Loading...
Search for:
faraji--h
0.132 seconds
Total 9987 records
Multivariable robust control of a horizontal wind turbine under various operating modes and uncertainties: A comparison on sliding mode and H∞ control
, Article International Journal of Electrical Power and Energy Systems ; Volume 115 , 2020 ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Wind turbines are generally controlled for the objectives of the turbine protection and generation of the acceptable power for the utility grid. In this paper, a nonlinear multivariable model of the wind turbine with a DFIG generator is considered. The rotor speed and the d-axis rotor current, as the controlled variables, are controlled via manipulation of the two generator voltages, as the control signals. Two robust control strategies including the sliding mode control and H∞ robust control, designed via μ-synthesis based on DK-iteration algorithm, are presented for switching between various operating modes. Development of an acceptable dynamic model and two innovative control strategies...
Sliding mode robust control of the horizontal wind turbines with model uncertainties
, Article 2020 9th International Conference on Modern Circuits and Systems Technologies, MOCAST 2020, 7 September 2020 through 9 September ; 2020 ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
Wind turbines are generally controlled based on two control objectives: Turbine protection and the generation of acceptable power for the grid. In this paper, a robust control strategy is presented for switching between various operating modes of the turbine. The rotor angular speed is hold below the allowable speed in all operation time. It is also attempted to catch a constant power in a desirable amount during the most of operation time. For the elimination of model/environmental uncertainties, sliding mode controllers are used. For the objective of power tracking, the stability of sliding mode controller is proved for a set of sliding surfaces. Advantages and disadvantages of the...
Analytical approach for analyzing tapered transmission lines
, Article 2005 European Conference on Circuit Theory and Design, Cork, 28 August 2005 through 2 September 2005 ; Volume 3 , 2005 , Pages 181-184 ; 0780390660 (ISBN); 9780780390669 (ISBN) ; Eghlidi, M. H ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
2005
Abstract
A new analytical method is introduced for the analysis of wave propagation in one-dimensional tapered transmission lines. Based on the analytical extension of ordinary transfer matrix into differential transfer matrix, this approach can be used for calculating reflection and transmission coefficients. Different numerical test cases are thoroughly studied and in each case an excellent agreement between the results of our differential transfer matrix method and exact solutions is observed. It is also shown that our approach is superior to the more common small reflection method
Quantum complexity of TT¯-deformation and its implications
, Article Journal of High Energy Physics ; Volume 2024, Issue 10 , 2024 ; 10298479 (ISSN) ; Sharif University of Technology
2024
Abstract
We employ holography to calculate the quantum complexity of TT¯-deformation, utilizing the complexity equals volume (CV) and the complexity equals action (CA) proposals within the bulk spacetime with a finite radius cutoff. We find that the complexity of the deformed theory differs from the renormalized complexity of the original theory by a geometric functional: the bending (Willmore) energy of the time-constant slice of the base manifold. We use this result to propose an unambiguous scheme for calculating holographic quantum complexity through the CA proposal. © The Author(s) 2024
Properties and mechanism of Al/St bimetal tube bonding produced by cold spin-bonding (CSB) process
, Article Transactions of the Indian Institute of Metals ; Volume 70, Issue 10 , 2017 , Pages 2673-2682 ; 09722815 (ISSN) ; Abrinia, K ; Akbarzadeh, A ; Bulaqi, H. A ; Faraji, G ; Sharif University of Technology
2017
Abstract
Spin-bonding is a novel tube cladding method for fabrication of bilayer tubes based on flow-forming process. The bimetal Al/St tubular components have extensive application in different industries. In this paper, an Al/St bimetal tube was successfully produced at different thickness reductions from 35 to 65% and mechanical and metallurgical aspects of the joint were investigated. Peeling tests were done to investigate the strength of the bond. The results showed that an increase in the thickness reduction led to a significant increase in the bond strength. Besides, the bonding mechanism between Al as inner tube to St as an outer one resulting from spin-bonding process was investigated. The...
