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moshtagh--mehrdad
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Effect of alkali-aggregate reactions in concrete dams using finite element method
, Article Scientia Iranica ; Volume 15, Issue 1 , 2008 , Pages 1-7 ; 10263098 (ISSN) ; Ghaemian, M ; Sharif University of Technology
Sharif University of Technology
2008
Abstract
The effect of Alkali-Aggregate Reactions (AAR) in concrete dams was investigated using the finite element method. Two models have been presented to assess the effects of the AAR in concrete dams. The stress dependency of AAR strains has been taken into account in the models and the degradation of concrete properties during the reaction has been implemented in the finite element program. The results of the isothermal and nonisothermal analyses of a gravity section of a Beauharnois power plant have been presented and compared with the measured data and the results are in close agreement. The results of the analysis demonstrate the importance of the AAR in concrete dams. High stresses and large...
Solving Traffic Assignment Problem with Side Constraints
, M.Sc. Thesis Sharif University of Technology ; Zokaei Aashtiani, Hedayat (Supervisor)
Abstract
In recent years, traffic assignment problem with side constraints has been considered because of the importance of transportation supply management. Side constraints which are appeared due to imposing the traffic control policies are usually represented in form of link, node or district capacity constraints. Although link capacity constraint has been extensively studied, only a few papers on the other types of constraints such as capacity constraint on inflow to a district of city exist in the literature. In this research a method based on dynamic penalty function (DPF) is presented to solve traffic assignment problem with side constraints. Solution algorithm has been coded in a programming...
Implementation of New Hybrid Conjugate Gradient Algorithms
Based on Modified BFGS Updates
,
M.Sc. Thesis
Sharif University of Technology
;
Mahdavi-Amiri, Nezam
(Supervisor)
Abstract
We describe two modified secant equations proposed by Yuan, Li and Fukushima. First, we study the approach proposed by Andrei. Then, we explain two hybrid conjugate gradient methods for unconstrained optimization problems. The methods are hybridizations of Hestenes-Stiefel and Dai-Yuan conjugate gradient methods. It is shown that one of the algorithms is globally convergent for uniformly convex functions and the other is globally convergent for general functions. Two approaches for computing the initial value of the steplength proposed by Babaie, Fatemi, and Mahdavi-Amiri and Andrei are used for accelerating the performance of the line search. We implement the algorithms and compare the...
Elastic properties of vertically aligned carbon nanotubes: A molecular dynamics study
, Article European Physical Journal Plus ; Volume 134, Issue 10 , 2019 ; 21905444 (ISSN) ; Firouz Abadi, R. D ; Vahid Moshtagh, A ; Sharif University of Technology
Springer Verlag
2019
Abstract
In the present study, the mechanical properties of vertically aligned carbon nanotube (VACNT) arrays in the most general case of anisotropic elasticity is studied. To quantify the elastic stiffness coefficients, continuum mechanics is employed, in which the constitutive relation is formulized in terms of the interatomic potential obtained via molecular dynamics (MDs) simulations. Detailed investigations into elastic stiffness coefficients with different geometrical parameters are performed and, consequently, their sensitivity on length and radius parameters is hereby studied. With such study it would be possible to tune the mechanical properties of VACNTs. © 2019, Società Italiana di Fisica...
Finding an optimal core on a tree network with M/G/c/c state-dependent queues
, Article Mathematical Methods of Operations Research ; 2018 ; 14322994 (ISSN) ; Fathali, J ; Smith, J. M. G ; Mahdavi Amiri, N ; Sharif University of Technology
Springer Verlag
2018
Abstract
We consider the stochastic queue core problem on a tree network. Our aim is to find an optimal path on a tree network subject to the average travel time of particles moving along the tree for service given by a server traversing along the optimal path. We assume that particles originating at a node on a tree network request their demands for service randomly and the server is modeled first by an M/M/1 and then by an M/G/1 queue using the FIFO discipline. We consider that all paths along which the particles travel are modeled with an M/G/c/c state-dependent queue with the particles being independent of each other having demands according to the Poisson distribution. Two algorithms are...
Finding an optimal core on a tree network with M/G/c/c state-dependent queues
, Article Mathematical Methods of Operations Research ; Volume 89, Issue 1 , 2019 , Pages 115-142 ; 14322994 (ISSN) ; Fathali, J ; Smith, J. M. G ; Mahdavi Amiri, N ; Sharif University of Technology
Springer Verlag
2019
Abstract
We consider the stochastic queue core problem on a tree network. Our aim is to find an optimal path on a tree network subject to the average travel time of particles moving along the tree for service given by a server traversing along the optimal path. We assume that particles originating at a node on a tree network request their demands for service randomly and the server is modeled first by an M/M/1 and then by an M/G/1 queue using the FIFO discipline. We consider that all paths along which the particles travel are modeled with an M/G/c/c state-dependent queue with the particles being independent of each other having demands according to the Poisson distribution. Two algorithms are...
