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Ensinar matemática por meio de atividades históricas: duas experiências pedagógicas
No full textInternational audienceThis article presents two examples of history-based activities in mathematics education for studentsaged 8 to 11. They are different in many ways; their historical resources are respectively a drawing board from Da Vinci's Codex Atlanticus and a wheeled calculating machine from the 1950s: different periods, very different objects, different mathematicsapproached; but they are also similar: for both, interdisciplinary artifacts are used, pedagogical potential is explored and rendered in a deliberately coordinated way. The fact is, these two experiments are part of a wider project to produce precise, concrete content for teachers (of these 8-11 year-old students) wishing to introduce a historical perspective into their teaching; this wider project is itself in some ways the result of a fairly long tradition of studying the history and epistemology of mathematics in an educational context in the IREM (Institut de Recherche sur l'Enseignement des Mathématiques) network in France. This context, also situated in this now international field of research, is explained, then the two activities are described in detail, with a priori objectives and analyses of the students' productions, a complete material for the reader presented according to the approach shared by the authors.Este artigo apresenta dois exemplos de atividades baseadas na história para o ensino de matemática a alunos de 8 a 11 anos. Elas diferem em vários aspectos: seus recursos históricos são, respectivamente, uma prancha de desenho do Códice Atlântico, de Leonardo da Vinci, e uma máquina de calcular com rodas, datada da décadade 1950 — períodos distintos, objetos bastante diferentes e conteúdos matemáticos diversos. No entanto, também apresentam semelhanças: em ambas, utilizam-se artefatos interdisciplinares, cujo potencial pedagógico é explorado e apresentado de forma intencionalmente articulada. Essas duas experiências integram um projeto mais amplo, que busca produzir materiais concretos e precisos para professores que atuam com essa faixa etária e desejam introduzir uma perspectiva histórica em suas aulas. Esse projeto insere-se em uma longa tradição de estudos sobre a história e a epistemologia da matemática em contextos educacionais, desenvolvidos no âmbito da rede IREM (Institut de Recherche sur l’Enseignement des Mathématiques), na França. Esse contexto, atualmente inserido em um campo internacional de pesquisa, é apresentado no início do artigo. Em seguida, as duas atividades são descritas em detalhes, com seus objetivos a priori, análises das produções dos alunos e materiais completos para o leitor, seguindo a abordagemproposta pelos autores
EcoWikiRS: Learning Ecological Representation of Satellite Images from Weak Supervision with Species Observations and Wikipedia
No full textInternational audienceThe presence of species provides key insights into the ecological properties of a location such as land cover, climatic conditions or even soil properties. We propose a method to predict such ecological properties directly from remote sensing (RS) images by aligning them with species habitat descriptions. We introduce the EcoWikiRS dataset, consisting of high-resolution aerial images, the corresponding geolocated species observations, and, for each species, the textual descriptions of their habitat from Wikipedia. EcoWikiRS offers a scalable way of supervision for RS vision language models (RS-VLMs) for ecology. This is a setting with weak and noisy supervision, where, for instance, some text may describe properties that are specific only to part of the species' niche or is irrelevant to a specific image. We tackle this by proposing WINCEL, a weighted version of the InfoNCE loss. We evaluate our model on the task of ecosystem zero-shot classification by following the habitat definitions from the European Nature Information System (EUNIS). Our results show that our approach helps in understanding RS images in a more ecologically meaningful manner
Effect of Operating Temperature on Ni–Fe Alloy Nanostructured Electrodes for Alkaline Electrolyzer
No full textInternational audienceHerein, the effect of operating temperature on alkaline electrolytic cells for hydrogen generation using nanostructured electrodes is studied. Nanostructured nickel-iron alloy electrodes are obtained by electrosynthesis in a template. These electrodes are characterized by a nanowire-like structure with a high active surface area and consequently a higher catalytic activity than non-nanostructured materials. The chemical and morphological features of nanostructured electrodes are evaluated by energydispersive spectroscopy, X-ray diffraction, and scanning electron microscopy analyses. The electrochemical behavior of the nanostructured electrodes is studied through different tests in alkaline solutions. Tests are performed at different temperatures, 25, 40, and 60 °C, to evaluate the performance in terms of hydrogen and oxygen production and to verify the medium-term stability under galvanostatic conditions. The electrodes demonstrate good stability over time without evident signs of performance decay. The performance of a homemade electrolyzer with nanostructured electrodes is also studied at different temperatures and under industrial operation conditions for 600 h. The environmental impacts through the application of life cycle assessment methodology are also evaluated.</div
