Cost of production and income development in sheep meat production

In France, the total sheep flock has fallen consistently since the 1980s, but this downward trend affects mostly the meat production as dairy flocks remain stable, boosted by official quality labels. Recently, the reform of the Common Agricultural Policy on sheep meat production helped improve the income from breeding ewes, and reduced imports from New Zealand and Great Britain helped improve meat prices. However, French consumption is stagnating and operating costs are rising continuously, thereby weakening the industry’s economic viability. Veterinarians can use some levers to help farmers improve the technical and economic performance of their farmsDepuis les années 1980, le troupeau ovin n’a cessé de diminuer en France. Cette évolution est nettement plus marquée dans les élevages producteurs de viande, alors que les élevages laitiers, bénéficiant d’une plus-value grâce à des produits sous signes officiels de qualité, présentent une stabilité de leur effectif. Récemment, le rééquilibrage de la politique agricole commune en faveur de la production de viande ovine a permis d’améliorer le revenu des ateliers de brebis allaitantes; la diminution des importations en provenance des Iles Britanniques et de Nouvelle Zélande a contribué à une amélioration des cours de la viande. Cependant, la consommation française stagne et les charges d’exploitation augmentent de façon continue, fragilisant la viabilité économique de la filière. Dans ce contexte, le vétérinaire dispose de leviers pour aider ces éleveurs à améliorer le bilan technico-économique de leur élevag

Stabilisation of Clay Mixtures and Soils by Alkali Activation

Alkali activation of clay minerals in soil can be used to form a stabilising phase, such as a geopolymer. Because this requires low-temperature curing, typically <100 °C, it has the potential to be a lower-energy method than fired brick or even cement or lime stabilisation. Whilst this has been demonstrated for individual clay minerals and soils, it is unknown how effective this stabilisation method is for naturally occurring soils from around the world. The potential for stabilisation by alkali activation of a given clay mixture or soil could be approximately, but not fully, predicted from its clay mineralogical composition

Geopolymer Synthetized Using Reactive or Unreactive Aluminosilicate. Influence on the Working Properties

International audienc

Dissolution of silica in solution required to form geopolymer binder

International audienc

Turbine Stator-well flow modelling

In axial gas turbines, hot air from the main annulus path tends to be ingested into the turbine disc cavities. This leads to overheating which will reduce the disc’s life time or lead to serious damage. Often, to overcome this problem, some air is extracted from the compressor to cool the rotor discs. This also helps seal the rim seals and to protect the disc from the hot annulus gas. However, this will deteriorate the overall efficiency. A detailed knowledge of the flow interaction between the main gas path and the disc cavities is necessary in order to optimise thermal effectiveness against overall efficiency due to losses of the cooling air from the main gas path. The aim of this study is to provide better understanding of the flow in a turbine stator-well, and evaluate the use of different CFD methods for this complex, 3-dimensional unsteady flow. This study presents CFD results for a 2-stage turbine. The stator-well cavity for the second row of stationary vanes is included in the calculation and results for both turbine performance and stator-well sealing efficiency are presented

Geopolymers shaping based on various metakaolins

International audienc

Parameters that influence silica dissolution in alkaline media

International audienceGeopolymers have been the object of numerous studies because of their low environmental impact. The synthesis of these geomaterials is achieved by the alkaline activation of aluminosilicates. Alkaline activation is typically accomplished by the activation of potassium silicate or sodium silicate. These alkaline silicate solutions are relatively expensive. We thus attempted to create these solutions by the dissolution of potassium hydroxide and silica in water. This study focuses on the various parameters that can influence the dissolution of silica in basic media (pH>13). The samples used were amorphous silica, quartz sand and quartz ground to five different size distributions. The study of the dissolution of siliceous species was performed mainly by infrared spectroscopy by varying several factors. Stirring and solution volume played no significant role. However, the size distribution and crystallinity of silica were observed to significantly affect the kinetics of dissolution and the quantities of siliceous species in solution, which varied greatly according to the quantity of KOH introduced

Role of the silica source on the geopolymerization rate ALL or

International audienceThe synthesis of geopolymer-silica composites was achieved at room temperature to determine the role of the silica source (quartz or amorphous silica) on the polycondensation rate and the mechanical properties of synthesized materials. Then, samples with a composition range from 100% quartz to 100% amorphous silica were formed, compared and characterized by XRD, infrared spectroscopy, thermal analysis, SEM, and compression tests. The results give evidence that the increase of amorphous silica in the mixture favors the polycondensation reaction (i.e., "geopolymerization") to form consolidated materials whereas quartz led to heterogeneous materials without cohesion. These facts are explained by the modification of the Si/Al ratio in the geopolymer matrix due to the increase of quartz in the mixtur