Dissertations / Theses on the topic 'Spectre de houle'

L’environnement maritime du littoral implique de nombreux processus complexes, mais le manque de données en haute résolution couvrant une large zone sur une longue période est souvent l’obstacle principal à des recherches plus approfondies. Le radar haute-fréquence (HF) est un moyen de faire de la télédétection afin d’obtenir pratiquement en temps réel de l’information sur la surface de la mer et sur une large zone. Ainsi l’étude de l’inversion des paramètres marins à partir de données issues de radars HF est réellement porteuse de sens. Cette thèse fait l’usage d’un jeu de données collectées durant 13 mois par deux réseaux de radar HF à commande de phase pour étudier les caractéristiques de signaux d’échos de la mer, étudier les données à traiter et les méthodes d’inversion, calculer les paramètres de la surface de la mer et évaluer la précision de l’inversion radar des paramètres de la houle.Cette thèse se réfère à l’onde de sol radar HF, dont les ondes radio interagissent avec l’océan du fait de la diffraction de résonance de Bragg. Nous passons en revue l’historique et les applications du radar HF. Nous rappelons les bases de la théorie des ondes électromagnétiques. Nous décrivons les principes d’inversion des courants de surface de la mer, direction du vent et paramètres de houles. La faisabilité de l’inversion de paramètres de houle est examinée. A partir de l’analyse théorique et des études statistiques de nombreux échantillons de données, cette thèse propose une série de méthodes sur le traitement du signal brut et le contrôle de qualité, ce qui inclut la détermination du niveau de bruit, le moyennage des données dans l’espace et le temps, l’identification correcte des pics spectraux, le seuil de largeur de pic, etc. Respectant les caractéristiques de différents processus physiques, les inversions de courant et de vent utilisent des spectres collectés toutes les 20 minutes ; l’inversion des paramètres de houle utilise des spectres moyennés sur 1 heure. Les statistiques des spectres utilisés pour le calcul des paramètres de houle sont présentées pour chacune des stations. Un ensemble de programme efficaces de calculs automatiques avec une complexité algorithme réduite sont développés pour réaliser le traitement et en tirer les paramètres marins.Les vitesses de courants radiales sont obtenues à partir d’une unique station radar. Les champs de vecteurs de courants sont obtenus en combinant chaque station. On montre une année de débit moyen dans la mer d’Iroise, ainsi que le calcul de la vorticité et de la divergence. On étudie un ensemble de données d’un mois du radar SeaSonde de Qingdao. Les schémas de débit moyen, ainsi que la vorticité et la divergence sur un mois sont présentés.La direction relative du vent par rapport à la direction de visée du radar est mesurée à travers le ratio des amplitudes des pics de Bragg. Différents modèles empiriques sont employés pour obtenir la vitesse relative du vent par inversion radar. Les résultats présentés sont en accord avec les estimations prédites par le modèle. Différents modèles de distribution directionnelle sont utilisés pour mesurer le facteur de diffusion pour la mer d’Iroise.Cette thèse se concentre sur l’étude des paramètres de houle. Les résultats sont validés à l’aide de bouées et de données du modèle de vagues (Wavewatch III). L’estimation montre que la précision de la fréquence de houle est très bonne, la précision sur la hauteur significative de houle est très raisonnable et la précision sur la direction absolue de la houle est faible. La cohérence des mesures par chacune des stations radars est vérifiée par comparaison entre les deux. L’utilisation conjointe des échantillons est également prise en charge pour réaliser l’inversion. L’utilisation de deux radars n’améliore pas seulement la précision, mais résout aussi l’ambiguïté de direction relative de houle à partir d’une unique station et donne la direction absolue de vague avec une certaine précision
Nearshore marine environment contains many complex processes, but the lack of high-resolution data over a large area during a long time is often the primary obstacle to further research. High-frequency (HF) radar is a mean of remote sensing which obtains continuous near-real time sea surface information over a large area. Thus the study of inversion of marine parameters from HF radar data is very meaningful. Thisthesis makes use of a 13-month-long dataset collected by two phased array HF radar to investigate the characteristics of the sea echo signals, study the data processing and inversion methods, compute sea surface parameters and evaluate the accuracy of radarinversion of swell parameters.The thesis refers to the ground wave HF radar, whose radio waves interact with ocean by Bragg resonance scattering. The development history and applications of HF radar is introduced. The basic theory of electromagnetic wave is reviewed. The principles of inversion of sea surface current, wind direction and swell parameters are described. The feasibility of the swell parameter inversion is investigated. Based on theoretical analysis and statistical studies of a large number of samples, the thesis proposes a series of methods on raw signal processing and quality control, including the determination of the noise level, data averaging in space and time, the proper identification of spectral peaks, the peak width threshold, etc. Respecting the characteristics of different physical processes, inversions of current and wind use spectra collected every 20 min; inversion of swell parameters uses one-hour averaged spectra. The statistics of qualified spectra for swell parameter calculations are presented for both stations. A set of efficient, with a reduced computational cost, automatic computing programs are developed to do the processing and derive marine parameters. Radial current velocities are derived from single radar station. Current vector fields are obtained by combination of both stations. One-year mean flow field in the Iroise Sea is shown, together with the computation of vorticity and divergence. A one-month SeaSonde radar dataset off Qingdao is studied. One-month mean flow pattern together with vorticity and divergence are presented.Relative wind direction with respect to radar look direction is measured through ratio of Bragg peaks amplitudes. Different empirical models are employed to derive radar-inverted relative wind direction. Results show reasonable agreement with model estimations. Different directional distribution models are used to measure the spreading factor for the Iroise Sea. The thesis focuses on the study of swell parameters. Results are validated by buoy and wave model (WAVEWATCH III) data. The assessments show that the accuracy of swell frequency is very good, the accuracy of swell significant waveheight is reasonable, and the accuracy of relative swell direction is low.Consistency of measurements by both radar stations is verified by comparison between the two. This also supports the use of double samples to do the inversion. Use of two radars not only further improves the accuracy but also solves the ambiguity of relative swell direction from single station and gives the absolute wave direction to a certain precision. The thesis proposes a constant relative directionmethod to derive swell significant waveheight, based on the studies of radar integral equation and the inverted results of relative swell direction. This proposal is demonstrated to improve the agreement of radar inversion and buoy/model provided significant waveheight and increases significantly the number of samples. The thesis investigates the accuracy of swell parameters obtained by HF radar. Contributions of random errors in radar observations are quantified. Comparing the differences between radar and buoy/model estimations gives assessments of the contribution of radar intrinsic uncertainty and contribution of other factors

En zone littorale, la houle subit de fortes transformations par effets bathymétriques. Une meilleure compréhension de ses modifications et des transferts d'énergie associés permet de mieux appréhender les problèmes de dimensionnement de structures côtières et d'aménagement du littoral (protection du littoral, influence des ouvrages sur la côte).
L'objectif de ce travail est d'étudier expérimentalement et numériquement la propagation et le déferlement
d'ondes de gravité.
La première partie, expérimentale, propose des méthodes de calcul, basées sur les houles de Stokes, pour la mesure d'ondes partiellement stationnaires à partir d'instruments de type électromagnétique (S4) ou
acoustique (ADV) donnant des mesures synchrones de vitesses et/ou de pression. Les influences du courant,
de la direction de propagation, de la profondeur d'immersion des appareils ainsi que des effets non
linéaires sont alors étudiés à partir de données en bassin et in situ.
La deuxième partie, numérique, consiste en la validation d'une méthode de suivi de surface libre de type
SL-VOF (Semi-Lagrangian Volume Of Fluid), insérée dans un code de calcul industriel (code EOLE de la
société Principia R&D). L'onde de gravité est modélisée par un soliton. L'étude de la propagation et du
déferlement du soliton est effectuée pour deux applications : sur une marche (discontinuité du fond) puis sur un fond de pente constante 1/15. L'évolution de la surface libre, son élévation et le champ de vitesses
sont alors comparés aux résultats expérimentaux.

L’objectif de cette thèse est d’améliorer les procédures de génération et de qualification des vagues pour les études de génie océanique. Le cadre est limité aux états de mer unidirectionnels générés dans des bassins d’essais expérimentaux et numériques. Les campagnes expérimentales ont été réalisées dans les bassins de l’ECN et les études numériques à l’aide du solveur HOS-NWT développé par l’ECN. Dans la première partie de la thèse, la propagation des états de mer dans les bassins d’essais est abordée d’un point de vue théorique, expérimental et numérique. Une attention particulière est accordée à l’évolution spatiale du spectre et des statistiques. En outre, les incertitudes expérimentales sont étudiées endétail. La deuxième partie de la thèse se concentre sur le contrôle des champs de vague à n’importe quelle position cible dans le domaine. Tout d’abord, une procédure axée sur la qualité du spectre de houle est étudiée. Ensuite, face à l’influence de la position cible sur les statistiques, une nouvelle procédure est introduite. Elle permet de mieux contrôler les distributions statistiques, indépendamment de la position cible
The objective of this thesis is to improve the wave generation and qualification procedures in the context of ocean engineering studies. The framework is limited to unidirectional irregular sea states generated in experimental and numerical wave tanks. Experiments were carried out using the ECN facilities and numerical studies were performed using the nonlinear potential wave solver HOS-NWT developed by ECN. In the first part of the thesis, the problem of irregular wave propagation in wave tank environments is addressed from theoretical, experimental, and numerical points of view. Paticular attention is paid to the evolution in space of the wave spectrum and statistics. In addition, experimental uncertainties arestudied in detail. The second part of the thesis focuses on developing methods to better control the wave fields at any target position in the domain. First, a procedure focusing on the quality of the wave spectrum is studied. Then, facing the dependence of the wave statistics on the target location, a new procedure is developed and tested to better control the statistical distributions independently of the target location

Cette thèse tente d'atteindre deux objectifs : premièrement, produire une analyse générale du cinéma de spectre contemporain dont nous définissons le point de départ en 1998 avec le film Ringu d'Hideo Nakata. Les films de spectres diffèrent des films de fantômes par le fait que leurs motifs sont à comprendre à partir des doutes technologiques, sociaux et métaphysiques de nos sociétés contemporaines. Par ailleurs, ce concept de spectre, que nous définissons tout au long de la recherche, est intrinsèquement lié à l'histoire de l'art et à la philosophie de l'image. C'est ainsi que nous arrivons au second objectif que tente d'atteindre notre recherche : proposer une théorie de notre rapport contemporain à l'image à partir de ce genre cinématographique. L'intuition théorique de départ est que nous vivons à une époque où l'image a une valeur politique prédominante, au point d'influencer l'agir, et que nous pouvons trouver, en l'image elle-même, une matière pour penser cette influence croissante. Ainsi, le cinéma « spectral », en tant que cinéma où le spectre est défini comme « une forme invisible qui va tout faire pour se rendre visible », nous semble être le cinéma même où se jouent cette puissance de l'image et sa part d'incarnation
This thesis attempts to achieve two objectives: first, to produce a general analysis of contemporary cinema of spectre where we define its genesis with Ringu (Hideo Nakata, 1998). What distinguishes spectral films from ghost films is the fact that their patterns are intimately linked to technological, social and metaphysical doubts of our contemporary societies. The concept of spectre, defined throughout this research, is intrinsically linked to the history of art and the philosophy of the image and perception. This is how we arrive at the second objective: to propose a theory of our contemporary relationship to the image based on this cinematographic genre. The initial theoretical intuition is that we live in times where the image has a predominant political value, to the point of influencing action and that we can find, in the image itself, the material for thinking about this growing influence. Thus, the "spectral" cinema, as a cinema where the spectre is defined as "an invisible form which will do everything to make itself visible", is to us the very cinema where this power of the image and its part of incarnation are played out

