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A general treatment of piezoelectric double-inhomogeneities and their associated interaction problems
, Article Acta Mechanica ; Volume 220, Issue 1-4 , 2011 , Pages 167-182 ; 00015970 (ISSN) ; Shodja, H. M ; Hashemi, R ; Sharif University of Technology
2011
Abstract
The present paper addresses an analytical method to determine the electroelastic fields over a double-phase piezoelectric reinforcement interacting with an ellipsoidal single-inhomogeneity. The approach is based on the extension of the electro-mechanical equivalent inclusion method (EMEIM) to the piezoelectric double-inhomogeneity system. Accordingly, the double-inhomogeneity is replaced by an electroelastic double-inclusion problem with proper polynomial eigenstrains-electric fields. The long- and short-range interaction effects are intrinsically incorporated by the homogenizing eigenfields. The equivalent double-inclusion is subsequently decomposed to the single-inclusion problems by means...
Photonic design of embedded dielectric scatterers for dye sensitized solar cells
, Article RSC Advances ; Volume 5, Issue 42 , Mar , 2015 , Pages 33098-33104 ; 20462069 (ISSN) ; Dabirian, A ; Nemati Kharat, A ; Taghavinia, N ; Sharif University of Technology
Abstract
Embedded dielectric scatterers comprise an important approach for light trapping in dye-sensitized solar cells (DSCs) due to their simple fabrication process. The challenge in applying these scatterers lies in finding the optimal dimensions and concentration of the scatterers. This requires many experiments and it is often quite difficult to have a starting point for optimizing the concentration. Based on theories of light propagation in random media, we propose a simple model for DSCs with embedded silica spherical particles. Then, by full-wave optical calculations, we determine a narrow range for the concentration of silica particles that leads to the largest optical absorption in the...
Extended gibbs free energy and laplace pressure of ordered hexagonal close-packed spherical particles: A wettability study
, Article Langmuir ; Volume 37, Issue 28 , 2021 , Pages 8382-8392 ; 07437463 (ISSN) ; Ebrahimi, M ; Rahemi Ardekani, S ; Saievar Iranizad, E ; Zaker Moshfegh, A ; Sharif University of Technology
American Chemical Society
2021
Abstract
The wetting property of spherical particles in a hexagonal close-packed (HCP) ordering from extended Gibbs free energy (GFE) and Laplace pressure view points is studied. A formalism is proposed to predict the contact angle (θ) of a droplet on the HCP films and penetration angle (α) of the liquid on the spherical particles. Then, the extended Laplace pressure for the layered HCP ordering is calculated and a correlation between the wetting angle, sign of pressure, and pressure gradient is achieved. Our results show that the sign and the slope of pressure are important criteria for determining the wettability state and it is found that the contact angle is independent of the particle radius, as...
Development of nanostructured porous TiO2 thick film with uniform spherical particles by a new polymeric gel process for dye-sensitized solar cell applications
, Article Electrochimica Acta ; Volume 89 , February , 2013 , Pages 90-97 ; 00134686 (ISSN) ; Mohammadi, M. R ; Sharif University of Technology
2013
Abstract
A novel simple synthetic procedure for fabrication of high surface area nanostructured TiO2 electrode with uniform particles for photovoltaic application is reported. Modifying the TiO2 particulate sol by pH adjustment together with employment of a polymeric agent, so-called polymeric gel process, was developed. The polymeric gel process was used to deposit nanostructured thick electrode by dip coating incorporated in dye-sensitized solar cells (DSSCs). X-ray diffraction (XRD) analysis revealed that deposited film was composed of primary nanoparticles with average crystallite size in the range 21-39 nm. Field emission scanning electron microscope (FE-SEM) images showed that deposited film...
Investigation of segregation of large particles in a pressurized fluidized bed with a high velocity gas: A discrete particle simulation
, Article Powder Technology ; Volume 246 , September , 2013 , Pages 398-412 ; 00325910 (ISSN) ; Hosseini, S. A ; Soleimani, R ; Sharif University of Technology
2013
Abstract
A numerical study on mixing/segregation phenomena in a pressurized fluidized bed with large particles of Geldart D type of binary density but same diameter with high velocity gas was performed by the use of discrete particle simulation. Particle mixtures are composed of spherical particles with 2mm diameter and 1g/cm3 flotsam density and different jetsam densities of 1.25, 2 and 2.5g/cm3 with jetsam volume fraction of 0.5. The particles are initially packed approaching perfect mixing state in a rectangular bed and then fluidized by gas uniformly injected at the bottom of the bed. Effect of increase of pressure and density ratio was investigated and mixing/segregation behavior is discussed in...
Long-lived and unstable modes of Brownian suspensions in microchannels
, Article Journal of Fluid Mechanics ; Volume 701 , 2012 , Pages 407-418 ; 00221120 (ISSN) ; Jalali, M. A ; Sharif University of Technology
2012
Abstract
We investigate the stability of the pressure-driven, low-Reynolds-number flow of Brownian suspensions with spherical particles in microchannels. We find two general families of stable/unstable modes: (i) degenerate modes with symmetric and antisymmetric patterns; (ii) single modes that are either symmetric or antisymmetric. The concentration profiles of degenerate modes have strong peaks near the channel walls, while single modes diminish there. Once excited, both families would be detectable through high-speed imaging. We find that unstable modes occur in concentrated suspensions whose velocity profiles are sufficiently flattened near the channel centreline. The patterns of growing unstable...
