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Wrapping bacteria by graphene nanosheets for isolation from environment, reactivation by sonication, and inactivation by near-infrared irradiation
, Article Journal of Physical Chemistry B ; Volume 115, Issue 19 , 2011 , Pages 6279-6288 ; 15206106 (ISSN) ; Ghaderi, E ; Esfandiar, A ; Sharif University of Technology
American Chemical Society
2011
Abstract
Bioactivity of Escherichia coli bacteria (as a simple model for microorganisms) and interaction of them with the environment were controlled by their capturing within aggregated graphene nanosheets. The oxygen-containing functional groups of chemically exfoliated single-layer graphene oxide nanosheets were reduced by melatonin as a biocompatible antioxidant. While each one of the graphene (oxide) suspension and melatonin solution did not separately show any considerable inactivation effects on the bacteria, aggregation of the sheets in the melatonin-bacterial suspension resulted in trapping the bacteria within the aggregated sheets, i.e., a kind of inactivation. The bacteria trapped within...
Photodegradation of graphene oxide sheets by TiO2 nanoparticles after a photocatalytic reduction
, Article Journal of Physical Chemistry C ; Volume 114, Issue 30 , July , 2010 , Pages 12955-12959 ; 19327447 (ISSN) ; Abdolahad, M ; Esfandiar, A ; Mohatashamifar, M ; Sharif University of Technology
2010
Abstract
TiO2 nanoparticles were physically attached to chemically synthesized single-layer graphene oxide nanosheets deposited between Au electrodes in order to investigate the electrical, chemical, and structural properties of the TiO2/graphene oxide composition exposed to UV irradiation. X-ray photoelectron spectroscopy showed that after effective photocatalytic reduction of the graphene oxide sheets by the TiO2 nanoparticles in ethanol, the carbon content of the reduced graphene oxides gradually decreased by increasing the irradiation time, while no considerable variation was detected in the reduction level of the reduced sheets. Raman spectroscopy indicated that, at first, the photocatalytic...
DC to 40-GHz compact single-layer crossover
, Article IEEE Microwave and Wireless Components Letters ; Volume 28, Issue 8 , 2018 , Pages 642-644 ; 15311309 (ISSN) ; Fakharzadeh, M ; Mehrany, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
In this letter, a compact, wideband, and fully planar microstrip crossover structure is proposed. This design is based on a compact microstrip to coplanar waveguide transition, which has a measured bandwidth extending from dc to 40 GHz. At 20 GHz, the measured insertion loss, return loss, and isolation are better than 0.35, 21, and 19 dB, respectively. This circuit is ultracompact with the core size of 3 mm ×3 mm, which is 0.2λ×0.2 λ at 20 GHz. © 2012 IEEE
Nanoscale vibrational behavior of single-layered graphene sheets
, Article ASME 2007 International Mechanical Engineering Congress and Exposition, IMECE 2007, 11 November 2007 through 15 November 2007 ; Volume 11 , 2007 , Pages 229-235 ; 079184305X (ISBN) ; Ahmadian, M. T ; Vafai, A ; ASME ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2007
Abstract
Molecular structural mechanics approach is implemented to investigate vibrational behavior of single-layered graphene sheets. By using the atomistic modeling, mode shapes and natural frequencies are obtained. Vibration analysis is performed under different chirality and boundary conditions. Numerical results from the finite element technique are applied to develop empirical equations via a statistical multiple nonlinear regression model. With the proposed empirical equations, fundamental frequencies of single-layered graphene sheets under considered boundary conditions can be predicted within 3 percent accuracy. Copyright © 2007 by ASME
Enhanced X-band wave dissipation performance in bilayer absorber composed of bare epoxy resin and epoxy resin filled with [CaTiO3/ZnFe2O4]@C nanocomposite
, Article Journal of Magnetism and Magnetic Materials ; Volume 539 , 2021 ; 03048853 (ISSN) ; Elveny, M ; Niaz Akhtar, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
In this study, a novel idea was utilized for designing high performance bilayer absorber for X-band frequency. The microwave dissipation features of the bilayer structure absorbers with one-layer bare resin epoxy and the other epoxy resin filled with [CaTiO3/ZnFe2O4]@C nanocomposite as lossy filler were simulated with CST studio suite within 2–18 GHz. The lossy filler was successfully developed via chemical method. In the first step two distinct single layer absorbers of bare resin epoxy and resin epoxy filled with [CaTiO3/ZnFe2O4]@C nanocomposite ([CT/ZF]@C) were prepared and in the second step the measured electromagnetic parameters were considered as input data of CST studio suite for...
