15 resultados para Pitimbu River Watershed. Urban growth. Urban Modeling. Cellular Automata. Sleuth
em Universidad Politécnica de Madrid
Resumo:
In this work, the algebraic properties of the local transition functions of elementary cellular automata (ECA) were analysed. Specifically, a classification of such cellular automata was done according to their algebraic degree, the balancedness, the resiliency, nonlinearity, the propagation criterion and the existence of non-zero linear structures. It is shown that there is not any ECA satisfying all properties at the same time.
Resumo:
Estudio de la dinmica de una poblacin donde los individuos son contribuyentes (pagadores de impuestos) o no mediante un autmata celular 2D
Resumo:
The Agent-Based Modelling and simulation (ABM) is a rather new approach for studying complex systems withinteracting autonomous agents that has lately undergone great growth in various fields such as biology, physics, social science, economics and business. Efforts to model and simulate the highly complex cement hydration process have been made over the past 40 years, with the aim of predicting the performance of concrete and designing innovative and enhanced cementitious materials. The ABM presented here - based on previous work - focuses on the early stages of cement hydration by modelling the physical-chemical processes at the particle level. The model considers the cement hydration process as a time and 3D space system, involving multiple diffusing and reacting species of spherical particles. Chemical reactions are simulated by adaptively selecting discrete stochastic simulation for the appropriate reaction, whenever that is necessary. Interactions between particles are also considered. The model has been inspired by reported cellular automata?s approach which provides detailed predictions of cement microstructure at the expense of significant computational difficulty. The ABM approach herein seeks to bring about an optimal balance between accuracy and computational efficiency.
Deforestacin y Prdida de hbitat en Bosques de montaa en la Cuenca alta del Ro Zamora (Loja, Ecuador)
Resumo:
Los bosques hmedos de montaa se encuentran reconocidos como uno de los ecosistemas ms amenazados en el mundo, llegando inclusive a ser considerado como un hotspot por su alta diversidad y endemismo. La acelerada prdida de cobertura vegetal de estos bosques ha ocasionado que, en la actualidad, se encuentren restringidos a una pequea fraccin de su rea de distribucin histrica. Pese a esto, los estudios realizados sobre cual es efecto de la deforestacin, fragmentacin, cambios de uso de suelo y su efecto en las comunidades de plantas presentes en este tipo de vegetacin an son muy escuetos, en comparacin a los realizados con sus similares amaznicos. En este trabajo, el cual se encuentra dividido en seis captulos, abordaremos los siguientes objetivos: a) Comprender cul es la dinmica que han seguido los diferentes tipos de bosques montanos andinos de la cuenca del Rio Zamora, Sur de Ecuador durante entre 1976 y 2002. b) Proveer de evidencia de las tasas de deforestacin y fragmentacin de todos los tipos diferentes de bosques montanos andinos presentes en la cuenca del Rio Zamora, Sur de Ecuador entre 1976 y 2002. c) Determinar qu factores inducen a la fragmentacin de bosques de montaa en la cuenca alta del ro Zamora entre 1976 y 2002. d) Determinar cules son y cmo afectan los factores ambientales y socioeconmicos a la dinmica de la deforestacin y regeneracin (prdida y recuperacin del hbitat) sufrida por los bosques de montaa dentro de la zona de estudio y e) Determinar si la deforestacin y fragmentacin actan sobre la diversidad y estructura de las comunidades de tres tipos de organismos (comunidades de rboles, comunidades de lquenes epfitos y comunidades de hepticas epfitas). Este estudio se centr en el cuenca alta del ro Zamora, localizada al sur de Ecuador entre las coordenadas 3 00 53 a 4 20 24.65 de latitud sur y 79 4958 a 78 35 38 de longitud oeste, que cubre alrededor de 4300 km2 de territorio situado entre las capitales de las provincias de Loja y Zamora-Chinchipe. Con objeto de predecir la dinmica futura de la deforestacin en la regin de Loja y cmo se vern afectados los diferentes tipos de hbitat, as como para detectar los factores que ms influyen en dicha dinmica, se han construido modelos basados en la historia de la deforestacin derivados de fotografas areas e imgenes satelitales de tres fechas (1976, 1989 y 2002). La cuantificacin de la deforestacin se realiz mediante la tasa de inters compuesto y para la caracterizacin de la configuracin espacial de los fragmentos de bosque nativo se calcularon ndices de paisaje los cuales fueron calculados utilizando el programa Fragstats 3.3. Se ha clasificado el recubrimiento del terreno en forestal y no forestal y se ha modelado su evolucin temporal con Modelos Lineales Generalizados Mixtos (GLMM), empleando como variables explicativas tanto variables ambientales espacialmente explcitas (altitud, orientacin, pendiente, etc) como antrpicas (distancia a zonas urbanizadas, deforestadas, caminos, entre otras). Para medir el efecto de la deforestacin sobre las comunidades modelo (de rboles, lquenes y hepticas) se monitorearon 11 fragmentos de vegetacin de distinto tamao: dos fragmentos de ms de cien hectreas, tres fragmentos de entre diez y noventa ha y seis fragmentos de menos de diez hectreas. En ellos se instalaron un total de 38 transectos y 113 cuadrantes de 20 x 20 m a distancias que se alejaban progresivamente del borde en 10, 40 y 80 m. Nuestros resultados muestran una tasa media anual de deforestacin del 1,16% para todo el perodo de estudio, que el tipo de vegetacin que ms alta tasa de destruccin ha sufrido, es el pramo herbceo, con un 2,45% anual. El anlisis de los patrones de fragmentacin determin un aumento en 2002 de ms del