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    Simulation of static recrystallization in non-isothermal annealing using a coupled cellular automata and finite element model

    , Article Computational Materials Science ; Volume 53, Issue 1 , 2012 , Pages 145-152 ; 09270256 (ISSN) Seyed Salehi, M ; Serajzadeh, S ; Sharif University of Technology
    2012
    Abstract
    A coupled cellular automata and finite element model has been proposed to evaluate static recrystallization kinetics during non-isothermal annealing of cold deformed low carbon steels. The effects of various factors including heating rate, annealing temperature, and initial microstructures have been considered in the model to accurately predict the static recrystallization kinetics and the final microstructures. In order to examine the employed algorithm, the predicted results have been compared with the experimental observations and a good agreement was found between the two sets of results  

    A neural network model for prediction of static recrystallization kinetics under non-isothermal conditions

    , Article Computational Materials Science ; Volume 49, Issue 4 , 2010 , Pages 773-781 ; 09270256 (ISSN) Seyed Salehi, M ; Serajzadeh, S ; Sharif University of Technology
    2010
    Abstract
    This paper presents a new scheme to apply artificial neural network (ANN) in prediction of static recrystallization (SRX) kinetics. Firstly, based on empirical data of SRX kinetics, a mathematical model is suggested to construct a neural network. Then, an appropriate neural network is trained on the basis of the first and the second derivatives of recrystallized fraction with respect to time. Finally, a thermo-mechanical finite element analysis is coupled with the proposed ANN to predict static recrystallization kinetics in hot rolling process of AA5083. To verify the model, the predicted results and the experimental data are compared and it is observed that there is a good consistency... 

    A model to predict recrystallization kinetics in hot strip rolling using combined artificial neural network and finite elements

    , Article Journal of Materials Engineering and Performance ; Volume 18, Issue 9 , 2009 , Pages 1209-1217 ; 10599495 (ISSN) Seyed Salehi, M ; Serajzadeh, S ; Sharif University of Technology
    2009
    Abstract
    A thermo-mechanical model has been developed to establish a coupled heat conduction and plastic flow analysis in hot-rolling process. This model is capable of predicting temperature, strain, and strain rate distributions during hot rolling as well as the subsequent static recrystallization fraction and grain size changes after hot deformation. Finite element and neural network models are coupled to assess recrystallization kinetics after hot rolling. A new algorithm has been suggested to create differential data sets to train the neural network. The model is then used to predict histories of various deformation variables and recrystallization kinetics in hot rolling of AA5083. Comparison... 

    A new upper bound solution for the analysis of the twist extrusion process with an elliptical die cross-section

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 223, Issue 9 , 2009 , Pages 1975-1981 ; 09544062 (ISSN) Salehi Seyed, M ; Serajzadeh, S ; Sharif University of Technology
    2009
    Abstract
    The twist extrusion process is a rather new route to produce highly strained materials. In this process, severe plastic deformation is applied by large shear strains. In this regard, prediction of materials behaviour and extrusion pressure is of importance to die designers and engineers. In this article, utilizing an admissible velocity field together with the upper bound technique, the required energy for twist extrusion is predicted. The proposed model is capable of considering the effect of various parameters such as die geometry and friction conditions. In addition, the model anticipates the critical die design parameters. To verify the proposed model, the predictions are compared with... 

    Simulation of Static Softening during Annealing of Cold Rolled Strip Using Cellular Automata and Finite Element Model

    , Ph.D. Dissertation Sharif University of Technology Seyed Salehi, Majid (Author) ; Serajzadeh, Siamak (Supervisor)
    Abstract
    In this study, static softening kinetics and microstructural evolution during isothermal and non-isothermal annealing of aluminum-magnesium alloy and low carbon steel after cold plastic deformation was investigated. It is known that in industrial cold forming processes, the material properties and microstructure changes during the annealing depends on the inhomogeneous initial microstructure and the deformation history of the cold worked material. To predict the microstructural changes during the annealing of cold worked alloys, a multiscale model based on probabilistic cellular automata (at mesoscale), and the finite element method (at macroscale), was used. To do so, a two-dimensional... 

