A two dimensional continuous numerical model based on Discrete Element Method is used to investigate the behaviour of accretionary wedges with different basal frictions. The models are based on elastic-plastic, brittle material and computational granular dynamics, and several characteristics of the influence of the basal friction are analysed. The model results illustrate that the wedge’s deformation and geometry, for example, fracture geometry, the compression force, area loss, displacement, height and length of the accretionary wedge etc., are strongly influenced by the basal friction. In general, the resulting wedge grows steeper, shorter  and higher, and the compression force is larger when shortened  above a larger friction basement.  Especially, when there is no basal friction, several symmetrical wedges will distribute symmetrically in the domain. The distribution of the internal stress when a new accretionary prime is forming is also studied. The results illustrate that when the stress in a certain zone is larger than a critical number, a new thrust will form there.

This dissertation demonstrates a procedure to view any quasitoric manifold as a “minimal” sub-manifold of an ambient quasitoric manifold of codimension two via the wedge construction applied to the quotient polytope. These we term wedge quasitoric manifolds. We prove existence utilizing a construction on the quotient polytope and characteristic matrix and demonstrate conditions allowing the base manifold to be viewed as dual to the first Chern class of the wedge manifold. Such dualization allows calculations of KO characteristic classes as in the work of Ochanine and Fast. We also examine the Todd genus as it relates to two types of wedge quasitoric manifolds. Background matter on polytopes and toric topology, as well as spin and complex cobordism are provided.

