Sharif Digital Repository

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,... 

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... 

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... 

Many Investigations have been carried out on high work hardening, strengthening and secondary hardening of MP35N superalloy. In this study, behavior of MP35N under uniaxial hot compression at 600 °C with true strain of 0.05, 0.10, 0.16 and 0.22 was investigated. After calculating on stress- true strain curve, work hardening rate versus strain come out. Serrated flow has been seen in all mentioned strains. In TEM investigation on these samples, dislocations array with extended faults and micro twinning have been seen. According to Suzuki mechanism with solute partitioning and diffusion of solute, stacking fault extended. Uninterrupted separations and combinations of partial dislocations lead... 

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... 

Few years ago, when people were talking about image sensors, the minds were automatically focusing on the pictures and photos that were/are taken for recording the memories. Nowadays, however, image sensors have prominent and unbelievable role in different aspects of our life, which "image" is only representing part of this role. A wide variety of applications image sensors can be enumerated such as, Scientific, security, medical, machine vision, ITs, biometrics, automotive, etc. To evaluate the quality of an image sensor, there are different parameters, from the dynamic range, high resolution and suitable speed to low noise, low power consumption and other parameters. The art of companies... 

The sustainable development in societies and the global energy challenge requires usage of clean energy systems that have attracted the attention of many researchers in recent decades. One of the major challenges in generating renewable resources is the problem of energy storage and imbalance between supply and demand cycles. Hydrogen as one of the clean energy carriers and due to having the highest energy density in terms of weight, is one of the important research topics. From this point of view, the preparation of electrocatalysts for hydrogen production, based on available materials, via simple and environmentally friendly production methods, was considered in this research.... 

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... 

In recent years, because of power system restructuring and load growth, much of transmission lines are reaching to their maximum capacity. Therefore, it is so essential to upgrade existing transmission system. However, constructing new lines is a very expensive and time consuming method. Dynamic thermal rating of overhead line is an alternative solution for upgrading transmission system capacity. In this method, allowable current capability of line in the next duration is calculated according to the environmental conditions. A method should be developed to perfectly model these environmental changes. Fuzzy method is a powerful tool that models uncertainties and measurement errors in a simple... 

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... 

Recently nanostructure materials have used in various technologies and hence an extensive part of research focused on preparing and optimization of growth of nanostructure materials. Usually common procedure is based on a two-step process. First, construction a pre-layer by means of different deposition methods and then formation a nanostructure with a thermal treatment which increases the cost of research. Hence with one step method such as glancing angle deposition (GLAD ( it is possible to form a desirable structure with low cost. In this research Nano columns of tungsten was deposited on Si(133) by means of GLAD-RF sputtering without any heat treatment at substrate rotational speed ( )... 

The present paper proposes a micromechanical damage model for two and three dimensional Representative Volume Element (RVE) with randomly distributed cohesive rough slit-like and penny-shaped micro cracks (Barenblatt-Dugdale type). First, the influence of crack roughness on the crack opening under macro hydrostatic stress state is studied and then the energy release contribution to material damage process is estimated. Considering the fractality of the crack trajectories yields to lower values of the volume crack opening. This will result in lower energy release rate in RVE and higher levels of material resistance. Based on the energy release rate of RVE, the effective material properties... 

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... 

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...