 (ISSN) ; Madaah Hosseini, H. R ; Memarzadeh Lotfabad, E ; Roostaie, S ; Sharif University of Technology
2010
Abstract
The nanocrystallization process of amorphous Fe73.5Si13.5B9Nb3Cu 1 was investigated by active screen plasma nitriding (ASPN) treatment at temperatures ranging from 410 °C to 560 °C for 3 h in two gas mixtures of 75% N2-25% H2 and 25% N2-75% H2 at 5 mbar atmosphere. The amorphous ribbons were then annealed under vacuum at the same time and temperatures mentioned above. The structure of the samples was analyzed using various techniques such as X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). Microhardness measurements, electrical resistivity and Vibrating Sample Magnetometer (VSM) were used to study mechanical, electrical and magnetic...
A size-dependent model for functionally graded micro-plates for mechanical analyses
, Article JVC/Journal of Vibration and Control ; Volume 19, Issue 11 , 2013 , Pages 1614-1632 ; 10775463 (ISSN) ; Taati, E ; Sharif University of Technology
2013
Abstract
In this paper, a size-dependent formulation is presented for mechanical analyses of inhomogeneous micro-plates based on the modified couple stress theory. The plate properties can arbitrarily vary through the thickness. The governing differential equations of motion are derived for functionally graded (FG) plates with arbitrary shapes utilizing a variational approach. Moreover, the boundary conditions are provided at smooth parts of the plate periphery and also at the sharp corners of the periphery. Utilizing the derived formulation, the free-vibration behavior as well as the static response of a rectangular FG micro-plate is investigated
Variational principles for stability analysis of multi-walled carbon nanotubes based on a nonlocal elastic shell model
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, Istanbul, 12 July 2010 through 14 July 2010 ; Volume 5 , 2010 , Pages 591-598 ; 9780791849194 (ISBN) ; Rafati, J ; Sharif University of Technology
2010
Abstract
The nonlocal continuum theories are capable to reflect the small length characteristic of nanostructures. In this work, variational principles are presented for the stability analysis of multi-walled carbon nanotubes under various mechanical loadings based on the nonlocal elastic Donnell's shell by the semi-inverse method. In this manner, a set of proper essential and natural boundary conditions for each layer of the multi-walled nanotube is derived
Flexural vibration characteristics of micro-rotors based on the strain gradient theory
, Article International Journal of Applied Mechanics ; Volume 7, Issue 5 , October , 2015 ; 17588251 (ISSN) ; Hashemi, M ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2015
Abstract
In this paper, the coupled three-dimensional flexural vibration of micro-rotors is investigated by taking into account the small-scale effects utilizing the strain gradient theory, which is a powerful nonclassical continuum theory in capturing small-scale effects. A micro-rotor consists mainly of a flexible micro-rotating shaft and a disk. With the aid of Hamilton's principle, governing equations of motion are derived and then transformed to the complex form. By implementing the Galerkin's method, a coupled ordinary differential equation is attained for the system. Expressions for the first two natural frequencies of the spinning micro-rotors are obtained with truncated two-term equation....
A three-dimensional elasticity solution for functionally graded rotating disks
, Article Composite Structures ; Volume 92, Issue 5 , 2010 , Pages 1092-1099 ; 02638223 (ISSN) ; Ghafoori, E ; Sharif University of Technology
2010
Abstract
A semi-analytical three-dimensional elasticity solution for rotating functionally graded disks for both of hollow and solid disks is presented. The aim is to generalize an available two-dimensional plane-stress solution to a three-dimensional one. Although for the thin disks problems the two-dimensional solution provides appropriate results, for the thick disks, a three-dimensional elasticity solution should be considered to avoid poor results. It is shown that although the plane-stress solution satisfies all the governing three-dimensional equations of motion and boundary conditions, it fails to give a compatible three-dimensional strain field. A valid three-dimensional solution has been...
The couple stress-based nonlinear coupled three-dimensional vibration analysis of microspinning Rayleigh beams
, Article Nonlinear Dynamics ; Volume 87, Issue 2 , 2017 , Pages 1315-1334 ; 0924090X (ISSN) ; Hashemi, M ; Sharif University of Technology
Springer Netherlands
2017
Abstract
The nonlinear coupled three-dimensional vibrations of microspinning Rayleigh beams are analytically studied utilizing the modified couple stress theory to take into account the small-scale effects. The considered nonlinearity is of geometrical type due to the mid-plane stretching. The rotary inertia and gyroscopic effects are both included in the formulation. Governing equations of motion are derived with the aid of the Hamilton Principle and then transformed into complex form. Then, the Galerkin and multiple scales methods are utilized to solve the nonlinear partial differential equation. Approximate analytical expressions for nonlinear natural frequencies of the spinning beams in forward...
On the objective corotational rates of eulerian strain measures
, Article Journal of Elasticity ; Volume 90, Issue 2 , 2008 , Pages 175-207 ; 03743535 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
2008
Abstract
In the present paper, some new basis-free expressions for an arbitrary objective corotational rate of the general Eulerian strain measures are provided which are in compact form. Moreover, a complete discussion on the requirements for the continuity of the objective corotational rates are presented. © 2008 Springer Science+Business Media B.V
Unified basis-free relation between two stress tensors conjugate to arbitrary Hill's strain measures
, Article ASME PVP2006/ICPVT-11 Conference, Vancouver, BC, 23 July 2006 through 27 July 2006 ; Volume 2006 , 2006 ; 0277027X (ISSN); 0791837823 (ISBN); 9780791837825 (ISBN) ; Naghdabadi, R ; Sharif University of Technology
American Society of Mechanical Engineers(ASME)
2006
Abstract
The concept of energy conjugacy for stress and strain measures states that a stress tensor T is conjugate to a strain measure E if T: Ė provides the rate of change of the internal energy per unit reference volume of the body in an adiabatic process. The applications of the conjugate stress and strain measures are in the development of the basic relations in nonlinear analysis of solids. In this paper using eigenprojection method, unified explicit basis-free relation between two arbitrary stress tensors T(f) and T (g), respectively conjugate to two measures of Hill's strains is determined. The result is valid for arbitrary dimension of the Euclidean inner product space and for all cases of...