doble de fragmentos presentes en 1976, lo cual se repite en el anlisis del ndice de densidad promedio. El ndice de proximidad media entre fragmentos muestra una reduccin progresiva de la continuidad de las reas forestadas. Si bien las formas de los fragmentos se han mantenido bastante similares a lo largo del perodo de estudio, la conectividad entre estos ha disminuido en un 84%. Por otro lado, de nuestros anlisis se desprende que las zonas con mayor probabilidad de deforestarse son aquellas que estn cercanas a zonas previamente deforestadas; la cercana a las vas tambin influye significativamente en la deforestacin, causando un efecto directo en la composicin y estructura de las comunidades estudiadas, que en el caso de los rboles viene mediado por el tamao del fragmento y en el caso del componente epfito (hepticas y lquenes), viene mediado tanto por el tamao del fragmento como por la distancia al borde del mismo. Se concluye la posibilidad de que, de mantenerse esta tendencia, este tipo de bosques desaparecer en corto tiempo y los servicios ecosistmicos que prestan, se vern seriamente comprometidos. ABSTRACT Mountain rainforests are recognized as one of the most threatened ecosystems in the world, and have even come to be considered as a hotspot due to their high degree of diversity and endemism. The accelerated loss of plant cover of these forests has caused them to be restricted today to a small fraction of their area of historic distribution. In spite of this, studies done on the effect of deforestation, fragmentation, changes in soil use and their effect on the plant communities present in this type of vegetation are very brief compared to those done on their analogues in the Amazon region. In this study, which is divided into six chapters, we will address the following objectives: a) To understand what the dynamic followed by the different types of Andean mountain forests in the Zamora River watershed of southern Ecuador has been between 1976 and 2002. b) To provide evidence of the rates of deforestation and fragmentation of all the different types of Andean mountain forests existing in the upper watershed of the Zamora River between 1976 and 2002. c) To determine the factors that induces fragmentation of all different types of Andean mountain forests existing in the upper watershed of the Zamora River between 1976 and 2002. d) To determine what the environmental and anthropogenic factors are driving the dynamic of deforestation and regeneration (loss and recuperation of the habitat) suffered by the mountain forests in the area of the study and e) To determine if the deforestation and fragmentation act upon the diversity and structure of three model communities: trees, epiphytic lichens and epiphytic liverworts. This study is centered on the upper Zamora River watershed, located in southern Ecuador between 3 00 53 and 4 20 24.65 south latitude and 79 49 58 to 78 35 38 west longitude, and covers around 4,300 km2 of territory located between Loja and Zamora-Chinchipe provinces. For the purpose of predicting the future dynamic of deforestation in the Loja region and how different types of habitats will be affected, as well as detecting the environmental and socioeconomic factors that influence landscape dynamics, models were constructed based on deforestation history, derived from aerial photographs and satellite images for three dates (1976, 1989 and 2002). Quantifying the deforestation was done using the compound interest rate; to characterize the spatial configuration of fragments of native forest, landscape indices were calculated with Fragstats 3.3 program. Land cover was classified as forested and not forested and its evolution over time was modeled with Generalized Linear Mixed Models (GLMM), using spatially explicit environmental variables (altitude, orientation, slope, etc.) as well as anthropic variables (distance to urbanized, deforested areas and roads, among others) as explanatory variables. To measure the effects of fragmentation on three types of model communities (forest trees and epiphytic lichen and liverworts), 11 vegetation fragments of different sizes were monitored: two fragments of more than one hundred hectares, three fragments of between ten and ninety ha and six fragments of fewer than ten hectares . In these fragments, a total of 38 transects and 113 20 x 20 m quadrats were installed at distances that progressively moved away from the edge of the fragment by 10, 40 and 80 m. Our results show an average annual rate of deforestation of 1.16% for the entire period of the study, and that the type of vegetation that suffered the highest rate of destruction was grassy paramo, with an annual rate of 2.45%. The analysis of fragmentation patterns determined the number of fragments in 2002 more than doubled the number of fragments present in 1976, and the same occurred for the average density index. The variation of the average proximity index among fragments showed a progressive reduction of the continuity of forested areas. Although fragment shapes have remained quite similar over the period of the study, connectivity among them has diminished by 84%. On the other hand, it emerged from our analysis that the areas of greatest probability of deforestation were those that are close to previously deforested areas; proximity to roads also significantly favored the deforestation causing a direct effect on the composition of our model communities, that in the case of forest trees is determined by the size of the fragment, and in the case of the epiphyte communities (liverworts and lichens), is determined, by the size of the fragment as well as the distance to edge. A subject under discussion is the possibility that if this tendency continues, this type of forest will disappear in a short time, and the ecological services it provides, will be seriously endangered.
