Analyse didactique d'un cours de Génie Logiciel basé sur l'approche orientée objets

The aim of this work is to study how concepts and techniques used in the development of large software in the framework of the object-oriented approach are acquired by students in "maîtrise d'informatique" (fourth year of university). A categorization of the object model's fundamental concepts was realized on the basis of various students works. This categorization is directly related to the stereotypic or prototypic way the students use the knowledge covered by the concepts they are learning. The result of the study is the definition of a criterion for a good understanding of the course, which is the notion of the abstraction. This notion is absolutely essential for the mastering of the object model, even though it is the only one for which no didactic transposition into the software engineering's teaching is available.Cette recherche a pour but d'étudier l'acquisition par des étudiants de maîtrise d'informatique des concepts et techniques de développement de grandes applications informatiques dans le cadre de l'approche orientée objets. L'observation de diverses productions d'un groupe d'étudiants a permis d'effectuer une catégorisation des concepts fondamentaux du modèle à objets en relation directe avec le mode d'utilisation stéréotypique ou prototypique adopté par les étudiants pour les connaissances que recouvrent ces concepts. Ces résultats ont mis en évidence l'existence d'un critère de bonne compréhension du cours : il s'agit de la notion d'abstraction, qui est absolument essentielle pour la maîtrise du modèle à objets, alors qu'elle est la seule à ne pas posséder de transposition didactique dans l'enseignement du Génie Logiciel.Surcin Sylvain, Choppy Christine, Sere Marie-Geneviève. Analyse didactique d'un cours de Génie Logiciel basé sur l'approche orientée objets. In: Sciences et techniques éducatives, volume 2 n°3, 1995. pp. 265-286

Carbon-Loaded Flexible Electrode Films for Li-O2 Cells: Preparation, Porosity, Homogeneity and Electrochemical Characterization

Porous (up to 70 vol. %) self-standing flexible carbon/polymer (Ketjen Black / PVdF-HFP) film electrodes are produced by leaching out a plasticizer-porogen agent (DBP = DiButyl Phtalate) from precursor films (80% ³ DBP w% ³ 40%). Textural analysis reveals that i) these films exhibit copious initial macroporosity, ii) extra open macro- and then meso-porosity are created along the leaching, iii) this leaching process impacts the internal films texture resulting in a partial closing of the pre-existing porosity, iv) only films with the lowest initial DBP contents (≤ 60 w%) are homogeneous in composition/porosity/texture. In Li/O2 cells, the first discharge capacities of these films are compared to those calculated assuming a total filling of this porosity by electrochemically formed solid Li2O2 (2700 mAh.cm-3 of pores). Up to 80 % of the maximum capacity can be reached (i.e. 80 % of the porosity filled by Li2O2), confirming the positive attributes of mixed interconnected macro/meso porosity. This is further emphasized by the very low capacities obtained with electrodes having similar porosity vol. % but totally different internal texture (GDL). These conclusions can be made despite a large discrepancy in the data, even for homogeneous films, due to reproducibility issues intrinsic to the system

Nonclassical Crystallization and Size Control of Ultra-Small MoO2 Nanoparticles in Water

International audienceSize tuning for MoO2 nanoparticles is demonstrated for the first time over a wide range 2-100 nm, through a colloidal route into water. A nucleation-growth mechanism based on oriented attachment is evidenced to rationalize the impact of two simple synthetic levers: reactant ratio and temperature. The smallest non-aggregated crystalline MoO2 nanoparticles are reported, with specific surface area reaching 86 m(2) g(-1). Size and morphology control, along with the ability to produce, non-aggregated ultra-small MoO2 particles are important for a wide range of applications, such as catalysis and energy storage. To exemplify the importance of size tuning, the impact of downscaling on the electrochemical properties in Li-ion batteries is investigated

Sustainable one-pot aqueous route to hierarchical carbon-MoO2 electrodes for Li-ion batteries

International audienceA route towards carbon-MoO2 core-shell spheres has been developed, through hydrothermal decomposition of ascorbic acid combined with precipitation of MoO2 nanoparticles. In this one-pot and green process, carbon spheres originating from ascorbic acid act as seeds for the in situ deposition of a corona made of 30 nm molybdenum dioxide particles. The as-obtained hierarchical nanostructured carbon-MoO2 core-shell spheres exhibit an ideal combination of electrical conductivity and lithium reactivity for Li-ion battery electrodes. This nanocomposite offers the opportunity to master the collector-active material and active material-electrolyte interfaces. Direct transfer ``from the beaker to the battery'' without any additives nor thermal treatment yields storage capacity values of ca. 600 mA h g(-1) at C/5 rate with excellent stability that challenges state-of-the-art molybdenum oxide-based batteries

Design of Hierarchical Porous Carbonaceous Foams from a Dual-Template Approach and Their Use as Electrochemical Capacitor and Li Ion Battery Negative Electrodes

Porous carbon foams were prepared by pyrolysis of phenolic resin from a dual-template approach using silica monoliths as hard templates and triblock copolymers as soft templating agents. Macroporosity of 50-80% arose from the Si(HIPE) hard template (the acronym "HIPE" refers to the high internal phase emulsion process), while the soft template generated micro- or mesoporosity, according to the operating procedure. The final materials exhibited a Brunauer-Emmett- Teller specific surface area of 600-900 m2 3 g-1. Their performances as electrodes for electrochemical capacitors or Li ion battery negative electrodes were investigated. The mesoporous foams gave the best capacitance, up to 20 F 3 g-1. In battery configuration, the microporous foams delivered an irreversible capacity of 500-600 mA 3 h 3 g-1 during the first discharge. Upon charging, partial extraction of Li gave reversible capacities of 125-150 mA 3 h 3 g-1

Nanoparticles of Low-Valence Vanadium Oxyhydroxides: Reaction Mechanisms and Polymorphism Control by Low-Temperature Aqueous Chemistry

An aqueous synthetic route at 95 °C is developed to reach selectively three scarcely reported vanadium oxyhydroxides. Häggite V₂O₃(OH)₂, Duttonite VO­(OH)₂, and Gain’s hydrate V₂O₄(H₂O)₂ are obtained as nanowires, nanorods, and nanoribbons, with sizes 1 order of magnitude smaller than previously reported. X-ray absorption spectroscopy provides evidence that vanadium in these phases is V^+IV. Combined with FTIR, XRD, and electron microscopy, it yields the first insights into formation mechanisms, especially for Häggite and Gain’s hydrate. This study opens the way for further investigations of the properties of novel V^+IV (oxyhydr)­oxides nanostructures