The aim of this thesis is to design a controller for an unmanned helicopter to perform target engagement. This mission is briefly defined as / the helicopter flies to a firing point under the commands of a trajectory controller, and then it is aligned to the target with attitude control. After weapon firing, the helicopter initiates a return maneuver under again the commands of the trajectory controller. This mission where the continuous systems and discrete guidance decisions are to be executed in coherence can be studied as a hybrid control problem. One hybrid control approach which is used in this study is the representation based on two motion primitives: trim trajectories and maneuvers. To obtain the desired trim trajectories and the maneuvers, a dynamic inversion based controller is developed. The controller has two loops: the inner loop which controls the helicopter attitudes and the outer loop which controls the helicopter trajectory. A guidance algorithm is developed which enables the controller to switch from the inner loop to the outer loop or vice versa. Simulations are generated to test the controller performance.

Integration of dynamic data is critical for reliable reservoir description and has been an outstanding challenge for the petroleum industry. This work develops practical dynamic data integration techniques using streamline approaches to condition static geological models to various kinds of dynamic data, including two-phase production history, interference pressure observations and primary production data. The proposed techniques are computationally efficient and robust, and thus well-suited for large-scale field applications. We can account for realistic field conditions, such as gravity, and changing field conditions, arising from infill drilling, pattern conversion, and recompletion, etc., during the integration of two-phase production data. Our approach is fast and exhibits rapid convergence even when the initial model is far from the solution. The power and practical applicability of the proposed techniques are demonstrated with a variety of field examples. To integrate two-phase production data, a travel-time inversion analogous to seismic inversion is adopted. We extend the method via a 'generalized travel-time' inversion to ensure matching of the entire production response rather than just a single time point while retaining most of the quasi-linear property of travel-time inversion. To integrate the interference pressure data, we propose an alternating procedure of travel-time inversion and peak amplitude inversion or pressure inversion to improve the overall matching of the pressure response. A key component of the proposed techniques is the efficient computation of the sensitivities of dynamic responses with respect to reservoir parameters. These sensitivities are calculated analytically using a single forward simulation. Thus, our methods can be orders of magnitude faster than finite-difference based numerical approaches that require multiple forward simulations. Streamline approach has also been extended to identify reservoir compartmentalization and flow barriers using primary production data in conjunction with decline type-curve analysis. The streamline 'diffusive' time of flight provides an effective way to calculate the drainage volume in 3D heterogeneous reservoirs. The flow barriers and reservoir compartmentalization are inferred based on the matching of drainage volumes from streamline-based calculation and decline type-curve analysis. The proposed approach is well-suited for application in the early stages of field development with limited well data and has been illustrated using a field example from the Gulf of Mexico.

This thesis describes the implementation of Yao’s adaptive robust control to an aircraft control system. This control law is implemented as a means to maintain stability and tracking performance of the aircraft in the face of failures and changing aerodynamic response. The control methodology is implemented as an outer loop controller to an aircraft under nonlinear dynamic inversion control. The adaptive robust control methodology combines the robustness of sliding mode control to all types of uncertainty with the ability of adaptive control to remove steady state errors. A performance measure is developed in to reflect more subjective qualities a pilot would look for while flying an aircraft. Using this measure, comparisons of the adaptive robust control technique with the sliding mode and adaptive control methodologies are made for various failure conditions. Each control methodology is implemented on a full envelope, high fidelity simulation of the F-15 IFCS aircraft as well as on a lower fidelity full envelope F-5A simulation. Adaptive robust control is found to exhibit the best performance in terms of the introduced measure for several different failure types and amplitudes.

