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Roughness of undoped graphene and its short-range induced gauge field
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 76, Issue 19 , 2007 ; 10980121 (ISSN) ; Neek Amal, M ; Asgari, R ; Shahbazi, F ; Nafari, N ; Rahimi Tabar, M. R ; Sharif University of Technology
2007
Abstract
We present both numerical and analytical studies of graphene roughness with a crystal structure including 500×500 atoms. The roughness can effectively result in a random gauge field and has important consequences for its electronic structure. Our results show that its height fluctuations in small scales have a scaling behavior with a temperature dependent roughness exponent in the interval of 0.6<χ<0.7. The correlation function of height fluctuations depends on temperature with a characteristic length scale of ≈90 Å (at room temperature). We show that the correlation function of the induced gauge field has a short-range nature with a correlation length of about 2-3 Å. We also treat the...
Structural Disorders of Graphene and Its Effects on Electronic Properties
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
In this thesis we would like to investigate structural disorder of Graphene and its effect on electronic properties. Graphene is a one-layer crystal of Carbon atoms which was the first two dimensional crystal observed experimentally. Low energy current carriers on Graphene behave like mass-less Dirac fermions and this interesting electronic property attracts much attention on studying Graphene. Structural disorder of Graphene highly affects its electronic properties. We study thermal fluctuations of Graphene sheet, disorder super lattice, and static ripples, as structural disorders of Graphene. Disorders due to thermal fluctuations of graphene induce a disordered gauge field on the graphene...
Reply: Abedpour, asgari, and tabar
, Article Physical Review Letters ; Volume 106, Issue 20 , 2011 ; 00319007 (ISSN) ; Asgari, R ; Tabar, M. R. R ; Sharif University of Technology
2011
Irreversibility in response to forces acting on graphene sheets
, Article Physical Review Letters ; Volume 104, Issue 19 , May , 2010 ; 00319007 (ISSN) ; Asgari, R ; Tabar, M. R. R ; Sharif University of Technology
2010
Abstract
The amount of rippling in graphene sheets is related to the interactions with the substrate or with the suspending structure. Here, we report on an irreversibility in the response to forces that act on suspended graphene sheets. This may explain why one always observes a ripple structure on suspended graphene. We show that a compression-relaxation mechanism produces static ripples on graphene sheets and determine a peculiar temperature Tc, such that for T
Conductance of a disordered graphene superlattice
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 79, Issue 16 , 2009 ; 10980121 (ISSN) ; Esmailpour, A ; Asgari, R ; Rahimi Tabar, M. R ; Sharif University of Technology
2009
Abstract
We study the conductance of disordered graphene superlattices with short-range structural correlations. The system consists of electron- and hole-doped graphenes of various thicknesses, which fluctuate randomly around their mean value. The effect of the randomness on the probability of transmission through the system of various sizes is studied. We show that in a disordered superlattice the quasiparticle that approaches the barrier interface almost perpendicularly transmits through the system. The conductivity of the finite-size system is computed and shown that the conductance vanishes when the sample size becomes very large, whereas for some specific structures the conductance tends to a...
Stochastic φ4-theory in the strong coupling limit
, Article Nuclear Physics B ; Volume 761, Issue 3 , 2007 , Pages 93-108 ; 05503213 (ISSN) ; Niry, M. D ; Bahraminasab, A ; Masoudi, A. A ; Davoudi, J ; Sahimi, M ; Rahimi Tabar, M. R ; Sharif University of Technology
2007
Abstract
The stochastic φ4-theory in d dimensions dynamically develops domain wall structures within which the order parameter is not continuous. We develop a statistical theory for the φ4-theory driven with a random forcing which is white in time and Gaussian-correlated in space. A master equation is derived for the probability density function (PDF) of the order parameter, when the forcing correlation length is much smaller than the system size, but much larger than the typical width of the domain walls. Moreover, exact expressions for the one-point PDF and all the moments 〈 φn 〉 are given. We then investigate the intermittency issue in the strong coupling limit, and derive the tail of the PDF of...
