Sharif Digital Repository

In this thesis, a Segmented Gama Scanning System for measuring total activity of the low/intermediate level radioactive waste drums is designed and a prototype 3-segmented commercial system is manufactured by using NaI detectors. The optimum distance of detector from drum surface and the optimum number of detectors on reconstruction of the radioactivity of the waste drum were studied by MCNP simulations. In addition, the effects of inhomogeneous distribution of radioactivity, the addition of lead filters to detectors, the change in collimator length and the asymmetrical placement of a drum on the rotary plate were also examined by the MCNP calculations. In the absence of a real radioactive... 

In this thesis, we address the problem of joint Range, Angle and Doppler frequency estimation in FDA-MIMO radars. Target parameter estimation is among the most important areas of research in radar signal processing. In this field of research, there are numerous challenges to overcome, including low estimation accuracy, a scarcity of snapshots, and the high computational complexity of algorithms. For this reason, diverse methods have been developed to solve this problem. Each of these methods has its own features and capabilities, focusing on one or more of the existing challenges. The application of these methods also depends on various factors, including the signal structure, which is... 

Melt blending of polymers is a rather cheap and easy approach for obtaining new set of properties compared to synthesizing new polymeric materials. For the same reason, binary and ternary polyethylene blends are made to provide added value for different applications. Polyethylene blends are commonly composed of high density polyethylene (HDPE), low density polyethylene (LDPE) and linear low density polyethylene (LLDPE). Although the Mechanical and physical properties of polyethylene binary blends have been studied extensively, microstructure and mechanical properties of polyethylene ternary blends have been the subject of very few studies. In this work, samples with 40-60 Wt. % HDPE and... 

Supersonic intakes with mixed compression has an appropriate performance in the critical point, but in the subcritical performance, when inlet mass flow rate is reduced to a certain amount, a self-sustained instability occurs in the flow. In this case, instability appears in the form of shock waves system oscillation which is called Buzz phenomenon. An axisymmetric supersonic air intake with mixed compression which is designed for a Mach number of 2 has been investigated experimentally in order to study buzz frequency. The intake has been experimented in different Mach numbers, angles of attack and mass flow rates. Besides, the intake with wind tunnel wall has been modeled and analyzed in... 

Lean premixed flames bring both benefits and challenges to combustion systems. While they have low emission levels and high efficiencies, they are also very susceptible to combustion instabilities. Low swirl burners have been shown to be very capable in stabilizing lean premixed flames.
In this thesis, behavior of low swirl flames under conditions of variable equivalence ratio (0.6 – 0.8), mean flow velocity (3.5 – 5.5 m/s), and excitation frequency is investigated. In static stability diagram of the flame, a region is observed in which stability mode of the flame is dependent on the path that takes the flame to its operating point (hysteresis region). Increasing the recess distance of... 

The present research aims to examine the influence of response format on the reliability and validity of grammaticality judgment tests, which will also reveal some facts about the superiority of each format. To this end, the grammaticality judgment (GJ) test developed by Gass (1994) was selected as the instrument of the study, which was manipulated in terms of the response format while the original items remained intact. Thus, in the first phase of the study, a multiple-choice GJ test (MCGJT) was constructed to be compared with the traditional form, i.e., the dichotomous type (DGJT). In an interval of a month, the two tests were administered to a group of 110 engineering-major BS students at... 

Today many videos in an interval of a particular scene in a different view angle to each other are filmed. Use these videos are used in numerous fields. Time synchronization between the video, is the basis for their use. In order to provide an automated process for creating time synchronization between the video, numerous studies have been conducted that each requires specific conditions are to achieve the desired result. The biggest challenge of this problem, which appears when the camera recorded video viewing angles, high and low, and when filming the shared vision between them, jump frames is taken. Players are coordinated. In experiments conducted on different data sets, the average... 

In the first work, a superhydrophobic polystyrene hollow fiber (PS–HF) was synthesized by electrospinning and used in microextraction of trazine herbicides from aquatic media followed by gas chromatography mass spectrometric (GC–MS) determination. Effects of different parameters influencing the extraction efficiency including the solvent extraction and its amount, the desorbing solvent and its amount, extraction time and ionic strength were optimized. The characteristic properties of the hollow fiber were studied by scanning electron microscopy (SEM). The limits of detection and quantification of the method under optimized condition were 2 and 6 ng L-1, respectively. The relative standard... 

This thesis is concerned with measurement and analysis of noise for an underwater propeller by means of numerical and experimental methods. A major cause of noise in buoyant bodies is the propeller. Detection and measurement of such noise is a part of various engineering and maritime applications. Thus detecting the sources of sound and ways of its propagation under water is the first step in many engineering and maritime applications of underwater acoustics which leads to noise reduction and control. Due to its wide subject, this thesis presents a phenomenology of propeller noise and discusses numerical and experimental methods. In the section that deals with numerical methods, the... 

This thesis is a part of national studies of “attractiveness analysis and strategy formulation of fuel cell technology in Iran" that was done during more than two years with the guidance of fuel cell steering committee. In this thesis, first of all the possibility of applying the technology strategy model of Arnold Hax in national level was investigated. For this purpose, with regard to the fuel cell technology specifications and status in the country, from the perspectives of national need to the technology, capabilities of technology in the country and new applications of technology, the technology strategy models of positioning school were studied and from the models of this approach,... 

