Sharif Digital Repository

Three dimensional or vertical integration is a new way of increasing the performance and expanding the capabilities of modern integrated circuits. Using this technology, 3D Networks on Chip has been proposed as one of the novel research fields and has been receiving a lot of attention. Using the third dimension, different topologies could be implemented in these chips and positive effects of this integration like decreasing the length of interconnections and decreasing the communication latency as the result of that could be utilized. In addition to common topologies like mesh and torus, it is possible to implement other structures in three dimensional integration. Topologies with lower... 

This dissertation on the Schrodinger-Virasoro algebra will begin by a brief historical review on the development of the symmetry arguments and its final overwhelming success in the 20th century physics. Testifying many successes of symmetry arguments and group theoretic methods in physics such as the theory of relativity, many physicists began to ask whether covariance under a larger group of symmetry transformation would explain a broader era of physical phenomena? As will be reviewed in the beginning of the second chapter, invariance under conformal group - which includes Poincaré group as a subgroup and thus underlies Lorentzian geometry as its natural background geometry – has been... 

Integrating hundreds of cores on a single chip necessitates high performance interconnection network. Due to great delay and power consumption of electrical networks in global connections, their use might be limited in future. Optical networks-on-chip are introduced recently as a proper alternative for electrical networks by providing high bandwidth, low latency, and low power consumption. Despite these outstanding advantages, optical component behavior is very sensitive to temperature fluctuations. Specifically, thermal variations affect refractive index of semiconductor, which in turn change resonating wavelength of micro-ring resonator. Therefore, the switch cannot operate properly and... 

In normal diffusion, the mean-square displacement (MSD) of a Brownian particle is proportional to time. However, diffusion in disordered systems, i.e. transport on fractal geometries, does not follow the classical laws of BM, and this leads to many anomalous physical properties. In the anomalous regime, the most famous definition of anomaly is the deviation of MSD, from the ‘normal’ linear dependence on time ⟨r2(t)⟩ ta. Specifically, we study the anomalous diffusion on the self-similar curves in two dimensions. The scaling properties of the mean-square displacement and mean first passage time (MFPT) of two sided and subordinated diffusion on the different fractal curves (loop-erased random... 

In this thesis, we investigate the effect of disorder on Majorana fermions at the boundary of one-dimensional topological superconductor. Starting from one-dimensional spin model nXY and then applying the Jordan-Wigner transformation result in one-dimensional topological superconductor. The Majorana fermions are found in the topological superconductor boundaries, protected by particle-hole and time-reversal symmetries. On the other hand, these fermions are highly localized at the boundary. Owing to non-trivial topology, the Majorana fermions are not affected by weak disorder. Increasing the disorder strength, the localization length of the Majorana fermions increases. Upon further increase in... 

Since oil prices continue to increase, energy conservation remains the prime industrial concern. Existing processes in power plants and oil refineries are not energy efficient as they should be therefore new projects can be defined to increase the energy efficiency without incurring any cost. The most appropriate utility for the processes should be explored to reduce emissions, increase the plant capacities and improve product qualities and energy efficiencies by one coherent strategic plan for the overall site which can be achieved by a full understanding of pinch technology and awareness of the available tools for applying it in practical way. Since the distillation unit of crude oil... 

We calculate NJL-Model free energy throughthe finite- temperature methods.Then according to the energy-gap equation, we determine symmetric and anti-symmetric phases under Chiral Transformation, in different regions of the phase diagram,with chemical potential() and temperature(T)as control parameter. We conclude with comparing the result of the finite temperature expansion to nonzero chemical potential to the result of,T=0 and finite ,andT=μregime.
 

Percolation is a simple probabilistic model which exhibits a phase transition. Here, we study this critical model from properties of random curves which in the scaling limit, appear as features seen on the macroscopic scale, in situations where the microscopic scale is taken to zero. Among the principal questions are the construction of the scaling limit, and the discription of some of the emergent properties, in particular the behavior under conformal maps Over the past few years, SLE has been developed as a valuable new tool to study the random paths of the scaling limit of two-dimensional critical models, and it is believed that SLE is the conformally invariant scaling limit of these... 

The number of transistors on a single chip is growing exponentially which results in a huge increase in consumed power and temperature. Parallel processing is a solution which concentrates on increasing the number of cores instead of improving single thread performance. Graphics Processing Units (GPUs) are parallel accelerators which are categorized as manycore systems. However, recent research shows that their consumed power and energy are increasing. In this research, we aim to propose methods to make GPGPUs energy effiecient. In this regard, we evaluated the detailed consummed power of GPGPUs. Our results show that memory sub-system is a critical bottelneck in terms of performance and... 

Among chemically enhanced oil recovery (CEOR) methods, polymer flooding has the highest commercial potential. However, the most widely used conventional polymers such as partially hydrolyzed polyacrylamide (HPAM) are not applicable for high-temperature and high-salinity reservoirs. To overcome above-mentioned problems, in this work, a series of water-soluble hydrophobically modified polymers (HMPs) nanostructures comprising 2-vinyl naphthalene (hydrophobic monomer) has been produced by freestyle method (without Surfactant), micellar (with Surfactant). The size of the particles was investigated using scanning electron microscopy (FE-SEM) and optical scattering (DLS). Results from FT-IR... 

Nowadays, applications of industrial robots are significantly increasing due to their flexibility, programmable, accuracy, rapidity and etc. Among these, machining robots play an important role at manufacturing industries. One of the main concerns of the researchers, is the tip vibrations of robot arms. In most times, these vibrations are self-excited, unpredictable and intolerable. Thus, finding a method for reducing vibration should be investigated. The purpose of vibration control is vibration suppression to enhance the reliability of the system. The aim of this project is the modeling of the machining robot arm in turning process and then application of robust control to reduce... 

Schramm – Loewner Evolution (SLE) is a framework which helps to classify interfaces in critical models. At criticality two or more phases of the model are separated by an interface. In two dimensions this interface is a simple random curve, which can be addressed by SLE theory. This classification has crucial rule in our understanding of statistical models. In spite of our understanding of2 dimensional statistical models and 1+1dimensional quantum field theories, little workhas been done on these models out of criticality. In this thesis we focus on the Schramm-Loewner Evolutions and conformal field theoriesin vicinity of critical points. To this end we state the theories which the... 

Understanding of how fluid flow through porous media has many application in industry like Water filters technology and Gravel dams. also it’s very important in oil industry in areas like oil tank engineering. For doing this important thing many peoples tried to find out how fluid flows through the porous media they already invented the various kind of models, .the model used in this thesise is called pipe flow model which people use this model before but what I did have a little difference I used random lattice which people did not paid attention to it so the result of this model will be more trustable and close to what happens in nature. The result of this simulation showed us that the... 

To explain the dependence of sliding friction on or between the layers of wet sand, one first needs to have a rather good understanding of the elastic properties of wet granular material. Experimental work that has been done on the subject so far, has shown that these elastic properties have a peculiar dependence on the water volume fraction of the sand system. But till nowno theoretical model has been presented that could illustrate the physical causes of such findings. More specifically, these handful of theoretical models have not been able to explain the complex relationship between the shear modulus of sand and the water volume percentage. In this thesis at first the nature and...