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salehi-abari--akbar
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Fault Tolerant Control of Flexible Launch Vehicle Using Fractional-Order Controller
, M.Sc. Thesis Sharif University of Technology ; Fathi Jegarkandi, Mohsen (Supervisor)
Abstract
In this research the attitude control of a flexible launch vehicle using fractional order proportional-integral-derivative controller in the presence of actuators failures is described. Other work done in this study is the investigation of on-line fault detection and diagnosis effects in the attitude control of flexible launch vehicle in the presence of actuator failures. Rigid-elastic equations of motion and assumed modes have been used to simulate dynamics of launch vehicle in the Simulink environment of MATLAB software using two elastic bending modes. The performance of fractional order controller has been compared with conventional proportional-integral-derivative and adaptive augmented...
Three Dimensional Dirac Materials in Weak Links
, Ph.D. Dissertation Sharif University of Technology ; Jafari, Akbar (Supervisor)
Abstract
We study the quantum transport properties of three dimensional Dirac materials within the framework of Landauer–Büttiker formalism. Charge carriers in normal metal satisfying the Schrödinger equation, can be split into four-component with appropriate matching conditions at the boundary with the three dimensional Dirac material (3DDM).We calculate the conductance and the Fano factor of an interface separating 3DDM from a normal metal, as well as the conductance through a slab of 3DDM. Under certain circumstances the 3DDM appears transparent to electrons hitting the 3DDM. We find that electrons hitting the metal-3DDM interface from metallic side can enter 3DDM in a reversed spin state as soon...
The electron density distribution and field profile in underdense magnetized plasma
, Article Physics of Plasmas ; Volume 17, Issue 3 , 2010 ; 1070664X (ISSN) ; Etehadi-Abari, M ; Sharif University of Technology
2010
Abstract
In this work propagation of a high frequency electromagnetic wave in underdense plasma in presence of an external magnetic field is investigated. When a constant magnetic field perpendicular to the motion of electrons is applied, then the electrons rotate around the magnetic field lines and generate electromagnetic part in the wake with a nonzero group velocity. By using of the Maxwell equations and nonlinear differential equation for the electric field a direct one-dimensional (1D) procedure for calculating hydrodynamic equations are developed and the electric and magnetic field profiles in the plasma are investigated. It is shown that by using the external (dc) magnetic field in constant...
Rehabilitation after ACL injury: A fluoroscopic study on the effects of type of exercise on the knee sagittal plane arthrokinematics
, Article BioMed Research International ; Volume 2013 , July , 2013 ; 23146133 (ISSN) ; Esfandiarpour, F ; Shakourirad, A ; Salehi, R ; Akbar, M ; Farahmand, F ; Sharif University of Technology
2013
Abstract
A safe rehabilitation exercise for anterior cruciate ligament (ACL) injuries needs to be compatible with the normal knee arthrokinematics to avoid abnormal loading on the joint structures. The objective of this study was to measure the amount of the anterior tibial translation (ATT) of the ACL-deficient knees during selective open and closed kinetic chain exercises. The intact and injured knees of fourteen male subjects with unilateral ACL injury were imaged using uniplanar fluoroscopy, while the subjects performed forward lunge and unloaded/loaded open kinetic knee extension exercises. The ATTs were measured from fluoroscopic images, as the distance between the tibial and femoral reference...
A 3-D and Time Dependent Software for Particles Tracking Base on Monte Carlo Method
, Ph.D. Dissertation Sharif University of Technology ; Salehi, Ali Akbar (Supervisor) ; Vosoughi, Naser (Co-Supervisor)
Abstract
A highly reliable tool for transient simulation is vital in the safety analysis of a nuclear reactor. Despite this fact most tools still use diffusion theory and point-kinetics that involve many approximations such as discretization in space, energy, angle and time. However, Monte Carlo method inherently overcomes these restrictions and provides an appropriate foundation to accurately calculate the parameters of a reactor. For this reason, in this thesis, a dynamic Monte Carlo code named MCSP (Monte Carlo dynamic Simulation of Particles tracking) is developed for both the steady state and time-dependent simulation of particle (neutrons, photons and electrons) tracking in an arbitrary 3D...
