Dissertations / Theses on the topic 'Wave based models'

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Jacobs, Laurence J.; Committee Member: Kim, Jin-Yeon; Committee Member: Qu, Jianmin. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Predicting performance metrics for the next-generation of multi-mode and multi-antenna wireless communication systems demands site-specific knowledge of the wireless channel's underlying radio wave propagation mechanisms. This thesis describes the first measurement system capable of characterizing individual propagation mechanisms in situ. The measurement system merges a high-resolution spatio-temporal wireless channel sounder with a new field reconstruction technique to provide complete knowledge of the wireless channel's impulse response throughout a 2-dimensional region. This wealth of data may be combined with space-time filtering techniques to isolate and characterize individual propagation mechanisms. The utility of the spatio-temporal measurement system is demonstrated through a measurement-based investigation of diffraction around building corners. These measurements are combined with space-time filtering techniques and a new linear wedge diffraction model to extract the first semi-mpirical diffraction coefficient. Specific contributions of this thesis are: * The first ultra-wideband single-input multiple-output (SIMO) channel sounder based upon the sliding correlator architecture. * A quasi 2-dimensional field reconstruction technique based upon a conjoint cylindrical wave expansion of coherent perimeter measurements. * A wireless channel ``filming' technique that records the time-domain evolution of the wireless channel throughout a 2-dimensional region. * High-resolution measurements of the space-time wireless channel near a right-angled brick building corner. * The application of space-time filtering techniques to isolate the edge diffraction problem from the overall wireless channel. * An approximate uniform geometrical theory of diffraction (UTD)-style linear model describing diffraction by an impedance wedge. * The first-ever semi-empirical diffraction coefficient extracted from in situ measurement data. This thesis paves the way for several new avenues of research. The comprehensive measurement data provided by channel "filming" will enable researchers to develop and implement powerful space-time filtering techniques that facilitate measurement-based investigations of radio wave propagation. The measurement procedure described in this thesis may be adapted to extract realistic reflection and rough-surface scattering coefficients. Finally, exhaustive measurements of individual propagation mechanisms will enable the first semi-empirical propagation model that integrates empirical descriptions of propagation mechanisms into a UTD-style mechanistic framework.

Cardiovascular disease is a leading cause of death in developed countries, and places a huge demand on healthcare services and economies across the globe. In this thesis computational models of the rabbit and mouse whole heart were developed and used to investigate a variety of phenomena related to cardiac electrophysiology. In part I, a heterogeneous family of single cell models was developed for the rabbit ventricles. The models were incorporated into a 3D anatomical reconstruction, and subsequently used to study the relationship between ventricular heterogeneity and the electrocardiographic T-wave. It was found that, in order of significance, apico-basal, inter-ventricular and transmural heterogeneity had a lead-dependent effect on the T-wave of the 12-lead electrocardiogram. Subsequently, a detailed model of the rabbit whole heart was developed using image data from X-ray computed tomography, from which detailed anatomical structures were segmented and myocardial architecture determined. The developed 3D whole heart model exhibited physiological fibre structure and experimentally justified patterns of activation. In part II, a mathematical model of the mouse atrioventricular node was developed. The model was validated by its ability to show physiological pacemaking and response to ion channel blocking. The model was subsequently adapted to consider the heterogeneous nature of the atrioventricular node, and incorporated into a 2D simplistic tissue model of the whole heart. The developed model exhibited physiological atrioventricular conduction, and provided insights into the nature of dual-pathway electrophysiology and the role of the funny current. Finally, an optimisation study was carried out for contrast enhancement of X-ray computed tomography, specifically for imaging the mouse heart, the results of which may be used to facilitate future high-throughput imaging of cardiac tissue.

The need for optimal air vessel sizing tools, in protecting large pipe networks from undue transient pressures is well known. Graphical and other heuristic methods reported in literature are limited to sizing the air vessels for simple rising mains. Although attempts have been made to utilize optimization techniques, they have been largely unsuccessful due to their impractical computational requirements. This research work proposes a robust framework for developing surge protection design tools and demonstrates the usefulness of the framework through an example air vessel sizing tool. Efficiency and robustness of the proposed framework are demonstrated by developing a design aid for air vessel sizing for protecting large pipe network systems against excessive high pressures generated by rapid valve closures. The essence of the proposed framework is in identification of key transient response parameters influencing air vessel parameters from seemingly unmanageable transient response data. This parameterization helps in exploiting the similarity between transient responses of small pipe networks and sub-sections of large pipe networks. The framework employs an extensive knowledgebase of transient pressure and flow scenarios defined from several small network models and corresponding optimal air vessel sizes obtained from a genetic algorithm optimizer. A regression model based on an artificial neural network was used on this knowledgebase to identify key parameters influencing air vessel sizes. These key parameters were used as input variables and the corresponding air vessel parameters as output variables to train the neural network model. The trained neural network model was successfully applied for large complex pipe networks to obtain optimal air vessel sizes for transient protection. The neural network model predictions were compared with optimal air vessel parameters to assess the efficacy of the proposed framework. The validity and limitation of the design aid developed and areas in the framework that need further research are also presented. The proposed frame work requires generation of hundreds of optimization data for small and simple network systems which is a daunting task since genetic algorithm-based optimization is computationally expensive. Selection of a numerically efficient and sufficiently accurate transient analysis method for use inside a genetic algorithm based optimization scheme is crucial as any reduction in transient analysis time for a network system would tremendously reduce the computational costs of bi-level genetic algorithm optimization scheme. This research work also demonstrate that the Wave Plan Method is computationally more efficient than the Method of Characteristics for similar accuracies and the resulting savings in computational costs in the transient analysis of pipe networks and subsequently in the genetic algorithm based optimization schemes are significant.

The velocity structures of southern and central part of Sweden have been derived with the local tomography (LET) method. The region has been divided into two study areas and the datasets come from the P- and S-wave traveltimes recorded by the Swedish National Seismic Network (SNSN). Man-made explosions and earthquakes occurring over the period of 5 years and 10 years, respectively, within the study areas have been used. One-dimensional starting models were derived based on an a priori model obtained from the SNSN, that were later used for starting models in the inversion for the 3-D crustal structures of the study areas. Attempts were also made to invert for Moho topography in the areas. The study areas are found to have an upper-crustal thickness of approximately 20 to 25 km and the Moho boundaries vary from 42 to 46 km in depth. The Vp/Vs ratios varies from about 1.68 to 1.78. The LET method appear to resolve the different between the Sveconorgwegian and Svecofennian orogen regions, but the stations and sources are too sparsely distributed for higher resolution models. The seismicity in the study areas are distributed in two distinctive depth ranges. The focal depth of the SNSN catalogued earthquakes concentrated in approximately 5 km and 15 - 20 km depth. Relocations of the earthquakes using a global search method reduced this tendency. The results also show that using 3-D models produces less biased results than using 1-D models with the same relocation method.

Recently, the growing demand for high data rates in wireless communication, together with the scarcity of spectrum in existing microwave bands, has motivated the use of millimeter-wave (mmWave) bands for 5G and future wireless communications. Even though mmWaves are potential candidates for fulfilling this rising demand, they come along with their own drawbacks that need to be addressed. Sensitivity to blockages is one of these drawbacks. It is a major channel impairment that is of concern in the design of mmWaves communication systems. As such, different industrial and academic research activities have been performed and are in progress for modeling and characterizing blockages in mmWave communication systems. However, most of the proposed blockage models failed to capture the temporal correlation of the blockages and the dynamics of the channel’s environment.In order to address this issue, this thesis work aims to develop a simple Stochastic Blockage Model for mmWave communication channels. The model uses two-states (ON and OFF states) to represent Line of Sight (LoS) and Non-Line of Sight (NLoS) conditions, respectively. Using simulation-based analysis, the behavior and probability of the LoS and the NLoS situations of a communication link over time have been analyzed. It is demonstrated that the proposed blockage model can capture the behaviors of the probability of a link being blocked or not in a dynamic environment. It was also found to be adequate to model and characterize the effects of blockage in mmWave communication systems. The accuracy of the model was evaluated to be satisfactory by validating the results against a benchmark which was derived from actual data. It is possible to characterize mmWave communication on a system-level by using this model. Thus, this work provides researchers with a simple simulation-based blockage model to help facilitate the study and design of mmWave communication systems.
Den växande efterfrågan på höga nedladdningshastigheter i trådlösa kommunikationssystem, i kombination med en brist på tillgängliga frekvensband i nuvarande mikrovågsband, har medfört att millimetervågsbandet ses som ett attraktivt alternativ för 5G och andra framtida trådlösa kommunikationssystem. Även om det är troligt att millimetervågsbandet kommer att vara en del av lösningen för att uppfylla efterfrågeökningen har det en del negativa egenskaper som måste beaktas och tas hänsyn till. Känslighet för blockering är en sådan typisk nackdel som avsevärt försämrar radiokanalen i ett millimetervågssystem. Både från näringslivets sida och inom den akademiska världen har det forskats inom detta område. Den har bestått av karakterisering och framtagning av modeller som beskriver kommunikationssystem på dessa frekvensband med avseende på blockering. Emellertid har de flesta föreslagna modellerna har misslyckats fånga upp de temporala korrelation av de blokeringar och de dynamiken av kanalens miljö.Den här avhandlingen har som mål att utveckla en enkel stokastisk blockeringsmodell för millimetervågsbandet för att ta itu med just dessa frågor. Modellen använder två tillstånd (ON och OFF tillstånd) för att representera Line of Sight (LoS) respektive Non-Line of Sight (NLoS) utbredning. Simuleringar av kanalen har gjorts för att analysera de tidsmässiga egenskaperna och sannolikheten för utbredning via direktvåg respektive skuggning. Det visas att den föreslagna skuggningsmodellen kan beskriva det dynamiska beteendet och sannolikheten för att länken är blockerad. Den konstateras också vara adekvat för att modellera och karakterisera kommunikationssystem för millimetervågsbandet med avseende på blockering. Modellens noggrannhet har utvärderats och den anses vara tillfredsställande genom att resultaten validerats mot ett riktmärke som är baserat på verkligt data. Det är möjligt att karakterisera millimetervågskommunikation på systemnivå genom att använda denna modell. Detta verk förser således forskare med en enkel simuleringsbaserad blockeringsmodell som främjar studier och framtagning av kommunikationssystem på millimetervågsbandet.

