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Empirical comparison of sliding friction and wear behaviors of gray and white cast iron
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 1 , 2010 , Pages 489-493 ; 9780791849156 (ISBN) ; Ghajar, R ; Sharif University of Technology
2010
Abstract
In this paper, sliding friction and wear behaviors of gray cast iron A35 and white cast iron manufactured by quenching from the same cast iron in water were studied and compared by employing pin-on-disk wear tests. Microstructure of the worn surfaces before and after the wear tests were investigated by optical microscope observations. These images show that flakes separated from the surface in gray cast iron due to delamination process, while in white cast iron, the separation of materials from its surface is in the form of powder. In addition, the gray cast iron had higher graphite volume fraction with Type-A graphite flake morphology. The results show that white cast iron has less rate of...
Chaotic dynamics of active topological defects
, Article Soft Materials ; Volume 19, Issue 3 , 2021 , Pages 316-322 ; 1539445X (ISSN) ; Ejtehadi, M. R ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
Topological defects are interesting phenomena which can be observed in ordered phases such as oriented active fluids or nematic liquid crystals. Topological defects are determined by the overall structure of the director field in an active fluid in nematic phase and by exerting force to the units of the active particles they can interact or cause motion in the environment. Studying them as particles with dynamical equations, instead of studying the director field of the nematic environment, would provide us the power to study the characteristics of their motion. The equations of motion for multi-defect systems have been previously studied and in this work we focus on the chaotic properties...
Equilibrium state of a cylindrical particle with flat ends in nematic liquid crystals
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 91, Issue 1 , January , 2015 ; 15393755 (ISSN) ; Ejtehadi, M. R ; Sharif University of Technology
American Physical Society
2015
Abstract
A continuum theory is employed to numerically study the equilibrium orientation and defect structures of a circular cylindrical particle with flat ends under a homeotropic anchoring condition in a uniform nematic medium. Different aspect ratios of this colloidal geometry from thin discotic to long rodlike shapes and several colloidal length scales ranging from mesoscale to nanoscale are investigated. We show that the equilibrium state of this colloidal geometry is sensitive to the two geometrical parameters: aspect ratio and length scale of the particle. For a large enough mesoscopic particle, there is a specific asymptotic equilibrium angle associated to each aspect ratio. Upon reducing the...
Computational study of spin caloritronics in a pristine and defective antimonene nanoribbon
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 120 , 2020 ; Faez, R ; Darvish, G ; Sharif University of Technology
Elsevier B.V
2020
Abstract
In this paper, by using first-principle density functional theory (DFT) combined with non-equilibrium Green's function (NEGF), thermally induced spin current in zigzag and armchair Antimonene Nanoribbon (SbNR) is investigated. Also, we obtain higher spin current in Armchair nanoribbon (ANR) than zigzag nanoribbon (ZNR), because the start energy of transmission for ANR is closer to the Fermi level than ZNR. The results show that the device has a perfect spin Seebeck effect under temperature difference without gate voltage or bias voltage. For the ANR configuration, the competition between spin up holes and spin down electrons leads to negative differential behavior of charge current, which is...
Spin caloritronics in a graphene-antimonene heterostructure with high figure of merit: a first principle study
, Article Journal of Computational Electronics ; Volume 22, Issue 1 , 2023 , Pages 80-87 ; 15698025 (ISSN) ; Faez, R ; Darvish, G ; Sharif University of Technology
Springer
2023
Abstract
In this paper, thermally induced spin current in graphene-antimonene heterostructure is investigated using first-principle density functional theory (DFT) combined with the non-equilibrium Green’s function (NEGF) method. We obtain a higher spin current in the graphene-antimonene heterostructure (Gr-Sb) than in the graphene zigzag nanoribbon (GrZNR). The current versus source temperature shows negative differential behavior. Also, the results show that graphene-antimonene heterostructure's figure of merit coefficient could be ZT = 37 ×10 - 3 in the energy range – 0.5 eV < E < 0.5 eV, while its value for monolayer graphene is about 4000 times less. These results show that the figure of merit...
