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Nanoscale modeling of an embedded multi-shell fullerene and its application to vibrational analysis
, Article International Journal of Engineering Science ; Volume 44, Issue 17 , 2006 , Pages 1156-1163 ; 00207225 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
2006
Abstract
In this paper, nanoscale modeling of a multi-shell fullerene embedded in an elastic medium and its application to vibrational analysis is investigated. The spherical layers of the multi-shell fullerene are concentrically nested, with carbon-carbon van der Waals interactions between them. Also, the whole multi-shell fullerene is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium. The elasticity generated by the carbon-carbon bonds is assumed to be distributed isotropically over the fullerene surfaces. Following derivation of explicit equations for the motion of the multi-shell fullerene, vibrational behavior of a double-shell fullerene is analyzed and...
Bending stiffness of a double-layered graphene sheet using a geometrically-based analytical approach
, Article 4th ASME Integrated Nanosystems Conference: Design, Synthesis, and Applications, Berkeley, CA, 14 September 2005 through 16 September 2005 ; 2005 , Pages 85-86 ; 0791842088 (ISBN); 9780791842089 (ISBN) ; Naghdabadi, R ; Sharif University of Technology
American Society of Mechanical Engineers
2005
Abstract
In this article, the bending stiffness of a double-layered graphene sheet is investigated using a geometrically-based analytical approach. The analysis is based on the van der Waals interactions of atoms belonging to two neighboring sheets. The inter-atomic spacing between the adjacent layers is geometrically determined when the sheet is applied by a couple of moments in the opposite sides. The bending potential energy is obtained by summing up the potentials at discrete hexagons over the length and width of the sheet. It is observed that the bending stiffness of a double-layered graphene sheet does not depend on the length of the sheet and be a material property for the associated sheet....
Nanoscale vibrational analysis of a multi-layered graphene sheet embedded in an elastic medium
, Article Composites Science and Technology ; Volume 65, Issue 7-8 , 2005 , Pages 1159-1164 ; 02663538 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
2005
Abstract
In this paper, nanoscale vibrational analysis of a multi-layered graphene sheet embedded in an elastic medium is investigated and the corresponding natural frequencies and the associated modes are determined. The modeling is based on the fact that the elastic moduli of a graphene sheet in two perpendicular orientations are different, so the plate is considered to be anisotropic. The graphene layers stacking at the top of each other bond with carbon-carbon van der Waals forces between two adjacent ones. Also, the whole multi-layered graphene sheet is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium. © 2005 Elsevier Ltd. Al rights reserved
Path and Cycle Factors in 3-Regular Graphs
, M.Sc. Thesis Sharif University of Technology ; Akbari, Saeed (Supervisor)
Abstract
Given a graph G and a set F of connected graphs, an F-packing of G is a subgraph of G whose components are isomorphic to one member of F. In addition, if H is a subgraph of G, then an H-packing is defined similarly. The maximum F-packing is an F-packing such that it has the maximum number of vertices. If the F-packing F is a spanning subgraph of G, then F is called an F-factor. If each member of F is a path of order at least two (cycle), then an F-factor is called a path (cycle) factor. In this thesis, the focus was on the path factor and cycle factor in 3-regular graphs and these factors were investigated in 2-connected graphs, 3-connected graphs and bipartite graphs. Moreovere special...
The Relationship between Microstructure, Properties and Processing in Bimodal Polyethylene with Medium Density Used in Drip Irrigation Tapes
, M.Sc. Thesis Sharif University of Technology ; Pircheraghi, Gholamreza (Supervisor)
Abstract
In recent years, Jam Petrochemical has produced and designed irrigation tape polyethylene grades but because these grades don’t have sufficient melt strength during high-speed processing, it hasn’t been welcomed by manufacturers. Therefore, in first step of this study we tried to characterize the specimens by using referenced grade and by taking advantages of thermal, rheological and mechanical analysis. We observed that main difference between jam petrochemical grades and referenced grade is related to type and content of comonomer and also long chain branches. Based on the obtained results, the ideal molecular structure of irrigation tape grade, include chains with bimodal distribution...
