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abdollahzadeh--amin
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Optimization of microgrooves for water–solid drag reduction using genetic algorithm
, Article Journal of Ocean Engineering and Marine Energy ; Volume 6, Issue 3 , 2020 , Pages 221-242 ; Moosavi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2020
Abstract
The friction on the water–solid interfaces continues to be the most important factor for the energy loss in many marine and submarine applications. Therefore, different techniques have been developed and are available to reduce friction and, as a result, the overall cost. In the past decades, the use of structured surfaces has been given considerable attention because of their specific characteristics such as their abilities in pressure drop reduction. However, an appropriate optimization method is required to find the best surface structure. In the present study, we consider a microgrooved substrate and examine the performance of three shapes including rectangular, elliptical, and...
An Investigation into the Al-6wt%Mg work Hardening Behavior after Cold Rolling
, M.Sc. Thesis Sharif University of Technology ; Kazeminezhad, Mohsen (Supervisor)
Abstract
Al-6wt%Mg alloy has been enormously exploited in aerospace industry. Since for production of this alloy in the form of sheets of different thickness, the cold rolling process is used, thus to understand the final mechanical properties of the rolled alloy products, their work hardening should be examined. Also, one of the important phenomena that occurs in cold state of the alloy is dynamic strain-aging (DSA), which can cause serrations in realistic stress-strain curve. The aforementioned issue is discussed in the current study. Therefore, the work-hardening values for the mentioned alloy during and after rolling is determined, and then compared with the experimental studies. The results of...
Experimental Study of Various Parameters of Electrospinning on the Morphology of Micro and Nano Fibers
, M.Sc. Thesis Sharif University of Technology ; Iraji zad, Azam (Supervisor)
Abstract
Electrospinning is a method for producing of micro and nanometer polymeric fibers. Nowadays, electrospun fibers have been demanded a lot because of various applications of fibers in optical industries, tissue engineering, and chemical and biological sensors. Producing of more complicated shape of fibers by using two new methods called Electrical Bending and Mechanical Buckling are interested in this field. The aim of this thesis is to prepare such fibers and study the effective parameters on the shapes of them. Fibers are collected on the aluminum and Fluorine-doped tin oxide (FTO) glass. Then they were observed by optical microscope. In the Electrical Bending method, we used PEO: PAMPS and...
Simulation of Fluid Flow on Superhydrophobic Surfaces
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Today, with rapid developments and advances in science and technology, different ways have been studied to reduce energy consumption in various industries. Reducing the drag force and thus reducing the friction force is one of these methods which has many applications (e. g, in submarine construction industries). Creating some microgrooves in the microchannels is one of the most effective methods in order to reduce the friction force in microchannels that has recently been studied. In this method the air is trapped within the microgrooves and when the fluid (e. g, water) enters the channel passes over the trapped air within these microgrooves instead of touching the channel walls (solid...
Enhancement of surface adsorption-desorption rates in microarrays invoking surface charge heterogeneity
, Article Sensors and Actuators, B: Chemical ; 2016 ; 09254005 (ISSN) ; Saidi, M. S ; Sadeghi, A ; Sharif University of Technology
Elsevier B.V
2016
Abstract
This investigation is devoted to the influences of non-uniform wall characteristics on the surface adsorption-desorption rates in an electrokinetic microarray. Utilizing already explored electroosmotic and electrophoretic velocities, the species transport equations are solved by a finite-volume-based numerical approach. Uniform, sinusoidal, and pulse-like distributions of the zeta potential are considered in the analysis. The developed model is validated by comparing the results with those of two analytical solutions that are derived for limiting conditions. The results reveal that, in some cases, the surface charge heterogeneity can reduce the saturation time by more than 60%. The efficacy...
