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Well-posedness of Two Mathematical Models for Alzheimer's Disease
, M.Sc. Thesis Sharif University of Technology ; Hesaaraki, Mahmoud (Supervisor)
Abstract
In season 1, we introduce a mathematical model of the in vivo progression of Alzheimer’s disease with focus on the role of prions in memory impairment. Our model consists of differential equations that describe the dynamic formation of Aβ -amyloid plaques based on the concentrations of Aβ oligomers, PrPC proteins, and the Aβ-×-PrPC complex, which are hypothesized to be responsible for synaptic tox- icity. We prove the well posedness of the model and provided stability results for its unique equilibrium, when the polymerization rate of β-amyloid is constant and also when it is described by a power law. In seson 2, We consider the existence and uniqueness of solutions of an initial-boundary...
Analysis of a Mathematical Model Describing the Geographical Spread of Dengue Disease
, Ph.D. Dissertation Sharif University of Technology ; Hesaaraki, Mahmoud (Supervisor)
Abstract
Dengue is one of the most important infectious diseases in the world. This disease is a viral infection that is transmitted to humans through the bite of a mosquito called Aedes aegypti. For this reason, geographical regions infected with this type of mosquito are at risk of Dengue outbreak. In this thesis, we first present a mathematical model describing the geographical spread of Dengue disease, which includes the movement of both the human population and the winged mosquito population. This model is derived from a mixed system of partial and ordinary differential equations. Our proposed model has the ability to consider the possibility of asymptomatic infection, so that the presence of...
Neutron Noise Calculation Using High order Nodal Expansion Method
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
This study consists of two parts: steady state calculations and neutron noise calculations in the frequency domain for two rectangular and hexagonal geometries. In the steady state calculation, the neutron diffusion and its adjoint equations are approximated by two-dimensional coordinates in two-group energy and are solved using the average current nodal expansion method. Then, by considering the node size in the dimensions of a fuel assembly, different orders of flux expansion are investigated. For verification purposes, the calculations have been performed by power iteration method for two test problems of BIBLIS-2D and IAEA-2D. For rectangular geometry with increasing flux expansion order...
Methylidyne (CH*)Chemiluminescence Measurement in Sooting Flames
, M.Sc. Thesis Sharif University of Technology ; Salehi, Mohammad Mahdi (Supervisor) ; Mardani, Amir (Supervisor)
Abstract
In this study, using a non-interference experimental method, the chemical luminosity of CH* in co-flow diffusion flames with soot and using natural gas hydrocarbon in a laminar flow regime has been investigated. In addition to experimental research, in current research, numerical simulation has been used to extract information such as temperature field, mass fraction of species, and flow structure and comparison and validation with experimental results. Numerical simulation has been used to simulate the mechanism of CH* species formation. Two different mechanisms have been used. In addition, the Soot simulation model from the Moss-Brookes model and radiation heat transfer mechanism...
Incorporation of CsPbI3 Perovskite Quantum Dots as Interrfacial Layer for Highly Efficient Cs0.05MA0.95PbI3 Perovskite Solar Cells
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor)
Abstract
Despite the excellent photovoltaic performance of perovskite solar cells (PSCs), the instability of PSCs under severe environment (e.g., humidity, intense light) limits further commercialization of such devices. Therefore, in recent years, many researches are conducted on utilizing Perovskite Quantum Dots (PQDs) to enhance performance of PSCs. Herein, CsPbI3 PQDs interfacial layer is incorporated in the perovskite/hole transport material (HTM) interface, on the purpose of increasing charge carrier mobility and preventing electron-hole recombination to increase performance of the PSCs. CsPbI3 PQDs is synthesized at 170℃ with oleic acid and oleylamine as organic ligands by hot-injection...
Mathematical Modeling of Molecular Diffusion for Gas Injection of Fractured Gas Condensate Reservoir – Single Block Approach
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Gerami, Shahab (Supervisor) ; Hashemi, Abdonabi (Supervisor)
Abstract
Gas condensate reservoirs show very complex behavior as wellbore pressure falls below the reservoir fluid dew point pressure and consequently liquid phase appears near the wellbore. Since pressure drawdown is the largest near the wellbore, therefore, this region is the first that experience the liquid dropouts. With continuing the production, reservoir pressures at the other parts of the reservoir fall below the dew point pressure and as a result, condensate appears at these regions. The more the condensate accumulates near the wellbore the more decreasing the gas relative permeability occurs. Condensate accumulating does as a liquid barrier and causes not only decreasing the gas production;...
Analyzing Effect of Perceived Risk on Intention to Use of Mobile Bank
, M.Sc. Thesis Sharif University of Technology ; Kiamehr, Mehdi (Supervisor)
Abstract
Mobile Bank is a service that has emerged for about a decadein Iran. while electronic methods and information technologies are used ininternational markets, in Iran using new technologies in the payment and financial industry is limited to the ATMs and Shetab network services. One of the mainreasons for the lack of tendency in using mobile banks and other electronic paymentmethods is these methods’ security concerns. Therefore, in this research, anattempt has been made to provide a model for technology acceptance in order toexamine the main factors of insecurity among users. As a case study, MellatMobile Bank's application has been evaluated in this research and an attempt hasbeen made to...
