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salehi--masoud
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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 TechnologyAn 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...
Optimum receiver design for transmitted-reference signaling [electronic resource]
, Article IEEE Transactions on Communications ; May 2010, Volume 58, Issue 5, P.1589-1598 ; Salehi, J. A ; Sharif University of Technology
Abstract
Autocorrelation receiver (AcR) is usually used as the general receiver for transmitted reference (TR) communication systems on a quite intuitive basis. In this paper, we apply the principle of statistical invariance to obtain the optimum TR receiver on a decision-theoretic basis, and it is shown that the autocorrelation receiver is optimal only in a special case. Performance of the optimum receiver and the suboptimum AcR for some important modulation schemes is also evaluated. The results imply that allocating a part of the transmitted energy and bandwidth to reference pulses would not help improve the performance of the system and the optimal performance might be achieved via much simpler...
Multi-rate and multi-quality of service passive optical network based on hybrid WDM/OCDM system [electronic resource]
, Article IEEE Communications Magazine ; February 2011, Volume 49, Issue 2, PP. S39-S44 ; Salehi, J. A ; Sharif University of Technology
Abstract
In this article we present a new scheme to support multirate and multi-quality-of-service transmission in passive optical networks based on a hybrid wavelength-division multiplexing/optical code-division multiplexing scheme. The idea is to use multilength variable-weight optical orthogonal codes as signature sequences of a hybrid WDM/OCDM system. To provide the requested classes of service, the code weight and code length of MLVW-OOCs are designed based on the characteristics of the requested classes of service. In order to mitigate multiple access interference, we propose to utilize a multilevel signaling technique and interference remover structure based on advanced optical logic gate...
Vibration Analysis of Dolid-Fluid Interaction to Improve the Aerodynamic Performance of Airfoils with Deflectable Skins
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
Progress aerodynamic and structural applications has lead to solid-fluid interaction (SFI) engineering. One major application of SFI is to improve of aerodynamic characteristics of airplanes. One option is to use elastic shells.this field of study is so novel and a challenge for future researches. This what current thesis is focused on We use numerical simulation in both fluid and solid parts.In other word, we employ the finite –element method to solve the solid mechanics governing equation and the finite volume element method to treat the fluid dynamics governing equations. The fluid governing equations are 2D navier- stokes equations and the solid part is the 1D Euler – Bernoulli equations...
Developing a Parallel DSMC Algorithm for Simulating Flow in Micro-Nano Propulsion Systems
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
With the rapid development of mico-nano propulsion systems in micro-spacecrafts and micro-sattelites, precise investigation of flow field in these devices has become necessary. Micro propulsion systems usually have a thrust in order of mili Newton, and they can be used for maneuvers of spacecrafts with mass of less than 10 kg. Micro propulsion systems are usually classified according to their thrust generation mechanism to different classes like cold gas, and chemical propulsion systems. Cold gas micro propulsion systems obtain their energy from thermodynamic expansion of gas and not by combustion. If the flow fiel dimensionare comparable to mean free path, rarefaction effects are observed...
Simulating Flow over Nanoparticles through Microchannels Using Lattice Boltzmann Method
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
Novel manufacturing technologies in micro scales, such as micro machining, guide us through constructing micro scale systems known as MEMS. These systems have a wide range of applications, from fabrication of electrostatic, magnetic, pneumatic sensors and actuators to micro mechanical gears and motors. Also, MEMS applications involve the manipulation of one or more fluids, known as microfluids. Simulation of flow through microchannels over nano particles has important applications in solid particles transport. In this flow, the rarefaction phenomenon will affect the flow behavior and its subsequent impacts such as aerodynamic drag forces. In this work, we use the Lattice Boltzmann method...
Nonlinear Performance of 3-D Steel Structures by Scaled Nonlinear Dynamic Procedure
,
M.Sc. Thesis
Sharif University of Technology
;
Mofid, Masoud
(Supervisor)
Abstract
It is well known that the most rigorous method to assess the performance and to predict the seismic demands of a structure subjected to earthquake is nonlinear time history analysis. However, this technique is accompanied by complexities and difficulties in evaluating the seismic demands of structures and requires superior knowledge and skill. As a result, in recent years, nonlinear static analysis has been proposed in performance based design procedures. One of the primary assumptions of nonlinear static procedures is that the behavior of a structure with multiple degrees of freedom (MDOF) subjected to seismic ground motion can be estimated from the response of an oscillator with a single...
A Feasibility Study in Fuel Cell Hydrogen Storage Capacity Increase Using Carbon Nanotubes Technology and Molecular Dynamics Simulation
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
Hydrogen fuel cell is one important choice to supply energy for vehicles in near future. The lack of a safe but inexpensive technology to store hydrogen in a vehicle tank is a serious challenge to commercialize the application of fuel cells. Past experiments have shown that carbon nanostructures, especially single walled carbon nanotubes, have considerable capacity to boost up hydrogen storage. Therefore, many studies have been performed to investigate the possibility of higher hydrogen storage capability using nanostructures for the past decade. Molecular dynamics method which is considered as one of the most important tools in studying nanostructures has shown vast applications in these...
