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yazdani--amir
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Free-edge stresses in general cross-ply laminates
, Article Scientia Iranica ; Vol. 21, issue. 2 , April , 2014 , p. 387-402 ; Sharif University of Technology
2014
Abstract
Within elasticity theory, the reduced form of a displacement field is obtained for general cross-ply composite laminates subjected to a bending moment. The firstorder shear deformation theory of plates and Reddy's layerwise theory are then utilized to determine the global deformation parameters and the local deformation parameters appearing in the displacement fields, respectively. For a special set of boundary conditions an elasticity solution is developed to verify the validity and accuracy of the layerwise theory. Finally, various numerical results are presented within the layerwise theory for edge-effect problems of several cross-ply laminates under the bending moment. The results...
Multicast Routing on Wireless Mesh Networks
, M.Sc. Thesis Sharif University of Technology ; Yazdani, Naser (Supervisor)
Abstract
Wireless mesh networks (WMN) appeared as popular communication networks supporting high speed and high throughput applications. They consist of mesh routers and mesh clients and they have unique characteristics like self organizing and self configuring of the mesh nodes that bring a great deal of efficiency, reliability and robustness to networks and decreases networks maintenance cost notably. Also WMNs provide an integration of different types of wireless networks by exploiting the gateway involvement. One of the important group communication technologies that offers high level of bandwidth conservation and efficiency is multicasting. It also decreases the cost of communication compared to...
Experimental Study of Pendulum Grinding of Superalloys
, M.Sc. Thesis Sharif University of Technology ; Akbari, Javad (Supervisor)
Abstract
Superalloys are widely used in aerospace and power industries due to the good performance at high temperatures for examples gas turbines, steam turbines and aircraft components. In addition to the turbines cobalt-base superalloys are used in medical implants such as knee and hip joints. The main strengths of the superalloys are heat-resistant, retaining their high mechanical and chemical properties at high temperatures, high melting temperatures, high corrosion resistance, resistance to thermal fatigue, thermal shock, creep, and erosion. Because of difficult to machine properties of superalloys, grinding is one of the effective methods for machining superalloys. The surface integrity of the...
Feyerabend’s Point of View on Scientific Progress
, M.Sc. Thesis Sharif University of Technology ; Taghavi, Mostafa (Supervisor)
Abstract
Feyarabend’s philosophy of science is against method and rule such that he believes that “anything goes”. However, he sometimes applies the term “progress”. Reviewing his publications shows that from his point of view, progress is qualitative and relative. So, unlike other philosophers of science Feyarabend ignores the clarification of the concept; subsequently, his applications of the term “progress” are somewhat ambiguous. However, by studying his philosophy, one may realize what should be done to achieve progress in any sense. The affirmative aspect of Feyerabend’s philosophy, while highlights the social and ethical elements, considering his humanitarian outlook as well as his special...
Aeroacoustic Simulation of Rod-Airfoil Noise
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
Wall systems are an essential part of the buildings and their capacity should be properly considered in their design. However, the seismic behavior of building systems with in-filled walls and their interaction is a very complex issue, yet to be understood. Using the in-filled walls in the buildings without including them in the design process changes the whole behavior of the structural system as well as their failure mechanism under earthquake excitations. On the other hand, there have been extensive researches on rehabilitation of the structures with in-filled walls or designing them as the main or one of the lateral load carrying systems against seismic input. In this research, first the...
Design and Implementation of High Efficient Charger for Plug-in Hybrid Vehicles with Power Factor Correction Feature
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
In this project the novel zero-voltage-switching topology for power factor correction bridgeless boost rectifier is proposed. By employing an improved ZVS pulse-width-modulation (PWM) switch cell, ZVS of all the main switches is achieved without additional current or voltage stress of main switches. Also for the auxiliary switch the zero-current-switching is provided. In all modes of opretion of this converter, the power path is provided by maximum two semiconductor so the conduction loss of converter is low as in conventional converter. With this features the efficiency of proposed converter is very high
Dynamic Model Identification of a 4th Generation Turbojet Engine’s FCU Using Parametric Frequency Response Analysis
, M.Sc. Thesis Sharif University of Technology ; Banazadeh, Afshin (Supervisor)
Abstract
In this thesis, dynamics of a turbojet’s fuel control unit is studied for the nature and the range of its inputs and outputs. Then, inputs and outputs involved in the system identification process are determined. Tools needed for the application of the input and the signal data sampling are recognized, and henceforth, with the appropriate input applied and the frequency-domain system identification process carried out, desired linear transformation functions representing dynamics of the fuel control unit are found. Using these transformation functions, the fuel control unit is simulated to be converted to an electronic control unit
Higher-order four-wave mixing modeling in DWDM networks
, Article Physica Scripta, Belgrade ; Volume T157 , 15 November , 2013 ; 02811847 (ISSN) ; Noshad, M ; Sharif University of Technology
2013
Abstract
In this paper, we derive a theoretical model for the higher-order four-wave mixing (FWM) power in wavelength division multiplexing networks with non-zero dispersion shifted fibers for the first time. We have investigated the higher-order FWM power theoretically and by numerical simulations. Dividing the fiber into a finite number of elements and applying the boundary conditions allow us to derive an expression for the second-order power penalty. At the end of each element, we derive the first-order FWM power for all wavelengths and use these values to calculate the second-order FWM power in the next element. Consequently, for each channel we can compute the total second-order FWM power...
