There is an old saying, that after Epaminondas nothing was ever the same again. In this thesis I will focus on three questions: "Epaminondas the man." Who was he? "Epaminondas the general." How did he change the technique of warfare that made it possible to beat the Spartans? "Epaminondas, founder of cities and wall-builder." How did he build the walls around the cities he initiated, that made them resist enemy attacks for many years to come? While seeking the answers to yhese questions I will make a contextual analysis to get the historical background to all the phenomina involved.

Le Golfe d'Aden sépare la plaque Somalie de la plaque Arabie. Il constitue un objet d'étude intéressant pour la compréhension du développement des marges continentales passives. Le rifting débute vers 35 Ma et l'accrétion se développe à partir de 17,6 Ma dans la zone étudiée. De plus, la direction d'ouverture du Golfe d'Aden est fortement oblique par rapport à sa direction. Sur la marge nord-est, la campagne Encens (N/O l'Atalante, 2006) a permis l'acquisition de nouvelles données de sismique réflexion 360 traces, notamment sur le segment de premier ordre entre les zones de fracture d'Alula-Fartak et de Socotra. À la segmentation de premier ordre (zones de fracture) s'ajoute une segmentation de second ordre qui présente des structures et des morphologies différentes selon les segments, notamment au niveau de la transition océan-continent (TOC). Les segments étudiés suggèrent que la partie ouest de la zone d'étude (segment d'Ashawq-Salalah) est caractérisée par un magmatisme post-rift conséquent tandis que la partie orientale de la zone d'étude (segment de Mirbat) possède une morphologie qui semble être fortement tectonisée. L'évolution tectono-stratigraphique du segment d'Ashawq-Salalah a pu être étudiée en détail (migration avant sommation profondeur et corrélation terre-mer des processus sédimentaires). La marge est tout d'abord structurée par des grabens et des horsts syn-rift. Puis on observe une localisation de la déformation sur la marge distale. Au début de la formation de la TOC, un soulèvement local ou régional induit un glissement de terrain au sommet du horst le plus distal. La déformation crustale est alors localisée dans la TOC, où la rupture continentale va finalement se produire. La nature de la TOC pourrait être du manteau serpentinisé, postérieurement intrudé par du matériel magmatique pendant la période post-rift. La couverture sédimentaire à proximité de la TOC montre qu'elle subit une surrection pendant le post-rift en relation avec la mise en place d'un volcan et des coulées et sills associés. Cette évolution peut être comparée aux modèles d'évolution les plus récents des marges passives. La marge conjuguée (au sud-est du Golfe d'Aden) présente la même segmentation que la marge nord-est (d'Acremont et al., 2005). Une analyse microstructurale de l'île de Socotra (marge sud émergée) permet de comparer les marges et de mieux contraindre le rifting oblique. Comme sur la marge nord, les directions des failles normales sont réparties en trois familles : N110°E perpendiculaire à l'extension, N70°E parallèle à la direction du Golfe, N90°E intermédiaire. L'inversion des données microstructurales montre des directions d'extension en accord avec les trois familles de failles. Des chronologies sont observées depuis une direction d'extension N20°E vers N160°E et réciproquement. Les variations de la direction d'extension suggèrent une alternance des champs de contraintes pendant la phase de rifting du Golfe d'Aden. Des modélisations analogiques dans le Golfe d'Aden ont permis de mieux cerner son développement en rifting oblique. Les horsts et les grabens sont disposés en échelons, avec des formes sigmoïdes. Les trois familles de failles liées à l'obliquité sont observées : N110°E, N90°E et N70°E. L'évolution des directions des failles montre une dominance des failles N90°E et N110°E au début de l'extension puis le développement plus tardif de failles N70°E et ce, avec ou sans la présence initiale d'une hétérogénéité oblique à l'extension. Enfin des failles N110°E sont de nouveau formées. Le modèle conceptuel de Bellahsen et al. (2006) serait donc applicable pour les premiers stades d'évolution : la réactivation de bassins N110°E et la formation de nouvelles failles en échelons s'effectuent sous la direction d'extension des plaques (N20°E) depuis 35 Ma. Puis l'amincissement de la lithosphère se poursuivant le long de la direction du Golfe (N70°E), les contraintes locales dues aux variations latérales d'épaisseur provoquent la formation de failles N70°E et la réactivation de failles N110°E. La chronologie d'extension N20°E puis N160°E observée sur les marges est donc expliquée. Nous proposons une troisième étape : une fois l'amincissement du rift suffisamment important, les contraintes locales ne s'exercent que sur les bords du rift ou sur les horsts majeurs. Partout ailleurs des failles N110°E sont formées et les failles N70°E sont réactivées de manière oblique. La seconde chronologie d'extension N160°E puis N20°E des études microstructurales est aussi expliquée. Les horsts peuvent subir des rotations horaires importantes qui induisent des zones de cisaillement senestres. Elles pourraient initier les nombreuses zones de transfert concordant avec la forte segmentation du le Golfe d'Aden.

