Sharif Digital Repository

Environmental issues and energy crisis have led the world attention to the renewable energies; especially wind power, since they have low cost and high reliability. One of the most challenging areas of studying for wind power is to increase the capacity of wind turbines. As a result, over the years, wind turbines have got progressively larger. Vibration is one of the problems that reduces the life and efficiency of wind turbines; and the growing size of the blades has worsen this problem due to the importance of nonlinear effects in large scale wind turbines. Researchers have been constantly working on this issue in order to make the wind turbines more efficient. In this research, a... 

The purpose of this thesis is sliding mode control of a roll-pitch seeker by considering the zenith pass problem. This problem takes place when the target appears in front of the seeker’s head. First, the mathematical model of the roll and pitch frames is obtained by the Newton-Euler equations of motion. Then, a MIMO sliding mode controller is designed. The performance of the controller is investigated in the presence of model uncertainties and seeker disturbances. The results indicate that the designed controller is robust enough and provides a suitable performance in the stabilization, tracking and guidance loops.
 

Due to largre number of patients treated by dialysis and its significant increasing progress, dialysis efficiency and patients' life quality are of great interest.Dialyzer, the dialysis beating heart, has the role of cleaning blood by removing toxic solutes and balancing volume of bood's water through hollow fiber membranes. In this thesis, firstly we tried to focus on performance characteristics of dialyzer by studying effective parameters influencing dialyzer efficiency and ultimately we set two important performance characteristics, ultrafiltration coefficient and solute clearance, as our goal parameters for evaluating dialyzer's yield. To this purpose, we designed an experimental set... 

Nowadays, economical extraction of oil and gas, and their products is an important issue for many countries. Up to now, vertical wells have been used for oil extraction but some wells exist that they cannot be reached by using vertical drilling; for example the wells under a sea. Therefore, this makes the governments and scientists determined to find a new way to reach them. Horizontal drilling is one of the new ways to reach such worthy wells. In this project, dynamics of the horizontal drill string is studied. Then, according to the forces that affect the dynamics of drilling, its vibration is analyzed. After finding the boundary conditions and normal modes of the system with using mode... 

Renewable energies and their various types have been recognized as sustainable solutions to address the challenges arising from increasing energy consumption and environmental issues. The use of wind energy as one of the renewable energy sources has particular advantages, considering it as one of the most sustainable energy sources. One of the key factors in wind turbine development is the diversity and multiplicity in their structural designs. Therefore, the design of wind turbine structures with characteristics such as suitable strength, high energy efficiency, optimal cost, and high reliability is of great importance. By employing various sciences such as vibrations and optimization in... 

Air conditioning systems are one of the main parts of buildings, and their performance is very important, especially during the peak heat and cold days, both in terms of providing comfort area for the people and in terms of energy consumption. These systems control the temperature and humidity inside one or more target zones using heating, cooling, humidification, and dehumidification processes. One of the most common solutions to optimize the performance of air conditioning systems is the use of control systems. In this study, a nonlinear multi input-multi output dynamic model of a two-zone variable air volume & temperature air handling unit is considered for operation in the summer season.... 

The microstructures of stainless steels consist of an austenitic matrix with almost continuous network of primery carbides.This class of steel had replaced the traditional super alloys with a reduction in costs and has similar properties under conditions of creep, which is one of the principal degradation mechanisms leading to failure in service at elevated temperaturs , therefore, their mechanical properties such as tensile strength and creep resistance are particularly important in hot deformation. Recently the effects of temperature and aging time on static strain aging in worked stainless steel have been investigated. In this study the deformation behavior of HP-series austenitic... 

In this M.S. dissertation numerical study of slinger fuel distributer has been studied. This type of atomizer has been used in mini turbojets like Teledyne CAE.
The main purpose of this work was obtaining spray structure of slinger atomizers. This goal was achieved by implementing a UDF code in FLUENT® software to model the primary atomization that include variation of fluid from exit of slinger disk bores till formation of primary droplet. In FLUENT® the DPM method and its ability to utilizing Lagrangian approaches have been used. The result of this model is validated by the data from experimental test that can be found in Articles. This is the first time that spray structure of slinger... 

Electric vehicles (EVs) will be used rampantly in future transportation system. Although the uncontrolled charging of these EVs will be threatening for the stability and sustainability of the grid, a well-suited energy trading policy may provide a number of beneficial services to the grid as well as preserving the sustainability of the system along with heightening the performance of operation. In this paper, by taking advantage of block rate tariff, a wholesale pricing policy is introduced. A multi-objective approach is utilized to address the cost reduction and load levelling services, concurrently, in order to guarantee the profits of the both the grid and EVs. Due to the high... 

