Estudio num��rico de flujo turbulento cargado con part��culas s��lidas a trav��s de canales y tuber��as de secci��n variable

La presente Tesis Doctoral tiene como objetivo el estudio de flujo turbulento cargado con part��culas s��lidas a trav��s de canales y tuber��as de secci��n constante usando un enfoque Euleriano-Lagrangiano. El campo de flujo de la fase de transporte (aire) se resuelve usando simulaci��n de grandes escalas (LES), implementada en un programa de vol��menes finitos mientras que las ecuaciones gobernantes de la fase dispersa son resueltas por medio de un algoritmo de seguimiento Lagrangiano de part��culas que ha sido desarrollado y acoplado al programa que resuelve el flujo. Se estudia de manera sistem��tica y progresiva la interacci��n fluido���part��cula (one-way coupling), a trav��s de diferentes configuraciones geom��tricas en coordenadas cartesianas (canales de secci��n constante y variable) y en coordenadas cil��ndricas (tuber��as de secci��n constante y secci��n variable) abarcando diferentes n��meros de Reynolds y diferentes tama��os de part��culas; todos los resultados obtenidos han sido comparados con datos publicados previamente. El estudio de flujo multif��sico a trav��s de, tuber��as de secci��n variable, ha sido abordada en otras investigaciones mayoritariamente de forma experimental o mediante simulaci��n usando modelos de turbulencia menos complejos y no mediante LES. El patr��n de flujo que se verifica en una tuber��a con expansi��n es muy complejo y dicha configuraci��n geom��trica se halla en m��ltiples aplicaciones industriales que involucran el transporte de part��culas s��lidas, por ello es de gran inter��s su estudio. Como hecho innovador, en esta tesis no solo se resuelven las estad��sticas de velocidad del fluido y las part��culas en tuber��as con diferentes tama��os de expansi��n y diferentes reg��menes de flujo sino que se caracteriza, usando diversas formulaciones del n��mero de Stokes y el par��metro de arrastre, el ingreso y acumulaci��n de part��culas dentro de la zona de recirculaci��n, obteni��ndose resultados coincidentes con datos experimentales. ABSTRACT The objective of this Thesis research is to study the turbulent flow laden with solid particles through channels and pipes with using Eulerian-Lagrangian approach. The flow field of the transport phase (air ) is solved using large eddy simulation ( LES ) implemented in a program of finite volume while the governing equations of the dispersed phase are resolved by means of a particle Lagrangian tracking algorithm which was developed and coupled to principal program flow solver . We studied systematically and progressively the fluid interaction ��� particle ( one- way coupling ) , through different geometric configurations in Cartesian coordinates ( channel with constant and variable section) and in cylindrical coordinates ( pipes with constant section and variable section ) covering different Reynolds numbers and different particle sizes, all results have been compared with previously published data . The study of multiphase flow through, pipes with variable section has been addressed in other investigations predominantly experimentally or by simulation using less complex models and no turbulence by LES. The flow pattern is verified in a pipe expansion is very complex and this geometry is found in many industrial applications involving the transport of solid particles, so it is of great interest to study. As an innovator fact , in this Thesis not only finds fluid velocity statistics and particles with different sizes of pipe expansion and different flow regimes but characterized, using various formulations of the Stokes number and the drag parameter are resolved, the entry and accumulation of particles within the recirculation zone , matching results obtained with experimental data.

Two design methods for radial line slot antennas with arbitrary or beam pattern

Two design procedures for Radial Line Slot Antennas (RLSAs) with circular polarization and either maximum gain or an arbitrary shaped pattern are proposed. Firstly, a method to design a RLSA with any desired pattern is presented. It is based on an optimization algorithm and some measures to ensure its fast convergence and stability need to be taken. Secondly, a fast technique to calculate the length and the position of every slot in a high gain RLSA with uniform field distribution is described. Both procedures are vali dated with the design of three antennas with different characteristics.

