Search for: layered-structured
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    Nanoscale vibrational analysis of an embedded multi-layered graphene sheet

    , Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 3 , 2004 , Pages 569-572 ; 0791841731 (ISBN); 9780791841730 (ISBN) Behfar, K ; Vafai, A ; Naghdabadi, R ; Estekanchi, H. E ; Sharif University of Technology
    American Society of Mechanical Engineers  2004
    In this paper, nanoscale vibrational analysis of a multi-layered graphene sheet embedded in an elastic medium is investigated and the corresponding resonant modes and frequencies are determined. It is known that the elastic moduli of a graphene sheet in two orientations x, y are different, so the graphene sheet is assumed to be a general form of an orthotropic plate. The orthotropic sheets stacking at the top of each other bond with carbon-carbon van der Waals forces, also the whole multi-layered graphene sheet is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium  

    Polynomial expansion for extraction of eigenmodes in layered waveguides

    , Article Aplications of Photonic Technology, Quebec City, 1 June 2002 through 6 June 2002 ; Volume 4833 , 2002 , Pages 769-775 ; 0277786X (ISSN) Mehrany, K ; Rashidian, B ; Sharif University of Technology
    In this article, polynomial expansion approach for extraction of guided and leaky modes in layered waveguides in which loss and gain can be present simultaneously is proposed. To verify the method, results of analysis of a typical test case have been compared to the other references, proving a good agreement. Polynomial expansion is a nonharmonic expansion and does not involve harmonic functions or intrinsic modes of homogenous layers. This approach has the benefit of leading to algebraic dispersion equations rather than transcendental dispersion equation; therefore, it will be easier to solve compared with other methods such as argument principle method (APM), reflection pole method (RPM)... 

    Surface Waves Propagation in a Piezoelectric/Piezomagnetic Half Space Overlaid With a Finnite Layer

    , M.Sc. Thesis Sharif University of Technology Soltanian Fard, Mohammad Amin (Author) ; Skandari, Morteza (Supervisor)
    The propagation of the surface waves in the piezoelectric (PE) and piezomagnetic (PM) layered media are studied. The surface BG waves in the PE half-spaces overlaid by a layer are considered and the closed-form dispersion relations for the open and short electromechanical surface boundary conditions are obtained. The numerical results for the phase velocities and the electromechanical coupling factor for PZT-2 and PZT-8 media are presented. Furthermore, the propagation of the Rayleigh waves in the PE-PM layered media is considered. The effects of the imperfect bonding between the half-space and the layer are discussed. Later, we study the propagation of the Rayleigh waves in 4 different... 

    Analysis of Time-Varying Epsilon-Near-Zero and Zero-Index Metamaterials

    , Ph.D. Dissertation Sharif University of Technology Heidarzadeh, Parham (Author) ; Memarian, Mohammad (Supervisor) ; Mehrany, Khashayar (Supervisor)
    Epsilon-near-zero media have attracted considerable attention in the last decade due to their exceptional behavior in wave propagation. The purpose of this research project is to analyze time-periodic ENZ structures. To this end, layered structures consisting of plasmonic metal and dielectric layers are used to achieve the epsilon-near-zero effect in a specific frequency range, and by time-variations of the dielectric layers, an effective time-varying (TV) ENZ is achieved. A method based on transfer matrix method is developed to analyze such structures while they are undergoing time-variations, and primarily under normal incident waves. Various structures based on such TV layered structures... 

    Co-precipitation Synthesis Parameters of Lithium-rich Cathode Material

    , M.Sc. Thesis Sharif University of Technology Seraji, Pardis (Author) ; Sadrnezhaad, Khatiboleslam (Supervisor)
    Electric vehicles and electronics such as laptops and smartphones require an efficient amount of energy conversion and storage. As one of the reliable systems in this field, lithium-ion batteries have high energy density and lower emissions. Cathodic material is a bottleneck in the development of lithium-ion systems due to its high cost and limited energy capacity. In this study, lithium-rich oxide cathode was synthesized in the liquid phase using the co-precipitation synthesis method using six-aqueous nickel nitrate and four-aqueous manganese chloride precursors. The material was analyzed by structural characterization analysis as well as electrochemical characterizations. In this project,... 

