The presented diploma thesis deals with a problem of a generalized stress intensity factor determination and a consecutive study of stress distribution around the bimaterial notch tip, combining analytical and numerical methods. This task is possible to sectionalize into three parts. The first part is dedicated to the fundamentals of the linear fracture mechanics and the mechanics of composite materials. The second part deals with methods of anisotropic plane elasticity solution. Pursuant to the solution the computational models in the third part are created. The first model makes for determination of a singularity exponent eigenvalue by dint of Lekhnitskii-Eshelby-Stroh formalism. The second model makes for determination of the generalized stress intensity factor using psi-integral method, which is based on the Betti reciprocal theorem. All needed calculation are performed in the software ANSYS 12, Maple 12 and Silverforst FTN95. Results will be compared with the values obtained from a direct method of the generalised stress intensity factor determination.

Les personnes vivant avec une lésion de la moelle épinière (LMÉ) subissent une réduction drastique de leurs capacités sensori-motrices en dessous du niveau de la lésion. Cette pathologie influence négativement leur contrôle postural, vu comme le résultat de contributions actives, passives et neuronales. Une approche par modèle est choisie afin de représenter ces différentes contributions et mieux comprendre le contrôle postural en position assise. Deux problèmes apparaissent. Tout d’abord les modèles existants de la position assise sont très rares et inapplicables à l’étude des personnes vivant avec une LMÉ qui, dans l’absence de contrôle musculaire au niveau du tronc, vont utiliser leurs membres supérieurs pour s’équilibrer. De plus, les équations non linéaires sous forme descripteur des modèles biomécaniques existant sont linéarisées dans la majorité des cas afin de simplifier les équations obtenues ce qui n’est plus valable dans le cas de mouvements de grande amplitude. Or des travaux récents fournissent des outils pour analyser ces modèles en utilisant le formalisme de Takagi-Sugeno issu de la logique floue. Ce travail est focalisé sur l’étude du contrôle postural des personnes vivant avec une LMÉ par des outils de l’automatique non linéaire, trois objectifs sont définis : 1. Proposer des modèles biomécaniques non linéaires de la stabilité en position assise pour les personnes vivant avec une LMÉ. 2. Utiliser des méthodes d’écriture de modèle du domaine de l’automatique non linéaire afin de créer les outils nécessaires à l’estimation des variables internes (non mesurées) au modèle. 3. Améliorer la connaissance de la stabilité chez les personnes vivant avec une LMÉ par l’estimation expérimentale d’efforts internes en fonction de paramètres personnels et des conditions expérimentales. Les modèles créés dans ce manuscrit sont, à notre connaissance, les premiers à représenter la stabilité assise en considérant le déplacement des membres supérieurs. Il s’agit également des premiers modèles biomécaniques à utiliser les avancées récentes de l’automatique non linéaire pour l’estimation d’efforts internes non mesurables. / The ability to maintain stability in an unsupported sitting position often becomes challenging after an individuals is affected by a spinal cord injury (SCI). In order to better understand sitting postural control as a combination of active, passive and neuronal contribution, a modelling approach is chosen. Two problems arise; first of all, existing models of sitting control are very scarse and inapplicable to people living with a SCI who will use their upper in a compensatory strategy to balance their trunk. Moreover, the majority of biomechanical models nonlinear equations are linearized with small angle hypothesis for an easier processing which is not acceptable when movements become large. Recent advances in nonlinear control theory provide the theoretical tools for the creation of nonlinear observers using the Takagi-Sugeno fuzzy formalism. This work aims at the study of postural control for people living with a SCI by use of nonlinear tools from control theory; three main goals are formulated: 1. Creating new nonlinear biomechanical models aiming at the study of sitting stability of people living with SCI. 2. Using tools coming from nonlinear control theory to estimate model unmeasured variable 3. Improve the current knowledge on stability for people living with a SCI by estimating internal efforts depending on personal parameters in experimental conditions. The models created in this manuscript are, to the best of our knowledge, the first to consider the upper limbs displacement for the control of sitting stability and the first biomechanical models to use the recent advances in nonlinear control theory for the estimation of unmeasured variables.

