Search results for "Mecànica"
showing 10 items of 25 documents
Optimization of 3-DOF Parallel Motion Devices for Low-Cost Vehicle Simulators
2017
Motion generation systems are becoming increasingly important in certain Virtual Reality (VR) applications, such as vehicle simulators. This paper deals with the analysis of the Inverse Kinematics (IK) and the reachable workspace of a three-degrees-of-freedom (3-DOF) parallel manipulator, proposing different transformations and optimizations in order to simplify its use with Motion Cueing Algorithms (MCA) for self-motion generation in VR simulators. The proposed analysis and improvements are performed on a 3-DOF heave-pitch-roll manipulator with rotational motors, commonly used for low-cost motion-based commercial simulators. The analysis has been empirically validated against a real 3-DOF …
Experimental demonstration of phase bistability in a broad-area optical oscillator with injected signal
2015
We demonstrate experimentally that a broad-area laserlike optical oscillator (a nondegenerate photorefractive oscillator) with structured injected signal displays two-phase patterns. The technique [de Valc\'arcel and Staliunas, Phys. Rev. Lett. 105, 054101 (2010)] consists in spatially modulating the injection, so that its phase alternates periodically between two opposite values, i.e., differing by $\ensuremath{\pi}$.
Data Acquisition System for the Characterization of Biomechanical and Ergonomic Thresholds in Driving Vehicles
2020
Directive (EU) 2015/653 on driving licenses has involved the modification of different codes that must appear on driver&rsquo
Increasing understanding and confidence in THM simulations of engineered barrier systems
2020
Previous studies on the modelling of coupled thermo-hydro-mechanical (THM) processes in bentonite-based engineered barrier systems (EBSs) showed the sensitivity of the output quantities to changes in the input parameters. To investigate the effects of uncertainties on the modelling results, to improve the understanding of the coupled processes active in the repository near field and to gain in-depth understanding of model uncertainties of different codes, a sensitivity analysis and code comparison of EBS simulations was performed within the Task Force on Engineered Barrier Systems. The analysis included variations in material parameter values, boundary and initial conditions, considered phy…
Utilidad de un nuevo sistema de cronometraje para proporcionar feedback inmediato a los nadadores
2007
El presente documento tiene dos objetivos, en primer lugar, describir un nuevo sistema de cronometraje que proporciona feedback en tiempo real y sin interferir en la ejecución del nadador y, en segundo lugar, comprobar su utilidad. El sistema consiste en una pantalla de leds, resistente al agua e instalada en el fondo de la piscina, conectada a una Unidad Central mediante una plataforma de contacto colocada en la pared donde se realiza el viraje. La pantalla de leds informa al nadador de los tiempos y número de vueltas e, incluso, puede presentar texto (consignas) escrito por el entrenador. Este sistema se puede conectar a un PC o una PDA, permitiendo registrar los tiempos para su posterior…
Impact Acceleration During Prolonged Running While Wearing Conventional Versus Minimalist Shoes.
2020
Purpose: In recent years a sub-group of minimalist runners have emerged who aim to perform physical exercise more naturally in an attempt to reduce running-related injuries. Here we aimed to determine the effect that running with minimalist footwear in a prolonged run has on footimpact accelerations. Method: Seventeen runners ran with minimalist and conventional shoes (MS and CS, respectively) in two separate sessions; the participants had experience with both footwear types. We measured the length and frequency of each stride, as well as the tibial and head impact acceleration every 5 minutes during a prolonged run (30 minutes at 80% of each individual's maximum aerobic speed). Results: Th…
Bionate biocompatibility: in vivo study in rabbits
2022
Response to foreign materials includes local tissue reaction, osteolysis, implant loosening, and migration to lymph nodes and organs. Bionate 80A human explants show minor wear and slight local tissue reaction, but we do not know the response at the spinal cord, nerve roots, lymph nodes, or distant organs. This study aims to figure out reactions against Bionate 80A when implanted at the spinal epidural space of 24 20-week-old New Zealand white rabbits. In one group of 12 rabbits, we implanted Bionate 80A on the spinal epidural space, and another group of 12 rabbits was used as the control group. We studied tissues, organs, and tissue damage markers on blood biochemistry, urine tests, and ne…
Design characteristics, primary stability and risk of fracture of orthodontic mini-implants: Pilot scan electron microscope and mechanical studies
2013
Objectives: Orthodontic mini-implants (OMIs) are increasingly used in orthodontics but can fail for various reasons. This study investigates the effects of OMI design characteristics on the mechanical properties in artificial bone. Material and Methods: Twelve self-drilling OMIs (2 small, 6 medium, 4 large) from 8 manufacturers were tested for their primary stability in simulated medium-high cancellous bone and the risk to fracture in high-density methacrylate blocks. For the assessments of the maximum insertion torque (IT) and torsional fracture (TF) 5 of each OMI were used and for the pull-out strength (POS) 10. The OMIs were inserted with a torque screwdriver (12 sec/360°) until the bott…
Evaluación de parámetros biomecánicos del lanzamiento de jabalina en lanzadores de diferente nivel de rendimiento
2000
Mediante análisis cinemático y utilizando como muestra a lanzadores agrupados en función de
 la marca conseguida (grupo internacional: atletas con marca superior a los 80 metros; y grupo
 nacional: atletas con marca inferior a 80 metros) el objetivo del estudio se centró en determinar si
 alguno de los parámetros utilizados para evaluar la eficacia del gesto establece diferencias entre
 uno y otro grupo de lanzadores.
 Los resultados muestran que algunos de dichos parámetros cinemáticos ayudan a establecer los
 márgenes para la pertenencia a los. Del total de las 41 variables contrastadas, sólo 8 de ellas
 establecían diferencias significativas entre grupo…
Self-sustained coherent phonon generation in optomechanical cavities
2016
Optical forces can set tiny objects in states of mechanical self-sustained oscillation, spontaneously generating periodic signals by extracting power from steady sources. Miniaturized self-sustained coherent phonon sources are interesting for applications such as mass-force sensing, intra-chip metrology and intra-chip time-keeping among others. In this paper, we review several mechanisms and techniques that can drive a mechanical mode into the lasing regime by exploiting the radiation pressure force in optomechanical cavities, namely stimulated emission, dynamical back-action, forward stimulated Brillouin scattering and self-pulsing.