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Applications of Hough Transform in Frequency Domain for Radar Systems
, M.Sc. Thesis Sharif University of Technology ; Nayebi, Mohammad Mehdi (Supervisor)
Abstract
Hough transform is frequently used in radar applications. The structure of using this transformation in radars is so that it has been used only in Range radars which transmit short pulses and their primary goal is to make better estimation of the range of the targets. In this work, we introduce the ways in which we can use the Hough transform in Doppler radars which transmit long pulses and their primary goal is to make better estimation of target doppler. We must use Hough transform in time-doppler domain for this class of radars including continuous-wave radars. To prepare this time-doppler domain image some time-frequency transform must be applied to the radar received signal and a part...
An Approach for Secure Data Outsourcing
, Ph.D. Dissertation Sharif University of Technology ; alili, Rasool (Supervisor)
Abstract
Data outsourcing is an approach to delegate the burden of data management to external servers. In spite of its clear advantages, data outsourcing requires security assurances including data confidentiality, query result correctness, and access control enforcement. Research proposals have identified solutions with disparate assumptions for different security requirements. It is a real obstacle towards having an integrated solution through the combination of existing approaches. The practicality of data outsourcing to the cloud is seriously affected by this challenge. In this thesis, a unified view based on secret sharing is proposed to simultaneously achieve confidentiality, correctness, and...
Analysis of fundamental Limits For Information Theoretic Secrecy in Large Wireless Networks
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor) ; Mirmohseni, Mahtab ($item.subfieldsMap.e)
Abstract
Against the computational security, which guarantees the confidentiality via computational complexity, information theoretic secrecy considers the full information secrecy. The full information secrecy is the case when the mutual information rate between received signal of eavesdropper and the confidential message converges to zero. In this thesis we consider the fundamental limits of transmission security. For this, we first consider basic models with one transmitter, one receiver and one eavesdropper and after investigating previous works, models and performance criteria, we state our owns models and criterion. Since the full knowledge of CSI is an optimistic assumption, we consider the...
Vehicle identification sensor models for origin-destination estimation
, Article Transportation Research Part B: Methodological ; Volume 89 , 2016 , Pages 82-106 ; 01912615 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
The traditional approach to origin-destination (OD) estimation based on data surveys is highly expensive. Therefore, researchers have attempted to develop reasonable low-cost approaches to estimating the OD vector, such as OD estimation based on traffic sensor data. In this estimation approach, the location problem for the sensors is critical. One type of sensor that can be used for this purpose, on which this paper focuses, is vehicle identification sensors. The information collected by these sensors that can be employed for OD estimation is discussed in this paper. We use data gathered by vehicle identification sensors that include an ID for each vehicle and the time at which the sensor...
Vehicle identification sensors location problem for large networks
, Article Journal of Intelligent Transportation Systems: Technology, Planning, and Operations ; 2018 ; 15472450 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Finding the optimal location for sensors is a key problem in flow estimation. There are several location models that have been developed recently for vehicle identification (ID) sensors. However, these location models cannot be applied to large networks because there are many constraints and integer variables. Based on a property of the location problem for vehicle ID sensors, given the initial vehicle ID sensors that are pre-installed and fixed on the network, this article presents a solution that greatly reduces the size of this location problem. An applied example demonstrates that when 8% of the arcs from a real network that are randomly selected have a vehicle ID sensor, the reductions...
Vehicle Identification Sensors Location Problem with the Purpose of Origin-destination Estimation
, Ph.D. Dissertation Sharif University of Technology ; Shafahi, Yousef (Supervisor)
Abstract
Origin-Destination (OD) table is an important input for managing and controling processes of transportation systems. OD flow estimation based on the observations of traffic sensors is a famous way of attaining this table. Technology developments in recent years reduce the cost and improve the quality of the results for this method. This research explores the methods for applying one of these technologies, vehicle identification systems, with the purpose of OD flow estimation.In this research several location models for vehicle identification systems are presented. These models have better performances comparing to the existing models in the literature. Furthermore, location models for some...