Optimization of a/b-axis regions of YBCO thin film for sensor applications
, Article Proceedings of the National Academy of Sciences India Section A - Physical Sciences ; Volume 88, Issue 4 , 2018 , Pages 625-628 ; 03698203 (ISSN) ; Hosseini, M ; Fardmanesh, M ; Sharif University of Technology
Springer
2018
Abstract
The effect of substrate temperature on epitaxial growth of Y1Ba2Cu3O7−x film deposited on (100) crystalline lanthanum aluminate (LAO) substrates by RF Sputtering method has been investigated. The crystal mismatch between film and substrate is about 1.6%. The sputtering was carried out in vacuum with base pressure better than 10−5 Torr and 10/20 Pa oxygen/argon partial pressures. Substrate temperature at this condition is about 730 °C based on Bormann–Hammond diagram. As well known, because of the small lattice mismatch between YBCO and LAO, fabricated thin films are not perfectly c-axis and there is tendency to form a/b-axis regions in the film. Due to substantial effects of the density and...
Nonlinear Structure of Electromagnetic Wave Propagation of an Ultra-Short Laser Pulse in Under-Dense Magnetized Plasma
, M.Sc. Thesis Sharif University of Technology ; Sadighi Bonabi, Rasool (Supervisor)
Abstract
In this work we studied the interaction of a high frequency electromagnetic wave in under relativistic and relativistic regims with a plasma taking into account of the ponderomotive fo per unit volume acting on plasma electrons.In under relativistic regim at first we assumed the plasma is collisionless, unmagnetized and non isothermal which occupying the semi - space Z 0 .We found the nonlinear differential equation for the electric field using theMaxwell and hydrodynamic equations.We obtain the profiles of the electric and magnetic fields in plasma and we see that the electron density oscillations appear highly peaked. Then in this regim a direct one dimensional (1D) procedure for...
MOD growth of epitaxial cerium oxide buffer layer on LAO substrates for fabrication of c-axis oriented YBCO
, Article Micro and Nano Letters ; Volume 7, Issue 10 , 2012 , Pages 1008-1010 ; 17500443 (ISSN) ; Foroughi Abari, F ; Vesaghi, M. A ; Fardmanesh, M ; Sharif University of Technology
2012
Abstract
Epitaxial cerium oxide (CeO2) buffer layer has been grown on lanthanum aluminate (LAO) single crystal substrates for fabrication of c-axis oriented YBa2Cu3O7-x (YBCO). Precursor solution of cerium acetylacetonates with viscosity of 0.6 centipoises was spin coated on the 1×1 cm area LAO substrates. The calcination was carried out by very slow ramp (1°C per minute) until the final temperature of 500°C in oxygen flow to remove most of the organic compounds. The final heat treatment has been done at 780°C by a ramp of 20° per minute in gas flow of mixed argon-oxygen with 5 Pa partial pressure of oxygen. The thickness of the deposited CeO2 buffer layer was 20 nm. Then, 100 nm thick YBCO film was...
Emerging OCDMA communication systems and data networks [electronic resource]
, Article Journal of Optical Networking ; Volume 6, Issue 9, 1 September 2007, Pages 1138-1178 ; Sharif University Of Technology
Abstract
I present an in-depth review of the trends and the directions taken by researchers worldwide in optical code-division multiple-access (OCDMA) systems. I highlight those trends and features that I believe are essential to the successful introduction of various OCDMA techniques in communication systems and data networks in the near future. In particular I begin by giving a comprehensive review of the construction of optical orthogonal codes (OOCs). Specifically I discuss the recently developed algorithms that are based on matrix algebra, which simplify and enhance the efficiencies of algorithms in OOC generation. In communication systems studies I first focus on and discuss various OCDMA...
