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mohammad-rahimi--h
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Sintering of Al2O3-SiC composite from sol-gel method with MgO, TiO2 and Y2O3 addition
, Article Ceramics International ; Volume 37, Issue 5 , 2011 , Pages 1681-1688 ; 02728842 (ISSN) ; Rezaie, H. R ; Nemati, A ; Sharif University of Technology
2011
Abstract
Al2O3-SiC composite ceramics were prepared by pressureless sintering with and without the addition of MgO, TiO2 and Y2O3 as sintering aids. The effects of these compositional variables on final density and hardness were investigated. In the present article at first α-Al2O3 and β-SiC nano powders have been synthesized by sol-gel method separately by using AlCl 3, TEOS and saccharose as precursors. Pressureless sintering was carried out in nitrogen atmosphere at 1600 °C and 1630 °C. The addition of 5 vol.% SiC to Al2O3 hindered densification. In contrast, the addition of nano MgO and nano TiO2 to Al 2O3-5 vol.% SiC composites improved densification but Y2O3 did not have positive effect on...
Tipping Cascades in Complex Networks: Dynamics and Control
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
Tipping points occur in diverse systems in various disciplines such as ecology, climate science, economy, sociology, and engineering. Critical thresholds in system parameters or state variables at which a tiny perturbation can lead to a qualitative change in the system exist in many subsystems in complex systems. These thresholds are called tipping points, and these subsystems are called tipping elements. Additionally, many systems with tipping points can be modeled as networks of coupled multistable subsystems. Domino-like tippings are called tipping cascades. Considering that these tipping cascades are primarily unprecedented, it is essential to study the dynamics and control of these...
The Impact of Economic Status on Educational Performance
, M.Sc. Thesis Sharif University of Technology ; Vesal, Mohammad (Supervisor)
Abstract
Considering the fact that human capital is a crucial element in explaining the differences in income per capita and economic growth among countries, this research focuses on the effect of initial endowments of individuals on the process of human capital accumulation. One of the most important questions one can ask in this regard is whether individuals that are born in households with a low level of endowments, cannot develop their level of human capital due to a lack in the ability to obtain the factors required for their educational attainment. To answer this question, and considering the limitations of obtaining educational data, we aim to answer this question using district-level data....
Design and Implementation of a Search and Rescue System on a Quadrotor
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
In this work, we try to develop a method for searching for an object which is known to us and also returning it back where the search was begun, through shortest possible path. The surrounding environment was assumed unknown and only a stereo camera and an IMU exist to work with. The proposed method was developed in Linux using GPU and with C++ language and also achieved 58 fps. Parallel programming was utilized in different parts of the algorithm and obstacle avoidance is guarranteed. The surrounding environment and obstacles are assumed changing over the time
Application of single-nucleotide polymorphisms in the diagnosis of autism spectrum disorders: a preliminary study with artificial neural networks
, Article Journal of Molecular Neuroscience ; Volume 68, Issue 4 , 2019 , Pages 515-521 ; 08958696 (ISSN) ; Taheri, M ; Omrani, M. D ; Daaee, A ; Mohammad Rahimi, H ; Kazazi, H ; Sharif University of Technology
Springer New York LLC
2019
Abstract
Autism spectrum disorder (ASD) includes different neurodevelopmental disorders characterized by deficits in social communication, and restricted, repetitive patterns of behavior, interests or activities. Based on the importance of early diagnosis for effective therapeutic intervention, several strategies have been employed for detection of the disorder. The artificial neural network (ANN) as a type of machine learning method is a common strategy. In the current study, we extracted genomic data for 487 ASD patients and 455 healthy individuals. All individuals were genotyped in certain single-nucleotide polymorphisms within retinoic acid-related orphan receptor alpha (RORA), gamma-aminobutyric...
State-Space Model for Speech Enhancement in VoIP
, M.Sc. Thesis Sharif University of Technology ; Ghorshi, Mohammad Ali (Supervisor)
Abstract
Speech enhancement in noisy environments improves the quality and intelligibility of speech and reduces communication fatigue. High performance speech enhancement models are based on Bayesian estimation models, requiring estimations of the parameters of the functions that describe the likelihood and the prior distributions of the signal and noise processes. Two Bayesian speech enhancement models which are used in this thesis are Bayesian-Kalman filter and Bayesian MAP estimation.In real time applications including VoIP, in addition to additive noise, packet loss or packet delays might also occur. In real time communications the receiver terminal replaces silence for the duration of lost...
