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mohammadi-kaji--mahsa
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Total 965 records
Visual Odometry using RGB-D Cameras
, M.Sc. Thesis Sharif University of Technology ; Kasaei, Shohreh (Supervisor)
Abstract
Vision-based localization and 3D orientation estimation of a moving camera, has been for long a vast research area including robot localization and mapping, virtual reality and structure from motion. By introduction of RGB-D cameras in 2010, many sparse methods which are based on key-point extraction and tracking, moved towards dense methods. Dense methods utilize the RGB-D depth and gray-scale values in the images and define the odometry estimation problem as an image registration optimization, without the need to make key-point correspondance in images. Although RGB-D cameras impose specific constraints such as limited depth, depth errors and medium resolution, dense methods have shown...
, M.Sc. Thesis Sharif University of Technology ; Parsafar, Gholamabbas (Supervisor)
Abstract
In 2009, a general equation of state (EOS-III) based on an effective near-neighbor pair interaction of an extended Lennard-Jones (3, 6, 12) type has been introduced as : , where is the compressibility factor, p and ρ stand for pressure and molar density , respectively, T is Temperature , and e, f and g are the temperature dependent coefficient of the equation of state . the Z_th and Z_in are the thermal and internal contributions of pressure in the compressibility factor, respectively. this equation of state gives a good description of all types of nano- and bulk –solid and bulk fluid at entire temperature and pressure ranges for which thee is experimental data. Investigation show that...
An experimental study of buzz instability in an axisymmetric supersonic inlet
, Article Scientia Iranica ; Volume 18, Issue 2 B , 2011 , Pages 241-249 ; 10263098 (ISSN) ; Farahani, M ; Asgari Kaji, M. H ; Sharif University of Technology
2011
Abstract
An experimental study was carried out on an axisymmetric supersonic inlet with external compression. The scope of this study was to investigate the general characteristics of the inlet buzz under various design and off-design conditions. The model was equipped with accurate and high frequency pressure sensors and the tests were conducted at Mach numbers varying from 1.8 to 2.5, at various angles of attack, and at different mass flow rates. Shadowgraph flow visualization, together with a high speed camera, was used to capture the external shock structure in front of the inlet. Frequencies of buzz were obtained from both the shadowgraph pictures and analysis of the pressure data. The amplitude...
An Experimental Study of the Buzz Frequency and its Relation with the Corresponding Eigen Frequency in an Axisymmetric Supersonic Inlet
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
All supersonic intakes with external compression, having a good level of performance at all the critical poin t. Exhibit a marked instability of flow in subcritical operation below some value of the flow ratio, in the form of an oscillation of the shock system, colloquially known as “buzz", which can lead to thrust loss, engine surge or even structural damages. Therefore the effort to understand the nature and cause of this phenomenon is important in order that the starting of buzz can be predicted and more effectively avoided without losing performance. This phenomenon has been the subject of many studies, mainly experimental. In this research, we design and build an axisymmetric supersonic...
Photoelectrocatalytic Performance of Mesoporous TiO2 Nanostructures Decorated with Cu-Ag-Zn Particles for CO2 Conversion
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor)
Abstract
The rise in carbon dioxide levels has led to the manifestation of numerous environmental challenges. Currently, the absorption and conversion of carbon dioxide into valuable fuel resources such as synthetic gas, methane, and ethylene are deemed crucial from both environmental and economic standpoints. Despite the presentation of photocatalysts such as titanium oxide and electrocatalysts such as copper, silver, and zinc, their efficiency in CO2 conversion is found to be insufficient. One potential solution to this problem is the utilization of photoelectrocatalytic CO2 recovery. In this study, the aim was to enhance the photoelectrocatalytic reduction of CO2 by designing and manufacturing...