Microstructure-based numerical modeling of the mechanical behavior of Mg alloys

Dentro de los materiales estructurales, el magnesio y sus aleaciones est��n siendo el foco de una de profunda investigaci��n. Esta investigaci��n est�� dirigida a comprender la relaci��n existente entre la microestructura de las aleaciones de Mg y su comportamiento mec��nico. El objetivo es optimizar las aleaciones actuales de magnesio a partir de su microestructura y dise��ar nuevas aleaciones. Sin embargo, el efecto de los factores microestructurales (como la forma, el tama��o, la orientaci��n de los precipitados y la morfolog��a de los granos) en el comportamiento mec��nico de estas aleaciones est�� todav��a por descubrir. Para conocer mejor de la relaci��n entre la microestructura y el comportamiento mec��nico, es necesaria la combinaci��n de t��cnicas avanzadas de caracterizaci��n experimental como de simulaci��n num��rica, a diferentes longitudes de escala. En lo que respecta a las t��cnicas de simulaci��n num��rica, la homogeneizaci��n policristalina es una herramienta muy ��til para predecir la respuesta macrosc��pica a partir de la microestructura de un policristal (caracterizada por el tama��o, la forma y la distribuci��n de orientaciones de los granos) y el comportamiento del monocristal. La descripci��n de la microestructura se lleva a cabo mediante modernas t��cnicas de caracterizaci��n (difracci��n de rayos X, difracci��n de electrones retrodispersados, as�� como con microscopia ��ptica y electr��nica). Sin embargo, el comportamiento del cristal sigue siendo dif��cil de medir, especialmente en aleaciones de Mg, donde es muy complicado conocer el valor de los par��metros que controlan el comportamiento mec��nico de los diferentes modos de deslizamiento y maclado. En la presente tesis se ha desarrollado una estrategia de homogeneizaci��n computacional para predecir el comportamiento de aleaciones de magnesio. El comportamiento de los policristales ha sido obtenido mediante la simulaci��n por elementos finitos de un volumen representativo (RVE) de la microestructura, considerando la distribuci��n real de formas y orientaciones de los granos. El comportamiento del cristal se ha simulado mediante un modelo de plasticidad cristalina que tiene en cuenta los diferentes mecanismos f��sicos de deformaci��n, como el deslizamiento y el maclado. Finalmente, la obtenci��n de los par��metros que controlan el comportamiento del cristal (tensiones cr��ticas resueltas (CRSS) as�� como las tasas de endurecimiento para todos los modos de maclado y deslizamiento) se ha resuelto mediante la implementaci��n de una metodolog��a de optimizaci��n inversa, una de las principales aportaciones originales de este trabajo. La metodolog��a inversa pretende, por medio del algoritmo de optimizaci��n de Levenberg-Marquardt, obtener el conjunto de par��metros que definen el comportamiento del monocristal y que mejor ajustan a un conjunto de ensayos macrosc��picos independientes. Adem��s de la implementaci��n de la t��cnica, se han estudiado tanto la objetividad del metodolog��a como la unicidad de la soluci��n en funci��n de la informaci��n experimental. La estrategia de optimizaci��n inversa se us�� inicialmente para obtener el comportamiento cristalino de la aleaci��n AZ31 de Mg, obtenida por laminado. Esta aleaci��n tiene una marcada textura basal y una gran anisotrop��a pl��stica. El comportamiento de cada grano incluy�� cuatro mecanismos de deformaci��n diferentes: deslizamiento en los planos basal, prism��tico, piramidal hc+ai, junto con el maclado en tracci��n. La validez de los par��metros resultantes se valid�� mediante la capacidad del modelo policristalino para predecir ensayos macrosc��picos independientes en diferentes direcciones. En segundo lugar se estudi�� mediante la misma estrategia, la influencia del contenido de Neodimio (Nd) en las propiedades de una aleaci��n de Mg-Mn-Nd, obtenida por extrusi��n. Se encontr�� que la adici��n de Nd produce una progresiva isotropizaci��n del comportamiento macrosc��pico. El modelo mostr�� que este incremento de la isotrop��a macrosc��pica era debido tanto a la aleatoriedad de la textura inicial como al incremento de la isotrop��a del comportamiento del cristal, con valores similares de las CRSSs de los diferentes modos de