    Order Flow Imbalance Effect on Price Movement in Tehran Stock Exchange

    , M.Sc. Thesis Sharif University of Technology Seyed Salehi, Mohammad Hossein (Author) ; Barakchian, Mahdi (Supervisor)
    Abstract
    We investigate order book events impacts on price movement, using the 31 stocks from the Tehran Stock Exchange. We show that in a low-depth market the mid-price change is explained mainly by a linear relationship with our proposed explanatory variable, modified order flow imbalance that represents the depth-adjusted differences of first level orders volumes in different sides of order book. Our results shows that the bid and ask spread has a negative effect on the power of events to move the price  

    Microstructure and mechanical properties of copper processed by twist extrusion with a reduced twist-line slope

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 4 , 2014 , pp. 2232-2241 ; Online ISSN: 1543-1940 Latypov, M. I ; Yoon, E. Y ; Lee, D. J ; Kulagin, R ; Beygelzimer, Y ; Seyed Salehi, M ; Kim, H. S ; Sharif University of Technology
    2014
    Abstract
    Pure copper processed by a twist extrusion process with a reduced twist-line slope is investigated. Twist extrusion is a severe plastic deformation technique which is promising for scale-up because it allows for processing of relatively large metallic bars. On the way to commercialization, decreasing costs associated with processing is critical for twist extrusion. As one of the measures, reducing the twist-line slope - an important geometrical feature of twist extrusion - can be advantageous in terms of processing costs. The current study seeks to elucidate effects of reducing the twist-line slope on the microstructure, mechanical properties, and their heterogeneity in the processed metal,... 

    Electroplating and characterization of Cr–Al2O3 nanocomposite film from a trivalent chromium bath [electronic resource]

    , Article Anti-Corrosion Methods and Materials ; Vol 61, No 4, 2014, 205-214 Salehi Doolabi, M. (Mohsen) ; Sadrnezhaad, Khatiboleslam ; Salehi Doolabi, Davood ; Sharif University of Technology
    Abstract
    The main aim of this study was to improve current efficiency and to obtain thicker coatings via aluminum oxide (Al2O3) addition to the chromium (Cr) (III) bath. Design/methodology/approach ‐ Pure Cr and nanocomposite Cr–Al2O3 coatings were electrodeposited from Cr (III) bath onto cathode copper substrates by conventional method. Dependence of current efficiency to current density, Al2O3 content and particle size were investigated. Findings ‐ Current efficiency increased with Al2O3 amount and decreased with Al2O3 particle size. Maximum current efficiency was achieved at 25 A/dm2 for pure Cr and 30 A/dm2 for composite coatings. Al2O3 bath content, current density and stirring rate increased... 

    Vortex with fourfold defect lines in a simple model of self-propelled particles

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 93, Issue 3 , 2016 ; 15393755 (ISSN) Seyed Allaei, H ; Ejtehadi, M. R ; Sharif University of Technology
    American Physical Society  2016
    Abstract
    We study the formation of a vortex with fourfold symmetry in a minimal model of self-propelled particles, confined inside a squared box, using computer simulations and also theoretical analysis. In addition to the vortex pattern, we observe five other regimes in the system: a homogeneous gaseous phase, band structures, moving clumps, moving clusters, and vibrating rings. All six regimes emerge from controlling the strength of noise and from the contribution of repulsion and alignment interactions. We study the shape of the vortex and its symmetry in detail. The pattern shows exponential defect lines where incoming and outgoing flows of particles collide. We show that alignment and repulsion... 

    Performance characterization of ultrahigh speed optically amplified spectral-phase encoded OCDMA systems with second-harmonic-generation effect in thin and thick crystal receiver structures [electronic resource]

    , Article IEEE Transactions on Communications ; October 2011, Vol 59, No. 10, P. 2818-2831 Matinfar, M. D ; Matinfar, M. D ; Salehi, J. A ; Sharif University of Technology
    Abstract
    In this paper we study and evaluate the performance of a spectral-phase encoded optical CDMA (SPE-OCDMA) system using advanced receiver structures based on second harmonic generation (SHG) effect imposed in a Thick or Thin crystal. This receiver structure is employed as the nonlinear pre-processor prior to the conventional low-speed photodetector. In our performance evaluation amplified spontaneous emission (ASE) of the optical amplifiers, receiver front end thermal noise and photodetector shot noise which are effective in low power conditions, and multiple access interference (MAI) noise which is the dominant source of noise in high power conditions in any coherent OCDMA communications... 

