31 research outputs found
Préface
La prĂ©servation des terres agricoles constitue un enjeu stratĂ©gique majeur au regard de la production agricole en lien avec lâalimentation et lâamĂ©nagement du territoire, aux diffĂ©rentes Ă©chelles â locale, nationale et internationale ; de nombreux pays dans le monde ont parfaitement identifiĂ© cet enjeu. Au niveau mondial et Ă long terme, lâenjeu est de maintenir le potentiel de production agricole pour assurer la sĂ©curitĂ© ..
Les terres agricoles face Ă lâurbanisation
La perte de terres agricoles liĂ©es Ă lâurbanisation constitue lâune des facettes de la consommation des terres. CommencĂ© dans les annĂ©es 1970, ce phĂ©nomĂšne â essentiellement dĂ» Ă lâĂ©talement urbain â prend des proportions jusque-lĂ inĂ©galĂ©es. Les consĂ©quences de ces processus dâartificialisation sont multiples et portent Ă la fois sur la production et sur la sĂ©curitĂ© alimentaire ainsi que sur la perte de biodiversitĂ©. Ces processus interrogent aussi les formes de solidaritĂ© territoriale entre les villes et les espaces pĂ©ri-urbains et ruraux. Issu dâune collaboration scientifique lancĂ©e au dĂ©but des annĂ©es 2010 entre lâUniversitĂ© de technologie de Sydney (University of Technology Sydney, UTS) et lâInstitut national de recherche en sciences et technologies pour lâenvironnement et lâagriculture (Irstea), cet ouvrage aborde des points clĂ©s de la problĂ©matique de la consommation des terres en se focalisant sur les terres agricoles en France et en Australie. PlutĂŽt que dâoffrir une analyse comparative approfondie de la planification des terres agricoles pĂ©riurbaines entre les deux pays, il propose une exploration des « boĂźtes Ă outils » de lâingĂ©nierie territoriale dĂ©veloppĂ©es et mobilisĂ©es pour faire face Ă lâenjeu de la perte de terres agricoles liĂ©e Ă lâurbanisation. Il offre Ă©galement un « arrĂȘt sur image » dans un panorama de champs de recherche en pleine Ă©volution, autant du point de vue thĂ©orique que mĂ©thodologique
Tourisme, écotourisme et stratégies de développement dans la Caraïbe
International audienc
Lâagroalimentaire, pilier de lâĂ©conomie rĂ©gionale, tient le cap : Ă©tat des lieux et Ă©volutions de la sphĂšre agroalimentaire du Languedoc-Roussillon de 1997 Ă 2009
NumĂ©ro spĂ©cial Agreste Languedoc-Roussillon, novembre 2011NumĂ©ro spĂ©cial Agreste Languedoc-Roussillon, novembre 2011Avec un chiffre d'affaires de 8,6 milliards d'euros en 2009, la sphĂšre agroalimentaire rĂ©gionale dans son ensemble a rĂ©sistĂ© Ă la crise. Cette derniĂšre a cependant affectĂ© la filiĂšre viticole ainsi que, dans une moindre mesure, la filiĂšre produits animaux. Les autres filiĂšres ont non seulement rĂ©sistĂ©, mais en plus font preuve dâun dynamisme certain : chiffre dâaffaires (CA) et exportations en hausse, dĂ©veloppement de nouveaux circuits de distribution. Le phĂ©nomĂšne de concentration des Ă©tablissements, dĂ©jĂ observĂ© en 2002, se poursuit et sâaccĂ©lĂšre : lâeffectif moyen par Ă©tablissement passe de 18 Ă 22 salariĂ©s entre 2002 et 2009, avec un CA moyen par Ă©tablissement en progression, qui atteint 9,6 millions dâeuros. Sur la mĂȘme pĂ©riode, le nombre dâĂ©tablissements a rĂ©gressĂ© de 25 % et lâemploi salariĂ© permanent de 6 %. Seuls les petits Ă©tablissements (de moins de 20 salariĂ©s) sont