Loading...
Search for:
shahrabi-farahani--mohammad
0.128 seconds
Total 5349 records
Investigation of Bioleaching Extraction of Heavy Metals from Spent Catalyst in a Bioreactor
, M.Sc. Thesis Sharif University of Technology ; Yaghmaei, Soheyla (Supervisor) ; Mousavi, Mohammad (Supervisor)
Abstract
Recovery of heavy metals from Hydrocracking spent catalyst was studied in a bioreactor by Acidithiobacillus thiooxidans. At first adaptation of microorganisms was done with spent catalyst in shaker flask. Using central composite design (CCD) the experiments were conducted in order to find optimized condition. Three factors such as particle size, pulp density and aeration rate were examined. Reduced cubic models were established to identify the relationship between the recovery percent of the metals and the variables. The results showed the maximum extraction of 87% Mo, 37% Ni and 15% Al were achieved after 7 days of batch process in bioreactor. The optimal values of variables were pulp...
Money, Economic Order & The Problem of Moral Responsibility
, M.Sc. Thesis Sharif University of Technology ; Taqhavi, Mostafa (Supervisor)
Abstract
In the history of philosophy, the discussion of moral responsibility is tied to "Free Will" metaphysical controversies. Philosophers generally expect that people have "alternative possibilities" -that require them not to be bound to a deterministic situation- or if they don't have such possibilities, at least be able to "control" their actions, and if they don't know all aspects of what they do, at least not to be in ignorance about that, according to Aristotle. In the case of having such minimal possibilities, it is that one can be considered morally responsible for his or her actions. This broad conception of moral responsibility can be traced from Aristotle's discussions in the...
Level crossing speech sampling and its sparsity promoting reconstruction using an iterative method with adaptive thresholding
, Article IET Signal Processing ; Volume 11, Issue 6 , 2017 , Pages 721-726 ; 17519675 (ISSN) ; Salarieh, N ; Shahrabi Farahani, E ; Marvasti, F ; Sharif University of Technology
Institution of Engineering and Technology
2017
Abstract
The authors propose asynchronous level crossing (LC) A/D converters for low redundancy voice sampling. They propose to utilise the family of iterative methods with adaptive thresholding (IMAT) for reconstructing voice from non-uniform LC and adaptive LC (ALC) samples thereby promoting sparsity. The authors modify the basic IMAT algorithm and propose the iterative method with adaptive thresholding for level crossing (IMATLC) algorithm for improved reconstruction performance. To this end, the authors analytically derive the basic IMAT algorithm by applying the gradient descent and gradient projection optimisation techniques to the problem of square error minimisation subjected to sparsity. The...
Numerical Modeling of Dynamic Instability in Soil Slopes and its Effect on the Response of Buried Pipelines
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
In this study, three dimensional analysis of soil slopes subjected to dynamic loading was conducted in order to investigate the interaction of soil-pipe system. For modeling of soil behavior, strain-dependent nonlinear elasticity along with Mohr-Coulomb plasticity was defined to the material and elasto-plastic behavior was used for the pipes. For dynamic modeling of soil slopes and analysis of buried pipelines, a Finite-Element-based software, ABAQUS was utilized. In this regard, first the numerical model was calibrated and verified based on the results obtained by physical shaking-table tests on a soil slope. Afterwards, a comparison was made between the results of numerical models and some...
Tipping Cascades in Complex Networks: Dynamics and Control
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
Tipping points occur in diverse systems in various disciplines such as ecology, climate science, economy, sociology, and engineering. Critical thresholds in system parameters or state variables at which a tiny perturbation can lead to a qualitative change in the system exist in many subsystems in complex systems. These thresholds are called tipping points, and these subsystems are called tipping elements. Additionally, many systems with tipping points can be modeled as networks of coupled multistable subsystems. Domino-like tippings are called tipping cascades. Considering that these tipping cascades are primarily unprecedented, it is essential to study the dynamics and control of these...
Performance Optimization of an Axisymmetric Supersonic Inlet
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor)
Abstract
The main aim of this study is to propose a new structure of compression surfaces of a supersonic inlet in order to improve target performance parameter i.e. total pressure recovery ratio. This idea resulted in developing a new type of supersonic inlet, utilizing four ramps and a cone as compression surfaces simultaneously.A prototype of this type of inlet has been designed for Mach 3 and its performance has been studied via numerical simulation in design point and off design conditions. Eventually the new inlet compared to experimental performance survey data from two cases of two-cone inlets and also analytical calculations of ideal performance of some types of supersonic inlets. Results of...
Experimental Investigation of the Effect of Nozzle Exit Flow on the Aerodynamic Behavior at Transonic Speed
, M.Sc. Thesis Sharif University of Technology ; 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 ; 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...
Design and Fabrication of a Vacuum Chamber Exhaust for a Thruster Testing in High Altitude Simulation
, M.Sc. Thesis Sharif University of Technology ; 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...
Effect of Geometric Distortion on the Flow Field and Performance of an Axisymmetric Supersonic Inlet
, M.Sc. Thesis Sharif University of Technology ; 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...
Installation, Simulation and Calibration of SARL Low-Speed Wind Tunnel
,
M.Sc. Thesis
Sharif University of Technology
;
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,...
