Shear banding is a commonly observed yet complex form of instability in granular media by which the deformation is localized in a narrow zone along a certain path. The aim of this study is to investigate the micromechanics of shear banding using the discrete element method (DEM). For this purpose, a model was developed and calibrated to simulate the macroscale behavior of sand under plane strain conditions. Upon validation against laboratory experiments, two types of confining boundaries, displacement- and force-controlled, were examined to study the kinematics of shear bands. A constant volume test was then used to investigate the evolution of antisymmetric stresses before, during, and after shear band formation. The results indicate that the antisymmetric stresses significantly increase within the shear band throughout the loading history, but may not describe the precursory shear band conditions. The DEM model is shown to properly capture the micromechanics of shear bands.

The quantum mechanical phenomenon of entanglement plays a key role in areas such as quantum computing and quantum information. Entangled half spin particles, often called qubits, are used to realize quantum based logic which means that studying systems of qubits and their properties is of vital importance to the development of the fields. In this paper we simulate the time evolution of a three-qubit system for varying Hamiltonians and initial states. We look at the revival structure of the classically treated survival probability and compare its structure to that of the quantum mechanical concept of residual entanglement, which is a measure of the system's total entanglement. We do this for three different types of initial states: Uniform, GHZ and W, as well as varying the contributions of certain types of spin-spin interaction models in the Hamiltonian. The spin-spin interaction models that are examined are the DM model and the Heisenberg model. Further we also examine the effect of an added magnetic field in the zdirection, in the form of a Zeeman term. In general, the Zeeman term only affects the behavior of the survival probability, unless the DM term is rotated to not be in a parallel direction, the Heisenberg term generally affects the survival probability and the residual entanglement in the same way. We also note that for the Uniform initial state a dominant Heisenberg seems to remove some of the rapid oscillations in the residual entanglement and survival probability that naturally occur in the DM model, the Zeeman term then reintroduces these high frequencies in the survival probability while not affecting the residual entanglement. For some Hamiltonians we do not see any connection between the revival structure of the survival probability and the residual entanglement, while for some there is a clear connection.

This study focuses on the response of flat unsymmetric laminates to an inplane compressive loading that for symmetric laminates are of sufficient magnitude to cause bifurcation buckling, postbuckling, and secondary buckling behavior. In particular, the purpose of this study is to investigate whether or not the concept of bifurcation buckling is applicable to unsymmetric laminates. Past work by other researchers has suggested that such a concept is applicable for certain boundary conditions. The study also has as an objective the determination of the response of flat unsymmetric laminates if bifurcation buckling does not occur. The finite-element program ABAQUS is used to obtain results, and a portion of the study is devoted to becoming familiar with the way ABAQUS handles such highly geometrically nonlinear problems, particularly for composite materials and particularly when instabilities and dynamic behavior are involved. Familiarity with the problem, in general, and with the use of ABAQUS, in particular, is partially gained by considering semi-infinite unsymmetrically laminated cross- and angle-ply plates, a one-dimensional problem that can be solve in closed form and with ABAQUS by making the appropriate approximations for the infinite geometry. In this portion of the study it is found that semi-infinite cross-ply laminates with clamped boundary conditions and semi-infinite angle-ply plates with simple-support boundary conditions remain flat under a compressive load until the load magnitude reaches a certain level, at which time the out-of-plane deflection become indeterminate, essentially an eigenvalue problem as encountered with classic bifurcation buckling analyses. Obviously, a linear analysis of such problems would not reveal this behavior and, in fact, there are other revealed significant differences between the predictions of linear and nonlinear analyses. Transversely-loaded and inplane-loaded finite