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    Levels of complexity in turbulent time series for weakly and high Reynolds number

    , Article Physica A: Statistical Mechanics and its Applications ; Volume 391, Issue 11 , 2012 , Pages 3151-3158 ; 03784371 (ISSN) Shayeganfar, F ; Sharif University of Technology
    2012
    Abstract
    We use the detrended fluctuation analysis (DFA), the detrended cross correlation analysis (DCCA) and the magnitude and sign decomposition analysis to study the fluctuations in the turbulent time series and to probe long-term nonlinear levels of complexity in weakly and high turbulent flow. The DFA analysis indicate that there is a time scaling region in the fluctuation function, segregating regimes with different scaling exponents. We discuss that this time scaling region is related to inertial range in turbulent flows. The DCCA exponent implies the presence of power-law cross correlations. In addition, we conclude its multifractality for high Reynold's number in inertial range. Further, we... 

    Methane molecule over the defected and rippled graphene sheet

    , Article Solid State Communications ; Volume 152, Issue 15 , August , 2012 , Pages 1493-1496 ; 00381098 (ISSN) Shayeganfar, F ; Neek Amal, M ; Sharif University of Technology
    Elsevier  2012
    Abstract
    Adsorption of a methane molecule (CH 4) onto a defected and rippled graphene sheet is studied using ab initio and molecular mechanics calculations. The optimal adsorption position and orientation of this molecule on the graphene surface (motivated by the recent realization of graphene sensors to detect individual gas molecules) is determined and the adsorption energies are calculated. In light of the density of states, we used the SIESTA code. It is found that (i) classical force field yields adsorption energy comparable with experimental result and ab initio calculation; (ii) the periodic nature of the van der Waals potential energy stored between methane and perfect sheet is altered due to... 

    Controlled nucleation and growth of CdS nanoparticles by turbulent dispersion

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 81, Issue 2 , 2010 ; 15393755 (ISSN) Shayeganfar, F ; Javidpour, L ; Taghavinia, N ; Rahimi Tabar, M. R ; Sahimi, M ; Bagheri Tar, F ; Sharif University of Technology
    2010
    Abstract
    We propose and test a method for controlling the size of nanoparticles, which plays a fundamental role in their electrical, optical, and mechanical properties. The method utilizes turbulent mixing, and is applicable to the fabrication of any type of nanoparticle that uses a solution environment in the preparation process. We show by well-controlled experiments on the CdS nanoparticles, which are semiconducting materials, that the average size □d□ of the particles decreases with Reynolds number Re  

    Discrimination of Sol and Gel states in an aging clay suspension

    , Article Chemical Physics ; Volume 423 , September , 2013 , Pages 167-172 ; 03010104 (ISSN) Shayeganfar, F ; Movahed, M. S ; Jafari, G. R ; Sharif University of Technology
    2013
    Abstract
    The dynamical scattered light intensity and multiplicative cascade model was employed to characterize the anisotropic charged colloidal particles suspension during the so-called Sol-Gel transition. Generally we looked for finding a criterion to distinguish the properties of Sol and Gel states systematically. The probability density function (PDF) of the light scattering intensity shows an obvious change with proceeding of the sample aging process (during of gelation state). Our results confirmed that in the so-called Sol state, the value of non-Gaussian parameter, kW, as a function of time is larger than that of for weak-Gel or in coexistence Sol-Gel state. The number of cascades in the... 

    A comprehensive review on planar boron nitride nanomaterials: From 2D nanosheets towards 0D quantum dots

    , Article Progress in Materials Science ; Volume 124 , 2022 ; 00796425 (ISSN) Angizi, S ; Alem, S. A. A ; Hasanzadeh Azar, M ; Shayeganfar, F ; Manning, M. I ; Hatamie, A ; Pakdel, A ; Simchi, A ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Moving from two-dimensional hexagonal boron nitride (2D h-BN) flatlands towards their quantum sized zero-dimensional (0D) islands, as the newest member of the h-BN family, has recently opened up novel research areas due to the emergence of unique optical and physicochemical properties, excellent thermal and chemical stability, and desirable biocompatibility. This review elaborates on the fundamental properties of 2D and 0D h-BN nanomaterials and covers the latest progress in the fabrication and applications of BN nanosheets (BNNSs) and quantum dots (BNQDs). Initially, the transformation of properties in h-BN nanomaterials is discussed when moving from the 2D realm towards the 0D quantum... 

