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sandoghchi--mohammad
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Oxygen and Rare Earth Doping Effects on REn 2BanCu2n 2Om Superconductor Compounds
, Ph.D. Dissertation Sharif University of Technology ; Akhavan, Mohammad (Supervisor)
Abstract
There are two challenging problems with the physical properties of the recently discovered cuprate, Y3Ba5Cu8O19 δ (Y358): (1) the value of its transition temperature (Tc) and (2) its unknown crystal structure. While some reports argue that Tc of Y358 and its crystal structure are completely different from those of the YBa2Cu3O7 δʹ (Y123) compound, other reports indicate the similarity of both transition temperatures and XRD patterns (or crystal structure) of these materials. It has been suggested that these similarities are due to oxygen deficiency (δ) of Y3Ba5Cu8O19 δ or the decomposition of Y358 to Y123. In this thesis, we address these issues. At first, we have tried to answer the...
Ab-initio Calculations of Electronic and Phonon Structures of Ba1-xKxFe2As2 (x = 0,0.5,1) Superconductor
, M.Sc. Thesis Sharif University of Technology ; Khosroabadi, Hossien (Supervisor) ; Akhavan Farshchi, Mohammad (Supervisor)
Abstract
After discovery of superconductivity in 1911 people try to find superconductors with higher Tc. High Tc superconductivity in cuprates and iron based superconductors was discovered in 1986 and 2008 respectively. However, there is not any unit theory for high Tc superconductivity in cuprates or iron based superconductors. Study of electronic and phonon structures of high Tc superconductor compounds can lead to find theory of high Tc superconductivity.
In this dissertation electronic structure of Ba1-xKxFe2As2, which belongs to class of 122 of iron based superconductor, under potassium doping x=0,0.5,1 has been studied. To this end ab-initio method and Density functional theory have been...
In this dissertation electronic structure of Ba1-xKxFe2As2, which belongs to class of 122 of iron based superconductor, under potassium doping x=0,0.5,1 has been studied. To this end ab-initio method and Density functional theory have been...
Doping of Sm3Ba5Cu8O19 compound with praseodymium
, Article Journal of Low Temperature Physics ; Volume 198, Issue 5-6 , 2020 , Pages 252-268 ; Akhavan, M ; Sharif University of Technology
Springer
2020
Abstract
An investigation has been carried out on the effects of praseodymium doping in Sm3−xPrxBa5Cu8O19 for different values of x. Results indicate that the transition temperature reduces almost linearly with x. Based on the Abrikosov–Gor’kov pair-breaking theory, it has been concluded that the exchange interaction constant is large (Jex = 110 meV) in the Sm3Ba5Cu8O19 compound. In addition, it seems that the hybridization of Pr4f states with O2p–Cu3d states has an important role in the depression of transition temperature of Sm3−xPrxBa5Cu8O19 for the Pr content < 10%. However, for the higher values of Pr, the two observed plateaus at the transition temperatures of ~ 60 K and ~ 17 K, respectively,...
Effects of K doping on electronic structure of Ba1-xKxFe2As2 superconductor by ab-initio density functional theory
, Article Physica C: Superconductivity and its Applications ; Vol. 507, issue , Dec , 2014 , p. 22-24 ; Khosroabadi, H ; Akhavan, M ; Sharif University of Technology
2014
Abstract
The crystal and electronic structures of normal phase of Ba1-xKxFe2As2 for x = 0.0, 0.5 and 1.0 have been studied by using pseudopotential Quantum Espresso code based on ab-initio density functional theory. Effects of K doping on the crystal structure and lattice parameters have been calculated and compared with the experimental and computational reported data for similar compounds. The metal-metal bonding scenario was used to explain the changes of lattice parameters by K doping. The electronic structure of this system including of density of states and band structure have been calculated and investigated by K doping. One of the interesting results is that a larger peak is appeared near the...
Electronic and phonon structures of BaFe2As2 superconductor by Ab-initio density functional theory
, Article Journal of Superconductivity and Novel Magnetism ; Volume 26, Issue 1 , January , 2013 , Pages 93-100 ; 15571939 (ISSN) ; Khosroabadi, H ; Almasi, H ; Akhavan, M ; Sharif University of Technology
2013
Abstract
Electronic and phonon structures of the BaFe2As2 superconductor in the magnetic-orthorhombic phase have been investigated by the ab-initio density functional theory using the pseudopotential Quantum Espresso code. Density of state and electronic band structure for this phase has been studied, but phonon dispersion has been obtained only for the nonmagnetic-orthorhombic phase. Electronic band structure and density of states are in good agreement with other calculations in the literature. The electronic state near the Fermi energy are essentially made from Fe3d and As4p orbital that indicate in-plane conductivity in FeAs layers in this system. Comparing calculated phonon dispersions with...