Identity recognition based on convolutional neural networks using gait data
, Article 26th International Computer Conference, Computer Society of Iran, CSICC 2021, 3 March 2021 through 4 March 2021 ; 2021 ; 9781665412414 (ISBN) ; Lotfi, F ; Majdolhosseini, M ; Jafarian, M ; Taghirad, H. D ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
As a critical part of any security system, identity recognition has become paramount among researchers. In this regard, several methods are presented while considering various sensors and data. In particular, gait data yields rich information about a person, including some exclusive moving patterns which can be utilized to distinguish between different individuals. On the other hand, convolutional neural networks are proved to be applicable for structured data, especially images. In this article, 12 markers are considered in gathering the gait data, each representing a lower-body joint location. Then, utilizing the gait data in a 2D tensor form, three different convolutional neural networks...
What surface maximizes entanglement entropy?
, Article Physical Review D - Particles, Fields, Gravitation and Cosmology ; Vol. 90, issue. 8 , 2014 ; Gibbons, G ; Solodukhin, S. N
2014
Abstract
For a given quantum field theory, provided the area of the entangling surface is fixed, what surface maximizes entanglement entropy? We analyze the answer to this question in four and higher dimensions. Surprisingly, in four dimensions the answer is related to a mathematical problem of finding surfaces that minimize the Willmore (bending) energy and eventually to the Willmore conjecture. We propose a generalization of the Willmore energy in higher dimensions and analyze its minimizers in a general class of topologies Sm×Sn and make certain observations and conjectures that may have some mathematical significance
Ag/TiO2-nanotube plates coated with reduced graphene oxide as photocatalysts
, Article Surface and Coatings Technology ; Volume 288 , 2016 , Pages 144-150 ; 02578972 (ISSN) ; Mohaghegh, N ; Sharif University of Technology
Elsevier
2016
Abstract
RGO/Ag/TiO2-nanotubes/Ti plates with high photocatalytic activity were fabricated via electrochemical reduction of graphene oxide on Ag/TiO2-nanotubes. The loading of silver nanoparticles was carried out by electroless reduction of Ag1+ onto TiO2 nanotubes previously formed by anodizing titanium. Microstructure studies show that reduced graphene oxide (RGO) layers having high surface area have been deposited on the as-prepared Ag/TiO2-nanotubes, where nanoparticles of Ag had grown on the walls of TiO2-nanotubes. The results of photocatalytic experiments demonstrate that the RGO/Ag/TiO2-nanotubes/Ti plate exhibits significantly enhanced photocatalytic activity for the photocatalytic...
The Impact of House’s Recession on Banks’ Default Rate In The Framework of Stress Testing
, M.Sc. Thesis Sharif University of Technology ; Nili, Farhad (Supervisor)
Abstract
The aim of this paper is to perform macro stress test for one of Iran’s private banks using bank’s quarterly data from Q-4 1383 to Q-4 1389. To do this, the relation of bank’s default rate with macroeconomic indicators like house prices and the growth rate of value added of services; as macroeconomic risk factors; was investigated by a linear model. Results show that the bank’s default rate has a negative relation with both risk factors.Stress testing, using monte carlo simulation; shows that reverse shocks to both house prices and the growth rate of value added of services leads to severe increase in bank’s default rate; so that with decrease of both house prices to 4 million rials at...
The Prediction Branching Polypropylene Monte Carlo Method
, M.Sc. Thesis Sharif University of Technology ; Mousavi, Ali (Supervisor)
Abstract
Linear structure of polypropylene, which is a direct result of Ziegler-Natta catalysts, led to the melt strength of the polymer is low and it does not show hardness strain. This defect is cause to the use of polypropylene in some processes, such as thermoforming, making foam etc. are limited. A main methods to solve this defect are branching structure of the polymer. There are three general methods for this purpose, which are modified by chemical, electron beam irradiation and polymerization in the presence of metallocene catalyst. The first two methods that past processing, polypropylene branching using linear type is produced, while the third method branching occurs during polymerization....
