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Experimental Study of Venturi-Enhanced Solar Evaporative Desalination System
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor)
Abstract
The scarcity of freshwater resources in many communities worldwide is a pressing challenge that requires immediate attention. One of the most promising solutions to address this issue is the conversion of seawater into freshwater using solar energy to power desalination processes. The efficiency of this process can be further enhanced by reducing energy consumption through the lowering of the vapor saturation temperature of saline water.To this end, the present study investigates the use of evacuated tube collector technology for water heating and a vacuum system to lower the evaporation temperature of saline water. Specifically, the system employs a water cycle with a venturi to facilitate...
Effect Analysis of Arrangement, Sequence and Plate Thickness of Spot Welding on Residual Stress and Fatigue Life of The Joint
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhosein (Supervisor)
Abstract
There are about 5,000 spot welds in the car body. Simulation of this number of spot welds to optimize the body of the car is practically impossible. In researches done in order to model and optimize the spot weld, standard spot weld sample with a nugget have been always used. Electrical current in spot welding process turns to heat according to the Ohm ratio, and causes the melting of the pieces and bonding. So amount of the electrical resistance, especially at the contact surface of the two pieces, is very important.In order to investigate the residual stresses induced in the connection of a three-sheet spot weld sample and its effect on fatigue life, first, a spot weld sample with...
A Survey in Inflation and Roots of Axionic Inflationary Models
,
M.Sc. Thesis
Sharif University of Technology
;
Abolhasani, Ali Akbar
(Supervisor)
Abstract
Inflation first introduced for solving the puzzles of the standard model of cosmology. Soon it became clear that this paradigm can provide a natural way for production of Initial conditions for the birth of large-scale structures: cosmological perturbations. But inflationary models are usually phenomenological models. They are constructed to solve the problems of the standard model of cosmology and explain the properties of cosmological fluctuations. Where do they come from? A property of a big family of inflationary models is the flatness of their potential. What would may be the cause of this flatness? . . .. In this thesis our purpose is searching about one probable field theoretic root...
A geographical question answering system
, Article 3rd International Conference on Web Information Systems and Technologies, Webist 2007, Barcelona, 3 March 2007 through 6 March 2007 ; Volume WIA , 2007 , Pages 308-314 ; Ghasemzadeh, H ; Sheykh Esmaili, K ; Minaei Bidgoli, B ; Sharif University of Technology
2007
Abstract
Question Answering systems are one of the hot topics in context of information retrieval. In this paper, we develop an open-domain Question Answering system for spatial queries. We use Google for gathering raw data from the Web and then in a few iterations density of potential answers will be increased, finally based on a couple of evaluators the best answers are selected to be returned to user. Our proposed algorithm uses fuzzy methods to be more precise. Some experiments have been designed in order to evaluate the performance of our algorithm and results are totally promising. We will describe that how this algorithm can be applied to other type of questions as well
Investigation and numerical simulation of two-phase ejectors for use in the water desalination cycle
, Article Case Studies in Thermal Engineering ; Volume 54 , 2024 ; 2214157X (ISSN) ; Riahi, A ; Payamiazad, P ; Minaei, M ; Shafii, M. B ; Sharif University of Technology
Elsevier
2024
Abstract
This study investigates enhancing energy efficiency in desalination by introducing a novel combined ejector-solar vacuum tube collector cycle. The cycle utilizes a two-phase state and lower-temperature saturated steam generation to overcome the energy consumption hurdle, particularly by compressors. Water enters the ejector's primary nozzle in a liquid phase, while steam from the solar collector aids in separation, yielding desalinated water in a variable phase. Fluent software's computational fluid dynamics assesses the ejector's performance, considering primary and secondary inlet pressures' impact on hydrodynamic characteristics. TRNSYS software models the cycle transiently over a year in...
Analysis of resistance spot welding process parameters effect on the weld quality of three-steel sheets used in automotive industry: Experimental and finite element simulation
, Article International Journal of Engineering, Transactions A: Basics ; Volume 33, Issue 1 , 2020 , Pages 148-157 ; Reza Kashyzadeh, K ; Minaei, M ; Sharifpour, A ; Riazi, S ; Sharif University of Technology
Materials and Energy Research Center
2020
Abstract
In the present research, the effects of spot-welding process parameters on the nugget diameter and electrode penetration depth of spot-welded joints were investigated. To achieve this, a spot-welded joint of three-thin sheet low carbon steels (same thicknesses of 0.8 mm) was simulated as an electerical-thermal-mechanical coupling of 3D finite element model. After validating the finite element simulation presented in this study by comparison with the experimental results for the spot diameter, various cases of spot welds were analyzed based on the design on experiment (i.e., Taguchi method). Six variables including electrode force, electric current, and quadrilateral times (squeeze, up-slope,...
