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Bicyclic N -dihalocyclopropylamide derivatives as precursors of nitrogen-containing fused polycyclic systems
No full textInternational audienceExamples of carbon–carbon bond-forming cyclisation reactions, involving allyl cations generated by the thermal ring-opening of halocyclopropanes, have been scarcely reported. In this contribution, we are describing the results of a study conducted with N-dihalocyclopropylamide substrates, designed as precursors of cyclic iminium intermediates that were aimed at participating in intramolecular reactions with electron-rich aromatic groups. Competitive side-reactions were identified, and access to the desired polycyclic products was carefully evaluated. The results were found to be strongly dependent on the substitution pattern of the nucleophilic aromatic moieties, as well as on the sizes of the rings of the target products. In spite of the rather moderate yields generally obtained, this approach represents a particularly short and inexpensive route to various interesting nitrogen-containing polycyclic systems, namely benzoindolizidine, benzoquinolizidine, piperidinobenzoazepane and azepanoisoquinoline compounds
The future of cooperative programs in Europe, paradox of a hybrid market
No full textInternational audienceFor European arms-producing countries, launching a cooperative program represents a compromise between preserving their domestic industrial base and achieving an affordable acquisition. Nevertheless, scientific literature is marred with criticisms regarding the effectiveness of such an approach. Paradoxically, this does not prevent European states from committing to new cooperative programs—the European Commission has set up mechanisms for improving the effectiveness of European defense industry based, de facto, on incentives to launch cooperative programs. This article looks at the place of cooperative programs in Europe to understand whether the new initiatives of the European Union can succeed in improving the effectiveness of military spending as well as enhancing European strategic autonomy. It analyzes the organization of the European armament market to explain why cooperative programs appear unavoidable. It explores how the European Commission could overcome current limitations through community-funded programs, given that such funding would foster the emergence of a European defense technological and industrial base
Boundary Element Method Analysis of 3D Effects and Free-Surface Proximity on Hydrofoil Forces in Varied Operating Conditions
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Fluid-Structure Interactions response of a composite hydrofoil modelled with 1D beam finite elements
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A survey on the discrete-time differentiators in closed-loop control systems: experiments on an electro-pneumatic system
No full textInternational audienceThis paper is dedicated to the experimental analysis of discrete-time differentiators implemented in closed-loop control systems. To this end, two laboratory setups, namely an electro-pneumatic system and a rotary inverted pendulum have been used to implement 25 different differentiators. Since the selected laboratory setups behave differently in the case of dynamic response and noise characteristics, it is expected that the results remain valid for a wide range of control applications. The validity of several theoretical results, which have been already reported in the literature using analytical analysis and numerical simulations, has been investigated, and several comments are provided to allow one to select an appropriate differentiation scheme in practical closed-loop control systems
Identification expérimentale des sources acoustiques à l'origine du bruit de décrochage d'un profil de pale d'éolienne
No full textIn response to the national low-carbon strategy, the number of onshore wind turbine installations in France has been steadily increasing since 2010. One of the challenging consequences for humans of this proliferation of onshore wind turbines is the noise generated by their operation. Wind turbine noise represents a sound nuisance that can be more bothersome for nearby residents than typical urban noise pollution, such as traffic or aircraft noise. Wind turbine noise is commonly described as a noticeable and irritating whooshing sound, even at relatively low sound levels. This characteristic has been attributed to the unique temporal fluctuations in its acoustic signal. Two aerodynamic mechanisms contribute to this amplitude modulation of noise: the interaction of turbulent structures in the blade boundary layer with the trailing edge of each section, generating a noise known as trailing-edge noise, and the separation of the blade boundary layer, producing dynamic stall noise. While these phenomena have been identified, the understanding of the mechanism behind the noise generation due to boundary layer separation remains imprecise. Therefore, as part of the ANR PIBE project (Predicting the Impact of Wind Turbine Noise), aimed at improving methods for predicting the acoustic impact of wind turbines, this thesis seeks to identify the aerodynamic structures responsible for dynamic stall noise under both static and dynamic conditions for an airfoil profile with similar geometry to wind turbine blades. To achieve this, two experiments were conducted in the anechoic wind tunnel at the École Centrale de Lyon using a NACA633418 airfoil profile. The first experiment involved synchronized