COMPUTER SIMULATION IN SPORT DIDACTICS AND COACHING

Modern athletics and gymnastics are characterized by very complex exercises whose mechanics Is very often difficult to understand by intuition so t h a t some problems may arise in teaching ,and coaching. Moreover, many exercises include an aerial phase composed of different sub-phases; while learning, they are experimented separately by the athlete who rebuilds the whole exercise afterwards: a difficult coaching item concerns. for example. the variations of the movements which allow t o obtain the same sub-phases once they are linked in the full exercise, since the initial conditions of each sub-phase are in fact different. This kind of reasons gave recently impulse t o the development of computer simulation systems, especially oriented to sport biomechanics for teachers and coaches. BACKGROUND Starting from the Denavit(l975) approach to the kinematics of multi-body chains. which is based on the adoption of 4x4 matrices to define the relative position of bodies in 3D space. we introduced a set of six 4x4 special matrices. Our main goal is to face coherently. with the same matrix approach, the whole question of the mathematical analysis and synthesis of human motion: from the position analysis to the direct and inverse dynamics. Three out of those matrices are related t o kinematics (generalized position, velocity and acceleration matrices). while the other ones deal with dynamics (generalized action, momentum and Inertia matrices); all of them feature both linear and rotational components (eg.:linear and angular velocity; forces and couples; momentum and angular momentum). The structure and the properties of those matrices easily allow t o build computer programs for 3D direct and inverse dynamics of human motion. in which the equation structure is quite simple and clear. and efficient for computer handling. APPLICATIONS The system of programs f o r the simulation of sport exercises developed in our Department in connection with the University of Brescia. consists of a set of cooperating modules, each performing a particular task; the basic modules are: SPACE-LIB: a library of routines to perform the operations Involving the described matrices; ANTHROPM: to compute geometrical parameters and to build the Inertia matrix from as many data as they are available; DY-MAN: the main module. for the solution of the direct dynamic problem: from the knowledge of the relative motion of body segments and the external forces applied it calculates the athlete's body trajectory and orientation during an hypothetical exercise; GRAPIIMAN: a graphic 3D post-processor for dy_man output. This kind of software can help to solve some of the teaching problems described in the introduction, showing for instance to the athlete the effect of hypothetical variations of limbs’ movement on the whole body motion. It can also be very useful to plan complex athletic exercises without exposing the athlete to the danger of the preliminary set-up phase

Technical Note: Real-time updating procedure for flood forecasting with conceptual HBV-type models

International audienceFlood forecasting is of increasing importance as it comes to an increasing variability in global and local climates. But rainfall-runoff models are far from being perfect. In order to achieve a better prediction for emerging flood events, the model outputs have to be continuously updated. This contribution introduces a rather simple, yet effective updating procedure for the conceptual distributed rainfall-runoff model PREVAH, whose runoff generation module relies on similar algorithms as the HBV-Model. The current conditions of the system, i.e. the contents of the upper soil reservoirs, are updated by the proposed method. The testing of the updating procedure on data from two mountainous catchments in Switzerland reveals a significant increase in prediction accuracy with regards to peak flow

Efecto del tiempo de superpulso de soldadura sobre la evolución microestructural de un acero de bajo carbono

