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safavi--mohammad-ali
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Numerical Simulation of Forced Impregnation in a Thick Capillary Tube
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Ali (Supervisor)
Abstract
Drop penetration into the capillary tube, as a classical problem, has been studied over 100 years. But there are a few studies that investigate forced impregnation of capillary tubes, which has major application in coating, inkjet printing and rain drop penetration into the soil, have been made. A comprehensive numerical investigation on millimeter droplet impact dynamics on a thick capillary tube with micrometer sized pore is conducted and validated against experimental data. This work is extended to oblique impact of drops into pores and normal impact on nanoscaled pores. We apply the finite volume numerical method to solve the time-dependent governing equations of continuity, momentum in...
Mechanical Design of an Anthropometric Lower Extremity Exoskeletal System
, M.Sc. Thesis Sharif University of Technology ; Meghdari, Ali (Supervisor)
Abstract
The main scope of this research is to develop an anthropometric lower extremity exoskeleal system in a virtual environment for augmentation purposes. The main challenge in the process of doing this research is to employ the biomechanical analysis of the human locomotion to provide the necessary background information for the design of devices that closely mimic the dynamics of the operator's motion. In this case, the appropriate degrees-of-freedom and associated range of motions for each joint should be determined. In addition, the kind of necessary actuators and measurement systems should be selected based on the muscle torque consumption analysis provided by a musculoskeletal model,...
A CDN Architecture to be used in SDN
, M.Sc. Thesis Sharif University of Technology ; Hemmatyar, Ali Mohammad Afshin (Supervisor)
Abstract
In recent years, the usage of Internet bandwidth has been increased by emerging applications such as Video on Demand (VoD).As the popularity of VoD increases among the Internet users, some new problems like bandwidth limitations and congestion embark. For solving mentioned problems, Content Delivery Networks (CDN) has been introduced. Using CDN approaches either in ISP or organization is also known as Telco CDN. Generally implementing CDN approaches to process all requests either in ISP or organization can cause bottleneck. On the other hand, Software Defined Networks (SDN) could bring us new tools and opportunities which enables us to implement novel methods to confront these problems....
Laboratory Study on the Effect of Thermal Cracking of Heavy Oil
, M.Sc. Thesis Sharif University of Technology ; Bastani, Dariush (Supervisor) ; Seifkordi, Ali Akbar (Supervisor) ; Safavi, Mohammad Ali (Supervisor) ; Shafeghat, Amin (Co-Advisor)
Abstract
The Visbreaking process is one of the Residue upgrading method, which, in addition to the production of mid-distillate products, also reduces the viscosity of feed. By reducing the viscosity of the feed, the amount of cutter stock is reduced to produce fuel oil. Since the refiners want to achieve the maximum conversion in the visbreaker unit, it is necessary to estimate the proper operating conditions and distribution of the products. Increasing in conversion in a visbreaker unit will lead to a refinancing profit. In this work, four Vacuum Residual oil from Iranian Refineries were selected for studying on visbreaking process. Experiments were carried out at RIPI-Petroleum Refining Technology...
Two-dimensional Numerical Simulation of Bubble Bursting in the Vicinity of a Corner, Using DIM Interfacial Modeling
, M.Sc. Thesis Sharif University of Technology ; Taeibi Rahni, Mohammad (Supervisor) ; Salimi, Mohammad Reza (Co-Supervisor)
Abstract
Bubble collapse is a two-phase problem whose numerical simulation has many important applications in science and technology. In hydrodynamics systems (pumps, ship propellers, …), bubbles form due to cavitation. These bubbles grow and collapse These bubbles grow and collapse farther downstream and their energy destroys the surrounding walls. In medical sciences, the shear force caused by collapse of a bubble can be used to destroy adipose tissues in arteries. The small scales time in this phenomenon, as well as the compressibility of the flow in bubble collapse, are interesting challenges researchers face. The present thesis targets are two-dimensional numerical simulation of bubble collapse...
Production of New Nanocomposites for Neutron and Gamma Shielding and Modeling of the Attenuation Phenomena Using Computational Methods
, M.Sc. Thesis Sharif University of Technology ; Outokesh, Mohammad (Supervisor) ; Vosoughi, Naser (Supervisor) ; Kiani, Mohammad Amin (Co-Supervisor)
Abstract
If nuclear radiation is not weakened and absorbed, it can cause serious damage to human devices or the environment. Dual-purpose dry casks are one of the sources of nuclear radiation production as a place to keep the spent fuel assemblies. One of the ways to protect against them is to use shield. One of the most common of them is composite shield. The composite used in this study has a polymer matrix. The matrix of the used polymer is epoxy resin. In this study, two separate composites have been made to attenuate neutron and gamma radiation. In this thesis, first, by using the MCNPX code, the necessary simulations for the design and construction of composite shields have been carried out....
