273 research outputs found
Dirichlet L-series with real and complex characters and their application to solving double sums
A description of the properties of \L with complex characters is given. By
using these, together with the more familiar \L with real characters, it is
shown how certain two dimensional lattice sums, which previously could not be
put into closed form, may now be expressed in this way.Comment: 21 pages, 1 tabl
On the applicability of non-resonant artificial diamagnetics
Artificial diamagnetics are prominent for achieving extraordinarily strong
diamagnetism in a wide frequency range. However, as far as the magnetic fields
outside the artificial medium are concerned, bulk conductors show a very
similar pattern. The question arises whether the complicated internal structure
of artificial diamagnetics can, to this end, be replaced by a simpler object.
We analyse the figure of merit for the application of diamagnetics in magnetic
levitation, and show that for an electrically small body, any internal
structuring makes the figure of merit worse than that of a simple conducting
object.Comment: 5 pages, 5 figure
Vortex-type elastic structured media and dynamic shielding
The paper addresses a novel model of metamaterial structure. A system of
spinners has been embedded into a two-dimensional periodic lattice system. The
equations of motion of spinners are used to derive the expression for the
chiral term in the equations describing the dynamics of the lattice. Dispersion
of elastic waves is shown to possess innovative filtering and polarization
properties induced by the vortextype nature of the structured media. The
related homogenised effective behavior is obtained analytically and it has been
implemented to build a shielding cloak around an obstacle. Analytical work is
accompanied by numerical illustrations.Comment: 24 pages, 13 figure
Active cloaking of finite defects for flexural waves in elastic plates
We present a new method to create an active cloak for a rigid inclusion in a
thin plate, and analyse flexural waves within such a plate governed by the
Kirchhoff plate equation. We consider scattering of both a plane wave and a
cylindrical wave by a single clamped inclusion of circular shape. In order to
cloak the inclusion, we place control sources at small distances from the
scatterer and choose their intensities to eliminate propagating orders of the
scattered wave, thus reconstructing the respective incident wave. We then vary
the number and position of the control sources to obtain the most effective
configuration for cloaking the circular inclusion. Finally, we successfully
cloak an arbitrarily shaped scatterer in a thin plate by deriving a
semi-analytical, asymptotic algorithm.Comment: 19 pages, 14 figures, 1 tabl
Electromagnetic surface states in structured perfect-conductor surfaces
Surface-bound modes in metamaterials forged by drilling periodic hole arrays
in perfect-conductor surfaces are investigated by means of both analytical
techniques and rigorous numerical solution of Maxwell's equations. It is shown
that these metamaterials cannot be described in general by local,
frequency-dependent permittivities and permeabilities for small periods
compared to the wavelength, except in certain limiting cases that are discussed
in detail. New related metamaterials are shown to exhibit exciting optical
properties that are elucidated in the light of our simple analytical approach.Comment: 5 figure
- …