Otimiza����o de antenas lineares e planares para aplica����es em sistemas de banda larga

O objetivo deste trabalho �� a otimiza����o da largura de banda de antenas linear e planar para aplica����es em sistemas de banda larga. Nesse sentido, foi feito um estudo das t��cnicas de an��lise, aumento da largura de banda e otimiza����o adequadas para o problema em quest��o. Como t��cnica de an��lise, foi utilizado o m��todo dos momentos, o qual est�� apresentado no cap��tulo II. Para aumentar a largura de banda, foram utilizadas as t��cnicas de coloca����o de elementos parasitas e constru����o de fendas no radiador, descritos sucintamente no cap��tulo III. Como algoritmo de otimiza����o, foi utilizado o algoritmo gen��tico, descrito sucintamente no cap��tulo II. Neste trabalho, s��o apresentadas duas propostas de antenas, uma antena dipolo linear combinada com quatros espiras parasitas, cap��tulo IV, e uma antena planar do tipo espira, cap��tulo V. No primeiro caso, foram utilizados elementos parasitas e o algoritmo gen��tico para aumentar a largura de banda e, no segundo, foram empregadas fendas no radiador e a otimiza����o param��trica para este objetivo.

Reconstru����o de contornos e cumeeiras de telhados de edif��cios a partir de imagens a��reas de alta-resolu����o e poliedros representativos de edif��cios extra��dos de dados LASER

P��s-gradua����o em Ci��ncias Cartogr��ficas - FCT

Sistemas aut��nomos de iluminac��o p��blica em corrente cont��nua

P��s-gradua����o em Engenharia El��trica - FEIS

Otimiza����o din��mica de rotores com eixos em comp��sito

P��s-gradua����o em Engenharia Mec��nica - FEG

Semiautomatic object-space road extraction combining a stereoscopic image pair and a TIN-Based DTM

In this letter, a semiautomatic method for road extraction in object space is proposed that combines a stereoscopic pair of low-resolution aerial images with a digital terrain model (DTM) structured as a triangulated irregular network (TIN). First, we formulate an objective function in the object space to allow the modeling of roads in 3-D. In this model, the TIN-based DTM allows the search for the optimal polyline to be restricted along a narrow band that is overlaid upon it. Finally, the optimal polyline for each road is obtained by optimizing the objective function using the dynamic programming optimization algorithm. A few seed points need to be supplied by an operator. To evaluate the performance of the proposed method, a set of experiments was designed using two stereoscopic pairs of low-resolution aerial images and a TIN-based DTM with an average resolution of 1 m. The experimental results showed that the proposed method worked properly, even when faced with anomalies along roads, such as obstructions caused by shadows and trees.

Evaluating bound-constrained minimization software

Bound-constrained minimization is a subject of active research. To assess the performance of existent solvers, numerical evaluations and comparisons are carried on. Arbitrary decisions that may have a crucial effect on the conclusions of numerical experiments are highlighted in the present work. As a result, a detailed evaluation based on performance profiles is applied to the comparison of bound-constrained minimization solvers. Extensive numerical results are presented and analyzed.

Metodi di ottimizzazione morfologica nel progetto preliminare di propulsori aeronautici avanzati

The aim of this Doctoral Thesis is to develop a genetic algorithm based optimization methods to find the best conceptual design architecture of an aero-piston-engine, for given design specifications. Nowadays, the conceptual design of turbine airplanes starts with the aircraft specifications, then the most suited turbofan or turbo propeller for the specific application is chosen. In the aeronautical piston engines field, which has been dormant for several decades, as interest shifted towards turboaircraft, new materials with increased performance and properties have opened new possibilities for development. Moreover, the engine���s modularity given by the cylinder unit, makes it possible to design a specific engine for a given application. In many real engineering problems the amount of design variables may be very high, characterized by several non-linearities needed to describe the behaviour of the phenomena. In this case the objective function has many local extremes, but the designer is usually interested in the global one. The stochastic and the evolutionary optimization techniques, such as the genetic algorithms method, may offer reliable solutions to the design problems, within acceptable computational time. The optimization algorithm developed here can be employed in the first phase of the preliminary project of an aeronautical piston engine design. It���s a mono-objective genetic algorithm, which, starting from the given design specifications, finds the engine propulsive system configuration which possesses minimum mass while satisfying the geometrical, structural and performance constraints. The algorithm reads the project specifications as input data, namely the maximum values of crankshaft and propeller shaft speed and the maximal pressure value in the combustion chamber. The design variables bounds, that describe the solution domain from the geometrical point of view, are introduced too. In the Matlab�� Optimization environment the objective function to be minimized is defined as the sum of the masses of the engine propulsive components. Each individual that is generated by the genetic algorithm is the assembly of the flywheel, the vibration damper and so many pistons, connecting rods, cranks, as the number of the cylinders. The fitness is evaluated for each individual of the population, then the rules of the genetic operators are applied, such as reproduction, mutation, selection, crossover. In the reproduction step the elitist method is applied, in order to save the fittest individuals from a contingent mutation and recombination disruption, making it undamaged survive until the next generation. Finally, as the best individual is found, the optimal dimensions values of the components are saved to an Excel�� file, in order to build a CAD-automatic-3D-model for each component of the propulsive system, having a direct pre-visualization of the final product, still in the engine���s preliminary project design phase. With the purpose of showing the performance of the algorithm and validating this optimization method, an actual engine is taken, as a case study: it���s the 1900 JTD Fiat Avio, 4 cylinders, 4T, Diesel. Many verifications are made on the mechanical components of the engine, in order to test their feasibility and to decide their survival through generations. A system of inequalities is used to describe the non-linear relations between the design variables, and is used for components checking for static and dynamic loads configurations. The design variables geometrical boundaries are taken from actual engines data and similar design cases. Among the many simulations run for algorithm testing, twelve of them have been chosen as representative of the distribution of the individuals. Then, as an example, for each simulation, the corresponding 3D models of the crankshaft and the connecting rod, have been automatically built. In spite of morphological differences among the component the mass is almost the same. The results show a significant mass reduction (almost 20% for the crankshaft) in comparison to the original configuration, and an acceptable robustness of the method have been shown. The algorithm here developed is shown to be a valid method for an aeronautical-piston-engine preliminary project design optimization. In particular the procedure is able to analyze quite a wide range of design solutions, rejecting the ones that cannot fulfill the feasibility design specifications. This optimization algorithm could increase the aeronautical-piston-engine development, speeding up the production rate and joining modern computation performances and technological awareness to the long lasting traditional design experiences.

