Search results for "slip"
showing 10 items of 471 documents
Non-smooth modelling of billiard- and superbilliard-ball collisions
2008
Abstract A description of billiard-ball collisions using a ‘discontinuous’ model is presented considering a two-step situation corresponding to the ball–ball interaction followed by ball-supporting surface interaction. It is applied to the inelastic impact of a cue ball having arbitrary pivotment and ‘English’ spins against an object ball initially at rest. This formulation provides a simplified approximation to the ‘continuous’ models of impact and considers two different regimes of impact: gross slip, and slip–stick, described in terms of coefficients of friction and restitution. As a result, the angles of scattering of the balls just after the impact (post-collision angles) and when the …
Superconductivity in one dimension
2008
Superconducting properties of metallic nanowires can be entirely different from those of bulk superconductors because of the dominating role played by thermal and quantum fluctuations of the order parameter. For superconducting wires with diameters below $ \sim 50$ nm quantum phase slippage is an important process which can yield a non-vanishing wire resistance down to very low temperatures. Further decrease of the wire diameter, for typical material parameters down to $\sim 10$ nm, results in proliferation of quantum phase slips causing a sharp crossover from superconducting to normal behavior even at T=0. A number of interesting phenomena associated both with quantum phase slips and with …
Negative magnetoresistance of ultra-narrow superconducting nanowires in the resistive state
2008
We present a phenomenological model qualitatively explaining negative magnetoresistance in quasi-one-dimensional superconducting channels in the resistive state. The model is based on the assumption that fluctuations of the order parameter (phase slips) are responsible for the finite effective resistance of a narrow superconducting wire sufficiently close to the critical temperature. Each fluctuation is accompanied by an instant formation of a quasi-normal region of the order of the non-equilibrium quasiparticle relaxation length 'pinned' to the core of the phase slip. The effective time-averaged voltage measured in experiment is a sum of two terms. First one is the conventional contributio…
E-sail test payload of the ESTCube-1 nanosatellite
2014
The scientific mission of ESTCube-1, launched in May 2013, is to measure the electric solar wind sail (E-sail) force in orbit. The experiment is planned to push forward the development of the E-sail, a propulsion method recently invented at the Finnish Meteorological Institute. The E-sail is based on extracting momentum from the solar wind plasma flow by using long thin electrically charged tethers. ESTCube-1 is equipped with one such tether, together with hardware capable of deploying and charging it. At the orbital altitude of ESTCube-1 (660–680 km) there is no solar wind present. Instead, ESTCube-1 shall observe the interaction between the charged tether and the ionospheric plasma. The E…
Application of Tunable-Slip Boundary Conditions in Particle-Based Simulations
2014
Compared to macroscopic systems, fluids on the micro- and nanoscales have a larger surface-to-volume ratio, thus the boundary condition becomes crucial in determining the fluid properties. No-slip boundary condition has been applied successfully to wide ranges of macroscopic phenomena, but its validity in microscopic scale is questionable. A more realistic description is that the flow exhibits slippage at the surface, which can be characterized by a Navier slip length. We present a tunable-slip method by implementing Navier boundary condition in particle-based computer simulations (Dissipative Particle Dynamics as an example). To demonstrate the validity and versatility of our method, we ha…
Numerical modelling of asymmetric boudinage
2002
Abstract Asymmetric boudinage structures are commonly used as shear sense indicators but their development is incompletely understood. This paper describes the influence of initial shape and kinematic parameters on the evolution of boudin trains using a numerical approach based on the finite difference code FLAC. Boudin trains are simulated as a series of competent objects embedded in a soft matrix subjected to general monoclinic ductile flow. Deformation of boudin trains includes heterogeneous stretching, rotation of boudins and offset along the neck regions. The sense of relative boudin offset is mainly influenced by the initial orientation of the interboudin plane in the boudinaging laye…
Asymmetric boudins as shear sense indicators—an assessment from field data
2003
Asymmetric boudins are potential but problematic shear sense indicators. They can be divided into two groups, with slip on the inter-boudin surface that is either synthetic (S-slip) or antithetic (A-slip) with respect to bulk shear sense. Since both groups have mirror-image symmetry, independent geometric criteria are needed to distinguish them if they are to be used as shear sense indicators. Investigation of asymmetric boudins in trains parallel to the main foliation from the Kaoko Belt in Namibia and elsewhere indicate that the geometry of both groups is in most cases different. Shearband boudins (formed by S-slip) have a long, curved lenticular shape and large relative displacement and …
Lipid-lowering nutraceuticals in clinical practice: position paper from an International Lipid Expert Panel
2017
In recent years, there has been growing interest in the possible use of nutraceuticals to improve and optimize dyslipidemia control and therapy. Based on the data from available studies, nutraceuticals might help patients obtain theraputic lipid goals and reduce cardiovascular residual risk. Some nutraceuticals have essential lipid-lowering properties confirmed in studies; some might also have possible positive effects on nonlipid cardiovascular risk factors and have been shown to improve early markers of vascular health such as endothelial function and pulse wave velocity. However, the clinical evidence supporting the use of a single lipid-lowering nutraceutical or a combination of them is…
1997
We have determined by forced Rayleigh scattering the diffusion coefficients of photo-labeled polystyrene micronetwork spheres (radii ≤ 10 nm) in melts of linear polyvinylmethylether (M W ≤ 40000 g/mol) at temperatures of 20-80°C. An expected slippage of the spheres through the meshes of the entanglement network appears possible but is still within the experimental uncertainty of our results.