Дисертації з теми "Multi level linear modelling"

The Met Office uses the NAME dispersion model to solve stochastic differential equations (SDEs) for predicting the transport and spread of atmospheric pollutants. Time stepping methods for this SDE dominate the computation time. In particular the slow convergence of the Monte Carlo Method imposes limitations on the accuracy with which predictions can be made on operational timescales. We review the theory of both the Standard and Multi Level Monte Carlo Methods, and in particular the complexity theorems discussed in [9] in a more general context. We then argue how it can potentially give rise to significant gains for this problem in atmospheric dispersion modelling. To verify these theoretical arguments numerically, we consider two model problems; a simplified problem which corresponds to homogeneous turbulence and is used by the Met Office for long term predictions, as well as a full non-linear model problem close to that used by the Met Office for atmospheric dispersion modelling. For both model problems we performed numerical tests in which we observed significant speed-up as a result of the implementation of the Multi Level Monte Carlo Method. The numerically observed convergence rates are also confirmed by a full theoretical analysis for the simplified model problem.

Beaucoup de procédés utilisés dans l'industrie sidérurgique (coulée de lingots,coulée continue, …) peuvent générer des défauts : macro-ségrégation, mauvaises propriétés de la microstructure, défauts surfaciques. Ces problèmes peuvent être résolus par un contrôle de la température et de l’écoulement d'acier liquide. Le brassage électromagnétique (EMS) est une technique largement utilisée pour contrôler l’écoulement d'acier liquide par l’imposition d'un champ électromagnétique. Cette technique est complexe car elle couple plusieurs types de problèmes physiques:écoulement multiphasique, solidification,transfert de chaleur et induction électromagnétique à basse fréquence.En outre, l’approche expérimentale est difficile de par la dimension,l'environnement et le coût des procédés considérés. Pour ces raisons, des simulations numériques efficaces sont nécessaires pour comprendre les applications EMS et améliorer les procédés évoqués. L'objectif de cette thèse est de développer une méthodologie numérique robuste,efficace et précise pour la simulation multi-physique de l'EMS, en particulier pour le brassage dans le moule dans le cadre de la coulée continue d'acier. Cette méthodologie a été mise en oeuvre dans le code commercial THERCAST® pour être utilisé dans le cadre d’applications industrielles
Many of the processes used in thesteelmaking industry (e.g. ingot casting,continuous casting, …) can lead todefects: macro-segregation, poormicrostructure properties, surfacedefects. These issues can be solved bycontrolling the temperature and the flowof molten steel. Electromagnetic stirring(EMS) is a widely used technique to steerthe flow of liquid steel by thesuperimposition of an electro-magneticfield. This application is complex becauseit couples several physical problems:multi-phase flow, solidification, heattransfer and low frequency electromagneticinduction. In addition,experimental work is difficult because ofthe size, environment and cost of theconsidered processes. For thesereasons, efficient and effective numericalsimulations are needed to understandEMS applications and improve theaforementioned processes.The objective of this thesis is to developa robust, efficient and accurate numericalprocedure for the multi-physicssimulation of EMS, especially for in-moldstirring in the framework of continuouscasting of steel. This procedure has beenimplemented in the commercial codeTHERCAST® in order to be used forindustrial applications

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
This work presents a method to generate games with multilevel and multiple users using Hierarchical Coloured Petri Nets. The design of a multiuser game containing multiple navigation environments (multilevel) is made from the model of a Hierarchical Coloured Petri Net, in which are specified all of the rules, properties and structures of the game. The created model for the game can be formally analysed, verifying the existence of deadlocks and invalid paths, for example, and others possible conception problems, that can be done with the tools available on CPN Tools. To validate this method, a tool has been developed, called CPN Games, which allows fast and dynamic development of simple conception games only using Hierarchical Coloured Petri Nets. The XML codes of the designed models in CPN Tools are interpreted by CPN Games following a set of predefined rules to instantiate different games, without additional programing. It is demonstrated the mechanisms of the design, analysis and validation of the models and finally it is presented several examples of games developed by this tool.
Este trabalho apresenta um mÃtodo para geraÃÃo de jogos multinÃveis e com mÃltiplos usuÃrios por meio de modelagem em Redes de Petri Coloridas HierÃrquicas. A concepÃÃo de um jogo multiusuÃrio, contendo mÃltiplos ambientes de navegaÃÃo (multinÃveis), à feita a partir da criaÃÃo de um modelo hierÃrquico em Rede de Petri Colorida, no qual se especificam todas as regras, propriedades e estruturas do jogo. O modelo criado para o jogo pode ser analisado formalmente, verificando-se, por exemplo, a existÃncia de bloqueios e de transiÃÃes mortas (caminhos invÃlidos), entre outros possÃveis problemas de concepÃÃo, o que pode ser feito com a utilizaÃÃo de ferramentas disponÃveis no CPN Tools. Para validar esse mÃtodo, foi concebida uma ferramenta, denominada CPN Games, que permite o desenvolvimento rÃpido e dinÃmico de jogos de concepÃÃo simples exclusivamente por Rede de Petri Colorida HierÃrquica. Os cÃdigos em XML de modelos constituÃdos com o CPN Tools sÃo interpretadas pelo CPN Games seguindo um conjunto de regras prà estabelecidas para instanciar diferentes jogos, sem a necessidade de programaÃÃo adicional. SÃo demonstrados os mecanismos de criaÃÃo, anÃlise e validaÃÃo dos modelos e diferentes exemplos de jogos construÃdos com a ferramenta.

In this thesis we examine exchange rates and monetary policy of four emerging Asian countries, namely Indonesia, Malaysia, the Philippines and South Korea. We model equilibrium exchange rates using a general behavioural specification consistent with a variety of theoretical approaches; and short-run dynamics using a general non-linear adjustment model. We find in all countries examined, equilibrium nominal and real exchange rates are a function of permanent relative output and one or more variables from domestic and foreign price levels, nominal and real interest rate differentials, the level of and changes in net foreign assets, and a time trend. These results imply that individual countries present significant elements of idiosyncratic behaviour, casting doubt on empirical models using panel-data techniques. We also obtain evidence of non-linear exchange rate dynamics, with the speed of adjustment to equilibrium being in all cases a function of the size, and in two cases, the sign of the misalignment term. With respect to monetary policy, we examined these countries' monetary policy reaction function based on an open economy augmented Taylor rule including the exchange rate and the foreign interest rate. Using a formal testing approach, our tests reject linearity, suggesting that monetary authorities in these four emerging economies are subject to nonlinear inflation effects and that they respond more vigorously to inflation when it is further from the target. Our results also lead us to speculate that policymakers in three countries may have been attempting to keep inflation within the range, while those in the other country may have been pursuing a point inflation target. Finally, we also find monetary policy is asymmetric as policy makers respond differently to upward and downward deviations of inflation away from the target.

This dissertation targets two important problems. The first one is the design of low-level DLA kernels for architectures comprising two (or more) classes of cores. The main question we have to address here is how to attain a balanced distribution of the computational workload among the heterogeneous cores while taking into account that some of the resources, in particular cache levels, are either shared or private. The second question is partially related to the first one. Concretely, this dissertation explores an alternative to runtime-based systems in order to extract “sufficient" parallelism from complex DLA operations while making an efficient use of the cache hierarchy of the architecture. Thus, the main goal of this thesis is the study, design, development and analysis of experimental solutions that are architecture-aware for the execution of DLA operations on low power architectures, more specically asymmetric platforms.
Esta tesis doctoral aborda dos problemas importantes. El primero es el diseño de kernels DLA de bajo nivel para arquitecturas compuestas por dos (o más) tipos de cores. La principal cuestión en este caso es como obtener un distribución de carga computacional balanceada entre los cores heterogéneos mientras se tiene en cuenta que algunos recursos, en particular los niveles de cache, son bien compartidos o privados. La segunda cuestión está parcialmente relacionada con la primera. Concretamente, en la teis se explora un alternativa a los sistemas basados en runtimes para extraer paralelismo sufciente para operaciones DLA complejas mientras se hace un uso eficiente de la jerarquía de cache de la arquitectura. Por tanto, el objetivo general de esta tesis es el estudio, diseño, desarrollo y análsis de soluciones experimentales que son conscientes de la arquitectura para la ejecución de operaciones DLA en arquitecturas de bajo consumo, más concretamente sistemas asimétricos.

An imaginative development of renewable energy schemes leads to power generation where the energy was previously dissipated. This thesis describes a generic model that integrates disciplines to address the barriers to deployment of hydro schemes; it uses North-West England as a case study for demonstration. The model focuses on the need to make an economic decision as to whether development is appropriate or not and is defined by a loop that links essential questions. Decision making is complex requiring a variety of data sources as evidence and forms of evaluation, in order to simplify, the process progresses through a number of iterations. By starting with simple questions regarding each component and identifying obvious show-stoppers the advice on the decision is made efficiently. Each iteration requires more detailed assessment, but by posing simple questions first, time is not wasted in solving detailed problems in one area before finding that the development is stymied by a much simpler issue in a later section of the loop. The decision requires information from a number of sources starting with the energy available at different times of year and under different conditions. To maximise the value of the research carried out, the model has been presented as a web- based tool', freely available to anyone with internet access. The tool follows standard web protocols and is intuitive in its application, using a hierarchy of menus. To demonstrate the operation of the model the quantitative aspects of the first iteration round the loop are described. Further iterations are presented without quantification. Schemes in different stages of development have been investigated ranging from initial concepts through to operating hydro systems. One scheme, at Heron Corn Mill on the river Bela just south of Milnthorpe has progressed through the course of this research from an initial idea through to a functioning power plant.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2018.
In this research, we undertake a numerical study of the interaction between laser beams and two as well as multi-level atoms. The main aim of this research is to obtain a deeper understanding of laser-atom interactions and non-linear processes such as optical four-wave mixing. This work will supplement experiments to be conducted by other members of the group, who are involved in generating entangled photons via four-wave mixing in cold rubidium atoms. We begin by performing a basic study of the interaction between laser beams and two-level atoms as an aid to gain knowledge of numerical techniques, as well as an understanding of the physics behind light-atom interactions. We make use of a semi-classical approach to describe the system where the atoms are treated quantum mechanically and the laser beams are treated classically. We study the interaction between atoms and laser beams using the density matrix operator and Maxwell's equations respectively. By solving the optical Bloch equations for two-level atoms we examine the atomic populations and coherences and present plots of the density matrix elements as a function of time. The e ects of various parameters such as laser intensity, detuning and laser modulation have been tested. The behaviour of the laser beam as it propagates through the atomic sample is also studied. This is determined by Maxwell's equation where the atomic polarization is estimated from the coherence terms of the density matrix elements.
French South African Institute of Technology National Research Foundation

Vector-borne diseases, such as those transmitted by mosquitoes, pose a significant public health concern in many countries worldwide. In this thesis, I explored the role of a number of risk factors defined at multiple scales on vector-borne disease prevalence, focusing on malaria and arboviral infections in several regions of North-Eastern Tanzania, with the principal aim of improving the overall diagnosis of febrile illness in this region. First, I investigated the influence of household-wealth on prevalence of malaria and arboviral infections using principal component analysis (PCA), and then described the methodological challenges associated with this statistical technique when used to compute indices from smaller datasets. I then employed a multilevel modelling approach to simultaneously incorporate household-level anthropogenic factors and village-level environmental characteristics to investigate key determinants of Anopheles malaria vector density among rural households. These analyses provided methodologically rigorous approaches to studying vector-borne diseases at a very fine-scale and also have significant public health relevance as the research findings can assist in guiding policy decisions regarding surveillance efforts as well as inform where and when to prioritize interventions.