Electroplating and characterization of Cr–Al2O3 nanocomposite film from a trivalent chromium bath [electronic resource]
, Article Anti-Corrosion Methods and Materials ; Vol 61, No 4, 2014, 205-214 ; Sadrnezhaad, Khatiboleslam ; Salehi Doolabi, Davood ; Sharif University of Technology
Abstract
The main aim of this study was to improve current efficiency and to obtain thicker coatings via aluminum oxide (Al2O3) addition to the chromium (Cr) (III) bath. Design/methodology/approach ‐ Pure Cr and nanocomposite Cr–Al2O3 coatings were electrodeposited from Cr (III) bath onto cathode copper substrates by conventional method. Dependence of current efficiency to current density, Al2O3 content and particle size were investigated. Findings ‐ Current efficiency increased with Al2O3 amount and decreased with Al2O3 particle size. Maximum current efficiency was achieved at 25 A/dm2 for pure Cr and 30 A/dm2 for composite coatings. Al2O3 bath content, current density and stirring rate increased...
Spatial heterodyning optical CDMA technique for near-field free-space optical communication systems [electronic resource]
, Article IEEE Journal of Optical Communications and Networking ; Vol. 1, No. 5, PP. 498-511, Oct. 2009 ; Salehi, J. A ; Sharif University Of TechnologyBioactivity of Surface Modified Titanium Alloy Ti-6Al-4V ELI by Pack Siliconizing in Simulated Body Fluid
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Ziaei Moayyed, Ali Akbar (Supervisor)
Abstract
Titanium alloy Ti-6Al-4V ELI with high biocompatibility and corrosion resistance, has a lot of applications in biomedical engineering. Disadvantage of this alloy is it’s disability to create a fast and good contact with the host/bone environment, after implanting in the body. Beside that it has low wear resistance. Nowadays to optimize the wear resistance, bioactivity and osteoconduction of surface of implants which are made from this alloy, the surface morphology are optimized in size and distribution. Different surface treatments are used for producing rough and porous surfaces to improve bioactivity along with wear resistance. In this study, surface modification of Ti-6Al-4V ELI was done...
Characterization of Metallurgical and Geometrical Parameters on Fracture Behavior of Pure Titanium thin Sheets
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Ziaei Moayyed, Ali Akbar (Supervisor)
Abstract
Commercially pure titanium (CP-Ti) is an important groups of titanium family and because of high strength, low density, high corrosion resistance and biocompatibility, this group of titanium is a suitable choice for application at chemical, petrochemical and medicine industry. Nowadays surgeons have a tendency toward use of CP-Ti instead of Ti-6Al-4V alloy. Moreover, because of body anatomy limitation, use of thick sheets result in high volume and damage soft tissue. Therefore, for sheet thickness reduction, study of the effects of metallurgical and geometrical parameter on fracture behavior of thin sheets is important. In this study, the fracture behavior of CP-Ti thin sheets investigated....
An automated simple algorithm for realistic pore network extraction from micro-tomography images
, Article Journal of Petroleum Science and Engineering ; Vol. 123, issue , 2014 , pp. 164-171 ; ISSN: 09204105 ; Jamshidi, S ; Salehi, S
2014
Abstract
Using 3-D scanned data to analyze and extract pore network plays a vital role in investigation of porous media's characteristics. In this paper, a new simple method is developed to detect pores and throats for analyzing the connectivity and permeability of the network. This automated method utilizes some of the common and well-known image processing functions which are widely accessible by researchers and this has led to an easy algorithm implementation. In this method, after polishing and quality control of images, using city-block distance function and watershed segmentation algorithm, pores and throats are detected and 3-D network is produced. This method can also be applied on 2-D images...
