Precipitation over sea: Validation against shipboard in-situ measurements

The satellite derived HOAPS (Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data) and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis data sets have been validated against in-situ precipitation measurements from ship rain gauges and optical disdrometers over the open-ocean by applying a statistical analysis for binary forecasts. For this purpose collocated pairs of data were merged within a certain temporal and spatial threshold into single events, according to the satellites' overpass, the observation and the forecast times. HOAPS detects the frequency of precipitation well, while ERA-Interim strongly overestimates it, especially in the tropics and subtropics. Although precipitation rates are difficult to compare because along-track point measurements are collocated with areal estimates and the numbers of available data are limited, we find that HOAPS underestimates precipitation rates, while ERA-Interim's Atlantic-wide average precipitation rate is close to measurements. However, regionally averaged over latitudinal belts, there are deviations between the observed mean precipitation rates and ERA-Interim. The most obvious ERA-Interim feature is an overestimation of precipitation in the area of the intertropical convergence zone and the southern sub-tropics over the Atlantic Ocean. For a limited number of snow measurements by optical disdrometers it can be concluded that both HOAPS and ERA-Interim are suitable to detect the occurrence of solid precipitation.

Statistical Calculation of the Main Reliability Functions of GaAs Concentrator III-V Solar Cells

This paper presents some of the results of a method to determine the main reliability functions of concentrator solar cells. High concentrator GaAs single junction solar cells have been tested in an Accelerated Life Test. The method can be directly applied to multi-junction solar cells. The main conclusions of this test carried out show that these solar cells are robust devices with a very low probability of failure caused by degradation during their operation life (more than 30 years). The evaluation of the probability operation function (i.e. the reliability function R(t)) is obtained for two nominal operation conditions of these cells, namely simulated concentration ratios of 700 and 1050 suns. Preliminary determination of the Mean Time to Failure indicates a value much higher than the intended operation life time of the concentrator cells.

An Intercomparison of Modelling Approaches for Simulating the Atmospheric Dispersion of Ammonia Emitted by Agricultural Sources