This thesis contributed to the development of a microscale drying model to predict the actual moisture distribution and physical quality of food material during the drying process. This research has developed a novel methodology to create realistic cellular geometry from microscopic images of food material which can be used as an exact computational domain for the microscale drying model. The model developed is capable of predicting of the cellular level transport and the anisotropic deformation of food material during the drying. The results obtained from the model were validated against extensive experimental investigations.

The objective of this study is to introduce a more refined methodological approach for signalling corporate collapse. The proposed methodological approach provides informed stakeholders in a corporation with a tool that would help them signal impending collapse with a higher degree of accuracy than the existing mainstream methodology. By doing so, the proposed methodological approach helps stakeholders take appropriate measures, if possible, to save their company from collapse. The motivation behind this study emanates from a need in the literature in relation to coming up with a new methodological approach that is superior to what is available. For example, Jones and Hensher (2004), one of the most recent studies in the field, stated that over the past three decades there has been a conspicuous absence of modelling innovation in the literature on financial distress prediction, as well as a failure to keep abreast of important methodological developments emerging in other fields of the social sciences. Specifically, this study introduces a new ratio-based multivariate methodological approach for signalling corporate collapse, called Multi-Level Modelling (MLM). Moreover, this study demonstrated that MLM provides informed stakeholders in a corporation with a tool that would help them signal impending collapse with a higher degree of accuracy than Multiple Discriminant Analysis (MDA), which is the mainstream benchmark methodological approach. By doing so, MLM helps stakeholders take appropriate measures, if possible, to save their company from collapse. The empirical results depicted the superiority of MLM over MDA. MLM generated better overall predictive power and dramatically reduced the occurrence of Type I error (classifying a collapsed company as non-collapsed). Moreover, MLM achieved those results while at the same time capturing variations in industry sectors among the data sample of companies. This is something that MDA was not capable of.

This thesis deals with issues pertaining the wireless multicomputer interconnection networks namely topology and Medium Access Control (MAC). It argues that new channel assignment technique based on regular low-dimensional hypergraph networks, the dual radio wireless hypermesh, represents a promising alternative high-performance wireless interconnection network for the future multicomputers to shared communication medium networks and/or ordinary wireless mesh networks, which have been widely used in current wireless networks. The focus of this work is on improving the network throughput while maintaining a relatively low latency of a wireless network system. By means of a Carrier Sense Multiple Access (CSMA) based design of the MAC protocol and based on the desirable features of hypermesh network topology a relatively high performance network has been introduced. Compared to the CSMA shared communication channel model, which is currently the de facto MAC protocol for most of wireless networks, our design is shown to achieve a significant increase in network throughput with less average network latency for large number of communication nodes. SystemC model of the proposed wireless hypermesh, validated through mathematical models, are then introduced. The analysis has been incorporated in the proper SystemC design methodology which facilitates the integration of communication modelling into the design modelling at the early stages of the system development. Another important application of SystemC modelling techniques is to perform meaningful comparative studies of different protocols, or new implementations to determine which communication scenario performs better and the ability to modify models to test system sensitivity and tune performance. Effects of different design parameters (e.g., packet sizes, number of nodes) has been carried out throughout this work. The results shows that the proposed structure has out perform the existing shared medium network structure and it can support relatively high number of wireless connected computers than conventional networks.

The study of past climates provides a unique opportunity to test our understanding of the Earth system and our confidence in climate models. The nature of this subject requires a fine balance between complexity and efficiency. While comprehensive models can capture the system’s behaviour more realistically, fast but less accurate models are capable of integrating on the long timescale associated with Palaeoclimatology. In this thesis, a statistical approach is proposed to address the limitation of our simple atmospheric module in simulating glacial climates by incorporating a statistical surrogate of a general circulation model of the atmosphere into our Earth system modelling framework, GENIE. To utilise the available model spectrum of different complexities, a multi-level Gaussian Process (GP) emulation technique is proposed to established the link between a computationally expensive atmospheric model, PLASIM (Planet Simulator), and a cheaper model, EMBM (energy-moisture balance model). The method is first demonstrated by emulating a scalar summary quantity. A dimensional reduction technique is then introduced, allowing the high-dimensional model outputs to be emulated as functions of high-dimensional boundary forcing inputs. Even though the two atmospheric models chosen are structurally unrelated, GP emulators of PLASIM atmospheric variables are successfully constructed using EMBM as a fast approximation. With the extra information gained from the cheap model, the emulators of PLASIM’s 2-D surface output fields, are built at a reduced computational cost. The emulated quantities are validated against simulated values, showing that the ensemble-wide behaviour of the spatial fields is well captured. Finally, the emulator of PLASIM’s wind field is incorporated into GENIE, providing an interactive statistical wind field which responds to changes in the bound- ary condition described by the ocean module. While exhibiting certain limitation due to the structural bias in PLASIM’s wind, the new hybrid model introduces additional variations to the over-diffusive spatial outputs of EMBM without incurring a substantial computational cost.

