A finalidade principal deste trabalho é o da obtenção de soluções numéricas de movimento de carga espacial livre em que as grandezas pertinentes dependem de mais de uma coordenada espacial (casos não unidimensionais). Mais especificamente, os problemas estudados versam sobre casos em que um eletródio plano a um dado potencial emite carga não uniformemente ao longo de sua extensão e procura-se obter a deformação das linhas de campo daí resultantes, no espaço até um outro eletródio aterrado disposto paralelamente ao primeiro. Um método baseado em soluções tentativas bem como um outro global usando a \"transformação hodográfica\" recentemente formulada por Budd e Wheeler são apresentados. E também realizado um estudo breve sobre a validade da muito empregada \"suposição de Deutsch\" / The aim of the present work is to obtain numerical solutions of free space charge motion in cases in which the pertinent quantites depend on more than one space coordinate (non uni-dimensional cases). More specifically, the problems under concern here are those in which a plane electrode, at a constant potential, emit charge in a non-uniform way along them and the resultant deformation of the field lines, in the space between it and another plane grounded electrode parallelly disposed, is looked for. A method based on guessed solutions and also a global one using the hodographic transformation recently developed by Budd and Wheeler are presented. A brief study of the validity of the often employed \"Deutsch assumption\" is also carried out

An affine transformation such as T(P)=Q is a locus of an affine conic. Any affine conic can be produced from this incidence construction. The affine type of conic (ellipse, parabola, hyperbola) is determined by the invariants of T, the determinant and trace of its linear part. The purpose of this thesis is to obtain a corresponding classification in the hyperbolic plane of conics defined by this construction.

<p>Photonic crystals are periodic structures that offers the possibility to control the propagation of light.</p><p>The revised plane wave method has been implemented in order to compute band structures for photonic crystals. The main advantage of the revised plane wave method is that it can handle lossless dispersive materials. This can not be done with a conventional plane wave method. The computational challenge is comparable to the conventional plane wave method.</p><p>Band structures have been calculated for a square lattice of cylinders with different parameters. Both dispersive and non-dispersive materials have been studied as well as the influence of a surface roughness.</p><p>A small surface roughness does not affect the band structure, whereas larger inhomogeneities affect the higher bands by lowering their frequencies.</p>

Extreme hurricane events of the past decade are responsible for several drag embedment anchor (DEA) mooring failures of mobile offshore drilling platforms stationed within the Gulf of Mexico. A proposed failure mechanism is caused by out-of-plane loading. The current status of DEA holding capacity is based on empirical design charts and does not include the effects of out-of-plane loading. Experimental modeling using a 1:10 scale generic DEA was performed at the Haynes Coastal Engineering Laboratory at Texas A & M University to examine the effects of out-of-plane load conditions. Instrumentation and specialized devices were constructed to measure the anchor's trajectory through a representative sample of Gulf of Mexico clay with average un-drained shear strength of 0.764 kPa (16 psf). The sediment basin allowed for drag distances of 4.87 m (16 ft) and an embedment depth of 1.37 m (4.5 ft). The measurements included pitch and roll of the anchor and line tension measured at the shank pad-eye. The variables modeled were fluke angle settings of 22°, 36° and 50°. The initial towline angle was varied from a minimum of 5° to upwards of 20°. Surface out-of-plane angles of 45° and 90° and embedment loading of 15°, 30° and 45° were examined. Curves of the ultimate holding capacity with respect to the out-of-plane towline angle and ultimate embedment depth were developed as functions of out-of-plane loading angles. Analysis of the rate effect indicates that a 46 percent increase in towing velocity causes an average 3 percent increase of holding capacity. The 50° fluke angle embeds an average of 0.7 fluke lengths deeper and has a holding capacity of 0.73 units greater than the 36° setting. The surface out-of-plane tests have a 5.1 percent reduction in holding capacity as the out-of-plane load angle increases from 45° to 90°. For all one fluke length initial towing distance tests, the ultimate holding capacity increases and the ultimate embedment depth decreases as the out-of-plane towing angle increases from 15° to 45°. The three fluke length initial towing distance tests indicate a contrasting trend, in that as the out-of-plane tow angle increases, both the ultimate holding capacity and ultimate embedment depth decrease.

