Two Different Approaches of Feature Extraction for Classifying the EEG Signals

The focus of this chapter is to study feature extraction and pattern classification methods from two medical areas, Stabilometry and Electroencephalography (EEG). Stabilometry is the branch of medicine responsible for examining balance in human beings. Balance and dizziness disorders are probably two of the most common illnesses that physicians have to deal with. In Stabilometry, the key nuggets of information in a time series signal are concentrated within definite time periods are known as events. In this chapter, two feature extraction schemes have been developed to identify and characterise the events in Stabilometry and EEG signals. Based on these extracted features, an Adaptive Fuzzy Inference Neural network has been applied for classification of Stabilometry and EEG signals.

¿Impact from road transport of radioactive wastes in Spain?

Transports of radioactive wastes in Spain are becoming issues of renewed interest, due to the increased mobility of these materials which can be expected after the building and operation of the planned central repository for this country in a near future. Such types of residues will be mainly of the medium and high activity classes and have raised concerns on the safety of the operations, the radiological protection of the individuals, the compliance with the legal regulations and their environmental consequences of all kind. In this study, relevant information for the assessment of radiological risk of road transport were taken into account, as the sources and destination of the radioactive transports, the amount of traveling to be done, the preferred routes and populations affected, the characterization of the residues and containers, their corresponding testing, etc. These data were supplied by different organizations fully related with these activities, like the nuclear power stations, the companies in charge of radioactive transports, the enterprises for inspection and control of the activities, etc., as well as the government institutions which are responsible for the selection and location of the storage facility and other decisions on the nuclear policies of the country. Thus, we have developed a program for computing the data in such a form that by entering the radiation levels at one meter of the transport loads and by choosing a particular displacement, the computer application is capable to calculate the corresponding radiological effects, like the global estimated impact, its relevance to the population in general or on those people living and driving near the main road routes, the doses received by the most exposed individuals (e.g. the workers for loading or driving the vehicle), or the probability of detrimental on the human health. The results of this work could be of help for a better understanding and management of these activities and their related impacts; at the same time that the generated reports of the computer application are considered of particular interest as innovative and complementary information to the current legal documentation, which is basically required for transporting radioactive wastes in the country, according with the international safety rules (like IAEA and ADR).Though main studies are still in progress, as the definite location for the Spanish storage facility has not been decided yet, preliminary results with the existing transports of residues of medium activity indicate that the radiological impact is very low in conventional operations. Nevertheless, the management of these transports is complex and laborious, making it convenient to progress further in the analysis and quantification of this kind of events, which constitutes one of the main objectives of the present study for the radioactive road mobility in Spain.

A robust numerical framework for the analysis of material failure of fibre reinforced soft tissue

In this work, robustness and stability of continuum damage models applied to material failure in soft tissues are addressed. In the implicit damage models equipped with softening, the presence of negative eigenvalues in the tangent elemental matrix degrades the condition number of the global matrix, leading to a reduction of the computational performance of the numerical model. Two strategies have been adapted from literature to improve the aforementioned computational performance degradation: the IMPL-EX integration scheme [Oliver,2006], which renders the elemental matrix contribution definite positive, and arclength-type continuation methods [Carrera,1994], which allow to capture the unstable softening branch in brittle ruptures. The IMPL-EX integration scheme has as a major drawback the need to use small time steps to keep numerical error below an acceptable value. A convergence study, limiting the maximum allowed increment of internal variables in the damage model, is presented. Finally, numerical simulation of failure problems with fibre reinforced materials illustrates the performance of the adopted methodology.

Geochemistry and risk assessment of street dust in Luanda, Angola, a tropical urban environment

