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motahari--tayebeh
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Experimental Study of the Aging Effect on the Oxidation Catalyst Performance as an Emission Control Device for 4-stroke Gasoline Carburetor Motorcycles
, M.Sc. Thesis Sharif University of Technology ; Hamzehlouyan, Tayebeh (Supervisor)
Abstract
There are more than one million motorcycles in the city of Tehran that are responsible for significant amounts of various air pollutants emissions such as carbon monoxide and hydrocarbons. Oxidation catalysis, as the exhaust aftertreatment system of motorcycles, can reduce the emission of CO and hydrocarbon pollutants. The efficiency of these catalysts under typical operating conditions of vehicle exhaust gas has been studied in the literature. However, due to the specific features of motorcycles exhaust gas in Tehran, such as ultra-rich combustion, low air to fuel ratio (lambdas as low as 0.6-0.7), different exhaust gas composition and significant amount of lubricating oil consumption,...
Synthesis and Evaluation of a Three-Way Catalyst for CO, Hydrocarbon and Nitrogen Oxide Emission Control in CNG-Fueled Vehicles
, M.Sc. Thesis Sharif University of Technology ; Hamzehlouyan, Tayebeh (Supervisor)
Abstract
According to the reports of the Tehran Air Quality Control Company, mobile sources are responsible for the emission of 70-85% of air pollutant in this metropolis. Over the past decades, compressed natural gas (CNG) is known as a cleaner fuel and a suitable alternative to gasoline and diesel fuels in the transportation section in some countries. However, methane emissions from natural gas vehicles is a significant challenge because it is a potent greenhouse gas and plays important role in global warming. In addition, because of another pollutant emissions from these vehicles, exhaust gas treatment is a crucial issue. Using Three-Way catalysts (TWC) is the conventional method in order to...
Modification of Three-Way Catalyst (Twc)Formulation for Gasoline Vehicles with the Goal of Improving Its Thermal Stability
, M.Sc. Thesis Sharif University of Technology ; Hamzehlouyan, Tayebeh (Supervisor)
Abstract
Vehicle exhaust gas catalysts play a significant role in air pollution control. In order to solve the problems of cold start and limited supply of precious metals, new studies have focused on the development of three-way catalysts for gasoline vehicles with small amounts of precious metals and increase thermal stability. Different metal ions, especially rare earth metals, due to different physical and chemical properties, show different reinforcing effects on the properties of ceria-zirconia-based materials. Previous studies have shown that the enhancing effect of these materials and the ceria-zirconia ratio on catalyst activity and stability, as well as studies on thermal stability at 1050...
, M.Sc. Thesis Sharif University of Technology ; Hamzehlouyan, Tayebeh (Supervisor) ; Khorasheh, Farhad (Supervisor)
Abstract
Diesel oxidizing catalysts (DOCs) based on precious metals of Platinum and Palladium are among the most important and most widely used catalysts in the exhaust aftertreatment system of diesel cars. DOCs are used to oxidize CO and hydrocarbons to reduce their emissions to the environment. In spite of the excellent performance of DOCs, sulfur exposure can lead to their deactivation. Sulfur is mainly in the form of SO2 at the combustion chamber exit, which can be further oxidezed to SO3 on the DOC. The deactivation impact of SO2 and SO3 on DOCs are different, with SO3 leadig to higher degrees of deactivation. In this study, a kinetic model for SO2 oxidation on a bimetallic Pt-Pd-based catalyst...
Synthesis and Microstructure of Multi Valent Heavily Doped TiO2 Ceramics
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor)
Abstract
In this project, the nanostructured titanium oxide with heaily doping of oxides of cerium and tin was synthesized using the sol-gel process and its properties were studied. To synthesize TiO2, titanium tetraisopropoxide precursor was used. Cerium nitrate and aqueous tin chloride precursors were utilized for cerium and tin synthesis. Then, they were mixed with Titania precursor causing a severe doping. After that, a gel was produced and it was aged and eventually, it was dried and calcined. XRD and SEM were used to determine the phase and particle size SEM and XRD results showed that doping had great impact on TiO2 crystals. The approximate size of nanoparticles was calculated using...
