Characterizing the Impact of Void Ratio and Stress Path on the Small Strain Shear Modulus of Unsaturated Silt

, M.Sc. Thesis Sharif University of Technology Rahimi, Mehrzad (Author) ; Khosravi, Ali (Supervisor)

Abstract

Early efforts in soil dynamics have shown that the analysis of soil behavior under cyclic or random loading conditions is highly dependent on some representative material properties, the dynamic shear modulus, the Poisson’s ratio, and the damping ratio. Of particular interest is the value of dynamic shear modulus for strains less than 10-6 defined as the maximum or small strain shear modulus Gmax. Improvements in experimental unsaturated soil mechanics have led to the definition of trends between Gmax with different parameters most notably unsaturated stress state, degree of saturation and void ratio. However, the tests in these studies were mostly conducted on specimens experiencing...

Distributed Verifiable Computing: Algorithms and Analysis

, M.Sc. Thesis Sharif University of Technology Rahimi, Ali (Author) ; Maddah Ali, Mohammad Ali (Supervisor)

Abstract

Zero knowledge proofs allow a person (prover) to convince another person (verifier) that he has performed a specific computation on a secret data correctly, and has obtained a true answer, without having to disclose the secret data. QAP (Quadratic Arithmetic Program) based zkSNARKs (zero knowledge Succinct Non-interactive Argument of Knowledge) are a type of zero knowledge proof. They have several properties that make them attractive in practice, e.g. verifier's work is very easy. So they are used in many areas such as Blockchain and cloud computing. But yet prover's work in QAP based zkSNARKs is heavy, therefore, it may not be possible for a prover with limited processing resource to run...

Effects of ion-exchange and hydrolysis mechanisms on lead silicate glass corrosion

, Article Corrosion ; Volume 68, Issue 9 , September , 2012 , Pages 793-800 ; 00109312 (ISSN) Ali Rahimi, R ; Sadrnezhaad, S. K ; Sharif University of Technology

2012

Abstract

Corrosion of lead silicate glass (LSG) contacting 0.5 M aqueous nitric acid (HNO 3) was investigated via scanning electron microscopy, energy-dispersive spectroscopy, inductively coupled plasma analysis, and weight-loss measurement to determine the respective contributions of the ion-exchange vs. the hydrolysis reactions. The LSG having X M ≡ Pb+K+Na/Si mole ratios of less than 0.7 showed very little weight loss with no Si network deterioration. At X M > 0.7, the mechanism changed into the hydrolysis, which caused the formation of a networkless gel layer resting at the solid/liquid interface. Addition of titania (TiO 2) and zirconia (ZrO 2) had disparate effects: X M < 0.7 improved corrosion...

State-Space Model for Speech Enhancement in VoIP

, M.Sc. Thesis Sharif University of Technology Rahimi, Alaa (Author) ; 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...

A Task Assignment Method to Reduce Aging in Multi-core Processors

, M.Sc. Thesis Sharif University of Technology Saadatmand, Faezeh Sadat (Author) ; Miremadi, Ghassem (Supervisor)

Abstract

Reducing the size of transistors has dramatically increased the impacts of NBTI, HCI, and EM phenomena in comparison with decade ago. These phenomena are able to have influence on properties of different parts of a chip to make it changed gradually; including threshold voltage of a transistor and electrical conductivity of interconnections. These changes are known as the aging of a transistors that diminish the performance and reliability of a chip. A common reason that plays a significant role in all these phenomena is temperature. The temperature becomes more important when the power density increases per unit area due to decreased size of transistors, which is a trend in multi-core...

Optimum Design of Air Jet Nozzle Preventing Hot Solid Particles Deposition on the Furnace Wall Using Numerical Simulation of Gas-Particle Two-Phase Flow

, M.Sc. Thesis Sharif University of Technology Hosseini, Faezeh Sadat (Author) ; Darbandi, Masoud (Supervisor)

Abstract

Deposition of solid particles present in the process air on the walls of furnaces is one of the challenges in industries. This phenomenon has various causes. For example, in a furnace, the temperature of particles increases as they pass in front of the furnace burners, and due to the softening of the particles, their chances of deposition increase when they collide with the walls. Over time, with the growth of deposited particle layers on the combustion chamber walls, the performance of the combustion system gradually becomes impaired. present research aims to design air jets intersecting with the process air path, with the purpose of reducing the temperature of particles prone to deposition...

Fabrication of Oleophobic Coating

, M.Sc. Thesis Sharif University of Technology Rahimi, Amir Mohammad (Author) ; Mousavi, Ali (Supervisor) ; Nouri Borujerdi, Ali (Supervisor)

Abstract

Wettability is the cause of many interactions today and is definitely effective in almost all processes where liquid and solid phases are in contact. Wetting controls by surface engineering can accelerate the process in the industry or improve the quality of daily life. Therefore, the fabrication of complex surfaces with a specific purpose and different wettability has attracted the attention of researchers. In this thesis, silica nanoparticles were synthesized to create roughness and reduce contact between surfaces and liquids at first. Then, using chemical compounds to reduce the surface energy, a transparent (94.20%) superhydrophobic and oleophobic coating was created on the glass. The...

