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ebrahimi-mamaghani--mohammad
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Magneto-mechanical stability of axially functionally graded supported nanotubes
, Article Materials Research Express ; Volume 6, Issue 12 , 2019 ; 20531591 (ISSN) ; Mirtalebi, H ; Ahmadian, M. T ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
In this paper, size-dependent vibration analysis of axially functionally graded (AFG) supported nanotubes conveying nanoflow under longitudinal magnetic fields are performed, aiming at performance improvement of fluid-interaction nanosystems. Either the density or the elastic modulus of the AFG nanotube varies linearly or exponentially along the axial direction. Based on the nonlocal continuum theory, the higher-order dynamical equation of motion of the system is derived considering no-slip boundary condition. Galerkin discretization technique and eigenvalue analysis are implemented to solve the modeled equation. The validity of the simplified model is justified by comparing the results with...
Magneto-mechanical stability of axially functionally graded supported nanotubes
, Article Materials Research Express ; Volume 6, Issue 12 , 2019 ; 20531591 (ISSN) ; Mirtalebi, H ; Ahmadian, M. T ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
In this paper, size-dependent vibration analysis of axially functionally graded (AFG) supported nanotubes conveying nanoflow under longitudinal magnetic fields are performed, aiming at performance improvement of fluid-interaction nanosystems. Either the density or the elastic modulus of the AFG nanotube varies linearly or exponentially along the axial direction. Based on the nonlocal continuum theory, the higher-order dynamical equation of motion of the system is derived considering no-slip boundary condition. Galerkin discretization technique and eigenvalue analysis are implemented to solve the modeled equation. The validity of the simplified model is justified by comparing the results with...
Developing an Analytical Model with Experimental Verification of Tapered Cantilevered Piezoelectric Vibration Energy Harvester
, M.Sc. Thesis Sharif University of Technology ; Hosseini Kordkhaili, Ali (Supervisor)
Abstract
Evolution of electrical devices and the need for wireless sensor and remote control has led to extensive research in field of energy harvesting. Regarding this approach, most studies devoted to use of piezoelectric effect in converting the dissipative vibration energy into usable electrical energy. Despite extensive progress made in this field of engineering, there were no significant growth in analytical solution and implementation of mathematical equations related to dynamic and electricity of piezoelectric harvester of beams with different geometries. The main focus of this thesis is solving constitutive and coupled electromechanical equations of piezoelectric harvester related to a...
Dynamic Simulation of Running Human Normal and with Below-Knee Prosthesis
, M.Sc. Thesis Sharif University of Technology ; Firoozbakhsh, Keykhosro (Supervisor) ; Zohoor, Hassan (Supervisor)
Abstract
Researches in the field of human gait have a lot of applications in medicine, ergonomics, sport science and technology. Lower limb prostheses design is one of the fields in which human gait is important. One of the best methods of gait analysis is to use analytical models. In this project, first, the normal human was simulated using a two-dimensional biped model with 7 segments, i.e., a HAT segment representing head, arms and trunk, and 6 segments representing thighs, shanks and feet of the two legs. In this model the foot-ground contact was is estimated using Taylor series after running experiment and it’s analysis which is expendable to people with different ages and different weight and...
Probabilistic Safety Assessment of A UF6 Production Process
, M.Sc. Thesis Sharif University of Technology ; Ghofrani, Mohammad Bagher (Supervisor)
Abstract
Identification of different hazards in a UF6 production process, and evaluation of the risk originated from these hazards is the main objective of this project. A number of hazards are present in a typical UF6 production process, such as leakage of chemical gases like HF and F2 and also radioactive UF6 gas release. In order to evaluate risk due to these hazards, probabilistic approach has been used. Due to lack of probabilistic safety criteria (PSC) for chemical releases, only for UF6 gas release risk assessment has been done. As a first step in PSA of this process eight groups of initiating events have been identified using HAZOP study, and for each initiating event, event tree analysis...
Evaluation and Simulation of using Magnetite as Heat Transfer Medium in Direct Solar Absorption Collectors
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
In this study, application of a Magnetic Nanofluid consisting of Magnetite as Nanoparticle and Water as base fluid in DASC systems is investigated. The DASC system is modeled theoretically and behavior of such system is predicted.In this study a comparison between magnetite Nanofluid and some other common Nanofluids is conducted. The study shows that Magnetite Nanofluid has a better performance and efficiency than Water, Al2O3 Nanofluid and SiO2 Nanofluid. Also magnetite Nanofluid and TiO2 Nanofluid function are almost similar.Also effect of external magnetic field on the performance of magnetite Nanofluid is investigated. It is showed that when the magnetic Nanofluid is subjected to an...
Aerodynamic Performance Improvement of Megawatt Wind Turbine Rotor Using Plasma Actuator
, M.Sc. Thesis Sharif University of Technology ; Ebrahimi, Abbas (Supervisor)
Abstract
For validation of simulation, plasma actuator was modelled on a flat plate in quiescent flow, which is result in low-speed jet near the wall. The results were compared with similar model and were showed good agreement with them. After that, blade was modelled in three-dimensional manner with MRF technique and periodic method and the results were validated in clean situation (absence of plasma). In the following, turbine was analysed with a code, which was written in MATLAB software based on BEM method and the results were compared with present CFD simulation. Then, plasma actuator was used in chordwise in parts of the blade to improve wind turbine performance. Also it was used in spanwise...