RESUMEN La dispersi��n del amoniaco (NH3) emitido por fuentes agr��colas en medias distancias, y su posterior deposici��n en el suelo y la vegetaci��n, pueden llevar a la degradaci��n de ecosistemas vulnerables y a la acidificaci��n de los suelos. La deposici��n de NH3 suele ser mayor junto a la fuente emisora, por lo que los impactos negativos de dichas emisiones son generalmente mayores en esas zonas. Bajo la legislaci��n comunitaria, varios estados miembros emplean modelos de dispersi��n inversa para estimar los impactos de las emisiones en las proximidades de las zonas naturales de especial conservaci��n. Una revisi��n reciente de m��todos para evaluar impactos de NH3 en distancias medias recomendaba la comparaci��n de diferentes modelos para identificar diferencias importantes entre los m��todos empleados por los distintos pa��ses de la UE. En base a esta recomendaci��n, esta tesis doctoral compara y eval��a las predicciones de las concentraciones atmosf��ricas de NH3 de varios modelos bajo condiciones, tanto reales como hipot��ticas, que plantean un potencial impacto sobre ecosistemas (incluidos aquellos bajo condiciones de clima Mediterr��neo). En este sentido, se procedi�� adem��s a la comparaci��n y evaluaci��n de varias t��cnicas de modelizaci��n inversa para inferir emisiones de NH3. Finalmente, se ha desarrollado un modelo matem��tico simple para calcular las concentraciones de NH3 y la velocidad de deposici��n de NH3 en ecosistemas vulnerables cercanos a una fuente emisora. La comparativa de modelos supuso la evaluaci��n de cuatro modelos de dispersi��n (ADMS 4.1; AERMOD v07026; OPS-st v3.0.3 y LADD v2010) en un amplio rango de casos hipot��ticos (dispersi��n de NH3 procedente de distintos tipos de fuentes agr��colas de emisi��n). La menor diferencia entre las concentraciones medias estimadas por los distintos modelos se obtuvo para escenarios simples. La convergencia entre las predicciones de los modelos fue m��nima para el escenario relativo a la dispersi��n de NH3 procedente de un establo ventilado mec��nicamente. En este caso, el modelo ADMS predijo concentraciones significativamente menores que los otros modelos. Una explicaci��n de estas diferencias podr��amos encontrarla en la interacci��n de diferentes ���penachos��� y ���capas l��mite��� durante el proceso de parametrizaci��n. Los cuatro modelos de dispersi��n fueron empleados para dos casos reales de dispersi��n de NH3: una granja de cerdos en Falster (Dinamarca) y otra en Carolina del Norte (EEUU). Las concentraciones medias anuales estimadas por los modelos fueron similares para el caso americano (emisi��n de granjas ventiladas de forma natural y balsa de purines). La comparaci��n de las predicciones de los modelos con concentraciones medias anuales medidas in situ, as�� como la aplicaci��n de los criterios establecidos para la aceptaci��n estad��stica de los modelos, permiti�� concluir que los cuatro modelos se comportaron aceptablemente para este escenario. No ocurri�� lo mismo en el caso dan��s (nave ventilada mec��nicamente), en donde el modelo LADD no dio buenos resultados debido a la ausencia de procesos de ���sobreelevacion de penacho��� (plume-rise). Los modelos de dispersi��n dan a menudo pobres resultados en condiciones de baja velocidad de viento debido a que la teor��a de dispersi��n en la que se basan no es aplicable en estas condiciones. En situaciones de frecuente descenso en la velocidad del viento, la actual gu��a de modelizaci��n propone usar un modelo que sea eficaz bajo dichas condiciones, m��xime cuando se realice una valoraci��n que tenga como objeto establecer una pol��tica de regularizaci��n. Esto puede no ser siempre posible debido a datos meteorol��gicos insuficientes, en cuyo caso la ��nica opci��n ser��a utilizar un modelo m��s com��n, como la versi��n avanzada de los modelos Gausianos ADMS o AERMOD. Con el objetivo de evaluar la idoneidad de estos modelos para condiciones de bajas velocidades de viento, ambos modelos fueron utilizados en un caso con condiciones Mediterr��neas. Lo que supone sucesivos periodos de baja velocidad del viento. El estudio se centr�� en la dispersi��n de NH3 procedente de una granja de cerdos en Segovia (Espa��a central). Para ello la concentraci��n de NH3 media mensual fue medida en 21 localizaciones en torno a la granja. Se realizaron tambi��n medidas de concentraci��n de alta resoluci��n en una ��nica localizaci��n durante una campa��a de una semana. En este caso, se evaluaron dos estrategias para mejorar la respuesta del modelo ante bajas velocidades del viento. La primera se bas�� en ���no zero wind��� (NZW), que sustituy�� periodos de calma con el m��nimo l��mite de velocidad del viento y ���accumulated calm emissions��� (ACE), que forzaban al modelo a calcular las emisiones totales en un periodo de calma y la siguiente hora de no-calma. Debido a las importantes incertidumbres en los datos de entrada del modelo (inputs) (tasa de emisi��n de NH3, velocidad de salida de la fuente, par��metros de la capa l��mite, etc.), se utiliz�� el mismo caso para evaluar la incertidumbre en la predicci��n del modelo y valorar como dicha incertidumbre puede ser considerada en evaluaciones del modelo. Un modelo din��mico de emisi��n, modificado para el caso de clima Mediterr��neo, fue empleado para estimar la variabilidad temporal en las emisiones de NH3. As�� mismo, se realiz�� una comparativa utilizando las emisiones din��micas y la tasa constante de emisi��n. La incertidumbre predicha asociada a la incertidumbre de los inputs fue de 67-98% del valor medio para el modelo ADMS y entre 53-83% del valor medio para AERMOD. La mayor��a de esta incertidumbre se debi�� a la incertidumbre del ratio de emisi��n en la fuente (50%), seguida por la de las condiciones meteorol��gicas (10-20%) y aquella asociada a las velocidades de salida (5-10%). El modelo AERMOD predijo mayores concentraciones que ADMS y existieron m��s simulaciones que alcanzaron los criterios de aceptabilidad cuando se compararon las predicciones con las concentraciones medias anuales medidas. Sin embargo, las predicciones del modelo ADMS se correlacionaron espacialmente mejor con las mediciones. El uso de valores din��micos de emisi��n estimados mejor�� el comportamiento de ADMS, haciendo empeorar el de AERMOD. La aplicaci��n de estrategias destinadas a mejorar el comportamiento de este ��ltimo tuvo efectos contradictorios similares. Con el objeto de comparar distintas t��cnicas de modelizaci��n inversa, varios modelos (ADMS, LADD y WindTrax) fueron empleados para un caso no agr��cola, una colonia de ping��inos en la Ant��rtida. Este caso fue empleado para el estudio debido a que supon��a la oportunidad de obtener el primer factor de emisi��n experimental para una colonia de ping��inos ant��rticos. Adem��s las condiciones eran propicias desde el punto de vista de la casi total ausencia de concentraciones ambiente (background). Tras el trabajo de modelizaci��n existi�� una concordancia suficiente entre las estimaciones obtenidas por los tres modelos. De este modo se pudo definir un factor de emisi��n de para la colonia de 1.23 g NH3 por pareja criadora por d��a (con un rango de incertidumbre de 0.8-2.54 g NH3 por pareja criadora por d��a). Posteriores aplicaciones de t��cnicas de modelizaci��n inversa para casos agr��colas mostraron tambi��n un buen compromiso estad��stico entre las emisiones estimadas por los distintos modelos. Con todo ello, es posible concluir que la modelizaci��n inversa es una t��cnica robusta para estimar tasas de emisi��n de NH3. Modelos de selecci��n (screening) permiten obtener una r��pida y aproximada estimaci��n de los impactos medioambientales, siendo una herramienta ��til para evaluaciones de impactos en tanto que permite eliminar casos que presentan un riesgo potencial de da��o bajo. De esta forma, lo recursos del modelo pueden Resumen (Castellano) destinarse a casos en donde la posibilidad de da��o es mayor. El modelo de C��lculo Simple de los L��mites de Impacto de Amoniaco (SCAIL) se desarroll�� para obtener una estimaci��n de la concentraci��n media de NH3 y de la tasa de deposici��n seca asociadas a una fuente agr��cola. Est�� t��cnica de selecci��n, basada en el modelo LADD, fue evaluada y calibrada con diferentes bases de datos y, finalmente, validada utilizando medidas independientes de concentraciones realizadas cerca de las fuentes. En general SCAIL dio buenos resultados de acuerdo a los criterios estad��sticos establecidos. Este trabajo ha permitido definir situaciones en las que las concentraciones predichas por modelos de dispersi��n son similares, frente a otras en las que las predicciones difieren notablemente entre modelos. Algunos modelos nos est��n dise��ados para simular determinados escenarios en tanto que no incluyen procesos relevantes o est��n m��s all�� de los l��mites de su aplicabilidad. Un ejemplo es el modelo LADD que no es aplicable en fuentes con velocidad de salida significativa debido a que no incluye una parametrizaci��n de sobreelevacion del penacho. La evaluaci��n de un esquema simple combinando la sobreelevacion del penacho y una turbulencia aumentada en la fuente mejor�� el comportamiento del modelo. Sin embargo m��s pruebas son necesarias para avanzar en este sentido. Incluso modelos que son aplicables y que incluyen los procesos relevantes no siempre dan similares predicciones. Siendo las razones de esto a��n desconocidas. Por ejemplo, AERMOD predice mayores concentraciones que ADMS para dispersi��n de NH3 procedente de naves de ganado ventiladas mec��nicamente. Existe evidencia que sugiere que el modelo ADMS infraestima concentraciones en estas situaciones debido a un elevado l��mite de velocidad de viento. Por el