Development and Validation of an EFL Self-Regulated Learning Questionnaire

, M.Sc. Thesis Sharif University of Technology Jafari, Hamid (Author) ; Salehi, Mohammad (Supervisor) ; Rahimi, Ali (Co-Advisor)

Abstract

Self-regulated learning, though having swept educational psychology's literature like a tidal wave (Boekaerts, 1999), and also, compared to other constructs such as metacognition and learning strategies, has remained comparatively uncharted in L2 research. One preliminary step to chart this concept is to develop questionnaires for it. With these and other things in mind, the principal purpose of this study was to develop a questionnaire in English and Persian to measure self-regulated language learning capacity and behavior of Iranian EFL learners. The development of the questionnaire was guided by two pilots (412 participants), content validation through expert judgment, cognitive...

Seismic Hazard Analysis Using Reliability-Based Methods for Cumalitive Absolute Velocity and Spectral Acceleration in the Iranian Plateau Depending on National Database

, M.Sc. Thesis Sharif University of Technology Rahimi, Hossein (Author) ; Bakhshi, Ali (Supervisor) ; Mahsuli, Mojtaba (Supervisor)

Abstract

This thesis presents a new approach to probabilistic seismic hazard analysis. Hazard in this context means the probability of exceeding a measure of earthquake intensity. The main components of the proposed approach are twofold: 1) Reliability methods compute the exceedance probabilities; 2) Multiple probabilistic models compute the earthquake intensity. These two components are presented in details. The proposed methodology is employed in a comprehensive seismic hazard analysis of Iran with an area of nearly 1.65 million square kilometers and 112 sources of seismicity. In this analysis, a grid of 2045 points is chosen to produce a high resolution hazard map. The analysis is carried out for...

An Analysis of Oil Revenues and Monetary and Financial Policies on Iran's Long-term Economic Growth

, M.Sc. Thesis Sharif University of Technology Mir Jafari, Faezeh Sadat (Author) ; Kianfar, Farhad (Supervisor)

Abstract

In many papers, GDP is used as a measure of economic growth, which is shown to possess a nonlinear structure. The study focuses on the nonlinear Granger causality between liquidity, government spending, oil revenues and economic growth by markov-switching vector autoregressive and markov- switching Granger causality approach for the period of 1369-1397 for Iran. The empirical results from MSAI(2)-VAR(4) suggest that Oil revenues and government spending have a significant impact on economic growth in both regimes. Also, markov- switching Granger causality results are quite different from the traditional Granger causality results, that suggests the nonlinear Granger causality has more...

Design and Fabrication of Brain Spinal Cord Electrodes for Rehabilitation of Rats with Spinal Cord Injuries

, M.Sc. Thesis Sharif University of Technology Mashayekhi, Fatemeh (Author) ; Fardmanesh, Mehdi (Supervisor) ; Shanehsazzadeh, Faezeh (Co-Supervisor)

Abstract

The use of microelectrode arrays in neural networks has offered a wonderful opportunity for evaluating numerous properties and interactions with excitable tissues such as the brain and spinal cord in the laboratory. In neural network applications, microelectrode arrays can be utilized to analyze nerve impulses or interact with neurons. They are either used to record neural data or to stimulate spinal cord nerves. Previous research has revealed that stimulating the spinal epidural region can help restore after spinal cord injuries (SCIs), which is the key to using them in the rehabilitation of living beings, including humans. According to the international campaign for the treatment of SCI...

Low Grade Heat Driven Multi-Effect Distillation and Desalination

, Book Rahimi, Bijan ; Chua, Hui Tong

Elsevier 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...

Characterization of V2O5 Spent Catalyst & Feasibility Study of its Regeneration

, M.Sc. Thesis Sharif University of Technology Soltani Nejad, Mohammad (Author) ; Sadrnezhaad, Khatiboleslam (Supervisor) ; Farzami, Faezeh ($item.subfieldsMap.e)

Abstract

In this study, at first the V2O5 spent catalysts were characterized. The aim was to identifying whether these catalyst may be regenerated. Then, for feasibility study of them, three methods were applied: washing, diffusion and milling the spent catalysts for their subsequent reproduction. A variety of techniques such as XRD, XRF, AAS, TPR and TPO were applied in order to identify factors contributing in vanadium pentoxide catalysts deactivation. The results showed that approximately all of pollutants caused their performance deterioration, while they still have some active phases. Then, the polluted catalysts were washed (their yield increased from 43% to 72.2%). In the underside of the...