Methodological improvement of 3D fluoroscopic analysis for the robust quantification of 3D kinematics of human joints

3D video-fluoroscopy is an accurate but cumbersome technique to estimate natural or prosthetic human joint kinematics. This dissertation proposes innovative methodologies to improve the 3D fluoroscopic analysis reliability and usability. Being based on direct radiographic imaging of the joint, and avoiding soft tissue artefact that limits the accuracy of skin marker based techniques, the fluoroscopic analysis has a potential accuracy of the order of mm/deg or better. It can provide fundamental informations for clinical and methodological applications, but, notwithstanding the number of methodological protocols proposed in the literature, time consuming user interaction is exploited to obtain consistent results. The user-dependency prevented a reliable quantification of the actual accuracy and precision of the methods, and, consequently, slowed down the translation to the clinical practice. The objective of the present work was to speed up this process introducing methodological improvements in the analysis. In the thesis, the fluoroscopic analysis was characterized in depth, in order to evaluate its pros and cons, and to provide reliable solutions to overcome its limitations. To this aim, an analytical approach was followed. The major sources of error were isolated with in-silico preliminary studies as: (a) geometric distortion and calibration errors, (b) 2D images and 3D models resolutions, (c) incorrect contour extraction, (d) bone model symmetries, (e) optimization algorithm limitations, (f) user errors. The effect of each criticality was quantified, and verified with an in-vivo preliminary study on the elbow joint. The dominant source of error was identified in the limited extent of the convergence domain for the local optimization algorithms, which forced the user to manually specify the starting pose for the estimating process. To solve this problem, two different approaches were followed: to increase the optimal pose convergence basin, the local approach used sequential alignments of the 6 degrees of freedom in order of sensitivity, or a geometrical feature-based estimation of the initial conditions for the optimization; the global approach used an unsupervised memetic algorithm to optimally explore the search domain. The performances of the technique were evaluated with a series of in-silico studies and validated in-vitro with a phantom based comparison with a radiostereometric gold-standard. The accuracy of the method is joint-dependent, and for the intact knee joint, the new unsupervised algorithm guaranteed a maximum error lower than 0.5 mm for in-plane translations, 10 mm for out-of-plane translation, and of 3 deg for rotations in a mono-planar setup; and lower than 0.5 mm for translations and 1 deg for rotations in a bi-planar setups. The bi-planar setup is best suited when accurate results are needed, such as for methodological research studies. The mono-planar analysis may be enough for clinical application when the analysis time and cost may be an issue. A further reduction of the user interaction was obtained for prosthetic joints kinematics. A mixed region-growing and level-set segmentation method was proposed and halved the analysis time, delegating the computational burden to the machine. In-silico and in-vivo studies demonstrated that the reliability of the new semiautomatic method was comparable to a user defined manual gold-standard. The improved fluoroscopic analysis was finally applied to a first in-vivo methodological study on the foot kinematics. Preliminary evaluations showed that the presented methodology represents a feasible gold-standard for the validation of skin marker based foot kinematics protocols.

Kinematics of the Sicily and Calabria Subduction System from Elastic Block Modeling of GPS Data

We use data from about 700 GPS stations in the EuroMediterranen region to investigate the present-day behavior of the the Calabrian subduction zone within the Mediterranean-scale plates kinematics and to perform local scale studies about the strain accumulation on active structures. We focus attenction on the Messina Straits and Crati Valley faults where GPS data show extentional velocity gradients of ���3 mm/yr and ���2 mm/yr, respectively. We use dislocation model and a non-linear constrained optimization algorithm to invert for fault geometric parameters and slip-rates and evaluate the associated uncertainties adopting a bootstrap approach. Our analysis suggest the presence of two partially locked normal faults. To investigate the impact of elastic strain contributes from other nearby active faults onto the observed velocity gradient we use a block modeling approach. Our models show that the inferred slip-rates on the two analyzed structures are strongly impacted by the assumed locking width of the Calabrian subduction thrust. In order to frame the observed local deformation features within the present- day central Mediterranean kinematics we realyze a statistical analysis testing the indipendent motion (w.r.t. the African and Eurasias plates) of the Adriatic, Cal- abrian and Sicilian blocks. Our preferred model confirms a microplate like behaviour for all the investigated blocks. Within these kinematic boundary conditions we fur- ther investigate the Calabrian Slab interface geometry using a combined approach of block modeling and ��2�� statistic. Almost no information is obtained using only the horizontal GPS velocities that prove to be a not sufficient dataset for a multi-parametric inversion approach. Trying to stronger constrain the slab geometry we estimate the predicted vertical velocities performing suites of forward models of elastic dislocations varying the fault locking depth. Comparison with the observed field suggest a maximum resolved locking depth of 25 km.

