Search for: structural-parameter
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    Irreversibility in response to forces acting on graphene sheets

    , Article Physical Review Letters ; Volume 104, Issue 19 , May , 2010 ; 00319007 (ISSN) Abedpour, N ; Asgari, R ; Tabar, M. R. R ; Sharif University of Technology
    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

    Multiwavelength Study of Structural Parameters of Early Type Galaxies

    , M.Sc. Thesis Sharif University of Technology Mirkazemi, Mohammad (Author) ; Rahvar, Sohrab (Supervisor) ; Khosroshahi, Habib (Supervisor)
    During the past decades, structural parameters are used as a tool for studying the formation and evolution of galaxies. Sersic parameter is one of these parameterswhich also known as shape parameter. Sometimes, measuring such parameters depend on the observed wavelength. So far, this dependence has been rarely attended. In this thesis we are trying to know how and why these parameters depend on the wavelength  

    The impact of MOF feasibility to improve the desalination performance and antifouling properties of FO membranes

    , Article RSC Advances ; Volume 6, Issue 74 , 2016 , Pages 70174-70185 ; 20462069 (ISSN) Zirehpour, A ; Rahimpour, A ; Khoshhal, S ; Firouzjaei, M. D ; Ghoreyshi, A. A ; Sharif University of Technology
    Royal Society of Chemistry  2016
    In this study, a hydrophilic metal-organic framework (MOF) was applied to improve the performance of a cellulosic membrane for forward osmosis (FO) desalination application. The characterization results confirmed that the MOF particles existed within the matrix of the modified membrane. The MOF loading led to adjustment of the membranes in terms of overall porosity, pore inter-connectivity and hydrophilicity. These features caused an improvement in the pure water permeability (72%) and reduce the structural parameter of the modified membrane to 136 μm. The FO water flux of the modified membrane enhanced by about 180% compared to an unmodified membrane, without decreasing its selectivity. FO... 

    Periodic structure of different dielectric layers for dielectric laser accelerators

    , Article Applied Optics ; Volume 60, Issue 13 , 2021 , Pages 3747-3752 ; 1559128X (ISSN) Shojaie, E ; Madanipour, K ; Bahrampour, A ; Sharif University of Technology
    The Optical Society  2021
    In this paper, a periodic structure of different dielectric layers is proposed and investigated for relativistic electron acceleration. The periodic dielectric structure provides an accelerating electric field inside the structure. Results show that the electron beam can experience a strong electric force in one direction during propagation in the structure, leading to the acceleration gradient increasing by more than double in comparison with dual-grating structures. Acceleration gradient enhancement occurs without increasing the electric field much inside the structure; therefore, the maximum achievable acceleration gradient and acceleration factor are increased by more than 100%, reaching... 

    Identifying the Effective Factors on Corporate Venturing as a Growth Strategy Path

    , M.Sc. Thesis Sharif University of Technology Ashkewari, Fedra (Author) ; Modarres, Abdolhamid (Supervisor)
    In this research, effective factors on corporate venturing are identified. These factors are categorized in three main groups including “corporate venturing objectives”, “Parent factors” and “Venture factores”. After examining the framework and decision making boundaries, the developed model identifies different corporate venturing types and in the next stage, these types are clusterd and labled. Specifically, this research makes a difference between two phases of “initating” the ventures and “designing” them. Based on the logic that different types of ventures need different types of designing and structuring, influencing parameters on designing corporate ventures are identified as a... 

    Preparation a Polymeric Membrane for Dehydration of Acetic Acid

    , M.Sc. Thesis Sharif University of Technology Mirfarah, Hesam (Author) ; Mousavi, Abbas (Supervisor) ; Bastani, Dariush (Supervisor)
    The separation ofacetic acids in binary water solutions hasbeenstudied using a reverse osmosis (RO) membrane. Thin film composite polyamide membrane is used in this study.Thin-film composite (TFC) membrane was prepared through the interfacial polymerization between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on the polysulphone support membrane.The solute permeation was carried out under applied pressure of 5 bar at 25°C. In this work the effect of various synthesis conditions on the membrane performance was investigated. Parametric studies were conducted by varyingconcentration of reactants, reaction time, curing time and curing temperature. By suitable combination of these... 

    An investigation on the structural characteristics and reinforcement of melt processed polyamide 66/multiwalled carbon nanotube composites

    , Article Polymers for Advanced Technologies ; Vol. 25, issue. 4 , 2014 , pp. 406-417 ; ISSN: 10427147 Shojaei, A ; Nourbakhsh, P ; Faghihi, M ; Sharif University of Technology
    Properties of melt processed polyamide 66 (PA66)/multiwalled carbon nanotube composite were first characterized experimentally. The experimental results exhibited the formation of crystalline layer around the nanotubes and a considerable enhancement in mechanical properties by incorporation of multiwalled carbon nanotube up to 1 wt%. Mechanical properties were analyzed in terms of structural parameters using micromechanical models proposed in this study. It was suggested that the mechanical properties were greatly dominated by crystalline layer and nanotube length. It was also deduced that the melt mixing process caused a significant nanotube breakage restricting further enhancement of... 

