Sharif Digital Repository

One of the attractive fields of applied quantum mechanics in recent two-three decades is the field of quantum computing. Up to now different substrates have been proposed for a quantum computer. One of them is cavity quantum electrodynamics in which some quantum systems with finite energy states like atoms interact with quantized Bosonic modes like photons inside a cavity. In this dissertation we study a particular structure in this substrate. This structure consists of some quantum dots inside coupled cavities. Since we would like to build these cavities in a photonic crystal slab, we first introduce two new methods for analysis of this type of crystals. These methods are much faster than... 

Textual news published in the media on a daily basis is a large and valuable source of unstructured data that can be used to analyze and model the financial market by using text mining methods. The purpose of this study is to design a news-reading system for economic analysis and modeling of gold prices using features extracted from textual news and text mining methods; it seeks to enable the machine to read news like financial analysts then analyze and forecast the economic situation and market trends. For this purpose, we collected news from the website of an Iranian economic news agency. To design the economic analyzer, we extracted important economic, political, and social factors from... 

One of the common motor disorders among children is cerebral palsy. On average, 1 to 4 out of every 1000 children born are affected by this disease. Defects in the central nervous system, along with musculoskeletal system disorders, are noticeable in cerebral palsy. In recent years, various methods have been proposed for motor control analysis. One of these methods is the synergy hypothesis, which can be used to explain the performance of the central nervous system in controlling and moving body parts. However, in previous studies, the kinematic synergies of healthy and cerebral palsy groups have often been extracted separately without considering their interrelation. Typically, four or five... 

In the present dissertation model based grasping of soft tissue with the laparoscopic gripper, tissue deformation under the applied load and control of the tissue-instrument interaction have been studied. As the first step a cantilevered beam under bending and tension has been modeled statically and dynamically using the meshless EFG based method. Results show that an increase in the number of nodes at the displacement boundary and the area of force insertion improves the accuracy of the predicted displacement in the model compared to the analytical solution. In the second step the model is developed for a hemisphere under vertical and lateral compression. Comparison of the deformation of... 

The aim of this project was to design, analyze and fabricate a 4 DOF robotic arm to be used as a slave robot for tool handling in laparoscopic surgery. The mechanism used for this purpose should have a remote center of motion in order to be able to manipulate the tool through the small incision point. The robot should also provide sufficient force to handle endoscopic tools used for large organ manipulation and be capable of measuring these forces. A variety of mechanisms were studied thoroughly, and the best solution was chosen by considering the design parameters such as workspace, manipulability, accuracy, ease of fabrication, etc. The final design consists of a 2 DOF serial spherical... 

Security of cryptographic devices lies amongst the most important issues in the field of hardware security. It is frequently seen that in the process of designing cryptographic systems insufficient attention is paid to the physical implementation details. This is happening while a lot of secret information is known to be leaked through side-channels such as power consumption, electromagnetic emission and execution time. Side-channel attacks are able to reveal secret keys by using these side-channel leakages. Additionally, side-channel attacks are one of the most powerful but low-cost attacks that put the security of cryptographic systems in vain. It can be claimed that the most dangerous... 

One of the satellite time-critical launch methods is air-launch, which is considered in this research thoroughly. The Large number of important parameters of this method makes the system highly complex. In such complex systems, usual methods of design and development will not be effective. Moreover, based on systemic approaches, interfaces between different elements of a complex system have significant effects on the performance of the whole system. One of the methods for analysis of such systems is “Design Structure Matrix” or DSM. This method is based on system engineering principles and has confirmed capabilities in analysis of highly coupled systems.
In this research, the air launch... 

Public-key cryptography is vital to secure digital communication. The classic instances of these cryptosystems are insecure against large-scale quantum computers. As a result, post-quantum cryptography has emerged as a replacement, which includes different categories. Isogeny-based schemes are one of the promising candidates mainly because of their smaller public key length. Due to high computational cost of such schemes, efficient implementations are significantly important. In this thesis, we have presented various solutions at three different abstraction layers. At the lowest layer, which deals with modular arithmetic, two hardware architectures are presented to perform modular... 

Cerebral palsy is the most common motor disorder among children, resulting from damage to the motor areas of the brain during fetal development or early infancy. Studying motor control changes in individuals with cerebral palsy helps better understand their motor abnormalities. In recent years, various methods for analyzing motor control have evolved, including synergy analysis. The current study aims to thoroughly examine the differences in muscle synergies between children with cerebral palsy and healthy children during walking. In the initial phase of the study, muscle synergies were compared among different groups of children with cerebral palsy (based on Rodda classification) and... 

Knee pain and injuries are very common in athletes. Anterior cruciate ligament (ACL) injury is one of the most important reason of knee acute and chronic pains. As ACL plays a significant role in knee stability and due to amount of reported ACL related injuries, much effort has been placed on finding proper and on time diagnosis and treatment of these injuries. Arthrometric methods are the most non-invasive reliable diagnosis option; however they are not fully capable of separating partial injuries from intact joint. This weakness can be investigated by quantifying the tests using computer simulations; so far few studies have been conducted toward this goal. In this study a two dimensional... 

Motorized intramedullary nails are a viable solution to treat patients with limb-length inequality. These fully implanted devices use external magnetic actuation to extend. This research examines the conceptual design of this type of nails by investigating various ideas and previous designs. The implant mechanism, body and controller are designed in detail. It was then simulated in standard tests to evaluate it. In addition, the implanted nail undergoes a biomechanical analysis and its stiffness is assessed. Finally, the controller design is carried out using dipole magnetic theory and verified by finite element simulations. As a proof of concept, we made a prototype that is twice the size... 

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... 

Suture anchors are implants used for reattaching torn soft tissues to bone. Tilting anchors, a subtype of suture anchors, not only maintain the features of conventional suture anchors but can also be manufactured via 3D printing with a porous surface, enabling bone ingrowth and thus ensuring secure, long-term fixation. Additionally, these anchors can achieve fixation beneath the cortical bone layer, making them effective for secure attachment in areas of low bone density. Despite these advantages, limited research exists on this type of anchor, particularly regarding its performance and strength. One of the most influential factors in suture anchor strength is the method of fixation within...