We study the hydrodynamics of wedge,knuckle and box cross-sectional profiles undergoing transient extreme motions, in particular forced entry and exit at constant velocity or acceleration. Extensive data for the forces, pressures and free-surface profiles is generated by an extension of a fully-nonlinear boundary-integral method. The code is thoroughly checked by altering the time step and particle spacing on the bodies and Lagrangian free-surface markers, and, for the wedge,checking self-similarity for the infinite Froude number (gravity free) constant velocity entry. Difficulties with inviscid flow around sharp corners are discussed. Results for exit are of particular interest since no zero-gravity approximation is valid and this precludes application of existing slamming theories in reverse. Whilst entry generally gives larger free-surface motions (spray jets), pressures and hence forces, calculation of exit is needed for the velocity of subsequent slamming and so is of practical interest too. These results are compared with an approximate analytical model, based on Schwarz-Christoffel transformations to calculate the infinite-frequency added mass of the cross-section below the mean water line. For constant acceleration of both entry and exit, the analytical theory is good during the early stages of motion. Later, the assumption of an undisturbed mean water level is clearly violated; the exact calculations show a large amount of draw-down (up-rise), the free-surface making contact with the body well below (above) the mean water level. We therefore examine the effect of reducing (increasing) the submerged body volume to take account of this, which prolongs the agreement between the results considerably and therefore might be used to improve practical calculation of extreme ship motions using existing strip theory codes. Full sets of numerical data input/output are provided in the appendices, together with some mathematical details. We also speculate on the possible application of John's equation to wedge entry.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23713号 / 理博第4803号 / 新制||理||1687(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 河上 哲生, 教授 田上 高広, 教授 下林 典正 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Information about tropical seabird communities is less abundant in the literature than for those that occur at higher latitudes. In research papers examining seabird breeding communities in tropical environments, it has been found that food availability was temporally and spatially variable in comparison to higher latitudes. This environmental variability would be expected to influence the life-history traits of tropical seabird species, and in turn, the structure of the communities in which they occur. To examine the impact of environmental variability upon the life-history traits and community structure of tropical seabirds, a comparative study of the breeding strategies of three tropical tern species and an outlier, shearwater species was carried out, at the Lowendal Islands, Western Australia (20o39’52S; 115o34’44E) between 1996 and 2000. Bridled Terns Sterna anaethetus and Wedge-tailed Shearwaters Puffinus pacificus shared the life-history traits of migration or dispersal from the breeding colony and east-Indian Ocean metapopulation when not breeding, a summer breeding schedule, nest-site fidelity, concealed nest-sites, clutch size of one, offshore and pelagic foraging regime, and protracted post-natal growth. Crested Terns Sterna bergii and Lesser Crested Terns Stern bengalenis bred within the same colony and shared the life-history traits of presence at the breeding colony when not breeding, an autumn breeding schedule, change in colony site each season, open dense nest-sites, brood size of one. inshore foraging regime (as well as offshore for Crested Terns) and rapid post-natal growth. It was found that each species experienced variation in nest-site occupancy and/or colony size, as well as variation in timing of breeding and breeding success between years. The effects upon each species seemed to operate independently, as concurrently breeding species did not appear affected by the same events, with the exception of cyclones. Late and/or poor breeding success in a species often coincided with oceanographic changes in the north-west region, such as fluctuations in the strength of flow and temperature of the Leewin Current. The Leewin Current is a warm water, low salinity current flowing southwards along most of the Western Australian coastline and has a stronger, warmer flow during El Nino Southern Oscillation (ENSO) events. Cyclone activity is also influenced by ENSO induced changes in the region’s water temperature. Changes in the Leewin Current affected the timing of breeding for Wedge-tailed Shearwaters, and feeding conditions for all study species, presumably as a result of changes in prey availability, while cyclone events delayed breeding for Crested Terns and Lesser Shearwaters in the years studied. Cyclone events were the most obvious cause of re-laying in the case of Crested Terns and Lesser Crested Terns, and breeding failure in the case of Bridled Terns and Wedge-tailed Shearwaters. Breeding failure was common among later breeders in the Crested Tern colonies. Breeding success was relatively high for lesser Crested Terns in all years studied, as they hatched and fledged their chicks within the Crested Tern colony among the first wave of breeders. There was some overlap in the diets and foraging grounds of the four study species. Crested terns and Lesser Crested Terns had the most similar diet, however, Crested Terns appeared to be the most opportunistic foragers, with the highest diversity of dietary prey, while Lesser Crested Terns diet consisted of a high proportion of atherinids. Bridled Terns has the next highest prey diversity, while half the diet of Wedge-tailed Shearwaters in this region, similar to conspecifics elsewhere, consisted of squid. Wedge-tailed Shearwaters were observed to be offshore and pelagic foragers. Their distribution in the waters surrounding the Lowendal Islands ranged to the full extent of observation transects(63 Km), and most likely beyond, excluding inshore waters (i.e. within 5 km of islands). They were not present in the vicinity of the Lowendal Islands when they were not breeding. Bridled Terns were observed to be offshore foragers, also ranging to the full extent of transects, and most likely beyond, occasionally including inshore waters. They were rarely observed when not breeding, with the exception of a small number of fledglings at the end of the breeding season. Crested Terns were observed to combine inshore and offshore foraging grounds, only ranging to the full extent of transects during their breeding season. Lesser Crested Terns were observed foraging inshore only. Chick provisioning, in terms of meal size and frequency, varied between years and within seasons for all species. It was demonstrated that there were differences in mean corrected meal sizes between years for Wedge-tailed Shearwaters, and the same was inferred from chick growth curves for Bridled Terns. Wedge-tailed Shearwaters provisioned their chicks with larger meal sizes and a higher occurrence of double feeds in 1996/97 than in other years studied. The amount of time spent feeding chicks in the burrow by Wedge-tailed Shearwaters adults became shorter as the breeding season progressed. It was demonstrated that all three tern species increased the meal size delivered to chicks as they grew. Wedge-tailed Shearwaters did not increase meal size as the season progressed, however they did increase feeding frequency. The feeding frequency of Crested Terns was highest in 1999, nearly doubling that observed in 1997 and 1998. In 1998 Lesser Crested Terns fed their chicks up to six times more frequently than Crested Terns. Chick growth varied for Wedge-tailed Shearwaters and Bridled Terns between seasons. Bridled Tern chicks grew more rapidly in 1997/98, were heavier and reached higher asymptotes for all linear parameters, the exception of wing length, than in 2000. On the other hand, Wedge-tailed Shearwater chicks grew more rapidly in 1999/2000 than in 1997/98, however, they attained similar asymototes for all parameters in both years. In the absence of repeat measures of same individuals, Crested Tern and Lesser Crested tern growth was examined using age categorization based on wing and tail feather development. Both species appeared to attain similar sizes at similar rates in each year. Wedge-tailed Shearwaters accumulated weight up to 30% in excess of mean adult weight in all seasons. This is a common trait exhibited in procellarigorms, and some weight loss occurs prior to fledging. It is suggested, based upon evidence from other studies in which weight loss prior to fledging was found to be water loss, that lipid accumulation acts as an insurance for the period after fledging when young are leaning to forage for themselves. The information gathered for this project found no direct evidence of competition among the species comprising the seabird community if Lowendal Islands. Niche overlap occurred amongst all species, particularly in the case of lesser Crested Terns and Crested Terns, which shared breeding phenology, breeding colonies, foraging grounds and dietary overlap. Niche overlap also occurred between Wedge-tailed Shearwaters and Bridled Terns, which shared breeding phenology and foraging grounds.