A total of 92 samples of street dust were collected in Luanda, Angola, were sieved below 100 μm, and analysed by ICP-MS for 35 elements after an aqua-regia digestion. The concentration and spatial heterogeneity of trace elements in the street dust of Luanda are generally lower than in most industrialized cities in the Northern hemisphere. These observations reveal a predominantly “natural” origin for the street dust in Luanda, which is also manifested in that some geochemical processes that occur in natural soils are preserved in street dust: the separation of uranium from thorium, and the retention of the former by carbonate materials, or the high correlation between arsenic and vanadium due to their common mode of adsorption on solid particles in the form of oxyanions. The only distinct anthropogenic fingerprint in the composition of Luanda's street dust is the association Pb–Cd–Sb–Cu (and to a lesser extent, Ba–Cr–Zn). The use of risk assessment strategies has proved helpful in identifying the routes of exposure to street dust and the trace elements therein of most concern in terms of potential adverse health effects. In Luanda the highest levels of risk seem to be associated (a) with the presence of As and Pb in the street dust and (b) with the route of ingestion of dust particles, for all the elements included in the study except Hg, for which inhalation of vapours presents a slightly higher risk than ingestion. However, given the large uncertainties associated with the estimates of toxicity values and exposure factors, and the absence of site-specific biometric factors, these results should be regarded as preliminary and further research should be undertaken before any definite conclusions regarding potential health effects are drawn.

Combined static and dynamic assertion-based debugging of constraint logic programs

We propose a general framework for assertion-based debugging of constraint logic programs. Assertions are linguistic constructions for expressing properties of programs. We define several assertion schemas for writing (partial) specifications for constraint logic programs using quite general properties, including user-defined programs. The framework is aimed at detecting deviations of the program behavior (symptoms) with respect to the given assertions, either at compile-time (i.e., statically) or run-time (i.e., dynamically). We provide techniques for using information from global analysis both to detect at compile-time assertions which do not hold in at least one of the possible executions (i.e., static symptoms) and assertions which hold for all possible executions (i.e., statically proved assertions). We also provide program transformations which introduce tests in the program for checking at run-time those assertions whose status cannot be determined at compile-time. Both the static and the dynamic checking are provably safe in the sense that all errors flagged are definite violations of the pecifications. Finally, we report briefly on the currently implemented instances of the generic framework.

A framework for assertion-based debugging in constraint logic programming

We propose a general framework for assertion-based debugging of constraint logic programs. Assertions are linguistic constructions which allow expressing properties of programs. We define assertion schemas which allow writing (partial) specifications for constraint logic programs using quite general properties, including user-defined programs. The framework is aimed at detecting deviations of the program behavior (symptoms) with respect to the given assertions, either at compile-time or run-time. We provide techniques for using information from global analysis both to detect at compile-time assertions which do not hold in at least one of the possible executions (i.e., static symptoms) and assertions which hold for all possible executions (i.e., statically proved assertions). We also provide program transformations which introduce tests in the program for checking at run-time those assertions whose status cannot be determined at compile-time. Both the static and the dynamic checking are provably safe in the sense that all errors flagged are definite violations of the specifications. Finally, we report on an implemented instance of the assertion language and framework.

A robust numerical framework to the analysis of material failure of fibre reinforced soft tissue

In this work, robustness and stability of continuum damage models applied to material failure in soft tissues are addressed. In the implicit damage models equipped with softening, the presence of negative eigenvalues in the tangent elemental matrix degrades the condition number of the global matrix, leading to a reduction of the computational performance of the numerical model. Two strategies have been adapted from literature to improve the aforementioned computational performance degradation: the IMPL-EX integration scheme [Oliver,2006], which renders the elemental matrix contribution definite positive, and arclength-type continuation methods [Carrera,1994], which allow to capture the unstable softening branch in brittle ruptures. The IMPL-EX integration scheme has as a major drawback the need to use small time steps to keep numerical error below an acceptable value. A convergence study, limiting the maximum allowed increment of internal variables in the damage model, is presented. Finally, numerical simulation of failure problems with fibre reinforced materials illustrates the performance of the adopted methodology.

A derivation of thermodynamic principles

A detailed macroscopic description as in continuum mechanics, and just the concept of microstate,have been used to derive thermodynamics from mechanics. In opposition to statistical physics, the derivation lays emphasis on a definite prescription for macrostates (and non-equilibrium entropy), and uses basic features of the macrostate concept: complementary descriptions, involving either conservative and additive quantities or densities;scale-free character; reference to finite velocities and regions distant in space, thus introducing time indirectly. On the other hand, the derivation keeps the particle substratum (limit of number of particles N taken at fixed densities), and makes no ergodic-type considerations.