Electromagnetic performance, optical and physiochemical features of CaTiO3/NiO and SrFe12O19/NiO nanocomposites based bilayer absorber
, Article Journal of Colloid and Interface Science ; 2021 ; 00219797 (ISSN) ; Liu, J ; Huynen, I ; Mahmoud, M. Z ; Niaz Akhtar, M ; Sharif University of Technology
Academic Press Inc
2021
Abstract
Herein, two distinct nanocomposites of CaTiO3 micro-cubes and polygonal SrFe12O19, both decorated with NiO nanoparticles, were successfully synthesized using hydrothermal method. The physico-chemical features of as-prepared samples were evaluated via XRD, FTIR, UV–vis, BET, XPS, FESEM and EDS analysis. Microwave attenuation features of as-prepared single layer absorbers were determined by VNA analysis in 2–18 GHz. Simulation confirmation was checked by preparing a bi-layer samples and evaluating it using VNA analysis after finding the appropriate thickness of each layer. The reflection loss from each single layer samples containing 20 wt% of each CaTiO3/NiO and SrFe12O19/NiO nanocomposites...
Development of high-efficient double layer microwave absorber based on Fe3O4/carbon fiber and Fe3O4/rGO
, Article Journal of Magnetism and Magnetic Materials ; Volume 537 , 2021 ; 03048853 (ISSN) ; Niaz Akhtar, M ; Boudaghi, R ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Recently, preparation of lightweight absorbers with high performance capability are urgently needed for practical demanded in order to solve the severe electromagnetic pollution. In the present study, two different composites (Fe3O4/carbon fiber and Fe3O4/rGO) were uniformly incorporated into resin epoxy matrix to obtain single and double layer X-band absorber with 20 wt% filler loading. Each of the composites were prepared via solvothermal process. According to the results, the minimum reflection loss values for each single layer Fe3O4/carbon fiber and Fe3O4/rGO absorber were −15 dB (3 mm thickness and 1.5 GHz bandwidth) and −50 dB (3 mm thickness and 4 GHz bandwidth) respectively. By...
The effect of nanopores geometry on desalination of single-layer graphene-based membranes: A molecular dynamics study
, Article Journal of Molecular Liquids ; Volume 339 , 2021 ; 01677322 (ISSN) ; Chogani, A ; Shariat, M ; Moosavi, A ; Kariminasab, H ; Sharif University of Technology
Elsevier B.V
2021
Abstract
The water desalination process using nanoporous single-layer graphene membranes is simulated through classical molecular dynamics. The effect of nanopores shapes on the capacity of the membrane for filtration of water is investigated. According to the results, the geometry of the nanopores considerably affects the performance of the membrane and can completely change the water flow rate and salt rejection. The results reveal that the effective area of the nanopores plays a critical role and for a better understanding of the impact of this parameter, aspect ratio and the equal diameter of noncircular pores based on different methods such as equal area, equal perimeter, and hydraulic diameter...
Atomistic simulations of mechanical properties and fracture of graphene: A review
, Article Computational Materials Science ; Volume 210 , 2022 ; 09270256 (ISSN) ; Kouchakzadeh, M. A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Material properties and fracture characteristics are among the most prominent parameters that should be considered for a wide range of graphene applications. This article reviews recent advances in theoretical studies on the mechanical properties and fracture behaviors of graphene, focusing on the effect of various simulation models. Most studies investigated single-layer graphene sheets (SLGSs) under uniaxial tensile tests using different common interatomic potentials, particularly AIREBO. Although researchers have examined a similar problem, specifically for pristine graphene, the differences in the reported values are considerable. These discrepancies are most evident in fracture...
Experimental studies on the effects of placement method and packing density of cubic armour units on the stability of low-crested breakwaters
, Article Ocean Engineering ; Volume 266 , 2022 ; 00298018 (ISSN) ; Pak, A ; Aliasgary, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Although concrete armour units have traditionally been used in two layers, the application of single-layer armour has attracted more attention in recent years because of its lower concrete volume and faster construction pace. Single-layer amour relies mainly on the contact between units to provide stability; however, installation of special armour types with surface projections for better interlocking, increases the possibility of breakage. During the last decade the idea of using bulky armour units such as cubes has been raised, and the application of these single-layer armour units has become common for high-crested breakwaters. However, the application of cube armours for low-crested...