Os concretos refratários são materiais que apresentam estrutura complexa contendo uma fração de partículas finas (D < 100?m) chamada de matriz e outra mais grosseira da ordem de até centímetros compostas por agregados. Dentre as propriedades importantes durante a aplicação dos concretos refratários, este trabalho aborda principalmente a energia de fratura e a resistência à erosão. Para a avaliação dessas propriedades vários estudos vêm sendo desenvolvidos nos últimos anos. A introdução do método da cunha para propagação estável da trinca é um exemplo, pois este método é utilizado para materiais com estrutura grosseira, como é o caso dos concretos. Já em se tratando de resistência a erosão, pouco se encontra na literatura a respeito desse assunto para concretos refratários. Tendo em vista a aplicação destes materiais, foi avaliado o comportamento da energia de fratura e resistência à erosão de concretos refratário aluminoso convencional antierosivo utilizado na indústria petroquímica com o objetivo de correlacionar os resultados de energia de fratura e a resistência à erosão. Para o desenvolvimento do trabalho foram usados dois concretos a com mesma composição química, variando somente o tamanho de agregado. Foram avaliadas além da energia de fratura e da resistência à erosão outras propriedades foram avaliadas como: os módulos elástico e de ruptura, porosidade aparente, fases cristalinas e microestrutura, e ainda foi realizado um estudo da matriz do concreto. Os resultados mostraram que a energia de fratura aumenta com o aumento do tamanho de agregado para o concreto estudado e a resistência a erosão aumenta com a temperatura de tratamento térmico devido a ceramização da matriz, conforme análise das imagens. Em função dos resultados, pode-se concluir que não foi observada uma boa correlação entre energia de fratura e resistência à erosão. Mas esta correlação de energia de fratura e de resistência à erosão pode ter o mesmo comportamento que a correlação entre comprimento característico e resistência á erosão para faixas específicas de tamanho de agregado. / Castables materials are known to be formed by a complex microstructure containing a fine fraction known as matrix (D<100?m) and another one known as aggregate containing thicker particles up to centimeters in size. Among its most notable properties regarding application, this research primarily addresses to the fracture energy and its erosion resistance. In recent years, some studies have been performed concerning such assessments. As an example, the wedge splitting procedure has been applied in the stable crack propagation method used for some thicker structured materials evaluation such the castables ones. On the other hand, a few data have been gathered concerning castable\'s erosion resistance. Facing such applications the main goal was the study of conventional aluminous anti erosive castables once it has been used in the petrochemical industry in order to correlate fracture energy and erosion resistance results. On this research, two castables samples with the same chemical composition were tested differing only its aggregate particle grain sizes. Besides fracture energy and erosion resistance, other important properties were evaluated as following: elastic modulus, rupture modulus, apparent porosity, crystalline phases and a castable matrix study was also carried out. The results demonstrate an increase on fracture energy as the studied castable aggregate size also increases and according to images studied, the erosion resistance suffers another increment regarding the thermal treatment temperature increase due matrix ceramization. Based on the obtained results, it can be concluded that no observation was made regarding the fracture energy and erosion resistance but it may exist an energy correlation between them once there is some observed between the characteristic length and the erosion resistance concerning the aggregate size range.

La détermination de la tenue mécanique de points soudés est un enjeu industriel important, eten particulier dans le cas d’aciers à Très Haute Résistance. Actuellement, l’essai de tractionen croix est l’essai mécanique le plus répandu caractérisant la tenue des points soudés.Toutefois, l’étude de l’influence des différentes zones constituant le point soudé sur la tenueest difficile en se basant sur cet essai.Un essai d’enfoncement de coin a été développé afin de caractériser les ruptures interfacialesdes points soudés. Une section transverse d’un point soudé est observée tandis qu’un coin estinséré entre les deux tôles soudés. Une caméra CCD enregistre l'observation de lapropagation de la fissure.Le pliage limité des tôles durant la fissuration rend efficace la classification des différentspoints soudés par l'énergie totale dissipée par unité de surface rompue. De plus, la mesure insitu de l’angle d’ouverture de fissure caractérise la fissuration stable de la zone fondue. Dessimulations par éléments finis de l’essai sont conduites afin d’estimer un lien entre cesmesures et la rupture du matériau, modélisée par des zones cohésives.La rupture interfaciale de points soudés d’aciers DP et TRIP a été étudiée. Les mesuresexpérimentales permettent d’estimer les paramètres de modèles cohésifs représentatifs de larupture de la zone fondue, constituant des données fiables susceptibles d’être utilisées danstoute simulation numérique du comportement du point soudé. / Characterization of spot weld strength is a key industrial issue, particularly in the case of Advanced High Strength Steels. Today, the most widely used mechanical test evaluating this strength is the Cross Tensile Test. However, investigating the role of the different zones of one spot weld based on this test is difficult.A wedge test has been developed in order to characterize interfacial failures of spot welds. A cross section of one spot weld is observed while a wedge is inserted in between the two welded sheets. A CCD camera records the observation of the propagating crack. The limited sheet bending occurring during crack propagation allows the spot weld classification based on the total energy dissipated per unit fractured area to be efficient.Furthermore, the stable crack propagation is characterized by the in situ measurement of the crack opening angle. Finite element simulations of the test are carried out to estimate a relation between these measurements and the material resistance, approached by a cohesive zone model.Interfacial failures of spot welds of DP and TRIP steels have been investigated. The experimental measurements allow to estimate parameters of a cohesive zone model representative of the molten material failure, providing reliable and appropriate data for simulations of the mechanical behavior of the complete spot weld.

