Science & Mathematics

S'inscrivant dans une démarche de développement durable, le bois s'impose de plus en plus comme un matériau à dimension environnementale et s'ancre dans le paysage français. Encore discrètes, de nombreuses innovations sortent peu à peu des laboratoires et trouvent des applications commerciales. Celles-ci bénéficient d’un soutien politique fort et sont plébiscitées par le grand public, qui y voit des alternatives plus respectueuses de l’environnement aux produits synthétiques dérivés de la pétrochimie, ou dont la production nécessite de lourdes dépenses énergétiques. Après une brève introduction portant sur le bois en tant que source de matériaux et de produits nouveaux, quelques exemplesd’innovations seront donnés dans cet article. Les matériaux de structure, puis les matériaux de fonction, seront traités à la lumière de travaux récents réalisés dans des laboratoires français.

We present ReViVD, a tool for exploring and filtering large trajectory-based datasets using virtual reality. ReViVD's novelty lies in using simple 3D shapes—such as cuboids, spheres and cylinders—as queries for users to select and filter groups of trajectories. Building on this simple paradigm, more complex queries can be created by combining previously made selection groups through a system of user-created Boolean operations. We demonstrate the use of ReViVD in different application domains, from GPS position tracking to simulated data (e. g., turbulent particle flows and traffic simulation). Our results show the ease of use and expressiveness of the 3D geometric shapes in a broad range of exploratory tasks.

An enantioselective organocatalytic reaction of indole-derived-1-azadienes with aldehydes leading the formation of enantioenriched cyclic N,O-acetals is reported. The corresponding products can be obtained with high levels of stereoselectivity (de >95 %, 65–99 % ee, 8–98 % yield). Furthermore, fused tetracyclic scaffolds can also be obtained by implementing a one-pot strategy involving an additional oxa-Michael reaction from aldehydes bearing an α,β-unsaturated ketone group.

The photovoltaic electricity is obtained by direct conversion of sunlight into electricity by solar cells. The objective of this work is the study and simulation of a Tandem photovoltaic structure based on Cd1-xMnxTe as top material cell. This paper describes the optimization of energy efficiency for Cd1-xMnxTe thin films deposited by epitaxy on CdTe substrat. We present the impact of the manganese concentration in Cd1-xMnxTe thin films on solar cells performances. Our study includes simulation results to show the conversion efficiency and main performances factors as function of the manganese concentration

Unlike many mollusc species, shells of Concholepas concholepas [Bruguière, 1789] do not show obvious annual morphological marks, neither at the macroscopic or the microscopic scales. The coarsely reticulated structure of the outer shell of this species is produced by the intersection of protuberant lamellae and radial ribs stemming from the apex. These lamellae do not seem to have a particular chronological significance, as they can be formed at rather constant intervals during the first year of growth, and at a diminishing frequency during the successive following years. Therefore, the counting of these concentric lamellae is of little help to determine the age of the shells, and the mechanism responsible for their formation still remain to be understood. At a microscopic level, thin sections of a transversal cut of a shell clearly exhibit that it is made up of two principal components: an external layer formed by prismatic crystals of calcite whose thickness increases from the apex toward the paleal edge and an internal aragonitic layer organized in a crossed lamellar structure. Under appropriate amplification and with a particular combination of transmitted and reflected light, the external layer shows growth structures with an alternating brownish and lighter coloured banding. These structures whose differences in colour seem to depend on their organic matter content typically measure between 20 and 150 µm in thickness. On another hand, scanning electron microscopy analyses reveal that the smallest growth structure consists in 2 µm-thick increments. Even though it has not been possible to directly “see” grouping of these bio-mineralisation units under SEM, it could be deduced that the brownish and light-grey bands are thus formed by a varying number of 2 µm-thick increments. Repeated staining experiments realized with fluorochromes (calcein) on living shells provided a precise chronological framework for the understanding of the growth modality of this species. The calcein marks allowed us to establish that the alternating bands correspond to day and night growth increments. The relative thickness of the bands depends on the number of elementary biomineralisation units or, in other terms, on the frequency of formation of these units. Within one of the conducted experiments which lasted a month and a half, it could be demonstrated that the rhythm at which the organism formed these 2 µm-thick units varied between half-an-hour to two hours. Understanding of the growth modality and the possibility to measure sub-daily increments within the shell of C. concholepas open new perspectives for a series of studies on the relationships between environmental conditions and shell growth on this species. It thus becomes possible to work now on variations of chemical composition of the calcitic increments (calibration of geochemical proxies for environmental conditions) at a time scale of the order of a few hours. This study was financed and conducted in the frame of the French PNEDC CONCHAS Project and also benefited from the support of the EU-project CENSOR (Climate variability and El Nino Southern Oscillation: Impacts for natural resources and management, contract 511071). It is CENSOR publication 0093. Contact Information: N. Guzmán, UR Paléotropique, Centre IRD-Ile de France, 32 avenue Henri Varagnat, 93143 Bondy Cedex, France. Phone: 00 331 48 02 55 88, Fax: 00 331 48 02 55 54, Email: [email protected]

On décrit trois applications typiques des transistors en avalanche: i) trigger : sensibilité 100 mV, délai 3 ns, amplitude de quelques volts à une centaine, temps de montée nanoseconde ; ii) circuit de coïncidences : résolution nanoseconde ; iii) générateur HT déclenché : 3,6 kV, délai 10 ns, temps de montée 10 ns.