Graphene as a flexible electrode: Review of fabrication approaches
, Article Journal of Materials Chemistry A ; Volume 5, Issue 34 , 2017 , Pages 17777-17803 ; 20507488 (ISSN) ; Reeves, S. P ; Hashemi, N ; Thomas, D. G ; Kavak, E ; Montazami, R ; Hashemi, N. N ; Sharif University of Technology
Royal Society of Chemistry
2017
Abstract
In recent years, the technological advancement of supercapacitors has been increasing exponentially due to the high demand in electronic consumer products. As so, researchers have found a way to meet that demand by fabricating graphene. As developments are made toward the future, two big advancements to be made are large-scale fabrication of graphene and fabricating graphene as a flexible electrode. This would allow for use in larger products and for manipulation of the unique properties of graphene to accommodate superior design alternatives. While large scale production is still mentioned, this review is specifically focusing on different methods used to fabricate graphene as a flexible...
Dimensional characterization of anesthesia dynamic in reconstructed embedding space
, Article 29th Annual International Conference of IEEE-EMBS, Engineering in Medicine and Biology Society, EMBC'07, Lyon, 23 August 2007 through 26 August 2007 ; 2007 , Pages 6483-6486 ; 05891019 (ISSN) ; 1424407885 (ISBN); 9781424407880 (ISBN) ; Rabiee, H. R ; Hashemi, M. R ; Ghanbari, M ; Sharif University of Technology
2007
Abstract
The depth of anesthesia quantification has been one of the most research interests in the field of EEG signal processing and nonlinear dynamical analysis has emerged as a novel method for the study of complex systems in the past few decades. In this investigation we use the concept of nonlinear time series analysis techniques to reconstruct the attractor of anesthesia from EEG signal which have been obtained from different hypnotic states during surgery to give a characterization of the dimensional complexity of EEG by Correlation Dimension estimation. The dimension of the anesthesia strange attractor can be thought of as a measure of the degrees of freedom or the 'complexity' of the...
Microwave-assisted synthesis of bithiazole derivatives under solvent-free conditions
, Article Russian Journal of Organic Chemistry ; Volume 41, Issue 4 , 2005 , Pages 623-624 ; 10704280 (ISSN) ; Asadollahi, H ; Mostaghim, R ; Sharif University of Technology
2005
Recent advances using equal-channel angular pressing to improve the properties of biodegradable Mg‒Zn alloys
, Article Journal of Magnesium and Alloys ; Volume 11, Issue 7 , 2023 , Pages 2260-2284 ; 22139567 (ISSN) ; Alizadeh, R ; Langdon, T. G ; Sharif University of Technology
KeAi Communications Co
2023
Abstract
Magnesium alloys are of considerable current interest for use as degradable implants due to their unique properties including biodegradability, biocompatibility, low density and adequate mechanical properties. Nevertheless, there is a need to further improve these properties either by alloying or through the use of appropriate processing. Among the different biodegradable Mg alloys now in use, the Mg‒Zn series are of special interest and have been the subject of many research investigations. This is primarily because Zn is an essential element for the human body in addition to its positive effects in improving the mechanical strength and lowering the degradation rate of the implant. The...
An analytical approach in prediction of necking and suitable load path in tube hydroforming by using the strain gradient
, Article SAE Technical Papers, 20 April 2009 through 20 April 2009, Detroit, MI ; 2009 ; Masoumi, E ; Safikhani, A. R ; Hashemi, R ; Abrinia, K ; Sharif University of Technology
2009
Abstract
A theoretical forming limit stress diagram (FLSD) for necking prediction which is based on the strain gradient theory of plasticity in conjunction with the M-K approach was represented and used in tube hydroforming. This approach introduces an internal length scale into conventional constitutive equations and takes into account the effects of deformation inhomogeneity and material softening. The nonlinear second order ordinary differential equation of the thickness of tube has been solved by collocation method. It has been shown that this method overcomes the imperfection sensitivity encountered in the conventional M-K method. The predicted FLSD has been compared with published experimental...