Resumo:
This paper introduces APA (?Artificial Prion Assembly?): a pattern recognition system based on artificial prion crystalization. Specifically, the system exhibits the capability to classify patterns according to the resulting prion self- assembly simulated with cellular automata. Our approach is inspired in the biological process of proteins aggregation, known as prions, which are assembled as amyloid fibers related with neurodegenerative disorders.
Resumo:
Processes of founding and expanding cities in coastal areas have undergone great changes over time driven by environmental conditions. Coastal settlements looked for places above flood levels and away from swamps and other wetlands whenever possible. As populations grew, cities were extending trying to avoid low and wet lands. No city has been able to limit its growth. The risk of flooding can never be eliminated, but only reduced to the extent possible. Flooding of coastal areas is today dramatically attributed to eustasic sea level rise caused by global climate change. This can be inaccurate. Current climate change is generating an average sea level upward trend, but other regional and local factors result in this trend being accentuated in some places or attenuated, and even reversed, in others. Then, the intensity and frequency of coastal flooding around the planet, although not so much as a unique result of this general eustasic elevation, but rather of the superposition of marine and crustal dynamic elements, the former also climate-related, which give rise to a temporary raising in average sea level in the short term. Since the Little Ice Age the planet has been suffering a global warming change leading to sea level rise. The idea of being too obeying to anthropogenic factors may be attributed to Arrhenius (1896), though it is of much later highlight after the sixties of the last century. Never before, the human factor had been able of such an influence on climate. However, other types of changes in sea levels became apparent, resulting from vertical movements of the crust, modifications of sea basins due to continents fracturing, drifting and coming together, or to different types of climate patterns. Coastal zones are then doubly susceptible to floods. Precipitation immediately triggers pluvial flooding. If it continues upland or when snow and glaciers melt eventually fluvial flooding can occur. The urban development presence represents modifying factors. Additional interference is caused by river and waste water drainage systems. Climate also influences sea levels in coastal areas, where tides as well as the structure and dynamic of the geoid and its crust come into play. From the sea, waters can flood and break or push back berms and other coastline borders. The sea level, controlling the mouth of the main channel of the basin's drainage system, is ultimately what governs flood levels. A temporary rise in sea level acts as a dam at the mouth. Even in absence of that global change, so, floods are likely going to increase in many urban coastal areas. Some kind of innovative methodologies and practices should be needed to get more flood resilience cities
Resumo:
The geochemical fingerprint of sediment retrieved from the banks of the River Manzanares as it passes through the City of Madrid is presented here. The river collects the effluent water from several Waste Water Treatment (WWT) plants in and around the city, such that, at low flows, up to 60% of the flow has been treated. A total of 18 bank-sediment cores were collected along the course of the river, down to its confluence with the Jarama river, to the southeast of Madrid. Trace and major elements in each sample were extracted following a double protocol: (a) Total digestion with HNO3, HClO4 and HF; (b) Weak digestion with sodium acetate buffered to pH=5 with acetic acid, under constant stirring. The digests thus obtained were subsequently analysed by ICP-AES, except for Hg which was extracted with aqua regia and sodium chloride-hydroxylamine sulfate, and analysed by Cold Vapour-AAS. X-ray diffraction was additionally employed to determine the mineralogical composition of the samples. Uni- and multivariate analyses of the chemical data reveal the influence of Madrid on the geochemistry of Manzanares' sediments, clearly manifested by a marked increase in the concentration of typically urban elements Ag, Cr, Cu, Pb and Zn, downstream of the intersection of the river with the city's perimeter. The highest concentrations of these elements appear to be associated with illegal or accidental dumping of waste materials, and with the uncontrolled incorporation of untreated urban runoff to the river. The natural matrix of the sediment is characterised by fairly constant concentrations of Ce, La and Y, whereas changes in the lithology intersected by the river cause corresponding variations in CaMg and AlNa contents. In the final stretch of the river, the presence of carbonate materials seems to exert a strong geochemical control on the amount of Zn and, to a lesser extent, Cu immobilised in the sediments. This fact suggests that a variable but significant proportion of both elements may be susceptible to reincorporation in the aqueous phase under realistic environmental conditions.