Le soutien actif aux sans-abri repose sur une organisation efficace de structures d'accueil, de banques alimentaires, d'associations locales, et de la mobilité des plus vulnérables. La gestion des ressources et des flux, ainsi que l'utilisation de technologies avancées, permettent de répondre à leurs besoins d'urgence. En optimisant la distribution des fournitures et l'accès aux services essentiels, des dispositifs logistiques modernes et bien coordonnés facilitent non seulement la survie des sans-abri, mais consolident aussi leur trajectoire vers une réinsertion sociale durable et inclusive. Ils contribuent également à réduire les inégalités structurelles, tout en renforçant les liens entre les différents acteurs oeuvrant pour une solidarité durable. Dès l'instant, n'est-il pas essentiel de mieux connaître et reconnaître le rôle central de ces dispositifs logistiques novateurs et indispensables pour combattre les effets dramatiques de la précarité ?

Nombreuses sont les études qui ont analysé la certification en matière de développement durable (DD) chez les différentes organisations (Stigzelius et Mark-Herbert, 2009; Eccles, Ioannou, & Serafeim, 2012; Brunsson et al, 2012). Nonobstant, les universités ont été presque négligées dans ce type d’étude. En effet, notre revue de littérature nous a amenés à identifier un manque dans cette littérature quant à la relation entre l’adoption des certifications en matière de développement durable et le degré d’intégration des pratiques de durabilité. Cette recherche se base sur l’étude de cas de deux universités canadiennes : l’une adopte les certifications en matière de DD, et l’autre ne les adopte pas. Notre étude apporte deux contributions à ce champ de recherche : la première est que la certification en matière de DD amène les universités qui les adoptent à mieux intégrer les pratiques de durabilité, et ceux, aux niveaux de tous les types d’activité de l’université. Et la deuxième est que les universités qui ne les adoptent pas n’ont qu’une intégration partielle de ces pratiques.

Despite decades of relatively intensive official excavation, the number of published sigillographic finds from Mahasthangarh, in northwest Bangladesh, corresponding to ancient Puṇḍravardhana, has remained surprisingly limited for an early-historic/early-medieval site of its importance. A recent overview covers just six items found at the site, only one of which endowed with a seal legend. We publish here two sealings that were issued from ancient Puṇḍravardhana. The devices and legends on these two specimens give occasion to publish at the same time four further sealing-types. All of these have very likely surfaced during unauthorised digging at Mahasthangarh.

Many active vehicle safety systems such as electronic stability control (ESC), rollover prevention, and lane departure avoidance could benefit from knowledge of the vehicle slip angle. However, it is a challenge to design an observer to estimate slip angle reliably under a wide range of vehicle maneuvers and operating conditions. This is due especially to nonlinear tire characteristics and system models which have nonlinear output equations. Hence this paper develops an extended H_∞ circle criterion observer for state estimation in systems with nonlinear output equations. The observer design approach utilizes a modified Young’s relation to include additional degrees of freedom in the linear matrix inequality (LMI) used for observer gain design. This enhanced LMI is less conservative than others proposed in the literature for Lipschitz nonlinear systems, both with and without nonlinear output equations. The observer is applied to slip angle estimation and utilizes inexpensive sensors available in all modern vehicles. Finally, experimental tests on a Volvo XC90 sport utility vehicle are used to evaluate the developed approach. The experimental results show that the slip angle estimates for a variety of test maneuvers on road surfaces with different friction coefficients are reliable.

In the rapidly evolving landscape of the Internet of Medical Things (IoMT), the demand for robust and trustworthy identification systems has become paramount due to the sensitive nature of healthcare data. Traditional identification methods, such as passwords, tokens and smart cards, are increasingly being replaced by advanced biometric systems, which provide a higher level of security and protection. The rapid advancements in biometric technology, with its potential to uniquely identify individuals, have driven its integration into a wide range of healthcare applications. Meanwhile, blockchain, a decentralized and immutable ledger technology, offers a powerful solution to address critical challenges in IoMT systems, including data security, privacy and trust. The integration of biometric systems with blockchain introduces innovative approaches for secure identity management and authentication, enhancing both security and trustworthiness in digital healthcare environments. This paper explores biometric systems and blockchain technology and their convergence within IoMT systems, focusing on how this combination strengthens the security and trustworthiness of healthcare systems. It also presents a comparative analysis of existing approaches and provides insights into their practical applications and potential for future advancements in secure IoMT systems.

Table des matières Deux sièges entre histoire et mémoire La résistance des Lillois face à la barbarie autrichienne… Un contexte spécifique La mémoire des sièges dans les combats politiques du XIXe siècle Les victimes de Verdun : entre compassion et expiation Les commémorations du siège de Lille en 1842 Autour du centenaire de la République