Design And Implementation Of An End-To-End Simulator For The BepiColombo Rotation Experiment

Among the scientific objectives addressed by the Radio Science Experiment hosted on board the ESA mission BepiColombo is the retrieval of the rotational state of planet Mercury. In fact, the estimation of the obliquity and the librations amplitude were proven to be fundamental for constraining the interior composition of Mercury. This is accomplished by the Mercury Orbiter Radio science Experiment (MORE) via a strict interaction among different payloads thus making the experiment particularly challenging. The underlying idea consists in capturing images of the same landmark on the surface of the planet in different epochs in order to observe a displacement of the identified features with respect to a nominal rotation which allows to estimate the rotational parameters. Observations must be planned accurately in order to obtain image pairs carrying the highest information content for the following estimation process. This is not a trivial task especially in light of the several dynamical constraints involved. Another delicate issue is represented by the pattern matching process between image pairs for which the lowest correlation errors are desired. The research activity was conducted in the frame of the MORE rotation experiment and addressed the design and implementation of an end-to-end simulator of the experiment with the final objective of establishing an optimal science planning of the observations. In the thesis, the implementation of the singular modules forming the simulator is illustrated along with the simulations performed. The results obtained from the preliminary release of the optimization algorithm are finally presented although the software implemented is only at a preliminary release and will be improved and refined in the future also taking into account the developments of the mission.

Computer simulations of colloidal fluids in confinement

Computer-Simulationen von Kolloidalen Fluiden in Beschr��nkten Geometrien Kolloidale Suspensionen, die einen Phasen��bergang aufweisen, zeigen eine Vielfalt an interessanten Effekten, sobald sie auf eine bestimmte Geometrie beschr��nkt werden, wie zum Beispiel auf zylindrische Poren, sph��rische Hohlr��ume oder auf einen Spalt mit ebenen W��nden. Der Einfluss dieser verschiedenen Geometrietypen sowohl auf das Phasenverhalten als auch auf die Dynamik von Kolloid-Polymer-Mischungen wird mit Hilfe von Computer-Simulationen unter Verwendung des Asakura-Oosawa- Modells, f��r welches auf Grund der ���Depletion���-Kr��fte ein Phasen��bergang existiert, untersucht. Im Fall von zylindrischen Poren sieht man ein interessantes Phasenverhalten, welches vom eindimensionalen Charakter des Systems hervorgerufen wird. In einer kurzen Pore findet man im Bereich des Phasendiagramms, in dem das System typischerweise entmischt, entweder eine polymerreiche oder eine kolloidreiche Phase vor. Sobald aber die L��nge der zylindrischen Pore die typische Korrelationsl��nge entlang der Zylinderachse ��berschreitet, bilden sich mehrere quasi-eindimensionale Bereiche der polymerreichen und der kolloidreichen Phase, welche von nun an koexistieren. Diese Untersuchungen helfen das Verhalten von Adsorptionshysteresekurven in entsprechenden Experimenten zu erkl��ren. Wenn das Kolloid-Polymer-Modellsystem auf einen sph��rischen Hohlraum eingeschr��nkt wird, verschiebt sich der Punkt des Phasen��bergangs von der polymerreichen zur kolloidreichen Phase. Es wird gezeigt, dass diese Verschiebung direkt von den Benetzungseigenschaften des Systems abh��ngt, was die Beobachtung von zwei verschiedenen Morphologien bei Phasenkoexistenz erm��glicht ��� Schalenstrukturen und Strukturen des Janustyps. Im Rahmen der Untersuchung von heterogener Keimbildung von Kristallen innerhalb einer Fl��ssigkeit wird eine neue Simulationsmethode zur Berechnung von Freien Energien der Grenzfl��che zwischen Kristall- bzw. Fl��ssigkeitsphase undWand pr��sentiert. Die Resultate f��r ein System von harten Kugeln und ein System einer Kolloid- Polymer-Mischung werden anschlie��end zur Bestimmung von Kontaktwinkeln von Kristallkeimen an W��nden verwendet. Die Dynamik der Phasenseparation eines quasi-zweidimensionalen Systems, welche sich nach einem Quench des Systems aus dem homogenen Zustand in den entmischten Zustand ausbildet, wird mit Hilfe von einer mesoskaligen Simulationsmethode (���Multi Particle Collision Dynamics���) untersucht, die sich f��r eine detaillierte Untersuchung des Einflusses der hydrodynamischen Wechselwirkung eignet. Die Exponenten universeller Potenzgesetze, die das Wachstum der mittleren Dom��nengr����e beschreiben, welche f��r rein zwei- bzw. dreidimensionale Systeme bekannt sind, k��nnen f��r bestimmte Parameterbereiche nachgewiesen werden. Die unterschiedliche Dynamik senkrecht bzw. parallel zu den W��nden sowie der Einfluss der Randbedingungen f��r das L��sungsmittel werden untersucht. Es wird gezeigt, dass die daraus resultierende Abschirmung der hydrodynamischen Wechselwirkungsreichweite starke Auswirkungen auf das Wachstum der mittleren Dom��nengr����e hat.

