Sharif Digital Repository

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... 

Direct Torque Control (DTC) is one of the vector methods to control Permanent Magnet Synchronous Machines (PMSM). In order to achieve an appropriate control in vector control methods, an accurate estimation of flux is indispensable. Flux estimation should be fulfilled in a wide speed range without considerable dependence on motor parameters. Prevalent flux estimation methods are based on integration of stator voltage which is not feasible in low speed, or performed based on assumption of decoupled equations on d and q axis which is not precise for applications with fast dynamic. Different flux estimation methods are investigated in this thesis with the aim of improving the flux estimation in... 

Drug targeting to specific organs and tissues has become one of the critical endeavors of the new century. Magnetic nanoparticles have gained a lot of attention in biomedical and industrial application. Doxorubicin is an effective anti-cancer drug in the treatment of many types of cancers. The aim of this study is to load doxorubicin on stimuli-responsive nanocarriers. These nanocarriers are prepared from magnetic nanoparticles. Then these magnetic nanparticles are coated by copolymer of poly(glycidyl methacrylate) then reacted with hydrazine and hydrazide functional group is formed that can chemically be bonded with the anticancer drug doxorubicin via a hydrazone bond formation. This... 

Hydrocephalus is a desease which causes by unnatural accumulation of cerebrospinal fluid in the brain ventricles. One of the most convenient ways to treat hydrocephalus disease is to use a brain shunt which consists of ventricular catheter, valve and distal catheter. Ventricular catheter obstruction is the main reason for shunt replacement in the human brain. This project attempts to remove obstruction of the ventricular catheter by mechanical forces. For this purpose, a magnet and a variable magnetic field suggested to apply mechanical force on a brush sliding on the shunt. On the inner surface of the ring-shaped magnet, brushes have been embedded and the magnet is placed on the outer... 

In this research dynamic modeling of a 3-DOF (degree of freedom) compliant parallel mechanism with flexible intermediate links has been investigated. Unlike conventional rigid mechanisms that gain their mobility from movable joints, the compliant mechanisms transmit or transform through elastic deformation of flexible members (flexible connector and joint), displacement, force, or energy from input into output. Eliminating clearance, friction, wear and demand of lubrication in compliant mechanisms, and having monolithic structure provides high-precision motion with micro/nanometer level resolution for them. Therefore compliant mechanisms play a significant role in modern technologies such as... 

A bolometer is a device for measuring electromagnetic waves, which uses the heating of a material with variable resistance to temperature. Due to the existing limitations and quality improvement, superconducting materials are used in the manufacture of these devices. In this dissertation, the construction and improvement of the components of a high temperature transient edge superconducting radiometer with terahertz detection capability is discussed. In the construction of these detectors, the superconducting material YBa2Cu3O7-x is used as a thermal sensor with a transition temperature of 93.5K. In order to characterize these detectors, an automatic system for measuring the voltage response...