concernĂ©s par ces baisses. Les Ă©tablissements de plus de 20 salariĂ©s ont vu leur nombre augmenter de 7 % et leur effectif salariĂ© de 16 %. Avec un CA en hausse de 13 %, cette catĂ©gorie dâĂ©tablissements contribue dĂ©sormais Ă 75 % du CA rĂ©gional. La taille a donc Ă©tĂ© un Ă©lĂ©ment clĂ© de rĂ©sistance Ă la crise. En amont de l'agroalimentaire rĂ©gional, les achats de matiĂšres premiĂšres agricoles se font de moins en moins en rĂ©gion en raison de la perte de vitesse de la viticulture et du dĂ©veloppement de filiĂšres moins consommatrices de matiĂšres premiĂšres agricoles rĂ©gionales (dĂ©rivĂ©s de cĂ©rĂ©ales, produits divers). En aval, le dĂ©veloppement des exportations favorise les destinations de plus en plus lointaines. Sur le marchĂ© domestique en revanche, on assiste Ă une reconquĂȘte des marchĂ©s de proximitĂ© Ă travers le dĂ©veloppement de circuits alternatifs (grossistes, restauration collective, vente directe, âŠ). ParallĂšlement, la volontĂ© dâappartenance au territoire reste prononcĂ©e avec lâutilisation importante de signes de qualitĂ© liĂ©s au terroir (appellation d'origine protĂ©gĂ©e â AOP, indication gĂ©ographique protĂ©gĂ©e â IGP) et de la marque rĂ©gionale Sud de France. Cette recherche de nouveaux dĂ©bouchĂ©s, ces stratĂ©gies de marquage, la poursuite de lâeffort dâinnovation, ou encore lâadoption dâune dĂ©marche dĂ©veloppement durable (qui concerne prĂšs dâun quart des Ă©tablissements), sont autant de moyens de diffĂ©renciation qui ont permis, malgrĂ© la crise, dâaccroĂźtre la valeur ajoutĂ©e des productions rĂ©gionales. Cette nouvelle enquĂȘte nous montre que lâagroalimentaire rĂ©gional a su prĂ©server son activitĂ© et sa compĂ©titivitĂ© et mĂȘme amĂ©liorer sa durabilitĂ© Ă©conomique par rapport Ă 2002
Morphing Hydrofoil Model Driven by Compliant Composite Structure and Cavity Pressure
In this work a collaborative experimental study is conducted in order to assess the effect on the hydrodynamic performanceofacompliantcompositehydrofoilcontrolled by an imposed cavity pressure. It is expected that the cavity pressure together with composite structures is suitable to control the hydrodynamic forces as well as cavitation inception and development. A new concept of morphing hydrofoil is developed by the authors and tested in the cavitation tunnel at the French Naval Academy Research Institute. The experiments are based on the measurements of hydrodynamic forces and hydrofoil deformations under various conditions of cavity pressure. Effect on cavitation inception are shortly studied too. In parallel to this experiment, a 2D numerical tool is developed in order to help to design a compliant hydrofoil shape. Numerically, the ïŹuid structure coupling is based on an iterative method under small perturbation hypothesis. The ïŹow model is based on a panel method and a boundary layer formulation and it is coupled with a ïŹnite-element method for the structure. It is shown that pressure driven compliant composite structure is suitable to some extent to control the hydrodynamics forces, allowing to enlarge the operational domain of the compliant hydrofoil according to the angle of attack and the cavity pressure. Preliminary results on cavitation inception driven by compliant composite wall are pointed out as well.