Prediction of new crystal structures under extreme conditions

One of the most important challenges in chemistry and material science is the connection between the contents of a compound and its chemical and physical properties. In solids, these are greatly influenced by the crystal structure.rnrnThe prediction of hitherto unknown crystal structures with regard to external conditions like pressure and temperature is therefore one of the most important goals to achieve in theoretical chemistry. The stable structure of a compound is the global minimum of the potential energy surface, which is the high dimensional representation of the enthalpy of the investigated system with respect to its structural parameters. The fact that the complexity of the problem grows exponentially with the system size is the reason why it can only be solved via heuristic strategies.rnrnImprovements to the artificial bee colony method, where the local exploration of the potential energy surface is done by a high number of independent walkers, are developed and implemented. This results in an improved communication scheme between these walkers. This directs the search towards the most promising areas of the potential energy surface.rnrnThe minima hopping method uses short molecular dynamics simulations at elevated temperatures to direct the structure search from one local minimum of the potential energy surface to the next. A modification, where the local information around each minimum is extracted and used in an optimization of the search direction, is developed and implemented. Our method uses this local information to increase the probability of finding new, lower local minima. This leads to an enhanced performance in the global optimization algorithm.rnrnHydrogen is a highly relevant system, due to the possibility of finding a metallic phase and even superconductor with a high critical temperature. An application of a structure prediction method on SiH12 finds stable crystal structures in this material. Additionally, it becomes metallic at relatively low pressures.

Development of an In Situ Measurement Device for Obtaining Material Thermal Properties

This thesis presents a methodology for measuring thermal properties in situ, with a special focus on obtaining properties of layered stack-ups commonly used in armored vehicle components. The technique involves attaching a thermal source to the surface of a component, measuring the heat flux transferred between the source and the component, and measuring the surface temperature response. The material properties of the component can subsequently be determined from measurement of the transient heat flux and temperature response at the surface alone. Experiments involving multilayered specimens show that the surface temperature response to a sinusoidal heat flux forcing function is also sinusoidal. A frequency domain analysis shows that sinusoidal thermal excitation produces a gain and phase shift behavior typical of linear systems. Additionally, this analysis shows that the material properties of sub-surface layers affect the frequency response function at the surface of a particular stack-up. The methodology involves coupling a thermal simulation tool with an optimization algorithm to determine the material properties from temperature and heat flux measurement data. Use of a sinusoidal forcing function not only provides a mechanism to perform the frequency domain analysis described above, but sinusoids also have the practical benefit of reducing the need for instrumentation of the backside of the component. Heat losses can be minimized by alternately injecting and extracting heat on the front surface, as long as sufficiently high frequencies are used.

Flujo de potencia entre estructuras complejas sometidas a excitaciones de alta frecuencia y aplicaciones a la detecci��n de da��o estructural

