A new model for conference submissions

5 pages, 4 figures. Submitted to Eur. Phys. J. BElectronic submission to a conference is a process that is known to evolve nonlinearly in time, with a dramatic increase when approaching the deadline. A model has recently been proposed by Alfi et al. (Nature Physics, 2007) for such a process, and the question of its universality has been raised. This problem is revisited here from a data analysis and modeling point of view, on the basis of a larger data set. A new model is proposed that better describes the complete evolution of the process (including saturation) and allows for a running prediction of the total number of submissions

A note on reassigned Gabor spectrograms of Hermite functions

An explicit form is given for the reassigned Gabor spectrogram of an Hermite function of arbitrary order. It is shown that the energy concentration sharply localizes outside the border of a clearance area limited by the ''classical'' circle where the Gabor spectrogram attains its maximum value, with a perfect localization that can only be achieved in the limit of infinite order

One or two Frequencies? The empirical Mode Decomposition Answers

19 pages, 7 figures. Submitted to IEEE Trans. on Signal Proc.This paper investigates how Empirical Mode Decomposition (EMD), a fully data-driven technique recently introduced for decomposing any oscillatory waveform into zero-mean components, behaves in the case of a composite two-tones signal. Essentially two regimes are shown to exist, depending on whether the amplitude ratio of the tones is greater or smaller than unity, and the corresponding resolution properties of EMD turn out to be in good agreement with intuition and physical interpretation. A refined analysis is provided for quantifying the observed behaviours, theoretical claims are supported by numerical experiments, and possible extensions to nonlinear oscillations are briefly outlined

On the Chirp Decomposition of Weierstrass-Mandelbrot Functions, and their Time-Frequency Interpretation

Weierstrass–Mandelbrot functions are given a time–frequency interpretation which puts emphasis on their possible decomposition on chirps as an alternative to their standard, Fourier-based, representation. Examples of deterministic functions are considered, as well as randomized versions for which the analysis is applied to empirical estimates of statistical quantities

Time-Frequency Surrogates for Nonstationary Signal Analysis

International audienceThe purpose of the present communication is, after a brief outline of the use of simple surrogates as introduced so far for stationarity tests, to deal with constructions of surrogates in ''time-frequency domains''. Indeed, for transient detection or cross-correlations analysis, one need to construct directly ''surrogate time-frequency distributions'', as opposed to distributions of surrogate time series, and keeping the `geometrical' structure in the plane of the quadratic distribution

Sparse time-frequency distributions of chirps from a compressed sensing perspective

International audienceConsidering that multicomponent chirp signals are sparse in the time-frequency domain, it is possible to attach to them highly localized distributions thanks to a compressed sensing approach based on very few measurements in the ambiguity plane. The principle of the technique is described, with emphasis on the choice of the measurement subset for which an optimality criterion is proposed

Revisiting and testing stationarity

6 pages, 4 figures, 10 references. To be presented at the 2008 Euro American Workshop on Information Optics will be held during June 1 - 5, 2008 at Les Tresoms in Annecy, France.The concept of stationarity is revisited from an operational perspective that explicitly takes into account the observation scale. A general framework is described for testing such a relative stationarity via the introduction of stationarized surrogate data