Synthesis of Tin and Ti2n Nanostructured Coatings on Ti alloys Using Magnetron Sputtering System And Comparison of Their Biocompatibility Properties

, M.Sc. Thesis Sharif University of Technology Kalantari Saghafi, Mahsa (Author) ; Nemati, Ali (Supervisor) ; Khamse, Sara (Supervisor)

Abstract

Considering the importance of biocompatibility of implantable prothesis’, metallic alloys have weaker corrosion resistance than ceramics. In order to extend usage of nanomaterials to improve the bio-properties of materials, Nano-structured ceramic coatings are being suggested to improve corrosion resistance and biocompatibility of prosthesis. Meanwhile, very good properties of TiN, such as corrosion resistance and mechanical properties as a thin film coating are undeniable. In this study, TiN and Ti2N thin film were deposited on Ti-based substrate, using PVD and Magnetron sputtering at different argon to nitrogen ratio. The crystal structure of the films was examined using Grazing XRD...

, M.Sc. Thesis Sharif University of Technology Boraghi, Mahsa Sadat (Author) ; Parsafar, Gholamabbas (Supervisor)

Abstract

In 2009, a general equation of state (EOS-III) based on an effective near-neighbor pair interaction of an extended Lennard-Jones (3, 6, 12) type has been introduced as : , where is the compressibility factor, p and ρ stand for pressure and molar density , respectively, T is Temperature , and e, f and g are the temperature dependent coefficient of the equation of state . the Z_th and Z_in are the thermal and internal contributions of pressure in the compressibility factor, respectively. this equation of state gives a good description of all types of nano- and bulk –solid and bulk fluid at entire temperature and pressure ranges for which thee is experimental data. Investigation show that...

Photoelectrocatalytic Performance of Mesoporous TiO2 Nanostructures Decorated with Cu-Ag-Zn Particles for CO2 Conversion

, M.Sc. Thesis Sharif University of Technology Adel Rastkhiz, Mahsa Sadat (Author) ; Simchi, Abdolreza (Supervisor)

Abstract

The rise in carbon dioxide levels has led to the manifestation of numerous environmental challenges. Currently, the absorption and conversion of carbon dioxide into valuable fuel resources such as synthetic gas, methane, and ethylene are deemed crucial from both environmental and economic standpoints. Despite the presentation of photocatalysts such as titanium oxide and electrocatalysts such as copper, silver, and zinc, their efficiency in CO2 conversion is found to be insufficient. One potential solution to this problem is the utilization of photoelectrocatalytic CO2 recovery. In this study, the aim was to enhance the photoelectrocatalytic reduction of CO2 by designing and manufacturing...

Analysis of Control Algorithms for Cooperative Systems Using Matrix Theory

, M.Sc. Thesis Sharif University of Technology Kalantari, Masoud (Author) ; Haeri, Mohammad (Supervisor)

Abstract

Consensus is the equality of desired states of agents. These states could be position, movement direction or other variables of agents. So far, different control algorithms are introduced which provide agents with consensus. In fact, one of the most significant topics in cooperative systems is the problem of determining the control algorithm so that agents reach consensus. These algorithms are called consensus algorithms. Properties of system matrices play an important role in consensus algorithms and analysis of their convergence. In this thesis, two consensus algorithms are presented for networks with fixed and switching topology respectively. In these algorithms an input signal is...

Optimal Design of Mircogrid Components Containing Renewable Resources

, M.Sc. Thesis Sharif University of Technology Kalantari, Alireza (Author) ; Parniani, Mostafa (Supervisor)

Abstract

Nowadays, microgrids which comprise decentralized generation (DG) have attracted considerable attention. Establishment of DG-based microgrids that are normally connected to the main grid, is a practical method to reduce the costs of power outage and to increase the electricity supply reliability. The aim of this thesis is optimum planning of a microgrid containing wind turbines, photovoltaic systems and diesel generators, considering both the grid-connected and isolated modes of operation.
In the areas with considerable solar radiation and wind potential valuable opportunities exist in utilizing these resources. In addition to these renewable resources, the use of controllable resources...