Ultra-sensitive detection of leukemia by graphene
, Article Nanoscale ; Vol. 6, issue. 24 , Dec , 2014 , p. 14810-14819 ; Ghaderi, E ; Hashemi, E ; Rahighi, R ; Sharif Universit of Technology
2014
Abstract
Graphene oxide nanoplatelets (GONPs) with extremely sharp edges (lateral dimensions ∼20-200 nm and thicknesses <2 nm) were applied in extraction of the overexpressed guanine synthesized in the cytoplasm of leukemia cells. The blood serums containing the extracted guanine were used in differential pulse voltammetry (DPV) with reduced graphene oxide nanowall (rGONW) electrodes to develop fast and ultra-sensitive electrochemical detection of leukemia cells at leukemia fractions (LFs) of ∼10-11 (as the lower detection limit). The stability of the DPV signals obtained by oxidation of the extracted guanine on the rGONWs was studied after 20 cycles. Without the guanine extraction, the DPV peaks...
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...
A modified SPH method for simulating motion of rigid bodies in Newtonian fluid flows
, Article International Journal of Non-Linear Mechanics ; Volume 47, Issue 6 , 2012 , Pages 626-638 ; 00207462 (ISSN) ; Fatehi, R ; Manzari, M. T ; Sharif University of Technology
2012
Abstract
A weakly compressible smoothed particle hydrodynamics (WCSPH) method is used along with a new no-slip boundary condition to simulate movement of rigid bodies in incompressible Newtonian fluid flows. It is shown that the new boundary treatment method helps to efficiently calculate the hydrodynamic interaction forces acting on moving bodies. To compensate the effect of truncated compact support near solid boundaries, the method needs specific consistent renormalized schemes for the first and second-order spatial derivatives. In order to resolve the problem of spurious pressure oscillations in the WCSPH method, a modification to the continuity equation is used which improves the stability of...
SPH simulation of interacting solid bodies suspended in a shear flow of an Oldroyd-B fluid
, Article Journal of Non-Newtonian Fluid Mechanics ; Volume 166, Issue 21-22 , November , 2011 , Pages 1239-1252 ; 03770257 (ISSN) ; Fatehi, R ; Manzari, M. T ; Sharif University of Technology
2011
Abstract
An explicit weakly compressible SPH method is introduced to study movement of suspended solid bodies in Oldroyd-B fluid flows. The proposed formulation does not need further stabilizing treatments and can be efficiently employed to study particulate flows with Deborah to Reynolds number ratios up to around 10. A modified boundary treatment technique is also presented which helps to deal with the movement of solid particles in the flow. The technique is computationally efficient and gives an improved evaluation of fluid-solid interaction forces.A number of test cases are solved to show performance of the proposed method in simulating particulate viscoelastic flows containing circular and...
Simulating fluid-solid interaction problems using an immersed boundary-SPH method
, Article Particle-Based Methods II - Fundamentals and Applications, 26 October 2011 through 28 October 2011 ; Octobe , 2011 , Pages 954-965 ; 9788489925670 (ISBN) ; Fatehi, R ; Manzari, M. T ; Sharif University of Technology
2011
Abstract
In this work, the Immersed Boundary Method (IBM) is adapted and implemented in the context of Smoothed Particle Hydrodynamics (SPH) method to study moving solid bodies in an incompressible fluid flow. The proposed computational algorithm is verified by solving a number of benchmark particulate flow problems. The results are also compared with those obtained using the same SPH scheme along with a direct solid boundary imposition technique
Electroelastic fields in interacting piezoelectric inhomogeneities by the electromechanical equivalent inclusion method
, Article Smart Materials and Structures ; Volume 19, Issue 3 , 2010 ; 09641726 (ISSN) ; Kargarnovin, M. H ; Hashemi, R ; Sharif University of Technology
2010
Abstract
Consider two piezoelectric ellipsoidal inhomogeneities of arbitrary size, orientation and material constants, which in turn are surrounded by an infinite isotropic medium. The system under consideration is subjected to far-field non-uniform electromechanical loadings. Based on the extension of the electromechanical equivalent inclusion method (EMEIM), the present paper develops a unified solution for determination of the associated electroelastic fields in the vicinity of interacting inhomogeneities. Accordingly, each of the piezoelectric inhomogeneities is broken down into two equivalent inclusions with proper polynomial eigenstrains and eigenelectric fields. The robustness and efficacy of...