contrario, existen evidencias de que AERMOD sobreestima concentraciones debido a sobreestimaciones a bajas Resumen (Castellano) velocidades de viento. Sin embrago, una modificaci��n simple del pre-procesador meteorol��gico parece mejorar notablemente el comportamiento del modelo. Es de gran importancia que estas diferencias entre las predicciones de los modelos sean consideradas en los procesos de evaluaci��n regulada por los organismos competentes. Esto puede ser realizado mediante la aplicaci��n del modelo m��s ��til para cada caso o, mejor a��n, mediante modelos m��ltiples o h��bridos. ABSTRACT Short-range atmospheric dispersion of ammonia (NH3) emitted by agricultural sources and its subsequent deposition to soil and vegetation can lead to the degradation of sensitive ecosystems and acidification of the soil. Atmospheric concentrations and dry deposition rates of NH3 are generally highest near the emission source and so environmental impacts to sensitive ecosystems are often largest at these locations. Under European legislation, several member states use short-range atmospheric dispersion models to estimate the impact of ammonia emissions on nearby designated nature conservation sites. A recent review of assessment methods for short-range impacts of NH3 recommended an intercomparison of the different models to identify whether there are notable differences to the assessment approaches used in different European countries. Based on this recommendation, this thesis compares and evaluates the atmospheric concentration predictions of several models used in these impact assessments for various real and hypothetical scenarios, including Mediterranean meteorological conditions. In addition, various inverse dispersion modelling techniques for the estimation of NH3 emissions rates are also compared and evaluated and a simple screening model to calculate the NH3 concentration and dry deposition rate at a sensitive ecosystem located close to an NH3 source was developed. The model intercomparison evaluated four atmospheric dispersion models (ADMS 4.1; AERMOD v07026; OPS-st v3.0.3 and LADD v2010) for a range of hypothetical case studies representing the atmospheric dispersion from several agricultural NH3 source types. The best agreement between the mean annual concentration predictions of the models was found for simple scenarios with area and volume sources. The agreement between the predictions of the models was worst for the scenario representing the dispersion from a mechanically ventilated livestock house, for which ADMS predicted significantly smaller concentrations than the other models. The reason for these differences appears to be due to the interaction of different plume-rise and boundary layer parameterisations. All four dispersion models were applied to two real case studies of dispersion of NH3 from pig farms in Falster (Denmark) and North Carolina (USA). The mean annual concentration predictions of the models were similar for the USA case study (emissions from naturally ventilated pig houses and a slurry lagoon). The comparison of model predictions with mean annual measured concentrations and the application of established statistical model acceptability criteria concluded that all four models performed acceptably for this case study. This was not the case for the Danish case study (mechanically ventilated pig house) for which the LADD model did not perform acceptably due to the lack of plume-rise processes in the model. Regulatory dispersion models often perform poorly in low wind speed conditions due to the model dispersion theory being inapplicable at low wind speeds. For situations with frequent low wind speed periods, current modelling guidance for regulatory assessments is to use a model that can handle these conditions in an acceptable way. This may not always be possible due to insufficient meteorological data and so the only option may be to carry out the assessment using a more common regulatory model, such as the advanced Gaussian models ADMS or AERMOD. In order to assess the suitability of these models for low wind conditions, they were applied to a Mediterranean case study that included many periods of low wind speed. The case study was the dispersion of NH3 emitted by a pig farm in Segovia, Central Spain, for which mean monthly atmospheric NH3 concentration measurements were made at 21 locations surrounding the farm as well as high-temporal-resolution concentration measurements at one location during a one-week campaign. Two strategies to improve the model performance for low wind speed conditions were tested. These were ���no zero wind��� (NZW), which replaced calm periods with the minimum threshold wind speed of the model and ���accumulated calm emissions��� (ACE), which forced the model to emit the total emissions during a calm period during the first subsequent non-calm hour. Due to large uncertainties in the model input data (NH3 emission rates, source exit velocities, boundary layer parameters), the case study was also used to assess model prediction uncertainty and assess how this uncertainty can be taken into account in model evaluations. A dynamic emission model modified for the Mediterranean climate was used to estimate the temporal variability in NH3 emission rates and a comparison was made between the simulations using the dynamic emissions and a constant emission rate. Prediction uncertainty due to model input uncertainty was 67-98% of the mean value for ADMS and between 53-83% of the mean value for AERMOD. Most of this uncertainty was due to source emission rate uncertainty (~50%), followed by uncertainty in the meteorological conditions (~10-20%) and uncertainty in exit velocities (~5-10%). AERMOD predicted higher concentrations than ADMS and more of the simulations met the model acceptability criteria when compared with the annual mean measured concentrations. However, the ADMS predictions were better correlated spatially with the measurements. The use of dynamic emission estimates improved the performance of ADMS but worsened the performance of AERMOD and the application of strategies to improved model performance had similar contradictory effects. In order to compare different inverse modelling techniques, several models (ADMS, LADD and WindTrax) were applied to a non-agricultural case study of a penguin colony in Antarctica. This case study was used since it gave the opportunity to provide the first experimentally-derived emission factor for an Antarctic penguin colony and also had the advantage of negligible background concentrations. There was sufficient agreement between the emission estimates obtained from the three models to define an emission factor for the penguin colony (1.23 g NH3 per breeding pair per day with an uncertainty range of 0.8-2.54 g NH3 per breeding pair per day). This emission estimate compared favourably to the value obtained using a simple micrometeorological technique (aerodynamic gradient) of 0.98 g ammonia per breeding pair per day (95% confidence interval: 0.2-2.4 g ammonia per breeding pair per day). Further application of the inverse modelling techniques for a range of agricultural case studies also demonstrated good agreement between the emission estimates. It is concluded, therefore, that inverse dispersion modelling is a robust technique for estimating NH3 emission rates. Screening models that can provide a quick and approximate estimate of environmental impacts are a useful tool for impact assessments because they can be used to filter out cases that potentially have a minimal environmental impact allowing resources to be focussed on more potentially damaging cases. The Simple Calculation of Ammonia Impact Limits (SCAIL) model was developed as a screening model to provide an estimate of the mean NH3 concentration and dry deposition rate downwind of an agricultural source. This screening tool, based on the LADD model, was evaluated and calibrated with several experimental datasets and then validated using independent concentration measurements made near sources. Overall SCAIL performed acceptably according to established statistical criteria. This work has identified situations where the concentration predictions of dispersion models are similar and other situations where the predictions are significantly different. Some models are simply not designed to simulate certain scenarios since they do not include the relevant processes or are beyond the limits of their applicability. An example is the LADD model that is not applicable to sources with significant exit velocity since the model does not include a plume-rise parameterisation. The testing of a simple scheme combining a momentum-driven plume rise and increased turbulence at the source improved model performance, but more testing is required. Even models that are applicable and include the relevant process do not always give similar predictions and the reasons for this need to be investigated. AERMOD for example predicts higher concentrations than ADMS for dispersion from mechanically ventilated livestock housing. There is evidence to suggest that ADMS underestimates concentrations in these situations due to a high wind speed threshold. Conversely, there is also evidence that AERMOD overestimates concentrations in these situations due to overestimation at low wind speeds. However, a simple modification to the meteorological pre-processor appears to improve the performance of the model. It is important that these differences between the predictions of these models are taken into account in regulatory assessments. This can be done by applying the most suitable model for the assessment in question or, better still, using multiple or hybrid models.