Synthesis and Application of Preformed Viscoelastic Hydrogels in Enhanced Oil Recovery
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Baghban Salehi, Mahsa (Supervisor)
Abstract
Preformed particle gels (PPGs) due to its advatantage over commonly used in situ gels has been successfully applied for controlling excess water production in mature oil reservoirs. Field results of using PPGs in oil fields shows that commonly used PPGs are highly sensitive to hard reservoir conditions such as high temperature and salinity and can not effectively block fractures and high permeability layers.Objects of this study are synthesis and evaluating performance of this novel polymer based hydrogel in oil reservoirs with high temperature and salinity. Central composite design ( which is a experiment design approach) was used for synthesizing thirteen gel samples and optimal sample was...
Coating of Sewage Pipes with Appropriate Nanomaterials Aimed at Preventing Biological Growth (Algae+Biofilm)
, M.Sc. Thesis Sharif University of Technology ; Borghei, Mehdi (Supervisor) ; Ghasemi, Shahnaz (Co-Supervisor)
Abstract
Biological layers are one of the main problems related to water transfer with pipe lines which are formed through time in the inner surface of the pipes by the water nutrients. Hence, the inner surfaces in the pipe lines and water refineries should be made in order not to let these biological layers to be made. The reason is that when the biofilm is formed on these surfaces, the traversing water is polluted. Dredging of these pipes is not only necessary in most of the countries in the world and needs huge amounts of water but is also very complex and expensive.In this research, nanomaterials, namely ZnO, T〖iO〗_2،S〖iO〗_2 have been used to cover the surface of concrete and steel pipes (The...
Design and Manufacture of Polymeric Nanocomposite in Order to Control the Production and Migration of Sand in Reservoirs
, Ph.D. Dissertation Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Baghban Salehi, Mahsa (Supervisor)
Abstract
Sand production from oil reservoirs leads to various problems, such as well productivity reduction, operating equipment corrosion, and increased production costs. Therefore, controlling sand production in unconsolidated reservoirs is crucial for operating companies. Chemical injection into the formation in order to strengthen and reduce sand production is one of the most important methods of sand control. In this study, a hydrogel nanocomposite was designed and its effectiveness in sand control was investigated. Various tests were carried out to define and assess its efficacy, as follows: Morphological tests demonstrated the creation of a dense, homogeneous, and porous structure. Structural...
Performance Evaluation of Rhamnolipid & Sophorolipid Biosurfactants Capable of Wettability Change and Oil Recovery Increase
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Baghban Salehi, Mahsa (Supervisor) ; Mokhtarani, Babak (Co-Supervisor)
Abstract
As fossil fuels are still the world's most important source of energy, as well as the maturity of most of the world's oil reservoirs, there is a need for enhanced oil recovery methods to meet the world's increasing oil demands. MEOR methods are new and promising methods that are still in the research and development stage. One of the MEOR methods is the use of biosurfactants, which increase the oil recovery by two mechanisms: 1) reducing the interfacial tension between water and oil and 2) changing the wettability of the rock. In this study, the performance of two glycolipid biosurfactants, rhamnolipid and sophorolipid, in increasing oil recovery has been investigated. Initially, surface...
Investigation of the Effect of Asphaltene on the Stability of Water-oil Emulsion
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Baghban Salehi, Mahsa (Supervisor) ; Masihi, Mohsen (Supervisor)
Abstract
During the production of crude oil from reservoirs, the production of quantities of formation water along with this oil, causes the crude oil does not have the necessary indicators for transportation, refining and ultimately export. The presence of water and salt along with crude oil causes corrosion of refinery and transmission equipment and makes oil unfavorable in terms of economic efficiency (both for domestic use and for export). water and salt produce stable emulsion with oil that can be stable for a long time and can not be easily separated from crude oil. Therefore, separation of water and salt from crude oil is one of the most important issues in the oil industry. Breaking this...