Evaluation of a pressure splitting formulation for Weakly Compressible SPH: Fluid flow around periodic array of cylinders
, Article Computers and Mathematics with Applications ; 2016 ; 08981221 (ISSN) ; Manzari, M. T ; Fatehi, R ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In this paper, a pressure splitting formulation is proposed for Weakly Compressible SPH (WC-SPH) method and its capability in the suppression of the spurious oscillations is studied by conducting a stability analysis. The proposed formulation is implemented within the framework of a consistent SPH method. The predictions from the theoretical analysis are verified by the results of numerical test-cases. This method is applied to the incompressible fluid flow around periodic array of circular cylinders. The accuracy and the convergence of the results are investigated for benchmark problems. The results are also compared with those of the conventional WC-SPH method. In a similar test-case, the...
A SPH solver for simulating paramagnetic solid fluid interaction in the presence of an external magnetic field
, Article Applied Mathematical Modelling ; Volume 40, Issue 7-8 , 2016 , Pages 4341-4369 ; 0307904X (ISSN) ; Manzari, M. T ; Fatehi, R ; Sharif University of Technology
Elsevier Inc
2016
Abstract
The Smoothed Particle Hydrodynamics (SPH) method is extended to solve magnetostatic problems involving magnetically interacting solid bodies. In order to deal with the jump in the magnetic permeability at a fluid-solid interface, a consistent SPH scheme is utilized and a modified formulation is proposed to calculate the magnetic force density along the interface. The results of the magnetostatic solver are verified against those of the finite element method. The governing fluid flow equations are discretized using the same SPH scheme, developing an efficient method for simulating the motion of paramagnetic solid bodies in a fluid flow. The proposed algorithm is applied to a benchmark problem...
Direct numerical simulation of magnetic particles suspended in a Newtonian fluid exhibiting finite inertia under SAOS
, Article Journal of Non-Newtonian Fluid Mechanics ; Volume 256 , 2018 , Pages 8-22 ; 03770257 (ISSN) ; Manzari, M. T ; Fatehi, R ; Sharif University of Technology
Elsevier B.V
2018
Abstract
A direct numerical simulation approach is utilized to understand the oscillatory shear rheology of a confined suspension of magnetic chains formed by paramagnetic circular cylinders under the influence of an external magnetic field. The common assumption of gap-spanning chains made in the literature is relaxed in this work, so that a fully suspended (periodic) array of magnetic chains is formed. In this sense, the effective rheological parameters are only influenced through a layer of fluid adjacent to the walls. All tests are conducted at very low but finite particle Reynolds numbers, and typical inertial effects are discussed. The main aim of the present study is to investigate the...
Non-linear stress response of non-gap-spanning magnetic chains suspended in a newtonian fluid under oscillatory shear test: a direct numerical simulation
, Article Physics of Fluids ; Volume 29, Issue 10 , 2017 ; 10706631 (ISSN) ; Taghizadeh Manzari, M ; Fatehi, R ; Sharif University of Technology
2017
Abstract
Adirect numerical simulation approach is used to investigate the effective non-linear viscoelastic stress response of non-gap-spanning magnetic chains suspended in a Newtonian fluid. The suspension is confined in a channel and the suspended clusters are formed under the influence of a constant external magnetic field. Large amplitude oscillatory shear (LAOS) tests are conducted to study the non-linear rheology of the system. The effect of inertia on the intensity of non-linearities is discussed for both magnetic and non-magnetic cases. By conducting magnetic sweep tests, the intensity and quality of the non-linear stress response are studied as a function of the strength of the external...