Regularization for sparsity in statistical analysis and machine learning

Pragmatism is the leading motivation of regularization. We can understand regularization as a modification of the maximum-likelihood estimator so that a reasonable answer could be given in an unstable or ill-posed situation. To mention some typical examples, this happens when fitting parametric or non-parametric models with more parameters than data or when estimating large covariance matrices. Regularization is usually used, in addition, to improve the bias-variance tradeoff of an estimation. Then, the definition of regularization is quite general, and, although the introduction of a penalty is probably the most popular type, it is just one out of multiple forms of regularization. In this dissertation, we focus on the applications of regularization for obtaining sparse or parsimonious representations, where only a subset of the inputs is used. A particular form of regularization, L1-regularization, plays a key role for reaching sparsity. Most of the contributions presented here revolve around L1-regularization, although other forms of regularization are explored (also pursuing sparsity in some sense). In addition to present a compact review of L1-regularization and its applications in statistical and machine learning, we devise methodology for regression, supervised classification and structure induction of graphical models. Within the regression paradigm, we focus on kernel smoothing learning, proposing techniques for kernel design that are suitable for high dimensional settings and sparse regression functions. We also present an application of regularized regression techniques for modeling the response of biological neurons. Supervised classification advances deal, on the one hand, with the application of regularization for obtaining a na����ve Bayes classifier and, on the other hand, with a novel algorithm for brain-computer interface design that uses group regularization in an efficient manner. Finally, we present a heuristic for inducing structures of Gaussian Bayesian networks using L1-regularization as a filter. El pragmatismo es la principal motivaci��n de la regularizaci��n. Podemos entender la regularizaci��n como una modificaci��n del estimador de m��xima verosimilitud, de tal manera que se pueda dar una respuesta cuando la configuraci��n del problema es inestable. A modo de ejemplo, podemos mencionar el ajuste de modelos param��tricos o no param��tricos cuando hay m��s par��metros que casos en el conjunto de datos, o la estimaci��n de grandes matrices de covarianzas. Se suele recurrir a la regularizaci��n, adem��s, para mejorar el compromiso sesgo-varianza en una estimaci��n. Por tanto, la definici��n de regularizaci��n es muy general y, aunque la introducci��n de una funci��n de penalizaci��n es probablemente el m��todo m��s popular, ��ste es s��lo uno de entre varias posibilidades. En esta tesis se ha trabajado en aplicaciones de regularizaci��n para obtener representaciones dispersas, donde s��lo se usa un subconjunto de las entradas. En particular, la regularizaci��n L1 juega un papel clave en la b��squeda de dicha dispersi��n. La mayor parte de las contribuciones presentadas en la tesis giran alrededor de la regularizaci��n L1, aunque tambi��n se exploran otras formas de regularizaci��n (que igualmente persiguen un modelo disperso). Adem��s de presentar una revisi��n de la regularizaci��n L1 y sus aplicaciones en estad��stica y aprendizaje de m��quina, se ha desarrollado metodolog��a para regresi��n, clasificaci��n supervisada y aprendizaje de estructura en modelos gr��ficos. Dentro de la regresi��n, se ha trabajado principalmente en m��todos de regresi��n local, proponiendo t��cnicas de dise��o del kernel que sean adecuadas a configuraciones de alta dimensionalidad y funciones de regresi��n dispersas. Tambi��n se presenta una aplicaci��n de las t��cnicas de regresi��n regularizada para modelar la respuesta de neuronas reales. Los avances en clasificaci��n supervisada tratan, por una parte, con el uso de regularizaci��n para obtener un clasificador naive Bayes y, por otra parte, con el desarrollo de un algoritmo que usa regularizaci��n por grupos de una manera eficiente y que se ha aplicado al dise��o de interfaces cerebrom��quina. Finalmente, se presenta una heur��stica para inducir la estructura de redes Bayesianas Gaussianas usando regularizaci��n L1 a modo de filtro.