    An analytical formulation enabling analysis of resonance eigenmodes and their interferences in scattering from plasmonic nanostructures, applications in engineering the radiation loss

    , Article IEEE Journal of Quantum Electronics ; Volume PP, Issue 99 , 2016 ; 00189197 (ISSN) Khajeahsani, M. S ; Shahmansouri, A ; Rashidian, B ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    An analytic formulation revealing exact contribution of different factors affecting the interference interaction between eigenmodes of a scatterer is presented by utilizing our previously reported modal scattering power formula. For special case of arbitrary multilayer concentric and nonconcentric nanoshells, a recursive method for analytically calculating the T-matrix, and each of these factors is derived. Results for a three layer structure showing the conditions for constructive and destructive interference interactions are discussed in details. It is shown that the interference interaction can occur in the vicinity of the overlapping resonance frequencies of the two spatially overlapping... 

    Private shotgun DNA sequencing: A structured approach

    , Article 2019 Iran Workshop on Communication and Information Theory, IWCIT 2019, 24 April 2019 through 25 April 2019 ; 2019 ; 9781728105840 (ISBN) Gholami, A ; Maddah Ali, M. A ; Motahari, S. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    DNA sequencing has faced a huge demand since it was first introduced as a service to the public. This service is often offloaded to the sequencing companies who will have access to full knowledge of individuals' sequences, a major violation of privacy. To address this challenge, we propose a solution, which is based on separating the process of reading the fragments of sequences, which is done at a sequencing machine, and assembling the reads, which is done at a trusted local data collector. To confuse the sequencer, in a pooled sequencing scenario, in which multiple sequences are going to be sequenced simultaneously, for each target individual, we add fragments of one non-target individual,... 

    A new multi level clustering model to increase lifetime in wireless sensor networks

    , Article 2nd International Conference on Sensor Technologies and Applications, SENSORCOMM 2008, Cap Esterel, 25 August 2008 through 31 August 2008 ; 2008 , Pages 185-190 ; 9780769533308 (ISBN) Masoum, A. R ; Jahangir, A. M ; Taghikhani, Z ; Azarderakhsh, R ; IARIA ; Sharif University of Technology
    IEEE Computer Society  2008
    Most of clustered models in wireless sensor networks use a double-layered structure. In these structures a node is considered as cluster-head and has the responsibility of gathering information of environment. Static attribute is the main disadvantage of these clustering method. because as traffic rises in environment as time passes, cluster-head nodes energy and its close nodes, is consumed rapidly and so these nodes that has important role in data gathering, are break down. This issue is considered as age decrease in network life time and finally, network death. In this paper, a new three-layered dynamic model is introduced that its main goal is to increase network life time. The dynamic... 

    Role of interfacial fracture energy and laminate architecture on impact performance of aluminum laminates

    , Article Composites Part A: Applied Science and Manufacturing ; Volume 39, Issue 11 , 2008 , Pages 1685-1693 ; 1359835X (ISSN) Marouf, B.T ; Bagheri, R ; Mahmudi, R ; Sharif University of Technology
    The impact behavior of aluminum/epoxy laminates was studied by changing the number of layers and the interface strength. It should be noted that although the overall thickness did not changed, the individual layers decreased in thickness when the number of layers increased. The results indicate that the impact resistance of the laminate increases with the number of layers, while the interface strength has a less pronounced influence (50%) on the impact resistance of the laminate. It is also deducted that if the ratio of layer thickness to plastic zone size is smaller than or equal to 1, the impact behavior of the laminates is sensitive to the interface strength. © 2008 Elsevier Ltd. All... 

    Stochastic analysis of two dimensional nonlinear panels with structural damping under random excitation

    , Article Aerospace Science and Technology ; Volume 10, Issue 3 , 2006 , Pages 192-198 ; 12709638 (ISSN) Fazelzadeh, S. A ; Pourtakdoust, S. H ; Assadian, N ; Sharif University of Technology
    Stochastic behavior of panels in supersonic flow is investigated to assess the significance of including the damping caused by the strains resulting from axial extension of the panel. The governing equations of motion are based on the Von Karman's large deflection equation and are considered with Kelvin's model of structural damping. The panel under study is two dimensional and simply supported for which the first order piston theory is used to account for the unsteady aerodynamic loading. Transformation of the governing partial differential equation to a set of ordinary differential equations is performed through the Galerkin averaging technique. The statistical response moment equations... 