Morphing Hydrofoil Model Driven by Compliant Composite Structure and Internal Pressure
In this work, a collaborative experimental study has been conducted to assess the effect an imposed internal pressure has on the controlling the hydrodynamic performance of a compliant composite hydrofoil. It was expected that the internal pressure together with composite structures be suitable to control the hydrodynamic forces as well as cavitation inception and development. A new concept of morphing hydrofoil was developed and tested in the cavitation tunnel at the French Naval Academy Research Institute. The experiments were based on the measurements of hydrodynamic forces and hydrofoil deformations under various conditions of internal pressure. The effect on cavitation inception was studied too. In parallel to this experiment, a 2D numerical tool was developed in order to assist the design of the compliant hydrofoil shape. Numerically, the fluid-structure coupling is based on an iterative method under a small perturbation hypothesis. The flow model is based on a panel method and a boundary layer formulation and was coupled with a finite-element method for the structure. It is shown that pressure driven compliant composite structure is suitable to some extent to control the hydrodynamic forces, allowing the operational domain of the compliant hydrofoil to be extended according to the angle of attack and the internal pressure. In addition, the effect on the cavitation inception is pointed out
Effects on cavitation inception of leading and trailing edge flaps on a high-performance hydrofoil
For the high-performance foiling yachts, cavitation is often a limiting factor for take-off and top speed. The present work investigates solutions to delay the onset of cavitation thanks to a combination of leading edge and trailing edge flaps. Both numerical studies based on a potential code and experiments in a hydrodynamic tunnel are conducted in order to assess the effect of specific geometric parameters on the hydrodynamic performance and cavitation inception. Experimentally the effect on the hydrodynamic performances and cavitation buckets of a 70% chord trailing edge flap and a 20% chord leading edge flap of NACA 0012 is investigated. The hydrofoils are manufactured using a 3D printer technique at IRENav and tested in the cavitation tunnel of the institute at an inflow velocity of 6.67 m/s (Re = 10â¶). The results show that the lift coefficient increases and the cavitation bucket gets larger with the flaps deflection. The experimental results are in good agreement with the numerical ones by highlighting the capacity of the flaps to enlarge both the operating domain and the cavitation bucket of the hydrofoil
Microbubble Generation through Porous Membrane under Aqueous or Organic Liquid Shear Flow
Gas-liquid reactors involving the production of bubbles are very useful in various industrial fields, such as chemistry, oil refining, or water treatment. Generating microbubbles at the inlet of gas-liquid reactors could improve both hydrodynamics and mass transfer. In this paper, the generation of microbubbles using commercial porous filtration membranes is studied, in aqueous or organic liquid under a liquid cross-flow. Different combinations of dispersed phase (air or nitrogen) and continuous phase (water or heptane) are studied. Since the size of the microbubbles may be correlated with physicochemical properties of both phases and the membrane surface, several tubular ceramic membranes were tested (made of alumina or zirconium oxides) with mean pore diameters d(p) varying from 20 to 800 nm. It was observed that these membranes were able to generate bubbles which became microbubbles under the application of a liquid cross-flow. Microbubbles with bimodal distribution (microbubble diameters d(b) in the range of 100-200 and 500-550 mu m) were obtained in heptane when using zirconium oxide membranes (d(p) varying from 20 to 100 nm) under a shear stress tau varying from 27 to 39 Pa with a gas fraction of nearly 3%. The present study shows that microbubbles can be generated in heptane using commercial porous filtration membranes under a liquid cross-flow. This is a promising way to provide microbubbles that could be used to improve the usual gas/liquid mass transfer operation
Le charisme en politique
Cet ouvrage confronte le concept wĂ©bĂ©rien de charisme aux pratiques politiques antiques. Ă quelles conditions peut-on parler du charisme de lâoligarque, du roi, du gĂ©nĂ©ral, du consul, de lâempereur ? Quelles Ă©taient, dans lâAntiquitĂ© grecque et romaine, les modalitĂ©s concrĂštes de construction et de mise en scĂšne du pouvoir charismatique ? Les contributions reviennent sur les rĂ©flexions de Weber en les mettant Ă lâĂ©preuve dâĂ©tudes de cas contextualisĂ©es, sâinscrivant dans le temps court des crises ou sur la longue durĂ©e. En se gardant de (re)lire toute la vie politique antique au prisme du charisme, il sâagit de souligner lâutilitĂ© de ce concept pour saisir certains pouvoirs personnels et, en retour, dâĂ©valuer lâintĂ©rĂȘt de ces cas concrets pour ajuster le concept wĂ©bĂ©rien. Lâouvrage insiste ainsi sur lâimportance de la rhĂ©torique des Ă©motions ou de la communautĂ© Ă©motionnelle, tout en soulignant la coexistence dâĂ©lĂ©ments charismatiques, lĂ©gaux-rationnels et bureaucratiques. Il tente Ă©galement de comprendre comment un pouvoir originairement rĂ©volutionnaire pouvait se « quotidienniser » sans pour autant disparaĂźtre