386 research outputs found
Quality criteria benchmark for hyperspectral imagery
Hyperspectral data appear to be of a growing interest
over the past few years. However, applications for hyperspectral
data are still in their infancy as handling the significant size of
the data presents a challenge for the user community. Efficient
compression techniques are required, and lossy compression,
specifically, will have a role to play, provided its impact on remote
sensing applications remains insignificant. To assess the data
quality, suitable distortion measures relevant to end-user applications
are required. Quality criteria are also of a major interest
for the conception and development of new sensors to define their
requirements and specifications. This paper proposes a method to
evaluate quality criteria in the context of hyperspectral images.
The purpose is to provide quality criteria relevant to the impact
of degradations on several classification applications. Different
quality criteria are considered. Some are traditionnally used in
image and video coding and are adapted here to hyperspectral
images. Others are specific to hyperspectral data.We also propose
the adaptation of two advanced criteria in the presence of different
simulated degradations on AVIRIS hyperspectral images. Finally,
five criteria are selected to give an accurate representation of the
nature and the level of the degradation affecting hyperspectral
data
Scattering at Interluminal Interface
Interest for spacetime structures has recently been revived, following
developments in metamaterials and ultrafast optics. Such structures essentially
consist of successions of space-time interfaces for which the theory is still
incomplete, in particular in the regime where the interface velocity lies
between the wave velocities in the two media involved. This paper addresses
this `interluminal' regime, providing exact scattering solutions for both
approaching and receding interfaces. The solutions are verified to be
consistent with the transmission matrix perspective and to be continuous at the
limits of the subluminal and superluminal regimes.Comment: conference paper with 2 pages, 2 figures
Diagrammatic Explanation of the Reverse Doppler Effect in Space-Time Modulated Photonic Crystals
An inverse Doppler shift occurs in a photonic crystal (PC) bounded by a
moving wall. The interpretation of this result has stirred some controversy. In
this paper, we address the problem using a diagrammatic approach. This visual
representation provides immediate insight into the phenomenon, and is a
powerful tool for the design of time-varying PCs.Comment: Submitted to 2016 AP-S Symposium. 2 pages, 2 figure
Direct Electrochemistry of Redox Enzymes as a Tool for Mechanistic Studies
International audienceThis review regards the use of dynamic electrochemistry to study the mechanism of redox enzymes, with exclusive emphasis on the configuration where the protein is adsorbed onto an electrode and electron tranfer is direct
New Electromagnetic Modes in Space-Time Modulated Dispersion-Engineered Media
We report on new electromagnetic modes in space-time modulated
dispersion-engineered media. These modes exhibit unusual dispersion relation,
field profile and scattering properties. They are generated by coupled
codirectional space-time harmonic pairs, and occur in space-time periodic media
whose constituent materials exhibit specific dispersion. Excitation of a slab
of such a medium with subluminal modulation results in periodic transfer of
energy between the incident frequency and a frequency shifted by a multiple of
the modulation frequency, whereas superluminal modulation generates
exponentially growing frequencies. These modes may find applications in optical
mixers, terahertz sources and other optical devices
Uniform-Velocity Spacetime Crystals
We perform a comprehensive analysis of uniform-velocity bilayer spacetime
crystals, combining concepts of conventional photonic crystallography and
special relativity. Given that a spacetime crystal consists of a sequence of
spacetime discontinuities, we do this by solving the following sequence of
problems: 1) the spacetime interface, 2) the double spacetime interface, or
spacetime slab, 3) the unbounded crystal, and 4) the truncated crystal. For
these problems, we present the following respective new results: 1) an
extension of the Stokes principle to spacetime interfaces, 2) an
interference-based analysis of the interference phenomenology, 3) a quick
linear approximation of the dispersion diagrams, a description of simultaneous
wavenumber and frequency bandgaps, and 4) the explanation of the effects of
different types of spacetime crystal truncations, and the corresponding
scattering coefficients. This work may constitute the foundation for a
virtually unlimited number of novel canonical spacetime media and metamaterial
problems
Electrodynamics of Accelerated-Modulation Space-Time Metamaterials
Space-time varying metamaterials based on uniform-velocity modulation have
spurred considerable interest over the past decade. We present here the first
extensive investigation of accelerated modulation space-time metamaterials.
Using the tools of general relativity, we establish their electrodynamic
principles and describe their fundamental phenomena, in comparison with the
physics of moving-matter media. We show that an electromagnetic beam
propagating in an accelerated modulation metamaterial is bent in its course,
which reveals that such a medium curves space-time for light, similarly to
gravitation. Finally, we illustrate the vast potential diversity of accelerated
modulation metamaterial by demonstrating related Schwarzschild holes
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