Resumo:
Urban areas benefit from significant improvements in accessibility when a new high speed rail (HSR) project is built. These improvements, which are due mainly to a rise in efficiency, produce locational advantagesand increase the attractiveness of these cities, thereby possibly enhancing their competitivenessand economic growth. However, there may be equity issues at stake, as the main accessibility benefits are primarily concentrated in urban areas with a HSR station, whereas other locations obtain only limited benefits. HSR extensions may contribute to an increase in spatial imbalance and lead to more polarized patterns of spatial development. Procedures for assessing the spatial impacts of HSR must therefore follow a twofold approach which addresses issues of both efficiency and equity. This analysis can be made by jointly assessing both the magnitude and distribution of the accessibility improvements deriving from a HSR project. This paper describes an assessment methodology for HSR projects which follows this twofold approach. The procedure uses spatial impact analysis techniques and is based on the computation of accessibility indicators, supported by a Geographical Information System (GIS). Efficiency impacts are assessed in terms of the improvements in accessibility resulting from the HSR project, with a focus on major urban areas; and spatial equity implications are derived from changes in the distribution of accessibility values among these urban agglomerations.
Resumo:
The need of decarbonization of urban mobility is one of the main priorities for all countries to achieve greenhouse gas (GHG) emissions reduction targets. In general, the transport modes which have experienced the most growth in recent years tend to be the most polluting. Most efforts have been focused on the vehicle efficiency improvements and vehicle fleet renewal; nevertheless more emphasis should be placed on strategies related to the management of urban mobility and modal share. Research of individual travel which analyzes CO2 emissions and car and public transport share in daily mobility will enable better assessments of the potential of urban mobility measures introduced to limit GHG emissions produced by transport in cities. This paper explores the sustainability impacts of daily mobility in Spain using data from two National Travel Surveys (NTSs) (2000 and 2006) and includes a method by which to estimate the CO2 emissions associated with each journey and each surveyed individual. The results demonstrate that in the 2000 to 2006 period, there has been an increase in daily mobility which has led to a 17% increase in CO2 emissions. When separated by transport mode, cars prove to be the main contributor to that increase, followed by public transport. More focus should be directed toward modal shift strategies which not only take the number of journeys into account but also consider distance. The contributions of this paper have potential applications in the assessment of current and future urban transport policies.
Resumo:
The need to decarbonize urban mobility is one of the main motivations for all countries to achieve reduction targets for greenhouse gas (GHG) emissions. In general, the transport modes that have experienced the most growth in recent years tend to be the most polluting. Most efforts have focused on improvements in vehicle efficiency and on the renewal of vehicle fleets; more emphasis should be placed on strategies related to the management of urban mobility and modal share. Research of individual travel that analyzes carbon dioxide (CO2) emissions and car and public transport share in daily mobility will enable better assessments of the potential of urban mobility measures introduced to limit GHG emissions produced by transport in cities. The climate change impacts of daily mobility in Spain are explored with data from two national travel surveys in 2000 and 2006, and a method for estimating the CO2 emissions associated with each journey and each surveyed individual is provided. The results demonstrate that from 2000 to 2006, daily mobility has increased and has led to a 17% increase in CO2 emissions. When these results are separated by transport mode, cars prove to be the main contributor to that increase, followed by public transport. More focus should be directed toward modal shift strategies, which take into account not only the number of journeys but also the distance traveled. These contributions have potential applications in the assessment of current and future urban transport policies related to low-carbon urban transportation.
Resumo:
The Web of Data currently comprises ? 62 billion triples from more than 2,000 different datasets covering many fields of knowledge3. This volume of structured Linked Data can be seen as a particular case of Big Data, referred to as Big Semantic Data [4]. Obviously, powerful computational configurations are tradi- tionally required to deal with the scalability problems arising to Big Semantic Data. It is not surprising that this ?data revolution? has competed in parallel with the growth of mobile computing. Smartphones and tablets are massively used at the expense of traditional computers but, to date, mobile devices have more limited computation resources. Therefore, one question that we may ask ourselves would be: can (potentially large) semantic datasets be consumed natively on mobile devices? Currently, only a few mobile apps (e.g., [1, 9, 2, 8]) make use of semantic data that they store in the mobile devices, while many others access existing SPARQL endpoints or Linked Data directly. Two main reasons can be considered for this fact. On the one hand, in spite of some initial approaches [6, 3], there are no well-established triplestores for mobile devices. This is an important limitation because any po- tential app must assume both RDF storage and SPARQL resolution. On the other hand, the particular features of these devices (little storage space, less computational power or more limited bandwidths) limit the adoption of seman- tic data for different uses and purposes. This paper introduces our HDTourist mobile application prototype. It con- sumes urban data from DBpedia4 to help tourists visiting a foreign city. Although it is a simple app, its functionality allows illustrating how semantic data can be stored and queried with limited resources. Our prototype is implemented for An- droid, but its foundations, explained in Section 2, can be deployed in any other platform. The app is described in Section 3, and Section 4 concludes about our current achievements and devises the future work.