    On the h-vector of a simplicial complex with Serre's condition

    , Article Journal of Pure and Applied Algebra ; Volume 216, Issue 1 , January , 2012 , Pages 91-94 ; 00224049 (ISSN) Goodarzi, A ; Pournaki, M. R ; Seyed Fakhari, S. A ; Yassemi, S
    2012
    Abstract
    Let δ be a (d-1)-dimensional simplicial complex and let h(δ)=(h0,h1,...,hd) be its h-vector. A recent result of Murai and Terai guarantees that if δ satisfies Serre's condition (Sr), then (h0,h1,...,hr) is an M-vector and hr+hr+1+...+hd is nonnegative. In this article, we extend the result of Murai and Terai by giving r extra necessary conditions. More precisely, we prove that if δ satisfies Serre's condition (Sr), then iihr+i+1ihr+1+...+i+d-rihd, 0≤i≤r≤d, are all nonnegative  

    Spectral classification and multiplicative partitioning of constant-weight sequences based on circulant matrix representation of optical orthogonal codes [electronic resource]

    , Article IEEE Transactions on Information Theory ; 2010 vol. 56, no. 9 Alem-Karladani, M. M. (Mohammad M.) ; Salehi, Jawad A ; $item.subfieldsMap.a ; Sharif University Of Technology

    Phase-induced intensity noise in digital incoherent all-optical tapped-delay line systems [electronic resource]

    , Article Lightwave Technology, Journal of ; 2006, Volume.24 , Issue. 8, p.3059-3072 Mansouri Rad, M. M. (Mohammad Mehdi) ; Salehi, J. A ; Sharif University of Technology
    Abstract
    In this paper, the authors analyze conditions under which they can be certain on the intensity addition of a given device, such as tapped-delay lines, used in digital incoherent all-optical communication systems. A general expression for phase-induced intensity noise that is applicable to all types of semiconductor lasers is derived by defining an optical self-SNR expression that can be used to analyze and measure phase-induced intensity noise. The result shows that in order to have a minimal phase-induced intensity noise in most digital optical incoherent systems, a large optical self-SNR, e.g., 20 dB or more, is needed. This in turn is shown to place a limit on the maximum rate of... 

    Influence of pulse parameters on electrocodeposition of Cr-Al2O3 nanocomposite coatings from trivalent chromium bath

    , Article International Heat Treatment and Surface Engineering ; Volume 6, Issue 4 , December , 2012 , Pages 178-184 ; 17495148 (ISSN) Salehi Doolabi, M ; Sadrnezhaad, S. K ; Salehi Doolabi, D ; Asadirad, M ; Sharif University of Technology
    2012
    Abstract
    Cr and Cr-Al2O3 coatings were electrodeposited from Cr(III) bath with both pulsating and direct current onto copper substrates. Pulsating current resulted in homogeneous films of higher Al2O3 content and lower particle agglomeration than the direct current. Differences were more tangible at shorter duty cycles and pulse frequencies. Pulsating current improved both microhardness and corrosion resistance. The presence of alumina nanoparticles resulted in greater current efficiency, higher film microhardness and better corrosion resistance. Maximum current efficiency, highest microhardness and densest electrodeposited coatings were achieved at current density of 20 A dm-2, duty cycle of 40% and... 

    Wireless optical CDMA lAN: digital design concepts [electronic resource]

    , Article IEEE Transaction on Communication ; Vol. 56, No. 12, PP. 2145-2155, December 2008 Ghaffari, B. M. (Babak M.) ; Matinfar, M ; Salehi, J. A ; Sharif University of Technology
    Abstract
    In this paper we study and present an in-depth analysis on the operability and the viability of a typical wireless optical CDMA (OCDMA) local area network. Three receiver structures for OCDMA systems, using optical orthogonal codes (OOC) with minimum auto and cross-correlations as signature sequence, namely, correlation, correlation with hard-limiter, and chip-level detection are studied and proposed for such a network. For the synchronization circuit design the performance of two algorithms for OOC based OCDMA networks, namely, simple serial-search and multiple-shift in the context of wireless OCDMA LAN are studied. Furthermore, we study a synchronization method based on matched filtering... 