Calibration of Rigid Connected Vision and Inertial Sensors
, M.Sc. Thesis Sharif University of Technology ; Manzuri, Mohammad Taghi (Supervisor)
Abstract
One of the major problems encountered in artificial intelligence is environment interaction. A sensible way for around-interaction is to collect information from sensors and make proper reactions. Generally, in the real world, an intelligent agent needs to know its pose. There are several ways to know the pose of an agent. One of them is based on the fusion of the output of an inertial sensor with the information retrieved from a camera. This leads to enhance the estimation of the pose of an agent. In this research different solutions for this problem are compared. Studies are done with the goal of attitude detection for vehicles and mini-robots, moving on planar surface. For this end, we...
Experimental Investigation of Geometric Parameters Effect on Energy Harvesting from FIV in Bluff Bodies
, M.Sc. Thesis Sharif University of Technology ; Ebrahimi, Abbas (Supervisor)
Abstract
The purpose of this research is to design and construct a test stand for the study of the kinematic and flow pattern of bluff bodies oscillating motion due to the induction of wake vortices. An experimental investigation was conducted to explore the effect of bluff bodies cross section to optimize the amount of electrical energy withdraw by electromagnetic harvester. The tests are carried out on cylinders with square section and rectangular sections with a length to width ratio of 1/2 and 2/1 and height of 50 cm, at speeds of 5 to 35 m/s in eiffel type wind tunnel. The effect of cylinder cross-section on the amount of energy harvested showed that the amplitude of oscillation in square-shaped...
Design of a Low-IF Phased-Array Receiver for 5G Applications
, M.Sc. Thesis Sharif University of Technology ; Fakharzadeh, Mohammad (Supervisor)
Abstract
The most important feature of the fifth generation of mobile telecommunications is the increase of information transfer rate and together with it the increase of the capacity of telecommunication channels in comparison with the previous generation. One solution is to increase the frequency toward millimeter-wave frequencies. Currently, the most suitable option for the millimeter-wave frequency band is the 28 GHz band, which has received a lot of attention due to its availability and the possibility of implementing cheap integrated circuits using CMOS technology in this band. In addition to the features that this frequency band has; This band has limitations such as high emission losses and...
Aerodynamic Analysis and Design of a Lifting Subsystem for a VTOL UAV in the Cruise phase
, M.Sc. Thesis Sharif University of Technology ; Ebrahimi, Abbas (Supervisor)
Abstract
It is necessary to evaluate the effect of the lifting arms of VTOL UAVs in increasing the drag of UAV and reducing the flight endurance of the cruise phase. In this study, the adverse effect of the lifting subsystem and its accessories on reducing the aerodynamic efficiency of the wing and optimizing its design for the cruise phase is studied. The base UAV is an integrated wing-body drone with a 2.12 m wing span, 7 kg maximum take-off weight and with about 65 km / h horizontal flight speed. To investigate the possibility of reducing the adverse aerodynamic effect of the arms of the lifting system, different positions are selected in terms of the geometric dimensions of the arms and their...
Use of Membrane Bioreactor to Bioethanol Production from Lignocellulosic Material
, M.Sc. Thesis Sharif University of Technology ; Soltanieh, Mohammad (Supervisor) ; Goodarznia, Iraj ($item.subfieldsMap.e)
Abstract
In this study production of bioethanol from corn fiber that is a lignocellulosic material is investigated. Experiments were performed in a membrane bioreactor. Bioethanol is a second generation biofuel that is considered recently because of the decrease in oil production and pollutions caused by fossil fuels.The feed was corn fiber which is considered suitable due to its low cost and availability in my country. Corn fiber is composed of cellulose, hemicellulose and lignin. We should increase cellulose fraction by pretreatment methods to get a higher conversion rate into bioethanol. We did this by acid pretreatment and the fraction was reached to 41%. In most of previous work experiments were...
Aerodynamic Control of Flow Around a Rigid Wing in Flapping Motion Using Geometry Modification Methods
, M.Sc. Thesis Sharif University of Technology ; Ebrahimi, Abbas (Supervisor) ; Farahani, Mohammad (Supervisor)
Abstract
The physics of the flow around the wing in the oscillatory motion of the wing has various patterns, including the leading edge vortex, the tip vortex and trailing edge vortex escape. The interaction of these vortices forms a complex flow structure around the wing, which will have a direct effect on the aerodynamic performance of the wing. Therefore, controlling these structures can be considered as a way to improve the performance of the flapping wing. One of the passive flow control techniques that has recently been taken into consideration is a leading-edge protuberance method. Another type of passive flow control is geometric correction, using corrugation method. According to studies, two...