Esta tesis se dedica en un estudio de estabilidad no lineal de la morfodinàmica de la zona de rompientes de playas de arena. El modelo numérico MORFO55 resuelve las ecuaciones de aguas someras no lineales para la hidrodinámica y actualiza la topografía a partir del transporte de sedimento. En primer lugar, se aplica en el caso de playas complejas longitudinalmente no uniformes con objeto de probar sus distintas formulaciones. En secundo lugar, se usa para estudiar la generación de estructuras rítmicas en playas longitudinalmente uniformes. Entre estos patrones se distinguen las barras transversales y oblicuas, las barras crescenticas y los sistemas de barras/surcos (ridges/runnels). La hipótesis de que emergen a partir de inestabilidades internas del acoplamiento entre la topografía y la hidrodinámica se investiga. Los estudios previos de modelización numérica se limitaban a las etapas iniciales de la generación de las barras. En particular, mostraban que las barras transversales y oblicuas pueden formarse en playas planas mientras que las barras crecenticas aparecen en playas con barra. La formación de los sistemas de barras/surcos se explica con modelos conceptuales de la observación mediante satélite según los cuales emergerán a partir de la deformación de la barra intermareal. Esta tesis estudia el régimen no lineal de la evolución de todos estos sistemas. Particularmente se obtiene un estado 'nal de equilibrio. Los resultados generales coinciden cualitativamente con las barras observadas en la naturaleza. Se da una interpretación física de la formación, de la evolución y de la saturación del crecimiento de las barras. / This thesis performs a nonlinear stability study of the surf zone morphodynamics of sandy beaches. To this end the MORFO55 model based on a wave and depth averaged nonlinear shallow water equations solver with wave driver, sediment transport and bed updating is presented. It is first applied to complex longitudinally non-uniform beaches in order to test different model formulations. Second, it is applied to study the generation of surf zone rhythmic features on alongshore uniform beaches. Shore-attached transverse or oblique bars, crescentic bars and ridge and runnel systems are well known examples of such features. The hypothesis that they emerge by self organisation of the coupling between topography, waves and currents is here tested. In absence of shore-parallel bars, the initial formation of transverse and oblique bars had been shown by previous modelling studies of linear stability analysis but is now extended to the finite amplitude regime. In most of barred beaches, crescentic bars and ridge and runnel systems appear. Conceptual models based on field observations suggest that ridges and runnels could emerge by the deformation of the alongshore intertidal bar intercepted by crescentic bars. Up to now, only the formation of crescentic bars had numerically succeeded with linear and non linear models. This study shows that a dynamical equilibrium state of each of these rhythmic bar systems may be described with a numerical model. General results are in qualitative agreement with the bar systems observed in nature. A physical explanation for their formation, their evolution and the saturation of their growth is given.

We propose a clustering algorithm which incorporates a similarity-based fuzzy clustering and principal component analysis. The proposed algorithm is capable of discovering clusters with hyper-spherical, hyperellipsoidal, or oblique hyper-ellipsoidal shapes. Besides, the number of the clusters need not be specified in advance by the user. For a given dataset, the orientation, locations, and the number of clusters obtained can truthfully reflect the characteristics of the dataset. Experimental results, obtained by running on datasets generated synthetically, show that our method performs better than other methods.

