Minimizing the Error of Set Point Tracking in MIMO Plants with Broken Actuators

, M.Sc. Thesis Sharif University of Technology Farahani Fard, Jaber (Author) ; Haeri, Mohammad (Supervisor)

Abstract

Fault occurrence is an inevitable problem in industrial plants. These faults have numerous types. Some common kinds of faults are faults in actuators, faults in system dynamics, and faults in sensors. In many cases it is not possible to change or repair the broken part immediately. On the other hand, it is not reasonable to shut-down the whole system due to a minor failure. Therefore we should take a measure to have the best output possible in a faulty plant. In this thesis we have proposed a new static compensator by which we distribute the contribution of the faulty actuator among the other ones. At the end we evaluate the method by means of simulations

Investigation of Flow Rate and Cooling Water Temperature Effects on the Process Parameters in Centrifuge Machine

, M.Sc. Thesis Sharif University of Technology Aghaei, Majid (Author) ; Otukesh, Mohammad (Supervisor) ; Safdari, Jaber (Supervisor)

Abstract

Centrifuge is a method in which great gravitational-like forces are used. Gravitational forces which cause molecules to move and are relevant to molecular weight; can cause isotope separation. The separation of light isotope from heavy one is done with a centrifugal field which produces a pressure gradient for the gas mixture. Pressure gradient is different for each of the isotopes due to the dependence of pressure gradient to the mass of the materials. But the separation in this way is very limited. The capacity of separation can be brought up by producing an additional axial flow in the rotor. This rotational flow can be produced with internal or external incitement. Rotational flow with...

Uranium Bioleaching from a Low Grade Ore

, Ph.D. Dissertation Sharif University of Technology Rashidi, Abbas (Author) ; Roosta Azad, Reza (Supervisor) ; Safdari, Jaber (Supervisor)

Abstract

In this work, bioleaching was used to extract valuable uranium from a low grade ore. Bioleaching experiments were carried out in batch cultures using a native strain of Acidithiobacillus ferrooxidans. Experiments were conducted to investigate the effects of rotation speed, initial redox potential, initially added Fe concentration, particle size, pH, temperature, pulp density, and culture type. In the shake flask systems, over 99% of the uranium was bioleached in 48 hours at some conditions. Uninoculated flasks gave only around 25% leaching. At each study, uranium and iron concentrations, solution oxidation– reduction potential and pH were measured. The results showed that 150 rpm, d80=100 ...

Estimation of the initial blank shape and strain distribution for complicated geometries in sheet metal forming by a nonlinear inverse finite element method

, Article SAE Technical Papers ; 2012 Farahani, M ; Assempour, A ; Sharif University of Technology

SAE 2012

Abstract

A nonlinear inverse finite element method is developed for estimation of initial blank shape and strain distribution in final shape. This method often based on implicit static algorithms, causes sometimes convergence problems because of strong nonlinearities. In order to avoid the converging problems, especially in the quasi vertical walls, an appropriate initial guess is introduced. By using this initial guess, the number of iterations in the nonlinear numerical solution is decreased, solution speed is significantly increased and complicated geometries can be analyzed by this method with good accuracy. Application to a Srail part shows good agreement between commercially available finite...

Study of buzz phenomenon using visualization of external shock structure

, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; 2018 ; 09544100 (ISSN) Farahani, M ; Jaberi, A ; Sharif University of Technology

SAGE Publications Ltd 2018

Abstract

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and...

Study of buzz phenomenon using visualization of external shock structure

, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 233, Issue 7 , 2019 , Pages 2690-2698 ; 09544100 (ISSN) Farahani, M ; Jaberi, A ; Sharif University of Technology

SAGE Publications Ltd 2019

Abstract

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and...

Fabrication of flexible self-powered humidity sensor based on super-hydrophilic titanium oxide nanotube arrays

, Article Scientific Reports ; Volume 10, Issue 1 , 2020 Farahani, E ; Mohammadpour, R ; Sharif University of Technology

Nature Research 2020

Abstract

Stable and flexible super-hydrophilic nanotubular-based titanium oxide electrode has been utilized as the active electrode of self-powered humidity sensor. TiO2 nanotubular electrodes fabricated through anodization method and utilized in combination with Kapton electrode as the triboelectric nanogenerator (TENG). Vertical contact-separation mode TENG performance has been examined in various range of frequencies and the maximum output voltage and current more than 300 V and 40 μA respectively with maximum power of 1.25 ± 0.67 mW has been achieved at 4 Hz. The fabricated TENG has been employed as the active self-powered humidity sensor. Super-hydrophilic feature of TiO2 nanotubes resulted in...

