HAL Portal UPHF (Université Polytechnique Hauts-de-France)
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Spectroscopie THz à Haute Résolution Basée sur des Peignes de Fréquences et des Lasers Moléculaires Pompes Optiquement
No full textThe objective of this thesis is to study the use of frequency combs for high-resolution molecular spectroscopy in the terahertz (THz) region of the electromagnetic spectrum. This approach is based on the conversion of an optical frequency comb into the THz domain. Nevertheless, the state of the art of these sources requires a highly sensitive THz heterodyne receiver to measure the amplitude of each comb tooth separately. We demonstrate the effectiveness of this approach at frequencies below 1 THz using Schottky diode-based heterodyne receivers. For higher frequencies, commercial mixers exist, but the challenge lies with the local oscillator (LO). We explored the use of optically pumped molecular lasers (OPML). Several active media were considered: ammonia (NH3), hydrogen cyanide (HCN), water vapor (H2O), and heavy water vapor (D2O). The experimental results show significant gains, though limited by the power of the available quantum cascade lasers (QCL) used to pump the gas. Sufficient THz power for pumping a mixer is nevertheless achieved, paving the way for more advanced OPML designs. Finally, the OPML is used as an LO in a molecular spectroscopy experiment involving synchrotron radiation. The experimental setup and techniques used for signal acquisition allow for high-precision measurements in the 1 – 4 THz range, where few solutions exist. This work ultimately envisions a compact and high-performance spectrometer for this entire range.L'objectif de cette thèse est d'étudier l'utilisation Peignes de fréquence pour la spectroscopie moléculaire à haute résolution dans la région du spectre électromagnétique Térahertz (THz). Cette approche est basée sur la conversion d'un peigne dans le domaine optique vers le domaine THz. Néanmoins l'état de l'art de ces sources nécessite un récepteur THz très sensible de type hétérodyne afin de mesurer séparément l'amplitude de chaque dent du peigne. Nous démontrons l'efficacité de cette approche à des fréquences inferieures à 1 THz à l'aide de récepteurs à base de diodes Schottky. Pour les fréquences supérieures des mélangeurs commerciaux existent mais il se pose le problème de l'oscillateur local (OL). Nous avons exploré l'utilisation de lasers moléculaires pompés optiquement (OPML). Plusieurs milieux actifs ont été considérés : l'ammoniac (NH3), le cyanure d'hydrogène (HCN), la vapeur d’eau (H2O), et la vapeur d'eau lourde (D2O). Les résultats expérimentaux mettent en evidence des gains significatifs toutefois limités par la puissance des lasers à cascade quantiques (quantum cascade lasers ou QCL) disponibles. Des puissances suffisantes pour le pompage d'un mélangeur sont néanmoins obtenues et ouvrent la voie à des conceptions plus avancées d'OPML. Enfin l’OPML est utilisé comme OL dans une expérience de spectroscopie moléculaire mettant en jeu le rayonnement synchrotron. Le montage expérimental et les techniques utilisées pour l'acquisition des signaux permettent des mesures de grande précision dans une gamme (1 – 4 THz) où il existe peu de solutions. Ce travail permet d'envisager à terme un spectromètre compact et performant dans toute cette gamme
FIDAVL: Fake Image Detection and Attribution Using Vision-Language Model
No full textInternational audienceWe introduce FIDAVL: Fake Image Detection and Attribution using a Vision-Language Model. FIDAVL is a novel and efficient multitask approach inspired by the synergies between vision and language processing. Leveraging the benefits of zero-shot learning, FIDAVL exploits the complementarity between vision and language along with soft prompt-tuning strategy to detect fake images and accurately attribute them to their originating source models. We conducted extensive experiments on a comprehensive dataset comprising synthetic images generated by various state-of-the-art models. Our results demonstrate that FIDAVL achieves an encouraging average detection accuracy of 95.42% and F1-score of 95.47% while also obtaining noteworthy performance metrics, with an average F1-score of 92.64% and ROUGE-L score of 96.50% for attributing synthetic images to their respective source generation models. The source code of this work will be publicly released at https://github.com/Mamadou-Keita/FIDAVL
Nanosciences and Nanotechnologies: A Scientific–Historical Introductory Review
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Conceptual Frameworks from Newton's Principia and Newton’s Principia Geneva Edition: Analysis of the Problem of Isochronism, Propositions XLVIII-LIII
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Details in Galileo’s Mechanism of Inertia as New Intellectual Historical Insights
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BB-MÉDCULT : Un projet de recherche collaborative sur les actions de médiation culturelle à destination des très jeunes enfants au sein des musées dans les Hauts-de-France
