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The design and testing of an ultrasensitive device with embedded phononic crystals for the detection and localisation of nonlinear guided waves
No full textInternational audienceThis work proposes a novel approach for designing and testing a sensing device with a high capability of filtering frequency bands.. The purpose of the device is the detection and localisation of nonlinear guided waves. Nonlinear guided waves are often associated with the presence of damage in structural components (considered here) but also can emanate from the cancerous tissue. Therefore the provided design framework applies to the broad class of problems. The proposed method is active and consists of a piezoelectric transducer attached to the inspected structure exciting a narrow frequency band wave packet and sensors placed at the proposed ultrasonic devices with embedded phononic crystals. Unit cells of phononic crystals are optimized to open a band gap at the excitation frequency so that the excited waves are attenuated, while the sensitivity to detection of higher harmonics is increased.The proposed approach is tested numerically and validated experimentally by considering various manufacturing methods, materials, and unit cell geometries. A parametric study of the angle of attachment of the ultrasonic devices with the embedded phononic crystals to the inspected structure is performed. Band gaps and filtering capabilities of several prototypes are tested.Numerical simulations of guided wave propagation that include the effect of delamination clapping proved that the proposed designs are sensitive enough to detect higher harmonics by simple signal thresholding. The most promising prototype is tested experimentally showing its capability of detection and localisation of a simulated damage
Optimal fault-tolerant adaptive fuzzy control of quadrotor UAV: a fixed-time stability approach
No full textInternational audienceThis paper introduces an optimal fault-tolerant adaptive fuzzy control approach for quadrotor unmanned aerial vehicles (UAVs). The proposed control framework addresses the challenges of unknown nonlinear dynamics, sensor and actuator faults, as well as external disturbances affecting the drone during flight trajectory tracking. For this purpose, a robust control law was developed by combining the backstepping technique, fixed-time stability approach, and fuzzy logic theory. The objective is to achieve rapid compensation for disturbances and faults to prevent stabilization issues and ensure the quick recovery of the UAV. First, the nonlinear dynamic functions and faults are estimated by an adaptive fuzzy system, which is updated online using output variable measurements to guarantee both robustness and performance of closed-loop system. Then, the tuning parameters are automatically selected using the metaheuristic whale optimization algorithm (WOA) to achieve optimal behavior of the drone. The obtained simulation results demonstrate the effectiveness of the proposed controller and highlight its potential for reliable real-world UAV applications.</div
100 Gbit/s and Beyond IEEE 802.15.3d Channelization Compatible THz Communications Enabled by a Broadband MUTC Photodiode
No full textInternational audienceWe present photonics-driven high data rate IEEE 802.15.3d compliant terahertz (THz) communication links operated at a center frequency of 280 GHz. We analyze wireless data transmission within selected single and dual channels of the IEEE 802.15.3d and assess the outcomes through additional back-to-back (B2B) data transmission measurements and calibrated link budgets of the THz link. The system architecture uses on-wafer probing of a single high-power and highly linear broadband modified uni-traveling-carrier photodiode (MUTC-PD). Using the MUTC-PD as THz transmitter, we report 16-QAM 100 Gbit/s 25-cm wireless links for single and dual channel data transmission with significantly low error vector magnitude (EVM) levels, that is, 12.3% and 10.9%, respectively. As for B2B demonstration, we successfully transmit 200 Gbit/s (32-QAM) in a single channel with 7.5% EVM and 160 Gbit/s (16-QAM) in dual channel with 7.8% EVM. We further display the highly linear nature of the MUTC-PD by efficient data transmission with higher modulation formats, which is also supported by the power-saturation characteristics of the PD. To the best of the authors´ knowledge, this is the first study investigating the IEEE 802.15.3d channelization compliancy through system level design and spectral verification while at the same time achieving 100 Gbit/s and beyond data rates with notably low EVM values
Andreas Neufert: Wolfgang Paalen. Traduction d'une notice de dictionnaire en ligne. In: DECAF - Dictionnaire des Echanges Culturels entre l'Autriche et la France / Projet-ANR-22-CE91-0001
No full textAndreas Neufert: Wolfgang Paalen. In: DECAF - Dictionnaire des Echanges Culturels entre l'Autriche et la France / Projet-ANR-22-CE91-0001Le peintre, sculpteur et théoricien de l’art Wolfgang Paalen (* 22 juillet 1905 à Vienne, † 24 septembre 1959 à Taxco de Alarcón, Mexique) est considéré comme le seul représentant de la ‘modernité viennoise’ au sein du surréalisme français. Outre son œuvre plastique hétérogène, il laisse derrière lui de nombreux écrits théoriques, des poèmes, des pièces de théâtre et des nouvelles. Après avoir fait partie du groupe parisien Abstraction-Création de 1934 à 1935, il intègre le groupe des surréalistes et joue par la suite un rôle éminent en tant que peintre et générateur d’idées novatrices. Pendant son exil au Mexique à partir de 1939, il publie la revue d’art anti-surréaliste DYN, dans laquelle il s’efforce de concilier les tendances matérialistes et mystiques divergentes du surréalisme par le biais d’une philosophie de la contingence, apparentée aux réflexions du Cercle de Vienne et de Ludwig Wittgenstein. Pendant son séjour à Paris entre 1951 et 1954, il se réconcilie avec André Breton et rejoint à nouveau le cercle surréaliste jusqu’à son retour au Mexique, où il met fin à ses jours en 1959
Two Types of Bound States in the Continuum in Photonic Comb Structure
