Portail HAL UHA (Université de Haute-Alsace)
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Highly Efficient UV-Activated TiO2/SnO2 Surface Nano-matrix Gas Sensor: Enhancing Stability for ppb-Level NOx Detection at Room Temperature
No full textInternational audienceThis study presents a new nanoporous TiO 2 /SnO 2 heterojunction for NO x gas detection by using a two-step sol-gel process. The unique TiO 2 and SnO 2 nanoheterojunction matrix right on the film surface enables the TiO 2 photocatalyst to absorb minimal UV power (3 μW/cm 2 ) and effectively transfer electrons to the SnO 2 conduction band. The sensor detects NO and NO 2 gases down to 4 ppb (response of 0.6%) and 10 ppb (response of 1.3%) at 1 V at room temperature. It also exhibits a fast recovery time (100 ± 40 s at 500 ppb NO x ), an improved response over a wide relative humidity range (10-60%), and a long lifetime over 30 days. The ultralow UV power required can be easily harvested from sunlight, eliminating the need for UV LEDs. XPS and SEM analyses indicated that the unique nanoporous TiO 2 /SnO 2 structure improves sensing performance, with oxygen vacancies playing a critical role in the NO x gas sensing mechanism. This work demonstrated the highly efficient UV catalyst effect in sensors with the surface heterojunction matrix. The low-power ppb-level NO x detection is suitable for environmental monitoring and respiratory disease detection.</div
The Analytic Stockwell Transform and its Zeros
No full textInternational audienceA recent original line of research in time--frequency analysis has shifted the interest in energy maxima toward zeros.Initially motivated by the intriguing uniform spread of the zeros of the spectrogram of white noise, it has led to fruitful theoretical developments combining probability theory, complex analysis and signal processing.In this vein, the present work proposes a characterization of the zeros of the Stockwell Transform of white noise, which consists in an hybrid time--frequency multiresolution representation.First of all, an analytic version of the Stockwell Transform is designed.Then, analyticity is leveraged to establish a connection with the hyperbolic Gaussian Analytic Function, whose zero set is invariant under the isometries of the Poincaré disk.Finally, the theoretical spatial statistics of the zeros of the hyperbolic Gaussian Analytic Function and the empirical statistics of the zeros the Analytic Stockwell Transform of white noise are compared through intensive Monte Carlo simulations, supporting the established connection.A publicly available documented Python toolbox accompanies this work
Effet d'un entraînement en résistance combiné à de la vibration sur la composition corporelle et la balance énergétique - Résultats de l'étude d'alitement prolongé MNX
No full textInternational audiencePurposeHigh volume exercise is crucial in preventing spaceflight-induced muscle atrophy but can induce reductions in body mass (BM) and fat mass (FM), due to a mismatch between energy intake (EI) and total energy expenditure (TEE). This randomized cross-over trial investigated whether short-duration resistive-vibration exercise (RVE) prevents muscle loss without inducing negative energy balance (EB) during a medium-duration bedrest (IDRCB n°2012-A00337-36).MethodsTwelve healthy young males underwent a 21-day bedrest with RVE or without (CNT) in a randomized cross-over trial, each trial being separated by at least 120 days. Subjects could leave unfinished the meals designed to match their estimated TEE. TEE was assessed using doubly labeled water and EB from dual X-ray absorptiometry-generated body composition changes.ResultsCompared to strict bedrest, RVE limited by 25% the bedrest-induced loss in BM (P<0.07) and lean BM (P=0.12), without reaching significance, and partially lessened the decline in overall muscle function and aerobic capacity. RVE reduced resting metabolic rate decrease (P=0.03) without increasing activity energy expenditure and TEE. Both groups adjusted their EI to match the reductions in TEE, resulting in equilibrated EB.ConclusionRVE may offer some benefits in mitigating muscle mass and function decline under microgravity conditions, without affecting EB and FM
Multi-Objective Approach for Efficient Grid Resources Allocation in Electric Vehicle Charging Schedules
No full textInternational audienceThis study presents a novel multi-objective optimization model for electric vehicle (EV) charging scheduling, addressing the trade-off between maximizing the energy delivered to clients and minimizing peak energy consumption. The model incorporates real-world constraints, including limited charging infrastructure, heterogeneous charging power levels, client availability, and the sequential nature of vehicle charging. By optimizing EV charging in urban settings, our approach mitigates grid stress while enhancing user satisfaction. Given the NP-hard nature of the problem, we adopt a metaheuristic approach to approximate the Pareto front and identify optimal trade-offs. Building on previous works, we introduce a multi-objective variant of Cuckoo Search with Genetically Replaced Nests (MOCS-GRN) and compare its performance against the standard multi-objective Cuckoo Search (MOCS). Both algorithms are tailored to the problem through specifically designed operators. Experimental results demonstrate that MOCS-GRN consistently outperforms MOCS in terms of hypervolume coverage, dominance percentage, and execution time, with small standard deviations ensuring robustness. These findings highlight the effectiveness of our approach in optimizing EV charging station operations while maintaining grid stability and meeting user demands
Optimization of interfacial adhesion and mechanical performance of flax fiber-based eco-composites through fiber fluorination treatment
