Sharif Digital Repository

In the year 2004 when the first instance of graphen was built in laboratory, entice the attraction of many research groups. Because in spite of absence of graphen to that time, physicists given the unique properties for it. So it was the time to use that marvel properties which only theoretically available, to design and built one atom thick circuits. In this dissertation for the first time, we want by using method of moment and multilayer green functions in spectral domain, analyze graphene-based ribbon and stepped electrical conductivity distribution waveguides and calculate their characteristics such as propagation constant, surface currents and characteristics impedance with external... 

So far, Investigations have shown that microstrip antennas (MSA) offer a lot of advantages at microwave and millimeter wave frequencies. These advantages include small size, large impedance bandwidth, high radiation efficiency, ease of fabrication, low price, and simple and easy excitation (such as probe coupling,aperture coupling or proximity coupling).Microstrip antennas are fabricated in many different shapes such as square,rectangle, circle, etc. The proposed antenna in this dissertation is a multi-beam millimeter wave antenna with annular ring strip. This antenna is a multi-beam antenna with the ability to switch between different beams. Beam direction switches by changing the position... 

Achieving low group velocity of light can result progress in many fields. In this project by using complex time domain frequency, achieving method to zero group velocity is proposed. The proposed structures in this thesis consist of two lossless and lossy structures which by considering the modes with complex time frequency are excitable. Using leaky modes to analyze these structures, made them suitable as they can be excited from free space. Using slow light can lead to optimized devices because of the more interaction of light and matter which besides smaller devices too. Additionally slow light is being considered in designing optical memories, quantum computers, optical processors and... 

Due to its extensive applications in imaging, data security, medication, etc., Terahertz has attaracted an ever-inceasing attention. Design and implementation of Terahertz sources and circuits as waveguide, filters, etc. in this band have attracted attention. The unique elec-tric characteristics of graphene, like showing plasmonic characteristics in Terahertz frequency band, made this recently recognized matter a promising one to build super-integrated plas-monic circuits in Terahertz band. In this text, the first section represents an introduction for a number of graphene waveguides as well as studying the effective refractive index method to analyze graphene waveguides. Due to the small... 

In this thesis, combustion of liquid fuel spray under the condition of hot and diluted oxidizer, has been investigated. To this end, a novel type laboratory-scale test rig was designed to study the physics governing the MILD-Spray combustion conditions with an applied approach. The underlined test rig eliminates the operational problems of its predecessor test stands and is used for a heavier fuel with much more complex chemical composition (kerosene). The test section is axially symmetrical, in which the fuel is injected by a pressure-swirl atomizer in the direction of hot and diluted co-flowing air. With the use of the aforesaid test rig, the effect of variables such as oxygen... 

Monitoring driving behaviors of drivers, would avoid their dangerous behaviors and remarkably raise the safety. Nowadays real-time supervision is considered as one of the modern methods of controlling driving behaviors. Previously, due to expensive costs of required equipments and other restrictions, this kind of supervision hasn't been considered fairly. Nowadays increasing usage of smart phones, which contain multiple sensors, enables this type of supervision with lower costs. In the present study we would present some models, to assess the driving behavior via smart phone sensors such as accelerometer, gyroscope and rotation vector  

In practice, structures made of concrete are full of cracks. The strength of concrete is mainly determined by the tensile strength, which is about 10% of the compressive strength. As long as cracking in concrete is unavoidable, we have to try to minimize their detrimental effects. This objective can be achieved by resisting (or limiting) propagation of existing cracks. Because of this, reinforcement (mostly steel) is used to increase the carrying capacity of the material and to control the development of cracks. Concrete structures that fail, already shows a large number of large and small cracks before their maximum carrying capacity is reached. The failure of concrete can be characterized... 

The purpose of this research is to monitor the health of structures using the updated finite element model, in which digital images are used to optimize the numerical model. Structural Health Monitoring (SHM) is always an important and significant issue that has attracted the attention of many researchers in recent years. In general, some researches have been conducted in this field using physical sensors that provide discrete data to the system for analysis. Using cameras to monitor the structure makes it possible to extract continuous and integrated data from the structure using digital images, which is a significant advantage compared to physical sensors.In this research, a steel... 

Conformal Field Theory provides an efficient method for studying physical problems in critical point. Correlation length becomes converge in this point. It can also be clarified that some curves are observed in geometrical phase transition which are conformal invariant and they can be studied using SLE(k). The first mathematical generalization of SLE(k) while keeping the self-similarity property, leads to SLE(k,p). Conformal field theory and SLE are interrelated and their parameters are interpretable for each other. One usually studies the problem in the upper-half plane. Here we consider the problem using a map like (w=L/π Ln z) between the upper-half plane and a special region (e.g. a...