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Symposium introduction: European defense from the perspective of the Ukraine war
No full textInternational audienceIntroduction to the EPSJ syposium of European defense in the light of the Ukariane war
Work in Progress: Thwarting Timing Attacks in Microcontrollers using Fine-grained Hardware Protections
No full textInternational audienceTiming side-channels are an identified threat for security critical software. Existing countermeasures have a cost either on the hardware requirements or execution time. We focus on low-cost microcontrollers that have a very low computational capacity. Although these processors do not feature out-of-order execution or speculation, they remain vulnerable to timing attacks exploiting the varying latencies of ALU operations or memory accesses. We propose to augment the RISC-V ISA with security primitives that have a guaranteed timing behavior. These primitives allow constant time ALU operations and memory accesses that do not alter the state of the cache. Our approach has a low overhead in terms of hardware cost, binary code size, and execution time both for the constant time secure program and other programs running concurrently on the same hardware
Long time behaviour of the solution of Maxwell's equations in dissipative generalized Lorentz materials (I) A frequency dependent Lyapunov function approach
No full textInternational audienceIt is well-known that electromagnetic dispersive structures such as metamaterials can be modelled by generalized Drude-Lorentz models. The present paper is the first of two articles dedicated to dissipative generalized Drude-Lorentz open structures. We wish to quantify the loss in such media in terms of the long time decay rate of the electromagnetic energy for the corresponding Cauchy problem. By using an approach based on frequency dependent Lyapounov estimates, we show that this decay is polynomial in time. These results extend to an unbounded structure the ones obtained for bounded media in [18] via a quite different method based on the notion of cumulated past history and semi-group theory. A great advantage of the approach developed here is to be less abstract and directly connected to the physics of the system via energy balances
Problèmes inverses de diffraction pour l'opérateur de Schrödinger magnétique harmonique
No full textThis thesis focuses on analyzing the inverse scattering problems by inhomogeneous medium for the time harmonic magnetic Schrödinger operator.The first inverse problem deals with the stability of the problem of identifying the magnetic and electric potentials from near field and far field patterns using geometrical optics solutions. However, we must first show that the direct scattering problem is well-posed. To do this, we used two different approaches: one is the variational approach and the other is a volume integral equation known as the Lippmann-Schwinger integral equation.Second, we consider the inverse medium scattering problem, we review the sampling methods used to determine the shape of a perturbation from measurements of scattered waves at a fixed frequency, where our focus is on the Linear Sampling Method (LSM) and the Factorization Method (FM). Several validating results are presented in 2D. In addition, it is shown that the shape of a perturbation is uniquely determined from the far field pattern for all incident plane waves.Finally, we investigate the well-posedness of the interior transmission problem and the discreteness of the set of transmission eigenvalues by applying Fredholm theory and the upper triangular Fredholm theory.Cette thèse se concentre sur l'analyse des problèmes inverses de diffraction par un milieu non homogène pour l'opérateur de Schrödinger magnétique harmonique.Le premier problème inverse traite de la stabilité de l'identification des potentiels magnétiques et électriques à partir de champ proche et de champ lointain en utilisant des solutions d'optique géométrique. Cependant, il est nécessaire de démontrer que le problème direct de diffraction est bien posé. Pour ce faire, nous avons utilisé deux approches différentes : l'approche variationnelle et une équation intégrale de volume connue sous le nom d'équation intégrale de Lippmann-Schwinger.Ensuite, on examine le problème inverse de diffraction dans un milieu non homogène, en passant en revue les méthodes d'échantillonnage utilisées pour déterminer la forme d'une perturbation à partir de mesures d'ondes diffractées à une fréquence fixe. Notre attention se porte particulièrement sur la Méthode d'Échantillonnage Linéaire (LSM) et la Méthode de Factorisation (FM). Plusieurs résultats de validation sont présentés en 2D. De plus, on démontre que la forme d'une perturbation est uniquement déterminée à partir de champ lointain pour toutes les ondes planes incidents.Enfin, on étudie le problème de transmission intérieure et la discrétion de l'ensemble des valeurs propres de transmission en appliquant la théorie de Fredholm et la théorie de Fredholm triangulaire supérieure
The Morphospace of Consciousness: Three Kinds of Complexity for Minds and Machines