Metabolomics is the methodical scientific study of biochemical processes associated with the metabolome—which comprises the entire collection of metabolites in any biological entity. Metabolome changes occur as a result of modifications in the genome and proteome, and are, therefore, directly related to cellular phenotype. Thus, metabolomic analysis is capable of providing a snapshot of cellular physiology. Untargeted metabolomics is an impartial, all-inclusive approach for detecting as many metabolites as possible without a priori knowledge of their identity. Hence, it is a valuable exploratory tool capable of providing extensive chemical information for discovery and hypothesis-generation regarding biochemical processes. A history of metabolomics and advances in the field corresponding to improved analytical technologies are described in Chapter 1 of this dissertation. Additionally, Chapter 1 introduces the analytical workflows involved in untargeted metabolomics research to provide a foundation for Chapters 2 – 5. Part I of this dissertation which encompasses Chapters 2 – 3 describes the utilization of mass spectrometry (MS)-based untargeted metabolomic analysis to acquire new insight into cancer detection. There is a knowledge deficit regarding the biochemical processes of the origin and proliferative molecular mechanisms of many types of cancer which has also led to a shortage of sensitive and specific biomarkers. Chapter 2 describes the development of an in vitro diagnostic multivariate index assay (IVDMIA) for prostate cancer (PCa) prediction based on ultra performance liquid chromatography-mass spectrometry (UPLC-MS) metabolic profiling of blood serum samples from 64 PCa patients and 50 healthy individuals. A panel of 40 metabolic spectral features was found to be differential with 92.1% sensitivity, 94.3% specificity, and 93.0% accuracy. The performance of the IVDMIA was higher than the prevalent prostate-specific antigen blood test, thus, highlighting that a combination of multiple discriminant features yields higher predictive power for PCa detection than the univariate analysis of a single marker. Chapter 3 describes two approaches that were taken to investigate metabolic patterns for early detection of ovarian cancer (OC). First, Dicer-Pten double knockout (DKO) mice that phenocopy many of the features of metastatic high-grade serous carcinoma (HGSC) observed in women were studied. Using UPLC-MS, serum samples from 14 early-stage tumor DKO mice and 11 controls were analyzed. Iterative multivariate classification selected 18 metabolites that, when considered as a panel, yielded 100% accuracy, sensitivity, and specificity for early-stage HGSC detection. In the second approach, serum metabolic phenotypes of an early-stage OC pilot patient cohort were characterized. Serum samples were collected from 24 early-stage OC patients and 40 healthy women, and subsequently analyzed using UPLC-MS. Multivariate statistical analysis employing support vector machine learning methods and recursive feature elimination selected a panel of metabolites that differentiated between age-matched samples with 100% cross-validated accuracy, sensitivity, and specificity. This small pilot study demonstrated that metabolic phenotypes may be useful for detecting early-stage OC and, thus, supports conducting larger, more comprehensive studies. Many challenges exist in the field of untargeted metabolomics. Part II of this dissertation which encompasses Chapters 4 – 5 focuses on two specific challenges. While metabolomic data may be used to generate hypothesis concerning biological processes, determining causal relationships within metabolic networks with only metabolomic data is impractical. Proteins play major roles in these networks; therefore, pairing metabolomic information with that acquired from proteomics gives a more comprehensive snapshot of perturbations to metabolic pathways. Chapter 4 describes the integration of MS- and NMR-based metabolomics with proteomics analyses to investigate the role of chemically mediated ecological interactions between Karenia brevis and two diatom competitors, Asterionellopsis glacialis and Thalassiosira pseudonana. This integrated systems biology approach showed that K. brevis allelopathy distinctively perturbed the metabolisms of these two competitors. A. glacialis had a more robust metabolic response to K. brevis allelopathy which may be a result of its repeated exposure to K. brevis blooms in the Gulf of Mexico. However, K. brevis allelopathy disrupted energy metabolism and obstructed cellular protection mechanisms including altering cell membrane components, inhibiting osmoregulation, and increasing oxidative stress in T. pseudonana. This work represents the first instance of metabolites and proteins measured simultaneously to understand the effects of allelopathy or in fact any form of competition. Chromatography is traditionally coupled to MS for untargeted metabolomics studies. While coupling chromatography to MS greatly enhances metabolome analysis due to the orthogonality of the techniques, the lengthy analysis times pose challenges for large metabolomics studies. Consequently, there is still a need for developing higher throughput MS approaches. A rapid metabolic fingerprinting method that utilizes a new transmission mode direct analysis in real time (TM-DART) ambient sampling technique is presented in Chapter 5. The optimization of TM-DART parameters directly affecting metabolite desorption and ionization, such as sample position and ionizing gas desorption temperature, was critical in achieving high sensitivity and detecting a broad mass range of metabolites. In terms of reproducibility, TM-DART compared favorably with traditional probe mode DART analysis, with coefficients of variation as low as 16%. TM-DART MS proved to be a powerful analytical technique for rapid metabolome analysis of human blood sera and was adapted for exhaled breath condensate (EBC) analysis. To determine the feasibility of utilizing TM-DART for metabolomics investigations, TM-DART was interfaced with traveling wave ion mobility spectrometry (TWIMS) time-of-flight (TOF) MS for the analysis of EBC samples from cystic fibrosis patients and healthy controls. TM-DART-TWIMS-TOF MS was able to successfully detect cystic fibrosis in this small sample cohort, thereby, demonstrating it can be employed for probing metabolome changes. Finally, in Chapter 6, a perspective on the presented work is provided along with goals on which future studies may focus.

Understanding and modeling seismic wave propagation is important in regional and exploration seismology. Ray tracing is a powerful and popular method for this purpose. Wavefront construction (WFC) method handles wavefronts instead of individual rays, thereby controlling proper ray density on the wavefront. By adaptively controlling rays over a wavefront, it efficiently models wave propagation. Algorithms for a quasi-P wave wavefront construction method and a new coordinate system used to generate wavefront construction mesh are proposed and tested for numerical properties and modeling capabilities. Traveltimes, amplitudes, and other parameters, which can be used for seismic imaging such as migrations and synthetic seismograms, are computed from the wavefront construction method. Modeling with wavefront construction code is applied to anisotropic media as well as isotropic media. Synthetic seismograms are computed using the wavefront construction method as a new way of generating synthetics. To incorporate layered velocity models, the model based interpolation (MBI) ray tracing method, which is designed to take advantage of the wavefront construction method as well as conventional ray tracing methods, is proposed and experimental codes are developed for it. Many wavefront construction codes are limited to smoothed velocity models for handling complicated problems in layered velocity models and the conventional ray tracing methods suffer from the inability to control ray density during wave propagation. By interpolating the wavefront near model boundaries, it is possible to handle the layered velocity model as well as overcome ray density control problems in conventional methods. The test results revealed this new method can be an effective modeling tool for accurate and effective computing.

Ocean wave energy is considered to be one of the important potential renewable energy resources for sustainable development. Various wave energy converter technologies have been proposed to harvest the energy from ocean waves. This thesis is based on the linear generator wave energy converter developed at Uppsala University. The research in this thesis focuses on the foundation optimization and the power absorption optimization of the wave energy converters and on the wave climate modelling at the Lysekil wave converter test site. The foundation optimization study of the gravity-based foundation of the linear wave energy converter is based on statistical analysis of wave climate data measured at the Lysekil test site. The 25 years return extreme significant wave height and its associated mean zero-crossing period are chosen as the maximum wave for the maximum heave and surge forces evaluation. The power absorption optimization study on the linear generator wave energy converter is based on the wave climate at the Lysekil test site. A frequency-domain simplified numerical model is used with the power take-off damping coefficient chosen as the control parameter for optimizing the power absorption. The results show a large improvement with an optimized power take-off damping coefficient adjusted to the characteristics of the wave climate at the test site. The wave climate modelling studies are based on the wave climate data measured at the Lysekil test site. A new mixed distribution method is proposed for modelling the significant wave height. This method gives impressive goodness of fit with the measured wave data. A copula method is applied to the bivariate joint distribution of the significant wave height and the wave period. The results show an excellent goodness of fit for the Gumbel model. The general applicability of the proposed mixed-distribution method and the copula method are illustrated with wave climate data from four other sites. The results confirm the good performance of the mixed-distribution and the Gumbel copula model for the modelling of significant wave height and bivariate wave climate.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references (p. 215-219).
A ship moving on the free surface produces energetic breaking bow waves which generate spray and air entrainment. Present experimental, analytic, and numerical studies of this problem are costly, inaccurate and not robust. This thesis presents new cost-effective and accurate computational tools for the design and analysis of such ocean systems through a combination of physics-based and learning-based models. Methods which immerse physical boundaries on Cartesian background grids can model complex topologies and are well suited to study breaking bow waves. However, current methods such as Volume of Fluid and Immersed Boundary methods have numerical and modeling limitations. This thesis advances the state of the art in Cartesian-grid methods through development of a new conservative Volume-of-fluid algorithm and the Boundary Data Immersion Method, a new approach to the formulation and implementation of immersed bodies. The new methods are simple, robust and shown to out perform existing approaches for a wide range of canonical test problems relevant to ship wave flows. The new approach is used to study breaking bow waves through 2D+T and 3D simulations. The 2D+T computations compare well with experiments and breaking bow wave metrics are shown to be highly sensitive to the ship geometry. 2D+T breaking bow wave predictions are compared quantitatively to 3D computations and shown to be accurate only for certain flow features and very slender high speed vessels. Finally the thesis formalizes the study and development of physics-based learning models (PBLM) for complex engineering systems. A new generalized PBLM architecture is developed based on combining fast simple physics-based models with available high-fidelity data.
(cont.) Models are developed and trained to accurately predict the wave field and breaking bow waves of a ship orders of magnitude faster than standard methods. Built on the new boundary immersion approaches, these computational tools are sufficiently cost-effective and robust for use in practical design and analysis.
by Gabriel David Weymouth.
Sc.D.

Reaction-diffusion models with nonlinear diffusion are widely used for studying population dynamics in biology and ecology. Yet, the relationship between nonlinear diffusion mechanisms in populations and the behaviours of individuals is hard to be intuitively interpreted in classical models. To address this problem, we develop a discrete-continuum modelling framework, where the movement of individuals influenced by crowding effects is connected to the nonlinear diffusivity functions in a well-defined continuum limit. Using this framework, we explore the influence of nonlinear diffusion on population extinction, and analyse the existence and stability of travelling waves in continuous equations which model the invasion process.

Les vibrations et les bruits de structure sont généralement des phénomènes indésirables pour des raisons de fiabilité et de confort. De nombreuses approches du contrôle des vibrations ont été étudiées au fil des ans, en utilisant diverses conceptions géométriques, des matériaux d'amortissement ou des stratégies de contrôle actif. En outre, l'allègement des structures mécaniques est un défi majeur en termes de consommation d'énergie, en particulier pour les applications de transport.Dans ces contextes combinés, l'objectif de cette thèse est de développer de nouveaux concepts de contrôle des vibrations en adaptant le principe des filtres de Herschel-Quincke (HQ), traditionnellement appliqué aux ondes acoustiques planes dans les tubes, au domaine des ondes élastiques dans les poutres et les plaques. En acoustique, les filtres HQ exploitent le principe de la différence de marche entre deux tubes parallèles de longueurs variables créés à partir d'un tube primaire, ce qui entraîne une interférence destructive et donc une transmission nulle à certaines fréquences.L'attrait des filtres HQ réside dans leur capacité à fournir de multiples pics de perte de transmission, ce qui constitue une alternative viable aux approches traditionnelles basées sur la résonance. Cette étude étend ce principe aux ondes de flexion en divisant une poutre mince en deux segments de longueur égale mais d'épaisseur différente. La différence de rigidité de flexion qui en résulte induit la différence de phase requise, ce qui conduit au filtrage des ondes. Cette approche fait des filtres HQ une solution prometteuse pour les applications de contrôle des vibrations et du bruit sans augmenter la masse de la structure considérée. Premièrement, le principe HQ pour la dynamique structurelle est analysé théoriquement à travers des modèles basés sur les ondes considérant les ondes longitudinales ou torsionnelles non dispersives et les ondes de flexion dans les poutres. Une étude expérimentale démontre également l'intérêt pratique de cette technique de filtrage. Ensuite, le principe est étendu aux structures de plaques, ce qui conduit à des filtres annulaires qui peuvent entourer une source de vibration et ainsi l'isoler du reste de la plaque. Enfin, des conceptions plus sophistiquées basées sur des arrangements sériels, parallèles ou périodiques de dispositifs structurels HQ sont proposées et analysées afin d'évaluer comment elles peuvent optimiser les performances de filtrage des vibrations
Vibration and structure borne noise are generally undesirable phenomena for both the reliability and comfort issues. Many approaches to vibration control have been studied over the years, using various geometrical designs, damping materials, or active control strategies. In addition, lightening mechanical structures is a major challenge in terms of energy consumption, particularly for transport applications. In these combined contexts, the aim of this thesis is to develop new vibration control concepts by adapting the principle of Herschel-Quincke (HQ) filters, traditionally applied to plane acoustic waves in tubes, to the realm of elastic waves in beams and plates. In acoustics, HQ filters exploit the principle of a phase shift between two parallel tubes of varying lengths created from a primary tube, resulting in destructive interference and hence zero transmission at certain frequencies. The attractiveness of HQ filters lies in their capacity to provide multiple transmission loss peaks, presenting a viable alternative to traditional resonance-based approaches. This study extends this principle to bending waves by partitioning a thin beam into two segments of equal length but different thicknesses. The resulting disparity in bending stiffness induces the requisite phase difference, leading to wave filtering. This approach positions HQ filters as a promising solution for vibration and noise control applications without increasing the mass of the considered structure. First, the HQ principle for structural dynamics is theoretically analysed through wave based models considering non dispersive longitudinal or torsional waves and bending waves in beams. An experimental study also demonstrates the practical interest of this filtering technique. Then, the principle is extended to plates structures, leading to annular filters that may surround a vibration source and so isolate it from the rest of the plate. Third, some more sophisticated designs based on serial, parallel or periodic arrangements of structural HQ devices are proposed and analyzed to assess how they can optimize vibration filtering performance