    Molecular dynamics simulation of formation and growth of CdS nanoparticles

    , Article Molecular Simulation ; Vol. 40, issue. 5 , Jul , 2014 , p. 361-369 ; ISSN: 08927022 Shayeganfar, F ; Eskandari, Z ; Rahimi Tabar, M. R ; Sahimi, M ; Sharif University of Technology
    2014
    Abstract
    Monodispersed semiconducting nanoparticles are usually synthesised in a liquid medium using injection of an appropriate solution. A key factor in attaining a narrow particle size distribution (PSD) is the temporal separation of the nucleation and growth stages, where the former takes place during the injection. Faster injection produces a larger number of nuclei and a narrower PSD. The injection speed is expected to affect the diffusion of the ions in the solution and to create uniformly high supersaturation for a short period of time. In this paper, we study the growth of CdS nanoparticles during the injection by molecular dynamics simulation. A solution of Cd ions is injected into the... 

    The level crossing and inverse statistic analysis of German stock market index (DAX) and daily oil price time series

    , Article Physica A: Statistical Mechanics and its Applications ; Volume 391, Issue 1-2 , 2012 , Pages 209-216 ; 03784371 (ISSN) Shayeganfar, F ; Hölling, M ; Peinke, J ; Rahimi Tabar, M. Reza ; Sharif University of Technology
    2012
    Abstract
    The level crossing and inverse statistics analysis of DAX and oil price time series are given. We determine the average frequency of positive-slope crossings, να+, where Tα=1να+ is the average waiting time for observing the level α again. We estimate the probability P(K,α), which provides us the probability of observing K times of the level α with positive slope, in time scale Tα. For analyzed time series, we found that maximum K is about ≈6. We show that by using the level crossing analysis one can estimate how the DAX and oil time series will develop. We carry out the same analysis for the increments of DAX and oil price log-returns (which is known as inverse statistics), and provide the... 

    Effects of functionalization and side defects on single-photon emission in boron nitride quantum dots

    , Article Physical Review B ; Volume 96, Issue 16 , 2017 ; 24699950 (ISSN) Shayeganfar, F ; Rahimi Tabar, M. R ; Simchi, A ; Beheshtian, J ; Sharif University of Technology
    2017
    Abstract
    Boron nitride quantum dots (BNQDs) functionalized with chemical ligands exhibit intriguing optoelectronic properties due to the quantum confinement effect. This paper presents peculiar insights on the effect of side defects on the electronic structure and optical properties of BNQDs functionalized with different chemical bonds including hydrogen (H), nitrogen (N), hydroxyl (OH), amine (NH2), and thiol groups (inspired by experimental reports of functionalized BN nanosheets and nanotubes) Weng, Chem. Soc. Rev. 45, 3989 (2016)0306-001210.1039/C5CS00869G. Hybrid density functional simulations and Green's function calculations indicate an intriguing coexistence of two different Peierls-like... 

    Controlled Nucleation and Growth of CDS Nanoparticles by Turbulent Dispersion and Statistical Processin of Light Scattering From Nanoparticles

    , Ph.D. Dissertation Sharif University of Technology SHayeganfar, Farzaneh (Author) ; Rahimitabar, Mohammad Reza (Supervisor) ; Taghavinia, Nima (Supervisor)
    Abstract
    In this thesis, We propose and test a method for controlling the size of nanoparticles, which plays a fundamental role in their electrical, optical, and mechanical properties. The method utilizes turbulent mixing, and is applicable to the fabrication of any type of nanoparticle that uses a solution environment in the preparation process. We show by well-controlled experiments on the CdS nanoparticles, which are semiconducting materials, that the average size < d > of the particles decreases with Reynolds number Re. To gain a deeper understanding of the phenomena reported here, we have carried out molecular dynamics simulations of the processes. In second investigation, We provide a simple... 

    Investigation of Electro-Optical Properties of Heterostructures based on 2-D Layered Materials by Quantum Simulation

    , M.Sc. Thesis Sharif University of Technology Saadat Somaeh Sofla, Zahra (Author) ; Simchi, Abdolreza (Supervisor) ; Shayeganfar, Farzaneh (Supervisor)
    Abstract
    Density Functional Theory is one of the most robust Ab-intio methods for describing the structural and electronic properties of a wide range of materials. The ability to predict the material properties changes due to targeted material manipulation at the atomic scale has reduced the cost of many empirical experiments. It has improved the knowledge and understanding of the investigation and producing new materials and devices. Tow dimensional heterostructures are highly regarded due to their unique optoelectronic properties, potential application in nanoelectronic devices, energy storage devices, solid-state devices, and photovoltaic devices. In this study, the two-dimensional materials... 