Stress Analysis of in Cross-ply Laminates in Bending
, M.Sc. Thesis Sharif University of Technology ; Nosier, Asghar (Supervisor)
Abstract
In the present study, an analytical solution is developed to calculate the interlaminar stresses in long generally cross-ply laminated composite plates subjected to bending. At first, upon the integration of the strain-displacement relations and using the existing patterns in deformation of the long laminate, the general displacement field is extracted and simplified to the final form. Presented solution is based on a combined method containing the equivalent single-layer (ESL) theories beside the Reddy’s layerwise theory. In this method, the equivalent single-layer theories are utilized because of their simplicity and low computational efforts rather than the layerwise theory in evaluation...
Temperature-Dependent Multiscale Simulation of Single Layer Graphene Sheet in Large Deformation
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor) ; Jahanshahi, Mohsen (Co-Advisor)
Abstract
In this study, two multiscale hierarchical atomisyic/molecular dynamics (MD)–finite element (FE) coupling methods are proposed to illustrate the influence of temperature on mechanical properties of SLGS in large deformation. The Tersoff interatomic potential is implemented, in addition, the Nose-Hoover thermostat and local harmonic approximation are employed to adjust the fluctuation of temperature in CB and MD, respectively. The atomic nonlinear elastic parameters are obtained via computing second-order derivative of Representative atom’s energy and RVE’s strain energy density with respect to deformation criterions (deformation gradient and Green strain tensor). To bridge between atomistic...
Numerical Modelling of Armour Layer Stability in Low-crested Breakwaters Using Smoothed Particle Hydrodynamics (SPH) and Discrete Element Method (DEM)
, Ph.D. Dissertation Sharif University of Technology ; Pak, Ali (Supervisor)
Abstract
Rubble mound low-crested breakwaters protect the structures and ships in the port against wave attacks. Due to the overtopping, these structures provide a more attractive landscape and helps preserve the port's environment. Stability of low-crested breakwaters relies on the stability of the armor layer against the wave action, requiring the choice of the appropriate diameter for the armour blocks. For cubic armours that are of interest to the designers, there is currently no design relationship, and they inevitably use formulae specified for high-crested breakwaters that may not be in the safe side. The conventional method for determining the required armour diameter for a breakwater is...
Probabilistic Evaluation of Nonlinear Behavior of Fixed- and Flexible-Base Shear Buildings
, M.Sc. Thesis Sharif University of Technology ; Ghannad, Mohammad Ali (Supervisor) ; Mahsoli, Mojtaba (Supervisor)
Abstract
This thesis revisits the effect of dynamic soil-structure interaction (SSI) on multistory buildings with a probabilistic approach. For this purpose, the relationship between the strength demands of fixed- and flexible-base multi-degree-of-freedom (MDOF) systems, or strength reduction factor thereof, with that of fixed- and flexible-base equivalent single-degree-of-freedom (eSDOF) systems is investigated considering prevailing uncertainties. To this end, Monte Carlo sampling analysis is employed in which a suite of nearly 2000 records are utilized to properly quantify the ground motion uncertainty. The soil-structure system is modeled by the sub-structure method. The uncertainty in the...
Genotoxicity of graphene nanoribbons in human mesenchymal stem cells
, Article Carbon ; Volume 54 , 2013 , Pages 419-431 ; 00086223 (ISSN) ; Ghaderi, E ; Emamy, H ; Akhavan, F ; Sharif University of Technology
2013
Abstract
Single-layer reduced graphene oxide nanoribbons (rGONRs) were obtained through an oxidative unzipping of multi-walled carbon nanotubes and a subsequent deoxygenation by hydrazine and bovine serum albumin. Human mesenchymal stem cells (hMSCs) were isolated from umbilical cord blood and used for checking the concentration- and time-dependent cyto- and geno-toxic effects of the rGONRs and reduced graphene oxide sheets (rGOSs). The cell viability assay indicated significant cytotoxic effects of 10 μg/mL rGONRs after 1 h exposure time, while the rGOSs exhibited the same cytotoxicity at concentration of 100 μg/mL after 96 h. The oxidative stress was found as the main mechanism involved in the...