Enhancement of surface adsorption-desorption rates in microarrays invoking surface charge heterogeneity
, Article Sensors and Actuators, B: Chemical ; Volume 242 , 2017 , Pages 956-964 ; 09254005 (ISSN) ; Saidi, M. S ; Sadeghi, A ; Sharif University of Technology
Elsevier B.V
2017
Abstract
This investigation is devoted to the influences of non-uniform wall characteristics on the surface adsorption-desorption rates in an electrokinetic microarray. Utilizing already explored electroosmotic and electrophoretic velocities, the species transport equations are solved by a finite-volume-based numerical approach. Uniform, sinusoidal, and pulse-like distributions of the zeta potential are considered in the analysis. The developed model is validated by comparing the results with those of two analytical solutions that are derived for limiting conditions. The results reveal that, in some cases, the surface charge heterogeneity can reduce the saturation time by more than 60%. The efficacy...
Advanced approach to modify friction stir spot welding process
, Article Metals and Materials International ; Volume 26, Issue 10 , 2020 , Pages 1562-1573 ; Abbasi, M ; Abdollahzadeh, A ; Omidvar, H ; Sharif University of Technology
Korean Institute of Metals and Materials
2020
Abstract
Abstract: Nowadays, friction stir spot welding (FSSW) is used in automotive, rail vehicle construction, the aerospace industry, and electrical industry. In the current research, a modified version of the FSSW process entitled friction stir spot vibration welding was introduced to join Al5083 specimens. The joining specimens were vibrated normal to the tool movement direction, while the joint position cooled by passing coolant through the fixture. Different characteristics of developed joint namely microstructure, mechanical properties, corrosion behavior were studied. The results showed that stir zone grain size decreased significantly as the vibration was employed and the joint position was...
Introducing a Simulation-Based Model to Improve the Design and Layout of Workstations Inside Airport Terminals in Iran
, M.Sc. Thesis Sharif University of Technology ; Alvanchi, Amin (Supervisor)
Abstract
The airport terminal is difficult to plan and design due to the different components and the intricate complexity of its parts. At the airport terminal, we face a queue system which simulation is always a good way to analyze. In addition, computer simulation using modern softwares with the capability to model different types of systems, including the airport terminal, while being less realistic than analytical models, is less costly than operational Exercise.In this study, a supportive approach for better and specific management of Iranian airport terminal buildings with discrete-event simulation is proposed, considering the need for managing the airport terminals building in the country and...
Experimental Investigation of Mass Transfer Coefficient and Specific Interfacial Area in a New TIJR in the Presence of Nanoparticles
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
The theory of mass transfer accompanied by chemical reaction for gas-liquid systems was used to measure the specific interfacial area and mass transfer coefficient in a two impinging jets reactor (TIJR) in the presence of γ-Al_2 O_3 nanoparticles.The absorption of oxygen in sulfite solutions used for the determination of mass transfer characteristics. First 3 liters of nanofluids were prepared at concentration of 1 w% then diluted To produce 10 Liters of nanofluids containing 0.3 w%. The stability of this nanofluid was determined using uv-vis to be less more than 95% in the first 3 hours. The influence of weight percent of nanoparticles (0, 0.05, 0.1, 0.15, 0.2, 0.3) on the specific...
A comparative study between friction stir processing and friction stir vibration processing to develop magnesium surface nanocomposites
, Article International Journal of Minerals, Metallurgy and Materials ; Volume 27, Issue 8 , 2020 , Pages 1133-1146 ; Abbasi, M ; Abdollahzadeh, A ; Kokabi, A. H ; Sharif University of Technology
University of Science and Technology Beijing
2020
Abstract
Friction stir processing (FSP) can be used to improve surface composites. In this study, a modified method of FSP called friction stir vibration processing (FSVP) was applied to develop a surface composite on AZ91 magnesium alloy. In this technique, the workpiece is vibrated normal to the processing direction. The results illustrated that compared with the FSP method, the FSVP caused a better homogeneous distribution of SiC particles in the microstructure. The results also showed that matrix grains of friction stir vibration processed (FSV-processed) samples ((26.43 ± 2.00) µm) were finer than those of friction stir processed (FS-processed) specimens ((39.43 ± 2.00) µm). The results...
