Social rationality, separability, and equity under uncertainty

Harsanyi (1955) proved that, in the context of uncertainty, social ratio- nality and the Pareto principle impose severe constraints on the degree of priority for the worst-off that can be adopted in the social evaluation. Since then, the literature has hesitated between an ex ante approach that relaxes rationality (Diamond (1967)) and an ex post approach that fails the Pareto principle (Hammond (1983), Broome (1991)). The Hammond-Broome ex post approach conveniently retains the separable form of utilitarianism but does not make it explicit how to give priority to the worst-off, and how much disre- spect of individual preferences this implies. Fleurbaey (2008) studies how to incorporate a priority for the worst-off in an explicit formulation, but leaves aside the issue of ex ante equity in lotteries, retaining a restrictive form of consequentialism. We extend the analysis to a framework allowing for ex ante equity considerations to play a role in the ex post approach, and find a richer configuration of possible criteria. But the general outlook of the Harsanyian dilemma is confirmed in this more general setting.risk, inequality, social welfare, ex ante, ex post, fairness, Harsanyi theorem

Dr Geo II: Adding Interactivity Planes in Interactive Dynamic Geometry

International audienceInteractive geometry environments support the creation and exploitation of interactive geometric sketches. However, such environments are often driven in a rigid manner, following a well specified construction path. This rigidity is not always compatible with: i. the internal cognitive representation of the learner about the geometric domain and ii. the way a geometric sketch is used in a paper-pen environment. This rigidity is therefore a source of internal tension for the learner and it can reduce the pedagogical added value of the interactive geometry environments. We think additional interactive planes to manipulate a geometric sketch differently can help the learner. We have developed DR. GEO II, an interactive geometry framework that is able to receive additional interactive planes such as a free sketching and a command-based one. We have experimented it in a junior high school class and we report here our first results

Evaluation of local stress and strain state at notch root by means of a new method valid for multiaxial random loadings

International audienceNeuber type methods are widely used to predict the local stress-strain behaviour at notch root in specimens or industrial components. Some limitations of these methods are pointed out in the present paper, especially when the global loading is multiaxial and/or random. A fully new approach is then presented: it introduces a phenomenological model describing the development of residual stresses that can be calibrated by reference to Eshelby's type approaches. A tensorial variable is used for this purpose. Its evolution rule allows us to represent the stress redistribution at the surface of the component. Isotropic and anisotropic constitutive equations are accepted for the description of the material behaviour. It has been successfully used for several complex situations (cyclic, multiaxial, random loadings)

De l'importance des plans d'interaction dans la géométrie interactive

International audienceInteractive geometry environments support creation and exploitation of geometric sketches. However, such environments are often driven in a rigid manner, following a well specified construction path. This rigidity is not always compatible with the internal cognitive representation of the learner about the geometric domain. This rigidity is therefore a source of internal tension for the learner and it can reduce the pedagogical added value of these environments. We think addi- tional interactive planes to manipulate a geometric sketch differently can help the learner. We have developed an interactive geometry framework that is able to receive additional interactive planes such as a free sketching and a command-based one. We have experimented it in a junior high school class and we report here our results.Les environnements de géométrie interactive permettent créations et explorations de figures géométriques. Ceux-ci imposent cependant à l'apprenant un formalisme fort lors de la construction d'une figure. Cette rigidité n'est pas toujours compatible avec la représentation cognitive de l'ap- prenant du domaine d'apprentissage. Elle est donc source de tensions internes chez celui-ci et peut réduire la portée pédagogique de ces environnements. Nous pensons que des plans d'interaction supplémentaires pour manipuler différemment une même figure géométrique peuvent aider l'appre- nant. Nous avons ainsi développé un framework de géométrie interactive permettant l'ajout de tels plans puis nous avons expérimenté son utilisation dans une classe de 3e

Guidage macroscopique de l'apprentissage

National audienceLes EIAH sont souvent spécialisés dans un domaine bien précis. Cela leur permet d'of- frir des modélisations fines du domaine et de l'apprenant. L'analyse alors produite à partir des traces est didactiquement très fine et spécifique au domaine en question. Elle permet de guider l'apprenant en cas de difficulté et de lui proposer des activités de soutien. Cependant cette ana- lyse est étroitement liée aux domaines didactiques, et différente d'un domaine à un autre. Face à la diversité des domaines enseignés, comment proposer un modèle tenant compte de cette multitude et permettant une analyse de l'activité de l'élève et son guidage ? Nous proposons une analyse de l'activité de l'élève hors du champ didactique pour un guidage que nous nommons macroscopique, par opposition à une analyse didactique fine. Le guidage proposé est générique mais paramétré par un réseau notionnel afin d'être transposable à diffé- rents domaines d'enseignement. Notre approche s'appuie sur les réseaux notionnels, les étayages pédagogiques, les traces d'ob- jets et l'inférence sur celles-ci. Leur utilisation conjointe permet la description du domaine, la modélisation de l'apprenant et son pilotage par l'EIAH. Nous présentons cette approche dans iSTOA.net

iSTOA: Artefacts for mathematical interactive learning exercises

International audienceIn primary schools, mathematics teachers use support tools to introduce new concepts. The objective of these tools is to reinforce a mental representation of the newly introduced concept. Tools can be physical objects or paper-pen based. We call these tools artefacts. In computer assisted environments, such artefacts are not always clearly present, those environments focus on the nature of the exercises (drills, quiz). To realise environments in closer relation to classroom teaching, we propose to analyse and categorise such artefacts: we used pedagogical literature and we extracted artefacts used in teaching multiplication. We present our infrastructure and a list of artefacts in the multiplication realm

Improving the oral language skills of elementary school students through video-recorded performances

This study is situated in the context of teaching first language (L1) oral communication in elementary school in Fr-Belgium. According to the literature, the quality of oral performances can be improved through revision. Using video recording could offer this possibility. However, research on this topic addresses neither elementary students, nor L1 instruction. We compared two conditions in which students either did live performances or created video performances with twelve school classes following a 3-week instructional program. Oral communication skills improved under both conditions. However, students in the video condition showed greater improvement in verbal and non-verbal communication for televisual genres

A strategy for the estimation of the fatigue life of notched components under random multiaxial fatigue

International audienceThis paper describes three new models that can be used (1) to determine the stress-strain response in stress concentration zones for components submitted to complex multiaxial loading paths, (2) to extract relevant cycle sequences from a general threedimensional loadin path, (3) to find the hypersphere enclosing any type of cyclic load history. These three models can be combined to post-process an elastic Finite Element Analysis, and provide a fast estimation of the fatigue life of the components