Flight envelope expansion in landing phase using classic, intelligent and adaptive controllers [electronic resource]
, Article Journal of aircraft ; 2006, Vol. 43, No. 1 ; Izadi, Hojjat Allah ; Pakme, Mehrdad
Abstract
An expanding flight envelope in the landing phase of a typical jet transport aircraft in presence of strong wind shears using a learning capable control system (LCCS) is investigated. The idea stems fromhuman beings functional architecture that gives them the ability to do more as they age and gain more experience. With the knowledge that classical controllers lack sufficient generality to cope with nonlinear as well as uncertain phenomenon such as turbulent air, the focuse is on different types of intelligent controllers due to their learning and nonlinear generalization capabilities as candidates for the landing flight phase. It is shown that the latter class of controllers could be used...
An efficient graphyne membrane for water desalination
, Article Polymer ; Volume 175 , 2019 , Pages 310-319 ; 00323861 (ISSN) ; Moosavi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Desalination of sea saline water seems a successful solution to supply clean water. For desalination, novel nanoporous membranes have been proposed as a substitute for the classic reverse osmosis (RO) membranes. The one-atom-thick graphyne membrane has shown great potential in water desalination. By applying functional groups (FGs) into the pores of the monolayer graphyne membranes, the water permeability and the ion rejection were passively increased. The effects of applying various FGs such as Hydrogen, Fluorine, Carboxyl and Amine, effect of the salt concentration, the applied pressure, and the effective diameter of the graphyne pores were determined by molecular dynamics (MD)...
Optimal Design of the Heliostat Field in the Solar Central Receiver Systems
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
In a solar central system plant about 40% of energy losses occurs in the heliostat field. Furtheremore, half of the investment costs for construction of the plant is related to the heliostat field. Therefore, an optimal design of the heliostat field is necessary for reduction of levelized cost of energy in solar tower power plants. In this study, in order to optimally design the heliostat field, first energy performance of the helistat field in one year is simulated. Solar power and sun’s position at each moment of the day is determined by mathematical relations. Then, loss factors in the field are modelled and heliostat field layout is designed by an algorithm. Finally, by using PSO...
Simulation and Multi-Objective Optimization of a Solar Micro CCHP Using Intelligent Techniques
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
Today, due to the scarcity of fossil energy resources, security of energy supply, and increasing environmental concerns, we need to develop new technologies to promote energy-saving and reduce greenhouse gas emissions. One of the suitable options for this purpose is to use the simultaneous production of electric power, cooling, and heating. Meanwhile, trigeneration systems that provide part of their energy needs from the sun, due to the free solar energy source and low environmental impact, can be an ideal technology for clean and safe scattered production. The present study has suggested a trigeneration system of cooling, heating, and power generation based on the organic Rankin cycle and...
Optimal Design of Induction MHD Generator for Electrical Power Generation from Exhaust of the Gas Turbine Power Plants
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
Today, due to increasing electricity consumption and demand, the use of conventional systems such as thermal, hydro and nuclear power plants is not enough to convert energy. Over the past century, scientists have sought to discover new technologies for exploiting different forms of energy and converting them into high-efficiency electrical energy. One of these ways is to use the phenomenon of magnetohydrodynamics (magnetic fluid dynamics) to convert thermal energy directly into electrical energy. Magnetohydrodynamics is a theoretical field that studies the dynamics of fluids with electrical conductivity. Induction magneto-hydrodynamic generators use ionized hot plasma (a quasi-neutral gas of...
Modeling and Optimal Design of a Solar Chimney Power Plant
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
The power generation system of this type of power plants operates on the air flowing through the power plant’s chimney and colliding with the turbine blades within the chimney. When the solar collector warms the nearby air and thus expands the air by absorbing the sunlight, a difference is created in the density. Then, this difference in the density creates the phenomenon of buoyancy, making the air pass to the top of the chimney through the collector.This study simulated and optimized a solar chimney power plant. The simulation and optimization were performed based on the information of Manzanares Solar Chimney Power Plant in Spain (located in 150 km from the south of Madrid). It was...
Intelligent Control of Hybrid Vehicles based on the Simultaneous Optimization of Fuel Consumption and Pollution Emission
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
The issue under discussion in this paper is to optimize the fuel consumption of the Toyota Prius hybrid car. In order to solve this problem, the ADVISOR design model used by NREL in the Matlab / Simulink environment has been used. Various parts of this model are described. The optimization performed on this issue is based on the emotional controller. This controller works by simulating learning in animals based on encouraging and punishing them. With the introduction of the controller, the model and its inclusion in the fuel consumption control and its implementation have achieved good results. In the initial state and the controller in the model, the fuel consumption was 4.9 liters per 100...