deformaci��n. Finalmente, el modelo se emple�� para analizar el efecto de la temperatura en el comportamiento del cristal de la aleaci��n de Mg-Mn-Nd. La introducci��n en el modelo de los efectos non-Schmid sobre el modo de deslizamiento piramidal hc+ai permiti�� capturar el comportamiento mec��nico a temperaturas superiores a 150_C. Esta es la primera vez, de acuerdo con el conocimiento del autor, que los efectos non-Schmid han sido observados en una aleaci��n de Magnesio. The study of Magnesium and its alloys is a hot research topic in structural materials. In particular, special attention is being paid in understanding the relationship between microstructure and mechanical behavior in order to optimize the current alloy microstructures and guide the design of new alloys. However, the particular effect of several microstructural factors (precipitate shape, size and orientation, grain morphology distribution, etc.) in the mechanical performance of a Mg alloy is still under study. The combination of advanced characterization techniques and modeling at several length scales is necessary to improve the understanding of the relation microstructure and mechanical behavior. Respect to the simulation techniques, polycrystalline homogenization is a very useful tool to predict the macroscopic response from polycrystalline microstructure (grain size, shape and orientation distributions) and crystal behavior. The microstructure description is fully covered with modern characterization techniques (X-ray diffraction, EBSD, optical and electronic microscopy). However, the mechanical behaviour of single crystals is not well-known, especially in Mg alloys where the correct parameterization of the mechanical behavior of the different slip/twin modes is a very difficult task. A computational homogenization framework for predicting the behavior of Magnesium alloys has been developed in this thesis. The polycrystalline behavior was obtained by means of the finite element simulation of a representative volume element (RVE) of the microstructure including the actual grain shape and orientation distributions. The crystal behavior for the grains was accounted for a crystal plasticity model which took into account the physical deformation mechanisms, e.g. slip and twinning. Finally, the problem of the parametrization of the crystal behavior (critical resolved shear stresses (CRSS) and strain hardening rates of all the slip and twinning modes) was obtained by the development of an inverse optimization methodology, one of the main original contributions of this thesis. The inverse methodology aims at finding, by means of the Levenberg-Marquardt optimization algorithm, the set of parameters defining crystal behavior that best fit a set of independent macroscopic tests. The objectivity of the method and the uniqueness of solution as function of the input information has been numerically studied. The inverse optimization strategy was first used to obtain the crystal behavior of a rolled polycrystalline AZ31 Mg alloy that showed a marked basal texture and a strong plastic anisotropy. Four different deformation mechanisms: basal, prismatic and pyramidal hc+ai slip, together with tensile twinning were included to characterize the single crystal behavior. The validity of the resulting parameters was proved by the ability of the polycrystalline model to predict independent macroscopic tests on different directions. Secondly, the influence of Neodymium (Nd) content on an extruded polycrystalline Mg-Mn-Nd alloy was studied using the same homogenization and optimization framework. The effect of Nd addition was a progressive isotropization of the macroscopic behavior. The model showed that this increase in the macroscopic isotropy was due to a randomization of the initial texture and also to an increase of the crystal behavior isotropy (similar values of the CRSSs of the different modes). Finally, the model was used to analyze the effect of temperature on the crystal behaviour of a Mg-Mn-Nd alloy. The introduction in the model of non-Schmid effects on the pyramidal hc+ai slip allowed to capture the inverse strength differential that appeared, between the tension and compression, above 150_C. This is the first time, to the author's knowledge, that non-Schmid effects have been reported for Mg alloys.

