scholarly journals Trapped mode resonances in metalo-dielectric structures with electric asymmetry materials

2011 ◽  
Vol 60 (1) ◽  
pp. 85-93
Author(s):  
Mihai Rotaru ◽  
Jan Sykulski
Keyword(s):  
Frequency Selective Surfaces ◽  
Trapped Modes ◽  
High Quality ◽  
Trapped Mode ◽  
Dielectric Substrates ◽  
Symmetric Structure ◽  
Resonant Modes ◽  
Metallic Inclusions ◽  
Dielectric Structures ◽  
Sub Wavelength

Trapped mode resonances in metalo-dielectric structures with electric asymmetry materialsThis paper investigates the possibility of exciting high quality trapped resonant modes on frequency selective surfaces consisting of identical sub-wavelength metallic inclusions (symmetrically split rings) with no structural asymmetry but exhibitting electrical asymmetry. The electrical symmetry is broken by using different dielectric substrates. The existence of such anti-symmetric trapped mode on geometrical symmetric structure is demonstrated through numerical simulation. Numerical results suggest that the high quality factor observed for these resonant modes is achieved via weak coupling between the "trapped modes" and free space which enables the excitation of these modes.

scholarly journals Trapped modes in a waveguide with a long obstacle

2000 ◽  
Vol 403 ◽  
pp. 251-261 ◽  
Author(s):  
N. S. A. KHALLAF ◽  
L. PARNOVSKI ◽  
D. VASSILIEV
Keyword(s):  
Two Dimensional ◽  
Trapped Modes ◽  
Acoustic Waveguide ◽  
Trapped Mode ◽  
Rectangular Obstacle

Consider an infinite two-dimensional acoustic waveguide containing a long rectangular obstacle placed symmetrically with respect to the centreline. We search for trapped modes, i.e. modes of oscillation at particular frequencies which decay down the waveguide. We provide analytic estimates for trapped mode frequencies and prove that the number of trapped modes is asymptotically proportional to the length of the obstacle.

Subharmonic resonance of proposed storm gates for Venice Lagoon

1994 ◽  
Vol 444 (1920) ◽  
pp. 257-265 ◽  
Keyword(s):  
Experimental Evidence ◽  
Incident Wave ◽  
Laboratory Tests ◽  
Venice Lagoon ◽  
Subharmonic Resonance ◽  
Horizontal Axis ◽  
Trapped Modes ◽  
Resonance Mechanism ◽  
Trapped Mode ◽  
Incident Waves

A recent design of storm barriers at the inlets of Venice Lagoon consists of a number of articulated inclined gates hinged on a horizontal axis on the seabed. In laboratory tests with normally incident waves the gates have been found to oscillate at half of the incident wave frequency and out of phase with their immediate neighbours. In this paper we identify the resonance mechanism by first showing the existence of trapped modes as a consequence of the articulated construction. Experimental evidence is shown for the trapped mode and its subharmonic resonance by normally incident waves.

scholarly journals Trapped modes around a row of circular cylinders in a channel

1999 ◽  
Vol 386 ◽  
pp. 259-279 ◽  
Author(s):  
T. UTSUNOMIYA ◽  
R. EATOCK TAYLOR
Keyword(s):  
Expansion Method ◽  
Wave Theory ◽  
Multipole Expansion ◽  
Circular Cylinders ◽  
Large Radius ◽  
Trapped Modes ◽  
Resonant Phenomenon ◽  
Trapped Mode ◽  
Linear Water Wave Theory ◽  
Multipole Expansion Method

Trapped modes around a row of bottom-mounted vertical circular cylinders in a channel are examined. The cylinders are identical, and their axes equally spaced in a plane perpendicular to the channel walls. The analysis has been made by employing the multipole expansion method under the assumption of linear water wave theory. At least the same number of trapped modes is shown to exist as the number of cylinders for both Neumann and Dirichlet trapped modes, with the exception that for cylinders having large radius the mode corresponding to the Dirichlet trapped mode for one cylinder will disappear. Close similarities between the Dirichlet trapped modes around a row of cylinders in a channel and the near-resonant phenomenon in the wave diffraction around a long array of cylinders in the open sea are discussed. An analogy with a mass–spring oscillating system is also presented.

Edge waves on a gently sloping beach: uniform asymptotics

1991 ◽  
Vol 233 ◽  
pp. 483-493 ◽  
Author(s):  
Peter Zhevandrov
Keyword(s):  
Finite Number ◽  
Shallow Water Equation ◽  
Uniform Asymptotics ◽  
Trapped Modes ◽  
Edge Waves ◽  
Trapped Mode ◽  
Complete Set ◽  
Constant Slope ◽  
Sloping Beach ◽  
Uniform Asymptotic Expansions