Effect of second-phase particle size and presence of vibration on AZ91/SiC surface composite layer produced by FSP
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 30, Issue 4 , 2020 , Pages 905-916 ; Abbasi, M ; Abdollahzadeh, A ; Mirsalehi, S. E ; Sharif University of Technology
Nonferrous Metals Society of China
2020
Abstract
An improved method of friction stir processing (FSP) was introduced for the processing of AZ91 magnesium alloy specimens. This novel process was called “friction stir vibration processing (FSVP)”. FSP and FSVP were utilized to develop surface composites on the studied alloy while SiC nanoparticles were applied as second-phase particles. The effect of reinforcing SiC particles with different sizes (30 and 300 nm) on different characteristics of the composite surface was studied. The results indicated that the microstructure was refined and mechanical properties such as hardness, ductility, and strength were enhanced as FSVP was applied. Furthermore, it was concluded that the effect of...
Modeling and sensitivity analysis of styrene monomer production process and investigation of catalyst behavior
, Article Computers and Chemical Engineering ; Volume 40 , 2012 , Pages 1-11 ; 00981354 (ISSN) ; Ebrahimi, A. N ; Ramazani S.A., A ; Abdollahzadeh, H ; Sharif University of Technology
2012
Abstract
In this work, a fundamental kinetic model based upon the Hougen-Watson non-porosity formalism was derived and used to simulate dehydrogenation and oxidation axial flow reactors. In addition, partial pressure profiles of components during styrene production process inside porous catalyst were obtained using Dusty-Gas model. The preservation equations are adopted to calculate temperature and flow profiles in the reactors filled with iron-potassium promoted catalyst pellets. The presented mathematical model for ethylbenzene dehydrogenation consists of nonlinear simultaneous differential equations with multiple dependent variables. Simulation results such as selectivity and operating temperature...
2D Compositional Simulation of Reservoirs using Finite Volume Method
, M.Sc. Thesis Sharif University of Technology ; Pishvaie, Mahmoud Reza (Supervisor) ; Fatemi, Mobin (Supervisor)
Abstract
One of the main purposes of this project is to propose an efficient and stable algorithm of a semi-discretized formulation for compositional simulation of oil reservoirs. In this algorithm, all the equations including both mass balances and equilibrium equations are solved simultaneously. The gradient terms are discretized by the Finite Volume Method (FVM). The resulting Differential Algebraic Equation, the so-called DAE, are solved by MATLAB functions. Another novel technique developed, handles each block equations set, separately. In this block-by-block scheme, there are two set of equations; the primary (mass balance) and secondary (equilibrium) equations. In the primary ones, the...
, M.Sc. Thesis Sharif University of Technology ; Alvanchi, Amin (Supervisor)
Abstract
Limited water resources in Iran have made dams an important part of the country’s infrastructure. As a result of the large number of in-progress and expected dam projects in the country, consideration of sustainability factors during planning, construction and operation phases of dam projects can create significant economical, social and environmental impacts in the long term. To come up with an inclusive sustainable development, new sustainability assessment approaches seek for sustainable development at the entire project’s life-cycle; they are looking for sustainable development at all design, construction, operation, maintenance and even demolition phases. In this research we have...
Comparison of the weldability of AA6061-T6 joint under different friction stir welding conditions
, Article Journal of Materials Engineering and Performance ; Volume 30, Issue 2 , 2021 , Pages 1110-1127 ; 10599495 (ISSN) ; Bagheri, B ; Abassi, M ; Kokabi, A. H ; Ostovari Moghaddam, A ; Sharif University of Technology
Springer
2021
Abstract
In this work, similar butt joints of AA6061-T6 alloy prepared by underwater friction stir welding (UWFSW) and friction stir vibration welding (FSVW) processes were examined. The characteristics of joints were compared with the joints obtained by conventional friction stir welding (CFSW). The different kinds of microstructural modifications that occurred during CFSW, FSVW, and UWFSW processes were analyzed. The results are employed to analyze the different behaviors in strength, ductility, weldability, and hardness of the joints in different processes at different traverse speeds, rotational speeds, and vibration frequency. It was found that mechanical vibration decreases the grain size in...