La propriété de creusement spectral, que l’on retrouve dans certains cristaux dopés aux ions de terres rares refroidis à basse température offre des possibilités prometteuses pour le traitement analogique de signaux radiofréquence. En effet, celle-ci permet de programmer des fonctions de traitement dans le spectre d’absorption du cristal.Partant des premières démonstrations de principe d’un analyseur spectral radiofréquence large bande instantanée, l’objectif est d’en améliorer les performances, ce qui requiert une modélisation précise de l’interaction laser-matière et de l’ensemble des perturbations inhérentes à la montée en maturité technologique du dispositif. Nous avons par conséquent développé un modèle et cherché à étendre son domaine de validité pour qu’il s’applique à un maximum de protocoles.Nous l’avons ensuite appliqué à un matériau en particulier, à savoir un cristal de Tm³ ⁺ :YAG. Après avoir effectué une série de mesures des différentes caractéristiques intrinsèques à ce cristal, nous avons choisi un protocole d’application relativement proche de celui de l’analyseur spectral que nous cherchons à optimiser, à savoir la création de réseaux spectraux large bande. La comparaison des résultats expérimentaux à ceux de notre modèle nous a permis de démontrer sa validité.Nous avons finalement appliqué notre modèle au cas précis de l’analyseur spectral radiofréquence. Les simulations nous ont permis de déterminer théoriquement comment optimiser ses performances, en particulier la dynamique, avec des paramètres réalistes, atteignables expérimentalement
The Spectral Hole Burning property, found in some rare-earth ion-doped crystals at low temperature is particularly relevant for analogic processing of radiofrequency signals. Indeed, it enables processing functions to be programmed in the crystal’s absorption spectrum.Starting with the first demonstrations of a wideband radiofrequency spectrum analyser, we aim at improving its performances, which requires an accurate modelling of the light-matter interaction and all the perturbations arising from the upgrade in TRL (Technology Readiness Level). Therefore, we have developed a model and extended its validity domain to a broad variety of SHB-based protocols.We applied this model on a particular material, namely a Tm³ ⁺:YAG crystal. After measuring experimentally the relevant intrinsic parameters of this crystal, we applied our model to a protocol which is quite similar to the one of the spectrum analyser we aim at optimizing, namely the engraving of wideband spectral gratings. The comparison of our experimental results to the simulations from our model proved its validity.Finally we applied it to the exact case of the radiofrequency spectrum analyser. With the simulations, we determined how to improve its performances, and particularly increase the dynamic range with realistic experimental parameters

Thesis (Sc. D.)--Joint Program in Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 1987.
Bibliography: p. 164-171.
Vita.
by James Henry Miller.
Sc.D.

The hard X-ray spectrum from black hole candidates, such as 1E1740.7-2942 and Cygnus X-1, has been attributed to an inner hot (Tₑ ≈ 10⁹ K) two-temperature disk which Comptonizes externally produced soft photons from the outer disk. We developed a natural extension of this model, wherein the innermost region of the two-temperature disk, is much hotter (Tₑ ≈ 5 x 10⁹ K) since it is shielded from the external photons and is forced to cool via bremsstrahlung self-comptonization. The emission from this region can account for the long term γ-ray variability in Cygnus X-1. The e⁺e⁻ pairs produced above the hot plasma give rise to the annihilation line observed in 1E1740.7-2942 and the residual pairs form the extended radio jets observed in this source. These early successes called for more detailed modeling of the hot disk. The effects of e⁺e⁻ pairs produced inside the disk were investigated using a better technique for the Comptonization process than what had been reported previously in the literature. This has important quantitative (but no qualitative implications) on the model. Another crucial effect is that of the proton thermal energy being advected to smaller radii. This makes the disk sensitive to the outer boundary conditions (i.e the structure of the transition zone between the outer cold disk and the inner hot region). To determine the physics of the transition region we have developed a scheme for the radiative cooling which is valid at all optical depths. The application of this scheme revealed that the transition region is an extended one. The disk has a hot two-temperature configuration even without the assumption that instabilities in the disk drive the cold disk to this stage (which has been doubted in the past). Moreover, the spectrum from the transition zone matches well with the observed X-ray spectrum of Cygnus X-1 and variations in the magnetic field can account for the two X-ray states. We conclude from this new self-consistent model that the soft X-ray photons observed arise from the cold disk, the X-ray continuum is produced in the transition zone, while the γ-rays and associated phenomena (like the e⁺e⁻ line and the radio jets) are due to the inner hot disk.

La décomposition fonctionnelle dans les équations de Navier-Stokes est un artifice mathématique tirant profit du fait que les échelles des phénomènes associés respectivement à la propagation de la houle et à l'évolution du champ diffracté ( et radié) par un corps sont nettement disctinctes. Les inconnues principales du problèmes sont divisées en une partie incidente représentant la propagation de la houle et une partie diffractée représentant la perturbation due à la présence du corps flottant ou immergé. Cette décomposition est alors introduite dans les équations de Navier-Stokes moyennées au sens de Reynolds. Les termes incidents sont obtenus explicitement sur un modèle de houle incidente en théorie potentielle non-linéaire (plus précisément par une méthode spectrale) et les termes diffractés sont déterminés par la résolution des équations RANS ainsi modifiées. La génération de la houle incidente étant réalisée par un modèle en théorie potentielle, le temps de calcul associé est très faible, la qualité de propagation est optimale et la gamme de houles envisageables est très importante. Cet avantage est combiné à une résolution globale de l'écoulement qui reste néanmoins sous l'hypothèse de fluide visqueux. Ce travail de tehèse constitue une contribution au développement de la méthode SWENSE (Spectral Ware Explicit Navier-Stokes Equations) et propose plusieurs cas de validation en houle régulière aussi bien qu'en houle irrégulière. Les limitations de la méthode sous sa forme actuelle, en particulier la problématique liée à la gestion du déferlement, sont discutées et des réponses pour y faire face sont suggérées
Functional decomposition in the Navier-Stokes equations is a mathematical tool with takes advantage of the fact that the swell propagation and the evolution of the diffracted field from a body are two phenomena with different spatial scales. The principal unknowns of the problem are divided into an incident part representing the swell propagation and a diffracted part representing the perturbation due to the presence of the floating or submerged body. This decomposition is then introduced in the Reynolds-averaged Navier-Stokes equations. Potential flow theory (more precisely spectral methods) is used to compute the incident waves while viscous effects are taken into account by using a modified RANSE solver to obtain the diffracted field in the full domain. By using this approach it is possible to simulate various nonlinear incident waves in an efficient and accurate manner: regular wave trains, focused waves, irregular 2D or 3D sea states. The present work is a contribution to the developent of the SWENSE (Spectal Ware Explicit Navier-Stokes Equations) method and offers several validation cases in regular sea as well as in irregular sea. The limitations of the method in its current form are discussed, especially the over-breaking problem, and answers to them are provided

Thesis (Ocean. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, and Woods Hole Oceanographic Institution, 1994.
Includes bibliographical references.
by Peter Traykovski.
Ocean.E.

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 1998.
Includes bibliographical references (leaves 113-115).
In this thesis I consider a scheme for quantum computation in which quantum bits (qubits) are stored in individual spectral holes of an in homogeneously broadened medium, such as a cryogenically cooled crystal of Pr:Y2 SiO 3 . Qubits are transferred between spectral holes by virtue of mutual coupling of the atoms to a single quantized cavity mode, which allows for easy implementation of two bit gate operations. I show that laser induced adiabatic passage can be used to transfer an arbitrary symmetric ground state coherence between two many-atom spectral holes. However, it is not clear how to construct entangled states of qubits which are represented by many atoms, and therefore we require that each spectral hole contain only a single atom. The many-atom coherence transfer is still useful for constructing N-photon Fock states in the cavity. The coherence transfer is susceptible to spontaneous emission and cavity decay; the latter is the dominant decay channel for Pr:YSO. I have shown that the coherence transfer can proceed in a cavity dark state which is invulnerable to cavity decay, at the cost of becoming especially susceptible to spontaneous emission, and vice versa for coherence transfer with an atomic dark state. We can achieve the strong atom-cavity coupling necessary for coherence transfer by using extremely high-finesse optical resonators and by reducing the cavity mode volume. The latter is achieved by either reducing the total cavity volume as with a microcavity, or by tightly focusing the mode to a small active volume as with a near-concentric cavity. I consider how the presense of multiple degenerate cavity modes affects the two-atom coherence transfer, and find that the transfer is only exact when both atoms couple to the same mode. For the prototype Pr:YSO material, using a tightly focused mode in a centimeter-length cavity, we can couple as many as 400 qubits with a ground state coherence lifetime of about 1 s, which would allow us to apply as many as 20 sequential gate operations.
by Jeffrey Allan Bowers.
S.B.
M.Eng.

The Victorian governess occupied a difficult position in Victorian society. Straddling the line between genteel and working-class femininity, the governess did not fit neatly into the rigid categories of gender and class according to which Victorian society organized itself. This troubling liminality caused the governess to become implicitly associated with another disturbing domestic presence caught between worlds: the Victorian literary ghost. Using Henry James’s novella The Turn of the Screw as a touchstone for each chapter, this thesis examines how the spectral mirrors the governess’s own spectrality – that is, her own discursive construction as a psychosocially unsettling force within the Victorian domestic sphere.

Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Dept. of Astronomy. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Le travail présenté dans ce manuscrit est dédié au développement d’un outil numérique destiné à la simulation de l’écoulement visqueux autour de structures marines soumises à une houle quelconque. Ce type de simulations est difficilement accessible par les codes de calcul fondés sur la résolution des équations de Navier-Stokes et c’est pour surmonter cette incapacité qu’une nouvelle formulation nommée par la suite SWENSE (Spectral Wave Explicit Navier-Stokes Equations) est développée ici en modifiant le problème initial pour ne résoudre que le champ diffracté en fluide visqueux. Cela consiste à décomposer les inconnues principales du problème en la somme d'un terme incident et d'un terme diffracté. Les termes incidents étant connus explicitement par l’intermédiaire d’un modèle potentiel non-linéaire, les termes diffractés sont alors calculés grâce aux équations SWENSE. Deux modèles de champ incident sont mis en œuvre : la méthode de Rienecker et Fenton pour les houles régulières non-linéaires et la méthode HOS (High-Order Spectral) pour tous les autres cas de houles non-déferlantes. La méthode de décomposition du champ est validée par comparaison à des codes de calcul potentiels et Navier-Stokes ainsi qu’à des données expérimentales. Les applications portent sur des carènes de navire (DTMB, Série60, Wigley) et des structures offshores (colonne circulaire verticale, TLP) pour diverses conditions de houle incidente allant de la houle régulière au paquet de vagues focalisé. Les résultats obtenus montrent la capacité de la méthode de traiter, en hypothèse de fluide visqueux, les interactions avec des houles complexes, tout en diminuant sensiblement le temps de calcul
The present work is dedicated to the development of a numerical tool intended for the simulation of the viscous flow around marine structures in complex waves. This type of simulations is still difficult to reach by the numerical models based on the resolution of the Navier-Stokes equations and to overcome this incapacity, a new formulation named thereafter SWENSE (Spectral Wave Explicit Navier-Stokes Equations) is developed here by modifying the initial problem to solve only the diffracted field. That consists in splitting the variables of the problem into the sum of an incident term and a diffracted term. The incident terms being known explicitly via a non-linear potential model, the diffracted terms are then calculated thanks to the SWENS equations. Two models are implemented to obtain the incident field : the Rienecker and Fenton method for the non-linear regular waves and the HOS (High-Order Spectral) method for all the other cases of waves. This new approch is validated by comparison with other codes based on inviscid assumption or Navier-Stokes equations like with experimental data. The code is applied on ships (DTMB, Série60, Wigley) and offshore structures (vertical circular column, TLP) for various conditions of incident waves from regular waves to a focused wave packet. The results obtained show the ability of the method to simulate, in assumption of viscous fluid, the interaction with complex waves. Moreover, the CPU time is significantly decreased

La prévision des états de mer est un domaine d'une extrême importance pour la planification des opérations en mer, pour des raisons évidentes de sécurité des personnels et des matériels mis en oeuvre. Les modèles de prévision actuels reposent sur une description stochastique de l'état de mer et ne prédisent pas de façon déterministe l'évolution de la houle, mais seulement celle des données spectrales dont on tire des grandeurs statistiques moyennes caractéristiques d'un état de mer. Face au besoin réel de données précises à court terme, un modèle de prévision déterministe a été développé dans le but d'améliorer l'efficacité des opérations offshore requérant une connaissance précise de la houle sur un site d'intérêt. Après avoir réalisé une étude théorique permettant de déterminer la zone spatio-temporelle de prévision disponible en fonction des caractéristiques du champ de vagues courant et des conditions de mesure, nous avons élaboré deux procédures d'assimilation de données variationnelles afin de combiner au mieux les mesures recueillies sur site et le modèle de propagation de houle choisi. Ce modèle est d'ordre deux dans le cas de houles faiblement à moyennement cambrées, ou d'ordre élevé reposant sur le modèle numérique High-Order Spectral (HOS) pour les houles cambrées non-linéaires. Les modèles à l'ordre deux étendu et à l'ordre HOS M = 3 ont été validés pour la prévision de houles 2D synthétiques et expérimentales : les erreurs moyennes de prévision obtenues sont au moins divisées par deux par rapport à une approche linéaire, l'amélioration étant d'autant plus probante que la cambrure de la houle et l'ordre du modèle sont élevés.

