Navier-Stokes equations with periodic boundary conditions and pressure loss

We present in this note the existence and uniqueness results for the Stokes and Navier-Stokes equations which model the laminar flow of an incompressible fluid inside a two-dimensional channel of periodic sections. The data of the pressure loss coefficient enables us to establish a relation on the pressure and to thus formulate an equivalent problem.Comment: 10 page

Semi-group theory for the Stokes operator with Navier-type boundary conditions on LpL^{p}-spaces

In this article we consider the Stokes problem with Navier-type boundary conditions on a domain $\Omega$, not necessarily simply connected. Since under these conditions the Stokes problem has a non trivial kernel, we also study the solutions lying in the orthogonal of that kernel. We prove the analyticity of several semigroups generated by the Stokes operator considered in different functional spaces. We obtain strong, weak and very weak solutions for the time dependent Stokes problem with the Navier-type boundary condition under different hypothesis on the initial data $\boldsymbol{u}_0$ and external force $\boldsymbol{f}$. Then, we study the fractional and pure imaginary powers of several operators related with our Stokes operators. Using the fractional powers, we prove maximal regularity results for the homogeneous Stokes problem. On the other hand, using the boundedness of the pure imaginary powers we deduce maximal $L^{p}-L^{q}$ regularity for the inhomogeneous Stokes problem

THE WAY TOWARDS OPEN INNOVATION: AIRBUS MULTI-FUNCTIONAL TEAMS

In times of crisis, innovation is a key to differentiation and thus to the survival of businesses. However, actions taken by managers to stimulate creativity are essentially within the framework of a conventional closed innovation made only internally. Yet, open innovation is a much more efficient and economical way to develop new products, new materials, new technologies and new methods. It requires that partner organizations operate in an open network in which they can work together, each bringing their expertise and talents. This is usually the purchasing function, transverse and connected to the business environment, which can best orchestrate this open innovation by selecting the best suppliers to work with them within new models of integration more or less advanced. The case study of the company Airbus, developed during a participant observation of one year, will define the role of the procurement function in this open innovation approach and the benefits, hazards and limits of this strategy. Examples of the design of the A380 and of the Technocampus EMC² environment illustrate the integrated supplier relationship management method combined with open innovation

IMPLEMENTING A SUSTAINABLE PURCHASING POLICY: AN EXPLORATORY STUDY IN THE COLAS GROUP

This article addresses the contribution of the purchasing function to Corporate Social Responsibility (CSR). Indeed, the purchasing function is playing an increasingly important role in businesses, averaging over 60% of turnover. Simultaneously, managers integrate societal and environmental challenges in the management of internal and external relations. Sustainable purchasing policies, aimed at changing practices throughout the value chain, are deployed. Suppliers are therefore gradually mobilized to implement more responsible practices, and invited to commit themselves through sustainability charters and certification. That leads to the research question: how to implement a sustainable purchasing policy aligned with the corporate strategy? The CSR approach represents a particularly difficult challenge for some companies, as in the construction and civil engineering sector. The Colas Group, world leader in road construction, faces this difficulty that implies radical changes in its relations with its suppliers. Faced with the image of environmental pollution, landscape destruction, illegal labor, and endangerment of its workers, the Colas Group has implemented a progressive, rigorous and structured sustainable approach. Through participatory action research during a one year immersion, a case study of the Colas Group has been developed to analyze this approach and determine its benefits and limits. The particularly difficult context of the implementation of this sustainable purchasing policy – in a multinational, in a post-merger period, in an unfavorable sector and during an economic crisis – implies potential transferability of some practices studied in this specific case

Décadence de l’Élevage Extensif dans le Delta du Fleuve Sénégal, l’Autre Revers de l’Agriculture Irriguée dans la Commune de Diama

Les politiques agricoles du Sénégal s’orientent plus vers l’intensification des systèmes de production. L’agriculture irriguée promue à partir des indépendances connaît un essor important ces dernières années à cause d’un contexte marqué par une péjoration climatique et des objectifs d’autosuffisance alimentaire parfois supranationale. Ce développement ne passe pas sans induire des effets sur les activités antérieures du territoire. A l’échelle du delta du fleuve Sénégal, le développement de l’agriculture irriguée sur cet espace jadis pastoral hypothèque le maintien et le développement de l’élevage et plus particulièrement celui extensif. Ainsi, l’objectif de cet article est d’analyser les effets altérants de l’agriculture irriguée sur cette activité et ses communautés. En plus d’une revue documentaire et des entretiens avec certains services, il s’appuie sur des enquêtes auprès des ménages d’éleveurs et d’un travail cartographique portant sur l’occupation de l’espace. D’une part, il ressort de ses résultats une réduction de l’espace pastoral doublée d’une obstruction des parcours pastoraux au profit de l’agriculture irriguée qui altère la situation sanitaire du cheptel. D’autre part, les résultats montrent une récupération de la main d’œuvre pastorale par cette dernière.   Senegal's agricultural policies are geared more towards the intensification of production systems. The irrigated agriculture promoted from independence has grown significantly in recent years. The latter does not pass without inducing effects on the previous activities of the territory. On the scale of the Senegal River delta, the development of irrigated agriculture in this formerly pastoral area mortgages the maintenance and development of breeding, and more particularly extensive livestock farming. Thus, the objective of this article is to analyze the altering effects of irrigated agriculture on this activity and its communities. In addition to a documentary review and interviews with certain departments, it is based on surveys of pastoralist households and cartographic work on the occupation of space. On the one hand, its results show a reduction in pastoral space coupled with an obstruction of pastoral routes in favor of irrigated agriculture which alters the health situation of the livestock. On the other hand, the results show a recovery of the pastoral workforce by the latter

General Union of Palestine Students (GUPS) : une jeunesse palestinienne politiquement engagée (1950-2008)

One of the historical reasons of the "Printemps Arabe" stems from the Palestinian Student struggling abroad for Democracy and Liberty during the 1950 years. At the beginning of the 1950 years, the Palestinian Youth were ready to organize and participate in movement of the liberation of their country. GUPS, gathering all of the Palestinian students of France, demonstrated, by its activism, its capacity in researching and claiming the truth. Obliged to readapt its strategies by the geopolitical realities the going on through Middle East, GUPS, showed again its aptitude to learn and to implement the judiciary arsenal produced by the United Nations Organization, in order to affirm clearly the rights of Palestinian People. Even in France, their land of exile, the Palestinian students kept mobilized and aware about the different positions adopted by French authorities.Dès les années 50, les jeunes palestiniens s'organisent et se préparent à participer à la libération de leur pays. La GUPS, regroupant tous les étudiants palestiniens de France, a démontré, de par ses interventions, ses activités sur le terrain de la contradiction, de la sensibilisation, de la mobilisation, ses capacités pour la manifestation de la vérité. Contrainte de s'adapter aux événements mondiaux, du Proche Orient, la GUPS, a su admirablement se repositionner, de redéployer, pour décrypter et lire les arsenaux juridiques de l'ONU, pour jeter un éclairage sur les droits du peuple palestinien. Même en France, leur terre d'accueil, les étudiants palestiniens restent vigilants quant aux positions adoptées par les plus hautes autorités métropolitaines