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What drives mergers and acquisitions waves in developing countries? Evidences from Iranian banking industry
, Article Iranian Economic Review ; Volume 19, Issue 2 , 2015 , Pages 123-137 ; 10266542 (ISSN) ; Alambeigi, A ; Karimi, P ; Zarei, B ; Sharif University of Technology
2015
Abstract
Many Middle-East countries, like Iran, have dynamic banking industries and have observed merger and acquisitions (M&A) waves. M&A waves are usually defined in the developed world context and some of their main drivers were identified as: market timing, environment's shocks, merger manias, government regulation and regulatory, and technological changes. It has been discussed that merger waves and their reasons are among the ten most important unsolved mysteries in the field of finance (Brealey and Myers, 1991, p. 923), and as a result of this, it was not possible to completely clarify the reasons behind emerging M&A waves, especially in developing countries; for this reason in these...
The effects of mergers and acquisitions (M&As) on bank performance and entrepreneurial orientation (EO)
, Article Iranian Entrepreneurship: Deciphering the Entrepreneurial Ecosystem in Iran and in the Iranian Diaspora ; 2017 , Pages 361-375 ; 9783319506395 (ISBN); 9783319506388 (ISBN) ; Alambeigi, A ; Zarei, B ; Karimi, P ; Sharif University of Technology
Springer International Publishing
2017
Abstract
This chapter aims at pointing out that how mergers and acquisitions (M&As) as popular strategies which they are based on external growth approach have affected the performance of banks and entrepreneurial orientation (EO) in the context of Iranian financial sector. In this regard, it has been tried to investigate in what way EO moderates the relationships between the performance of banks in one hand, and M&As on the other hand. For this goal, 114 participants including the top and middle managers of the Iranian banks were chosen to be closely considered. The research is an applied research and a cross-correlation methodology has been used to spotlight on the probable relationships between EO...
Self-Reconfiguration & Autonomous Algorithm for Spacecraft Formation Flight Using Virtual Structure Approach
, M.Sc. Thesis Sharif University of Technology ; 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 ; 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 ; 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 ; 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...
Development of a Vision-Based Position and Attitude Estimation Algorithm for Close Proximity Operation of Small Satellite
, M.Sc. Thesis Sharif University of Technology ; 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 ; 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 ; 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 ; 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...
Machine-Vision-Based Auotomatic Landing of Unmanned Helicopter
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
In this project an algorithm is designed for automatic landing of unmanned helicopter on a pad moving with six degrees of freedom. The designed controller is based on state dependent riccati equations (SDRE).by developing nonlinear mathematical model of helicopter and then converting this model to state dependent coefficient (SDC) form. A nonlinear compensator is added to controller to compensate effect of some nonlinear terms of model that are not able to translate and then state dependent riccati equations are solved.
The relative pose-estimation of landing pad is based on vision. Corner detection algorithm is used to identify and detect features by processing of image taken from...
The relative pose-estimation of landing pad is based on vision. Corner detection algorithm is used to identify and detect features by processing of image taken from...
Numerical Optimization and Parametric Study of Cooperative Salvo Attack Using Particle Swarm Optimization Algorithm
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
In this research work, several guidance laws have been utilized and validated, considering the contraints on the missslie seeker angle and maximum acceleration, in order to simultaneously intercept the so-called Close-in Weapon System (CIWS) by multiple missiles. First of all, the existing guidance laws for salvo-attack are reveiwed. Then, a simulation program has been developed and validated for the misslie and CIWS as a five and two degrees of freedom systems, respectively. Optimization of the system is then carried out by the method of Particle Swarm Optimization, considering the given constraints. In the next step, for the improvement of the optimized guidance law, paramertic study has...
Experimental Investigation of Microjet Engine Anomaly Detection Based on ANN Data Clustering Analysis
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
In this study, the possibility of detecting known and unknown anomalies in a micro jet engine is evaluated. the proposed method is neural network and clustering analysis. The process consists of two main parts, first part is experimental abnormal behavior simulation and second part is validation of proposed detection method. In the first part a micro jet engine (Olympuse HP) were used and we created pre-designed errors in engine normal behavior to record significant changes in its performance. Recorded outputs consist of six different variables: RPM, Exhaust gas temperature, Throttle command, Fuel pump voltage, Thrust and Fuel weight. In the second part, for analyzing data, we used...
