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Light security scheme for Cooperative, Connected and Automated Mobility (CCAM)
No full textInternational audienceCooperative, Connected and Automated Mobility (CCAM) is a new paradigm adopted by academia and industry in order to provide safe, secure and sustainable mobility on all kinds of roads (highways, urban and rural roads). CCAM takes advantage of Cooperative Intelligent Transport Systems (C-ITS) to improve safety and to reduce traffic congestion thanks to communication and cooperation among all relevant actors (vehicle, road infrastructure, pedestrians, etc.). In Europe and the USA, adapted communication protocols have been proposed to ensure cooperation through the exchange of specific messages. In this study, we focus on the European protocols, particularly the Cooperative Awareness Messages (CAMs) as defined by the European Telecommunications Standards Institute (ETSI). CAMs are composed of a payload containing information about the vehicle status (speed, location, heading, etc.) and additional security information. This information includes a Pseudonym Certificate (PC) and a signature to guarantee the sender's authentication. However, since CAMs are sent periodically by vehicles at frequencies from 1 to 10 Hz, this addition of security data to the payload significantly increases the load and bandwidth of the communication channel. Instead of exhaustive authentication, we propose a new approach that allows vehicles to authenticate each other for the first time when they meet. Once this level of trust is reached, vehicles stop sending authenticated messages during a variable period of time (called a trust period). In addition, we propose a trust verification process to avoid malicious activities during this trust period. Our approach significantly reduces the number of signed sent CAMs, the verification and signature computations, leading to reduce communication overhead. Simulation tests conducted over the OMNET++ platform demonstrate that our approach leads to a significant decrease in communication overhead, reducing the volume of CAMs exchanged by 56%
Drying Behavior of Flax Stems at Different Degrees of Dew Retting Under Simulated Rainfall: Implications for Smart Agriculture and Sensor Development
No full textInternational audienceDew retting of flax stems is a key agricultural process which facilitates fiber extraction from parent stems. If sensors are to be developed to monitor the degree of retting for optimal fiber extraction, then stem characteristics such as water uptake and loss need to be accurately known. Here, the moisture uptake and drying behavior of short flax stem samples in different degrees of dew retting is studied. Their drying is characterized in laboratory conditions following simulated light and heavy rainfall. The data were accurately fitted with the Page model of moisture loss. It was observed that the drying rate constant of small flax stem samples is smaller for simulated light rain compared to simulated heavy rain. Also, over-retted stem samples dry more rapidly compared to under-retted samples. The findings suggest that this is due to the degradation of the external tissue of the stems observed in the over-retted samples. The results could be useful for laboratory testing of flax stems and designers of emerging technological sensor-based tools used to monitor the degree of retting in controlled conditions
Pas de conflit négatif en cas d'absence d'identité d'objet des demandes devant les deux ordres
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La prime s’était égarée : pas de préjudice fiscal pour le souscripteur
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Les obligations d'information, de conseil et de mise en garde du conseiller en gestion de patrimoine dans le cadre d'un crédit in fine adossé à un contrat d'assurance-vie antérieurement souscrit
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A hybrid column generation-based heuristic for solving the parallel machine scheduling problem with sequence-dependent set-up times
No full textInternational audienceThis study explores a hybrid quantum–classical algorithm for the parallel machine scheduling problem with sequence-dependent setup times, a key problem with applications across multiple industries. We propose a column-generation-based heuristic that combines a classical linear relaxation for the master problem with quantum annealing to solve the pricing subproblem. The pricing subproblem generates columns (i.e., job sequences assigned to a machine), while the master problem selects columns to minimize the schedule makespan.To generate columns, the pricing subproblem solves a traveling salesman problem formulated as a quadratic unconstrained binary optimization (QUBO). A key advantage of this formulation is that subtours can be eliminated using quadratic penalty terms in the objective. In addition, our approach leverages the quantum annealer’s ability to rapidly produce many high-quality candidate solutions (i.e., columns).We evaluate the proposed hybrid heuristic through computational experiments. The results highlight the benefits of hybrid methods for complex decision-making problems, yielding competitive solution quality and computational advantages compared with classical approaches
Carbon Nanotubes-Based Air-Filled Waveguide for D-Band Applications
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Nanophononique quantique à basse température: vers une manipulation de la chaleur à l'échelle nanométrique
No full textNanoscale heat transport has long been under investigation, because of its importance both in fundamental physics and practical applications. On one hand, there is still a large knowledge gap in the field, especially in nanoscale systems at very low temperatures (down to 1K or below). Under these conditions, the mean free path (Λ) and dominant wavelength (λ_DOM) of phonons become comparable to or greater than the sample size, accesing the ballistic and coherent phonon transport regimes. On the other hand, the miniaturization of electronic devices and new trends on nanoscale integrated circuits have introduced significant challenges in heat management. This becomes increasingly important for applications in quantum computers or the development of cryo-CMOS technologies.The aim of the Hanibal project is to learn more about the different thermal-transport regimes and investigate some interesting phenomena encountered THERE, such as thermal rectification, the reduction of thermal conductance in phononic crystal systems and quantization of thermal transport. Being able to demonstrate such counter intuitive heat transport mechanisms means to convert tiny amount of energy into a measurable quantity. To achieve these objectives, silicon-based suspended thermal devices have