Recent activities in science and technology and the progress of women in physics in the last three years in Iran
, Article AIP Conference Proceedings, Stellenbosch ; Volume 1517 , 2013 , Pages 108-109 ; 0094243X (ISSN); 9780735411388 (ISBN) ; Azad, M. T ; Mahmoudi, N ; Izadipanah, N ; Eshghi, N ; Sharif University of Technology
2013
Abstract
For the 4th IUPAP International Conference of Women in Physics, we report on activities in science and engineering in Iran, and conditions for women in physics, in the three years since the 3rd IUPAP International Conference of Women in Physics was held in 2008. Iran has made prominent advancements and astonishing progress in laser technology, biotechnology, nanotechnology, genetics, computer software and hardware, and robotics. Iranian scientists have been very productive in several experimental fields, such as pharmaceutical, organic, and polymer chemistry. Conditions for women in physics have improved greatly in recent years. A project to improve the environment for learning physics, and...
Ab initio study of electronic effects in the ZnO/TiO2 core/shell interface: Application in dye sensitized solar cells
, Article RSC Advances ; Vol. 4, issue. 1 , April , 2014 , p. 301-307 ; Nafari, N ; Taghavinia, N ; Sharif University of Technology
2014
Abstract
Core/shell structure of ZnO nanowires coated with a monolayer of TiO 2 is investigated using Density Functional Theory (DFT). The electronic states of the semiconductor is calculated and compared before and after coating of the TiO2 monolayer on a ZnO [101 0] surface. The effect of TiO2 coating induce surface states changes and shifts the conduction and valence band edges to higher energies. Our results, in qualitative agreement with the experimental work of Matt Law et al. (J. Phys. Chem. B, 110, 22652), show an increase in open circuit voltage and a decrease in short circuit current in ZnO/TiO2 core shell dye sensitized solar cells. Regarding the semiconductor density of states (DOS), TiO2...
Analyzing factors effective on the development of relationship commitment
, Article Proceedings of the 2012 International Conference on Artificial Intelligence, ICAI 2012, 16 July 2012 through 19 July 2012 ; Volume 1 , July , 2012 , Pages 398-404 ; 1601322186 (ISBN) ; 9781601322180 (ISBN) ; Lotfi, N ; Karami, N ; Sharif University of Technology
2012
Abstract
Due to the important role of commitment and trust in the relationship marketing, the factors which can directly result in a committed relationship along with the factors which can influence the commitment through influencing trust, according to the model of commitment and trust by (Morgan & Hunt, 1994) have been introduced and their level of importance has been investigated here. The article uses fuzzy cognitive maps (FCMs) in the proposed model to find the most important paths leading to relationship commitment. The FCM analyzes the responses of a group of 30 people including general practitioners in dentistry, managers of dental departments in some of the public clinics and hospitals who...
Morphological dependence of light backscattering from metallic back reflector films: Application in dye-sensitized solar cells
, Article Physica Status Solidi (A) Applications and Materials Science ; Volume 212, Issue 4 , January , 2015 , Pages 785-790 ; 18626300 (ISSN) ; Ghazyani, N ; Taghavinia, N ; Sharif University of Technology
Wiley-VCH Verlag
2015
Abstract
Conventionally, a film of TiO2 particles of 300 nm size is employed in Dye-sensitized solar cells (DSCs) as the back reflector film to enhance the light harvesting. Perfect reflectance of silver in visible and near infrared motivates to investigate its potential as the material for the light back reflector film in DSCs. In this study, light back reflector films consisting of 300 nm-sized silver particles, as well as vacuum evaporated silver flat film, were fabricated and compared to 300 nm-sized rutile-type TiO2 particulate reflector film to study their optical aspects. Conventional TiO2 rutile-type particulate film demonstrates slightly lower performance...
Monolithic dye sensitized solar cell with metal foil counter electrode
, Article Organic Electronics ; Volume 57 , June , 2018 , Pages 194-200 ; 15661199 (ISSN) ; Taghavinia, N ; Ghazyani, N ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Monolithic dye-sensitized solar cells are conventionally fabricated using carbon composite layer as the counter electrode. In the current research, the brittle carbon composite layer is replaced with a metal foil, aiming to decrease the device series resistance and using less catalyst material in counter electrode. This metallic structure has also an advantage of mechanical strength and decreases the fabrication complexity. The counter electrode is prepared by electrodepositing Cr film followed by electrodepositing Pt nanoparticles on a metal foil. As the porous spacer layer, different composite layers of SiO2, TiO2, and Al2O3 are investigated and the best results are obtained for TiO2...