Dynamic Modeling of a Quadrotor UAV Transporting a Variable Mass Payload Suspended by Continuous Flexible Cable
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
Quadrotors are one of the most popular unmanned aerial vehicle (UAVs) that has been subject of extensive research in recent years. One of the most important applications of these aerial vehicles is transporting a cable-suspended payload from one point to another. The major challenge in modeling of this system is dynamic coupling which exist between all components of the system i.e. payload, cable and quadrotor. The purpose of this research is mathematical modeling and dynamic analysis of the system in presence of this dynamic coupling and considering the effects of cable's flexibility. In this regard, it is assumed that the payload has variable mass. In this thesis, in the first step, by...
Dynamic Modelling of Multiple Quadrotor Suspended Load Transporting System with Variable Center of Mass via Flexible Cables
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
Using unmanned aerial vehicles in aerial payload carrying leads many changes requiring significant study and research. In recent years, there has been considerable maturation in Micro Aerial Vehicles (MAV) developement especially quadcopters. In addition to the endurance restriction, considerations on volume and weight that can be carried, and safety issues are also obstacles to the development of unmanned aerial payload carrying in urban environments. One of the ways to make a quadcopter more agile while carrying a load is to hang the cargo from the quadcopter via a cable. In this way, it is possible that quadcopters carry the cargo in a cooperative way, which if properly arranged,...
Cooperative Slung-Load Transportation by Quadrotors in Urban Environment, Path Planning and Tracking
, Ph.D. Dissertation Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
In this research, the aerial load transportation in the urban environment by cooperative quadrotors is investigated. This system requires two sub-systems: path planning and control. The path planning subsystem designs the payload's path and at the same time determines the shape of the flight formation of agents in order to be able to carry the payload. The design of the path-formation is done in the presence of constraints such as the collision avoidance with obstacles, inter-collision avoidance to each other, the collision avoidance of the slung load with the obstacles and the minimum and maximum allowable cables' forces. Therefore, the shape of the formation flight is determined...
Conceptual Study of an Unmanned Water-Thrusted Aerial Firefighting System (UWFS)
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
In this research work, the concept of an unmanned aerial firefighting system with water thrusters has been studied. This system consists of a platform head, a waterhose and a ground pump. The concept is briefly to pump water through the hose and then fall it down on fire from the platform. This conceptual system may have many other applications. The other applications have also been addressed in the introduction section. This platform can be considered as an unmanned aerial vehicle whose lift and control forces is provided by water thrusters. The conceptual study has been carried out based on three subjects of preliminary sizing, system dynamic modeling and controller design for platform...
Modeling and Simulation of 12-DOF Parafoil-Payload System Flight Dynamics
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
This thesis is concerned with the modeling and simulation of twelve degrees of freedom parafoil-payload system, as a multibody aircraft configuration. This 12-DOF dynamic model represents three degrees of freedom each for rotational motion of the parafoil (including suspension lines and canopy) and payload, and three degrees of freedom for translational motion of the parafoil, and one degree of freedom for relative translational motion of the payload, also two degrees of freedom for rotation of the canopy frame respect to the parafoil frame.
For evaluation of the flight dynamic behavior of parafoil-payload system, the nonlinear differential equations of the system have been derived and...
For evaluation of the flight dynamic behavior of parafoil-payload system, the nonlinear differential equations of the system have been derived and...
Cooperative Search and Localization Using Multiple Fixed Wing Unmanned Aircraft
, Ph.D. Dissertation Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
Nowadays, regarding the advancement of unmanned aerial vehicles and low cost sensors, the idea of utilizing a group of aerial vehicles to perform risky and complicated missions has attracted the attentions of researchers. One of the main subjects in aerial missions is target search and localization. Cooperative target search by the use of multiple aerial vehicles equipped with sensors, could construct a sensor network that makes the system more robust against failures and reduce noises and uncertainties. In addition, the observability and quality of sensor signals could increase if the motion and positions of the vehicles are intelligently optimized.In this research, establishing an...
Study of the Effect of Canopy Lateral Incidence Angle on Autonomous Guidance and Control of Parafoil-Payload System
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
The trailing edge brakes are the conventional controller mechanisms for autonomous precision delivery parafoil systems. Asymetric braking creates differential drag on the left and right sides of canopy leading to generation of turn rate, whereas symmetric deflection changes the aangle of attack which in turn affects airspeed and limit the glide slope. In the current work , in addition to the conventional controller , the canopy is considered to have the ability of changing its longitudinal and lateral incidence angles. This can be achieved by changing the length of sidelong suspension lines.Unlike brakes, the lateral incidence angle creates heavily coupling in lateral dynamics.The results...