10,287 research outputs found
Gibbs attractor: a chaotic nearly Hamiltonian system, driven by external harmonic force
A chaotic autonomous Hamiltonian systems, perturbed by small damping and
small external force, harmonically dependent on time, can acquire a strange
attractor with properties similar to that of the canonical distribution - the
Gibbs attractor. The evolution of the energy in such systems can be described
as the energy diffusion. For the nonlinear Pullen - Edmonds oscillator with two
degrees of freedom the properties of the Gibbs attractor and their dependence
on parameters of the perturbation are studied both analytically and
numerically.Comment: 8 pages RevTeX, 3 figure
Simulation of Stress-Strain State of Shovel Rotary Support Kingpin
The article presents the sequence of computational simulation of stress-strain state of shovel's rotary support. Computation results are analyzed, the kingpin is specified as the most loaded element, maximum stress zones are identified. Kingpin design modification such as enhancement of fillet curvature radius to 25 mm and displacement of eyebolt holes on the diameter of 165 mm are proposed, thus diminishing impact of stress concentrators and improving reliability of the rotary support
Visual ecology of the Australian lungfish (Neoceratodus forsteri)
Background. The transition from water to land was a key event in the evolution of vertebrates that occurred over a period of 15-20 million years towards the end of the Devonian. Tetrapods, including all land-living vertebrates, are thought to have evolved from lobe-finned (sarcopterygian) fish that developed adaptations for an amphibious existence. However, while many of the biomechanical and physiological modifications necessary to achieve this feat have been studied in detail, little is known about the sensory adaptations accompanying this transition. In this study, we investigated the visual system and visual ecology of the Australian lungfish Neoceratodus forsteri, which is the most primitive of all the lungfish and possibly the closest living relative to the ancestors of tetrapods. Results. Juvenile Neoceratodus have five spectrally distinct retinal visual pigments. A single type of rod photoreceptor contains a visual pigment with a wavelength of maximum absorbance (max) at 540 nm. Four spectrally distinct single cone photoreceptors contain visual pigments with max at 366 (UVS), 479 (SWS), 558 (MWS) and 623 nm (LWS). No double cones were found. Adult lungfish do not possess UVS cones and, unlike juveniles, have ocular media that prevent ultraviolet light from reaching the retina. Yellow ellipsoidal/paraboloidal pigments in the MWS cones and red oil droplets in the LWS cones narrow the spectral sensitivity functions of these photoreceptors and shift their peak sensitivity to 584 nm and 656 nm, respectively. Modelling of the effects of these intracellular spectral filters on the photoreceptor colour space of Neoceratodus suggests that they enhance their ability to discriminate objects, such as plants and other lungfishes, on the basis of colour. Conclusion. The presence of a complex colour vision system based on multiple cone types and intracellular spectral filters in lungfishes suggests that many of the ocular characteristics seen in terrestrial or secondarily aquatic vertebrates, such as birds and turtles, may have evolved in shallow water prior to the transition onto land. Moreover, the benefits of spectral filters for colour discrimination apply equally to purely aquatic species as well as semi-aquatic and terrestrial animals. The visual system of the Australian lungfish resembles that of terrestrial vertebrates far more closely than that of other sarcopterygian fish. This supports the idea that lungfishes, and not the coelacanth, are the closest living relatives of the ancestors of tetrapods
Chirality inversion and radius blow-up of a N\'eel-type skyrmion by a Pearl vortex
We develop a theory for the coaxial configuration of a N\'eel-type skyrmion
and a Pearl vortex in thin superconductor-chiral ferromagnetic
heterostructures. Using direct numerical solution of the Euler-Lagrange
equation and micromagnetic simulations we demonstrate that the inhomogeneous
magnetic field of the Pearl vortex significantly modifies the skyrmion profile
with respect to the one in the absence of the vortex. We discover drastic
enlargement of the skyrmion's radius and inversion of the skyrmion's chirality.
To unravel physics behind these effects we invent novel two-parameter ansatz
for the magnetization profile of the skyrmion in the presence of the vortex.
Chirality inversion and radius blow-up are controlled not only by the material
parameters of the heterostructure but also by the thickness of the
superconductor. Our findings can have implications for Majorana modes localized
at skyrmion-vortex pairs.Comment: 6 pages, 2 figures; 1 video file and its description (as ancillary
files
Basket of Growth: New Export Industries in Sverdlovsk Region
The authors examine an export basket and reveal the new export goods for Sverdlovsk region, which might be used to transform the productive structure and upgrade export of the region. For each product, in which the region might develop its comparative advantage, the authors develop a measure of efforts, which are supposed to be made to include this good into the export basket, and a measure of the income level for the product. As a result the authors get a cluster of new and the most attractive export goods. Special methodology is used to choose the best cities to allocate the production of the new export goods.Export goods, comparative advantages, industrial cluster, production allocation
Resonant behaviour in double charge exchange reaction of \pi^+ mesons on the nuclear photoemulsion
The invariant mass spectra of the and systems produced in the
double charge exchange (DCX) of positively charged pions on photoemulsion are
analysed. A pronounced peak is observed in the invariant mass
spectrum, while the spectrum exhibits a strong Migdal-Watson effect of
the proton-proton final state interaction. These findings are in favor of the
-decoupled pseudoscalar resonance with T=0 called .Comment: 13 pages, 5 figures, revised versio
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