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    Modeling age hardening kinetics of an Al-Mg-Si-Cu aluminum alloy

    , Article Journal of Materials Processing Technology ; Volume 205, Issue 1-3 , 26 August , 2008 , Pages 388-393 ; 09240136 (ISSN) Eivani, A. R ; Karimi Taheri, A ; Sharif University of Technology
    2008
    Abstract
    In this paper, an Al-Mg-Si-Cu aluminum alloy was exposed to various heat treatment processes and the effect of precipitation hardening on hardness was investigated as a function of time and temperature. It was concluded that the variation in time and temperature can improve the hardness of the alloy. The work revealed that time and temperature play an important role in the precipitation hardening process of the alloy. To achieve the maximum hardness, an optimum aging cycle should be used which is heating at 180-190 °C for 15-18 h. Kinetics studies show an apparent activation energy of 58 kJ/mol. A relationship was derived which can be used to estimate the hardness at a given time and... 

    A study on strain ageing during and after warm rolling of a carbon steel

    , Article Materials Letters ; Volume 62, Issue 6-7 , 2008 , Pages 946-948 ; 0167577X (ISSN) Serajzadeh, S ; Akhgar, J. M ; Sharif University of Technology
    2008
    Abstract
    In this study, strain ageing during and after warm rolling of a carbon steel has been investigated. At the first step, the occurrence of serrated flow was studied by means of tensile tests at different temperatures and strain rates. In the next stage, warm rolling experiments were performed under different rolling conditions and then the samples were aged at the room temperature for a period of 3 months. For both aged and non-aged samples, tensile tests were employed to evaluate their mechanical properties. The results show that static strain ageing is possible to happen in the utilized ageing period and increases the yield stress of the aged steel. However, the samples that experience both... 

    Studies on recycling of zinc-containing waste

    , Article REWAS'04 - Global Symposium on Recycling, Waste Treatment and Clean Technology, Madrid, 26 September 2004 through 29 September 2004 ; 2005 , Pages 2797-2799 ; 8495520060 (ISBN) Taghavi, S. M ; Halali, M ; Sharif University of Technology
    2005
    Abstract
    In this report, the possibility of recovering zinc oxide from zinc containing wastes, also the effect of temperature, time and depth of bed on recycling has been studied. Zinc oxide with a purity of 93.5% was obtained  

    Similarity solution of free convection in a stratified porous medium with variable permeability

    , Article 2005 ASME Summer Heat Transfer Conference, HT 2005, San Francisco, CA, 17 July 2005 through 22 July 2005 ; Volume 4 , 2005 , Pages 485-491 ; 0791847314 (ISBN); 9780791847312 (ISBN) Kalantarian, A ; Khodabakhsh, M ; Saidi, M. H ; Sharif University of Technology
    2005
    Abstract
    In this paper, similarity solution of free convection from inclined permeable wall embedded in a stratified porous medium is investigated. It is assumed that the heated wall has constant temperature and permeability along the wall is variable. Energy equation and Darcy's law as momentum have been used. Due to similarity solution we consider only large wall inclination angle. Effects of mass flux, permeability variation function, and wall inclination angle on thermal and velocity boundary layer thickness and heat transfer at the wall are investigated. Copyright © 2005 by ASME  

    Thermal effects on quantum communication through spin chains

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 71, Issue 4 , 2005 ; 10502947 (ISSN) Bayat, A ; Karimipour, V ; Sharif University of Technology
    2005
    Abstract
    We study the effect of thermal fluctuations in a recently proposed protocol for transmission of unknown quantum states through quantum spin chains. We develop a low-temperature expansion for general spin chains. We then apply this formalism to study exactly thermal effects on short spin chains of four spins. We show that optimal times for extraction of output states are almost independent of the temperature, which lowers only the fidelity of the channel. Moreover we show that thermal effects are smaller in the antiferromagnetic chains than the ferromagnetic ones. © 2005 The American Physical Society  

    Thermal entanglement of spins in an inhomogeneous magnetic field

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 71, Issue 2 , 2005 ; 10502947 (ISSN) Asoudeh, M ; Karimipour, V ; Sharif University of Technology
    American Physical Society  2005
    Abstract
    We study the effect of inhomogeneities in the magnetic field on the thermal entanglement of a two-spin system. We show that in the ferromagnetic case a very small inhomogeneity is capable of producing large values of thermal entanglement. This shows that the absence of entanglement in the ferromagnetic Heisenberg system is highly unstable against inhomogeneity of magnetic fields, which is inevitably present in any solid state realization of qubits. © 2005 The American Physical Society  