    Adaptive output feedback tracking controller for a class of uncertain strict feedback nonlinear systems in the absence of state measurements

    , Article International Journal of Systems Science ; Volume 43, Issue 2 , 2012 , Pages 201-210 ; 00207721 (ISSN) Salehi, S ; Shahrokhi, M ; Sharif University of Technology
    2012
    Abstract
    In this article, design of an adaptive control scheme for a class of uncertain single-input single-output systems in strict feedback form via a backstepping technique has been proposed. It is assumed that system output and its derivatives are available. By virtue of the observability concept, it is shown that for this class of systems there exists a one-to-one map, which maps output and its derivatives to system states. By means of this mapping and using linearly parametrised approximators, such as fuzzy logic systems or neural networks, the uncertain nonlinear dynamics and unavailable states are estimated. The proposed adaptive controller guarantees that the closed-loop system is uniformly... 

    Adaptive fuzzy backstepping approach for temperature control of continuous stirred tank reactors

    , Article Fuzzy Sets and Systems ; Volume 160, Issue 12 , 2009 , Pages 1804-1818 ; 01650114 (ISSN) Salehi, S ; Shahrokhi, M ; Sharif University of Technology
    2009
    Abstract
    In this paper, an adaptive fuzzy controller, based on backstepping technique, has been proposed for temperature control of a general class of continuous stirred tank reactors (CSTRs). Using the observability concept, an adaptive fuzzy controller using temperature measurement has been designed. A fuzzy logic system is used to estimate the concentration dependent terms and other unknown system parameters appearing in the control law. It is shown that the closed loop system is asymptotically stable and influences of minimum approximation error and external disturbance on the L2 norm of the output tracking error can be attenuated arbitrarily. The performance of the proposed controller has been... 

    Adaptive fuzzy approach for H∞ temperature tracking control of continuous stirred tank reactors

    , Article Control Engineering Practice ; Volume 16, Issue 9 , September , 2008 , Pages 1101-1108 ; 09670661 (ISSN) Salehi, S ; Shahrokhi, M ; Sharif University of Technology
    2008
    Abstract
    In this paper, an adaptive fuzzy temperature controller is proposed for a class of continuous stirred tank reactors (CSTRs) based on input-output feedback linearization. Since for control implementation concentrations of all species are needed, based on the observability concept, a fuzzy logic system is used to estimate the concentration dependent terms and other unknown system parameters in the control law, using temperature measurements. It has been shown that the H∞ tracking control performance with a prescribed attenuation level is achieved, by using the proposed controller. Finally the effectiveness of the proposed controller has been demonstrated by applying it to a benchmark chemical... 

    Two observer-based nonlinear control approaches for temperature control of a class of continuous stirred tank reactors

    , Article Chemical Engineering Science ; Volume 63, Issue 2 , 2008 , Pages 395-403 ; 00092509 (ISSN) Salehi, S ; Shahrokhi, M ; Sharif University of Technology
    2008
    Abstract
    In this paper, two nonlinear observer based controllers for temperature control of a continuous stirred tank reactor in which a special class of parallel exothermic reactions take place are proposed. A reduced order nonlinear observer is constructed to estimate the concentration in the reactor. The observer is coupled with two nonlinear controllers, designed based on two well-known techniques, namely input-output linearization and backstepping for controlling the reactor temperature. For dampening the effect of observer error dynamics, a compensating term is used in each control law. The asymptotical stability of the closed-loop system is shown by the Lyapunov's stability theorem. The... 

    A packet based photonic label switching router for a multi-rate all-optical CDMA based GMPLS switch

    , Article IEEE Journal of Selected Topics in Quantum Electronics ; Vol.13, No.5 , September/October , 2007 , PP. 1522-1530 Farnoud, F ; Ibrahimi, M ; Salehi, J. A ; Sharif University Of Technology
    2007
    Abstract
    A novel packet-based photonic label switching router for a multirate all-optical switch using generalized multiprotocol label switching is proposed. The idea is based on using optical code-division multiple access (OCDMA) as multiplexing technique and treating OCDMA codes as labels. The system can coexist with current wavelength division multiplexing systems on the same infrastructure. The concept of switch fabric is introduced. Label processing and label swapping functionalities of the switch are discussed. In-depth analyses are made for spectrally phase-encoded OCDMA (SPE-OCDMA) due to its capabilities of supporting high data rates, large code cardinality, and its secure transmission....