two-dimensional wall pressure measurements at mid-span and far-field microphone measurements. It revealed the conditions and spectral characteristics of the noise generated during static stall and dynamic stall when the profile was subjected to sinusoidal pitch motion. The influence of pitch oscillation frequency and amplitude was also identified. Three noise regimes were identified during static and quasi-static stall: separation noise, light stall noise, and deep stall noise. The second experiment involved time-resolved particle image velocimetry synchronized with acoustic measurements to identify the coherent aerodynamic structures responsible for these noises. By developing an analysis protocol that included spectral proper orthogonal decomposition (SPOD) and cross-correlation calculations between aerodynamic and acoustic measurements, it was found that deep stall noise is induced by the generation and convection of a large-scale von Kármán vortex. The analysis under dynamic conditions highlighted additional challenges in the analysis protocol, although differences between the aerodynamic and acoustic characteristics of quasi-static and dynamic stall regimes of the pitching airfoil were still identified.Sous l'impulsion de la stratégie nationale bas carbone, le nombre d'implantations d'éoliennes terrestres en France ne cesse d'augmenter depuis 2010. Une des répercussions contrariantes pour l'humain de cette multiplication des éoliennes terrestres est le bruit induit par le fonctionnement des éoliennes. En effet, le bruit éolien représente une gêne sonore se révélant plus incommodante pour les riverains que la pollution acoustique urbaine habituelle telle que le trafic routier ou aérien. Le bruit éolien est communément décrit comme un chuintement facilement détectable et gênant à des niveaux sonores pourtant relativement faibles. Cette caractéristique a été expliquée par la nature particulière de son signal acoustique qui présente des fluctuations temporelles d'intensité. Deux mécanismes aérodynamiques sont à l'origine de cette modulation d'amplitude de bruit : l'interaction des structures turbulentes dans la couche limite des pales avec le bord de fuite de chaque section, générant un bruit appelé bruit de bord de fuite, et le décollement de la couche limite des pales produisant le bruit de décrochage dynamique. Bien que ces phénomènes aient été identifiés, la compréhension du mécanisme à l'origine de la génération de bruit par le décollement de la couche limite reste encore imprécise. Ainsi, dans le cadre du projet ANR PIBE (Prévoir l'Impact du Bruit des Éoliennes) visant à améliorer les méthodes de prévision de l'impact sonore des éoliennes, cette thèse propose d'identifier les structures aérodynamiques à l'origine du bruit de décrochage à la fois en condition statique et dynamique pour un profil aérodynamique de géométrie similaire aux pales d'éoliennes. Dans ce but, deux expériences ont été réalisées au sein de la soufflerie anéchoïque de l'école centrale de Lyon pour un profil NACA633418. Une première expérience de mesures synchronisées de pression pariétales bidimensionnelles à mi-envergure et de microphone en champ lointain a permis de révéler les conditions d'apparition et les caractéristiques spectrales du bruit généré lors du décrochage en condition statique et en condition dynamique lorsque le profil est soumis à un mouvement de tangage sinusoïdal. L'influence de la fréquence et de l'amplitude d'oscillation a également été identifiée. Trois régimes de bruit ont alors été identifiés lors du décrochage statique et quasi-statique : le bruit de séparation, le bruit de décrochage léger et le bruit de décrochage profond. Une seconde expérience de vélocimétrie par imagerie de particules résolue en temps synchronisée avec des mesures acoustiques a ensuite été réalisée afin d'identifier les structures aérodynamiques cohérentes à l'origine de ces bruits. Par le développement d'un protocole d'analyse comprenant l'application d'une méthode de décomposition modale spectrale (SPOD) et le calcul de corrélations croisées entre les mesures aérodynamiques et acoustiques, il a été identifié que le bruit de décrochage profond est induit par la génération et la convection d'un tourbillon de von Kármán de grande échelle. L'analyse en condition dynamique a mis en évidence que le protocole d'analyse présentait des défis supplémentaires nécessitant une investigation approfondie. Néanmoins, les différences entre les caractéristiques aérodynamiques et acoustiques des régimes quasi-statique et dynamique du profil en mouvement de tangage ont tout de même pu être identifiées
Evaluating students’ experiences in hybrid learning environments: A comparative analysis of Kubi and double telepresence robots
No full textSocial Robotics15th International Conference, ICSR 2023, Doha, Qatar, December 3–7, 2023, Proceedings, Part IIInternational audienceAmidst the Covid-19 pandemic, distance learning was employed on an unprecedented level. As the lockdown measures have eased, it has become a parallel option alongside traditional in-person learning. Nevertheless, the utilization of basic videoconferencing tools such as Zoom, Microsoft Teams, and Google Meet comes with a multitude of constraints that extend beyond technological aspects. These limitations are intricately linked with human behavior, psychology, but also pedagogy, drastically changing the interactions that take place during learning. Telepresence robots have been widely used due to their advantages in enhancing a sense of in-person. To investigate the opportunities, the impact, and the risks associated with the usage of telepresence robots in an educational context, we conducted an experiment in a real setting, in the specific use case of a design school and a project-based class. We are interested in the experience of a classroom and the relationships between a distance student, his/her peers, and the professor/instructor. This study employed two types of robots: a Kubi robot (a semi-static tablet-based system) and a Double robot (a mobile telepresence robot). The primary objective was to ascertain the perceptions and experiences of both remote and in-person students during their interaction with these robots. The results of the study demonstrate a marked preference among students for the Double robot over the Kubi, as indicated by their feedback