On the existence of periodic solutions in time-invariant fractional order systems
, Article Automatica ; Volume 47, Issue 8 , 2011 , Pages 1834-1837 ; 00051098 (ISSN) ; Salarieh, H ; Sharif University of Technology
2011
Abstract
Periodic solutions and their existence are one of the most important subjects in dynamical systems. Fractional order systems like integer ones are no exception to this rule. Tavazoei and Haeri (2009) have shown that a time-invariant fractional order system does not have any periodic solution. In this article, this claim has been investigated and it is shown that although in any finite interval of time the solutions do not show any periodic behavior, when the steady state responses of fractional order systems are considered, periodic orbits can be detected
Position convergence of informed agents in flocking problem with general linear dynamic agents
, Article IET Control Theory and Applications ; Volume 9, Issue 3 , February , 2015 , Pages 392-398 ; 17518644 (ISSN) ; Haeri, M ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
In most existing works on the flocking problem, results were obtained for the case where a double integrator dynamic is used to describe motion of agents and virtual leader. These results, however, may not be generalised to agents with general linear dynamic. In this study, it is shown that in the flocking of agents with a linear dynamic, the velocity convergence of agents does not generally lead to the position convergence of informed agents and the position convergence is possible only for a specified group of linear dynamics. In this study, a control protocol is proposed to flock agents with specified linear dynamics and guarantee the velocity convergence of all agents as well as average...
Flocking of multi-agent systems with multiple second-order uncoupled linear dynamics and virtual leader
, Article IET Control Theory and Applications ; Volume 10, Issue 8 , 2016 , Pages 853-860 ; 17518644 (ISSN) ; Haeri, M ; Sharif University of Technology
Institution of Engineering and Technology
2016
Abstract
In this study, flocking of multi-agent systems with virtual leader and linear dynamics is investigated. It is assumed that the dynamics of agents in each dimension is represented by a general second-order linear model. The proposed control protocol is composed of two terms, one for feed backing each agent's states and one for cooperative control. At first, the flocking problem of multi-agent systems with identical agents is discussed and then the proposed protocol is generalised to flock heterogeneous multi-agent systems. Under the proposed algorithm, the velocity convergence of whole group to a velocity of virtual leader is guaranteed while the connectivity of network is preserved and...
Robust adaptive fault-tolerant control for leader-follower flocking of uncertain multi-agent systems with actuator failure
, Article ISA Transactions ; Volume 71 , 2017 , Pages 227-234 ; 00190578 (ISSN) ; Haeri, M ; Sharif University of Technology
2017
Abstract
In this work, we study the flocking problem of multi-agent systems with uncertain dynamics subject to actuator failure and external disturbances. By considering some standard assumptions, we propose a robust adaptive fault tolerant protocol for compensating of the actuator bias fault, the partial loss of actuator effectiveness fault, the model uncertainties, and external disturbances. Under the designed protocol, velocity convergence of agents to that of virtual leader is guaranteed while the connectivity preservation of network and collision avoidance among agents are ensured as well. © 2017 ISA
A sampled-data algorithm for flocking of multi-Agent systems
, Article 7th Conference on Artificial Intelligence and Robotics, IRANOPEN 2017, 9 April 2017 ; 2017 , Pages 147-152 ; 9781538628621 (ISBN) ; Haeri, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
This paper investigates a new algorithm for flocking of multi-Agent systems with virtual leader. In this algorithm, unlike the existing algorithms, receiving of information by agents are not continuous and it is assumed that each agents receives information of neighbors and virtual leader as sampled data in fixed time intervals. A sufficient condition on sampling period is derived to guarantee the velocity convergence of agents to that of virtual leader, preserve network connectivity, and ensure collision avoidance. Finally, a numerical simulation is provided to illustrate the theoretical results. © 2017 IEEE
Design of dual active bridge isolated bidirectional DC converter based on current stress optimization
, Article 8th Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2017, 14 February 2017 through 16 February 2017 ; 2017 , Pages 247-252 ; 9781509057665 (ISBN) ; Zolghadri, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Dual active bridge isolated bidirectional DC converter (DAB-IBDC) has a poor efficiency at light loads and non-unity voltage conversion ratio. In this paper the current stress of the converter is analyzed and the effect of maximum phase shift ratio and leakage inductance on the current stress of the converter is investigated. In order to increase the efficiency of the converter and reduce the current stress, the current stress optimization has been done and the design procedure is presented. Simulation results are used to validate the results of the theoretical analysis. © 2017 IEEE
Distributed Observer Type Protocol for Flocking of Linear Second-Order Multi-Agent Systems Subject to External Disturbance
, Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Volume 141, Issue 6 , 2019 ; 00220434 (ISSN) ; Haeri, M ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2019
Abstract
This paper studies the leader-follower flocking of multi-agent systems for the linear second-order dynamics, subject to the external disturbance problem. It is assumed that the dynamic of the leader is Lipschitz-type. Also, the velocity is the output of the system, and full-state information is not available for feedback. A distributed full-order observer is employed to estimate every agent's states and external disturbance. A control protocol for each agent is designed based on the measurement of its output/velocity and relative velocity of its neighbors. Under the proposed protocol, the velocity convergence of whole agents to the velocity of the virtual leader is guaranteed as well as the...