El modelado se ha convertido en los últimos años en una herramienta esencial en el diseño de motores de combustión interna alternativos, ya que permite reducir considerablemente el tiempo y los costes de desarrollo. Las metodologías de diseño clásicas se basan en la fabricación de prototipos y la realización de pruebas de ensayo y error. Actualmente, la mayoría de estas pruebas han sido sustituidas por cálculos numéricos, de modo que sólo las opciones de diseño más prometedoras se prueban en realidad en banco motor. Durante años, los códigos unidimensionales de dinámica de gases en el dominio del tiempo han sido suficientes para modelar tanto las prestaciones y el consumo del motor como el ruido de admisión y escape. Sin embargo, para un nivel más exigente de diseño, una representación 1D puede no ser suficiente para describir con precisión el flujo en ciertos elementos. Esto es especialmente importante en el caso de silenciadores, donde la hipótesis unidimensional sólo se puede aplicar a geometrías simples. En el caso de las uniones de conductos es la existencia de estructuras tridimensionales de flujo complejas lo que establece el límite de la aplicabilidad de una descripción simple cero-dimensional. En vista de estas limitaciones, la primera opción sería el uso de un modelo de dinámica de fluidos computacional (CFD); sin embargo, su aplicación conllevaría un tiempo de cálculo excesivo. Una posible solución de compromiso viene dada por los modelos cuasi-3D, basados en esquemas tridimensionales, pero con ciertas simplificaciones capaces de reducir significativamente el tiempo de cálculo sin afectar excesivamente a la precisión. Tales soluciones se han convertido en estándar en los códigos comerciales y se han aplicado con éxito a los silenciadores, tanto para excitaciones acústicas en el régimen lineal como en condiciones reales de motor, típicamente no lineales. Esta tesis tiene como objetivo el desarrollo de un nuevo método numérico cuasi-3D en una malla escalonada, basado en la simplificación de la ecuación de la cantidad de movimiento, para ser incluido en un código unidimensional existente. Tal método, sin embargo, no está libre de inconvenientes. En particular, se ve afectado por la aparición de oscilaciones no físicas, especialmente en gradientes de presión significativos. De la revisión bibliográfica se determina que este comportamiento es típico en esquemas de segundo orden y se puede ver acentuado por las simplificaciones adoptadas. Tras estudiar las posibles soluciones aplicables a este problema, se desarrollan tres limitadores de flujo diferentes, basados en las metodologías MDT, FCT y TVD. Una vez definido el método numérico y asegurada su estabilidad, es necesario desarrollar las condiciones de contorno adecuadas que permitan su utilización. Con este objetivo, se desarrollan las condiciones de pulso de presión de entrada y de extremo anecoico, los cuales permiten simular un banco de impulso. No hay que olvidar, sin embargo, que el objetivo final es la conexión con un código unidimensional, por lo que hay que comprobar que el método numérico cuasi-3D creado es compatible con los unidimensionales existentes, mostrando algunos resultados preliminares. Finalmente, con el método ya completamente operativo, se procede a su validación en las aplicaciones para las que ha sido diseñado principalmente, las cuales son, modelado de silenciadores y uniones de conductos. Para el caso de los silenciadores, se modelan dispositivos de complejidad creciente, pasando por geometrías de sección constante hasta sistemas con geometrías reales. Los resultados obtenidos se validan con otras herramientas tanto lineales como no lineales. En el caso de las uniones de conductos, el objetivo principal es el de establecer el potencial del nuevo método numérico frente a los tradicionales unidimensionales, por lo que los resultados de ambos se comparan con datos experiment
Engine modelling has become an essential tool in the design of internal combustion engines, allowing considerable reductions in development time and cost. Classical design methodologies are based on prototype manufacturing and trial-and-error tests, but currently, most of those tests have been replaced by numerical computations, so that only the most promising design options are actually tested on engine bench. For years, one-dimensional gas dynamics codes in the time domain have offered sufficiently good solutions for modelling both engine performance and intake and exhaust noise. However, for a more demanding level of design, a 1D representation may not be sufficient to describe accurately the flow in certain elements. This is especially important in the case of silencers. In the case of duct junctions, the existence of complex 3D flow structures is what sets the applicability limit for a simple zero-dimensional description. In view of these limitations, the first option would typically be the use of a computational fluid dynamics (CFD) model; however, the application of such a model to a complete intake or exhaust system entails an excessive computational time. A possible compromise solution is given by quasi-3D models, based on three-dimensional schemes, but with certain simplifications able to significantly reduce the calculation time without excessively affecting the accuracy. Such solutions have become standard in commercial codes and have been successfully applied to silencers with perforated tubes and absorbing material, both in the linear acoustic regime and in real engine conditions, typically non-linear. The objective of this thesis is the development a new quasi-3D numerical method in a staggered-grid, based on the simplification of the momentum equation, to be included in an existing one-dimensional code. Such method however, is not hassle free. In particular, it is affected by the appearance of non-physical oscillations, specially near significant pressure gradients. From the literature review it is determined that this behaviour is typical among second-order schemes and it can be aggravated by the simplifications adopted. After researching the possible solutions to face this problem, three different flux limiters are developed, based on the MDT, FCT and TVD methodologies. In the case of the two latter methods, its effectiveness is well established for finite differences schemes, thus defining a clear improving line for quasi-3D models. Once the numerical method is defined and its stability assured, proper boundary conditions that allow its use must be developed. With this objective, a pressure pulse inlet and an anechoic termination boundary condition are developed, which allow the simulation of an impulse test rig. It should not be forgotten, however, that the ultimate objective is the connection with a one-dimensional code, therefore the compatibility of the quasi-3D numerical method created with the existing one-dimensional methods has to be tested, showing some preliminary results. Eventually, with a fully operative method, the validation process for the applications which it has been mainly developed for, takes place, namely, mufflers and duct junctions modelling. In the case of mufflers, increasingly complex devices are modelled, from constant section geometries to real geometry systems. The results obtained are validated with both linear and non-linear tools. In the case of duct junctions, the main objective is to establish the potential of the new numerical method against the traditional one-dimensional schemes, consequently, results from both approaches are compared to experimental measures, obtaining promising results.
El modelatge s'ha convertit en els últims anys en una eina essencial en el disseny de motors de combustió interna alternatius, ja que permet reduir considerablement el temps i els costos de desenvolupament. Les metodologies de disseny clàssiques es basen en la fabricació de prototips i la realització de proves d'assaig i error. Actualment, la majoria d'aquestes proves han sigut substituïdes per càlculs numèrics, de manera que només les opcions de disseny més prometedores es proven en realitat en banc motor. Durant anys, els codis unidimensionals de dinàmica de gasos en el domini del temps han sigut suficients per a modelar tant les prestacions i el consum del motor com el soroll d'admissió i escapament. No obstant això, per a un nivell més exigent de disseny, una representació 1D pot no ser prou per a descriure amb precisió el flux en certs elements. Açò és especialment important en el cas de silenciadors, on la hipòtesi unidimensional només es pot aplicar a geometries simples. En el cas de les unions de conductes és l'existència d'estructures tridimensionals de flux complexes el que establix el límit de l'aplicabilitat d'una descripció simple zero-dimensional. En vista d'estes limitacions, la primera opció seria típicament l'ús d'un model de dinàmica de fluids computacional (CFD); no obstant això, l'aplicació comporta un temps de càlcul excessiu. Una possible solució de compromís ve donada pels models quasi-3D, basats en esquemes tridimensionals, però amb certes simplificacions capaços de reduir significativament el temps de càlcul sense afectar excessivament la precisió. Tals solucions s'han convertit en estàndard en codis comercials i s'han aplicat amb èxit als silenciadors, tant per a excitacions acústiques en el règim lineal com en condicions reals de motor, típicament no lineals. Aquesta tesi té com a objectiu el desenvolupament d'un nou mètode numèric quasi-3D en una malla escalonada, basat en la simplificació de l'equació de la quantitat de moviment, per a ser inclòs en un codi unidimensional existent. Tal mètode, però, no està lliure d'inconvenients. En particular, es veu afectat per l'aparició d'oscil·lacions no físiques, especialment en gradients de pressió significatius. De la revisió bibliogràfica es determina que aquest comportament és típic en esquemes de segon ordre i es pot veure accentuat per les simplificacions adoptades. Després d'estudiar les possibles solucions aplicables a aquest problema, es desenvolupen tres limitadors de flux diferents, basats en les metodologies MDT, FCT i TVD. En el cas dels dos últims mètodes, la seua efectivitat està ben establida per als esquemes de diferències finites, la qual cosa definix una clara via de millora per als models quasi-3D. Una vegada definit el mètode numèric i assegurada la seua estabilitat, és necessari desenvolupar les condicions de contorn adequades que permeten la seua utilització. Amb aquest objectiu, es desenvolupen les condicions de pols de pressió d'entrada i d'extrem anecoic, els quals permeten simular un banc d'impuls. No cal oblidar que l'objectiu final és la connexió amb un codi unidimensional, per la qual cosa cal comprovar que el mètode numèric cuasi-3D creat és compatible amb els unidimensionals existents, mostrant alguns resultats preliminars. Finalment, es procedix a la seua validació en les aplicacions per a les que ha sigut dissenyat principalment, les quals són, modelatge de silenciadors i unions de conductes. Per al cas dels silenciadors, es modelen dispositius de complexitat creixent, passant per geometries de secció constant fins a sistemes amb geometries reals. Els resultats obtinguts es validen amb altres eines tant lineals com no lineals. En el cas de les unions de conductes, l'objectiu principal és el d'establir el potencial del nou mètode numèric front als unidimensionals tradicionals, per la qual cosa els resultats d'ambdós es comparen amb dades experim
Hernández Marco, M. (2018). A non-linear quasi-3D model for air management modelling in engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/103683
TESIS

As unmanned vehicle capabilities have matured, the design and development of autonomous collaborative Systems-of-Systems (SoS) has gained increased attention. This has been motivated by the indication that significant improvements in overall effectiveness may be possible by employing many systems in cooperation with one another. However, as the potential combinations of vehicles, subsystems, and operational concepts becomes increasingly large, a systematic approach is needed for designing and analyzing alternatives. Furthermore, the discrete nature of the problem can cause variations in effectiveness that are counter-intuitive, such as a point of diminishing returns as the number of systems grows. Systems-of-systems are hierarchical in nature, consisting of top-level mission requirements that are decomposed into system- and subsystem-level performance measures. The overarching research objectives of this dissertation are to show that the analysis of alternatives should be performed at varying levels of the SoS hierarchy and to provide novel means for performing those analyses. In particular, it has been postulated that a formulation built on an energy-based approach to multi-level analysis of SoS components will enable more accurate and transparent subsystem and system trade-offs. Various steps of the design process are established and argued for or against, and significant focus is placed on the analysis of alternatives. The foundation of the new method is laid on structured SoS engineering principles. The full substance comes together by incorporating unique aspects developed within this dissertation. A new virtual experimentation approach is presented for creating sensor performance representations that are functions of vehicle operations. The sonar equation is used as a baseline sensor model for comparison against the new virtual experimentation method. Dozens of forward-looking and side-scan sonar experiments are designed, and data is provided to show the extent to which typical sensor modeling over-predicts performance without vehicle operations considered. In addition, comparisons are made between possible representations of vehicle performance. An underwater vehicle sizing and synthesis process is developed to enable comparisons between system-level component modeling approaches. The experiments attest to significant gaps in accuracy when performing sensor and operational trade-offs without energy-based modeling of the collaborative vehicles. Finally, a heuristic path-planning algorithm is formulated, and mixed-integer linear programming is used to choose between alternative SoS designs. The developed method is demonstrated through a representative example problem: a group of unmanned underwater vehicles (UUVs) operating in a collaborative fashion to search for underwater objects. The example scenario provides an application for illustrating the phenomenon discussed in regards to the analysis of alternatives of collaborative SoS. The significance of providing more or less analytic detail is traced and the effect on mission requirements is quantified. Counter-intuitive results are highlighted, such as the observation that the increased energy required for systems to effectively collaborate can often out-weigh the benefits gained in overall mission effectiveness.

The application of multi-concentration group mathematical modelling to the leaching of radionuclide waste-forms which have continuous porous matrix such as cemented waste form is described. The modelling is illustrated analysing a hypothetical of some transport mechanisms such as molecular diffusion, ionic migration and convective flow for release of interest radionuclide from a solidified waste form which contains discrete particles of radioactive Sr-85 nuclides into the aqueous environment. The group parameters are derived from the classical electrochemistry concept of ion transport in dilute electrolytic solution. The numerical analysis is based on the Crank-Nicolson Implicit Methods which assures the stability of the solution at a practical time step. The results show that, for a short-time period of leaching in demineralized water the leaching behavior follows the predominating diffusion mechanism. After this point, the role of other processes apparent and continue until all radionuclides in the cement waste are leached out when compared to the Semi-Infinite Diffusion model which is based on pure diffusion mechanism. The multi-concentration group model can also be applied to long-term prediction of complicated release mechanisms of the radionuclides in the waste form of a particular disposal environment, unless the variables of interest such as the corrosion rate, the chemical reaction, erosion rate and etc. are determined by experiment or theoretical hypothesis. The appropriate differential equation then can be solved by the same general numerical approach. Also, the results of the modelling indicate which parameters should be measured experimentally in order to provide a quantitative test of the hypothetical release mechanism.

The hood, doors and other panels of a car can be made by aluminium sheets, through complex forming operations. Design of forming processes requires trustable models and simulations. Forming properties are different in different directions. There are two principle ways to describe this plastic anisotropy of metals. The first one is the continuum theories for materials. The flow properties in various directions are described by the yield function. It is a parametric function calibrated by experimental tests. Unfortunately only a few mechanical tests can be directly used. The second approach takes into account that metals consist of many small crystals. The properties of each crystal are determined by crystal planes, but crystals are rotated in many directions. The crystal models either resolve all the details of thousands of crystals in a small volume element, requiring huge computer capacity, or simplified statistical models can be applied. In both cases the models are much more demanding than continuum models. In practice these models can be used to perform virtual experiments for calibration of continuum models. In his PhD work Kai Zhang (kai.zhang@ntnu.no) implemented and tested both type of models. More efficient numerical algorithms for computer simulations were developed and programmed for the detailed crystal plasticity approach. Three different cases were investigated experimentally. In one of the cases it was found that even for the detailed computer implementation the predictions could not replace experiments for design purposes. A combination of real and virtual experiments was recommended for calibration. For the other two cases the virtual experiments could be trusted. It was found that the best statistical models, that are more than thousand times faster, can replace detailed simulations of the crystal structure with high accuracy.

