27,203 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
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
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
Determination of Critical Exponents in Nuclear Systems
Signatures of critical behaviour in nuclear fragmentation are often based on
arguments from percolation theory. We demonstrate with general thermodynamic
considerations and studies of the Ising model that the reliance on percolation
as a reference model bears the risk of missing parts of the essential physics.Comment: 10 pages, TeX with 1 included figure; Proceedings of the 1st Catania
Relativistic Ion Studies: Critical Phenomena and Collective Observables,
Acicastello, May 27-31, 1996, to be published by World Scientific Publ. Co.;
also available from http://www-kp3.gsi.de/www/kp3/aladin_publications.htm
Wigner Crystallization in inhomogeneous one dimensional wires
We explore the theory of electrons confined by one dimensional power law
potentials. We calculate the density profile in the high density electron gas,
the low density Wigner crystal, and the intermediate regime. We extract the
momentum space wavefunction of the electron at the Fermi surface, which can be
measured in experiments on tunneling between parallel wires. The onset of
localization leads to a dramatic broadening of the momentum space wavefunction
together with pronounced sharpening (in energy) of the tunneling spectrum.Comment: 11 pages, 10 figures, RevTeX4: v2. Revised+Expande
Nonvacuum pseudoparticles, quantum tunneling and metastability
It is shown that nonvacuum pseudoparticles can account for quantum tunneling
and metastability. In particular the saddle-point nature of the pseudoparticles
is demonstrated, and the evaluation of path-integrals in their neighbourhood.
Finally the relation between instantons and bounces is used to derive a result
conjectured by Bogomolny and Fateyev.Comment: Latex, 16 pages, no figure
Fluctuation dynamo amplified by intermittent shear bursts in convectively driven magnetohydrodynamic turbulence
Intermittent large-scale high-shear flows are found to occur frequently and
spontaneously in direct numerical simulations of statistically stationary
turbulent Boussinesq magnetohydrodynamic (MHD) convection. The energetic
steady-state of the system is sustained by convective driving of the velocity
field and small-scale dynamo action. The intermittent emergence of flow
structures with strong velocity and magnetic shearing generates magnetic energy
at an elevated rate over time-scales longer than the characteristic time of the
large-scale convective motion. The resilience of magnetic energy amplification
suggests that intermittent shear-bursts are a significant driver of dynamo
action in turbulent magnetoconvection
Flight test of a pure-tone acoustic source
Static and flight testing of a pure-tone acoustic source were conducted in order to: (1) determine if a 4-KHz tone radiated by a source in flight and mixed with broadband aircraft flyover noise could be measured on the ground with a high degree of statistical confidence; (2) determine how well a comparison could be made of flight-to-static tone radiation pattern and a static radiation pattern; and (3) determine if there were any installation effects on the radiation pattern due to the flight vehicle. Narrow-band acoustic data were measured and averaged over eight microphones to obtain a high statistical confidence. The flight data were adjusted to an equivalent static condition by applying corrections for retarded time, spherical spreading, atmospheric absorption, ground impedance, instrumentation constraints, convective amplification, and the Doppler shift. The flight-to-static results are in excellent agreement with the measured static data. No installation effects were observed on the radiation pattern
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