During last decade, the fast-growing communication need has promoted the development of 1.3 £gm~1.6 £gm laser light source. The Cr4+ doped YAG solid-state laser has potential to meet this broadband demand. In addition, diode-laser-pumped solid state laser has the merits of high laser beam quality, long lifetime, compact, and simple structure. In this thesis, crystal fiber was used as the laser gain medium, and coated with optical thin film at its end facets as the laser cavity. Using this configuration, the volume and cost of the laser can be appreciatively reduced, and the heat dissipation can be improved. The laser-heated-pedestal-growth method was used to grow crystal fiber, which can obtain small diameter at very fast rate. Outside the glass clad Cr4+:YAG crystal fiber, Al-Cu alloy was employed as the heat sink to improve heat dissipation. After grinding, polishing, and coating of this device, the Cr4+:YAG crystal fiber laser was fabricated. Some characteristics of Cr4+:YAG crystal fiber, such as the distribution of Cr2O3 and CaO doping concentration, fluorescence intensity, refraction index, propagation loss, and absorption coefficient were measured and analyzed. A record-low threshold of 0.75 mW was achieved. It is more than 500 times lower than any previously reported Cr4+:YAG lasers, and a slope efficiency of 6.9% was obtained. The ultralow-threshold lasing is made possible by the low propagation loss of 0.08 dB/cm and the high pump intensity of the core. Such a low-threshold operation makes the double-clad crystal fiber laser be compatible to present optical communication systems. In the meanwhile, some simulations of the laser output power have been developed to predict the experimental results.

Shallow water acoustics is one of the most challenging areas of underwater acoustics; it deals with strong sea bottom and surface interactions, multipath propagation, and it often involves complex variability in the water column. The sea bottom is the dominant environmental influence in shallow water. An accurate solution to the Helmholtz equation in a shallow water waveguide requires accurate seabed acoustic parameters (including seabed sound speed and attenuation) to define the bottom boundary condition. Direct measurement of these bottom acoustic parameters is excessively time consuming, expensive, and spatially limited. Thus, inverted geo-acoustic parameters from acoustic field measurements are desirable. Because of the lack of convincing experimental data, the frequency dependence of attenuation in sandy bottoms at low frequencies is still an open question in the ocean acoustics community. In this thesis, geo-acoustic parameters are inverted by matching different characteristics of a measured sound field with those of a simulated sound field. The inverted seabed acoustic parameters are obtained from long range broadband acoustic measurements in the Yellow Sea '96 experiment and the Shallow Water '06 experiment using the data-derived mode shape, measured modal attenuation coefficients, measured modal arrival times, measured modal amplitude ratios, measured spatial coherence, and transmission loss data. These inverted results can be used to test the validity of many seabed geo-acoustic models (including Hamilton model and Biot-Stoll model) in sandy bottoms at low frequencies. Based on the experimental results in this thesis, the non-linear frequency dependence of seabed effective attenuation is justified.

The presented thesis deals with the multi-dimensional reconstruction of the earth's conductivity distribution based on DC resistivity data. This task represents a nonlinear and ill-posed minimization problem with many degrees of freedom. In this work, techniques for regularization and controlling of this problem are depicted and classified. Particularly, it is concentrated on explicit regularization types, which impose constraints onto the model. The system of equations as resulting from the application of the Gauss-Newton minimization can be solved efficiently. Furthermore, it is shown how the regularization strength can be controlled. The method of non-linear resolution analysis plays a central role in the thesis. It represents a powerful tool to estimate the quality of inversion results. Furthermore, the derived resolution measures provide the basis for the optimization of experimental design concerning information content and efficiency. Methods of error estimation, forward modeling and the calculation of the Jacobian matrix for DC resistivity data are developed. Procedures for appropriate parameterization and inversion control are pointed out by studies of synthetic models. Different inversion and regularization methods are examined in detail. A linearized study is used to compare different data sets considering their efficiency. Moreover, a triplegrid-technique for the incorporation of topography into three-dimensional inversion is presented. Finally the inversion methods are applied to field data. The depicted optimization strategies are realized in practice, which increases the economic relevance of threedimensional data acquisition. The structure of the subsurface is imaged in detail for several applications in the fields of cavity detection, archaeology and the investigation of ground falls. The resolution analysis is successfully established to appraise the obtained results.

No description available.