The process of injecting acid or acidizing, is one of the most common ways to stimulate oil and gas wells. The purpose of this process is to increase the productivity of the well by increasing the permeability of the reservoir rock around the well. This is especially important in carbonate reservoirs due to damage to the formation and low intrinsic permeability in some places. In order to minimize the effects of structural damage, conventional wormhole channels are created to pass through the injured area. One of the important factors in acid validation is achieving optimal injection rate, which means obtaining the highest permeability with the lowest amount of injected acid.Numerous... 

The purpose of this study is to present a suitable model for calculating the costs imposed on society due to deaths and injuries due to infrastructure failure due to earthquakes, which is used in the analysis of community resilience. Much research has been done to date to calculate the economic costs of infrastructure failure. However, no suitable analytical framework has been provided to quantify the costs of deaths and injuries to people due to earthquake failure. Previous research has provided methods such as the value of statistical life to quantify the social costs caused by accidents and environmental pollution. However, the literature review results in the field of seismic resilience... 

The economic activities in a country involved with depletion of natural resources and emission of pollutants and gases to the environment. Depletion of exhaustible resources and environmental pollutions are two determinants of sustainability of development. The present research work is aimed at studying the sustainability of Iranian economy in 2009. The analysis of sustainable development of economy is based the concept of exergy, exergy efficiency and ecological exergy efficiency. Exergy efficiency is the ratio of the exergy of a product in economic activity to the exergy of input streams to that section of economy. Ecological exergy efficiency is defined as the ratio of exergy of product... 

In this project railway industry is introduced as an optimal alternative for transportation in this country. To select the best choice, four railway technologies that have commercial capacity are presented and the most appropriate one is selected with respect to several criteria, including fuel consumption. The purpose of this thesis is to present the best technology in order to improve Iranian railway transportation by considering the shortage of fossil resources as well as pollution.In this project,the copmparison of alternatives and assessment criteria for best technology selection is done by Analytical Hierarchy Process (AHP) and the questionaries are filled out by industry and... 

In this study, integrated navigation systems that utilize velocity-matching algorithm and are used in automatic landing of Unmanned Aerial Vehicles (UAV) are investigated. At first, the accuracy of the navigation system in the landing phase is analyzed and the relationship between the accuracy of inertial sensors, flight parameters and the accuracy of the navigation system is derived analytically. Then, by integrating the dynamic model of the UAV and the inertial measurement unit, a new algorithm for navigation of fixed-wing UAVs is presented. The integration mechanism of the proposed algorithm is tightly coupled; hence, it is capable to eliminate the errors of UAV model and inertial system.... 

Sanctions are one of the most important variables influencing Iran's domestic and international decision-making and have had many effects on Iran's economy and politics in recent years. Iran's ability to influence the oil market and harm the interests of the sanctioning countries in this market raises the question of whether such a capability could affect the outcome of sanctions and lead to the withdrawal of those sanctioning countries. A theoretical examination of the issue of sanctions using game theory shows that if the sanctioned country is not able to retaliate in areas other than the disputed issue, the sanctions game may not reach an equilibrium in which the sanctions are lifted but... 

Governments and organizations need to classify network trac using deep packet inspection systems, by protocols, applications, and user’s behavior, to monitor, control, and enforce law and governance to the online behavior of its citizens and human resources. The high capacity of machine learning in the classication problem has led trac monitoring systems to use machine learning.The development of machine learning-based trac monitoring systems in the eld of research has reached relative maturity and has reached the border of industrial, commercial and governmental use. In the latest trac classi-cation studies using neural networks, as the most ecient machine learning methods, the classication... 

Many lattice-based public key encryption schemes are forced to use long keys. To deal with this problem, structured lattices such as NTRU can be used. Lattice-based searchable public key encryption schemes are no exception. Furthermore, in most existing searchable public key encryption schemes, it is assumed that the user searches documents with only one keyword. However, using a conjunctive keyword search, we can search for documents containing several keywords by executing the trapdoor generation algorithm only once. On the other hand, in most of the published searchable public key encryption schemes, storing and searching encrypted keywords are responsibility of a central entity called... 

The human brain can be described as a dynamic system with multiple subsystems interacting with one another and multi-channel observations of these subsystems are available. The modeling of a system from its observations allows us to gain insight into how its various components interact with one another and also provides intuition about the desired system. Hidden Markov Model (HMM) is a probabilistic model with hidden states that is suitable for modeling these types of systems. Multi-channel observations are available from several subsystems interacting with each other within a general system. In this case, it may be necessary to develop more comprehensive models incorporating multi-channel... 

Exoskeletons, or wearable robots, are electromechanical devices that have become the focus of academic and industrial research in recent years, and their applications in power augmentation have increased. One of the most important challenges of these applications is controlling the robot and synchronizing it with the user. The close interaction of the robot with the user and the change of movement pattern between different users and different gait cycles show the importance of estimating the user's movement intention, but the need for online method of estimating the movement intention and the complexity of accurate dynamic modeling has caused researchers to use reinforcement learning (RL) in...