    Thermal conductivity of polyamide-6,6 in the vicinity of charged and uncharged graphene layers: A molecular dynamics analysis

    , Article Journal of Physical Chemistry C ; Volume 116, Issue 26 , May , 2012 , Pages 14115-14122 ; 19327447 (ISSN) Alaghemandi, M ; Gharib-Zahedi, M. R ; Spohr, E ; Böhm, M. C ; Sharif University of Technology
    The thermal conductivity (λ) of nanoconfined polyamide-6,6 (PA) oligomers in polymer-graphene nanocomposites has been investigated by reverse nonequilibrium molecular dynamics (RNEMD) simulations. The preferential alignment of the PA chains parallel to the graphene plane as well as their elongation implies that λ of the polymer in nanocomposites is larger than that in the neat polymer system. The ordering of the polymer phase is enhanced in an arrangement of charged graphene surfaces made of one layer with a charge deficit and one with a charge excess. The consequence of the enhanced polymer ordering as well as the denser packing is an increase in λ in the polymer network. Differences in the... 

    Investigating optimum procedures needed to maintain a model satellite's CG stable about design point, under subsystem configuration changes

    , Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 4 , 2010 , Pages 585-588 ; 9780791849187 (ISBN) Dastoom Laatleyli, H ; Abedian, A ; Teimouri, H ; Sharif University of Technology
    During design, microsatellites are subject to different changes like the changes in weight, location and dimension of parts and elements of subsystems and the payload. These changes should be accumulated by the structure subsystem in a way that some key structural parameters like the center of gravity (CG) and inertia moments remain unchanged. This subject is also important regarding the design of a modular structure of a satellite. In the present study it is tried to accommodate any changes in weight and location of any part(s) and element(s) of a microsatellite by optimum (minimum) rearrangement of other parts on their plane of rest in order to keep the CG and inertia moments unchanged.... 

    Singularity-free planning for a robot cat free-fall with control delay: role of limbs and tail

    , Article 2017 8th International Conference on Mechanical and Aerospace Engineering, ICMAE 2017, 22 July 2017 through 25 July 2017 ; 2017 , Pages 215-221 ; 9781538633052 (ISBN) Sadati, S. M. H ; Meghdari, A ; Sharif University of Technology
    Cat free fall righting maneuverer has inspired many aerial, space and legged robotic research. Conservation of angular momentum principle is used to derive the inverse differential kinematic and TMT vector form dynamics of the motion for three robotic models: a two-link model, a three-link model with tail, and a comprehensive eight-link model with the addition of legs. The path planning problem in the presence of geometric and kinematic constraints is addressed using a novel singularity free single shooting optimization method. While a 2 DOF torso is sufficient to perform a full maneuver, the addition of the tail reduces the time and increases the maneuverability despite the leg motions that... 

    Simultaneous optimization and simulation of a-Si1-xC x layers on n-type silicon solar cells

    , Article Solar Energy Materials and Solar Cells ; Volume 85, Issue 4 , 2005 , Pages 467-476 ; 09270248 (ISSN) Vesaghi, M. A ; Asadi, K ; Sharif University of Technology
    We have applied Rosenbrock's optimization algorithm to obtain the optimized efficiency of a solar cell and its structural parameters. To obtain these parameters, we have developed a computer program for simultaneous optimization and simulation of the solar cell. We have used experimental data on the electrical and optical properties of a-Si1-xCx layers, put them into the written code and obtained the optimized parameters of this solar cell. The maximum efficiency is 6.32% which is close to one experimental result. © 2004 Elsevier B.V. All rights reserved  

    Incorporating multiscale micromechanical approach into PLSNs with different intercalated morphologies

    , Article Journal of Applied Polymer Science ; Volume 119, Issue 6 , September , 2011 , Pages 3347-3359 ; 00218995 (ISSN) Yazdi, A. Z ; Bagheri, R ; Kazeminezhad, M ; Heidarian, D ; Sharif University of Technology
    The objective of the present study is to predict Young's modulus of polymer-layered silicate nanocomposites (PLSNs) containing fully intercalated structures. The particular contribution of this article is to consider the changes in structural parameters of different intercalated morphologies in vicinity of each other. These parameters include aspect ratio of intercalated stacks, number of silicate layers per stack, d-spacing between the layers, modulus of the gallery phase, and volume fraction of each intercalated morphology. To do this, the effective particle concept has been employed and combined with the Mori-Tanaka micromechanical model. It has been shown that the simultaneous effects of... 

    Electrokinetic behavior of asphaltene particles

    , Article Fuel ; Volume 178 , 2016 , Pages 234-242 ; 00162361 (ISSN) Hosseini, A ; Zare, E ; Ayatollahi, Sh ; M. Vargas, F ; G. Chapman, W ; Kostarelos, K ; Taghikhani, V ; Sharif University of Technology
    Elsevier Ltd 
    The effect of electrostatic field on the aggregation rate and aggregate size of asphaltene particles precipitated from three different crude oil samples suspended in a mixture of toluene and n-heptane (a model oil) was investigated. An electrode-embedded glass micro-model utilizing a high-voltage direct current power supply was utilized in this study. The asphaltene particle size and the rate of aggregation under the electric field were monitored using a high-resolution optical microscope and the average aggregate size for asphaltene particles was estimated using image processing software. To investigate the effects of structural parameters on asphaltene aggregation rate, aggregate size and... 