La técnica de las ondas de Lamb acopladas por aire representa un importante avance en el área de los Ensayos No Destructivos (END) de materiales laminares.
Sin embargo la compleja naturaleza de las vibraciones mecánicas encontradas en acústica, hacen que el análisis y el estudio de esta área del conocimiento sea un tema muy complejo. De allí que la posibilidad de contar con una herramienta de simulación de software que permita la evaluación y prueba de diferentes configuraciones de excitación y recepción acústica utilizando la flexibilidad de un modelo de computadora sea de una gran utilidad y ayuda.
El objetivo de la presente tesis es proveer al área de los END con un software de simulación gratuito: The LAMB Matlab® toolbox basado en el modelo del software libre de la GNU.
El software es capaz de simular el comportamiento de sistemas de END basados en ondas de Lamb acopladas por aire en láminas isótropas simples utilizando transductores tipo array.
El programa se basa en un arreglo tipo C-scan de un sistema de END y está compuesto por tres bloques principales: 1) Excitación, 2) Propagación y 3) Recepción.
La verificación individual del funcionamiento de dichos módulos se presenta a lo largo de la tesis mediante una serie de comparaciones entre simulaciones y datos experimentales provenientes de diferentes pruebas. Por otro lado, la validación del programa completo se llevo a cabo por medio de experimentos en láminas de cobre y aluminio; utilizando un sistema real de END por ondas de Lamb acopladas en aire mediante arrays cóncavos.
La influencia negativa en el desempeño general de dicho sistema de END real basado en este tipo de transductores se comprobó efectivamente mediante el simulador desarrollado. Esto se debió fundamentalmente al efecto de directividad de los sensores individuales en los transductores y a la simetría cóncava de los arrays.
Para emular este comportamiento la tesis presenta un modelo geométrico bidimensional simple de un filtro espacial, junto a las simulaciones de un nuevo tipo de array plano propuesto.
El programa desarrollado comprobó así mismo la naturaleza coherente de los campos acústicos emitidos en aire por las láminas sujetas a vibraciones de Lamb. Esto se realizó mediante la implementación de un conformador de haz simple de suma y demora; constituyéndose así la etapa inicial de procesamiento de señal del bloque de recepción del programa.
El objetivo principal del presente trabajo fue contribuir con un modelo operativo de simulación y prueba de nuevos diseños de arrays e implementación de estrategias de procesado de señal útiles en sistemas de END basados en ondas de Lamb acopladas por aire.
Finalmente, si bien el objetivo de la calibración del programa no se pudo conseguir; si se logró efectivamente un notable grado de similitud con un sistema de END real.
Air-coupled ultrasonic Lamb waves represent an important advance in Non- Destructive Testing and Evaluation (NDT & NDE) techniques of plate materials and structures. Examples of these advances are the characterization and quality assessment of laminate materials in manufacturing processes, the location of damaged parts in aircrafts and structure monitoring in the aerospace industry.
However the rich and complex nature of mechanical vibrations encountered in acoustics make the subject of analysis and study of these systems a very complex task. Therefore a simulation tool that permits the evaluation and testing of different configuration scenarios using the flexibility of a computer model is an invaluable aid and advantage.
The objective of this thesis is to provide the field of NDT with free open source software i.e. the LAMB Matlabrtoolbox. The toolbox is capable of simulating the behaviour of Lamb wave based NDE systems for single ideal isotropic laminates using air-coupled ultrasonic arrays. The programme usesa pitch-catch type of a Cscan NDE arrangement and is composed of three integrated sections each individually modelling a feature in the system: 1) Excitation, 2) Propagation, and 3) Reception.
For assessment of the individual modules of the toolbox the thesis presents comparisons between each section simulations and the data obtained from different acoustic experiments. The validation of the complete simulator was carried out by evaluation tests on the copper and aluminium plates by use of a real hardware prototype of a Lamb wave based NDE system with aircoupled concave arrays.
The negative impact on the performance of the real air-coupled NDE systembased on concave arrays was effectively confirmed by the programme. This was produced by the inherent directivity of the individual sensors as well as their concave arrangement. To emulate this behaviour the thesis introduces a simple two-dimensional geometric model for the inclusion of the spatial filtering effect of the sensors plus a group of simulations for a new proposed air-coupled plane array transducer.
The software also verified the spatial coherent nature of the Lamb wave fields emitted by a plate in air. This was demonstrated by the implementation of a delay and sum beamformer to constitute an initial signal processing stage in the reception section.

Extensive research has been undertaken to improve the robustness of runoff quantity predictions for urban catchments. However, equally robust predictions for runoff quality have yet to be attained. Past studies addressing this issue have typically been confined to the use of simple conceptual or empirical models which forgo the tedious steps of providing a physical representation of the actual system to be modelled. Consequently, even if the modelling results for the test catchments are satisfactory, the reliability and applicability of these models for other catchments remain uncertain. It is deemed that by employing process-based, deterministic models, many of these uncertainties can be eliminated. A lack of understanding of the hydrological processes occurring during storm events and the absence of good calibration data, however, hamper the advancement of such models and limit their use in the field. This research proposes that the development of a hydrologic model based on the kinematic wave equations linked to an advection-dispersion model that simulates pollutant detachment and transport will improve both runoff quantity and quality simulations and enhance the robustness of the predictions. At the very worst, a model of this type could still highlight the underlying issues that inhibit models from reproducing the recorded historical hydrographs and pollutographs. In actual fact, this approach has already been applied by various modellers to simulate the entrainment of pollutants from urban catchments. Also, the paradigm shift to using the Water Sensitive Urban Design (WSUD) approach in designing urban stormwater systems has prompted the need to differentiate the various sources of pollutants in urban catchments such as roads, roofs and other impervious surfaces. The primary objective of the study reported herein is to model runoff quantity and quality from small urban catchments, facilitated by the procurement of the necessary field data to calibrate and validate the model via implementation of a comprehensive field exercise based in Sydney. From a water quality perspective, trace metals were selected as the foci. The study outcomes include the formulation of a linkage of models capable of providing accurate and reliable runoff quantity and quality predictions for the study catchments by taking into consideration: - The different availability of pollutants from urban catchments, i.e. roads vs. roofs; - The build-up characteristics of pollutants on the distinct urban surfaces and their spatial distribution; - The contribution of rainwater to urban runoff pollution; - The partitioning of pollutants according to particulate bound and dissolved phases; - The respective role of rainfall and runoff in the detachment and entrainment of pollutants; - The influence of particle properties such as particle size distribution and density on pollutant transport; and - The relationship associating particulate bound metals to suspended solids. The simulation results obtained using the proposed model were found to be suitable for modelling the detachment and transport of pollutants for small urban catchments. Interpretation of these results reveals several key findings which could help to rectify shortcomings of existing modelling approaches. Even though the robustness of the model presented here may not translate into a significant improvement in the overall robustness of model predictions, the physical basis on which this process-based model was developed nevertheless provides the flexibility necessary for implementation at alternative sites. It is also shown that the availability of reliable runoff data is essential for implementation of the model for other similar urban catchments. In conclusion, the proposed model in this study will serve as a worthy tool in future urban catchment management studies.

In this thesis, the effect of pitch based optimisation was explored for a 80 turbine wind farm. Using a modified Jensen wake model and the Particle Swarm Optimisation (PSO) model, a pitch optimisation strategy was created for the dominant turbulence and atmospheric condition for the wind farm. As the wake model was based on the FLORIS model developed by P.M.O Gebraad et. al., the wake and power model was compared with the FLORIS model and a -0.090% difference was found. To determine the dynamic predictive capability of the wake model, measurement values across a 10 minute period for a 19 wind turbine array were used and the wake model under predicted the power production by 17.55%. Despite its poor dynamic predictive capability, the wake model was shown to accurately match the AEP production of the wind farm when compared to a CFD simulation done in FarmFlow and only gave a 3.10% over-prediction. When the optimisation model was applied with 150 iterations and particles, the AEP production of the wind farm increased by 0.1052%, proving that the pitch optimisation method works for the examined wind farm. When the iterations and particles used for the optimisation was increased to 250, the power improvement between optimised results improved by 0.1144% at a 222.5% increase in computational time, suggesting that the solution has yet to fully converge. While the solutions did not fully converge, they converged sufficiently and an increase in iterations gave diminishing results. From the results, the pitch optimisation model was found to give a significant increase in power production, especially in wake intensive wind directions. However, the dynamic predictive capabilities will have be improved upon before the control strategy can be applied to an operational wind farm.

Ce travail porte sur la conception de déphaseurs de type réflectif (RTPS) sur silicium à ondes millimétriques avec des moyens de test basé sur l'oscillation (OBT). Pour plus de cohérence, une seule technologie a été utilisée, la BiCMOS STM 55 nm. Tout d'abord, la théorie et les mises en œuvre pratiques des coupleurs 3-dB sont discutées. Une attention particulière est portée à la topologie du guide d'onde coplanaire couplé à ondes lentes (CS-CPW), en raison de ses bonnes performances. En utilisant cette topologie, les mesures de deux coupleurs 3-dB sont rapportées : (i) un coupleur de 120 GHz, et (ii) un coupleur de 185 GHz.Ensuite, les topologies existantes des varactors intégrés sont discutées. Les résultats des mesures sont présentés pour un varactor MOS en mode inversion (I-MOS) de 1 à 325 GHz. En outre, l'architecture de varactor MOS de source commune (CS-MOS) est proposée et les résultats des mesures de 1 à 145 GHz pour cette architecture sont présentés.Puis, la théorie des RTPS est présentée et les coupleurs basés sur CS-CPW ainsi que les varactors MOS en mode d'accumulation (A-MOS), I-MOS et CS-MOS sont utilisés pour la conception de quatre RTPS. Les résultats des mesures et des simulations de ces RTPS, avec des fréquences centrales allant de 60 à 200 GHz, sont présentés.Ensuite, la théorie et les résultats des mesures de l'OBT sur un RTPS intégré de 60 GHz sont discutés.Enfin, une technique de compactage du calibrage TRL des ondes millimétriques est décrite à l'aide d'outils d'apprentissage sur machine
This work focuses on the design of on-silicon mm-wave Reflection-Type Phase Shifters (RTPS) with Oscillation-Based Test (OBT) capabilities. For more consistency, a single technology was considered, the STM 55-nm BiCMOS. First, the theory and practical implementations of 3-dB couplers is discussed. Particular attention is brought to the Coupled Slow-wave CoPlanar Waveguide (CS-CPW) topology, due to its good performance. Using this topology, the measurements of two 3-dB couplers are reported: (i) a 120-GHz, and (ii) a 185-GHz coupler.Next, the existing topologies of integrated varactors are discussed. Measurement results are reported for an Inversion-mode MOS (I-MOS) varactor from 1 up to 325 GHz. Additionally, the Common-Source MOS (CS-MOS) varactor architecture is proposed and measurement results from 1 to 145 GHz for this architecture are reported.Then, the theory of RTPS is presented and CS-CPW-based couplers together with Accumulation-mode MOS (A-MOS), I-MOS and CS-MOS varactors are used for the design of four RTPS. The measurement and simulation results of these RTPS, with central frequencies ranging from 60 to 200 GHz, are presented.Subsequently, the theory and measurement results of the OBT on an integrated 60-GHz RTPS are discussed.Finally, a mm-wave TRL calibration compaction technique is described using machine-learning tools

This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3σblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.