been fabricated. The devices are produced from silicon-on-insulator (SOI) wafers using micro-/nano-fabrication techniques, mainly e-beam lithography and dry etching (RIE, ICP-RIE). Superconductive NbTi wires ensure no parasitic heating during device control, while sensing is performed by NbN thin layers, reaching sensitivities in the femtowatt (10⁻15 W) range. Various samples —nanowires and 2D-patterned membranes— have been fabricated for the intended studies. The work is carried out in collaboration with CEA-LITEN (for theoretical simulations) and Institut Néel (for sample fabrication and dilution-refrigerator measurements). At Institut Néel, SiN-based samples have also been produced to compare amorphous SixNy with crystalline Si behavior. Contrary to these expectations, the SiN based asymmetric phononic patterned membranes exhibit a reproducible ∼ 20 % rectification ratio below 4 K, demonstrating directional heat transport with potential application. Results for our silicon-based samples are pending.In summary, the high sensitivity of these thermometry devices and their ability to accommodate multiple types of samples between reservoirs will push forward experimental capabilities in low-temperature thermal-transport measurements. In this thesis defence, we will discuss the main scientific and technological challenges of the project, highlight the fully finished devices and the measurement method. The first thermal rectification data will be presented. Finally, we will outline future perspectives for sample characterization and research paths.Le transport thermique à l'échelle nanométrique fait depuis longtemps l'objet de recherches, en raison de son importance tant en physique fondamentale que dans les applications pratiques. D'une part, il existe encore un important déficit de connaissances dans ce domaine, en particulier dans les systèmes nanométriques à très basse température (jusqu'à 1 K ou moins). Dans ces conditions, le libre parcours moyen (Λ) et la longueur d'onde dominante (λ_DOM) des phonons deviennent comparables ou supérieurs à la taille de l'échantillon, ce qui permet d'accéder aux régimes de transport balistique et cohérent des phonons. D'autre part, la miniaturisation des dispositifs électroniques et les nouvelles tendances en matière de circuits intégrés à l'échelle nanométrique ont introduit des défis importants en matière de gestion thermique. Cela devient de plus en plus important pour les applications dans les ordinateurs quantiques ou le développement des technologies cryo-CMOS.Le projet Hanibal a pour objectif d'approfondir les connaissances sur les différents régimes de transport thermique et d'étudier certains phénomènes intéressants observés dans ce domaine, tels que la rectification thermique, la réduction de la conductance thermique dans les systèmes à cristaux phononiques et la quantification du transport thermique. Être capable de démontrer ces mécanismes de transport thermique contre-intuitifs signifie convertir de minuscules quantités d'énergie en une quantité mesurable. Pour atteindre ces objectifs, des dispositifs thermiques suspendus à base de silicium ont été fabriqués. Ces dispositifs sont produits à partir de plaquettes de silicium sur isolant (SOI) à l'aide de techniques de micro/nanofabrication, principalement la lithographie par faisceau électronique et la gravure à sec (RIE, ICP-RIE). Des fils supraconducteurs en NbTi garantissent l'absence de chauffage parasite pendant le contrôle du dispositif, tandis que la détection est assurée par de fines couches de NbN, atteignant des sensibilités de l'ordre du femtowatt (10⁻15 W). Divers échantillons (nanofils et membranes à motifs 2D) ont été fabriqués pour les études prévues. Ce travail est mené en collaboration avec le CEA-LITEN (pour les simulations théoriques) et l'Institut Néel (pour la fabrication des échantillons et les mesures par réfrigérateur à dilution). À l'Institut Néel, des échantillons à base de SiN ont également été produits afin de comparer le comportement du SixNy amorphe à celui du Si cristallin. Contrairement à ces attentes, les membranes asymétriques à motifs phononiques à base de SiN présentent un taux de rectification reproductible d'environ 20 % en dessous de 4 K, démontrant un transport de chaleur directionnel avec une application potentielle. Les résultats pour nos échantillons à base de silicium sont en attente.En résumé, la haute sensibilité de ces dispositifs de thermométrie et leur capacité à accueillir plusieurs types d'échantillons entre les réservoirs permettront de faire progresser les capacités expérimentales en matière de mesures de transport thermique à basse température. Dans cette soutenance de thèse, nous discuterons des principaux défis scientifiques et technologiques du projet, mettrons en avant les dispositifs entièrement finis et la méthode de mesure. Les premières données de rectification thermique seront présentées. Enfin, nous esquisserons les perspectives d'avenir pour la caractérisation des échantillons et les pistes de recherche
Les pratiques numériques des mouvements sociaux, entre autonomie communicationnelle et dépendance institutionnelle
No full textInternational audienceLa médiatisation des mouvements sociaux s’est transformée sous l’influence des technologies numériques, au point que certaines mobilisations ont fait le pari de s’émanciper des logiques traditionnelles de représentation en s’appuyant sur une communication en ligne. Jusqu’à quel point l’usage des plateformes numériques a-t-il permis de remplir cet objectif
Grades of Operational and Tactical Automation in rail domain for an Artificial Intelligence Driving Assistance System
No full textInternational audienceThis work proposes new additional levels of progressive driver assistance, extending the traditional Grades Of Automation (GoA) in order to allow both dedicated Operational and Tactical assistances. The second contribution is an Artificial Intelligence Driving Assistance System (AIDAS) that aims to restore the driver to their central role in the train driving activity, with the new Grades of Operational and Tactical Automation (GOTA) defined previously, taking into account human factors. The framework of Digital Co-Driver (DCD) is comprised of multiple monitoring and modules, each addressing a distinct issue arising from the augmented level of automation. The Driver State, Driving Performance and Environmental Monitoring provide indicators of global driver involvement to maintain a high level of performance in manual driving and to deal with system failures. The GOTA Selector Module then helps the driver to be optimally engaged while driving by adapting the GOTA to the specific needs. Finally, the Driver Companion Module learns about the driver's preferences and needs to adapt the assistance and help the driver to improve their own driving skills