Cette thèse explore des aspects du monde naturel par la lentille de l'information algorithmique. La notion de l'émergence, intuitivement reliée à tant de phénomènes naturels, se voit offrir une définition cadrée dans le domaine plus spécifique des statistiques algorithmiques. Capturant toutes deux l'organisation non triviale d'un objet, la sophistication et la profondeur logique sont relativisées à un objet auxiliaire puis remises en relation. Enfin, des modèles proposant une description locale des systèmes quantiques sont démontrés équivalents, ont leur coût de description quantifié et sont généralisés aux systèmes continus. / This thesis explores aspects of the physical world through the lens of algorithmic information. The notion of emergence, intuitively linked to many natural phenomena, is offered a definition framed in the field of algorithmic statistics. Both capturing non-trivial organization of an object, sophistication and logical depth are compared once relativized to an auxiliary object. Finally, models proposing a local description of the quantum systems are shown equivalent, have their description cost quantified and are generalized to continuous systems.

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This study examines the specific aspects of the reception of Russian formalism and the development of the Formal method in Soviet Ukrainian culture in the 1920s - the beginning of 1930s. Russian formalism in the process of reception becomes an important tool for the "modernization" of national culture and, as a result, an instrument for a new phase in the construction of national cultural identity. On that basis, the cultural-historical and ideological context of the development of Ukrainian literary criticism, criticism and (partially) literature of the late 19th - first decades of the 20th century is consistently reconstructed in eight chapters of the work. The first chapter highlights theoretical aspects of the study, reviews critical literature, reconstructs the history of reception of Russian formalism in Russian and Western criticism and the history of literature. The second chapter addresses the historical and theoretical premises of the reception of Formal theory in Ukrainian culture. The next chapter discusses historical and political context of the development of literature and literary criticism in 1917-1920 using the example of multinational post-revolutionary Kiev; a brief review of the theoretical and historical works of the 1920s also appears here. A special focus is put on the...

Carbon-based conductors like carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) have many properties, which make them relevant for potential electronic applications. Among them are high conductances and tunable band gap sizes. These properties make CNTs and GNRs useful in many circumstances, e.g. as channel material in transistors or transparent electrodes in solar cells. Plenty of literature can be found on the topic of single linear CNTs/GNRs. Some applications however require a large network of these conductors. In addition, a single conductor has only a small impact on the network conductance, which reduces the need to control the properties of each individual nanotube/-ribbon. This leads to networks being easier to apply. In this work, the conductance of large networks of GNRs is calculated using the quantum-transport formalism (QT). This has not been done before in literature. In order to apply QT to such a large amount of atoms, the recursive Green's function formalism is used. For this the networks are devided into subcells, which are represented by tight-binding matrices. Similar networks are also examined using two different nodal analysis (NA) approaches, where the nanoribbons are treated as ohmic conductors. For NA with one-dimensional conductors, major discrepancies are found in regards to the QT model. However, networks consisting of two-dimensional conductors (NA-2D) have many properties similar to the QT networks. A recipe to approximate the QT results with NA-2D is presented.:1. Introduction 2. Theoretical Principles 2.1 Carbon-based Conductors 2.1.1 Structure and Properties 2.1.2 Networks 2.2 Tight-Binding Model 2.3 Quantum Transport 2.3.1 Introduction 2.3.2 Level Broadening 2.3.3 Current Flow 2.3.4 Transmission 2.4 Nodal Analysis 3. Implementation 3.1 Quantum Tranport 3.1.1 Network Generation 3.1.2 Density-Functional based Tight-Binding Method 3.1.3 Recursive Green's Function Algorithm 3.1.4 Conductance 3.2 Nodal Analysis 3.2.1 One-dimensional Conductors 3.2.2 Two-dimensional Conductors 4. Results 4.1 Quantum Transport 4.1.1 Band Structures and Fermi Energies 4.1.2 Ideal Transmission and Consistency Tests 4.1.3 Percolation 4.1.4 Transmission 4.1.5 Conductance 4.1.6 Power Law Scaling 4.1.7 Size Dependence and Confinement Effects 4.1.8 Calculation Time 4.2 Nodal Analysis 4.2.1 One-dimensional Conductors 4.2.2 Two-dimensional Conductors 4.2.3 Calculation Time 4.3 Approximating QT with NA 4.3.1 Optimal Parameters 4.3.2 Percolation 4.3.3 Conductance 4.3.4 Power Law Scaling 5. Conclusions / Graphenbasierte Leiter wie Kohlenstoff-Nanoröhrchen (engl. 