Theoretical aspects of the enhancement of metal binding affinity by intramolecular hydrogen bonding and modulating p: K a values
, Article New Journal of Chemistry ; Volume 41, Issue 24 , 2017 , Pages 15110-15119 ; 11440546 (ISSN) ; Fattahi, A ; Sharif University of Technology
Royal Society of Chemistry
2017
Abstract
Polyols were used as model ligands for Mg2+, Ca2+, and Zn2+ complexes to study the role of the hydrogen bond network on the metal binding affinity and modulation of successive pKa values using density functional theory. The results confirm that the acidity of polyols dramatically increases upon metal complexation in the order Zn2+ > Mg2+ > Ca2+. For example, the three H-site positions in the hydroxyl groups of the heptaol, bound to Zn2+, are 11.2, 29.9, and 30.9 pKa units (in methanol) more acidic than those of pure heptaol. This acidity enhancement leads to making polyols as good ligands toward complexation. For instance, the formation constants of the heptaol in the presence of Zn2+, Mg2+,...
Analysis of Genes Regulating Beta Cells Cell Cycle
, M.Sc. Thesis Sharif University of Technology ; Motahari, Abolfazl (Supervisor)
Abstract
Diabetes mellitus is a group of disorders where the level of blood sugar remains high for a long period of time. This increase may be due to either reduced insulin secretion from the pancreatic gland, or insulin resistance, or both. Another key reason is the destruction of beta cells due to functional defect in the body’s immune system. Current treatments include controlling diet, insulin injection and pancreatic transplantation, all of which are temporary. For this reason, finding genetic factors participating in the progression of the disease and adapting treatments to these factors are under intensive studies.In this thesis, available information resources including genomic, biological...
Effects of altitude and temperature on the performance and efficiency of turbocharged direct injection gasoline engine
, Article Journal of Applied Fluid Mechanics ; Volume 12, Issue 6 , 2019 , Pages 1825-1836 ; 17353572 (ISSN) ; Chitsaz, I ; Sharif University of Technology
Isfahan University of Technology
2019
Abstract
Iran is located at the high altitude region and has a diverse four season climate. The temperature difference of two locations at the same time reaches to 50° C. Therefore, the modern direct injection turbocharged engines are highly affected at this condition. This paper deals with the effects of temperature and pressure variations on the engine performance and fuel consumption of turbocharged gasoline direct injection engine. Ford ecoboost is selected for this study and the base experiments are performed at the sea level. At the next step, a comprehensive one-dimensional model of the engine is constructed in GT power and validated with experimental data. Validated model is implemented to...
Effects of altitude and temperature on the performance and efficiency of turbocharged direct injection gasoline engine
, Article Journal of Applied Fluid Mechanics ; Volume 12, Issue 6 , 2019 , Pages 1825-1836 ; 17353572 (ISSN) ; Chitsaz, I ; Sharif University of Technology
Isfahan University of Technology
2019
Abstract
Iran is located at the high altitude region and has a diverse four season climate. The temperature difference of two locations at the same time reaches to 50° C. Therefore, the modern direct injection turbocharged engines are highly affected at this condition. This paper deals with the effects of temperature and pressure variations on the engine performance and fuel consumption of turbocharged gasoline direct injection engine. Ford ecoboost is selected for this study and the base experiments are performed at the sea level. At the next step, a comprehensive one-dimensional model of the engine is constructed in GT power and validated with experimental data. Validated model is implemented to...
High Dimensional Sparse Learning in Distributed Systems
, M.Sc. Thesis Sharif University of Technology ; Motahari, Abolfazl (Supervisor)
Abstract
Distributed learning has been a popular area of machine learning for researchers according to having access to an unprecedented amount of data distributed over many clients in a network. Moreover, high dimensional learning, when the dimensions of data are high but the effective features are low, has great usage in learning especially in medical science. In this paper, we attempted to develop a method for learning high-dimensional sparse problems in a distributed manner, whit a star shape network. Our main focus in this research is on optimizing the communication flow in the network. The prominent idea of our proposed method is to extract the main feature in the first step, then continuing...