    On the sensitivity of the nanostructural parameters on youngg"s modulus of PLSNs in fully intercalated structures

    , Article Journal of Composite Materials ; Volume 43, Issue 24 , 2009 , Pages 2921-2941 ; 00219983 (ISSN) Zehtab Yazdi, A ; Bagheri, R ; Kazeminezhad, M ; Sharif University of Technology
    Polymer-layered silicate nanocomposites have been observed to demonstrate enhanced mechanical properties particularly at low weight fractions of silicate. Experimental and theoretical investigations reveal that numerous structural parameters strongly influence the modulus of such nanocomposites. A multiscale micromechanical model is developed which considers a wide range of different affecting parameters including the particle aspect ratio, the number of silicate layers per stack, the d-spacing ratio between the layers, the penetration of polymer chains along silicate sheets, the intercalation feature, and the particle volume fraction. The developed model illustrates the accuracy and... 

    DFT and experimental study of the host-guest interactions effect on the structure, properties, and electro-catalytic activities of N 2O 2-Ni(II) schiff-base complexes incorporated into zeolite

    , Article Journal of Physical Chemistry C ; Volume 116, Issue 34 , 2012 , Pages 18518-18532 ; 19327447 (ISSN) Jafarian, M ; Rashvand Avei, M ; Khakali, M ; Gobal, F ; Rayati, S ; Mahjani, M. G ; Sharif University of Technology
    Ni II-(N,N′-bis(2,4-dihydroxyacetophenone)-2, 2-dimethylpropandiimine (Ni II{salnptn(4-OH) 2}) complex has been encapsulated within the supercage of zeolite-NaY by reacting Ni 2+-exchanged NaY with the flexible Schiff-base ligand that diffuses into the cavities. The encapsulated complex is characterized by EDX, scanning electron microscopy, powder X-ray diffraction, FT-IR, and cyclic voltammetry studies. Density functional calculation is being carried out on both the free nickel Schiff-base complex and that encapsulated in NaY zeolite to investigate changes in structural parameters, energies of the HOMO and LUMO, and absolute hardness and softness. Electrochemical properties of the NaY... 

    A numerical analysis of thermal conductivity, thermal dispersion, and structural effects in the injection part of the resin transfer molding process

    , Article Journal of Porous Media ; Volume 13, Issue 4 , 2010 , Pages 375-385 ; 1091028X (ISSN) Layeghi, M ; Karimi, M ; Seyf, H. R ; Sharif University of Technology
    Thermal conductivity, thermal dispersion, and structural effects in resin transfer molding (RTM) process are studied numerically. The injection part of the RTM process is modeled as a transport of resin flow through a fibrous porous medium in a long rectangular channel. The fluid flow is modeled using the Darcy-Brinkman-Forchheimer model and the heat transfer process using the energy equation based on local thermal equilibrium assumption. Both isotropic and anisotropic heat transfer in porous media are investigated. The governing equations are solved numerically for the isotropic heat transfer case and analytically for the anisotropic case. The numerical results are fitted to the available... 

    Preparation and investigations on the thermal, structural and magnetic behavior of Co-Ce substituted Ni nanoferrites

    , Article Materials Research Express ; Volume 6, Issue 11 , 2019 ; 20531591 (ISSN) Qamar, S ; Yasin, S ; Ramzan, N ; Iqbal, T ; Niaz Akhtar, M ; Sharif University of Technology
    Institute of Physics Publishing  2019
    Co-Ce doped Ni nanocrystalline ferrites having composition Ni0.8Ce0.2CoxFe2-xO4 with x = 0.00, 0.25, 0.50, 0.75, 1.00 were fabricated by sol gel auto combustion method. Synthesized samples were investigated by thermal gravimetric and differential thermal analysis (TGA-DTA), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis (EDX) and vibrating sample magnetometer (VSM) to study the phase, vibrational modes, structure, surface analysis and magnetic properties respectively. Structural parameters (lattice parameters, cell volume, crystallite size and micro strains) were also calculated from XRD recorded data.... 

    CDM-based design and performance evaluation of a robust AQM method for dynamic TCP/AQM networks

    , Article Computer Communications ; Volume 32, Issue 1 , 2009 , Pages 213-229 ; 01403664 (ISSN) Bigdeli, N ; Haeri, M ; Sharif University of Technology
    A new robust AQM strategy for dynamically varying TCP/AQM networks is proposed and its performance is investigated through computer simulations in MATLAB and ns-2 environments. The developed AQM is designed based on coefficient diagram method (CDM), which is a new indirect pole placement method that considers the speed, stability and robustness of the closed loop system in terms of time domain specifications. Simulation results indicate that the new method (CDM-AQM) performs very well for network variations both in topology and traffic. Besides, a new adaptive controller based on CDM as an AQM method is introduced. In the developed adaptive AQM (ACDM), the output feedback pole placement is...