Analyses of mass and heat transport interactions in a direct methanol fuel cell

, Article International Journal of Hydrogen Energy ; Vol. 39, issue. 21 , July , 2014 , p. 11224-11240 ; ISSN: 03603199 Kalantari, H ; Baghalha, M ; Sharif University of Technology

2014

Abstract

In this paper, a two-dimensional, two-phase, non-isothermal model is presented to predict the electrochemical, mass transfer and heat transfer behaviors in a direct methanol fuel cell (DMFC). Governing equations including the momentum, continuity, heat transfer, proton and electron transport, species transport for water, methanol, and all the gas species (carbon dioxide, methanol vapor, water vapor, oxygen, and nitrogen) and the auxiliary equations are coupled to studying the various phenomena in DMFC. The modeling results agree well with the four different experimental data in an extensive range of operation conditions. A parametric study is also performed to examine the effects of the cell...

Design and Fabrication of Sensor Probe and Active Noise Reduction Circuit for SQUID MCG System in Magnetically Unshielded Environment

, M.Sc. Thesis Sharif University of Technology Kalantari, Nafise (Author) ; Fardmanesh, Mehdi (Supervisor)

Abstract

Characterization of local magnetic activity of the heart muscles is named magnetocardiography (MCG), which measures magnetic field generated by electrical activity around heart. RF SQUID sensors are appropriate choice for measuring magnetic activity of the heart muscles. Because squid detects weak signals as low as fTesla, while heart magnetic field is near 50 pt which is one millionth of earth magnetic field and thousands of time weaker than the environment noise. One of the problems of mcg system is its urgency to shielding of unwanted magnetic field. In this project design of holders and resonators for well coupled input coil with RF SQUID is improved. As a result, at the first stage...

Speaker Verification using Limited Enrollment Data

, M.Sc. Thesis Sharif University of Technology Kalantari, Elaheh (Author) ; Sameti, Hossein (Supervisor)

Abstract

In this thesis, we investigate speaker verification as a biometric technology to verify a person based on his/her claim. Text-dependent speaker verification systems are preferred in commercial and security applications and these systems have better performance in limited data condition based on a prior knowledge about speakers that are assumed to be cooperative. Limited amount of enrollment data is a major concern in this thesis. Speaker dependent model construction and channel variability issues on telephone-based text-dependent speaker verification applications are surveyed. Due to the lack of an appropriate database for the task, we collected a database which is referred to as text-prompt...

Numerical study on water distribution in different layers of direct methanol fuel cells

, Article Journal of the Electrochemical Society ; Vol. 161, issue. 8 , 2014 , pp. E3110-E3124 ; ISSN: 00134651 Kalantari, H ; Baghalha, M ; Sharif University of Technology

2014

Abstract

In this paper, a two-dimensional, two-phase, isothermal model is presented to investigate the water transport characteristic and water distribution in a direct methanol fuel cell (DMFC) with emphasis on exploring the water distribution in different layers of DMFC. The liquid-gas two-phase mass transport in the porous anode and cathode is formulated based on multi-fluid model in porous media and water and methanol crossover through the membrane are considered with the effect of diffusion, electro-osmotic drag, and convection. The modeling results agree well with the three different experimental data in an extensive range of operation conditions. A parametric study is also performed to examine...

Modeling and Simulating of Water Distribution in Different Layers of Direct Methanol Fuel Cell

, M.Sc. Thesis Sharif University of Technology Kalantari, Hossein (Author) ; Baghalha, Morteza (Supervisor)

Abstract

A two-dimensional, two-phase, nonisothermal model was developed in this work to investigate the water transport characteristic and water distribution in a direct methanol fuel cell (DMFC). Emphasis is placed on exploring the water distribution in different layers of DMF. The water and methanol crossover through the membrane were considered with the effect of diffusion, electro-osmotic drag, and convection. Governing equations including the prton and electron transport, continuity, momentum, species transport for methanol, water, and gases species, and the auxiliary equations are coupled to determine the output parameters. These parameters are the concentration distribution of the species,...

