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structured-surfaces
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Multifunctional hyperelastic structured surface for tunable and switchable transparency
, Article Applied Sciences (Switzerland) ; Volume 11, Issue 5 , 2021 , Pages 1-11 ; 20763417 (ISSN) ; Goudarzi, T ; Fleury, R ; Naghdabadi, R ; Sharif University of Technology
MDPI AG
2021
Abstract
We leverage the crucial hyperelastic properties of a multifunctional structured surface to optimize the reconfigurability of the electromagnetic transmission under large nonlinear mechanical deformations. This multiphysics, multifunctional, hyperelastic structured surface (HSS) offers two simultaneous intriguing functionalities; tunability and switchability. It is made of copper reso-nators and a Polydimethylsiloxane (PDMS) substrate, which is one of the most favorable deformable substrates due to its hyperelastic behavior. The proposed HSS is fabricated via an original cost-effective technique and the multiphysics functionalities are captured in both experimental tests and numerical...
Aerodynamic and Aeroacoustic performance of a wing with structured surface inspired by owl’s wings
, Article Journal of Applied Fluid Mechanics ; Volume 15, Issue 4 , 2022 , Pages 1243-1253 ; 17353572 (ISSN) ; Taeibi Rahni, M ; Zareh, M ; Ahmadi, G ; Etemadi Haghighi, S ; Sharif University of Technology
Isfahan University of Technology
2022
Abstract
With the advent of various advanced materials, the idea of flying like birds has attracted considerable attention in recent years. In addition, aeroacoustics has become an important issue and is being widely studied. In this work, based on the shape of Owls’ wings, an attempt was made to improve the aeroacoustic and aerodynamic performances of conventional aircraft wings. For this purpose, wings with different elements, namely, square, triangular, and semicircular, on their top surface were examined. In addition, three different spatial distributions of the elements according to the Owl’s wings shape were considered. For incompressible airflow, aerodynamic and aeroacoustic parameters of wing...
Morphology of nanodroplets on structured surfaces
, Article Journal of Physics D: Applied Physics ; Volume 46, Issue 21 , May , 2013 ; 00223727 (ISSN) ; Moosavi, A ; Sharif University of Technology
2013
Abstract
We report different morphologies of nanodroplets over various topographical features of the supporting substrates. The effects of different parameters such as the profile of the disjoining pressure, droplet size and the geometrical parameters are studied and discussed. Also, the effects of a coating layer on the surface of the substrate are determined. It is demonstrated that the nanodroplets at some positions are not stable and gradually move to more stable positions so that the system has less energy. For grooves this results in a series of morphology diagrams of the nanodroplets over the grooves as a function of the grooves' width and the liquid volume
Influence of Au thickness on the performance of plasmonic enhanced hematite photoanodes
, Article RSC Advances ; Volume 3, Issue 39 , 2013 , Pages 17837-17842 ; 20462069 (ISSN) ; Kikhavani, M. R ; Sheshyekani, K ; Dabirian, A ; Sharif University of Technology
2013
Abstract
The surface plasmon effect of Au nanostructures placed on the surface of hematite has recently been used to enhance light absorption within its carrier collection distance of 10 nm from the water-hematite interface. Despite significant narrow band absorption enhancements in the visible region, the reported enhancements in the overall performance of the cell under standard AM1.5 sunlight illumination are not significant. We numerically design an array of Au stripes on the surface of an extremely thin layer of hematite to maximize the number of charge carriers that can reach the hematite-water interface and explore the optical processes involved. The lateral dimensions and in particular the...
Heat transfer on topographically structured surfaces for power law fluids
, Article International Journal of Heat and Mass Transfer ; Volume 121 , 2018 , Pages 857-871 ; 00179310 (ISSN) ; Moosavi, A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
The three-dimensional power law fluid flow through rough microchannels has been studied numerically to determine the effects of the topographic structures on the thermal and hydrodynamic characteristics of the system. Rectangular, triangular and sinusoidal element shapes have been considered in order to investigate the effects of roughness height, width, pitch and channel separation on the pressure drop and heat transfer. Uniform wall heat flux boundary condition has been applied for all the peripheral walls. The results indicate that the global heat transfer performance can be improved or reduced by the roughness elements at the expense of pressure head when compared with the smooth...