Haploblock Detection Based on Reads and Population Structure
, M.Sc. Thesis Sharif University of Technology ; Motahari, Abolfazl (Supervisor)
Abstract
Human is diploid specie that inherits a set of chromosomes from their mother and a set from their father. The process of separating the nucleotide content of a set of extracted maternal and paternal chromosomes for an individual or a population is called phasing the genome of the individual or the population. The placement of any two variants relative to each other in diploid species is possible in two forms: cis (placement of both variants on one chromosome), and trans (placement of variants on different chromosomes). Each of these conditions leads to different phenotypes. Thus, understanding how variants are placed relative to each other is a crucial problem in human biology which is...
Inference of Recombination Rate in Iranian Population Genetics
,
M.Sc. Thesis
Sharif University of Technology
;
Motahari, Abolfazl
(Supervisor)
Abstract
Population genetics studies the distribution and changes in allele frequencies under the influence of five main evolutionary processes: natural selection, genetic drift, mutation, gene flow, and recombination. Among these, the recombination process can influence a wide range of biological processes by rearranging genes, repairing DNA structure, and participating actively in cell division mechanisms. Recombination has the ability to create genetic diversity through gene rearrangement, which is the main reason for creating diversity and evolution in organisms. Models such as Hill-Robertson have proven the influential role of recombination in accelerating evolutionary mechanisms. Also,...
Genome-wide Association Studies: Controlling False Discovery Rate using Knockoffs
, M.Sc. Thesis Sharif University of Technology ; Motahari, Abolfazl (Supervisor)
Abstract
In recent years, with the advancement of genetics technologies, many data from this field have been made available to researchers. Therefore, many analytical problems have been defined for these data. Genome-wide association studies, or GWAS for short, is one of these issues that deals with finding genetic positions affecting traits or diseases. Common approaches to this problem either examine genetic variants one by one or fail to consider the specific structure of genetic data. Also, both mentioned approaches do not provide a guarantee to control the rate of false positives. In this thesis, an attempt has been made to propose a method to solve the GWAS problem by using the new statistical...
Fundamental Bounds for Clustering of Bernoulli Mixture Models
, M.Sc. Thesis Sharif University of Technology ; Motahari, Abolfazl (Supervisor)
Abstract
A random vector with binary components that are independent of each other is referred to as a Bernoulli random vector. A Bernoulli Mixture Model (BMM) is a combination of a finite number of Bernoulli models, where each sample is generated randomly according to one of these models. The important challenge is to estimate the parameters of a Bernoulli Mixture Model or to cluster samples based on their source models. This problem has applications in bioinformatics, image recognition, text classification, social networks, and more. For example, in bioinformatics, it pertains to clustering ethnic groups based on genetic data. Many studies have introduced algorithms for solving this problem without...
Examination of Activity of Three-Way Catalysts Toward CO and Hydrocarbon Emission Reduction from Tehran Gasoline Taxis
, M.Sc. Thesis Sharif University of Technology ; Hamzehlouyan, Tayebeh (Supervisor) ; Hosseini, Vahid (Co-Supervisor)
Abstract
Air pollution is one of the main environmental problems in Iran's metropolises, especially in the city of Tehran. Taxis have a significant contribution to pollution due to the long distances they travel during the day. Due to the fact that the operation of automotive three-way catalysts is a function of their operating conditions, and considering the different fuel composition in Iran and the specific conditions of engine performance, exhaust gas composition can be different from similar cases abroad. A commercial three-way catalyst was tested to evaluate its performance under conditions relevant to the exhaust gas of Tehran's taxis fleet. In this study, CO and C3H6 were considered as the...
