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Three-dimensional dynamic Green's functions in transversely isotropic tri-materials
, Article Applied Mathematical Modelling ; Volume 37, Issue 5 , March , 2013 , Pages 3164-3180 ; 0307904X (ISSN) ; Rahimian, M ; Eskandari, M ; Sharif University of Technology
2013
Abstract
An analytical derivation of the elastodynamic fundamental solutions for a transversely isotropic tri-material full-space is presented by means of a complete representation using two displacement potentials. The complete set of three-dimensional point-load, patch-load, and ring-load Green's functions for stresses and displacements are given, for the first time, in the complex-plane line-integral representations. The formulation includes a complete set of transformed stress-potential and displacement-potential relations in the framework of Fourier expansions and Hankel integral transforms, that is useful in a variety of elastodynamic as well as elastostatic problems. For the numerical...
Green's functions of an exponentially graded transversely isotropic half-space
, Article International Journal of Solids and Structures ; Volume 47, Issue 11-12 , June , 2010 , Pages 1537-1545 ; 00207683 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2010
Abstract
By virtue of a complete set of displacement potential functions and Hankel transform, the analytical expressions of Green's function of an exponentially graded elastic transversely isotropic half-space is presented. The given solution is analytically in exact agreement with the existing solution for a homogeneous transversely isotropic half-space. Employing a robust asymptotic decomposition technique, the Green's function is decomposed to the closed-form Green's function corresponding to the homogeneous transversely isotropic half-space and grading term with strong decaying integrands. This representation is very useful for numerical methods which are based on boundary-integral formulations...
Love waves propagation in functionally graded piezoelectric materials with quadratic variation
, Article Journal of Sound and Vibration ; Volume 313, Issue 1-2 , 2008 , Pages 195-204 ; 0022460X (ISSN) ; Shodja, H. M ; Sharif University of Technology
2008
Abstract
The propagation behavior of Love waves in a semi-infinite functionally graded piezoelectric material (FGPM) with a quadratic variation is addressed. The coupled electromechanical field equations are solved, and the dispersion relations, displacement, electric potential, and stress fields are obtained analytically for both electrically open and short conditions. The effects of gradient coefficient on phase velocity, group velocity, and electromechanical coupling factor are plotted and discussed. It is shown that the phase velocity associated with the non-piezoelectric case coincides with that of the corresponding piezoelectric material under electrically open conditions. Because of gradual...
An analytical study on the elastic-plastic pure bending of a linear kinematic hardening curved beam
, Article International Journal of Mechanical Sciences ; Volume 144 , 2018 , Pages 274-282 ; 00207403 (ISSN) ; Arghavani, J ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this study, an analytical solution is presented for elastic-plastic pure bending of a linear kinematic hardening curved beam with rectangular cross section both in monotonic loading and unloading. Compared to exact plane plasticity solution (already reported in the literature in loading) which needs solution of a system of equations, the proposed method is based on the hyperbolic strain distribution on the cross section which yields a simple approximate solution. To this end, we employ Winkler's theory, and assume plane cross sections remain plane after loading proved by the exact elasticity and plasticity solutions for pure bending of curved beams with rectangular cross section. At the...
A novel solution for root-MUSIC with reduced complexity
, Article 6th Iranian Conference on Radar and Surveillance Systems, ICRSS 2019, 4 December 2019 through 6 December 2019 ; 2019 ; 9781728129372 (ISBN) ; Karbasi, S. M ; Bastani, M. H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
The root-MUSIC algorithm is a popular method to estimate Angle of Arrival (AoA) as an extension of multiple signal classification (MUSIC). In this paper, we have proposed a novel solution for the root-MUSIC algorithm. The new method exhibits a much lower computational complexity, while maintaining the same theoretical performance as the root-MUSIC. © 2019 IEEE
Microfluidic on-chip production of microgels using combined geometries
, Article Scientific Reports ; Volume 11, Issue 1 , 2021 ; 20452322 (ISSN) ; Saadatmand, M ; Eskandari, M ; Bastani, D ; Sharif University of Technology
Nature Research
2021
Abstract
Microfluidic on-chip production of microgels using external gelation can serve numerous applications that involve encapsulation of sensitive cargos. Nevertheless, on-chip production of microgels in microfluidic devices can be challenging due to problems induced by the rapid increase in precursor solution viscosity like clogging. Here, a novel design incorporating a step, which includes a sudden increase in cross-sectional area, before a flow-focusing nozzle was proposed for microfluidic droplet generators. Besides, a shielding oil phase was utilized to avoid the occurrence of emulsification and gelation stages simultaneously. The step which was located before the flow-focusing nozzle...