Transport and mixing enhancement in fluid-thermal microsystems

En esta tesis se investiga de forma experimental el transporte pasivo de magnitudes físicas en micro-sistemas con carácter de inmediata aplicación industrial, usando métodos innovadores para mejorar la eficiencia de los mismos optimizando parámetros críticos del diseño o encontrar nuevos destinos de posible aplicación. Parte de los resultados obtenidos en estos experimentos han sido publicados en revistas con un índice de impacto tal que pertenecen al primer cuarto del JCR. Primero de todo se ha analizado el efecto que produce en un intercambiador de calor basado en micro-canales el hecho de dejar un espacio entre canales y tapa superior para la interconexión de los mismos. Esto genera efectos tridimensionales que mejoran la exracción de calor del intercambiador y reducen la caída de presión que aparece por el transcurso del fluido a través de los micro-canales, lo que tiene un gran impacto en la potencia que ha de suministrar la bomba de refrigerante. Se ha analizado también la mejora producida en términos de calor disipado de un micro-procesador refrigerado con un ampliamente usado plato de aletas al implementar en éste una cámara de vapor que almacena un fluido bifásico. Se ha desarrollado de forma paralela un modelo numérico para optimizar las nuevas dimensiones del plato de aletas modificado compatibles con una serie de requerimientos de diseño en el que tanto las dimensiones como el peso juegan un papel esencial. Por otro lado, se han estudiado los fenomenos fluido-dinámicos que aparecen aguas abajo de un cuerpo romo en el seno de un fluido fluyendo por un canal con una alta relación de bloqueo. Los resultados de este estudio confirman, de forma experimental, la existencia de un régimen intermedio, caracterizado por el desarrollo de una burbuja de recirculación oscilante entre los regímenes, bien diferenciados, de burbuja de recirculación estacionaria y calle de torbellinos de Karman, como función del número de Reynolds del flujo incidente. Para la obtención, análisis y post-proceso de los datos, se ha contado con la ayuda de un sistema de Velocimetría por Imágenes de Partículas (PIV). Finalmente y como adición a este último punto, se ha estudiado las vibraciones de un cuerpo romo producidas por el desprendimiento de torbellinos en un canal de alta relación de bloqueo con la base obtenida del estudio anterior. El prisma se mueve con un movimiento armónico simple para un intervalo de números de Reynolds y este movimiento se transforma en vibración alrededor de su eje a partir de un ciero número de Reynolds. En relación al fluido, el régimen de desprendimiento de torbellinos se alcanza a menores números de Reynolds que en el caso de tener el cuerpo romo fijo. Uniendo estos dos registros de movimientos y variando la relación de masas entre prisma y fluido se obtiene un mapa con diferentes estados globales del sistema. Esto no solo tiene aplicación como método para promover el mezclado sino también como método para obtener energía a partir del movimiento del cuerpo en el seno del fluido. Abstract In this thesis, experimental research focused on passive scalar transport is performed in micro-systems with marked sense of industrial application, using innovative methods in order to obtain better performances optimizing critical design parameters or finding new utilities. Part of the results obtained in these experiments have been published into high impact factor journals belonged to the first quarter of the Journal Citation Reports (JCR). First of all the effect of tip clearance in a micro-channel based heat sink is analyzed. Leaving a gap between channels and top cover, letting the channels communicate each other causes three-dimensional effects which improve the heat transfer between fluid and heat sink and also reducing the pressure drop caused by the fluid passing through the micro-channels which has a great impact on the total cooling pumping power needed. It is also analyzed the enhancement produced in terms of dissipated heat in a micro-processor cooling system by improving the predominantly used fin plate with a vapour chamber based heat spreader which contains a two-phase fluid inside. It has also been developed at the same time a numerical model to optimize the new fin plate dimensions compatible with a series of design requirements in which both size and wight plays a very restrictive role. On the other hand, fluid-dynamics phenomena that appears downstream of a bluff body in the bosom of a fluid flow with high blockage ratio has been studied. This research experimentally confirms the existence of an intermediate regime characterized by an oscillating closed recirculation bubble intermediate regime between the steady closed recirculation bubble regime and the vortex shedding regime (Karman street like regime) as a function of the incoming flow Reynolds number. A particle image velocimetry technique (PIV) has been used in order to obtain, analyze and post-process the fluid-dynamic data. Finally and as an addition to the last point, a study on the vortexinduced vibrations (VIV) of a bluff body inside a high blockage ratio channel has been carried out taking advantage of the results obtained with the fixed square prism. The prism moves with simple harmonic motion for a Reynolds number interval and this movement becomes vibrational around its axial axis after overcoming at definite Reynolds number. Regarding the fluid, vortex shedding regime is reached at Reynolds numbers lower than the previous critical ones. Merging both movement spectra and varying the square prism to fluid mass ratio, a map with different global states is reached. This is not only applicable as a mixing enhancement technique but as an energy harvesting method.