Backlash nonlinearity modeling and adaptive controller design for an electromechanical power transmission system

, Article Scientia Iranica ; Volume 16, Issue 6 B , 2009 , Pages 463-469 ; 10263098 (ISSN) Kalantari, R ; Saadat Foomani, M ; Sharif University of Technology

2009

Abstract

Nonlinearity characteristics, such as backlash, in various mechanisms, limit the performance of feedback systems by causing delays, undesired oscillations and inaccuracy. Backlash influence analysis and modeling is necessary to design a precision controller for this nonlinearity. Backlash between meshing gears in an electromechanical system is modeled by the use of differential equations and a nonlinear spring-damper. According to this model, the paper shows that oscillations and delays cannot be compensated by a state feedback controller. Therefore, an adaptive algorithm is designed, based on different regions of the system angular position error. Since this controller needs an estimation...

Self-Reconfiguration & Autonomous Algorithm for Spacecraft Formation Flight Using Virtual Structure Approach

, M.Sc. Thesis Sharif University of Technology Sharifian, Shakib (Author) ; Saghafi, Fariborz (Supervisor)

Abstract

One of the most important technologies in space missions is capability of moving satellites together with a predefined structure (virtual structure). This structure can reconfigure itself to any desired space mission and it is known as reconfiguration maneuver, in this maneuver all of the satellites have to follow needed virtual structure from any initial configuration to any desired second composition. In available virtual structure methods, there are a lot of limitations in maneuver because of algorithm constraints, in this project we try to extend available algorithm in virtual structure method and reach an algorithm which can start from any initial condition and complete the maneuver in...

Robust Nonlinear Control of a Jet Tail-sitter UAV in Hovering Flight Phase

, M.Sc. Thesis Sharif University of Technology Sarafraz, Yasin (Author) ; Saghafi, Fariborz (Supervisor)

Abstract

In this thesis, the theory of robust control is applied to design a controller for the longitudinal dynamics of a tail-sitter jet engine unmanned aerial vehicle. The engine thrust deflection is considered as the input controller of the system. The aircraft dynamical model is developed based on the assumption of no aerodynamic loads in low speed flight associated with the hovering condition. The controller is primarily designed using both classical and modern control techniques. Then and synthesis approaches are applied to design the robust controller. The results obtained from different approaches are compared. It is shown that the robust controller techniques are more stable and robust...

Development of a Distributed Algorithm for Flocking of Non-Holonomic Aerial Agents

, M.Sc. Thesis Sharif University of Technology Soleymani, Touraj (Author) ; Saghafi, Fariborz (Supervisor)

Abstract

The goal of this project is the development of a control algorithm for a flock of non-holonomic aerial agents. For this purpose,the swarm architecture having some unique features such as robustness, flexibility, and scalability is utilized. Swarm is defined as a group of simple agents having local interactions between themselves and the environmentwhich shows an unpredictable emergent behavior.Behavior based control which is inspired from the animal behaviors is employed to control the swarm of mobile agents. Accordingly, the necessary behaviors which are distance adjustment, velocity agreement, and virtual leader tracking together with a fuzzy coordinator are designed. In this study, in...

Optical Flow Based Flight of a Small Fixed-Wing Aircraft in Ideal Urban Environments

, Ph.D. Dissertation Sharif University of Technology Rezaei, Mahdi (Author) ; Saghafi, Fariborz (Supervisor)

Abstract

This thesis represents the obstacle avoidance of a fixed-wing small aircraft using optical flow information of cameras mounted on the aircraft. The thesis consists of two main sections. In section one, the ideal optical flow has been simulated based on the camera model, complete six DOF of flight equations, and the geometry of the environment. An analytical formula has been derived to relate the obstacle detection distance to the maneuverability of the aircraft. Having the obstacle detection distance, the control and navigation algorithms have been developed to achieve a collision-free flight for the aircraft in urban canyons and junctions. The effect of some parameters such as approach...

