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Patch-like, two dimensional WSe2-based hetero-structures activated by a healing catalyst for H2 photocatalytic generation
Get PDF2D photoactive materials may offer interesting opportunities in photocatalytic devices since they combine strong light absorption and shortening of charge carriers’ diffusion path. Because of their high surface defect concentration and the formation of a majority of edge/plane vs plane/plane contacts between the anisotropic building blocks, surface defect passivation and improvement of charge carrier transport are critical for the large development of high surface area, 2D photo-catalysts. Here, we propose a hetero-structure nanoporous network with a patch-like coating as high performance 2D photo-catalysts. The hetero-structured building blocks are composed of a photo-active WSe2 nanoflake in direct contact with both a conducting rGO nanosheet and an ultrathin layer of healing catalyst. The resulting nanoporous film achieves a H2 evolution photocurrent density up to 5 mA cm−2 demonstrating that the patch-like hetero-structures represent an effective strategy to simultaneously improve hole collection, defect passivation and charge transfer. These hetero-structures made of an ultrathin healing catalyst layer represent promising building blocks for the bottom-up fabrication of high surface area photocathodes particularly for 2D photo-catalysts displaying high defect concentration
Les métabolites secondaires des plantes et des champignons, prohibes dans le contrôle antidopage chez le cheval
Get PDFCertaines plantes et champignons produisent des métabolites secondaires à effet pharmacologique et peuvent se retrouver dans l’alimentation du cheval. En tant qu’athlète, le cheval de sport et de courses hippiques est soumis aux contrôles antidopage. Une contamination, volontaire ou non, de son alimentation par des plantes présentant ces propriétés peut provoquer une positivité au contrôle antidopage. L’objectif de cette étude est de présenter l’ensemble des espèces végétales et des champignons éventuellement comestibles par le cheval mais contenant des principes actifs potentiellement dopants, afin de disposer d’une base de données complète et à jour des substances alimentaires naturelles prohibées
Modeling the oxidation kinetics of titanium alloys: Review, method and application to Ti-64 and Ti-6242s alloys
Get PDFThe oxidation kinetics of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-Si were reviewed in the range 450−650 °C. A method to fit these data was conceived and applied to these alloys, allowing the prediction of mass gain, oxygen diffusion coefficient, embrittlement depth and oxide scale thickness. Prediction diagrams are produced and discussed through the prism of aeronautical applications; discrepancies between modeled and experimental data are discussed. This paper shows that despite Ti-6Al-4V experienced larger mass gains than Ti-6Al-2Sn-4Zr-2Mo-Si, the two alloys have an equivalent behavior in terms of oxygen dissolution and diffusion, over a wide range of exposure durations
Impact of communication delay and temporal sensitivity on perceived workload and teleoperation performance
Get PDFAs teleoperated robotic units operate in remote and distant environments such as outer space, the communication latency impacts the operator’s performance. Yet, the delay impact on teleoperation performance and mental workload has scarcely been evaluated. Human temporal sensitivity appears to modulate the impact of latency on operators’ performance but no joint assessment of temporal sensitivity and subjective workload has been reported. In this study, we assess the relationship between the impact of communication delay on teleoperation performance, mental workload, and operators’ temporal sensitivity. Sixteen participants completed two online tasks: a duration reproduction task in which they were asked to reproduce the duration of previously presented visual stimuli, and an egocentric maze navigation task which required participants to escape a static maze, under an input latency of 0, 400, and 3000 ms. Completion time, move count, and error rate were recorded for each trial, along with perceived workload using the NASA-TLX questionnaire. The results showed that performance was significantly deteriorated by an increase in communication delay. Moreover, participants’ self-rated performance decreased with a larger communication delay, while their reported frustration, effort, and mental demands significantly increased. Interestingly, a possible effect of the temporal sensitivity profile on teleoperation performance - number of moves - was found, with a reduced number of moves for sensitive participants compared to insensitive ones, following a speed/accuracy trade-off (yet not significant). Hence, different operators’ strategies were uncovered, depending on their temporal sensitivity profile, to mitigate the impact of communication delay on the mission outcome
Grand Field Challenges for Cognitive Neuroergonomics in the Coming Decade
Get PDFNeuroergonomics as defined by Raja Parasuraman is the study of “the brain at work and in everyday life” (Parasuraman, 2003). This rapidly growing research field aims at understanding human brain function underlying the many facets of human interaction with technical systems (Dehais et al., 2020). The term “cognition” is used to describe different processes (e.g., attention, memory, decision making) relevant to human-technology interaction. Cognitive neuroergonomics, then, can be defined as a section of neuroergonomics concerned with the investigation of the neural bases of those cognitive processes involved in the user's interaction with a technical system at work or during everyday life. One of the defining aspects of cognitive neuroergonomics is that it uses insights from analyzing neural dynamics in these settings to inform cognitive theory and models, as well as to improve our understanding of human brain function underlying cognition, in general.