Edge waves on a beach of gentle slope ε [Lt ] 1 are considered. For constant slope, Ursell (1952) has obtained a complete set of trapped modes and shown that there exists only a finite number n of such modes, (2n + 1)β < ½π, β = tan−1ε. For non-uniform slope the formulae for the trapped-mode frequencies were heuristically derived by Shen, Meyer & Keller (1968). For small n ∼ O(1) Miles (1989) has obtained formulae which coincide with Shen et al.'s (1968) with accuracy to O(ε) and differ from them by O(ε2). However, Miles’ formulae fail at n ∼ 1/ε. In this paper it is proved that Shen et al.'s (1968) formulae are valid for all n (including n ∼ 1/ε) with accuracy to O(ε) and corrections of any order in ε are given. Uniform asymptotic expansions are obtained for the corresponding eigenfunctions. These expansions give Miles’ (1989) result for small n. The formulae for the frequencies and the eigenfunctions have the same structure for both the full dispersion system and the shallow-water equation. For small n the frequencies for both models coincide with accuracy to O(ε2), but for n ∼ 1/ε they differ by O(1). In the last section the effect of rotation following Evans (1989) is taken into account. All the asymptotics have formal character, i.e. they satisfy the corresponding equations with accuracy to O(εN), N being arbitrarily large. The rigorous justification of these asymptotics is under way.

Trapped modes with extremely high quality factor in a circular array of dielectric nanorods

2018 ◽  
Vol 43 (21) ◽  
pp. 5403
Author(s):  
Hai-Long Han ◽  
He Li ◽  
Hai-bin Lü ◽  
Xiaoping Liu
Keyword(s):  
Quality Factor ◽  
High Quality Factor ◽  
Circular Array ◽  
Trapped Modes ◽  
High Quality

Online Electromagnetic Filtration of Molten Aluminum Using a Multistage Separator System

2015 ◽  
Vol 15 (1) ◽  
pp. 89-92
Author(s):  
Da Shu ◽  
Jun Wang ◽  
Baode Sun
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Molten Aluminum ◽  
External Electromagnetic Field ◽  
Grain Refiner ◽  
High Quality ◽  
Inclusion Content ◽  
Average Efficiency ◽  
Filtration System ◽  
Metallic Inclusions

AbstractElectromagnetic filtration is a new method for the removal of micro-sized non-metallic inclusions from molten aluminum by means of an external electromagnetic field. This paper introduces a multistage electromagnetic filtration system using alternating magnetic field and its application in semi-continuous casting of aluminum billets. The inclusion content was quantitatively determined through PoDFA sampling and analysis. Results showed that the average efficiency of the removal of inclusion particles and oxide films could reach 93.8% and 80.9%, respectively. The content of inclusion particles without grain refiner could be decreased to a level of 0.02 mm2/kg aluminum, satisfying the requirements in terms of the cleanliness of high-quality aluminum products.

Wave diffraction by a long array of cylinders

1997 ◽  
Vol 339 ◽  
pp. 309-330 ◽  
Author(s):  
H. D. MANIAR ◽  
J. N. NEWMAN
Keyword(s):  
Boundary Conditions ◽  
Wave Diffraction ◽  
Water Wave ◽  
Dirichlet Boundary ◽  
Dirichlet Boundary Conditions ◽  
Circular Cylinders ◽  
Trapped Modes ◽  
Homogeneous Solutions ◽  
Resonant Modes ◽  
Trapped Wave

Water wave diffraction by an array of bottom-mounted circular cylinders is analysed under the assumptions of linear theory. The cylinders are identical, and equally spaced along the array. When the number of cylinders is large, but finite, near-resonant modes occur between adjacent cylinders at critical wavenumbers, and cause unusually large loads on each element of the array. These modes are associated with the existence of homogeneous solutions for the diffraction by an array which extends to infinity in both directions. This phenomenon is related to the existence of trapped waves in a channel. A second trapped wave is established, corresponding to Dirichlet boundary conditions on the channel walls, as well as a sequence of higher wavenumbers where ‘nearly trapped’ modes exist.

Passive trapped modes in the water-wave problem for a floating structure

2010 ◽  
Vol 657 ◽  
pp. 456-477 ◽  
Author(s):  
C. J. FITZGERALD ◽  
P. MCIVER
Keyword(s):  
Water Wave ◽  
Finite Energy ◽  
Frequency Domain Analysis ◽  
Trapped Modes ◽  
Wave Problem ◽  
Floating Structure ◽  
Water Wave Problem ◽  
Floating Structures ◽  
Trapped Mode ◽  
Motion Modes

Trapped modes in the linearized water-wave problem are free oscillations of an unbounded fluid with a free surface that have finite energy. It is known that such modes may be supported by particular fixed structures, and also by certain freely floating structures in which case there is, in general, a coupled motion of the fluid and structure; these two types of mode are referred to respectively as sloshing and motion trapped modes, and the corresponding structures are known as sloshing and motion trapping structures. Here a trapped mode is described that shares characteristics with both sloshing and motion modes. These ‘passive trapped modes’ are such that the net force on the structure exerted by the fluid oscillation is zero and so, in the absence of any forcing, the structure does not move even when it is allowed to float freely. In the paper, methods are given for the construction of passive trapping structures, a mechanism for exciting the modes is outlined using frequency-domain analysis, and the existence of the passive trapped modes is confirmed by numerical time-domain simulations of the excitation process.

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