The capability to observe ocean swell using spaceborne Synthetic Aperture Radar (SAR) has been demonstrated starting with ERS-1 mission in 1992. This dissertation shows how ocean swell properties can be used to combine swell observations of heterogeneous quality and acquired at various times and locations for the observation and forecast of ocean swell fieldsusing ASAR instrument on-board ENVISAT. The first section is a review of how ocean swell spectra can be derived from the SAR complex images of the ocean surface using a quasi-linear transformation. Then, significant swell heights, peak periods and peak directions from in situ measurements are used to assess the accuracy of the SAR observed swell spectra. Using linear propagation in deep ocean, a new swell field reconstruction methodologyis developed in order to gather SAR swell observations related to the same swell field. Propagated from their generation region, these observations render the spatio-temporal properties of the emanating ocean swell fields. Afterwards, a methodology is developed for the exclusion of outliers taking advantage of the swell field consistency. Also, using the irregularly sampled SAR observations, quality controlled estimations of swell field integral parameters are produced on a regular space-time grid. Validation against in situ measurements reveals the dramatic impact of the density of propagated observations on the integral parameters estimated accuracy. Specifically, this parameter is shown to be very dependent on the satellite orbit. Finally, comparisons with the numerical wave model WAVEWATCH-III prove it could potentially benefit from the SAR swell field estimates for assimilation purposes.

This dissertation presents a new development of the wave method for structural health monitoring (SHM) of buildings. Robust and reliable SHM methods help save lives and reduce economic losses caused by earthquakes and other extreme events. Previously, in system identification and health monitoring, it was assumed that waves of different frequency propagate with constant velocity and the identification was based on the non-dispersive shear beam model of the structure. This study presents the first effort to consider dispersive wave propagation in system identification and health monitoring by the wave method. To consider dispersion due to bending deformation in buildings a Timoshenko beam model is used. Although buildings as a whole deform primarily in shear, bending deformation is always present to some degree especially for shear wall buildings. To identify allowable ranges of important parameters of the model parametric studies are performed. The model is further generalized to a non-uniform Timoshenko beam model which can take into account variation of properties with height and be used for higher resolution structural health monitoring. The models together with the suggested method to estimate initial values were validated on three full scale buildings. They were used to identify two full scale building from earthquake records and also to monitor the changes in a full-scale 7-story slice of shear wall building which was progressively damaged on UCSD-NEES shake table. It was shown that the model is robust for structural identification and health monitoring of a wide range of building systems and can successfully model dispersion due to bending deformation.

Since the fuel crisis of the 1970s, aerodynamic design has become essential to the vehicle design process in order to reduce fuel consumption and lower emissions as well as (in more recent years) increase the range on vehicles with alternative powertrains. Production car manufacturers have developed shape optimisation techniques that have generated significant improvements over the years however, in order to achieve further gains, a deeper understanding of the fundamental flow structures around vehicles must be achieved. This thesis reports the findings of three studies that aim to understand how the base pressure is manipulated on vehicle like geometries by applying shape optimisations. The base pressure typically contributes approximately 30% of the overall vehicle drag on production vehicles and so presents an opportunity for significant drag saving. A fundamental One-Box model was used to investigate how changing fore-body drag can effect the base pressure and wake topology at varying ground clearances. It was found that at high ground clearances the total drag changes were generated by base pressure changes however when the model was lowered into ground effect the fore-body and skin friction drag produced significantly larger changes than the base pressure. Analysis of the unsteady results showed that with a thinner boundary layer over the model the unsteadiness in the wake was increased. A second study was then conducted on a generic vehicle geometry, the Windsor model, where the lower separation was manipulated through the use of different underbody profiles . As the lower boundary layer on the model was thickened the lower recirculation region grew and lowered the pressure on the base. This was also seen to increase the unsteadiness of the pressures recorded on the base when the upper and lower shear layers were of significantly different strengths. Finally, a rear end optimisation was conducted on the Windsor model using high aspect ratio tapers on the top and bottom trailing edges. It was seen that the amount of downwash or upwash created by the tapers acted on the wake balance which moved the impingement region on the base. This changed the near wall velocities of the wake flow and resulted in changing base pressures. Overall the work has shown that, by controlling the flow conditions at separation, the base pressure can be modified, particularly by altering the relative strengths of the upper and lower shear layers and the impingement location on the base.

A new class of unmanned marine research vessels makes use of wave propulsion to minimise energy requirements during voyages. Existing models of these hybrid sea-surface and underwater craft have not considered if the platform’s interaction with the immediate surrounding sea could be incorporated to allow for more accurate navigation and path planning. To this end a detailed three-dimensional model of one such vessel, the Liquid Robotics’ Wave Glider, has been developed in this study. The multi-body system is described using DenavitHartenberg parametrisation and a Lagrangian approach is used to generate the equations of motion for the body. Physical dimensions are derived from platform measurements and from the product specification sheet, hydrodynamic factors are derived from a SolidWorks model of the system, and added mass components are determined from empirical data. Finally, the dynamic model is verified for a given sea state and multiple sea states are tested to investigate the effect on the model’s performance. The developed Wave Glider model is shown to have a realistic response when hydrodynamic factors, added mass and hydrodynamic damping forces, are included and to sea states in terms of the hydrostatic restorative response. The wave-driven propulsion provided by the hydrofoils is shown to have dependence on the sea state by running the model in an open-loop simulation. Following the model validation, a control system is developed for the Wave Glider model to allow yaw attitude control of the glider using the controllable glider rudder input. The control system is generated making use of quantitative feedback theory (QFT) methods to provide robust control for the under-actuated system. The control scheme is shown to provide suitable performance for sea states that result in variable glider velocities. The model’s performance, in terms of the average velocity, is shown to have dependence on the direction of the sea state by running the model in an open-loop simulation for multiple sea states with sinusoidal waves approaching the Wave Glider model from different directions.

A fundamental aerodynamic analysis technique for a single straight fixed wing has been expounded upon and turned into a modern technique that can analyze multiple wings of more realistic shapes common on aircraft. This modern technique is extended further to apply towards propellers. A method to overcome propeller analysis problems at low airspeeds is presented. This method is compared to more traditional propeller analysis techniques.

A novel cyclopentadienylruthenium(II) thiolato Schiff base, [Ru(SC6H4NC(H)C6H4OCH2CH2SMe)(&eta
5-C2H5]2 was synthesized and deposited as a selfassembled monolayer (SAM) on a gold electrode. Effective electronic communication between the Ru(II) centers and the gold electrode was established by electrostatically cycling the Shiff base-doped gold electrode in 0.1 M NaOH from -200 mV to +600 mV. The SAMmodified gold electrode (Au/SAM) exhibited quasi-reversible electrochemistry. The integrity of this electro-catalytic SAM, with respect to its ability to block and electro-catalyze certain Faradaic processes, was interrogated using Cyclic and Osteryoung Square Wave voltammetric experiments. The formal potential, E0', varied with pH to give a slope of about - 34 mV pH-1. The surface concentration, &Gamma
, of the ruthenium redox centers was found to be 1.591 x 10-11 mol cm-2. By electrostatically doping the Au/SAM/Horseradish peroxidase at an applied potential of +700 mV vs Ag/AgCl, a biosensor was produced for the amperometric analysis of hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide. The electrocatalytic-type biosensors displayed typical Michaelis-Menten kinetics with their limits of detection of 6.45 &mu
M, 6.92 &mu
M and 7.01 &mu
M for hydrogen peroxide, cumene hydroperoxide and tert-butylhydroperoxide respectively.

This thesis details the refinement and numerical solution of a preexisting model for predicting the strengths and positions of so-called wake-vortices that are generated from the lift of heavy aircraft. The ultimate objective is to implement a numerical scheme for the model that is fast enough to allow for probabilistic methods, such as Monte Carlosimulations, in order to deal with the inherent uncertainty in input parameters for wake-vortex predictions. The differential equation system of the wake-vortex model is stated clearly, which has not been done before. The refinement consists in reducing the number of necessary state variables in the differential equation system. A numerical algorithm based on the mathematical properties of the model is implemented and different ways of optimizing the computations are considered, e.g. through parallelization. Finally, a study will be made trying to assess the validity of the results through analyses of the accuracy and of the model’s sensitivity to small input parameter variations.
Detta exjobb avhandlar förfining och numerisk beräkning av en redan existerande modell för förutsägelse av styrka och position hos så kallade wake-virvlar som uppkommer som ett resultat av lyftkraften på stora flygplan. Det långsiktiga målet med arbetet är att implementera en numerisk lösare som är tillräckligt snabb för att möjliggöra probabilistiska metoder, t ex Monte Carlo-simuleringar. Detta för att bättre kunna hantera den generella osäkerhet som råder i input-parametrar vid wake-virvelförutsägelse. Modellens differentialekvationssystem kommer redogöras för, något som inte gjorts tidigare. Modellförfiningen består i en minskning av antalet tillståndsvariabler i differentialekvationssystem. En numerisk lösare baserad på modellens inneboende matematiska egenskaper utvecklas och olika sätt att optimera beräkningarna kommer övervägas, t ex genom parallellisering. Slutligen så kommer även en studie där resultatens giltighet valideras göras genom att undersöka noggrannheten i lösningen samt känsligheten för variationer i inputparametrar.