M��todos computacionales para visco-hiperelasticidad anis��tropa en grandes deformaciones

El comportamiento mec��nico de muchos materiales biol��gicos y polim��ricos en grandes deformaciones se puede describir adecuadamente mediante formulaciones isoc��ricas hiperel��sticas y viscoel��sticas. Las ecuaciones de comportamiento el��stico y viscoel��stico y las formulaciones computacionales para materiales incompresibles is��tropos en deformaciones finitas est��n ampliamente desarrolladas en la actualidad. Sin embargo, el desarrollo de modelos anis��tropos no lineales y de sus correspondientes formulaciones computacionales sigue siendo un tema de investigaci��n de gran inter��s. Cuando se consideran grandes deformaciones, existen muchas medidas de deformaci��n disponibles con las que poder formular las ecuaciones de comportamiento. Los modelos en deformaciones cuadr��ticas facilitan la implementaci��n en c��digos de elementos finitos, ya que estas medidas surgen de forma natural en la formulaci��n. No obstante, pueden dificultar la interpretaci��n de los modelos y llevar a resultados pocos realistas. El uso de deformaciones logar��tmicas permite el desarrollo de modelos m��s simples e intuitivos, aunque su formulaci��n computacional debe ser adaptada a las exigencias del programa. Como punto de partida, en esta tesis se demuestra que las deformaciones logar��tmicas representan la extensi��n natural de las deformaciones infinitesimales, tanto axiales como angulares, al campo de las grandes deformaciones. Este hecho permite explicar la simplicidad de las ecuaciones resultantes. Los modelos hiperel��sticos predominantes en la actualidad est��n formulados en invariantes de deformaciones cuadr��ticas. Estos modelos, ya sean continuos o microestructurales, se caracterizan por tener una forma anal��tica predefinida. Su expresi��n definitiva se calcula mediante un ajuste de curvas a datos experimentales. Un modelo que no sigue esta metodolog��a fue desarrollado por Sussman y Bathe. El modelo es s��lo v��lido para isotrop��a y queda definido por una funci��n de energ��a interpolada con splines, la cual reproduce los datos experimentales de forma exacta. En esta tesis se presenta su extensi��n a materiales transversalmente is��tropos y ort��tropos utilizando deformaciones logar��tmicas. Asimismo, se define una nueva propiedad que las funciones de energ��a anis��tropas deben satisfacer para que su convergencia al caso is��tropo sea correcta. En visco-hiperelasticidad, aparte de las distintas funciones de energ��a disponibles, hay dos aproximaciones computational t��picas basadas en variables internas. El modelo original de Sim�� est�� formulado en tensiones y es v��lido para materiales anis��tropos, aunque s��lo es adecuado para peque��as desviaciones con respecto al equilibrio termodin��mico. En cambio, el modelo basado en deformaciones de Reese y Govindjee permite grandes deformaciones no equilibradas pero es, en esencia, is��tropo. Las formulaciones anis��tropas en este ��ltimo contexto son microestructurales y emplean el modelo is��tropo para cada uno de los constituyentes. En esta tesis se presentan dos formulaciones fenomenol��gicas viscoel��sticas definidas mediante funciones hiperel��sticas anis��tropas y v��lidas para grandes desviaciones con respecto al equilibrio termodin��mico. El primero de los modelos est�� basado en la descomposici��n multiplicativa de Sidoroff y requiere un comportamiento viscoso is��tropo. La formulaci��n converge al modelo de Reese y Govindjee en el caso especial de isotrop��a el��stica. El segundo modelo se define a partir de una descomposici��n multiplicativa inversa. Esta formulaci��n est�� basada en una descripci��n co-rotacional del problema, es sustancialmente m��s compleja y puede dar lugar a tensores constitutivos ligeramente no sim��tricos. Sin embargo, su rango de aplicaci��n es mucho mayor ya que permite un comportamiento anis��tropo tanto el��stico como viscoso. Varias simulaciones de elementos finitos muestran la gran versatilidad de estos modelos cuando se combinan con funciones hiperel��sticas formadas por splines. ABSTRACT The mechanical behavior of many polymeric and biological materials may be properly modelled be means of isochoric hyperelastic and viscoelastic formulations. These materials may sustain large strains. The viscoelastic computational formulations for isotropic incompressible materials at large strains may be considered well established; for example Ogden���s hyperelastic function and the visco-hyperelastic model of Reese and Govindjee are well known models for isotropy. However, anisotropic models and computational procedures both for hyperelasticity and viscohyperelasticity are still under substantial research. Anisotropic hyperelastic models are typically based on structural invariants obtained from quadratic strain measures. These models may be microstructurallybased or phenomenological continuum formulations, and are characterized by a predefined analytical shape of the stored energy. The actual final expression of the stored energy depends on some material parameters which are obtained from an optimization algorithm, typically the Levenberg-Marquardt algorithm. We present in this work anisotropic spline-based hyperelastic stored energies in which the shape of the stored energy is obtained as part of the procedure and which (exactly in practice) replicates the experimental data. These stored energies are based on invariants obtained from logarithmic strain measures. These strain measures preserve the metric and the physical meaning of the trace and deviator operators and, hence, are interesting and meaningful for anisotropic formulations. Furthermore, the proposed stored energies may be formulated in order to have material-symmetries congruency both from a theoretical and from a numerical point of view, which are new properties that we define in this work. On the other hand, visco-hyperelastic formulations for anisotropic materials are typically based on internal stress-like variables following a procedure used by Sim��o. However, it can be shown that this procedure is not adequate for large deviations from thermodynamic equilibrium. In contrast, a formulation given by Reese and Govindjee is valid for arbitrarily large deviations from thermodynamic equilibrium but not for anisotropic stored energy functions. In this work we present two formulations for visco-hyperelasticity valid for anisotropic stored energies and large deviations from thermodynamic equilibrium. One of the formulations is based on the Sidoroff multiplicative decomposition and converges to the Reese and Govindjee formulation for the case of isotropy. However, the formulation is restricted to isotropy for the viscous component. The second formulation is based on a reversed multiplicative decomposition. This last formulation is substantially more complex and based on a corotational description of the problem. It can also result in a slightly nonsymmetric tangent. However, the formulation allows for anisotropy not only in the equilibrated and non-equilibrated stored energies, but also in the viscous behavior. Some examples show finite element implementation, versatility and interesting characteristics of the models.

Determining electric vehicle charging point locations considering drivers' daily activities

In this paper the daily temporal and spatial behavior of electric vehicles (EVs) is modelled using an activity-based (ActBM) microsimulation model for Flanders region (Belgium). Assuming that all EVs are completely charged at the beginning of the day, this mobility model is used to determine the percentage of Flemish vehicles that cannot cover their programmed daily trips and need to be recharged during the day. Assuming a variable electricity price, an optimization algorithm determines when and where EVs can be recharged at minimum cost for their owners. This optimization takes into account the individual mobility constraint for each vehicle, as they can only be charged when the car is stopped and the owner is performing an activity. From this information, the aggregated electric demand for Flanders is obtained, identifying the most overloaded areas at the critical hours. Finally it is also analyzed what activities EV owners are underway during their recharging period. From this analysis, different actions for public charging point deployment in different areas and for different activities are proposed.

