Dans le cadre de la détection radar en environnement gaussien comme non-gaussien, de nombreux détecteurs ont été développés en se basant sur des modèles de fouillis précis et des estimateurs de matrices adaptés à ces modèles. Les modèles gaussiens, simples d’utilisation, montrent rapidement leurs limites face à la réalité physique et laissent ainsi place aux SIRP, processus aléatoires sphériquement invariants qui rendent compte beaucoup plus fidèlement de la non-gaussianité du fouillis. Les détecteurs adaptés à ces environnements sont alors construits sur la base d’un estimateur de la matrice de covariance adapté. Or, dans de nombreuses applications, cette matrice de covariance présente une structure particulière dite persymétrique. L’objet de cette thèse est donc d’exploiter cette structure particulière de la matrice de covariance du fouillis afin d’en diminuer l’erreur d’estimation. Par cette exploitation, deux nouveaux estimateurs de la matrice ont été déterminés pour les environnements gaussiens et non-gaussiens. Ces détecteurs nommés PAMF et GLRT-PFP, ont été caractérisés statistiquement et une validation des travaux théoriques a été menée sur des données opérationnelles tant gaussiennes que non-gaussiennes. Une application de la persymétrie a également été effectuée dans le cadre des algorithmes spatio-temporels (STAP) ainsi que sur des algorithmes dits "à rang réduit". Les résultats probants en détection obtenus sur tous ces types de données confirment donc l’intérêt de la technique étudiée. Enfin, un élargissement de la structure persymétrique a été étudié par l’extension des détecteurs aux matrices dites de Toeplitz. Ces matrices obtenues dans le cas de traitements spatio-temporels présentent une structuration plus riche encore que la persymétrie et permettent d’envisager des développements futurs intéressants en vue de l’amélioration des performances des détecteurs. Les premiers résultats sont présentés pour conclure ce travail de thèse. / This thesis deals with Radar detection in Gaussian and non-Gaussian noise. In this context, the clutter covariance matrix commonly exhibits a particular persymmetric structure. This structure is exploited into a particular matrix transformation to provide two new covariance matrices estimates for Gaussian and non-gaussian noise. We use then this particular linear transformation in order to develop and to study the statistical property of the two new detectors based on these estimates for both Gaussian and non-Gaussian environments. The improvement in terms of detection performances of these new detectors is shown through a lots of simulations and validation on operational data, for both Gaussian and non- Gaussian noise. Moreover this exploitation is extended to space-time adaptive processing and reduced rank technical. All the results confirm then the high interest of taking into account this particular structure in radar detection process compared to classical detection schemes. The case of Toeplitz matrices is also studied. The Toeplitz matrices are a particular class of structured matrices obtain with space-time processing which theoretically allows to improve the performance of detectors based on this matrix assumption. In this context, some preliminary results are presented in order to conclude this thesis.

Nous avons cherché à mieux connaître les potentialités ontogéniques des ouvriers de R. santonensis (espèce introduite) et R. grassei (espèce endémique) à se différencier en reproducteurs secondaires néoténiques, ainsi que les mécanismes physiologiques sous jacents à cette différenciation. Les conséquences de cette production de reproducteurs seront discutées dans le cas de processus invasifs. Les insectes sociaux introduits présentent des modifications de leur structure sociale, ce qui leur confère des capacités invasives importantes. Chez R. santonensis, ces modifications consécutives à une introduction portent sur la capacité à produire des néoténiques. Ces néoténiques sont capables de pondre abondamment et les larves de se développer rapidement. L’Hormone Juvénile semble impliquée dans cette potentialité. Après avoir confirmé l’introduction de R. urbis, nous montrons que, dans un nouveau milieu, la structure coloniale est de type étendu avec une reproduction par bouturage. / No summary available

Double perovskites with a single s = ½ magnetic ion and rocksalt order can show geometric frustration, due to arrangement of electron spins such that they cannot satisfy all nearest-neighbour antiferromagnetic interactions simultaneously. This can give rise to exotic magnetic states at low temperature. Compounds with unpaired 4d and 5d electrons have in this respect been studied far less than 3d compounds. Here, results of studies on the compounds Sr2CuWO6, Ba2YWO6 and LaSrMgWO6 are presented. The synthesis of the previously reported compound Ba2Y1WO6 (W5 +, 5d1) was attempted by many methods, but yttrium deficiencies were present in all samples. This led to the series Ba2YxWO6 with ⅔ ≤ x ≤ 0.8, dependent on the synthesis conditions. The x = ⅔ compound is known to exist as a metastable cubic phase and an 18H rhombohedral thermodynamic phase. The one-third vacant B sites on the x = ⅔ cubic material are doped with lithium, resulting in the Ba2Y2/3LixWO6 compound. This thesis focuses on the new x = 0.75 phase, and characterises its structural and magnetic properties. The Jahn-Teller distorted Sr2CuWO6, with the Cu2+ (3d9) magnetic ion, has an elongated c axis leading to separation of ab planes. This compound had been proposed as a pseudo-2D spin liquid model candidate, following a lack of evidence of transition to long-range order in SQUID magnetometry and heat capacity. However, recent μSR measurements did show a transition to long-range ordered state at 24K. This thesis details further bulk and local probe measurements which indicate that the low-temperature state is type-2 antiferromagnetic, and which point to a thermally activated spin-liquid-like state which occurs between 24K and ∼100K. La0.5Sr1.5MgWO6, has also been synthesised. The 1:1 compound LaSrMgWO6 had previously been reported as W5+ and described as “pseudo-cubic”: X-ray and neutron diffraction studies here characterise the low-temperature structure within the P2₁/n monoclinic space group, and suggest that no ordering of the atoms on the A site is observed.