Discussion of “rocking vibration of a rigid disk embedded in any depth of a coupled seawater-visco-poro-elastic seabed half-space”
, Article Soil Dynamics and Earthquake Engineering ; Volume 104 , 2018 , Pages 449-450 ; 02677261 (ISSN) ; Samea, P ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2018
Bonded boojum-colloids in nematic liquid crystals
, Article Langmuir ; Volume 29, Issue 33 , 2013 , Pages 10360-10367 ; 07437463 (ISSN) ; Silvestre, N. M ; Telo Da Gama, M. M ; Sharif University of Technology
2013
Abstract
We investigate bonded boojum-colloids in nematic liquid crystals, configurations where two colloids with planar degenerate anchoring are double-bonded through line defects connecting their surfaces. This bonded structure promotes the formation of linear chains aligned with the nematic director. We show that the bonded configuration is the global minimum in systems that favor twist deformations. In addition, we investigate the influence of confinement on the stability of bonded boojum-colloids. Although the unbonded colloid configuration, where the colloids bundle at oblique angles, is favored by confinement, the bonded configuration is again the global minimum for liquid crystals with...
Molecular interaction between three-dimensional graphene aerogel and enzyme solution: effect on enzyme structure and function
, Article Journal of Molecular Liquids ; Volume 265 , 2018 , Pages 565-571 ; 01677322 (ISSN) ; Bagheri, Z ; Eskandari, F ; Ahadian, M. M ; Sharif University of Technology
2018
Abstract
New membrane materials and processes have been extensively developed due to urgent needs for much more economic separation processes. Recently, graphene has been confirmed to be an excellent separation membrane. As there is no support in the obtained three-dimensional (3D) architecture constructed from tubular graphene network, it is possible to take full advantage of the large surface of graphene. In this study 3D graphene aerogels were synthesized by a simple method and modified to adjust hydrophilicity of the samples to achieve high liquid volumetric rate. Modified samples were used for the filtration of the enzymes including amylase, cellulase, lipase and protease. Slightly differently...
Blokus Duo game on FPGA
, Article roceedings - 17th CSI International Symposium on Computer Architecture and Digital Systems, CADS 2013 ; 2013 , Pages 149-152 ; 9781479905621 (ISBN) ; Taram, M. K ; Eskandari, N ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
There are a number of Artificial In elligence (AI) algorithms for implementation of 'Blokus Duo' game. We needed an implementation on FPGA, and moreover, the design had to respond under a given time constraint. In this paper we examine some of these algorithms and propose a heuristic algorithm to solve the problem by considering intelligence, time constraint and FPGA implementation limitations
Axisymmetric response of a bi-material full-space reinforced by an interfacial thin film
, Article International Journal of Solids and Structures ; Volume 90 , July , 2016 , Pages 251–260 ; 00207683 (ISSN) ; Samea, P ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Analytical treatment of a linear elastic isotropic bi-material full-space reinforced by an interfacial thin film under axisymmetric normal loading is addressed. The thin film is modeled as an extensible membrane perfectly bonded to the half-spaces. By virtue of Love's potential function and Hankel integral transform, elastic fields of the system are explicitly written in the form of semi-infinite line integrals. The analytical results are verified by the special cases corresponding to the surface stiffened half-space and classical bi-material problem. The limiting cases of reinforced homogeneous full-space and inextensible membrane are presented and discussed. The proposed formulation is...
Discussion of "Rocking vibration of a rigid disk embedded in any depth of a coupled seawater-visco-poro-elastic seabed half-space" by R. He [Soil Dyn. Earthq. Eng. 85(2016), 130-133]
, Article Soil Dynamics and Earthquake Engineering ; 2016 ; 02677261 (ISSN) ; Samea, P ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2016
Shear horizontal surface acoustic waves in functionally graded magneto-electro-elastic half-space
, Article Journal of Engineering Mathematics ; Volume 97, Issue 1 , 2016 , Pages 83-100 ; 00220833 (ISSN) ; Eskandari, S ; Eskandari, M ; Sharif University of Technology
Springer Netherlands
2016
Abstract
The propagation of shear horizontal surface acoustic waves (SHSAWs) in an inhomogeneous magneto-electro-elastic (MEE) half-space with 6-mm symmetry is studied. By virtue of both the direct approach and Stroh-formalism, the dispersion relations corresponding to two general cases of material properties variation are obtained. In the first case, it is assumed that all material properties involving the MEE properties and density vary similarly in depth, whereas, the second case considers identical variation for the MEE properties, which differs from the variation of the density. The non-dispersive SHSAW velocities pertinent to the homogeneous MEE media are obtained under eight different surface...
A time-dependent finite element formulation for thick shape memory polymer beams considering shear effects
, Article International Journal of Applied Mechanics ; Volume 10, Issue 4 , 2018 ; 17588251 (ISSN) ; Baghani, M ; Sohrabpour, S ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2018
Abstract
In this paper, employing a thermomechanical small strain constitutive model for shape memory polymers (SMP), a beam element made of SMPs is presented based on the kinematic assumptions of Timoshenko beam theory. Considering the low stiffness of SMPs, the necessity for developing a Timoshenko beam element becomes more prominent. This is due to the fact that relatively thicker beams are required in the design procedure of smart structures. Furthermore, in the design and optimization process of these structures which involves a large number of simulations, we cannot rely only on the time consuming 3D finite element analyses. In order to properly validate the developed formulations, the numeric...