The effect of direct and cross-rolling on mechanical properties and microstructure of severely deformed aluminum
, Article Journal of Materials Engineering and Performance ; Vol. 23, Issue 1 , 2014 , pp. 115-124 ; ISSN: 10599495 ; Kazeminezhad, M ; Sharif University of Technology
2014
Abstract
Severely deformed commercial pure aluminum sheets by constrained groove pressing are direct and crossrolled. The grain size evolution and dislocation density during rolling are studied using Williamson-Hall analysis on x-ray diffraction patterns of the deformed samples. These results and optical microscopy observations show that subsequent direct or cross-rolling of constrained groove pressed aluminum can produce elongated fine grains. The minimum crystallite size is achieved after cross-rolling of constrained groove pressed samples. By direct-rolling or cross-rolling of annealed sheet, the maximum intensity in x-ray diffraction patterns remains on (200) like annealed aluminum but...
Covariance Statistic and a Significance Test for Selecting All Active Variables
in Lasso
,
M.Sc. Thesis
Sharif University of Technology
;
Abstract
Testing the significance of the predictor variables and finding an appropriate method for inference on the coefficients is an important question in the sparse linear regression setting. Covariance statistic is a new method that tries to give an answer to this question. This statistic is defined based on lasso fitted values, and when the true model is linear, this statistic has an Exp(1) asymptotic distribution under the null hypothesis (the null being that all truly active variables are contained in the current lasso model). From classical statistics, we have known some methods like chi-squared test for testing the significance of an additional variable between two nested linear models. But...
Seismic behavior of concrete moment frame reinforced with GFRP bars
, Article Composites Part B: Engineering ; Volume 163 , 2019 , Pages 324-338 ; 13598368 (ISSN) ; Khaloo, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this research, four types of concrete moment frame were designed with glass fiber reinforced polymer (GFRP) bars according to ACI 440.1R-15 and the seismic behavior was assessed using pushover analysis. The frames were three and five stories with two and three bays. A computer code was developed to calculate the amount of fiber reinforced polymer bars in beams of the frames. In order to evaluate nonlinear behavior in plastic hinge regions, sections of beams and columns were analyzed on the basis of moment-curvature diagram and also P-M interaction curve for columns. Performance levels of frames were determined considering ATC-40 criteria. Behavior of concrete moment frames reinforced with...
Redundancy Allocation Problem in Systems with Dependent Components
, M.Sc. Thesis Sharif University of Technology ; AkhavanNiaki, Mohammad Taghi (Supervisor)
Abstract
Consider a serie_parallel system in which the lifetimes of parallel components in series subsystems are independent. But, the lifetimes of series subsystems are dependent due to their similar components. In this thesis, the redundancy allocation problem is studied for this system in order to maximize system reliability. A model is developed and a genetic algorithm is utilized to find near-optimum solution
Supplementary Effects of Fluorine Doping and Pressure on Electronic Structure of LaO1-xFxFeAs Superconductor
, M.Sc. Thesis Sharif University of Technology ; Khosroabadi, Hossein (Supervisor) ; Akhavan Farshchi, Mohammad (Co-Advisor)
Abstract
Iron based superconductors that are studied more in recent years, have the same and different features with copper oxide high temperature superconductors which they can help in solving problems related to high temperature superconductors. In addition, these compounds have attractive physical characteristics such as superconductivity despite of presence of magnetic Iron element or other magnetic elements like nickel and cobalt (In other superconductivity groups, low doping of magnetic elements destroys superconductivity) and also concurrent presence of magnetic and superconductivity phases. The most reported transition temperature in these compounds is 56.3K in Gd0.8Th 0.2FeAsO compound....
Calculation and Distribution of Transmission Loss in Restructured Power Systems
, M.Sc. Thesis Sharif University of Technology ; Ehsan, Mehdi (Supervisor)
Abstract
The electric power industry is experiencing important changes brought about by the deregulation. Electric power generators and users engage in power transactions which take place over the transmission system and create losses. Transmission losses represent up to 1⎯5% of the total generation, and cost millions of dollars per year. Consequently, the problem of “who should pay for losses” arises and the satisfactory sharing of the transmission system utilization costs among all market participants has become a key issue. Unfortunately, losses are expressed as a nonlinear function of line flows, and it becomes almost impossible to calculate exactly the losses that are incurred by each generator,...
Feasibility Study of RFID Application for Items Tracking and Identification in Chain Stores
,
M.Sc. Thesis
Sharif University of Technology
;
Akbari Jokar, Mohammad Reza
(Supervisor)
Abstract
Today, using Radio Frequency Identification (RFID) technology is of a remarkable interest to the industry and services sectors. Application of this technology could result in higher levels of productivity and effectiveness. On the other hand, department stores are increasing in number and size in the country. Application of RFID technology could play an undeniable role in both reducing the time each customer must spend in order to complete their purchase, and accelerating the logistics operations of these stores.
Through literature review, this research studies application of RFID technology instead of other identification technologies such as Bar-Code, reveals strengths and weaknesses...
Through literature review, this research studies application of RFID technology instead of other identification technologies such as Bar-Code, reveals strengths and weaknesses...