Statistical models for short-term wind power ramp forecasting

La predicci��n de energ��a e��lica ha desempe��ado en la ��ltima d��cada un papel fundamental en el aprovechamiento de este recurso renovable, ya que permite reducir el impacto que tiene la naturaleza fluctuante del viento en la actividad de diversos agentes implicados en su integraci��n, tales como el operador del sistema o los agentes del mercado el��ctrico. Los altos niveles de penetraci��n e��lica alcanzados recientemente por algunos pa��ses han puesto de manifiesto la necesidad de mejorar las predicciones durante eventos en los que se experimenta una variaci��n importante de la potencia generada por un parque o un conjunto de ellos en un tiempo relativamente corto (del orden de unas pocas horas). Estos eventos, conocidos como rampas, no tienen una ��nica causa, ya que pueden estar motivados por procesos meteorol��gicos que se dan en muy diferentes escalas espacio-temporales, desde el paso de grandes frentes en la macroescala a procesos convectivos locales como tormentas. Adem��s, el propio proceso de conversi��n del viento en energ��a el��ctrica juega un papel relevante en la ocurrencia de rampas debido, entre otros factores, a la relaci��n no lineal que impone la curva de potencia del aerogenerador, la desalineaci��n de la m��quina con respecto al viento y la interacci��n aerodin��mica entre aerogeneradores. En este trabajo se aborda la aplicaci��n de modelos estad��sticos a la predicci��n de rampas a muy corto plazo. Adem��s, se investiga la relaci��n de este tipo de eventos con procesos atmosf��ricos en la macroescala. Los modelos se emplean para generar predicciones de punto a partir del modelado estoc��stico de una serie temporal de potencia generada por un parque e��lico. Los horizontes de predicci��n considerados van de una a seis horas. Como primer paso, se ha elaborado una metodolog��a para caracterizar rampas en series temporales. La denominada funci��n-rampa est�� basada en la transformada wavelet y proporciona un ��ndice en cada paso temporal. Este ��ndice caracteriza la intensidad de rampa en base a los gradientes de potencia experimentados en un rango determinado de escalas temporales. Se han implementado tres tipos de modelos predictivos de cara a evaluar el papel que juega la complejidad de un modelo en su desempe��o: modelos lineales autorregresivos (AR), modelos de coeficientes variables (VCMs) y modelos basado en redes neuronales (ANNs). Los modelos se han entrenado en base a la minimizaci��n del error cuadr��tico medio y la configuraci��n de cada uno de ellos se ha determinado mediante validaci��n cruzada. De cara a analizar la contribuci��n del estado macroescalar de la atm��sfera en la predicci��n de rampas, se ha propuesto una metodolog��a que permite extraer, a partir de las salidas de modelos meteorol��gicos, informaci��n relevante para explicar la ocurrencia de estos eventos. La metodolog��a se basa en el an��lisis de componentes principales (PCA) para la s��ntesis de la datos de la atm��sfera y en el uso de la informaci��n mutua (MI) para estimar la dependencia no lineal entre dos se��ales. Esta metodolog��a se ha aplicado a datos de rean��lisis generados con un modelo de circulaci��n general (GCM) de cara a generar variables ex��genas que posteriormente se han introducido en los modelos predictivos. Los casos de estudio considerados corresponden a dos parques e��licos ubicados en Espa��a. Los resultados muestran que el modelado de la serie de potencias permiti�� una mejora notable con respecto al modelo predictivo de referencia (la persistencia) y que al a��adir informaci��n de la macroescala se obtuvieron mejoras adicionales del mismo orden. Estas mejoras resultaron mayores para el caso de rampas de bajada. Los resultados tambi��n indican distintos grados de conexi��n entre la macroescala y la ocurrencia de rampas en los dos parques considerados. Abstract One of the main drawbacks of wind energy is that it exhibits intermittent generation greatly depending on environmental conditions. Wind power forecasting has proven to be an effective tool for facilitating wind power integration from both the technical and the economical perspective. Indeed, system operators and energy traders benefit from the use of forecasting techniques, because the reduction of the inherent uncertainty of wind power allows them the adoption of optimal decisions. Wind power integration imposes new challenges as higher wind penetration levels are attained. Wind power ramp forecasting is an example of such a recent topic of interest. The term ramp makes reference to a large and rapid variation (1-4 hours) observed in the wind power output of a wind farm or portfolio. Ramp events can be motivated by a broad number of meteorological processes that occur at different time/spatial scales, from the passage of large-scale frontal systems to local processes such as thunderstorms and thermally-driven flows. Ramp events may also be conditioned by features related to the wind-to-power conversion process, such as yaw misalignment, the wind turbine shut-down and the aerodynamic interaction between wind turbines of a wind farm (wake effect). This work is devoted to wind power ramp forecasting, with special focus on the connection between the global scale and ramp events observed at the wind farm level. The framework of this study is the point-forecasting approach. Time series based models were implemented for very short-term prediction, this being characterised by prediction horizons up to six hours ahead. As a first step, a methodology to characterise ramps within a wind power time series was proposed. The so-called ramp function is based on the wavelet transform and it provides a continuous index related to the ramp intensity at each time step. The underlying idea is that ramps are characterised by high power output gradients evaluated under different time scales. A number of state-of-the-art time series based models were considered, namely linear autoregressive (AR) models, varying-coefficient models (VCMs) and artificial neural networks (ANNs). This allowed us to gain insights into how the complexity of the model contributes to the accuracy of the wind power time series modelling. The models were trained in base of a mean squared error criterion and the final set-up of each model was determined through cross-validation techniques. In order to investigate the contribution of the global scale into wind power ramp forecasting, a methodological proposal to identify features in atmospheric raw data that are relevant for explaining wind power ramp events was presented. The proposed methodology is based on two techniques: principal component analysis (PCA) for atmospheric data compression and mutual information (MI) for assessing non-linear dependence between variables. The methodology was applied to reanalysis data generated with a general circulation model (GCM). This allowed for the elaboration of explanatory variables meaningful for ramp forecasting that were utilized as exogenous variables by the forecasting models. The study covered two wind farms located in Spain. All the models outperformed the reference model (the persistence) during both ramp and non-ramp situations. Adding atmospheric information had a noticeable impact on the forecasting performance, specially during ramp-down events. Results also suggested different levels of connection between the ramp occurrence at the wind farm level and the global scale.

A quality assessment system for fresh fruits in hypermarkets and fruit trading centres.

When the fresh fruit reaches the final markets from the suppliers, its quality is not always as good as it should, either because it has been mishandled during transportation or because it lacks an adequate quality control at the producer level, before being shipped. This is why it is necessary for the final markets to establish their own quality assessment system if they want to ensure to their customers the quality they want to sell. In this work, a system to control fruit quality at the last level of the distribution channel has been designed. The system combines rapid control techniques with laboratory equipment and statistical sampling protocols, to obtain a dynamic, objective process, which can substitute advantageously the quality control inspections carried out visually by human experts at the reception platform of most hypermarkets. Portable measuring equipment have been chosen (firmness tester, temperature and humidity sensors...) as well as easy-to-use laboratory equipment (texturometer, colorimeter, refractometer..,) combining them to control the most important fruit quality parameters (firmness, colour, sugars, acids). A complete computer network has been designed to control all the processes and store the collected data in real time, and to perform the computations. The sampling methods have been also defined to guarantee the confidence of the results. Some of the advantages of a quality assessment system as the proposed one are: the minimisation of human subjectivity, the ability to use modern measuring techniques, and the possibility of using it also as a supplier's quality control system. It can be also a way to clarify the quality limits of fruits among members of the commercial channel, as well as the first step in the standardisation of quality control procedures.

Hardware-Based Particle Filter with Evolutionary Resampling Stage

Autonomous systems require, in most of the cases, reasoning and decision-making capabilities. Moreover, the decision process has to occur in real time. Real-time computing means that every situation or event has to have an answer before a temporal deadline. In complex applications, these deadlines are usually in the order of milliseconds or even microseconds if the application is very demanding. In order to comply with these timing requirements, computing tasks have to be performed as fast as possible. The problem arises when computations are no longer simple, but very time-consuming operations. A good example can be found in autonomous navigation systems with visual-tracking submodules where Kalman filtering is the most extended solution. However, in recent years, some interesting new approaches have been developed. Particle filtering, given its more general problem-solving features, has reached an important position in the field. The aim of this thesis is to design, implement and validate a hardware platform that constitutes itself an embedded intelligent system. The proposed system would combine particle filtering and evolutionary computation algorithms to generate intelligent behavior. Traditional approaches to particle filtering or evolutionary computation have been developed in software platforms, including parallel capabilities to some extent. In this work, an additional goal is fully exploiting hardware implementation advantages. By using the computational resources available in a FPGA device, better performance results in terms of computation time are expected. These hardware resources will be in charge of extensive repetitive computations. With this hardware-based implementation, real-time features are also expected.

Statistical distributions obtained from the compression of monodisperse, soft and frictionless particles

The cyclic compression of several granular systems has been simulated with a molecular dynamics code. All the samples consisted of bidimensional, soft, frictionless and equal-sized particles that were initially arranged according to a squared lattice and were compressed by randomly generated irregular walls. The compression protocols can be described by some control variables (volume or external force acting on the walls) and by some dimensionless factors, that relate stiffness, density, diameter, damping ratio and water surface tension to the external forces, displacements and periods. Each protocol, that is associated to a dynamic process, results in an arrangement with its own macroscopic features: volume (or packing ratio), coordination number, and stress; and the differences between packings can be highly significant. The statistical distribution of the force-moment state of the particles (i.e. the equivalent average stress multiplied by the volume) is analyzed. In spite of the lack of a theoretical framework based on statistical mechanics specific for these protocols, it is shown how the obtained distributions of mean and relative deviatoric force-moment are. Then it is discussed on the nature of these distributions and on their relation to specific protocols.

Adaptive spatio-temporal filter for low-cost camera depth maps

In this paper we present an adaptive spatio-temporal filter that aims to improve low-cost depth camera accuracy and stability over time. The proposed system is composed by three blocks that are used to build a reliable depth map of static scenes. An adaptive joint-bilateral filter is used to obtain consistent depth maps by jointly considering depth and video information and by adapting its parameters to different levels of estimated noise. Kalman filters are used to reduce the temporal random fluctuations of the measurements. Finally an interpolation algorithm is used to obtain consistent depth maps in the regions where the depth information is not available. Results show that this approach allows to considerably improve the depth maps quality by considering spatio-temporal information and by adapting its parameters to different levels of noise.

