Mountain papaya fruits (Vasconcella pubescens) were tested for firmness with a nondestructive acoustic method for 14 days after harvest. The response of each fruit was analyzed with the Fourier transform to obtain a firmness index (FI) based on the second resonant frequency and with the Short Time Fourier Transform (STFT) to obtain a spectrogram frequency centroid (FC) index. The indexes were p...

We study the spectrum of the distributional kernel Kα,β(x), where α and β are complex numbers and x is a point in the space Rn of the n-dimensional Euclidean space. We found that for any nonzero point ξ that belongs to such a spectrum, there exists the residue of the Fourier transform (−1)k ̂ K2k,2k(ξ), where α = β = 2k, k is a nonnegative integer and ξ ∈Rn. 2000 Mathematics Subject Classificati...

1 Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ Paris Diderot, UMR 7154 CNRS, F-75005 Paris, France. 2 InSARlab Geohazards InSAR laboratory, Geoscience Research dept., Geological Survey of Spain, Alenza 1, 28003, Spain. 3 Université Joseph Fourier Grenoble I, OSUG Observatoire des Sciences de l’Univers de Grenoble, ISTerre Institut des Sciences de la Terre Maison des Géoscie...

Time-frequency representations provide a convenient method for analyzing signals whose frequency content changes with time, and speciically those signals with components that overlap in time and/or frequency. In this paper we suggest a technique for optimally concentrating components of a signal in the time-frequency plane via a particular choice of analysis window for the short-time Fourier tr...

This paper considers the proposed algorithm submitted to the Music Information Retrieval Evaluation eXchange (MIREX) 2010 “Audio Melody Extraction” task. The proposed melody extraction algorithm can be divided into three steps: (1) a spectral analysis using a variable length window, (2) a pitch candidate estimation, and (3) a pitch sequence identification. In the first step, the short-time Four...

The paper presents an obstacle detection method for mobile robots using a structured background. This method is based on differences of appearance between obstacles and the background in the camera images. The basic idea is to cover the ground of the workspace with a known structure. If part of this structure is obscured, this can be detected and indicates the existence of an obstacle. The meth...

Time-frequency reassignment may be viewed as a refinement of the short-time Fourier transform, in which phase information is used to reduce the smearing of energy associated with the standard spectrogram. However, even given the perceptibly clearer visual representation yielded by the reassignment method in the case of musical signals, the task remains of extracting useful information from it f...

An entirely new set of criteria for the design of kernels for time-frequency representations (TFRs) has been recently proposed [1], [2], [3]. The goal of these criteria is to produce kernels (and thus, TFRs) which will enable accurate classification without explicitly defining, a priori, the underlying structure that differentiates individual classes. These kernels, which are optimized to discr...

Micro-Doppler signatures provide unique information about properties of the target. These micro-Doppler features can be used for real time target recognition in military applications and surveillance operations. In this paper, we present Gabor-Wigner transform for extracting micro-Doppler features from the radar returns. The effectiveness of the GaborWigner transform in extracting micro-Doppler...