No full textInternational audienceIn this perspective article, we show that a morphospace, based on information-theoretic measures, can be a useful construct for comparing biological agents with artificial intelligence (AI) systems. The axes of this space label three kinds of complexity: (i) autonomic, (ii) computational and (iii) social complexity. On this space, we map biological agents such as bacteria, bees, C. elegans, primates and humans; as well as AI technologies such as deep neural networks, multi-agent bots, social robots, Siri and Watson. A complexity-based conceptualization provides a useful framework for identifying defining features and classes of conscious and intelligent systems. Starting with cognitive and clinical metrics of consciousness that assess awareness and wakefulness, we ask how AI and synthetically engineered life-forms would measure on homologous metrics. We argue that awareness and wakefulness stem from computational and autonomic complexity. Furthermore, tapping insights from cognitive robotics, we examine the functional role of consciousness in the context of evolutionary games. This points to a third kind of complexity for describing consciousness, namely, social complexity. Based on these metrics, our morphospace suggests the possibility of additional types of consciousness other than biological; namely, synthetic, group-based and simulated. This space provides a common conceptual framework for comparing traits and highlighting design principles of minds and machines
X-ray generation by fs-laser processing of biological material
No full textInternational audienceThe use of ultrashort pulse lasers in medical treatments is increasing and is already an essential tool, particularly in the treatment of eyes, bones and skin. One of the main advantages of laser treatment is that it is fast and minimally invasive. Due to the interaction of ultrashort laser pulses with matter, X-rays can be generated during the laser ablation process. This is important not only for the safety of the patient, but also for the practitioner to ensure that the legally permissible dose is not exceeded. Although our results do not raise safety concerns for existing clinical applications, they might impact future developments at higher peak powers. In order to provide guidance to laser users in the medical field, this paper examines the X-ray emission spectra and dose of several biological materials and describes their dependence on the laser pulse energy
Acoustic waveguide with a dissipative inclusion
No full textInternational audienceWe consider the propagation of acoustic waves in a waveguide containing a penetrable dissipative inclusion. We prove that as soon as the dissipation, characterized by some coefficient η, is non zero, the scattering solutions are uniquely defined. Additionally, we give an asymptotic expansion of the corresponding scattering matrix when η → 0+ (small dissipation) and when η → +∞ (large dissipation). Surprisingly, at the limit η → +∞, we show that no energy is absorbed by the inclusion. This is due to the so-called skin-effect phenomenon and can be explained by the fact that the field no longer penetrates into the highly dissipative inclusion. These results guarantee that in monomode regime, the amplitude of the reflection coefficient has a global minimum with respect to η. The situation where this minimum is zero, that is when the device acts as a perfect absorber, is particularly interesting for certain applications. However it does not happen in general. In this work, we show how to perturb the geometry of the waveguide to create 2D perfect absorbers in monomode regime. Asymptotic expansions are justified by error estimates and theoretical results are supported by numerical illustrations
Finite element simulation of high cycle fretting wear using an implicit adaptive cycle jump
No full textInternational audienceFretting motion between two contacting solids can, under gross slip conditions, induce wear. A finite element model and a simulation strategy aiming at predicting wear under fretting motion are presented. The numerical results obtained are compared with experimental data from the literature. The proposed simulation process is particularly suitable for computing high numbers of cycles. To this end, a cycle jump technique is used, and different integration schemes are investigated. Results show that instabilities may arise when an explicit scheme is used, which limits the size of the cycle jump. On the other hand, using an implicit scheme involves a trade-off between the possibility of considering a larger cycle jump and the number of iterations required for convergence. It is shown that the more cycles we perform, the faster the implicit scheme converges. Therefore, the implicit scheme is especially appropriate for high-cycle computations. Moreover, an adaptive cycle jump is used with the implicit scheme, enabling to accelerate the computations for high numbers of cycles
Experimental Validation of an Ellipsoidal State Estimation Procedure for a Magnetic Levitation System
No full textInternational audienceSet-based state estimation procedures have the advantage of enclosing all possible system states under the assumption of bounded measurement uncertainty, the structural correctness of dynamic systems models, and the representation of external disturbances and imperfectly known parameters by finitely large sets. In contrast to stochastic counterparts, often employing one of the available variants of Kalman filters, set-based approaches are less widely used. The reason for this observation is the fact that naive implementations often suffer from a non-negligible degree of overestimation and that (unless certain monotonicity properties are satisfied) set-based computations come with a notable increase of the computational complexity, resulting among others from required interval splitting procedures. This paper tries to resolve both issues by means of an ellipsoidal implementation of a discrete-time set-valued state estimation procedure that is validated experimentally and compared with an Unscented Kalman Filter (UKF) for a laboratory-scale magnetic levitation system