Application of TiO2 Nanotubes Fabricated by Anodizing of Titanium as a Suitable Substrate for Deposition of Active Materials for Use in the Supercapacitors
, Ph.D. Dissertation Sharif University of Technology ; Gobal, Fereydoon (Supervisor)
Abstract
In this thesis, the improving effects of TiO2 nanotubes (TiO2NTs) fabricated by anodizing of titanium as suitable substrate for deposition active materiales in supercapacitors were considered. PANI/Pd/TiO2NTs electrodes with highly porous structures and good capacitive characteristics were prepared by electrodeposition of polyaniline on palladium nanoparticles loaded TiO2 nanotubes. The results illustrated that the specific capacitance of these electrodes was around 1060 Fg−1 in 1.0 M H2SO4 electrolyte as measured at a constant current of 2.0 Ag−1, whereas it was 210 Fg−1 for the PANI/TiO2NTs electrode. NiO-ZnO/TiO2NTs electrodes were synthesized by the electrodeposition of...
The effect of fractionality nature in differences between computer simulation and experimental results of a chaotic circuit
, Article Central European Journal of Physics ; Volume 11, Issue 6 , 2013 , Pages 836-844 ; 18951082 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
2013
Abstract
In practice, some differences are usually observed between computer simulation and experimental results of a chaotic circuit. In this paper, it is tried to obtain computer simulation results having more correlation with those obtained in practice by using more realistic models for chaotic circuits. This goal is achieved by considering the fractionality nature of electrical capacitors in the model of a chaotic circuit
Energy of decomposition and entanglement thermodynamics for T2-deformation
, Article Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics ; Volume 839 , 2023 ; 03702693 (ISSN) ; Allameh, K ; Sharif University of Technology
Elsevier B.V
2023
Abstract
We have presented a set of laws of entanglement thermodynamics for TT¯-deformed CFTs and in general for T2-deformed field theories. In particular, the first law of this set, states that although we are dealing with a non-trivial deformed theory, the change of the entanglement entropy is simply translated to the change of the bending energy of the entangling surface. We interpret this energy as the energy of decomposition. Probing the whole spectrum of the deformed theory, a second law also results, which suggests an inequality that the first law is derived from its saturation limit. We explain that this second law guarantees the preservation of the unitarity bound. The thermodynamical form...
Numerical and experimental investigations of weld pool geometry in GTA welding of pure aluminum
, Article Journal of Central South University ; Vol. 21, issue. 1 , 2014 , p. 20-26 ; Bahmani, A ; Goodarzi, M ; Seyedein, S. H ; Shabani, M. O ; Sharif University of Technology
2014
Abstract
A 2-D numerical model was developed to predict the shape of weld pool in stationary GTA welding of commercial pure aluminium, without considering fluid flow in the weld pool. A Gaussian current density and heat input distribution on the surface of the workpiece were considered. The parameters of Gaussian distribution were modified by comparing calculated results with experimental ones. It was found that these distribution parameters are functions of applied current and arc length. Effects of arc length, applied current and welding time on the geometry of the weld pool were investigated. To check the validity of the model, a series of experiments were also conducted. In general, the agreement...
Ternary composite of TiO2 nanotubes/Ti plates modified by g-C3N4 and SnO2 with enhanced photocatalytic activity for enhancing antibacterial and photocatalytic activity
, Article Journal of Photochemistry and Photobiology B: Biology ; Volume 178 , 2018 , Pages 124-132 ; 10111344 (ISSN) ; Mohaghegh, N ; Abedini, A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
A series of g-C3N4-SnO2/TiO2 nanotubes/Ti plates were fabricated via simple dipping of TiO2 nanotubes/Ti in a solution containing SnCl2 and g-C3N4 nanosheets and finally annealing of the plates. Synthesized plates were characterized by various techniques. The SEM analysis revealed that the g-C3N4-SnO2 nanosheets with high physical stability have been successfully deposited onto the surface of TiO2 nanotubes/Ti plate. Photocatalytic activity was investigated using two probe chemical reactions: oxidative decomposition of acetic acid and oxidation of 2-propanol under irradiation. Antibacterial activities for Escherichia coli (E. coli) bacteria were also investigated in dark and under UV/Vis...
