908 research outputs found
Generation of megatesla magnetic fields by intense-laser-driven microtube implosions
A microtube implosion driven by ultraintense laser pulses is used to produce
ultrahigh magnetic fields. Due to the laser-produced hot electrons with
energies of mega-electron volts, cold ions in the inner wall surface implode
towards the central axis. By pre-seeding uniform magnetic fields on the
kilotesla order, the Lorenz force induces the Larmor gyromotion of the
imploding ions and electrons. Due to the resultant collective motion of
relativistic charged particles around the central axis, strong spin current
densities of ~ peta-ampere/cm2 are produced with a few tens of nm size,
generating megatesla-order magnetic fields. The underlying physics and
important scaling are revealed by particle simulations and a simple analytical
model. The concept holds promise to open new frontiers in many branches of
fundamental physics and applications in terms of ultrahigh magnetic fields.Comment: 22 pages, 7 figure
The variations of the δ<sup>13</sup>C and δ<sup>18</sup>O in the Middle Permian rocks, Volga river outcrops, Russia
© 2006-2017 Asian Research Publishing Network (ARPN). Data on stable isotopes of carbon and oxygen of the Permian carbonate rocks play an important role to create geochemical frame of the Permian formations. The stable isotopes records reflect changes in chemical composition of carbonate rocks in dependence on regional and global factors in history of the Permian period. Variations of stable isotopes across the Middle Permian rocks correlate with the stratigraphic boundaries and paleoenvironmental changes
Effect of operating conditions of mine monorail locomotives on the durability of drive wheel polymeric rims
An increase in the rate of coal mining and a reduction of its prime cost can be ensured by comprehensive mechanization and automation of the system of mine auxiliary transport through the widespread introduction of overhead monorail tracks. The potential use of mine monorail tracks are conditioned by the following factors: low payload ratio of the train; reduction of the mine workings cross-section area due to transfer of auxiliary transport to the upper part of the workings; high operational safety; as well as the possibility of dismantling the track in the unused sections and subsequently installing it in new mine workings. The use of rubberized rollers in the drives of mine monorail locomotives enables the coefficient of adhesion of the wheel with the monorail to be increased. It also reduces dynamic loads and the noise level during operation. The purpose of this research is to assess the durability of polymeric rims of drive wheels for mine monorail locomotives, taking into account their operating conditions. Stress distribution over the contact area of the wheel rim with the monorail was determined, enabling the development of measures to increase the service life of drive wheels of mine monorail locomotives to be developed. It was established that the effect of the monorail track deformation has no significant impact on the durability of drive wheel rims of mine monorail locomotives. A mathematical model was obtained to determine the durability of drive wheel polymeric rims, taking into account the maximum dynamic forces arising during the contact of drive wheels with the monorail. The durability of wheel polymeric rims of mine monorail locomotives was assessed in accordance with the Bailey criterion with regard to the maximum values of dynamic contact loads arising during the monorail train movement. It was also established that an increase in the carriage mass from 20 to 47 kN leads to 32 % less durability of a monorail locomotive drive wheel rim (from 8700 to 5900 hours)
The Unexpected Role of Evolving Longitudinal Electric Fields in Generating Energetic Electrons in Relativistically Transparent Plasmas
Superponderomotive-energy electrons are observed experimentally from the
interaction of an intense laser pulse with a relativistically transparent
target. For a relativistically transparent target, kinetic modeling shows that
the generation of energetic electrons is dominated by energy transfer within
the main, classically overdense, plasma volume. The laser pulse produces a
narrowing, funnel-like channel inside the plasma volume that generates a field
structure responsible for the electron heating. The field structure combines a
slowly evolving azimuthal magnetic field, generated by a strong laser-driven
longitudinal electron current, and, unexpectedly, a strong propagating
longitudinal electric field, generated by reflections off the walls of the
funnel-like channel. The magnetic field assists electron heating by the
transverse electric field of the laser pulse through deflections, whereas the
longitudinal electric field directly accelerates the electrons in the forward
direction. The longitudinal electric field produced by reflections is 30 times
stronger than that in the incoming laser beam and the resulting direct laser
acceleration contributes roughly one third of the energy transferred by the
transverse electric field of the laser pulse to electrons of the
super-ponderomotive tail
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