A methodology to analyze, design and implement very fast and robust controls of Buck-type converters

La electr��nica digital moderna presenta un desaf��o a los dise��adores de sistemas de potencia. El creciente alto rendimiento de microprocesadores, FPGAs y ASICs necesitan sistemas de alimentaci��n que cumplan con requirimientos din��micos y est��ticos muy estrictos. Espec��ficamente, estas alimentaciones son convertidores DC-DC de baja tensi��n y alta corriente que necesitan ser dise��ados para tener un peque��o rizado de tensi��n y una peque��a desviaci��n de tensi��n de salida bajo transitorios de carga de una alta pendiente. Adem��s, dependiendo de la aplicaci��n, se necesita cumplir con otros requerimientos tal y como proveer a la carga con ���Escalado din��mico de tensi��n���, donde el convertidor necesitar cambiar su tensi��n de salida tan r��pidamente posible sin sobreoscilaciones, o ���Posicionado Adaptativo de la Tensi��n��� donde la tensi��n de salida se reduce ligeramente cuanto m��s grande sea la potencia de salida. Por supuesto, desde el punto de vista de la industria, las figuras de m��rito de estos convertidores son el coste, la eficiencia y el tama��o/peso. Idealmente, la industria necesita un convertidor que es m��s barato, m��s eficiente, m��s peque��o y que a��n as�� cumpla con los requerimienos din��micos de la aplicaci��n. En este contexto, varios enfoques para mejorar la figuras de m��rito de estos convertidores se han seguido por la industria y la academia tales como mejorar la topolog��a del convertidor, mejorar la tecnolog��a de semiconducores y mejorar el control. En efecto, el control es una parte fundamental en estas aplicaciones ya que un control muy r��pido hace que sea m��s f��cil que una determinada topolog��a cumpla con los estrictos requerimientos din��micos y, consecuentemente, le da al dise��ador un margen de libertar m��s amplio para mejorar el coste, la eficiencia y/o el tama��o del sistema de potencia. En esta tesis, se investiga c��mo dise��ar e implementar controles muy r��pidos para el convertidor tipo Buck. En esta tesis se demuestra que medir la tensi��n de salida es todo lo que se necesita para lograr una respuesta casi ��ptima y se propone una gu��a de dise��o unificada para controles que s��lo miden la tensi��n de salida Luego, para asegurar robustez en controles muy r��pidos, se proponen un modelado y un an��lisis de estabilidad muy precisos de convertidores DC-DC que tienen en cuenta circuiter��a para sensado y elementos par��sitos cr��ticos. Tambi��n, usando este modelado, se propone una algoritmo de optimizaci��n que tiene en cuenta las tolerancias de los componentes y sensados distorsionados. Us ando este algoritmo, se comparan controles muy r��pidos del estado del arte y su capacidad para lograr una r��pida respuesta din��mica se posiciona seg��n el condensador de salida utilizado. Adem��s, se propone una t��cnica para mejorar la respuesta din��mica de los controladores. Todas las propuestas se han corroborado por extensas simulaciones y prototipos experimentales. Con todo, esta tesis sirve como una metodolog��a para ingenieros para dise��ar e implementar controles r��pidos y robustos de convertidores tipo Buck. ABSTRACT Modern digital electronics present a challenge to designers of power systems. The increasingly high-performance of microprocessors, FPGAs (Field Programmable Gate Array) and ASICs (Application-Specific Integrated Circuit) require power supplies to comply with very demanding static and dynamic requirements. Specifically, these power supplies are low-voltage/high-current DC-DC converters that need to be designed to exhibit low voltage ripple and low voltage deviation under high slew-rate load transients. Additionally, depending on the application, other requirements need to be met such as to provide to the load ���Dynamic Voltage Scaling��� (DVS), where the converter needs to change the output voltage as fast as possible without underdamping, or ���Adaptive Voltage Positioning��� (AVP) where the output voltage is slightly reduced the greater the output power. Of course, from the point of view of the industry, the figures of merit of these converters are the cost, efficiency and size/weight. Ideally, the industry needs a converter that is cheaper, more efficient, smaller and that can still meet the dynamic requirements of the application. In this context, several approaches to improve the figures of merit of these power supplies are followed in the industry and academia such as improving the topology of the converter, improving the semiconductor technology and improving the control. Indeed, the control is a fundamental part in these applications as a very fast control makes it easier for the topology to comply with the strict dynamic requirements and, consequently, gives the designer a larger margin of freedom to improve the cost, efficiency and/or size of the power supply. In this thesis, how to design and implement very fast controls for the Buck converter is investigated. This thesis proves that sensing the output voltage is all that is needed to achieve an almost time-optimal response and a unified design guideline for controls that only sense the output voltage is proposed. Then, in order to assure robustness in very fast controls, a very accurate modeling and stability analysis of DC-DC converters is proposed that takes into account sensing networks and critical parasitic elements. Also, using this modeling approach, an optimization algorithm that takes into account tolerances of components and distorted measurements is proposed. With the use of the algorithm, very fast analog controls of the state-of-the-art are compared and their capabilities to achieve a fast dynamic response are positioned de pending on the output capacitor. Additionally, a technique to improve the dynamic response of controllers is also proposed. All the proposals are corroborated by extensive simulations and experimental prototypes. Overall, this thesis serves as a methodology for engineers to design and implement fast and robust controls for Buck-type converters.