Numerical Modeling of Terrestrial Planet Temperature Distribution Effect on Polar Vortex Forming: Venus Modeling
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
A global rotating atmosphere with polar vortex and super rotation is simulated using a simplified Venus General Circulation Model (GCM). The polar vortex is maintained strongly by meridional circulation develops in the form of a simple Hadley cell, extending from the equator to the pole in both hemispheres and rotation terrestrial planet. Venus Total Polar Vortex Parameter (PVP) was defined like globally integrated super-rotation but at polar skullcaps (60-90 deg). Venus Polar Vortex Parameter is PVP=1.5 that’s qualitatively similar to observed polar vortex. Then with study in terrestrial planet and Titan modeling, we appointed the Polar Vortex Parameter and critical limit of Polar Vortex...
On the Dynamic Response of Funicular Shells and Evaluation of the Behavior Factor
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor)
Abstract
Dynamic behavior of space structures are of great complexities. On the event of severe earthquake these structures exhibit high resistance and on the other hand, their high rigidity and small deformation makes it necessary to pay attention to their dynamic behavior, especially when combined with other types of structural systems. Also due to lack of sufficient codes and references, their dynamic behavior is still unknown to a great extend. Among these kinds of structures, reinforced concrete double curvature shells, and especially funicular shells, are much more important than others. In this thesis, dynamic response of these kind of structures, especially reinforced concrete domes, in...
Numerical Simulation of Nano-Impinging-Jet in Electronic Cooling Applications
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
With a fast progress in nanotechnology devices and components, e.g., MEMS/NEMS, heat transfer study in micro/nanoscales has become so critical for the systematic design and precise control of such miniaturized devices towards the integration and automation of Lab-on-a-chip devices. Demands in high heat transfer rates have returned the concerns to impinging jet cooling systems. However, studying impinging jets in the micro/nano scales is requires the molecular dynamics knowledge to analyze the true micro/nanoscale flow behavior accurately. According to the importance of this subject, we use direct simulation Monte Carlo (DSMC) method to simulate nano impinging jet gas flows. The thesis is...
The Role of Socio-Political Institutions in Economic Performance of Developing Countries
, M.Sc. Thesis Sharif University of Technology ; Nili, Masoud (Supervisor)
Abstract
Findings of economics in last decade shows that social and economic institutions have direct influence on economic performance of a society. However, these institutions are determined by the state. In different regimes, the political power is in the hand of different social groups with different preferences and goals; as a result, different social and economic policies and institutions are take place in different political regimes. In this research, we study economic performance of a society under control of two different political regimes: in first, the majority rules the state and in second, there is a totalitarian regime in which; the political power is concentrated in hand of a group of...
The Political Economy Aspects of the Redistributive Role of Government in a General Equilibrium Micro-founded Macro Model
, M.Sc. Thesis Sharif University of Technology ; Nili, Masoud (Supervisor)
Abstract
The role of government in economy has been a controversial subject in economics. Lately, there has been some fundamental change in evaluating this subject. One could mention two of these as 1) realizing the importance of micro-founded macro model for evaluating policy, and 2) taking into consideration the rent-seeking behavior of politicians. In this research, a general equilibrium in a micro-founded macro model will be discussed and then in political economics framework, the effect of government on this equilibrium will be investigated. Only the redistribution role of government has been considered. First, the model in which a benevolent government is seeking optimal policy is Discussed....
Modelling Point and non Point Source of Nitrate with SWAT in the Jajrood River Watershed
, M.Sc. Thesis Sharif University of Technology ; Tajrishy, Masoud (Supervisor)
Abstract
To investigate boiling heat transfer characteristics of nanofluids, transient quenching¬ experiments of a high temperature silver sphere in water-based nanofluids with Ag and TiO2 nanoparticles were performed. A silver sphere of 10 mm in diameter at the initial temperature of 700o C was quenched in the nanofluids at the temperature of 90o C. The results showed considerable reduction in the quenching ability of nanofluids compared to that of pure water. The presence of nanoparticles in water caused film boiling mode to vanish at lower temperatures depending on the mixture concentration. Computed heat transfer rates in nanofluids were lower than those in pure water. In the quenching...
Water Quality Modeling of Urban Streams
, M.Sc. Thesis Sharif University of Technology ; Tajrishy, Masoud (Supervisor)
Abstract
With altering natural state and increasing impervious surfaces, traditional urbanization leads to deteriorating the environment and water catchments. During the years most efforts in order to control the urban runoff outflow, have been focused on quantity; and awareness about improving water quality has been raised just in the last few years and, which emphasizes on pollution source control. Standard water quality sampling methods are time consuming, expensive and because of sampling in broad geographic areas, difficult; however modeling is a more efficient way in assessing water quality and as worries about non-point source pollution grows, different kinds of models have been used to...