A compact versatile microbial fuel cell from paper
, Article ASME 2013 11th Int. Conf. on Fuel Cell Science, Eng. and Technology Collocated with the ASME 2013 Heat Transfer Summer Conf. and the ASME 2013 7th Int. Conf. on Energy Sustainability, FUELCELL 2013 ; 2013 ; 9780791855522 (ISBN) ; Hashemi, N ; Hashemi, N ; Sharif University of Technology
2013
Abstract
Microbial fuel cells (MFCs) have been a potential green energy source for a long time but one of the problems is that either the technology must be used on a large scale or special equipment have been necessary to keep the fuel cells running such as syringe pumps. Paper-based microbial fuel cells do not need to have a syringe pump to run and can run entirely by themselves when placed in contact with the fluids that are necessary for it to run. Paper-based microbial fuel cells are also more compact than traditional MFCs since the device doesn't need any external equipment to run. The goal of this paper is to develop a microbial fuel cell that does not require a syringe pump to function. This...
Decentralized model predictive voltage control of islanded DC microgrids
, Article 11th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2020, 4 February 2020 through 6 February 2020 ; 2020 ; Mahdian Dehkordi, N ; Sadati, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This paper proposes a novel decentralized control approach for islanded direct-current (DC) microgrids (MGs) based on model predictive control (MPC) to regulate the distributed generation unit (DGU) output voltages, i.e. the voltages of the point of common coupling (PCC). A local controller is designed for each DGU, in the presence of uncertainties, disturbances, and unmodeled dynamics. First, a discrete-time state-space model of an MG is derived. Afterward, an MPC algorithm is designed to perform the PCC voltage control. The proposed MPC scheme ensures that the PCC voltages remain within an acceptable range. Several simulation studies have been conducted to illustrate the effectiveness of...
Intelligent optimal feed-back torque control of a 6DOF surgical rotary robot
, Article 11th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2020, 4 February 2020 through 6 February 2020 ; 2020 ; Ebrahimi Toulkani, N ; Zhilakzadeh, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
Sophisticated surgeons are widely indicating the use of surgical robots in order to reject human error, increase precision, and speed. Among well-known robotic mechanisms, parallel robots are broadly more investigated regarding their special characters as higher acceleration, speed, and accuracy, and less weight. Specific surgical procedures confine, and restrict their workspace, while controlling and validating the robots are complicated regarding to their complex dynamic. To this end, in this paper, a 6-DOF robot, with rotary manipulators, is designed and controlled. Addressing nonlinearity of parallel robots, an innovative methodology is formulated to robustly penalize the error of...
Semi-Real evaluation, and adaptive control of a 6DOF surgical robot
, Article 11th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2020, 4 February 2020 through 6 February 2020 ; 2020 ; Ebrahimi Toulkani, N ; Zhilakzadeh, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
Sophisticated surgeons are widely indicating the use of surgical robots in order to reject human error, increase precision, and speed. Among well-known robotic mechanisms, parallel robots are broadly more investigated regarding their special characters as higher acceleration, speed, and accuracy, and less weight. Specific surgical procedures confine and restrict their workspace, while controlling and validating the robots are complicated based on their complex dynamic. To this end, in this paper, a 6-DOF robot, with linear manipulators, is designed and controlled. Addressing the inherent nonlinearity of the robot mechanism, an adaptive PID manipulator is employed and validated with nonlinear...
Modeling superconductive fault current limiter using constructive neural networks
, Article 2007 IEEE International Symposium on Industrial Electronics, ISIE 2007, Caixanova - Vigo, 4 June 2007 through 7 June 2007 ; 2007 , Pages 2859-2863 ; 1424407559 (ISBN); 9781424407552 (ISBN) ; Sadati, N ; Hosseini, M. N ; Sharif University of Technology
2007
Abstract
Although so many advances have been proposed in the field of artificial intelligence and superconductivity, there are few reports on their combination. On the other hand, because of the nonlinear and multivariable characteristics of the superconductive elements and capabilities of neural networks in this field, it seems useful to apply the neural networks to model and control the superconductive phenomena or devices. In this paper, a new constructive neural network (CNN) trained by two different optimization algorithms; back-propagation and genetic algorithm, is proposed which models the behavior of the superconductive fault current limiters (SFCLs). Simulation results show that the proposed...