Sleep Apnea Detection Using Wearable Devices

, M.Sc. Thesis Sharif University of Technology Rahimi, Hamid Reza (Author) ; Fotowat Ahmady, Ali (Supervisor) ; Akbar, Fatemeh (Supervisor)

Abstract

Approximately 1.36 billion people worldwide suffer from sleep apnea, necessitating accurate diagnosis and treatment. Traditional sleep clinics rely on Polysomnography (PSG)-based monitoring devices. However, these devices are not only voluminous but also prohibitively expensive, requiring numerous sensors and wires that disrupt sleep and cause discomfort for patients. To address these challenges, we have developed a wireless wearable system. This system comprises three sensor blocks, each capable of capturing vital signs from the body, resulting in a total of eight signals. The first two sensor blocks capture signals from the body, which are subsequently modulated and transmitted to a user's...

Electrochemical Synthesis of Ni-Mn-Cu-Se@NF Nanostructure by Different Applied Voltage Regimes as an Effective and Stable Electrode for Hydrogen Production

, M.Sc. Thesis Sharif University of Technology Ali Rahimi, Faezeh (Author) ; Ghorbani, Mohammad (Supervisor) ; Barati Darband, Ghasem (Co-Supervisor)

Abstract

Among the new energies, hydrogen has been noticed due to its high energy density. Electrochemical production of hydrogen using electrocatalysts with high efficiency and cheap price is one of the effective solutions to achieve a clean and renewable energy source. Various studies have shown that after noble metals such as Pt, nickel has the highest electrocatalytic activity for hydrogen production. Alloying nickel with other intermediate metals is one of the effective methods to improve the catalytic activity of this metal, and among the intermediate metals that increase electrocatalytic properties, manganese and copper have a special place. Also, among different non-noble metals, selenide...

Analysis and data-based reconstruction of complex nonlinear dynamical systems : using the methods of stochastic processes

, Book Rahimi Tabar, M. Reza

Springer International Publishing 2019

Abstract

This book focuses on a central question in the field of complex systems: Given a fluctuating (in time or space), uni- or multi-variant sequentially measured set of experimental data (even noisy data), how should one analyse non-parametrically the data, assess underlying trends, uncover characteristics of the fluctuations (including diffusion and jump contributions), and construct a stochastic evolution equation?
Here, the term "non-parametrically" exemplifies that all the functions and parameters of the constructed stochastic evolution equation can be determined directly from the measured data.
The book provides an overview of methods that have been developed for the analysis of...

Tipping Cascades in Complex Networks: Dynamics and Control

, M.Sc. Thesis Sharif University of Technology Shahrabi, Ali (Author) ; 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...

Experimental Study of Using Cellulosic Compounds in Tissue Engineering

, M.Sc. Thesis Sharif University of Technology Golizadeh, Mortaza (Author) ; Vossoughi, Manouchehr (Supervisor) ; Karimi, Afzal (Supervisor) ; Faghihi, Faezeh (Co-Supervisor)

Abstract

Fabrication and characterization of different surface charged cellulose electrospun scaffolds including cellulose acetate, cellulose, carboxymethyl cellulose and quaternary ammonium cationic cellulose for biomedical applications have been reported in this research. We describe preparation of cellulosic nanofibers through the electrospinning following deacetylation cellulose acetate. Moreover, surface modification of electrospun cellulose nanofibers is carried out to obtain carboxymethyl cellulose and quaternized cellulose nanofibers, respectively. At last, the structural, morphological, mechanical, swelling, wettability and the cell culture properties of the scaffolds were analyzed and...

Minimum control effort trajectory planning and tracking of the CEDRA brachiation robot [electronic resource]

, Article Robotica ; Robotica / Volume 31 / Issue 07 / October 2013, pp 1119-1129 Meghdari, A. (Ali) ; Lavasan, S. M. H ; Norouz, M ; Rahimi Mousavi, M. S ; Sharif University of Technology

Abstract

The control of a brachiation robot has been the primary objective of this study. A brachiating robot is a type of a mobile arm that is capable of moving from branch to branch similar to a long-armed ape. In this paper, to minimize the actuator work, Pontryagin's minimum principle was used to obtain the optimal trajectories for two different problems. The first problem considers “brachiation between fixed branches with different distance and height,” whereas the second problem deals with the “brachiating and catching of a moving target branch”. Theoretical results show that the control effort in the proposed method is reduced by 25% in comparison with the “target dynamics” method which was...

Effects of Higher Order Interactions and Data-Driven Stability Analysis in Tipping Networks

, M.Sc. Thesis Sharif University of Technology Nikpanjeh, Fatemeh (Author) ; Rahimi Tabar, Rahimi Tabar (Supervisor)

Abstract

Recent studies in various fields such as the environment, climate, economics, and neuroscience have shown that many systems exhibit dynamic responses based on catastrophic shifts—sudden and unexpected changes in the system's state and behavior in response to environmental changes. One of the simplest cases of these shifts occurs when the dynamical bifurcation diagram of a system has a tipping point, which serves as a critical threshold for system parameters, allowing small disturbances to lead to significant changes in the system's state. Research on many natural systems has revealed that tipping elements as the subsystems of a complex system are not independent, and the tipping of one...