Resumo:
El programa Europeo HORIZON2020 en Futuras Ciudades Inteligentes establece como objetivo que el 20% de la energa elctrica sea generada a partir de fuentes renovables. Este objetivo implica la necesidad de potenciar la generacin de energa elica en todos los mbitos. La energa elica reduce drsticamente las emisiones de gases de efecto invernadero y evita los riesgos geo-polticos asociados al suministro e infraestructuras energticas, as como la dependencia energtica de otras regiones. Adems, la generacin de energa distribuida (generacin en el punto de consumo) presenta significativas ventajas en trminos de elevada eficiencia energtica y estimulacin de la economa. El sector de la edificacin representa el 40% del consumo energtico total de la Unin Europea. La reduccin del consumo energtico en este rea es, por tanto, una prioridad de acuerdo con los objetivos "20-20-20" en eficiencia energtica. La Directiva 2010/31/EU del Parlamento Europeo y del Consejo de 19 de mayo de 2010 sobre el comportamiento energtico de edificaciones contempla la instalacin de sistemas de suministro energtico a partir de fuentes renovables en las edificaciones de nuevo diseo. Actualmente existe una escasez de conocimiento cientfico y tecnolgico acerca de la geometra ptima de las edificaciones para la explotacin de la energa elica en entornos urbanos. El campo tecnolgico de estudio de la presente Tesis Doctoral es la generacin de energa elica en entornos urbanos. Especficamente, la optimization de la geometra de las cubiertas de edificaciones desde el punto de vista de la explotacin del recurso energtico elico. Debido a que el flujo del viento alrededor de las edificaciones es exhaustivamente investigado en esta Tesis empleando herramientas de simulacin numrica, la mecnica de fluidos computacional (CFD en ingls) y la aerodinmica de edificaciones son los campos cientficos de estudio. El objetivo central de esta Tesis Doctoral es obtener una geometra de altas prestaciones (u ptima) para la explotacin de la energa elica en cubiertas de edificaciones de gran altura. Este objetivo es alcanzado mediante un anlisis exhaustivo de la influencia de la forma de la cubierta del edificio en el flujo del viento desde el punto de vista de la explotacin energtica del recurso elico empleando herramientas de simulacin numrica (CFD). Adicionalmente, la geometra de la edificacin convencional (edificio prismtico) es estudiada, y el posicionamiento adecuado para los diferentes tipos de aerogeneradores es propuesto. La compatibilidad entre el aprovechamiento de las energas solar fotovoltaica y elica tambin es analizado en este tipo de edificaciones. La investigacin prosigue con la optimizacin de la geometra de la cubierta. La metodologa con la que se obtiene la geometra ptima consta de las siguientes etapas: - Verificacin de los resultados de las geometras previamente estudiadas en la literatura. Las geometras bsicas que se someten a examen son: cubierta plana, a dos aguas, inclinada, abovedada y esfrica. - Anlisis de la influencia de la forma de las aristas de la cubierta sobre el flujo del viento. Esta tarea se lleva a cabo mediante la comparacin de los resultados obtenidos para la arista convencional (esquina sencilla) con un parapeto, un voladizo y una esquina curva. - Anlisis del acoplamiento entre la cubierta y los cerramientos verticales (paredes) mediante la comparacin entre diferentes variaciones de una cubierta esfrica en una edificacin de gran altura: cubierta esfrica estudiada en la literatura, cubierta esfrica integrada geomtricamente con las paredes (planta cuadrada en el suelo) y una cubierta esfrica acoplada a una pared cilindrica. El comportamiento del flujo sobre la cubierta es estudiado tambin considerando la posibilidad de la variacin en la direccin del viento incidente. - Anlisis del efecto de las proporciones geomtricas del edificio sobre el flujo en la cubierta. - Anlisis del efecto de la presencia de edificaciones circundantes sobre el flujo del viento en la cubierta del edificio objetivo. Las contribuciones de la presente Tesis Doctoral pueden resumirse en: - Se demuestra que los modelos de turbulencia RANS obtienen mejores resultados para la simulacin del viento alrededor de edificaciones empleando los coeficientes propuestos por Crespo y los propuestos por Bechmann y Srensen que empleando los coeficientes estndar. - Se demuestra que la estimacin de la energa cintica turbulenta del flujo empleando modelos de turbulencia RANS puede ser validada manteniendo el enfoque en la cubierta de la edificacin. - Se presenta una nueva modificacin del modelo de turbulencia Durbin k e que reproduce mejor la distancia de recirculacin del flujo de acuerdo con los resultados experimentales. - Se demuestra una relacin lineal entre la distancia de recirculacin en una cubierta plana y el factor constante involucrado en el clculo de la escala de tiempo de la velocidad turbulenta. Este resultado puede ser empleado por la comunidad cientfica para la mejora del modelado de la turbulencia en diversas herramientas computacionales (OpenFOAM, Fluent, CFX, etc.). - La compatibilidad entre las energas solar fotovoltaica y elica en cubiertas de edificaciones es analizada. Se demuestra que la presencia de los mdulos solares provoca un descenso en la intensidad de turbulencia. - Se demuestran conflictos en el cambio de escala entre simulaciones de edificaciones a escala real y simulaciones de modelos a escala reducida (tnel de viento). Se demuestra que para respetar las limitaciones de similitud (nmero de Reynolds) son necesarias mediciones en edificaciones a escala real o experimentos en tneles de viento empleando agua como fluido, especialmente cuando se trata con geometras complejas, como es el caso de los mdulos solares. - Se determina el posicionamiento ms adecuado para los diferentes tipos de aerogeneradores tomando en consideracin la velocidad e intensidad de turbulencia del flujo. El posicionamiento de aerogeneradores es investigado en las geometras de cubierta ms habituales (plana, a dos aguas, inclinada, abovedada y esfrica). - Las formas de aristas ms habituales (esquina, parapeto, voladizo y curva) son analizadas, as como su efecto sobre el flujo del viento en la cubierta de un edificio de gran altura desde el punto de vista del aprovechamiento elico. - Se propone una geometra ptima (o de altas prestaciones) para el aprovechamiento de la energa elica urbana. Esta optimizacin incluye: verificacin de las geometras estudiadas en el estado del