Doctor of Philosophy / Department of Mathematics / David R. Auckly / We study geometric variational problems for a class of models in quantum field theory known as Faddeev-Skyrme models. Mathematically one considers minimizing an energy functional on homotopy classes of maps from closed 3-manifolds into homogeneous spaces of compact Lie groups. The energy minimizers known as Hopfions describe stable configurations of subatomic particles such as protons and their strong interactions. The Hopfions exhibit distinct localized knot-like structure and received a lot of attention lately in both mathematical and physical literature. High non-linearity of the energy functional presents both analytical and algebraic difficulties for studying it. In particular we introduce novel Sobolev spaces suitable for our variational problem and develop the notion of homotopy type for maps in such spaces that generalizes homotopy for smooth and continuous maps. As the spaces in question are neither linear nor even convex we take advantage of the algebraic structure on homogeneous spaces to represent maps by gauge potentials that form a linear space and reformulate the problem in terms of these potentials. However this representation of maps introduces some gauge ambiguity into the picture and we work out 'gauge calculus' for the principal bundles involved to apply the gauge-fixing techniques that eliminate the ambiguity. These bundles arise as pullbacks of the structure bundles H[arrow pointing right with hook on tail]G[arrow pointing right]G/H of homogeneous spaces and we study their topology and geometry that are of independent interest. Our main results include proving existence of Hopfions as finite energy Sobolev maps in each (generalized) homotopy class when the target space is a symmetric space. For more general spaces we obtain a weaker result on existence of minimizers only in each 2-homotopy class.

The ‘missing wedge’ is a long-standing problem in electron tomography, caused by the use of slab-like flat specimens, which increase in thickness when tilted to high angles. Attempts have been made to reduce the undesirable effects caused by the missing wedge, but the problem remains, particularly for the radiation-sensitive frozen-hydrated specimens used for high resolution imaging. Specimens with cylindrical symmetry offer a way to overcome this problem, since the thickness remains constant at all viewing angles. However, while this has been suggested before, it has never been demonstrated for frozen-hydrated specimens. In this work, I present a way to make cylindrical specimens for electron cryo-tomography, using thin-walled carbon tubes as specimen holders. The tubes are made in a multi-step process, involving carbon deposition on glass micropipette templates and subsequent removal of the glass. Tube diameters are typically a few hundred nanometres, with a wall thickness of 10–20 nm. To make frozen-hydrated specimens, the tubes are filled with an aqueous sample and then plunge-frozen in liquid ethane. Electron images acquired from the tubes have equal quality at all viewing angles, with a tilt range restricted only by the physical limits of the microscope. Tomograms from specimens such as gold particles and liposomes show that the effects of the missing wedge are substantially reduced, with much improved resolution along the electron beam axis. Structural features oriented in all directions are visible in the reconstructions, in marked contrast to tomograms acquired over a more restricted angular range. These results are promising, however some technical challenges remain before this method can be used routinely.

This work deals with tax wedges (effective tax rates) for businesses in the Czech Republic. The goal is to use a methodology for measuring the tax wedges for analysis of tax burden on particular business in period 2004 to 2008. Effective tax rate particular firm is compared with the effective tax rates of enterprises in the Czech Republic and the European Union. To achieve that goal literature review, analysis and comparison method are used. The results of the analysis showed that the particular firm had at the beginning of the period a very high tax burden compared to the statutory tax rate. During the period, however, the effective tax rate of the company significantly reduced and thereby was closer to statutory tax rate. The company had a lot of nondeductible expenses which most significantly contributed to the high tax burden. Tax on corporate income for companies is included in the costs, so the company should try to minimize this expense and thereby reduce the effective tax rate.