Influence of driving style on fuel consumption and Emissions in diesel-powered passenger car

This paper presents the main results of a study on the influence of driving style on fuel consumption and pollutant emissions of diesel passenger car in urban traffic. Driving styles (eco, normal or aggressive) patterns were based on the ���eco-driving��� criteria. The methodology is based on on-board emission measurements in real urban traffic in the city of Madrid. Five diesel passenger cars, have been tested. Through a statistical analysis, a Dynamic Performance Index was defined for diesel passenger cars. Likewise, the CO, NOX and HC emissions were compared for each driving style for the tested vehicles. Eco-driving reduces by 14% fuel consumption and CO2 emissions, but aggressive driving increase consumption by 40%. Aggressive driving increases NOX emission by more than 40%. CO and HC, show different trends, but being increased in eco-driving style.

Analyzing training dependencies and posterior fusion in discriminant classification of apnoea patients based on sustained and connected speech

We present a novel approach using both sustained vowels and connected speech, to detect obstructive sleep apnea (OSA) cases within a homogeneous group of speakers. The proposed scheme is based on state-of-the-art GMM-based classifiers, and acknowledges specifically the way in which acoustic models are trained on standard databases, as well as the complexity of the resulting models and their adaptation to specific data. Our experimental database contains a suitable number of utterances and sustained speech from healthy (i.e control) and OSA Spanish speakers. Finally, a 25.1% relative reduction in classification error is achieved when fusing continuous and sustained speech classifiers. Index Terms: obstructive sleep apnea (OSA), gaussian mixture models (GMMs), background model (BM), classifier fusion.

Improving automatic detection of obstructive sleep apnea through nonlinear analysis of sustained speech

We present a novel approach for the detection of severe obstructive sleep apnea (OSA) based on patients' voices introducing nonlinear measures to describe sustained speech dynamics. Nonlinear features were combined with state-of-the-art speech recognition systems using statistical modeling techniques (Gaussian mixture models, GMMs) over cepstral parameterization (MFCC) for both continuous and sustained speech. Tests were performed on a database including speech records from both severe OSA and control speakers. A 10 % relative reduction in classification error was obtained for sustained speech when combining MFCC-GMM and nonlinear features, and 33 % when fusing nonlinear features with both sustained and continuous MFCC-GMM. Accuracy reached 88.5 % allowing the system to be used in OSA early detection. Tests showed that nonlinear features and MFCCs are lightly correlated on sustained speech, but uncorrelated on continuous speech. Results also suggest the existence of nonlinear effects in OSA patients' voices, which should be found in continuous speech.

Evaluaci��n de la contribuci��n y el impacto de las tecnolog��as del habla en la detecci��n autom��tica del S��ndrome de la Apnea Obstructiva del Sue��o = Contributions and impact assessment of speech technologies on the automatic detection of severe Obstructive Sleep Apnea syndrome

