Sharif Digital Repository

Ant algorithms are optimization algorithms inspired by natural behavior of real ants, which can find the shortest path between nest and food. These algorithms are used to solve numerous complex optimization and combinatorial problems. In recent years, ant algorithms have been used in image processing, specially in edge detection. Edge detection being important and having applications in image processing, several edge detection algorithms have been presented. Our goal is to study edge detection processes based on ant algorithms. Four algorithms recently proposed in the literature are implemented, and the results presented by their authors are verified. Furthermore, implemented algorithms are... 

Image processing is very important in several applications. Here we use a rectangular grid for image processing. Other approaches exist in the literature. One new approach is to change the grid from rectangular to hexagonal, due to its various advantages over the latter. Main advantage of the hexagonal structure in image processing is its resemblance with the arrangement of photoreceptors in the human eyes. The change in arrangement amounts to requiring less pixels. There is no inconsistency in pixel connectivity and thus angular resolution is higher in this arrangement. Our goal here is to study lossless compression algorithms for images with hexagonal pixels. First, we consider the... 

Skin cancer is a common type of cancer in the world. Melanoma is considered as the deadliest form of human skin cancer that causes approximately 75% of deaths associated with this cancer. However, melanoma is curable if diagnosed in an early stage. Due to high visual similarities and diverse characteristics of lesions, it is a challenging task to differentiate between different types of skin lesions. Therefore, it is worthwhile to develop a reliable automatic system increasing the accuracy and efficiency of pathologists. Here, we propose sparse representation and dictionary learning based methods for skin lesion segmentation and classification. First, we review the steps of a computer aided... 

By using an encoding scheme based on Algebraic Integers (AIs), we study in this thesis how to map the real numbers needed in the computation of the FFT to integer numbers, in order to prevent error production and propagation throughout the intermediate stages of the FFT computation. To reconstruct encoded data, a decoding stage is to be used at the end of the FFT computation. AI-encoding poses two challenges; how to determine suitable AI bases and an unwanted growth in the number of data passes. This research work, firstly, determines an appropriate FFT architecture, and then, proposes a dedicated architecture based on AI-encoding. The basic and also the proposed dedicated architecture are... 

Design and production of a drug is a very time and money consuming process. It takes more than a decade and about 2.5 million dollars on various stages to design a drug. Attempts to reduce this cost and time to market will make drugs available to customers at a more reasonable time. Some stages such as animal testing phase and clinical trials, can not be replaced and must take place in practice. Fortunately, some laboratory steps are interchangeable with software algorithms. These algorithms can significantly reduce the cost and time to market of the drug if they are accurate enough. On the other hand, the remarkable results of machine learning, in particular, Deep Neural Networks, in areas... 

Nowadays, power systems and substations are the most important components of the vital infrastructure of a country, which handle the production, transmission and distribution of the electrical energy. Automation systems increase the efficiency of the power industry while making remote control possible, but the use of computer-based control systems is a potential field for cyberattacks which may cause equipment destruction and electricity network destabilization. One of the main requirements for the utilization of digital substations is the synchronization between different equipment used in it. Several algorithms and protocols have been proposed so far for time synchronization in distributed... 

Micro-Robotics is implemented by researchers inclusively in last decades in different fields such as, biolotechnology, space, army and medical engineering. However, micropositioning is the main challenge in such projects, since determination and control of micro-robot’s position for drug delivery, artificial insemination and other medical applications are too significant. In this thesis, a method for controlling a microswimmer’s position in two dimention by an external magnetic field has been proposed. Modelling of magnetic field and magnetic gradient are some important challenges due to the fact that in control loop, a fast and optimal model for estimation of magnetic filed and gradient is... 

The use of aluminum and its alloys in different industries is increasing. To increase the deformability of Aluminum alloys, it is usually deformed at high temperatures. In Such working conditions, the chemical composition, temperature of deformation, strain rate and high temperature activating phenomena will affect the microstructure and final properties of the material. In this thesis the hot and cold deformation behavior of a Al-11.77%Si-0.2%Mg are evaluated. In the cold deformation, the alloy was first annealed and then ECAEed. The mechanical properties and the related microstructure were evaluated via the microhardness test. The results indicated that the alloy could not be deformed... 