arte, anlisis de la influencia de las aristas de la cubierta en el flujo del viento, estudio del acoplamiento entre la cubierta y las paredes, anlisis de sensibilidad del grosor de la cubierta, exploracin de la influencia de las proporciones geomtricas de la cubierta y el edificio, e investigacin del efecto de las edificaciones circundantes (considerando diferentes alturas de los alrededores) sobre el flujo del viento en la cubierta del edificio objetivo. Las investigaciones comprenden el anlisis de la velocidad, la energa cintica turbulenta y la intensidad de turbulencia en todos los casos. ABSTRACT The HORIZON2020 European program in Future Smart Cities aims to have 20% of electricity produced by renewable sources. This goal implies the necessity to enhance the wind energy generation, both with large and small wind turbines. Wind energy drastically reduces carbon emissions and avoids geo-political risks associated with supply and infrastructure constraints, as well as energy dependence from other regions. Additionally, distributed energy generation (generation at the consumption site) offers significant benefits in terms of high energy efficiency and stimulation of the economy. The buildings sector represents 40% of the European Union total energy consumption. Reducing energy consumption in this area is therefore a priority under the "20-20-20" objectives on energy efficiency. The Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings aims to consider the installation of renewable energy supply systems in new designed buildings. Nowadays, there is a lack of knowledge about the optimum building shape for urban wind energy exploitation. The technological field of study of the present Thesis is the wind energy generation in urban environments. Specifically, the improvement of the building-roof shape with a focus on the wind energy resource exploitation. Since the wind flow around buildings is exhaustively investigated in this Thesis using numerical simulation tools, both computational fluid dynamics (CFD) and building aerodynamics are the scientific fields of study. The main objective of this Thesis is to obtain an improved (or optimum) shape of a high-rise building for the wind energy exploitation on the roof. To achieve this objective, an analysis of the influence of the building shape on the behaviour of the wind flow on the roof from the point of view of the wind energy exploitation is carried out using numerical simulation tools (CFD). Additionally, the conventional building shape (prismatic) is analysed, and the adequate positions for different kinds of wind turbines are proposed. The compatibility of both photovoltaic-solar and wind energies is also analysed for this kind of buildings. The investigation continues with the buildingroof optimization. The methodology for obtaining the optimum high-rise building roof shape involves the following stages: - Verification of the results of previous building-roof shapes studied in the literature. The basic shapes that are compared are: flat, pitched, shed, vaulted and spheric. - Analysis of the influence of the roof-edge shape on the wind flow. This task is carried out by comparing the results obtained for the conventional edge shape (simple corner) with a railing, a cantilever and a curved edge. - Analysis of the roof-wall coupling by testing different variations of a spherical roof on a high-rise building: spherical roof studied in the litera ture, spherical roof geometrically integrated with the walls (squared-plant) and spherical roof with a cylindrical wall. The flow behaviour on the roof according to the variation of the incident wind direction is commented. - Analysis of the effect of the building aspect ratio on the flow. - Analysis of the surrounding buildings effect on the wind flow on the target building roof. The contributions of the present Thesis can be summarized as follows: - It is demonstrated that RANS turbulence models obtain better results for the wind flow around buildings using the coefficients proposed by Crespo and those proposed by Bechmann and S0rensen than by using the standard ones. - It is demonstrated that RANS turbulence models can be validated for turbulent kinetic energy focusing on building roofs. - A new modification of the Durbin k e turbulence model is proposed in order to obtain a better agreement of the recirculation distance between CFD simulations and experimental results. - A linear relationship between the recirculation distance on a flat roof and the constant factor involved in the calculation of the turbulence velocity time scale is demonstrated. This discovery can be used by the research community in order to improve the turbulence modeling in different solvers (OpenFOAM, Fluent, CFX, etc.). - The compatibility of both photovoltaic-solar and wind energies on building roofs is demonstrated. A decrease of turbulence intensity due to the presence of the solar panels is demonstrated. - Scaling issues are demonstrated between full-scale buildings and windtunnel reduced-scale models. The necessity of respecting the similitude constraints is demonstrated. Either full-scale measurements or wind-tunnel experiments using water as a medium are needed in order to accurately reproduce the wind flow around buildings, specially when dealing with complex shapes (as solar panels, etc.). - The most adequate position (most adequate roof region) for the different kinds of wind turbines is highlighted attending to both velocity and turbulence intensity. The wind turbine positioning was investigated for the most habitual kind of building-roof shapes (flat, pitched, shed, vaulted and spherical). - The most habitual roof-edge shapes (simple edge, railing, cantilever and curved) were investigated, and their effect on the wind flow on a highrise building roof were analysed from the point of view of the wind energy exploitation. - An optimum building-roof shape is proposed for the urban wind energy exploitation. Such optimization includes: state-of-the-art roof shapes test, analysis of the influence of the roof-edge shape on the wind flow, study of the roof-wall coupling, sensitivity analysis of the roof width, exploration of the aspect ratio of the building-roof shape and investigation of the effect of the neighbouring buildings (considering different surrounding heights) on the wind now on the target building roof. The investigations comprise analysis of velocity, turbulent kinetic energy and turbulence intensity for all the cases.