La presente Tesis analiza las posibilidades que ofrecen en la actualidad las tecnolog��as del habla para la detecci��n de patolog��as cl��nicas asociadas a la v��a a��rea superior. El estudio del habla que tradicionalmente cubre tanto la producci��n como el proceso de transformaci��n del mensaje y las se��ales involucradas, desde el emisor hasta alcanzar al receptor, ofrece una v��a de estudio alternativa para estas patolog��as. El hecho de que la se��al emitida no solo contiene este mensaje, sino tambi��n informaci��n acerca del locutor, ha motivado el desarrollo de sistemas orientados a la identificaci��n y verificaci��n de la identidad de los locutores. Estos trabajos han recibido recientemente un nuevo impulso, orient��ndose tanto hacia la caracterizaci��n de rasgos que son comunes a varios locutores, como a las diferencias existentes entre grabaciones de un mismo locutor. Los primeros resultan especialmente relevantes para esta Tesis dado que estos rasgos podr��an evidenciar la presencia de caracter��sticas relacionadas con una cierta condici��n com��n a varios locutores, independiente de su identidad. Tal es el caso que se enfrenta en esta Tesis, donde los rasgos identificados se relacionar��an con una de la patolog��a particular y directamente vinculada con el sistema de f��sico de conformaci��n del habla. El caso del S��ndrome de Apneas Hipopneas durante el Sueno (SAHS) resulta paradigm��tico. Se trata de una patolog��a con una elevada prevalencia mundo, que aumenta con la edad. Los pacientes de esta patolog��a experimentan episodios de cese involuntario de la respiraci��n durante el sue��o, que se prolongan durante varios segundos y que se reproducen a lo largo de la noche impidiendo el correcto descanso. En el caso de la apnea obstructiva, estos episodios se deben a la imposibilidad de mantener un camino abierto a trav��s de la v��a a��rea, de forma que el flujo de aire se ve interrumpido. En la actualidad, el diagnostico de estos pacientes se realiza a trav��s de un estudio polisomnogr��fico, que se centra en el an��lisis de los episodios de apnea durante el sue��o, requiriendo que el paciente permanezca en el hospital durante una noche. La complejidad y el elevado coste de estos procedimientos, unidos a las crecientes listas de espera, han evidenciado la necesidad de contar con t��cnicas r��pidas de detecci��n, que si bien podr��an no obtener tasas tan elevadas, permitir��an reorganizar las listas de espera en funci��n del grado de severidad de la patolog��a en cada paciente. Entre otros, los sistemas de diagnostico por imagen, as�� como la caracterizaci��n antropom��trica de los pacientes, han evidenciado la existencia de patrones anat��micos que tendr��an influencia directa sobre el habla. Los trabajos dedicados al estudio del SAHS en lo relativo a como esta afecta al habla han sido escasos y algunos de ellos incluso contradictorios. Sin embargo, desde finales de la d��cada de 1980 se conoce la existencia de patrones espec��ficos relativos a la articulaci��n, la fonaci��n y la resonancia. Sin embargo, su descripci��n resultaba dif��cilmente aprovechable a trav��s de un sistema de reconocimiento autom��tico, pero apuntaba la existencia de un nexo entre voz y SAHS. En los ��ltimos anos las t��cnicas de procesado autom��tico han permitido el desarrollo de sistemas autom��ticos que ya son capaces de identificar diferencias significativas en el habla de los pacientes del SAHS, y que los distinguen de los locutores sanos. Por contra, poco se conoce acerca de la conexi��n entre estos nuevos resultados, los s�� que hab��an obtenido en el pasado y la patog��nesis del SAHS. Esta Tesis continua la labor desarrollada en este ��mbito considerando espec��ficamente: el estudio de la forma en que el SAHS afecta el habla de los pacientes, la mejora en las tasas de clasificaci��n autom��tica y la combinaci��n de la informaci��n obtenida con los predictores utilizados por los especialistas cl��nicos en sus evaluaciones preliminares. Las dos primeras tareas plantean problemas simbi��ticos, pero diferentes. Mientras el estudio de la conexi��n entre el SAHS y el habla requiere de modelos acotados que puedan ser interpretados con facilidad, los sistemas de reconocimiento se sirven de un elevado n��mero de dimensiones para la caracterizaci��n y posterior identificaci��n de patrones. As��, la primera tarea debe permitirnos avanzar en la segunda, al igual que la incorporaci��n de los predictores utilizados por los especialistas cl��nicos. La Tesis aborda el estudio tanto del habla continua como del habla sostenida, con el fin de aprovechar las sinergias y diferencias existentes entre ambas. En el an��lisis del habla continua se tomo como punto de partida un esquema que ya fue evaluado con anterioridad, y sobre el cual se ha tratado la evaluaci��n y optimizaci��n de la representaci��n del habla, as�� como la caracterizaci��n de los patrones espec��ficos asociados al SAHS. Ello ha evidenciado la conexi��n entre el SAHS y los elementos fundamentales de la se��al de voz: los formantes. Los resultados obtenidos demuestran que el ��xito de estos sistemas se debe, fundamentalmente, a la capacidad de estas representaciones para describir dichas componentes, obviando las dimensiones ruidosas o con poca capacidad discriminativa. El esquema resultante ofrece una tasa de error por debajo del 18%, sirvi��ndose de clasificadores notablemente menos complejos que los descritos en el estado del arte