El tema central de investigaci��n en esta Tesis es el estudio del comportamientodin��mico de una estructura mediante modelos que describen la distribuci��n deenerg��a entre los componentes de la misma y la aplicaci��n de estos modelos parala detecci��n de da��os incipientes.Los ensayos din��micos son un modo de extraer informaci��n sobre las propiedadesde una estructura. Si tenemos un modelo de la estructura se podr��a ajustar ��stepara que, con determinado grado de precisi��n, tenga la misma respuesta que elsistema real ensayado. Despu��s de que se produjese un da��o en la estructura,la respuesta al mismo ensayo variar�� en cierta medida; actualizando el modelo alas nuevas condiciones podemos detectar cambios en la configuraci��n del modeloestructural que nos condujeran a la conclusi��n de que en la estructura se haproducido un da��o.De este modo, la detecci��n de un da��o incipiente es posible si somos capacesde distinguir una peque��a variaci��n en los par��metros que definen el modelo. Unr��gimen muy apropiado para realizar este tipo de detecci��n es a altas frecuencias,ya que la respuesta es muy dependiente de los peque��os detalles geom��tricos,dado que el tama��o caracter��stico en la estructura asociado a la respuesta esdirectamente proporcional a la velocidad de propagaci��n de las ondas ac��sticas enel s��lido, que para una estructura dada es inalterable, e inversamente proporcionala la frecuencia de la excitaci��n. Al mismo tiempo, esta caracter��stica de la respuestaa altas frecuencias hace que un modelo de Elementos Finitos no sea aplicable enla pr��ctica, debido al alto coste computacional.Un modelo ampliamente utilizado en el c��lculo de la respuesta de estructurasa altas frecuencias en ingenier��a es el SEA (Statistical Energy Analysis). El SEAaplica el balance energ��tico a cada componente estructural, relacionando la energ��ade vibraci��n de estos con la potencia disipada por cada uno de ellos y la potenciatransmitida entre ellos, cuya suma debe ser igual a la potencia inyectada a cadacomponente estructural. Esta relaci��n es lineal y viene caracterizada por los factoresde p��rdidas. Las magnitudes que intervienen en la respuesta se consideranpromediadas en la geometr��a, la frecuencia y el tiempo.Actualizar el modelo SEA a datos de ensayo es, por lo tanto, calcular losfactores de p��rdidas que reproduzcan la respuesta obtenida en ��ste. Esta actualizaci��n,si se hace de manera directa, supone la resoluci��n de un problema inversoque tiene la caracter��stica de estar mal condicionado. En la Tesis se propone actualizarel modelo SEA, no en t��rmino de los factores de p��rdidas, sino en t��rminos depar��metros estructurales que tienen sentido f��sico cuando se trata de la respuestaa altas frecuencias, como son los factores de disipaci��n de cada componente, susdensidades modales y las rigideces caracter��sticas de los elementos de acoplamiento.Los factores de p��rdidas se calculan como funci��n de estos par��metros. Estaformulaci��n es desarrollada de manera original en esta Tesis y principalmente sefunda en la hip��tesis de alta densidad modal, es decir, que en la respuesta participanun gran n��mero de modos de cada componente estructural.La teor��a general del m��todo SEA, establece que el modelo es v��lido bajounas hip��tesis sobre la naturaleza de las excitaciones externas muy restrictivas,como que ��stas deben ser de tipo ruido blanco local. Este tipo de carga es dif��cil dereproducir en condiciones de ensayo. En la Tesis mostramos con casos pr��cticos queesta restricci��n se puede relajar y, en particular, los resultados son suficientementebuenos cuando la estructura se somete a una carga arm��nica en escal��n.Bajo estas aproximaciones se desarrolla un algoritmo de optimizaci��n por pasosque permite actualizar un modelo SEA a un ensayo transitorio cuando la carga esde tipo arm��nica en escal��n. Este algoritmo actualiza el modelo no solamente parauna banda de frecuencia en particular sino para diversas bandas de frecuencia demanera simult��nea, con el objetivo de plantear un problema mejor condicionado.Por ��ltimo, se define un ��ndice de da��o que mide el cambio en la matriz dep��rdidas cuando se produce un da��o estructural en una localizaci��n concreta deun componente. Se simula num��ricamente la respuesta de una estructura formadapor vigas donde producimos un da��o en la secci��n de una de ellas; como se tratade un c��lculo a altas frecuencias, la simulaci��n se hace mediante el M��todo delos Elementos Espectrales para lo que ha sido necesario desarrollar dentro de laTesis un elemento espectral de tipo viga da��ada en una secci��n determinada. Losresultados obtenidos permiten localizar el componente estructural en que se haproducido el da��o y la secci��n en que ��ste se encuentra con determinado grado deconfianza.AbstractThe main subject under research in this Thesis is the study of the dynamic behaviourof a structure using models that describe the energy distribution betweenthe components of the structure and the applicability of these models to incipientdamage detection.Dynamic tests are a way to extract information about the properties of astructure. If we have a model of the structure, it can be updated in order toreproduce the same response as in experimental tests, within a certain degree ofaccuracy. After damage occurs, the response will change to some extent; modelupdating to the new test conditions can help to detect changes in the structuralmodel leading to the conclusi��n that damage has occurred.In this way incipient damage detection is possible if we are able to detect srnallvariations in the model parameters. It turns out that the high frequency regimeis highly relevant for incipient damage detection, because the response is verysensitive to small structural geometric details. The characteristic length associatedwith the response is proportional to the propagation speed of acoustic waves insidethe solid, but inversely proportional to the excitation frequency. At the same time,this fact makes the application of a Finite Element Method impractical due to thehigh computational cost.A widely used model in engineering when dealing with the high frequencyresponse is SEA (Statistical Energy Analysis). SEA applies the energy balance toeach structural component, relating their vibrational energy with the dissipatedpower and the transmitted power between the different components; their summust be equal to the input power to each of them. This relationship is linear andcharacterized by loss factors. The magnitudes considered in the response shouldbe averaged in geometry, frequency and time.SEA model updating to test data is equivalent to calculating the loss factorsthat provide a better fit to the experimental response. This is formulated as an illconditionedinverse problem. In this Thesis a new updating algorithm is proposedfor the study of the high frequency response regime in terms of parameters withphysical meaning such as the internal dissipation factors, modal densities andcharacteristic coupling stiffness. The loss factors are then calculated from theseparameters. The approach is developed entirely in this Thesis and is mainlybased on a high modal density asumption, that is to say, a large number of modescontributes to the response.General SEA theory establishes the validity of the model under the asumptionof very restrictive external excitations. These should behave as a local white noise.This kind of excitation is difficult to reproduce in an experimental environment.In this Thesis we show that in practical cases this assumption can be relaxed, inparticular, results are good enough when the structure is excited with a harmonicstep function.Under these assumptions an optimization algorithm is developed for SEAmodel updating to a transient test when external loads are harmonic step functions.This algorithm considers the response not only in a single frequency band,but also for several of them simultaneously.A damage index is defined that measures the change in the loss factor matrixwhen a damage has occurred at a certain location in the structure. The structuresconsidered in this study are built with damaged beam elements; as we are dealingwith the high frequency response, the numerical simulation is implemented witha Spectral Element Method. It has therefore been necessary to develop a spectralbeam damaged element as well. The reported results show that damage detectionis possible with this algorithm, moreover, damage location is also possible withina certain degree of accuracy.

