7,812 research outputs found
Study of aerodynamic technology for single-cruise-engine VSTOL fighter/attack aircraft, phase 1
A conceptual design and analysis on a single engine VSTOL fighter/attack aircraft is completed. The aircraft combines a NASA/deHavilland ejector with vectored thrust and is capable of accomplishing the mission and point performance of type Specification 169, and a flight demonstrator could be built with an existing F101/DFE engine. The aerodynamic, aero/propulsive, and propulsive uncertainties are identified, and a wind tunnel program is proposed to address those uncertainties associated with wing borne flight
Multi-hadron states in Lattice QCD spectroscopy
The ability to reliably measure the energy of an excited hadron in Lattice
QCD simulations hinges on the accurate determination of all lower-lying
energies in the same symmetry channel. These include not only single-particle
energies, but also the energies of multi-hadron states. This talk deals with
the determination of multi-hadron energies in Lattice QCD. The
group-theoretical derivation of lattice interpolating operators that couple
optimally to multi-hadron states is described. We briefly discuss recent
algorithmic developments which allow for the efficient implementation of these
operators in software, and present numerical results from the Hadron Spectrum
Collaboration.Comment: 5 pages, 3 figures, talk given at Hadron 2009, Tallahassee, Florida,
December 1, 200
Simulated Annealing Determination Of Shear Wave Travel Time
The method of simulated annealing is introduced to obtain relative moveouts between
different depths from an iso-offset section. This method has been shown to be more
consistent than conventional picks based on peaks, troughs, or zero crossings especially
in situations where the signal-to-noise ratio is low or the wavelet is emergent. This
method also provides a means of quantifying the relative confidence in each pick over
the entire depth of the well. The method has been applied to the data obtained by
the ARCO shear wave logging tool and compared favorably with more conventional
estimates of shear wave slowness and was shown to be robust, even in areas of weak
arrivals.Massachusetts Institute of Technology. Full Waveform Acoustic Logging Consortiu
The heavy quark's self energy from moving NRQCD on the lattice
We present a calculation of the heavy quark's self energy in moving NRQCD to
one-loop in perturbation theory. Results for the energy shift and external
momentum renormalisation are discussed and compared with non-perturbative
results. We show that the momentum renormalisation is small, which is the
result of a remnant of re-parameterisation invariance on the lattice.Comment: Talk given at Lattice2004(heavy), Fermilab, June 21-26, 200
The excited hadron spectrum in lattice QCD using a new method of estimating quark propagation
Progress in determining the spectrum of excited baryons and mesons in lattice
QCD is described. Large sets of carefully-designed hadron operators have been
studied and their effectiveness in facilitating the extraction of excited-state
energies is demonstrated. A new method of stochastically estimating the
low-lying effects of quark propagation is proposed which will allow reliable
determinations of temporal correlations of single-hadron and multi-hadron
operators.Comment: 5 pages, 4 figures, talk given at Hadron 2009, Tallahassee, Florida,
December 1, 200
Nanocrystal dispersed amorphous alloys
Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided
Solar Coronal Structures and Stray Light in TRACE
Using the 2004 Venus transit of the Sun to constrain a semi-empirical
point-spread function for the TRACE EUV solar telescope, we have measured the
effect of stray light in that telescope. We find that 43% of 171A EUV light
that enters TRACE is scattered, either through diffraction off the entrance
filter grid or through other nonspecular effects. We carry this result forward,
via known-PSF deconvolution of TRACE images, to identify its effect on analysis
of TRACE data. Known-PSF deconvolution by this derived PSF greatly reduces the
effect of visible haze in the TRACE 171A images, enhances bright features, and
reveals that the smooth background component of the corona is considerably less
bright (and hence much more rarefied) than commonly supposed. Deconvolution
reveals that some prior conlclusions about the Sun appear to have been based on
stray light in the images. In particular, the diffuse background "quiet corona"
becomes consistent with hydrostatic support of the coronal plasma; feature
contrast is greatly increased, possibly affecting derived parameters such as
the form of the coronal heating function; and essentially all existing
differential emission measure studies of small features appear to be affected
by contamination from nearby features. We speculate on further implications of
stray light for interpretation of EUV images from TRACE and similar
instruments, and advocate deconvolution as a standard tool for image analysis
with future instruments such as SDO/AIA.Comment: Accepted by APJ; v2 reformatted to single-column format for online
readabilit
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