Resumo:
En las ltimas tres dcadas, las dinmicas de restructuracin econmica a nivel global han redefinido radicalmente el papel de las ciudades. La transicin del keynesianismo al neoliberalismo ha provocado un cambio en las polticas urbanas de los gobiernos municipales, que han abandonado progresivamente las tareas de regulacin y redistribucin para centrarse en la promocin del crecimiento econmico y la competitividad. En este contexto, muchas voces crticas han sealado que la regeneracin urbana se ha convertido en un vehculo de extraccin de valor de la ciudad y est provocando la expulsin de los ciudadanos ms vulnerables. Sin embargo, la regeneracin de reas consolidadas supone tambin una oportunidad de mejora de las condiciones de vida de la poblacin residente, y es una poltica necesaria para controlar la expansin de la ciudad y reducir las necesidades de desplazamiento, promoviendo as ciudades ms sostenibles. Partiendo de la hiptesis de que la gobernanza de los procesos de regeneracin urbana es clave en el resultado final de las operaciones y determina el modelo de ciudad resultante, el objetivo de esta investigacin es verificar si la regeneracin urbana es necesariamente un mecanismo de extraccin de valor o si puede mejorar la calidad de vida en las ciudades a travs de la participacin de los ciudadanos. Para ello, propone un marco de anlisis del proceso de toma de decisiones en los planes de regeneracin urbana y su impacto en los resultados de los planes, tomando como caso de estudio la ciudad de Boston, que desde los aos 1990 trata de convertirse en una ciudad de los barrios, fomentando la participacin ciudadana al tiempo que se posiciona en la escena econmica global. El anlisis se centra en dos operaciones de regeneracin iniciadas a finales de los aos 1990. Por un lado, el caso de Jackson Square nos permite comprender el papel de la sociedad civil y el tercer sector en la regeneracin de los barrios ms desfavorecidos, en un claro ejemplo de urbanismo desde abajo (bottom-up planning). Por otro, la reconversin del frente martimo de South Boston para la construccin del Distrito de Innovacin nos acerca a las grandes operaciones de regeneracin urbana con fines de estmulo econmico, tradicionalmente vinculadas a los centros financieros (downtown) y dirigidas por las lites gubernamentales y econmicas (la growth machine) a travs de procesos ms tecnocrticos (top-down planning). La metodologa utilizada consiste en el anlisis cualitativo de los procesos de toma de decisiones y la relacin entre los agentes implicados, as como de la evaluacin de la implementacin de dichas decisiones y su influencia en el modelo urbano resultante. El anlisis de los casos permite afirmar que la gobernanza de los procesos de regeneracin urbana influye decisivamente en el resultado final de las intervenciones; sin embargo, la participacin de la comunidad local en la toma de decisiones no es suficiente para que el resultado de la regeneracin urbana contrarreste los efectos de la neoliberalizacin, especialmente si se limita a la fase de planeamiento y no se extiende a la fase de ejecucin, y si no est apoyada por una movilizacin poltica de mayor alcance que asegure una accin pblica redistributiva. Asimismo, puede afirmarse que los procesos de regeneracin urbana suponen una redefinicin del modelo de ciudad, dado que la eleccin de los espacios de intervencin tiene consecuencias sobre el equilibrio territorial de la ciudad. Los resultados de esta investigacin tienen implicaciones para la disciplina del planeamiento urbano. Por una parte, se confirma la vigencia del paradigma del urbanismo negociado, si bien bajo discursos de liderazgo pblico y sin apelacin al protagonismo del sector privado. Por otra parte, la planificacin colaborativa en un contexto de responsabilizacin de las organizaciones comunitarias puede desactivar la potencia poltica de la participacin ciudadana y servir como amortiguador hacia el gobierno local. Asimismo, la sustitucin del planeamiento general como instrumento de definicin de la ciudad futura por una planificacin oportunista basada en la actuacin en reas estratgicas que tiren del resto de la ciudad, no permite definir un modelo coherente y consensuado de la ciudad que se desea colectivamente, ni permite utilizar el planeamiento como mecanismo de redistribucin. ABSTRACT In the past three decades, the dynamics of global economic restructuring have radically redefined the role of cities. The transition from keynesianism to neoliberalism has caused a shift in local governments urban policies, which have progressively abandoned the tasks of regulation and redistribution to focus on promoting economic growth and competitiveness. In this context, many critics have pointed out that urban regeneration has become a vehicle for extracting value from the city and is causing the expulsion of the most vulnerable citizens. However, regeneration of consolidated areas is also an opportunity to improve the living conditions of the resident population, and is a necessary policy to control the expansion of the city and reduce the need for transportation, thus promoting more sustainable cities. Assuming that the governance of urban regeneration processes is key to the final outcome of the plans and determines the resulting city model, the goal of this research is to verify whether urban regeneration is necessarily a value extraction mechanism or if it can improve the quality of life in cities through citizens participation. It proposes a framework for analysis of