isotropic plates are studied by way of semi-closed form Rayleigh-Ritz-based solutions and ABAQUS in a step to approaching the problem with unsymmetric laminates. A method to investigate the unloading behavior of postbuckled finite isotropic plates is developed that reveal multiple plate configurations in the postbuckled region of the response, and this method is then extended to the study of finite inplane-loaded unsymmetric laminates. To that end, two specific laminates, a symmetric and an unsymmetric cross-ply laminates, and a variety of boundary conditions are used to study the response of inplane-loaded unsymmetric laminates. The symmetric laminate is included to provide a familiar baseline case and a means of comparison. Plates with all four edges clamped and a variety of inplane boundary conditions are studied. Of course the symmetric cross-ply laminate exhibits bifurcation behavior, and when the tangential displacement on the loaded edges and the normal displacement on the unloaded edges are restrained, secondary buckling behavior occurs. For the unsymmetric cross-ply laminate, bifurcation buckling behavior does not occur unless the tangential displacement on the loaded edges and the normal displacement on the unloaded edges are restrained, or the tangential displacement on the loaded edges and the normal displacement on the unloaded edges are free. If either of these conditions are not satisfied, the unsymmetric cross-ply laminate exhibits what could be termed 'near-bifurcation' behavior. In all cases rather complex behavior occurs for high levels of inplane load, including asymmetric postbuckling and secondary buckling behavior. For clamped loaded edges and simply-supported unloaded edges, bifurcation buckling behavior does not occur unless the tangential displacement on the loaded edges and the normal displacement on the unloaded edges are restrained. For this case, rather unusual asymmetric bifurcation and associated limit point behavior occur, as well as secondary buckling. This is a very interesting boundary condition case and is studied further for other unsymmetric cross-ply laminates, including the use of a Rayleigh-Ritz-based solution in attempt to quantify the problem parameters responsible for the asymmetric response. The overall results of the study have led to an increased understanding of the role of laminate asymmetry and boundary conditions on the potential for bifurcation behavior, on the response of the laminate for loads beyond that level. / Ph. D.

No description available.

This thesis is concerned with applications of modern solid-state NMR spectroscopy. Investigations of three quite different types are undertaken, each of which attempt to advance knowledge in the fields of chemistry and NMR. The goal of each project is to obtain insight into the effects of chemical environment, in particular bonding, on the NMR observables. Carbon-13 and nitrogen-15 solid-state nuclear magnetic resonance has been used to study solid samples containing the dicyanoaurate(I) anion, [Au(CN)2]-, with n-butylammonium, potassium, and thallium counterions. Differences in Au-Tl metallophilic bonding are shown to cause a difference in the isotropic cyanide carbon-13 chemical shift of up to 15.7 ppm, while differences in Au-Au aurophilic bonding are found to be responsible for a change of up to 5.9 ppm. Disordered polymeric gold(I) monocyanide was also investigated, and a range of 7+-2% to 25+-5% of the AuCN chains are found to be "slipped" instead of aligned with the neighbouring chains at the metal position. An investigation of the chemical shift tensors of the 13C-labelled carbons in solid samples of Ph13C≡13CPh and (η2-Ph13C≡13CPh)Pt(PPh3)2·(C6H6) has also been carried out. Coordination of diphenylacetylene to platinum causes a change in the 13C chemical shift tensor orientation and a net increase in the isotropic chemical shift. The carbon chemical shift tensors in the platinum complex bear a striking similarity to those of the alkenyl-carbons in trans-Ph(H)C=C(H)Ph, and a theoretical discussion of these observations is presented. Each of the fundamental NMR interaction tensors (σ, J, D and V) may be decomposed into isotropic, symmetric, and antisymmetric components. Observations of all theoretically allowed components other than the antisymmetric portion of J (Janti) have previously been published. Andrew and Farnell's theory (Mol. Phys. 15, 157 (1968)) for the effects of Janti on NMR spectra has been extended to powdered samples, and methods for analyzing the resultant line shapes have been determined. Finally, the first reported experimental attempts to measure Janti are presented, and experimental proof that no elements of Janti(119Sn,119Sn) in hexa(p-tolyl)ditin are larger than 2900 Hz is given.

