Sharif Digital Repository

Wireless sensor networks (WSNs) are tiny devices with limited computation and power supply. For such devices, data transmission is a very energy-consuming operation. Data aggregation eliminates redundancy and minimizes the number of transmissions in order to save energy. This research explores the efficiency of data aggregation by focusing on different aspects of the problem such as energy efficiency, latency and accuracy. To achieve this goal, we first investigate data aggregation efficiency with constraint on delay, which can be compatible with other important system properties such as energy consumption and accuracy. By simulation, we will show that, depending on the application, we can... 

In the present thesis, the movement of the clusters of fullerenes and nanocars are separately investigated on graphene surface, using molecular dynamics simulations. Investigating the fullerene clusters with different populations, it is concluded that, as the number of molecules inside the cluster increases, the displacement range of the motion decreases. In fact, some parts of the energy of the fullerene cluster are wasted through the intermolecular interactions, and as a result, the mobility of the cluster diminishes. During the investigation of the three-dimensional structures of fullerene, the wetting property of the clusters is revealed relative to the graphene surface. The decrease of... 

The main focus of this project is the fabrication of surface engineering scaffolds based on polyurethane and titanium dioxide. The research's aim is the creation of the synergistic properties of TiO2 and PU as a new strategy for engineering artificial autologous blood vessels. In the first section, PU-TiO2 nanocomposites were synthesized by co-insitu synthesis of nanoparticles and polymer. The nanocomposite films were prepared by solvent casting and thermally induced phase separation methods. Mechanical and biological properties of films were compared with pure PU film. In solvent casting method, the outcomes revealed that the rate of endothelialization of the nanocomposite scaffold after 7... 

Nanomachines are molecules inspired by natural molecular machines and are able to move and transport at the nanoscale. Due to the advancement of nanotechnology, the need to move materials and energy on a small scale is necessary more than ever. Nanocars are artificial molecular machines with chassis, axles, and wheels designed for nanoscale transport at materials’ surfaces. Understanding the dependence of surface dynamics of nanocars on the substrate’s physico-chemical properties is critical to the design of the transport properties of such man-made nanoscale devices. Among the multitude of potential substrates for the nanotransporters, graphene exhibits intrinsic ripples on its surface,... 

The broad range of applicability of nano devices particularly in electronics, optoelectronics, and micro/ nano-electro- mechanical systems has drawn the attentions of the industrial and scientific communities of various disciplines. This work is devoted to study the effect of surface and interface elasticity in the analysis of the mechanical behavior of ultra-thin objects in the presence of some statical or dynamical loadings. Based on the fact that the surface-volume ratio increases in nano-scale, description of the behavior of such a small structure via usual classical theories, which generally neglect the surface/interface effect, ceases to hold. In the present study, first, a... 

Today, the rapid and increasing growth of various human societies has led to an increased consumption of energy and the need for new resources. In fact, the excessive consumption of energy, especially fossil fuels, has caused adverse and sometimes irreversible effects on the human environment. Also, the consumption of different types of fossil fuels such as coal, oil, and natural gas, leads to a significant increase in greenhouse gases in the atmosphere. On the other hand, population growth and technological advancements in the last century have led to an increase in the demand for energy carriers. Therefore, the use of new energy sources instead of fossil fuels is an inevitable matter.... 

This research uses systems dynamics modeling to present an integrated assessment of the energy-economic damage caused by climate change in Iran under different climate scenarios. Implementing these policies will cause a change in the use of global oil, followed by a change in the outlook for oil price changes in the future. Due to the high dependence of the country's economy on fossil fuels, oil price changes affect the country's economy. In the first step of this thesis, the system dynamics method examines the prospect of oil price change in climate scenarios. Then, according to the oil supply and production, in different scenarios, the assessment of the future conditions of the oil market... 

In recent years, the significant growth of the population has led to an increase in energy demand and subsequent rise in waste production. A substantial share of the energy demand and consumption in the industrial sector, particularly in steel production, requires the utilization of renewable technologies for energy and clean fuel production, such as hydrogen, to address this growing demand and mitigate environmental impact. This study focuses on a waste-to-energy technique as a viable solution to facilitate the transition towards green steel production in the industrial sector of Kerman province, primarily targeting the decarbonization of utility generation in steel production process.... 

Air pollution has been one of the most important problems in Tehran in recent years. So that the number of deaths due to air pollution in Tehran reaches more than 7000 cases per year. More than 75% of air pollutant emissions in Tehran city (including 60% of PM2.5 emissions) originate from mobile sources. Considering the harmful effects and damages caused by air pollutants, it is important to examine and evaluate the effects of hybrid-electric vehicles on the emissions of the transportation sector and air quality, especially in areas with a large population and realized high traffic load. On the other hand, the continuous reduction of renewable electricity production costs makes electricity a... 

The main purpose of this research is to select a suitable solution for regeneration of ion exchange resins of TR system of Bushehr nuclear power plant and also to compare and evaluate the possibility of using industrial cationic resin (Amberlite IR120) instead of nuclear grade cationic resin (Amberlite IRN97).First, different solutions for regeneration of cationic resins were investigated. For this purpose, three strong acids including hydrochloric acid (HCl), sulfuric acid (H2SO4) and nitric acid (HNO3) were selected and each of these acids was tested in two different concentrations and two different linear velocities; Also, to evaluate the appropriate solution for anionic resin... 