Polypyrrole nanowires network for convenient and highly efficient microextraction in packed syringe
, Article Analytical Methods ; Volume 3, Issue 11 , 2011 , Pages 2630-2636 ; 17599660 (ISSN) ; Ayazi, Z ; Sharif University of Technology
Abstract
A novel method based on microextraction in packed syringe (MEPS), as a sample preparation technique in combination with gas chromatography-mass spectrometry (GC-MS) was developed using a polypyrrole (PPy) nanowires network as the extracting medium. The PPy nanowires network was prepared using a soft template technique and its characterization was studied by scanning electron microscopy (SEM). The use of micelles in this methodology has an important role in the shape of the growing polymer. The pyrrole monomer was introduced into cetyltrimethylammonium bromide (CTAB) micelles and this has led to the formation of nanowires with diameters ranging from 30 to 60 nm. The bulk PPy prepared without...
Guided mode extraction in monolayer colloidal crystals based on the phase variation of reflection and transmission coefficients
, Article Optics Communications ; Volume 364 , 2016 , Pages 44-49 ; 00304018 (ISSN) ; Akbari, M ; Khavasi, A ; Sharif University of Technology
Elsevier
Abstract
An accurate and fast method for guided modes extraction in monolayer colloidal crystals and their inverse replicas is presented. These three-dimensional structures are composed of a monolayer of spherical particles that can easily and simply be prepared by self-assembly method in close packed hexagonal lattices. In this work, we describe how the guided modes, even or odd modes and light cone boundary can be easily determined using phase variations of reflection and transmission coefficients. These coefficients are quickly calculated by Fourier modal method. The band structures are obtained for a monolayer of polystyrene particles and two-dimensional TiO2 inverse opal by this proposed method
Strain energy-based homogenization of nonlinear elastic particulate composites
, Article International Journal of Engineering Science ; Volume 47, Issue 10 , 2009 , Pages 1038-1048 ; 00207225 (ISSN) ; Naghdabadi, R ; Sharif University of Technology
2009
Abstract
The macroscopic constitutive law for a heterogeneous solid containing two dissimilar nonlinear elastic phases undergoing finite deformation is obtained. Attention is restricted to the case of spherical symmetry such that only the materials consisting of an irregular suspension of perfectly spherical particles experiencing all-round uniform loading are considered which leads to a one-dimensional modeling. For the homogenization procedure, a strain-energy based scheme which utilizes Hashin's composite sphere is employed to obtain the macroscopic stress-deformation relation added by the initial volume fraction of the particles. As applications of the procedure, the closed-form macroscopic...
Images of finite sized spherical particles in confocal and conventional microscopes when illuminated with arbitrary polarization
, Article Applied Optics ; Volume 47, Issue 3 , 2008 , Pages 453-458 ; 1559128X (ISSN) ; Massoumian, F ; Sharif University of Technology
OSA - The Optical Society
2008
Abstract
We investigate the form of the image of a finite sized spherical particle in confocal and conventional microscopes when the illuminating light has an arbitrary polarization. In particular, we take the cases of radial and azimuthal polarizations and use the Mie theory to find the scattered field from differently sized particles for these cases. We present numerical results for the changes in the detected intensity when subresolution and resolvable spherical particles are illuminated with particular wavelengths and polarizations. Further, we find the limiting size of a particle for which it can be considered a point scatterer for a particular wavelength. © 2008 Optical Society of America
Piezoelectric composites with periodic multi-coated inhomogeneities
, Article International Journal of Solids and Structures ; Volume 47, Issue 21 , October , 2010 , Pages 2893-2904 ; 00207683 (ISSN) ; Weng, G. J ; Kargarnovin, M. H ; Shodja, H. M ; Sharif University of Technology
Abstract
A new, robust homogenization scheme for determination of the effective properties of a periodic piezoelectric composite with general multi-coated inhomogeneities is developed. In this scheme the coating does not have to be thin, the shape and orientation of the inclusion and coatings do not have to be identical, their centers do not have to coincide, their properties do not have to remain uniform, and the microstructure can be with the 2D elliptic or the 3D ellipsoidal inclusions. The development starts from the local electromechanical equivalent inclusion principle through the introduction of the position-dependent equivalent eigenstrain and electric field. Then with a Fourier series...
Improved electron transportation of dye-sensitized solar cells using uniform mixed CNTs-TiO2 photoanode prepared by a new polymeric gel process
, Article Journal of Nanoparticle Research ; Volume 15, Issue 9 , 2013 ; 13880764 (ISSN) ; Mohammadi, M. R ; Masihi, N ; Akhlaghi, M. H ; Sharif University of Technology
2013
Abstract
A new facile strategy for fabrication of high surface area electrode in the form of mixtures of coated carbon nanotubes (CNTs) and TiO2 nanoparticles with various weight ratios is reported. The so-called polymeric gel process was used to deposit thick film containing uniform distribution of TiO2 nanoparticles and coated CNTs with high porosity by dip coating for dye-sensitized solar cells (DSSCs) applications. Based on simultaneous differential thermal analysis, the minimum annealing temperature to obtain inorganic- and organic-free films was determined at 500°C. X-ray diffraction analysis revealed that deposited films were composed of primary nanoparticles with crystallite size in the range...