Sharif Digital Repository

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... 

Due¬ to the volatile nature of material prices, projecting highway construction costs are proven to be very difficult, leading to many challenges in cost estimation process. Bid preparations as well as project planning and control processes are also negatively affected by the concerns about the inaccuracy of cost projections. There is a growing body of evidence that suggests the use of inaccurate cost estimate can result in bid loss or profit loss for contractors and hidden price contingencies, delayed or cancelled projects, inconsistency in budgets and unsteady flow of projects for owner organizations. Analysis of historical data indicates that a relationship between construction materials... 

This study develops a new framework for the assessment of land subsidence occurrence rate. The proposed framework considers the combined effects of saturated and unsaturated soil behavior. Accordingly, the biot consolidation theory was used for investigating subsidence in the saturated zone while the soil shrinkage curve, i.e., the void ratio-suction curve, was used in the determination of unsaturated zone subsidence. Specifically, groundwater decline and land climate change were used as the main contributing factor in investigating the land subsidence in the saturated and unsaturated zone, respectively. The approach presented in this study is based on using numerical modeling in PLAXIS 2D... 

With the advent of new technologies in everyday human life, issues related to the use of vehicles have become crucial subjects of investigation. In this context, vibrations transmitted from the vehicle to the human body, especially in terms of long-term health effects, have garnered special attention and significance. The main objective of this research is to develop a control system for the active control of vibrations transmitted to the human body. To achieve this goal, a 5-DOF model of the human body has been employed as the study system. Considering the uncertainties in the parameters and dynamics of this model, H∞ and µ-synthesis methods have been utilized for robust control design. The... 

Nowadays, horizontal drill string is a powerful tool for drilling in the oil and gas industry and an efficient method for constructing underground tunnels in cities. Despite its many uses, this method is exclusive to limited countries and is considered among the most advanced methods for drilling. One of the most important problems in the field of horizontal drilling is the existence of destructive axial, torsional and lateral vibrations. If these vibrations are not controlled, they can cause irreparable damage to the plant and drilling well. Among the introduced vibrations, axial and torsional vibrations have a very dominant effect on the drilling process, so the purpose of this research is... 

Non-compliance with engineering standards in the installation of reinforcement bars (rebar) in concrete structures leads to a reduction in both load-bearing capacity and seismic performance, potentially resulting in damage in the event of an earthquake. Accurate and rigorous supervision of rebar installation is, therefore, critical to minimizing seismic vulnerability. Traditionally, this supervision and quality control process is carried out manually by experts, which is often time-consuming, costly, and, in some cases, hazardous. Given the limitations of traditional inspection methods, such as their complexity and susceptibility to human error, it is evident that execution errors stemming... 

Through the last decades, due to environmental issues and to confine CO2 emission and also dependency to the fossil fuels, renewable energy resources has been developed. It’s been expected up to 2035, the renewable energy resources will be scaled three times and among those resources, the wind energy will stand prominently. Out of this king of renewable resource, the horizontal wind turbine has been subjected in this research. The focus of is to design the controller in third of a 2 MW turbine operation by which stable rotor speed and nominal output power to be attained. Besides, to enhance the accuracy of the wind turbine profiles, the TURBSIM software (At the National Renewable Energy... 

Through the last decades, due to environmental issues and to confine CO2 emission and also dependency to the fossil fuels, renewable energy resources has been developed. It’s been expected up to 2035, the renewable energy resources will be scaled three times and among those resources, the wind energy will stand prominently. Out of this king of renewable resource, the horizontal wind turbine has been subjected in this research.The focus of is to design the controller in third of a 2 MW turbine operation by which stable rotor speed and nominal output power to be attained. Besides, to enhance the accuracy of the windturbine profiles, the TURBSIM software (At the National Renewable Energy... 

In quantum communication,polarization degree of freedom is of particular importance, as polarization is used in many quantum key sharing protocols. During the transmission of photons, the polarization may be affected by environmental factors and change, for exam- ple, changes in tension and temperature disturb the polarization. In this thesis, methods of compensation for polarization change is investigated like by applying electric field, mag- netic field, strain,also a review of methods of measuring polarization disturbance and its compensation in quantum transmission lines, especially fiber optics, design and construction of compensators (electrical polarization controllers), based on... 

Due to restrictions on connecting beams to columns in steel structures when moment-resisting connections in two perpendicular directions are employed, the use of ordinary wide-flange sections or fabricated boxes becomes impractical. Application of Cruciform sections, especially when fabricated from two split-I sections (IPE sections) seems to be a reasonable solution to this problem. In this study, using Finite Elements Method and a commercial FEM software, the nonlinear behaviour of a number of cruciform columns, already tested by others, were modeled numerically. After reaching results in acceptable agreement with those of the tests, potentially suitable sections for fabrication of... 

Earthquakes can cause significant economic damage to society. These damages include direct economic damage, ie, the cost incurred by the community to rebuild damaged infrastructure. In addition, damaging the infrastructure, the earthquake reduces the level of infrastructure service, and thus, disrupts the businesses that rely on it. The consequences of such disruptions, such as a decline in the level of productivity and efficiency of firms, or an increase in the rate of unemployment and migration from the community, can cause indirect economic damage to society. The costs incurred to society by disasters can be reduced by adopting appropriate solutions. In many cases, however, the incentives... 

Earth dams are among the most important and widely used civil structures, playing a significant role in water supply, energy production, and flood control. Monitoring dam behavior provides professionals with insights into its performance over time. Dam displacement is a crucial factor in deformation and potential failure, making it essential to use various measurement tools to control deformation and numerous simulation models to analyze data and monitor the dam continuously. However, it is not always possible to record data regularly and without disturbance, and some dams may lack these measurement tools altogether. In such cases, new technologies like remote sensing can significantly aid... 

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... 

At each stages of oil and gas production, from the time of drilling of the wells to the state of production and development of the reservoirs, formation damage would hinders the oil/gas rate and causes high pressure drop in the drainage area. To eliminate the damage caused by the formation blockage, several remediation techniques are used, which are called well stimulation methods. The most common method for the past tens of years is matrix acidizing which lead to the improvement of the performance of the well. To optimize this operation, optimal acidizing design is needed, otherwise the acidizing process face failure and lead to blocking of the well through acid-induced damage. One of the... 

Occurrence of natural disasters such as earthquake could seriously damage most buildings especially those with insufficient resistance located in urban worn-out textures. In order to reduce unpleasant consequences of an earthquake, appropriate policies need to be considered to persuade the beneficiaries to follow retrofitting standards in the process of planning, designing, and construction of buildings. These policies shall be implemented through institutions in arbitrary or obligatory forms, by encouragement or penalty mechanisms. In order to consider these policies, first of all we need to identify the beneficiaries and their particulars. By studying and considering subjects discussed in...