To this end, new imaging methods are continuously adapted and used in a wide range of experimental scenarios that cover the entire area of ergonomics from highly controlled laboratory research protocols, to less controlled translational research, to research in the real world with little control over the factors of interest (Parada, 2018). This decreasing level of control is accompanied by an increasing level of ecological validity. Laboratory experiments provide very good control over experimental factors with high internal validity of the investigated constructs but often suffer from low levels of ecological validity. In contrast, real-world experiments might show low internal validity and lack of experimental control but provide high ecological validity that cannot be further improved. Here, the real world is the laboratory (Gramann et al., 2017). Furthermore, with increasing ecological validity, inter-acting with technical systems often involves expanding physical activity of the user. System interactions range from very low input (e.g., interaction with mobile devices; McKendrick, 2019) to larger scale interaction (e.g., Human-Robot Interaction, HRI; Tsarouchi et al., 2016) to very large scale interactions (e.g., assisted navigation; Wunderlich and Gramann, 2020). Active behavior is the basis for physically demanding workplaces as well as less physically challenging tasks that, nonetheless, require body, head and eye movements when users actively seek information or respond to external stimuli (Doshi and Trivedi, 2009). Traditionally, however, active behavior is not allowed in brain imaging protocols because established imaging modalities are usually too heavy to follow participants' movements and movement-related artifacts render the analyses of neural activity difficult (Makeig et al., 2009; Gramann et al., 2011).
With cognitive neuroergonomics maturing into a new research area with widespread research questions and methods, the focus should be put back into theory-driven studies of the human brain at work and in everyday life. Good scientific practices have to be adapted to allow for replicable science including the integration of new mobile imaging methods into the existing range of established imaging protocols. New findings have to be related to parameters known from established laboratory protocols and integrated into larger theoretical frameworks that allow for systematic replication as well as the development of robust parameters reflecting cognitive processes. From this perspective, it is our belief that the following challenges will have to be met to further develop this scientific field
Analyse intégrative des données multi-dimensionnelles pour l'étude de la vaccination vis-à-vis des infections mammaires et pulmonaires chez les bovins
Get PDFDans le but de prévenir la sélection de bactéries résistantes aux antibiotiques, la volonté de réduire leur usage en médecine vétérinaire est un choix sociétal largement affiché. Le développement de méthodes alternatives telles que la vaccination est nécessaire. Dans l’espèce bovine, les infections mammaires et pulmonaires restent très présentes, et de nombreuses zones d’ombre subsistent sur la compréhension des mécanismes immunitaires de défense pour les prévenir. Cette thèse s’inscrit dans le cadre de l’étude de la vaccination à l’aide d’approches multidimensionnelles dans le double objectif de comprendre les mécanismes qu’elles mobilisent et d’élaborer de nouvelles méthodes vaccinales plus performantes. Les techniques dites de haut débit telles que la transcriptomique ou encore la protéomique ciblée sont de plus en plus utilisées dans les questions de recherche. En effet, leur utilisation permet d’identifier et d’étudier de façon large et sans a priori des mécanismes encore méconnus notamment dans le domaine de l’infectiologie. La stratégie vaccinale associant une immunisation par les voies systémique et locale permet une meilleure protection des vaches laitières vis-à-vis d’une infection expérimentale par E. coli, comparée à l’immunisation systémique seule. Pour la compréhension des mécanismes immunitaires protecteurs induits par la vaccination locale, une étude transcriptomique haut débit à l’aide du séquençage de l’ARN a été réalisée sur les cellules du sang, puis