This study focuses on the evaluation of seismic safety of masonry buildings in Turkey by using fragility curves. Fragility curves for masonry buildings are generated by two behavior modes for load bearing walls: in-plane and out-of-plane. By considering the previous research and site investigations, four major parameters have been used in order to classify masonry buildings with in-plane behavior mode. These are number of stories, strength of load-bearing wall material, regularity in plan and the arrangement of walls (required length, openings in walls, etc.). In addition to these four parameters, floor type is also taken into account for the generation of fragility curves by considering out-of-plane behavior mode. During generation of fragility curves, a force-based approach has been used. In this study there exist two limit states, or in other words three damage states, in terms of base shear strength for in-plane behavior mode and flexural strength for out-of-plane behavior mode. To assess the seismic vulnerability of unreinforced masonry buildings in Turkey, generated fragility curves in terms of in-plane behavior, which is verified by damage statistics obtained during the 1995 Dinar earthquake, and out-of-plane behavior, which is verified by damage statistics obtained during the 2010 Elazig earthquake, is combined. Throughout the analysis, ground motion uncertainty, material variability and modeling uncertainty have also been considered. In the final part of the study, a single-valued parameter, called as &lsquo / vulnerability score&rdquo / , has been proposed in order to compare the seismic safety of unreinforced masonry buildings in Fatih sub province of Istanbul and to assess the influence of out-of-plane behavior together with the in-plane behavior of these existing masonry buildings.

This thesis concerns the study of time reversal and plane-wave decomposition in various geophysical applications. Time reversal is a key step in seismic interferometry, reverse time migration and full waveform inversion. The plane-wave transform, also known as the tau-p transform or slant-stack, can separate waves based on their ray parameters or their emergence angles at the surface. I propose a new approach to retrieve virtual full-wave seismic responses from crosscorrelating recorded seismic data in the plane-wave domain. Unlike a traditional approach where the correlogram is obtained from crosscorrelating recorded data, which contains the full range of ray parameters, this method directly chooses common ray parameters to cancel overlapping ray paths. Thus, it can sometime avoid spurious arrivals when the acquisition requirement of seismic interferometry is not strictly met. I demonstrate the method with synthetic examples and an ocean bottom seismometer data example. I show a multi-scale application of plane-wave based full waveform inversion (FWI) with the aid of frequency domain forward modeling. FWI uses the two-way wave-equation to produce high-resolution velocity models for seismic imaging. This technique is implemented by an adjoint-state approach, which viii involves a time-reversal propagation of the residual wavefield at receivers, similar to seismic interferometry. With a plane-wave transformed gather, we can decompose the data by ray parameters and iteratively update the velocity model with selected ray parameters. This encoding approach can significantly reduce the number of shots and receivers required in gradient and Hessian calculations. Borrowing the idea of minimizing different data residual norms in FWI, I study the effect of different scaling methods to the receiver wavefield in the reverse time migration. I show that this type of scaling is able to significantly suppress outliers compared to conventional algorithms. I also show that scaling by its absolute norm generally produces better results than other approaches. I propose a robust stochastic time-lapse seismic inversion strategy with an application of monitoring Cranfield CO2 injection site. This workflow involves two steps. The first step is the baseline inversion using a hybrid starting model that combines a fractal prior and the low-frequency prior from well log data. The second step is to use a double-difference inversion scheme to focus on the local areas where time-lapse changes have occurred. Synthetic data and field data show the effectiveness of this method. / text

Photonic crystals are periodic structures that offers the possibility to control the propagation of light. The revised plane wave method has been implemented in order to compute band structures for photonic crystals. The main advantage of the revised plane wave method is that it can handle lossless dispersive materials. This can not be done with a conventional plane wave method. The computational challenge is comparable to the conventional plane wave method. Band structures have been calculated for a square lattice of cylinders with different parameters. Both dispersive and non-dispersive materials have been studied as well as the influence of a surface roughness. A small surface roughness does not affect the band structure, whereas larger inhomogeneities affect the higher bands by lowering their frequencies.

Thesis (M.S.)--Air Force Institute of Technology, 2007. / AFIT/GCA/ENV/07-M10. "March 2007." Title from title page of PDF document (viewed on: Nov. 15, 2007). Includes bibliographical references (leaves 37-39).

Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, June 2005. / Thesis Advisor(s): R.M. Howard, I.M. Ross. Includes bibliographical references (p. 215-217). Also available online.