El tipo de arco Súper Pulso fue desarrollado para proporcionar una solución a los cordones de pasada de raíz de juntas a tope, en el proceso de soldadura semiautomático con protección gaseosa (GMAW). A diferencia de la soldadura por pulsos estándar, el Súper Pulso utiliza una secuencia de diferentes formas de onda de pulso para crear una forma y aspecto de cordón similar al proceso GTAW. Utiliza bajo amperaje en la fase primaria para reducir el calor aportado y más alto amperaje en la segunda fase para mejorar la penetración. La velocidad de soldadura e incluso la penetración se proporcionan durante la fase de transferencia en spray, mientras que la entrada de calor se reduce durante la segunda fase (transferencia en corto, arco corto o pulsado). Se utiliza la transferencia de spray en la fase primaria para mejorar la penetración y arco pulsado en la fase secundaria para enfriar el baño de soldadura dando menos transferencia de calor y menos distorsión al material de base. En la literatura hay poca información respecto a la relación entre las variables del Súper Pulso y las características microestructurales del metal depositado. El objetivo de este trabajo fue evaluar la influencia de los tiempos de cada fase en modo Súper Pulso, sobre las características geométricas del cordón, la dilución y la solidificación en depósitos de soldadura de aceros con bajo contenido de carbono. Para tal fin, se soldaran cordones sobre una chapa IRAM - IAS U500 - 42 - F24 variando el tiempo de fases del Súper Pulso. Sobre cortes transversales se determinó la geometría de los cordones, el grado de dilución, la microestructura y sobre cortes longitudinales las características de las zonas fundidas y afectadas. Resultados preliminares mostraron que la geometría del cordón y la solidificación estuvieron fuertemente influenciadas por los parámetros del pulso.Superpulse system was a motivation to provide a GMAW solution for root pass on steel. Unlike standard pulse welding, pulse/pulse (superpulse) uses a sequence of varying pulse wave shapes to create a bead shape and appearance similar to the GTAW process. It utilizes low amperage in the primary phase for heat reduction and higher amperage in the second phase for enhanced penetration. The welding speed and even penetration are provided during the spray arc phase, whereas heat input is reduced during pulse phase. It utilises spray arc transfer in the primary phase for enhanced penetration and pulse arc in the secondary phase, which serves to cool the weld pool for less heat transfer to the base material and less distortion. Pulsing in the second phase also allows spray type transfer to be achieved in all positions of welding. Nowadays there is scare information about the relationship between variables of procedure and microstructural characteristics of the weld metal. Therefore the aim of this work was to evaluate the influence of pulse time on the dilution and solidification of F24 steel plate. For this purpose, four coupons modifying the time of pulse were welded. On each coupon, chemical composition was determined and microstructure was studied using both optical and electronic microscopy. The dilution and microhardness of beads and phases were measured. Preliminary results show that the geometry of the bead and the solidification were strongly influenced by the pulse parameters

HIGH JUMP DIRECT DYNAMIC SIMULATION

INTRODUcrION High jumps are composed of a complex sequence of movements whose single contribution to the whole body motion cannot be intuitively predicted. While most of the movements are well learned by the elite athletes in order to reach the result, few are not effective or negative from the mechanical point of view and are probably performed for an erroneous feeling of their effects. The direct dynamic simulation of jumping can be useful in order to more fully understand the mechanics of high jump techniques; to explain to the athletes the consequences of some errors; and to test possible evolution of the exercise. When the external forces and the relative movements of the limbs are known, the calculation of the whole body trajectory and orientation is a direct dynamic problem

Technical Note: Updating procedure for flood forecasting with conceptual HBV-type models

International audienceFlood forecasting is of increasing importance as it comes to an increasing variability in global and local climates. But rainfall-runoff models are far from being perfect. In order to achieve a better prediction for emerging flood events, the model outputs have to be continuously updated. This contribution introduces a rather simple, yet effective updating procedure for the conceptual semi-distributed rainfall-runoff model PREVAH, whose runoff generation module relies on similar algorithms as the HBV-Model. The current conditions of the system, i.e. the contents of the upper soil reservoirs, are updated by the proposed method. The testing of the updating procedure on data from two mountainous catchments in Switzerland reveals a significant increase in prediction accuracy with regards to peak flow

Storylines of atmospheric circulation change for European regional climate impact assessment

There is increasing interest to understand the regional impacts of different global warming targets. However, several regional climate impacts depend on the atmospheric circulation, whose response to climate change remains substantially uncertain and not interpretable in a probabilistic sense in multi–model ensemble projections. To account for these uncertainties, a novel approach where regional climate change is analysed as a function of carbon emissions conditional on plausible storylines of atmospheric circulation change is here presented and applied to the CMIP5 models future projections. The different storylines are determined based on the response in three remote drivers of regional circulation: the tropical and polar amplification of global warming, and the stratospheric vortex strength. As an illustration of this approach, it is shown that the severity of the projected wintertime Mediterranean precipitation decline and Central European windiness increase strongly depends on the storyline of circulation change. For a given magnitude of global warming, the highest impact storyline for these aspects of European climate is found for a high tropical amplification and a strengthening of the vortex. The difference in the precipitation and wind responses between the storylines is substantial and equivalent to the contribution from several degrees of global warming. Improving the understanding of the remote driver responses is thus needed to better bound the projected regional impacts in the European sector. The value of these storylines to represent the uncertainty in regional climate projections and to inform the selection of CMIP5 models in regional climate impact studies is discussed

Monthly hydrometeorological ensemble prediction of streamflow droughts and corresponding drought indices