A novel methodology for planning reliable wireless sensor networks

Wireless sensor networks (WSNs) have shown their potentials in various applications, which bring a lot of benefits to users from both research and industrial areas. For many setups, it is envisioned thatWSNs will consist of tens to hundreds of nodes that operate on small batteries. However due to the diversity of the deployed environments and resource constraints on radio communication, sensing ability and energy supply, it is a very challenging issue to plan optimized WSN topology and predict its performance before real deployment. During the network planning phase, the connectivity, coverage, cost, network longevity and service quality should all be considered. Therefore it requires designers coping with comprehensive and interdisciplinary knowledge, including networking, radio engineering, embedded system and so on, in order to efficiently construct a reliable WSN for any specific types of environment. Nowadays there is still a lack of the analysis and experiences to guide WSN designers to efficiently construct WSN topology successfully without many trials. Therefore, simulation is a feasible approach to the quantitative analysis of the performance of wireless sensor networks. However the existing planning algorithms and tools, to some extent, have serious limitations to practically design reliable WSN topology: Only a few of them tackle the 3D deployment issue, and an overwhelming number of works are proposed to place devices in 2D scheme. Without considering the full dimension, the impacts of environment to the performance of WSN are not completely studied, thus the values of evaluated metrics such as connectivity and sensing coverage are not sufficiently accurate to make proper decision. Even fewer planning methods model the sensing coverage and radio propagation by considering the realistic scenario where obstacles exist. Radio signals propagate with multi-path phenomenon in the real world, in which direct paths, reflected paths and diffracted paths contribute to the received signal strength. Besides, obstacles between the path of sensor and objects might block the sensing signals, thus create coverage hole in the application. None of the existing planning algorithms model the network longevity and packet delivery capability properly and practically. They often employ unilateral and unrealistic formulations. The optimization targets are often one-sided in the current works. Without comprehensive evaluation on the important metrics, the performance of planned WSNs can not be reliable and entirely optimized. Modeling of environment is usually time consuming and the cost is very high, while none of the current works figure out any method to model the 3D deployment environment efficiently and accurately. Therefore many researchers are trapped by this issue, and their algorithms can only be evaluated in the same scenario, without the possibility to test the robustness and feasibility for implementations in different environments. In this thesis, we propose a novel planning methodology and an intelligent WSN planning tool to assist WSN designers efficiently planning reliable WSNs. First of all, a new method is proposed to efficiently and automatically model the 3D indoor and outdoor environments. To the best of our knowledge, this is the first time that the advantages of image understanding algorithm are applied to automatically reconstruct 3D outdoor and indoor scenarios for signal propagation and network planning purpose. The experimental results indicate that the proposed methodology is able to accurately recognize different objects from the satellite images of the outdoor target regions and from the scanned floor plan of indoor area. Its mechanism offers users a flexibility to reconstruct different types of environment without any human interaction. Thereby it significantly reduces human efforts, cost and time spent on reconstructing a 3D geographic database and allows WSN designers concentrating on the planning issues. Secondly, an efficient ray-tracing engine is developed to accurately and practically model the radio propagation and sensing signal on the constructed 3D map. The engine contributes on efficiency and accuracy to the estimated results. By using image processing concepts, including the kd-tree space division algorithm and modified polar sweep algorithm, the rays are traced efficiently without detecting all the primitives in the scene. The radio propagation model iv is proposed, which emphasizes not only the materials of obstacles but also their locations along the signal path. The sensing signal of sensor nodes, which is sensitive to the obstacles, is benefit from the ray-tracing algorithm via obstacle detection. The performance of this modelling method is robust and accurate compared with conventional methods, and experimental results imply that this methodology is suitable for both outdoor urban scenes and indoor environments. Moreover, it can be applied to either GSM communication or ZigBee protocol by varying frequency parameter of the radio propagation model. Thirdly, WSN planning method is proposed to tackle the above mentioned challenges and efficiently deploy reliable WSNs. More metrics (connectivity, coverage, cost, lifetime, packet latency and packet drop rate) are modeled more practically compared with other works. Especially 3D ray tracing method is used to model the radio link and sensing signal which are sensitive to the obstruction of obstacles; network routing is constructed by using AODV protocol; the network longevity, packet delay and packet drop rate are obtained via simulating practical events in WSNet simulator, which to the best of our knowledge, is the first time that network simulator is involved in a planning algorithm. Moreover, a multi-objective optimization algorithm is developed to cater for the characteristics of WSNs. The capability of providing multiple optimized solutions simultaneously allows users making their own decisions accordingly, and the results are more comprehensively optimized compared with other state-of-the-art algorithms. iMOST is developed by integrating the introduced algorithms, to assist WSN designers efficiently planning reliable WSNs for different configurations. The abbreviated name iMOST stands for an Intelligent Multi-objective Optimization Sensor network planning Tool. iMOST contributes on: (1) Convenient operation with a user-friendly vision system; (2) Efficient and automatic 3D database reconstruction and fast 3D objects design for both indoor and outdoor environments; (3) It provides multiple multi-objective