Boundary conformal invariants and the conformal anomaly in five dimensions
, Article Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics ; Volume 816 , 2021 ; 03702693 (ISSN) ; Solodukhin, S. N ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In odd dimensions the integrated conformal anomaly is entirely due to the boundary terms [1]. In this paper we present a detailed analysis of the anomaly in five dimensions. We give the complete list of the boundary conformal invariants that exist in five dimensions. Additionally to 8 invariants known before we find a new conformal invariant that contains the derivatives of the extrinsic curvature along the boundary. Then, for a conformal scalar field satisfying either the Dirichlet or the conformal invariant Robin boundary conditions we use the available general results for the heat kernel coefficient a5, compute the conformal anomaly and identify the corresponding values of all boundary...
Nickel-based nanosheets array as a binder free and highly efficient catalyst for electrochemical hydrogen evolution reaction
, Article International Journal of Hydrogen Energy ; Volume 47, Issue 82 , 2022 , Pages 34887-34897 ; 03603199 (ISSN) ; Hemmati, K ; Mirabbaszadeh, K ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Hydrogen technology through water electrolyzer systems has attracted a great attention to overcome the energy crisis. So, rationally designed non-noble metal based-electrocatalysts with high activity and durability can lead to high performance water electrolyzer systems and high purity hydrogen generation. Herein, a facile two-step method: hydrothermal and electrodeposition, respectively, are developed to decorate highly porous three-dimensional binder-free structure NiFeO/NiO nanosheets array on Ni foam (NiFeO/NiO/NF) with robust adhesion as a high-performance electrode for Hydrogen Evolution Reaction (HER). The electrodeposition process applied after the initial hydrothermal process...
Fermions, boundaries, and conformal and chiral anomalies in d=3, 4 and 5 dimensions
, Article Physical Review D ; Volume 108, Issue 8 , 2023 ; 24700010 (ISSN) ; Solodukhin, S. N ; Sharif University of Technology
American Physical Society
2023
Abstract
In the presence of boundaries, the quantum anomalies acquire additional boundary terms. In odd dimensions, the integrated conformal anomaly, for which the bulk contribution is known to be absent, is nontrivial due to the boundary terms. These terms became a subject of active study in the recent years. In the present paper, we continue our previous study [1,2] and compute explicitly the anomaly for fermions in dimensions d=3, 4 and 5. The calculation in dimension 5 is new. It contains both contributions of the gravitational field and the gauge fields to the anomaly. In dimensions d=3 and 4, we reproduce and clarify the derivation of the results available in the literature. Imposing the...
Processing and Investigation of the Properties of Chitosan/Celloluse Nanocomposite Wound Dressing Fabricated by Electrospinning Method
, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza (Supervisor)
Abstract
It is a common method to use some proper materials such as honey, herbal fibers, and minerals for covering the wounds as an effective treatment. Nowadays biopolymers and new methods of nanofiber production to build a structure similar to the natural extracellular matrix (ECM) like electrospinning are used to reduce the time of restoration and prevent from the effects of wounds such as bedsores, diabetic ulcers, and severe burns. For effective design of a wound dressing, wound feature, recovery time, physical, mechanical, and biological properties should be considered in order to best as possible heal the bound. In this research, cellulose nanocrystals with average aspect ratio of 11.8 and...
Investigation of Information Paradox in Charged Black Holes Using the Holography
, M.Sc. Thesis Sharif University of Technology ; Faraji Astaneh, Amin (Supervisor)
Abstract
Bonding gravity with Quantum mechanics has always been a challenging issue. So that, accomplishing a theory of quantum gravity is one of the most important research topics in High-Energy Physics.Information paradox in black holes is among such issues which connect quantum mechanics with gravity. Black holes as a natural solution of Einstein equations have a distinction, with other solutions, since there exists an event horizon that imparts space-time into two causally disconnected regions.According to Hawking’s calculations, black holes would evaporate over time by the thermal radiation. This resulting thermal radiation has less information than the initial collapsed matter in a pure state....