Core physics and safety analysis of Generation-IV Sodium Fast Reactors using existing and newly developed computational tools

El futuro de la energía nuclear de fisión dependerá, entre otros factores, de la capacidad que las nuevas tecnologías demuestren para solventar los principales retos a largo plazo que se plantean. Los principales retos se pueden resumir en los siguientes aspectos: la capacidad de proporcionar una solución final, segura y fiable a los residuos radiactivos; así como dar solución a la limitación de recursos naturales necesarios para alimentar los reactores nucleares; y por último, una mejora robusta en la seguridad de las centrales que en definitiva evite cualquier daño potencial tanto en la población como en el medio ambiente como consecuencia de cualquier escenario imaginable o más allá de lo imaginable. Siguiendo estas motivaciones, la Generación IV de reactores nucleares surge con el compromiso de proporcionar electricidad de forma sostenible, segura, económica y evitando la proliferación de material fisible. Entre los sistemas conceptuales que se consideran para la Gen IV, los reactores rápidos destacan por su capacidad potencial de transmutar actínidos a la vez que permiten una utilización óptima de los recursos naturales. Entre los refrigerantes que se plantean, el sodio parece una de las soluciones más prometedoras. Como consecuencia, esta tesis surgió dentro del marco del proyecto europeo CP-ESFR con el principal objetivo de evaluar la física de núcleo y seguridad de los reactores rápidos refrigerados por sodio, al tiempo que se desarrollaron herramientas apropiadas para dichos análisis. Efectivamente, en una primera parte de la tesis, se abarca el estudio de la física del núcleo de un reactor rápido representativo, incluyendo el análisis detallado de la capacidad de transmutar actínidos minoritarios. Como resultado de dichos análisis, se publicó un artículo en la revista Annals of Nuclear Energy [96]. Por otra parte, a través de un análisis de un hipotético escenario nuclear español, se evalúo la disponibilidad de recursos naturales necesarios en el caso particular de España para alimentar una flota específica de reactores rápidos, siguiendo varios escenarios de demanda, y teniendo en cuenta la capacidad de reproducción de plutonio que tienen estos sistemas. Como resultado de este trabajo también surgió una publicación en otra revista científica de prestigio internacional como es Energy Conversion and Management [97]. Con objeto de realizar esos y otros análisis, se desarrollaron diversos modelos del núcleo del ESFR siguiendo varias configuraciones, y para diferentes códigos. Por otro lado, con objeto de poder realizar análisis de seguridad de reactores rápidos, son necesarias herramientas multidimensionales de alta fidelidad específicas para reactores rápidos. Dichas herramientas deben integrar fenómenos relacionados con la neutrónica y con la termo-hidráulica, entre otros, mediante una aproximación multi-física. Siguiendo este objetivo, se evalúo el código de difusión neutrónica ANDES para su aplicación a reactores rápidos. ANDES es un código de resolución nodal que se encuentra implementado dentro del sistema COBAYA3 y está basado en el método ACMFD. Por lo tanto, el método ACMFD fue sometido a una revisión en profundidad para evaluar su aptitud para la aplicación a reactores rápidos. Durante ese proceso, se identificaron determinadas limitaciones que se discutirán a lo largo de este trabajo, junto con los desarrollos que se han elaborado e implementado para la resolución de dichas dificultades. Por otra parte, se desarrolló satisfactoriamente el acomplamiento del código neutrónico ANDES con un código termo-hidráulico de subcanales llamado SUBCHANFLOW, desarrollado recientemente en el KIT. Como conclusión de esta parte, todos los desarrollos implementados son evaluados y verificados. En paralelo con esos desarrollos, se calcularon para el núcleo del ESFR las secciones eficaces en multigrupos homogeneizadas a nivel nodal, así como otros parámetros neutrónicos, mediante los códigos ERANOS, primero, y SERPENT, después. Dichos parámetros se utilizaron más adelante para realizar cálculos estacionarios con ANDES. Además, como consecuencia de la contribución de la UPM al paquete de seguridad del proyecto CP-ESFR, se calcularon mediante el código SERPENT los parámetros de cinética puntual que se necesitan introducir en los típicos códigos termo-hidráulicos de planta, para estudios de