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Effect of Angular Momentum of Light in Interaction with Dirac Matter

, M.Sc. Thesis Sharif University of Technology Ghadimi, Rasoul (Author) ; Jafari, Akbar (Supervisor) ; Miri, Mir Faez (Co-Advisor)

Abstract

In this project, we investigate the inﬂuence of angular momentum of Light on the Dirac matter. We show that polarization or spin of light can change the population of [pseudo-]spins. In graphene, pseudo-spins indicate the probability of existing elec-trons in each sub-lattice. However, the two diﬀerent sub-lattices are the same and the contribution from two distinct Dirac cones cancel out. Therefore, the change in the population of pseudo-spins does not happen. On the other hand, in topological insulators we have just one Dirac cone; thus, polarization of light can change the population of [pseudo-]spins

Rigidity and Tolerance for Perturbed Lattic

, M.Sc. Thesis Sharif University of Technology Miri Cheshmeh Gachi, Sadegh (Author) ; Haji Mirsadeghi, Mir Omid (Supervisor)

Abstract

A perturbed lattice is a point process π={x+Y_x ∶x ∈Z^d} where the lattice points in Z^d are perturbed by i.i.d . random variables {Y_x }_(x∈Z^d ). A random point process π is said to be rigid if π∩B_1 (0) , the number of points in a ball , can be exactly determined given π∩B_1^c (0) , the points outside the ball . The process π is called deletion tolerant if removing one point of π yields a process with distribution indistinguishable from that of π . Suppose that Y_x~N_d (0,σ^2 I) are Gaussian vectors with d independent components of variance σ^2 . Holroyd and Soo showed that in dimensions d = 1 , 2 the resulting Gaussian perturbed lattice π is rigid and deletion...

A transmission line resonator model for fast extraction of electromagnetic properties of cavities in two-dimensional photonic crystals

, Article IEEE Photonics Journal ; Volume 2, Issue 4 , August , 2010 , Pages 677-685 ; 19430655 (ISSN) Miri, M. A ; Khavasi, A ; Miri, M ; Mehrany, K ; Sharif University of Technology

2010

Abstract

In this paper, photonic cavities made of point defects in 2-D photonic crystals are modeled by finite-size transmission lines terminated at both ends by appropriate scalar impedances. The proposed model forms a simple transmission line resonator and is demonstrated to be quite beneficial in fast extraction of resonant frequency, quality factor, and mode profile of such photonic cavities. In this manner, an approximate yet quite accurate approach is introduced to characterize the electromagnetic properties of photonic crystal cavities. This method is successfully applied to different structures for both major polarizations and is shown to be as accurate as rigorous numerical methods, viz. the...

Applications of Statistical Learning in Dynamic Pricing

, M.Sc. Thesis Sharif University of Technology Torkashvand, Sina (Author) ; Haji Mir Sadeghi, Mir Omid (Supervisor)

Abstract

In the era of the internet and with the emergence of online stores, the possibility of changing prices for these e-commerce platforms has become simple and virtually cost-free. This allows them to adjust prices optimally in response to environmental and surrounding factors, maximizing their revenue from product sales. This development has led to numerous applications of statistical learning methods, particularly online learning, in these markets. In this thesis, we explore the issue of online pricing from various perspectives. One aspect is that product pricing is based on their features, which can be numerous. This leads us to the use of online learning methods and statistical learning in...

MapReduce Algorithm for Anonymity Problem

, M.Sc. Thesis Sharif University of Technology Miri, Hamid (Author) ; Ghodsi, Mohammad (Supervisor)

Abstract

In this research, we focus on r-gather and (r; ϵ)-gather clustering. In the r-gather clustering, the input points are in metric space and must be clustered such that each cluster has at least r points and the objective is to minimize the radius of clustering. (r; ϵ)-gather clustering is a kind of r-gather clustering such that at most nϵ points can be unclustered. MapReduce model is one of the most used parallel models to process huge data and processes the input data in some machine simultaneously in parallel.In this research, we give a lower bound for the approximation factor of r-gather clustering in MapReduce model. This lower bound works in MapReduce model even an optimal algorithm...

Robust Optimization Model for The Distribution Process of Petroleum Products

, M.Sc. Thesis Sharif University of Technology Miri, Ali (Author) ; Eshghi, Kourosh (Supervisor)

Abstract

The human need for reliable and accessible energy sources for household, industrial, transportation, etc. caused the discovery of the first oil well to move towards exploitation and use of this large, cheap and available energy source, accelerated. With the start of this movement, oil and its products in the last two centuries have quickly established themselves as a major part of the energy basket of most countries in the world. The entry of crude oil and its products into the energy industry has faced new issues and challenges for decision makers in this field. One of the most important challenges has been the planning and management of the process of distribution and transfer of petroleum...