Time-resolved evolution of coherent structures in turbulent channels

El objetivo de esta tesis es estudiar la din��mica de la capa logar��tmica de flujos turbulentos de pared. En concreto, proponemos un nuevo modelo estructural utilizando diferentes tipos de estructuras coherentes: sweeps, eyecciones, grupos de vorticidad y streaks. La herramienta utilizada es la simulaci��n num��rica directa de canales turbulentos. Desde los primeros trabajos de Theodorsen (1952), las estructuras coherentes han jugado un papel fundamental para entender la organizaci��n y din��mica de los flujos turbulentos. A d��a de hoy, datos procedentes de simulaciones num��ricas directas obtenidas en instantes no contiguos permiten estudiar las propiedades fundamentales de las estructuras coherentes tridimensionales desde un punto de vista estad��stico. Sin embargo, la din��mica no puede ser entendida en detalle utilizando s��lo instantes aislados en el tiempo, sino que es necesario seguir de forma continua las estructuras. Aunque existen algunos estudios sobre la evoluci��n temporal de las estructuras m��s peque��as a n��meros de Reynolds moderados, por ejemplo Robinson (1991), todav��a no se ha realizado un estudio completo a altos n��meros de Reynolds y para todas las escalas presentes de la capa logar��tmica. El objetivo de esta tesis es llevar a cabo dicho an��lisis. Los problemas m��s interesantes los encontramos en la regi��n logar��tmica, donde residen las cascadas de vorticidad, energ��a y momento. Existen varios modelos que intentan explicar la organizaci��n de los flujos turbulentos en dicha regi��n. Uno de los m��s extendidos fue propuesto por Adrian et al. (2000) a trav��s de observaciones experimentales y considerando como elemento fundamental paquetes de v��rtices con forma de horquilla que act��an de forma cooperativa para generar rampas de bajo momento. Un modelo alternativo fu�� ideado por del ��lamo & Jim��nez (2006) utilizando datos num��ricos. Basado tambi��n en grupos de vorticidad, planteaba un escenario mucho m��s desorganizado y con estructuras sin forma de horquilla. Aunque los dos modelos son cinem��ticamente similares, no lo son desde el punto de vista din��mico, en concreto en lo que se refiere a la importancia que juega la pared en la creaci��n y vida de las estructuras. Otro punto importante a��n sin resolver se refiere al modelo de cascada turbulenta propuesto por Kolmogorov (1941b), y su relaci��n con estructuras coherentes medibles en el flujo. Para dar respuesta a las preguntas anteriores, hemos desarrollado un nuevo m��todo que permite seguir estructuras coherentes en el tiempo y lo hemos aplicado a simulaciones num��ricas de canales turbulentos con n��meros de Reynolds lo suficientemente altos como para tener un rango de escalas no trivial y con dominios computacionales lo suficientemente grandes como para representar de forma correcta la din��mica de la capa logar��tmica. Nuestros esfuerzos se han desarrollado en cuatro pasos. En primer lugar, hemos realizado una campa��a de simulaciones num��ricas directas a diferentes n��meros de Reynolds y tama��os de cajas para evaluar el efecto del dominio computacional en las estad��sticas de primer orden y el espectro. A partir de los resultados obtenidos, hemos concluido que simulaciones con cajas de longitud 2vr y ancho vr veces la semi-altura del canal son lo suficientemente grandes para reproducir correctamente las interacciones entre estructuras coherentes de la capa logar��tmica y el resto de escalas. Estas simulaciones son utilizadas como punto de partida en los siguientes an��lisis. En segundo lugar, las estructuras coherentes correspondientes a regiones con esfuerzos de Reynolds tangenciales intensos (Qs) en un canal turbulento han sido estudiadas extendiendo a tres dimensiones el an��lisis de cuadrantes, con especial ��nfasis en la capa logar��tmica y la regi��n exterior. Las estructuras coherentes han sido identificadas como regiones contiguas del espacio donde los esfuerzos de Reynolds tangenciales son m��s intensos que un cierto nivel. Los resultados muestran que los Qs separados de la pared est��n orientados de forma is��tropa y su contribuci��n neta al esfuerzo de Reynolds medio es nula. La mayor contribuci��n la realiza una familia de estructuras de mayor tama��o y autosemejantes cuya parte inferior est�� muy cerca de la pared (ligada a la pared), con una geometr��a compleja y dimensi��n fractal �� 2. Estas estructuras tienen una forma similar a una ���esponja de placas���, en comparaci��n con los grupos de vorticidad que tienen forma de ���esponja de cuerdas���. Aunque el n��mero de objetos decae al alejarnos de la pared, la fracci��n de esfuerzos de Reynolds que contienen es independiente de su altura, y gran parte reside en unas pocas estructuras que se extienden m��s all�� del centro del canal, como en las grandes estructuras propuestas por otros autores. Las estructuras dominantes en la capa logar��tmica son parejas de sweeps y eyecciones uno al lado del otro y con grupos de vorticidad asociados que comparten las dimensiones y esfuerzos con los remolinos ligados a la pared propuestos por Townsend. En tercer lugar, hemos estudiado la evoluci��n temporal de Qs y grupos de vorticidad usando las simulaciones num��ricas directas presentadas anteriormente hasta n��meros de Reynolds ReT = 4200 (Reynolds de fricci��n). Las estructuras fueron identificadas siguiendo el proceso descrito en el p��rrafo anterior y despu��s seguidas en el tiempo. A trav��s de la interseci��n geom��trica de estructuras pertenecientes a instantes de tiempo contiguos, hemos creado gratos de conexiones temporales entre todos los objetos y, a partir de ah��, definido ramas primarias y secundarias, de tal forma que cada rama representa la evoluci��n temporal de una estructura coherente. Una vez que las evoluciones est��n adecuadamente organizadas, proporcionan toda la informaci��n necesaria para caracterizar la historia de las estructuras desde su nacimiento hasta su muerte. Los resultados muestran que las estructuras nacen a todas las distancias de la pared, pero con mayor probabilidad cerca de ella, donde la cortadura es m��s intensa. La mayor��a mantienen tama��os peque��os y no viven mucho tiempo, sin embargo, existe una familia de estructuras que crecen lo suficiente como para ligarse a la pared y extenderse a lo largo de la capa logar��tmica convirti��ndose en las estructuras observas anteriormente y descritas por Townsend. Estas estructuras son geom��tricamente autosemejantes con tiempos de vida proporcionales a su tama��o. La mayor��a alcanzan tama��os por encima de la escala de Corrsin, y por ello, su din��mica est�� controlada por la cortadura media. Los resultados tambi��n muestran que las eyecciones se alejan de la pared con velocidad media uT (velocidad de fricci��n) y su base se liga a la pared muy r��pidamente al inicio de sus vidas. Por el contrario, los sweeps se mueven hacia la pared con velocidad -uT y se ligan a ella m��s tarde. En ambos casos, los objetos permanecen ligados a la pared durante 2/3 de sus vidas. En la direcci��n de la corriente, las estructuras se desplazan a velocidades cercanas a la convecci��n media del flujo y son deformadas por la cortadura. Finalmente, hemos interpretado la cascada turbulenta, no s��lo como una forma conceptual de organizar el flujo, sino como un proceso f��sico en el cual las estructuras coherentes se unen y se rompen. El volumen de una estructura cambia de forma suave, cuando no se une ni rompe, o lo hace de forma repentina en caso contrario. Los procesos de uni��n y rotura pueden entenderse como una cascada directa (roturas) o inversa (uniones), siguiendo el concepto de cascada de remolinos ideado por Richardson (1920) y Obukhov (1941). El an��lisis de los datos muestra que las estructuras con tama��os menores a 30�� (unidades de Kolmogorov) nunca se unen ni rompen, es decir, no experimentan el proceso de cascada. Por el contrario, aquellas mayores a 100�� siempre se rompen o unen al menos una vez en su vida. En estos casos, el volumen total ganado y perdido es una fracci��n importante del volumen medio de la estructura implicada, con una tendencia ligeramente mayor a romperse (cascada directa) que a unirse (cascade inversa). La mayor parte de interacciones entre ramas se debe a roturas o uniones de fragmentos muy peque��os en la escala de Kolmogorov con estructuras m��s grandes, aunque el efecto de fragmentos de mayor tama��o no es despreciable. Tambi��n hemos encontrado que las roturas tienen a ocurrir al final de la vida de la estructura y las uniones al principio. Aunque los resultados para la cascada directa e inversa no son id��nticos, son muy sim��tricos, lo que sugiere un alto grado de reversibilidad en el proceso de cascada. ABSTRACT The purpose of the present thesis is to study the dynamics of the logarithmic layer of wall-bounded turbulent flows. Specifically, to propose a new structural model based on four different coherent structures: sweeps, ejections, clusters of vortices and velocity streaks. The tool used is the direct numerical simulation of time-resolved turbulent channels. Since the first work by Theodorsen (1952), coherent structures have played an important role in the understanding of turbulence organization and its dynamics. Nowadays, data from individual snapshots of direct numerical simulations allow to study the threedimensional statistical properties of those objects, but their dynamics can only be fully understood by tracking them in time. Although the temporal evolution has already been studied for small structures at moderate Reynolds numbers, e.g., Robinson (1991), a temporal analysis of three-dimensional structures spanning from the smallest to the largest scales across the logarithmic layer has yet to be performed and is the goal of the present thesis. The most interesting problems lie in the logarithmic region, which is the seat of cascades of vorticity, energy, and momentum. Different models involving coherent structures have been proposed to represent the organization of wall-bounded turbulent flows in the logarithmic layer. One of the most extended ones was conceived by Adrian et al. (2000) and built on packets of hairpins that grow from the wall and work cooperatively to gen- �� erate low-momentum ramps. A different view was presented by del Alamo & Jim��enez (2006), who extracted coherent vortical structures from DNSs and proposed a less organized scenario. Although the two models are kinematically fairly similar, they have important dynamical differences, mostly regarding the relevance of the wall. Another open question is whether such a model can be used to explain the cascade process proposed by Kolmogorov (1941b) in terms of coherent structures. The challenge would be to identify coherent structures undergoing a turbulent cascade that can be quantified. To gain a better insight into the previous questions, we have developed a novel method to track coherent structures in time, and used it to characterize the temporal evolutions of eddies in turbulent channels with Reynolds numbers high enough to include a non-trivial range of length scales, and computational domains sufficiently long and wide to reproduce correctly the dynamics of the logarithmic layer. Our efforts have followed four steps. First, we have conducted a campaign of direct numerical simulations of turbulent channels at different Reynolds numbers and box sizes, and assessed the effect of the computational domain in the one-point statistics and spectra. From the results, we have concluded that computational domains with streamwise and spanwise sizes 2vr and vr times the half-height of the channel, respectively, are large enough to accurately capture the dynamical interactions between structures in the logarithmic layer and the rest of the scales. These simulations are used in the subsequent chapters. Second, the three-dimensional structures of intense tangential Reynolds stress in plane turbulent channels (Qs) have been studied by extending the classical quadrant analysis to three dimensions, with emphasis on the logarithmic and outer layers. The eddies are identified as connected regions of intense tangential Reynolds stress. Qs are then classified according to their streamwise and wall-normal fluctuating velocities as inward interactions, outward interactions, sweeps and ejections. It is found that wall-detached Qs are isotropically oriented background stress fluctuations, common to most turbulent flows, and do not contribute to the mean stress. Most of the stress is carried by a selfsimilar family of larger wall-attached Qs, increasingly complex away from the wall, with fractal dimensions �� 2. They have shapes similar to ���sponges of flakes���, while vortex clusters resemble ���sponges of strings���. Although their number decays away from the wall, the fraction of the stress that they carry is independent of their heights, and a substantial part resides in a few objects extending beyond the centerline, reminiscent of the very large scale motions of several authors. The predominant logarithmic-layer structures are sideby- side pairs of sweeps and ejections, with an associated vortex cluster, and dimensions and stresses similar to Townsend���s conjectured wall-attached eddies. Third, the temporal evolution of Qs and vortex clusters are studied using time-resolved DNS data up to ReT = 4200 (friction Reynolds number). The eddies are identified following the procedure presented above, and then tracked in time. From the geometric intersection of structures in consecutive fields, we have built temporal connection graphs of all the objects, and defined main and secondary branches in a way that each branch represents the temporal evolution of one coherent structure. Once these evolutions are properly organized, they provide the necessary information to characterize eddies from birth to death. The results show that the eddies are born at all distances from the wall, although with higher probability near it, where the shear is strongest. Most of them stay small and do not last for long times. However, there is a family of eddies that become large enough to attach to the wall while they reach into the logarithmic layer, and become the wall-attached structures previously observed in instantaneous flow fields. They are geometrically self-similar, with sizes and lifetimes proportional to their distance from the wall. Most of them achieve lengths well above the Corrsin��� scale, and hence, their dynamics are controlled by the mean shear. Eddies associated with ejections move away from the wall with an average velocity uT (friction velocity), and their base attaches very fast at the beginning of their lives. Conversely, sweeps move towards the wall at -uT, and attach later. In both cases, they remain attached for 2/3 of their lives. In the streamwise direction, eddies are advected and deformed by the local mean velocity. Finally, we interpret the turbulent cascade not only as a way to conceptualize the flow, but as an actual physical process in which coherent structures merge and split. The volume of an eddy can change either smoothly, when they are not merging or splitting, or through sudden changes. The processes of merging and splitting can be thought of as a direct (when splitting) or an inverse (when merging) cascade, following the ideas envisioned by Richardson (1920) and Obukhov (1941). It is observed that there is a minimum length of 30�� (Kolmogorov units) above which mergers and splits begin to be important. Moreover, all eddies above 100�� split and merge at least once in their lives. In those cases, the total volume gained and lost is a substantial fraction of the average volume of the structure involved, with slightly more splits (direct cascade) than mergers. Most branch interactions are found to be the shedding or absorption of Kolmogorov-scale fragments by larger structures, but more balanced splits or mergers spanning a wide range of scales are also found to be important. The results show that splits are more probable at the end of the life of the eddy, while mergers take place at the beginning of the life. Although the results for the direct and the inverse cascades are not identical, they are found to be very symmetric, which suggests a high degree of reversibility of the cascade process.

