Archives Ouvertes HAL

Toutes les publications de l'ENAC en direct.
All ENAC publications.

[hal-02474585] Preconditioned P-ULA for Joint Deconvolution-Segmentation of Ultrasound Images

Publications ENAC - Vendredi, 14 février 2020 - 02:38:23
Joint deconvolution and segmentation of ultrasound images is a challenging problem in medical imaging. By adopt- ing a hierarchical Bayesian model, we propose an accelerated Markov chain Monte Carlo scheme where the tissue reflectivity function is sampled thanks to a recently introduced proximal unadjusted Langevin algorithm. This new approach is combined with a forward-backward step and a preconditioning strategy to accelerate the convergence, and with a method based on the majorization-minimization principle to solve the inner noncon- vex minimization problems. As demonstrated in numerical ex- periments conducted on both simulated and in vivo ultrasound images, the...

[hal-02044223] Sensitivity analysis in general metric spaces

Publications ENAC - Mercredi, 12 février 2020 - 02:46:22
In this paper, we introduce new indices adapted to outputs valued in general metric spaces. This new class of indices encompasses the classical ones; in particular, the so-called Sobol indices and the Cramér-von-Mises indices. Furthermore, we provide asymptotically Gaussian estimators of these indices based on U-statistics. Surprisingly, we prove the asymp-totic normality straightforwardly. Finally, we illustrate this new procedure on a toy model and on two real-data examples.

[hal-02461523] On the sensitivity of third-order Volterra MVDR beamformers to interference-pulse shaping filter

Publications ENAC - Mercredi, 5 février 2020 - 17:42:57
Linear beamformers are optimal, in a mean square (MS) sense, when the signal of interest (SOI) and observations are jointly Gaussian and circular. Otherwise, optimal beamformers become non-linear with a structure depending on the unknown joint probability distribution of the SOI and observations. In this context, third-order Volterra minimum variance distortionless response (MVDR) beamformers have been proposed recently to improve the performance of linear beamformers in the presence of non-Gaussian and potentially non-circular interference, omnipresent in practical situations. High performance gains have been obtained for binary phase shift keying (BPSK) and quadrature...

[hal-02466360] Anomaly detection in mixed telemetry data using a sparse representation and dictionary learning

Publications ENAC - Mercredi, 5 février 2020 - 02:32:52
Spacecraft health monitoring and failure prevention are major issues in space operations. In recent years, machine learning techniques have received an increasing interest in many fields and have been applied to housekeeping telemetry data via semi-supervised learning. The idea is to use past telemetry describing normal spacecraft behaviour in order to learn a reference model to which can be compared most recent data in order to detect potential anomalies. This paper introduces a new machine learning method for anomaly detection in telemetry time series based on a sparse representation and dictionary learning. The main advantage of the proposed method is the possibility...

[hal-02459971] Cognitive Workload and Personality Style in PilotsHeart Rate Study

Publications ENAC - Samedi, 1 février 2020 - 02:25:14
The cognitive overload and emotion experienced by drivers become a primordial issue to study distraction. This is also the case in aviation, where pilots are commonly exposed to different sources of cognitive and emotional stressors and distractors. Therefore, the integration of an online monitoring to assess the cognitive variations into the cockpit would be highly desirable to alert of delicate mental states. To this aim, reliable physiological measures are required. Electrocardiography (ECG) can be considered as one of the most suitable and cost-effective techniques providing powerful and relevant features to study driver distraction and cognitive workload. Heart rate...

[hal-01280172] On Fourier coefficients of modular forms of half integral weight at squarefree integers

Publications ENAC - Jeudi, 30 janvier 2020 - 02:41:38
We show that the Dirichlet series associated to the Fourier coefficients of a half-integral weight Hecke eigenform at squarefree integers extends analytically to a holomorphic function in the half-plane $\re s>\tfrac{1}{2}$. This exhibits a high fluctuation of the coefficients at squarefree integers.

[tel-02063761] Optimisation topologique de structures sous contraintes de flambage

Publications ENAC - Jeudi, 30 janvier 2020 - 02:25:32
L'optimisation topologique vise à concevoir une structure en recherchant la disposition optimale du matériau dans un espace de conception donné, permettant ainsi de proposer des designs optimaux innovants. Cette thèse est centrée sur l'optimisation topologique pour des problèmes de conception de structures prenant en compte des contraintes de flambage. Dans une large variété de domaines de l'ingénierie, la conception innovante de structures est cruciale. L'allègement des structures lors la phase de conception tient une place prépondérante afin de réduire les coûts de fabrication. Ainsi l'objectif est souvent la minimisation de la masse de la structure à concevoir. En ce...

[hal-02456167] Characterization of a 8-Ports Vector Antenna for Measurement Applications

Publications ENAC - Mercredi, 29 janvier 2020 - 11:30:29
A wideband and radiation-pattern-reconfigurable vector antenna that presents eight ports is characterized for antenna measurement applications. This vector antenna can be advantageously employed either as a multi-polarized probe in a classical measurement setup or as a reference antenna in a multi-probe antenna system with the test-zone-field (TZF) compensation method. Thank to the capability of polarization diversity inherent to vector antennas and to the radiation pattern reconfigurability of the proposed antenna, the complexity and time of the measurement process can be reduced.

[hal-02456138] SINGLE-FED CIRCULARLY POLARIZED DIELECTRIC RESONATOR ANTENNA USING A UNIAXIAL ANISOTROPIC MATERIAL

Publications ENAC - Mercredi, 29 janvier 2020 - 11:15:47
A Dielectric Resonator Antenna operating in circular polarization is presented. The proposed antenna is formed by a uniaxial anisotropic dielectric and a ground plane. The optimization of the permittivity tensor and antenna dimensions is performed both theoretically and numerically using an Eigen mode analysis in Ansys HFSS. A good agreement is obtained for the resonant frequencies and quality factors of the different modes. The uniaxial anisotropic DRA radiates two degenerate orthogonal modes, TE111 x and TE111 y , with equal amplitudes and 90° phase difference in order to achieve circular polarization. An impedance bandwidth of 9.8% is accomplished and a broadside...

[hal-02073283] Preconditioned P-ULA for Joint Deconvolution-Segmentation of Ultrasound Images - Extended Version

Publications ENAC - Samedi, 25 janvier 2020 - 02:36:43
Joint deconvolution and segmentation of ultrasound images is a challenging problem in medical imaging. By adopting a hierarchical Bayesian model, we propose an accelerated Markov chain Monte Carlo scheme where the tissue reflectivity function is sampled thanks to a recently introduced proximal unadjusted Langevin algorithm. This new approach is combined with a forward-backward step and a preconditioning strategy to accelerate the convergence, and with a method based on the majorization-minimization principle to solve the inner non-convex minimization problems. As demonstrated in numerical experiments conducted on both simulated and in vivo ultrasound images, the proposed...
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