'carbon nanotubes', CNTs) oder Graphen-Nanobänder (engl. 'graphene nanoribbons', GNRs) haben viele Eigenschaften, die sie für potenzielle elektronische Anwendungen interessant machen. Darunter sind hohe Leitfähigkeiten und einstellbare Bandlückengrößen. Dadurch sind CNTs und GNRs in vielen Bereichen nützlich, z.B. als Kanalmaterial in Transistoren oder als transparente Elektroden in Solarzellen. Es gibt viel Literatur über einzelne, lineare CNTs/GNRs. Einige Anwendungen benötigen jedoch ein großes Netzwerk dieser Leiter. Zusätzlich hat ein einzelner Leiter wenig Einfluss auf die Leitfähigkeit des Netzwerks, wodurch die Eigenschaften der einzelnen Nanoröhrchen/-streifen weniger streng kontrolliert werden müssen. Dies führt dazu, dass es einfacher ist Netzwerke zu nutzen. In dieser Arbeit wird die Leitfähigkeit von großen GNR-Netzwerken mittels Quantentransport (QT) berechnet. Dies wurde in der Literatur noch nicht getan. Um QT auf eine so große Menge an Atomen anzuwenden wird der rekursive Greenfunktions-Formalismus benutzt. Dazu werden die Netzwerke in Unterzellen unterteilt, die durch Tight-Binding-Matrizen dargestellt werden. Ähnliche Netzwerke werden auch mit zwei Versionen der Knotenanalyse (engl. 'nodal analysis', NA) untersucht, welche die Nanobänder wie ohmische Leiter behandelt. Die Ergebnisse der NA mit eindimensionalen Leitern weisen deutliche Unterschiede zu den mit QT erzielten Ergebnissen auf. Wenn jedoch zweidimensionale Leiter in NA verwendet werden (NA-2D) gibt es viele parallelen zu den QT Ergebnissen. Zuletzt wird ein Vorgehen präsentiert, mit dem QT Resultate durch NA-2D Rechnungen genähert werden können.:1. Introduction 2. Theoretical Principles 2.1 Carbon-based Conductors 2.1.1 Structure and Properties 2.1.2 Networks 2.2 Tight-Binding Model 2.3 Quantum Transport 2.3.1 Introduction 2.3.2 Level Broadening 2.3.3 Current Flow 2.3.4 Transmission 2.4 Nodal Analysis 3. Implementation 3.1 Quantum Tranport 3.1.1 Network Generation 3.1.2 Density-Functional based Tight-Binding Method 3.1.3 Recursive Green's Function Algorithm 3.1.4 Conductance 3.2 Nodal Analysis 3.2.1 One-dimensional Conductors 3.2.2 Two-dimensional Conductors 4. Results 4.1 Quantum Transport 4.1.1 Band Structures and Fermi Energies 4.1.2 Ideal Transmission and Consistency Tests 4.1.3 Percolation 4.1.4 Transmission 4.1.5 Conductance 4.1.6 Power Law Scaling 4.1.7 Size Dependence and Confinement Effects 4.1.8 Calculation Time 4.2 Nodal Analysis 4.2.1 One-dimensional Conductors 4.2.2 Two-dimensional Conductors 4.2.3 Calculation Time 4.3 Approximating QT with NA 4.3.1 Optimal Parameters 4.3.2 Percolation 4.3.3 Conductance 4.3.4 Power Law Scaling 5. Conclusions

The work focuses on the analysis of the poetics of Vladimir Nabokov's novel Invitation to a Beheading in terms of its cultural context. Specifically deals with its relation to the Soviet theatrical avant-garde, with mythopoetic symbolism and early avant-garde. We approach to the novel as a parody of the post-revolutionary avant-garde Soviet theater experiments. Special attention is paid to the fact that due to the theatralization of the text, i.e. assimilation of the novel space with the theatricals, diegesis of Invitation to a Beheading is divided into two equal opposing worlds, each of which represents particular poetics. World built around main character of Cincinnatus is comparable to symbolism, namely to the symbol and symbolistic perception of Andrei Bely. The central principle of this reality is semiotization of the world. The surrounding fictional world creates its opposite as it is shaped by the principle of desemiotization which - as a central aspect of formalistic-futuristic avant- garde - systematically dismantles hero's world. However neither of these worlds is winning. In the end it is the synthesis, which helps the hero get emancipated from the novel's world. The Invitation to a Beheading can therefore be interpreted as original artist's world manifesto which through presentation and...

