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haghparast--nastaran
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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...
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...
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)
Assessment of Existing Offshore Platforms for In-Place Conditions
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor)
Abstract
Assessment of existing jacket type offshore platforms in Persian Gulf for life extension is of great importance in the field of offshore platforms in recent years. The main question to answer is whether an existing platform is safe enough to be used beyond the design life. Evaluation of existing jacket type offshore platforms under extreme environmental (wave) loading in Persian Gulf is a part of this major assessment. Two general approaches exist in this context, deterministic and probabilistic assessment. In this thesis, a new probabilistic method (reliability analysis) to assess offshore structures under environmental loading (extreme wave) is introduced. This method is a...
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...
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...
Growth of Perovskite Film based on Lead Iodide by Controlling Deposition Parameters for Solar Cells Application
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor) ; Seyed Reihani, Morteza (Supervisor) ; Riahi, Nastaran (Co-Advisor)
Abstract
Perovskite solar cells, with high efficiency operation, have been candidated as a cost-effective and environmentally friendly technology. Despite the great progress, there are some primarily issues remained regarding to the perovskite film and its fabrication methods. A very common perovskite cell structure is FTO/TiO2/CH3NH3PbI3/Spiro-OMeTAD/Au. Although, this structure has some advantages, lack of full surface coverage of perovskite film leads researchers to put much effort on finding other constructions. This surface inhomogeneity reduces the amount of light absorption and therefore efficiency. One way to produce a complete and uniform film is applying mixed-halide composition; such as...
Solvent Engineering for Preparation of Perovskite Film based on Lead Iodide for Solar Cells Applications
, M.Sc. Thesis Sharif University of Technology ; Seyed Reyhani, Morteza (Supervisor) ; Mohammadi, Mohammad Reza (Supervisor) ; Riahi Noori, Nastaran (Co-Advisor)
Abstract
The microstructure, morphology and quality of the perovskite organic-inorganic layer as an absorber layer in perovskite solar cells has a significant role on the efficiency and energy conversion of the device. Different solvent engineering methods have been employed to prepare the perovskite layer with the desired properties and thier reproducibility have been studied. Herein, we applied a two-step solution approach by solvent engineering method, using solvents such as isopropyl alcohol, acetone and thier mixture, for preparation of lead iodide films. Moreover, their metallurgical and photovoltaic properties were investigated. The impact of solvent engineering, using solvents such as...
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...