Doctor of Philosophy
Department of Chemistry
Ryszard J. Jankowiak
This dissertation reports the low temperature frequency domain spectroscopic study of three different natural pigment protein complexes and one artificial antenna system. The main focus of this work is to better understand electronic structure, excitation energy transfer (EET), and electron transfer (ET) dynamics in these systems that could have impact on achieving higher efficiency in future artificial solar cells. In the first part of this dissertation, electronic structure and EET pathways in isolated intact CP43 prime protein complex, which is isolated from Cyanobacterium synechocystis PCC 6803 grown under iron stressed conditions, are investigated using low-temperature absorption, fluorescence, fluorescence excitation, and hole-burning (HB) spectroscopies. This work suggests that, in analogy to the CP43 complex of PSII core, CP43 prime possesses two quasi-degenerate low energy states, A prime and B prime. The various low-temperature optical spectra are fitted considering an uncorrelated EET model. This work suggests that for optimal energy transfer from CP43 prime to PSI, the A prime and B prime state chlorophylls belonging to each CP43 prime should face towards the PSI core. The second part of dissertation reports the photochemical HB study on novel Zinc bacterial reaction center (Zn-RC) from Rhodobacter sphaeroides and its β-mutant (Zn-β-RC). This study shows that ET in the two samples is similar; however, the quantum efficiency of charge separation in the mutant decreases by 60 %. This finding suggests that the coordination state of the HA site zinc bacteriochlorophyll does not tune the active branch ET. Simultaneous fits of various optical spectra using experimentally determined inhomogeneity provides more reliable electron phonon coupling parameters for the P870 state of both RC samples. In the last part of this dissertation, EET in a novel artificial antenna system (ethynyl linked chlorophyll trefoil, ChlT1) is investigated. EET time in ChlT1 is ~2 ps. ChlT1 in MTHF/ethanol glass forms four different types of aggregates, A1-A4. The EET time in A1 and A2 type aggregates slows down only by a factor of 5 and 7, respectively. This study suggests that ChlT1 and its aggregates can be used as efficient antenna systems in designing organic solar cells.

Une discussion des methodes d'analyse temporelle et spectrale des fluctuations de la surface libre dans la zone de deferlement aboutit a une amelioration du reperage des vagues individuelles par des filtrages appropries du signal. Cette nouvelle methode est testee sur des mesures effectuees en bassin a houle directionnelle. Les equations hydrodynamiques moyennes integrees sur la verticale sont ensuite etablies. La separation des equations dynamiques de la houle et du courant, incluse dans ce developpement, est adoptee apres analyse critique des travaux les plus recents realisant leur couplage. Un etat de l'art de l'approche spectrale discrete appliquee a la propagation d'etats de mer en zone cotiere met en evidence les lacunes de la connaissance actuelle et justifie ainsi l'utilisation d'une approche spectrale parametrique. Deux modeles publies sont analyses et testes par comparaison avec des mesures obtenues en nature et en laboratoire. Cette critique conclut sur des recommandations pratiques d'utilisation. L'approche probabiliste plus precise bien que moins etudiee est ensuite detaillee. Les equations de fermeture necessaires sont proposees apres etablissement d'un etat de l'art complet concernant le developpement des non-linearites, les criteres de deferlement, la creation et l'evolution du rouleau de deferlement et les dissipations d'energie associees. Ce modele de houle est utilise dans le modele hydrodynamique dont la pertinence et la fiabilite sont evaluees par comparaison avec des mesures de laboratoire couvrant des conditions de houle monochromatique et aleatoire

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.
Includes bibliographical references (p. 97-100).
The power density spectrum is an essential tool for determining the frequency content of X-ray radiation from astronomical sources. For neutron star systems, power density spectra reveal coherent oscillations for those sources that are pulsars, while quasi-periodic oscillations over a wide range of frequencies (0.01 to 1300 Hz) are used to identify subclasses and to probe the details of accretion physics. For black hole binaries, the power density spectrum is useful in many important contexts: distinguishing black hole binaries from neutron star binaries, tracking the evolution of X-ray states, and understanding the dynamics of accretion disks, in particular the high-frequency oscillations that appear to be rooted in general relativity for strong gravitational fields. However, measurements of the power density spectrum are modified by the effects of deadtime in X-ray detectors. In this work, we focus on the Proportional Counter Array (PCA) instrument of the Rossi X-ray Timing Explorer (RXTE), an orbiting observatory that offers fast, microsecond-level time resolution and modest spectral resolution for celestial X-ray sources. We derive a new model for the effect of detector deadtime on measurements of the power density spectrum.
(cont.) The model treats in a unified manner the contributions from self-deadtime among selected events and interference from non-selected events. Using high-frequency power density spectra obtained from observations of X-ray sources, the new model is shown to be more accurate than existing approaches. The comparison between the model and the observations leads to a measurement of 8.83 s for the fundamental instrument deadtime timescale, which is dominated by the analog-to-digital conversion time. We additionally measure 59 jts and 137 /is for the Very Large Event deadtime related to observer-specified settings 1 and 2 respectively. Future refinements to the deadtimle model are discussed, such as corrections for highly variable sources and for individual X-ray energy bands.
(cont.) A preliminary comparison between power density spectra from black hole binaries and neutron star binaries is undertaken using the new deadtime model. While it may be possible to use high-frequency cut-offs in the power continuum to distinguish neutron star binaries from black hole binaries in the thermal and hard X-ray states, the comparison is inconclusive for black hole binaries in the steep power-law state. Since state definitions require considerations of X-ray spectral properties, the comparison results dispute a suggestion in the literature that accreting neutron stars and black holes can be distinguished on the basis of power density spectra alone.
by Dennis Wei.
S.B.

I will analyze the spectral uncanny in Carmilla by Sheridan Le Fanu and The Haunting of Hill House by Shirley Jackson focusing on spectral spaces, spectral and uncanny bodies, spectral and uncanny hauntings of the mind, uncanny visitations, the spectral mother, and spectral courtships. The uncanny visitations and phantasmagoria blur the boundaries between the terror of the mind and the horror of reality, making the protagonists of both novels unable to distinguish reality from dreams or imagination, affecting the characters' sense of self and leading them to merge with the supernatural. There is an equal longing and abjection of the maternal together with transgressive desire. Homoeroticism and passionate love erupt from contact with the spectres and the journey of both protagonists ends upon meeting their lover, either in death or in a perpetual haunting. I seek to demonstrate that a subtype of the uncanny, the spectral uncanny, can be recognized as part of some Gothic texts which is used to represent and challenge contemporary anxieties through an ephemeral creature. Both novels share the manifestation of the spectral uncanny, the spatial, temporal, and authorial differences, from the Old World to the New World, from the 19th century to the 20th, from a male author to a female author. The fear of the unknown and of cultural taboos prevails from text to text, making the spectral uncanny at the heart of gothic anxieties, both as cause, as a mirror, and as a relief.

Magnetotransport properties of modulation-doped p-type Si₁-ₓGeₓ/Si and Si₁-ₓGeₓ/Si₁₋_yGe_y heterostructures were studied, in the magnetic field range 0-12 T, and in the temperature range 0.35-300 K. The experimental data within the classical regime have been analysed by mobility spectrum analysis, in order to separate the influences of different parallel conduction paths. A new method of mobility spectrum analysis has been developed by the author, based on the concept of maximum-entropy, and this computation has been shown to overcome several drawbacks or limitations of previous mobility spectrum methods of calculation. The data have also been analysed by Beck & Anderson's analysis and the multicarrier fitting method for comparison. Analysis of the magnetic-field-dependent resistivity tensors reveals a two-dimensional hole gas (2DHG) in the Si/SiGe/Si quantum well, carriers in the boron-doped cap layer, and an unknown electron-like carrier. The carrier density of the 2DHG can either remain constant (x = 0.1), increase (x = 0.13), or decrease (x ≥ 0.2), with increasing temperatures. Differences in the temperature dependences are partly attributed to different growth conditions. A decreasing carrier density with increase in temperatures may indicate the presence of acceptor-like defect states near the valence band edge of the SiGe channel. The mobility of the 2DHG between 100-300 K has the form AT⁻^γ and γ has the bowl shape with the minimum at x ~ 0.25-0.3. These characteristics suggest a possible influence of alloy disorder scattering. The mobilities and activation energies of the carriers in the boron-doped cap vary between samples and this is believed to be due to boron-spike near the Si/Si-substrate interface, in some samples. The source of electron-like carrier is presently unknown.

Doctor of Philosophy
Chemistry
Ryszard J. Jankowiak
The structure-function relationships of natural pigment–protein complexes are of great interest, as the electronic properties of the pigments are tuned by the protein environment to achieve high quantum yields and photon utilization. Determination of electronic structure and exciton dynamics in protein complexes is complicated by static disorder and uncertainties in the properties of system-bath coupling. The latter is described by the phonon profile (or spectral density), whose shape can only be reliably measured experimentally for the lowest energy state. Low-temperature, laser-based spectroscopies are applied towards model pigment–protein complexes, i.e., the Fenna-Matthews-Olson (FMO) and water-soluble chlorophyll-binding (WSCP) complexes, in order to study system-bath coupling and energy transfer pathways. Site-selective techniques, e.g., hole burning (HB) and fluorescence line narrowing, are utilized to overcome static disorder and reveal details on homogeneous broadening. In addition, excitonic calculations with non-Markovian lineshapes provide information on electronic structure and exciton dynamics. A new lognormal functional form of the spectral density is recommended which appropriately defines electron-phonon parameters, i.e., Huang-Rhys factor and reorganization energy. Absorbance and fluorescence spectral shifts and HB spectra reveal that samples of FMO may contain a subpopulation of destabilized proteins with modified HB efficiencies. Simulations of spectra corresponding to intact proteins indicate that the entire trimer has to be taken into account in order to properly describe fluorescence and HB spectra. The redshifted fluorescence spectrum of WSCP is described by uncorrelated energy transfer as opposed to previous models of excited state protein relaxation. Also, based on nonconservative HB spectra measured for WSCP, a mechanism of electron transfer between chlorophylls and aromatic amino acids is proposed.

The objectives of this research are to measure residual stress in both unblasted and sandblasted mild steel specimens by using three different techniques: X-ray diffraction (XRD), strain-gage hole drilling (SGHD), and electronic speckle pattern interferometry (ESPI) hole drilling, and to validate the new ESPI hole drilling method by comparing its measurement results to those produced by the SGHD method. Both the XRD and SGHD methods were selected because they are accurate and well-verified approaches for residual stress measurements. The ESPI hole drilling technique is a new technology developed based on the SGHD technique, without the use of strain gage. This technique is incorporated into a new product referred to as the PRISM system, manufactured by Hytec, Incorporated, in Los Alamos, New Mexico. Each method samples a different volume of material at different depths into the surface. XRD method is especially different compared to the other two methods, since XRD only measures stresses at a depth very close to the surface (virtually zero depth). For this reason, no direct comparisons can be made between XRD and SGHD, as well as between XRD and ESPI hole drilling. Therefore, direct comparisons can only be made between SGHD and ESPI hole drilling methods.