    Temperature and voltage dependence of magnetic barrier junctions with a nonmagnetic spacer

    , Article European Physical Journal B ; Volume 42, Issue 2 , 2004 , Pages 187-191 ; 14346028 (ISSN) Shokri, A. A ; Saffarzadeh, A ; Sharif University of Technology
    2004
    Abstract
    The temperature and voltage dependence of spin transport is theoretically investigated in a new type of magnetic tunnel junction, which consists of two ferromagnetic outer electrodes separated by a ferromagnetic barrier and a nonmagnetic (NM) metallic spacer. The effect of spin fluctuation in magnetic barrier, which plays an important role at finite temperature, is included by taking the mean-field approximation. It is found that, the tunnel magnetoresistance (TMR) and the electron-spin polarization depend strongly on the temperature and the applied voltage. The TMR and spin polarization at different temperatures show an oscillatory behavior as a function of the NM spacer thickness. Also,... 

    Temperature dependence of the amplifying parameters of a copper vapor laser

    , Article Laser Physics ; Volume 14, Issue 8 , 2004 , Pages 1050-1053 ; 1054660X (ISSN) Behrouzinia, S ; Sadighi Bonabi, R ; Parvin, P ; Zand, M ; Sharif University of Technology
    2004
    Abstract
    A pair of copper vapor lasers in an oscillator-amplifier configuration were used to investigate the temperature dependence of the small-signal gain and saturation intensity and output power of the laser at the 510.6 and 578.2 nm transitions individually. An optimum working temperature of 1520°C was determined, and a maximum output power equivalent to 33 W/l was extracted  

    Electrical and magnetic properties of Pr-doped Nd123

    , Article Physica Status Solidi C: Conferences ; Volume 1, Issue 7 , 2004 , Pages 1871-1874 ; 16101634 (ISSN) Maleki, P ; Khosroabadi, H ; Akhavan, M ; Sharif University of Technology
    2004
    Abstract
    Single-phase polycrystalline NdBa2-xPrxCu 3O7+δ (0 ≤ x ≤ 0.5) have been prepared by the standard solid-state reaction. The results of X-ray diffraction measurements confirm the formation of 123 single phase. A superconductor-insulator transition at XcSIT = 0.3 has been observed for the samples. The magnetoresistance of the samples have been investigated within the thermally activated flux creep model. The pinning energy decreases with the magnetic field application and Pr-doping. A scaling relation as power law dependence of pinning energy to the magnetic field has been obtained. The derived pinning energy shows that the Pr-doping plays the role of weak link. The normal state resistivity... 

    Modelling and simulation of syngas unit in large scale direct reduction plant

    , Article Ironmaking and Steelmaking ; Volume 30, Issue 1 , 2003 , Pages 18-24 ; 03019233 (ISSN) Farhadi, F ; Motamed Hashemi, M. Y ; Bahrami Babaheidari, M ; Sharif University of Technology
    IOM Communications Ltd  2003
    Abstract
    The production of reducing gas is usually a bottleneck to capacity increase in direct reduction plants. Modelling and simulation of reducing gas production result in better design and operation of these plants. In the present work, a mathematical model is discussed that relates to a Midrex reformer, which is different from conventional steam reformers in some respects. Both process side and furnace side have been included in an integrated model. Simulation results have been tested against available data from an actual plant. The model predictions have been found to be reasonably accurate. The effects of three process variables, feed gas temperature, feed gas pressure and excess air, on... 

    Stress analysis of multilayer thin walled pipes with circular cut-outs

    , Article World Congress on Engineering 2016, WCE 2016, 29 June 2016 through 1 July 2016 ; Volume 2224 , 2016 , Pages 1146-1150 ; 20780958 (ISSN); 9789881404800 (ISBN) Kamalarajah, R ; Bull, J.W ; Chizari, M ; Ao S.I ; Ao S.I ; Gelman L ; Ao S.I ; Gelman L ; Hukins D.W.L ; Hunter A ; Korsunsky A.M ; et al.; IAENG Society of Artificial Intelligence; IAENG Society of Bioinformatics; IAENG Society of Computer Science; IAENG Society of Data Mining; IAENG Society of Electrical Engineering ; Sharif University of Technology
    Newswood Limited  2016
    Abstract
    A finite element analysis of a double layered shell with a circular hole is carried out with the computer aided engineering software Abaqus (Dassault Systèmes, FR). The model proposed has been used to perform a stress analysis on three pipes with different sized hole. Moreover, thermal expansion has been implemented in the testing. For the purpose of the research, the elastic properties of the materials have been considered and the results compared with the ones previously published in literature. The outcome of the investigation will benefit towards the design of optimal and sustainable pipes with circular cut outs  