In the method treatment of thermobrachytherapy, the method of this project, simultaneously use of two processes of thermotherapy and brachytherapy is considered, which can be a more effective treatment for the destruction of tumor tissue. In thermotherapy, the temperature of the tissue is artificially raised to a temperature that leads to cell dysfunction resulting in cell death. In brachytherapy, the destruction of defective tissue is done by placing a source in the tissue. In the present project, we supposed to consider both mechanisms simultaneously for treatment at the same time. In this project, radioactive material 125I is used as a source of radiation emission for brachytherapy. In... 

nowadays, due to population growth, unconventional use of water resources and on the other hand, climate change, limited renewable water resources, reduction of groundwater cavities, the need for water for agricultural use and energy production are increasing. Due to the fact that each cubic meter of dirty water pollutes 40 to 60 cubic meters of clean water and the entry of polluted effluent into the receiving sources of environmental degradation leads to a lot of wastewater treatment, water consumption management and The development of wastewater treatment processes is also becoming increasingly important. At present, wastewater treatment plants face the challenges of high energy... 

Steels as structural materials of pressure vessels of nuclear reactors, in addition to high temperatures and pressures, are exposed to ionizing radiation such as neutrons. The primary effects of damage caused by exposing these solids to radiation are the displacement of atoms from their equilibrium positions and the formation of point defects and damage clusters caused by damage accumulation due to displacement cascades produced by transmitting the energy of the incident particle to an atom by interactions such as elastic and inelastic scatterings neutrons with the nucleus. These microstructural changes cause large structural defects such as swelling, cracking, cracking, creep, reducing... 

The water and energy demand increase as the population grows. Increased usage of energy leads to scarcity of available resources and limited absorption capacity of environment. Development of efficient and environmentally compatible energy conversion technologies are conceived as an important option for resolving pressing challenges. Compatibility with environment requires considerable reduction in the share of fossil fuels and efficient utilization of renewable energy sources. Hence, development of high-efficiency solar energy systems is becoming an important challenge in the energy sector. The present study is involved with development an integrated solar system based on the application of... 

Concentrated photovoltaic systems (CPVs) allow simultaneous production of electrical energy and high-temperature thermal energy. These systems consist of a concentrator for collecting solar rays onto the surface of the recipient cells. Moreover, these systems are always facing the sun using a sun tracker. The heat generated by these systems can be used in industrial processes, heating, cooling, and water desalinating. Given the concurrent generation of power and high-temperature heat, it is possible to achieve higher efficiency than that of conventional solar systems. Furthermore, the electrical efficiency is also higher than conventional systems due to the use of multi-junction solar cells... 

The safety and optimal performance of nuclear reactors require online monitoring in the core. One of the most important requirements of core monitoring is the knowledge at all time of the neutron flux distribution in the core. The present M.Sc thesis describes a method which avoids the solution of time dependent neutron diffusion equation and uses online readings of the fixed in-core neutron detectors to reconstruct the three-dimensional (3D) neutron flux distribution. The essential idea of nodal synthesis method is separation of time and space dependence of the neutron flux distribution. The time dependent section of the flux distribution is determined by neutron detector readings and space... 

Uranium recovery from wastes produced in every stage of nuclear fuel cycle is very important from both the economic and environmental points of view. Zircon, zirconium-containing ore that is the input feed to Zirconium sponge production factories, contains considerable amounts of uranium compounds. The majority of this uranium will enter to the different waste streams of the plant. In this study, by analyzing the waste streams of the Zirconium Production Plant (ZPP) located at Isfahan, Iran, total mass balance of uranium in waste streams was identified. It was concluded that bottom residuals at furnaces of the chlorination unit is the primary uranium-containing waste stream. The preliminary... 

One layer mirrors are inexpensive and perform robustly across a broad range of angles, wavelengths, but they exhibit limited reflectivity. Multilayer interference mirrors are routinely used for optical applications requiring high reflectivity and wavelength selectivity. Although they can be designed to achieve a wide range of optical characteristics. One of the main applications of this multilayers in accelerators is guide outpot beamline to receive user. We can optimize these mirrors to give hight reflectivities, and outpot beam with reflect in canal that is equiped this mirrors reach to user. Conditions such as: material of layers, thickness and number of layers, surface roughness, …etc.... 

Renewable energy sources have significantly used in recent years and the associated technologies have been widely developed. Grid connection of most renewable technologies, such as photovoltaic and wind turbine, is accomplished using power electronic converters. Control of injected active and reactive power as well as current and frequency control of is, so, implemented through the power converter. Inverter is among the equipments widely used for grid connection The purpose of this project was to design and develop an inverter for grid connection of renewable generation technologies for laboratory use. The inverter is aimed to control both injected active and reactive power. A full-bridge... 

Total air particulate matter of the city of Isfahan has been measured for elemental characterization in four principal directions of the city and during the year 2007-2008. High volume air samplers using whatman 41 filters have been utilized and instrumental neutron activation analysis has been used as the analytical method. Twenty one elements arising from seasonal and geographical distributions of the various elements have been determined. These distribution patterns have been discussed in view of the prevailing wind direction, location of the industrial facilities, and the Pearson correlation coefficients