The study of high-resolution X-ray spectra of neutron star low-mass X-ray binaries (LMXBs) allows the investigation of the innermost parts of the accretion disk and immediate surroundings of the compact object. The weak magnetic eld of old neutron stars present in such systems allows the accretion disk to approach very close to the compact object, like in black hole X-ray binaries. Using data from X-ray satellites such as XMM-Newton, RXTE, and BeppoSAX, I studied the reection component in two neutron star LMXBs: MXB 1728-34 and 4U 1735-44. I showed that the iron line at 6:4

Thesis (Ph.D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering/Woods Hole Oceanographic Institution), 2000.
Includes bibliographical references (leaves 202-211).
The thesis develops and demonstrates methods of classifying ocean processes using an underwater moving platform such as an Autonomous Underwater Vehicle (AUV). The "mingled spectrum principle" is established which concisely relates observations from a moving platform to the frequency-wavenumber spectrum of the ocean process. It clearly reveals the role of the AUV speed in mingling temporal and spatial information. For classifying different processes, an AUV is not only able to jointly utilize the time-space information, but also at a tunable proportion by adjusting its cruise speed. In this respect, AUVs are advantageous compared with traditional oceanographic platforms. Based on the mingled spectrum principle, a parametric tool for designing an AUVbased spectral classifier is developed. An AUV's controllable speed tunes the separability between the mingled spectra of different processes. This property is the key to optimizing the classifier's performance. As a case study, AUV-based classification is applied to distinguish ocean convection from internal waves. The mingled spectrum templates are derived from the MIT Ocean Convection Model and the Garrett-Munk internal wave spectrum model. To allow for mismatch between modeled templates and real measurements, the AUVbased classifier is designed to be robust to parameter uncertainties. By simulation tests on the classifier, it is demonstrated that at a higher AUV speed, convection's distinct spatial feature is highlighted to the advantage of classification. Experimental data are used to test the AUV-based classifier. An AUV-borne flow measurement system is designed and built, using an Acoustic Doppler Velocimeter (ADV). The system is calibrated in a high-precision tow tank. In February 1998, the AUV acquired field data of flow velocity in the Labrador Sea Convection Experiment. The Earth-referenced vertical flow velocity is extracted from the raw measurements. The classification test result detects convection's occurrence, a finding supported by more traditional oceanographic analyses and observations. The thesis work provides an important foundation for future work in autonomous detection and sampling of oceanographic processes.
by Yanwu Zhang.
Ph.D.

As visual display technologies move closer to producing true three dimensional displays, pixel technologies need to be ever smaller and more functional to keep pushing the boundaries. Plasmonic metasurfaces have been shown to control the phase, amplitude and/or polarisation of incoming electromagnetic radiation. Nano-fabrication advancements have resulted in the fabrication of the building blocks of such metasurfaces at nano-scale dimensions, allowing the surfaces to interact with visible light, opening up applications in visual displays. As pixel sizes shrink, smaller colour filters will be required. The excitation of plasmonic resonances in metallic nano-structure arrays have resulted in colour filters an order of magnitude smaller than what is currently commercially available. As colour filters, plasmonic metasurfaces offer numerous advantages over pigment-based colour filters used in modern commercial liquid crystal (LC) displays, including environmental, size and longevity factors. Furthermore, exploiting the wavelength and polarisation dependant scattering of nano-structures, optical components, including lenses, waveplates and holograms containing sub-wavelength pixels have been demonstrated in the visible wavelength spectrum. The metasurfaces are able to mould optical wavefronts into arbitrary shapes with sub-wavelength resolution by introducing spatial variations in the optical response of the light scatterers. The applications demonstrated so far are, on the whole, static devices, that is to say their optical properties may not be altered post fabrication. To realise the full potential of plasmonic metasurfaces to visual applications the devices must be made active. By activating structural colour surfaces, not only may pixel densities potentially be increased simply by removing the need for separate red, green and blue filters, but a new class of high definition ultra-thin display devices may be accessible, whilst the dynamic manipulation of the wavelength and polarisation properties of nano-scattering elements would open up the possibilities to create sub-wavelength holographic pixels. This thesis investigates ways to activate static metasurfaces for colour, flat optic, and holographic applications. First, methods of dynamic control of the structural colour of plasmonic nano-hole arrays are investigated. By combining nano-hole arrays with liquid crystals, transmissive electrically tunable LC-nanohole pixels operating across the visible spectrum with un-polarised input light are experimentally demonstrated. An output analyser in combination with a nematic LC layer enables pixel colour to be electronically controlled through an applied voltage across the device, where LC re-orientation leads to tunable mixing of the relative contributions from the plasmonic colour input. Furthermore, exploiting the strong surface anchoring effects between an aluminium surface and LC molecules a twisted nematic LC cell, using a metallic grating as a combined colour filter, electrode and alignment layer, was shown to act a variable amplitude colour filter. The colour of these pixels was improved greatly utilising a grating-insulator-grating structure unique to this work. Second, a new process for fabricating aluminium nano-rod structures embedded in an elastomeric medium, with high spatial accuracy, is presented. The process is used to create nano-rod plasmonic resonator arrays whose optical properties may be altered by mechanical deformation. The pattern transfer process is further utilised to create dynamic optical elements, including nano-rod arrays for colour filters, tunable focal length Fresnel zone plates and photon sieves, and stretchable holograms with dynamic replay fields.

We report on the diversity in quasar spectra from the Baryon Oscillation Spectroscopic Survey. After filtering the spectra to mitigate selection effects and Malmquist bias associated with a nearly flux-limited sample, we create high signal-to-noise ratio composite spectra from 58,656 quasars (2.1 <= z <= 3.5), binned by luminosity, spectral index, and redshift. With these composite spectra, we confirm the traditional Baldwin effect (BE, i. e., the anticorrelation of C IV equivalent width ( EW) and luminosity) that follows the relation W-lambda alpha L-beta w with slope beta(w) = -0.35 +/- 0.004, -0.35 +/- 0.005, and -0.41 +/- 0.005 for z. =. 2.25, 2.46, and 2.84, respectively. In addition to the redshift evolution in the slope of the BE, we find redshift evolution in average quasar spectral features at fixed luminosity. The spectroscopic signature of the redshift evolution is correlated at 98% with the signature of varying luminosity, indicating that they arise from the same physical mechanism. At a fixed luminosity, the average C IV FWHM decreases with increasing redshift and is anti-correlated with C IV EW. The spectroscopic signature associated with C IV FWHM suggests that the trends in luminosity and redshift are likely caused by a superposition of effects that are related to black hole mass and Eddington ratio. The redshift evolution is the consequence of a changing balance between these two quantities as quasars evolve toward a population with lower typical accretion rates at a given black hole mass.

Les études et développement menés dans ce travail de thèse ont porté sur divers aspects du traitement de l'évolution réaliste des états de mer, notamment sur les spécificités d'une approche déterministe non-linéaire, sur la prise en compte d'un forçage par le vent et de la dissipation dans une approche à phase résolue, et sur un développement à but opérationnel des techniques de modélisations réalistes. En parvenant à une meilleure modélisation des états de mer, ils visent à permettre une meilleure interprétation des images radar rétrodiffusées par la surface de la mer. Les applications concernent entre autres la caractérisation et la prévision court terme en temps réel des conditions de mer, ainsi que la détection de cibles marines. Un modèle numérique tridimensionnel basé sur une méthode High Order Spectral sert de support à l'étude des processus non-linéaires à l'œuvre en conditions océaniques. Une première partie de cette étude permet de mettre en lumière un ensemble de critères nécessaires à la bonne mise en œuvre de cette méthode. On met notamment plus particulièrement en évidence une problématique d'initialisation liée à un besoin de simulations de référence dès les premiers instants de modélisation. Une méthode d'initialisation non-linéaire est proposée et évaluée. La prise en compte d'un forçage par le vent et de dissipation par moutonnement est ensuite proposée. La paramétrisation du couplage rétroactif océan-atmosphère et de la dissipation, en pression, à l'œuvre dans les modèles stochastiques de prévision d'état de mer est adaptée à la formulation déterministe. Une formulation récente du couplage (Bidlot et al. (2005)) est testée et validée comparativement avec la modélisation stochastique usuelle issue du modèle WAVEWATCH3. L'approche déterministe est finalement capable de prendre efficacement en compte les termes de forçage et dissipation et permet des évolutions d'états de mer réalistes. Le problème de modélisation opérationnelle des états de mer, à moindre coût calcul mais avec une prise en compte suffisamment réaliste des spécificités océaniques est abordé. Une méthode numérique est proposée et testée comparativement à l'approche complètement non-linéaire de référence.

Active galactic nuclei (AGN) are known to vary in brightness in all regions of the electromagnetic spectrum and over a wide range of timescales. Many methods have been utilized to transform this observed variability into meaningful information about the central engines of AGN. One such technique, adapted from time series analysis of galactic x-ray binary systems, has been used to detect a characteristic break timescale in the power density spectra of x-ray variability in Seyfert galaxies. This timescale, thought to be related to instabilities in the accretion disk, appears to scale with black hole mass over many orders of magnitude. This dissertation performs similar time series analyses with the optical data of eight blazars. The majority of these objects also display a characteristic break timescale. In cases where a black hole estimate is known, the timescales are in good agreement with the relationship observed for galactic x-ray binary systems and Seyfert galaxies. For objects of unknown mass, this relationship can be used to provide a mass estimate of the supermassive black hole. Comparisons are made between the structure function and power density spectrum for each object, and the implications for the connection between the accretion disk and the relativistic jet in AGN are discussed.