seguridad. En concreto, dichos parámetros sirvieron para el análisis del impacto que tienen los actínidos minoritarios en el comportamiento de transitorios. Concluyendo, la tesis presenta una aproximación sistemática y multidisciplinar aplicada al análisis de seguridad y comportamiento neutrónico de los reactores rápidos de sodio de la Gen-IV, usando herramientas de cálculo existentes y recién desarrolladas ad' hoc para tal aplicación. Se ha empleado una cantidad importante de tiempo en identificar limitaciones de los métodos nodales analíticos en su aplicación en multigrupos a reactores rápidos, y se proponen interesantes soluciones para abordarlas. ABSTRACT The future of nuclear reactors will depend, among other aspects, on the capability to solve the long-term challenges linked to this technology. These are the capability to provide a definite, safe and reliable solution to the nuclear wastes; the limitation of natural resources, needed to fuel the reactors; and last but not least, the improved safety, which would avoid any potential damage on the public and or environment as a consequence of any imaginable and beyond imaginable circumstance. Following these motivations, the IV Generation of nuclear reactors arises, with the aim to provide sustainable, safe, economic and proliferationresistant electricity. Among the systems considered for the Gen IV, fast reactors have a representative role thanks to their potential capacity to transmute actinides together with the optimal usage of natural resources, being the sodium fast reactors the most promising concept. As a consequence, this thesis was born in the framework of the CP-ESFR project with the generic aim of evaluating the core physics and safety of sodium fast reactors, as well as the development of the approppriated tools to perform such analyses. Indeed, in a first part of this thesis work, the main core physics of the representative sodium fast reactor are assessed, including a detailed analysis of the capability to transmute minor actinides. A part of the results obtained have been published in Annals of Nuclear Energy [96]. Moreover, by means of the analysis of a hypothetical Spanish nuclear scenario, the availability of natural resources required to deploy an specific fleet of fast reactor is assessed, taking into account the breeding properties of such systems. This work also led to a publication in Energy Conversion and Management [97]. In order to perform those and other analyses, several models of the ESFR core were created for different codes. On the other hand, in order to perform safety studies of sodium fast reactors, high fidelity multidimensional analysis tools for sodium fast reactors are required. Such tools should integrate neutronic and thermal-hydraulic phenomena in a multi-physics approach. Following this motivation, the neutron diffusion code ANDES is assessed for sodium fast reactor applications. ANDES is the nodal solver implemented inside the multigroup pin-by-pin diffusion COBAYA3 code, and is based on the analytical method ACMFD. Thus, the ACMFD was verified for SFR applications and while doing so, some limitations were encountered, which are discussed through this work. In order to solve those, some new developments are proposed and implemented in ANDES. Moreover, the code was satisfactorily coupled with the thermal-hydraulic code SUBCHANFLOW, recently developed at KIT. Finally, the different implementations are verified. In addition to those developments, the node homogenized multigroup cross sections and other neutron parameters were obtained for the ESFR core using ERANOS and SERPENT codes, and employed afterwards by ANDES to perform steady state calculations. Moreover, as a result of the UPM contribution to the safety package of the CP-ESFR project, the point kinetic parameters required by the typical plant thermal-hydraulic codes were computed for the ESFR core using SERPENT, which final aim was the assessment of the impact of minor actinides in transient behaviour. All in all, the thesis provides a systematic and multi-purpose approach applied to the assessment of safety and performance parameters of Generation-IV SFR, using existing and newly developed analytical tools. An important amount of time was employed in identifying the limitations that the analytical nodal diffusion methods present when applied to fast reactors following a multigroup approach, and interesting solutions are proposed in order to overcome them.

