A unified model for the long and high jump

A simple model based on the maximum energy that an athlete can produce in a small time interval is used to describe the high and long jump. Conservation of angular momentum is used to explain why an athlete should run horizontally to perform a vertical jump. Our results agree with world records.Comment: Accepted for publication in Am. J. Phy

THE PLANARITY OF THE STICK AND ARM MOTION IN THE FIELD HOCKEY HIT

The development of relevant simulation models is one way in which our knowledge of the field hockey hit may be improved. The aim of this study was to test the appropriateness of a planar pendulum model for the motion of the stick and arms during the downswing. The hits of 13 experienced female players were filmed, and swing planes were fitted to the motion of the stickface during the downswing. Low variability in the length of a segment’s projection onto the swing plane was taken as evidence for the validity of a planar model. Coefficients of variation of less than 5% for the stick and forearm lengths supported the use of such a model for these segments, but its validity for the upper arms is less certain

Optimum take-off angle in the long jump

In this study, we found that the optimum take-off angle for a long jumper may be predicted by combining the equation for the range of a projectile in free flight with the measured relations between take-off speed, take-off height and take-off angle for the athlete. The prediction method was evaluated using video measurements of three experienced male long jumpers who performed maximum-effort jumps over a wide range of take-off angles. To produce low take-off angles the athletes used a long and fast run-up, whereas higher take-off angles were produced using a progressively shorter and slower run-up. For all three athletes, the take-off speed decreased and the take-off height increased as the athlete jumped with a higher take-off angle. The calculated optimum take-off angles were in good agreement with the athletes' competition take-off angles

La participación privada en la financiación de infraestructuras públicas : la experiencia de la Generalitat de Catalunya

El desarrollo de fórmulas de colaboración público-privada por parte de los países de nuestro entorno tiene su origen en la necesidad de compatibilizar el impulso de las infraestructuras públicas, elemento indispensable para mantener la competitividad, el crecimiento económico y cohesión social, con e l cumplimiento de los límites al déficit y endeudamiento público fijados en e l Plan de Estabilidad y Crecimiento. La Generalitat de Catalunya no ha sido ajena a este proceso, y desde hace unos años ha incorporado estos sistemas para la construcción y financiación de carreteras, material ferroviario, centros penitenciarios, y otras infraestructuras. En el artículo se analizan las diferentes fórmulas aplicadas y las variables a considerar para optimizar su aplicación por parte de las Administraciones. El interés de organismos de la Unión Europea en estos sistemas, los planes de inversión a ejecución y, e l Proyecto de Ley de Contratos del Sector Público, actualmente en tramitación parlamentaria, apuntan a una intensificación en su utilización.Digitalitzat pel SEDA

La participación privada en la financiación de infraestructuras públicas : ¿una opción de futuro?

Forma part del Anuario Partners 2010 : Realidades y prospectivas de la cooperación público-privada / Serra Martín, Albert (Ed.

Algunos aprendizajes y elementos clave para una nueva etapa de colaboración público-privada

Format part del Anuario Partners 2011 : Reflexiones sobre la cooperación público-privada ; Monográfico: la cooperaciónpúblico-privada en el sector salud / Serra Martín, Albert (Ed.

A Novel Strategy for Improving the Quality of Embedded Zerotree Wavelet Images Transmitted over Alamouti Coding Systems

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-21501-8[Abstract] This work deals with the transmission of images, previously coded using the Embedded Zerotree Wavelet (EZW) transform, over wireless systems in which Space-Time Coding (STC) is used. It is shown how the system performance, measured in terms of Peak Signal to Noise Ratio (PSNR), can be improved using bit allocation strategies that take into account the special structure of the EZW bitstream, where the bits firstly allocated are associated to the lowest frequency subbands, and therefore, an error–free transmission of such bits will be crucial to appropriately recover the transmitted image.Galicia. Consellería de Economía e Industria; 10TIC105003PRGalicia. Consellería de Economía e Industria; 09TIC008105PRMinisterio de Ciencia e Innovación; TEC2010-19545-C04-01Ministerio de Ciencia e Innovación; CSD2008-0001