Sharif Digital Repository

The focus of this thesis is on robust control of hybrid systems using tube-based model predictive control. Hybrid systems are systems that contain both continuous and discrete components. The hybrid nature of these systems can stem from inherent switching behavior that occurs in many dynamical or digitally controlled systems, or from approximation of nonlinear systems. The ability of these systems to model a vast amount of physical phenomena has been attracted a lot of attention from control society. Although much effort have been made on the control of “nominal” hybrid systems, robust stabilization of these systems still seems to be immature. One of the most successful approaches toward... 

First, we peruse the intraction between a quantized light and a two level atom which has been described by Janes-Cummings-Paul Hamiltonian. By solving Heisenberg equations in Fourier space and describing electric field by a generalized-transverse Green function, we obtain spectral density for a quantum dot which is in the strong coupling to a slab photonic crystal cavity. Afterward, by solving Shrouding equations precisely we demonstrate when quantum dot is in a very strong coupling to cavity, rotate wave approximation is not reliable anymore. It means that if coupling constant gets comparable to cavity mode frequency then the prevalent approach to solve this Hamiltonian will not be correct.... 

In this project, we were intended to study the ultra-strong coupling in optical waveguides. Hence, we analyze the interaction of an electromagnetic wave with a quantum well embedded in a dielectric slab waveguide. First, we designed a QW with and alloys, which the energy of its electron-heavy holes transition is . By exploiting the envelope function approximation, we derived the wavefunction of electrons and holes, their eigen-energies, and the dipole moment of electon-holes. For finding the wavefunction of holes and their eigen-energies, we used the Luttinger Hamiltonian. Next, we calculated the electrical susceptibility of a three level quantum system (as a model for QW), by using... 

Cavity Quantum Electro-Dynamics (CQED) in Weak, Strong and Ultra-Strong coupling Regimes are studied. A MATLAB m-file is written which is able to solve any arbitrary CQED configuration. This program demands input data such as number of Quantum Dots, number of energy levels of each Quantum Dot, energies of each energy level of Quantum Dots, Number of cavity modes, eign-frequency of each cavity mode, coupling constant, dipole strength of each allowed transition of Quantum Dots and initial state of system from user and begins to solve the Schrodinger equation for annihilation and atomic ladder operators. In addition, coefficients of each possible ket will be calculated. Since, any approximation... 

Thin Walled Beams are widely used in engineering applications with the minimum weight design criteria, ranging from civil to aerospace and many other industrial fields. The weight reduction of the beam leads to importance of the dynamic behavior of the structure. Frequently used thin walled beams have low torsional stiffness and their torsional deformations may be of such magnitudes that it is not adequate to treat the angles of cross section rotation as small. When the vibration amplitudes are moderate or large, the geometric nonlinearity must be included and some new phenomena which do not exist in linear torsional dynamic come into play. Unfortunately, the equations of motion of nonlinear... 

In the recent years, photonic crystal (PhC) devices vastly have been paid attention due to their ignorable loss, very low group velocity, flexibility in shape and dimension.In this thesis a PhC coupled cavity ring known as superresonator is introduced and its properties and applications is studied. Also modes of the structure are extracted through both coupled-resonator model and FDTD method, and two of its application is described and studied. Add-drop filter is one of the essential devices in WDM systems. First, an application of superresonator in designing add-drop filters is explained and a novel filter based on the superresonator is introduced and analyzed by FDTD and coupled mode... 

Control of powered lower limb prostheses has a locomotion mode- ependent structure which demands a pattern recognizer that can classify the current locomotion mode and also detect transitions between them in an appropriate time. In the way to achieve this goal, this project presents a locomotion mode recognition system to classify daily locomotion modes consist of level- walking, stair climbing, slope walking, standing and sitting using low-cost mechanical sensors. Since these signals have a quasi-periodic nature, using sequential pattern recognition tools, such as Hidden Markov Model(HMM) improves the recognition performance,because they use sequences of information to make a decision. On... 

The growing demand for scalable and cost-effective computing resources has led to the widespread adoption of the Infrastructure as a Service (IaaS) model in cloud computing. One of the pricing models for resources, or virtual machines, in this service is the Spot model, which allows customers to access unused cloud server capacity at significantly lower costs compared to other models. However, despite their affordability, these virtual machines do not come with a Service Level Agreement (SLA) and may experience interruptions during use. Such interruptions increase the time required for customers to complete their tasks. In this study, we utilize discrete-event system simulations to examine... 

My dissertation includes four chapters; three introductory chapters and a final conclusion. The first chpter is a comprehensive introduction to the problem of consciousness. The next chapter is allocated to representationalism, especially Michael Tye's PANIC theory, as a solution to the hard problem of consciousness and related phenomena. The third chapter is a brife look at causal theories of mental content. And the last chapter contains my arguments agaisnt Tye's theory. Apparently, mental states are of two categories; some mental states have representational content and some other have phenomenal aspect; there is something it is like to undergo latter states. Representationalism holds...