In this thesis, we propose a QoS-aware routing algorithm for multimedia streaming that uses cross-layer information (application layer and physical layer) in Wireless Multimedia Sensor Networks (WMSN). Our goal is to use cross-layer information to route video packets efficiently and deliver a higher quality video in streaming applications. Our QoS-Aware Multi-Path Selection (QAMPS) method is based on multi-path multi-priority selection algorithm that uses Two-Phase geographic Greedy Forwarding (TPGF) as a routing algorithm. The proposed method guarantees QoS by splitting video streams into I-frames, P-frames and B-frames in the application layer and passes them to the network layer for... 

Excavation of metro tunnel beneath groundwater level causes disturbance of hydro geological balance and change in stress conditions at its environment. One of the usual methods of the tunnel construction is utilizing tunnel boring machine and one of the most important of them is called TBM-EPB which takes advantage of the earth pressure balance method. Control of surface settlements which is a result of creating underground space in urban area is a matter of great importance and is influenced by various parameters. This thesis has tried to investigate factors such as geotechnical properties among cohesion, internal friction angle, elasticity modulus, permeability and porosity and also... 

The main subject of this project is to present a new algorithm for multiple RF sources localization by means of a group of robots. This problem (locating multiple radio sources) could be utilized in many domains, either military (passive radars) or civil (search and rescue) uses. Confronting detrimental effects of real environment on wave’s propagation pattern is the main challenge in this problem. Optimized movement of robots has been chosen as basic strategy to overcome this challenge. Presenting a general solution for this problem requires researches in four topics. The first one is simulation of environment and sensor with main objective of evaluating obtained algorithms’ performance.... 

Aluminum sulfate is widely used in water treatment as a polyelectrolyte. Its dissolution and recrystallization into nanoparticles directly affects the working conditions. This study concerns determination of the metastable zone and induction time in nucleation of aluminum sulfate nanoparticles in aqueous media and in presence of acetone as anti-solvent. Later the effect of SDS on the metastable zone and induction time are also studied.. The study also shows if the presence of anti-solvents and surface active agents can vary this phenomenon. The study also adds to our understanding of the media in creation and stabilization of nanoparticles. This project has a special focus on the changes... 

The ability of human to analyze the environment around them has been an inspiring source for event analysis research. Since human perception of the environment is formed in a multi-modal space, many efforts have been made to fuse information to create an intelligent fusion. In this study, we want to better understand the environment using information fusion. For this purpose, fuzzy fusion of audio and video signals based on ink drop spread operator is performed for recognizing and tracking of the targets using several scenarios of the AV16.3 dataset. We then focused on the fusion of audio data for sound source localization, one of the most important applications in evaluating fusion... 

Nowadays, with the increasing number of polyethylene terephthalate wastes, the issue of its recycling has become very important. Among the problems of polyethylene terephthalate recycling are its loss of crystallinity and mechanical properties. Recycled polyethylene terephthalate does not have the properties of new polyethylene terephthalate and using its mixture with other materials is an effective way to remove its waste from nature and return it to the production cycle. The aim of this study is to produce a mixture of recycled polyethylene terephthalate with polycarbonate and glass fibers with mechanical properties such as good impact strength, which ultimately leads to the production of... 

Asphaltene precipitation and deposition may cause severe problems during different stages of oil recovery. All proposed remediation techniques have proven costly and not highly effective, so prevention becomes the most beneficial way to counteract the problem. Revelation of the deposition mechanism and determination of the parameters are necessary in order to devise reliable prevention strategies.This work presents results of the effect of lean gas and CO2 injection process as well as natural depletion on dynamic asphaltene precipitation and deposition. In addition sets of experiments were performed in the same porous media using STO and solvent (with different volume ratios) to investigate... 

Computer-Aided Diagnosis (CAD) systems are widely used for detection of various kinds of abnormalities in mammography images. In this work, mass classification is investigated and its steps are explained in detail, for each step a main method is presented and other methods are also discussed. For mass segmentation a relatively new method based on level set and Morphological Component Analysis (MCA) is used.After this step, various kinds of features such as shape, geometrical, and textural ones are introduced. Moreover, a set of proposed features based on wavelet transformation,for this application are presented. The proposed features can describe margin and texture characterizations of a... 

In gas-condensate reservoirs, when pressure reduces to less than dew point pressure, condensate will form out of the gas phase. Gas recycling is one of the most common methods to enhance the production of gas-condensate reservoirs.The purpose of this thesis is to optimize gas recycling process in a gas condensate reservoir in order to produce the accumulated condesate in the reservoir and maximize reservoir economic efficiency.The parameters that need optimization are:
• Injection gas ratio
• Injection gas allocation amongst injection wells
• Bottomhole pressure of production wells
Genetic algorithm was considered as optimization method and Proxy model is used in order to... 

In many fields, due to the lack of thickness of the reservoir layer, vertical drilling cannot be used due to low wellbore efficiency, so to solve this problem, directional and horizontal drilling is used. During drilling of highly deviated wells, to increase the efficiency of directional drilling, it should be tried to keep the path of the well completely in the reservoir layer, so that the full capacity of this type of drilling is used and the efficiency of the well is increased. To achieve this goal, Geo-Steer drilling technology is proposed in which decisions on the path of the well are made with the help of current reservoir and geological data. In this type of drilling, instantaneous...