In this thesis, it is aimed to determine the ballistic limit thicknesses of ST-37 steel plates under oblique impact of bullets having hard steel core (DIN 100Cr6 at 61-62 HRc) by using both experimental and numerical methods. In experimental part, angles of attack of the bullets are changed from 0 to 70 degrees by 10 degrees increments. Bullet velocities are measured for each shot just before the impact and they are found to be between 790-830 m/s. The minimum plate thickness that is not perforated and the maximum plate thickness that is perforated are determined by conducting three shots for each angle of attack - plate thickness combination. After the monolithic case, for some angles, layered plate combinations are also investigated. In the numerical analysis part, Johnson Cook constitutive and failure models are used together with the data obtained from literature. Experiments are simulated numerically by using a commercial non-linear explicit hydrocode software package, ANSYS AUTODYN. Results of the numerical simulations and the experimental findings are presented in tabular and graphical forms and then compared to each other.

In orthogonal frequency division multiplexing (OFDM) systems, when transmitted blocks of signal through the multipath channel, the present transmitted blocks of signal will be interfered by the previous one due to the effect of channel delay spread. In order to solve this problem, conventionally we introduce a guard interval in transmitted blocks of signal to avoid inter-block interference (IBI). The most popular methods of the guard interval insertion are zero-padding (ZP) and cyclic prefixing (CP). ZP insert the guard interval at the end of the transmitted blocks of signal, in which all elements are zeros. The length of this interval must be equal to or greater then the channel order. In this way we can avoid IBI, at the expense of lossing the orthogonality between subcarrier due to the multipath channel. However, we can use CP to cope whit this problem. In CP we copy the 25% length at the end of the transmitted blocks of signal, and put it in front of the transmitted block to suppress the inter-block interference and inter-carrier interference. In this thesis, we consider OFDM system without the guard interval, hence the received signal contains IBI and ICI. In our proposed scheme, we use an oblique projector (OB) to suppress IBI at first. Then we combine it with a generalized sidelobe canceller (GSC) based equalizer [1] for ICI supppression and demodulate the receiver signal. In computer simulations, we use the GSC-based equalizer with oblique projector to suppress IBI/ICI in the time-invariant channel and time-varying channel. As we will see, in the CP-free OFDM system, the oblique projector can suppress IBI exactly. Moreover we can get better performance in channel with larger order.

Specific defence of interests of a creditor, as a distinct legal institute, as yet has lacked any systematic analysis, therefore many practical questions regarding due application of the said remedies arise. The target of this final paper is thorough and systematic analysis of all three specific defences of creditor’s interests, including the analysis of application requirements, the nature and essence, the aims of the said remedies, also including comparative analysis of the similar remedies established in other countries in order to reveal the nature of the specific defences of creditor’s interests, to provide with practical advice and proposals regarding more efficient application of the said remedies in practice. Summarizing the studied judicial practice of the Supreme Court of Lithuania and the Appeal Court of Lithuania, relevant laws, scientific articles, monographs, official commentaries to laws, internet resources and the legal regulation of the other countries on these issues, the specific defences of creditor’s interests (actio Pauliana, oblique action, right of retention) provided in the Civil Code are important creditor’s additional remedies to defend his interests and the efficient application of such remedies ensures the defence of violated interests.