Expert Finding in Community Question Answering

, M.Sc. Thesis Sharif University of Technology Miri, Mohammad (Author) ; Beigy, Hamid (Supervisor)

Abstract

Community question answering are the systems in which users can propose their needs with asking questions. Moreover, they can share their own knowledge with the others by responding their questions. Widely spreading this sort of communities and growth of questions and answers has made some challenges. One of these challenges is finding an appropriate users who can answer questions. For instance, some user might ask a question and has to wait some times to receive another user's response. On the other hand, the users who have expertise in some fields have to spend time a lot seeking to find related questions. Therefore, expert finding systems are used to meet these needs.The main issue is...

Out-of-plane stresses in composite shell panels: Layerwise and elasticity solutions

, Article Acta Mechanica ; Volume 220, Issue 1-4 , 2011 , Pages 15-32 ; 00015970 (ISSN) Miri, A. K ; Nosier, A ; Sharif University of Technology

2011

Abstract

Boundary-layer effects in lengthy cross-ply laminated circular cylindrical shell panels under uniform axial extension are investigated by two analytical solutions. First, Reddy's layerwise theory with state-space approach is utilized to determine the local interlaminar stresses. In this method, the general displacement field is discretized through the shell thickness by a linear shape function. When the shell panel is subjected to an axial force, the axial strain is estimated by an equivalent single-layer theory. Second, the stress-function approach along with Fourier series expansion is applied to develop a novel elasticity solution. The elasticity solution, which is based on simply-support...

Ferromagnetic Single Electron Transistor

, M.Sc. Thesis Sharif University of Technology Asgari, Somaieh (Author) ; Faez, Rahim (Supervisor)

Abstract

This thesis completely introduses ferromagnetic single electron transistor while that identifies the application and types of the transistor.Master equation is used for simulationing of the transistor. This simulation is divided to two general sections.In the first section proposed thermal equilibrium the normal island and The two spin subsystems , however, are in thermal equilibrium and quantized nature of energy spectrum of a small central electrode and ﬂuctuations in the spin accumulation were ignored , however, we simplify the problem and assume that the charging energy are independent of the electron distribution, and number of electrons in the normal island. ،hat tunnel rates can be...

Quantum Dot Infrared Photodetector

, M.Sc. Thesis Sharif University of Technology Davari, Narges (Author) ; Faez, Rahim (Supervisor)

Abstract

Conventionally all objects radiate most of its energy in the from of infrared waves, therefore, infrared photodetectors for detecting objects is important and more study is done on improve the detecting parameters. The proposed structures are developed from bulk to quantum well and quantum dots in recently years. In this work at reason insensitivity to incident light polarization, flexible operation wavelength, high operation temperature, inherent photovoltaic effect, low capture probability we study the structure of quantum dot infrared photodetectors and then for improve the detecting parameters structure of two layers quantum dot separated with a layer thin barrier (bilayer). And then a...

Investigation of Impurities and Structural Defects in Graphene

, M.Sc. Thesis Sharif University of Technology Rostami, Melika (Author) ; Faez, Rahim (Supervisor)

Abstract

In this thesis the effects of impurities and different defects on electrical and magnetic properties of monolayer and bilayer graphene is investigated. Calculations are performed using density function theory. Alloying monolayer graphene with boron and nitrogen the energy gaps of 0.7 and 0.6 eV are obtained, respectively. Moreover, we show that BN is a good candidate for opening the band gap in graphene. Alloying monolayer graphene with BN the energy gap of 1.2 eV is obtained. Another way of opening band gap is to somehow break the symmetry between layers of the bilayer graphene. By alloying one layers of bilayer graphene with B, N or B-N, although the symmetry of layers is broken, each...

A Simulation Study of Graphene Nanoribbon Field Effect Transistor

, M.Sc. Thesis Sharif University of Technology Samadi, Mohsen (Author) ; Faez, Rahim (Supervisor)

Abstract

In this thesis, a field effect transistor (FET) using armchair graphene nanoribbon as the channel is simulated, and the effects of changing nanoribbon width and length, as well as adding defects, are also studied. To obtain the Hamiltonian matrix and the energy band structure of graphene nanoribbon, tight binding method is used in which the first and third neighbor approximation is considered. Also, to maximize accuracy, we also considered the edge bond reconstruction. To obtain the transport characteristics of the transistor, such as the transmission coefficient and the density of states (DOS), Poisson and Schrodinger equations are solved self-consistently. We used the nonequilibrium...

Design of Graphene Spintronic Devices

, M.Sc. Thesis Sharif University of Technology Barami, Soode (Author) ; Faez, Rahim (Supervisor)

Abstract

Magnetization have an important role in spintronic devices based on graphene. In this study the effect of stone-wales and vacancy defect on electrical and magnetic properties of zigzag and armchair graphene nanoribbons were investigated. Calculations are performed using tight-binding and hubard model combining with Green's function techniques. When the balance between A and B sub-lattices gets disturbed, magnetization will be appeared. In stone-wales defect we have local magnetization because of changing the position of sub-lattices and the total magnetization is zero. In addition the stone-wales defect can change and modify the band structures and band gaps. Vacancy of carbon atom in...