The Impact of Conditions for Organizational Knowledge Creation on Strengthening Interpersonal Knowledge Sharing
, M.Sc. Thesis Sharif University of Technology ; Isaai, Mohammad Taghi (Supervisor)
Abstract
Knowledge sharing as one of the most important knowledge management processes has been discussed in this research. The purpose of this study is investigating relationship between the Nonaka’s conditions for organizational Knowledge Creation and strengthening interpersonal Knowledge Sharing in the “Oil Industries Engineering and Construction Co. (OIEC)”. A quantitative questionnaire based servey was used to collect the required data and Structural Equation Modeling (SEM) to test the questions. The findings suggest that the “project intention”, ”personal autonomy”, “autonomy of project team” and “requisite variety” have impact on “attitude toward knowledge sharing”, and there is no significant...
Detection and Classification of Partial Discharges in High Voltage DC
, M.Sc. Thesis Sharif University of Technology ; Vakilian, Mehdi (Supervisor)
Abstract
In past decades, the measurement of partial discharges (PDs) in high voltage equipments, was appreciated as one of the most efficient methods for evaluation of the equipment insulation condition. Generators, transformers, cables and transmission lines are especially checked to detect the presence of any partial discharge.
In AC high voltage systems, the measurement method is well established and known. The Phase resolved method is used to determine the partial discharge signals. These methods have been used for many years and their success in differentiating the various sources of partial discharge have proven. Although phase resolved method works on AC; due to lack of frequency...
In AC high voltage systems, the measurement method is well established and known. The Phase resolved method is used to determine the partial discharge signals. These methods have been used for many years and their success in differentiating the various sources of partial discharge have proven. Although phase resolved method works on AC; due to lack of frequency...
Modeling Aphron-Based Drillng Fluid Penetration Rate into the Reservoir Formation and Analyzing the Permeability Change Behavior
, M.Sc. Thesis Sharif University of Technology ; Jamshidi, Saeed (Supervisor)
Abstract
Aphron drilling fluids or CGA fluids are the wellknown updated drilling fluids in recent years.this kind of drilling fluids can control the mud loss into the formation and thus reduce formation damage and drilling costs. its structure consists of two phase fluid (gas and liquid) that the aphrons are the micro bubbles with 10 to 100 micrometer diameter that have strong stability in liquid phase compared to foamy drilling fluids. Generally aphron drilling fluids are made of base drilling fluid and surfactants, for more stability, mixed surfactant-polymer additive is so beneficial. in the last two decades, the Lattice-Boltazmann method is introduced for computational fluid dynamic area and...
Improving Physical Layer Security for Cellular Users in Threat of Eavesdroppers
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
Security for wireless communication networks has become a crucial issue because of the broadcast nature of wireless channels. On every cellular network Since it is possible for passive nodes to easily overhear the confidential information transmitted between transmitter and receiver, it is necessary to provide secure communication.When a cellular user wants to communicate with a node or base station on the cellular network, it expects that information will be transmitted and received without interference, with enough quality and without eavesdropping. On the other hand In practical scenarios, we know that cellular network nodes are not equipped with ideal equipment and some percent...
Multi-depot Vehicle Routing Using Predictive Distributed Cooperative Method
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
Due to conspicuous increases in shopping and goods transportation in this unbridled world, a significant part of companies’ final interest and final cost are related to their distributions of goods. Meanwhile, because of practical constraints of service hours and service distances, logistics companies usually build multiple depots to serve a great number of dispersed customers. Hence, multi-depot vehicle routing problems (MDVRP) win more and more engineers’ and companies’ attention to thrift their cost by using optimization methods. Considering NP-hardness of MDVRP and the lack of optimal solution derived by heuristic and meta-heuristic approaches in the large scale problems, in this...
Design a Microfluidics System for Drug Testing of Leukemia Patient's Bone Marrow Aspirate
, M.Sc. Thesis Sharif University of Technology ; Saidi, Mohammad Said (Supervisor)
Abstract
Cancer is one of the most causes of mortality in the world. Leukemia is a type of cancer initiated by the rapid proliferation of blood cells including WBCs, RBCs, and Platelets, that classified into four general types of AML, ALL, CML, and CLL. The main treatment of leukemia is chemotherapy. Because of many problems that patients have with this treatment and not so good results of chemotherapy, we design a microfluidic chip that can perform personalized medicine treatment for leukemia patients.This microchip consists of two main parts, Concentration Gradient Generator (CGG), and cell culture. CGG system is a tree CGG with two inlets and four outlets, which makes a linear concentration of...
Application of artificial neural network for prediction of risk of multiple sclerosis based on single nucleotide polymorphism genotypes
, Article Journal of Molecular Neuroscience ; Volume 70, Issue 7 , 2020 , Pages 1081-1087 ; Taheri, M ; Omrani, M. D ; Daaee, A ; Mohammad Rahimi, H ; Sharif University of Technology
Humana Press Inc
2020
Abstract
The artificial neural network (ANN) is a sort of machine learning method which has been used in determination of risk of human disorders. In the current investigation, we have created an ANN and trained it based on the genetic data of 401 multiple sclerosis (MS) patients and 390 healthy subjects. Single nucleotide polymorphisms (SNPs) within ANRIL (rs1333045, rs1333048, rs4977574 and rs10757278), EVI5 (rs6680578, rs10735781 and rs11810217), ACE (rs4359 and rs1799752), MALAT1 (rs619586 and rs3200401), GAS5 (rs2067079 and rs6790), H19 (rs2839698 and rs217727), NINJ2 (rs11833579 and rs3809263), GRM7 (rs6782011 and rs779867), VLA4 (rs1143676), CBLB (rs12487066) and VEGFA (rs3025039 and...
