Time-scale analysis of abrupt changes corrupted by multiplicative noise

Multiplicative Abrupt Changes (ACs) have been considered in many applications. These applications include image processing (speckle) and random communication models (fading). Previous authors have shown that the Continuous Wavelet Transform (CWT) has good detection properties for ACs in additive noise. This work applies the CWT to AC detection in multiplicative noise. CWT translation invariance allows to define an AC signature. The problem then becomes signature detection in the time-scale domain. A second-order contrast criterion is defined as a measure of detection performance. This criterion depends upon the first- and second-order moments of the multiplicative process's CWT. An optimal wavelet (maximizing the contrast) is derived for an ideal step in white multiplicative noise. This wavelet is asymptotically optimal for smooth changes and can be approximated for small AC amplitudes by the Haar wavelet. Linear and quadratic suboptimal signature-based detectors are also studied. Closed-form threshold expressions are given as functions of the false alarm probability for three of the detectors. Detection performance is characterized using Receiver Operating Characteristic (ROC) curves computed from Monte-Carlo simulations

Hybridation and Fusion of Satellite and Telecommunication Network Based Positioning Methods

1. Browsing over the satellite Navigation Systems: 1.1 Basic Principles 1.2 Augmentation with external navigation means Contents 1.3 Augmentation with self-sensory means 2. Positioning with wireless communication networks: 2.1 Positioning capabilities of wireless networks 2.2 Hybridation: Fusion Algorithm

Influence of cutting parameters and wear in drilling of 3D wowen carbon/epoxy composite

International audienceno abstrac

Etude expérimentale de l'influence des paramètres de coupe et de l'usure de l'outil sur la qualité de percage d'un composite tissé 3D.

International audienceno abstrac

Detection of T wave beta-to-beat variations prior to ventricular arrythmias onset in ICD-stored intracardiac electrograms: the endocardial T-wave alternans study (ETWAS)

International audienceBackground: The aim of the Endocardial T-Wave Alternans Study was to prospectively assess thepresence of T-wave alternans (TWA) or beat-to-beat repolarization changes on implantable cardioverter-defibrillator (ICD)-stored electrograms (EGMs) immediately preceding the onset of spontaneous ventriculartachycardia (VT) or fibrillation (VF). Methods: Thirty-seven VT/VF episodes were compared to 116 baseline reference EGMs from the same57 patients. A Bayesian model was used to estimate the T-wave waveform in each cardiac beat and a setof 10 parameters was selected to segment each detected T wave. Beat-by-beat differences in each T-waveparameter were computed using the absolute value of the difference between each beat and the followingone. Fisher criterion was used for determining the most discriminant T-wave parameters, then top-Mranked parameters yielding a normalized cumulative Fisher score>95% were selected, and analysis wasapplied on these selected parameters. Simulated TWA EGMs were used to validate the algorithm. Results: In the simulation study, TWA was detectable even in the case of the smallest simulatedalternans of 25μV. In 13 of the 37 episodes (35%) occurring in nine of 16 patients, significant largerbeat-to-beat variations before arrhythmia onset were detected compared to their respective references(median one positive episode per patient). Parameters including the T-wave apex amplitude seem themore discriminant parameters.Conclusions:Detection of beat-by-beat repolarization variations in ICD-stored EGMs is feasible ina significant subset of cases and may be used for predicting the onset of ventricular arrhythmias