Detection of inappropriate working conditions for the timing belt in internal-combustion engines using vibration signals and data mining
, Article Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering ; Volume 231, Issue 3 , 2017 , Pages 418-432 ; 09544070 (ISSN) ; Banakar, A ; Ghobadian, B ; Agha Mirsalim, M ; Minaei, S ; Jafari, S. M ; Sharif University of Technology
SAGE Publications Ltd
2017
Abstract
Abnormal operating conditions for the timing belt can lead to cracks, fatigue, sudden rupture and damage to engines. In this study, an intelligent system was developed to detect and classify high-load operating conditions and high-temperature operating conditions for timing belts. To achieve this, vibration signals in normal operating conditions, high-load operating conditions and high-temperature operating conditions were collected. Time-domain signals were transformed to the frequency domain and the time-frequency domain using the fast Fourier transform method and the wavelet transform method respectively. In the data-mining stage, 25 statistical features were extracted from different...
Numerical study of shunting effect in three-steel sheets resistance spot welding
, Article International Journal of Engineering, Transactions B: Applications ; Volume 35, Issue 2 , 2022 , Pages 406-416 ; 1728144X (ISSN) ; Farrahi, G. H ; Minaei, M ; Masajedi, R ; Gholamnia, M ; Shademani, M ; Sharif University of Technology
Materials and Energy Research Center
2022
Abstract
The main purpose of the present research is to investigate the shunting phenomenon in a three-sheet RSW joint usingfinite element simulation. To this end, a three-sheet resistance spot weldingjoint was simulatedas an electrical-thermal-mechanical couplingproblem.Tovalidate the presentedsimulation, the finite element results were compared with the experimental results, including nugget size and geometric shapein theresistance spot weldingjoint.Afterwards, the multi-spot welds of three-sheet low carbon steels with the same thicknesses were analyzed considering the sequential distance of 45 mm. Various techniques, includingnewspot-welddiametermeasurement, electrical current density, electrical...
Fatigue life analysis in the residual stress field due to resistance spot welding process considering different sheet thicknesses and dissimilar electrode geometries
, Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 237, Issue 1 , 2023 , Pages 33-51 ; 14644207 (ISSN) ; Farrahi, G ; Ahmadi, A ; Minaei, M ; Ostad Rahimi, M ; Barforoushan, S ; Sharif University of Technology
SAGE Publications Ltd
2023
Abstract
A typical vehicle body contains many 3-sheet spot-welded connections with different sheet thicknesses. In addition, the use of dissimilar electrode geometries is extremely common in the automotive industry. These two factors lead to an asymmetric spot weld with asymmetric residual stress distribution and heat-affected zone. This asymmetry has considerable effects on the fatigue behavior of these joints. Although many previous studies were dedicated to the analysis of spot welds, consideration of different electrode geometries and fatigue analysis of 3-sheet spot-welded joints are absent in the literature. To this end, in the present paper, the resistance spot weld process of three-sheet low...
Construction of an Experimental Device for Foaming Agent and an Experimental Study of the Properties of Foaming Agent
, M.Sc. Thesis Sharif University of Technology ; Bazargan, Mohammad (Supervisor)
Abstract
The primary purpose of acidizing operations in the oil and gas industry is to enhance hydrocarbon production. Acidizing has been a common and conventional method for years, especially when production engineers face issues like declining reservoir pressure leading to reduced production rates. Initially, the treatment solution is referred to as matrix acidizing. In acidizing operations, different additives are combined with the acid to control its behavior in the reservoir. These additives may include iron control agents, corrosion inhibitors, friction reducers, and more. Incompatibility among these additives, the acid, and reservoir fluids can lead to severe damage to the reservoir....
Numerical Analysis of An Annular Gas Turbine Combustor
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
The goal of this research is the simulation of the annular combustion chamber of the turbine engine utilized by liquid fuel. The achievement to this goal will lead to create numerical tools for parametric study, analysis and combustion chamber designing.For this reason simple geometry has been considered. This simplicity of geometry causes to facilitate in parametric study and decrease in saving time for modeling and meshing. This combustion chamber is a simplified model of engine CF6. In recent study, the k – ε realizable model has been used for turbulence modeling. For non-adiabatic condition, chemical reaction is dissolved by utilizing probability density function along with laminar...
A misbehavior‐tolerant multipath routing protocol for wireless Ad hoc networks [electronic resource]
, Article International Journal of Research in Wireless Systems (IJRWS) ; Vol. 2, Issue 9, pp. , Sep. 2013 ; Pakravan, Mohammad Reza ; Aref, Mohammad Reza ; Sharif University of Technology
Abstract
Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network...