Capsule endoscopy is a minimally invasive diagnostic technology for gastrointestinal diseases providing images from the human’s digestion system. Developing a robust and real-time localization algorithm to determine the orientation and position of the endoscopic capsule is a crucial step toward medical diagnostics. In this thesis, we propose a novel model-aided real-time localization approach to estimate the position and orientation of a magnetic endoscopic capsule swimming inside the stomach. In the proposed method, the governing equations of the motion of an ellipsoidal capsule inside the fluid, considering different hydrodynamics interactions, are derived. Then, based on the dynamic... 

The IEC61850 Standard was introduced for IED, Intelligent Electronic Device, in a power substation so that different devices from different manufacturers could work together. Each of these devices must be configured to start communication. Chapter 6 of the IEC61850 Standard discusses the configuration language of these devices, SCL, Substation Configuration Language, as well as how to write it in detail.A failure or denial-of-service attack can occur in a power substation if a tampering or embedding a breach in devices’ configuration occurs. To discover such attack, one can model the behavior of all the components in the SCL language using a language describing the behavior, and then compare... 

In present thesis, the effect of cosmological constant, Λ, in bending of light by spherical symmetric mass has been studied. At first we obtain the Schwarzschild-de Sitter solution as spherical symmetric solution of General relativity field equations with cosmological constant, without we suppose the solution is static. Then we obtain gravitational lens equation by considering the space geometry and we benefited from several approach to specify the contribution of cosmological constant to the deflection angle. Furthermore we put new upper bounds on the value of the lambda independently of cosmological constraints. Finally for study the contribution of lambda in gravitational lensing... 

Planning safe rendezvous and docking trajectories between two spacecrafts has a high importance in the space applications. In order to make two spacecrafts moving in different orbits closer, two stages must be completed simultaneously: First the implementation of rendezvous maneuver which deals with the generation of control/guidance commands leading to trajectories that lead the chaser towards the target. Second the docking maneuver incorporation which makes the two spacecrafts closer with the relative zero attitude. Various approaches have been dealt with till now using the analytical and numerical approaches generally considering rendezvous, not the docking maneuver. These approaches... 

Today, the global environmental restrictions as well as; energy problems have directed researchers toward developing ideas of producing a clean liquid fuel from coal or natural gas as a major research topic. In this regard, a special attention is paid to the dimethyl ether (DME) as a clean material containing 34.8% oxygen possessing enough positive potential to replace the diesel and LPG fuels. One of the most economic routes for producing the DME is known to be the direct conversion of the synthesis gases and carbon dioxide first to the methanol and then its dehydration to the DME. Moreover, the DME is not limited to a particular country or resource area since small reservoirs of natural... 

In recent years, ability of computers to recognize human actions, because of numerousapplications, has attracted scientists. Surveillancesystems in house, work and public places, human computer interaction, study of human movement problems, remote supervision of ill or old people and sport training are only some of the applications. In this thesis 10 actions are considered. These actions are Walking, Running, Galloping side, Bending, Jump jacking, Jumping, Jumping in place, Skipping, Waving one hand and Waving two hands. All actions exist in Weisemann dataset so this dataset is used as training and testing dataset. Here important objectives are recognising human action so that it is... 

We have tried this for the first time to reperesent a comprehensive description of the evolution of a perfect fluid in inhomogeneous relativistic models.We solve Einstein equations using numerical methods.In this procedure we can evaluate the effect of pressure in perfect fluid evolution.Also we look at the behavior of the various horizons, and in the end we will present a cosmological model to a black hole  

Knowledge about travel demand patterns is an important requirement for strategic planning and management of urban transportation networks. Use of theoretical trip distribution models such as growth, gravity or intervening opportunities, estimation with the help of questionnaire surveys and development of volume- based O-D estimation methods have been major fields of scientific efforts in recent years.Rapid changes in land use and transportation networks especially in developing countries has raised the importance level of knowledge about changes in travel demand.Traditional approaches are costly, time consuming and suffer from inaccuracies, so,...