    Stochastic qualifier of gel and glass transitions in laponite suspensions

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 81, Issue 6 , Jun , 2010 ; 15393755 (ISSN) Shayeganfar, F ; Jabbari Farouji, S ; Movahed, M. S ; Jafari, G. R ; Rahimi Tabar, M. R ; Sharif University of Technology
    2010
    Abstract
    The existence of the important similarities between gelation and glass transition makes it hard to distinguish between the two types of nonergodic states experimentally. Here, we report on a stochastic analysis of the scattered light intensity through a colloidal particles suspension during the gel and glass formation. In this analysis, we exploit the methods developed for complex hierarchical systems, such as turbulence. Using the multiplicative log-normal cascade models, we provide a criterion to distinguish gels from glasses  

    Multifractal analysis of light scattering-intensity fluctuations

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 80, Issue 6 , 2009 ; 15393755 (ISSN) Shayeganfar, F ; Jabbari Farouji, S ; Movahed, M. S ; Jafari, G. R ; Rahimi Tabar, M. R ; Sharif University of Technology
    2009
    Abstract
    We provide a simple interpretation of non-Gaussian nature of the light scattering-intensity fluctuations from an aging colloidal suspension of Laponite using the multiplicative cascade model, Markovian method, and volatility correlations. The cascade model and Markovian method enable us to reproduce most of recent empirical findings: long-range volatility correlations and non-Gaussian statistics of intensity fluctuations. We provide evidence that the intensity increments Δx (τ) =I (t+τ) -I (t), upon different delay time scales τ, can be described as a Markovian process evolving in τ. Thus, the τ dependence of the probability density function p (Δx,τ) on the delay time scale τ can be... 

    Optical absorption and electronic spectra of chlorophylls a and b

    , Article RSC Advances ; Volume 6, Issue 111 , 2016 , Pages 109778-109785 ; 20462069 (ISSN) Hedayatifar, L ; Irani, E ; Mazarei, M ; Rasti, S ; Azar, Y. T ; Rezakhani, A. T ; Mashaghi, A ; Shayeganfar, F ; Anvari, M ; Heydari, T ; Tabar, A. R ; Nafari, N ; Vesaghi, M. A ; Asgari, R ; Rahimi Tabar, M. R ; Sharif University of Technology
    Royal Society of Chemistry  2016
    Abstract
    Photosynthesis includes capturing sunlight by an assembly of molecules, called chlorophylls, and directing the harvested energy in the form of electronic excitations to the reaction center. Here we report, using real-space density functional theory and time-dependent density functional theory together with GW calculations, the optical and electronic properties of the two main chlorophylls in green plants, namely, chlorophylls a and b. Furthermore, we estimate the dipole and primitive quadrupole electric moments of these molecules. We employ Casida's assignment ansatz to study the absorption spectra of the chlorophylls in the two main red and blue regions at various environments with... 

    Effect of heating profile on desorption curve in temperature programmed desorption analysis: Case study of acid sites distribution of SAPO-34

    , Article Journal of Porous Materials ; Volume 16, Issue 5 , 2009 , Pages 599-603 ; 13802224 (ISSN) Izadbakhsh, A ; Farhadi, F ; Khorasheh, F ; Yan, Z. F ; Sharif University of Technology
    2009
    Abstract
    Comparison of the traditional linear heating method of TPD with an original stepwise heating scheme was reported for the first time. Stepwise heating TPD was carried out by keeping the temperature constant as soon as ammonia desorption signal rises until the signal returns to the baseline. More ammonia desorption peaks on a SAPO-34 catalyst were identified using TPD with stepwise heating. The effect of temperature ramp on desorption peak broadening in TPD curve was also addressed. The more distinct ammonia desorption peaks in stepwise TPD indicates that ammonia adsorbs in about five or six different ways on SAPO-34, and attribution of different adsorptions may be explained considering some... 