Multiscale Multiphysics Analysis of Deformable Microwave Metasurfaces Under Large Deformations and Prototype Fabrication
, Ph.D. Dissertation Sharif University of Technology ; Naghdabadi, Reza (Supervisor) ; Sohrabpour, Saeed (Supervisor) ; Goudarzi, Taha (Co-Supervisor)
Abstract
Electromagnetic metamaterials are designed artificial materials with sub-wavelength resonant inclusions. They can exhibit extraordinary properties such as negative permittivity, negative permeability, and anomalous reflection/refraction. Metasurfaces are 2D counterparts of metamaterials. Here, we proposed a framework for the multiscale multiphysics analysis of deformable metasurfaces. Nonlinear mechanical analysis (Geometry and material behavior), periodic boundary conditions, homogenization, multiscale analysis, and electromagnetic analysis are implemented in this framework. Benefiting from the framework, we proposed a multifunctional hyperelastic structured surface that can generate...
Design and physicochemical characterization of lysozyme loaded niosomal formulations as a new controlled delivery system
, Article Pharmaceutical Chemistry Journal ; Volume 53, Issue 10 , 2020 , Pages 921-930 ; Ehsani, P ; Cohan, R. A ; Sardari, S ; Akbarzadeh, I ; Bakhshandeh, H ; Norouzian, D ; Sharif University of Technology
Springer
2020
Abstract
Lysozyme loaded niosomes containing various molar ratios of two kinds of surfactants were prepared and the properties of these niosomal formulations were studied. The results revealed that the size of niosomes varied between 240.06 ± 32.41 and 895.2 ± 20.84 nm. Formulations with the lowest size and no precipitation had entrapment efficiencies ranging from 60.644 ± 3.310 to 66.333 ± 1.98%. Their controlled release profiles after 48 h were 15.67, 20.67 and 31.50%. After 2 months, the most stable formulation in terms of size, PDI, zeta potential, and entrapment efficiency was used to study the secondary structures of lysozyme in niosomal and free forms. Lysozyme loaded niosome and lysozyme...
Influence of new superhydrophobic micro-structures on delaying ice formation
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 595 , 2020 ; Taeibi Rahni, M ; Javadi, K ; Davoudian, S. H ; Miller, R ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Drop motion on different types of new proposed micro-structure surfaces has been numerically investigated to find the optimum structure in view point of ice formation delaying. The droplet automatically moves on the inclined surfaces due to gravity forces. To validate the numerical algorithm, three different bench mark problems have been considered. The results indicate that the present algorithm is trustable for the presented numerical simulations. Then the validated numerical approach has been used to simulate droplet motion on nine proposed superhydrophobic surfaces in the same conditions. Comparison the drop motion on different micro-structure surfaces at different time indicate that...
A three dimensional simulation of spray cooling and its evaporating liquid film generated on patterned surfaces
, Article International Journal of Multiphase Flow ; Volume 155 , 2022 ; 03019322 (ISSN) ; Jowkar, S ; Morad, M. R ; Shen, X ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Liquid impingement cooling in the form of jet or spray is an appropriate method to remove heat from small surfaces progressively utilized in industry. In this study, numerical simulations are conducted to investigate the effect of surface structure on heat transfer characteristics. Five different three-dimensional structured surfaces are investigated using Euler-Lagrangian approach. The effect of surface structures is discussed on the liquid film thickness, the liquid film velocity, and the heat flux with its uniformity for a given spray and temperature characteristics. The results show that the convective heat transfer strongly depends on both liquid film thickness and velocity. While the...
Operation of an opto-mechanical scanning system for surface profiling using a plastic double-fiber probe
, Article POF 2011: 20th International Conference on Plastic Optical Fibers - Conference Proceeding ; 2011 , Pages 459-464 ; Knowledge Development for POF; POF Application Center; Sojitz Corporation; Hamamatsu Photonics; Optogear ; Sharif University of Technology
Abstract
Operation of an optical system for surface profiling is reported here. Reflection signals for the plane and cylindrical surfaces with different materials are reported. To investigate the precision and sensitivity of the reported system the reflection results of the curved and flat structured surface are compared with that of a structure-free surface. Reported system provides a simple and accurate means for the object shape study through the optical reflection measurements
Electrowetting-induced droplet jumping over topographically structured surfaces
, Article Materials Research Express ; Volume 6, Issue 8 , 2019 ; 20531591 (ISSN) ; Moosavi, A ; Shafii, M. B ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
We analyze the process of electrowetting-induced jumping of droplets away from a substrate with a geometric heterogeneity in the form of a cone and compare the results with those of a flat substrate in different wettabilities and hydrophobicities. Our results reveal that the droplet dynamics can be enhanced through applying a topographic heterogeneity. However, increasing the height of the cones does not always provide a better condition for the jumping and there is an optimum value for the height of the cones. The enhancement is due to the fact that more liquid flowing affects the pressure gradient within the droplet leading to a higher jumping velocity. It is shown that for the flat...