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
In this thesis, we study the resilience of complex systems under structural perturbations. After a brief review of the resilience and its importance, we show that how one can map a system of N-coupled dynamical equations onto an effective one-dimensional dynamics. This procedure is based on a nearest neighbor averaging. The obtained map, helps us study the response of the system to the effective one-dimensional control parameter, instead of all parameters that are affecting the structure of the network. Next, we use this procedure and unveil the resilience pattern of second-order Kuramoto oscillators on complex networks. Moreover, we propose a control strategy for complex systems which is...
Studying Synchronization Control in Complex Systems
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
In this thesis, we review recent advances on controlling of complex systems. We provide in details, the concepts of synchronizability and synchronization controllability.Then we will investigate synchronization controllability under different pinning schemes, and propose a new pinning strategy to increase controllability and consequently decrease the number of required pinned nodes (known as driver nodes) to assure a stable synchronized state. We also study the network characteristics of resulted sequence of driver nodes. Finally, we will employ our proposed schemes to study the controllability of complex networks of chaotic Rossler oscillators
Collapse assessment of steel moment frames using endurance time method
, Article Earthquake Engineering and Engineering Vibration ; Volume 14, Issue 2 , 2015 , Pages 347-360 ; 16713664 (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
Institute of Engineering Mechanics (IEM)
2015
Abstract
In endurance time (ET) method structures are subjected to a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specified spectrum, intensifies with time so they can be used approximately to simulate the average effects of several ground motions scaled to different intensities. In this paper applicability of the ET method for evaluating collapse potential of buildings is investigated. A set of four steel moment frames is used for collapse assessment. The process of using ET method in collapse evaluation is explained and the results are compared with incremental dynamic analysis (IDA) results. It is shown...
Low grade heat driven multi-effect distillation and desalination
, Article Low Grade Heat Driven Multi-Effect Distillation and Desalination ; 2017 , Pages 1-194 ; 9780128052709 (ISBN); 9780128051245 (ISBN) ; Chua, H. T ; Sharif University of Technology
Elsevier Inc
2017
Abstract
Low Grade Heat Driven Multi-effect Distillation and Desalination describes the development of advanced multi-effect evaporation technologies that are driven by low grade sensible heat, including process waste heat in refineries, heat rejection from diesel generators or microturbines, and solar and geothermal energy. The technologies discussed can be applied to desalination in remote areas, purifying produced water in oil-and-gas industries, and to re-concentrate process liquor in refineries. This book is ideal for researchers, engineering scientists, graduate students, and industrial practitioners working in the desalination, petrochemical, and mineral refining sectors, helping them further...
Control of Complex Networks Dynamics by a Minimum Energy Approach
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
Control of complex networks is the main topic in this study. In this thesis, we consider the methods to steer the dynamics of a network from an initial state to the desired final state. To achieve this goal, one needs to inject appropriate control signals from some of the network nodes, known as driver nodes. We consider the quadratic sum of control signals as a cost function, to control the dynamics of the network. By minimising the cost function, we obtain the control signals as well as driver nodes for a linear time-invariant system. As an example, we provide the results of an energy minimization strategy to control the second order Kuramoto and Rössler dynamics in Erdos-Renyi and...
Structural Disorders of Graphene and Its Effects on Electronic Properties
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
In this thesis we would like to investigate structural disorder of Graphene and its effect on electronic properties. Graphene is a one-layer crystal of Carbon atoms which was the first two dimensional crystal observed experimentally. Low energy current carriers on Graphene behave like mass-less Dirac fermions and this interesting electronic property attracts much attention on studying Graphene. Structural disorder of Graphene highly affects its electronic properties. We study thermal fluctuations of Graphene sheet, disorder super lattice, and static ripples, as structural disorders of Graphene. Disorders due to thermal fluctuations of graphene induce a disordered gauge field on the graphene...
Study of Surface Growth of Organic Thin Film
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
In recent decades the Due to development of coating techniques and the diversity of high organic matter, Discussion of organic coating materials being raised. Moreover, because of many applications of organic thin film in electronic and optical systems for example OTFTs and OLEDs Organic thin film growth topic is very interesting for scientists. Among these, some scientists study the theory and another bunch of scientists pay to practical aspects of this topic. In this thesis I pay to the theoretical level of Organic thin film growth and I simulate the system includes a collection of molecules, Went on to study some statistical properties of the system will be discussed and the dynamic...