4,352 research outputs found
Statistics of resonance states in a weakly open chaotic cavity
In this letter, we demonstrate that a non-Hermitian Random Matrix description
can account for both spectral and spatial statistics of resonance states in a
weakly open chaotic wave system with continuously distributed losses. More
specifically, the statistics of resonance states in an open 2D chaotic
microwave cavity are investigated by solving the Maxwell equations with lossy
boundaries subject to Ohmic dissipation. We successfully compare the statistics
of its complex-valued resonance states and associated widths with analytical
predictions based on a non-Hermitian effective Hamiltonian model defined by a
finite number of fictitious open channels
Integrated Scenario-based Design Methodology for Collaborative Technology Innovation
The paper presents a scenario-based methodology developed and tested throughout cooperative research and development projects. It is aimed at supporting information technology innovation with an end-to-end Human and Social Sciences assistance. This methodology provides an integrated approach combining a vision of the potential users, business aspects and technological challenges throughout the design process. An original combination of different methods is proposed and experimented: user-centred design, scenario-based design, user and functional requirements analysis, business value analysis, user acceptance studies, and visualization methods. This methodology has been implemented in three European R&D projects, in the domain of the telecommunications and Internet infrastructure. The key contributions of this approach are that it unifies brings together visions of the users, potential business value and technology challenges thanks to scenario construction.Scenario-based design ; user requirements ; business economics ; functional requirements ; visualization
Complete S-matrix in a microwave cavity at room temperature
We experimentally study the widths of resonances in a two-dimensional
microwave cavity at room temperature. By developing a model for the coupling
antennas, we are able to discriminate their contribution from those of ohmic
losses to the broadening of resonances. Concerning ohmic losses, we
experimentally put to evidence two mechanisms: damping along propagation and
absorption at the contour, the latter being responsible for variations of
widths from mode to mode due to its dependence on the spatial distribution of
the field at the contour. A theory, based on an S-matrix formalism, is given
for these variations. It is successfully validated through measurements of
several hundreds of resonances in a rectangular cavity.Comment: submitted to PR
Diffractive orbits in the length spectrum of a 2D microwave cavity with a small scatterer
In a 2D rectangular microwave cavity dressed with one point-like scatterer, a
semiclassical approach is used to analyze the spectrum in terms of periodic
orbits and diffractive orbits. We show, both numerically and experimentally,
how the latter can be accounted for in the so-called length spectrum which is
retrieved from 2-point correlations of a finite range frequency spectrum.
Beyond its fundamental interest, this first experimental evidence of the role
played by diffractive orbits in the spectrum of an actual cavity, can be the
first step towards a novel technique to detect and track small defects in wave
cavities.Comment: 14 pages, format IO
Green IT, China – France: similar reactions?
Based upon a study carried out both in France and in China, this communication aims to answer the following question: Is it useful to invest in Green IT for Universities? This research provides information on the perception of individuals with respect to the label "green" placed on an IT object and also highlights the need to take into account the affective dimension of attitude in the Technology Acceptance Model. Our results may help in investment decisions regarding "green" technologyTechnology Acceptance Model, Green IT, intercultural study
Combining EEG source connectivity and network similarity: Application to object categorization in the human brain
A major challenge in cognitive neuroscience is to evaluate the ability of the
human brain to categorize or group visual stimuli based on common features.
This categorization process is very fast and occurs in few hundreds of
millisecond time scale. However, an accurate tracking of the spatiotemporal
dynamics of large-scale brain networks is still an unsolved issue. Here, we
show the combination of recently developed method called dense-EEG source
connectivity to identify functional brain networks with excellent temporal and
spatial resolutions and an algorithm, called SimNet, to compute brain networks
similarity. Two categories of visual stimuli were analysed in this study:
immobile and mobile. Networks similarity was assessed within each category
(intra-condition) and between categories (inter-condition). Results showed high
similarity within each category and low similarity between the two categories.
A significant difference between similarities computed in the intra and
inter-conditions was observed at the period of 120-190ms supposed to be related
to visual recognition and memory access. We speculate that these observations
will be very helpful toward understanding the object categorization in the
human brain from a network perspective.Comment: 5 pages, 2 figures. Accepted for 2016 IEEE Workshop on Statistical
Signal Processin
Localized Modes in a Finite-Size Open Disordered Microwave Cavity
We present measurements of the spatial intensity distribution of localized
modes in a two-dimensional open microwave cavity randomly filled with
cylindrical dielectric scatterers. We show that each of these modes displays a
range of localization lengths and successfully relate the largest value to the
measured leakage rate at the boundary. These results constitute unambiguous
signatures of the existence of strongly localized electromagnetic modes in
two-dimensionnal open random media
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