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 Taheri, Arman (Author) ; 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 Esperi, Melika (Author) ; 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...

Experimental Study of the Three-Way Catalyst Aging in a Reactor System

, M.Sc. Thesis Sharif University of Technology Salehi, Armin (Author) ; Hamzehlouyan, Tayebeh (Supervisor)

Abstract

Due to the significant role of vehicles in air pollution in Tehran and other metropolitan areas of the country, continuous monitoring and ensuring the quality and durability of automotive after-treatment catalysts based on valid standard methods is essential. One of the methods for evaluating the performance and durability of automotive after-treatment catalysts is using a reactor system that provides test conditions using simulated exhaust gas. In this method, the catalyst sample is exposed to a stream of simulated exhaust gases, and a specific aging cycle is performed by controlling the catalyst's operating conditions, including temperature and air-to-fuel ratio in the exhaust gas. The...

Kinetic Study of Selective Catalytic Reduction of over a Cu/Zeolite Catalyst for Emission Control from Diesel Engines

, M.Sc. Thesis Sharif University of Technology Nozari, Sara (Author) ; Hamzehlouyan, Tayebeh (Supervisor)

Abstract

Urban air pollution has become a significant environmental concern in recent times. NOx recognized as a criterion pollutant, is especially problematic. In 2021, the Tehran Air Quality Control Company reported that the ambient concentration of NOx in Tehran was around 50 ppb, which surpasses both the initial and final targets recently established by the World Health Organization (40 ppb and 10 ppb, respectively). To control and predict NOx emissions from diesel engines, A detailed selective catalytic reduction (SCR) model has been developed to describe the global kinetic reactions within the catalyst. This model incorporates two types of sites for high- and low-temperature NH3...

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 Razmara, Shadi (Author) ; 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...

Evaluation of Zeolite-Based Catalysts for Selective Catalytic Reduction of Nox As Part of Diesel After-Treatment System

, M.Sc. Thesis Sharif University of Technology Asadimanesh, Hoda (Author) ; Hamzehlouyan, Tayebeh (Supervisor)

Abstract

Urban air pollution has emerged as a significant environmental concern in recent times. NOx is classified as a criterion pollutant. In 2021, the Tehran Air Quality Control Company reported that the ambient concentration of this pollutant in Tehran is around 50 ppb which exceeds both the initial and final target recently established by the World Health Organization (40 ppb and 10 ppb, respectively). Diesel vehicles are the primary contributor to NOx emissions in Tehran. To control NOx emissions from diesel engines, Selective Catalytic Reduction (SCR) systems are used according to Euro 4 and Euro 5 standards. Considering the novelty of this technology within the nation, it is critical to...

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) Motahari, A ; 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+,...

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) Motahari, S ; 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) Motahari, S ; 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...

Analysis of Genes Regulating Beta Cells Cell Cycle

, M.Sc. Thesis Sharif University of Technology Saraei, Tannaz (Author) ; 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...

Haploblock Detection Based on Reads and Population Structure

, M.Sc. Thesis Sharif University of Technology Akbari, Elahe (Author) ; 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...

High Dimensional Sparse Learning in Distributed Systems

, M.Sc. Thesis Sharif University of Technology Borghi, Hanieh (Author) ; 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...

Synthesis and Microstructure of Multi Valent Heavily Doped TiO2 Ceramics

, M.Sc. Thesis Sharif University of Technology Motahari, Majid (Author) ; 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...

Fundamental Bounds for Clustering of Bernoulli Mixture Models

, M.Sc. Thesis Sharif University of Technology Behjati, Amin (Author) ; 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...

Inference of Recombination Rate in Iranian Population Genetics

, M.Sc. Thesis Sharif University of Technology Ansari, Ehsan (Author) ; 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,...

Traffic Congestion Prediction based on Tehran Traffic Data using Machine-Learning Algorithms

, M.Sc. Thesis Sharif University of Technology Shabani, Zeinab (Author) ; Motahari, Abolfazl (Supervisor)

Abstract

Metropolitan development and increase in urban population cause a significant rise in intra-city travels and transportation, leading to many problems such as heavy traffic and air pollution, loud noise, and waste of time and human resources. To tackle these problems, it is essential to study the reasons for arising traffic and ways to reduce it. There is a line of research on traffic prediction as one of the potential solutions to the above-mentioned problem. In this research, we intend to analyze the traffic data of Tehran to find the correlation between the traffic density of different streets and provide a method for short-term traffic prediction. This research could be beneficial from...

Genome-wide Association Studies: Controlling False Discovery Rate using Knockoffs

, M.Sc. Thesis Sharif University of Technology Kafi, Mahdi (Author) ; 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...

Design of High Frequency Auxiliary Power Supplies for 1500 Photovoltaic Systems with Voltage Equalization of DC Link Capacitors

, M.Sc. Thesis Sharif University of Technology Motahari, Mahdi (Author) ; Tahami, Farzad (Supervisor)

Abstract

With the rapid expansion of photovoltaic (PV) system applications and the increasing power capacity of solar inverters, the use of 1500 V DC links has become a common standard in the industry. However, employing such a high voltage level in the design of auxiliary power supplies poses challenges, including high voltage stress on switches and the need for voltage balancing across the series-connected DC link capacitors. In this thesis, an innovative auxiliary power supply topology, referred to as a centrally clamped series-input flyback converter with active clamp, is introduced. This topology provides zero-voltage switching (ZVS) by adding only one switch to the conventional series-input...

Discovery of Effective Genes Via Differential Gene Expression Networks

, M.Sc. Thesis Sharif University of Technology Rastegar, Soheil (Author) ; Motahari, Abolfazl (Supervisor)

Abstract

With the emergence of high-throughput gene expression data collection methods, the development of more precise analytical techniques to extract patterns from these data is increasingly necessary. These methods, of course, vary depending on the specific pattern being targeted for extraction. However, identifying key genes and biological pathways responsible for major changes remains the primary challenge in understanding the structure of gene regulatory networks. Understanding these regulatory networks serves as a foundation for a wide range of biological intervention strategies, which can have diverse objectives. In the field of gene expression network inference, numerous challenges exist,...

, M.Sc. Thesis Sharif University of Technology Bakhshi, Bahare (Author) ; 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...