Submitted by Hemily Gomes Marciano (hemily.gomes@gmail.com) on 2018-04-17T18:10:25Z No. of bitstreams: 1 versão final.pdf: 751892 bytes, checksum: 22aa973b490af1ca393b304a45758dbb (MD5) / Rejected by Pamella Benevides Gonçalves null (pamella@feg.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: Favor basta apenas Inserir a capa, porém é um elemento obrigatório. Deve conter a identificação do trabalho, na seguinte ordem: • Nome da Instituição (centralizado) • Nome completo do autor (centralizado) • Título do trabalho (centralizado) • Subtítulo: se houver, deve ser precedido de dois pontos, evidenciando a sua subordinação ao título • Número do volume, se houver mais de um • Local (cidade) da instituição onde será apresentado (centralizado) • Ano da entrega (centralizado) Agradecemos a compreensão. on 2018-04-18T13:06:59Z (GMT) / Submitted by Hemily Gomes Marciano (hemily.gomes@gmail.com) on 2018-04-18T16:51:34Z No. of bitstreams: 1 Versão Final Tese.pdf: 803694 bytes, checksum: c2cc93bc2be66aef333d543d606bd2f8 (MD5) / Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-04-19T18:58:37Z (GMT) No. of bitstreams: 1 fortes_hgm_dr_guara.pdf: 803694 bytes, checksum: c2cc93bc2be66aef333d543d606bd2f8 (MD5) / Made available in DSpace on 2018-04-19T18:58:37Z (GMT). No. of bitstreams: 1 fortes_hgm_dr_guara.pdf: 803694 bytes, checksum: c2cc93bc2be66aef333d543d606bd2f8 (MD5) Previous issue date: 2018-03-23 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Partículas massivas de spin-2 são usualmente descritas pela conhecida teoria de Fierz-Pauli através de um tensor de rank-2 simétrico hµν = hνµ. Recentemente, tem havido um aumento no interesse por teorias que descrevam esse tipo de partícula, principalmente pela possibilidade de oferecer uma explicação alternativa para o problema da aceleração da expansão do universo, pois se o gráviton tivesse uma pequena massa, a força gravitacional diminuiria a grandes distâncias, produzindo tal aceleração. Trabalhos mais recentes têm trazido à tona outras possibilidades além de Fierz-Pauli para se descrever partículas de spin-2 massivas partindo de um tensor de rank-2 não simétrico eµν 6= eνµ, os chamados modelos L(a1). Tendo em vista que toda partícula deve interagir com a gravitação, no presente trabalho buscamos estudar o acoplamento desses novos modelos com um campo gravitacional de fundo. Para isso, a partir da manipulação das equações de movimento, procuramos obter os vínculos necessários para se ter uma teoria com a contagem de graus de liberdade correta. Fizemos também um estudo preliminar da versão sem massa dos modelos L(a1) no espaço curvo a partir da análise das simetrias de gauge existentes. Identificamos ainda os modelos parcialmente simétricos presentes em L(a1) / Massive spin-2 particles are usually described by the well-known Fierz-Pauli theory via a symmetric rank-2 tensor hµν = hνµ. Recently there has been an increase of interest in theories describing this kind of particle, especially because they can contribute to explain the accelerated expansion of the universe, since if the graviton has a small mass, the gravitational force would decrease at large distances, producing such accelerattion. In recent works other possibilities, besides the Fierz-Pauli model, which describe massive spin-2 particles starting from a non-symmetric rank-2 tensor eµν 6= eνµ have been found, the so-called L(a1) models. Since every particle has to interact with the gravitation, we have studied the coupling of the new models with a background gravitational field. Therefore, from the manipulation of the equations of motion, we seek for the necessary constraints in order to achieve the correct counting of degrees of freedom. We also have done a preliminary study of the massless version of the L(a1) models in the curved space from the analysis of the gauge symmetries of the theory. We also have identified the partially symmetric models present in L(a1). / 2013/25368-0