Vehicle identification sensors location problem for large networks
, Article Journal of Intelligent Transportation Systems: Technology, Planning, and Operations ; Volume 23, Issue 4 , 2019 , Pages 389-402 ; 15472450 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Taylor and Francis Inc
2019
Abstract
Finding the optimal location for sensors is a key problem in flow estimation. There are several location models that have been developed recently for vehicle identification (ID) sensors. However, these location models cannot be applied to large networks because there are many constraints and integer variables. Based on a property of the location problem for vehicle ID sensors, given the initial vehicle ID sensors that are pre-installed and fixed on the network, this article presents a solution that greatly reduces the size of this location problem. An applied example demonstrates that when 8% of the arcs from a real network that are randomly selected have a vehicle ID sensor, the reductions...
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...
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
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...
Equilibrium Flow with Side Constraint
, M.Sc. Thesis Sharif University of Technology ; Zakai Aashtiani, Hedayat (Supervisor)
Abstract
Wardrop’s first principle for defining the equilibrium flow in transportation networks is one of the mostly accepted assumptions in traffic assignment models. Optimization Models, Variational Inequalities, and Complementarity Equations are among the known models based on this assumption. In these models with the assumption of unlimited capacity for the network’s arcs and use of nonlinear cost functions, the constraint of arc capacity is considered implicitly. Another approach is to consider the arc capacity, explicitly. In recent decade this approach was the subject of some researches. In this thesis, these researches will be discussed. Then, researches about explicit consideration of the...
A new MCMC sampling based segment model for radar target recognition
, Article Radioengineering ; Volume 24, Issue 1 , 2015 , Pages 280-287 ; 12102512 (ISSN) ; Radmard, M ; Nayebi, M ; Sharif University of Technology
Czech Technical University
2015
Abstract
One of the main tools in radar target recognition is high resolution range profile (HRRP). However, it is very sensitive to the aspect angle. One solution to this problem is to assume the consecutive samples of HRRP identically independently distributed (IID) in small frames of aspect angles, an assumption which is not true in reality. However, based on this assumption, some models have been developed to characterize the sequential information contained in the multi-aspect radar echoes. Therefore, they only consider the short dependency between consecutive samples. Here, we propose an alternative model, the segment model, to address the shortcomings of these assumptions. In addition, using a...
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...
Privacy Preserving Communication Schemes for Light Clients in Blockchain Networks: Algorithms and Analysis
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Maddah Ali, Mohammad Ali (Co-Supervisor)
Abstract
Lightweight clients are a type of blockchain users who do not store all the blocks in the blockchain due to limited resources. These users store only a small part of each block and when needed, request transactions from full nodes that store the entire blockchain. These users have no role in block validation and only want to receive transactions related to their addresses with proof of the inclusion in the block from full nodes.Since light clients rely on full nodes for receiving transactions, their privacy against full nodes is important. The current implementation of Bitcoin uses Bloom filters for privacy, but this offers very little privacy to the users.In this thesis, we study the...
The Effect of Soli-Structure Interaction on Dynamic Characteristics of Structures with Embedded Fondation
, M.Sc. Thesis Sharif University of Technology ; Ghannad, Mohammad Ali (Supervisor)
Abstract
Soil-structure interaction has significant effect on dynamic behavior of the super structure. This effect is usually investigated in two separate parts, i.e., the Kinematic Interaction effect and the Inertial Interaction effect. The first modifies the input ground motion to the foundation as a result of difference in soil and foundation stiffness. The later, i.e., the II effect, introduces the effect of soil flexibility and radiation of waves into the supporting medium on the response of the structure. These effects are usually considered by introducing a replacement oscillator with modified natural period and damping ratio subjected...
Perusing Metal Perusing Metal Insulator Transistors with in the Dynamical Field Approximation at Finite Temperature
, Ph.D. Dissertation Sharif University of Technology ; Vesaghi, Mohammad ALi (Supervisor)
Abstract
The aim of this work is to investigate some theoretical models developed in recent years for describing electronic correlation and apply them to some special problems and metallicity and insulating behavior of one type of paramagnetic systems. One of the vast‐applied and effective routines for investigating the strongly correlated electron systems is Dynamical Mean Field Theory (DMFT). In the first part, the equations of DMFT are solved on nearly real frequency axis with a effective and more reliable solver a little parameter γ above the real axis. This approach appears fine structures that can’t be captured with the ...