The works contributes to the need to design more efficient heating and domestic hot water preparation systems. Dynamic building and simulation plays an important role in the development of domestic hot water (DHW) preparation systems for residential buildings, in order to evaluate and optimize the final energy and the DHW comfort. The case study of this work is a big multi-family building composed of 96 flats. District heating (DH) is used to heat up the water in the storage tank located in the technical room. A distribution system connects the storage to all the fresh water stations (FWS) located in each flat. The chosen approach is to simulate the building-level DHW preparation with a single heat exchanger (HX) which approximates the behaviour of all the HXs of the building. For this purpose, the simultaneity factor (fs) should be considered. First, a representative model of the FWS for each flat is implemented in Matlab/Simulink and tested with two different control strategies of the circulation pump and two different DHW profiles, derived either from standard EN16147 or created as a stochastic profile. From the flat-level model, a building-level model is derived. Four different building-level DHW profiles are used to evaluate the simultaneity factor, and so the peak load of the building, in order to size the HX for the whole building. The DHW profiles (and so the simultaneity factor) and the parametrization of the HX influence the results. Final energy and DHW comfort (i.e. the DHW temperature and the “waiting time” to reach this temperature) are compared in each case. The return temperature of the fluid sent back to the storage is also analysed. The development of the return temperature to the storage is influenced by the DHW profiles and the thermal capacity of the pipe.

Despite an expanding interest in the concept of Emotional Intelligence (EI), difficulties in definition, measurement and reconciling competing models has led to an argument that the practical application of EI has overtaken current levels of understanding and research (Matthews, Roberts, & Zeidner, 2004; Zeidner, Roberts, & Matthews, 2002). This is particularly relevant within education where a large range of social and emotional learning (SEL) programmes, designed to increase EI in pupils, vary drastically in their intended outcomes and methods, quality of material and the frequency and quality of evaluation (Hoffman, 2009). To date, the majority of research has been US based and the small quantity of UK research has been focused either at the primary level, or has assessed the perception of impact. This means the potential success for SEL to positively improve UK secondary aged pupil outcomes is untested. The aim of the current study was the assessment of the SEAL programme, a National Strategy for English secondary schools designed to positively influence a range of pupil outcomes, including increased emotional literacy, better behaviour and improved mental well-being. Additionally, the validity of the underlying relationship between EI and favourable outcomes, beyond identified socio-demographics, was measured. The study utilised a predominately quantitative design with a final sample of 22 schools (approximately 2360 pupils) implementing the SEAL programme, and 19 ‘matched comparison’ schools (approximately 1991 pupils), selected on the basis of similar school level characteristics. Pupils from every school completed annual self-rated assessments of their emotional literacy (using the ELAI), mental well-being and pro social behaviour (using the SDQ) over a three year period. A small case study element (9 SEAL Schools) was selected from the larger quantitative sample to provide context to the quantitative results. Multi-level modelling (a statistical technique for examining hierarchically clustered data) was used to analyse the results. After controlling for socio-demographic factors, results indicated a marginal non-significant effect in pupil’s emotional literacy and mental health difficulties as a result of attending a SEAL school, however no effect on prosocial behaviour was found. Results also indicated a differential effect on the basis of the pupil variables of SEN provision, gender and ethnicity, which was consistent with very little variation at school level reported. A significant relationship was found between emotional literacy, mental health difficulties and pro social behaviour, indicating a valid theoretical framework, despite the lack of a significant effect of the SEAL programme. Further examination revealed that the relationship between the variables may be more complex than originally theorised, although difficulties with high degrees of confound between the factors limit this interpretation. Implications and directions for future research are also discussed.

Incorporation of more sophisticated human factors (HF) in mathematical models for driving behavior has become an increasingly popular and important research direction in the last few years. Such models enable us to simulate under which conditions perception errors and risk-taking lead to interactions that result in unsafe traffic conditions and ultimately accidents. In this paper, we present a generic multi-level microscopic traffic modelling and simulation framework that supports this important line of research. In this framework, the driving task is modeled in a multi-layered fashion. At the highest level, we have idealized (collision-free) models for car following and other driving tasks. These models typically contain HF parameters that exogenously “govern the human factor”, such as reaction time, sensitivities to stimuli, desired speed, etc. At the lowest level, we define HF variables (task demand and capacity, awareness) with which we maintain what the information processing costs are of performing driving tasks as well as non-driving related tasks such as distractions. We model these costs using so-called fundamental diagrams of task demand. In between, we define functions that govern the dynamics of the high-level HF parameters with these HF variables as inputs. When total task demand increases beyond task capacity, first awareness may deteriorate, where we use Endsley's three-level awareness construct to differentiate between effects on perception, comprehension, anticipation and reaction time. Secondly, drivers may adapt their response in line with Fullers risk allostasis theory to reduce risk to acceptable levels. This framework can be viewed as a meta model, that provides the analyst possibilities to combine and mix a wide variety of microscopic models for driving behavior at different levels of sophistication, depending on which HF are studied, and which phenomena need to be reproduced. We illustrate the framework with a distraction (rubbernecking) case. Our results show that the framework results in endogenous mechanisms for inter- and intra-driver differences in driving behavior and can generate multiple plausible HF mechanisms to explain the same observable traffic phenomena and congestion patterns that arise due to the distraction. We believe our framework can serve as a valuable tool in testing hypotheses related to the effects of HF on traffic efficiency and traffic safety in a systematic way for both the traffic flow and HF community.

L'objectif de cette thèse est de proposer une approche de couplage des niveaux métabolique et écologique dans un système biologique complexe. Cette approche se présente sous la forme d'un modèle formel décrivant le métabolisme d'un organisme vivant, qui grâce au formalisme DEVS (Discret Event System Specification) adopté, permet un couplage avec des modèles d'interaction entre les organismes et entre l'organisme et son environnement. Une étude des différents paradigmes de modélisation, nous a permis d'identifier d'un côté le paradigme adéquat pour chaque niveau et d'un autre côté les facteurs de couplage formés par les variables à l'interface des mondes internes et externes d'un individu. Ce couplage permet d'explorer l'effet de la dynamique du niveau inférieur sur l'émergence des caractéristiques du niveau supérieur. Deux modèles multi-agents, le premier sur l'allocation sexuelle et le deuxième sur la recherche optimale de nourriture, concrétisent le couplage physiologie/écologie et montrent que ce couplage permet de relier le monde interne de l'individu à son monde externe. Le couplage fort, dans le sens de l'intégration des modèles, exploré dans une première phase, a été amélioré par la proposition d'un modèle formel, nommé DEB-DEVS, du modèle métabolique (de la théorie du budget d'énergie dynamique (DEB)) commun aux modèles précédents. Cette proposition est le résultat d'une réflexion sur la représentation de la dynamique interne des agents dans des modèles de l'écologie. DEB-DEVS a été illustré par deux modèles classiques de l'écologie théorique
The objective of this thesis is to propose an approach for coupling metabolic and ecological levels in a complex biological system. This approach is presented as formal model describing the organism metabolism , which, thanks to DEVS formalism (Discrete Event System Specification), allows a coupling with models of interaction between organisms and between organisms and their environment. A study of the different modeling paradigms allowed us to identify, on the one hand the appropriate paradigm for each level and on the other hand the coupling factors formed by the variables at the interface of individual's internal and external worlds. This coupling explores the effect of lower-level dynamics on the emergence of higher-level characteristics. Two multiagent models, the first on sexual allocation and the second on optimal foraging, concretize the physiology/ecology coupling and show that this coupling makes it possible to connect the individual's internal world with its external world. The strong coupling, in the sense of model integration, explored in a first phase, was improved by the proposal of a formal model, called DEB-DEVS, of the metabolic model (of the Dynamic Energy Budget Theory (DEB)) common to the previous models. This proposal is the result of a reflection on the representation of internal dynamics of agents in ecological models. DEB-DEVS has been illustrated by two classical models of theoretical ecology

The class of models which is studied in this paper, multi-unit longitudinal models, combines both the cross-sectional and the longitudinal aspects of observations. Many empirical investigations involve the analysis of data structures that are both cross-sectional (observations are taken on several units at a specific time period or at a specific location) and longitudinal (observations on the same unit are taken over time or space). Multi-unit longitudinal data structures arise in economics and business where panels of subjects are studied over time, biostatistics where groups of patients on different treatments are observed over time, and in situations where data are taken over time and space. Modelling issues in multi-unit longitudinal models with random coefficients and patterned correlation structure are illustrated in the context of two data sets. The first data set deals with short time series data on annual death rates and alcohol consumption for twenty-five European countries. The second data set deals with glaceologic time series data on snow temperature at 14 different locations within a small glacier in the Austrian Alps. A practical model building approach, consisting of model specification, estimation, and diagnostic checking, is outlined. (author's abstract)
Series: Forschungsberichte / Institut für Statistik