decision-making in urban regeneration processes and their impact on the results of the plans, taking as a case study the city of Boston, which since the 1990s is trying to become a "city of neighborhoods", encouraging citizen participation, while seeking to position itself in the global economic scene. The analysis focuses on two redevelopment plans initiated in the late 1990s. The Jackson Square case allows us to understand the role of civil society and the third sector in the regeneration of disadvantaged neighborhoods, in a clear example of bottom-up planning. On the contrary, the conversion of the South Boston waterfront to build the Innovation District takes us to the big redevelopment efforts with economic stimulus goals, traditionally linked to downtowns and led by government and economic elites (the local growth machine) through more technocratic processes (top-down planning). The research is based on a qualitative analysis of the processes of decision making and the relationship between those involved, as well as the evaluation of the implementation of those decisions and their influence on the resulting urban model. The analysis suggests that the governance of urban regeneration processes decisively influences the outcome of interventions; however, community engagement in the decision-making process is not enough for the result of the urban regeneration to counteract the effects of neoliberalization, especially if it is limited to the planning phase and does not extend to the implementation of the projects, and if it is not supported by a broader political mobilization to ensure a redistributive public action. Moreover, urban regeneration processes redefine the urban model, since the choice of intervention areas has important consequences for the territorial balance of the city. The results of this study have implications for the discipline of urban planning. On the one hand, it confirms the validity of the "negotiated planning" paradigm, albeit under public leadership discourse and without a direct appeal to the leadership role of the private sector. On the other hand, collaborative planning in a context of "responsibilization" of community based organizations can deactivate the political power of citizen participation and serve as a "buffer" towards the local government. Furthermore, the replacement of comprehensive planning, as a tool for defining the city's future, by an opportunistic planning based on intervention in strategic areas that are supposed to induce change in the rest of the city, does not allow a coherent and consensual urban model that is collectively desired, nor it allows to use planning as a redistribution mechanism.
Resumo:
The urban microclimate plays an important role in building energy consumption and thermal comfort in outdoor spaces. Nowadays, cities need to increase energy efficiency, reduce pollutant emissions and mitigate the evident lack of sustainability. In light of this, attention has focused on the bioclimatic concepts use in the urban development. However, the speculative unsustainability of the growth model highlights the need to redirect the construction sector towards urban renovation using a bioclimatic approach. The public space plays a key role in improving the quality of todays cities, especially in terms of providing places for citizens to meet and socialize in adequate thermal conditions. Thermal comfort affects perception of the environment, so microclimate conditions can be decisive for the success or failure of outdoor urban spaces and the activities held in them. For these reasons, the main focus of this work is on the definition of bioclimatic strategies for existing urban spaces, based on morpho-typological components, urban microclimate conditions and comfort requirements for all kinds of citizens. Two case studies were selected in Madrid, in a social housing neighbourhood constructed in the 1970s based on Rational Architecture style. Several renovation scenarios were performed using a computer simulation process based in ENVI-met and diverse microclimate conditions were compared. In addition, thermal comfort evaluation was carried out using the Universal Thermal Climate Index (UTCI) in order to investigate the relationship between microclimate conditions and thermal comfort perception. This paper introduces the microclimate computer simulation process as a valuable support for decision-making for neighbourhood renovation projects in order to provide new and better solutions according to the thermal quality of public spaces and reducing energy consumption by creating and selecting better microclimate areas.
Resumo:
Physical and social transformation processes that take place in urban contexts with strong spatial growth and hardly any economic development frequently have significant adverse impacts for the affected people, which tend to be made invisible. This paper presents an analytical framework to explore different ways to approach urban transformation processes (supply side), their impacts on the set of needs of the community (demand side) and their consequences on the urban environment as a whole (context). The proposed method has been used to assess three actions related to the physical and social transformation of the largest self-made settlement in the city of Dakar, Senegal, during the 20052012 period. Research findings show how exogenous interests are privileged over the common good when the affected citizens are not effectively involved in decision-making processes.