y de una ��nica grabaci��n de voz de corta duraci��n. En relaci��n a la conexi��n entre el SAHS y los patrones observados, fue necesario considerar las diferencias inter- e intra-grupo, centr��ndonos en la articulaci��n caracter��stica del locutor, sustituyendo los complejos modelos de clasificaci��n por el estudio de los promedios espectrales. El resultado apunta con claridad hacia ciertas regiones del eje de frecuencias, sugiriendo la existencia de un estrechamiento sistem��tico en la secci��n del tracto en la regi��n de la orofaringe, ya prevista en la patog��nesis de este s��ndrome. En cuanto al habla sostenida, se han reproducido los estudios realizados sobre el habla continua en grabaciones de la vocal /a/ sostenida. Los resultados son cualitativamente an��logos a los anteriores, si bien en este caso las tasas de clasificaci��n resultan ser m��s bajas. Con el objetivo de identificar el sentido de este resultado se reprodujo el estudio de los promedios espectrales y de la variabilidad inter e intra-grupo. Ambos estudios mostraron importantes diferencias con los anteriores que podr��an explicar estos resultados. Sin embargo, el habla sostenida ofrece otras oportunidades al establecer un entorno controlado para el estudio de la fonaci��n, que tambi��n hab��a sido identificada como una fuente de informaci��n para la detecci��n del SAHS. De su estudio se pudo observar que, en el conjunto de datos disponibles, no existen variaciones que pudieran asociarse f��cilmente con la fonaci��n. ��nicamente aquellas dimensiones que describen la distribuci��n de energ��a a lo largo del eje de frecuencia evidenciaron diferencias significativas, apuntando, una vez m��s, en la direcci��n de las resonancias espectrales. Analizados los resultados anteriores, la Tesis afronta la fusi��n de ambas fuentes de informaci��n en un ��nico sistema de clasificaci��n. Con ello es posible mejorar las tasas de clasificaci��n, bajo la hip��tesis de que la informaci��n presente en el habla continua y el habla sostenida es fundamentalmente distinta. Esta tarea se realizo a trav��s de un sencillo esquema de fusi��n que obtuvo un 88.6% de aciertos en clasificaci��n (tasa de error del 11.4%), lo que representa una mejora significativa respecto al estado del arte. Finalmente, la combinaci��n de este clasificador con los predictores utilizados por los especialistas cl��nicos ofreci�� una tasa del 91.3% (tasa de error de 8.7%), que se encuentra dentro del margen ofrecido por esquemas m��s costosos e intrusivos, y que a diferencia del propuesto, no pueden ser utilizados en la evaluaci��n previa de los pacientes. Con todo, la Tesis ofrece una visi��n clara sobre la relaci��n entre el SAHS y el habla, evidenciando el grado de madurez alcanzado por la tecnolog��a del habla en la caracterizaci��n y detecci��n del SAHS, poniendo de manifiesto que su uso para la evaluaci��n de los pacientes ya ser��a posible, y dejando la puerta abierta a futuras investigaciones que contin��en el trabajo aqu�� iniciado. ABSTRACT This Thesis explores the potential of speech technologies for the detection of clinical disorders connected to the upper airway. The study of speech traditionally covers both the production process and post processing of the signals involved, from the speaker up to the listener, offering an alternative path to study these pathologies. The fact that utterances embed not just the encoded message but also information about the speaker, has motivated the development of automatic systems oriented to the identification and verificaton the speaker���s identity. These have recently been boosted and reoriented either towards the characterization of traits that are common to several speakers, or to the differences between records of the same speaker collected under different conditions. The first are particularly relevant to this Thesis as these patterns could reveal the presence of features that are related to a common condition shared among different speakers, regardless of their identity. Such is the case faced in this Thesis, where the traits identified would relate to a particular pathology, directly connected to the speech production system. The Obstructive Sleep Apnea syndrome (OSA) is a paradigmatic case for analysis. It is a disorder with high prevalence among adults and affecting a larger number of them as they grow older. Patients suffering from this disorder experience episodes of involuntary cessation of breath during sleep that may last a few seconds and reproduce throughout the night, preventing proper rest. In the case of obstructive apnea, these episodes are related to the collapse of the pharynx, which interrupts the air flow. Currently, OSA diagnosis is done through a polysomnographic study, which focuses on the analysis of apnea episodes during sleep, requiring the patient to stay at the hospital for the whole night. The complexity and high cost of the procedures involved, combined with the waiting lists, have evidenced the need for screening techniques, which perhaps would not achieve outstanding performance rates but would allow clinicians to reorganize these lists ranking patients according to the severity of their condition. Among others, imaging diagnosis and anthropometric characterization of patients have evidenced the existence of anatomical patterns related to OSA that have direct influence on speech. Contributions devoted to the study of how this disorder affects scpeech are scarce and