Evaluaci��n del tiempo de reacci��n en velocistas con y sin discapacidad auditiva: aplicaciones para la inclusi��n

Este trabajo de investigaci��n trata de aportar luz al estudio del tiempo de reacci��n (TR) en velocistas con y sin discapacidad auditiva desde las Ciencias del Deporte. El planteamiento del presente estudio surgi�� al cuestionarnos la existencia de las diferencias en cuanto al TR visual y auditivo aplicado a velocistas con y sin discapacidad auditiva, pensando en el desarrollo futuro de competiciones inclusivas entre ambos colectivos. Por ello, este estudio trata de resolver las dificultades que los velocistas con discapacidad se encuentran habitualmente en las competiciones. A priori, los atletas con discapacidad auditiva compiten en inferioridad de condiciones como consecuencia de una salida que no parece la m��s adecuada para ellos (desde los tacos, han de mirar hacia la pistola del juez o el movimiento de un rival). El documento se divide en tres partes. En la primera parte se realiza la pertinente revisi��n del marco te��rico y justificaci��n del estudio. La segunda parte se centra en los objetivos de la investigaci��n, el material y el m��todo, donde se muestran los resultados, discusi��n y conclusiones del estudio realizado, as�� como las limitaciones del presente trabajo y sus futuras l��neas de investigaci��n. La tercera parte corresponde a la bibliograf��a y la cuarta parte a los anexos. En la primera parte, presentamos el marco te��rico compuesto por cinco cap��tulos organizan la fundamentaci��n que hemos realizado como revisi��n sobre los aspectos m��s destacados del TR, determinado por las caracter��sticas de la tarea y otros factores que influyen en el TR como objeto de nuestro estudio. Despu��s exponemos los principales aspectos estructurales y funcionales del sistema nervioso (SN) relacionados con el TR visual y auditivo. Tras ello se expone la realidad del deporte para personas con discapacidad auditiva, indagando en sus peculiaridades y criterios de elegibilidad que tiene ese colectivo dentro del ��mbito deportivo. A continuaci��n abordamos el estudio de la salida de velocidad en el atletismo, como aspecto clave que va a guiar nuestra investigaci��n, especialmente los par��metros determinantes en la colocaci��n de los tacos de salida para atletas con y sin discapacidad auditiva, la posici��n de salida y la propia colocaci��n de los est��mulos en dicha situaci��n. Es la segunda parte se desarrolla el trabajo de investigaci��n que tiene como objetivos estudiar los valores de TR visual simple manual, TR en salida de tacos y los tiempos de desplazamiento a los 10m y 20m de velocistas con y sin discapacidad auditiva, as�� como analizar las posibles diferencias en TR seg��n posici��n y tipo de est��mulo luminoso, respecto a ambos grupos de atletas. Como tercer objetivo de estudio se eval��a cualitativamente, por parte de los propios atletas, el dispositivo luminoso utilizado. La toma de datos de este estudio se llev�� a cabo entre los meses de febrero y mayo del 2014, en el m��dulo de atletismo del Centro de Alto Rendimiento Joaqu��n Blume (Madrid), con dos grupos de estudio, uno de 9 velocistas con discapacidad auditiva (VDA), conformando ��stos el 60% de toda la poblaci��n en Espa��a, seg��n el n��mero de las licencias de la FEDS en la modalidad de atletismo (velocistas, pruebas de 100 y 200 m.l.), en el momento del estudio, y otro de 13 velocistas sin discapacidad (VsDA) que se presentaron de manera voluntaria con unos mismos criterios de inclusi��n para ambos grupos. Para la medici��n y el registro de los datos se utilizaron materiales como hoja de registro, Medidor de Tiempo de Reacci��n (MTR), tacos de salida, ReacTime��, dispositivo luminoso conectado a los tacos de salida, c��lulas fotoel��ctricas, ordenador y software del ReacTime, y c��mara de video. La metodolog��a utilizada en este estudio fue de tipo correlacional, analizando los resultados del TR simple manual seg��n v��a sensitiva (visual y auditiva) entre los dos grupos de VDA y VsDA. Tambi��n se estudiaron los TR desde la salida de tacos en funci��n de la colocaci��n del dispositivo luminoso (en el suelo y a 5 metros, v��a visual) y pistola de salida atl��tica (v��a auditiva) as�� como el tiempo de desplazamiento a los 10m (t10m) y 20m (t20m) de ambos grupos de velocistas. Finalmente, se desarroll�� y llev�� a cabo un cuestionario de evaluaci��n por parte de los atletas VDA con el objetivo de conocer el grado de satisfacci��n despu��s de haber realizado la serie de experimentos con el dispositivo luminoso y adaptado para sistemas de salida en la velocidad atl��tica. Con el objetivo de comprobar la viabilidad de la metodolog��a descrita y probar en el contexto de an��lisis real el protocolo experimental, se realiz�� un estudio piloto con el fin de conocer las posibles diferencias del TR visual desde los tacos de salida en velocistas con discapacidad auditiva, usando para dicha salida un est��mulo visual mediante un dispositivo luminoso coordinado con la se��al sonora de salida (Soto-Rey, P��rez-Tejero, Rojo-Gonz��lez y ��lvarez-Ortiz, 2015). En cuanto a los procedimientos estad��sticos utilizados, con el fin de analizar la distribuci��n de los datos y su normalidad, se aplic�� la prueba de Kolmogorov-Smirnof, dicha prueba arroj�� resultados de normalidad para todas las variables analizadas de las situaciones experimentales EA, EVsuelo y EV5m. Es por ello que en el presente trabajo de investigaci��n se utiliz�� estad��stica param��trica. Como medidas descriptivas, se calcularon el m��ximo, m��nimo, media y la desviaci��n est��ndar. En relaci��n a las situaciones experimentales, para estudiar las posibles diferencias en las variables estudiadas dentro de cada grupo de velocistas (intragrupo) en la situaci��n experimental 1 (MTR), se emple�� una prueba T de Student para muestras independientes. En las situaciones experimentales 2, 3 y 4, para conocer las diferencias entre ambos grupos de velocistas en cada situaci��n, se utiliz�� igualmente la prueba T para muestras independientes, mientras que un ANOVA simple (con post hoc Bonferroni) se utiliz�� para analizar las diferencias para cada grupo (VDA y VsDA) por situaci��n experimental. As�� mismo, se utiliz�� un ANOVA de medidas repetidas, donde el tipo de est��mulo (situaci��n experimental) fue la variable intra-grupo y el grupo de velocistas participantes (VDA y VsDA) la entre-grupo, realiz��ndose esta prueba para evaluar en cada situaci��n el TR, t1m0 y t20m y las interacciones entre las variables. Para el tratamiento estad��stico fue utilizado el paquete estad��stico SPSS 18.0 (Chicago, IL, EEUU). Los niveles de significaci��n fueron establecidos para un ������0.05, indicando el valor de p en cada caso. Uno de los aspectos m��s relevantes de este trabajo es la medici��n en diferentes situaciones, con instrumentaci��n distinta y con situaciones experimentales distintas, del TR en velocistas con y sin discapacidad auditiva. Ello supuso el desarrollo de un dise��o de investigaci��n que respondi�� a las necesidades planteadas por los objetivos del estudio, as�� como el desarrollo de instrumentaci��n espec��fica (Rojo-Lacal, Soto-Rey, P��rez-Tejero y Rojo-Gonz��lez, 2014; Soto-Rey et al., 2015) y distintas situaciones experimentales que reprodujeran las condiciones de pr��ctica y competici��n real de VsDA y VDA en las pruebas atl��ticas de velocidad, y m��s concretamente, en las salidas. El an��lisis estad��stico mostr�� diferencias significativas entre los est��mulos visuales y sonoros medidos con el MTR, siendo menor el TR ante el est��mulo visual que ante el sonoro, tanto para los atletas con discapacidad auditiva como para los que no la presentaron (TR visual, 0.195 s �� 0.018 vs 0.197 s �� 0.022, p���0.05; TR sonoro 0.230 s �� 0.016 vs 0.237 s �� 0.045, p���0.05). Teniendo en cuenta los resultados seg��n poblaci��n objeto de estudio y situaci��n experimental, se registraron diferencias significativas entre ambas poblaciones, VDA y VsDA, siendo m��s r��pidos los VDA que VsDA en la situaci��n experimental con el est��mulo visual en el suelo (EVsuelo, 0.191 ��0.025 vs 0.210 ��0.025, p���0.05, respectivamente) y los VsDA en la situaci��n experimental con el est��mulo auditivo (EA, 0.396 ��0.045 vs 0.174 ��0.021, p���0.05), aunque sin diferencias entre ambos grupos en la situaci��n experimental con el est��mulo visual a 5m de los tacos de salida. Es de destacar que en el TR no hubo diferencias significativas entre EA para VsDA y EVsuelo para VDA. El ANOVA simple registr�� diferencias significativas en todas las situaciones experimentales dentro de cada grupo y para todas las variables, por lo que estad��sticamente, las situaciones experimentales fueron diferentes entre s��. En relaci��n al de ANOVA medidas repetidas, la prueba de esfericidad se mostr�� adecuada, existiendo diferencias significativas en las varianzas de los pares de medias: el valor de F indic�� que existieron diferencias entre las diferentes situaciones experimentales en cuanto a TR, incluso cuando ��stas se relacionaban con el factor discapacidad (factor interacci��n, p���0,05). Por ello, queda patente que las situaciones son distintas entre s��, tambi��n teniendo en cuenta la discapacidad. El ��2 (eta al cuadrado, tama��o del efecto, para la interacci��n) indica que el 91.7% de la variaci��n se deben a las condiciones del estudio, y no al error (indicador de la generalizaci��n de los resultados del estudio). Por otro lado, la evaluaci��n del dispositivo luminoso fue positiva en relaci��n a la iluminaci��n, comodidad de uso, ubicaci��n, color, tama��o, adecuaci��n del dispositivo y del equipamiento necesario para adaptar al sistema de salida. La totalidad de los atletas afirman rotundamente que el dispositivo luminoso favorecer��a la adaptaci��n al sistema de salida atl��tica para permitir una competici��n inclusiva. Asimismo concluyen que el dispositivo luminoso favorecer��a el rendimiento o mejora de marca en la competici��n. La discusi��n de este estudio presenta justificaci��n de las diferencias demostradas que el tipo de est��mulo y su colocaci��n son clave en el TR de esta prueba, por lo que podr��amos argumentar la necesidad de contar con dispositivos luminosos para VDA a la hora de competir con VsDA en una misma prueba, inclusiva. El presente trabajo de investigaci��n ha demostrado, aplicando el m��todo cient��fico, que el uso de estos dispositivos, en las condiciones t��cnicas y experimentales indicadas, permite el uso por parte del VDA, usando su mejor TR visual posible, que se muestra similar (ns) al TR auditivo de VsDA, lo que indica que, para competiciones inclusivas, la salida usando el sem��foro (para VDA) y la salida habitual (est��mulo sonoro) para VsDA, puede ser una soluci��n equitativa en base a la evidencia demostrada en este estudio. De esta manera, y como referencia, indicar que la media de los TR de los velocistas en la