La tomographie optique diffuse (TOD) est une modalité d’imagerie biomédicale 3D peu dispendieuse et non-invasive qui permet de reconstruire les propriétés optiques d’un tissu biologique. Le processus de reconstruction d’images en TOD est difficile à réaliser puisqu’il nécessite de résoudre un problème non-linéaire et mal posé. Les propriétés optiques sont calculées à partir des mesures de surface du milieu à l’étude. Dans ce projet, deux méthodes de reconstruction non-linéaire pour la TOD ont été développées. La première méthode utilise un modèle itératif, une approche encore en développement qu’on retrouve dans la littérature. L’approximation de la diffusion est le modèle utilisé pour résoudre le problème direct. Par ailleurs, la reconstruction d’image à été réalisée dans différents régimes, continu et temporel, avec des mesures intrinsèques et de fluorescence. Dans un premier temps, un algorithme de reconstruction en régime continu et utilisant des mesures multispectrales est développé pour reconstruire la concentration des chromophores qui se trouve dans différents types de tissus. Dans un second temps, un algorithme de reconstruction est développé pour calculer le temps de vie de différents marqueurs fluorescents à partir de mesures optiques dans le domaine temporel. Une approche innovatrice a été d’utiliser la totalité de l’information du signal temporel dans le but d’améliorer la reconstruction d’image. Par ailleurs, cet algorithme permettrait de distinguer plus de trois temps de vie, ce qui n’a pas encore été démontré en imagerie de fluorescence. La deuxième méthode qui a été développée utilise l’apprentissage machine et plus spécifiquement l’apprentissage profond. Un modèle d’apprentissage profond génératif est mis en place pour reconstruire la distribution de sources d’émissions de fluorescence à partir de mesures en régime continu. Il s’agit de la première utilisation d’un algorithme d’apprentissage profond appliqué à la reconstruction d’images en TOD de fluorescence. La validation de la méthode est réalisée avec une mire aux propriétés optiques connues dans laquelle sont inséres des marqueurs fluorescents. La robustesse de cette méthode est démontrée même dans les situations où le nombre de mesures est limité et en présence de bruit.
Abstract : Diffuse optical tomography (DOT) is a low cost and noninvasive 3D biomedical imaging technique to reconstruct the optical properties of biological tissues. Image reconstruction in DOT is inherently a difficult problem, because the inversion process is nonlinear and ill-posed. During DOT image reconstruction, the optical properties of the medium are recovered from the boundary measurements at the surface of the medium. In this work, two approaches are proposed for non-linear DOT image reconstruction. The first approach relies on the use of iterative model-based image reconstruction, which is still under development for DOT and that can be found in the literature. A 3D forward model is developed based on the diffusion equation, which is an approximation of the radiative transfer equation. The forward model developed can simulate light propagation in complex geometries. Additionally, the forward model is developed to deal with different types of optical data such as continuous-wave (CW) and time-domain (TD) data for both intrinsic and fluorescence signals. First, a multispectral image reconstruction algorithm is developed to reconstruct the concentration of different tissue chromophores simultaneously from a set of CW measurements at different wavelengths. A second image reconstruction algorithm is developed to reconstruct the fluorescence lifetime (FLT) of different fluorescent markers from time-domain fluorescence measurements. In this algorithm, all the information contained in full temporal curves is used along with an acceleration technique to render the algorithm of practical use. Moreover, the proposed algorithm has the potential of being able to distinguish more than 3 FLTs, which is a first in fluorescence imaging. The second approach is based on machine learning techniques, in particular deep learning models. A deep generative model is proposed to reconstruct the fluorescence distribution map from CW fluorescence measurements. It is the first time that such a model is applied for fluorescence DOT image reconstruction. The performance of the proposed algorithm is validated with an optical phantom and a fluorescent marker. The proposed algorithm recovers the fluorescence distribution even from very noisy and sparse measurements, which is a big limitation in fluorescence DOT imaging.

Dans le contexte de la montée des eaux associée au réchauffement climatique et d’une pression anthropique dans les zones côtières toujours plus forte, une bonne compréhension et modélisation du niveau d’eau total à la côte sont primordiales pour anticiper au mieux le risque côtier et déployer à temps des solutions efficaces. En particulier, l’action des vagues appelée jet de rive joue un rôle important le long des côtes exposées aux houles océaniques. Dans cette étude, nous avons étudié la dynamique du jet de rive dans une plage de poche urbanisée à forts enjeux car soumise aux aléas submersion. Cette étude s’appuie sur de la modélisation numérique à phase-résolue ainsi que des observations. Dans un premier temps, le modèle numérique est validé sur un jeu de données issu d’une expérience en canal à houle. Ensuite, le modèle est appliqué au cas réel de la Grande Plage de Biarritz, et est comparé à des mesures de pression pour les vagues et à des mesures vidéo-métriques pour le jet de rive. Ces applications démontrent les performances du modèle pour estimer le jet de rive, y compris dans un cas réel complexe comme celui de la Grande Plage. Ensuite, les résultats du modèle validé et les observations sont utilisés pour analyser les processus physiques observés à la Grande Plage. Il a tout d’abord été montré que la marée a un impact significatif sur le jet de rive. Á marée basse des conditions dissipatives sont observées où le jet de rive est dominé par les ondes infragravitaires en raison de la faible pente dans la zone de déferlement (2%). Á marée haute, la forte pente présente dans la fin de la zone subtidale et la zone supratidale génère des conditions plutôt réflectives avec une domination des ondes courtes du jet de rive. Cette variation du niveau d’eau a aussi poureffet de moduler la dissipation d’énergie associée aux ondes longues. Pour de faibles niveaux d’eau une dissipation de l’énergie de la bande infragravitaire croissante avec la fréquence est observée, suggérant une dissipation des ondes longues par déferlement. Á l’inverse, à marée haute la forte pente a pour effet de ne plus totalement dissiper l’énergie et un régime nodal estmis en place dû à la réflexion des ondes à la côte. Dans des conditions énergétiques, les vagues ont tendance à déferler en partie sur la pente douce qu’importe le niveau d’eau, réduisant la modulation tidale. Ces résultats montrent la complexité du comportement du jet de rive dans des configurations tridimensionnelles et le potentiel des modèles à phase-résolue pour capturer ces processus
Due to the ever growing anthropogenic pressure at the coast and the perspectives of sea levelrise, coastal hazards such as overtoping are more threatening than ever. In this context, accurateestimations of the wave contributions to the total water level (TWL) at the shoreline, namelythe run-up, are crucial for coastal engineers and those involved in coastal zone managementand engineering design. In this work, we propose to investigate wave run-up in an urban-ized embayed beach based on observations and phase-resolving numerical modeling. First, thephase-resolving model based on the Boussinesq equations BOSZ is validated against laboratoryLiDAR measurements to provide an extensive validation and sensitivity analysis. Then, themodel is applied to the real configuration of the Grande Plage of Biarritz, a complex urbanizedembayed beach. A data-set from a 3-day field campaign carried out in 2018 including pressuremeasurements and video-derived run-up data is utilized for the model validation. These ap-plications demonstrate that the model reproduces wave transformations and subsequent swashmotions reasonably well. The validated model results and observations are then used to investi-gate the swash motions, under varying conditions of waves and tide. Results show that the tidallevel played a key-role in the swash dynamics. At low tide, the conditions were dissipative andthe swash was dominated by the infragravity motions. At high tide reflective conditions wereobserved with a domination of the short-wave frequencies. These changes are explained by thedouble-slope profile where a low sloping area is found in the intertidal zone and a steep slope onthe foreshore. The tidal modulation also influenced the dissipation of infragravity waves, whichwere found to dissipate energy substantially at low tide through breaking, while at mid andhigh tide standing wave patterns, characteristic of shoreline reflection, were observed. Underenergetic conditions the influence of the tide was minimized as the large waves tended to breakon the low sloping portion, regardless of the tide. These results highlight the complexity of theswash behavior in 3D conf

Ce travail de recherche a été réalisé au sein du Laboratoire de Tribologie et Dynamique des Systèmes de l’École Centrale de Lyon (FRANCE) en cotutelle avec l’Unité de Mécanique, Modélisation et Productique (U2MP) à l’École Nationale d’Ingénieurs de Sfax (TUNISIE) dans le cadre du projet européen "Mid-Frequency". La prédiction du comportement dynamique des structures est une tâche importante dans la phase de conception de tout produit mécanique. Le choix de l’outil ou de la méthode utilisée dépend de plusieurs facteurs. Pour un système dynamique, la bande de fréquence d’étude est l’un des paramètres essentiels étant donné qu’il existe des approches appropriées pour chaque domaine fréquentiel. Ces derniers seront rapidement inapplicables en changeant le domaine d’application. Par exemple, les méthodes dites hautes fréquences ou globales sont très limitées dans la partie basse du spectre. De même, les méthodes dites basses fréquences deviennent, numériquement, très lourdes et peu performantes si l’on monte en fréquence. Les moyennes fréquences représentent alors les hautes fréquences pour les méthodes globales et les basses fréquences pour les méthodes locales. Comme les incertitudes jouent un rôle important dans les comportements vibratoires en moyennes fréquences, le travail présenté de ce mémoire est une contribution à la recherche d’une approche peu coûteuse en temps de calcul permettant l’extension d’une méthode locale : la méthode des éléments finis ondulatoires, à cette bande de fréquence pour les systèmes à caractère non déterministe. Cette contribution consiste à tenir compte des incertitudes présentes dans le système étudié pour évaluer la dispersion des différents paramètres (spectraux, de diffusion, dynamiques, etc.) et leurs effets sur la réponse globale (cinématique et énergétique) de la structure. Le travail présenté peut être partagé en deux parties. La première concerne le développement des formulations explicites et directes des dispersions des différents paramètres. Cette partie se base sur l’utilisation de la méthode de perturbation à l’ordre un. La deuxième partie est une généralisation de la première. En effet, l’utilisant de la projection des variables aléatoires sur la base des polynômes de chaos permet une évaluation plus générale des effets des incertitudes sur la dynamique des structures périodiques en moyennes fréquences
The prediction of dynamic behavior of structures is an important task in the design step of any mechanical product. There are many factors affecting the choice of the used methods. For a dynamic system, the frequency band under study is one of the important parameters since for each frequency range exists its appropriate approach which can be quickly inapplicable in other domains. For example, the high frequency methods are very limited in the lower part of the spectrum. Similarly, the so-called low-frequency methods become numerically inefficient if it goes up in frequency range. The mid-frequencies then represent the high-frequencies for global and low frequencies for local methods. Knowing that uncertainties play an important role on the vibro-acoustics behavior in mid-frequencies, the presented work is a contribution to the research approach, with inexpensive computing time, allowing the extension of a local method, called ’the wave finite element method’, in this frequency band. These contributions consist in taking into account uncertainties in the studied system to evaluate the dispersion of all parameters (spectral, diffusion, dynamics, etc.) and their effects on the global response (kinematic and energetic) of the structure. The presented work can be divided into two main parts. The first one involves the development of an explicit and direct formulation describing the dispersion of different parameters; this part is based on the first-order perturbation method. The second part is a generalization of the first one; indeed, using the chaos polynomial projection of all random variables allows a more general assessment of the effects of uncertainties on the dynamics of periodic structure in mid-frequency range

Pour des raisons de coût, de consommation et de volume, l'intégration complète des systèmes de communication apparaît comme un sujet porteur pour l'industrie de la microélectronique. C'est pourquoi, de nouveaux résonateurs à ondes acoustiques de volume (BAW) se développent. Un des avantages de ces résonateurs est la possibilité de les intégrer dans un système complet sur substrat silicium pour des applications de type filtrage. En revanche, il existe des variations dans le procédé de fabrication qui font que les épaisseurs des matériaux déposés fluctuent légèrement. Cela impacte directement la fréquence de résonance des résonateurs et il convient de palier à ces variations si on souhaite réaliser un système intégré. Le sujet de travail de cette thèse s'inscrit dans le cadre de cette réflexion et porte sur l'étude et la réalisation de nouvelles architectures de filtres permettant l'utilisation de résonateurs BAW accordables en fréquence
For reasons of cost, consumption, and volume, the complete integration of communication systems seems a subject carrying for the micro-electronic industry. That is why, new resonators with bulk acoustic waves (BAW) are developed. One of the advantages of these resonators is the possibility of integrating them in a complete system on silicon substrate for filtering applications. On the other band, there are variations in the manufacturing process which make that the thicknesses of the deposited materials fluctuate slightly. That directly impacts the resonance frequency of the resonators and it is necessary to compensate these variations if one wishes to carry out an integrated system. The thesis work subject deals with the study and the realization of new filters architectures allowing the use of tuneable BAW resonators

In order to fully understand the role methane (CH₄) plays in the microwave emission spectra of the deep atmospheres of the outer planets, over 280 laboratory measurements of the opacity of ammonia in a methane environment have been made in the 5-20 cm wavelength range. All opacity measurements were made with either 100 or 200 mbars of ammonia and with 1 to 3 bars of added methane in the 330-450K temperature range. A formalism for the absorptivity of ammonia broadened by methane has now been developed and had been applied to the Hanley et al. (Icarus, v. 202, 2009) model for the opacity of ammonia. Due to methane's relatively low abundance at Jupiter (~0.2% by volume), its effect on the microwave spectrum which will be observed by the Juno MWR (Microwave Radiometer) will be minimal. However, these experimental results will significantly improve the understanding of the microwave emission spectrum of Uranus and Neptune where methane plays a more dominant role.