In dieser Arbeit werden das Wachstum mittels Molekularstrahlepitaxie und die Eigenschaften der Ferromagneten Fe und Fe_3Si auf niedrig-symmetirschen GaAs(113)A-Substraten studiert. Drei wichtige Aspekte werden untersucht: (i) Wachstum und strukturelle Charakterisierung, (ii) magnetische Eigenschaften und (iii) Magnetotransporteigenschaften der Fe und Fe_3Si Schichten auf GaAs(113)A-Substraten. Das Wachstum der Fe- und Fe_3Si-Schichten wurde bei einer Wachstumstemperatur von = bzw. 250 °C optimiert. Bei diesen Wachstumstemperaturen zeigen die Schichten eine hohe Kristallperfektion und glatte Grenz- und Oberflächen analog zu [001]-orientierten Schichten. Weiterhin wurde die Stabilität der Fe_(3+x)Si_(1-x) Phase über einen weiten Kompositionsbereich innerhalb der Fe_3Si-Stoichiometry demonstriert. Die Abhängigkeit der magnetischen Anisotropie innerhalb der Schichtebene von der Schichtdicke weist zwei Bereiche auf: einen Beresich mit dominanter uniaxialer Anisotropie für Fe-Schichten = 70 MLs. Weiterhin wird eine magnetische Anisotropie senkrecht zur Schichtebene in sehr dünnen Schichten gefunden. Der Grenzflächenbeitrag sowohl der uniaxialen als auch der senkrechten Anisotropiekonstanten, die aus der Dickenabhängigkeit bestimmt wurden, sind unabhängig von der [113]-Orientierung und eine inhärente Eigenschaft der Fe/GaAs-Grenzfläche. Die anisotrope Bindungskonfiguration zwischen den Fe und den As- oder Ga-Atomen an der Grenzfläche wird als Ursache für die uniaxiale magnetische Anisotropie betrachtet. Die magnetische Anisotropie der Fe_3Si-Schichten auf GaAs(113)A-Substraten zeigt ein komplexe Abhängigkeit von der Wachstumsbedingungen und der Komposition der Schichten. In den Magnetotransportuntersuchungen tritt sowohl in Fe(113)- als auch in Fe_3Si(113)-Schichten eine antisymmetrische Komponente (ASC) im planaren Hall-Effekt (PHE) auf. Ein phänomenologisches Modell, dass auf der Kristallsymmetrie basiert, liefert ein gute Beschreibung sowohl der ASC im PHE als auch des symmetrischen, anisotropen Magnetowiderstandes. Das Modell zeigt, dass die beobachtete ASC als Hall-Effekt zweiter Ordnung beschreiben werden kann. / In this work, the molecular-beam epitaxial growth and properties of ferromagnets, namely Fe and Fe_3Si are studied on low-symmetric GaAs(113)A substrates. Three important aspects are investigated: (i) growth and structural characterization, (ii) magnetic properties, and (iii) magnetotransport properties of Fe and Fe_3Si films on GaAs(113)A substrates. The growth of Fe and Fe_3Si films is optimized at growth temperatures of 0 and 250 degree Celsius, respectively, where the layers exhibit high crystal quality and a smooth interface/surface similar to the [001]-oriented films. The stability of Fe_(3+x)Si_(1-x) phase over a range of composition around the Fe_3Si stoichiometry is also demonstrated. The evolution of the in-plane magnetic anisotropy with film thickness exhibits two regions: a uniaxial magnetic anisotropy (UMA) for Fe film thicknesses = 70 MLs. The existence of an out-of-plane perpendicular magnetic anisotropy is also detected in ultrathin Fe films. The interfacial contribution of both the uniaxial and the perpendicular anisotropy constants, derived from the thickness-dependent study, are found to be independent of the [113] orientation and are hence an inherent property of the Fe/GaAs interface. The origin of the UMA is attributed to anisotropic bonding between Fe and As or Ga at the interface, similarly to Fe/GaAs(001). The magnetic anisotropy in Fe_3Si on GaAs(113)A exhibits a complex dependence on the growth conditions and composition. Magnetotransport measurements of both Fe(113) and Fe_3Si(113) films shows the striking appearance of an antisymmetric component (ASC) in the planar Hall effect (PHE). A phenomenological model based on the symmetry of the crystal provides a good explanation to both the ASC in the PHE as well as the symmetric anisotropic magnetoresistance. The model shows that the observed ASC component can be ascribed to a second-order Hall effect.