somehow contradictory. However, since the late 1980s the existence of specific patterns related to articulation, phonation and resonance is known. By that time these descriptions were virtually useless when coming to the development of an automatic system, but pointed out the existence of a link between speech and OSA. In recent years automatic processing techniques have evolved and are now able to identify significant differences in the speech of OSAS patients when compared to records from healthy subjects. Nevertheless, little is known about the connection between these new results with those published in the past and the pathogenesis of the OSA syndrome. This Thesis is aimed to progress beyond the previous research done in this area by addressing: the study of how OSA affects patients��� speech, the enhancement of automatic OSA classification based on speech analysis, and its integration with the information embedded in the predictors generally used by clinicians in preliminary patients��� examination. The first two tasks, though may appear symbiotic at first, are quite different. While studying the connection between speech and OSA requires simple narrow models that can be easily interpreted, classification requires larger models including a large number dimensions for the characterization and posterior identification of the observed patterns. Anyhow, it is clear that any progress made in the first task should allow us to improve our performance on the second one, and that the incorporation of the predictors used by clinicians shall contribute in this same direction. The Thesis considers both continuous and sustained speech analysis, to exploit the synergies and differences between them. On continuous speech analysis, a conventional speech processing scheme, designed and evaluated before this Thesis, was taken as a baseline. Over this initial system several alternative representations of the speech information were proposed, optimized and tested to select those more suitable for the characterization of OSA-specific patterns. Evidences were found on the existence of a connection between OSA and the fundamental constituents of the speech: the formants. Experimental results proved that the success of the proposed solution is well explained by the ability of speech representations to describe these specific OSA-related components, ignoring the noisy ones as well those presenting low discrimination capabilities. The resulting scheme obtained a 18% error rate, on a classification scheme significantly less complex than those described in the literature and operating on a single speech record. Regarding the connection between OSA and the observed patterns, it was necessary to consider inter-and intra-group differences for this analysis, and to focus on the articulation, replacing the complex classification models by the long-term average spectra. Results clearly point to certain regions on the frequency axis, suggesting the existence of a systematic narrowing in the vocal tract section at the oropharynx. This was already described in the pathogenesis of this syndrome. Regarding sustained speech, similar experiments as those conducted on continuous speech were reproduced on sustained phonations of vowel / a /. Results were qualitatively similar to the previous ones, though in this case perfomance rates were found to be noticeably lower. Trying to derive further knowledge from this result, experiments on the long-term average spectra and intraand inter-group variability ratios were also reproduced on sustained speech records. Results on both experiments showed significant differences from the previous ones obtained from continuous speech which could explain the differences observed on peformance. However, sustained speech also provided the opportunity to study phonation within the controlled framework it provides. This was also identified in the literature as a source of information for the detection of OSA. In this study it was found that, for the available dataset, no sistematic differences related to phonation could be found between the two groups of speakers. Only those dimensions which relate energy distribution along the frequency axis provided significant differences, pointing once again towards the direction of resonant components. Once classification schemes on both continuous and sustained speech were developed, the Thesis addressed their combination into a single classification system. Under the assumption that the information in continuous and sustained speech is fundamentally different, it should be possible to successfully merge the two of them. This was tested through a simple fusion scheme which obtained a 88.6% correct classification (11.4% error rate), which represents a significant improvement over the state of the art. Finally, the combination of this classifier with the variables used by clinicians obtained a 91.3% accuracy (8.7% error rate). This is within the range of alternative, but costly and intrusive schemes, which unlike the one proposed can not be used in the preliminary assessment of patients��� condition. In the end, this Thesis has shed new light on the underlying connection between OSA and speech, and evidenced the degree of maturity reached by speech technology on OSA characterization and detection, leaving the door open for future research which shall continue in the multiple directions that have been pointed out and left as future work.