Satellite attitude tracking using optimal neuro-controller
, Article 2003 IEEE Aerospace Conference, Big Sky, MT, 8 March 2003 through 15 March 2003 ; Volume 6 , 2003 , Pages 2663-2669 ; 1095323X (ISSN); 078037651X (ISBN); 9780780376519 (ISBN) ; Sadati, N ; Tehrani, N. D ; Sharif University of Technology
2003
Abstract
In this paper, a new control strategy for optimal attitude tracking control of a multivariable satellite system has been presented. The approach is based on a Multilayer Perceptron Neural Network (MLPNN) and a classical PD Controller for its initial stabilization. It is shown how the network can be employed as a multivariable self-organizing and self-learning controller in conjunction with a PD controller for attitude control of a satellite. By using three thrusters and quaternion for kinematics representation, the attitude dynamics of the satellite has been presented. In contrast to the previous classical approaches, it is shown how this controller can be carried out in an on-line manner...
Effect of heat treatment cycle on the mechanical properties of machinable austempered ductile iron
, Article 16th International Metallurgical and Materials Conference, METAL 2007, 22 May 2007 through 24 May 2007 ; 2007 ; Baghersaee, N ; Varahram, N ; Hanumantha Rao, M ; Rao, G. V.S. N ; Sharif University of Technology
TANGER spol. s r.o
2007
Abstract
ADI have been used for a wide variety of application in automotive,rail,and heavy engineering industry because of its excellent mechanical properties such as high strength with good ductility,good wear resistance,and good fatigue properties. The properties of austempered ductile iron are dependent on both chemistry and heat treatment, which has lead to invention of MADI (machinable austempered ductile iron). MADI is a new class of ductile iron with superior mechanical property than regular ductile iron with the same machinability characteristic. In this study Different cycles of austempering process (austenitization and austempering cycle) applied Due to the effect of heat treatment cycle on...
Effect of heat treatment cycle on the mechanical properties of machinable austempered ductile iron
, Article 24th ASM International Heat Treating Conference and Exposition, Detroit, MI, 17 September 2007 through 19 September 2007 ; 2007 , Pages 323-327 ; 9781604239300 (ISBN) ; Baghersaee, E. N ; Varahram, N ; Rao, M. H ; Rao, G. V. S. N ; Sharif University of Technology
2007
Abstract
ADI have been used for a wide variety of applications in automotive, rail, and heavy engineering industry because of its excellent mechanical properties such as high strength with good ductility, good wear resistance, and good fatigue properties. The properties of austempered ductile iron are dependent on both chemistry and heat treatment, which has lead to invention of MADI (machinable austempered ductile iron). MADI is a new class of ductile iron with superior mechanical property than regular ductile iron with the same machinability characteristic. In this study Different cycle of austempering process (austenitization and austempering cycle) applied Due to the effect of heat treatment...
Dynamic relay selection and resource allocation in cooperative networks based on OFDM
, Article 17th European Wireless Conference 2011, EW 2011 ; 2011 , Pages 328-332 ; (Print ISBN): 978-3-8007-3343-9 ; Alizadeh, N. N ; Razavizadeh, S. M ; Sharif University of Technology
2011
Abstract
In this paper, we are planning to introduce a new method for relay selection and resource allocation in OFDM-based cooperative networks. Up to now, there have been relatively few works clearly concentrating on the combination of relay selection and resource allocation in such networks. In our work, a network with a single transmitter, a single receiver and a group of relays is considered. Relays work on Amplify and Forward (AF) method and there is no direct link between the transmitter and the receiver. The optimization problem is to maximize the throughput of the receiver with constraints on the amounts of the power of the transmitter and relays, and subcarriers. We will introduce an...