Gold films do not adhere well on glass substrates, so plasmonics experiments typically use a thin adhesion layer of titanium or chromium to ensure a proper adhesion between the gold film and the glass substrate. While the absorption of light into gold structures is largely used to generate heat and control the temperature at the nanoscale, the influence of the adhesion layer on this process is largely overlooked.
The linear instability of a vortex ring with swirl with Gaussian distributions of azimuthal vorticity and velocity in its core is studied by direct numerical simulation.
We investigate theoretically and experimentally the stability of two interlaced helical vortices with respect to displacement perturbations having wavelengths that are large compared to the size of the vortex cores. First, existing theoretical results are recalled and applied to the present configuration. Various modes of unstable perturbations, involving different phase relationships between the two vortices, are identified and their growth rates are calculated.
La construction d'un matériau numérique repose sur des descripteurs morphologiques qui caractérisent un matériau réel à l'aide d'informations statistiques et géométriques. La microstructure numérique générée est qualifié statistiquement semblable par rapport à la réalité. Or deux microstructures statistiquement semblables peuvent présenter des comportements de fissuration différents. Ces différences peuvent avoir une influence sur la perméabilité des enceintes.
In Nuclear Magnetic Resonance (NMR) spectroscopy, an efficient analysis and a relevant extraction of different molecule properties from a given chemical mixture are important tasks, especially when processing bidimensional NMR data. To that end, using a blind source separation approach based on a vari-ational formulation seems to be a good strategy. However, the poor resolution of NMR spectra and their large dimension require a new and modern blind source separation method.
We use tail expectiles to estimate alternative measures to the Value at Risk (VaR) and Marginal Expected Shortfall (MES), two instruments of risk protection of utmost importance in actuarial science and statistical finance. The concept of expectiles is a least squares analogue of quantiles. Both are M-quantiles as the minimizers of an asymmetric convex loss function, but expectiles are the only M-quantiles that are coherent risk measures.
We address the problem of filtering out localized time-frequency components in signals. The problem is formulated as a minimization of a suitable quadratic form, that involves a data fidelity term on the short-time Fourier transform outside the support of the undesired component, and an energy pe-nalization term inside the support. The minimization yields a linear system whose solution can be expressed in closed form using Gabor multipliers.
The interaction between an impinging electromagnetic wave and a target results in a scattered wave, which depends upon the frequency, the size, shape and electromagnetic properties of the target. The measurement of a scattered signal can be used to detect or characterize a target, and the applications range from radar systems at large scale to optical tomography at the microscale.