The growing complexity of integrated circuits and the large variety of architectures of Field Programmable Gate Arrays (FPGAs) require sophisticated logic design tools. In the beginning of the eighties the research in logic design was concentrated on the development of fast two-level AND-OR logic minimizers like the well known ESPRESSO. However, most logic functions have a smaller and often faster circuit realization as a multi-level circuit. Thus, synthesis tools emerged for the minimization of the circuit area in a multi-level realization. Most of these synthesis tools are based on the "unate paradigm". Therefore, the synthesis methods are only advantageous for functions having a minimal circuit realization based on AND-OR gates. However, many common functions have a minmal circuit realization having a mix of AND, OR and EXOR gates like counters, adders, multipliers, and parity generators. Therefore, the design of such functions with synthesis tools based on the "unated paradigm" is very inefficient. Circuits incorporating the EXOR gate have received less attention than AND-OR circuits because the EXOR gate was perceived as slower and larger in terms of its circuit realization than the AND and the OR gate. However, the upcoming of Field Programmable Gate Arrays (FPGAs) like the Xilinx Table-Look-Up (TLU) architecture the Actel ACTâ„¢ series and the CLi 6000 series from Concurrent Logic, which allow the realization of the EXOR gate with the same speed and circuit cost as the AND and OR gate, eliminates the disadvantages of the EXOR gate over the AND and OR gate. Thus, there is a strong need for logic synthesis tools that take advantage of EXOR gates. The mapping to the new FPGAs recently obtained an increased interest. The developed synthesis algorithms for FPGAs are based on the mapping and restructuring of the Directed Acyclic Graph (DAG) representation of the logic function. Even though the new FPGAs allow the realization of the EXOR gate without any speed and circuit size penalty in comparison to the AND and OR gate, the synthesis methods have been based on the "unate paradigm". To overcome the disadvantages of the current logic synthesis tools with respect to (nearly) linear functions and FPGA synthesis, this dissertation introduces an extended theory of spectral methods for multiple-valued input, incompletely specified binary output logic. The spectral methods have not been popular in logic synthesis because of their four major drawbacks: (1) the computational complexity, especially if no Fast Transform exists, (2) the memory requirement to store the function in the necessary minterm representation, (3) they cannot take efficiently advantage of incompletely specified functions, (4) suitable only for few applications in logic synthesis. To overcome the two last stated drawbacks, this dissertation introduces the T spectrum. The T spectrum separates the information obtained for the specified and not specified parts of the underlying function. Thus, it is possible to determine directly the contribution of the specified and the not specified part of the function to a single spectral coefficient. Moreover, the T spectrum is an extension of the known spectra like Walshtype, Adding, Arithmetic, and Reed-Muller spectra to any orthogonal and nonorthogonal transform describing logic functions. Thus, transforms can be constructed that describe certain gate structures, as for example the realizable functions of a FPGA macrocell. This allows the development of special synthesis algorithms for the different types of FPGA architectures. As an exemplification of this method, a complete multi-level synthesis algorithm is introduced for the circuit realization with multiplexer modules, which form the basic macrocell of the Actel ACfâ„¢ FPGA series. Additionally, this dissertation presents the classification of the applications of spectral methods in logic synthesis into three categories: (1) The decomposition of logic functions based on the information obtained by the computation of a single spectrum. As an example the linearization procedure developed by Karpowsky is generalized to incompletely specified multi-output Boolean functions. The linearization procedure is based on the computation of the Rademacher-Walsh spectrum with a following decomposition of the underlying function based on high value spectral coefficients. (2) The circuit realization of a logic function based on the repetitive application of (1). This synthesis method is exemplified by an multi-level synthesis algorithm for multiplexer gates. (3) The realization of a logic function as an AND-EXOR circuit based on a GF 2 (Galois Field (2)) spectrum. The GF 2 transforms exhibit the property that they describe a realization of the underlying function as a two-level AND-EXOR circuit. The Multiple-Valued Input Kronecker Reed-Muller (MIKRM) form is introduced as an application of GF 2 transforms. To overcome the drawbacks of spectral methods concerning the computational complexity and high memory requirements, this dissertation presents a computation method for spectra from disjoint representations. The introduced application of the disjoint cube representation and the Ordered Decision Diagrams for the computation of spectra proves to be an ideal concept. Thus, this dissertation presents general synthesis methods based on new spectral methods that overcome the deficiencies of current logic synthesis methods with respect to the synthesis for FPGAs as well as the computational complexity and memory requirements of spectral methods.

This research develops efficient solution methods for linear systems with scalar and multi-level Toeplitz structure. Toeplitz systems are common in one-dimensional signal-processing applications, and typically correspond to temporal- or spatial-invariance in the underlying physical phenomenon. Over time, a number of algorithms have been developed to solve these systems economically by exploiting their structure. These developments began with the Levinson-Durbin recursion, a classical fast method for solving Toeplitz systems that has become a standard algorithm in signal processing. Over time, more advanced routines known as superfast algorithms were introduced that are capable of solving Toeplitz systems with even lower asymptotic complexity. For multi-dimensional signals, temporally- and spatially-invariant systems have linear-algebraic descriptions characterized by multi-level Toeplitz matrices, which exhibit Toeplitz structure on multiple levels. These matrices lack the same algebraic properties and structural simplicity of their scalar analogs. As a result, it has proven exceedingly difficult to extend the existing scalar Toeplitz algorithms for their treatment. This research presents algorithms to solve scalar and two-level Toeplitz systems through a constructive approach, using methods devised for specialized cases to build more general solution methods. These methods extend known scalar Toeplitz inversion results to more general scalar least-squares problems and to multi-level Toeplitz problems. The resulting algorithms have the potential to provide substantial computational gains for a large class of problems in signal processing, such as image deconvolution, non-uniform resampling, and the reconstruction of spatial volumes from non-uniform Fourier samples.

Rheumatoid Arthritis (RA) is a chronic auto-immune disease that causes in ammation in the joints. Left uncontrolled, this prolonged in ammation can lead to pain and structural damage, resulting in erosions to the bones and total breakdown of the surrounding cartilage. Structural joint damage, measured by plain radiographs, is an important outcome measure of RA. It provides an objective marker of disease activity to assess any improvements or failures of treatments in controlling for the disease. Increased long-term joint damage has been linked with increased functional disability and decreased quality of life for RA patients. While a range of studies have looked at radiographic outcomes from observational data, they tend to be restricted to historical cohorts, with little long-term data on how radiographic progression may have changed in line with changes in clinical management. Additionally, these studies have not used the appropriate statistical methods to account for non-normal data distributions and within-patient variation over time. As a result, the main aim of this thesis is to investigate the long-term progression of structural joint damage in patients with early RA. The speci c objectives were to; (1) investigate the current evidence base to identify common methods in measuring and analysing radiographic outcomes, (2) assess what statistical methods are most appropriate in modelling long-term radiographic data, (3) use these models to understand the natural progression of radiographic damage using data from two UK inception cohorts, and nally, (4) expand these models to investigate the long-term relationship of radiographic damage with two important clinical outcomes; disease activity and functional disability. The analysis is based on longitudinal data from two UK prospective, multi-centre, early RA observational cohorts. These cohorts represent two distinct eras in the management and treatment of RA, making them invaluable for investigating how key RA outcomes have progressed in clinical practice over time. Using multi-level count models, precise rates of radiographic progression for both cohorts are presented. The models look at how seropositive RA and increased disease activity are related to increased radiographic progression, and what impact this has on functional disability. The results show that rates of radiological damage have declined dramatically in recent years. Possible attributable factors to these declines include both milder disease and more e ective treatment strategies. Analysis of the earlier cohort (1986-2001) shows how seropositive RA and increased disease activity lead to clinically meaningful increases in radiological damage. Conversely, their impact on patients in the more recent cohort (2002-2011) suggest that their e ect on radiographic progression is reduced, where increases in radiological damage were not larger than clinically meaningful thresholds. This has large implications on the debate around the use of biologic therapies in patients with less severe RA. However more data is sorely needed, particularly long-term radiographic data from those patients on biologics treatments, before any de nitive conclusions can be made. The possible impact of these declines on functional disability appears to be relatively small. The analysis shows that radiographic damage is more strongly associated with functional disability in later disease, but there is little evidence to indicate that declines in radiographic damage has lead to large improvements in long-term functional disability. These ndings are explored within the framework of a dual-pathway model, which suggests that functional disability is caused by two distinct mechanisms, either structural joint damage, or through increased pain. Research so far has predominantly focused on pharmacological treatments in reducing in ammation. More research is needed to explore the role of psychosocial factors and pain perception in order to create a more holistic treatment programme for RA patients.

This thesis aims to contribute to the developments of wireless communication systems. The work generally consists of three parts: the first part is a discussion on general digital communication systems, the second part focuses on wireless channel modelling and fading mitigation techniques, and in the third part we discuss the possible application of advanced digital signal processing, especially time-frequency representation and blind source separation, to wireless communication systems. The first part considers general digital communication systems which will be incorporated in later parts. Today's wireless communication system is a subbranch of a general digital communication system that employs various techniques of A/D (Analog to Digital) conversion, source coding, error correction, coding, modulation, and synchronization, signal detection in noise, channel estimation, and equalization. We study and develop the digital communication algorithms to enhance the performance of wireless communication systems. In the Second Part we focus on wireless channel modelling and fading mitigation techniques. A modified Jakes' method is developed for Rayleigh fading channels. We investigate the level-crossing rate (LCR), the average duration of fades (ADF), the probability density function (PDF), the cumulative distribution function (CDF) and the autocorrelation functions (ACF) of this model. The simulated results are verified against the analytical Clarke's channel model. We also construct frequency-selective geometrical-based hyperbolically distributed scatterers (GBHDS) for a macro-cell mobile environment with the proper statistical characteristics. The modified Clarke's model and the GBHDS model may be readily expanded to a MIMO channel model thus we study the MIMO fading channel, specifically we model the MIMO channel in the angular domain. A detailed analysis of Gauss-Markov approximation of the fading channel is also given. Two fading mitigation techniques are investigated: Orthogonal Frequency Division Multiplexing (OFDM) and spatial diversity. In the Third Part, we devote ourselves to the exciting fields of Time-Frequency Analysis and Blind Source Separation and investigate the application of these powerful Digital Signal Processing (DSP) tools to improve the performance of wireless communication systems.

Agriculture is becoming more dependent on computerized solutions to make thefarmer’s job easier. The big step that many companies are working towards is fullyautonomous vehicles that work the fields. To that end, the equipment fitted to saidvehicles must also adapt and become autonomous. Making this equipment autonomoustakes many incremental steps, one of which is developing an accurate and reliable tanklevel measurement system. In this thesis, a system for tank level measurement in a seedplanting machine is evaluated. Traditional systems use load cells to measure the weightof the tank however, these types of systems are expensive to build and cumbersome torepair. They also add a lot of weight to the equipment which increases the fuel consump-tion of the tractor. Thus, this thesis investigates the use of radar sensors together witha number of Machine Learning algorithms. Fourteen radar sensors are fitted to a tankat different positions, data is collected, and a preprocessing method is developed. Then,the data is used to test the following Machine Learning algorithms: Bagged RegressionTrees (BG), Random Forest Regression (RF), Boosted Regression Trees (BRT), LinearRegression (LR), Linear Support Vector Machine (L-SVM), Multi-Layer Perceptron Re-gressor (MLPR). The model with the best 5-fold crossvalidation scores was Random For-est, closely followed by Boosted Regression Trees. A robustness test, using 5 previouslyunseen scenarios, revealed that the Boosted Regression Trees model was the most robust.The radar position analysis showed that 6 sensors together with the MLPR model gavethe best RMSE scores.In conclusion, the models performed well on this type of system which shows thatthey might be a competitive alternative to load cell based systems.