No full textThe BB-MÉDCULT research collective investigates the cultural and artistic awakening of children aged 0 to 3, with a particular focus on museum contexts. Bringing together researchers and professionals from developmental psychology, education sciences, and museology, the collective explores the role of the museum as a space for interaction and shared discovery between parent and young child. This report presents a study conducted at the Palais des Beaux-Arts de Lille with 32 families, using questionnaires and video recordings. The findings highlight the museum’s role as an environment that supports adult-infant interactions and the evolution of families’ cultural practices, opening new perspectives for research on early artistic engagement in infancy.Le collectif de recherche BB-MÉDCULT étudie l’éveil culturel et artistique des enfants de 0 à 3 ans, en particulier dans le contexte muséal. Réunissant chercheurs et professionnels de la psychologie du développement, des sciences de l’éducation et de la muséologie, il explore le rôle du musée comme lieu d’interactions et de découvertes partagées entre le parent et le jeune enfant. Ce rapport présente une étude menée au Palais des Beaux-Arts de Lille auprès de 32 familles, à partir de questionnaires et d’enregistrements vidéo. Les résultats mettent en lumière le rôle du musée comme espace soutenant les interactions adulte-bébé et l’évolution des pratiques culturelles familiales, ouvrant ainsi de nouvelles perspectives pour la recherche sur l’éveil artistique des tout-petits
Joint Sub-6 GHz and mm-Wave V2I MIMO Radio Channel Characterization
No full textInternational audienceThe development of 5G and 6G networks has driven to the development of two key technologies: massive Multiple-Input Multiple-Output (mMIMO) and access to millimeter wave (mm-Wave) frequencies [1], and the concept of distributed cell-free massive MIMO (CF-mMIMO), primarily targeting sub-6GHz frequencies [2], [3]. In this context, the demand for very high-speed systems is growing rapidly, especially for scenarios with a high density of users. In particular, the transmission of navigation, safety and multimedia entertainment data in vehicles is a major challenge, requiring a communication scheme with very high throughput, low latency and very high coverage quality. To meet these objectives, CF-mMIMO technology is a promising candidate: distributed antennas provide seamless coverage and their synchronization reduces latency, while guaranteeing high throughput. The spectrum for these systems is generally in the sub-6 GHz range (FR1), where moderate attenuation ensures a favorable link budget. In order to increase capacity, wider frequency bands are also being investigated in other parts of the radio spectrum, for example in the millimetre-wave range (FR2) where bandwidths of up to 100 MHz are available in the 26–28 GHz and 40 GHz bands.The coexistence of these technologies would require a fine exploitation of radio channel characteristics considering vehicle and user mobility for Vehicule-to- Infrastructure (V2I) and Vehicle-to-Vehicle (V2V) applications. At mm-Wave frequencies, most current mm- Wave V2X measurements are conducted in static environments rather than dynamic ones, and primarily focus on propagation losses [4]. The limited number of mm- Wave V2V channel measurements makes it difficult to draw statistically significant conclusions about real-world mm-Wave V2V channels. In [5], [6] dynamic V2V SISO channel measurements were performed to investigate the large-scale parameters and stationarity. Channel sounder and first measurements for CF-mMIMO have been presented in [7], [8]. More recently investigations on large-scale parameters have been presented in [9]. V2V measurements at 3 GHz and 30 GHz in urban scenarios have been described in [10].In this article, we present a dual-band channel measurement campaign for the V2I scenario, in which the sub-6GHz and mm-Wave frequency ranges are jointly sounded. More specifically, the multipath channel is evaluated simultaneously at 5.93 GHz and 26.5 GHz using two complementary real-time MIMO sounders. The experimental setup is provided in Section II. The measurement campaign is described in Section III. Data processing is detailed in Section IV, and the results in terms of Power Delay Profile (PDP), Doppler Spectral Density (DSD) and path loss are illustrated in Section V
Topological Berry Antenna on a Silicon Chip for Terahertz Wireless Communication
No full textInternational audienceNonzero Berry curvature is central to the existence of topological edge states in electronic and photonic valley-Hall systems. While manipulating the Berry curvature in condensed matter systems is challenging, valley-Hall topological photonics offer unprecedented control, where the broken spatial inversion symmetry alters the Berry curvature. Herein, an all-silicon Berry antenna is presented, using a continuously varying geometry corresponding to a gradual change in Berry curvature. The on-chip topological edge mode with a tunable field extent is achieved to enhance effective antenna aperture, creating a high-gain on-chip photonic antenna with perfectly planar wavefronts. Experimentally, a maximum gain of 17 dBi that supports 20 Gbps chip-to-chip wireless communication is demonstrated, with active optical tunability of the antenna gain with modulation depths of 8 dBi. This Berry antenna paves the way for the development of complementary metal-oxide-semiconductor (CMOS) compatible topological Berry devices, with potential applications in integrated micro-/nano-photonics, next-generation wireless communications (6G to Xth generation), and terahertz detection and ranging