Interactions of distinct quadrupolar nematic colloids
, Article Soft Matter ; Volume 8, Issue 39 , 2012 , Pages 10100-10106 ; 1744683X (ISSN) ; Silvestre, N. M ; Tasinkevych, M ; Telo Da Gama, M. M ; Sharif University of Technology
2012
Abstract
The effective interaction between spherical colloids in nematic liquid crystals is investigated in the framework of the Landau-de Gennes theory. The colloids differ in their surface interaction with the nematic liquid crystal. The particles induce quadrupolar far-field distortions in the nematic matrix, favouring homeotropic and the other degenerate planar anchoring of the nematic director. In the strong anchoring regime the colloids with homeotropic anchoring are accompanied by an equatorial disclination line defect, known as "Saturn-ring", while the colloids with degenerate planar anchoring nucleate a pair of antipodal surface defects, called "boojums". In the linear (large-distance)...
Love Wave Propagation in PiezoElectroMagnetic Functionally Graded Materials
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shoja, Hossein (Supervisor) ; Eskandari, Morteza (Co-Advisor)
Abstract
The propagation of anti-plane surface waves in an inhomogeneous magneto-electro-elastic MEE) half-space with 6mm symmetry is studied. By virtue of both direct and indirect methods, the dispersion relations corresponding to two general cases of material properties variation are obtained. In the first case, it is assumed that all material properties involving MEE properties and density vary similarly in depth. Whereas, the second case considers different variations for MEE properties and density. The non-dispersive shear surface wave velocities pertinent to homogeneous MEE media under eight different surface electromagnetic boundary conditions are obtained as the limiting cases of the current...
Three-dimensional dynamic Green's functions for a multilayered transversely isotropic half-space
, Article International Journal of Solids and Structures ; Volume 48, Issue 9 , 2011 , Pages 1349-1361 ; 00207683 (ISSN) ; Rahimian, M ; Eskandari, M ; Pak, R. Y. S ; Sharif University of Technology
2011
Abstract
With the aid of a method of displacement potentials, an efficient and accurate analytical derivation of the three-dimensional dynamic Green's functions for a transversely isotropic multilayered half-space is presented. Constituted by proper algebraic factorizations, a set of generalized transmission-reflection matrices and internal source fields that are free of any numerically unstable exponential terms are proposed for effective computations of the potential solution. Three-dimensional point-load Green's functions for stresses and displacements are given, for the first time, in the complex-plane line-integral representations. The present formulations and solutions are analytically in exact...
Asymmetric wave propagation in a transversely isotropic half-space in displacement potentials
, Article International Journal of Engineering Science ; Volume 46, Issue 7 , 2008 , Pages 690-710 ; 00207225 (ISSN) ; Rahimian, M ; Eskandari, M ; Pak, R. Y. S ; Sharif University of Technology
2008
Abstract
With the aid of a complete representation using two displacement potentials, an efficient and accurate analytical derivation of the fundamental Green's functions for a transversely isotropic elastic half-space subjected to an arbitrary, time-harmonic, finite, buried source is presented. The formulation includes a complete set of transformed stress-potential and displacement-potential relations that can be useful in a variety of elastodynamic as well as elastostatic problems. The present solutions are analytically in exact agreement with the existing solutions for a half-space with isotropic material properties. For the numerical evaluation of the inversion integrals, a quadrature scheme...
Boussinesq indentation of a transversely isotropic half-space reinforced by a buried inextensible membrane
, Article Applied Mathematical Modelling ; Vol. 38, issue. 7-8 , April , 2014 , p. 2163-2172 ; Ahmadi, S. F ; Eskandari, M ; Sharif University of Technology
2014
Abstract
The normal indentation of a rigid circular disk into the surface of a transversely isotropic half-space reinforced by a buried inextensible thin film is addressed. By virtue of a displacement potential function and the Hankel transform, the governing equations of this axisymmetric mixed boundary value problem are represented as a dual integral equation, which is subsequently reduced to a Fredholm integral equation of the second kind. Two important results of the contact stress distribution beneath the disk region as well as the equivalent stiffness of the system are expressed in terms of the solution of the Fredholm integral equation. When the membrane is located on the surface or at the...
IMAC: An Interference-aware duty-cycle MAC protocol for wireless sensor networks employing multipath routing
, Article Proceedings - 2011 IFIP 9th International Conference on Embedded and Ubiquitous Computing, EUC 2011 ; 2011 , Pages 288-293 ; 9780769545523 (ISBN) ; Yousefi, H ; Movaghar, A ; Khansari, M ; Sharif University of Technology
2011
Abstract
The main source of energy consumption in the current MAC protocols for wireless sensor networks is idle listening. To mitigate this problem, duty cycling is used. However, it increases data delivery latency. In this paper, we propose an Interference-aware duty-cycle MAC (IMAC) protocol for wireless sensor networks that uses cross-layer information to reserve multiple paths for each source and send data packets along them efficiently. IMAC also handles the existing interference between these paths such that data packets can be delivered in the minimum required number of cycles. Simulation results in ns-2 show that the proposed algorithm has an average reduction of 49% in data delivery latency...