Butanol Production from Bagasse Sugarcane Black Liquor by Native Strain and Clostridium Acetobutylicum Species
,
M.Sc. Thesis
Sharif University of Technology
;
Shayegan, Jalaleddin
(Supervisor)
;
Vossoughi, Manouchehr
(Supervisor)
;
Sedighi, Mahsa
(Co-Supervisor)
Abstract
Considering the limitations of fossil fuels in recent years, as well as increasing demand for biofuels, it is anticipated that future attention to biofuels will increase further. Among biofuels, due to some disadvantages of bioethanol and biodiesel fuel, there is a tendency to use biobutanol, which does not have the disadvantages of the mentioned fuels. The cost of chemical production of butanol also led researchers to use biotechnology production of butanol. According to studies, butanol production can be achieved by fermenting some sugars such as glucose, xylose, and ... by anaerobic microorganism, but the cost of using these sugars has resulted in the use of natural sources of these...
Providing A New Solution to Enhance Oil Recovery (Eor) by Using Properties of Imidazolium Ionic Liquids and Synthesis of Microgels
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Baghban Salehi, Mahsa (Supervisor) ; Mokhtarani, Babak (Co-Supervisor)
Abstract
The methods of Enhanced Oil Recovery (EOR) from reservoirs have been taken into consideration recently due to the decline in oil reserves and the rise in energy demand. Studies and investigations indicate the tremendous potential of chemical approaches based on injecting ionic liquids into the porous media with the goal of improving oil recovery. Additionally, hydrogels and polymers, which are two of the process' primary materials, are thought to be good alternatives. In the current study, a hydrogel based on carboxymethyl cellulose was first created and synthesized. Ionic liquids based on imidazolium and triflate anion were then added, and their effectiveness in enhancing the properties...
3D distributed modeling of trolling-mode AFM during 2D manipulation of a spherical cell
, Article Journal of Nanoparticle Research ; Volume 23, Issue 4 , 2021 ; 13880764 (ISSN) ; Nejat Pishkenari, H ; Mohammadi Moghaddam, M ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
In this study, a general 3D distributed modeling of Trolling-Mode AFM (TR-AFM) as a nanorobot is presented to analyze the 2D manipulation process of a spherical cell. To this aim, the analysis is categorized into 3 sections. In the first section, 6 deformations of TR-AFM are taken into account, and the standard model of the system is obtained. Moreover, the system is simulated in ANSYS Workbench. The results of modal and transient analyses of the system from both analytical and software methods reveal high agreement, which confirms the accuracy of the presented analytical model. In the second section, by utilizing the 3D derived model, displacement of a spherical yeast single cell (W303)...
Sol-gel nanostructured titanium dioxide: Controlling the crystal structure, crystallite size, phase transformation, packing and ordering
, Article Microporous and Mesoporous Materials ; Volume 112, Issue 1-3 , 2008 , Pages 392-402 ; 13871811 (ISSN) ; Fray, D. J ; Mohammadi, A ; Sharif University of Technology
2008
Abstract
The anatase phase of titania was stabilised with physically modifying particulate sol-gel process. Two major parameters, peptisation temperature and drying temperature, were identified which were responsible for retarding the anatase to rutile phase transformation, crystal growth and packing of primary particles. The critical nucleus size of transformation was controlled by natural (at 25 °C) and artificial (at 50 and 70 °C) peptisation techniques. Moreover, sintering of primary particles was controlled by cool (at 0 and 5 °C) and normal (at 25 °C) drying techniques. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that a full conversion of titanium isopropoxide is obtained...
Evaluation of the Surface Activity of Novel Ionic Liquids and Their Application in the Enhanced Oil Recovery Process
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Mokhtarani, Babak (Supervisor) ; Baghban Salehi, Mahsa (Co-Supervisor)
Abstract
The following dissertation discusses Ionic Liquids (ILs) as an alternative to commercial surfactants for use in the Enhanced Oil Recovery process. Ionic Liquids came to researchers’ attention due to their environmental nature and their tolerance for high temperatures and salinity. In this work, firstly, an extensive literature review is carried out, and then, experiments are designed and performed to evaluate ILs’ surface activity and performance in a lab-scale EOR set-up. The Ionic Liquids used in this work consist of three types of methylimidazolium nitrate, [MIM]+[NO3]-, with three different alkyl chain lengths. This combination, and specifically the effect of nitrate anions on EOR and...
