33,235 research outputs found
The Helios experiment 5 antenna mechanism
The Experiment 5 Antenna deployment problem onboard Helios A, the failure analysis, and changes in design, test, and operation which led to a successful deployment of both antennas during the early Helios B mission phase are described
On the origin of surface states in a correlated local-moment film
The electronic quasiparticle structure of a ferromagnetic local moment film
is investigated within the framework of the s-f model. For the special case of
a single electron in an otherwise empty energy band being exchange coupled to a
fully ordered localised spin system the problem can be solved exactly and, for
the spin-down electron, some marked correlation effects can be found. We extend
our model to incorporate the influence of the surface on the electronic
structure. Therefore we modify the hopping integrals in the vicinity of the
surface. This leads to the existence of surface states, both for the spin-up
and the spin-down spectral density of states. The interplay between the
modification of the hopping integrals and the existence of surface states and
correlation effects is discussed in detail.Comment: 9 pages, 9 figures, accepted for publication in European Physical
Journal
The Helios mechanical despin drive assembly for the high-gain antenna reflector
Helios is the German-American solar probe which comes within 0.31 Astronomical Units of the sun. A special thermal design and a dry lubrication system have resulted in successful operation up to now, with Helios having finished its first orbit around the sun
Study of stator-vane fluctuating pressures in a turbofan engine for static and flight tests
As part of a program to study the fan noise generated from turbofan engines, fluctuating surface pressures induced by fan-rotor wakes were measured on core- and bypass-stator outlet guide vanes of a modified JT15D-1 engine. Tests were conducted with the engine operating on an outdoor test stand and in flight. The amplitudes of pressures measured at fan-rotor blade-passage fundamental frequencies were generally higher and appeared less stable for the static tests than for the flight tests. Fluctuating pressures measured at the blade-passage frequency of the high-speed core compressor were interpreted to be acoustic; however, disturbance trace velocities for either the convected rotor wakes or acoustic pressures were difficult to interpret because of the complex environment
A comparison of the three methods used to obtain acoustic measurements for the NASA Flight Effects Program
The NASA Flight Effects Program has a requirement to compare acoustic data obtained from flyover, static test stand, and wind tunnel tests. Results a laboratory study of the acoustic characteristics of the three technqiues used to measure noise during these tests are presented. Recommendations are made to allow for a comparison of data obtained with each technique
Elastomer coated filler and composites thereof comprising at least 60% by weight of a hydrated filler and an elastomer containing an acid substituent
The impact resistance of flame retardant composites, especially thermoplastic molding: compounds containing over 60% hydrated mineral filler such as Al(OH)3 or Mg(OH)2 as improved by coating the filler with 1 to 20% of an elastomer. The composite will fail by crazing or shearing rather than by brittle fracture. A well bonded elastomeric interphase resulted by utilizing acidic substituted resins such as ethyl-hexyl acrylate-acrylic acid copolymers which bond to and are cross-linked by the basic filler particles. Further improvement in impact resistance was provided by incorporating 1 to 10% of a resin fiber reinforcement such as polyvinyl alcohol fibers that decompose to yield at least 30% water when heated to decomposition temperature
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