Study of buzz phenomenon using visualization of external shock structure

, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 233, Issue 7 , 2019 , Pages 2690-2698 ; 09544100 (ISSN) Farahani, M ; Jaberi, A ; Sharif University of Technology

SAGE Publications Ltd 2019

Abstract

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and...

Basis free relations for the conjugate stresses of the strains based on the right stretch tensor

, Article International Journal of Solids and Structures ; Volume 40, Issue 22 , 2003 , Pages 5887-5900 ; 00207683 (ISSN) Farahani, K ; Naghdabadi, R ; Sharif University of Technology

Elsevier Ltd 2003

Abstract

In this paper, general relations between two different stress tensors Tf and Tg, respectively conjugate to strain measure tensors f(U) and g(U) are found. The strain class f(U) is based on the right stretch tensor U which includes the Seth-Hill strain tensors. The method is based on the definition of energy conjugacy and Hill's principal axis method. The relations are derived for the cases of distinct as well as coalescent principal stretches. As a special case, conjugate stresses of the Seth-Hill strain measures are then more investigated in their general form. The relations are first obtained in the principal axes of the tensor U. Then they are used to obtain basis free tensorial equations...

Conjugate stresses of the Seth-Hill strain tensors

, Article International Journal of Solids and Structures ; Volume 37, Issue 38 , 2000 , Pages 5247-5255 ; 00207683 (ISSN) Farahani, K ; Naghdabadi, R ; Sharif University of Technology

Elsevier Ltd 2000

Abstract

In this paper, conjugate stresses of the Seth-Hill strain measures are treated by means of the definition of energy conjugacy and Hill's principal axis method. This approach results in relations between components of two different conjugate stress tensors. The results are valid for distinct as well as coalescent principal stretches. Illustrative examples are solved to demonstrate the simplicity and usefulness of the derived relations between conjugate stress tensors. © 2000 Elsevier Science Ltd

Modeling Propagation of Cardiac Action Potential at Cellular Level

, M.Sc. Thesis Sharif University of Technology Farahani, Mojtaba (Author) ; Jahed, Mehran (Supervisor)

Abstract

Heartbeat is the result of contractions of over 10 billion cardiac cells. These cells’ cytoplasms are connected to each other by gap junctions which are arrays of intercellular protein channels. Thus action potential can propagate from one cell to another and cause its contraction. In core-conductor model, one-dimensional microscopic representation of cardiac tissue, cells are attached to each other to form a ladder network. The parallel elements are connected to each other by series resistors which represent gap junctions. These resistors are nearly always considered as static elements. In this thesis I have investigated the effects of incorporating the dynamicity of gap junction resistors...

The Inventory-Location Model under Disruption Risk

, M.Sc. Thesis Sharif University of Technology Farahani, Maryam (Author) ; Shavandi, Hassan (Supervisor)

Abstract

In this research we study multi-commodity inventory-location problem under disruption risk that is formulated to a nonlinear integer-programming model. The objective function of this model is minimization of inventory and location costs simultaneously under disruption risk. These disruptions may be caused by natural events such as earthquake, flood, fire and man-made sources like labor strike or terrorist attack. The structural design of a supply chain greatly affects how these kinds of disruption risks influence the network. In this regard, this study proposes a strategy to reduce the impacts of disruption risk by considering substitute commodity in the multi-commodity inventory-location...

Experimental Investigation of the Effect of Nozzle Exit Flow on the Aerodynamic Behavior at Transonic Speed

, M.Sc. Thesis Sharif University of Technology Ayati, Hossein (Author) ; Farahani, Mohammad (Supervisor)

Abstract

The aim of this investigation is the experimental study of nozzle exhaust jet flow effects on aerodynamic behavior of an air vehicle at transonic speeds. For this sake, a secondary jet injection is used by the ejector into test model. The ejector total pressure for jet injection varies between 0 (jet off) to 4 bar for simulating nozzle exhaust jet flow and supplying intake’s required mass flow rate. All tests were conducted at QRC Trisonic wind tunnel and at Mach number of 0.5 to 0.85 and angles of -4 to 6 deg. The aerodynamic force and pressure results were recorded in order to analyze the exhaust jet flow. This study revealed that the aerial vehicle drag becomes bigger than its free flight...