final de los 100 m.l. en los Juegos Ol��mpicos de Londres 2012 fue de 0.162 ��0.015. De esta manera, creemos que estos par��metros sirven de referencia a t��cnicos deportivos, atletas y futuros trabajos de investigaci��n. Las aplicaciones de este trabajo permitir��n modificaciones y reflexiones en forma de apoyo al entrenamiento y la competici��n para el entrenador, o juez de salida en la competici��n que, creemos, es necesaria para proporcionar a este colectivo una atenci��n adecuada en las salidas, especialmente en situaciones inclusivas de pr��ctica. ABSTRACT This research aims to study of reaction time (RT) in sprinters with and without hearing impairment from the Sports Science perspective. The approach of this study came asking whether there were differences in the visual and auditory RT applied to sprinters with and without hearing impairment, thinking about the future development of inclusive competition between the two groups. Therefore, this study attempts to resolve the difficulties commonly founded by sprinters with hearing impairments during competitions. A priori, sprinters with hearing impairment would compete in a disadvantage situation as a result of the use of a staring signal not suitable for them (from the blocks, they have to look to the judge��s pistol or the movement of an opponent). The document is divided into three parts. In the first part of the review of relevant theoretical framework and justification of the study is presented. The second part focuses on the research objectives, material and method, where results, discussion and conclusions of the study, as well as the limitations of this study and future research are presented. The third part contains references and the fourth, annexes. In the first part, we present the theoretical framework consisting of five chapters, organizing the state of the art of RT, determined by the characteristics of the task and other factors that influence the RT as object of our study. Then we present the main structural and functional aspects of the nervous system associated with visual and auditory RT. After that, sport for people with hearing disabilities is presented, investigating its peculiarities and eligibility criteria is that group within the deaf sport. Finally, we discuss the theoretical foundation of the study of start speed in athletics as a key aspect that will guide our research, especially the determining parameters in placing the starting blocks for athletes with and without hearing impairment, the starting position and the actual placement of stimuli in such a situation. The second part of the research aims to study the values of simple manual visual RT, RT start from blocks and travel times up to 10m and 20m of sprinters with and without hearing impairment, and to analyze possible differences in RT as position and type of light stimulus with respect to both groups of athletes. The third objective of the study is to assess the pertinence of the lighting device developed and used in the study, in a qualitatively way by athletes themselves. Data collection for this study was carried out between February and May 2014, in the Athletics module at the High Performance Centre Joaquin Blume (Madrid) with the two study groups: 9 sprinters with hearing impairments(VDA, reaching 60% of the population in Spain, according to the number of licenses for athletics at FEDS: sprint, 100 and 200 m.l., at the time of the study), and another 13 sprinters without disability (VsDA) who voluntarily presented themselves, with same inclusion criteria for both groups. For measuring and data collection materials such as recording sheet, gauge reaction time (MTR), starting blocks, ReacTime��, luminous device connected to the starting blocks, photocells, computer and software ReacTime, and video camera were used. The methodology used in this study was correlational, analyzing the results of simple manual RT according sensory pathway (visual and auditory) between the two groups (VsDA and VDA). Also auditory and visual RT was studied depending the placement of the start light signal (on the ground and 5 meters, visual pathway) and athletic start gun signal (auditory pathway, conventional situation) and travel time up to 10m (t10m) and 20m (t20m) for both groups of sprinters. Finally, we developed and carried out an evaluation questionnaire for VDA athletes in order to determine the degree of satisfaction after completing the series of experiments with lighting device and adapted to start systems in athletic speed. In order to test the feasibility of the methodology described and tested in the context of real analysis of the experimental protocol, a pilot study in order to know the possible differences visual RT from the starting blocks in sprinters with hearing impairments was performed, to said output using a visual stimulus coordinated by a lighting device with sound output signal (Soto-Rey Perez-Tejero, Rojo-Gonz��lez y ��lvarez-Ortiz, 2015). For the statistical procedures, in order to analyze the distribution of the data and their normality, Kolmogorov-Smirnov test was applied, this test yielded normal results for all variables analyzed during EA, EVsuelo and EV5m experimental situations. Parametric statistics were used in this research. As descriptive measures, the maximum, minimum, mean and standard deviation were calculated. In relation to experimental situations, to study possible differences in the variables studied in each group sprinters (intragroup) in the experimental situation 1 (MTR), a Student t test was used for independent samples. Under the experimental situations 2, 3 and 4, to know the differences between the two groups of sprinters in every situation, the T test for independent samples was used, while a simple ANOVA (with post hoc Bonferroni) was used to analyze differences for each group (VDA and VsDA) by experimental situation. Likewise, a repeated measures ANOVA, where the type of stimulus (experimental situation) was variable intra-group and participants sprinters group (VDA and VsDA) the variable between-group, was performed to assess each situation for RT, t10m and t20m, and also interactions between variables. For the statistical treatment SPSS 18.0 (Chicago, IL, USA) was used. Significance levels were set for ��� ���0.05, indicating the value of p in each case. One of the most important aspects of this work is the measurement of RT in sprinters with and without hearing impairment in different situations, with different instrumentation and different experimental situations. This involved the development of a research design that responded to the needs raised by the study aims and the development of specific instrumentation (Rojo-Lacal, Soto-Rey Perez-Tejero and Rojo-Gonzalez, 2014; Soto-Rey et al., 2015) and different experimental situations to reproduce the conditions of practical and real competition VsDA and VDA in athletic sprints, and more specifically, at the start. Statistical analysis showed significant differences between the visual and sound stimuli measured by the MTR, with lower RT to the visual stimulus that for sound, both for athletes with hearing disabilities and for those without (visual RT, 0.195 s �� 0.018 s vs 0.197 �� 0.022, p���0.05; sound RT 0.230 s �� 0.016 vs 0.237 s �� 0.045, p���0.05). Considering the results according to study population and experimental situation, significant differences between the two populations, VDA and VsDA were found, being faster the VDA than VsDA in the experimental situation with the visual stimulus on the floor (EVsuelo, recorded 0.191 s �� 0.025 vs 0.210 s �� 0.025, p���0.05, respectively) and VsDA in the experimental situation with the auditory stimulus (EA, 0.396 s �� 0.045 vs 0.174 s �� 0.021, p���0.05), but no difference between groups in the experimental situation with the 5m visual stimulus to the starting blocks. It is noteworthy that no significant differences in EA and EVsuelo between VsDA to VDA, respectively, for RT. Simple ANOVA showed significant differences in all experimental situations within each group and for all variables, so statistically, the experimental situations were different. Regarding the repeated measures ANOVA, the sphericity test showed adequate, and there were significant differences in the variances of the pairs of means: the value of F indicated that there were differences between the different experimental situations regarding RT, even when they were related to the disability factor (factor interaction, p���0.05). Therefore, it is clear that the situations were different from each other, also taking into account impairment. The ��2 (eta squared, effect size, for interaction) indicates that 91.7% of the variation is due to the conditions of the study, not by error (as indicator of the generalization potential of the study results). On the other hand, evaluation of the light signal was positively related to lighting, ease of use, location, color, size, alignment device and equipment necessary to adapt the start system. All the athletes claim strongly in favor of the lighting device adaptation system to enable athletic competition inclusive. Also they concluded that light device would enhance performance or would decrease their RT during the competition. The discussion of this study justify the type of stimulus and the start light positioning as key to the RT performance, so that we could argue the need for lighting devices for VDA when competing against VsDA the same competition, inclusive. This research has demonstrated, applying the scientific method, that the use of these devices, techniques and given experimental conditions, allows the use of the VDA, using his best visual RT, shown similar (ns) auditory RT of VsDA, indicating that for inclusive competitions, the start signal using the light (for VDA) and the usual start (sound stimulus) to VsDA can be an equitable solution based on the evidence shown in this study. Thus, and as a reference, indicate that the average of the RT sprinters in the 100 m. final at the 2012 Summer Olympic Games was 0.162 s �� 0.015. Thus, we believe that these parameters become a reference to sports coaches, athletes and future research. Applications of this work will allow modifications and reflections in the form of support for training and competition for the coach, or judge, as we believe is necessary to provide adequate attention to VDA in speed starts, especially in inclusive practice situations.

Revival of oscillation from mean-field-induced death : Theory and experiment

Submitted ACKNOWLEDGMENTS T. B. acknowledges the financial support from SERB, Department of Science and Technology (DST), India [Project Grant No.: SB/FTP/PS-005/2013]. D. G. acknowledges DST, India, for providing support through the INSPIRE fellowship. J. K. acknowledges Government of the Russian Federation (Agreement No. 14.Z50.31.0033 with Institute of Applied Physics RAS).