Sharif Digital Repository

Atmospheric corrosion as one of the most principal factors of destruction is not Climatic map of atmospheric corrosion is closely related to air and atmospheric factors among which we can point out to different types of atmospheric pollutions such as NOX, SOX gases and pendant materials as well as the rate of humidity and rain and even the rate of sun radiation. The effects of these factors beside each other cause the speed of corrosion from a climate to another climate to be changed, which is presentable in form of a map. There is a 2 method to provide this map. First build up a station to measure the corrosion data and collect them in a long period of time. This method are time consuming... 

Bearing capacity of foundations is one of the most controversial issues in foundation engineering. In this study regarding to the previous researches which has done by the other researchers the bearing capacity factors of a footing has calculatedusing finite element method. On the next step of this study some footings has modeled on different positions near slopes with different angles and bearing capacity of them has calculated, then some strip foundation has modeled and bearing capacity of them has calculated and compared with the values of the footings in this study and strip foundations of the other researches. Furthermore some foundations have modeled on the solpe and bearing capacity... 

Each year, large quantities of low/intermediate operational radioactive wastes are produced in different matrices. Usually, these wastes are temporarily stored within the plants and after a certain period, they have to be transferred to landfill sites for final disposal. According to international regulations recommended by IAEA as well as, requirements imposed by national regulatory bodies, waste packages must clear certain requirments called Waste Acceptance Criteria. As such, all waste packages are subject to certain inspections in plant or at disposal facilities. Computerized Tomography (CT) is proven to be one of the most efficient inspection tools for waste packages that can reveal... 

With the spread of threats against industrial control systems, preserving the security of these systems faces serious challenges. On the other hand, with the increase of communication between industrial control networks and external communication networks, the entry points of these networks have also increased and this exposes them to IP network threats. Beside that, traditional attacks on these systems, which generally occur by infiltrating the internal network, are also constantly changing and becoming more complex. These attacks mainly have a phase of hiding the attack from the monitoring systems, which eliminates the possibility of identifying the attacker's operations to a great extent... 

In recent years, due to urban expansion and population growth, number of floors and excavations depth has increased. Stabilization of excavations is one of the most important issues in geotechnical engineering. Today, one of the most widely used methods that is used in deep excavations is brace soil by steels and pretension them. In this thesis tries to evaluate static behavior of flexible supporting structures with pretension anchors by using PLAXIS2D, FLAC3D and GEOSTUDIO softwares. The objective of this modeling is better understanding the static behavior of walls, comparing the two and three dimensional modeling and the effect of corners of excavation on deformation. The results shows... 

Modern broadband microwave and millimeter-wave systems often struggle with excessive pass band ripple and negative gain slopes due to the loss of transmission lines such as coaxial cables, or ripples in the gain characteristic of broadband amplifiers. The common solution for this problem is using a gain equalizer to compensate for the intrinsic pass band variation with some extra loss in the band of interest in return.Designed equalizers often have a constant slope in their bandwidth. However, having ripples in pass band or in other words slope changing in some parts of the band is one of the issues that designers should deal with. In this thesis, after reviewing the previous works on the... 

In this study, a novel multiscale analysis is proposed to utilize atomistic properties of crystalline nano-materials as an input to continuum problems in the range of large deformation. The main purpose of presented work is investigating the capability of different hyperelasticity models based on molecular statics (MS) and molecular dynamics methods to attain proper hyperelastic strain energy density function to illustrate atomistic information under various types of deformation loadings. Also, the proficiency of hyperelastic model is investigated for nano-structure including different percentages of voids. The material parameters of hyperelastic strain energy density can be obtained from... 

This dissertation focuses on addressing electromagnetic forward and inverse scattering problems using physics-based deep learning models. A key challenge in integrating physics with data-driven models lies in the implicit nature and nonlinearity of the forward scattering operator. To address this, a novel closed-form expression is proposed for piecewise homogeneous media. By formulating the scattered field as an implicit function of the permittivity values in each homogeneous region, the computational complexity of solving the forward problem for a fixed geometry is changed from O(N^3 ) to O(NΣM_k^2), where N is the total number of meshes, and M_k refers to the meshes in the kth region. This... 

In this study TiO2/SiO2 thin films were prepared by sol-gel method from Tetra isopropylortho Titanate(TIPT) as the principle of TiO2 material with Tera ethoxysilane(TEOS) as the principle of SiO2 material to achieve high scratch-resistant , antibacterial and self-cleaning surface area under the effect of various percentage of SiO2 . Film deposition was carried out using a dip-coating technique and heat-treatment was used at 700ºC to achieve crystalline of films with excellent adherence the of substrate.
The surface morphology of the films has been observed by Scanning Electron Microscope (SEM) and the tribological properties of the surface were investigated by Atomic Force Microscope... 

Ball mills are a category of industrial mills used for crushing and grinding non-metallic materials into powder. In these mills, as the mill rotates, steel balls move and by falling on materials, the process of crushing and grinding takes place. The mismatch between the rotation speed of the mill and the volume of balls inside it can result in ineffective collisions between the balls or between the balls and the inner protective layers of the mill, causing damage to the balls and liners and leading to repair costs and loss of production. The aim of this project is to design and prototype an intelligent system for monitoring the ball mass inside the mill to increase production efficiency and... 

