123,093 research outputs found
Radar studies of bird migration
Observations of bird migration with NASA radars were made at Wallops Island, Va. Simultaneous observations were made at a number of radar sites in the North Atlantic Ocean in an effort to discover what happened to those birds that were observed leaving the coast of North America headed toward Bermuda, the Caribbean and South America. Transatlantic migration, utilizing observations from a large number of radars is discussed. Detailed studies of bird movements at Wallops Island are presented
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Tracking radar studies of bird migration
The application of tracking radar for determining the flight paths of migratory birds is discussed. The effects produced by various meteorological parameters are described. Samples of radar scope presentations obtained during tracking studies are presented. The characteristics of the radars and their limitations are examined
Population imbalanced fermions in harmonically trapped optical lattices
The attractive Fermi-Hubbard Hamiltonian is solved via the Bogoliubov-de
Gennes formalism to analyze the ground state phases of population imbalanced
fermion mixtures in harmonically trapped two-dimensional optical lattices. In
the low density limit the superfluid order parameter modulates in the radial
direction towards the trap edges to accommodate the unpaired fermions that are
pushed away from the trap center with a single peak in their density. However
in the high density limit while the order parameter modulates in the radial
direction towards the trap center for low imbalance, it also modulates towards
the trap edges with increasing imbalance until the superfluid to normal phase
transition occurs beyond a critical imbalance. This leads to a single peak in
the density of unpaired fermions for low and high imbalance but leads to double
peaks for intermediate imbalance.Comment: 4 pages with 4 figures, accepted to appear in PR
Morphology investigation on direct current pulsed gas tungsten arc welded additive layer manufactured Ti6Al4V alloy
The effects of pulsed gas tungsten arc weldingparameters on the morphology of
additive layer manufacturedTi6Al4V has been investigated in this study. Thepeak/
base current ratio and pulse frequency are found tohave no significant effect on
the refinement of prior betagrain size. However, it is found that the wire feed
ratehas a considerable effect on the prior beta grainrefinement at a given heat
input. This is due to the extrawire input being able to supply many
heterogeneousnucleation sites and also results in a negative temperaturegradient
in the front of the liquidus which blocks thecolumnar growth and changes the
columnar growth toequiaixal growth
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