    Steady state and liquefaction characteristics of gravely sands

    , Article Geotechnical and Geological Engineering ; Volume 23, Issue 2 , 2005 , Pages 141-156 ; 09603182 (ISSN) Haeri, S. M ; Hamidi, A ; Sharif University of Technology
    Liquefaction of loose and saturated soils during earthquakes and strong ground motions has been a major cause of damage to buildings and earth embankments as well as other civil engineering structures. In order to evaluate the liquefaction potential and steady state characteristics of gravely sand of south west Tehran, a subsoil exploration program conducted dividing the region into 10 zones. In each zone of 500 m × 500 m a borehole of 20 m deep was drilled. SPT was performed at one meter intervals in each borehole and a total of 200 samples were recovered. Soils of similar grain size distribution have been considered to have similar steady state characteristics,therefore consolidated... 

    Dynamic response of a delaminated composite beam with general lay-ups based on the first-order shear deformation theory

    , Article Composites Part B: Engineering ; Volume 55 , 2013 , Pages 65-78 ; 13598368 (ISSN) Jafari Talookolaei, R. A ; Kargarnovin, M. H ; Ahmadian, M. T ; Sharif University of Technology
    The dynamic response analysis of a delaminated composite beam with a general lay-up traversed under an arbitrary moving/non-moving force is presented. By employing the energy method and introducing a new finite element, the global mass and stiffness matrices for a Laminated Composite Beam (LCB) of Timoshenko type are derived in which the material couplings (bending-tension, bending-twist, and tension-twist couplings) with the Poisson's effect are considered. In deriving the governing equation the non-penetration condition is imposed by employing the method of Lagrange multipliers. Out of a self-developed finite element program, the natural frequencies and time response of such LCB are... 

    Semi-analytical solution for the free vibration analysis of generally laminated composite Timoshenko beams with single delamination

    , Article Composites Part B: Engineering ; Volume 45, Issue 1 , 2013 , Pages 587-600 ; 13598368 (ISSN) Kargarnovin, M. H ; Ahmadian, M. T ; Jafari Talookolaei, R. A ; Abedi, M ; Sharif University of Technology
    A rather new semi-analytical method towards investigating the free vibration analysis of generally laminated composite beam (LCB) with a delamination is presented. For the first time the combined effects of material couplings (bending-tension, bending-twist, and tension-twist couplings) with the effects of shear deformation, rotary inertia and Poisson's effect are taken into account. The semi-analytical solution for the natural frequencies and mode shapes are presented by incorporating the constraint conditions using the method of Lagrange multipliers. To verify the validity and the accuracy of the obtained results, they were compared with the results from other available references. Very... 

    Analytical solution for vibration of generally laminated conical and cylindrical shells

    , Article International Journal of Mechanical Sciences ; Volume 131-132 , 2017 , Pages 414-425 ; 00207403 (ISSN) Shakouri, M ; Kouchakzadeh, M. A ; Sharif University of Technology
    In the present study, a simple analytical method is introduced for determination of natural frequencies of generally laminated conical and cylindrical shells with arbitrary boundary conditions. The governing equations of motion employed are those of thin-walled shell theory of Donnell. The free-vibration equations are solved using state space method and series solution in meridional direction. The results are compared and validated with the available especial results in the literature. The effects of bending-stretching coupling, semi-vertex angle, meridional length, shell thickness, fiber directions of composite plies, and lamination sequences on the natural frequency of conical and... 

    Monolithic quantum dot sensitized solar cells

    , Article Journal of Physics D: Applied Physics ; Volume 46, Issue 48 , December , 2013 ; 00223727 (ISSN) Samadpour, M ; Ghane, Z ; Ghazyani, N ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
    We report a new design of solar cells based on semiconductor quantum dots (QDs), monolithic quantum dot sensitized solar cells (MQDSCs). MQDSCs offer the prospect of having lower cost and a simpler manufacturing process in comparison to conventional double substrate QDSCs. Our proposed monolithic QDSCs have a triple-layer structure, composed of a CdS sensitized mesoporous TiO2 photoanode, a scattering layer made by a core-shell structure of TiO 2/SiO2, and a carbon active/graphite counter electrode layer, which are all deposited on a single fluorine doped tin oxide (FTO) glass substrate. Mesoporous TiO2 was sensitized with CdS QDs by successive ionic layer adsorption and reaction. Here,... 

