58,714 research outputs found
The impact of circulation control on rotary aircraft controls systems
Application of circulation to rotary wing systems is a new development. Efforts to determine the near and far field flow patterns and to analytically predict those flow patterns have been underway for some years. Rotary wing applications present a new set of challenges in circulation control technology. Rotary wing sections must accommodate substantial Mach number, free stream dynamic pressure and section angle of attack variation at each flight condition within the design envelope. They must also be capable of short term circulation blowing modulation to produce control moments and vibration alleviation in addition to a lift augmentation function. Control system design must provide this primary control moment, vibration alleviation and lift augmentation function. To accomplish this, one must simultaneously control the compressed air source and its distribution. The control law algorithm must therefore address the compressor as the air source, the plenum as the air pressure storage and the pneumatic flow gates or valves that distribute and meter the stored pressure to the rotating blades. Also, mechanical collective blade pitch, rotor shaft angle of attack and engine power control must be maintained
Generalized Quantum Hall Projection Hamiltonians
Certain well known quantum Hall states -- including the Laughlin states, the
Moore-Read Pfaffian, and the Read-Rezayi Parafermion states -- can be defined
as the unique lowest degree symmetric analytic function that vanishes as at
least p powers as some number (g+1) of particles approach the same point.
Analogously, these same quantum Hall states can be generated as the exact
highest density zero energy state of simple angular momentum projection
operators. Following this theme we determine the highest density zero energy
state for many other values of p and g.Comment: 9 page
Optical response of high- cuprates: possible role of scattering rate saturation and in-plane anisotropy
We present a generalized Drude analysis of the in-plane optical conductivity
(,) in cuprates taking into account the effects of
in-plane anisotropy. A simple ansatz for the scattering rate
(,), that includes anisotropy, a quadratic frequency
dependence and saturation at the Mott-Ioffe-Regel limit, is able to reproduce
recent normal state data on an optimally doped cuprate over a wide frequency
range. We highlight the potential importance of including anisotropy in the
full expression for (,) and challenge previous
determinations of () in which anisotropy was neglected and
() was indicated to be strictly linear in frequency over a wide
frequency range. Possible implications of our findings for understanding
thermodynamic properties and self-energy effects in high- cuprates will
also be discussed.Comment: 8 pages, 7 figures. To be published in Physical Review
Incompressible liquid state of rapidly-rotating bosons at filling factor 3/2
Bosons in the lowest Landau level, such as rapidly-rotating cold trapped
atoms, are investigated numerically in the specially interesting case in which
the filling factor (ratio of particle number to vortex number) is 3/2. When a
moderate amount of a longer-range (e.g. dipolar) interaction is included, we
find clear evidence that the ground state is in a phase constructed earlier by
two of us, in which excitations possess non-Abelian statistics.Comment: 5 pages, 5 figure
Spin 1 inversion: a Majorana tensor force for deuteron alpha scattering
We demonstrate, for the first time, successful S-matrix to potential
inversion for spin one projectiles with non-diagonal yielding a
interaction. The method is a generalization of the
iterative-perturbative, IP, method. We present a test case indicating the
degree of uniqueness of the potential. The method is adapted, using established
procedures, into direct observable to potential inversion, fitting ,
, , and for d + alpha scattering over
a range of energies near 10 MeV. The interaction which we find is
very different from that proposed elsewhere, both real and imaginary parts
being very different for odd and even parity channels.Comment: 7 pages Revtex, 4 ps figure
A nu=2/5 Paired Wavefunction
We construct a wavefunction, generalizing the well known Moore-Read Pfaffian,
that describes spinless electrons at filling fraction nu=2/5 (or bosons at
filling fraction nu=2/3) as the ground state of a very simple three body
potential. We find, analogous to the Pfaffian, that when quasiholes are added
there is a ground state degeneracy which can be identified as zero-modes of the
quasiholes. The zero-modes are identified as having semionic statistics. We
write this wavefunction as a correlator of the Virasoro minimal model conformal
field theory M(5,3). Since this model is non-unitary, we conclude that this
wavefunction is a quantum critical state. Nonetheless, we find that the
overlaps of this wavefunction with exact diagonalizations in the lowest and
first excited Landau level are very high, suggesting that this wavefunction may
have experimental relevance for some transition that may occur in that regime.Comment: 13 pages, 2 figure
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