29,435 research outputs found
Noise characteristics of upper surface blown configurations: Summary
A systematic experimental program was conducted to develop a data base for the noise and related flow characteristics of upper surface blown configurations. The effect of various geometric and flow parameters was investigated experimentally. The dominant noise was identified from the measured flow and noise characteristics to be generated downstream of the trailing edge. The possibilities of noise reduction techniques were explored. An upper surface blown (USB) noise prediction program was developed to calculate noise levels at any point and noise contours (footprints). Using this noise prediction program and a cruise performance data base, aircraft design studies were conducted to integrate low noise and good performance characteristics. A theory was developed for the noise from the highly sheared layer of a trailing edge wake. Theoretical results compare favorably with the measured noise of the USB model
Effect of neck cut position on time to collapse in halal slaughtered cattle without stunning
This study examined the effect of neck cut position on the time to physical collapse in upright restrained halal slaughtered cattle (n = 644). Time to collapse was used as an indirect indicator of the early stages of onset of unconsciousness. Cattle were slaughtered with either a conventional low (LNC) (n = 561) or a high neck cut (HNC) (n = 83). Mean time to final collapse was higher in the LNC compared to HNC group (18.9 ± 1.1 s and 13.5 ± 1.3 s respectively (P 20 s to final collapse had larger false aneurysms. In summary, the HNC reduced the mean time to final collapse and the frequency of animals that took longer than 20 s to collapse
A Non-Centrosymmetric Superconductor with a Bulk 3D Dirac Cone Gapped by Strong Spin Orbit Coupling
Layered, non-centrosymmetric, heavy element PbTaSe2 is found to be
superconducting. We report its electronic properties accompanied by electronic
structure calculations. Specific heat, electrical resistivity and magnetic
susceptibility measurements indicate that PbTaSe2 is a moderately coupled,
type-II BCS superconductor (Tc = 3.72 K, Ginzburg-Landau parameter Kappa = 14)
with an electronphonon coupling constant of Lambda_ep = 0.74. Electronic
structure calculations reveal a single bulk 3D Dirac cone at the K point of the
Brillouin Zone derived exclusively from its hexagonal Pb layer; it is similar
to the feature found in graphene except there is a 0.8 eV gap opened by
spin-orbit coupling. The combination of large spin-orbit coupling and lack of
inversion symmetry also results in large Rashba splitting on the order of
tenths of eV
Turbulence and turbulent mixing in natural fluids
Turbulence and turbulent mixing in natural fluids begins with big bang
turbulence powered by spinning combustible combinations of Planck particles and
Planck antiparticles. Particle prograde accretions on a spinning pair releases
42% of the particle rest mass energy to produce more fuel for turbulent
combustion. Negative viscous stresses and negative turbulence stresses work
against gravity, extracting mass-energy and space-time from the vacuum.
Turbulence mixes cooling temperatures until strong-force viscous stresses
freeze out turbulent mixing patterns as the first fossil turbulence. Cosmic
microwave background temperature anisotropies show big bang turbulence fossils
along with fossils of weak plasma turbulence triggered as plasma photon-viscous
forces permit gravitational fragmentation on supercluster to galaxy mass
scales. Turbulent morphologies and viscous-turbulent lengths appear as linear
gas-proto-galaxy-clusters in the Hubble ultra-deep-field at z~7. Proto-galaxies
fragment into Jeans-mass-clumps of primordial-gas-planets at decoupling: the
dark matter of galaxies. Shortly after the plasma to gas transition,
planet-mergers produce stars that explode on overfeeding to fertilize and
distribute the first life.Comment: 23 pages 12 figures, Turbulent Mixing and Beyond 2009 International
Center for Theoretical Physics conference, Trieste, Italy. Revision according
to Referee comments. Accepted for Physica Scripta Topical Issue to be
published in 201
The optical transmission spectrum of the hot Jupiter HAT-P-32b: clouds explain the absence of broad spectral features?
We report Gemini-North GMOS observations of the inflated hot Jupiter
HAT-P-32b during two primary transits. We simultaneously observed two
comparison stars and used differential spectro-photometry to produce
multi-wavelength light curves. 'White' light curves and 29 'spectral' light
curves were extracted for each transit and analysed to refine the system
parameters and produce transmission spectra from 520-930nm in ~14nm bins. The
light curves contain time-varying white noise as well as time-correlated noise,
and we used a Gaussian process model to fit this complex noise model. Common
mode corrections derived from the white light curve fits were applied to the
spectral light curves which significantly improved our precision, reaching
typical uncertainties in the transit depth of ~2x10^-4, corresponding to about
half a pressure scale height. The low resolution transmission spectra are
consistent with a featureless model, and we can confidently rule out broad
features larger than about one scale height. The absence of Na/K wings or
prominent TiO/VO features is most easily explained by grey absorption from
clouds in the upper atmosphere, masking the spectral features. However, we
cannot confidently rule out clear atmosphere models with low abundances (~10^-3
solar) of TiO, VO or even metal hydrides masking the Na and K wings. A smaller
scale height or ionisation could also contribute to muted spectral features,
but alone are unable to to account for the absence of features reported here.Comment: 17 pages, 11 figures, 2 tables, accepted for publication in MNRA
A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720nm
We report Gemini-South GMOS observations of the exoplanet system WASP-29
during primary transit as a test case for differential spectrophotometry. We
use the multi-object spectrograph to observe the target star and a comparison
star simultaneously to produce multiple light curves at varying wavelengths.
The 'white' light curve and fifteen 'spectral' light curves are analysed to
refine the system parameters and produce a transmission spectrum from 515 to
720nm. All light curves exhibit time-correlated noise, which we model using a
variety of techniques. These include a simple noise rescaling, a Gaussian
process model, and a wavelet based method. These methods all produce consistent
results, although with different uncertainties. The precision of the
transmission spectrum is improved by subtracting a common signal from all the
spectral light curves, reaching a typical precision of ~1x10^-4 in transit
depth. The transmission spectrum is free of spectral features, and given the
non-detection of a pressure broadened Na feature, we can rule out the presence
of a Na rich atmosphere free of clouds or hazes, although we cannot rule out a
narrow Na core. This indicates that Na is not present in the atmosphere, and/or
that clouds/hazes play a significant role in the atmosphere and mask the broad
wings of the Na feature, although the former is a more likely explanation given
WASP-29b's equilibrium temperature of ~970 K, at which Na can form various
compounds. We also briefly discuss the use of Gaussian process and wavelet
methods to account for time correlated noise in transit light curves.Comment: 15 pages, 9 figures, 3 tables. Published in MNRAS. Figure 2 corrected
in version
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