    MAO-derived hydroxyapatite/TiO 2 nanostructured multi-layer coatings on titanium substrate

    , Article Applied Surface Science ; Volume 261 , 2012 , Pages 37-42 ; 01694332 (ISSN) Abbasi, S ; Golestani Fard, F ; Rezaie, H. R ; Mirhosseini, S. M. M ; Sharif University of Technology
    In this study, titanium substrates which previously oxidized through Micro arc oxidation method, was coated by Hydroxyapatite (HAp) coating once more by means of the same method. Morphology, topography and chemical properties as well as phase composition and thickness of layers were studied to reveal the effect of the electrolyte concentration on coating features. According to results, the obtained coatings are consisted of HAp and titania as the major phases along with minor amounts of calcium titanate and α-tri calcium phosphate. Ca and P are present on surface of obtained layers as well as predictable Ti and O based on the XPS results. Thickness profile of coatings figured out that by... 

    Investigation of structural and mechanical properties of magnetic pulse welded dissimilar aluminum alloys

    , Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 292-304 ; 15266125 (ISSN) Pourabbas, M ; Abdollah zadeh, A ; Sarvari, M ; Pouranvari, M ; Miresmaeili, R ; Sharif University of Technology
    Elsevier Ltd  2019
    The present study aimed to join AA4014 to AA7075 by using magnetic pulse welding (MPW). In addition, acceptable joints were achieved by selecting welding parameters such as collision angle and discharge energy appropriately. Changing collision angle and discharge energy can influence the velocity, leading to the formation of three different types of welding interfaces with wavy, molten wavy and porous morphologies. The formation of these various morphologies is mainly associated with different collision angle parameters. The hardness of the welding interface with molten layer was significantly higher than that of the base metals due to the grain refinement phenomenon occurring through the... 

    Detection of Apnea Bradycardia from ECG Signals of Preterm Infants Using Layered Hidden Markov Model

    , Article Annals of Biomedical Engineering ; Volume 49, Issue 9 , 2021 , Pages 2159-2169 ; 00906964 (ISSN) Sadoughi, A ; Shamsollahi, M. B ; Fatemizadeh, E ; Beuchée, A ; Hernández, A. I ; Montazeri Ghahjaverestan, N ; Sharif University of Technology
    Springer  2021
    Apnea-bradycardia (AB) is a common complication in prematurely born infants, which is associated with reduced survival and neurodevelopmental outcomes. Thus, early detection or predication of AB episodes is critical for initiating preventive interventions. To develop automatic real-time operating systems for early detection of AB, recent advances in signal processing can be employed. Hidden Markov Models (HMM) are probabilistic models with the ability of learning different dynamics of the real time-series such as clinical recordings. In this study, a hierarchy of HMMs named as layered HMM was presented to detect AB episodes from pre-processed single-channel Electrocardiography (ECG). For... 

    A novel method for band structure analysis of photonic crystal slabs

    , Article IEEE Photonics Journal ; Volume 3, Issue 6 , 2011 , Pages 1111-1122 ; 19430655 (ISSN) Nekuee, S. A. H ; Akbari, M ; Mehrany, K ; Sharif University of Technology
    We propose a new method to extract the modes of photonic crystal slabs and, thus, obtain their band structures. These slabs, which are 2-D periodic structures with finite thickness, can completely confine light and have the important advantage of simple construction for applications in integrated optic devices. In this paper, reflection pole method (RPM) is utilized to analyze photonic crystal slabs. Modes are poles of reflection and transmission coefficients of multilayered structures. According to this principle, modes can be detected by only pursuing phase variations of transmission coefficients that are equal to π rad. Therefore, extraction of modes becomes fast and simple through... 

    Incorporating multiscale micromechanical approach into PLSNs with different intercalated morphologies

    , Article Journal of Applied Polymer Science ; Volume 119, Issue 6 , September , 2011 , Pages 3347-3359 ; 00218995 (ISSN) Yazdi, A. Z ; Bagheri, R ; Kazeminezhad, M ; Heidarian, D ; Sharif University of Technology
    The objective of the present study is to predict Young's modulus of polymer-layered silicate nanocomposites (PLSNs) containing fully intercalated structures. The particular contribution of this article is to consider the changes in structural parameters of different intercalated morphologies in vicinity of each other. These parameters include aspect ratio of intercalated stacks, number of silicate layers per stack, d-spacing between the layers, modulus of the gallery phase, and volume fraction of each intercalated morphology. To do this, the effective particle concept has been employed and combined with the Mori-Tanaka micromechanical model. It has been shown that the simultaneous effects of...