<p>The Lattrell-Dax method of nitrite-mediated substitution of carbohydrate triflates is an efficient method to generate structures of inverse configuration. In this study it has been demonstrated that a neighboring equatorial ester group plays a highly important role in this carbohydrate epimerization reaction, inducing the formation of inversion compounds in good yields. Based on this effect, efficient synthetic routes to a range of carbohydrate structures, notably β-D-mannosides and β-D-talosides, were designed. By use of the ester activation effect for neighboring groups, a double parallel as well as a double serial inversion strategy was developed.</p>

L'objectif de la thèse est de développer une méthodologie d'identification expérimentale de modèles probabilistes qui prédisent le comportement dynamique de structures. Nous focalisons en particulier sur l'inversion de modèles probabilistes à paramétrage minimal, introduits par Soize, à partir de fonctions de transfert expérimentales. Nous montrons d'abord que les méthodes classiques d'estimation de la théorie des statistiques mathématiques, telle que la méthode du maximum de vraisemblance, ne sont pas bien adaptées pour aborder ce problème. En particulier, nous montrons que des difficultés numériques, ainsi que des problèmes conceptuels dus au risque d'une mauvaise spécification des modèles, peuvent entraver l'application des méthodes classiques. Ces difficultés nous motivent à formuler l'inversion de modèles probabilistes alternativement comme la minimisation, par rapport aux paramètres recherchés, d'une fonction objectif, mesurant une distance entre les données expérimentales et le modèle probabiliste. Nous proposons deux principes de construction pour la définition de telles distances, basé soit sur la fonction de logvraisemblance, soit l'entropie relative. Nous montrons comment la limitation de ces distances aux lois marginales d'ordre bas permet de surmonter les difficultés mentionnées plus haut. La méthodologie est appliquée à des exemples avec des données simulées et à un problème en ingénierie civile et environnementale avec des mesures réelles.

Cette thèse étudie la cinématique du disque de la galaxie en vue de contraindre les modèles de sa formation. Elle se place dans le cadre du projet RAVE qui a pour but de faire des mesures spectroscopiques de vitesses radiales et de paramètres stellaires d'un million d'étoiles de l'hémisphère céleste Sud. Pour déterminer les caractéristiques cinématiques du disque, deux méthodes ont été utilisées l'inversion directe des comptages d'étoiles en fonction de la distance et de la vitesse et la modélisation cinématique du disque de la galaxie. Pour l'inversion, la distance photométrique des étoiles a été déterminée à partir de leur magnitude apparente, en faisant une sélection en couleur judicieuse. Les mouvements propres ont ensuite été transformés en vitesse. La méthode d'inversion directe a permis d'obtenir une décomposition cinématique du disque qui présente une nette séparation entre le disque mince et le disque épais. Cependant, cette méthode présente un certain nombre de biais. Le modèle cinématique combine les comptages en magnitude obtenus à partir du catalogue 2MASS avec les mesures de mouvements propres du catalogue UCAC2 et de vitesses radiales de RAVE. Ce modèle est un modèle auto-cohérent qui relie la densité d'étoiles aux dispersions de vitesse via le potentiel gravitationnel. La décomposition cinématique du disque galactique obtenu grâce au modèle montre clairement trois composantes : une première composante (disque mince) avec des dispersions de vitesses verticales compris entre 10 et 25 km.s−1, une deuxième (disque épais) avec des dispersions de [30−45] km.s−1 et une troisième (disque épais sousmétallique ou halo) avec une dispersion de 65 km.s−1. Les deux méthodes donnent une décomposition cinématique qui montre la même séparation cinématique entre les disques mince et épais. En conséquence, les scénarios qui envisagent la possibilité d'un disque mince initial qui aurait été « chauffé »par des nuages moléculaires ou par les bras spiraux sont exclus par ces résultats. D'autres mécanismes de formation du disque épais comme l'accrétion progressive d'étoiles venant de galaxies satellites ou le chauffage voire la création d'étoiles au moment de la rencontre entre une galaxie satellite importante et notre galaxie restent possibles.