Construction of an Experimental Device for Foaming Agent and an Experimental Study of the Properties of Foaming Agent
, M.Sc. Thesis Sharif University of Technology ; Bazargan, Mohammad (Supervisor)
Abstract
The primary purpose of acidizing operations in the oil and gas industry is to enhance hydrocarbon production. Acidizing has been a common and conventional method for years, especially when production engineers face issues like declining reservoir pressure leading to reduced production rates. Initially, the treatment solution is referred to as matrix acidizing. In acidizing operations, different additives are combined with the acid to control its behavior in the reservoir. These additives may include iron control agents, corrosion inhibitors, friction reducers, and more. Incompatibility among these additives, the acid, and reservoir fluids can lead to severe damage to the reservoir....
Numerical Analysis of An Annular Gas Turbine Combustor
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
The goal of this research is the simulation of the annular combustion chamber of the turbine engine utilized by liquid fuel. The achievement to this goal will lead to create numerical tools for parametric study, analysis and combustion chamber designing.For this reason simple geometry has been considered. This simplicity of geometry causes to facilitate in parametric study and decrease in saving time for modeling and meshing. This combustion chamber is a simplified model of engine CF6. In recent study, the k – ε realizable model has been used for turbulence modeling. For non-adiabatic condition, chemical reaction is dissolved by utilizing probability density function along with laminar...
A misbehavior‐tolerant multipath routing protocol for wireless Ad hoc networks [electronic resource]
, Article International Journal of Research in Wireless Systems (IJRWS) ; Vol. 2, Issue 9, pp. , Sep. 2013 ; Pakravan, Mohammad Reza ; Aref, Mohammad Reza ; Sharif University of Technology
Abstract
Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network...
Theoretical and Experimental Study to Conversion of AUC to UO2 by Microwave Heating
, Ph.D. Dissertation Sharif University of Technology ; Otukesh, Mohammad (Supervisor) ; Ghannadi Maragheh, Mohammad (Co-Advisor) ; Ghasemi, Mohammad Reza (Co-Advisor)SAR Imaging Using the TomoSAR Technique to Resolve Multiple Scatterers
, M.Sc. Thesis Sharif University of Technology ; Bastani, Mohammad Hassan (Supervisor) ; Karbasi, Mohammad (Co-Supervisor)
Abstract
During the last few years, the study of urban environment structures is considered as a research field of interest in remote sensing. In satellite observations of the earth's surface, continuous imaging in terms of time and space has caused the remote sensing technique to be proposed as a useful and efficient tool for the analysis of urban areas. Obtaining quantitative spatial information from the urban environment in fields such as determining the height of buildings plays an essential role in urban planning, monitoring damage to buildings, establishing communication bases and digital cities. During the last two decades, the use of Tomosar approach in order to reconstruct the structures of...
Estimating Possible Effects of Subsidies in Competition and Development of Fixed Broadband Internet
, M.Sc. Thesis Sharif University of Technology ; Vesal, Mohammad (Supervisor) ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
In this work, the dynamic competition between firms providing internet services is studied. The framework is Markov equilibrium whereby structural parameters are obtained using two-step estimations, allowing for analyzing the situation in case of subsidies for service upgrade. The results show that such subsidy has little effect on the number of firms while increasing the number of fast firms
Estimating Price Elasticity of Natural Gas Demand in Iran's Residential Sector: A Regression Discontinuity Approach
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Vesal, Mohammad (Supervisor)
Abstract
Estimating the price elasticity of gas demand involves complexities depending on the gas market structure and pricing mechanisms in different countries. Distinguishing between supply and demand shocks and block pricing are among the main challenges that can cause endogeneity in elasticity estimates. Iran's domestic gas network, one of the largest and most extensive household gas markets, is divided into five climatic zones based on weather conditions. The pricing steps for these five climates during the five cold months are such that a customer in a warmer climate pays higher prices. Conversely, the pricing steps for the seven warm months are the same for all climates. This policy creates a...