The Role of N Plant Glycosilation in act d 2 allergenicity.

Plant allergens have hitherto been included in only several protein families that share no common biochemical features. Their physical, biochemical and immunological characteristics have been widely studied, but no definite conclusion has been reached about what makes a protein an allergen. N-glycosylation is characteristic of plant allergen sources but is not present in mammals.

Thermographic imaging: assessment of drought and heat tolerance in Spanish germplasm of Brachypodium distachyon.

The annual grass Brachypodium distachyon has been recently recognized as the model plant for functional genomics of temperate grasses, including cereals of economic relevance like wheat and barley. Sixty-two lines of B. distachyon were assessed for response to drought stress and heat tolerance. All these lines, except the reference genotype BD21, derive from specimens collected in 32 distinct locations of the Iberian Peninsula, covering a wide range of geo- climatic conditions. Sixteen lines of Brachypodium hybridum, an allotetraploid closely related to B. distachyon were used as reference of abiotic-stress well-adapted genotypes. Drought tolerance was assessed in a green-house trial. At the rosette-stage, no irrigation was applied to treated plants whereas their replicates at the control were maintained well watered during all the experiment. Thermographic images of treated and control plants were taken after 2 and 3 weeks of drought treatment, when stressed plants showed medium and extreme wilting symptoms. The mean leaf temperature of stressed (LTs) and control (LTc) plants was estimated based upon thermographic records from selected pixels (183 per image) that strictly correspond to leaf tissue. The response to drought was based on the analysis of two parameters: LTs and the thermal difference (TD) between stressed and control plants (LTs – LTc). The response to heat stress was based on LTc. Comparison of the mean values of these parameters showed that: 1) Genotypes better adapted to drought (B. hybridum lines) presented a higher LTs and TD than B. distachyon lines. 2) Under high temperature conditions, watered plants of B. hybridum lines maintained lower LTc than those of B. distachyon. Those results suggest that in these species adaptation to drought is linked to a more efficient stomata regulation: under water stress stomata are closed, increasing foliar temperature but also water use efficiency by reducing transpiration. With high temperature and water availability the results are less definite, but still seems that opening stomata allow plants to increase transpiration and therefore to diminish foliar temperature.

Molecular physiology of nickel and cobalt homeostasis in Rhizobium leguminosarum.

Transition metals such as Fe, Cu, Mn, Ni, or Co are essential nutrients, as they are constitutive elements of a significant fraction of cell proteins. Such metals are present in the active site of many enzymes, and also participate as structural elements in different proteins. From a chemical point of view, metals have a defined order of affinity for binding, designated as the Irving-Williams series (Irving and Williams, 1948) Mg2+ menor que Mn2+ menor que Fe2+ menor que Co2+ menor que Ni2+ menor que Cu2+mayor queZn2+ Since cells contain a high number of different proteins harbouring different metal ions, a simplistic model in which proteins are synthesized and metals imported into a ?cytoplasmic soup? cannot explain the final product that we find in the cell. Instead we need to envisage a complex model in which specific ligands are present in definite amounts to leave the right amounts of available metals and protein binding sites, so specific pairs can bind appropriately. A critical control on the amount of ligands and metal present is exerted through specific metal-responsive regulators able to induce the synthesis of the right amount of ligands (essentially metal binding proteins), import and efflux proteins. These systems are adapted to establish the metal-protein equilibria compatible with the formation of the right metalloprotein complexes. Understanding this complex network of interactions is central to the understanding of metal metabolism for the synthesis of metalloenzymes, a key topic in the Rhizobium-legume symbiosis. In the case of the Rhizobium leguminosarum bv viciae (Rlv) UPM791 -Pisum sativum symbiotic system, the concentration of nickel in the plant nutrient solution is a limiting factor for hydrogenase expression, and provision of high amounts of this element to the plant nutrient solution is required to ensure optimal levels of enzyme synthesis (Brito et al., 1994).

Enriched mannose glycosylation contributes to Act d 2 allergenicity.

