Tensile response and fracturing process in moderate and high plasticity clays

Sinkholes in clay soils can be considered as the collapse of a soil layer previously bridging a void. Here, flexural deformation in the clay drives the formation of tensile cracks from the lowest surface of the layer and the consequent soil collapse is from crack propagation. Considering a simplified model of the sinkhole geometry, this paper aims to describe the tensile and fracture behaviour of clay soils with different plasticity indices. Speswhite kaolin, London and Durham clays were tested using direct tensile and bending tests. Moderate and high plasticity clays showed a nonlinear fracture response with increasing moisture content, while low plasticity clays demonstrated a linear response. Bending tests confirmed the importance of the moisture content while the plasticity index confirmed the difference in ductile or fragile collapse for fracture propagation. To assess the results, Elasto-Plastic Fracture Mechanics (EPFM) theory was applied to clays with appropriate modifications. The analysis demonstrated that EPFM theory provides a good baseline for predicting tensile fracture behaviour in clay soils which can be extended in future research

Measuring the coefficient of restitution for all six degrees of freedom

The coefficient of restitution is a cornerstone empirical parameter of any model where energy is dissipated by particle collisions. However, completely determining this parameter experimentally is challenging, as upon collision, a particle’s material properties (such as roughness, sphericity and shape) or minor imperfections, can cause energy to be shifted to other translational or rotational components. When all degrees of freedom are not resolved, these shifts in energy can easily be mistaken for dissipated energy, affecting the derivation of the coefficient of restitution. In the past, these challenges have been highlighted by a large scatter in values of experimental data for the restitution coefficient. In the present study, a novel experimental procedure is presented, determining all six degrees of freedom of a single, spherical, nylon particle, dropped on a glass plate. This study highlights that only by using all six degrees of freedom, can a single reliable and consistent coefficient of restitution be obtained for all cases and between subsequent collisions

Growth of (111) oriented thin film platinum by room temperature sputtering

This application note describes the growth Pt thin films in the Royce Deposition System. X-ray reflectivity and diffraction shows that these sputtered Pt thin films have low surface roughness and are (111) textured. These properties are desirable for the growth of Pt in magnetic multilayers and as seed layers for other materials

Polycrystalline SrTiO3 thin film grown by pulsed laser deposition on a (111) oriented platinum seed layer

This application note describes the growth and characterisation of a polycrystalline SrTiO3 thin film grown in the Royce Deposition System by pulsed laser deposition. The film was characterised by X-ray reflectivity and diffraction and impedance spectrocopy

Growth of BiFeO₃ thin films by pulsed laser deposition

This application note describes the growth and characterisation of BiFeO3 thin films grown in the Royce Deposition System by pulsed laser deposition. The film was characterised by X-ray reflectivity and X-ray diffraction

Supercurrent diode effect in thin film Nb tracks

We demonstrate nonreciprocal critical current in 65 nm thick polycrystalline and epitaxial Nb thin films patterned into tracks. The nonreciprocal behavior gives a supercurrent diode effect, where the current passed in one direction is a supercurrent and the other direction is a normal state (resistive) current. We study the variation of the diode effect with temperature and magnetic field, and find an unexpected dependence with the width of the Nb tracks from 2-10 $\mu$m. For both polycrystalline and epitaxial samples, we find that tracks of width 4 $\mu$m provides the largest supercurrent diode efficiency of up to $\approx30\%$, with the effect reducing or disappearing in the widest tracks of 10 $\mu$m. It is anticipated that the supercurrent diode will become a ubiquitous component of the superconducting computer.Comment: 15 pages, 4 figure

Variation in Stemmatal Morphology of Larvae of Liodessus noviaffinis Miller (Dytiscidae: Hydroporinae: Bidessini)

Second and third instars tentatively identified as Liodessus noviaffinis Miller have six dorsolateral stemmata near the origin of each antenna. However, each stemma lacks a corneal (cuticular) lens on the surface exterior to its internal sensory pigmented components

Evolutionary Laws, Initial Conditions, and Gauge Fixing in Constrained Systems

We describe in detail how to eliminate nonphysical degrees of freedom in the Lagrangian and Hamiltonian formulations of a constrained system. Two important and distinct steps in our method are the fixing of ambiguities in the dynamics and the determination of inequivalent initial data. The Lagrangian discussion is novel, and a proof is given that the final number of degrees of freedom in the two formulations agrees. We give applications to reparameterization invariant theories, where we prove that one of the constraints must be explicitly time dependent. We illustrate our procedure with the examples of trajectories in spacetime and with spatially homogeneous cosmological models. Finally, we comment briefly on Dirac's extended Hamiltonian technique.Comment: 23 pages; plain TeX. To appear: Classical & Quantum Gravit