    Theoretical and experimental study of cascade solar stills

    , Article Solar Energy ; Volume 90 , April , 2013 , Pages 205-211 ; 0038092X (ISSN) Ziabari, F. B ; Sharak, A. Z ; Moghadam, H ; Tabrizi, F. F ; Sharif University of Technology
    2013
    Abstract
    Most part of Iran is dominated by arid and semi-arid areas due to low annual rainfall. The need for production of fresh water from brackish water is considerably high, especially in dry regions. In this study 1 month daily-based experimental data from a solar still site has been reported. The technical and operational problems of this site which finally contributed to the total cease of the site are described. Then a detailed analysis is investigated on progress of a prototype which constructed in order to solve the site's problems. The results of 1 month of experimental data of the final design showed that the last prototype could be used to solve the current problems of the site. The... 

    Application of a continuous kinetic model for the hydrocracking of vacuum gas oil

    , Article Petroleum Science and Technology ; Vol. 32, Issue. 18 , 2014 , Pages 2245-2252 ; ISSN: 10916466 Arefi, A ; Khorasheh, F ; Farhadi, F ; Sharif University of Technology
    2014
    Abstract
    Hydrocracking is one of the most versatile petroleum refining processes for production of valuable products including gasoline, gas oil, and jet fuel. In this paper, a five-parameter continuous lumping model was used for kinetic modeling of hydrocracking of vacuum gas oil (VGO). The model parameters were estimated from industrial data obtained from a fixed bed reactor operating at an average temperature of 400°C and residence time of 0.3 h. Product distributions were obtained in terms of the weight fraction of various boiling point cuts. The model parameters were estimated using the Nelder-Mead optimization procedure and were correlated with temperature. Comparison of experimental and... 

    An improved methodology for design of custom-made hip prostheses to be fabricated using additive manufacturing technologies

    , Article Rapid Prototyping Journal ; Volume 18, Issue 5 , 2012 , Pages 389-400 ; 13552546 (ISSN) Rahmati, S ; Abbaszadeh, F ; Farahmand, F ; Sharif University of Technology
    Emerald  2012
    Abstract
    Purpose - The purpose of this paper is to present an improved methodology for design of custom-made hip prostheses, through integration of advanced image processing, computer aided design (CAD) and additive manufacturing (AM) technologies. Design/methodology/approach - The proposed methodology for design of custom-made hip prostheses is based on an independent design criterion for each of the intra-medullary and extra-medullary portions of the prosthesis. The intra-medullar part of the prosthesis is designed using a more accurate and detailed description of the 3D geometry of the femoral intra-medullary cavity, including the septum calcar ridge, so that an improved fill and fit performance... 

    Evaluation and enhancing of operational performance and training objective in accordance with Line Operations Safety Audit (LOSA)

    , Article International Air Safety Seminar Proceedings, 1 November 2011 through 3 November 2011 ; November , 2011 , Pages 78-99 ; 02705176 (ISSN) ; 9781618393975 (ISBN) Khoshkhoo, R ; Goodarzi, F ; Sharafbafi, F ; Sharif University of Technology
    2011

    Real-time impulse noise suppression from images using an efficient weighted-average filtering

    , Article IEEE Signal Processing Letters ; Volume 22, Issue 8 , 2015 , Pages 1050-1054 ; 10709908 (ISSN) Hosseini, H ; Hessar, F ; Marvasti, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    In this letter, we propose a method for real-time high density impulse noise suppression from images. In our method, we first apply an impulse detector to identify the corrupted pixels and then employ an innovative weighted-average filter to restore them. The filter takes the nearest neighboring interpolated image as the initial image and computes the weights according to the relative positions of the corrupted and uncorrupted pixels. Experimental results show that the proposed method outperforms the best existing methods in both PSNR measure and visual quality and is quite suitable for real-time applications  

    Kinetic modeling of pyrolysis of scrap tires

    , Article Journal of Analytical and Applied Pyrolysis ; Volume 84, Issue 2 , 2009 , Pages 157-164 ; 01652370 (ISSN) Mazloom, G ; Farhadi, F ; Khorasheh, F ; Sharif University of Technology
    2009
    Abstract
    The disposal of used tires is a major environmental problem. With increasing interest on recovery of wastes, pyrolysis is considered as an alternative process for recovering some of the value in scrap tires. An accurate kinetic model is required to predict product yields during thermal or catalytic pyrolysis of scrap tires. Pyrolysis products contain a variety of hydrocarbons over a wide boiling range. A common approach for kinetic modeling of such complex systems is lumping where each lump is defined by a boiling point range. Available experimental data for thermal and catalytic pyrolysis of scrap tires from the literature were used to evaluate two types of lumping models; discrete and...