12,549 research outputs found
Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs
In a composite system of gravitationally coupled stellar and gaseous discs,
we perform linear stability analysis for axisymmetric coplanar perturbations
using the two-fluid formalism. The background stellar and gaseous discs are
taken to be scale-free with all physical variables varying as powers of
cylindrical radius with compatible exponents. The unstable modes set in as
neutral modes or stationary perturbation configurations with angular frequency
.Comment: 7 pages using AAS styl
Approximate perturbed direct homotopy reduction method: infinite series reductions to two perturbed mKdV equations
An approximate perturbed direct homotopy reduction method is proposed and
applied to two perturbed modified Korteweg-de Vries (mKdV) equations with
fourth order dispersion and second order dissipation. The similarity reduction
equations are derived to arbitrary orders. The method is valid not only for
single soliton solution but also for the Painlev\'e II waves and periodic waves
expressed by Jacobi elliptic functions for both fourth order dispersion and
second order dissipation. The method is valid also for strong perturbations.Comment: 8 pages, 1 figur
Identification of parallel flows in congestion management with multiple electricity markets
Parallel flow is a direct result of interconnected system operation. In this paper, the methodologies to calculate parallel flows for both market and non-market entities including market flows are investigated in order to identify the cause of potential loop flow issue in the congestion management process. In an interconnected system, the parallel flow identification is a complex issue because transmission congestion can be affected by all the entities of the system. To deal with it, the impact of market operation on loop flow is analyzed through market flow. In addition, for a system consisting of both market and non-market entities, the parallel flow due to the market flow methodology is investigated in details. To mitigate the loop flow, we propose to change the method to calculate the transaction impacts using generation-to-load instead of generation-to-generation. The numerical results on a simplified Eastern Interconnection system are described to demonstrate. © 2014 IEEE.postprin
Spin injection from perpendicular magnetized ferromagnetic -MnGa into (Al,Ga)As heterostructures
Electrical spin injection from ferromagnetic -MnGa into an (Al,Ga)As
p-i-n light emitting diode (LED) is demonstrated. The -MnGa layers show
strong perpendicular magnetocrystalline anisotropy, enabling detection of spin
injection at remanence without an applied magnetic field. The bias and
temperature dependence of the spin injection are found to be qualitatively
similar to Fe-based spin LED devices. A Hanle effect is observed and
demonstrates complete depolarization of spins in the semiconductor in a
transverse magnetic field.Comment: 4 pages, 3 figure
A Model for the Moving `Wisps' in the Crab Nebula
I propose that the moving `wisps' near the center of the Crab Nebula result
from nonlinear Kelvin-Helmholtz instabilities in the equatorial plane of the
shocked pulsar wind. Recent observations suggest that the wisps trace out
circular wavefronts in this plane, expanding radially at speeds approximately
less than c/3. Instabilities could develop if there is sufficient velocity
shear between a faster-moving equatorial zone and a slower moving shocked
pulsar wind at higher latitudes. The development of shear could be related to
the existence of a neutral sheet -- with weak magnetic field -- in the
equatorial zone, and could also be related to a recent suggestion by Begelman
that the magnetic field in the Crab pulsar wind is much stronger than had been
thought. I show that plausible conditions could lead to the growth of
instabilities at the radii and speeds observed, and that their nonlinear
development could lead to the appearance of sharp wisplike features.Comment: 7 pages; 3 postscript figures; LaTex, uses emulateapj.sty; to Appear
in the Astrophysical Journal, Feb. 20, 1999, Vol. 51
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