Active Control of Drag Force in Automobile in Order to Reduce Fuel Consumption
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
In this thesis, an attempt has been made to provide a smart and innovative system to optimize fuel consumption in cars by using the combination of engineering sciences, aerospace, and machine learning. Considering the current challenges of societies, the economic importance of saving fuel, as well as recent developments in the fields of machine learning and reinforcement learning, this research tries to improve the performance of cars in order to minimize the air resistance force of car bodies. In this regard, deep neural networks have been used to learn the dynamics of aerodynamic forces and reinforcement learning algorithms, especially DDPG (Deep Deterministic Policy Gradient), have been...
The Impact of Human Capital on Labour Productivity in Manufacturing Sectors of Iran
,
M.Sc. Thesis
Sharif University of Technology
;
Sepahvand, Mehrdad
(Supervisor)
Abstract
This research has been surveyed the impact of intermediate skilled and high skilled human labor force on the productivity of manufacturing sectors by the Nelson & Phelps and also Lucas approaches. first model is related to the level of productivity and the second model is related to the growth of it. We has been prepared the needed statistics from the raw figures of iran statistics center. regression analysis has been done on the basis of panel data model by the use of stata software. the results show that not good efficiency to optimize technology factor of Cobb-Douglas model although it shows higher marginal labor productivity of high skilled human labor force. we has proposed some...
Design of a Wide Band Power Amplifier for Power DAC
, M.Sc. Thesis Sharif University of Technology ; Sharifbakhtiar, Mehrdad (Supervisor)
Abstract
Today’s radio transmitters must be able to send information in several standards. One problem involved in these wide band electronic systems lies in its end part, ie power amplifier. To have a broad band width either switching must be made among several power amplifiers with narrow band width (tuned) or the transistor part of power amplifier must be the same and single and selection be made only among matching networks. In this thesis, a power amplifier with broad band width without requiring a matching network has been designed and laid out. Also considering the low breakdown voltage of the gate oxide of the today’s standard CMOS transistors, it is very difficult to get a high output power...
Design of a HEV’s Controller Using Learning-based Methods
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
Hybrid electric vehicles (HEV) are proving to be one of the most promising innovations in advanced transportation systems to reduce air pollution and fossil fuel consumption. EMS is one of the most vital aspects of the HEV powertrain system. This research aims to design an optimal EMS under the condition of meeting the goals of drivability control, fuel consumption reduction, and battery charge stability. The current EMS is based on the classical rule-based method derived from fuzzy logic, which guides to the suboptimal solution in episodic driving cycles. Previous experiences in implementing Reinforcement Learning (RL) suffer from late convergence, instability in tracking the driving...
Optimal Design of Permanent Magnet Vernier Generator for Wind Power Plants Application
, M.Sc. Thesis Sharif University of Technology ; Boroushaki, Mehrdad (Supervisor)
Abstract
In recent decades, renewable energy resources (especially wind power as the fastest-growing energy source) have increasingly been employed for providing electrical energy all over the world given to the rising energy demands, reduction in non-renewable fossil fuels as well as severe restrictions applied to the utilization of these fuels because of their contribution in environmental pollution, generating greenhouse gas emissions, and consequently earth warming. The main factors in the development of wind energy systems to date are the easy access to this energy source in all seasons and its cost-effectiveness compared to other counterparts. One of the key components utilized for converting...
Design and Implementation of a Linear, 1 Watt, High Efficiency Power Amplifier with Controllable Output Power for UHF-RFID Application
, M.Sc. Thesis Sharif University of Technology ; Sharifbakhtiar, Mehrdad (Supervisor)
Abstract
Design and implementation of an efficient, 1 Watt, linear power amplifier (PA) with CMOS technology for UHF-RFID applications is presented in this thesis. Poor quality factor of inductors, high substrate noise and low breakdown voltage of CMOS, makes the implementation of Watt-level PAs challenging on this technology. Also the trade-off between linearity and efficiency, further hardens achieving an efficient high power linear PA. So the literature was reviewed first to come up with the appropriate structure of a linearized efficient PA. Afterwards, the structure was reformed and optimized for the application mentioned above with reasonable stability margins. Baseband relevant blocks were...
A Novel Design Methodology for the Design of Low Phase Noise Oscillators Based on the ISF
, M.Sc. Thesis Sharif University of Technology ; Sharif Bakhtiar, Mehrdad (Supervisor)
Abstract
We present a novel and simple method to calculate each Fourier series coefficient of ISFs in LC oscillators, analytically. This new approach explains the relationship between Fourier series coefficient of ISF and oscillator topology and parameters. This technique helps designers to obtain the great insight of how to decrease the output noise in oscillators. This method also can be used to derive the waveform of ISFs in time domain.Based on the features of our new technique and by presenting a general method to change the stationary noises to Cyclo-stationary ones, we suggest a step by step design guide which elucidates new ideas for designers to manipulate the oscillator parameters and...