Sharif Digital Repository

The development of communication infrastructure in power systems has provided the grid with the availability of accurate information and has increased the reliability of the grid and its responsibility to disturbances. However, there have been some concerns about the negative impacts of the reliance on the information infrastructure. Inadequacies in the control and communication systems have been reported to be the contributing factors to situations that led to major blackouts. The functionality and reliability of the power grid is undoubtedly influenced by its communication infrastructure. In this thesis we are trying to model and analyze the failures that may occur in a power system and... 

Synthetic Aperture Radar (SAR) is a coherent imaging technique capable of generating fine resolution images from long term standoff ranges, either day or night. The use of multiple antennas for SAR is referred to as multichannel SAR or Multiple-Input Multiple-Output(MIMO) SAR and offers the additional abilities to perform height estimation of the ground, improve the resolution and suppress undesired interferences. Ground moving target indication (GMTI) is the one that we explored in this research. Since the pattern of moving target in imaging zone is sparse, we can use compressed sensing for reducing computational complexity caused by additional channels. In our thesis, after modelling the... 

Today with the development of te?nology, human ?allenges and problems have become even more complicated. In a way that as time went by the need for higher processing power to solve these problems has increased. High performance computers, are a category of computers whi? are used to solve su? problems. In the last two decade, distributed systems have become the most common way of gaining high performance. Here, Virtualization, an old te?nology whi? has revived in the last decade, providing spectacular features like isolation, migration, ease of management and creating opportunities like virtual clusters has proved to facilitate distributed processing. With the improvement of virtualizer’s... 

Power systems aredynamic and complex systems that are always subject to continuous changes and disturbance. Power system stability is a requirement for its satisfactory utilization. High speed Automatic voltage controllers with high gain tend to deteriorate both the electromechanical oscillation damping and small signal stability margin. Power system stabilizer (PSS) is a complementary controller that uses exciter voltage reference modulation to improve the electromechanical oscillation damping and stability margin. Optimal operation of PSS requires appropriate tuning according to the grid and power plant characteristics. In a largepower grid, absence or improper tuning of PSSs may cause one... 

Modeling of contact is a important problem in word science, so a lot of method presented by researchers .
In practical industry, if members of contact have complex shape or large deformation, analytical method can not solve the problem and use numerical method.
This method by using ansys , first analyze one-area contact and compare between numerical result and analitical result, then analyze two-area contact between two body with vertical force, and compare result with considering effect of slip and target surface.
Finaly to analyze a practical multiple contact problem, use modeling of tyre and road surface partial slip, and compare between ansys result with experimental result ,... 

Dynamic properties such as the natural frequency of a structure have a significant role in the design process. The importance of this consideration is because of resonance. In this case, the amplitude of the vibration is magnified to levels that may lead to a catastrophic event. While the usual design process depends on the collected experiences and statistical data, a developing trend is to implement smart technologies to develop smart structures that are capable of self-monitoring, diagnostics and repair. Smart material components such as shape memory alloys (SMAs) and piezoelectric ceramics are increasingly being used by vibration control practitioners. Shape memory alloys are applied as... 

Leaking of leachate contamination into the clayey isolation layer at the bottom of the landfills is one of the most important environmental issues, which influences living creatures' lives by affecting groundwater quality. Coupled phenomena that play a role in contamination and fluid transportation in a saturated clayey layer are hydraulic and osmotic flow, diffusion and convection. The targeted contaminate of leachate is monovalent salts. The clayey layer is also saturated. According to the governing differential equation, membrane efficiency and hydraulic conductivity coefficients highly affect the contamination transport. Experimental results and existing models have shown that these... 

Stock price patterns are a technical analysis approach to forecast future trends with tremendous practical benefits. However, the current algorithms solely rely on machine learning techniques and deep neural networks which could be a problem in countries where data sets such as these are not available. We propose an algorithm based on geometry and mathematics for this problem, leading to an O(n^3logn + n^2k) complexity, where k is the number of triangular patterns