Modern traffic signal control systems have not changed significantly in the past 40-50 years. The most widely applied traffic signal control systems are still time-of-day, coordinated-actuated system, since many existing advanced adaptive signal control systems are too complicated and fathomless for most of people. Recent advances in communications standards and technologies provide the basis for significant improvements in traffic signal control capabilities. In the United States, the IntelliDriveSM program (originally called Vehicle Infrastructure Integration - VII) has identified 5.9GHz Digital Short Range Communications (DSRC) as the primary communications mode for vehicle-to-vehicle (v2v) and vehicle-to-infrastructure (v2i) safety based applications, denoted as v2x. The ability for vehicles and the infrastructure to communication information is a significant advance over the current system capability of point presence and passage detection that is used in traffic control systems. Given enriched data from IntelliDriveSM, the problem of traffic control can be solved in an innovative data-driven and mathematical way to produce robust and optimal outputs.In this doctoral research, three different problems within a v2x environment- "enhanced pseudo-lane-level vehicle positioning", "robust coordinated-actuated multiple priority control", and "multimodal platoon-based arterial traffic signal control", are addressed with statistical techniques and mathematical programming.First, a pseudo-lane-level GPS positioning system is proposed based on an IntelliDriveSM v2x environment. GPS errors can be categorized into common-mode errors and noncommon-mode errors, where common-mode errors can be mitigated by differential GPS (DGPS) but noncommon-mode cannot. Common-mode GPS errors are cancelled using differential corrections broadcast from the road-side equipment (RSE). With v2i communication, a high fidelity roadway layout map (called MAP in the SAE J2735 standard) and satellite pseudo-range corrections are broadcast by the RSE. To enhance and correct lane level positioning of a vehicle, a statistical process control approach is used to detect significant vehicle driving events such as turning at an intersection or lane-changing. Whenever a turn event is detected, a mathematical program is solved to estimate and update the GPS noncommon-mode errors. Overall the GPS errors are reduced by corrections to both common-mode and noncommon-mode errors.Second, an analytical mathematical model, a mixed-integer linear program (MILP), is developed to provide robust real-time multiple priority control, assuming penetration of IntelliDriveSM is limited to emergency vehicles and transit vehicles. This is believed to be the first mathematical formulation which accommodates advanced features of modern traffic controllers, such as green extension and vehicle actuations, to provide flexibility in implementation of optimal signal plans. Signal coordination between adjacent signals is addressed by virtual coordination requests which behave significantly different than the current coordination control in a coordinated-actuated controller. The proposed new coordination method can handle both priority and coordination together to reduce and balance delays for buses and automobiles with real-time optimized solutions.The robust multiple priority control problem was simplified as a polynomial cut problem with some reasonable assumptions and applied on a real-world intersection at Southern Ave. & 67 Ave. in Phoenix, AZ on February 22, 2010 and March 10, 2010. The roadside equipment (RSE) was installed in the traffic signal control cabinet and connected with a live traffic signal controller via Ethernet. With the support of Maricopa County's Regional Emergency Action Coordinating (REACT) team, three REACT vehicles were equipped with onboard equipments (OBE). Different priority scenarios were tested including concurrent requests, conflicting requests, and mixed requests. The experiments showed that the traffic controller was able to perform desirably under each scenario.Finally, a unified platoon-based mathematical formulation called PAMSCOD is presented to perform online arterial (network) traffic signal control while considering multiple travel modes in the IntelliDriveSM environment with high market penetration, including passenger vehicles. First, a hierarchical platoon recognition algorithm is proposed to identify platoons in real-time. This algorithm can output the number of platoons approaching each intersection. Second, a mixed-integer linear program (MILP) is solved to determine the future optimal signal plans based on the real-time platoon data (and the platoon request for service) and current traffic controller status. Deviating from the traditional common network cycle length, PAMSCOD aims to provide multi-modal dynamical progression (MDP) on the arterial based on the real-time platoon information. The integer feasible solution region is enhanced in order to reduce the solution times by assuming a first-come, first-serve discipline for the platoon requests on the same approach. Microscopic online simulation in VISSIM shows that PAMSCOD can easily handle two traffic modes including buses and automobiles jointly and significantly reduce delays for both modes, compared with SYNCHRO optimized plans.

[EN] In today's information society, there is a growing need to access data communication services ubiquitously, with mobility and increasingly higher data rates. This society's demand has motivated the development of the fourth generation of mobile communications (4G) and its evolution towards the fifth generation (5G). This development has required a revolution on the radio interface of the mobile communications systems, and, consequently, has significantly modified their capabilities and their radio resource management. This is the case of the technology known as Long Term Evolution (LTE) and its 4G version called LTE-Advanced. This Doctoral Thesis addresses the modelling, the radio resource management analysis, and the performance evaluation of the downlink of LTE and LTE-Advanced where, among the different features of LTE-Advanced, the focus is on the Coordinated Multi-Point (CoMP) transmission. The Thesis provides a detailed description of the main characteristics of LTE and LTE-Advanced. The high complexity of these systems, has prompted the use of computer simulations as the primary research methodology. The Thesis makes a detailed description of the simulation methodology and the system modelling required, including some contributions of the author in this field. Among them, it is of significant relevance the link-level simulation results used in the European project WINNER + for the LTE evaluation. With regard to the analysis of the radio resource management in LTE, the fundamentals of link adaptation and scheduling are explained in the first place. In relation to the scheduling, the Thesis includes a thorough study of the proportional fairness concept and the suboptimal implementation typically used in LTE to maximize this metric. This study has resulted in a series of ideas embodied in a modification of the typical implementation, which has proved to be capable of increasing the proportional fairness of the resource allocations. Moreover, the link adaptation analysis has revealed the "flash-light" effect problem, which is characterized by a high interference variability due to rapid changes in the scheduling decisions. The Thesis demonstrates that a particular implementation that stabilizes the scheduling decisions can improve the system performance. The radio resource management analysis of this Thesis is completed with the study of CoMP. Specifically, the CoMP scheme studied in this Thesis is a solution with coordinated scheduling and beamforming (CS/CB), that takes into account realistic and robust assumptions concerning the knowledge that the coordinated points have about the channel state. The Thesis proposes this solution for its simplicity and its ability to improve high data rates coverage and capacity even with incomplete channel knowledge. Concerning LTE and LTE-Advanced evaluation, it is performed in two different types of scenarios. On the one hand, the scenarios defined in the process of evaluation of IMT-Advanced. In this framework, it is evaluated the importance of different multi-antenna techniques, including CoMP, considering full-buffer traffic models. The most important conclusions in these scenarios are the significant performance improvement achieved with spatial multiplexing of users and the fact that CoMP mechanisms provide a reduced benefit. The second group of scenarios are those defined by the European project METIS for the evaluation of 5G technologies. Specifically, an indoor office scenario and an outdoor sports stadium have been selected. In these scenarios, a realistic traffic model is used, and it has been demonstrated the utility of CoMP to satisfy the first 5G requirement definitions with feasible frequency bandwidths. In these scenarios with less homogeneous deployments, or with a limited number of transmitters originating the major part of interference, is where this Thesis has found CoMP to be more useful and where the Thesis promotes its use.
[ES] En la actual sociedad, hay una creciente necesidad de acceso a servicios de comunicación de datos de forma ubicua, móvil y a velocidades cada vez más altas. Esta demanda ha motivado el desarrollo de la cuarta generación de comunicaciones móviles (4G) y su evolución hacia la quinta generación (5G). Este desarrollo ha requerido una revolución en la interfaz radio de los sistemas de comunicaciones móviles modificando en gran medida sus capacidades y la forma en la que se gestionan sus recursos. Este es el caso de la tecnología conocida como Long Term Evolution (LTE) y su versión 4G llamada LTE-Advanced. En concreto, esta Tesis Doctoral aborda el modelado, análisis de la gestión de recursos radio y evaluación de prestaciones del enlace descendente de LTE y LTE-Advanced, donde, de entre las características de LTE-Advanced, se ha puesto el foco de atención en la transmisión multipunto coordinada (CoMP). La Tesis proporciona una descripción detallada de las principales características de LTE y LTE-Advanced. La gran complejidad del sistema descrito ha motivado que la metodología de estudio haya sido la simulación mediante ordenador. La Tesis realiza una descripción detallada de dicha metodología y del modelado del sistema empleado, incluyendo algunas aportaciones del autor en este campo. De entre éstas, destaca la provisión de resultados de simulación de nivel de enlace que se usaron en el proyecto europeo WINNER+ para la evaluación de LTE. En cuanto al análisis de la gestión de recursos radio en LTE, en primer lugar, se explican los fundamentos de la adaptación al enlace y el scheduling. En relación con el scheduling, se realiza un estudio del concepto de proportional fairness y de la implementación subóptima típicamente usada en LTE para maximizar esta métrica. Este estudio ha dado como resultado una modificación de la implementación típica que ha demostrado ser capaz de aumentar la proportional fairness en la asignación de recursos con un bajo incremento de complejidad. Además, el análisis de la adaptación al enlace ha revelado el problema del efecto de "luz de flash" consistente en la alta variabilidad de la interferencia debida a rápidos cambios en las decisiones del scheduler. La Tesis demuestra que se pueden mejorar las prestaciones del sistema estabilizando dichas decisiones mediante una implementación concreta. El bloque de análisis de la gestión de recursos se completa con el estudio de CoMP. Específicamente, se estudia una solución con coordinación de scheduling y conformación de haz (CS/CB) que tiene en cuenta suposiciones reales y robustas en cuanto al conocimiento que los puntos coordinados tienen de los canales radio. La Tesis propone esta solución por su sencillez y capacidad de mejorar la eficiencia de los sistemas de comunicaciones móviles, tanto en cobertura de velocidades altas de transmisión como en capacidad, aun teniendo un conocimiento incompleto del canal. En cuanto a la evaluación de LTE y LTE-Advanced, ésta se realiza en dos tipos de escenarios. Por un lado, los escenarios definidos en el proceso de evaluación de IMT-Advanced. En este marco, se evalúa la importancia de diferentes técnicas de transmisión multiantena, incluyendo CoMP, y considerando tráfico de tipo full-buffer. Se ha obtenido una gran mejora de prestaciones por la multiplexación espacial de usuarios y mejoras discretas por el uso de CoMP. El segundo grupo de escenarios son los definidos por el proyecto europeo METIS para evaluación de tecnologías 5G, concretamente se han elegido un escenario de interiores con una oficina, y uno de exteriores con un estadio deportivo. En estos escenarios se utiliza un tráfico realista y se ha demostrado la utilidad de CoMP para mejorar las prestaciones del sistema. En estos escenarios con despliegues menos uniformes, o con un número limitado de transmisores provocando la mayor parte de la interferencia, es donde esta Tesis ha encontrado la mayor u
[CAT] En l'actual societat de la informació, hi ha una creixent necessitat d'accés a serveis de comunicació de dades de forma ubiqua, mòbil i a velocitats cada vegada més altes. Aquesta demanda de la societat, ha motivat el desenrotllament de la quarta generació de comunicacions mòbils (4G) i la seua evolució cap a la quinta generació (5G). Aquest desenrotllament ha requerit una revolució en la interfície ràdio dels sistemes de comunicacions mòbils i ha modificat en gran manera les seues capacitats i la forma en què es gestionen els seus recursos. Aquest és el cas de la tecnologia coneguda com a Long Term Evolution (LTE) i la seua versió 4G anomenada LTE-Advanced. En concret, aquesta Tesi Doctoral aborda el modelatge, anàlisi de la gestió de recursos ràdio i avaluació de prestacions de l'enllaç descendent de LTE i LTE-Advanced, on, d'entre les característiques de LTE-Advanced, s'ha posat el centre d'atenció en la transmissió multipunt coordinada (CoMP). La Tesi proporciona una descripció detallada de les principals característiques de LTE i LTE-Advanced. La gran complexitat del sistema descrit ha motivat que la metodologia d'estudi s'haja basat en simulació per mitjà d'ordinador. La Tesi realitza una descripció detallada de la metodologia de simulació i del modelatge del sistema empleat, incloent-hi algunes aportacions de l'autor en aquest camp. D'entre aquestes, destaca la provisió de resultats de simulació de nivell d'enllaç que es van usar en el projecte europeu WINNER+ per a l'avaluació de LTE. Pel que fa a l'anàlisi de la gestió de recursos ràdio en LTE, en primer lloc, s'expliquen els fonaments de l'adaptació a l'enllaç i el scheduling. En relació amb el scheduling, es realitza un estudi del concepte de proportional fairness i de la implementació subòptima típicament usada en LTE per a maximitzar aquesta mètrica. L'estudi ha donat com a resultat una modificació de la implementació típica que ha demostrat ser capaç d'augmentar la proportional fairness en l'assignació de recursos amb un baix increment de complexitat. A més, l'anàlisi de l'adaptació a l'enllaç ha desvetllat el problema de l'efecte de "llum de flaix" consistent en la alta variabilitat de la interferència deguda a una ràpida variació de les assignacions de recursos. La Tesi demostra que es poden millorar les prestacions del sistema estabilitzant les decisions del scheduler mitjançant una implementació concreta. En el bloc d'anàlisi de la gestió de recursos d'aquesta Tesi es completa amb l'estudi de CoMP. Específicament, s'estudia una solució amb coordinació de scheduling i conformació de feix (CS/CB), que té en compte suposicions reals i robustes quant al coneixement que els punts coordinats tenen dels canals ràdio dels usuaris servits. La Tesi proposa aquesta solució per la seua senzillesa i capacitat de millorar l'eficiència dels sistemes de comunicacions mòbils, tant en cobertura de velocitats altes de transmissió com en capacitat, encara tenint un coneixement incomplet del canal. Quant a l'avaluació de LTE i LTE-Advanced, aquesta es realitza en dos tipus d'escenaris diferents. D'una banda, els escenaris definits dins del procés d'avaluació de tecnologies IMT-Advanced. Dins d'aquest marc, s'avalua la importància de diferents tècniques de transmissió multi-antena, incloent-hi CoMP, i considerant tràfic de tipus full-buffer. S'ha obtingut una gran millora de prestacions amb la multiplexació espacial d'usuaris i una discreta millora amb CoMP. El segon grup d'escenaris són els definits pel projecte europeu METIS per a l'avaluació de tecnologies 5G, concretament s'han triat un escenari d'interiors amb una oficina, i un d'exteriors amb un estadi esportiu, on s'ha utilitzat un tràfic realista. En aquests escenaris amb desplegaments menys uniformes, o amb un nombre limitat de transmissors provocant la major part de la interferència, és on aquesta Tesi ha trobat la utilitat més gran de
Martín-Sacristán Gandía, D. (2016). 3GPP Long Term Evolution: Performance Analysis and Evolution towards 4G with Coordinated Multi-Point Transmission [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63261
TESIS