Plasma nitriding of gradient structured AISI 304 at low temperature: Shot peening as a catalyst treatment
, Article Vacuum ; Volume 164 , 2019 , Pages 194-197 ; 0042207X (ISSN) ; Maleki, E ; Varol, R ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This study involves the capability of severe shot peening (SSP) as a catalyst intake for plasma nitriding process and the probability of reducing the requirement of thermal energy individually on the diffusion of interstitial atoms. To this end, combination of mechanical-thermal energy is run with pure thermal plasma assisted energy. Therefore, SSP is exposed to AISI 304 austenitic stainless steel as a former treatment and gradient structured surface (nanograined zone, ultrafine grain martensite-twin intersections zone and twin densed zone) is created. Then, plasma nitriding at 400 0 C-4h and 475 0 C-2h temperature-duration conditions. The condition of 475 0 C-2h provides the requirements of...
Surface electromagnetic waves supported by nano conducting layers with inhomogeneities in the conductivity profile
, Article Optical and Quantum Electronics ; Volume 40, Issue 1 , 2008 , Pages 23-40 ; 03068919 (ISSN) ; Mehrany, K ; Sharif University of Technology
2008
Abstract
Conducting interfaces and nano conducting layers can support surface electromagnetic waves. Uniform charge layers of non-zero thickness and their asymptotic behavior toward conducting interfaces of infinitely small thicknesses, where the thin charge layer is modeled via a surface conductivity σ s , are already studied. Here, the possible effects of inhomogeneity in the conductivity profile of the thin conducting layers are investigated for the first time and a new approximate yet accurate enough analytical formulation for mode extraction in such structures is given. In order to rigorously analyze the structure and justify the proposed approximate formulation, the Galerkin's method with...
Design and operation of a double-fiber scanning system for surface profiling
, Article Optics and Lasers in Engineering ; Volume 49, Issue 8 , 2011 , Pages 1032-1039 ; 01438166 (ISSN) ; Sharif University of Technology
2011
Abstract
Design and operation of an opto-mechanical system for surface profiling are reported in this study. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In this arrangement one fiber transmits the source light to the object surface and the second one transmits the light reflected off the surface to a photodetector. By scanning the double-fiber assembly in one-direction, reflection properties of different curved surfaces are investigated. Reflection signals for the cylindrical surfaces made with different curvatures and materials are reported. In order to see the effect of the surface material, for a fixed radius cylinder, the surface is...
Improved fourier analysis of periodically patterned graphene sheets embedded in multilayered structures and its application to the design of a broadband tunable wide-angle polarizer
, Article IEEE Journal of Quantum Electronics ; Volume 53, Issue 3 , 2017 ; 00189197 (ISSN) ; Borji, A ; Zeidaabadi Nezhad, A ; Shahabadi, M ; Sharif University of Technology
Abstract
Numerical modeling of periodically patterned graphene sheets (PPGS) embedded in planar multilayered media using Fourier-based methods suffers from very slow convergence because of the fact that the conductivity is zero in unfilled areas of the patterned surface and, thus, the so-called Li's inverse rule is not applicable. In this paper, a simple and efficient approach is proposed to overcome this problem such that the exact boundary condition can be applied and the surface current density on PPGS can be obtained accurately. Here, the PPGS is modeled as a conductive surface and only its conductivity representation by the Fourier series is modified. The proposed method can be used easily for...
