270 research outputs found
Ultra-hard fluid and scalar field in the Kerr-Newman metric
An analytic solution for the accretion of ultra-hard perfect fluid onto a
moving Kerr-Newman black hole is found. This solution is a generalization of
the previously known solution by Petrich, Shapiro and Teukolsky for a Kerr
black hole. Our solution is not applicable for an extreme black hole due to
violation of the test fluid approximation. We also present a stationary
solution for a massless scalar field in the metric of a Kerr-Newman naked
singularity.Comment: 9 pages, 3 figures, revtex4; v2: presentation improved, figures
added, matches published versio
Solar activity beyond the disk and variations of the cosmic ray gradient
Part of galactic cosmic rays (CR) observed near the Earth and on the Earth come from beyond-disk regions of circumsolar space. But CR of those energies which undergo substantial modulation cover too large a path across the lines of force of the interplanetary magnetic field (IMF) in order that they could provide an effective transfer of information about beyond-disk solar activity. And if it is still possible, the most probable channel for transferring such information must be a neutral layer of heliomagnetosphere in which the transverse CR transport is facilitated by their drift in an inhomogeneous magnetic field. A simple diffusion model for an expected CR variation in a neutral layer near the Earth is discussed. It is of importance that variations of the CR gradient are not at all always accompanied by considerable variations of IMF and solar wind velocity at the point of observation
Fuzzy neural networks' application for substation integral state assessment
This paper addresses the problems connected with fuzzy neural networks' application in equipment technical state assessment problems at electrical substations. This paper discusses the main principles of fuzzy neural network formation and its construction algorithm. Also, the case study for the determination of fuzzy neural network synaptic weights for the unit "disconnector" on the basis of technical diagnostic statistical data and tests is presented. © 2014 WIT Press.International Journal of Safety and Security Engineering;International Journal of Sustainable Development and Planning;WIT Transactions on Ecology and the Environmen
The Phantom Bounce: A New Oscillating Cosmology
An oscillating universe cycles through a series of expansions and
contractions. We propose a model in which ``phantom'' energy with
grows rapidly and dominates the late-time expanding phase. The universe's
energy density is so large that the effects of quantum gravity are important at
both the beginning and the end of each expansion (or contraction). The bounce
can be caused by high energy modifications to the Friedmann equation, which
make the cosmology nonsingular. The classic black hole overproduction of
oscillating universes is resolved due to their destruction by the phantom
energy.Comment: Four pages, one figure. V3: version to appear in JCA
Mechanical properties of magnesium alloy for medical applications after deformation treatment
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