    An investigation on the calcination kinetics of zinc carbonate hydroxide and Calsimin zinc carbonate concentrate

    , Article Chemical Engineering Journal ; Volume 121, Issue 2-3 , 2006 , Pages 79-84 ; 13858947 (ISSN) Nobari, A. H ; Halali, M ; Sharif University of Technology
    2006
    Abstract
    In this study the thermal calcination of two materials, high purity zinc carbonate hydroxide and the Calsimin zinc carbonate concentrate have been investigated. Isothermal studies have been performed on samples at different temperatures and times. Non-isothermal analysis has been carried out by TGA and DSC. It has been found that the calcination behaviour of both materials corresponds to the shrinking core model. The activation energy for the calcination of zinc carbonate hydroxide is found to be 88.7 kJ/mol, and that for the Calsimin sample is 97.3 kJ/mol. © 2006 Elsevier B.V. All rights reserved  

    Influence of Darcy number on the onset of convection in a porous layer with a uniform heat source

    , Article International Journal of Thermal Sciences ; Volume 47, Issue 8 , August , 2008 , Pages 1020-1025 ; 12900729 (ISSN) Nouri Borujerdi, A ; Noghrehabadi, A. R ; Rees, D. A. S ; Sharif University of Technology
    2008
    Abstract
    This note considers the effect of different Darcy numbers on the onset of natural convection in a horizontal, fluid-saturated porous layer with uniform internal heating. It is assumed that the two bounding surfaces are maintained at constant but equal temperatures and that the fluid and porous matrix are in local thermal equilibrium. Linear stability theory is applied to the problem, and numerical solutions obtained using compact fourth order finite differences are presented for all Darcy numbers between Da = 0 (Darcian porous medium) and Da → ∞ (the clear fluid limit). The numerical work is supplemented by an asymptotic analysis for small values Da. © 2007 Elsevier Masson SAS. All rights... 

    Synthesis of PMN pyrochlore free ceramics via a modified mixed oxide method

    , Article Journal of Electroceramics ; Volume 19, Issue 2-3 , 2007 , Pages 207-213 ; 13853449 (ISSN) Moetakef, P ; Nemati, A ; Sharif University of Technology
    2007
    Abstract
    A modified mixed oxide method which is based on a two step reaction sintering process was designed to obtain single phase PMN ceramics. In this regard, pyrochlore phase formation during calcination process at different calcination temperatures was studied to determine the best soaking temperature for the first step in the specified method. In other words, the calcination temperature in which the least pyrochlore phase produced was chosen as the first step soaking temperature. The results showed that by utilizing this new method, single phase PMN ceramics with a high relative density of 98% can be synthesized successfully using conventional mixed oxide starting materials. © 2007 Springer... 

    A study on flow behavior of A-286 superalloy during hot deformation

    , Article Materials Chemistry and Physics ; Volume 101, Issue 1 , 2007 , Pages 153-157 ; 02540584 (ISSN) Salehi, A. R ; Serajzadeh, S ; Yazdipour, N ; Sharif University of Technology
    2007
    Abstract
    The hot deformation behavior of A-286 superalloy has been characterized using hot compression experiments in the temperatures between 1000 and 1100 °C and strain rates varying between 0.001 and 0.1 s-1. In addition, hot workability of this alloy has been analyzed by employing flow-localization parameter. The results show that both kinds of softening mechanism, dynamic recovery and dynamic recrystallization, occur during hot working, where at 1000 °C the main mechanism is dynamic recovery and at higher temperatures and strain rate of 0.001-0.01 s-1 dynamic recrystallization takes place. Calculations demonstrates that this alloy mainly have a good workability for the utilized deformation... 