Comparison of the Weldability of AA6061-T6 Joint under Different Friction Stir Welding Conditions
, Article Journal of Materials Engineering and Performance ; Volume 30, Issue 2 , 2021 , Pages 1110-1127 ; 10599495 (ISSN) ; Bagheri, B ; Abassi, M ; Kokabi, A. H ; Ostovari Moghaddam, A ; Sharif University of Technology
Springer
2021
Abstract
In this work, similar butt joints of AA6061-T6 alloy prepared by underwater friction stir welding (UWFSW) and friction stir vibration welding (FSVW) processes were examined. The characteristics of joints were compared with the joints obtained by conventional friction stir welding (CFSW). The different kinds of microstructural modifications that occurred during CFSW, FSVW, and UWFSW processes were analyzed. The results are employed to analyze the different behaviors in strength, ductility, weldability, and hardness of the joints in different processes at different traverse speeds, rotational speeds, and vibration frequency. It was found that mechanical vibration decreases the grain size in...
Experimental Study and Optimization of Calcium Ion Extraction Using Emulsion Liquid Membrane with Isotope Separation Perspective
, Ph.D. Dissertation Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Karimi Sabet, Javad (Supervisor)
Abstract
The aim of this dissertation is to investigate the extraction of calcium ions using an emulsion liquid membrane (ELM) with an isotopic perspective. Considering the importance of ion extraction as a preliminary step to isotope separation, the factors affecting the extraction of Ca(II) ions in the ELM process were investigated and optimization of the process was performed in this study. Dicyclohexano-18-crown-6 (DC18C6) was used as the carrier due to isotopic considerations. However, its extractability for calcium ions is limited. In order to address this issue, it is possible to introduce an organic acid, specifically di-(2-ethylhexyl) phosphoric acid (D2EHPA), into the membrane phase. This...
The Insider Threat: Analyzing and Modeling
, M.Sc. Thesis Sharif University of Technology ; Hendesi, Faramarz (Supervisor)
Abstract
Nowadays, most of businesses are becoming computer-based. This trend causes the organizations to become more vulnerable to internal and external threats. Internal threats are done through insiders. Insiders unlike outsiders have capabilities which aid them to easily carry out their illicit activities. Unfortunately, most of research in computer security has focused on the outsider threats, whereas the most damaging is the result of insiders’ illicit activities.This dissertation addresses three primary necessities of the research in the area of insider threat: a consistent definition of insider threat, a classification of types of insider threats, and a classification of vulnerabilities which...
Integrity Analysis in the Time-Delay Systems
, M.Sc. Thesis Sharif University of Technology ; Nobakhti, Amin (Supervisor)
Abstract
Integrity of closed-loop systems with integral action control is characterized by using a series of successively more difficult to obtain conditions: Integral Stabilizable (IS), Integral Controllable (IC), Integral Controllable with Integrity (ICI), and Decentralized Integral Controllability (DIC). The IS condition requires that for a Linear Time-Invariant (LTI) finitedimensional (FD) plant, G(s), one finds a stabilizing decentralized controller with integral action. For G(s) to be IC, in addition to being IS, one should be able to reduce the gain of
all control loops by the same factor from a finite value to (but not including) zero without introducing instabilities. ICI requires that...
all control loops by the same factor from a finite value to (but not including) zero without introducing instabilities. ICI requires that...
Design of a Plantwide Decentrlized Structure Controller for the Tennessee Eastman Challenge Problem
, M.Sc. Thesis Sharif University of Technology ; Nobakhti, Amin (Supervisor)
Abstract
This project focuses on the Tennessee East-man challange problem(TEP) and the impact of setpoint changes and controller tunning on plant performance and profitability. TE has four major units. it is an unstable system due to the reaction within the reactor and a recycle streamcausing snow ball effect. As a result the control of this system is not easy. The study has been conducted along two main directions. First, selecting the optimal values for the setpoints and applying them in the simulation. secondly, try to find better parameter for controller in simulation. Simulation is based on working of Ricker. In TEP like the other multivariable systems, it is ameanable to use a centralized...