Mathematical analysis of parallel convective exchangers with general lateral boundary conditions using generalized graetz modes

We propose a mathematical analysis of parallel convective exchangers for any general but longitudinally invariant domains. We analyze general Dirichlet or Neumann prescribed boundary conditions at the outer solid domain. Our study provides general mathematical expressions for the solution of convection/diffusion problems. Explicit form of generalized solutions along longitudinal coordinate are found from convoluting elementary base Graetz mode with the applied sources at the boundary. In the case of adiabatic zero flux counter-current configuration, we recover the longitudinally linearly varying solution associated with the zeroth eigenmode which can be considered as the fully developed behavior for heat-exchangers. We also provide general expression for the infinite asymptotic behavior of the solutions which depends on simple parameters such as total convective flux, outer domain perimeter and the applied boundary conditions. Practical considerations associated with the numerical precision of truncated mode decomposition is also analyzed in various configurations for illustrating the versatility of the formalism. Numerical quantities of interest are investigated, such as fluid/solid internal and external fluxes

CEO compensations in a stakeholders' regime : an empirical investigation with French listed companies

Ces dernières années, la publication du niveau de rémunération des dirigeants a soulevé d’intenses controverses. Un certain nombre d’études ont mis en évidence une relation positive entre le salaire des dirigeants et la performance de la société, aux Etats-Unis et en Grande- Bretagne. La rémunération des dirigeants est également proche de la structure du gouvernement d’entreprise. Or la structure française de gouvernement d’entreprise est différente de celle observée aux États-Unis ou en Grande-Bretagne. En France, la tradition voulait que l’on ne divulgue pas ou peu d’information sur le niveau de rémunération des dirigeants. Cependant depuis 2002, les sociétés cotées doivent indiquer dans leurs rapports annuels le montant des rémunérations des dirigeants et des membres du conseil d’administration. (loi NRE, 15 mai 2001). A partir d’un échantillon de 110 sociétés cotées françaises sur la période 2002-2004 (indice SBF 120), l’objet de cette recherche est d’apporter des éclairages sur la rémunération des dirigeants dans un pays connu pour être plutôt conservateur sur le sujet. Pour étudier les déterminants de la rémunération des dirigeants, nous avons utilisé trois mesures de cette rémunération : la partie fixe du salaire, le bonus annuel et la rémunération globale. Les premiers résultats montrent que les trois mesures de la rémunération des dirigeants peuvent être expliquées par la taille de la société, et la partie variable (bonus) par la performance boursière. Les résultats sur le risque sont plus mitigés et indiquent que le risque spécifique de la firme est négativement associé à la rémunération des dirigeants, ce qui confirme les résultats de Gray et Cannela (1997). Enfin, les variables de gouvernance ont un impact significatif sur le niveau de rémunération des dirigeants.CEO compensation; Corporate governance; Performance

Erreurs humaines et défaillances organisationnelles : résultats de la mise en oeuvre de la méthode Tripod Delta

National audienceTripod Delta est une méthode d'analyse qui permet d'identifier les défaillances organisationnelles susceptibles d'avoir un impact sur la santé et la sécurité au travail. Les défaillances sont représentées sous la forme de 11 facteurs organisationnels. La méthode permet d'évaluer, à l'aide d'un questionnaire individuel, le niveau de maîtrise et de contrôle de chacun de ces facteurs. Elle se fonde essentiellement sur la perception des salariés de l'entreprise de l'état des pratiques en santé et sécurité au travail

Towards a new tool for measuring Safety Management Systems performance

Available on: http://www.resilience-engineering.org/REPapers/Cambon_Guarnieri_Groeneweg_P.pdfInternational audienceThis paper deals with the assessment of Safety Management Systems performance and presents a new tool developed for that purpose. It recognizes two dimensions in a SMS: a structural facet corresponding to the formal description of the system and an operational one focused on the system's influence on the working environment and practices of people. Building up the operational performance of a SMS actually strengthens the overall resilience of the organization. Authors of the paper believes that the operational performance of SMS can be measured using Tripod Delta. This method is actually designed to detect weak areas in the environment in which people are working and the level of control that the organization has on it. The method and its interesting model of organizational resilience are presented in the paper. In the framework of this paper, Tripod is used as an input to measure the SMS operational performance. Both of the tools designed to measure the structural and operational performances of Safety Management Systems are then described

Online tests based on contributions provided by teachers and students during face-to-face lectures

National audienceOur previous work has introduced the "Tsaap-Notes" platform to increase the motivation and engagement of students in the process of collaborative note taking during lectures. In this paper, we introduce the approach "Notes as Feedback" which consists of recycling interactive questions asked during a lecture in order to semi-automatically build computer based self-assessment tests where feedback provided to students is based on the notes taken by students. A first experimentation on a group of 54 students enrolled in a computer science Master course helped to highlight the benefits of this work: increased participation in note-taking, a massive engagement of students to play the self-assessment tests, and improved student results at the final exam

Tsaap-Notes -- An Open Micro-Blogging Tool for Collaborative Notetaking during Face-to-Face Lectures

International audienceSocial theories of learning demonstrated that collaborative note taking during face-to-face lecture provides important benefits: better learner engagement, collaborative learning, and knowledge building. In this paper we present Tsaap-Notes, an open micro-blogging platform dedicated to collaborative note taking that can be used as a standalone application, or fully integrated into existing virtual learning environments. Tsaap-Notes provides users with advanced features such as annotations, questions, or filtering that encourage learners to participate in the collaborative activity. Our tool has been experimented with a cohort of forty students during a short period of time, results show that learners are getting more and more familiar with Tsaap-Notes and that this application becomes useful when the time of preparing exams has come

Génération semi-automatique de tests d'auto-évaluation pourvus de feedback résultant de la prise de notes collaborative

International audienceNos travaux prédécents ont introduit la plate-forme Tsaap-Notes pour augmenter la motivation et l'engagement des étudiants dans le processus de prise de notes collaborative pendant les cours dispensées en face-à-face. Dans cet article, nous introduisons l'approche « Notes as Feedback » consistant à recycler les questions interactives posées pendant le cours afin de produire semi-automatiquement des tests d'auto-évaluation informatisés pourvus de feedback issus des notes prises par les étudiants. Une première expérimentation réalisée sur un groupe de 54 étudiants inscrits en Master Informatique a permis de mettre en avant les bénéfices de ces travaux : une participation accrue à la prise de notes collaborative, un engagement significatif des étudiants dans les tests de révision, et des résultats en hausse à l'examen terminal

Optic Flow Based Autopilots: Speed Control and Obstacle Avoidance

International audienceThe explicit control schemes presented here explain how insects may navigate on the sole basis of optic flow (OF) cues without requiring any distance or speed measurements: how they take off and land, follow the terrain, avoid the lateral walls in a corridor and control their forward speed automatically. The optic flow regulator, a feedback system controlling either the lift, the forward thrust or the lateral thrust, is described. Three OF regulators account for various insect flight patterns observed over the ground and over still water, under calm and windy conditions and in straight and tapered corridors. These control schemes were simulated experimentally and/or implemented onboard two types of aerial robots, a micro helicopter (MH) and a hovercraft (HO), which behaved much like insects when placed in similar environments. These robots were equipped with opto-electronic OF sensors inspired by our electrophysiological findings on houseflies' motion sensitive visual neurons. The simple, parsimonious control schemes described here require no conventional avionic devices such as range finders, groundspeed sensors or GPS receivers. They are consistent with the the neural repertoire of flying insects and meet the low avionic payload requirements of autonomous micro aerial and space vehicles