Road Opening and Emergency Relief Since the Time of Severe Earthquake Occurence
, M.Sc. Thesis Sharif University of Technology ; Poorzahedy, Hossein (Supervisor)
Abstract
The abstract is the most important section of the thesis because many readers limit most of their reading to abstracts, saving in-depth reading for specific theses. It should give the reader a "preview" of what's to come. The abstract should emphasize new and important aspects of the study or observations. The purpose of the abstract is to allow researchers to decide whether or not to read the whole thesis. The abstract is what researchers read first to decide if the thesis is important, interesting, and it allows them to assess the relevance of a thesis to their own research, without having to read the entire thesis. Thus, it is crucial that the abstract both summarize succinctly the key...
Measuring Contagion Effects between Crude Oil and Iran Stock Market Sectors
, M.Sc. Thesis Sharif University of Technology ; Zamani, Shiva (Supervisor)
Abstract
The Contagion of markets to each other, due to their role in the occurrence of financial crises and the transmission of shocks, is an important topic in the financial literature. In this dissertation, we study this issue by examining the number of positive and negative co-exeedances in the oil market and Tehran Stock Exchange. The data examined are the daily time series of Tehran Stock Market Index and Oil Prices (WTI) in the period of 2009 to 2019.First of all we find the time cut-off rate of the daily returns of the stock indexes of different industries and of oil prices, using the generalized Pareto distribution (GPD). Then we count the number of days when the returns have negative or...
Sustainability in Supply Chain with Key Performance Indicators
, M.Sc. Thesis Sharif University of Technology ; Najafi, Mehdi (Supervisor)
Abstract
Background: Sustainability is one of the most controversial issues in companies’ supply chain these days. Moreover, growing environmental, social, and ethical concerns have scrambled up the push of organizations to adopt sustainable business enforcement into their operations.Purpose: The aim of the study was to examine the current status of sustainability of supply chains and how it is measured. The goal of this study is to answer the research question: How organizations measure their sustainable supply chain performance with Key Performance Indicators? Method: To comprehensively answer the research question, a qualitative research approach was chosen, and the primary empirical data was...
Vortex Transport in Separating flows and Role of Vortical Structures in Reynolds Stress Production and Distribution
, Article 2005 ASME Fluids Engineering Division Summer Meeting, FEDSM2005, Houston, TX, 19 June 2005 through 23 June 2005 ; Volume 2005 , 2005 , Pages 11-18 ; 0791837602 (ISBN); 9780791837603 (ISBN) ; Khakpour, Y ; Sharif University of Technology
2005
Abstract
In this paper we will present some approaches on Reynolds stress production by vortex transport phenomena and nonlinear voracity generation in momentum equation. First of all we represent a history of recent works to describe how fluid particle motions can be associated with Reynolds stress through either displacement or acceleration terms. In the next section we will describe how vortex stretching causes the Reynolds stress production and what is the dominant effect near and far from the boundary where viscous effects have to be considered. On the other hand, some vortex considered methodologies such as those synthesize boundary layer, as a collection of vortical objects seem to be...
Vortex transport in separating flows and role of vortical structures in reynolds stress production and distribution
, Article 2005 ASME Fluids Engineering Division Summer Conference, Houston, TX, 19 June 2005 through 23 June 2005 ; Volume 1 PART A , 2005 , Pages 429-436 ; 0791841987 (ISBN); 9780791841983 (ISBN) ; Khakpour, Y ; Sharif University of Technology
2005
Abstract
In this paper we will present some approaches on Reynolds stress production by vortex transport phenomena and nonlinear vorticity generation in momentum equation. First of all we represent a history of recent works to describe how fluid particle motions can be associated with Reynolds stress through either displacement or acceleration terms. In the next section we will describe how vortex stretching causes the Reynolds stress production and what is the dominant effect near and far from the boundary where viscous effects have to be considered. On the other hand, some vortex considered methodologies such as those synthesize boundary layer, as a collection of vortical objects seem to be...