Sharif Digital Repository

Industrialization has brought about air pollution which is one of the most important factors threatening human health. The most efficient method to improve air quality include preventing the emission of pollutants by making laws and regulations. In order to set appropriate regulations, there needs to be a correct understanding of the problem. The purpose of this research is to identify such factors and create a correct understnding of the problem in Iran by constructing a Model of Iranian air qulity. The model used in this research, CMAQ is one of the most comprehensive and state of the art models in transport of pollutnts and chemical reactions in the atmosphere. The inputs into CMAQ... 

As mobile multimedia services become popular, it is expected that mobile devices provide more multimedia functions such as real-time video playback, TV watching, and video games. However, real-time video applications running on mobile devices are heavily constrained by their limited computing power, compared to high-end consumer devices. In order to playback a high resolution video on mobile devices, a typical approach would be to fully decode video bitstream into the pixel-domain, and then spatially downscale the decoded frames at a desired resolution. However, due to large computation and memory required for decoding followed by downscaling, this approach is unsuitable for real-time video... 

Free and Open-Source Software (FOSS) is grown rapidly and many researches are conducted to study FOSS developments. The studies aim to help FOSS development by finding bugs, analyzing developers, modeling evolution of software and categorizing them. Finding proper developers or key developers of each group is essential in developing software, recommend developers and assigning bugs to proper developers. Community detection detects groups of nodes having dense connections. The groups represent developers which cooperate closely on developing FOSS. The thesis proposes a method based on evolutionary algorithms and topological analysis to detect communities in open-source software development... 

In recent years, advances in computer technology and widespread use of computers have alleviated the wide usage of network-based services in contrast to traditional services like radio and television. These facilities made it possible to integrate various type of services with adding new features whenever is necessary.
Video has specific characteristics that its transport over the network imposes some challenges to service providers. In the literature several solutions have been offered for solving the problems of network-based video services. A set of these solutions use routers and other network assisted devices to gather information for better transportation. These router-assisted... 

This thesis discusses design and, simulation procedure of a mono-injector combustion chamber, in order to study and, analyze the ignition and, stable combustion characteristics, for Kerosene and, liquid Oxygen cryogenic propellants. Accordingly, the design and, simulation for the combustion chamber, for Kerosene and, liquid Oxygen propellants is performed. Also, effective parameters on the flame taking place are studied, and finally an algorithm for design and, properties study of cryogenic propellant ignition is presented  

In the current study, the dispersion of four major air pollutants, sulphur dioxide, nitrogen oxide, carbon monoxide, and particulate matter from gas flares of an oil field, in Iran, was investigated for year 2011 by application of a conventional steady state Gaussian dispersion model, AERMOD. Two scenarios were applied in modeling, first application of flare parameters based on technologies that exist and the other one using new technologies in flares such as steam assisted with better combustion efficiency. Due to the complexity of meteorological parameters in modeling area, CALPUFF model was used in this study. CALPUFF which is a more advanced model that considers the effect of... 

Gas turbine discs must be tested before they are installed in an engine for their mechanical properties and resistance to crack growth. Such test is usually done in a device called Spin Tester in which high rotational speed and temperature fluctuations can be applied to a disc. In this project a plug-in software is developed by which life of gas turbine discs under sever fluctuations of rotating speed and temperature can be assessed. The tests performed in the software are; stress analysis, fatigue analysis, crack initiation point, and finally 3-D fatigue crack growth path. The software is written using Python programming in ABAQUS. The software adds a sub-menu in ABAQUS Plugins as "Engine... 

Slosh phenomenon is described as the motion of the fluid’s free surface in a tank or partially-filled container. This motion can induce undesired forces that can change the path of a vehicle. In some liquid carrying vehicles these undesired changes is sensed by the driver or control system and can lead to instability. Some examples of this phenomenon are aircrafts, rockets, ships and fuel carrier trucks.
In this project, a coupling between the dynamics of the vehicle and the contained fluid is implemented for in depth understanding of the interactions. This is done by Co-Simulation. With the help of Co-Simulation, corrective control actions can be taken and the design of more powerful... 

The Cu2ZnSnS4 (CZTS) quaternary compound, with suitable optical and electrical properties, is one of the most interesting materials for absorber layer of thin film solar cell. Since all constituents of CZTS, are abundant in earth’s crust and non-toxic, it is a proper replacement for the materials like CdTe and CuInSe2. The CZTS pellet was synthesized by the solid-state reaction and deposited on soda lime glass substrates by pulsed laser deposition (PLD) method. PLD technique has the advantages of offering stoichiometric preservation during the materials transformation from target to substrate and good crystallinity due to the highly energetic species. CZTS has was deposited in order to... 

Most of dynamical models in the real world, have various restrictions and complexities in their structures. These constraints make the controller design much more difficult. In this work, it has been tried to design the controller for two kinds of common dynamical systems in the presence of these restriction by using the fuzzy logic systems. Several restrictions are investigated in this project such as unknown dynamic of the model, unmeasured state variables, unknown control directions, existence of time delay in the input and the state variables, input saturation and controller singularity.The backstepping technique and the dynamic surfaces control approach have been used to design the... 

