Showing papers by "David Rousseau published in 2007"
TL;DR: It is shown that the theoretical model, although it captures basic features of the dynamics, is not complex enough to reflect the multifractal irregularities of microvascular mechanisms.
23 citations
TL;DR: Noise-assisted image transmission is a novel instance of stochastic resonance phenomena by which nonlinear signal processing benefits from a constructive action of noise.
Abstract: A coherent imaging system with speckle noise is devised and analyzed. This demonstrates the possibility of improving the nonlinear transmission of a coherent image by increasing the level of the multiplicative speckle noise. This noise-assisted image transmission is a novel instance of stochastic resonance phenomena by which nonlinear signal processing benefits from a constructive action of noise.
21 citations
TL;DR: The results extend the possible forms of stochastic resonance or improvement by noise accessible in neuronal systems for the processing of information.
19 citations
TL;DR: It is demonstrated that, for input signals of arbitrary amplitude, the performance in the estimation can be improved by the addition of independent noises onto the thresholds in the array.
Abstract: A noisy input signal is observed by means of a parallel array of one-bit threshold quantizers, in which all the quantizer outputs are added to produce the array output. This parsimonious signal representation is used to implement an optimal Bayesian estimation from the output of the array. Such conditions can be relevant for fast real-time processing in large-scale sensor networks. We demonstrate that, for input signals of arbitrary amplitude, the performance in the estimation can be improved by the addition of independent noises onto the thresholds in the array. These results constitute a novel instance of the phenomenon of suprathreshold stochastic resonance in arrays, by which nonlinear transmission or processing of signals with arbitrary amplitude can be improved through cooperative coupling with noise.
18 citations
TL;DR: In this paper, the feasibility of stochastic resonance or improvement by noise in optimal processing has been investigated and an optimal detector is shown, the overall best performance of which is not at zero noise, but at a finite nonzero level of noise.
Abstract: A report is presented on the feasibility in principle of a new property for stochastic resonance or improvement by noise in optimal processing. An optimal detector is shown, the overall best performance of which is not at zero noise, but at a finite nonzero level of noise.
12 citations
22 Oct 2007
TL;DR: N numerically simulated data generated by a model based on nonlinear coupled oscillators, showing that linear couplings seem more adequate than parametric couplings to describe power spectra at frequencies higher than 1 Hz will now serve as a basis to elaborate more powerful models of LDF data.
Abstract: Laser Doppler flowmetry (LDF) technique is widely used in clinical investigations to monitor microvascular blood flow. It can be a very interesting tool to diagnose impairment in the microcirculation caused by pathologies. However, this can be done in an efficient way only if the processed signals are well understood. Therefore, in order to gain a better insight into LDF signals, this work presents numerically simulated data generated by a model based on nonlinear coupled oscillators. Linear and parametric couplings, as well as fluctuations are analyzed. Each simulated signal is processed to obtain its power spectrum in the frequency domain and a comparison with real data is proposed. The results show that the power spectra of the simulated signals reflect the presence of the cardiac, respiration, myogenic, neurogenic and endothelial related metabolic activities. However, their amplitude in the frequency domain are more pronounced than they are on real LDF signals. Moreover, the modeling of fluctuations is essential to reproduce the noise present on real data. Finally, linear couplings seem more adequate than parametric couplings to describe power spectra at frequencies higher than 1 Hz. This work will now serve as a basis to elaborate more powerful models of LDF data.
6 citations
11 Sep 2007
TL;DR: In this article, the authors studied the performance of a nonlinear imaging system with threshold, in the presence of multiplicative speckle noise or additive noise like the thermal noise, as they are encountered in coherent imaging and incoherent imaging.
Abstract: The possibility of a beneflcial in∞uence of noise is studied on the performance of a nonlinear imaging system with threshold, in the presence of multiplicative speckle noise or additive noise like the thermal noise, as they are encountered in coherent imaging and incoherent imaging. We show, for these two types of noise, the existence of operating conditions for which the action of noise can improve the quality of the transmission by the imaging system. Exact analytical expressions of the optimal performance, as well as the corresponding level of noise to inject, are obtained. These expressions allow a better understanding of the speciflc efiects of useful noise with images.
1 citations
TL;DR: The usefulness of the optical Doppler effect in physiological and pharmacological applications is demonstrated by showing a significant decrease of the myogenic and neurogenic activities when isoflurane dose increases.
Abstract: The optical Doppler effect resulting from interactions between laser light photons and red blood cells of the microcirculation is used to characterize the influence of isoflurane, an halogenated volatile anesthetic, on the peripheral cardiovascular system. After having recorded laser Doppler flowmetry blood perfusion signals on isoflurane-induced anesthetized healthy rats, wavelet analyses show a significant decrease of the myogenic and neurogenic activities when isoflurane dose increases from 1.5% to 3%. Moreover, the approximate entropy shows a weak decrease of signal irregularity when dose of isoflurane increases. These findings demonstrate the usefulness of the optical Doppler effect in physiological and pharmacological applications.
1 citations
Proceedings Article•
01 Jan 2007
TL;DR: This paper proposes a synthetic presentation on the phenomenon of stochastic resonance or improvement through the action of noise, in the context of measurement and sensors, data and information processing, with examples on digital images.
Abstract: This paper proposes a synthetic presentation on the phenomenon of stochastic resonance or improvement through the action of noise. Several situations and mechanisms are reported, demonstrating a constructive role of noise, in the context of measurement and sensors, data and information processing, with examples on digital images.