Streamflow droughts, characterized by low runoff as consequence of a drought event, affect numerous aspects of life. Economic sectors that are impacted by low streamflow are, e.g., power production, agriculture, tourism, water quality management and shipping. Those sectors could potentially benefit from forecasts of streamflow drought events, even of short events on the monthly time scales or below. Numerical hydrometeorological models have increasingly been used to forecast low streamflow and have become the focus of recent research. Here, we consider daily ensemble runoff forecasts for the river Thur, which has its source in the Swiss Alps. We focus on the evaluation of low streamflow and of the derived indices as duration, severity and magnitude, characterizing streamflow droughts up to a lead time of one month. <br><br> The ECMWF VarEPS 5-member ensemble reforecast, which covers 18 yr, is used as forcing for the hydrological model PREVAH. A thorough verification reveals that, compared to probabilistic peak-flow forecasts, which show skill up to a lead time of two weeks, forecasts of streamflow droughts are skilful over the entire forecast range of one month. For forecasts at the lower end of the runoff regime, the quality of the initial state seems to be crucial to achieve a good forecast quality in the longer range. It is shown that the states used in this study to initialize forecasts satisfy this requirement. The produced forecasts of streamflow drought indices, derived from the ensemble forecasts, could be beneficially included in a decision-making process. This is valid for probabilistic forecasts of streamflow drought events falling below a daily varying threshold, based on a quantile derived from a runoff climatology. Although the forecasts have a tendency to overpredict streamflow droughts, it is shown that the relative economic value of the ensemble forecasts reaches up to 60%, in case a forecast user is able to take preventive action based on the forecast

Experiment Investigating the Connection between Weak Values and Contextuality

Weak value measurements have recently given rise to a large interest for both the possibility of measurement amplification and the chance of further quantum mechanics foundations investigation. In particular, a question emerged about weak values being proof of the incompatibility between Quantum Mechanics and Non-Contextual Hidden Variables Theories (NCHVT). A test to provide a conclusive answer to this question was given in [M. Pusey, Phys. Rev. Lett. 113, 200401 (2014)], where a theorem was derived showing the NCHVT incompatibility with the observation of anomalous weak values under specific conditions. In this paper we realize this proposal, clearly pointing out the strict connection between weak values and the contextual nature of Quantum Mechanics.Comment: 5 pages, 4 figure

EVALUATION OF TRAINING METHODS BY MEANS OF KINEMATIC MEASUREMENTS

INTRODUCTIONAim of this work is the evaluation of different training techniques developed for increasing the hip joint range of motion.The standard technique has been comparedwith a training program based on PNF(Proprioceptive Neuromuscolar Facilitation).The experimental data were acquired by using an electrogoniometer system for its easy application in sport exercices, for its reduced dimensions and weight and for its high sample rate (up to 1000 Hz).The quality of the results has been critically analysed and compared with experimental tests made by using both electrogoniometer and optoelectronic system. MATERIAL AND METHODS The flexion extension movement of hip joint of101 male volunteer students, aged between19 and 23 years, was evaluated before and after a training with PNF. The subjects, fastened to an experimental table in supine position, were asked top erform the maximum hip flexion. The tests consist also on passive movements. Preliminary 'results seem to confirm the adequacy of the training technique but the high dispersion of the results leads the authors to analyse the possible causes related to the phenomena. With this aim further tests have been acquired both with electrogoniometer and with an automated optoelectronic system. The experimental analysis included both planar motion of two hinged bar and athletes movement during the standard test. For these analysis reflective markers where rigidly fixed on the electrogonio meter bases. From the 3Dmarker coordinates the angle (a*) between the electrogoniometer bases has been evaluated and compared with that one obtained by the electrogoniometer output. RESULTS The results of the training program showed that the range of motion of the subjects increases after the PNF technique both for passive and active movements The angle between the bases is evaluated in[1.11in which RCHA and RCHB are the electrogoniometer output data representing the two active channels, a and 8 the angles represented in Fig. I.Fig.I In the evaluation of athlete movements the analysis of the result differences of the two systems adopted leads to these following considerations. For the analysed movement the effect of the goniometer cable torsion seems to be negligible while an incorrect calibration procedure seems to be the main source of errors. In fact in the evaluation of athlete movement the gauges have been zeroed at the initial movement position and not with the basis perfectly aligned. This error can be easily corrected if the relative position of the bases is known by using the [ I .2]where k~ and k~ are the output of the electrogoniometer previously correctly calibrated and then placed on the subjects. Another source of errors may be due to the skin where the bases and consequently the markers are fixed. This effect can be partially solved by using rigid cluster linked to the moving body segment. CONCLUSION This study leads to consider new aspects of the movement evaluation by using electrogoniometer and suggest some practical rules to correct the electrogoniometer acquired data