Essentials of sla for l2 teachers: A transdisciplinary framework, joan kelly hall, routledge, New york
, Article Iranian Journal of Language Teaching Research ; Issue 1 , 2020 , Pages 154-156 ; Sharif University of Technology
Urmia University
2020
Influence of pulse parameters on electrocodeposition of Cr-Al2O3 nanocomposite coatings from trivalent chromium bath
, Article International Heat Treatment and Surface Engineering ; Volume 6, Issue 4 , December , 2012 , Pages 178-184 ; 17495148 (ISSN) ; Sadrnezhaad, S. K ; Salehi Doolabi, D ; Asadirad, M ; Sharif University of Technology
2012
Abstract
Cr and Cr-Al2O3 coatings were electrodeposited from Cr(III) bath with both pulsating and direct current onto copper substrates. Pulsating current resulted in homogeneous films of higher Al2O3 content and lower particle agglomeration than the direct current. Differences were more tangible at shorter duty cycles and pulse frequencies. Pulsating current improved both microhardness and corrosion resistance. The presence of alumina nanoparticles resulted in greater current efficiency, higher film microhardness and better corrosion resistance. Maximum current efficiency, highest microhardness and densest electrodeposited coatings were achieved at current density of 20 A dm-2, duty cycle of 40% and...
An orthogonal pulse amplitude modulation signaling for high-speed wireline communications
, Article Proceedings - IEEE International Symposium on Circuits and Systems ; Volume 2023-May , 2023 ; 02714310 (ISSN); 978-166545109-3 (ISBN) ; Gharibdoust, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
This work presents a new signaling method operating based on a Nyquist-rate orthogonal pulse amplitude modulation (NOPAM) scheme for high-speed wireline communication systems. The proposed signaling approach provides a 2 bit/symbol throughput like PAM-4 signaling while requiring only three voltage levels for data transmission. Thus, it is less sensitive to non-idealities of the lossy interfaces in long/medium reach links. A transceiver (TRx) architecture using NOPAM signaling is presented and realization of its main blocks is described. A 56 Gbps NOPAM TRx using a medium-reach link with 20 dB loss at 14 GHz is modeled and simulated in MATLAB. Performance of the system is provided and...
Evaluating and Improving the Reliability of Reversible Adiabatic Logic Styles
, M.Sc. Thesis Sharif University of Technology ; Ejlali, Alireza (Supervisor)
Abstract
Adiabatic logic families are a group of logic circuits which operate based on adiabatic principles to tremendously reduce power consumption. These families have basic difference with common logic families in transistor level structure and there signals are not quadrangular but trapezoidal. Also, in these systems the source lines and clock pulse are the same. Research on Adiabatic families needs theoretical information in reversible computing. So we will start this project with explaining fundamental information in this field. After that some of these logic families are introduced and three important and widely used of them (SCRL-RERL-2LAL) are chosen to simulate. In each of these families...
Experimental and Theoretical Investigation on the Frictional Performance of Friction Materials of Brake System
, M.Sc. Thesis Sharif University of Technology ; Shojaei, Akbar (Supervisor)
Abstract
Various composite friction materials containing 40 vol.% organic binder (phenolic resin plus styrene-butadiene-rubber (SBR)) with varying phenolic-resin/SBR ratio were prepared. The content of phenolic resin in each composite was indicated by the resin value (RV) index ranging between 0-100%. The composites with RVs greater than 50% form resin-based friction materials in which the primary binder is the phenolic resin. For RVs less than 50%, the composites become the rubber-based materials where the primary binder is the SBR. The analysis of mechanical properties exhibited that the conformability of the composites increases upon incorporation of SBR. The frictional analysis revealed that type...
Neutral Spin Collective Mode in Carbon Nanotubes
, M.Sc. Thesis Sharif University of Technology ; Jafari, Akbar (Supervisor)
Abstract
In 2002 Baskaran and Jafari published an article that was about a spin-1 collective mode. Similarity between carbon nanotubes and graphene was a motivation for working on this project, in order to find another spin mode by considering random phase approximation as a simple way of finding collective motion of a physical systems. Moreover rolling graphene sheet induce diffrent physical properties as a result of chiral axis . In this project we focus only on achiral nanotubes and at last find two collective modes in this structures