The Synthesis and Characterization of Nano Zeolitic Molecular Sieve for Separation of 133Xe from 85Kr
, Ph.D. Dissertation Sharif University of Technology ; Kazemeini, Mohammad (Supervisor) ; Ahmadi, Javad (Supervisor)
Abstract
In this study the feasibility of xenon separation from xenon-krypton mixture was investigated by utilizing of the chromatographic column filled with nano and micron sized NaY zeolite. For this purpose the nano NaY with the yield of 100% related to Al2O3 and the average size of 98.6 nm was synthesized through the clear solution method with the mid-adding of NaOH. Furthermore, a novel method for granulation of nano zeolite was developed by utilizing sodium alginate as an external template. In this method the production of uniform spherical granules with the different sizes in the range of several milimiteres to 100 µm was easily performed. Moreover, the results showed that the adding of...
Dynamic Simulation of Wettability Alteration Induced by Low-Salinity-Effect: Study of Phenomena within Thin Water Film
, M.Sc. Thesis Sharif University of Technology ; Mahani, Hassan (Supervisor) ; Joekar Niasar, Vahid (Co-Supervisor)
Abstract
Recent experimental studies have demonstrated that the lowering of brine could alter the wettability of the oil-brine-rock systems from an oil-wetting state toward a more water-wetting state. This so-called “Low-salinity effect” (LSE) is one of the main effects of the enhanced oil recovery technology based on low-salinity waterflooding. “Double layer expansion” (DLE) in the thin brine film is proposed as the principal mechanism of this phenomenon. Nonetheless, the role of the electrical behavior of the oil/brine and rock/brine interfaces on the kinetics and dynamics of this process is not well understood. Moreover, since most of the previous works have either dealt with a thin film at...
Measurement of Gas Permeation Though Carbonized Membranes and Determination of Mass Transfer Mechanisms
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Taghikhani, Vahid (Supervisor) ; Mahdyarfar, Mohammad (Supervisor)
Abstract
In this project, using experimental results for permeation of gases H2, He, N2, and CO on a microporous membrane (the applied sample was a ceramic membrane) and modified equations, pore diameter, tortuosity, and porosity were determined for this type of membrane. Furthermore, pore diameter, critical volume, and characteristic energy of a carbon molecular sieve membrane were calculated using experimental data for CO2 adsorption on this type of membrane. Diffusivities of CO2, N2, and Ar were also calculated by means of the uptake, time lag/adsorption, and permeability/adsorption tests on carbon molecular sieve membranes utilizing experimental data obtained for this type of membranes and the...
Investigation of the Starting Process of a Second Throat Exhaust Diffuser in a High-Altitude Test Stand
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor) ; Fouladi, Nematollah (Supervisor)
Abstract
In the present study, the effect of the diffuser inlet-to-nozzle exit area ratio (A_d/A_e ) on the gradual starting performance of a second throat exhaust diffuser has been investigated experimentally. Experiments have been carried out with four conical nozzles with different expansion ratios and considering two approaches of gradual increase and gradual decrease of nozzle chamber pressure by a high-pressure air tank. Investigations show that at high area ratios before starting the diffuser, oscillations in the pressure of the test chamber are created due to the instability of the flow at the diffuser inlet. By frequency analysis of the vacuum chamber pressure, it is observed that as A_d/A_e...
Analysis and Evaluation of Heterogeneous Diffusion Model in Accordance with DWI Data
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Abolfazl (Supervisor) ; Jahed, Mehran (Co-Advisor)
Abstract
Conventional MRI has been used to diagnose different types of brain injuries. However these methods have generally failed to diagnose mild types of injury. We are working on the specification of mild traumatic brain injury, using diffusion MRI data, based on a multi compartment simulation of white matter tissue. This effort is essential for better understanding of underlying tissue micro-structure changes in patients with trauma. Some studies have been used in similar data fitting approaches in order to estimate axon diameter distribution. Specifically, a comparative study between different Compartment Models has shown that “ActiveAx” model has the best agreement with underlying tissue...
Expanding Visibility Polygons by Mirrors
, M.Sc. Thesis Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
We consider extending the visibility polygon of a given point q inside a simple polygon by converting one or some of the edges to mirrors. It is known that the visibility polygon of a point inside a polygon in the presence of a mirror can be computed in linear time. We propose a linear time algorithm that checks whether a given segment inside a simple polygon is visible by a given point q via a mirror-edge, and finds all such edges. And we prove that finding edges to add exactly k unit squares to the visibility polygon of a query point q in most cases is NP-complete and its minimization is NP-hard. These cases contain single and muliple, either with secular or difuse reflections. Moreover,...
Visibility Via Reflection
, Ph.D. Dissertation Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
This document deals with the following results in details:Given a simple polygon P with $n$ vertices, the visibility polygon (VP) of a point q, or a segment pq inside P can be computed in linear time. It is known that the visibility polygon of a point inside a polygon in the presence of a mirror can be computed in linear time. We propose a linear time algorithm to extend the VP of a viewer (point or segment) by converting some edges of P into mirrors (reflecting-edges with specular type of reflection), such that a given non-visible segment uw can also be seen from the viewer.Various definitions for the visibility of a segment, such as weak, strong, or complete visibility, are considered. Our...