Theoretical and Experimental Study to Conversion of AUC to UO2 by Microwave Heating
, Ph.D. Dissertation Sharif University of Technology ; Otukesh, Mohammad (Supervisor) ; Ghannadi Maragheh, Mohammad (Co-Advisor) ; Ghasemi, Mohammad Reza (Co-Advisor)SAR Imaging Using the TomoSAR Technique to Resolve Multiple Scatterers
, M.Sc. Thesis Sharif University of Technology ; Bastani, Mohammad Hassan (Supervisor) ; Karbasi, Mohammad (Co-Supervisor)
Abstract
During the last few years, the study of urban environment structures is considered as a research field of interest in remote sensing. In satellite observations of the earth's surface, continuous imaging in terms of time and space has caused the remote sensing technique to be proposed as a useful and efficient tool for the analysis of urban areas. Obtaining quantitative spatial information from the urban environment in fields such as determining the height of buildings plays an essential role in urban planning, monitoring damage to buildings, establishing communication bases and digital cities. During the last two decades, the use of Tomosar approach in order to reconstruct the structures of...
Estimating Possible Effects of Subsidies in Competition and Development of Fixed Broadband Internet
, M.Sc. Thesis Sharif University of Technology ; Vesal, Mohammad (Supervisor) ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
In this work, the dynamic competition between firms providing internet services is studied. The framework is Markov equilibrium whereby structural parameters are obtained using two-step estimations, allowing for analyzing the situation in case of subsidies for service upgrade. The results show that such subsidy has little effect on the number of firms while increasing the number of fast firms
Estimating Price Elasticity of Natural Gas Demand in Iran's Residential Sector: A Regression Discontinuity Approach
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Vesal, Mohammad (Supervisor)
Abstract
Estimating the price elasticity of gas demand involves complexities depending on the gas market structure and pricing mechanisms in different countries. Distinguishing between supply and demand shocks and block pricing are among the main challenges that can cause endogeneity in elasticity estimates. Iran's domestic gas network, one of the largest and most extensive household gas markets, is divided into five climatic zones based on weather conditions. The pricing steps for these five climates during the five cold months are such that a customer in a warmer climate pays higher prices. Conversely, the pricing steps for the seven warm months are the same for all climates. This policy creates a...
Estimate the Effect of Religiosity on Voter Turnout
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Vesal, Mohammad (Supervisor)
Abstract
The correlation between religious adherence and voter turnout is widely studied. However, whether the relation is causal is an open question. We use Household Expenditures and Income Survey (HEIS) data in Iran, which encompasses nine distinct religious expenditures. These expenditures have low correlation with each other and represent different aspects of religious adherence. We use Imamzadeh (some historical holy shrines) as Instruments to estimate the causal effect of religious expenditures on voter turnout. The results reveal that religious expenditures influence both presidential and parliamentary voter turnout, with a notably stronger impact on presidential elections
Joint Optimization of Computation Offloading and Resource Allocation in Mobile Edge Computing Networks
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Hadi, Mohammad (Co-Supervisor)
Abstract
Mobile edge computing (MEC) is a promising technology that aims to resolve cloud computing’s issues by deploying computation resources at the edge of mobile network and in the proximity of users. The advantages of MEC include reduced latency, energy consumption, and load on access and mobile core networks, to name but a few. Despite all the aforementioned advantages, the mobility of mobile network users causes the traditional MEC architecture to suffer from several issues, such as decreased efficiency and frequent service interruption. One of the methods to manage users’ mobility is virtual machine (VM) migration, where the VM containing the user’s task is migrated to somewhere closer to...
Non-Scratch, Antibacterial And Self-cleaning SiO2/TiO2 Nano Composite Coating on Surgical Tools By Sol-Gel
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
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...
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...
Simulation and Control of an Aromatic Extractive Distillation Column
,
M.Sc. Thesis
Sharif University of Technology
;
Shahrokhi, Mohammad
(Supervisor)
Abstract
In this study steady state and dynamic simulation of an NFM extractive distillation unit for seperation of aromatics and non-aromatic components has been carried out. Column output composition obtained with experimental binary coefficients is compared with those obtainded by UNIFAC equation. The results indicate that using UNIFAC for all binrary coefficients results in an unacceptable error in concentration of benzene. If the experimental binary coefficents of benzene with NFM are used and the rest are calculated by UNIFAC equation, the simulation results will be very close to those obtained via experimental binary coefficients. Also it is shown that considering a constant efficiency for all...