Allergens are responsible for the Th2 response in patients as part of complex mixtures of proteins, fatty acids and other molecules. Plant allergens have hitherto been included in several protein families that share no common biochemical features. Their physical, biochemical and immunological characteristics have been widely studied, but no definite conclusion has been reached about what makes a protein an allergen. N-glycosylation is characteristic of plant allergen sources but is not present in mammals.

Emergencia y convergencia de las corrientes urbanísticas alternativas al desarrollo disperso. Europa y los EE.UU. 1980/2010

La presente tesis doctoral identifica el reciente fenómeno de la emergenciai de corrientes urbanísticas que actúan en la periferia urbana a partir de una concepción del diseño urbano que propugna modelos más compactos, a escala humana, de carácter integral y sostenible, como alternativa al desarrollo disperso y difusoii que caracteriza en gran medida a la ciudad contemporánea. Se develan las diferencias de origen y las coincidencias entre las distintas líneas de pensamiento que definen a estas emergentes corrientes alternativas, situándolas dentro de determinados enfoques planteados en la presente tesis, y demostrando con ello, las progresivas áreas de convergencia que permiten su ordenamiento como fenómeno histórico común. Estas distintas líneas de pensamiento, que derivan en las corrientes urbanísticas alternativas, se manifiestan primeramente como reacción a las operaciones modernistas de la posguerra, pero crecientemente expresan una visión contestataria a la expansión urbana descontrolada iii, de bajas densidades, zonificación excluyente y dependiente del automóvil; modelo asociado a las autopistas urbanas, los llamados nuevos artefactos urbanos y las grandes parcelas destinadas a proyectos habitacionales. Una realidad expresada en variados contextos en el ámbito de la globalización económica y cultural que, en gran medida, se singulariza como responsable de las profundas transformaciones urbanas, de la consecuente gradual pérdida de habitabilidad en las ciudades y del impacto sobre el medio natural; cuestión a tratar en el “Marco conceptual” referido al contexto y problema de la tesis. Se estudian los planteamientos fundamentales que postulan estas corrientes alternativas en el contexto de la expansión urbana horizontal, con el fin de identificar las distintas vertientes o líneas existentes, de establecer sus orígenes, enfoques, vínculos y alcances, permitiendo con ello caracterizar el fenómeno en sí desde una visión original e integradora. Estas corrientes a tratar han surgido en diversos momentos y con diversas particularidades, pero con mayor intensidad, articulación y visibilidad a partir de los años ochenta y especialmente en los noventa del siglo recién pasado, fundamentalmente en Europa y en los Estados Unidos de América, representando el “Cuerpo teórico” de esta tesis. Emergen en un escenario de creciente empoderamiento ciudadano, en tiempos de una mayor conciencia ambiental y social, y desde la convicción extendida de las limitaciones de un desarrollismo que, en términos del territorio físico, se manifiesta en el crecimiento urbano por extensión, incremental y desarticulado; tienen distintos idearios de origen, algunos en aparente contradicción o manifiesta oposición entre sí; se articulan desde diversos énfasis y surgen a partir de distintas aproximaciones. Para poder comprender el fenómeno de manera integral, se identifican y observan las tendencias contemporáneas y las correspondientes corrientes principales del diseño urbano; se indaga en sus discursos críticos y se ordenan en función de tres enfoques, los cuales reúnen los fundamentos esenciales de las distintas miradas críticas al modelo disperso y difuso: el enfoque neotradicional, el enfoque de la movilidad, y el enfoque ecológicoiv. Reconociendo la importancia de las operaciones de renovación urbana en la “ciudad intramuros” y siendo partícipes de estas intervenciones, las diferentes corrientes observadas desde los tres enfoques planteados, tienen un común denominador disciplinar en cuanto a su preocupación por generar actuaciones urbanas viables y practicables que causen un menor impacto sobre el territorio y que ofrezcan las condiciones para mejorar la habitabilidad en la ciudad, asumiendo el crecimiento hacia las periferias desde una aproximación alternativa a los modelos hoy predominantes. Las distintas corrientes, desde los particulares enfoques señalados, pretenden en síntesis, un desarrollo que refuerce el rol del diseño urbano, que promueva modelos más compactosv, de usos mixtos compatibles con la residencia y con espacios públicos de calidad, a una escala apropiada para la movilidad peatonal, favoreciendo de esta manera el uso del transporte público y velando consecuentemente por aquellos aspectos que mejoren las condiciones de sostenibilidad. En definitiva, el ideario de las corrientes caracterizadas