Mechanical behavior of 2G REBCO HTS at 77 and 300 K

El gran esfuerzo realizado durante la ��ltima d��cada con el fin de integrar los diferentes materiales superconductores en el campo de los sistemas el��ctricos y en otras aplicaciones tecnol��gicas ha dado lugar a un campo de investigaci��n amplio y prometedor. El comportamiento el��ctrico de los Superconductores de Alta Temperatura (SAT) cr��tica (masivo y cintas) depende de diferentes par��metros desde su fabricaci��n hasta la aplicaci��n final con imanes o cables. Sin embargo, las aplicaciones pr��cticas de estos materiales est��n fuertemente vinculadas con su comportamiento mec��nico tanto a temperatura ambiente (manipulaci��n durante fabricaci��n o instalaci��n) como a temperaturas criog��nicas (condiciones de servicio). En esta tesis se ha estudiado el comportamiento mec��nico de materiales masivos y cintas de alta temperatura cr��tica a 300 y 77 K (utilizando nitr��geno l��quido). Se han obtenido la resistencia en flexi��n, la tenacidad de fractura y la resistencia a tracci��n a la temperatura de servicio y a 300 K. Adicionalmente, se ha medido la dureza mediante el ensayo Vickers y nanoindentaci��n. El m��dulo Young se midi�� mediante tres m��todos diferentes: 1) nanoindentaci��n, 2) ensayos de flexi��n en tres puntos y 3) resonancia vibracional mediante grindosonic. Para cada condici��n de ensayo, se han analizado detalladamente las superficies de fractura y los micromecanismos de fallo. Las propiedades mec��nicas de los materiales se han comparado con el fin de entender la influencia de las t��cnicas de procesado y de las caracter��sticas microestructurales de los monocristales en su comportamiento mec��nico. Se ha estudiado el comportamiento electromec��nico de cintas comerciales superconductoras de YBCO mediante ensayos de tracci��n y fatiga a 77 y 300 K. El campo completo de deformaciones en la superficie del material se ha obtenido utilizando Correlaci��n Digital de Im��genes (DIC, por sus siglas en ingl��s) a 300 K. Adem��s, se realizaron ensayos de fragmentaci��n in situ dentro de un microscopio electr��nico con el fin de estudiar la fractura de la capa superconductora y determinar la resistencia a cortante de la intercara entre el substrato y la capa cer��mica. Se ha conseguido ver el proceso de la fragmentaci��n aplicando tensi��n axial y finalmente, se han implementado simulaciones mediante elementos finitos para reproducir la delaminaci��n y el fen��meno de la fragmentaci��n. Por ��ltimo, se han preparado uniones soldadas entre las capas de cobre de dos cintas superconductoras. Se ha medido la resistencia el��ctrica de las uniones con el fin de evaluar el metal de soldadura y el proceso. Asimismo, se ha llevado a cabo la caracterizaci��n mec��nica de las uniones mediante ensayos "single lap shear" a 300 y 77 K. El efecto del campo magn��tico se ha estudiado aplicando campo externo hasta 1 T perpendicular o paralelo a la cinta-uni��n a la temperatura de servicio (77 K). Finalmente, la distribuci��n de tensiones en cada una de las capas de la cinta se estudi�� mediante simulaciones de elementos finitos, teniendo en cuenta las capas de la cinta mec��nicamente m��s representativas (Cu-Hastelloy-Cu) que influyen en su comportamiento mec��nico. The strong effort that has been made in the last years to integrate the different superconducting materials in the field of electrical power systems and other technological applications led to a wide and promising research field. The electrical behavior of High Temperature Superconducting (HTS) materials (bulk and coated conductors) depends on different parameters since their processing until their final application as magnets or cables. However, practical applications of such materials are strongly related with their mechanical performance at room temperature (handling) as well as at cryogenic temperatures (service conditions). In this thesis, the mechanical behavior of HTS bulk and coated conductors was investigated at 300 and 77 K (by immersion in liquid nitrogen). The flexural strength, the fracture toughness and the tensile strength were obtained at service temperature as well as at 300 K. Furthermore, their hardness was determined by Vickers measurements and nanoindentation and the Young's modulus was measured by three different techniques: 1) nanoindentation, 2) three-point bending tests and 3) vibrational resonance with a grindosonic device. The fracture and deformation micromechanics have been also carefully analyzed for each testing condition. The comparison between the studied materials has been performed in order to understand the influence of the main sintering methods and the microstructural characteristics of the single grains on the macroscopic mechanical behavior. The electromechanical behavior of commercial YBCO coated conductors was studied. The mechanical behavior of the tapes was studied under tensile and fatigue tests at 77 and 300 K. The complete strain field on the surface of the sample was obtained by applying Digital Image Correlation (DIC) at 300 K. Addionally, in situ fragmentation tests inside a Scanning Electron Microscope (SEM) were carried out in order to study the fragmentation of the superconducting layer and determine the interfacial shear strength between substrate and ceramic layer. The fragmentation process upon loading of the YBCO layer has been observed and finally, Finite Element Simulations were employed to reproduce delamination and fragmentation phenomena. Finally, joints between the stabilizing Cu sides of two coated conductors have been prepared. The electrical resistivity of the joints was measured for the purpose of qualifying the soldering material and evaluating the soldering process. Additionally, mechanical characterization under single lap shear tests at 300 and 77 K has been carried out. The effect of the applied magnetic field has been studied by applying external magnetic field up to 1 T perpendicular and parallel to the tape-joint at service temperature (77 K). Finally, finite element simulations were employed to study the distribution of the stresses in earch layer, taking into account the three mechanically relevant layers of the coated conductor (Cu-Hastelloy-Cu) that affect its mechanical behavior

