9,378 research outputs found
A synoptic description of coal basins via image processing
An existing image processing system is adapted to describe the geologic attributes of a regional coal basin. This scheme handles a map as if it were a matrix, in contrast to more conventional approaches which represent map information in terms of linked polygons. The utility of the image processing approach is demonstrated by a multiattribute analysis of the Herrin No. 6 coal seam in Illinois. Findings include the location of a resource and estimation of tonnage corresponding to constraints on seam thickness, overburden, and Btu value, which are illustrative of the need for new mining technology
Detailed Structure and Dynamics in Particle-in-Cell Simulations of the Lunar Wake
The solar wind plasma from the Sun interacts with the Moon, generating a wake
structure behind it, since the Moon is to a good approximation an insulator,
has no intrinsic magnetic field and a very thin atmosphere. The lunar wake in
simplified geometry has been simulated via a 1-1/2-D electromagnetic
particle-in-cell code, with high resolution in order to resolve the full phase
space dynamics of both electrons and ions. The simulation begins immediately
downstream of the moon, before the solar wind has infilled the wake region,
then evolves in the solar wind rest frame. An ambipolar electric field and a
potential well are generated by the electrons, which subsequently create a
counter-streaming beam distribution, causing a two-stream instability which
confines the electrons. This also creates a number of electron phase space
holes. Ion beams are accelerated into the wake by the ambipolar electric field,
generating a two stream distribution with phase space mixing that is strongly
influenced by the potentials created by the electron two-stream instability.
The simulations compare favourably with WIND observations.Comment: 10 pages, 13 figures, to be published in Physics of Plasma
Data compression for the Cassini radio and plasma wave instrument
The Cassini Radio and Plasma Wave Science experiment will employ data compression to make effective use of the available data telemetry bandwidth. Some compression will be achieved by use of a lossless data compression chip and some by software in a dedicated 80C85 processor. A description of the instrument and data compression system are included in this report. Also, the selection of data compression systems and acceptability of data degradation is addressed
First-Order Vortex Lattice Melting and Magnetization of YBaCuO$_{7-\delta}
We present the first non-mean-field calculation of the magnetization
of YBaCuO both above and below the flux-lattice melting
temperature . The results are in good agreement with experiment as a
function of transverse applied field . The effects of fluctuations in both
order parameter and magnetic induction are included in the
Ginzburg-Landau free energy functional: fluctuates within the
lowest Landau level in each layer, while fluctuates uniformly according to
the appropriate Boltzmann factor. The second derivative is predicted to be negative throughout the vortex liquid state and
positive in the solid state. The discontinuities in entropy and magnetization
at melting are calculated to be per flux line per layer and
~emu~cm at a field of 50 kOe.Comment: 11 pages, 4 PostScript figures in one uuencoded fil
The K-theoretic Farrell-Jones Conjecture for hyperbolic groups
We prove the K-theoretic Farrell-Jones Conjecture for hyperbolic groups with
(twisted) coefficients in any associative ring with unit.Comment: 33 pages; final version; to appear in Invent. Mat
Buneman instability in a magnetized current-carrying plasma with velocity shear
Buneman instability is often driven in magnetic reconnection. Understanding
how velocity shear in the beams driving the Buneman instability affects the
growth and saturation of waves is relevant to turbulence, heating, and
diffusion in magnetic reconnection. Using a Mathieu-equation analysis for weak
cosine velocity shear together with Vlasov simulations, the effects of shear on
the kinetic Buneman instability are studied in a plasma consisting of strongly
magnetized electrons and cold unmagnetized ions. In the linearly unstable
phase, shear enhances the coupling between oblique waves and the sheared
electron beam, resulting in a wider range of unstable eigenmodes with common
lower growth rates. The wave couplings generate new features of the electric
fields in space, which can persist into the nonlinear phase when electron holes
form. Lower hybrid instabilities simultaneously occur at
with a much lower growth
rate, and are not affected by the velocity shear.Comment: Accepted by Physics of Plasm
Constitution
Constitution of the Law Club of the Utah Agricultural College, with club members listed
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