Introdução: A avaliação dos resultados de políticas públicas de suplementação alimentar em condições reais de sua operacionalização (efetividade) é um instrumento imprescindível para área de saúde pública. Objetivos: Avaliar a efetividade de programa governamental de suplementação alimentar no crescimento de crianças, segundo o estado nutricional ao ingressar. Métodos: Estudo de coorte com dados secundários de 25.433 crianças de baixa renda com idade entre 6 a 24 meses que ingressaram em programa de distribuição de leite fortificado \"Projeto Vivaleite\" de 2003 a 2008, em 311 municípios do Estado de São Paulo. O crescimento foi medido por meio dos valores de escore z de peso para idade (PI), calculados pelo padrão OMS/2006, obtidos, na rotina do programa, ao ingressar e a cada 4 meses durante a permanência. Os critérios de inclusão foram ter idade ao ingressar entre 6 a 24 meses, ter pelo menos duas pesagens, incluindo a obtida na entrada, e não ter relatos de problemas de saúde. As crianças foram divididas em três grupos de escore z ao entrar: sem comprometimento de peso (z> -1); risco de baixo peso (-2 ≤z< -1) e baixo peso (z<-2). Utilizou-se regressão linear multinível (modelo misto), permitindo a comparação, em cada idade, das médias ajustadas do escore z de ingressantes e participantes há pelo menos quatro meses, ajustadas para correlação entre medidas repetidas. Resultados: Verificou-se efeito positivo do Programa no ganho de peso das crianças, variando em função do estado nutricional ao ingressar; para as que entraram sem comprometimento de peso o ganho médio ajustado foi 0,1827 escore z, entre as que entraram com risco de baixo peso foi 0,5659 e entre as ingressantes com baixo peso foi 1,0049 escore z. Conclusões: O programa é efetivo para o crescimento infantil, medido pelo escore z PI, com efeito mais pronunciado entre as crianças que entram no programa em condições menos favoráveis de peso.
OBJECTIVE: To assess the effectiveness of a state-run food supplementation program for child growth according to childrens nutritional status at enrollment. METHODS: Cohort study including secondary data of 25,433 low-income children aged between 6 and 24 months enrolled in a fortified milk program \"Projeto Vivaleite\" in 311 cities in the State of São Paulo, Brazil, between 2003 and 2008. Children\'s growth was assessed based on weight-for-age (WA) z-scores, estimated following WHO criteria (2006). Data was routinely collected at the program enrollment and every 4 months. Inclusion criteria were: being 6 to 24 months of age at enrollment; having at least two weight measures including the first measure at enrollment; and not having any ill health conditions. At enrollment, children were categorized into three groups based on their z-scores: no compromised weight gain (z> 1); at risk of low weight (-2 ≤z< -1), and low weight (z< -2). Multilevel linear regression analysis (mixed model) was performed for comparison, considering age, of adjusted average z-scores between new children enrolled and those in the program for at least four months, adjusted for correlation between repeat measures. RESULTS: The program had a positive effect on children\'s weight gain. Based on their nutritional status at enrollment, adjusted average weight gain z-score was 0,1827 in children with compromised weight gain, 0,5659 in those at risk of low weight, and 1,0049 in those with low weight. CONCLUSIONS: The milk program is effective for child growth, as measured by WA z-scores. The most pronounced effect was seen among children who showed less favorable levels of weight at enrollment.

The blood oxygen level dependent functional MRI (BOLD-fMRI) signal is an indirect measure of the neuronal activity that most BOLD studies are interested in. This thesis uses generative embedding algorithms to investigate some of the challenges and opportunities that this presents for BOLD imaging. It is standard practice to analyse BOLD signals using general linear models (GLMs) that assume fixed neurovascular coupling. However, this assumption may cause false positive or negative neural activations to be detected if the biological manifestations of brain diseases, disorders and pharmaceutical drugs (termed "neuromodulations") alter this coupling. Generative embedding can help overcome this problem by identifying when a neuromodulation confounds the standard GLM. When applied to anaesthetic neuromodulations found in preclinical imaging data, Fentanyl has the smallest confounding effect and Pentobarbital has the largest, causing extremely significant neural activations to go undetected. Half of the anaesthetics tested caused overestimation of the neuronal activity but the other half caused underestimation. The variability in biological action between anaesthetic modulations in identical brain regions of genetically similar animals highlights the complexity required to comprehensively account for factors confounding neurovascular coupling in GLMs generally. Generative embedding has the potential to augment established algorithms used to compensate for these variations in GLMs without complicating the standard (ANOVA) way of reporting BOLD results. Neuromodulation of neurovascular coupling can also present opportunities, such as improved diagnosis, monitoring and understanding of brain diseases accompanied by neurovascular uncoupling. Information theory is used to show that the discriminabilities of neurodegenerative-diseased and healthy generative posterior parameter spaces make generative embedding a viable tool for these commercial applications, boasting sensitivity to neurovascular coupling nonlinearities and biological interpretability. The value of hybrid neuroimaging systems over separate neuroimaging technologies is found to be greatest for early-stage neurodegenerative disease.

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In this dissertation a new methodology of based convex optimization in linear matrix inaqualities is proposal as basic instrument for the synthesis of robust controllers of discrete and linear dynamic systems that take care of to the specifications of perturbations of worse case.
Nesta dissertação é proposta uma nova metodologia de otimização convexa baseada em desigualdades matriciais lineares como instrumento básico para a síntese de controladores robustos de sistemas dinâmicos discretos e lineares que atendam às especificações de pertubações de pior caso.