Optimizaci��n del consumo de combustible de un veh��culo dependiendo de las condiciones de la carretera

El consumo de combustible en un autom��vil es una caracter��stica que se intenta mejorar continuamente debido a los precios del carburante y a la creciente conciencia medioambiental. Esta tesis doctoral plantea un algoritmo de optimizaci��n del consumo que tiene en cuenta las especificaciones t��cnicas del veh��culo, el perfil de orograf��a de la carretera y el tr��fico presente en ella. El algoritmo de optimizaci��n calcula el perfil de velocidad ��ptima que debe seguir el veh��culo para completar un recorrido empleando un tiempo de viaje especificado. El c��lculo del perfil de velocidad ��ptima considera los valores de pendiente de la carretera as�� como tambi��n las condiciones de tr��fico vehicular de la franja horaria en que se realiza el recorrido. El algoritmo de optimizaci��n reacciona ante condiciones de tr��fico cambiantes y adapta continuamente el perfil ��ptimo de velocidad para que el veh��culo llegue al destino cumpliendo el horario de llegada establecido. La optimizaci��n de consumo es aplicada en veh��culos convencionales de motor de combusti��n interna y en veh��culos h��bridos tipo serie. Los datos de consumo utilizados por el algoritmo de optimizaci��n se obtienen mediante la simulaci��n de modelos cuasi-est��ticos de los veh��culos. La t��cnica de minimizaci��n empleada por el algoritmo es la Programaci��n Din��mica. El algoritmo divide la optimizaci��n del consumo en dos partes claramente diferenciadas y aplica la Programaci��n Din��mica sobre cada una de ellas. La primera parte corresponde a la optimizaci��n del consumo del veh��culo en funci��n de las condiciones de tr��fico. Esta optimizaci��n calcula un perfil de velocidad promedio que evita, cuando es posible, las retenciones de tr��fico. El tiempo de viaje perdido durante una retenci��n de tr��fico debe recuperarse a trav��s de un aumento posterior de la velocidad promedio que incrementar��a el consumo del veh��culo. La segunda parte de la optimizaci��n es la encargada del c��lculo de la velocidad ��ptima en funci��n de la orograf��a y del tiempo de viaje disponible. Dado que el consumo de combustible del veh��culo se incrementa cuando disminuye el tiempo disponible para finalizar un recorrido, esta optimizaci��n utiliza factores de ponderaci��n para modular la influencia que tiene cada una de estas dos variables en el proceso de minimizaci��n. Aunque los factores de ponderaci��n y la orograf��a de la carretera condicionan el nivel de ahorro de la optimizaci��n, los perfiles de velocidad ��ptima calculados logran ahorros de consumo respecto de un perfil de velocidad constante que obtiene el mismo tiempo de recorrido. Las simulaciones indican que el ahorro de combustible del veh��culo convencional puede lograr hasta un 8.9% mientras que el ahorro de energ��a el��ctrica del veh��culo h��brido serie un 2.8%. El algoritmo fusiona la optimizaci��n en funci��n de las condiciones del tr��fico y la optimizaci��n en funci��n de la orograf��a durante el c��lculo en tiempo real del perfil ��ptimo de velocidad. La optimizaci��n conjunta se logra cuando el perfil de velocidad promedio resultante de la optimizaci��n en funci��n de las condiciones de tr��fico define los valores de los factores de ponderaci��n de la optimizaci��n en funci��n de la orograf��a. Aunque el nivel de ahorro de la optimizaci��n conjunta depende de las condiciones de tr��fico, de la orograf��a, del tiempo de recorrido y de las caracter��sticas propias del veh��culo, las simulaciones indican ahorros de consumo superiores al 6% en ambas clases de veh��culo respecto a optimizaciones que no logran evitar retenciones de tr��fico en la carretera. ABSTRACT Fuel consumption of cars is a feature that is continuously being improved due to the fuel price and an increasing environmental awareness. This doctoral dissertation describes an optimization algorithm to decrease the fuel consumption taking into account the technical specifications of the vehicle, the terrain profile of the road and the traffic conditions of the trip. The algorithm calculates the optimal speed profile that completes a trip having a specified travel time. This calculation considers the road slope and the expected traffic conditions during the trip. The optimization algorithm is also able to react to changing traffic conditions and tunes the optimal speed profile to reach the destination within the specified arrival time. The optimization is applied on a conventional vehicle and also on a Series Hybrid Electric vehicle (SHEV). The fuel consumption optimization algorithm uses data obtained from quasi-static simulations. The algorithm is based on Dynamic Programming and divides the fuel consumption optimization problem into two parts. The first part of the optimization process reduces the fuel consumption according to foreseeable traffic conditions. It calculates an average speed profile that tries to avoid, if possible, the traffic jams on the road. Traffic jams that delay drivers result in higher vehicle speed to make up for lost time. A higher speed of the vehicle within an already defined time scheme increases fuel consumption. The second part of the optimization process is in charge of calculating the optimal speed profile according to the road slope and the remaining travel time. The optimization tunes the fuel consumption and travel time relevancies by using two penalty factors. Although the optimization results depend on the road slope and the travel time, the optimal speed profile produces improvements of 8.9% on the fuel consumption of the conventional car and of 2.8% on the spent energy of the hybrid vehicle when compared with a constant speed profile. The two parts of the optimization process are combined during the Real-Time execution of the algorithm. The average speed profile calculated by the optimization according to the traffic conditions provides values for the two penalty factors utilized by the second part of the optimization process. Although the savings depend on the road slope, traffic conditions, vehicle features, and the remaining travel time, simulations show that this joint optimization process can improve the energy consumption of the two vehicles types by more than 6%.