General derivations for conjugate strains of eshelby-like stress tensors
, Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 1 , 2004 , Pages 353-356 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Sheshmani, A ; Naghdabadi, R ; Sharif University of Technology
American Society of Mechanical Engineers
2004
Abstract
In this paper, a general type of Eshelby-like stress tensor is defined which is based on the right stretch tensor and is equal to the product of a general class of strain and the corresponding conjugate stress tensor. The Eshelby-like stress tensor depending on the fact that from which side the stress tensor is multiplied by, is categorized into the right-weighted and left-weighted ones. General relations for conjugate strains of Eshelby-like stress tensors are investigated using the method, based on the definition of energy conjugacy and Hill's principal axis method
Effects of molecular structure on thermal, rheological and mechanical properties of drip irrigation PE tapes
, Article Journal of Polymer Research ; Volume 29, Issue 10 , 2022 ; 10229760 (ISSN) ; Pircheraghi, G ; Houshmandmoayed, S ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
Considering the microstructure-processing-properties relationship, the attempt was made to distinguish the main structural features of drip irrigation tape grades. In this regards, two different commercial polyethylene grades using for irrigation tape application (DB and MD samples) with various microstructural features were fully characterized by means of thermal, rheological and mechanical measurements and microscopic observations. A set of DSC techniques revealed that DB sample has faster crystallization kinetic probably due to its high crystallizable segments in chains and broad molecular weight distribution. It was found, the type of co-monomer used in DB sample is 1-hexene and in MD...
The existence of uniform hypergraphs for which the interpolation property of complete coloring fails
, Article Discrete Mathematics ; Volume 345, Issue 3 , 2022 ; 0012365X (ISSN) ; Hasanvand, M ; Ohno, Y ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In 1967 Harary, Hedetniemi, and Prins showed that every graph G admits a complete t-coloring for every t with χ(G)≤t≤ψ(G), where χ(G) denotes the chromatic number of G and ψ(G) denotes the achromatic number of G which is the maximum number r for which G admits a complete r-coloring. Recently, Edwards and Rza̧żewski (2020) showed that this result fails for hypergraphs by proving that for every integer k with k≥9, there exists a k-uniform hypergraph H with a complete χ(H)-coloring and a complete ψ(H)-coloring, but no complete t-coloring for some t with χ(H)
Frame Rate Upconversion Using Image Registration Techniques on Echocardiography
, M.Sc. Thesis Sharif University of Technology ; Fatemizadeh, Emadoddin (Supervisor)
Abstract
In this research a novel method is proposed which uses the concept of image registration to forecast frames as a new frame up conversion method. This frame rate up conversion method is specially designed for medical videos because of the medical structure of the none rigid image registration used as a field to forecast new frames which causes better results for these kinds of videos. In this method we interpolate new frames in the field of none rigid transformation grid in order to improve video parameters such as blocking, blurriness, etc. which can help doctors to detect abnormalities in such videos much preciously. By analyzing existing methods, we can find that this field is bereft of a...
An analytical approach to determination of bending modulus of a multi-layered graphene sheet
, Article Thin Solid Films ; Volume 496, Issue 2 , 2006 , Pages 475-480 ; 00406090 (ISSN) ; Seifi, P ; Naghdabadi, R ; Ghanbari, J ; Sharif University of Technology
2006
Abstract
In this paper, the bending modulus of a multi-layered graphene sheet is investigated using a geometrically based analytical approach. For this purpose, a bending potential energy is derived, based on the van der Waals interactions of atoms belonging to the two neighboring sheets of a double-layered graphene sheet. The inter-atomic spacing between the adjacent layers is determined along the line of action of the applied bending moments. The bending potential of the double-layered sheet is calculated by summing up the potentials at discrete hexagons over the length and width of the sheet. A multi-layered graphene sheet is considered as consisting of many stacking double-layers. It is observed...
Basis-free relations for conjugate strains of eshelby-like stress tensors
, Article Mechanics of Materials ; Volume 39, Issue 7 , 2007 , Pages 637-642 ; 01676636 (ISSN) ; Naghdabadi, R ; Arghavani, J ; Asghari, M ; Sharif University of Technology
2007
Abstract
In this paper, a general class of Eshelby-like or weighted stress tensors based on the right stretch tensor is defined as the product of a general type of Lagrangian stress tensor and a class of stretch measure. In addition, basis free relations for conjugate strains of Eshelby-like stress tensors are investigated, which are based on Hill's definition of energy conjugacy. The equations for strain tensors conjugate to Eshelby-like stress tensors are generally determined, but the case in which the conjugate strains are coaxial with the right stretch tensor is mostly investigated. © 2006 Elsevier Ltd. All rights reserved
Nanoscale vibrational analysis of an embedded multi-layered graphene sheet
, Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 3 , 2004 , Pages 569-572 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Vafai, A ; Naghdabadi, R ; Estekanchi, H. E ; Sharif University of Technology
American Society of Mechanical Engineers
2004
Abstract
In this paper, nanoscale vibrational analysis of a multi-layered graphene sheet embedded in an elastic medium is investigated and the corresponding resonant modes and frequencies are determined. It is known that the elastic moduli of a graphene sheet in two orientations x, y are different, so the graphene sheet is assumed to be a general form of an orthotropic plate. The orthotropic sheets stacking at the top of each other bond with carbon-carbon van der Waals forces, also the whole multi-layered graphene sheet is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium
Observer-Based Adaptive Backstepping Sliding-Mode Control of the Satellite Attitude with a Partially Filled Spherical Fuel Tank
, Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 47, Issue 4 , 2023 , Pages 1761-1775 ; 22286187 (ISSN) ; Salarieh, H ; Nejat Pishkenari, H ; Abdollahi, T ; Sharif University of Technology
Institute for Ionics
2023
Abstract
Modeling and controlling the fuel slosh phenomenon in a satellite is a vital problem in the field of satellite attitude control. In this paper, a satellite with a partially filled spherical fuel tank that uses diaphragm as a propellant management device (PMD), has been considered. The fuel slosh dynamics is modeled by a spherical pendulum with two degrees of freedom (DOF) and a rigid arm, which represents the first mode of sloshing. The effects of the diaphragm that surround the fuel surface, are considered as torsional spring-damper attached to the satellite body. The coupled equations of satellite motion and fuel are derived using the Lagrange method. The nonlinear control method based on...