Modeling and Simulation of a High Power Photoconductive Semiconductor Switch (PCSS)

, M.Sc. Thesis Sharif University of Technology Hemmat, Zahra (Author) ; Faez, Rahim (Supervisor)

Abstract

There are a wide variety of light-triggered switches. Photoconductive semiconductor switches (PCSSs) have been investigated intensively for many applications owing to their unique advantages over other switches. The advantages of PCSSs make them a perfect choice for many important applications where high switching accuracy and high-power capability are required. Photoconductive switches are fabricated from a variety of semiconductors, including silicon carbide (SiC), gallium arsenide (GaAs) and gallium nitride (GaN). In Photoconductive semiconductor switches (PCSSs) the switching mechanism is initiated by optical illumination and laser source controls the flow of current. In the off or...

Simulation and Analysis Graphene Based Bio-chemical Sensor Using Localized Surface Plasmon Resonance

, M.Sc. Thesis Sharif University of Technology Tareh, Batool (Author) ; Faez, Rahim (Supervisor)

Abstract

One of the different sensing techniques for biosensors is based on surface plasmon resonance which provides high reliability and efficiency. In this project working operating principles of biosensors based on surface plasmon resonance will be examined. For investigation of sensing meachanism we assume that there an array consisting of alternating graphen ribbons which by applying light leads to an effective magnetic field coupling to the localized surface plasmon. The numerical calculations are based on the exact solution of Maxwell's equation using Fuorier Model Method and Matlab coding. In these calculations, the coefficients of transmission, reflection and absorption of light versus...

Simulation of Graphene Nanoribbon based Photodetector

, M.Sc. Thesis Sharif University of Technology Faramarzi, Vahid (Author) ; Faez, Rahim (Supervisor)

Abstract

In this work, we have simulated graphene nanoribbon based photodetector and impact of changing the width, and Boron-Nitride doping and Stone-Wales defects on the optical properties of GNR has study. The energy band structure of GNR with nearest-neighbor approximation in a tight binding model calculated. To correspond with experiment and accuracy, we need to consider the impact of third nearest neighbors and edge bond relaxation. By Using the band structure, we calculated joint density of state and optical matrix elements and obtain inter band selection rule for A-GNR and Z-GNR. Then, using the Fermi’s golden rule, we investigate optical properties of GNR such as optical conductivity and...

, M.Sc. Thesis Sharif University of Technology Sajadian, Ali (Author) ; Faez, karim (Supervisor)

Abstract

In this thesis all the information about different techniques and methods used in Local Area Network (LAN) are described and organized as follows:
Chapter 1: The network properties are described including Network definitions and different types of LAN and their relative applications
Chapter 2 :Different techniques and protocols of data transfer and switching methods are being described and compared.
Chapter 3 : Network technology consists of different topologies for physical connections and various transfer Medias are covered.
Chapter 4 :All network protocols are described including different methods of DATA access in LOOP, RING and BUS topologies and the ISO and IEEE...

Spin effect on band structure of zigzag and armchair graphene nanoribbones with Stone-Wales defect

, Article 2013 21st Iranian Conference on Electrical Engineering ; May , 2013 , Page(s): 1 - 4 ; 9781467356343 (ISBN) Faez, R ; Barami, S ; Sharif University of Technology

2013

Abstract

In this paper the band structure of spin polarized zigzag graphene nanoribbons(ZGNRs) and armchair graphene nanoribons(AGNRs) with Stone-Wales defect are investigated. The results show when the spin effect is considered, the band structures of ZGNRs and AGNRs will be changed and modified. A larger gap will be created and the degenerate bands in ZGNRs will become far from each other. Tight-binding and hubard model were used to simulate the band structures

Simulation and Comparative Study of Tunneling FETs Based on Graphene Nanoribbon and Phosphorene Monolayer

, M.Sc. Thesis Sharif University of Technology Almasi, Hossein (Author) ; Faez, Rahim (Supervisor)

Abstract

In this thesis, we simulate and investigate two transistors which both have tunneling FET (TFET) structure but the channel in the first one is graphene nanoribbon (GNR) and in the second one is a monolayer of phosphorene (PML). To describe the quantum systems of the transistors, we use the tight binding method and its models for the channel materials. In case of the PML TFET, based on the behavior of the phosphorene nanoribbon in different widths, we obtain a proper amount for the width to model the infinite-width channel. To extract the channel quantum transport, the Schrodinger-Poisson equations are self-consistently solved. In the next step, we simulate the GNR TFET and present the...

Simulation of Organic Solar Cells

, M.Sc. Thesis Sharif University of Technology Bahrami, Ali (Author) ; Faez، Rahim (Supervisor)

Abstract

Solar cells are one of the most promising clean and readily available energy sources. Organic solar cells as a new generation of solar cells, have attracted strong attention in recent years, due to the advantages of flexibility, thinness, and simple manufacturing process. This work focuses on the electrical processes in organic solar cells and approaches for enhancing the efficiency of solar cell by employing two-dimensional drift-diffusion model. At the first step. We investigate the role of different parameters such as mobility (considering different recombination mechanisms), active layer thickness, light intensity, barrier injections and energetic disorder on the performance of single...