摘要:
An imaging method using shear waves for observing a viscoelastic medium (2), comprising: several successive excitation steps j during which elastic shear waves are generated respectively at different excitation loci (L j ) in the viscoelastic medium (2) by an imaging device, the different excitation loci being separated from one another by a maximum distance Dm, - an imaging step corresponding to each excitation step j, in which a set j of successive raw images Im j (t k ) of the viscoelastic medium at times t k are determined during propagation of the shear wave, the raw images having a resolution R which is larger than the maximum distance Dm, an averaging step in which raw images Im j (t k ) corresponding to the same relative time t k are averaged to determine an average image Im' (t k ).
摘要:
A device for receiving and/or emitting an electromagnetic wave having a free space wavelength λ 0 comprised between 1 mm and 10 cm, comprising a medium (11) of solid dielectric material and the free space wavelength λ 0 corresponding to a wavelength λ inside the medium, a plurality of conductor elements (12) incorporated inside the medium and spaced apart from each other of a distance lower than λ/10, and one antenna element (13). The conductor elements form small loop elements. A tuned conductor element among the conductor elements has a first end at a distance from the antenna element which is lower than λ/10, and has an electric resonance frequency corresponding to the wavelength λ.
摘要:
Method for focusing an electromagnetic or acoustic wave on a point near which one or more diffusers are placed, comprising a learning step in which the pulsed responses hij (t) between the focus point and each antenna (2) of the network are determined. Waves corresponding to signals Sji(t) = Si(t) ⊗ hij(-t), where Si(t) is a function of time and hij(-t) is a temporal inversion of the pulsed response hij(t), can then be transmitted from said antennas (2) of the network.
摘要:
According to the invention, a wave, corresponding to a signal s(t), may be temporally inverted by application of a first transformation to lower the central frequency thereof to produce a first set of transformed signals Ki(t), then a second set of transformed signals K'i(t) is produced, representing the temporal inversion signal s(-t) and a third transformation is applied to said second set to generate the temporally-inverted signal s (-t) .
摘要:
A wave shaping device which comprises a tunable impedance surface and a controller connected to the surface in order to control its impedance. The shaping device further comprises a transmission module for receiving a pilot signal used to control the impedance of the surface.