Sharif Digital Repository

Nowadays, one of the most challenging issues concerning the manufacturing industries is the shortage of available resources and their increased costs. As a matter of the fact, for these industries, optimizing the processes is not something to be ignored and one of the most important goals is reducing the costs of manufacturing and increasing the profits of sales. On the other hand, in actual situations, due to the complexities of optimization problem and numerous calculations, the classical methods would be limited to very simplistic cases in which most of the practical changes are ignored. In such problems, the need to use strong optimization techniques like the genetic algorithm is evident... 

In this research, we want to address the question of universality classes in BTW and Manna sandpile models. So far, number of works has been devoted to this issue but the the answer remained unsolved. We will try another approach to study this question by perturbing the original models. To this end, we introduce three models that have evolution rules between BTW model and Manna model. By simulating this models, we observe that in the presence of perturbation, the probability dis- tribution has two regimes of behaviour which are separated by a new characteristic scale. The regime of small avalanches is described by the exponent of BTW model and the regime of large avalanches by the exponent... 

Existing face forgery detection methods mainly focus on certain features of images, such as features related to image noise, local textures or frequency statistics of images for forgery detection. This makes the extracted representations and the final decision depend on the data in the database and makes it difficult to detect forgery with unknown manipulation methods. Solving this challenge, which is called the generalization challenge in artificial intelligence literature, has become the main goal of researchers in this field. In this thesis, the focus is on extracting effective features for success in forgery detection and preventing the performance of the forgery detection network from... 

Introduction: Today, backward and forward scattering tomography of dispersive medium is of great interest because of its broad applications, especially in medical imaging, of breast cancer, Distinguishing different tissues of the body from each other is one of the necessities. Increasing the quality of the image by just a few percents has great improvement on the tomography resolution.
Materials and Methods: In this project we made phantom of the tissue and tumor from Intralipid 10% plus Agarose and Indian ink for soft tissue and plastic fibers as tumor having birefringence factor of 0.001.After putting the plastic tumor in soft tissue phantom, the polarized white light and a digital... 

Investigation of electrohydrodynamic behavior of fluids under electric fields is a challenging and impressive matter in condensed matter physics. In this thesis, inspired from previous works on liquid film motor, a new phenomenon has been observed and its properties has been investigated.Here by making a new device named “Liquid Film Electric Generator” we produced potential difference on the rotating suspended liquid film under electric field. The power conducted by electrodes has been generated on the surfaces of the film. By this method, under electric field of 1000 V/cm, micro-watt electric power can be achieved on a liquid film of diameter of about 1 cm.We explained this phenomenon on... 

In many regions of Iran, arid and semiarid climate and increase of water consumption, lead water managers to use optimal operating of water resources systems. During periods of drought, when inflows to the reservoir are low, it may not be possible to satisfy the target delivery (planned demand), and shortage occurs. Also, During periods of drought, the underground water resource’s pollution and inordinate consumption of underground water resources, increase density of water pollution. These reasons always appoint water resource planner to develop models for determine optimal surface water resource operating rules. Using of hedging rules that are attended by many researchers in these... 

The classical approaches of drought analysis are performed using historical records and univariate statistical methods. In the use of historical records it is assumed that statistical characteristics of droughts will be exactly repeated in the future (the assumption of stationarity) and in the use of univariate methods it is assumed that drought variables (e.g. duration and severity) are independent; while on the contrary, global warming changes long-term climate patterns, which is called climate change, and also drought variables have significant correlation. Thus, results of classical approaches of drought analysis have uncertainties.The primary objective of this thesis is to propose an... 

Using thick plates is common in different industries including ship and pressure vessel manufacturing.In this research a plate forming method called line heating is examined. This method requires basic equipment and is very economical.Heat transfer between gas torch and plate is studied in more detail. Impingement jet model is used to simulate the effect of torch on plate. Velocity and temperature fields of exiting air are calculated in Fluent, a commercial software. Then heat is transferred between hot air and plate, which is related to velocity field and both temperature distribution of air and plate. In this method torch moves along the plate. In order to simulate this movement, a moving... 

Sheet Metals are widely used in different industries such as ship building and pressure vessels. One important subject in these industries is to create the desired sheets through line heating process. Designing the heating lines in order to get the desired shape with the sufficient accuracy has always been a concern for the engineers in this process. In this thesis, the Strain-Based Method in designing the heat lines for creating special surfaces is discussed. Two sets of surfaces were considered. The first one is 2D surfaces set such as cylindrical surfaces. The second set is 3D surfaces set. The examples of such surfaces are double-curved surfaces such as a pillow and a saddle shape. The... 

In recent years, two-layer sheets have been used in various industries. In this research, the formability of a two-layer sheet which is made of 1.35 mm steel and 0.45 mm copper sheets has been studied. The two-layer sheet used in this study was made by explosive welding method. In order to investigate the formability of the sheet, forming limit diagram was determined. First, Marciniak-Kuczynski (M-K) model was used. In order to determine forming limit diagram using this method, the two-layer sheet was equated with a single-layer sheet and MATLAB software was used. The two-layer sheet was also modeled in finite element software ABAQUS. In order to determine the forming limit diagram, Nakazima... 