Experimental and detailed kinetics modeling study of the fire suppressant properties of di(2,2,2trifluoroethyl) carbonate
No full textInternational audienc
Design of Fluorescent Carbon Dots (CDs) for the Selective detection of Metal‐Containing Ions
No full textInternational audienceAbstract The pollution caused by heavy metals (HMs) may occur through both natural processes and anthropogenic activities and is found in complex media. The purpose of this review is to summarize the state‐of‐art of fluorescent CDs and the sensing applications in a systematic manner. This review intends to provide clues on the origin on the observed selectivity in chemiluminiscence sensors, which was until now a stated but unaddressed question, and still remains open for debate. Indeed, it is tempting to think that CDs possessing functional groups with soft bases at the surface are able to detect soft metal acids, while the opposite is to be suspected for hard acid‐base pairs. However, the literature shows several examples where this trend does not hold. We found that such observation is explained by the involvement of dynamic quenching, which does not involve the formation of a non‐fluorescent complex, as in the case of static quenching. We have provided an interpretation of published data that was not provided by the original authors and offer guidelines to enable the design of CDs to target ions in solution
A la recherche de jeunes talents : Comprendre les pratiques de recrutement de l'industrie pour embaucher des étudiants en apprentissage du diplôme d'ingénieur
No full textInternational audienceThis study aims to investigate industrial companies’ recruitment practices and standards for hiring their engineering degree apprentices. We examine (1) how they find their future engineering degree apprentices, (2) their recruitment standards and (3) to what extent organisational characteristics shape their recruitment decisions. To answer these questions we have carried out an online quantitative study, comprising exclusively closed questions, with the participation of workplace mentors of engineering apprenticeship students (n=70). Subsequently, we have conducted a descriptive statistical data analyse on SPSS. Our results indicate that industrial companies find their engineering apprentices by means of students’ speculative applications or via engineering schools which have already conducted their academic recruitment process. Surprisingly, technical knowledge or transversal competences have a limited influence on their recruitment decisions, but students’ motivation and personal attitudes (e.g.: personal engagement, perseverance, adaptability) have a very marked, nearly decisive influence on their hiring choices. In addition, we have identified some slight differences between large international and domestic industrial companies’ and SME’s recruitment decisions. Based on our results, we highlight the importance of collaboration between industrial companies and engineering schools in order to develop a more inclusive engineering apprenticeship recruitment process.Cette étude a pour objectif d'étudier les pratiques et les normes de recrutement des entreprises industrielles pour l'embauche de leurs apprentis ingénieurs. Nous examinons (1) comment elles trouvent leurs futurs apprentis ingénieurs, (2) leurs normes de recrutement et (3) dans quelle mesure les caractéristiques organisationnelles influencent leurs décisions de recrutement. Pour répondre à ces questions, nous avons mené une étude quantitative en ligne, comprenant exclusivement des questions fermées, avec la participation de mentors d'apprentis ingénieurs sur leur lieu de travail (n=70). Nous avons ensuite procédé à une analyse statistique descriptive des données à l'aide du logiciel SPSS. Nos résultats indiquent que les entreprises industrielles trouvent leurs apprentis ingénieurs par le biais de candidatures spéculatives d'étudiants ou par l'intermédiaire d'écoles d'ingénieurs qui ont déjà mené leur processus de recrutement académique. De manière surprenante, les connaissances techniques ou les compétences transversales ont une influence limitée sur leurs décisions de recrutement, mais la motivation et les attitudes personnelles des étudiants (par exemple : l'engagement personnel, la persévérance, l'adaptabilité) ont une influence très marquée, presque décisive, sur leurs choix d'embauche. En outre, nous avons identifié de légères différences entre les décisions de recrutement des grandes entreprises industrielles internationales et nationales et celles des PME. En appuyant sur nos résultats, nous soulignons l'importance de la collaboration entre les entreprises industrielles et les écoles d'ingénieurs afin de développer un processus de recrutement d'apprentis ingénieurs plus inclusif