The Bondi-Metzner-Sachs-van der Burg (BMS) group is the asymptotic symmetry group of radiating asymptotically flat spacetimes. It has recently received renewed interest in the context of the flat holography and the infrared structure of gravity. In this thesis, we investigate the consequences of considering extensions of the BMS group in four dimensions with superrotations. In particular, we apply the covariant phase space methods on a class of first order gauge theories that includes the Cartan formulation of general relativity and specify this analysis to gravity in asymptotically flat spacetime. Furthermore, we renormalize the symplectic structure at null infinity to obtain the generalized BMS charge algebra associated with smooth superrotations. We then study the vacuum structure of the gravitational field, which allows us to relate the so-called superboost transformations to the velocity kick/refraction memory effect. Afterward, we propose a new set of boundary conditions in asymptotically locally (A)dS spacetime that leads to a version of the BMS group in the presence of a non-vanishing cosmological constant, called the Λ-BMS asymptotic symmetry group. Using the holographic renormalization procedure and a diffeomorphism between Bondi and Fefferman-Graham gauges, we construct the phase space of Λ-BMS and show that it reduces to the one of the generalized BMS group in the flat limit. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

One-nucleon halo nuclei are exotic nuclei which can be seen as a core around which orbits a loosely-bound valence nucleon. They are usually studied through reactions such as elastic scattering and breakup. The ratio method has been developed as a tool to study one-neutron halo nuclei at high energies. It consists of the ratio of angular cross sections, breakup and elastic scattering, which removes most of the sensitivity to the reaction mechanism and to the reaction model. In the simple recoil excitation and breakup (REB) model, the ratio simplifies to a form factor dependent solely on the wave function of the projectile. By measuring this observable and comparing it to the REB form factor, i.e. in the ratio method, more detailed information on the structure of the halo could be obtained. For neutron-halo nuclei at high energy, the ratio observable obtained from accurate CDCC and DEA theoretical calculations follows its REB prediction. I study the extension of this method to lower energies of the reaction which could make the measurement appropriate to facilities such as SPIRAL2 (GANIL, Caen, France) and ReA12 at FRIB (Michigan State University) and to proton halos. This is done by comparing the REB form factor to dynamical calculations of the ratio. The reactions investigated are the reaction of 11Be, the archetypical one-neutron halo nucleus, on 12C, 40Ca and 208Pb targets at 20 MeV/nucleon and of 8B, the archetypical one-proton halo nucleus, on 12C, 58Ni and 208Pb targets at44 MeV/nucleon.For these reactions, the adiabatic assumption is no longer valid due to the effect of the Coulomb interaction. This effect is mainly visible at forward angle for 11Be and is aggravated for 8B by the fact that the halo is charged. The ratio works less well than for neutron-halos at intermediate and high energies. Nevertheless, the ratio is shown to be very sensitive to the orbital angular momentum l0 in which the halo is bound and its binding energy E0, i.e. the single-particle structure of the projectile. Variations of l0 and E0 induce visible changes in shape and in magnitude (up to several orders) of the ratio. Also, the agreement of the ratio with its REB prediction is best when the projectile is loosely-bound and for low l0, i.e. for s and p waves. The validity of the method is not affected by the use of energy ranges—or bins— in the projectile continuum. These tend to increase the cross section without changing the agreement of the ratio with its REB prediction. The applicability of the method is finally explored at high energy for proton-rich nuclei 17F, 25Al and 27P. I show that the ratio method works the latter since this nucleus is bound by a mere 0.870 MeV in the s-wave. For the other nuclei, although the agreement of the ratio with its REB prediction is less good than for neutron-halo nuclei at high energy, it still provides estimates of nuclear-structure features, such as l0 and E0 and could be applied in what can be called an approximate application of the ratio method. Heavy nuclei exhibit a neutron skin, i.e. a thin layer around the nucleus where only neutrons are found. The thickness of the skin is highly correlated with the slope of the symmetry energy. The process of coherent neutral-pion photoproduction is used to extract the nuclear density and hence the