Experimental Study of a Side Intake in Transonic Speed

, M.Sc. Thesis Sharif University of Technology Dehghan, Saeed (Author) ; Farahani, Mohammad (Supervisor)

Abstract

This study aims to evaluate aerodynamic coefficients of an airplane with air breathing engine experimentally. In these experiments, an ejector is used to better simulate flying conditions and aerodynamic interferences generated in inlet and exhaust engine. Therefore, at first, an ejector was designed for simultaneous simulation of exit cold flow and inlet flow of engine. All tests were conducted at QRC Trisonic wind tunnel and at Mach number of 0.5 to 0.85, angles of -4 to 6 deg. and for various amounts of pressure ejector and control surfaces angles. Finally, for the Mach number of 0.5, effect of roughness on the aerodynamic coefficients was examined. The results showed that, drag...

Investigating the Behavior of a Type of Energy Absorbing Bracing System

, M.Sc. Thesis Sharif University of Technology Farahani, Hossein (Author) ; Khonsari, Vahid (Supervisor)

Abstract

Bracing Systems are usually a set of inclined members that are embedded in structures to resist lateral forces and control lateral displacements. There are different types and behaviors for Bracing Systems depending on the way of assembling and locating them in the structure. Braced Frames, such as Concentrically Braced Frames (CBFs), generally have high stiffness and low ductility. Another Type of Braced Frames is Eccentrically Braced Frames (EBFs) which improves CBFs by establishing suitable ductility as well as stiffness. Inelastic behavior of Links involved with EBFs caused this in EBFs. Nevertheless, these systems have no efficiency in next earthquake, because links are parts of beams...

Installation, Simulation and Calibration of SARL Low-Speed Wind Tunnel

, M.Sc. Thesis Sharif University of Technology Zavaree, Sam (Author) ; Farahani, Mohammad (Supervisor)

Abstract

As an essential laboratory instrument in aerospace engineering, wind tunnels need to be calibrated. Therefore, this thesis takes into account the calibration of the subsonic wind tunnel at the Sharif University of Technology, with the test section dimensions of 90 × 42 × 30 cm3. It is necessary to accurately and correctly determine the effective parameters for the wind tunnel results to be reliable. A pitot-static tube, a standard wing, pressure sensors, a force balance, a turbulence sphere, rake, yawhead, a digital level, a protractor, and a data acquisition system were used for this experiment. For calibration, variables including flow uniformity, flow Angularity, turbulence intensity,...

Effect of Geometric Distortion on the Flow Field and Performance of an Axisymmetric Supersonic Inlet

, M.Sc. Thesis Sharif University of Technology Akbarzadeh, Hossein (Author) ; Farahani, Mohammad (Supervisor)

Abstract

Inlets must decelerate the air with lowest loss and drag together with a given pressure and Mach number with best quality and uniformity to the engine. This is done based on flight Mach number, by an arrangement of shock waves and surfaces gradient in the inlet. Any distortion in the flow field and the inlet geometry parameters may disrupt such arrangement and influence on the inlet performance, in addition, under critical conditions, it might affect the stability of the intakes. Any distortion in the flow field and the inlet geometry parameters may disrupt such arrangement and influence on the inlet performance, in addition, under critical conditions, it might affect the stability of the...

Design and Fabrication of a Vacuum Chamber Exhaust for a Thruster Testing in High Altitude Simulation

, M.Sc. Thesis Sharif University of Technology Ghorbi, Mohammad (Author) ; Farahani, Mohammad (Supervisor)

Abstract

High-altitude simulation lab of chemical thrusters is one of the most important infrastructures for the development of space thrusters technology. In these laboratories, different sections are designed according to the requirements for simulation of the thrusters at specific pressure and temperature. The purpose of this research is to design a subset of the creation and preservation of vacuum for the purpose of ground testing of chemical thrusters. Vacuum preservation is more comprehensive than the vacuum creation and is usually the bottleneck of design, so the design of this subset is intended in the present study. To illustrate this, after introducing the basic concepts required, two...

Investigating the Behaviour of A Type of Energy Absorbing Bracing System

, M.Sc. Thesis Sharif University of Technology Farahani, Hossein (Author) ; Khonsari, Vahid (Supervisor)

Intelligent Fault Diagnosis of Rotating Machines by Convolutional Neural Network

, M.Sc. Thesis Sharif University of Technology Farahani, Ali (Author) ; Behzad, Mehdi (Supervisor)

Abstract

Early and confident detection of faults in rolling element bearings plays a significant role in enhancing the reliability of equipment and optimizing future decisions within a set. The purpose of this research is to investigate and compare raw signals and various signal processing transformations, including Fast Fourier Transform, Frequency Domain Envelope Analysis, Time Domain Envelope Analysis, Wavelet Transform, Short-Time Fourier Transform, and Cepstrum Transform, in order to find the best representation of vibration signals for more accurate equipment fault diagnosis. Additionally, examining and comparing simple convolutional neural network, wide-kernel convolutional neural network, and...