No full textInternational audienceWe propose the design of a comb-shaped cavity that can support several BICs when attached to a waveguide. The cavity consists of a finite comb made of one stub of length placed between two stubs of length via two guides of length and the whole comb is attached vertically along a waveguide. In order to classify these BICs, we compare their frequencies with those of an infinite periodic comb in the presence of a stub defect of length . Therefore, we show that beyond the resonances associated with the defect stub in the gaps, there exist two types of BICs: (i) BICs induced by the upper guides of the finite system, which fall in the wide passband of the infinite system and (ii) BICs induced by the whole finite comb which coincide with the flat band domain. These latter BICs appear as anti-symmetric and symmetric modes, giving rise to a doubly-degenerate BIC (D-BIC) when they fall at the same frequency. By deviating from the BIC condition, we show that these two types of BICs transform into quasi-BICs in the shape of electromagnetically induced reflection (EIR) or electromagnetic induced transparency (EIT) resonances. The analytical results obtained by the Green’s function method are confirmed by experiments using coaxial cables operating in the radio-frequency regime. This investigation contributes to an enhanced theoretical and experimental comprehension of BICs in stubbed structures, offering valuable insights for prospective applications
Topological Interface States in a One-Dimensional Mesoscopic Crystal Using Su-Schrieffer-Heeger Model
No full textInternational audienceWe investigate the existence of topological interface states between two periodic comb-like mesoscopic crystals with different topological properties based on the Su-Schrieffer-Heeger (SSH) model. This model enables us to predict the existence of topological interface states between two connected mesoscopic crystals based on Dirac point (closing and reopening of the gaps). These states are characterized by their robustness to any external perturbations or a disorder in the system. First, we discuss the existence of topological interface states based on the analyses of the symmetry of the band-edge states and the Zak phase of each band in the infinite mesoscopic crystal. This approach is equivalent to an analysis of the sign of the reflection phase in two gaps surrounding a bulk band. Multiple topological states are successfully realized at the interface when two conditions are satisfied, namely: (i) the two systems share common gaps; (ii) the symmetry of the band-edge states are opposite. The interface states can be obtained as peaks in the local density of states (LDOS) as well as in the transmission spectra of two connected mesoscopic crystals. The proposed MC may have several applications in scientific fields ranging from quantum information science and filters
Approche pour une imagerie passive haute fréquence des structures anisotropes (Cas de Silicium)
No full textInternational audienceCes travaux visent à faire progresser l'industrie microélectronique en développant une méthode d'inspection non destructive pourimager et localiser les défauts sur les wafer de silicium. Cette thèse s'inscrit dans le cadre du projet ANR DACLOS dont l'objectif est de développer une méthode d'inspection non destructive basée sur la corrélation de champ diffus HF dans les wafers de silicium. Le projet vise à détecter et imager des défauts en combinant la détection optique avec l'approche de corrélation des ondes acoustiques de surfac
The effectiveness of OPEC and OPEC+ from 2009 to 2024: An empirical appraisal
No full textInternational audienceThis empirical study focuses on the effectiveness of the coordination strategies developed in the oil market between 2009 and 2024 with a focus on the OPEC + oil cartel settled-up by the end of 2016. One uses various econometric techniques specific to panel data to assess the ability of oil producers adherent to OPEC and/or OPEC + to exercise an impact on the oil price. The study integrates the time horizon followed by oil producers in the definition of their collusion strategies. The analysis reveals that some coordination mechanisms were already present amongst the set of ten countries that will later adhere to the OPEC+ and this before the official set-up of this cartel. However, these strategies proved to be ineffective to exercise a significant impact on oil price in 2009–2016. In addition, the analysis suggests the existence of a significant link between the time horizon considered by a country and its incitation to conform to official production quotas. Thirdly, results indicate that both OPEC and OPEC + have been more able to impact the oil price in 2017–2022. The invasion of Ukraine by Russia in February 2022 seems to have disorganized the oil market, which explains a significant loss of influence of both OPEC and OPEC + on the oil price.Cette étude empirique se centre sur l’efficacité des stratégies de coordination développées sur le marché pétrolier entre 2009 et 2024 avec un centrage opéré sur le cartel pétrolier de l’OPEP+ mis en place fin 2016. On utilise différentes techniques économétriques propres aux données de panel pour évaluer l’aptitude des producteurs pétroliers adhérents à l’OPEP et/ou à l’OPEP+ à exercer une influence sur le prix du pétrole. L’étude prend en compte de l’horizon temporel suivi par les producteurs de pétrole dans la détermination de leurs stratégies de collusion. L’étude mise en œuvre souligne la présence de mécanismes de coordination dans le groupe des dix pays qui adhéreront ultérieurement à l’OPEP+ et ce avant même l’instauration officielle de ce cartel. Toutefois, ces stratégies se sont avérées peu efficaces pour exercer un impact significatif sur le prix du pétrole en 2009-2016. De plus, l’étude indique l’existence d’une liaison significative entre l’horizon temporel considéré par un pays et son incitation à respecter les quotas de production officiels. Troisièmement, les résultats obtenus indiquent que l’OPEP et l’OPEP+ ont été davantage en mesure d’influer sur le prix du pétrole en 2017-2022. L’invasion de l’Ukraine par la Russie en février 2022 semble avoir désorganisé le marché du pétrole, ce qui explique une perte significative d’influence de l’OPEP et de l’OPEP+ sur le prix du pétrole
Optimisation des paramètres de capteurs SAW basée sur la théorie COM
No full textInternational audienc