neutron-skin thickness of heavy nuclei. In order to analyse recent data on the photoproduction on 12C, 40,48Ca, 116, 120, 124Sn and 208Pb, I build a reaction code. My model uses the formalism of Kerman, McManus and Thaler (KMT) which allows to build the photoproduction matrix on a nucleus from the ones describing the elementary process on a single nucleon. Within the impulse approximation, the photoproduction is seen as the coherent sum of the photoproduction on each of the nucleons. In the plane wave impulse approximation (PWIA), no rescattering of the pion is considered after its production and the cross section is directly proportional to the Fourier transform of the density. Such process is taken into account at the distorted wave impulse approximation (DWIA) by considering a potential simulating the pion-nucleus interaction and built from the KMT formalism.The agreement of my model with the data is good, especially for 208Pb. The distortion has a significant impact on the photoproduction process. The sensitivity of the process to the density of the target is analysed by performing the calculations with several different densities calculated in different structure models. The distortion has the effect of deteriorating this sensitivity. In the particular case of a 208Pb target, the impact of variations of the neutron-skin thickness of around 0.1 fm on the photoproduction cross section is ten times smaller than the size of the error bars on the experimental data. These results, although less dramatic, hold for the tin targets, for which preliminary data exists. In the light of these results, the coherent neutral-pion photoproduction process does not seem to be suited in the study of the neutron-skin thickness. This conclusion goes in contrast to the results of recent measurements on 208Pb, for which the method was shown to be sensitive to fine details of the density. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Cette thèse présente un travail théorique effectué dans le domaine de la physique de la matière condensée, et plus particulièrement la physique des solides. Ce domaine de la physique décrit le comportement des électrons dans les cristaux à très basses températures dans le but d'observer des effets quantiques à l'échelle mésoscopique.Cette thèse se situe à l'interface entre deux types de matériaux : le graphène et les isolants topologiques. Le graphène est une couche d’épaisseur monoatomique d’atomes de carbone arrangés en réseau nid d’abeilles, qui présente de nombreuses propriétés impressionnantes en optique, en mécanique et en électronique. Les isolants topologiques sont des matériaux qui sont isolants en volume et conduisent l'électricité sur les bords. Cette caractéristique découle d'une propriété topologique des électrons dans le volume. La topologie est une branche des mathématiques qui décrit des objets dans leur globalité en ne retenant que les caractéristiques invariantes par certaines déformations continues. Les états de bords des isolants topologiques sont robustes à certaines perturbations comme le désordre créé par des impuretés dans le matériau. Le lien entre ces deux sujets est double. D’une part les premiers modèles d’isolants topologiques de bande ont été formulés pour le graphène, par Haldane en 1988 et Kane et Mele en 2005, ouvrant ainsi la voie à la découverte des isolants topologiques à 2D et 3D dans des matériaux à fort spin-orbite. D’autre part, il a été prédit que le graphène, même sans spin-orbite, devient un isolant topologique lorsqu'il est irradié par une onde électromagnétique. Dans cette thèse, nous suivons deux directions en parallèle : décrire les caractéristiques topologiques d’une part et les propriétés de transport électronique d’autre part.En premier lieu, nous passons en revue le modèle des liaisons fortes pour le graphène, puis le modèle effectif qui décrit les électrons de basse énergie comme des fermions de Dirac sans masse. Nous introduisons ensuite le modèle de Haldane, un modèle simple défini sur le réseau en nid d’abeille et qui présente des bandes non triviales caractérisées par un invariant topologique, le nombre de Chern, non nul. Du fait de cette propriété topologique, ce modèle possède un état de bord chiral se propageant au bord de l’échantillon et une conductance de Hall quantifiée. Lorsque le graphène est irradié par un laser ayant une fréquence plus large que la largeur de bande du graphène, il acquiert un gap dynamique similaire au gap topologique du modèle de Haldane. Lorsque la fréquence est réduite, nous montrons que des transitions topologiques se produisent et l'apparition d'états de bords.Le travail principal de cette thèse est l'étude du transport électronique dans le graphène irradié dans un régime de paramètres réalisables