Cette thèse porte sur l’étude des inégalités dans un cadre macroéconomique, d’un point de vue théorique ainsi qu’empirique. Dans un premier chapitre, j’écris et simule un modèle basé-agents capable de répliquer les distributions fat-tailed des richesses observées empiriquement dans les économies développées. Dans un second chapitre, je prolonge ce modèle théorique pour étudier l’impact économique des discriminations interpersonnelles et institutionnelles. Lorsque les discriminations institutionnelles cessent, l’état final des inégalités dépend de l’économie au moment de la fin de ces discriminations : plus l’économie est organisée, plus le temps nécessaire à une égalisation des revenus et richesses entre ethnies est long, voire infini. Dans un troisième chapitre empirique, j’étudie l’évolution des inégalités de salaire entre Noirs et Blancs aux États-Unis entre 1960 et 2015, en me concentrant sur la période 2000-2015. Je traite les biais de sélection liés à l’asymétrie raciale envers l’emprisonnement, et montre que l’écart - en conditionnant par l'âge et les diplômes - entre salaires médians des Noirs et des Blancs atteint un maximum en 2012. En utilisant la méthode de régression quantiles non-conditionnelles conjointement avec la décomposition de Blinder-Oaxaca, j’établis que la part non-expliquée de cet écart reste stable durant la Grande Récession. Enfin, dans une post-face, en utilisant les métadonnées de RePEC, j’établis que la part des articles scientifiques consacrés à l’étude des crises augmente significativement après 2008 pour 13 des 30 « top journals » en économie
This PhD dissertation focuses on wealth and wage inequality, and the macro-economy. In a first chapter, I write and run a small macro agent-based model (M-ABM) in which I study the resultant distribution of wealth among households. I show that this model generates fat- tailed distributions of wealth in the household sector, as empirically observed in advanced economies. In a second chapter, I extend this model to study the macroeconomics of interpersonal and institutional discriminations against racial minorities. When discrimination is at work, racial disparities in income and wealth arise. The effect of the abolition of institutional discrimination is path-dependant: the more the economy is organized when this institutional change occurs, the more time it takes to get back to the counter-factual situation where no institutional discrimination was set up in the first place. In a third chapter, I study the evolution of the difference of median log-annual earnings between Blacks and Whites in the US between 1960 and 2015, focusing on the 2008 crisis. I control for selection arising from racial differentials in institutionalised population, and find that the unconditional racial wage gap attains a maximum in 2012. Controlling for age and education, I obtain the same result. Using unconditional quantile regressions, I show that the unexplained part of the unconditional racial wage gap has not increased during the crisis. Finally, in an afterword, I use metadata from RePEC to show that the share of economics papers published in the 13 of the 30 "top" journals containing "crisis" in their titles and/or abstracts has significantly increased in 2008

Divorce is a potentially destructive reality in society. According to the bio-ecological model of Bronfenbrenner, the development of the child takes place within two micro family systems when a family is reconstituted following divorce: the primary micro family system, where the child resides permanently with his/her biological parent who has parental rights and responsibilities, as well as the secondary micro family system of the other biological parent who also has parental rights and responsibilities, where the child visits periodically. Challenges that the child faces in the context of the reconstituted family thus include shared membership of the two micro family systems and the complexity of the mesosystem. Resilience can be defined as a process of the inborn ability to achieve positive outcomes and to adjust successfully despite challenges and adverse living conditions. The purpose of the study was twofold: firstly, to achieve understanding of the way in which middle-adolescents of divorced parents, in moving between the two micro family systems of their reconstituted families, utilise their resilience to develop optimally in spite of a probably dysfunctional relationship between their biological parents at the mesosystemic level and secondly, to contribute to the fields of knowledge on resilience and bio-ecological theory in order to enhance educational psychology praxis with regard to the adaptation of adolescents of divorced parents in reconstituted families. The study was qualitative, and conducted in the interpretive paradigm. A multiple case study with a purposeful sampling of four participants was used. Unstructured narrative conversations were conducted, which included a resilience-based therapeutic intervention to facilitate sensitisation regarding personal strengths and assets in accordance with the assetbased approach. The format of the data description and analysis was defined by the narrative way of working. The participants’ utilisation of resilience qualities was evaluated in accordance with a definition of resilience which had been newly constructed by means of a synthesis of the bio-ecological model, positive psychology and the focuses of the first three waves of resilience research. The findings of the study indicated that the way in which middle-adolescents utilise their resilience depends on a therapeutic process (a personal, controlled process) as well as the nature of the mesosystem in their developmental context (a factor that can only be controlled by the divorced biological parents). In respect of a therapeutic process, the utilisation of the middle-adolescents’ resilience depends on their emotional security to make conscious choices to mobilise their resilience and consequently change their behaviour in order to cope effectively with difficult family circumstances in both their micro-family systems. In respect of the nature of the mesosystem, the utilisation of the middle-adolescents’ resilience depends on the effectiveness of the relationship between their divorced biological parents at the mesosystemic level. The utilisation of resilience per se is apparently dependent on some consistent systemic foundation in the developmental context of the child, which is, in the case of divorce, the mesosystem.
Thesis (PhD)--University of Pretoria, 2011.
Educational Psychology
unrestricted

Cette étude porte sur la modélisation de la perméabilité magnétique de ferrites pour leur utilisation en tant qu'absorbants aux ondes hyperfréquences. Les ferrites étudiés se trouvent sous la forme de matériaux frittés ou de composites. L’absorption d'une onde électromagnétique par des ferrites frittés est provoquée par la rotation de l'aimantation dans des domaines magnétiques et par le déplacement des parois entre ces domaines. Nous développons des modèles basés sur l'association de phénomènes résonants et/ou relaxants pour représenter la dépendance en fréquence de la perméabilité magnétique. Ces différents modèles sont validés expérimentalement pour déterminer celui qui représente le mieux les mesures de perméabilité de ferrites frittés ou de composites à base de ferrite. Les matériaux composites sont constitués d'une matrice polymère non magnétique au sein de laquelle sont dispersées des particules magnétiques de ferrite. De nombreuses lois de mélange ont été développées dans le but de modéliser la perméabilité de tels matériaux. Certaines de ces lois, basées sur l'approximation quasi-statique ou sur l'hypothèse du milieu effectif, sont appliquées à des mesures expérimentales. Cependant, ces lois, au contraire de la loi du milieu effectif généralisé (GEM), ne peuvent représenter la transition entre l'état non magnétique et l'état magnétique du composite à la percolation. L’analyse d'image effectuée sur les composites permet de valider les paramètres de la GEM et de vérifier si cette loi peut devenir prédictive

Ce mémoire traite de l’ étude et de la réalisation de composants à ondes élastiques de surface (SAW) pour des applications de filtrage dans les gammes VHF et UHF. Nous y étudions différentes structures de ces filtres, à commencer par des filtres à couplage acoustique longitudinal centrés aux alentoursdu gigahertz, de bande passante relative inférieure à 0,1 % réalisés sur quartz. Leur fabrication et leur caractérisation ont révélé des pertes d’insertion inférieures à 5 dB et des niveaux de rejet supérieurs à 20 dB, conformément aux prévisions de notre modèle de matrice mixte. Un tel filtre a été inséré dans un oscillateur pour valider la fonction réalisée. Pour une maîtrise accrue de la conception de ces filtres, nous avons développé un modèle tenant compte de la contribution des modes transverses sur leur fonction de transfert. Des comparaisons entre théorie et expérience ont permis de démontrer la précision de ce modèle. Nous nous sommes également intéressés à des structures de filtres à éléments d’impédance et à transducteurs en éventails (fan-shaped) pour la réalisation de bandes passantes relatives comprises entre 1 et 15 % dans la bande 100 − 300 MHz. Pour chacune de ces structures, nous avons développé un modèle permettant d’en étudier le comportement. Une configuration de filtre en treillis de bande passante relative proche de 2 %a été fabriquée et caractérisée, ainsi que plusieurs filtres à transducteurs en éventails de bandes passantes relatives supérieures à 10 %. Enfin, nous avons étudié deux approches qui nous ont permis de réaliser des dispositifs fonctionnant à des fréquences voisines de 3 GHz. La première, consiste à exploiter les vitesses de phase supérieures à 5 km.s−1 d’un guide d’ondes à base de carbone-diamant. La seconde exploite la résolution d’un procédé de lithographie par nano-impression pour réduire la période des réseaux d’ électrodes
This thesis deals with the development of surface acoustic wave devices (SAW) for filtering applications in the VHF and UHF bands. Several filter structures are studied. The first ones are longitudinally coupled resonator filters (LCRF) manufactured on Quartz with a relative pass-band narrower than 0,1 % centered at about 1 GHz. These filters have been fabricated and characterized, yielding less than 5 dB insertion loss with rejection levels in excess of 20 dB as predicted by our P-matrix model. One of these filters has been mounted in an oscillator to validate its characteristics.To improve the design of such filters, we have developed a model accounting for transverse mode contributions on their spectral function. Comparisons between theory and experiment emphasizes the accuracy of the developed model. We also have investigated impedance element and slanted transducers (fan-shaped) filter structures to produce filters with relative pass-band ranging from 1 to 15 % in the 100 − 300 MHz frequency range. For each type of filters, we have developed a model to predict their electrical response. A balanced-bridge filter configuration with a 2 % relative pass-band and four fan-shaped filters with pass-band larger than 10 % have been fabricated and characterized. Finally, we have studied two approaches for the development of SAW devices operating at frequencies in the vicinity of 3 GHz. The first approach exploits Diamond-based substrates, providing phase velocity higher than 5 km.s−1. The second one uses a nano-imprint lithography process to reduce the pitch of electrode gratings