Two-dimensional isostatic meshes in the finite element method

In a Finite Element (FE) analysis of elastic solids several items are usually considered, namely, type and shape of the elements, number of nodes per element, node positions, FE mesh, total number of degrees of freedom (dot) among others. In this paper a method to improve a given FE mesh used for a particular analysis is described. For the improvement criterion different objective functions have been chosen (Total potential energy and Average quadratic error) and the number of nodes and dof's of the new mesh remain constant and equal to the initial FE mesh. In order to find the mesh producing the minimum of the selected objective function the steepest descent gradient technique has been applied as optimization algorithm. However this efficient technique has the drawback that demands a large computation power. Extensive application of this methodology to different 2-D elasticity problems leads to the conclusion that isometric isostatic meshes (ii-meshes) produce better results than the standard reasonably initial regular meshes used in practice. This conclusion seems to be independent on the objective function used for comparison. These ii-meshes are obtained by placing FE nodes along the isostatic lines, i.e. curves tangent at each point to the principal direction lines of the elastic problem to be solved and they should be regularly spaced in order to build regular elements. That means ii-meshes are usually obtained by iteration, i.e. with the initial FE mesh the elastic analysis is carried out. By using the obtained results of this analysis the net of isostatic lines can be drawn and in a first trial an ii-mesh can be built. This first ii-mesh can be improved, if it necessary, by analyzing again the problem and generate after the FE analysis the new and improved ii-mesh. Typically, after two first tentative ii-meshes it is sufficient to produce good FE results from the elastic analysis. Several example of this procedure are presented.

Evaluating approximations generated by the GNG3D method for mesh simplification

In this paper we present different error measurements with the aim to evaluate the quality of the approximations generated by the GNG3D method for mesh simplification. The first phase of this method consists on the execution of the GNG3D algorithm, described in the paper. The primary goal of this phase is to obtain a simplified set of vertices representing the best approximation of the original 3D object. In the reconstruction phase we use the information provided by the optimization algorithm to reconstruct the faces thus obtaining the optimized mesh. The implementation of three error functions, named Eavg, Emax, Esur, permitts us to control the error of the simplified model, as it is shown in the examples studied.