Robust Hover-flight Control Design for a Tail-sitter UAV with Ducted-fan Propulsion

, M.Sc. Thesis Sharif University of Technology Karami, Hossein (Author) ; Saghafi, Faribourz (Supervisor)

Abstract

In this thesis, the theory of robust control is applied to design a controller for hover flight of a tail-sitter unmanned aerial vehicle with 2 ducted-fan propulsion. The control surface deflection (in propeller slipstream) is considered as the input controller of the system. The aircraft dynamical model is developed based on the assumption of no aerodynamic loads on other parts of uav in low speed flight associated with the hovering condition. The controller is primarily designed using both classical and modern control techniques. Then H ∞ and µ synthesis approaches are applied to design the robust controller. The results obtained from different approaches are compared. It is shown that...

Development of a Vision-Based Position and Attitude Estimation Algorithm for Close Proximity Operation of Small Satellite

, M.Sc. Thesis Sharif University of Technology Pasand, Milad (Author) ; Saghafi, Fariborz (Supervisor)

Abstract

One of the key technologies in the future space missions is the formation flight of small satellites. Currently, widespread research in this field is being carried out and remarkable developments have been achieved. In the mentioned laboratory researches, satellite navigation is performed by conventional sensors like infrared and ultrasonic. Both of these sensors are of active type and energy consuming. Also, use of the ultrasonic sensors is impractical in space missions (due to vacuum condition). Therefore, as an alternative for space missions, visual sensors are good candidates. The main goal of this research is to present a method for the relative navigation in proximity operations in an...

Robust Control of Satellites Formation Flying

, M.Sc. Thesis Sharif University of Technology Hassani, Ali (Author) ; Saghafi, Fariborz (Supervisor)

Abstract

Recent developments in space industry and the great tendency for definition of efficient, precise and low cost missions are the main reasons for the growing interest in satellites formation flight. Regarding the aforementioned, the study of the multiple satellite control methods is the subject of the present project. In this project, the governing equations of motion of satellite formation flight are developed. Based on this development, it is shown that the satellite linear equations of motion like many other linear system presentations, can not sufficiently model the real system. Therefore, some of the most famous uncertainties in space dynamics such as semimajor axis and eccentricity...

Flight Performance and Maneuverability Enhancement of a Twin Engine Fighter Aircraft Using Integrated Thrust-Vector and Aerodynamic controls

, M.Sc. Thesis Sharif University of Technology Mazinani, Morteza (Author) ; Saghafi, Fariborz (Supervisor)

Abstract

In this thesis, maneuverability enhancement of a given twin engine fighter aircraft with integrated thrust-vector and conventional aerodynamic control surfaces havebeen studied. For this purpose a nonlinear 6DOF simulation program base on a near exact mathematical model has been prepared for the aircraft, and then a thrust vectoring system for producing moments about three body axes, like that used in F/A-18, has been added to the simulation. The control method that is employed to control the aircraft in simulation environment is based on Nonlinear Dynamic Inversion (NDI). Finally the Velocity Vector Roll (VVR) maneuver has been considered as an example tostudymaneuverability enhacement. It...

Application of Nonlinear System Identification Techniques in the Modeling of Agile Fighter Aircraft Dynamics

, Ph.D. Dissertation Sharif University of Technology Roudbari, Alireza (Author) ; Saghafi, Fariborz (Supervisor)

Abstract

Modeling and simulation are widely used as essential tools to predict and analyze complex systems in various scientific and engineering fields. For an aerospace system such as aircraft, mathematical models are useful used to carry out such tasks as dynamic analysis, autopilot development and combination of flight control laws, hazardous behaviors prediction, the controller design and validation, the study of the handling qualities, or the implementing simulators used for training pilots and many other tasks. In general, the aircraft flight dynamics is a nonlinear and coupled system whose dynamic modeling, in addition to pilot control inputs, depends on flight conditions (i.e., Mach and...