Primary investigation of oxidation influence on the cutting front profile during high-thickness laser cutting
No full textInternational audienceIn laser cutting, numerous studies have investigated the kerf profile to prevent striation formation and improve the cutting quality. This preliminary work discusses laser cutting for dismantling, where the cutting quality is not a relevant parameter. However, the shape of the cutting front, particularly its inclination, plays a crucial role in the propagation of the residual laser energy. Two approaches are presented to quantify the cutting front angle using high-speed cameras. One method observes the cutting front, while the other captures the transmitted laser energy reaching the background. The effect of oxidation on the cutting front angle is studied by changing the assist gas type between nitrogen and air, as well as varying the flow rate
Robust nonlinear control of permanent magnet synchronous motor drives: An evolutionary algorithm optimized passivity-based control approach with a high-order sliding mode observer
No full textInternational audiencePermanent Magnet Synchronous Machines (PMSMs) have revolutionized motor design by replacing traditional components like rotor windings, brushes, and sliding contacts with permanent magnets. This innovation has significantly improved operational efficiency and reduced maintenance needs. However, controlling PMSMs remains challenging due to the changing dynamics of the machine over time and its sensitivity to different environmental conditions.To tackle these challenges, this study presents a novel nonlinear control approach called passivity-based control (PBC). Unlike conventional methods, PBC manages both the electrical and mechanical dynamics of the system, focusing on energy flow and dissipation to maintain stability. To make the control more robust, the approach combines a nonlinear observer and a high-order sliding mode controller (HSMC), which enhance the system's ability to handle disturbances and parameter changes. Additionally, the study uses Genetic Algorithm (GA) optimization to fine-tune the parameters of the PBC, observer, and HSMC. This optimization improves the motor's tracking accuracy and robustness against external disruptions.The result is a control framework that preserves the natural dynamics of PMSMs while improving their stability and performance. Experimental validation using the platform for real-time simulation (OPAL-RT) and real world on a PMSM using dSPACE DS1202 board demonstrates that this method outperforms existing techniques under a variety of operating conditions, highlighting its effectiveness and reliability
Facial Expressions in Conversational AI: the Hot Trend that Boosts Empathy but Flops on Trust
No full textInternational audienceDynamic facial expressions in AI conversational agents are a rising trend, enhancing emotional engagement and user satisfaction by making interactions feel more personal and engaging. An experimental design comparing two chatbots—one with dynamic expressions and one without—showed that while expressions enhance emotional connection, they fall short in improving trust or advice quality. Absence of expressions fits contexts requiring objectivity and transparency. These findings stress the growing importance of a context-sensitive design in conversational AI, where emotional cues are carefully balanced to match user expectations
Towards new ways of transmitting information in biodynamic processes
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Transcriptomic analyses in European seabass during Vibrio anguillarum infection: a beneficial modulation of disease response induced by marine synbiotic
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On angular and volumetric interactions in elastic cubic lattices
No full textInternational audienceAbstract This paper investigates statics and natural vibration of linear elastic cubic lattices, together with their continuum approximations. The lattice endowed with central and angular interactions, referred to as Gazis et al . ’s, is considered first: since the stiffness of each lattice phase must be positive, the equivalent macroscopic Poisson’s ratio must be lower than its central limit 1/4. A volumetric interaction based on a volume-dependent internal pressure is introduced as an additional non-central interaction for a complete calibration of the equivalent Poisson’s ratio up to its incompressibility limit 1/2. This volumetric interaction can also be classified as Fuchs-type, providing a potential energy that depends on the volume variation of each cell. The mixed differential-difference equations of the associated lattice derive from Hamilton’s principle applied to the discrete energies. The algebraic properties of the stiffness matrix of the discrete cell provide information on the positive definiteness of the potential energy, for each lattice with central and non-central interactions. The convergence of this finite lattice towards a linear elastic continuous right parallelepiped is shown in several static loading schemes. The discrete Lamé problem for the free vibration of this parallelepiped is solved for all the considered lattices. It is concluded that discrete and continuum elasticity can be connected by this cubic lattice within a complete range of elasticity parameters