Theoretical methods for studying molecules of biological importance are reviewed, both ab initio and semi-empirical. The Group Function Approach is developed in detail in its strong orthogonal form and corrections to the energy are added for taking into account non-orthogonality effects, depending on the overlaps of the group functions. Approximations are introduced and tested so that this method can be applied to large molecules. In particular, a system (or a relevant fragment of it) is built up from localized two-electron groups, each one described by a two-electron group function (geminal). Each group function is optimized by using an SCF method with an effective hamiltonian consisting of the two-electron hamiltonian of the group together with the effective potential due to the presence of the other electron groups (and to the external environment, eventually). The wavefunction for the whole molecule is an antisymmetrized product of geminals. The energy is computed as a sum of group contributions. Corrections, depending on up to the second power of the overlaps of two groups at a time, are particularly important in conformational studies. The approximations introduced are based on the consideration that distant groups consisting of two positive and two negative charges see each other as neutral entities and thus do not contribute appreciably in the definition of the effective hamiltonian: the computing effort is greatly reduced in this way, the error introduced is small and can be estimated easily. The theoretical method presented in this thesis offers a powerful tool for making qualitative predictions of the changes resulting from localized effects, such as twisting around a bond, and it can be usefully applied to conformational studies and geometry optimizations. The other properties which can be calculated axe for the most part directly related to the electron density; this determines, for example, the electrostatic potential outside a molecule and hence the position of attack by approaching ions or polar species. Chemical reactions, which involve breaking or re-arrangement of bonds, provide another vast field of application. Such processes usually involve only localized regions in a molecule and the admission of intragroup CI ensures that the study of bond breaking remains valid throughout the whole process. All necessary computer programmes have been developed and numerical applications have been made to a range of molecules, including hydrocarbons, small molecules containing double bonds and lone pairs, and the amino acid glycine.

The Western Limassol Forest Complex (WLFC), Cyprus, forms an anomalous ophioliteterrain in the south of the Troodos Massif. Detailed studies have revealed magmatic and structural histories that differ markedly from the Penrose-type ophiolite of the Troodos Massif to the north. In the WLFC, a tectonised harzburgite of upper mantle origin has been intruded by multiple ultramafic and gabbroic plutons and swarms of mainly NE-SW trending dykes. The entire complex has been sheared along E-W trending serpentinite shear zones, the orientation of which indicate sinistral displacement. The various styles of deformation from ductile to brittle, and the progressive cooling history of the Intrusive plutons and dykes indicate a history of about 4km of uplift for the host upper mantle lithologies, while in a sea floor setting. The geochemistry of the intrusive plutons and dykes is similar to the lavas that crop out around the periphery of the WLFC, and Indicate derivation from a depleted upper mantle source. Geochemical comparison with the Troodos massif basalts suggests a tectonic history involving rapid extension across the WLFC and adiabatic melting of the upper mantle producing boninitic magmas. The regional setting for the WLFC suggests a model of formation involving the development of a transtensional transform fault zone and an extensional relay zone that off-set to the south, sinistral transform movement along the Arakapas fault belt. Comparison of the WLFC with a transpressional palaeo-transform fault preserved in the Antalya complex of Turkey suggests that the Neo-Tethyan spreading system (within which the Troodos massifformed) was experiencing an anticlockwise rotational torque during the final stages of oceanic crustal formation.

No description available.

With the emergence of nano-devices and nano-scale research, gaining further understanding of the evolution of drag forces exerted by molecular flows, at low Knudsen numbers (-0.1-0.5), over nano-scaled objects with 20-100 nm size is a realistic expectation. The proposed research examines the fluid-structure interaction at nano-scales from first principles. It has also critically evaluated, and if necessary modified, the assumptions made during the development of a computational model. The research has provided new insights in modelling molecular interaction with continuum as well as molecular walls and calculation procedures for predicting macroscopic properties such as velocity, pressure and drag coefficients. The proposed formulation has been compared with the state of the art formulations as published in recent journals and verified on number numerical and molecular tests as experimental and analytical results are unavailable at this scale. The effect of various geometry configurations (slit pore, inclined and stepped wall) to model the pressure driven molecular flow through confined walls is studied for number of surface roughness and driving force values given by adjusting molecular accelerations. The molecular flow over diamond, circular and square shaped cylinders confined within parallel walls has also been modelled at various input conditions. It is expected that the proposed research will have impact in developing future nanoscale applications, in the field of drug delivery, surface cleaning and protein movement, where adsorption, drag resistance or, in general, understanding of the knowledge of fluid-structure interaction at 50-100nm scale is important. Some of the future research areas resulting from this research have also been identified.