Nozzle Design with Considertion for Chemical Reactions
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor)
Abstract
In this thesis a computational method for the design of optimum nozzle contour with consideration for chemical reactions has been presented. This method combines the method of characteristics, CFD and an optimization algorithm to develop a nozzle suitable for a specific operational condition. First using the method of characteristics an isentropic nozzle contour is achieved. then using the FLUENT solver, this initial contour is solved for flow containing finite-rate reactions and boundary layer effects and by iterating this process combined with an optimization algorithm, an optimum nozzle is found. Properties took into consideration in this method, in addition to chemical reaction between...
Experimental Investigation of a Monopropellant Thruster Using Hydrogen Peroxide
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor)
Abstract
Monopropellant thrusters are one of the most common types of propulsion systems that are used extensively in space applications. Especially thrusters with a capacity of less than 50N, they are used on space satellites and are developing rapidly. Problems such as contamination, toxicity of the propellant, difficulty in storing and custody, as well as price, led to the removal of the hydrazine from the focus of attention and focus on green propulsion. One of these, is the green propellant of hydrogen peroxide, which is decomposed in the proper catalytic vicinity, and the only chemical decomposition products are oxygen and water vapour. The present study aims to design and construct mono...
Analysis of Unsteady Flow Field around a Pitching Finite Wing
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor)
Abstract
The characteristics of unsteady flow field around a low-aspect-ratio pitching wing with an airfoil section used in horizontal axis wind turbine are investigated at Reynolds number 2.8×105 and Mach number 0.06. The major objective of this study was to investigate the effects of reduced frequency, oscillating amplitude, mean angle of attack and 3D effects on aerodynamic coefficients. Using aerodynamic coefficients, the unsteady aerodynamics in pre-, near-, and post-static stall regions are analyzed and the results are validated with the corresponding experimental data. The two-dimensional simulation results demonstrate the significant effects of reduced frequency, mean angle of attack and...
Design and Performance Optimization of a Diverterless Supersonic Inlet
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor)
Abstract
One of the most modern types of inlets in aircraft is the Diverterless supersonic inlet, which is used in some new UAVs and fighters, and has many advantages over other types of inlets, especially in removing the boundary layer. The most important part of DSI design is the creation of bump geometry, which requires special precision and elegance. There are various methods for designing and creating bump geometry, some of which are mentioned in this report, and finally the method of creating bump geometry is selected based on the flow around the primary cone, which is in accordance with the analytical method and is in fact the most basic and widely used method.In this study, a DSI with cowl...
Experimental Investigation of Buzz Frequency on an Axisymmetric Supersonic Air Intake Using Pressure Distribution on the Wind Tunnel Wall
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor) ; Farahani, Mohammad (Co-Advisor)
Abstract
Supersonic intakes with mixed compression has an appropriate performance in the critical point, but in the subcritical performance, when inlet mass flow rate is reduced to a certain amount, a self-sustained instability occurs in the flow. In this case, instability appears in the form of shock waves system oscillation which is called Buzz phenomenon. An axisymmetric supersonic air intake with mixed compression which is designed for a Mach number of 2 has been investigated experimentally in order to study buzz frequency. The intake has been experimented in different Mach numbers, angles of attack and mass flow rates. Besides, the intake with wind tunnel wall has been modeled and analyzed in...
Minimizing the Error of Set Point Tracking in MIMO Plants with Broken Actuators
, M.Sc. Thesis Sharif University of Technology ; 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
Modeling Effects of Regional Windblown Dust on Particulate Matter Concentration of Tehran using CMAQ
, M.Sc. Thesis Sharif University of Technology ; Arhami, Mohammad (Supervisor)
Abstract
In recent years, dust storms have turned into one of the most prominence environmental issues, existing in Tehran. The infiltration of dust through west borders has led to significant increase in the concentration of Tehran’s pollutants. The main abroad source of these dusts are deserts located in Middle East. The contribution of Middle East deserts in daily concentration of PM10, without the inclusion of local emission sources, was analyzed in previous studies. In this study, we analyzed the contribution of dust storms, formed in Middle East, in Tehran’s PM10 and PM2.5 concentration, using CMAQ model. Dust periods between 2012 and 2014, was identified using observation data and satellite...
Experimental Measurement of Aerodynamic Characteristics of a Projectile at Subsonic and Supersonic Regims
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor) ; Farahani, Mohammad (Supervisor)
Abstract
A projectile was tested in a wind tunnel at various free sream Mach numbers and angles of attack. The tests were carried out at the transonic wind tunnel of the Imam Hussein University.The experiments were performed at subsonic and supersonic speeds and at different angles of attack. The aerodynamic behavior of the model was investigated using force and moment measurements. The results showed that in the range of measured angles of attack the separation did not occurr and variations of lift coefficient remained linear for all Mach numbers except for a free stream Mach number of 2.0. For this Mach number, the asymmetric bow shock makes a pressure difference between leeward and windward sides,...
Analytical Solution of the Swirl Flow in Combustion Chamber of a Hybrid Rocket Engine
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor) ; Rezayi, Hadi ($item.subfieldsMap.e)
Abstract
Hybrid engines are one of a variety of chemical propulsion systems that have been given special attention in recent years by various industries such as space and defense. The most important reasons for considering this type of system are its high safety, its affordable price compared with liquid fuel propulsion systems, the possibility of switching on and off and changing thrust. This system has a lot of disadvantages as well. This system cannot meet all the needs of different industries due to the low regression rate and, consequently, the limitation of the operating range, thrusts and special impulse. As a result, increasing the fuel regression rate in these engines can greatly expand...