Electrokinetic mixing and displacement of charged droplets in hydrogels
, Article Transport in Porous Media ; Vol. 104, Issue. 3 , Jun , 2014 , pp. 469-499 ; ISSN: 01693913 ; Sharif University of Technology
2014
Abstract
Mixing in droplets is an essential task in a variety of microfluidic systems. Inspired by electrokinetic mixing, electric field-induced hydrodynamic flow inside a charged droplet embedded in an unbounded polyelectrolyte hydrogel is investigated theoretically. In this study, the polyelectrolyte hydrogel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which is located at the plane of shear, with the electrostatic potential ζ. The fluid inside the droplet attains a finite velocity owing to hydrodynamic coupling with the...
Electric-field-induced response of a droplet embedded in a polyelectrolyte gel
, Article Physics of Fluids ; Volume 25, Issue 8 , 2013 ; 10706631 (ISSN) ; Sharif University of Technology
2013
Abstract
The electric-field induced response of a droplet embedded in a quenched polyelectrolyte gel is calculated theoretically. The response comprises the droplet translation and the electric-field induced flow fields within the droplet. The gel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no free charge. An analytical solution, using the perturbation methodology and linear superposition, is obtained for the leading-order steady response to a DC electric-field. The fluid within the droplet is driven due to hydrodynamic coupling with the electroosmotic flow. The fluid velocity...
Oscillatory response of charged droplets in hydrogels
, Article Journal of Non-Newtonian Fluid Mechanics ; Volume 234 , 2016 , Pages 215-235 ; 03770257 (ISSN) ; Sharif University of Technology
Elsevier
2016
Abstract
Characterization of droplet-hydrogel interfaces is of crucial importance to engineer droplet-hydrogel composites for a variety of applications. In order to develop electrokinetic diagnostic tools for probing droplet-hydrogel interfaces, the displacement of a charged droplet embedded in a polyelectrolyte hydrogel exposed to an oscillating electric field is determined theoretically. The polyelectrolyte hydrogel is modeled as an incompressible, charged, porous, and elastic solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no charges within the droplet. The droplet-hydrogel interface is modeled as a surface with the thickness of zero...
Transport in droplet-hydrogel composites: response to external stimuli
, Article Colloid and Polymer Science ; Volume 293, Issue 3 , March , 2015 , Pages 941-962 ; 0303402X (ISSN) ; Sharif University of Technology
Springer Verlag
2015
Abstract
Determination of effective transport properties of droplet-hydrogel composites is essential for various applications. The transport of ions through a droplet-hydrogel composite subjected to an electric field is theoretically studied as an initial step toward quantifying the effective transport properties of droplet-hydrogel composites. A three-phase electrokinetic model is used to derive the microscale characteristics of the polyelectrolyte hydrogel, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which encloses the interior fluid. The surface has the thickness of zero and the electrostatic potential ζ. Standard...
A simple particulate sol-gel route to synthesize nanostructural TiO2-Ta2O5 binary oxides and their characteristics
, Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 142, Issue 1 , 2007 , Pages 16-27 ; 09215107 (ISSN) ; Fray, D. J ; Sadrnezhaad, S. K ; Mohammadi, A ; Sharif University of Technology
2007
Abstract
Nanostructured and mesoporous TiO2-Ta2O5 films and powders with various TiO2:Ta2O5 molar ratios and high specific surface area (SSA) have been prepared by a straightforward particulate sol-gel route. Titanium isopropoxide and tantalum ethoxide were used as precursors and hydroxypropyl cellulose (HPC) was used as a polymeric fugitive agent (PFA) in order to increase the SSA. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that powders contained both hexagonal δ-Ta2O5 and monoclinic β-Ta2O5 phases, as well as anatase and rutile. It was observed that Ta2O5 retarded anatase-to-rutile transformation. Furthermore, δ → β phase transformation temperature increased...