en esta tesis como alternativas, se origina y se sostiene a partir de la convicción de situar a la disciplina del diseño urbano en su justa medida en el desarrollo contemporáneo, en el convencimiento de la relevancia del proyecto urbano en el ordenamiento del territorio y el crecimiento de las ciudades actuales. Una convergencia implícita a tratarse en la “Discusión de resultados”. La preocupación que reflejan las distintas corrientes estudiadas por el hábitat construido, en cuanto a su condición de acoger y estimular la dimensión humana de las ciudades, puede resumirse en una cita del arquitecto danés Jan Gehl, que interpreta a muchas de las líneas de pensamiento que se abordan en esta tesis, en cuanto al deseo de crear mejores ciudades: “Aspiramos generar ciudades animadas, saludables, atractivas, sostenibles y seguras, con el propósito de mejorar la calidad de vida de la gente”. ABSTRACT This Ph.D thesis identifies the recent phenomenon of the emergence of alternative urban design currents in the city edge, that focus on a more compact, human-scale oriented, comprehensive and sustainable urban design as an alternative to the overwhelming advance of sprawl that largely characterizes the contemporary city. It singles out the differences in origin, as well as the similarities drawn from the different lines of thought that define these emergent alternative currents, placing them within certain approaches proposed in this thesis, and thereby demonstrating the progressive areas of convergence that allow to arrange them as a common historical phenomenon. Indeed, the different lines of thought that drift towards these alternative urbanistic currents, first appear as a reaction to the post- World War II Modernist housing projects, and increasingly more so as a response to urban sprawl; an ever expanding phenomemnon expressed in different contexts within the economic and cultural globalization, largely singled out as being responsible for the deep urban transformations, the consequent gradual loss of livability and the impact on natural environment, setting the “Conceptual framework” of this thesis. Within the context of urban sprawl, the fundamental principles of these alternative currents are studied to establish their origins, approaches, linkages and scope, in order to zero in on the various aspects or existing lines and thereby allowing the identification of the phenomenon from an original and inclusive vision. The alternative currents to be dealt with, emerged at different times and with diverse characteristics, nonetheless it is in the eighties and especially during the nineties, mainly in Europe and the United States, where they appear with greater intensity, coordination and visibility, representing the “Theoretical body” of this thesis. The above mentioned currents arise in a scenario of increasing citizen empowerment in times of growing environmental and social awareness, along with the widespread conviction of the limitations of a quantitative development expressed as a physical manifestation in urban sprawl. These alternative currents have a different philosophy in origin, some are in apparent contradiction or in definite opposition, being organized from different approaches and emphases. To comprehend this phenomenon, it is necessary to identify and analize the contemporary trends and the main currents of urban design, inquiring and arranging their critical discourses according to three approaches that meet the essential foundations of the various critical perspectives of urban sprawl: the neo-traditional approach, the mobility approach, the ecological approach. Acknowledging the importance of urban renovation in the “Inner City”, and being partakers of these interventions, the different currents identified from these three approaches, concur in their concern for the development of viable and workable alternatives to urban sprawl; models that cause a lower impact on the territory, whilst improving livability in the city. The different currents recognized within the above mentioned approaches, advocate in brief, for a development that strengthens the role of urban design, that encourages more compact models, mixed-uses, and quality public spaces, considering the human scale and walkability; thereby increasing public transport and promoting consequently, the conditions for sustainable development. Ultimately, the philosophy of the so called alternative currents, is based on the belief of placing urban design as a fundamental discipline in contemporary urban development. The concern for the built habitat reflected by the various currents studied, as of their condition to accept and stimulate the human dimension of the city, can be summed up in a quote from Danish architect Jan Gehl, who represents many of the lines of thought addressed, in the belief of creating better cities: “We aspire to create cities that are lively, healthy, attractive, sustainable and safe-and thereby improve people’s quality of life”.