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sargolzaei-aval--yasaman
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Investigation of Light Emission Effects on the I-V Characteristics of High-Tc Superconductor Josephson Junction
, M.Sc. Thesis Sharif University of Technology ; Fardmanesh, Mehdi (Supervisor)
Abstract
High photonic responsivity and excellent quantum efficiency of high-Tc superconductors make them a promising candidate for photonic detectors. Interesting features of detectors which are based on Josephson Junctions such as high sensitivity in a wide range of frequencies, potentially have many advantages over other semiconductor-based photo-detectors. According to variety of applications of high-Tc superconductors, particularly YBCO, and significant progress in manufacturing of thin films and Josephson junctions, this thesis mainly focuses on investigation of light emission effects on high-Tc Josephson Junctions and its theory. In our work, at the beginning, the current-voltage...
Performance evaluation of hybrid transfer switches in grounded and ungrounded medium-voltage electrical systems
, Article CIGRE/IEEE PES International Symposium Quality and Security of Electric Power Delivery Systems, CIGRE/PES 2003, 8 October 2003 through 10 October 2003 ; 2003 , Pages 91-96 ; 2858730156 (ISBN); 9782858730155 (ISBN) ; Mokhtari, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2003
Abstract
Application of a fast hybrid transfer switch (HTS) as a suitable tool for protection of sensitive electrical loads against power quality problems has attracted much attentions these days. In this paper, methods for desired control of a HTS which consists of a fast fault-detection method and a suitable firing and transfer strategy are proposed. Simulation results of a HTS under various operating conditions for two types of medium-voltage electrical systems, i.e. grounded (star connection) and ungrounded (delta connection) systems, with respect to total transfer time are presented. The results show the capability of the HTS and the proposed control methods in fast transferring of sensitive...
Cosmic Neutrinos at Neutrino Telescopes CP-violation, Source Properties and Beyond the Standard Model Physics
, Ph.D. Dissertation Sharif University of Technology ; Farzan, Yasaman (Supervisor)
Abstract
In this thesis, we studied the oscillation of neutrino flavors and the measurement of mixing parameters through the detection of cosmic neutrinos at neutrino telescopes. Most of the astrophysical explosions predict the emission of neutrino flux and kilometer-scale detectors are under construction for the observation of these neutrinos. Detection of astrophysical neutrinos opens a new window to understand the neutrino properties and also the properties of astrophysical sources.In this thesis first we review the phenomenology of neutrino flavor oscillation and characteristics of neutrino mass matrix. By introducing a new class of invariants (under general transformation of lepton fields bases)...
Dynamics of Two Coupled Neurons of Different Types of Excitability
, Ph.D. Dissertation Sharif University of Technology ; Razvan, Mohammad Reza (Supervisor)
Abstract
Excitability is one of the most important characteristics of a neuron. In 1948, Hodgkin identified three different types of excitability of neurons. Excitability an all of its types can be observed in Hodgkin-Huxley model of neuronal dynamics (H-H model) as a four-dimensional system of differential equations and in at least two dimensional reductions of H-H type models. By applying the theory of dynamical systems (e.g. bifurcation theory), one can give a mathematical definition of excitability.Excitability of the neuron is equivalent to that the neuronal model is near a bifurcation through which the state of the system approaches to a stable limit cycle. In this thesis, a two-dimensional...
Statistical assessment of starch removal from starchy wastewater using membrane technology
, Article Korean Journal of Chemical Engineering ; Volume 28, Issue 9 , 2011 , Pages 1889-1896 ; 02561115 (ISSN) ; Moghaddam, A. H ; Shayegan, J ; Sharif University of Technology
2011
Abstract
The present work deals with application of 25-2 fractional factorial design (FFD) to evaluate the operating parameters on starch separation from synthetic starchy wastewater using a hydrophilic polyethersulfone membrane with 0.65 μm pore size in a plate and frame handmade membrane module. The analysis of variance (ANOVA) combined with F-test was also used to recognize non-significant terms. The performance of the filtration process was evaluated by calculating the COD removal percentage (rejection factor) and permeate flux. In this experiment, five input parameters were surveyed, including trans membrane pressure (TMP), flow and temperature of feed, pH and concentration of wastewater. In...