Estimate the Effect of Religiosity on Voter Turnout
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Vesal, Mohammad (Supervisor)
Abstract
The correlation between religious adherence and voter turnout is widely studied. However, whether the relation is causal is an open question. We use Household Expenditures and Income Survey (HEIS) data in Iran, which encompasses nine distinct religious expenditures. These expenditures have low correlation with each other and represent different aspects of religious adherence. We use Imamzadeh (some historical holy shrines) as Instruments to estimate the causal effect of religious expenditures on voter turnout. The results reveal that religious expenditures influence both presidential and parliamentary voter turnout, with a notably stronger impact on presidential elections
Joint Optimization of Computation Offloading and Resource Allocation in Mobile Edge Computing Networks
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Hadi, Mohammad (Co-Supervisor)
Abstract
Mobile edge computing (MEC) is a promising technology that aims to resolve cloud computing’s issues by deploying computation resources at the edge of mobile network and in the proximity of users. The advantages of MEC include reduced latency, energy consumption, and load on access and mobile core networks, to name but a few. Despite all the aforementioned advantages, the mobility of mobile network users causes the traditional MEC architecture to suffer from several issues, such as decreased efficiency and frequent service interruption. One of the methods to manage users’ mobility is virtual machine (VM) migration, where the VM containing the user’s task is migrated to somewhere closer to...
Non-Scratch, Antibacterial And Self-cleaning SiO2/TiO2 Nano Composite Coating on Surgical Tools By Sol-Gel
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
In this study TiO2/SiO2 thin films were prepared by sol-gel method from Tetra isopropylortho Titanate(TIPT) as the principle of TiO2 material with Tera ethoxysilane(TEOS) as the principle of SiO2 material to achieve high scratch-resistant , antibacterial and self-cleaning surface area under the effect of various percentage of SiO2 . Film deposition was carried out using a dip-coating technique and heat-treatment was used at 700ºC to achieve crystalline of films with excellent adherence the of substrate.
The surface morphology of the films has been observed by Scanning Electron Microscope (SEM) and the tribological properties of the surface were investigated by Atomic Force Microscope...
The surface morphology of the films has been observed by Scanning Electron Microscope (SEM) and the tribological properties of the surface were investigated by Atomic Force Microscope...
Simulation and Control of an Aromatic Extractive Distillation Column
,
M.Sc. Thesis
Sharif University of Technology
;
Shahrokhi, Mohammad
(Supervisor)
Abstract
In this study steady state and dynamic simulation of an NFM extractive distillation unit for seperation of aromatics and non-aromatic components has been carried out. Column output composition obtained with experimental binary coefficients is compared with those obtainded by UNIFAC equation. The results indicate that using UNIFAC for all binrary coefficients results in an unacceptable error in concentration of benzene. If the experimental binary coefficents of benzene with NFM are used and the rest are calculated by UNIFAC equation, the simulation results will be very close to those obtained via experimental binary coefficients. Also it is shown that considering a constant efficiency for all...
Investigation the Effects of Parking Pricing and Improving Public Transportation Policies on Private Car Use Reduction in Central Business District
, M.Sc. Thesis Sharif University of Technology ; Kermanshah, Mohammad (Supervisor)
Abstract
Nowadays, with population growth and vehicle traffic increase, only providing transportation supply couldn’t answer the transportation demand. One of the most important solutions to reduce traffic is transportation demand management (TDM). In this research, the effects of parking pricing and improving public transportation services on private car demand reduction in city center are examined. The data are collected from private cars users in the city center of Isfahan through interviews. By stated preference method, the impacts of parking price and public transit travel time and other related factors were investigated. For this purpose, binary logit, multinomial logit and nested logit models...
Iran’s Air Quality Modeling Using CMAQ-WRF Coupled Model
, M.Sc. Thesis Sharif University of Technology ; Arhami, Mohammad (Supervisor)
Abstract
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...
H.264 Decoder for Portable Application
, M.Sc. Thesis Sharif University of Technology ; Sharifkhani, Mohammad (Supervisor)
Abstract
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...
Design and Manufacture of a Burner for Transforming Natural Gas to Reduction Gas
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
Different methods can be used to produce reduction gas. One example is using coal. But today there’s a tendency to use natural gas. One way of transforming natural gas to reduction gas is to burn it with gases produced by combustion, such as or vapor; usually a catalyst is used in this method. Another method is burning natural gas directly with oxygen or air. The recent method is of benefit especially in Iran, because of available natural gas resources and avoiding catalyst problems. Designing a burner for this purpose is an important step in reaching this goal. In this project such a burner is designed and manufactured. The burner manufactured in this project burns natural gas with...