4,301 research outputs found
Impact resistance of spar-shell composite fan blades
Composite spar-shell fan blades for a 1.83 meter (6 feet) diameter fan stage were fabricated and tested in a whirling arm facility to evaluate foreign object damage (FOD) resistance. The blades were made by adhesively bonding boron-epoxy shells on titanium spars and then adhesively bonding an Inconel 625 sheath on the leading edge. The rotating blades were individually tested at a tip speed of 800 feet per second. Impacting media used were gravel, rivets, bolt, nut, ice balls, simulated birds, and a real bird. Incidence angles were typical of those which might be experienced by STOL aircraft. The tests showed that blades of the design tested in this program have satisfactory impact resistance to small objects such as gravel, rivets, nuts, bolts, and two inch diameter ice balls. The blades suffered nominal damage when impacted with one-pound birds (9 to 10 ounce slice size). However, the shell was removed from the spar for a larger slice size
Electrochemical Energy Storage Subsystems Study, Volume 2
The effects on life cycle costs (LCC) of major design and performance technology parameters for multi kW LEO and GEO energy storage subsystems using NiCd and NiH2 batteries and fuel cell/electrolysis cell devices were examined. Design, performance and LCC dynamic models are developed based on mission and system/subsystem requirements and existing or derived physical and cost data relationships. The models are exercised to define baseline designs and costs. Then the major design and performance parameters are each varied to determine their influence on LCC around the baseline values
Electrochemical energy storage subsystems study, volume 1
The effects on life cycle costs (LCC) of major design and performance technology parameters for multi kW LEO and GEO energy storage subsystems using NiCd and NiH2 batteries and fuel cell/electrolysis cell devices were examined. Design, performance and LCC dynamic models are developed based on mission and system/subsystem requirements and existing or derived physical and cost data relationships. The models define baseline designs and costs. The major design and performance parameters are each varied to determine their influence on LCC around the baseline values
Mudas de videiras.
Brotou um pequeno ramo de uva que plantei sem enxerto e direto na terra, mas será que ele produzirá frutos?bitstream/item/200760/1/12938-2011-p.108.pd
Generalized Berry Conjecture and mode correlations in chaotic plates
We consider a modification of the Berry Conjecture for eigenmode statistics
in wave-bearing systems. The eigenmode correlator is conjectured to be
proportional to the imaginary part of the Green's function. The generalization
is applicable not only to scalar waves in the interior of homogeneous isotropic
systems where the correlator is a Bessel function, but to arbitrary points of
heterogeneous systems as well. In view of recent experimental measurements,
expressions for the intensity correlator in chaotic plates are derived.Comment: 5 pages, 1 figur
Laser cooling of a nanomechanical resonator mode to its quantum ground state
We show that it is possible to cool a nanomechanical resonator mode to its
ground state. The proposed technique is based on resonant laser excitation of a
phonon sideband of an embedded quantum dot. The strength of the sideband
coupling is determined directly by the difference between the electron-phonon
couplings of the initial and final states of the quantum dot optical
transition. Possible applications of the technique we describe include
generation of non-classical states of mechanical motion.Comment: 5 pages, 3 figures, revtex
A Theoretical Model for the Relation for Supermassive Black Holes in Galaxies
We construct a model for the formation of black holes within galactic bulges.
The initial state is a slowly rotating isothermal sphere, characterized by
effective transport speed \aeff and rotation rate . The black hole
mass is determined when the centrifugal radius of the collapse flow exceeds the
capture radius of the central black hole. This model reproduces the observed
correlation between black hole masses and galactic velocity dispersions, \mbh
\approx 10^8 M_\odot (\sigma/200 \kms)^4, where \sigma = \sqrt{2} \aeff.
This model also predicts the ratio \mrat of black hole mass to host mass:
\mrat 0.004 (\sigma/200 \kms).Comment: 9 pages, 2 figures, submitted to Astrophysical Journal Letter
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