Hydraulic and Sediment Simulation of Rivers Passing Throw the City Affected by Land-Use Changes and Expansion of Human Activities (Case Study-Kan River’s Basin)
, M.Sc. Thesis Sharif University of Technology ; Tajrishi, Massoud (Supervisor) ; Torabi, Oveis ($item.subfieldsMap.e)
Abstract
understanding basin’s sediment transportation forms and river’s bed erosion in next years in addition to rivers’ response to watershed upstream activities, gives useful information to relevant experts for fundamental studies on expanding of development projects in neighborhood of kan River. This project is an effort to assess the amount of sediment production of Kan River’s basin using SWAT, modeling calibration by using measured data with SWAT-CUP and also prediction of river’s response to watershed activities in modeling river’s sediment in next years by using HEC-RAS. Several management approaches in different scenarios has been studied in order to control the sediment production and...
Image Categorization Using Deep Learning
, M.Sc. Thesis Sharif University of Technology ; Jafari Siavoshani, Mahdi (Supervisor) ; Rabiee, Hamid Reza (Co-Advisor)
Abstract
The representation of data influences the explanation factors of data variations. Thus,the success of learner algorithms depends on the data representation. Our main contribution in this thesis is learning of high level and abstract representation using deep structure. One of the fundamental examples of representation learning is the AutoEncoders. The auto-encoder is a rigid framework that doesn’t consider explanation factors in terms of statistical concepts. So, the auto-encoders can be re-interpreted by seeing the decoder as the statistical model of interest. The role of encoder is a mechanism for inference in the model described by the decoder. Our purpose is to design such model with...
Satellite Attitude Control with Consideration of the Fuel Sloshing Dynamics
, M.Sc. Thesis Sharif University of Technology ; Salarieh, Hassan (Supervisor) ; Nejat Pishkenari, Hossein (Supervisor)
Abstract
Modeling and Controlling of a satellites fuel slosh is considered a vital problem in the field of satellite attitude control. In this paper modeling and control of the attitude of a satellite carrying a partially filled spherical fuel tank, which uses the diaphragm as a propellant management device (PMD), has been studied. The fuel slosh dynamics is modeled using a spherical pendulum with two degrees of freedom and a rigid arm, which represents the first mode of sloshing. The effects of the diaphragm that surround the fuel surface, are considered as torsional springs and dampers attached to the satellite body. The combined dynamics equations of the satellite rigid motion and the fuel slosh...
Benchmarking of Monte Carlo model of Siemens Oncor® linear accelerator for 18MV photon beam: determination of initial electron beam parameters
, Article Journal of X-Ray Science and Technology ; Volume 27, Issue 6 , 2 January , 2020 , Pages 1047-1070 ; Hoseini Ghafarokhi, M ; Bolagh, R. S. M ; Haghparast, M ; Zarifi, S ; Nickfarjam, A ; Farhood, B ; Chow, J. C. L ; Sharif University of Technology
IOS Press
2020
Abstract
OBJECTIVE: This study aims to benchmark a Monte Carlo (MC) model of the 18 MV photon beam produced by the Siemens Oncor® linac using the BEAMnrc and DOSXYZnrc codes. METHODS: By matching the percentage depth doses and beam profiles calculated by MC simulations with measurements, the initial electron beam parameters including electron energy, full width at half maximum (spatial FWHM), and mean angular spread were derived for the 10×10 cm2 and 20×20 cm2 field sizes. The MC model of the 18 MV photon beam was then validated against the measurements for different field sizes (5×5, 30×30 and 40×40 cm2) by gamma index analysis. RESULTS: The optimum values for electron energy, spatial FWHM and mean...