Ultraluminous X-ray sources (ULXs) are a class of extragalactic, off nuclear and point-like sources with isotropic X-ray luminosities higher than 1e39 erg/s. They are supposed to be accreting Black Hole binaries systems but the accretion mechanisms at the basis of their extremely high X-ray luminosity are still matter of debate. We carried out a detailed spectral analysis of all the available XMM-Newton observations of two ULXs in NGC 1313, adopting a common model based on a multicolor disc plus a comptonizing component. We were able to describe the spectral evolution of the two sources within such a common framework. Furthermore, we investigated the chemical abundances of their local environments making use of both EPIC and RGS data. The results appear to indicate sub-solar metallicity for both sources. The possible existence of two spectral states in NGC 1313 X-1 and X-2 suggested to look for similar behaviours also in other ULXs. We then studied a larger sample of sources, including IC 342 X-1, NGC 5204 X-1, NGC 5408 X-1, Holmberg IX X-1, Holmberg II X-1, NGC 55 ULX1 and NGC 253 X-1. These sources were selected because they have a luminosity higher than 2e39 erg/s, are nearby, have one long observation and at least three other observations. The high quality observations provide at least 10000 counts in the EPIC instruments allowing us to constrain the curvature at high energy and to perform an analysis of the abundances of the material along the line of sight. We found that, in most of the spectra of the sources of our sample, the high energy component has a low temperature and is optically thick. However, because of the poor quality of some observations, the spectral fits are sometimes affected by a degeneracy between the spectral parameters and the roll-over of the spectrum at high energy is not easy to detect. For these reasons, similarly to what has been done for low counting statistics spectra of Galactic X-ray binaries (XRBs), we adopted the method of the hardness ratios that has also the advantage to allow us to study the spectral variability in a way completely independent of the spectral models. This analysis suggests the existence of possible characteristic evolutionary patterns on the color-color and intensity-color diagrams linking at least two different spectral states. This behaviour can be explained in terms of a non-standard accretion disc in which the increment of the accretion rate produces outflows that become more and more important at the highest luminosities. We tested the scenario of the ejection of a wind jointly analyzing the spectral and timing properties of the source NGC 55 ULX1 which shows a puzzling flux variability. In fact, fast drops in the flux are observed on time scales of minutes to hours that may be produced by optically thick blobs of matter that from time to time encounter our line of sight. We compared its variability properties with those of a Galactic accreting systems, EXO 0748-676, which is powered by a neutron star and is a known dipping source. We characterised the nature of the variability observed in the power density spectrum and, in particular, we checked the presence of a linear relation between the Root Mean Square (RMS) variability and the flux in several energy bands. We found that, in EXO 0748-676, the predominance of an (ionised) absorber strongly affects the RMS-flux relation which may anticorrelate when the absorption lines are unsaturated. On the other hand, no further variability is introduced when they are saturated and the variability is dominated by the accretion flow. In this case the source shows a positive correlation between RMS and flux. Since we found an anticorrelation in NGC ULX1, we suggest that at the highest flux levels, massive and unsaturated turbulent outflows are ejected. Finally, persistent ULXs, as those discussed above, do not allow us an easy comparison with the behaviour of Galactic XRBs. Transient ULXs are much more promising in this respect as they span different accretion regimes. Till now, only a handful of transient ULXs has been discovered and the link between them and the persistent sources is still unclear. We monitored the evolution of a new ULX (XMMU J004243.6+41251) discovered in January, 2012 in M31 by XMM-Newton. Its outburst showed that, at maximum luminosity, it entered in the ULX regime. It was then extensively followed by Swift during the flux decay. The source has experienced a fast rise in flux after discovery during which the XMM-Newton spectra changed from a powerlaw-like to a disk-like shape in the Swift spectra, suggesting a transition between the canonical low/hard and high/soft states. Its luminosity remained fairly constant for at least 40 days and then it faded below 1e38 erg/s. During the decay the disc emission softened and the temperature decreased from ~0.9 keV to ~0.5 keV. An optical follow-up and the UVOT images failed to provide evidence of a counterpart down to 22 mag in the optical band and to 23-24 mag in the near Ultraviolet. We compared the properties of XMMU J004243.6+412519 with those of other known ULXs and Galactic black hole transients, finding more similarities with the latter.
Le Ultraluminous X-ray sources (ULXs) sono una classe di sorgenti extragalattiche, lontane dal nucleo della galassia ospite e puntiformi, con una luminosità isotropica maggiore di 1e39 erg/s. Si pensa siano buchi neri in accrescimento in sistemi binari ma i meccanismi di accrescimento alla base della loro estrema luminosità X sono ancora lontani dall'essere totalmente compresi. In questo lavoro è stata svolta una dettagliata analisi spettrale di tutte le osservazioni disponibili di XMM-Newton di due ULXs in NGC 1313, adottando un modello comune basato su un disco multicolore più una componente di comptonizzazione. Noi siamo stati capaci di descrivere l'evoluzione spettrale delle due sorgenti all'interno di tale scenario. Inoltre, è stato possibile determinare le abbondanze chimiche dei loro ambienti locali facendo uso sia di dati EPIC che di dati RGS. I risultati sembrano indicare metallicità sub-solare per entrambe le sorgenti. La possibile esistenza di due stati spettrali in NGC 1313 X-1 e X-1 hanno suggerito di cercare comportamenti simili anche in altre ULXs. Per questo motivo, un campione più vasto di sorgenti, il quale include IC 342 X-1, NGC 5204 X-1, NGC 5408 X-1, Holmberg IX X-1, Holmberg II X-1, NGC 55 ULX1 e NGC 253 X-1, è stato studiato. Queste sorgenti sono state selezionate poichè la loro luminosità è maggiore di 2e39 erg/s, sono sorgenti vicine e posseggono un'osservazione lunga e almeno altre tre ulteriori osservazioni. L'alta qualità delle osservazioni fornisce almeno 10000 conteggi nello strumento EPIC, consentendoci di determinare con più precisione la curvatura ad alta energia e di svolgere un'analisi delle abbondanze del materiale presente lungo la linea di vista. E' stato trovato che, nella maggior parte degli spettri delle sorgenti del nostro campione, la componente ad alta energia mostra una bassa temperatura ed è otticamente spessa. Ad ogni modo, a causa della bassa qualità di alcune osservazioni, i fit spettrali sono a volte influenzati da una degenerazione fra i parametri spettrali e la curvatura ad alta energia dello spettro non è facilmente individuata. Per queste ragioni, in modo simile a ciò che è stato ampiamente fatto per gli spettri di sorgenti binarie Galattiche di raggi X, abbiamo adottato il metodo degli hardness ratios che hanno anche il vantaggio di consentirci di studiare la variabilità spettrale in un modo completamente indipendente dal modello spettrale. Questa analisi suggerisce l'esistenza di un possibile caratteristico cammino evolutivo sui diagrammi colore-colore and intensità-colore collegando almeno due differenti stati spettrali. Questo comportamento può essere spiegato in termini di un disco di accrescimento non standard in cui l'aumento del tasso di accrescimento produce fuoriuscite di materiale che diventano via via più importanti alle più alte luminosità. Lo scenario di emissione di vento è stato ulteriormente studiato analizzando le proprietà spettrali e temporali della sorgente NGC 55 ULX1 che mostra un'enigmatica variabilità nel flusso. Infatti, rapide diminuzioni del flusso emesso sono osservate su tempi scala di minuti od ore che potrebbero essere prodotti da nuvole di materiale otticamente spesso che di tanto in tanto entrano all'interno della nostra linea di vista, oscurando le regioni centrali della sorgente. E' stata fatta un'analisi comparativa fra le proprietà della sua variabilità con quelle di un sistema Galattico in accrescimento, EXO 0748-676, conosciuto per ospitare una stella di neutroni e per essere una sorgente con “dips". Abbiamo caratterizzato la natura della variabilità osservata negli spettri di potenza e, in particolare, abbiamo testato la presenza di una relazione lineare tra la variabilità quadratica media (RMS) e il flusso in diverse bande di energia. E' stato trovato che, in EXO 0748-676, la predominanza di un mezzo assorbente (ionizzato) influenza fortemente la relazione fra RMS e flusso che potrebbero anti-correlare qualora le linee in assorbimento fossero non sature. D'altra parte, nessuna variabilità ulteriore è introdotta quando esse sono sature e la variabilità è dominata dal flusso d'accrescimento. In questo caso la sorgente mostra una correlazione positiva tra flusso ed RMS. Poichè noi abbiamo individuato un'anti-correlazione in NGC 55 ULX1, proponiamo che ai livelli di flusso più alti, imponenti venti, non saturi e turbolenti, siano eiettati. Infine, ULX persistenti come quelle discusse sopra, non consentono una facile comparazione con il comportameno delle sorgenti binarie Galattiche. ULX transienti sono molto più promettenti sotto questo punto di vista poichè esse attraversano differenti regimi di accrescimento. Fino ad ora, solo una manciata di ULX transienti sono state scoperte e la connessione tra loro e le sorgenti persistenti è ancora poco chiara. Noi abbiamo monitorato l'evoluzione di una nuova ULX (XMMU J004243.6+41251) scoperta nel Gennaio 2012 nella galassia M31 da XMM-Newton. La sua accensione ha mostrato che, alla luminosità di picco, la sorgente è entrata nel regime ULX. E' stata poi ampiamente seguita da Swift durante la sua fase di decadimento in flusso. La sorgente ha sperimentato un veloce incremento del flusso dopo la sua scoperta, durante il quale gli spettri ottenuti da XMM-Newton si sono evoluti da un semplice andamento a legge di potenza fino ad una forma tipica per un disco d'accrescimento in tutti gli spettri Swift, suggerendo una transizione tra gli stati canonici low/hard and high/soft. La sua luminosità è rimasta abbastanza costante per almeno 40 giorni, per poi scendere al di sotto di 1e38 erg/s. Durante il decadimento, l'emissione del disco è diventata più soft e la temperatura è diminuita da ~0.9 keV fino a ~0.5 keV. Un follow-up ottico e immagini UVOT non sono riuscite a fornire evidenze di una controparte fino a 22 mag in banda ottica e fino a 23-24 mag nel vicino Ultravioletto. Noi abbiamo comparato le proprietà di XMMU J004243.6+41251 con quelle di altre ULX transienti e buchi neri Galattici, trovando più similitudini con le ultime.

Thesis (Ph.D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences and the Woods Hole Oceanographic Institution), 2000.
Includes bibliographical references (p. 179-187).
A simple dynamic model is used with various observations to provide an approximate spectral description of low frequency oceanic variability. Such a spectrum has wide application in oceanography, including the optimal design of observational strategy for the deployment of floats, the study of Lagrangian statistics and the estimate of uncertainty for heat content and mass flux. Analytic formulas for the frequency and wavenumber spectra of any physical variable, and for the cross spectra between any two different variables for each vertical mode of the simple dynamic model are derived. No heat transport exists in the model. No momentum flux exists either if the energy distribution is isotropic. It is found that all model spectra are related to each other through the frequency and wavenumber spectrum of the stream-function for each mode, ... , where ... represent horizontal wavenumbers, w stands for frequency, n is vertical mode number, and ... are latitude and longitude, respectively. Given ... , any model spectrum can be estimated. In this study, an inverse problem is faced: ... is unknown; however, some observational spectra are available. I want to estimate ... if it exists. Estimated spectra of the low frequency variability are derived from various measurements: (i) The vertical structure of and kinetic energy and potential energy is inferred from current meter and temperature mooring measurements, respectively. (ii) Satellite altimetry measurements produce the geographic distributions of surface kinetic energy magnitude and the frequency and wavenumber spectra of sea surface height. (iii) XBT measurements yield the temperature wavenumber spectra and their depth dependence. (v) Current meter and temperature mooring measurements provide the frequency spectra of horizontal velocities and temperature. It is found that a simple form for ... does exist and an analytical formula for a geographically varying ... is constructed. Only the energy magnitude depends on location. The wavenumber spectral shape, frequency spectral shape and vertical mode structure are universal. This study shows that motion within the large-scale low-frequency spectral band is primarily governed by quasigeostrophic dynamics and all observations can be simplified as a certain function of ... The low frequency variability is a broad-band process and Rossby waves are particular parts of it. Although they are an incomplete description of oceanic variability in the North Pacific, real oceanic motions with energy levels varying from about 10-40% of the total in each frequency band are indistinguishable from the simplest theoretical Rossby wave description. At higher latitudes, as the linear waves slow, they disappear altogether. Non-equatorial latitudes display some energy with frequencies too high for consistency with linear theory; this energy produces a positive bias if a lumped average westward phase speed is computed for all the motions present.
by Xiaoyun Zang.
Ph.D.

L'analyse des processus non-linéaires de génération et de propagation de la houle a constitué le cadre de cette thèse. Afin d'améliorer la compréhension de ces phénomènes, une méthode numérique dite High-Order Spectral (HOS), résolvant le problème de façon non-linéaire, a été développée. Cette méthode, avec une formulation surfacique et résolue de manière spectrale, associe précision et efficacité.

Un traitement original de la génération de houle non-linéaire est proposé. Il permet l'accès à des simulations de champs de vagues tridimensionnels complexes, fortement cambrés, dans un bassin de houle. Diverses comparaisons avec des expériences menées dans le bassin du Laboratoire de Mécanique des Fluides de l'ECN sont présentées.

Des simulations océaniques, en milieu ouvert, sont également proposées. Un intérêt particulier est porté à l'étude de l'apparition des vagues scélérates au sein de l'océan. L'importance des effets non-linéaires est pointée ainsi que l'aptitude de la méthode à modéliser de tels phénomènes. Des comparaisons avec les méthodes classiquement employées dans ce genre de problématique indiquent l'intérêt de l'approche utilisée ici.

La résolution du problème de tenue à la mer est également envisagée. L'utilisation de la méthode HOS dans les codes couplés, développés au Laboratoire de Mécanique des Fluides (potentiel, RANS, SPH), est envisagée. Elle permettra la description précise de la houle incidente ; le couplage est mis en place et validé sur un certain nombre de cas d'application.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2013.
"February 2013." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 175-184).
Efforts to monitor the ocean for signs of climate change are hampered by ever-present noise, in the form of stochastic ocean variability, and detailed knowledge of the character of this noise is necessary for estimating the significance of apparent trends. Typically, uncertainty estimates are made by a variety of ad hoc methods, often based on numerical model results or the variability of the data set being analyzed. We provide a systematic approach based on the four-dimensional frequency-wavenumber spectrum of low-frequency ocean variability. This thesis presents an empirical model of the spectrum of ocean variability for periods between about 20 days and 15 years and wavelengths of about 200-10,000 km, and describes applications to ocean circulation trend detection, observing system design, and satellite data processing. The horizontal wavenumber-frequency part of the model spectrum is based on satellite altimetry, current meter data, moored temperature records, and shipboard ADCP data. The spectrum is dominated by motions along a "nondispersive line". The observations considered are consistent with a universal [omega] -² power law at the high end of the frequency range, but inconsistent with a universal wavenumber power law. The model spectrum is globally varying and accounts for changes in dominant phase speed, period, and wavelength with location. The vertical structure of the model spectrum is based on numerical model results, current meter data, and theoretical considerations. We find that the vertical structure of kinetic energy is surface intensified relative to the simplest theoretical predictions. We present a theory for the interaction of linear Rossby waves with rough topography; rough topography can explain both the observed phase speeds and vertical structure of variability. The improved description of low-frequency ocean variability presented here will serve as a useful tool for future oceanographic studies.
by Cimarron James Lemuel Wortham, IV.
Ph.D.

An Electronic Speckle Pattern Interferometer residual stress measurement device based on the hole-drilling technique was designed and built: by carefully design both the mechanical and the optical systems, it has been possible to achieve very nice measurement results, with a compact and cheap device, which promise great on-field capabilities but also large room for further improvement.