sur les lymphocytes CD4 extraits du tissu mammaire. En parallèle, une étude protéomique moyen débit via le dosage de cytokines par une méthode multiplexe utilisant des billes magnétiques a été conduite en parallèle. Une intégration de l’ensemble des données couplées à des informations sur l’état clinique après l’épreuve infectieuse a permis d’attribuer la protection induite par la vaccination à l’activité des lymphocytes producteurs d’interleukine 17 dans le tissu mammaire. La deuxième étude s’inscrit dans le cadre de l’étude de la vaccination contre les maladies respiratoires des bovins. Les effets d’un protocole de préparation des animaux incluant la vaccination ont été mesurés chez des jeunes bovins et un suivi de la réponse immunitaire, en parallèle des performances zootechniques et de la morbidité a été réalisé. Via l’utilisation de méthodes multidimensionnelles, les résultats montrent que la prévalence des signes cliniques et des lésions pulmonaires n’ont pas été efficacement prévenus par les interventions vaccinales. Des conditions d’hébergement défavorables ont un impact négatif sur la santé respiratoire malgré la vaccination. Ces travaux, outre la collection d’informations nouvelles sur la réponse immunitaire induite par la vaccination, ouvrent des perspectives sur de nouvelles modalités de prévention des deux principales maladies justifiant l’utilisation d’antibiotiques en élevage bovin
Influence des paramètres électriques et géométriques sur les procédés DBD : étude de cas sur les lampes excimer
Get PDFLes Décharges de Barrière Diélectrique (DBD) sont une technologie qui a été développée depuis le début du siècle dernier et ces dernières années, leurs applications se sont étendues à divers domaines de l'industrie. Malheureusement, dans le présent, il n'y a pas de relation claire entre la géométrie du réacteur DBD, son alimentation électrique et l'efficacité du processus piloté par le DBD. De cette manière, il serait souhaitable de disposer d'un système permettant la caractérisation des DBD pour établir les relations entre les paramètres d'entrée et de sortie du procédé pour améliorer son efficacité ou sa cadence de production. Par conséquent, la proposition, la mise en oeuvre et le test d'un tel système seront expliqués dans ce travail. La méthodologie à employer peut-être étendue à plusieurs procédés DBD mais l'application choisie est la production d'ultraviolets (UV) au moyen de lampes à excimère DBD destinées à la production d'UV. La conception de la plate-forme de caractérisation comprend la sélection des valeurs limites des paramètres électriques pour couvrir une plage de puissance élevée dans les différentes configurations géométriques que le DBD peut avoir. Ceci est réalisé en considérant une modélisation théorique et expérimentale du DBD pour identifier un circuit électrique équivalent qui peut être étudié en interaction avec l'alimentation. La conception de l'alimentation est basée sur les meilleurs critères de contrôle et d'ajustement des paramètres électriques de la puissance pulsée injectée dans le DBD couvrant une large plage de puissance pour l'ensemble des dimensions DBD à tester. La topologie choisie permet de changer indépendamment trois variables dans la forme d'onde de courant que le DBD reçoit, ce qui permet de les relier à la sortie du processus DBD, dans ce cas la production UV des lampes à excimère. Pour compléter la plateforme de caractérisation, une interface de contrôle et d'acquisition est développé et mise en oeuvre permettant la caractérisation automatique d'un DBD, balayant un ensemble de points de fonctionnement et, collectant et sauvegardant les mesures électriques et de procédé (rayons UV) pour analyser ultérieurement. Les données acquises permettent de décider quelles sont les meilleures conditions, en termes de dimensions physiques pour le réacteur DBD et des paramètres électriques pour l'alimentation électrique, qu’il soit pour améliorer l'efficacité de la conversion d'énergie (dans ce cas de l'électrique vers l'UV) ou pour maximiser le rendement du processus (dans ce cas les rayons UV) que le DBD peut fournir
Hybrid electric distributed propulsion overall aircraft design process and models for general aviation (FAST GA)
