Search for: wave
Total 1316 records
Viscous wave interaction due to motion of a surface wave over a sediment bed, Article 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, BC, 20 June 2004 through 25 June 2004 ; Volume 3 , 2004 , Pages 833-838 ; Lawrence, G. A ; Sharif University of Technology
The results of a flume investigation of surface wave motion over a fluidized bed are presented. It is shown that a resonant wave interaction between a surface wave and two interfacial waves at the interface of the fresh water and the fluidized bed is a strong mechanism for instability of the interface and the subsequent mixing of the layers. The interfacial waves are subharmonic to the surface wave and form a standing wave at the interface. The interaction is investigated theoretically using a fully viscous interaction analysis. It is shown that surface wave height and viscous effects are the determining factors in the instability mechanism. The results indicate that the net effect of...
Four suggested plans of underwater Robo-snake, Article World Academy of Science, Engineering and Technology ; Volume 38 , 2009 , Pages 1094-1099 ; 2010376X (ISSN) ; Sharifazadeh, H ; Sharif University of Technology
Throughout this paper four locomotion mechanisms have been presented for underwater robo-sankes. In this respect; initially, two methods of locomotion including traveling and standing wave have been examined. Next, applications of these methods are described. Ultimately, assessing and comparison of those mechanisms have been studied and the best plan is determined. © 2009 WASET.ORG
Impact of loss on the wave dynamics in photonic waveguide lattices, Article Physical Review Letters ; Vol. 113, Issue. 12 , 2014 ; ISSN: 00319007 ; Weimann, S ; Jafari, K ; Nezhad, M. K ; Langari, A ; Bahrampour, A. R ; Eichelkraut, T ; Mahdavi, S. M ; Szameit, A ; Sharif University of Technology
We analyze the impact of loss in lattices of coupled optical waveguides and find that, in such a case, the hopping between adjacent waveguides is necessarily complex. This results not only in a transition of the light spreading from ballistic to diffusive, but also in a new kind of diffraction that is caused by loss dispersion. We prove our theoretical results with experimental observations
Gravitational grating, Article Monthly Notices of the Royal Astronomical Society ; Volume 479, Issue 1 , 2018 , Pages 406-414 ; 00358711 (ISSN) ; Sharif University of Technology
Oxford University Press 2018
In this work, we study the interaction of the electromagnetic wave (EW) from a distant quasar with the gravitational wave (GW) sourced by the binary stars.While in the regime of geometric optics the light bending due to this interaction is negligible, we show that the phase shifting on the wavefront of an EW can produce the diffraction pattern on the observer plane. The diffraction of the light (with the wavelength of λe) by the gravitational wave playing the role of gravitational grating (with the wavelength of λg) has the diffraction angle of Δβ ~ λe/λg. The relative motion of the observer, the source of gravitational wave, and the quasar results in a relative motion of the observer...
Coupling reduction of printed yagi antenna arrays for millimeter-wave imaging applications, Article 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019, 7 July 2019 through 12 July 2019 ; 2019 , Pages 1767-1768 ; 9781728106922 (ISBN) ; Fakharzadeh, M ; Ranjbar Naeini, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2019
In this paper, methods for reduction of coupling between receiving and transmitting antenna arrays are proposed and tested. Coupling between RX and TX causes saturation and a higher noise level in IF. So, coupling reduction improves image quality of system. Antenna element of arrays are printed antipodal Yagi-Uda antenna with greater than 8 dBi gain and higher than 4 GHz bandwidth. Frequency bandwidth of this imaging system is 27 to 30.5 GHz. Half power beamwidth of this antenna element is larger than 90 dB. Front to back ratio of this antenna is improved in this paper to 30 dB at 29 GHz. © 2019 IEEE
A technique for detection of interfacial waves forming a two-dimensional pattern, Article Fluid Dynamics Research ; Vol. 46, issue. 1 , 2014 ; ISSN: 01695983 ; Fazeli M ; Jamali, M ; Sharif University of Technology
In this paper, we consider resonant interaction between a surface wave and sub-harmonic interfacial waves forming a two-dimensional pattern at the interface between two fluid layers. The resulting interfacial pattern changes both in time and space. An image processing technique is proposed to extract information about the evolution of the component interfacial waves in a wave flume. The technique proved to give accurate and consistent results when applied to different stages of the interaction. The experimental measurements were used to verify the theoretical predictions. The method can be used for detection of some other wave motions
Numerical investigation of distance effect between two searasers for hydrodynamic performance, Article Alexandria Engineering Journal ; Volume 55, Issue 3 , 2016 , Pages 2257-2268 ; 11100168 (ISSN) ; Jafari, M ; Hafezi Sefat, P ; Sharif University of Technology
Elsevier B.V 2016
Nowadays, researchers are interested in investigation of the ocean wave energy conversion (OWEC) because this device can convert wave energy into electricity economically. The aim of this study was to evaluate a novel ocean wave energy converter named Searaser which may be capable of being used in the Caspian Sea. One of the ways for improving the efficiency of Searasers is to use numerous Searasers simultaneously. Increasing the number of Searasers not only increases the electricity production but also can help producing more stable electricity. In this article the function of two Searasers three different distances (10, 15 and 20 m) was evaluated numerically by solving momentum and...