Single photon emission mammography with convergent collimators

Tese de doutoramento, Engenharia Biom��dica e Biof��sica, Universidade de Lisboa, Faculdade de Ci��ncias, 2016

The Microphysical Structure of Mesoscale Convective Systems

Thesis (Ph.D.)--University of Washington, 2016-05

Optimizing amino acid groupings for GPCR classification

MOTIVATION: There is much interest in reducing the complexity inherent in the representation of the 20 standard amino acids within bioinformatics algorithms by developing a so-called reduced alphabet. Although there is no universally applicable residue grouping, there are numerous physiochemical criteria upon which one can base groupings. Local descriptors are a form of alignment-free analysis, the efficiency of which is dependent upon the correct selection of amino acid groupings. RESULTS: Within the context of G-protein coupled receptor (GPCR) classification, an optimization algorithm was developed, which was able to identify the most efficient grouping when used to generate local descriptors. The algorithm was inspired by the relatively new computational intelligence paradigm of artificial immune systems. A number of amino acid groupings produced by this algorithm were evaluated with respect to their ability to generate local descriptors capable of providing an accurate classification algorithm for GPCRs.

A decision support system for supplier selection and order allocation in stochastic, multi-stakeholder and multi-criteria environments

Integrated supplier selection and order allocation is an important decision for both designing and operating supply chains. This decision is often influenced by the concerned stakeholders, suppliers, plant operators and customers in different tiers. As firms continue to seek competitive advantage through supply chain design and operations they aim to create optimized supply chains. This calls for on one hand consideration of multiple conflicting criteria and on the other hand consideration of uncertainties of demand and supply. Although there are studies on supplier selection using advanced mathematical models to cover a stochastic approach, multiple criteria decision making techniques and multiple stakeholder requirements separately, according to authors' knowledge there is no work that integrates these three aspects in a common framework. This paper proposes an integrated method for dealing with such problems using a combined Analytic Hierarchy Process-Quality Function Deployment (AHP-QFD) and chance constrained optimization algorithm approach that selects appropriate suppliers and allocates orders optimally between them. The effectiveness of the proposed decision support system has been demonstrated through application and validation in the bioenergy industry.

Coverage versus supply cost in facility location:physics of frustrated spin systems

A comprehensive coverage is crucial for communication, supply, and transportation networks, yet it is limited by the requirement of extensive infrastructure and heavy energy consumption. Here, we draw an analogy between spins in antiferromagnet and outlets in supply networks, and apply techniques from the studies of disordered systems to elucidate the effects of balancing the coverage and supply costs on the network behavior. A readily applicable, coverage optimization algorithm is derived. Simulation results show that magnetized and antiferromagnetic domains emerge and coexist to balance the need for coverage and energy saving. The scaling of parameters with system size agrees with the continuum approximation in two dimensions and the tree approximation in random graphs. Due to frustration caused by the competition between coverage and supply cost, a transition between easy and hard computation regimes is observed. We further suggest a local expansion approach to greatly simplify the message updates which shed light on simplifications in other problems. �� 2014 American Physical Society.

Transporte longitudinal de sedimento na zona costeira de Natal/RN

The longshore sediment transport (LST) is determinant for the occurrence of morphological changes in coastal environments. Understanding their movement mechanisms and transport is an essential source of information for the project design and coastal management plans. This study aims to characterize, initially, the active hydrodynamic circulation in the study area, comprised of four beach sectors from the south coast of Natal, assessing the average annual LST obtained through three proven equations (CERC, Kamphuis and Bayram et al.), defining the best formulation for the study area in question, and analyze the seasonal variability and the decadal transport evolution. The coastal area selected for this work constitutes one of the main tourist corridors in the city, but has suffered serious damage resulting from associated effects of hydrodynamic forcings and their disorderly occupation. As a tool was used the Coastal Modelling System of Brazil (SMC-Brazil), which presents integrated a series of numerical models and a database, properly calibrated and validated for use in developing projects along the Brazilian coastline. The LST rates were obtained for 15 beach profiles distributed throughout the study area. Their extensions take into account the depth of closure calculated by Harllermeier equation, and regarding the physical properties of the sediment, typical values of sandy beaches were adopted, except for the average diameter, which was calculated through an optimization algorithm based on equilibrium profile formulation proposed by Dean. Overall, the results showed an intensification of hydrodynamic forcings under extreme sea wave conditions, especially along the headlands exist in the region. Among the analyzed equations, Bayram et al. was the most suitable for this type of application, with a predominant transport in the south-north direction and the highest rates within the order of 700.000 m3 /year to 2.000.000 m3 /year. The seasonal analysis also indicated a longitudinal transport predominance in the south to north, with the highest rates associated with the fall and winter seasons. In these periods are observed erosive beach states, which indicate a direct relationship between the sediment dynamics and the occurrence of more energetic sea states. Regarding the decadal evolution of transportation, it was found a decrease in transport rate from the 50���s to the 70���s, followed by an increase until the 2000���s, coinciding with the beginning of urbanization process in some stretches of the studied coastline.