Analysis of Ratcheting in Elastic-plastic Behavior of Li-ion Battery Electrodes
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor)
Abstract
Among the various materials, silicon anodes have the highest lithium absorption in lithium-ion batteries. But this high lithium absorption capacity can cause 300 percent volume expansion and large stresses. Experimental observations show that charge and discharge cycles may cause plastic deformation in some parts of the electrode particle. On the other hand, there is a possibility of a ratcheting phenomenon due to changing in elastic properties of the electrode material during the charging and discharging processes. However, this phenomenon has not been reported for silicon spherical electrode particles yet.This study aims to model the elastic-plastic behavior of silicon spherical electrode...
Modeling and Motion Analysis of a Nano Mobile Robot Using Molecular Dynamics
, Ph.D. Dissertation Sharif University of Technology ; Meghdari, Ali (Supervisor) ; Sohrabpour, Saeed (Supervisor) ; Nejat Pishkenari, Hossein ($item.subfieldsMap.e)
Abstract
With the rapid progress of technology, the fabrication of smaller electronic and mechanical systems becomes more necessary. To make a small-scale system with better performance, one way is to create it from molecular components. In recent decade, many attempts have been devoted to the fabrication of molecular machines for manipulation of particles at nanoscales. In this project, the motion of two of most basic nanocars namely the Nanocar and the Nanotruck were simulated on gold and silver substrate at different conditions, both of four wheels and the nanotruck chassis is flexible. In the first chapter of this report, some of the most important natural and artificial machines are mentioned...
Study on Optimization of the EDC Model for Highly Preheated and Diluted Condition
, M.Sc. Thesis Sharif University of Technology ; Mardani, Amir (Supervisor)
Abstract
Moderate and Intense Low-oxygen Dilution(MILD) is the new member of combustion field. Highly preheated reactants and lowering the oxygen level in MILD combustion has some promising advantages. In this study the MILD burner, Jet-in-Hot-Coflow(JHC), is taken as the main test case. In this Research, Eddy Dissipation Concept combustion model ,introduced by Magnussen et al,is investigated in detail and governing equations are re-extracted. EDC combsution model due to moderate compuational cost in comparison with other combustion model and well prediction ability has drawn attention. Simulations on the Jet-in-Hot-Coflow(JHC) has shown the promising performance of the EDC combustion model. It seems...
Synthesis and Evaluation of Modified Zeolites for Separation of Acidic Gases
, M.Sc. Thesis Sharif University of Technology ; Khorasheh, Farhad (Supervisor) ; Soltanali, Saeed (Supervisor) ; Ghasabzadeh, Hamid (Co-Supervisor)
Abstract
The adsorption equilibria of carbon dioxide, methane, and nitrogen on pelletized cation-exchanged faujasite zeolite (with alkali, alkaline earth, and transition metal ions) have been investigated by a volumetric apparatus. The standard instrumental analytical techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray spectroscopy (EDX), and atomic absorption spectroscopy (AAS) were utilized to characterize binder-free modified zeolites. The EDX spectra and AAS results revealed that the ion-exchange was successfully achieved with expected tendencies. The results indicate that the type of cation present in the zeolite...
Experimental Investigation of Molecular Diffusion Coefficients of Gas-Oil for the Iranian Oil Field Fluids
, M.Sc. Thesis Sharif University of Technology ; Kazemeini, Mohammad (Supervisor) ; Kharat, Reyaz (Supervisor) ; Ghazanfari, Mohammad Hossein (Co-Advisor)
Abstract
Molecular diffusion of gases in crude oils plays a crucial role in several oil recovery processes especially in cold-based production process. Nowadays, heavy oil is a considerable part of the world hydrocarbon reservoirs and its importance increases as the ordinary oil reserves decrease. The main obstacle in heavy oil production is its low mobility (i.e. high viscosity). This difficulty can be easily solved by injecting gas solvent in these reservoirs. However, experimental data concerning CO2 diffusivity in heavy oils due to the tedious nature of diffusivity measurements are relatively rare in the open literature. In this work, a comprehensive experimental investigation of the effective...
Design and Analysis of an Optimal Cooling System for a Supersonic Exhaust Diffuser Using a Water Jacket
, M.Sc. Thesis Sharif University of Technology ; Farahani, Mohammad (Supervisor) ; Fouladi, Nematollah (Supervisor)
Abstract
Often in a vacuum test facility, a supersonic exhaust diffuser uses the energy of the outflow from the nozzle to create and maintain a vacuum condition in the engine test chamber. In this system, the temperature of the motor exhaust gas, which directly hits the diffuser walls, is much higher than the tolerance of the metal body of the diffuser. The purpose of this research is to design a cooling system for thermal protection of diffuser walls of a vacuum simulator using a water-jacket tool. At the beginning of this study, the effective parameters in the design of the water-jacket cooling system were identified. Then, a new algorithm to design and optimize the water-jacket cooling system was...