Thesis (S.M.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 117-119).
The Acoustic Doppler Current Profiler (ADCP) is a proven technology which is capable of measuring surface wave height and directional information, however it is generally limited to rigid, bottom mounted applications which limit its capabilities for measuring deep water waves. By employing an upward looking ADCP on a moving platform, such as an autonomous underwater vehicle or submerged float, we show that it is possible to remove the wave induced motion of the platform and accurately measure surface ocean wave information. The platform selected for testing was a REMUS-100 vehicle equipped with an upward and downward looking ADCP and high accuracy Kearfott inertial navigation unit. Additionally, a Microstrain 3DM-GX3-25 Attitude Heading Reference System was tested as a low cost alternative to the Kearfott system. An experiment consisting of multiple REMUS deployments was conducted near the Martha's Vineyard Coastal Observatory (MVCO). The wave induced motion was measured by various inertial and acoustic sensors and removed from the ADCP data record. The surface wave height and mean directional estimates were compared against a Datawell MKIII directional Waverider buoy and bottom mounted 1200 kHz upward looking ADCP at the MVCO. Results demonstrate that the non-directional spectrum of wave height and the mean wave direction as a function of frequency can be accurately measured from an underway autonomous underwater vehicle in coastal depth waters using an ADCP.
by Scott Haven.
S.M.

Les propriétés de la matière peuvent être révélées en faisant interagir la matière avec la lumière. En particulier, les spectroscopies à rayons X sont largement utilisées pour étudier la structure électronique d'éléments isolés ou d'atomes et molécules dans un environnement donné, et sont spécifiques de la nature de l'élément. De telles capacités démontrent leur potentiel en terme d'analyse chimique. Le développement récent des lasers à électrons libres à rayons X (XFEL en anglais) permet de sonder la matière avec une résolution spatiale (angström) et temporelle (femtoseconde) hors de portée avec les lasers optiques et les sources synchrotron de troisième génération. Les caractéristiques uniques du rayonnement XFEL sont exploitées dans plusieurs domaines de recherche, comme la chimie, la physique et la biologie. En particulier, la spectroscopie de double trous a connu un nouvel essor avec l'apparition des XFELs. Les états double trous possèdent deux lacunes électroniques en couche interne. En régime XFEL, ces états sont produits principalement par l'absorption séquentielle de deux photons X d'une impulsion laser ultracourte (femtoseconde) et intense, avec la formation d'un état intermédiaire simplement ionisé. Au cours de cette thèse, nous avons étudié la formation de molécules doublement ionisées en couche de cœur, induite par l'absorption séquentielle de deux photons X d'une impulsion laser femtoseconde et intense. D'une part, nous mettons en évidence l'influence de la dynamique nucléaire sur les processus d'ionisation en couche de cœur. D'autre part, nous démontrons qu'un contrôle actif sur la compétition entre l'absorption de photon et le déclin Auger dans l'état intermédiaire simplement ionisé est possible en faisant varier la durée de l'impulsion laser. Afin d'atteindre ces objectifs, nous avons développé pour la première fois un modèle dépendant du temps et purement quantique, qui traite explicitement la dynamique nucléaire ainsi que l'absorption de photon, tandis que le déclin Auger est décrit de manière phénoménologique. Ce travail de recherche théorique ouvre la voie à une description complète de la formation de molécules doublement ionisées en couche de cœur en régime XFEL
Properties of matter can be revealed through its interaction with light. In particular, X-ray based spectroscopies are widely used to gain insight into the local electronic structure of isolated elements or atoms or molecules embedded in an environment, and are element specific. Such capabilities evidence their potential as tools for chemical analysis. The recent development of X-ray free electron laser (XFEL) allows to probe matter with spatial (angström) and temporal (femtosecond) resolutions out of reach so far with optical lasers or third generation synchrotron sources. The unique characteristics of XFEL radiation are exploited in several areas, such as chemistry, physics and biology. In particular, double core hole spectroscopy, whose sensitivity is considerably enhanced compared to conventional X-ray spectroscopies, is on the rise. Double core hole states, also referred as hollow states, are characterized by two electron vacancies in the inner shell(s). In the XFEL regime, the dominant pathway to produce them is the sequential absorption of two x-ray photons, where a singly core ionized species is produced in the intermediate step. In the present thesis, we tackle the study of double core hole state formation induced by the sequential absorption of two x-ray photons from an intense femtosecond laser pulse. On one hand, we bring forward the influence of the nuclear dynamics on core photoionization processes. On the other hand, we demonstrate that an active control over the competition between photoabsorption and Auger decay in the intermediate single core hole state is possible by varying the laser pulse duration. In pursuing these goals, we develop for the first time a time-dependent full quantum model treating both the photon absorption and the nuclear dynamics explicitly as well as the Auger decay phenomenologically. This purely theoretical work paves the road for a complete description of molecular double core hole state formation in th XFEL regime

Dans cette thèse, nous appliquons le phénomène de "hole burning" spectral (SHB), dans des matrices cristallines dopées par des ions terres rares, au traitement optique de l'information. Nous présentons la première démonstration expérimentale d'un analyseur spectral de signaux radio fréquence (RF) à très large bande instantanée, exploitant la sélectivité spectrale de ces matériaux photosensibles. L'utilisation de la technologie SHB, à basse température, permet d'atteindre des performances remarquables en terme de largeur de bande et de produit temps×bande passante. Le principe du spectromètre repose sur la séparation angulaire des composantes spectrales du signal RF préalablement transposé sur une porteuse optique. On grave un ensemble de réseaux de diffraction monochromatiques, multiplexés en longueur d'onde, dans un cristal dopé par des ions terres rares. Le faisceau lumineux, porteur du signal RF, est dirigé vers le cristal. Les différentes composantes spectrales sont alors diffractées et simultanément séparées angulairement à la sortie du cristal. Nous avons ainsi pu démontrer expérimentalement l'analyse spectrale de signaux RF sur une bande passante instantanée de 3,3 GHz avec une capacité de 100 canaux spectraux et une résolution ultime de 500 kHz. Ce dispositif possède une dynamique de 35 dB optique, limitée par la détection. Nous montrons la capacité de zoom spectral dans une région spécifique du domaine total couvert, avec augmentation de la résolution spectrale.

In this study, we investigate the energy spectrum and collective effects in the system of excitons in strained SiGe layers in a series of Si/Si1-xGex/Si heterostructures with 0.05 x 0.25 and the layer thickness d 2 5 nm. We use the low-temperature photoluminescence spectroscopy both in the near-infrared and the visible spectral regions. In the latter case, the luminescence originates from simultaneous recombination of two electrons with two holes. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34876

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.
Includes bibliographical references (p. 61-62).
In this thesis, we describe the analysis of 0.1-4 Hz quasi-periodic oscillations (QPOs) of the black hole X-ray binary XTE J1550-564 using data obtained with the Rossi X-ray Timing Explorer (RXTE) satellite. Data from 13 consecutive observations spanning eight days were included in this analysis. By comparing the spectra of the source when it is in the high intensity phase with the low intensity phase of its QPO cycle, we hoped to gain insight into the cause of QPOs and how they relate to structures and processes in the vicinity of black holes. Like observations from the black hole X-ray binary GRS 1915+105 (Miller and Homan 2005), our observations from XTE J1550-564 showed a significant difference in the Fe ... line equivalent width between the high and low intensities of the QPO for 6 of 13 observations. However, 2 of 13 observations exhibited the opposite effect in that the Fe K [alpha] line equivalent width actually dropped significantly during periods of high intensity. Moreover, we found that the integrated flux of the Fe K [alpha] line was proportional to the flux of the continuum in 5 of 13 observations. Despite these competing effects, the ratios of the low intensity and high intensity spectra indicate an increase in the QPO strength up to about 10 keV, above which it decreases only slightly. We also found dramatic changes in the QPO strength at low energies as the QPO frequency increases. We believe this to be the result of an increase in relative contributions to the spectra as the disk blackbody component becomes more important.
(Cont.) In this thesis, we discuss five possible spectral models to explain QPOs based on the behavior of Fe K [alpha] emission lines. Then we describe whether or not our results agree with those predictions. Although our results show correlations similar to those found by Miller and Homan (2005), they also show anti-correlations in several observations. Our results support Miller and Homan's suggestion of a link between discrete timing features (QPOs) and spectral features (Fe K [alpha] emission lines) which occur in the inner disk around black holes. Our work shows that current explanations for QPOs have some physical basis, suggesting that QPOs are due to either a quasi-periodically changing reflector area in the accretion disk or an episodic modulation of the hard flux component in the corona or jets that irradiates the accretion disk. Our results also suggest that perhaps the correct model is something more complex that goes beyond current models and is able to explain the multiple effects observed in the Fe K [alpha] line.
by Steven N. Cho.
S.M.

General relativity has been tested by many experiments, which, however, almost exclusively probe weak spacetime curvatures. In this thesis, I create two frameworks for testing general relativity in the strong-field regime with observations of black holes in the electromagnetic spectrum using current or near-future instruments. In the first part, I design tests of the no-hair theorem, which uniquely characterizes the nature of black holes in terms of their masses and spins in general relativity and which states that these compact objects are described by the Kerr metric. I investigate a quasi-Kerr metric and construct a Kerr-like spacetime, both of which contain an independent parameter in addition to mass and spin. If the no-hair theorem is correct, then any deviation from the Kerr metric has to be zero. I show that already moderate changes of the deviation parameters in either metric lead to significant modifications of the observed signals. First, I apply this framework to the imaging of supermassive black holes using very-long baseline interferometry. I show that the shadow of a black hole as well as the shape of a bright and narrow ring surrounding the shadow depend uniquely on its mass, spin, inclination, and the deviation parameter. I argue that the no-hair theorem can be tested with observations of the supermassive black hole Sgr A*. Second, I investigate the potential of quasi-periodic variability observed in both galactic black holes and active galactic nuclei to test the no-hair theorem in two different scenarios. Third, I show that the profiles of relativistically broadened iron lines emitted from the accretion disks of black holes imprint the signatures of deviations from the Kerr metric. In the second part, I devise a method to test the predicted evaporation of black holes in the Randall-Sundrum model of string theory-inspired braneworld gravity through the orbital evolution of black-hole X-ray binaries and obtain constraints on the size of the extra dimension from A0620-00 and XTE J1118+480. I predict the first detection of orbital evolution in a black-hole binary.

La connaissance de la climatologie des états de mer est primordiale pour le dimensionnement de structures marines, la gestion des zones côtières ou encore la récupération de l’énergie des vagues. L'estimation de la climatologie nécessite de disposer de données d'observation sur une longue durée, ce qui n'est pas le cas de l'Afrique de l'Ouest. Pour dépasser les limites en durée imposées par les observations, nous proposons dans ces travaux une approche stochastique pour estimer une climatologie de vagues en Afrique de l’Ouest, en s’appuyant sur une représentation “par événements” des données d’états de mer. Un “événement” désigne un système de vagues (houle ou mer du vent) en évolution au cours du temps, observable pendant une durée significative et que l’on peut relier à un unique phénomène météorologique source (e.g. dépressions, tempêtes, etc.). La représentation par événements permet de reproduire la cohérence temporelle des systèmes de vagues et de structurer les données d'états de mer avec une base physique. La démarche adoptée peut se décomposer suivant trois étapes. Nous avons d'abord extrait les événements à partir d’une série temporelle de spectres directionnels d’états de mer. Nous avons ensuite développé un modèle pour représenter chacun des événements par un nombre réduit de paramètres. Enfin, nous avons construit un générateur stochastique permettant la simulation d’événements individuels et la reconstitution de climatologies sur des durées de longueurs arbitraires. Les résultats ont montré un bon accord entre la climatologie reconstituée et celle de référence, permettant de conclure que le générateur peut valablement servir à la simulation de données d’états de mer en Afrique de l’Ouest pour les applications en génie océanique
Accurate estimation of long-term sea conditions is a major issue in design of coastal and offshore structures, coastal zone management or wave energy harvesting. An estimation of long-term sea conditions requires long duration observational data while in West Africa, only a few (3 years) years of observational data are available. To overcome the limits in duration that observations impose, a stochastic approach, event-based representation of sea state data, is proposed to model the wave climate in West Africa. An “event” refers to a wave system (swell or wind sea) evolving over time, that can be observed for a finite, yet significant duration and that can be linked to a single meteorological source phenomenon (e.g. low pressure systems, storms, etc.). Event-based approach provides structures with physical meaning and temporal consistence for the representation of sea states data. The procedure we have used is decomposed into three following steps. First, we have extracted events from a time series of directional spectra. We have then developed a model to represent each event by a reduced number of parameters. In the last step, we have constructed the stochastic events generator which allows for simulation of individual events and for reconstruction of wave climate over durations of arbitrary lengths. Results showed good agreement between reconstructed climate and that of reference and allow to conclude that the stochastic events generator can reliably be used to simulate sea state data in West Africa for a ocean engineering applications