Étude numérique et expérimentale du procédé de forgeage des produits en laiton CuZn40Pb2 (CW617N)
No full textBrass is a material widely used in the faucet industry. The shaping of this material primarily relies on the forging technique. To better understand the forging process of brass components, research has been undertaken to analyze and model the behavior of this material. Initially, a series of hot compression experiments was carried out using a thermo-mechanical simulator. These experiments allowed for the identification of parameters for a numerical model, the Hansel-Spittel law, which describes the behavior of the CuZn40Pb2 alloy within a temperature range of 550 to 750°C and strain rates of 0.1, 1, and 10/s. The model parameters were then integrated into finite element software, Forge 3D, to simulate the actual behavior of the forging process. Subsequently, a damage study was conducted through forging tests to determine the mechanical defects likely to occur during forging and to establish the material's formability limits. The results obtained enabled the determination of optimal combinations of temperature and forging speed to avoid crack formation on the components. Finally, tribological behavior was studied using UST friction tests. These tests revealed that each parameter influenced the friction coefficient as well as the surface condition of the components.Le laiton est un matériau très utilisé dans le secteur robinetterie. La mise en forme de ce matériau repose principalement sur la technique de forgeage. Afin d'avoir une meilleure compréhension du procédé de forgeage des pièces en laiton, des recherches ont été entreprises pour analyser et modéliser le comportement de ce matériau. Au début, une série d'expériences de compression à chaud a été réalisée à l'aide d'un simulateur thermomécanique. Ces essais ont permis de déterminer les valeurs des paramètres nécessaires pour un modèle numérique, loi de Hansel Spittel, qui décrit le comportement de l'alliage CuZn40Pb2 dans un intervalle de températures compris entre 550 à 750 °C, ainsi que des vitesses de déformation de 0,1, 1 et 10/s. Les paramètres du modèle ont par la suite été incorporés dans le logiciel Forge NxT d'analyse par éléments finis, pour simuler le comportement réel du processus de forgeage. Par la suite, une étude de l'endommagement a été menée à travers des essais de forgeage, dans le but de déterminer les défauts mécaniques susceptibles de survenir lors du forgeage et d'établir les limites de formabilité du matériau. Les résultats obtenus ont permis de déterminer les bonnes combinaisons de température et de vitesse de forgeage pour éviter la formation de fissures sur les pièces. Enfin, des essais de frottement UST ont été utilisés pour examiner le comportement tribologique. Ces essais ont révélé que chaque paramètre influençait le coefficient de frottement ainsi que l'état de surface des pièces
Hybridising photovoltaics and thermoelectrics: A detailed-balance analysis
No full textInternational audienceThe combination of photovoltaic and thermoelectric converters could potentially lead to an improvement in the efficiency with which solar energy is converted into electricity, thanks to the improved exploitation of the residual heat generated in the PV cells. Using the detailed balance formalism, we develop a simple model enabling to derive the ultimate efficiency limits of PV-TE systems on the basis of a restricted number of operating parameters, including the bandgap of the semiconductor materials used, the cell temperature and the concentration ratio of the solar flux to which the PV cells are subjected. It is shown that in the radiative limit, the added value of PV-TE systems remains relatively modest, with an improvement in the electrical power generated of the order of 5% relative to conventional PV systems, and up to 15% for CPV systems operating under concentrated solar flux. Secondly, the limited capacity of real photovoltaic cells to approach their own theoretical limits is taken into account. We demonstrate a substantial improvement in the performance of PV-TE systems incorporating realistic solar cells operating at only a fraction of their theoretical limit, compared with reference PV systems. The value of solar concentration, which provides an additional leverage in the quest for high temperatures, while mitigating the adverse effect of temperature on PV cell efficiency, is also highlighted. Finally, the paper discusses the practical limitations of the model and outlines the operating and material parameters that need to be taken into account in order to rigorously determine the added value of these systems compared with conventional PV modules