Cette thèse est consacrée à la modélisation mathématique de l'hématopoïèse et des maladies sanguines. Plusieurs modèles traitant d'aspects différents et complémentaires de l'hématopoïèse y sont étudiés.Tout d'abord, un modèle multi-échelle de l'érythropoïèse est analysé, dans lequel sont décrits à la fois le réseau intracellulaire, qui détermine le comportement individuel des cellules, et la dynamique des populations de cellules. En utilisant des données expérimentales sur les souris, nous évaluons les rôles des divers mécanismes de retro-contrôle en réponse aux situations de stress.Ensuite, nous tenons compte de la distribution spatiale des cellules dans la moelle osseuse, question qui n'avait pas été étudiée auparavant. Nous décrivons l'hématopoïèse normale à l'aide d'un système d'équations de réaction-diffusion-convection et nous démontrons l'existence d'une distribution stationnaire des cellules. Puis, nous introduisons dans le modèle les cellules malignes. Pour certaines valeurs des paramètres, la solution "disease-free" devient instable et une autre solution, qui correspond à la leucémie, apparaît. Cela mène à la formation d'une tumeur qui se propage dans la moelle osseuse comme une onde progressive. La vitesse de cette propagation est étudiée analytiquement et numériquement. Les cellules de la moelle osseuse échangent des signaux qui régulent le comportement cellulaire. Nous étudions ensuite une équation integro-différentielle qui décrit la communication cellulaire et nous prouvons l'existence d'une solution du type onde progressive en utilisant la théorie du degré topologique et la méthode de Leray et Schauder. L'approche multi-agent est utilisée afin d'étudier la distribution des différents types de cellules dans la moelle osseuse.Finalement, nous étudions un modèle de type "Physiologically Based Pharmacokinetics-Pharmacodynamics" du traitement de la leucémie par l'AraC. L'AraC agit comme chimiothérapie et induit l'apoptose de toutes les cellules proliférantes, saines et malignes. La pharmacocinétique donne accès à la concentration intracellulaire d'AraC. Cette dernière, à son tour, détermine la dynamique des populations cellulaires et, par conséquent, l'efficacité de différents protocoles de traitement
This PhD thesis is devoted to mathematical modelling of haematopoiesis and blood diseases. We investigate several models, which deal with different and complementary aspects of haematopoiesis.The first part of the thesis concerns a multi-scale model of erythropoiesis where intracellular regulatory networks, which determine cell choice between self-renewal, differentiation and apoptosis, are coupled with dynamics of cell populations. Using experimental data on anemia in mice, we evaluate the roles of different feedback mechanisms in response to stress situations. At the next stage of modelling, spatial cell distribution in the bone marrow is taken into account, the question which has not been studied before. We describe normal haematopoiesis with a system of reaction-diffusion-convection equations and prove existence of a stationary cell distribution. We then introduce malignant cells into the model. For some parameter values the disease free solution becomes unstable and another one, which corresponds to leukaemia, appears. This leads to the formation of tumour which spreads in the bone marrow as a travelling wave. The speed of its propagation is studied analytically and numerically. Bone marrow cells exchange different signals that regulate cell behaviour. We study, next, an integro-differential equation which describes cell communication and prove the existence of travelling wave solutions using topological degree and the Leray-Schauder method. Individual based approach is used to study distribution of different cell types in the bone marrow. Finally, we investigate a Physiologically Based Pharmacokinetics-Pharmacodynamics model of leukaemia treatment with AraC drug. AraC acts as chemotherapy, inducing apoptosis of all proliferating cells, normal and malignant. Pharmacokinetics provides the evolution of intracellular AraC. This, in turn, determines cell population dynamics and, consequently, efficacy of treatment with different protocols

In this paper, I analyze the effectiveness of state level Earned Income Tax Credit programs on improving of poverty levels. I conducted this analysis for the years 1991 through 2011 using a panel data model with fixed effects. The main independent variables of interest were the state and federal EITC rates, minimum wage, gross state product, population, and unemployment all by state. I determined increases to the state EITC rates provided only a slight decrease to both the overall white below-poverty population and the corresponding white childhood population under 18, while both the overall and the under-18 black population for this category realized moderate decreases in their poverty rates for the same time period. I also provide a comparison of the effectiveness of the state level EITCs and minimum wage at the state level over the same time period on these select demographic groups.

Les Energies Marines Renouvelables (EMR) se développent aujourd’hui très vite tant au niveau de la recherche amont que de la R&D, et même des premiers démonstrateurs à la mer. Parmi ces EMR, l'énergie des vagues présente un potentiel particulièrement intéressant. Avec une ressource annuelle brute moyenne estimée à 40 kW/m au large de la côte atlantique, le littoral français est plutôt bien exposé. Mais l’exploitation à grande échelle de cette énergie renouvelable ne sera réalisable et pertinente qu'à condition d'une bonne intégration au réseau électrique (qualité) ainsi que d'une gestion et d'un dimensionnement optimisé au sens du coût sur cycle de vie. Une première solution de génération tout électrique pour un houlogénérateur a d’abord été évaluée dans le cadre de la thèse de Marie RUELLAN menée sur le site de Bretagne du laboratoire SATIE (ENS de Cachan). Ces travaux ont mis en évidence le potentiel de viabilité économique de cette chaîne de conversion et ont permis de poser la question du dimensionnement de l’ensemble convertisseur-machine et de soulever les problèmes associés à la qualité de l’énergie produite. Puis une seconde thèse a été menée par Judicaël AUBRY dans la même équipe de recherche. Elle a consisté, entre autres, en l’étude d’une première solution de traitement des fluctuations de la puissance basée sur un système de stockage par supercondensateurs. Une méthodologie de dimensionnement de l’ensemble convertisseur-machine et de gestion de l’énergie stockée fut également élaborée, mais en découplant le dimensionnement et la gestion de la production d’énergie et de ceux de son système de stockage. Le doctorant devra donc : 1. S’approprier les travaux antérieurs réalisés dans le domaine de la récupération de l’énergie des vagues ainsi que les modèles hydrodynamiques et mécaniques réalisés par notre partenaire : le LHEEA de l’Ecole Centrale de Nantes - 2. Résoudre le problème du couplage entre dimensionnement/gestion de la chaîne de conversion et dimensionnement/gestion du système de stockage. 3. Participer à la réalisation d’un banc test à échelle réduite de la chaine électrique et valider expérimentalement les modèles énergétiques du stockage et des convertisseurs statiques associés - 4. Proposer une méthodologie de dimensionnement de la chaine électrique intégrant le stockage et les lois de contrôle préalablement élaborées 5. Déterminer les gains en termes de capacités de stockage obtenus grâce à la mutualisation de la production (parc de machines) et évaluer l’intérêt d’un stockage centralisé - 6. Analyser l’impact sur le réseau d’une production houlogénérée selon divers scenarii, modèles et outils développés par tous les partenaires dans le cadre du projet QUALIPHE. L’exemple traité sera celui de l’Ile d’Yeu (en collaboration avec le SyDEV
The work of this PhD thesis deals with the minimization of the per-kWh cost of direct-drive wave energy converter, crucial to the economic feasibility of this technology. Despite the simplicity of such a chain (that should provide a better reliability compared to indirect chain), the conversion principle uses an oscillating system (a heaving buoy for example) that induces significant power fluctuations on the production. Without precautions, such fluctuations can lead to: a low global efficiency, an accelerated aging of the fragile electrical components and a failure to respect power quality constraints. To solve these issues, we firstly study the optimization of the direct drive wave energy converter control in order to increase the global energy efficiency (from wave to grid), considering conversion losses and the limit s from the sizing of an electrical chain (maximum force and power). The results point out the effect of the prediction horizon or the mechanical energy into the objective function. Production profiles allow the study of the flicker constraint (due to grid voltage fluctuations) linked notably to the grid characteristics at the connection point. Other models have also been developed to quantify the aging of the most fragile and highly stressed components, namely the energy storage system used for power smoothing (with super capacitors or electrochemical batteries Li-ion) and power semiconductors.Finally, these aging models are used to optimize key design parameters using life-cycle analysis. Moreover, the sizing of the storage system is co-optimized with the smoothing management

L’allogreffe de cellules souches hématopoïétiques, ou greffe de moelle osseuse, fait partie des traitements proposés pour enrayer la course d’hémopathies malignes telles que la leucémie aiguë. Cette intervention consiste à remplacer les cellules du sang malades par des cellules saines, grâce à un donneur compatible afin de maximiser les chances de réussite. Bien que l’injection du greffon apparaisse comme une intervention relativement simple, il n’en demeure pas moins que cet acte s’inscrit dans un processus qui commence bien avant l’intervention et qui a des conséquences durant les mois, voire les années qui suivent l’allogreffe. Ainsi, le parcours de soin du patient peut être divisé en trois étapes : l’avant-greffe, l’hospitalisation en secteur protégé et l’après-greffe avec le retour à domicile. On peut observer à ces différents stades une altération de la qualité de vie, la présence de symptômes de détresse psychologique, voire un état de stress post-traumatique (ESPT). Cependant, ces conséquences psychologiques peuvent différer d’un individu à l’autre suggérant que certains facteurs, autres que médicaux, pourraient influer les conséquences tant physiques que psychologiques de la greffe. C’est dans cette perspective et en s’appuyant sur le modèle Multidimensionnel Intégratif et Transactionnel de Bruchon –Schweitzer et Boujut (2014) ainsi que sur l’approche complète de l’état de santé mentale de Keyes et Lopez (2002), que quatre études ont été réalisées dans ce travail de thèse en psychologie de la santé. L’objectif était de mettre en avant les différents facteurs psychologiques protecteurs et délétères aux différents stades de la greffe sur la santé mentale et physique des patients, en mettant l’accent sur des facteurs peu explorés à ce jour et issus de la troisième vague des thérapies cognitives et comportementales telle que la thérapie d’acceptation et d’engagement. Après avoir validé une version française de l’échelle AFQ (article 1), il ressort de la première étude « psygreffe » que le niveau de bonheur avant la greffe contribue à une meilleure qualité de vie avant la greffe (article 2). La seconde étude psygreffe a mis en avant l’effet prospectif des préoccupations anxieuses durant l’hospitalisation sur la survenue d’un état de stress post-traumatique, et l’effet positif de l’esprit combatif sur le niveau de résilience et de bonheur cinq mois après la greffe (article 3). La troisième étude psygreffe a révélé que plus les personnes tendaient à être dans l’évitement expérientiel plus elles risquaient de présenter des symptômes d’ESPT, tandis que les patients présentant des scores élevés de non-jugement (une facette de la pleine conscience) avaient de moindre risques de présenter une telle symptomatologie (article 4). La quatrième étude psygreffe montre que l’expérience de changements de vie positifs dans la vie des patients après la greffe est loin d’être systématique. Les patients montrent plutôt un déclin de leur santé psychologique cinq mois après la greffe qui serait relié à un faible niveau d’acceptation (article 5). L’ensemble de ces résultats nous a amené à réfléchir et à proposer une intervention adaptée aux besoins des patients (i.e. une plateforme numérique) basée sur des interventions efficaces en psycho-oncologie et sur les thérapies basées sur internet. Dans cette perspective, un premier dispositif (i.e. DESP task) visant à remédier les biais attentionnels impliqués dans l’anxiété et la dépression a été élaborée et testé, dans un premier temps en laboratoire (article 6). La DESP a fait l’objet d’une déclaration d’invention (déclaration d’invention n°0487-UCADESPTASK). Proposer une continuité dans la prise en charge et tenter de pallier les obstacles inhérents aux spécificités du parcours de greffe s’avère essentiel pour améliorer la prise en charge des patients et les accompagner durant ce parcours
Hematopoietic stem cells allograft, or bone marrow transplantation, is one of the treatments proposed to stop the course of hematopoietic malignancies such as acute leukemia. This procedure consists of replacing the cells in the diseased blood with healthy cells from a compatible donor to maximize the chances of success. Although injecting the graft appears to be a relatively simple procedure, it is nonetheless part of a whole process that begins well before the procedure and has consequences in the months and even years following the allograft. Thus, the patient's care pathway can be divided into three stages: the pre-transplant, hospitalization in a protected sector, and the post-transplant period with the return home. At these different stages, an alteration in quality of life, the presence of symptoms of psychological distress and even a state of post-traumatic stress disorder (PTSD) can be observed. However, these psychological consequences may differ from one individual to another, suggesting that certain factors, other than medical ones, could influence both the physical and psychological consequences of the allograft. It is in this perspective and based on the Transactional Integrative and Multidimensional Model of Bruchon-Schweitzer and Boujut (2014) and the Complete State Health Approach of Keyes and Lopez (2002) that four studies were conducted in this thesis work in health psychology. The objective was to highlight the different protective and deleterious psychological factors at the different stages of allograft on the mental and physical health of patients, focusing on factors little explored to date and from the third wave of cognitive and behavioural therapies such as acceptance and commitment therapy. After validating a French version of the AFQ scale (article 1), the first study found that the level of happiness before the transplant contributes to a better quality of life before the procedure (article 2). The second highlighted the prospective effect of anxious preoccupations during hospitalization on the occurrence of post-traumatic stress disorder and the positive effect of fighting spirit on the level of resilience and happiness five months post-transplant (article 3). The third one revealed that the more people tended to be in experiential avoidance, the more likely they were to develop symptoms of PTSD, while patients with high non-judgmental scores (a facet of mindfulness) were less likely to develop such symptomatology (article 4). Finally, the fourth study shows that the experience of positive life changes in patients' lives after transplantation is far from systematic. Rather, patients show a decline in their psychological health that is related to a low level of acceptance (article 5). All of these results led us to reflect and propose an intervention adapted to the needs of patients (i.e. a digital platform) based on effective interventions in psycho-oncology and web-based therapies. In this perspective, a first device (i.e. DESP task) aimed at remedying the attentional biases involved in anxiety and depression has been developed and tested (article 6). The DESP has been the subject of a declaration of invention (declaration of invention n°0487-UCADESPTASK). Proposing a continuity of care and trying to overcome the obstacles inherent to the specificities of the allograft course is essential to improve the care of patients and accompany them during this pathway