The objective of this thesis is to further extend the application range of immersed computational approaches in the context of hydrodynamics and present a novel general framework for the simulation of fluid-structure interaction problems involving rigid bodies, flexible solids and multiphase flows. The proposed method aims to overcome shortcomings such as the restriction of having to deal with similar density ratios among different phases or the restriction to solve single-phase flows. The new framework will be capable of coping with large density ratios, multiphase flows and will be focussed on hydrodynamic problems. The two main challenges to be addressed are: - the representation, evolution and compatibility of the multiple fluid-solid interface - the proposition of unified framework containing multiphase flows, flexible structures and rigid bodies with possibly large density ratios First, a new variation of the original IBM is presented by rearranging the governing equations which define the behaviour of the multiple physics involved. The formulation is compatibile with the "one-fluid" equation for two phase flows and can deal with large density ratios with the help of an anisotropic Poisson solver. Second, deformable structures and fluid are modelled in a identical manner except for the deviatoric part of the Cauchy stress tensor. The challenging part is the calculation of the deviatoric part the Cauchy stress in the structure, which is expressed as a function of the deformation gradient tensor. The technique followed In this thesis is that original ISP, but re-expressed in terms of the Cauchy stress tensor. Any immersed rigid body is considered as an incompressible non-viscous continuum body with an equivalent internal force field which constrains the velocity field to satisfy the rigid body motion condition. The "rigid body" spatial velocity is evaluated by means of a linear least squares projection of the background fluid velocity, whilst the immersed force field emerges as a result of the linear momentum conversation equation. This formulation is convenient for arbitrary rigid shapes around a fixed point and the most general translation- rotation. A characteristic or indicator function, defined for each interacting continuum phase, evolves passively with the velocity field. Generally, there are two families of algorithms for the description of the interfaces, namely, Eulerian grid based methods (interface tracking). In this thesis, the interface capturing Level Set method is used to capture the fluid-fluid interface, due to its advantages to deal with possible topological changes. In addiction, an interface tracking Lagrangian based meshless technique is used for the fluid-structure interface due to its benefits at the ensuring mass preservation. From the fluid discretisation point of view, the discretisation is based on the standard Marker-and-Cell method in conjunction with a fractional step approach for the pressure/velocity decoupling. The thesis presents a wide range of applications for multiphase flows interacting with a variety of structures (i.e. rigid and deformable) Several numerical examples are presented in order to demonstrate the robustness and applicability of the new methodology.

Orientador: Maria Encarnação Beltrão Sposito / Banca: Angelo Szaniecki Perret Serpa / Banca: Gloria da Anunciação Alves / Banca: Arthur Magon Whitacker / Banca: Everaldo Santos Melazzo / Resumo: A partir da metade do século XX, ocorreram transformações políticas e econômicas que influenciaram a urbanização de Salvador/BA. Essas mudanças provocaram alterações em sua estrutura urbana, sendo mais importantes: a redefinição nas relações tempo-espaço, a implantação de novos equipamentos e a constituição de uma nova lógica na centralidade urbana, marcando o início do processo de reestruturação urbana e da cidade. As bases foram engendradas pelo Estado, junto com outros agentes, dentre os quais destacam-se os produtores imobiliários, aliado ao capital financeiro e o capital comercial. As conseqüências revelam a constituição de uma nova feição à estrutura urbana, entendida como expressão de uma cidade poli(multi)nucleada. As atuais áreas centrais de Salvador apresentam-se diferenciadas, tanto no que diz respeito à quantidade de centros, quanto aos interesses dos grupos que estão a esses articulados. Os antigos centros e sub-centros passam por um processo de mudança em suas características fundamentais e os novos correspondem à materialidade de uma lógica urbana hodierna que impera na cidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: After 1950 some economic and political transformations occurred, influencing in the urbanization process of the city of Salvador/BA. These changes provoked some important changes in the urban structure, such as the redefinition of the time-space relationship and the introduction of new equipments, marking the start of urban and city restructuration. The process was produced by the State, among with other agents, and its consequences demonstrate the formation of a new characteristics of the urban structure, understood as the multi(poly)centralité. The current centers are differentiated by the amount and by the interests of the social groups. The old centers and sub-centers had gone through a process of change in its characteristics. The new centers are related to the materiality of the current urban logic and its influences in the city. Due to the social inequality and the high value of the urban ground, the access to market spaces translates conflicts and group interests. / Doutor

No description available.