Out-of-plane stresses in composite shell panels: Layerwise and elasticity solutions
, Article Acta Mechanica ; Volume 220, Issue 1-4 , 2011 , Pages 15-32 ; 00015970 (ISSN) ; Nosier, A ; Sharif University of Technology
Abstract
Boundary-layer effects in lengthy cross-ply laminated circular cylindrical shell panels under uniform axial extension are investigated by two analytical solutions. First, Reddy's layerwise theory with state-space approach is utilized to determine the local interlaminar stresses. In this method, the general displacement field is discretized through the shell thickness by a linear shape function. When the shell panel is subjected to an axial force, the axial strain is estimated by an equivalent single-layer theory. Second, the stress-function approach along with Fourier series expansion is applied to develop a novel elasticity solution. The elasticity solution, which is based on simply-support...
Photocatalytic reduction of graphene oxides hybridized by ZnO nanoparticles in ethanol
, Article Carbon ; Volume 49, Issue 1 , January , 2011 , Pages 11-18 ; 00086223 (ISSN) ; Sharif University of Technology
2011
Abstract
Graphene oxide platelets synthesized by using a chemical exfoliation method were dispersed in a suspension of ZnO nanoparticles to fabricate ZnO/graphene oxide composite. Formation of graphene oxide platelets (with average thickness of ∼0.8 nm) hybridized by ZnO nanoparticles (with average diameter of ∼20 nm) was investigated. The 2D band in Raman spectrum confirmed formation of single-layer graphene oxides. The gradual photocatalytic reduction of the graphene oxide sheets in the ZnO/graphene oxide suspension of ethanol was studied by using X-ray photoelectron spectroscopy for different ultra violet (UV)-visible irradiation times. After 2 h irradiation, the relative concentration of the...
Nonlinear vibrational analysis of single-layer graphene sheets
, Article Nanotechnology ; Volume 21, Issue 10 , 2010 ; 09574484 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
2010
Abstract
Recent experiments have shown the applicability of single-layer graphene sheets (SLGSs) as electromechanical resonators. Existing theoretical models, based on linear continuum or atomistic methods, are limited to the study of linear vibrations of SLGSs. Here we introduce a hybrid atomistic-structural element which is capable of modelling nonlinear behaviour of graphene sheets. This hybrid element is based on an empirical inter-atomic potential function and can model the nonlinear dynamic response of SLGSs. Using this element, nonlinear vibrational analysis of SLGSs is performed. It is shown that the nonlinear vibrational analysis of SLGSs predicts significantly higher fundamental...
The effect of heat treatment on formation of graphene thin films from graphene oxide nanosheets
, Article Carbon ; Volume 48, Issue 2 , February , 2010 , Pages 509-519 ; 00086223 (ISSN) ; Sharif University of Technology
2010
Abstract
Graphene thin films with very low concentration of oxygen-containing functional groups were produced by reduction of graphene oxide nanosheets (prepared by using a chemical exfoliation) in a reducing environment and using two different heat treatment procedures (called one and two-step heat treatment procedures). The effects of heat treatment procedure and temperature on thickness variation of graphene platelets and also on reduction of the oxygen-containing functional groups of the graphene oxide nanosheets were studied by atomic force microscopy and X-ray photoelectron spectroscopy. While formation of the thin films composed of single-layer graphene nanosheets with minimum thickness of...
Free vibration analysis of rotating laminated cylindrical shells under different boundary conditions using a combination of the layerwise theory and wave propagation approach
, Article Scientia Iranica ; Volume 16, Issue 2 B , 2009 , Pages 168-176 ; 10263098 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
2009
Abstract
In this paper, vibration analysis of rotating laminated composite cylindrical shells using a combination of the layerwise theory and wave propagation approach is investigated. This combination enables us to study all the conventional boundary conditions in our analysis. Results obtained have been compared with those available in the literature and a good agreement has been observed. In contrast to the Equivalent Single Layer theories (ESL), the layerwise theory is constructed on the basis ofC°- continuity through the laminate thickness. For the surface of the shell, a displacement field based on the wave propagation approach is proposed. The effect of Coriolis and centrifugal accelerations...