expérimentalement. Une feuille de graphène est connectée à deux électrodes avec une différence de potentiel qui génère un courant. Nous calculons la conductance différentielle de l'échantillon selon le formalisme de Landauer-Büttiker étendu aux systèmes soumis à une modulation périodique. Il nous est possible d'obtenir la conductance en fonction de la géométrie de l’échantillon et de différents paramètres tels que le potentiel chimique, la fréquence et l'intensité de l’onde.Un autre type d'isolant topologique est l’isolant d’effet Hall quantique de spin. Ce type de phase possède deux états de bords dans lesquels les spins opposés se propagent dans des directions opposées. Le second travail de cette thèse concerne le transport électronique à travers cet état de bord irradié. Nous observons l'apparition d'un courant pompé en l'absence de différence de potentiel. Nous distinguons deux régimes : un pompage adiabatique quantifié à basse fréquence, et un régime de réponse linéaire non quantifiée à hautes fréquences. Par rapport aux études précédentes existantes, nous montrons un effet important de la présence des électrodes de mesure. / This thesis presents a theoretical work done in the field of condensed matter physics, and in particular solid state physics. This field of physics aims at describing the behaviour of electrons in crystalline materials at very low temperature to observe effects characteristic of quantum physics at the mesoscopic scale.This thesis lies at the interface between two types of materials : graphene and topological insulators. Graphene is a monoatomic layer of carbon atoms arranged in a honeycomb lattice that presents a wide range of striking properties in optics, mechanics and electronics. Topological insulators are materials that are insulators in the bulk and conduct electricity at the edges. This characteristic originates from a topological property of the electrons in the bulk. Topology is a branch of mathematics that aims to describe objects globally retaining only characteristics invariant under smooth deformations. The edge states of topological insulators are robust to certain king of perturbations such as disorder created by impurities in the bulk. The link between these two topics is two-fold. On one hand, the first models of band topological insulators were formulated for graphene, by Haldane in 1988 and Kane and Mele in 2005, opening the way to the discovery of 2D and 3D topological insulators in materials with strong spin-orbit coupling. On the other hand, it was predicted that graphene, even without spin-orbit coupling, turns to a topological insulator under irradiation by an electromagnetic wave. In this thesis, we follow two directions in parallel : describe the topological properties on one hand, and the electronic transport properties on the other hand.First, we review the tight-binding model of graphene, and the effective model that describes low-energy electrons as massless Dirac fermions. We then introduce the Haldane model, a simple model defined on the honeycomb lattice that presents non-trivial bands characterised by a topological invariant, the Chern number. Due to this topological property, this model possesses a chiral edge state that propagates around the sample and a quantized Hall conductance. When graphene is irradiated by a laser with a frequency larger than the graphene bandwidth, it acquires a dynamical gap similar to the topological gap of the Haldane model. When the frequency is lowered, we show that topological transitions happens and that different edge states appear.The main work of this thesis is the study of electronic transport in irradiated graphene in a regime of experimentally achievable parameters. A graphene sheet is connected to two electrodes with a potential difference that generates a current. We compute the differential conductance of the sample according to Landauer-Büttiker formalism extended to periodically driven systems. Using this simple formalism, we are able to obtain the conductance as a function of the geometry of the sample and of several parameters such as the chemical potential, the frequency and the intensity of the electromagnetic wave.Another kind of topological insulator is the quantum spin Hall insulator. This type of phase possesses two edge states in which opposite spins propagate in opposite directions. The second work of this thesis concerns electronic transport through this irradiated edge state. We observe the apparition of a pumped current in the absence of a potential difference. We observe two regimes : a quantized adiabatic at low frequency, and a non-quantized linear response regime at high frequency. Compared to previous studies, we show an important effect originating from the presence of electrodes.