Viscous wave interaction due to motion of a surface wave over a sediment bed, Article Journal of Offshore Mechanics and Arctic Engineering ; Volume 128, Issue 4 , 2006 , Pages 276-279 ; 08927219 (ISSN) ; Lawrence, G. A ; Sharif University of Technology
The results of a flume experiment and a theoretical study of surface wave motion over a fluidized bed are presented. It is shown that a resonant wave interaction between a surface wave and two interfacial waves at the interface of the fresh water and the fluidized bed is a strong mechanism for instability of the interface and the subsequent mixing of the layers. The interfacial waves are subharmonic to the surface wave and form a standing wave at the interface. The interaction is investigated theoretically using a viscous interaction analysis. It is shown that surface wave height and viscous effects are the determining factors in the instability mechanism. The results indicate that the net...
Improved coupled wave analysis of two-dimensional planar multiple gratings, Article IEEE Transactions on Antennas and Propagation ; Volume 52, Issue 1 , 2004 , Pages 165-171 ; 0018926X (ISSN) ; Rashidian, B ; Sharif University of Technology
An improved coupled wave approach is presented for the analysis of diffraction behavior of a two-dimensional spatially periodic or almost periodic dielectric layer illuminated by TE polarized plane waves. This method applies to any simultaneous composition of arbitrarily modulated planar transmission gratings with any permittivity in neighboring regions. Two major improvements have been made. In the first part, the eigenvalues and eigenvectors of coupled wave system of equations are first-order corrected to reduce the inherent errors generated by neglecting second-order derivatives. In the second part, a scattering matrix method is used to model the effect of boundaries. Using this method,...
Interface electromagnetic waves between Kronig-Penney photonic crystals, Article Aplications of Photonic Technology, Quebec City, 1 June 2002 through 6 June 2002 ; Volume 4833 , 2002 , Pages 535-541 ; 0277786X (ISSN) ; Momeni, B ; Khorasani, S ; Rashidian, B ; Sharif University of Technology
The electromagnetic interface states formed in a heterostructure composed of two semi-infinite Kronig-Penny photonic crystals were studied. Modified transfer matrices were used for the study to show strong similarity between solid-state physics and electromagnetics. The calculations were limited to TE polarization and the numerical examples for both surface and interface states were given
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) ; 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)...
Detonatlve travelling waves for combustions, Article Applicable Analysis ; Volume 77, Issue 3-4 , 2001 , Pages 405-418 ; 00036811 (ISSN) ; Razani, A ; Sharif University of Technology
The existence of travelling wave solution to equations of a viscous heat conducting combustible fluid is proved. The reactions are assumed to be one step exothermic reactions with a natural discontinuous reaction rate function. The problem is studied for a general gas. Instead of assuming the ideal gas conditions we consider a general thermodynamics which is described by a fairly mild set of hypotheses. Travelling waves for detonations reduce to specific heteroclinic orbits of a discontinuous system of ODE's. The existence proof for heteroclinic orbits corresponding to weak and strong detonation waves is carried out by some general topological arguments in ODE. The uniqueness and...
Propagation of electromagnetic waves in MOG: Gravitational lensing, Article Monthly Notices of the Royal Astronomical Society ; Volume 482, Issue 4 , 2019 , Pages 4514-4518 ; 00358711 (ISSN) ; Moffat, J. W ; Sharif University of Technology
Oxford University Press 2019
We investigate the solution of Maxwell’s equations in curved spacetime within the framework of modified gravity (MOG). We show that besides the null-geodesic treatment of photons in MOG, using Maxwell’s equations and covariant coupling with the extra vector sector of gravitation in MOG, we can extract the equation for the propagation of light. We obtain Fermat’s potential and calculate the deflection angle of light during lensing from a point-like star. Our results show that the deflection angle obtained from the solution of the wave equation in MOG for the large-scale structures with larger impact parameter of light rays is proportional to that of general relativity (GR). For solar mass...
A scheme for spatial wave function teleportation in three dimensions, Article International Journal of Quantum Information ; Volume 4, Issue 5 , 2006 , Pages 781-790 ; 02197499 (ISSN) ; Rezakhani, A. T ; Golshani, M ; Sharif University of Technology
We propose a theoretical scheme for teleportation of a general wave function of a quantum object. In principle, this protocol provides teleportation of discrete N-level spatial states of an object with various degrees of freedom, e.g. spin, in ordinary three-dimensional space. All necessary Bell states and their corresponding operators to measure and reconstruct the initial state are represented. © 2006 World Scientific Publishing Company
The interaction of a surface wave with waves on a diffuse interface, Article Journal of Physical Oceanography ; Volume 34, Issue 1 , 2004 , Pages 204-213 ; 00223670 (ISSN) ; Seymour, B ; Sharif University of Technology
American Meteorological Society 2004
A resonant interaction analysis is used to study the two-dimensional interaction of a surface wave with two waves on a diffuse interface in a stratified fluid. The fluid system is modeled as a combination of two homogenous finite-depth layer with a free surface, divided by a thin third layer. Two possibilities for the interaction are found: one between the surface wave and two first-mode interfacial waves and a second between the surface wave, a first-mode, and a second-mode interfacial wave. By taking the nondimensional density difference δ as a small perturbation parameter, the evolution equations of the interfacial waves are derived asymptotically. The analysis indicates that growth of...