Investigating and modeling the cleaning-in-place process for retrieving the membrane permeate flux: Case study of hydrophilic polyethersulfone (PES)
, Article Journal of the Taiwan Institute of Chemical Engineers ; Volume 62 , May , 2016 , Pages 150–157 ; 18761070 (ISSN) ; Shayegan, J ; Sargolzaei, J ; Sharif University of Technology
Taiwan Institute of Chemical Engineers
2016
Abstract
In this work the effects of backwash pressure, duration of acid and sodium hydroxide backwashing, sodium hydroxide concentration, and the duration of forward washing on performance of permeate flux recovery (PFR) were investigated. A two-level fractional factorial design (FFD) was used to design the experiments. The ability of back propagation neural network (BPNN) and radial basis function neural network (RBFNN) in predicting the performance of cleaning-in-place (CIP) of hydrophilic polyethersulfone (PES) membrane were investigated. It is found that BPNN has better ability in predicting the PFR performance than RBFNN. The best architecture of BPNN was a network consisting of 1 hidden layer...
Global analysis of a delay SVEIR epidemiological model
, Article Iranian Journal of Science and Technology, Transaction A: Science ; Volume 37, Issue A4 , 2013 , Pages 483-489 ; 10286276 (ISSN) ; Razvan, M. R ; Yasaman, S ; Sharif University of Technology
2013
Abstract
This paper is concerned with global analysis of a delay SVEIR epidemiological model in a population of varying size. By using Lyapunov stability method and LaSalle's invariance principle for delay systems, we prove that when there is no endemic equilibrium, the disease free equilibrium is globally asymptotically stable, otherwise the endemic equilibrium is globally stable
Particles in the early Universe: Interface of Cosmology and Particles Massive Neutrinos and Cosmology
, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor) ; Farzan, Yasaman (Supervisor)
Abstract
Neutrino flavor oscillations are clear evidence of massive neutrinos. It has been for more than a decade that neutrino physics became one of active topics in the field of particle physics and various experiments started studying the flavor oscillation of neutrinos. Unfortunately, experiments studying the flavor oscillations are only sensitive to the mass square difference, and they are incapable of providing more information about the absolute mass scale of neutrinos. Additionally, sterile neutrinos having non-standard interactions are under vast investigations and studies. Determination of neutrino masses and their effective number is among the most challenging problems by which...
A study on natural aging behavior and mechanical properties of friction stir-welded AA6061-T6 plates
, Article International Journal of Advanced Manufacturing Technology ; Vol. 71, issue. 5-8 , 2014 , pp. 933-941 ; ISSN: 02683768 ; Serajzadeh, S ; Sharif University of Technology
2014
Abstract
Mechanical properties, microstructural events, residual stresses, and aging behavior of friction stir-welded AA6061-T6 were investigated in this work. Microstructural and mechanical characterizations of the friction stir-welded joints in as-welded and post-welded conditions were made by means of optical metallography, transmission electron microscopy, X-ray diffraction for determination of residual stresses, tensile testing, and hardness measurements. It was found that weld strength and hardness variations after welding are mainly dependent on the imposed heat input per unit length. Besides, the kinetics of natural aging in the welded samples was found to be noticeable within the first 14...
Response surface methodology for modeling and optimizing the treatment of synthetic starchy wastewater using hydrophilic PES membrane
, Article Desalination and Water Treatment ; Volume 51, Issue 37-39 , 2013 , Pages 7036-7047 ; 19443994 (ISSN) ; Shayegan, J ; Sargolzaei, J ; Bahadori, T ; Sharif University of Technology
2013
Abstract
In this work, the process of starch removal from starchy wastewater using a hydrophilic polyethersulfone membrane was investigated. The pore size of the membrane was 0.65 μm and the pattern of stream in plate and frame handmade membrane module was cross-flow. To design the layout of the experiments, response surface methodology was applied. The performance of the filtration process was evaluated by calculating the (chemical oxygen demand) COD removal percentage (rejection factor) and permeate flux. In this study, five operative parameters were investigated, including trans-membrane pressure, flow rate and temperature of feed, pH, and the COD concentration of starch wastewater. Two models...