In this study, numerical investigations of stability and transition problems were performed for 2D compressible boundary layers over a flat plate in adiabatic wall condition. Emphasis was placed on linear stability theory. The mathematical formulation for 3D boundary layers with oblique waves including detailed theoretical information was followed by use of the numerical techniques for the solution of resulting differential system of the instability problem, consequently an eigenvalue problem. First, two-dimensional sinusoidal disturbances were analyzed at various Mach numbers including the subsonic, transonic, supersonic and even hypersonic flow speeds. In this case, the second mode (acoustic mode), namely the Mack mode, and its behavior with the increasing Mach number were visualized. The results were then compared with the available data in literature concluding with good agreements. Secondly, similar analysis was carried out for oblique waves. Here, not only the effect of flow speed but also the effect of wave orientation was demonstrated. For this purpose, instability problem was solved for several wave angles at each Mach number in the range of M=0 and M=5. In this respect, the angle at which the waves were most unstable was also obtained at each investigated flow speed. The resultant stability diagrams corresponding to M=4 and higher Mach numbers for which both first and the second modes appear revealed that plane waves were more stable than oblique waves for the Tollmien-Schlichting mode, however, this was the opposite for the acoustic mode where oblique waves were observed to be more stable. As a final step, estimation of the transition location was handled for the most unstable wave condition. Smith-Van Ingen transition method was applied as the prediction device. The results representing the influence of Mach number on transition Reynolds number were then compared with the experimental data as well as the numerical ones in literature ending up with very good agreements.

Over the past several decades increasing focus has been paid to the impact of structures where energy, during the impact event, needs to be absorbed in a controlled manner. This has led to considerable research being carried out on energy absorbers, devices designed to dissipate energy during an impact event and hence protect the structure under consideration. Energy absorbers have found common usage in applications such as vehicles, aircraft, highway barriers and at the base of lift shafts. A type of energy absorber which has received relatively limited attention in the open literature is the tapered rectangular tube. Such a structure is essentially a tube with a rectangular cross-section in which one or more of the sides are inclined to the tube's longitudinal axis. The aim of this thesis was to analyse the impact and energy absorption response of tapered and non-tapered (straight) rectangular tubes. The energy absorption response was quantified for both axial and oblique loading, representative of the loading conditions typically encountered in impact applications. Since energy absorbers are commonly used as components in energy absorbing systems, the response of such a system was analysed which contained either straight or tapered rectangular tubes as the energy absorbing components. This system could typically be used as the front bumper system of a vehicle. Detailed finite element models, validated using experiments and existing theoretical and numerical models, were used to assess the energy absorption response and deformation modes of straight and tapered tubes under the various loading conditions. The manner in which a thin-walled tube deforms is important since it governs its energy absorption response. The results show that the energy absorption response of straight and tapered rectangular tubes can be controlled using their various geometry parameters. In particular, the wall thickness, taper angle and the number of tapered sides can be effectively used as parameters to control the amount of absorbed energy. Tapered rectangular tubes display less sensitivity to inertia effects compared with straight rectangular tubes under impact loading. This is beneficial when the higher crush loads associated with inertia effects need to be reduced. Furthermore, though the energy absorption capacity of thin-walled rectangular tubes diminishes under oblique impact loading, the capacity is more maintained for tapered rectangular tubes compared with non-tapered rectangular tubes. Overall, the results highlight the advantages of using tapered rectangular tubes for absorbing impact energy under axial and oblique loading conditions. Understanding is gained as to how the geometry parameters of such structures can be used to control the absorbed energy. The thesis uses this knowledge to develop design guidelines for the use of straight and tapered rectangular tubes in energy absorbing systems such as for crashworthiness applications. Furthermore, the results highlight the importance of analysing thin-walled energy absorbers as part of an energy absorbing system, since the response of the absorbers may be different to when they are treated on their own.

This thesis presents and evaluates different methods to semantically segment 3D-models by rendered 2D-views. The 2D-views are segmented separately and then merged together. The thesis evaluates three different merge strategies, two different classification architectures, how many views should be rendered and how these rendered views should be arranged. The results are evaluated both quantitatively and qualitatively and then compared with the current classifier at Vricon presented in [30]. The conclusion of this thesis is that there is a performance gain to be had using this method. The best model was using two views and attains an accuracy of 90.89% which can be compared with 84.52% achieved by the single view network from [30]. The best nine view system achieved a 87.72%. The difference in accuracy between the two and the nine view system is attributed to the higher quality mesh on the sunny side of objects, which typically is the south side. The thesis provides a proof of concept and there are still many areas where the system can be improved. One of them being the extraction of training data which seemingly would have a huge impact on the performance.