In this study thermodynamics and kinetics effects of two ionic liquids (ILs) on the formation and dissociation of methane and carbon dioxide hydrates were investigated. The ILs used in this study are 1-butyle-3-metylimidazolium tetrafluoroborate, [Bmim][BF4], and 1-butyle-3-metylimidazolium methyl sulfate, [Bmim][MS]. At the first step of experimental section, the tetrahydrofuran (THF) was used in atmospheric pressure. The structure of THF hydrate is similar to natural gas hydrate; therefore it is used as a model for studying the properties and investigation of inhibitors effects on gas hydrates. In order to consider the effects of foregoing ILs on the formation and dissociation of gas... 

Deployment of demands, increase in users and new services highlight the necessity of effective frequency allocation i.e. dynamic allocation instead of fixed allocation. Cognitive radio is a proper solution for dynamic frequency allocation. Cognitive radio can scan the spectrum and use the idle bands for transmitting and receiving data. The main part of this radio which is responsible for the most pivotal task is spectrum sensing. Recently, varied methods have been proposed to sense the spectrum. The scope of this research is on designing a very high-speed spectrum sensing system. In this thesis, in order to meet the required scan rate, a tunable complex filter with 40MHz pass-band has... 

The potential future use of hydrogen as a transportation fuel must be evaluated from a supply chain perspective. However, the main challenge in motivating the hydrogen supply chain network is the lack of existing hydrogen infrastructure. Strategic decisions for planning sustainable infrastructure can be analyzed hierarchically in time-related stages (2025-2030-2035). Meanwhile, a time- and location-based design has been specifically applied to a few selected ports in southern Iran, with limited focus on a national or countrywide scale. This study proposes a mixed-integer linear programming (MILP) optimization model to logically design the hydrogen supply chain, considering primary energy... 

In this thesis, the transmission characteristics of a vertical tunneling transistors based on graphene-hBN-MoSe2 heterostructure is studied. We first obtain the tight-binding parameters required for Hamiltonian matrix and bandstructure calculations using density functional theory results. Once we have the tight-binding parameters, Hamiltonian and coupling matrices are calculated both of size 326×326. We then proceed to calulate the density of stated for source and drain contacts using the aforementioned matrices and nonequilibrium Green’s function(NEGF) formalism. We can then calculate the quantum capacitances of source and drain and acquire source/drain potentials using a capacitive circuit... 

The objective of this research is to investigate fluid flow in cracked porous media. Fluid, mass, and heat transfer in porous and cracked porous media, particularly in subsurface environments characterized by complexity and uncertainty—such as hydraulic fracturing, lowـpressure groundwater flow, and more—are of great importance in the oil and geothermal energy industries. The problem domain consists of three main sections: the saturated porous medium, the crack or channel within this porous medium, and the boundary layer between the crack and the adjacent environment. The phase field method is utilized in this study to model these discontinuities. Phase field models are similar to... 

The aim of this study was electrodeposition of Zn-Ni-P/Zn-Ni multilayer coatings by single-bath method from a citrate bath to produce a sacrificial coating with high barrier properties compared to Zn-Ni monolayer coating. The coatings that were prepared at 10 mA/cm2 was Zn-Ni-P (Ni-rich and percentage of zinc, nickel and phosphorus, respectively: 40, 50 and 10 %), and the alloy deposited in 60 mA/cm2 were practically Zn-Ni (Zn-rich, 85% zinc) and almost phosphorus free. Galvanostatic pulse deposition method through switching of the current density between the two values mentioned in monolayers (10 and 60 mA/cm2) in different time periods to create bilayers corresponding to the monolayers,... 

Many processes and real world systems indicate nonlinear behavior and operate either naturally in multiple regions or in a wide range of operation space. Modelling and control of these systems by nonlinear methods needs to have a deep insight. Furthermore, the nonlinear methods leads to complexity issues. To overcome these problems, multi-model methods are introduced which consist of two steps, decomposition and combination. In decomposition step, the complex system is divided into a set of simple models; in the combination step, the behavior of local models are combined. How to decompose to local models and how to combine them are two main questions in this area which not answered... 

By studying and evaluating methods for producing deuterium gas from heavy water, the electrolysis method with polymer membranes (PEM) was defined as the proposed method.The (PEMWEs) is a new method in electrolysis, which utilizes solid polymer electrolyte (SPE) membranes as electrolytes to play a significant role in reducing the resistivity in the electrolysis and also in comparison with alkaline electrolysis in terms of energy consumption and optimal being in condition is also a better condition for the purity of the produced gas.In this regard, a polymer electrolyte membrane water electrolysers (PEMWEs) was designed and developed on a laboratory scale. After analysis of the sample gas, and... 

Electromagnetic levitation(EML) provides a process producing nanoparticles using gas condensation method. In gas condensation processes, vapor is produced by heating the sample then inert gas is applied to provide the inert atmosphere and also cool and condense the sample vapor into a nano powder to obtain a sample nanoparticle. In the EML method, rapidly alternating electromagnetic field induces eddy current in the conducting sample which will heat the sample. The current in the sample result in an induced magnetic field. Consequently, the sample droplet is heated and levitated simultaneously by an induction furnace as a generator. The sample temperature is dependent on parameters such as... 

Shallow geothermal energy is a renewable and sustainable form of energy that has the potential to help alleviate the growing climate and energy crisis. The most common system used to extract shallow geothermal energy is the ground source heat pump (GSHP) system. The concept of using underground structures in exploiting shallow geothermal energy for space heating and cooling has received increasing attention. This study focuses on the use of geothermal tunnels as a means of extracting shallow geothermal energy.This research examines the effects of different heat transfer mechanisms, and highlights the effects of this phenomenon by focusing on the effects of natural convection around the...