Le crissement de frein est une nuisance sonore qui représente des coûts importants pour l'industrie automobile. Il tire son origine dans des phénomènes complexes à l'interface frottante entre les plaquettes de frein et le disque. L'analyse de stabilité reste aujourd'hui la méthode privilégiée dans l'industrie pour prédire la stabilité d'un système de frein malgré ses aspects sur- et sous-prédictifs.Afin de construire un système de frein robuste, il est nécessaire de trouver la technologie qui permette de limiter les instabilités malgré certains paramètres incertains présents dans le système. Ainsi, l'un des objectifs de la thèse est de développer une méthode permettant de traiter et de propager l'incertitude et la variabilité de certains paramètres dans le modèle éléments finis de frein avec des coûts numériques abordables.Dans un premier temps, l'influence d'un premier groupe de paramètres correspondant à des contacts internes au système a été étudiée afin de mieux comprendre les phénomènes physiques mis en jeu et leurs impacts sur le phénomène de crissement. Une approche basée sur l'utilisation d'un algorithme génétique a été également mise en place afin d'identifier le jeu de paramètres le plus défavorable en terme de propension au crissement sur le système.Dans un second temps, différentes méthodes de méta-modélisation ont été proposées afin de prédire la stabilité du système de frein en fonction de différents paramètres qui peuvent être des paramètres de conception ou des paramètres incertains liés à l'environnement du système.Dans un troisième temps, une méthode d'analyse non-linéaire complémentaire de l'analyse de stabilité a été proposée et développée. Elle se base sur le suivi de la stabilité d'une solution vibratoire approchée et permet d'identifier les modes instables présents dans la réponse dynamique du système. Cette méthode a été appliquée sur un modèle simple avant d'illustrer sa faisabilité sur le modèle éléments finis de frein complet
Brake squeal is a noise nuisance that represents significant costs for the automotive industry. It originates from complex phenomena at the frictional interface between the brake pads and the disc. The stability analysis remains the preferred method in the industry today to predict the stability of a brake system despite its over- and under-predictive aspects.In order to build a robust brake system, it is necessary to find the technology that limits instabilities despite some uncertain parameters present in the system. Thus, one of the main objectives of the PhD thesis is to develop a method to treat and propagate the uncertainty and variability of some parameters in the finite element brake model with reasonable numerical costs.First, the influence of a first group of parameters corresponding to contacts within the system was studied in order to better understand the physical phenomena involved and their impacts on the squealing phenomenon. An approach based on the use of a genetic algorithm has also been implemented to identify the most unfavourable set of parameters in terms of squeal propensity on the brake system.In a second step, different meta-modelling methods were proposed to predict the stability of the brake system with respect to different parameters that may be design parameters or uncertain parameters related to the environment of the brake system.In a third step, a non-linear analysis method complementary to the stability analysis was proposed and developed. It is based on the tracking of the stability of an approximate vibrational solution and allows the identification of unstable modes present in the dynamic response of the system. This method was applied to a simple academic model before demonstrating its feasibility on the complete industrial brake finite element model under study

The next generation wireless networks i.e. 5G aim to provide multi-Gbps data traffic, in order to satisfy the increasing demand for high-definition video, among other high data rate services, as well as the exponential growth in mobile subscribers. To achieve this dramatic increase in data rates, current research is focused on improving the capacity of current 4G network standards, based on Long Term Evolution (LTE), before radical changes are exploited which could include acquiring additional/new spectrum. The LTE network has a reuse factor of one; hence neighbouring cells/sectors use the same spectrum, therefore making the cell edge users vulnerable to inter-cell interference. In addition, wireless transmission is commonly hindered by fading and pathloss. In this direction, this thesis focuses on improving the performance of cell edge users in LTE and LTE-Advanced (LTE-A) networks by initially implementing a new Coordinated Multi-Point (CoMP) algorithm to mitigate cell edge user interference. Subsequently Device-to-Device (D2D) communication is investigated as the enabling technology for maximising Resource Block (RB) utilisation in current 4G and emerging 5G networks. It is demonstrated that the application, as an extension to the above, of novel power control algorithms, to reduce the required D2D TX power, and multihop transmission for relaying D2D traffic, can further enhance network performance. To be able to develop the aforementioned technologies and evaluate the performance of new algorithms in emerging network scenarios, a beyond-the-state-of-the-art LTE system-level simulator (SLS) was implemented. The new simulator includes Multiple-Input Multiple-Output (MIMO) antenna functionalities, comprehensive channel models (such as Wireless World initiative New Radio II i.e. WINNER II) and adaptive modulation and coding schemes to accurately emulate the LTE and LTE-A network standards. Additionally, a novel interference modelling scheme using the 'wrap around' technique was proposed and implemented that maintained the topology of flat surfaced maps, allowing for use with cell planning tools while obtaining accurate and timely results in the SLS compared to the few existing platforms. For the proposed CoMP algorithm, the adaptive beamforming technique was employed to reduce interference on the cell edge UEs by applying Coordinated Scheduling (CoSH) between cooperating cells. Simulation results show up to 2-fold improvement in terms of throughput, and also shows SINR gain for the cell edge UEs in the cooperating cells. Furthermore, D2D communication underlaying the LTE network (and future generation of wireless networks) was investigated. The technology exploits the proximity of users in a network to achieve higher data rates with maximum RB utilisation (as the technology reuses the cellular RB simultaneously), while taking some load off the Evolved Node B (eNB) i.e. by direct communication between User Equipment (UE). Simulation results show that the proximity and transmission power of D2D transmission yields high performance gains for a D2D receiver, which was demonstrated to be better than that of cellular UEs with better channel conditions or in close proximity to the eNB in the network. The impact of interference from the simultaneous transmission however impedes the achievable data rates of cellular UEs in the network, especially at the cell edge. Thus, a power control algorithm was proposed to mitigate the impact of interference in the hybrid network (network consisting of both cellular and D2D UEs). It was implemented by setting a minimum SINR threshold so that the cellular UEs achieve a minimum performance, and equally a maximum SINR threshold to establish fairness for the D2D transmission as well. Simulation results show an increase in the cell edge throughput and notable improvement in the overall SINR distribution of UEs in the hybrid network. Additionally, multihop transmission for D2D UEs was investigated in the hybrid network: traditionally, the scheme is implemented to relay cellular traffic in a homogenous network. Contrary to most current studies where D2D UEs are employed to relay cellular traffic, the use of idle nodes to relay D2D traffic was implemented uniquely in this thesis. Simulation results show improvement in D2D receiver throughput with multihop transmission, which was significantly better than that of the same UEs performance with equivalent distance between the D2D pair when using single hop transmission.

Les dispositifs thermoélectriques, basés sur la conversion d'énergie thermique, offrent des perspectives intéressantes pour le développement de systèmes autonomes. Les principaux défis pour le développement de telles technologies reposent sur l'obtention de dispositifs flexibles, écologiquement et économiquement viables pouvant alimenter des appareils électroniques à faible consommation d'énergie. Le but de cette thèse a donc été de proposer une méthodologie pour l'analyse globale de dispositifs thermoélectriques pour des applications à température ambiante. Dans un premier temps, une approche multi-échelle pour la modélisation de dispositifs thermoélectriques a été développée. A cet effet, trois niveaux d'abstraction ont été considérés. A l'échelle du système, un modèle compact a été développé afin d'évaluer les performances du dispositif dans son environnement. A l'échelle du dispositif, des prototypes virtuels de TEG ont été évalués par le biais de la simulation numérique. A l'échelle des matériaux, la DFT combinée à une approche semi-classique basée sur l'équation de transport de Boltzmann ont été utilisées afin de calculer les propriétés électroniques. La tétraédrite et la famatinite ont été sélectionnées en raison de leurs propriétés prometteuses à température ambiante ainsi que de leur abondance et faible coût. Dans un second temps, des travaux expérimentaux sur la synthèse de nanoparticules de Cu-Sb-S ont été menés. Des nanoparticules quasi-monodisperses avec des tailles inférieures à 50 nm ont été obtenues grâce à la mise au point d'un procédé basé sur la synthèse solvothermale avec surfactant, une méthode faible coût et facilement adaptable à grande échelle
Thermoelectric devices, capitalizing on waste heat conversion, offer good prospects for the development of autonomous systems. The main challenges for technology development are to obtain flexible, environmentally friendly and low-cost thermoelectric devices with performances sufficient enough to power small electronic devices. The aim of this thesis was thus to propose a methodology for the global analysis of thermoelectric devices for ambient temperature applications. The developed methodology enables the evaluation of key parameters impact on the global system. First, a multiscale approach for thermoelectric devices modelling is developed. In this scope, three parallel levels of modeling are addressed. At the system level, a compact model is developed in order to evaluate overall system efficiency as a function of the thermal environment. At the device level, virtual prototypes of printed devices are built and their performances are evaluated via a finite-element simulation tool. Low temperature gradient has to be dealt with by appropriate architecture design. At the material level, quantum DFT is used in conjunction with semi-classical approach using Boltzmann transport theory to calculate electronic properties. Tetrahedrite and famatinite compounds are chosen due to their promising thermoelectric properties at room temperature and their relative abundance and low cost. Secondly, an experimental work has been conducted on the synthesis of sulphide nanoparticles. Quasi-monodisperse nanoparticles with a size not exceeding 50 nm have successfully been fabricated via a low cost and easily scalable surfactant assisted solvothermal technique

Cette thèse présente une contribution à la surveillance des pompes à pistons axiaux des hélicoptères par modélisation et simulation. Un modèle de pompe à paramètres localisés est développé pour servir de banc d'essai pour les études de surveillance. L'auteur propose des améliorations de l'état de l'art de la modélisation à paramètres localisés des pompes à pistons axiaux, en se concentrant sur le besoin industriel de surveillance. La proposition se concentre sur la simulation du régulateur de pression dans des conditions dégradées, et sur le calcul des fuites de patin/plateau à travers un jeu de hauteur variable. Le modèle de pompe développé est comparé à des données expérimentales. Un outil graphique (la Courbe d'Identification des Dommages, DIC) est ensuite proposé. Cet outil permet d'isoler la dégradation de la pompe dans le système hydraulique à l'aide de mesures en régime permanent de la pression de refoulement et de la pression de drain. L'étude se termine par des recommandations pour augmenter le niveau de maturité technologique de l'approche proposée
This dissertation presents a contribution to helicopter axial piston pump monitoring through modelling and simulation. A lumped-parameter model of such pump is developed to serve as a virtual test bench for monitoring studies. As lumped-parameter models of axial piston pumps are less detailed than distributed-parameter models, the author proposes improvements of lumped-parameter modelling state-of-the-art, focusing on the monitoring industrial need. The proposal concentrates on the pressure compensator simulation in degraded conditions, and on the slipper/swashplate leakage computation through a variable gap height. The developed pump model is compared to experimental data. Then, a graphical tool is proposed, (the Damage Identification Curve, DIC), which allows for the isolation of pump degradation within the hydraulic system using discharge and case drain pressure steady-state measurements. The study is concluded by recommendations for increasing the maturity level of the proposed monitoring approach