Get PDFIn the frame of the European objectives in terms of CO2 emissions, the aeronautics is looking for a technological rupture to achieve them, in particular, the aircraft design domain pursuits this through the research of innovative architectures. One of these innovative configurations currently being explored includes the hybrid electric energy source (thermal/electric) for Distributed Electric Propulsion (DEP) architecture. This Paper details a code developed to size a general aviation aircraft at concept level, by only defining its top level requirements and the main architecture parameters. The code can manage both conventional and hybrid power source as well as concentred or distributed propulsion architectures in order to allow the user to evaluate and compare the feasibility and benefits respectively of these innovative architectures. This code is a branch of the code “FAST-CS25” (Future Aircraft Sizing Tool for conventional CS-25 type) held by ONERA/ISAE-SUPAERO. The presented work aims at the expansion of the FAST code to CS-23 conventional type, hybrid electric energy source, and distributed propulsion system configurations. Through this paper, the models and the main sizing loops for the concept design are described, but putting special emphasis on the distributed propulsion aerodynamics and wing mass estimation. These detailed models where validated with the NASA X-57 DEP aircraft satisfactory. The whole concept design loop of a hybrid energy aircraft was validated with the eGenius hybrid energy aircraft
Further insight on amine-metal reaction in epoxy systems
Get PDFAmong thermosetting polymers, epoxy resins are major components of adhesives, sealants, paints and composites. Polymerization is often achieved by reaction of epoxy monomers like DGEBA with amine hardeners such as DETA. Previous works showed that polyamines interact with metal (hydr/oxide) substrates leading to the formation of an interphase involving the chelation of surface metal ions. In this work, we further explored the interaction between DETA and aluminum (hydr)oxide, denoted Al, via a combined experimental and modeling approach. We inspected in depth by DSC the modifications of glass transition temperature Tg and change in heat capacity ΔCp after curing, allowing us quantifying the impact of Al amount on DGEBA/DETA degree of cure α. A new parameter, the “percentage of inhibition of cure” denoted α¯, was defined reaching up to ~4 % in our experimental conditions. In parallel, in situ mixing calorimetry confirmed the exothermic character of DETA interaction with Al with various degrees of division. DFT calculations were carried out to examine DETA/Al3+ chelates. Among plausible chelate configurations, one was associated with a lower conformational energy and shorted Al-N bond lengths, suggesting greater stability. Calculated and experimental Raman spectra were additionally investigated, allowing us to discuss further about the DETA/Al3+ chelates at play
Virtual reality for pilot training: study of cardiac activity
No full textFlight training is provided through real flights with real aircraft and virtual flights using simulators. Nowadays a third alternative way emerges which is the use of immersive virtual reality (VR) flight deck. However, the effectiveness of this technology as a training tool for pilots has not yet been fully assessed. We, therefore, conducted an experiment involving four pilots that had to perform the same traffic pattern scenario (take off, downwind, and landing) in a VR simulator and real flight conditions. We collected subjective (perceived task difficulty) and objective data (trajectory, cardiac activity). In this this preliminary study, the first descriptive results disclosed that pilots had similar flying trajectories in both conditions. As one could expect, the pilots reported higher task difficulty and exhibited higher heart rate and lower heart rate variability in the real flight condition compared to the VR one. However, similar patterns of subjective rating and cardiac activation were found across the different segments of the scenarios (landing > take off > downwind) for the two conditions. These latter findings suggest that VR offer promising prospects for training purpose but that more experiments have to be conducted following the proposed methodology