Scattering theory on locally symmetric space first was studied by Peter Lax and Ralph Phillips. They studied the and develop scattering theory on it. Without the Fourier analysis tools this theory was completed with a lot of computations. In this thesis first we try to construct Fourier analysis by definition Fourier transform then by means of new tools we prove very short version of scattering theory on locally symmetric space . In general case for studying scattering theory we need firs spectral decomposition of Hilbert space of square integrable functions locally symmetric spaces of rational rank one is achieved by quotient of symmetric space where G is Lie group and K is maximal... 

Despite of existing advanced routines and concepts of Maintenance, which are imported along with Metro System hardware, and valuable experience of maintenance personnel, which has been gathered during years of operation, there are some undeniable shortages in current Maintenance Policy of Tehran Metro. These shortages can be classified in two major groups: first, lake of reasonability in performing maintenance tasks and second, general reluctancy about runnig scientific works. Treating those two deficiencies, can improve the performance of Tehran Metro Maintenance System dramatically. Above mentioned shortages can be seen in whole Maintenance System of Tehran Metro, for the reason of having... 

According to the rapid growing in communication devices, users need higher rates for their usages. Fiber optics is one the major choices to support such rates. One of the simplest and cheapest networks is Local Area Network (LAN) as a Passive Optical Network (PON). In these networks, some computers are locally connected to a passive optical device and communicate through it. Multiple access to a shared channel is an important task in such a network. In this thesis, Code Division Multiple Access (CDMA) is used and a new algorithm for Multiple Access Control Sublayer (MAC) based on scheduling will be developed to improve Quality of Service (QoS) and stabilize the network.
In the scheduling... 

In comparison with flood, drought is a phenomenon that happens gradually and causes significant changes in water resources, environmental and economic damages specially farming. Due to random features of involving factors in occurrence and intensity of drought, it is assumed as a random process. Drought forecast has an important role in water resources management and control. Data validation, in drought forecast, is a matter of utmost importance. In recent years, satellite data is a type of data that has been used. Markov chain has been used here because one of the features of this method is that occurrence of each variable in current stage is dependent on its previous stage. On the other... 

Nowadays, by development of technology and population, rivers have been faced environmental issues. In one hand, due to the several factors that can affect rivers pollution, it is not easy to propose a comprehensive solution for the above mentioned issues, while, on the other hand, it is necessary to address and resolve some of these issues as soon as possible. Considering rives as a system, there are lots of economic, political and quite a few other factors which try to change the condition to their own interest. In order to find a solution that satisfies all the effective parameters up to a certain limit, a mathematical tool, called the Game theory method, is utilized. In this research, we... 

Oil and gas industries are always considered as one of the most polluting industries in the world. Many pollutants are emitted from the industry into the environment every year. Equipment’s leak and flaring off additional gases produced by various processes of oil and gas production are the main sources of waste in these industries. In order to control these hazardous wastes, it is necessary to provide effective solutions and make appropriate decisions so policymakers will be able to implement policies in order to reduce the emissions of air pollutants. In order to reduce the emissions, it is necessary to conduct the correct and reliable methods and have sufficient information about the... 

In this dissertation, a proper closed-form representation has been presented for the site specific indoor radio-wave propagation. Characteristic Green’s function (CGF) technique is used to obtain the integral representation of the Green’s function of a rectangular 2D room with dielectric slab walls. Based on numerical simulations, this method provide quite accurate results for wave propagation in the interior region (away from the walls) but the error increases for source or field points near the walls. The presented integral form of Green’s function has slow convergence and computed using Real images, complex images and rational function fitting methods. An error of less than 20 percent is... 

Despite of passing many years from invention of Computational Fluid Dynamics (CFD), simulation of the fluid-solid interfaces and free surfaces are still completely challenging and progressive problems. In addition knowing and understanding nanotechnology huge applications,modeling of nano-fluids have been became a priority for researchers. Adding importance of Non-Newtonian fluids (especially polymeric solutions) to this two subjects, triangle topics of this research becomes vivid. In this research tried to consider and examine behavior of Newtonian,Generalized-Newtonian, Viscoelastic and nano-filled viscoelastic fluids in one and two phase mediums. we followed mesh free methods which are... 

Today, energy has a great impact on the economy, political relations, prosperity, and lifestyle of human societies. Energy sustainable development has become inevitable because of factors such as increasing population growth and as a result, increasing the energy consumption, consuming more energy from fossil fuels, decreasing in reserves of fossil fuel resources, environmental damage caused by the burning down of fossil fuels and greenhouse gas emissions,high cost of energy from burning fossil fuels.Generally, the sustainable development isall steps in order to comply with economic development and protecting the environment, resources and living standards. Considering that a large part of...