Modeling the Removal of Phenol Dyes Using a Photocatalytic Reactor with SnO2/Fe3O4 Nanoparticles by Intelligent System
, Article Journal of Dispersion Science and Technology ; Volume 36, Issue 4 , Apr , 2015 , Pages 540-548 ; 01932691 (ISSN) ; Hedayati Moghaddam, A ; Nouri, A ; Shayegan, J ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
The objective of this study was to model the extent of improvement in the degradability of phenol dyes by SnO2/Fe3O4 nanoparticles using a photocatalytic reactor. The effect of operative parameters including catalyst concentration, initial dye concentration, stirring intensity, and UV radiation intensity on the photocatalytic batch reactor during removal of phenol red was investigated. Fractional factorial design and response surface methodology were used to design the experiment layout. The SnO2/Fe3O4 nanoparticles were synthesized using the core-shell method. The results of x-ray diffraction and transmission electron microscopy showed the successful synthesis of these nanoparticles. The...
Theoretical and experimental investigation into friction stir welding of AA 5086
, Article International Journal of Advanced Manufacturing Technology ; Volume 52, Issue 5-8 , 2011 , Pages 531-544 ; 02683768 (ISSN) ; Serajzadeh, S ; Kokabi, A.H ; Sharif University of Technology
2011
Abstract
This research investigates the relationship between the microstructures of thermomechanically affected zone (TMAZ) and heat input in friction stir welding (FSW) of 5086 aluminum alloy. First, welding heat input has been predicted using a three-dimensional finite element analysis; then, welding experiments have been carried out on annealed and work-hardened conditions to study the developed microstructures and the mechanical properties of the welded metal. The results show that the temperature field in the FSW process is asymmetrically distributed with respect to the welding line. Also, both experimental and predicted data illustrates that peak temperatures are higher on the advancing side...
A Study on Flow Behavior of AA5086 Over a Wide Range of Temperatures
, Article Journal of Materials Engineering and Performance ; Volume 25, Issue 3 , 2016 , Pages 1076-1084 ; 10599495 (ISSN) ; Jamshidi Aval, H ; Serajzadeh, S ; Sharif University of Technology
Springer New York LLC
2016
Abstract
Flow stress behavior of AA5086 was determined using tensile testing at different temperatures from room temperature to 500 °C and strain rates varying between 0.002 and 1 s−1. The strain rate sensitivity parameter and occurrence of dynamic strain aging were then investigated in which an Arrhenius-type model was employed to study the serrated flow. Additionally, hot deformation behavior at temperatures higher than 320 °C was evaluated utilizing hyperbolic-sine constitutive equation. Finally, a feed forward artificial neural network model with back propagation learning algorithm was proposed to predict flow stress for all deformation conditions. The results demonstrated that the strain rate...
Numerical and experimental investigation on influence of initial microstructure on GTA-welded age-hardened AA2024
, Article International Journal of Advanced Manufacturing Technology ; Volume 97, Issue 1-4 , 2018 , Pages 1335-1346 ; 02683768 (ISSN) ; Serajzadeh, S ; Jamshidi Aval, H ; Sharif University of Technology
Springer London
2018
Abstract
Influence of gas tungsten arc welding on the thermal responses, residual stress distribution and final mechanical properties of the naturally age-hardened (T4) and artificially age-hardened (T6) AA2024 plates was studied. The results showed that age hardening and over-aging occurred in various sections of the heat-affected zone (HAZ) of T4 sample, depending on their locations, while in the HAZ of T6 sample, over-aging is the governing phenomenon. Also, subsequent natural aging occurred in HAZ, weld metal (WM) and partially melted material (PMM) of both weldments. This recent phenomenon is more obvious in the T4 sample in comparison with the T6 one. In both microstructures, weld metal is the...
A new variable structure control methodology for electrical/mechanical parameter estimation of induction motor
, Article 2003 American Control Conference, Denver, CO, 4 June 2003 through 6 June 2003 ; Volume 5 , 2003 , Pages 4047-4052 ; 07431619 (ISSN) ; Faezian, G ; Tabatabaei Y, H ; Sargolzaei, N ; Sharif University of Technology
2003
Abstract
Induction motor parameter estimation is generally needed for such purposes as fault detection and the achievement of high dynamic performance drives. This paper is an attempt to use variable structure control (VSC) methodology for the on-line estimation of several significant mechanical and electrical induction motor parameters. The estimated parameters are rotor resistance, magnetizing inductance, stator resistance and viscous damping coefficient In this combined control/estimation method, we propose to apply field-oriented control to the non-linear model of induction motor, and then transform the model by Input-state linearization into canonical form. Application of variable structure...