Structuring research methods and data with the research object model: genomics workflows as a case study

Background: One of the main challenges for biomedical research lies in the computer-assisted integrative study of large and increasingly complex combinations of data in order to understand molecular mechanisms. The preservation of the materials and methods of such computational experiments with clear annotations is essential for understanding an experiment, and this is increasingly recognized in the bioinformatics community. Our assumption is that offering means of digital, structured aggregation and annotation of the objects of an experiment will provide necessary meta-data for a scientist to understand and recreate the results of an experiment. To support this we explored a model for the semantic description of a workflow-centric Research Object (RO), where an RO is defined as a resource that aggregates other resources, e.g., datasets, software, spreadsheets, text, etc. We applied this model to a case study where we analysed human metabolite variation by workflows. Results: We present the application of the workflow-centric RO model for our bioinformatics case study. Three workflows were produced following recently defined Best Practices for workflow design. By modelling the experiment as an RO, we were able to automatically query the experiment and answer questions such as ���which particular data was input to a particular workflow to test a particular hypothesis?���, and ���which particular conclusions were drawn from a particular workflow?���. Conclusions: Applying a workflow-centric RO model to aggregate and annotate the resources used in a bioinformatics experiment, allowed us to retrieve the conclusions of the experiment in the context of the driving hypothesis, the executed workflows and their input data. The RO model is an extendable reference model that can be used by other systems as well.

Visual attention and perception models for assessing quality in 2D and 3D stereoscopic video

