Sharif Digital Repository

Exact Renormalization Equations (ERGE) are powerful non-perturbative tools to study the dynamics of Quantum Field theories, with respect to the change of energy. Putting cut-off on momentums of the system, is the specific regularization that is used to obtain ERGEs. This regularization breaks the gauge symmetry in the case of gauge theories. So the symmetry will be lost through the energy flow as well.Finding a gauge symmetry for a regularized system is the aim of this research. Also we have investigated the related ERGEs and the behavior of symmetry through the flow  

Most of the real-world systems can be modeled as closed loop systems which are made up of a LTI subsystem in the forward path and a memoryless nonlinear subsystem in the feedback path. Such systems are called “Lur’e systems”, the name of the first who introduced these systems. Because of the generality and the wide applicability of this type of systems, studying the stability of them has been notable and interesting to many scientists for a long time. Meanwhile, in recent decades, many scientists in physics and engineering sciences have been interested in applications of the fractional order systems and as a result focused on studying the features of the fractional order systems. An... 

Searching for images of the same object or scene in a large number of images is a major problem in computer vision. It has many applications specially in the search engines.For the goal of efficient image search, we need descriptors that are not only discriminative, but also short and need small amount of memory.In this thesis we analyze the image search methods in two categories: The first methods are based on converting the existed descriptors such as gist into a compact binary code. The second methods are based on building short descriptors, especially by some modifications in the framework of bag of features descriptor.Finally we will introduce a novel descriptor "bag of codes" which... 

In the first part of thesis, the electropolymerization of pyrrole was performed in the presence of new coccine (NC) as a dopant anion on the surface of the electrode precoated with SWCNT. The modified electrode was used to study the voltammetric response of salbutamol (SAL). The results showed a remarkable increase in the anodic peak current of SAL in comparison to the bare GCE. The surface morphology PPY/CNT/GCE was thoroughly characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques. Under the optimized analysis conditions, the modified electrode showed two linear dynamic ranges of 0.02 – 0.1 μM and 0.1-10 μM with a detection limit of 6 nM for the... 

The project scheduling problem is one of the classic problems in project management that includes a range of optimization problems. One of the limitations we face in project scheduling problem is the resource constraint limitation. In many studies in the literature review, problems are based on the false assumption that a resource can be transferred between activities of a project or different projects without spending time and cost. The resource availability method in many fundamental researches in the context of resource constrained project scheduling problem (RCPSP) is considered as resource investment problems (RIP); while in many real world projects resources are rented for projects and... 

The measurement of saturated hydraulic conductivity in conventional methods is based on the assumption of non-deformable porous media. However, this assumption is violated in most cases, especially when dealing with highly deformable soils such as collapsible and expansive soils. An alternative is to use flexible wall triaxial devices, yet the deformation characteristics during wetting and sample saturation are missed. This issue is of great importance in soils with considerable amount of volume changes (e.g., problematic soils). It should be noted that errors included in measuring sample volume changes, water inflow/outflow rates, and the creation of sidewall leakage are essential factors... 

Nowadays, wireless communications for multimedia purposes is widely spreaded especially due to video communication demands. One of important considerations in this area is to receive video stream with less effect of errors related to transition channel as well as optimal utilization of bandwidth. The H.264 is exploited as the most efficient video compression standard and because of its predictive nature of encoder and decoder, it is very sensitive to error propagation, so error resilient technics should be applied along with the video compression to reduce the visual impacts of error occurrence and propagation. In this thesis existing methods of video error resilience, video quality measures... 

Guarding terrains(or covering terrains) is a well known problem in the field of visibility and computational geometry. The aim of this problem is to select a minimal set of elements (such as points on terrain, line segment, points above terrain ,...),as guard set, such that every point of the terrain is visible from at least one member of the guard set.
This problem was introduced in 2-dimensions as art gallery problem. Various types of this problem have been defiend and studied in the literature. Guarding 3-dimensional terrains is an example of this problem. In 3-dimentional case, the guarded terrain can be modeled with triangulated irregullar network(TIN), as one of the surface models,... 

Nowadays, with progresses made in manufacturing technologies, it is possible to produce micro-scale products such as micro-electromechanical systems. Micro-motors are one type of these systems that can be used in such applications as power supply of electronic devices. To achieve a better performance, these systems must rotate at high rotational speeds (about one million revolutions per minute). At such a high rotational speed, vibrational analysis is highly crucial. The results of recent studies indicate the inability of classical theories of continuum mechanics to analyze the behavior of these micro systems. Therefore, in this research, the rotor of micro-motors are modeled using the... 

In this study, a new bioink was introduced for the production of tubular tissue structures for cardiac tissue engineering by bioprinter using the FRESH (Freeform Reversible Embedding of Suspended Hydrogels) method. The novel bioink that we used was a combination of cardiac extracellular matrix (cECM) and oxidized alginate. The cardiac extracellular matrix was used to increase the biomimetic of the printed structures to the actual tissue of the body, and also to create sites for cell adhesion, and to improve cell growth and survival. We used alginate oxide (oxidation degree: 5%) to increase the mechanical properties of the tissue. Alginate oxidation has been due to extracellular matrix (ECM)... 

The use of concrete and steel composite structural systems has been extensively studied both numerically and experimentally. Composite concrete and steel beams consist of a steel beam on which the concrete slab is constructed using shear connections. The performance of concrete slabs and steel beams in steel composite concrete structures is generally provided by welded shear connectors on the upper flange of the steel beam. In this study, a more accurate model in numerical form will be conducted to investigate the effect of shear connectors installed in the composite beam in the critical area of beam to column connection, which is considered as a protected zone. The main objective of this... 

Detection and Tracking objects in various environmental conditions is a challenging task in computer vision. Abrupt changes in illumination, object size and noise level make this task even harder. Due to these problems, it is somehow impossible to propose a fully functional system for tracking every type of object. In this thesis we propose a new method for detection and tracking vehicles in traffic scenes. The problem is solved by dividing it into two parts: at First we have evaluated more than ten state-of-the art trackers, the final multi-vehicle tracker is chosen, and then, like any other object tracking method, we have used a unique identiy for each vehicle. This traffic identity is... 

Emotion recognition from speech signals has become one of the most popular researches in recent years. In order to increase human-machine interaction, a proper connection must be established between them. To achieve this goal, a machine must be able to understand the situation and respond accordingly. Part of this process involves understanding the user's emotional state. In recent years, various methods have been proposed to increase the efficiency of the speech emotion recognition system. These methods include collecting various audio databases, extracting efficient features from speech signals, using feature selection algorithms, designing different classifiers, as well as combining...