In this thesis, we study the problem of guarding art galleries with sliding cameras and k-transmitter. This problem is a new version of classic art gallery problem, which the goal is covering the entire region with minimum number of guards. In early version of art gallery problem, usually point guards with 360 degree vision were used, but in this thesis we use sliding cameras instead. This new guards specified by an orthogonal segment which entirely settled interior of polygon and can see up to k walls. Based on this two notions (sliding camera and k-transmitter) we say that a guard can see point p, if the intersections number of normal segment through p to corresponding segment of guard... 

Windows are the main source of energy loss in buildings. One way to improve thermal performance of insulation windows is to use inert gases in them. Some of these gases are expensive and there is a need to find the optimum mixture of theses gases with cheaper ones in order to reduce the initial price of these windows. In the first section of this research through calculating the U-Value, thermal performance of sample windows which are filled with different mixtures of Argon, Carbon dioxide and Air is investigated in order to determine the optimum mixture of them. For this purpose a two and a three glazed sample window was prepared and each one was filled with different ratios of the... 

Spent fuel assemblies are kept in spent fuel maintenance pools, designed at the vicinity of the reactor, after consuming. As capacity of these pools are limited, fuel assemblies should be transported to outside of the reactor building for maintenance. Transportation cask is used for this reason which is Russian type, named TUK-13, at Bushehr Nuclear Power Plant. The aim of this project is to ensure proper removal of heat from the transportation cask(TUK-13). For this purpose, numerical computational fluid dynamics method is used. The software used in this study is the Comsol. The temperature range suitable for any part of the chamber is different; but the most sensitive and the most... 

In this thesis, study the design of a compact low-cost integrated time modulated array(TMA). In TMAs, a switch is used instead of a phase shifter, which reduces the area, complexity, power consumption and the final price of the array. The TMAs uses the switch as a control element for array weighting that causes beamforming and beam steering. For the lower cost, designed IC compacted as small as possible and use inexpensive CMOS 180nm technology of TSMC fabrication. Initially, maximum layout size forced 0.7 by 1.5 mm2. The proposed switch type is SPDT that one of its output paths terminated by a matched load and another end to a pad and then by a bond wire connected to an external board that... 

The economic effects of large dams that were constructed during 1370-1393 in Iran are explored in this thesis and their effects on agriculture and welfare of their own district and downstream districts are analyzed. Ordinary Least Squares (OLS) method is used to investigate these effects and for more accurate results, we control for geographical variables and rainfall. The results of this study show that dam construction leads to higher agricultural yield, production value and irrigated area in the dam’s own district; but it doesn’t affect yield, production and irrigated area of downstream districts. Also dam construction results in planting more water-intensive crops in their own district... 

Automatic theorem proving has been attractive in artificial intelligence (AI). The aim of the usual automatic theorem proving methods is applying of the mathematical logic rules to decide intelligently, and reasoning automatically. In contrast the aim of our research is to apply computers abilities and artificial intelligence methods to simulate human abilities to prove mathematical theorems. For this purpose, we invent a typed formal language (TFL) to describe mathematical theories. The language must be clearly computable and should cover the First Order Logic (FOL) and the usual mathematical sentences. Then some algorithms and inference rules to compare sentences conceptually are... 

Limited fossil energy resources and problems with greenhouse gas emissions, has increasingly focused attentions on renewable energy as a solution to this issue. Marine energy due to the the vast amount of wind, current and wave available resources, can play a major role in providing renewable energy and reducing CO2 emissions. However, using one renewable energy, in some cases due to its high volatility and high costs is impractical. Combining different marine renewable energies, can be mentioned as a solution to increase competitiveness with fossil fuels. The aim of the current research, is to introduce a method to select the best location in terms of renewable energy farms wind, current... 

Motion simulators have been highly sought after by the growth of the aerospace industry. In the meantime, the Stewart mechanism, or the so-called Hexapads, is a robot that, in addition to being used in machining tools, is mainly used to simulate the flight. The robot is considering the project to test parts and equipment installed in marine vessels under sea movements and waves. Therefore, according to information obtained through real case studies, the purpose of this project is to design and implement a hexapad controller and user interface for samples weighing up to 2 tons which can handle linear accelerations up to 1 g, rotary accelerations up to 200 º / s2 performs at a frequency... 

The main aim of this study is to propose a new structure of compression surfaces of a supersonic inlet in order to improve target performance parameter i.e. total pressure recovery ratio. This idea resulted in developing a new type of supersonic inlet, utilizing four ramps and a cone as compression surfaces simultaneously.A prototype of this type of inlet has been designed for Mach 3 and its performance has been studied via numerical simulation in design point and off design conditions. Eventually the new inlet compared to experimental performance survey data from two cases of two-cone inlets and also analytical calculations of ideal performance of some types of supersonic inlets. Results of... 

Considering the fact that human capital is a crucial element in explaining the differences in income per capita and economic growth among countries, this research focuses on the effect of initial endowments of individuals on the process of human capital accumulation. One of the most important questions one can ask in this regard is whether individuals that are born in households with a low level of endowments, cannot develop their level of human capital due to a lack in the ability to obtain the factors required for their educational attainment. To answer this question, and considering the limitations of obtaining educational data, we aim to answer this question using district-level data....