Design and Manufacture Controller and Converter of Standard G-Code for CNC Hexaglide
, M.Sc. Thesis Sharif University of Technology ; Alasty, Aria (Supervisor) ; Movahedi, Mohammad Reza (Supervisor)
Abstract
Typical Numerical Control Machines, mainly are made a mechanism with axes perpendicular to each other. Because of lower weight, the parallel mechanisms are focused by CNC manufacturers. the Hexaglide mechanism is popular in parallel mechanisms used in CNC.Today, software of Solid modelling, generate G-Codes but this Codes works for conventional Numerical Control machines. for use of this G-Code for Parallel Mechanism CNC, a new controller should be designed to convert the standard G-Code motion command for Hexaglide CNC.The End of this project, is design and manufacture a controller for Hexaglide CNC that convert conventional G-Code for that and initiate drivers.Finally, the controller is...
Modification of carbohydrate polymers via grafting in air. 1. Ceric-Induced synthesis of starch-g-polyacrylonitrile in presence and absence of oxygen [electronic resource]
, Article Starch - Starke ; Volume 54, Issue 3-4, pages 140–147, April 2002 ; Zohurian Mehr, Mohammad J
Abstract
Monomer grafting, a unique technique for polysaccharide modification, is always performed under inert (e.g., N2) atmosphere. This work is the first report related to evaluating the possibility and efficiency of the grafting of acrylonitrile (AN) onto starch in presence of oxygen. Thus, corn starch (in both granular and gelatinized states) as well as soluble starch were grafted by AN using a ceric-carbohydrate redox initiating system. Graft copolymerizations were performed under nitrogen, air, and oxygen atmospheres at similar conditions. Grafting occurrence was verified using chemical and spectral proofs. The polymerization mechanism and kinetics were investigated by recording the...
Modification of carbohydrate polymers via grafting in Air. 2. Ceric-Initiated graft copolymerization of acrylonitrile onto natural and modified polysaccharides [electronic resource]
, Article Starch - Stärke ; Volume 54, Issue 10, pages 482–488, October 2002 ; Zohuriaan-Mehr, Mohammad J
Abstract
Acrylonitrile (AN) was grafted onto various natural and modified polysaccharides (i.e., gum arabic, gum tragacanth, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) by using ceric-carbohydrate redox initiating system. After overcoming practical problems, mainly from the high viscosity of the aqueous solutions of the different substrates, the graft copolymerization reactions were run either in air or in N2 atmosphere under similar conditions. Grafting was confirmed using chemical and spectral (FTIR) proofs. The reactions were kinetically investigated using semi-empirical expressions and time-temperature profiles. An anomalous...
Design and Implementation of a Spectrum Sensor for Cognitive Radio
, M.Sc. Thesis Sharif University of Technology ; Shabani, Mahdi (Supervisor)
Abstract
Frequency scarcity has emerged the necessity of opportunistic utilization of frequency bands, which can be realized through a cognitive radio system. During an agile communication between unlicensed users, a cognitive radio system must avoid collision with licensed users. Hence it should continuously observe the band of interest and report the presence of licensed user signals. This task is fulfilled by a vital part of a cognitive radio system, called the spectrum sensing core. Recently several techniques have been proposed for the spectrum sensing in literature. Some of them like matched filtering, cyclostationarity based detection are based on primary user signal features. However energy...
Environmental Impact of Seawater on GGBFS-Based Alkali-Activated Concrete
, M.Sc. Thesis Sharif University of Technology ; Toufigh, Vahab (Supervisor)
Abstract
This study seeks to compare the effect of curing conditions in the sea, coast, and middle of the island environment on five mix designs of alkali-activated concrete (AAC) based on ground granulated blast furnace slag (GGBFS) and fly ash (FA) and the effect of the ratio of sodium silicate (SS) to sodium hydroxide (SH) and alkali activated solutions (AAMS) to the binder on mechanical properties. The compressive strength and load-deflection test was conducted to obtain uniaxial compressive strengths (UCS), modulus of elasticity ("E" _"S" ), elastic and ultimate strain, and dissipated energy. The most significant decrease in strength was observed in the coastal area and the sea. Also, the...