Cette thèse propose un algorithme efficace pour la simulation numérique des interactions houle-structure avec des solveurs CFD bi-phasiques. L'algorithme est basé sur le couplage de la théorie potentielle et des équations bi-phasiques de Navier-Stokes. C'est une extension de la méthode Spectral Wave Explicit Navier-Stokes Equations (SWENSE) pour les solveurs CFD bi-phasiques avec une technique de capture d'interface. Dans cet algorithme, la solution totale est décomposée en une composante incidente et une composante complémentaire. La partie incidente est explicitement obtenue avec des méthodes spectrales basées sur la théorie des écoulements potentiels ; seule la partie complémentaire est résolue avec des solveurs CFD, représentant l'influence de la structure sur les houles incidentes. La décomposition assure la précision de la cinématique des houles incidentes quel que soit le maillage utilisé parles solveurs CFD. Une réduction significative de la taille du maillage est attendue dans les problèmes typiques des interactions houle structure. Les équations sont présentées sous trois formes : la forme conservative, la forme non conservative et la forme Ghost of Fluid Method. Les trois versions d'équations sont implémentées dans OpenFOAM et validées par une série de cas de test. Une technique d'interpolation efficace pour reconstruire la solution des houles irrégulières donnée par la méthode Higher-Order Spectral (HOS) sur le maillage CFD est également proposée
This thesis proposes an efficient algorithm for simulating wave-structure interaction with two-phase Computational Fluid Dynamics (CFD) solvers. The algorithm is based on the coupling of potential wave theory and two phase Navier-Stokes equations. It is an extension of the Spectral Wave Explicit Navier-Stokes Equations (SWENSE) method for generalized two-phase CFD solvers with interface capturing techniques. In this algorithm, the total solution isdecomposed into an incident and acomplementary component. The incident solution is explicitly obtained with spectral wave models based on potential flow theory; only the complementary solution is solved with CFD solvers, representing the influence of the structure on the incident waves. The decomposition ensures the accuracy of the incident wave’s kinematics regardless of the mesh in CFD solvers. A significant reduction of the mesh size is expected in typical wave structure interaction problems. The governing equations are given in three forms: the conservative form, the non conservative form, and the Ghost of Fluid Method (GFM) form. The three sets of governing equations are implemented in OpenFOAM and validated by a series of wave-structure interaction cases. An efficient interpolation technique to map the irregular wave solution from a Higher-Order Spectral (HOS) Method onto the CFD grid is also proposed

Cette thèse vise à étudier expérimentalement, analytiquement et numériquement, les conséquences de variations et d'oscillations hydrodynamiques à forte variabilité temporelle en milieux poreux partiellement saturés. Les problèmes que nous étudions comportent des surfaces libres tant à l'extérieur qu'à l'intérieur des milieux poreux, celles-ci étant définies comme des isosurfaces de pression d'eau égale à la pression atmosphérique (Pwater = Patm). Les différentes études expérimentales réalisées en laboratoire sont, respectivement : une expérience d'imbibition dans une boite à sable avec effets capillaires importants; la transmission d'oscillations de la surface libre à travers un massif sableux intercalaire dans un petit canal à houle (IMFT, Toulouse); l'étude de la dynamique et de la propagation des oscillations des niveaux d'eau dans un grand canal à houle (HYDRALAB, Barcelone), partiellement recouvert d'un fond sableux incliné, avec mesures de niveaux d'eau en pleine eau et sous le sable, et mesures du fond sableux (érosion/dépôts). Pour les études théoriques, nous avons développés des solutions analytiques linéarisées. Un exemple de problème traité analytiquement est: l'équation linéarisée de Dupuit-Boussinesq (D-B) transitoire à surface libre, en hypothèse d'écoulements plans et vidange/remplissage instantané : oscillations forcées, transmission et dissipation d'ondes à travers une boite à sable rectangulaire. Nous avons aussi développé une solution de l'équation faiblement non linéaire de Dupuit- Boussinesq (D-B) pour étudier le problème d'imbibition avec variation abrupte du niveau d'eau amont (suivi temporel du front de saturation). Nous avons pu étudier les différents types de problèmes transitoires liés aux expériences citées plus haut par simulation numérique. En particulier, nous avons simulé des écoulements partiellement saturés et insaturés, en coupe verticale, à l'aide d'un code de calcul (BIGFLOW 3D) qui résoud l'équation de Richards généralisée en régime transitoire. Nous avons ainsi étudié numériquement en régime non saturé, l'expérience d'imbibition dans un sable initialement sec à frontières verticales (IMFT sandbox), puis l'expérience de propagation d'ondes dans le grand canal à houle de Barcelone (laboratoire HYDRALAB) comportant une plage de sable inclinée, avec un couplage complètement intégré entre les zones micro-poreuse (sable) et “macro-poreuse” (pleine eau). Pour analyser les résultats de cette dernière expérience et les comparer aux simulations, nous avons utilisé plusieurs méthodes de traitement et d'analyse des signaux : analyse de Fourier (spectres de fréquences) ; ondelettes discrètes multi-résolution (Daubechies) ; analyses corrélatoires simple et croisée. Ces méthodes sont combinées avec des méthodes de préfiltrage pour estimer dérives et résidus (moyennes mobiles ; ondelettes multi-résolution). Cette analyse des signaux a permis de comprendre et quantifier la propagation à travers une plage de sable. Au total, les différentes approches de modélisation mis en oeuvre, associé à des procédures de calage en situation de couplage transitoire non linéaire ont permis de reproduire globalement les phénomènes de propagation de teneur en eau et de niveau d'eau dans les différentes configurations étudiées
This thesis aims at investigating experimentally, analytically and numerically, the consequences of hydrodynamic variations and oscillations with high temporal variability in partially saturated porous media. The problems investigated in this work involve “free surfaces” both outside and inside the porous media, the free surface being defined as the “atmospheric” water pressure isosurface (Pwater = Patm). The laboratory experiments studied in this work are, respectively: Lateral imbibition in a dry sand box with significant capillary effects; Transmission of oscillations of the free surface through a vertical sand box placed in a small wave canal (IMFT, Toulouse); Dynamics of free surface oscillations and wave propagation in a large wave canal (HYDRALAB, Barcelona), partially covered with sand, with measurements of both open water and groundwater levels, and of sand topography (erosion / deposition). For theoretical studies, we have developed linearized analytical solutions. Here is a sample problem that was treated analytically in this work: The linearized equation of Dupuit-Boussinesq (DB) for transient free surface flow, assuming horizontal flow and instantaneous wetting/drainage of the unsaturated zone: forced oscillations, wave transmission and dissipation through a rectangular sandbox. We also developed a weakly nonlinear solution of the Dupuit-Boussinesq equation to study the sudden imbibition (temporal monitoring of the wetting front). We have studied the different types of transient flow problems related to the experiments cited above by numerical simulation. In particular, we have simulated unsaturated or partially saturated transient flows in vertical cross-section, using a computer code (BIGFLOW 3D) which solves a generalized version of Richards’ equation. Thus, using the Richards / BIGFLOW 3D model, we have studied numerically the experiment of unsaturated imbibition in a dry sand (IMFT sandbox), and then, with the same model, we have also studied the partially saturated wave propagation experiment in the large Barcelona wave canal (HYDRALAB laboratory), focusing on the sloping sandy beach, with coupling between the micro-porous zone (sand) and the “macro-porous” zone (open water). To interpret the results of the latter experiment and compare them to simulations, we use several methods of signal analyzis and signal processing, such as: Fourier analysis, discrete multi-resolution wavelets (Daubechies), auto and cross-correlation functions. These methods are combined with pre-filtering methods to estimate trends and residuals (moving averages; discrete wavelet analyses). This signal analyzis has allowed us to interpret and quantify water propagation phenomena through a sandy beach. To sum up, different modeling approaches, combined with model calibration procedures, were applied to transient nonlinear coupled flow problems. These approaches have allowed us to reproduce globally the water content distributions and water level propagation in the different configurations studied in this work

L'imagerie médicale optique est limitée par la perte de résolution spatiale due à la diffusion des tissus biologiques. L'imagerie acousto-optique permet de palier à ce problème car elle utilise à la fois de lumière et des ondes ultrasonores. Par conséquent elle donne accès au contraste optique local en profondeur dans les tissus biologiques avec la résolution submillimétrique des ultrasons. Diverses méthodes interférométriques ont été développées pour détecter le signal acousto-optique, mais elles ne sont pas adaptées à l'imagerie in vivo. Au cours de cette thèse nous avons développé un filtre spectral intrinsèquement robuste à une mise en œuvre in vivo et capable de filtrer le signal de photons marqués. Ce filtre est basé sur le phénomène de creusement spectral, il est réalisé dans un cristal de grenat d'yttrium aluminium dopé au thulium (Tm:YAG) sous champ magnétique. Le manuscrit décrit d'abord la caractérisation du filtre spectral en condition d'imagerie. Ensuite nous présentons le montage expérimental qui a permis d' imager un gel diffusant simulant un tissu biologique. Dans la suite nous avons changé le laser principal et nous l'avons asservi en fréquence dans le but d'augmenter le niveau de maturation de la technologie. Enfin, la dernière partie du manuscrit détaille comment l'expérience a été compactée pour être apportée à un laboratoire pharmaceutique afin de lancer une campagne d'imagerie in vivo
Optical imaging for Medicine is limited by the spatial resolution loss due to light scattering in turbid media. A hybrid imaging method called ultrasound optical tomography can overcome this botteneck. Indeed the simultaneous use of light and ultrasound gives access to optical contrast in depth within scattering medium with the ultrasounds resolution. Several interferometric methods have been developed in order to detect an acousto-optic signal. However, none of them is adapted to in vivo imaging. For this reason a filter created with spectral hole burning is of special interest. This thesis presents the development of an ultra-narrow filter based on spectral hole burning in a thulium doped yttrium aluminum garnet crystal (Tm:YAG) under magnetic field. The first part of the manuscript describes the characterization of the filter in the imaging setup. Next, the actual imaging of a scattering gel is described. The following part presents the change of the main laser and its frequency stabilization for technological maturation. The last part of the manuscript details how the experiment have been compacted to be bring in a pharmacetical laboratory in order to launch in vivo imaging trials

En esta tesis utilizamos los instrumentos de altas energías del satélite INTEGRAL para hacer espectroscopía y la cámara OMC para hacer fotometría de dos tipos diferentes de objetos celestes emisores de rayos X. INTEGRAL permite obtener la espectroscop´ıa en rayos X y γ (cubriendo un rango espectral de 3–8000 keV) y OMC es una cámara CCD que opera en el filtro V de Johnson, capaz de proporcionar una monitorización continua de las fuentes científicas incluídas en el OMC Input Catalogue. La capacidad de hacer espectroscopía nos permitió el estudio de la emisión de alta energía de dos sistemas transitorios con agujero negro (i.e. GRO J1655–40 y GX 339–4) dando nuevas pistas acerca de la física de los procesos de emisión en alta energía (rayos X y γ) de este tipo de objetos. OMC, el monitor óptico a bordo del satélite INTEGRAL, nos permitió hacer un análisis multi-longitud de onda de TYC 2675- 663-1, desvelando que se trata de un sistema binario con propiedades dominadas por acreción. Mientras que el estudio de los sistemas transitorios con agujero negro estudiados en esta tesis corresponden a observaciones dedicadas tras la aceptación de un programa de observación, TYC 2675- 663-1 corresponde a parte de un programa de ciencia serendípita. En esta tesis se presenta el descubrimiento de 3 nuevos sistemas binarios (TYC 2675 663 1, TYC 237 363 1 y HD 86222) en base a sus propiedades fotométricas, todos mostrando emisión en rayos X blandos ya que pertenecen al catalogo ROSAT. Para dos de estos sistemas, la emisión en rayos X es la esperada en estrellas de rotación rápida y debido a actividad cromosférica. Para TYC 2675- 663-1 la situación es diferente ya que se detectó un exceso en la emisión en rayos X blandos de ≈50%. Se inició una campaña fotométrica y espectroscópica para desvelar el origen de este exceso y la naturaleza de ambas componentes del sistema binario. Como resultado, se detectaron un pronunciado efecto O-Connell, comportamiento errático en forma de erupciones y la presencia de mínimos asimétricos y diferentes máximos ocasionalmente en la curva de luz. La espectroscopía permitió detectar emisión notable y ensanchada de las líneas Hα y He I con perfil P Cygni. Esto es debido a procesos de acreción y a la presencia de vientos estelares notables en el sistema binario. Todas estas propiedades llevan a pensar que este sistema es un candidato a sistema de tipo Algol, presentando cambios drásticos y que podría convertirse en un sistema cataclísmico en el futuro. Finalmente, actividad en forma de erupciones en rayos X es probable que suceda en este sistema.