Endurance wave analysis (EWA) and its application for assessment of offshore structures under extreme waves, Article Applied Ocean Research ; Volume 37 , 2012 , Pages 98-110 ; 01411187 (ISSN) ; Matin Nikoo, H ; Estekanchi, H ; Sharif University of Technology
The aim of this paper is to introduce a novel approach, called Endurance Wave Analysis (EWA), for non-linear dynamic analysis and assessment of offshore structures subjected to irregular wave forces. This is, in fact, an extension of the Endurance Time Analysis (ETA) already presented by previous researchers for the seismic assessment of onshore structures. With the EWA method, the offshore structure is simulated under a predefined Intensifying Wave Train Function (IWTF), corresponding to a gradually deteriorating sea state at a specific site. The function is designed so that the roughness of the sea state represented by them increases over the time and even goes well beyond the design sea...
Impulse waves effects on coastlines and onshore industrial structures, Article Proceedings of the 5th International Conference on Asian and Pacific Coasts, APAC 2009, 13 October 2009 through 16 October 2009 ; Volume 4 , 2010 , Pages 29-36 ; 9789814466561 (ISBN) ; Ataie Ashtiani, B ; Sharif University of Technology
Laboratory investigations have been performed on impulse wave's effects near the coastlines such as shoaling effects and run-up. Wave run-up over on smooth impermeable slope are studied in over than 100 experimental tests. The influences of the bed slope angle, incident impulse wave height and still water depth are investigated. The available empirical equations for impulsive wave run-up have been examined by comparison with the collected experimental data. A new equation has been presented for run-up estimation based on the laboratory measurements. It has been compared with others empirical equations and the differences have been discussed. The shoaling effects on the impulse wave feature...
Influence of channel shape on wave-generated parameters by a pressure source in shallow water, Article Journal of Waterway, Port, Coastal and Ocean Engineering ; Volume 143, Issue 5 , 2017 ; 0733950X (ISSN) ; Binns, J ; Renilson, M ; Thomas, G ; Sharif University of Technology
The present work is a numerical investigation into the waves generated by a pressure source moving in straight channels with a nonrectangular cross-channel depth profile. Wave fields generated by the moving pressure source are described, and the effects of channel bathymetry on the generated wave characteristics of wave height, wave-breaking location, wave-breaking type and intensity, and peel angle are presented. Four different channel cross-section shapes were investigated, and the results were analyzed. It was concluded that the maximum wave height depended primarily on pressure-source parameters and that the investigated channel shapes did not have a significant effect on the maximum...
Optical wave evolution due to interaction with elastic wave in a phoxonic crystal slab waveguide, Article Applied Physics B: Lasers and Optics ; Volume 123, Issue 8 , 2017 ; 09462171 (ISSN) ; Khorasani, S ; Sharif University of Technology
Springer Verlag 2017
Phoxonic crystal as a means of guiding and confining electromagnetic and elastic waves has already attracted attentions. Lack of exact knowledge on how these two types of waves interact inside this crystal and how electromagnetic wave evolves through this interaction has increased this field complexity. Here we explain how an elastic wave affects an electromagnetic wave through photoelasticity and interface displacement mechanisms in a phoxonic crystal slab waveguide. We obtain a master equation which can describe electromagnetic wave evolution. In this equation we define a coupling parameter and calculate its value for different modes of electromagnetic and elastic waves and show it...
Modification of endurance wave analysis based on New-wave theory, Article Ships and Offshore Structures ; Volume 12, Issue 3 , 2017 , Pages 330-340 ; 17445302 (ISSN) ; Dastan Diznab, M. A ; Mehdigholi, H ; Seif, M. S ; Tabeshpour, M. R ; Sharif University of Technology
Taylor and Francis Ltd 2017
The main objective of this investigation is to modify endurance wave analysis (EWA) based on New-wave theory for convenient assessment of offshore structures under extreme waves. EWA is a novel time history based approach to evaluate structural performance in various excitation levels of wave loading by intensifying wave records. In this article, modifications are proposed to determine appropriate time duration and intensifying trend for reliable and practical assessment of offshore structures. In this way, a simplified model of a real jacket platform is utilised to investigate the application of this approach under extreme wave conditions in the Persian Gulf and results are compared with...