This paper deals with specific hydrological problems in large and international river basins. It considers the peculiarities of the hydrology of such basins and the consequences for water resources management. Reviewing the anthropogenic impacts and the availability of data, the necessity of international cooperation with the aim of preventive protection of water is stressed.
Hydrologie pour l'aménagement des eaux des grands bassins fluviauxRésumé L'article traite des problèmes hydrologiques spécifiques aux grands bassins fluviaux internationaux. Les particularités de l'hydrologie de ces bassins sont analysées et les conséquences pour l'aménagement des eaux en sont déduites. Partant des effets des activités humaines et de la disponibilité des données, on souligne la nécessité d'une coopération internationale ayant pour objet la protection préventive des eaux.
There is an increasing interest to use novel elastomers with inherent or modified advanced dielectric and mechanical properties, as components of dielectric elastomer actuators (DEA). This requires corresponding techniques to assess their electromechanical performance. One performance criterion is the electrically induced deformation of the active electrode area. In this work, a rectangular DEA is used to investigate the influence of the ratio between the active electrode and the passive area on the actuator deformation. For this purpose, a dielectric silicone film is bonded on one surface to a unidirectional carbon fiber fabric. Thereby, highly anisotropic mechanical properties are implemented. When strains are applied perpendicular to the fiber direction, the composite hardly contracts in the fiber direction due to the superior stiffness of the fibers. In addition, the conductive fiber structure also acts as a highly anisotropic compliant electrode. By application of a second paste-like electrode onto the silicone film a DEA is created that operates in a pure shear configuration. This assembly enables the modification of the active-to-passive area ratio and the investigation of its effect on the actuator deformation. Image-based measurements are used to determine the strain of the active electrode area. The experimental results are compared to a lumped-parameter model that considers the electromechanical properties of the fiber-reinforced DEA. In summary, the ratio of the active-to-passive area has a significant influence on the measured deformation. Especially for novel actuator materials that do not exhibit large strains, an active-to-passive ratio of 50 % proves to be particularly advantageous.
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