L’objectif principal de cette étude est de développer des outils de simulation numérique pour évaluer la vulnérabilité des constructions en maçonnerie sous chargements variés. Ainsi, le comportement de la maçonnerie non armée sous chargement monotone en macro- et micro-échelles est étudié. La simulation du comportement non linéaire du mur de maçonnerie avant et après le pic et la capture de son mécanisme de rupture sont les points centraux de ce travail. Tout d'abord, le mur de maçonnerie d’un panneau est remplacé par deux barres simples utilisant la stratégie des macros-éléments et un comportement tri-linéaire est proposé pour évaluer la résistance à la rupture de la paroi ainsi que son comportement avant et après le pic. L'absence de l'information sur le mécanisme de rupture du mur de maçonnerie et la relation entre le mécanisme de rupture et les propriétés mécaniques des éléments barres dans ce type de modélisation conduisent à opter pour une autre description de ces structures à savoir la stratégie de micro-modélisation. Dans cette stratégie, les unités et les mortiers sont modélisés séparément et l’ensemble du comportement inélastique du mur de maçonnerie est supposé se produire dans les mortiers. Par conséquent, une attention particulière sera accordée au développement d'une description fiable des propriétés matérielles de ces éléments à l'aide d'une loi constitutive précise. La représentation tridimensionnelle d'un mur de maçonnerie faite dans ce travail, améliore la capacité des méthodes actuelles pour prédire le comportement de la maçonnerie sous les deux chargements en plan et hors du plan. D’abord, des enveloppes de rupture comprenant la tension limite et la surface de charge de Mohr-Coulomb sont assignées à l'élément d'interface du code éléments finis GEFDyn. Ensuite, la loi de comportement est améliorée en ajoutant un seuil de compression aux surfaces de charge pour inclure l’endommagement en compression de la maçonnerie à travers l'élément d'interface. Dans le nouveau modèle élastoplastique, les écrouissages négatifs des seuils de traction et de compression ainsi que la cohésion du mortier sont pris en considération. La capacité des deux modèles pour reproduire le comportement avant et après le pic de la résistance au cisaillement du mur de maçonnerie est vérifiée en comparant les résultats numériques avec les données expérimentales. L'importance de l’interaction entre les seuils de compression et celui du cisaillement est montrée en comparant les résultats obtenus avec ceux d'un test réel. Les résultats ont révélé que le second modèle est capable de simuler le comportement du mur de maçonnerie avec une bonne précision. Ensuite, l'effet des propriétés géométriques de la paroi telles que l’existence d’une ouverture et l'élancement, les propriétés des mortiers comme la cohésion, la résistance en traction et la résistance en compression ainsi que la contrainte verticale initiale dans le mur, sur la résistance latérale et le mécanisme de rupture des murs de maçonnerie est démontré. En outre, afin de présenter l’état d’endommagement, des indices de dommage, portant sur la longueur totale des fissures dans différentes rangées et colonnes de mortiers sont introduits et comparés pour différentes configurations. Les longueurs de glissement et d’ouverture de fissures dans les mortiers horizontale et verticale respectivement, sont les paramètres les plus importants qui contrôlent le comportement du mur. Enfin, la relation entre les profils de fissuration différents et les propriétés des matériaux y contribuant sont résumées dans un tableau. / The aim of this thesis is to develop numerical models for evaluating the vulnerability of unreinforced masonry construction under different types of loading. Therefore, the behavior of unreinforced masonry panels under monotonic loading in both macro- and micro- scales is studied. Simulating the nonlinear behavior of the masonry wall in pre and post-peak regions and capturing its failure mechanism is the main focus of this study. First, the masonry wall in the panel is substituted by two simple bars using the so-called macro-element strategy and a tri-linear behavior is proposed to assess the ultimate strength of the wall as well as its response before and after peak. The lack of information about the failure mechanism of the masonry wall and relation between the failure mechanism and mechanical properties of the bar elements in this type of modeling lead to another description of this structure namely micro-modeling strategy. In this strategy, units and mortars are modeled separately and all inelastic behavior of the masonry wall is supposed to happen in mortars. Hence, special attention is paid to development of a reliable description of material properties for these elements using an accurate constitutive law. Three dimensional representation of a masonry wall in this work enhances the capability of existing methods to predict the masonry behavior under both in-plane and out-of-plane loadings. Firstly, failure envelopes including tension cut-off and the Mohr-Coulomb yield surface are assigned to interface elements in GEFDyn finite element software. Then, the elstoplastic constitutive law is improved by adding a compression cap to the yield surfaces in order to include compressive failure of masonry in the interface element. In the new model, softening behavior for tensile and compressive strength as well as cohesion of mortar is considered. The ability of both models to reproduce the pre- and post-peak behavior of the masonry wall is verified by comparing the numerical results with experimental data. The importance of defining the compression failure of masonry by limiting the shear strength of the wall with its compressive strength is shown by comparing the obtained results with those of a real test. The results showed that the second model is capable to simulate the behavior of masonry wall with a good accuracy. Then, the effect of initial stresses and geometrical properties of the wall such as opening and aspect ratio and material properties of the mortar like its cohesion, tensile strength and compressive strength, on lateral strength and failure mechanism of the masonry walls are demonstrated. Moreover, in order to comprehend failure characteristics damage indexes based on the total length of cracks in different rows and columns of mortars are introduced and compared for different configurations. The lengths of sliding in horizontal mortars and opening in vertical ones are the most important parameters that control the behavior of the wall. Finally, the relation between different cracking profiles and contributing material properties are summarized into a table.