No full textInternational audienceNatural fibers, such as flax, are more and more used as biobased reinforcement for eco-composites manufacturing but their natural polarity makes them incompatible with most polymers (mostly dispersive). Nowadays, treatments such as torrefaction are known to reduce the polarity of natural fibers and thus increase the mechanical performance of the reinforced composites. However, these treatments could harm fibers and limit the gain in performance. Thereby, the use of a controlled fluorination treatment allowed, via the grafting of fluorine on the fiber surface, to decrease the polarity of these fibers while maintaining an equivalent Young's modulus and limiting the reduction of at break performance to just ∼30 %. Therefore, by incorporating these fluorinated reinforcements in an epoxy matrix and by mechanically testing these composites, not only superior mechanical performances to those reinforced by raw fibers, but also superior to torrefied fiber-reinforced composites were measured, e.g.: the flexural modulus increased by 25 % after fluorination vs. 10 % after torrefaction and the flexural strain at break was enhanced by 10 % after fluorination vs. decrease by 35 % after torrefaction)
The effect of different exchangeable cations on the CO<sub>2</sub> adsorption capacity of Laponite RD<sup>®</sup>
No full textInternational audienceTri-octahedral clay minerals have a potential to be used as CO2 sorbents for intermediate temperatures (200-400 °C) owing to their thermal stability in this temperature range. In this study, laponite RD ® , a commercially synthesized hectorite (with Na+ as exchangeable cation) was used to investigate its capacity of CO2 adsorption at 200 °C and ambient pressure. Different cations such as Co2+ , Ni2+ , Mg2+ and Ca2+ were employed to exchange Na+ with the aim to study their effect on the capacity of adsorbing CO2. The commercial sample showed an adsorption capacity of 144 µmolCO2/g. Most of other exchanged sample displayed a deficit in the quantity of CO2 adsorbed. An exception was the Ca 2+ saturated sample, which exhibited a better performance (163 µmolCO2/g) compared to the Laponite RD ® . Thus, with higher affinity towards CO2, such sample could be a good candidate for CO2 capture. For all samples, most of 2 the CO2 was desorbed, and the formation of carbonate bonds was not observed by FTIR spectroscopy suggesting that the CO2 was mainly physisorbed
Collision-Aware Traversability Analysis for Autonomous Vehicles in the Context of Agricultural Robotics
No full textThis work has been submitted to the IEEE for possible publicationIn this paper, we introduce a novel method for safe navigation in agricultural robotics. As global environmental challenges intensify, robotics offers a powerful solution to reduce chemical usage while meeting the increasing demands for food production. However, significant challenges remain in ensuring the autonomy and resilience of robots operating in unstructured agricultural environments. Obstacles such as crops and tall grass, which are deformable, must be identified as safely traversable, compared to rigid obstacles. To address this, we propose a new traversability analysis method based on a 3D spectral map reconstructed using a LIDAR and a multispectral camera. This approach enables the robot to distinguish between safe and unsafe collisions with deformable obstacles. We perform a comprehensive evaluation of multispectral metrics for vegetation detection and incorporate these metrics into an augmented environmental map. Utilizing this map, we compute a physics-based traversability metric that accounts for the robot's weight and size, ensuring safe navigation over deformable obstacles
Introduction to Economists at War: How World War II Changed Economics (and Vice Versa)
No full textInternational audienceThe 2023 HOPE conference aimed to understand the interrelationships between the Second World War and economics. Examining this back-and-forth means examining the transformative effect of the war on the content and status of economics but also symmetrically examining the role played by economics and economists in the conduct of the Second World War
Les débuts de l’âge du Bronze dans le sud de la plaine du Rhin supérieur
No full textInternational audienceJusqu’au début des années 2000, le Bronze ancien pouvait être considéré comme le parent pauvre de la recherchearchéologique en Alsace, uniquement documenté par quelques tombes isolées, des découvertes de surfaces et quelques fouillesponctuelles sur des habitats ne livrant que de rares fosses au matériel souvent indigent. Les courtes synthèses produites, souventde simples notices et l’absence de documentation graphique, contrastaient fortement avec les productions des chercheurstravaillant sur les grands ensembles fouillés sur le Plateau suisse et en Allemagne du Sud-Ouest. Dans ce tableau peu attrayant,seule la nécropole d’Illzach “Ile Napoléon” 1, publiée à la fin des années 1960, faisait exception. Jusqu’à la fin des années 1990,la seule synthèse englobant les découvertes alsaciennes est celle de C. Strahm, qui intègre la région au sein d’un groupe,l’Oberrhein-Hochreingruppe 2, constitué d’éléments disparates souvent mal datés, et attribué dans son ensemble au BzA1. Lamultiplication des découvertes, conséquence de la montée en puissance de l’archéologie préventive dans les années 2000 etle recours systématique aux datations radiométriques, ont radicalement modifié la perception que l’on pouvait avoir de cettepériode, faisant table rase de l’Oberrhein-Hochreingruppe et permettant aux chercheurs régionaux de s’atteler à la constructiond’un cadre chronologique précis. L’acte de naissance de ce nouveau cycle de recherche peut être fixé en 2009, lors de la tenue dela table ronde internationale de Strasbourg, publiée l’année suivante 3, durant laquelle ont été présentés les résultats des fouillesles plus récentes conduites en Alsace, ainsi que les premières synthèses sur les rites funéraires et la périodisation céramique.Deux ans après, la publication de la maison de Mussig 4, premier bâtiment formellement identifié dans le sud de la plainedu Rhin, ouvrait de nouvelles perspectives de recherche sur l’architecture du Bronze ancien. Depuis, les découvertes se sontmultipliées à un rythme soutenu, fondant nos réflexions sur un corpus significatif ayant notamment très récemment autoriséla production de nouvelles synthèses sur les rites funéraires 5 et sur l’architecture 6. Les zones d’ombre demeurent bien sûrnombreuses, mais les progrès réalisés sur les questions de chronologie, relative et absolue, la définition du système funéraire, lareconnaissance d’une architecture spécifique, une meilleure intégration de la région dans un cadre élargi à l’Europe, permettentde proposer un état de l’art qui ne le cède en rien aux autres périodes de la Protohistoire régionale