by Lee Yat Fai, Frederick, Pang Fai.
Thesis (M.B.A.)--Chinese University of Hong Kong, 2000.
Includes bibliographical references (leaf 34).
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Background --- p.2
Chapter 2. --- Methodology --- p.4
Chapter 2.1 --- Approach --- p.5
Chapter 2.2 --- Model Automation Tools --- p.7
Chapter 2.2.1 --- Data --- p.7
Chapter 2.2.2 --- Trend Identification by Regression --- p.8
Chapter 2.2.3 --- Programming variables --- p.13
Chapter 2.2.4 --- Execution --- p.13
Chapter 3. --- Literature Review --- p.16
Chapter 4. --- Trading Models --- p.19
Chapter 4.1 --- 2Premises --- p.19
Chapter 4.2 --- Trading rules --- p.20
Chapter 4.3 --- THE IMPLEMENTATION OF THE TRADING MODEL AND ITS TESTING --- p.20
Chapter 4.4 --- The Test --- p.23
Chapter 4.5 --- Some Arbitrary Inputs and Limitations --- p.24
Chapter 4.6 --- Preliminary Testing and the Grand Trend --- p.25
Chapter 5. --- RESULT & ANALYSIS --- p.26
Chapter 5.1 --- Deals made along Trends Identified --- p.27
Chapter 5.2 --- Pseudo Trends Identified during Corrections of Trends --- p.30
Chapter 5.3 --- Deals made during Corrections of Trends --- p.30
Chapter 6. --- CONCLUSIONS --- p.33
Chapter 6.1 --- Further Studies Recommended --- p.33
Bibliography --- p.34
Appendices
Chapter a. --- Table1 --- p.35
Chapter b. --- Table2 --- p.36

Structural Health Monitoring (SHM) systems for future structures and vehicles would involve a process of damage identification and prediction of certain quantities of interest that concerns the function and safety. This process provides SHM systems the ability to not only save cost but also enhance the service life, safety and reliability of the structures and vehicles. Integrated SHM system (ISHM) is an advancement of SHM system that has additional capability of predicting the component life/failure. ISHM system development involves detailed understanding of diagnostic waves, hardware components, signal processing paradigms and intelligent use of algorithms. Diagnostic waves like the guided waves are the elastic waves that propagate in a direction defined by the material boundaries. These waves have the capability of traveling large distance probing the entire thickness in plates/shells. Thus, they are widely used by SHM systems in monitoring the plate structures. Piezoelectric transducers are often employed in the interrogation using guided waves. Most SHM systems employing guided waves are designed for specific structures. Current paradigms of SHM systems are unable to enable the transition from simple or ideal structures to realistic and complicated structures. This is due to the challenges at the fundamental level involving transducer, wave propagation and phenomena of guided wave scattering with damages to evaluate the possible solutions through mathematical modeling and signal analysis capability required by ISHM systems. This thesis aims to develop understanding of these problems at a fundamental level. Complex system level understanding is still needed which is left out as open problem. A primary requirement in designing SHM system is the proper understanding of wave characteristics such as number of modes, wavelength and dispersiveness. Although three-dimensional elasticity solution and simplified theories are available to understand them, their applicability in SHM problem requires a much more detailed look. Effort toward this direction has led to the development of simpler models. However, mathematical models are not available for understanding the wave characteristics in complex structures involving stiffeners and adhesive joints. This problem is addressed in this thesis. There is a fair amount of understanding developed regarding transducer characteristics. This is accomplished by analytical and finite element models of transducers in the past. However, simplified transducer model that are computationally fast to suit SHM system requirements needs to be developed. The development of such model is presented in this thesis. Apart from modeling the transducers and wave scattering due to damage, signal correlation and calibration are needed for practical implementation in SHM. Characterization studies reported in published literature are limited to quasi-static and low frequencies applications. However, SHM of aerospace structures employ guided waves typically in the frequency range of 100-500 kHz. Methods to characterize the transducers at this frequency range needs to be developed, which is addressed in this thesis. Another major requirement of SHM system is the design and development of sensor-actuator network and appropriate algorithm. Techniques developed earlier involving transducer arrays in this regard have limitation due to complexity of geometry and signal interpretation that needs to be addressed. The network with suitable algorithm should ideally monitor large area including the critical areas of failure with minimum number of transducers. ISHM systems further require some capability to estimate the useful life of the damaged structure in order to take suitable decisions. Efficient techniques to achieve these are not developed. Overall, there is a need to improve highly interdisciplinary areas involving mathematical modeling, transducer design, fabrication and characterization, damage detection and monitoring strategies. In this thesis, various novel techniques to combine mathematical model with experimental signals to enhance the damage detection capability are presented. In this thesis, developments in the three main aspects of SHM systems are focused upon. They are (1) development of mathematical models of sensors/actuators, wave propagation and scattering due to damage (2) characterization and calibration of transducers and (3) development of technique to monitor wide variety of damages within the scope of ultrasonic guided wave based SHM. The thesis comprises of ten chapters. First chapter is devoted to the background and motivation for the problem addressed in this thesis. In second chapter, brief overview of available mathematical models and conventional damage monitoring strategy is presented. The significant contributions reported in the subsequent chapters in this thesis are outlined below In chapter 3, a reduced-order model of guided wave propagation in thick structures with reduced-order approximation of higher-order elasto-dynamic field is formulated. The surface normal and shear tractions of the thick structure are satisfied in a closed form. The time-frequency Fourier spectral finite element is developed and is validated using detailed and computationally intensive finite element simulations. Natural frequencies obtained from the developed spectral finite element and the detailed finite element simulations are compared. Transient response due to broad frequency band and narrow frequency band excitations given in the form of surface tractions are validated by comparing with the detailed finite element simulations. Using the developed spectral finite element, wave scattering from a free edge and a notch are simulated and validated by comparing with the detailed finite element simulations. In chapter 4, two-dimensional plane wave and flexural wave scattering models for more complicated features such as stiffener with delamination and stiffener with bolt failures in a stiffened panel are derived using ultrasonic ray tracing based approach combined with wave-field representation. Dispersion relations are reformulated for the base plate where it is bolted with the stiffener. Surface conditions due to contact stiffness and contact damping are modeled by introducing springs and dampers. Scattering coefficients for the bonded and bolted stiffeners are derived. The scattering coefficients are evaluated for various different frequencies. Results are compared for different stiffener parameters. In chapter 5, a simplified analytical model of a piezoelectric actuator with uniform electrodes is modeled. The problem is to determine the launched guided wave characteristics in the structure. The analytical model is derived considering two-dimensional elasticity based approach and Airy’s stress function. The actuator model is used to specify the displacement boundary conditions in the detailed finite element model. The radiated wave patterns in a plate due to actuation from transducers of different shapes are obtained and validated with experiments. Phased array actuators are modeled in the detailed finite element model using the displacements estimated from the actuator model. The radiated wave pattern from the detailed finite element simulations are validated with experiments. Chapter 6 is devoted to the design and characterization of transducers for ultrasonic guided wave applications. The characterization techniques involve the estimation of voltage response for the induced strain by the guided wave at various different frequencies. First, a novel removable bonding technique and a calibration technique are demonstrated and related advantages are discussed. Performance of the piezoelectric thin film under quasi-static, dynamic and transient impact loadings are analyzed first. Next, a guided wave technique is developed to characterize piezoelectric thin film sensors and actuators at ultrasonic frequencies. The transducers with inter digital electrodes are characterized for frequency tuning and directional sensitivity. This characterization study enables in the selection of optimal frequency bands for interrogation. Further, the characterization of transducers with thermal degradation is presented. In chapter 7, a novel guided wave technique to calibrate the thin film sensors for ultrasonic applications is presented. Calibration procedure involves the estimation of the piezoelectric coefficient at ultrasonic range of frequencies. Calibration is done by the measurement of voltage generated across thin films when guided waves are induced on them. With the proposed technique, piezoelectric coefficient can be estimated accurately at any frequency of the propagating wave. Similarly, the measurement of piezoelectric coefficient of thin films with inter digital electrodes is presented. The estimation of piezoelectric coefficient at various different directions using laser Doppler vibrometer is presented. Lastly, the degradation of piezoelectric coefficient is studied for increasing thermal fatigue. In chapter 8, toward SHM methodology development, a guided wave based technique to detect and monitor cracks in a structure is presented. To establish the methodology, a detailed study is carried out on the effect of crack and specimen size on the guided wave propagation characteristics. Using the wave characteristics, an analytical way of modeling Lamb wave propagation in the specimen with plastic zone is proposed. The feasibility to determine plastic zone and fatigue crack propagation with integrated piezoelectric transducers is demonstrated experimentally and the results are verified analytically. A method is further established to detect damage at initial stage and crack-tip plastic zone size along with crack length for a given stress amplitude or vice-versa. An approach to estimate fatigue life from the transducer signals is also proposed. In chapter 9, a compact circular array of sensor-actuator network and an algorithm is presented to monitor large plate structures. A method based on the wavelet transforms of transducer signals is established to localize and estimate the severity of damages. Experiments are conducted to demonstrate the capability of the circular array based method in the localization and quantification of various types of damages like debonding of stiffeners, failure of bolted joints, corrosion and hole-enlargement. A damage index is then computed from wavelet time-frequency map that indicates the severity of damage. Chapter 10 ends with the concluding remarks on the work done with simultaneous discussion on the future scope. The work reported in this thesis is interdisciplinary in nature and it aims to combine the modeling and simulation techniques with realistic data in SHM to impart higher confidence levels in the prediction of damages and its prognosis. The work also aims in incorporating various mathematical models of wave propagation and ray tracing based algorithm to optimize the detection scheme employed in SHM. The future direction based on this study could be aimed at developing intelligent SHM systems with high confidence levels so that statistical machine learning would be possible to deal with complex real-world SHM problems.