optimized 3D deployment solutions and allows users to configure the network properties, hence it can adapt to various WSN applications; (4) Deployment solutions in the 3D space and the corresponding evaluated performance are visually presented to users; and (5) The Node Placement Module of iMOST is available online as well as the source code of the other two rebuilt heuristics. Therefore WSN designers will be benefit from v this tool on efficiently constructing environment database, practically and efficiently planning reliable WSNs for both outdoor and indoor applications. With the open source codes, they are also able to compare their developed algorithms with ours to contribute to this academic field. Finally, solid real results are obtained for both indoor and outdoor WSN planning. Deployments have been realized for both indoor and outdoor environments based on the provided planning solutions. The measured results coincide well with the estimated results. The proposed planning algorithm is adaptable according to the WSN designer���s desirability and configuration, and it offers flexibility to plan small and large scale, indoor and outdoor 3D deployments. The thesis is organized in 7 chapters. In Chapter 1, WSN applications and motivations of this work are introduced, the state-of-the-art planning algorithms and tools are reviewed, challenges are stated out and the proposed methodology is briefly introduced. In Chapter 2, the proposed 3D environment reconstruction methodology is introduced and its performance is evaluated for both outdoor and indoor environment. The developed ray-tracing engine and proposed radio propagation modelling method are described in details in Chapter 3, their performances are evaluated in terms of computation efficiency and accuracy. Chapter 4 presents the modelling of important metrics of WSNs and the proposed multi-objective optimization planning algorithm, the performance is compared with the other state-of-the-art planning algorithms. The intelligent WSN planning tool iMOST is described in Chapter 5. RealWSN deployments are prosecuted based on the planned solutions for both indoor and outdoor scenarios, important data are measured and results are analysed in Chapter 6. Chapter 7 concludes the thesis and discusses about future works. vi Resumen en Castellano Las redes de sensores inal��mbricas (en ingl��s Wireless Sensor Networks, WSNs) han demostrado su potencial en diversas aplicaciones que aportan una gran cantidad de beneficios para el campo de la investigaci��n y de la industria. Para muchas configuraciones se prev�� que las WSNs consistir��n en decenas o cientos de nodos que funcionar��n con bater��as peque��as. Sin embargo, debido a la diversidad de los ambientes para desplegar las redes y a las limitaciones de recursos en materia de comunicaci��n de radio, capacidad de detecci��n y suministro de energ��a, la planificaci��n de la topolog��a de la red y la predicci��n de su rendimiento es un tema muy dif��cil de tratar antes de la implementaci��n real. Durante la fase de planificaci��n del despliegue de la red se deben considerar aspectos como la conectividad, la cobertura, el coste, la longevidad de la red y la calidad del servicio. Por lo tanto, requiere de dise��adores con un amplio e interdisciplinario nivel de conocimiento que incluye la creaci��n de redes, la ingenier��a de radio y los sistemas embebidos entre otros, con el fin de construir de manera eficiente una WSN confiable para cualquier tipo de entorno. Hoy en d��a todav��a hay una falta de an��lisis y experiencias que orienten a los dise��adores de WSN para construir las topolog��as WSN de manera eficiente sin realizar muchas pruebas. Por lo tanto, la simulaci��n es un enfoque viable para el an��lisis cuantitativo del rendimiento de las redes de sensores inal��mbricos. Sin embargo, los algoritmos y herramientas de planificaci��n existentes tienen, en cierta medida, serias limitaciones para dise��ar en la pr��ctica una topolog��a fiable de WSN: S��lo unos pocos abordan la cuesti��n del despliegue 3D mientras que existe una gran cantidad de trabajos que colocan los dispositivos en 2D. Si no se analiza la dimensi��n completa (3D), los efectos del entorno en el desempe��o de WSN no se estudian por completo, por lo que los valores de los par��metros evaluados, como la conectividad y la cobertura de detecci��n, no son lo suficientemente precisos para tomar la decisi��n correcta. A��n en menor medida los m��todos de planificaci��n modelan la cobertura de los sensores y la propagaci��n de la se��al de radio teniendo en cuenta un escenario realista donde existan obst��culos. Las se��ales de radio en el mundo real siguen una propagaci��n multicamino, en la que los caminos directos, los caminos reflejados y los caminos difractados contribuyen a la intensidad de la se��al recibida. Adem��s, los obst��culos entre el recorrido del sensor y los objetos pueden bloquear las se��ales de detecci��n y por lo tanto crear ��reas sin cobertura en la aplicaci��n. Ninguno de los algoritmos de planificaci��n existentes modelan el tiempo de vida de la red y la capacidad de entrega de paquetes correctamente y pr��cticamente. A menudo se emplean formulaciones unilaterales y poco realistas. Los objetivos de optimizaci��n son a menudo tratados unilateralmente en los trabajos actuales. Sin una evaluaci��n exhaustiva de los par��metros importantes, el rendimiento previsto de las redes inal��mbricas de sensores no puede ser fiable y totalmente optimizado. Por lo general, el modelado del entorno conlleva mucho tiempo y tiene un coste muy alto, pero ninguno de los trabajos actuales propone alg��n m��todo para modelar el entorno de despliegue 3D con eficiencia y precisi��n. Por lo tanto, muchos investigadores est��n limitados por este problema y sus algoritmos s��lo se pueden evaluar en el mismo escenario, sin la posibilidad de probar la solidez y viabilidad para las implementaciones en diferentes entornos. En esta tesis, se propone una nueva metodolog��a de planificaci��n as�� como una herramienta inteligente de planificaci��n de redes de sensores inal��mbricas para ayudar a los dise��adores a planificar WSNs fiables de una manera eficiente. En primer lugar, se propone un nuevo m��todo para modelar demanera eficiente y autom��tica los ambientes interiores y exteriores en 3D. Seg��n nuestros conocimientos hasta la fecha, esta es la primera vez que las ventajas del algoritmo de _image understanding_se aplican para reconstruir autom��ticamente los escenarios exteriores e interiores en 3D para analizar la propagaci��n de la se��al y viii la planificaci��n de la red. Los resultados experimentales indican