La medida de calidad de v��deo sigue siendo necesaria para definir los criterios que caracterizan una se��al que cumpla los requisitos de visionado impuestos por el usuario. Las nuevas tecnolog��as, como el v��deo 3D estereosc��pico o formatos m��s all�� de la alta definici��n, imponen nuevos criterios que deben ser analizadas para obtener la mayor satisfacci��n posible del usuario. Entre los problemas detectados durante el desarrollo de esta tesis doctoral se han determinado fen��menos que afectan a distintas fases de la cadena de producci��n audiovisual y tipo de contenido variado. En primer lugar, el proceso de generaci��n de contenidos debe encontrarse controlado mediante par��metros que eviten que se produzca el disconfort visual y, consecuentemente, fatiga visual, especialmente en lo relativo a contenidos de 3D estereosc��pico, tanto de animaci��n como de acci��n real. Por otro lado, la medida de calidad relativa a la fase de compresi��n de v��deo emplea m��tricas que en ocasiones no se encuentran adaptadas a la percepci��n del usuario. El empleo de modelos psicovisuales y diagramas de atenci��n visual permitir��an ponderar las ��reas de la imagen de manera que se preste mayor importancia a los p��xeles que el usuario enfocar�� con mayor probabilidad. Estos dos bloques se relacionan a trav��s de la definici��n del t��rmino saliencia. Saliencia es la capacidad del sistema visual para caracterizar una imagen visualizada ponderando las ��reas que m��s atractivas resultan al ojo humano. La saliencia en generaci��n de contenidos estereosc��picos se refiere principalmente a la profundidad simulada mediante la ilusi��n ��ptica, medida en t��rminos de distancia del objeto virtual al ojo humano. Sin embargo, en v��deo bidimensional, la saliencia no se basa en la profundidad, sino en otros elementos adicionales, como el movimiento, el nivel de detalle, la posici��n de los p��xeles o la aparici��n de caras, que ser��n los factores b��sicos que compondr��n el modelo de atenci��n visual desarrollado. Con el objetivo de detectar las caracter��sticas de una secuencia de v��deo estereosc��pico que, con mayor probabilidad, pueden generar disconfort visual, se consult�� la extensa literatura relativa a este tema y se realizaron unas pruebas subjetivas preliminares con usuarios. De esta forma, se lleg�� a la conclusi��n de que se produc��a disconfort en los casos en que se produc��a un cambio abrupto en la distribuci��n de profundidades simuladas de la imagen, aparte de otras degradaciones como la denominada ���violaci��n de ventana���. A trav��s de nuevas pruebas subjetivas centradas en analizar estos efectos con diferentes distribuciones de profundidades, se trataron de concretar los par��metros que defin��an esta imagen. Los resultados de las pruebas demuestran que los cambios abruptos en im��genes se producen en entornos con movimientos y disparidades negativas elevadas que producen interferencias en los procesos de acomodaci��n y vergencia del ojo humano, as�� como una necesidad en el aumento de los tiempos de enfoque del cristalino. En la mejora de las m��tricas de calidad a trav��s de modelos que se adaptan al sistema visual humano, se realizaron tambi��n pruebas subjetivas que ayudaron a determinar la importancia de cada uno de los factores a la hora de enmascarar una determinada degradaci��n. Los resultados demuestran una ligera mejora en los resultados obtenidos al aplicar m��scaras de ponderaci��n y atenci��n visual, los cuales aproximan los par��metros de calidad objetiva a la respuesta del ojo humano. ABSTRACT Video quality assessment is still a necessary tool for defining the criteria to characterize a signal with the viewing requirements imposed by the final user. New technologies, such as 3D stereoscopic video and formats of HD and beyond HD oblige to develop new analysis of video features for obtaining the highest user���s satisfaction. Among the problems detected during the process of this doctoral thesis, it has been determined that some phenomena affect to different phases in the audiovisual production chain, apart from the type of content. On first instance, the generation of contents process should be enough controlled through parameters that avoid the occurrence of visual discomfort in observer���s eye, and consequently, visual fatigue. It is especially necessary controlling sequences of stereoscopic 3D, with both animation and live-action contents. On the other hand, video quality assessment, related to compression processes, should be improved because some objective metrics are adapted to user���s perception. The use of psychovisual models and visual attention diagrams allow the weighting of image regions of interest, giving more importance to the areas which the user will focus most probably. These two work fields are related together through the definition of the term saliency. Saliency is the capacity of human visual system for characterizing an image, highlighting the areas which result more attractive to the human eye. Saliency in generation of 3DTV contents refers mainly to the simulated depth of the optic illusion, i.e. the distance from the virtual object to the human eye. On the other hand, saliency is not based on virtual depth, but on other features, such as motion, level of detail, position of pixels in the frame or face detection, which are the basic features that are part of the developed visual attention model, as demonstrated with tests. Extensive literature involving visual comfort assessment was looked up, and the development of new preliminary subjective assessment with users was performed, in order to detect the features that increase the probability of discomfort to occur. With this methodology, the conclusions drawn confirmed that one common source of visual discomfort was when an abrupt change of disparity happened in video transitions, apart from other degradations, such as window violation. New quality assessment was performed to quantify the distribution of disparities over different sequences. The results confirmed that abrupt changes in negative parallax environment produce accommodation-vergence mismatches derived from the increasing time for human crystalline to focus the virtual objects. On the other side, for developing metrics that adapt to human visual system, additional subjective tests were developed to determine the importance of each factor, which masks a concrete distortion. Results demonstrated slight improvement after applying visual attention to objective metrics. This process of weighing pixels approximates the quality results to human eye���s response.