Modeling of in Plane Behavior of Retrofitted Adobe Walls with Finite Element Method under Cyclic Loading
, M.Sc. Thesis Sharif University of Technology ; Bakhshi, Ali (Supervisor) ; Ghannad, Mohammad Ali (Co-Advisor)
Abstract
Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by...
Silica chloride/wet SiO2 as a novel heterogeneous system for the deprotection of acetals under mild conditions [electronic resource]
, Article Phosphorus, Sulfur, and Silicon and the Related Elements ; Volume 178:2667-2670, Issue 12, 2003 ; Pourjavadi, Ali ; Zolfigol, Mohammad Ali ; Bamoniri, Abdolhamid
Abstract
A combination of silica chloride and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under mild and heterogeneous condition
A real-time, low-power implementation for high-resolution eigenvalue-based spectrum sensing
, Article Analog Integrated Circuits and Signal Processing ; Volume 77, Issue 3 , December , 2013 , Pages 437-447 ; 09251030 (ISSN) ; Shabany, M ; Sharif University of Technology
2013
Abstract
In this paper, a novel multiple antenna, high-resolution eigenvalue-based spectrum sensing algorithm based on the FFT of the received signal is introduced. The proposed platform overcomes the SNR wall problem in the conventional energy detection (ED) algorithm, enabling the detection of the weak signals at -10 dB SNR. Moreover, the utilization of FFT for the input signal channelization provides a simple, low-power design for a high-resolution spectrum sensing regime. A real-time, low-area, and low-power VLSI architecture is also developed for the algorithm, which is implemented in a 0.18 μm CMOS technology. The implemented design is the first eigenvalue-based detection (EBD) architecture...
A VLSI architecture for multiple antenna eigenvalue-based spectrum sensing
, Article 2012 19th IEEE International Conference on Electronics, Circuits, and Systems, ICECS 2012, 9 December 2012 through 12 December 2012 ; December , 2012 , Pages 153-156 ; 9781467312615 (ISBN) ; Shabany, M ; Sharif University of Technology
2012
Abstract
An Eigenvalue-based detection (EBD) scheme, is proposed as an efficient method to overcome the noise uncertainty and the SNR wall problem in conventional energy detection (ED) schemes. Despite remarkable efforts made to analyze the EBD performance, a VLSI implementation is missing in literature. In this paper, a new FFT-based EBD algorithm is introduced, which eliminates the need for filter banks and discrete wavelet packet transform to channelize the input signal. The proposed method enables the utilization of the EBD algorithm in high-resolution spectrum sensing approaches. Moreover, it enables the detection of signals with SNRs as low as -10 dB. A low-power, area-efficient yet real-time...
Cooperative diversity of distributed network beamforming under long-term power constraints
, Article Proceedings - IEEE Symposium on Computers and Communications, 22 June 2010 through 25 June 2010 ; June , 2010 , Pages 268-271 ; 15301346 (ISSN) ; 9781424477555 (ISBN) ; Hossein Khalaj, B ; Sharif University of Technology
2010
Abstract
In this paper, we analyze the cooperative diversity of amplify-and-forward half-duplex relay networks under longterm power constraints. The system model we consider consists of one transmit-receive pair and an arbitrary number of relays. This paper analyzes bit error rate and network diversity for two different power distribution scenarios in network. Using the derived network error probability, the distributed signal to noise ratio for network is introduced
Distributed Fault-tolerant Computation for Massive Data
, M.Sc. Thesis Sharif University of Technology ; Maddah-Ali, Mohammad Ali (Supervisor)
Abstract
In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without...
Incomplete Reduction of Iron Ore in a Fluidized Bed Reactor
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
The main goal of current investigation was partial reduction of Fe2O3 available in Hematite-rich ore to Magnetite by Fludization Bed method. The reductive gas, CO, was produced by incomplete combustion of Acetylene and Airmixed in inappropriate ratio. X-Ray Diffraction and X-Ray Florescence analyses were implemented in order to conducting qualitative analysis of present phases before and after reduction of the ore. Quantitative analysis of the same phases was also conducted by Titration. The latter analysis revealed the precise magnitude of available iron in each of the oxide containing phases. The chemical composition of the reactor gas was also determined before and after reduction...
Sequential Competitive Facility Location In Continuous Geometric Space
, M.Sc. Thesis Sharif University of Technology ; Abam, Mohammad Ali (Supervisor)
Abstract
Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to...
Distributed Verifiable Computing: Algorithms and Analysis
, M.Sc. Thesis Sharif University of Technology ; 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...