    An investigation on the sintering behavior of high strength Al-Zn-Mg-Cu alloy prepared from elemental powders

    , Article 2006 Powder Metallurgy World Congress and Exhibition, PM 2006, Busan, 24 September 2006 through 28 September 2006 ; Volume 534-536, Issue PART 1 , 2007 , Pages 489-492 ; 02555476 (ISSN); 0878494197 (ISBN); 9780878494194 (ISBN) Shahmohammadi, M ; Sirnchi, A ; Danninger, H ; Arvand, A ; Sharif University of Technology
    Trans Tech Publications Ltd  2007
    Abstract
    In the present work, the sintering behavior of high strength Al-5.6Zn-2.5Mg-1.6Cu (in wt.%) alloy compacts was investigated. Green parts made by pressing of mixed elemental powders were sintered at different temperatures between 400 and 600°C The effect of the sintering temperature on density, dimensional change and microstructure of the Al alloy was studied. Microstructural evaluation was accompanied by XRD and DSC methods in order to determine the temperature and chemical composition of the liquid phases formed during sintering. It was found that three transient liquid phases are formed at 420, 439 and 450°C Microstructural study revealed the progressive formation of sintered contacts due... 

    Kinetic study of catalytic hydrolysis reaction of methyl acetate to acetic acid and methanol

    , Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 30, Issue 5 , 2006 , Pages 595-606 ; 03601307 (ISSN) Ehteshami, M ; Rahimi, N ; Eftekhari, A. A ; Nasr, M. J ; Sharif University of Technology
    2006
    Abstract
    The reaction kinetics and chemical equilibrium of the reversible catalytic hydrolysis reaction of a methyl acetate to acetic acid and methanol using a strongly acidic ion exchange resin catalyst named Amberlyst 15 were studied. To investigate the different behavior of Amberlyst 15 in the adsorption of reactants and product species, the equilibrium behavior of binary non-reactive liquid mixtures, consisting of one reactant and one product were studied experimentally. The Langmuir model was used to describe the equilibrium condition, quantitatively. Then the employed model was compared with the more complicated thermodynamic models to describe the equilibrium between the catalytic polymer... 

    Kinetic investigation of NDMA to UDMH hydrogenation on a pd/C catalyst

    , Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 30, Issue 5 , 2006 , Pages 581-593 ; 03601307 (ISSN) Gorji, M ; Kazemeini, M ; Bozorgmehri, R ; Sharif University of Technology
    2006
    Abstract
    Unsymmetrical dimethyl hydrazine (UDMH) is a strong propellant, which due to its very good physical properties and high power of repellency has been utilized as a liquid fuel for fighter jet engines for so many years. There are different methods for production of this material. One of the more efficient ones which results in higher yields compared to others is the catalytic hydrogenation of Nitroso Dimethylamine (NDMA). In this work hydrogenation of NDMA to UDMH on a 5% Pd/C in aqueous solution of NDMA was studied experimentally. Experiments were carried out in a Semi-batch three phase STR reactor under constant pressure and temperature in the range of 40 to 70°C, pressures of up to 15 bar... 

    Behaviour of metal powders during cold and warm compaction

    , Article Powder Metallurgy ; Volume 49, Issue 3 , 2006 , Pages 281-287 ; 00325899 (ISSN) Simchi, A ; Veltl, G ; Sharif University of Technology
    2006
    Abstract
    An instrumented die was used to investigate the behaviour of metal powders during cold (ambient temperature) and warm (up to 140°C) compaction. This instrument enables simultaneous measurement of density, die wall friction coefficient, the triaxial stresses acting on the powder during the course of compaction and ejection pressure. Commercial iron, titanium, aluminium, 316L stainless steel (SS) and aluminium-silicon powders were employed for investigation. The results demonstrated the advantages of powder preheating on the compaction behaviour of metal powders concerning green density, dimensional changes, frictional behaviour, ejection characteristics and compactibiiity. However, the... 

    Experimental modeling of air temperature and velocity distribution in an engine compartment

    , Article 2006 2nd ASME Joint U.S.-European Fluids Engineering Summer Meeting, FEDSM 2006, Miami, FL, 17 July 2006 through 20 July 2006 ; Volume 2006 , 2006 ; 0791837831 (ISBN); 9780791837832 (ISBN) Mozafari, A. A ; Saidi, M. H ; Neyestani, J ; Sany, A. E ; Sharif University of Technology
    2006
    Abstract
    Investigation of air distribution and wind effect on a vehicle body from the point of view of underhood heat transfer effect and proper positioning of vehicle elements such cooler, condenser and engine configuration is an important area for engine researchers and manufacturers as well. In this research, the effect of air velocity distribution and wind effect around a vehicle is simulated and temperature and velocity distribution around engine block which is influenced by the wind effect is investigated. Thermal investigation of the engine compartment components is performed using results of underhood air temperature and velocity distribution. The heat transfer from engine surface is...