que la metodolog��a propuesta es capaz de reconocer con precisi��n los diferentes objetos presentes en las im��genes satelitales de las regiones objetivo en el exterior y de la planta escaneada en el interior. Su mecanismo ofrece a los usuarios la flexibilidad para reconstruir los diferentes tipos de entornos sin ninguna interacci��n humana. De este modo se reduce considerablemente el esfuerzo humano, el coste y el tiempo invertido en la reconstrucci��n de una base de datos geogr��fica con informaci��n 3D, permitiendo as�� que los dise��adores se concentren en los temas de planificaci��n. En segundo lugar, se ha desarrollado un motor de trazado de rayos (en ingl��s ray tracing) eficiente para modelar con precisi��n la propagaci��n de la se��al de radio y la se��al de los sensores en el mapa 3D construido. El motor contribuye a la eficiencia y la precisi��n de los resultados estimados. Mediante el uso de los conceptos de procesamiento de im��genes, incluyendo el algoritmo del ��rbol kd para la divisi��n del espacio y el algoritmo _polar sweep_modificado, los rayos se trazan de manera eficiente sin la detecci��n de todas las primitivas en la escena. El modelo de propagaci��n de radio que se propone no s��lo considera los materiales de los obst��culos, sino tambi��n su ubicaci��n a lo largo de la ruta de se��al. La se��al de los sensores de los nodos, que es sensible a los obst��culos, se ve beneficiada por la detecci��n de objetos llevada a cabo por el algoritmo de trazado de rayos. El rendimiento de este m��todo de modelado es robusto y preciso en comparaci��n con los m��todos convencionales, y los resultados experimentales indican que esta metodolog��a es adecuada tanto para escenas urbanas al aire libre como para ambientes interiores. Por otra parte, se puede aplicar a cualquier comunicaci��n GSM o protocolo ZigBee mediante la variaci��n de la frecuencia del modelo de propagaci��n de radio. En tercer lugar, se propone un m��todo de planificaci��n de WSNs para hacer frente a los desaf��os mencionados anteriormente y desplegar redes de sensores fiables de manera eficiente. Se modelan m��s par��metros (conectividad, cobertura, coste, tiempo de vida, la latencia de paquetes y tasa de ca��da de paquetes) en comparaci��n con otros trabajos. Especialmente el m��todo de trazado de rayos 3D se utiliza para modelar el enlace de radio y se��al de los sensores que son sensibles a la obstrucci��n de obst��culos; el enrutamiento de la red se construye utilizando el protocolo AODV; la longevidad de la red, retardo de paquetes ix y tasa de abandono de paquetes se obtienen a trav��s de la simulaci��n de eventos pr��cticos en el simulador WSNet, y seg��n nuestros conocimientos hasta la fecha, es la primera vez que simulador de red est�� implicado en un algoritmo de planificaci��n. Por otra parte, se ha desarrollado un algoritmo de optimizaci��n multi-objetivo para satisfacer las caracter��sticas de las redes inal��mbricas de sensores. La capacidad de proporcionar m��ltiples soluciones optimizadas de forma simult��nea permite a los usuarios tomar sus propias decisiones en consecuencia, obteniendo mejores resultados en comparaci��n con otros algoritmos del estado del arte. iMOST se desarrolla mediante la integraci��n de los algoritmos presentados, para ayudar de forma eficiente a los dise��adores en la planificaci��n de WSNs fiables para diferentes configuraciones. El nombre abreviado iMOST (Intelligent Multi-objective Optimization Sensor network planning Tool) representa una herramienta inteligente de planificaci��n de redes de sensores con optimizaci��n multi-objetivo. iMOST contribuye en: (1) Operaci��n conveniente con una interfaz de f��cil uso, (2) Reconstrucci��n eficiente y autom��tica de una base de datos con informaci��n 3D y dise��o r��pido de objetos 3D para ambientes interiores y exteriores, (3) Proporciona varias soluciones de despliegue optimizadas para los multi-objetivo en 3D y permite a los usuarios configurar las propiedades de red, por lo que puede adaptarse a diversas aplicaciones de WSN, (4) las soluciones de implementaci��n en el espacio 3D y el correspondiente rendimiento evaluado se presentan visualmente a los usuarios, y (5) El _Node Placement Module_de iMOST est�� disponible en l��nea, as�� como el c��digo fuente de las otras dos heur��sticas de planificaci��n. Por lo tanto los dise��adores WSN se beneficiar��n de esta herramienta para la construcci��n eficiente de la base de datos con informaci��n del entorno, la planificaci��n pr��ctica y eficiente de WSNs fiables tanto para aplicaciones interiores y exteriores. Con los c��digos fuente abiertos, son capaces de comparar sus algoritmos desarrollados con los nuestros para contribuir a este campo acad��mico. Por ��ltimo, se obtienen resultados reales s��lidos tanto para la planificaci��n de WSN en interiores y exteriores. Los despliegues se han realizado tanto para ambientes de interior y como para ambientes de exterior utilizando las soluciones de planificaci��n propuestas. Los resultados medidos coinciden en gran medida con los resultados estimados. El algoritmo de planificaci��n x propuesto se adapta convenientemente al deise��o de redes de sensores inal��mbricas, y ofrece flexibilidad para planificar los despliegues 3D a peque��a y gran escala tanto en interiores como en exteriores. La tesis se estructura en 7 cap��tulos. En el Cap��tulo 1, se presentan las aplicaciones de WSN y motivaciones de este trabajo, se revisan los algoritmos y herramientas de planificaci��n del estado del arte, se presentan los retos y se describe brevemente la metodolog��a propuesta. En el Cap��tulo 2, se presenta la metodolog��a de reconstrucci��n de entornos 3D propuesta y su rendimiento es evaluado tanto para espacios exteriores como para espacios interiores. El motor de trazado de rayos desarrollado y el m��todo de modelado de propagaci��n de radio propuesto se describen en detalle en el Cap��tulo 3, evalu��ndose en t��rminos de eficiencia computacional y precisi��n. En el Cap��tulo 4 se presenta el modelado de los par��metros importantes de las WSNs y el algoritmo de planificaci��n de optimizaci��n multi-objetivo propuesto, el rendimiento se compara con los otros algoritmos de planificaci��n descritos en el estado del arte. La herramienta inteligente de planificaci��n de redes de sensores inal��mbricas, iMOST, se describe en el Cap��tulo 5. En el Cap��tulo 6 se llevan a cabo despliegues reales de acuerdo a las soluciones previstas para los escenarios interiores y exteriores, se miden los datos importantes y se analizan los resultados. En el Cap��tulo 7 se concluye la tesis y se discute acerca de los trabajos futuros.