Sharif Digital Repository

After discovery of superconductivity in 1911 people try to find superconductors with higher Tc. High Tc superconductivity in cuprates and iron based superconductors was discovered in 1986 and 2008 respectively. However, there is not any unit theory for high Tc superconductivity in cuprates or iron based superconductors. Study of electronic and phonon structures of high Tc superconductor compounds can lead to find theory of high Tc superconductivity.
In this dissertation electronic structure of Ba1-xKxFe2As2, which belongs to class of 122 of iron based superconductor, under potassium doping x=0,0.5,1 has been studied. To this end ab-initio method and Density functional theory have been... 

The discovery of Iron-based superconductors with maximum transition temperature of 56 Kelvin and High critical magnetic field of the order of 50T at temperature 20K has created evolution in different fields of superconductivity including practical issues. BaFe2As2 family is one of the most important compounds of Iron-based superconductors and with different doping elements for instanse elements of the first column like Potassium inters superconducting state with critical temperature of 36K.
The purpose of this thesis is to localize the technology of making this compound in Iran which no project has been done in this field in the country before. In this thesis manufacturing, Optimization... 

Nowadays there are various means in the field of orbital mechanics used in different levels and their accuracy depends on the theory and complexity of the governing equations used in their development. Most of them just simulate the motion of an orbiting satellite while there exist some commercial products able to provide the user with the orbital performance specifications and almost none of them have a module to design an orbit, based on a required performance such as specific coverage / ground track, shadow/light duration, etc .... Although satisfying performance requirements and a set of orbital elements simultaneously only seems to be possible for some particular orbits, there is an... 

Various applications of speech processing systems are gaining more and more attention. Performances of these systems are dramatically affected in presence of background noise. Attempts toward improving quality of degraded speech have emerged into filed of speech enhancement which is one of the interesting topics in speech processing domain. In this thesis various single channel speech enhancement methods are studied briefly. Statistical methods as one of the most successful methods are studied more deeply. These methods are divided into two categories of short-term modeling of speech and long-term modeling. The aim of this thesis is to improve the performance of long-term methods of... 

The present study aims at determining the elastic fields of ultra-small flaws and defects. These defects are often introduced undesirably in elastic solids during fabrication and their sizes are normally in the order of couple of nano-meters. In this work, the elastic fields around a circular nano-void subjected to a uniform farfield uniaxial tension, also the elastic fields of a nano-sized mode I crack under remote uniform loading are studied. In this paper the strain gradient theory developed by Mindlin and co-workers in 1960s is employed. According to this theory, the strain energy density assumes the form of a positive-definite function of the strain components and their first gradient.... 

The purpose of this paper is to design an integrated controller and observer (ICO) for a nonlinear system using genetic programming. ICO is a function that constructs control command directly from the measured state variables of the system. It means that, this function should imitate the behavior of the observer and controller and control the system with acceptable performance in different initial conditions, at the presence of disturbances and system uncertainties. The complexity of this design method, is not related to the complexity of the plant, in fact, the complexity in plant just effects at run time, but the design procedure does not change. So, if exact model of plant exist, using... 

One of the most important parts of vehicles and most of mechanical machines is power transmission system, especially the Gearbox used in them.In order to optimize the use of energy, especially fossil fuel, researchers are looking for new mechanisms to refine the operation of vehicles and other machines.One of the mechanisms which absorbed researcher’s attention during recent years is the Continuously Variable Transmission. By using these gearboxes which are replaced with older samples, we can have the continuous range of aspect ratio between two constant values. This important property causes the decrease of the use of fuel.In recent decades many manufacturers have used different kinds of... 

There are different classes of event-driven softwares. These softwares include Graphical user interface, web application or embedded software. In these kinds of softwares, each user's action while using application is known as "event". The application responds to the action through changing behaviour and then waiting for another event. Testing software is the best way for checking the quality assurance of event-driven softwares. However, there are some problems as cause of creating lots of event sequences in testing these kinds of softwares. Therefore, many solutions are introduced for these problems. The goal of this report, is presenting new testing procedure for event-driven web...