An investigation of the microstructures and properties of metal inert gas and friction stir welds in aluminum alloy 5083
, Article Sadhana - Academy Proceedings in Engineering Sciences ; Volume 36, Issue 4 , 2011 , Pages 505-514 ; 02562499 (ISSN) ; Shafieim, A ; Aval, H. J ; Sharif University of Technology
2011
Abstract
Two different types of welds, Metal Inert Gas (MIG) and Friction Stir Welding (FSW), have been used to weld aluminum alloy 5083. The microstructure of the welds, including the nugget zone and heat affected zone, has been compared in these two methods using optical microscopy. The mechanical properties of the weld have been also investigated using the hardness and tensile tests. The results show that both the methods could successfully be used to weld such alloy. The strength of the joints is comparable to the strength of the base metal in both cases. However, FSWed samples have shown higher strength in comparison to the MIG samples. The results also show that the extension of the heat...
Experimental and theoretical evaluations of thermal histories and residual stresses in dissimilar friction stir welding of AA5086-AA6061
, Article International Journal of Advanced Manufacturing Technology ; Volume 61, Issue 1-4 , 2012 , Pages 149-160 ; 02683768 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
2012
Abstract
In this work, the thermomechanical responses during the dissimilar friction stir welding of aluminum alloys have been evaluated employing a three-dimensional model and the finite element software ABAQUS. Furthermore, welding experiments have been conducted under different working conditions and the temperature variations during and after welding as well as the produced residual stresses in various positions of the welded samples were measured using hole-drilling technique. The model results were then examined by experimental data, and a reasonable agreement was observed. It is found that tool rotational speed significantly affects the amount of maximum tensile residual stress while traverse...
The influence of tool geometry on the thermo-mechanical and microstructural behaviour in friction stir welding of AA5086
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 225, Issue 1 , 2011 , Pages 1-16 ; 09544062 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
In this work, the effect of tool geometric parameters on thermo-mechanical behaviour in friction stir welding of AA5086 has been investigated. For doing so, the thermo-mechanical responses of material during welding with different tools have been predicted by a three-dimensional finite-element model using the finite-element code ABAQUS. In addition, welding experiments have been carried out to study the developed microstructures and the mechanical properties of welded alloy. The results show that tool geometry significantly affects the energy input, deformation pattern, plunge force, microstructures, and mechanical properties of the joint. The conical tool with the shoulder angle of 2° has...
Evolution of microstructures and mechanical properties in similar and dissimilar friction stir welding of AA5086 and AA6061
, Article Materials Science and Engineering A ; Volume 528, Issue 28 , 2011 , Pages 8071-8083 ; 09215093 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
In this work, thermo-mechanical behavior and microstructural evolution in similar and dissimilar friction stir welding of AA6061-T6 and AA5086-O have been investigated. Firstly, the thermo-mechanical behaviors of materials during similar and dissimilar FSW operations have been predicted using three-dimensional finite element software, ABAQUS, then, the mechanical properties and the developed microstructures within the welded samples have been studied with the aid of experimental observations and model predictions. It is found that different strengthening mechanisms in AA5086 and AA6061 result in complex behaviors in hardness of the welded cross section where the hardness variation in similar...
Thermo-mechanical and microstructural issues in dissimilar friction stir welding of AA5086-AA6061
, Article Journal of Materials Science ; Volume 46, Issue 10 , 2011 , Pages 3258-3268 ; 00222461 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Sharif University of Technology
2011
Abstract
In this research, thermo-mechanical behavior and microstructural events in dissimilar friction stir welding of AA6061-T6 and AA5086-O have been evaluated. The thermo-mechanical responses of materials during the process have been predicted employing a three-dimensional model together with a finite element software, ABAQUS. Then, mechanical properties and microstructures of the weld zone were studied with the aid of experimental observations and model predictions. It is found that the mixing of material in the weld nugget is performed more efficiently when AA5086 is in the advancing side and also the temperature field is distributed asymmetrically resulting in larger thermally affected region...