Electrodeposition of nanocrystalline Zn/Ni multilayer coatings from single bath: influences of deposition current densities and number of layers on characteristics of deposits
, Article Applied Surface Science ; Volume 404 , 2017 , Pages 101-109 ; 01694332 (ISSN) ; Ghorbani, M ; Lotfi Kordkolaei, N ; Sharif University of Technology
Abstract
Zn/Ni nanocrystalline multilayer coatings were electrodeposited using single bath method and switching current densities. Effect of deposition current densities (i1 and i2) and number of layers (n) on composition, surface morphology and roughness, microhardness, phase structure and corrosion resistance of Zn/Ni multilayers were studied and compared with that of single layer. Analyzing and optimizing the influences of mentioned parameters on corrosion resistance of multilayers carried out through Response Surface Methodology. The model based on RSM results demonstrated that improvement in corrosion resistance due to increase in “difference of deposition current densities” was more effective...
Physical bounds of metallic nanofingers obtained by mechano-chemical atomic force microscope nanolithography
, Article Applied Surface Science ; Volume 255, Issue 6 , January , 2009 , Pages 3513-3517 ; 01694332 (ISSN) ; Abdolahad, M ; Sharif University of Technology
2009
Abstract
To obtain metallic nanofingers applicable in surface acoustic wave (SAW) sensors, a mechano-chemical atomic force microscope (AFM) nanolithography on a metallic thin film (50 nm in thickness)/piezoelectric substrate covered by a spin-coated polymeric mask layer (50-60 nm in thickness) was implemented. The effective shape of cross-section of the before and after etching grooves have been determined by using the AFM tip deconvolution surface analysis, structure factor, and power spectral density analyses. The wet-etching process improved the shape and aspect ratio (height/width) of the grooves and also smoothed the surface within them. We have shown that the relaxed surface tension of the...
A Rapid synthesis of vertically aligned taper-like k-doped zno nanostructures to enhance dye-sensitized solar cell efficiency
, Article JOM ; Volume 71, Issue 12 , 2019 , Pages 4850-4856 ; 10474838 (ISSN) ; Musavi, M ; Nanchian, H ; Pezeshkzadeh, S. A ; Sharif University of Technology
Springer
2019
Abstract
Large-scale K-doped ZnO nanotapers were successfully grown on an indium tin oxide (ITO) substrate using a facile electrochemical route. The structural and morphologic analysis exhibited that the K-doped ZnO nanostructures had a nanotaper morphology and strong preferential [0001] c-axis direction with a hexagonal polycrystalline structure. The optical results show that the incorporation of K+ ions as the donors in a ZnO lattice leads to substantial modulation of the band gap structure of ZnO nanotapers, which results in a redshift in the ultraviolet emission peaks. The considerable enhancement of performance in K-doped ZnO-based dye-sensitized solar cells (DSSCs) can be related to the doping...
Optimization of microgrooves for water–solid drag reduction using genetic algorithm
, Article Journal of Ocean Engineering and Marine Energy ; Volume 6, Issue 3 , 2020 , Pages 221-242 ; Moosavi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2020
Abstract
The friction on the water–solid interfaces continues to be the most important factor for the energy loss in many marine and submarine applications. Therefore, different techniques have been developed and are available to reduce friction and, as a result, the overall cost. In the past decades, the use of structured surfaces has been given considerable attention because of their specific characteristics such as their abilities in pressure drop reduction. However, an appropriate optimization method is required to find the best surface structure. In the present study, we consider a microgrooved substrate and examine the performance of three shapes including rectangular, elliptical, and...
Nonlinear frequency conversions via weak surface polaritonic wave breaking in a hybrid plasmonic waveguide
, Article Optics Letters ; Volume 45, Issue 19 , 2020 , Pages 5432-5435 ; Sanders, B. C ; Sharif University of Technology
OSA - The Optical Society
2020
Abstract
Material design and input field properties limit high-harmonic excitation efficiency of surface-plasmon polaritons (SPPs) in a nanoscopic device. We remedy these limitations by developing a concept for a plasmonic waveguide that exploits spatiotemporal control of a weak surface polaritonic field to create efficient four-wave mixing (FWM) and periodic phase singularities. Our configuration comprises four-level double 3-type atomic medium (43 As) doped in a lossless dielectric situated above a negative-index metamaterial (NIMM) layer. We report the coherent excitation and propagation of the multiple surface polaritonic shock waves (SWs) and establish the highly efficient frequency combs by...