Dans de nombreux systèmes de traitement de l'information, le signal est numérisé, traité informatiquement, puis reconverti dans le domaine analogique. La faible bande passante de ces étapes de conversion numérique/analogique limite considérablement le débit d'informations traitées. Une solution purement analogique améliorerait donc considérablement le temps de traitement et la bande passante. Notre approche consiste à transférer le signal RF à traiter sur une porteuse optique puis à procéder à son traitement dans le domaine optique. L'étape de traitement est assurée par la traversée d'un cristal dopé en ions terres rares convenablement "programmé". Cette étape de programmation consiste à graver dans le profil d'absorption du cristal une fonction caractéristique de l'opération de traitement du signal à réaliser. Deux opérations ont ainsi été implémentées : 1) le renversement temporel de signaux RF : c'est l'opération consistant à générer analogiquement le signal renversé temporellement s(−t) d'un signal incident s(t). La fonction à graver dans le profil d'un cristal d'Er:YSO est alors un réseau spectral de pas variable. 2) l'analyse spectrale large bande instantanée : c'est l'opération permettant d'accéder au contenu spectral d'un signal. On impose au protocole de fournir instantanément le spectre d'un signal large bande. La fonction à graver dans le profil d'un cristal de Tm:YAG est alors un réseau spectro-spatial de pas variable
Many signal processing devices rely on the digitalization of the incoming signal. After being processed by a computer, the signal needs to be converted back to its original analog form. Due to the limited bandwidth of analog-to-digital and digital-to-analog stages, the data flow rate is significantly limited. A purely analog solution would then significantly improve the processing time and bandwidth. In our approach, we first transfer the incoming RF signal on an optical carrier, allowing us to process it in the optical domain. For the processing stage, we propose to engrave the absorption profile of a rare earth ion-doped crystal with different shapes (each shape is specific to one processing operation). In this work, two operations are implemented: 1) time reversal of RF signals: we analogically generate the time reversed replica s(−t) of an incoming signal s(t). For this purpose, the shape to be engraved in the absorption profile of a Er:YSO crystal is a non-periodic spectral grating. 2) instantanous broadband spectral analysis: we want to instantaneously access the spectral components of a broadband signal. For this purpose, the shape to be engraved in the absorption profile of a Tm:YAG crystal is a spectro-spatial grating with a variable period

Une binaire X est un système constitué de une étoile et d'un objet compact (étoile à neutron ou trou noir). La matière de l'étoile compagnon qui tombe sur l'objet compact avec une géométrie de disque, est un puissant émetteur de rayons X et gamma. Un des objectifs de la mission en bande Gamma INTEGRAL est justement la recherche et l'étude de ce type d'objets, qu'ils soient transitoires ou persistants. Un balayage périodique du plan et de la région du Centre galactique, riches de tels systèmes binaires est prévu dans le cadre du " INTEGRAL Core Programme ". Grâce au télescope IBIS/ISGRI, permettant la formation d'images haute résolution et fonctionnant dans la bande 20-600 keV, il est possible de résoudre ces objets jusqu'à 12' FWHM et d'en étudier le spectre à haute énergie. Le travail de doctorat décrit dans ce manuscrit se divise en deux phases distinctes trouvant leur continuité dans l'instrument IBIS. La première phase concerne, dans une première partie plus expérimentale, la calibration au sol et en vol de l'instrument IBIS à l'aide d'observations du Crabe et l'étude de ses performances à l'aide d'observations de Cyg X-1. D'autre part, elle décrit les premiers résultats scientifiques, parmi lesquels la réalisation du premier catalogue de IBIS et l'attribution de l'émission diffuse entre 20-100 keV à des sources ponctuelles galactiques. La seconde phase concerne les observations, l'analyse et l'interprétation des données de trois objets binaires contenant un trou noir observées simultanément par INTEGRAL et d'autres satellites en bande X comme XMM et RXTE. En particulier, je présent les deux candidates trois noirs transitoires, XTE J1720-318 et IGRJ 17464-3213 et l'évolution spectral et de luminosité durant un sursaut d'activité (" outburst "). Le troisième est par contre un objet persistant, 1E1740. 7-2942, qui se trouve à peu d'arcs minutes du Centre galactique. Nous en avons suivi l'évolution temporelle avec IBIS lors de la première année d'observations d'INTEGRAL (Février–Octobre 2003), durant laquelle le flux a varié d'un facteur 3. Une étude spectrale à bande large a également été réalisée à l'aide d'observations RXTE/PCA et INTEGRAL. A partir de Septembre 2003, la source a initié une phase de décroissance du flux, laquelle a coïncidé avec un changement d'état spectral. Le spectre d'émission de dur est devenu mou dans un régime de faible accrétion. Les différents états spectraux sont discutés dans le cadre d'un modèle thermique de Comptonization. A partir de Mars 2004, le flux est descendu au dessous des valeurs de sensibilité des détecteurs, soit IBIS/ISGRI que PCA, un état de quiescence unique qui se poursuit encore actuellement
An X-ray binary is a system containing a compact object (black hole, neutron star or white dwarf) accreting material from a companion star. The matter falling on the compact object is an emitter of X and even soft-gamma radiation. Searching and studying these objects, either transient or persistent, is one of the main goal of INTEGRAL, the in-orbit ESA mission devoted to X-ray and gamma-ray astrophysics. Scans of the Galactic plane and deep exposures of the Galactic Centre are performed periodically by INTEGRAL in the framework of the Core Programme guaranteed time. These regions are well known to be rich of X-ray binaries. Thanks to its unprecedented combined spatial resolution (12' FHM) and sensitivity, the IBIS/ISGRI telescope on board INTEGRAL provides high resolution images and good quality spectra in the energy range 15-600 keV. The work reported in this thesis is divided in two different parts which are linked to the status of the IBIS instrument during the different stages of its operation. In the first part, on-ground and in-flight calibration activities of the IBIS telescope are described. Observations of the Crab have been used in order to improve the spectral response matrix of the instrument; sensitivity and imaging capabilities have been accurately tested with several pointings of the Cyg X-1 region. In order to give an idea of the IBIS scientific performances, among the several results of the first year of observations, I briefly report on two key results I have been contributing: the first IBIS source catalogue and the origin of the Galactic diffuse emission between 20 and 100 keV, explained as being mainly due to the emission of previously unresolved Galactic point sources. The second part concerns data analysis and interpretation of three black hole binaries observed with INTEGRAL and simultaneously with two other X-ray satellites, namely XMM-Newton and RXTE. I present in this thesis the spectral evolution and luminosity variation of two transient black hole candidates, XTE J1720-318 and IGR J17464-3213, observed during their 2003 outburst activities. .

Les méthodes spectrales sont connues pour leurs propriétés de convergence rapide et de précision. Cependant, leur application à l'hydrodynamique navale reste encore aujourd'hui peu étendue. Le but de ce doctorat est d'étudier les possibilités de leur application à la génération et propagation de houle, dans le cadre de la théorie des écoulements potentiels.
Un bilan des différentes approches spectrales employées jusqu'à présent en hydrodynamique navale est d'abord dressé, étayant le choix des techniques développées au cours de ce travail. L'étude des propriétés de ces techniques est ensuite réalisée sur le ‘noyau' de la méthode, i.e. une cuve tri-dimensionnelle de géométrie figée. En particulier, différentes techniques High-Order Spectral sont comparées entre elles et à la méthode directe, et une nouvelle variante est proposée. Des validations sur des cas de lâchers de surface libre et d'oscillations forcées de surface libre sont présentées et confrontées à diverses méthodes.
L'approche est ensuite étendue, à partir de ce ‘noyau' et au moyen de stratégies de ‘potentiel additionnel', donnant lieu au développement de divers modèles. Ainsi, des houles non-linéaires sont modélisées à l'aide de doublets tournants instationnaires spécifiquement développés. Des cas de reproduction de signaux temporels cibles à une distance, et de génération et propagation de houle irrégulière sont présentés. De plus, une caractéristique avantageuse d'une telle approche spectrale est exploitée pour proposer des modèles originaux de diffraction autour de corps. Ceux-ci allient une génération de houle par méthode spectrale à des modèles de diffraction en fluide parfait ou visqueux, formulés en changement de variable. Des exemples illustratifs de diffraction de cette houle autour de corps bi- ou tri-dimensionnels sont proposés.
Enfin, un modèle original de simulation complète, au second-ordre, du processus de génération et propagation en bassin de houle tri-dimensionnel est réalisé. Il inclut la modélisation de différents batteurs, ainsi qu'un modèle d'absorption, permettant notamment de reproduire les caractéristiques complètes du nouveau bassin de houle de l'École Centrale de Nantes. Ce modèle est validé par comparaison à une solution analytique en régime établi et ses propriétés numériques sont étudiées. L'investigation des ondes libres et leur suppression, ainsi que la caractérisation de zones utiles sont proposées à titre d'application.

Questa tesi è frutto della collaborazione tra l'Università e Lofarma S.p.A., un’azienda farmaceutica italiana leader nel settore che produce preparati per pazienti allergici come kit diagnostici e immunoterapie. A tale scopo nel reparto di Acarologia ogni anno vengono allevati e raccolti decine di chilogrammi di acari adulti e, dopo alcune manipolazioni, utilizzati nel reparto produttivo come materia prima per la maggior parte delle formulazioni. Lo scopo di questo progetto è analizzare l'attuale metodo di produzione e studiare se alcuni passaggi potrebbero essere ottimizzati per migliorare la resa, il tasso di produzione e la qualità della materia prima, cercando nel contempo di ridurre costi e tempi di lavorazione. La ricerca è stata suddivisa in 2 aree principali: 1) Procedure di Allevamento (valutazione della qualità della dieta e del ceppo allevato) e 2) Manipolazioni della Materia Prima (ottimizzazione del processo di pulizia e valorizzazione della materia prima). Tra questi, i risultati più significativi sono stati raggiunti nella sezione Manipolazione delle Materie Prime, dove viene descritto un nuovo processo di rifinitura in grado di ottenere rese finali più elevate in tempistiche più brevi. Dopo aver analizzato l'intero ciclo produttivo, è possibile concludere che, nel contesto del Reparto di Acarologia, è più conveniente procedere con una migliore manipolazione della materia prima piuttosto che modificare le attuali metodiche di allevamento, che sembrano già adatte per le esigenze di Lofarma.
This thesis is based on collaboration between University and Lofarma S.p.A., a leading Italian pharmaceutical company which produce preparation for allergic patients like diagnostic kits and immunotherapies. To this purpose every year dozens of kilograms of adult mites are reared and collected in the Acarology department and, after manipulations, used in the Production Department as raw material for most of the preparation. The aim of this project is to analyze the current production methodology of Acarology department and investigate if some steps could be optimized to improve the yield, the production rate and the quality of the raw material while trying to reduce costs and processing times. The research has been divided in 2 main areas: 1) Rearing Procedures (quality assessment about the diet and the strain enacted) and 2) Raw Material Manipulations (optimization of the refining process and valorization of the Raw Material). Between those, most significant results have been achieved in the Raw Material Manipulation section, where is described a novel refining process capable of obtaining higher final yields in a shorter working time. After analyzing the whole manufacturing cycle, is possible to conclude that, within the context of the Acarology Department, is more convenient to proceed with a better manipulation of the raw material in the refining process rather than modifying the actual rearing procedure, which is already suitable for Lofarma needs.