Routing Techniques Using Nature-Inspired Metaheuristic Algorithms
, M.Sc. Thesis Sharif University of Technology ; Motahari, Abolfazl (Supervisor)
Abstract
One of the complex problems is routing. This problem becomes more difficult and important in certain situations, which cannot be solved straightforwardly. In this thesis, a model for vehicle (ambulance) routing problem during hospital evacuation in disaster conditions is described and solved using Gray Wolf Optimization (GWO) algorithm in combination with a local search algorithm called Great Deluge Algorithm (GDA). It is shown that the combination of GWO and GDA can improve the efficiency of GWO and avoid local optima. The results are compared with some metaheuristic algorithms. To test the model of 11 hospitals in Tehran, three different modes have been considered, and in each mode, 7...
Deep Neural Networks: Tradeoff Between Compression and Communication Rates
, M.Sc. Thesis Sharif University of Technology ; Motahari, Abolfazl (Supervisor)
Abstract
In recent years, the use of Deep Neural Networks in solving various problems has grown considerably. Possessing a large number of parameters, these networks have the ability to reconstruct complex functions and relations from large amounts of data and have been able to achieve the best results in a wide range of problems. But using these models comes with its own problems. These networks typically require considerable resources in order to run. This makes it inefficient or impossible to use them in systems with limited processing capabilities, e.g mobile phones. The existing approaches, e.g. the deployment of the model on a powerful server and network compression, have their own drawbacks...
Kinetic Modeling of Hydrothermal Aging of an Oxidation Catalyst with Wiremesh Structure as Part of the Motorcycle Emission Control System
, M.Sc. Thesis Sharif University of Technology ; Hamzehlouyan, Tayebeh (Supervisor) ; Khorasheh, Farhad (Supervisor)
Abstract
Diesel oxidation catalysts (DOCs) containing precious metals such as platinum and palladium are crucial components of the after-treatment system for exhaust gas purification in diesel vehicles and motorcycles. These catalysts aid in reducing the emission of pollutants into the environment by oxidizing carbon monoxide (CO) and hydrocarbons (HCs). However, their efficiency in removing environmental pollutants diminishes over time due to various deactivation mechanisms, especially by sintering. Given the significant contribution of motorcycles to CO and HC emissions, especially in least-developed countries, experimental and simulation studies on fresh and aged DOCs are essential for the optimal...
Photocatalytic Degradation of Organic Pollutants in the Presence of Nanocomposites Based on Graphitic Carbon Nitride under Visible Light Illumination
, M.Sc. Thesis Sharif University of Technology ; Hamzehlouyan, Tayebeh (Supervisor) ; Rahman Setayesh, Shahrbanoo (Co-Supervisor)
Abstract
The susceptible light-harvesting and tremendous reduction capability along with the potentiality (photo)electrochemical merits of the thiospinels like CuCo2S4 (CCS) bring forth appreciably an advancement in efficacious photocatalytic reactions. However, scant oxidation potential originated from 3p orbitals of sulfur atoms puts a damper on their performance and is even conducive to self-oxidation. In this research, the surfactant/template free of hierarchical CCS thiospinels was synthesized using solvothermal sulfidation of the affordable glycerate-based CuCo-alkoxide and successfully was embedded with Z-scheme V2O5 deposited on wrinkled g-C3N4 lamella (VO-UCN) in the interest of developing...
Evaluation of the Effect of the Presence of Activated Carbon Powder on the Microbial Removal of Azomethyl Red Dye by Klebsiella Bacteria
,
M.Sc. Thesis
Sharif University of Technology
;
Yaghmaei, Soheila
(Supervisor)
;
Bagheri Lotfabad, Tayebeh
(Supervisor)
Abstract
Synthetic azo dyes are one of the most common environmental pollutants in wastewater due to their many uses in various industries such as textile, printing, food, cosmetics, etc. In this project, the bacterial removal method is used to remove azo methyl red dye, and according to the functional groups on the surface of activated carbon, its effect on the efficiency and rate of the microbial removal process of azo methyl red dye is investigated. For this purpose, dye removal tests for each dye concentration (0.1 to 6 mM) in three separate series, as (1) dye removal in the presence of bacteria, (2) dye removal in the presence of activated carbon, and (3) dye removal was investigated in the...