2,950 research outputs found
Sideslip-induced static pressure errors in flight-test measurements
During lateral flight-test maneuvers of a V/STOL research aircraft, large errors in static pressure were observed. An investigation of the data showed a strong correlation of the pressure record with variations in sideslip angle. The sensors for both measurements were located on a standard air-data nose boom. An algorithm based on potential flow over a cylinder that was developed to correct the pressure record for sideslip-induced errors is described. In order to properly apply the correction algorithm, it was necessary to estimate and correct the lag error in the pressure system. The method developed for estimating pressure lag is based on the coupling of sideslip activity into the static ports and can be used as a standard flight-test procedure. The estimation procedure is discussed and the corrected static-pressure record for a typical lateral maneuver is presented. It is shown that application of the correction algorithm effectively attenuates sideslip-induced errors
Ionization processes in a local analogue of distant clumpy galaxies: VLT MUSE IFU spectroscopy and FORS deep images of the TDG NGC 5291N
We present IFU observations with MUSE@VLT and deep imaging with FORS@VLT of a
dwarf galaxy recently formed within the giant collisional HI ring surrounding
NGC 5291. This TDG-like object has the characteristics of typical z=1-2
gas-rich spiral galaxies: a high gas fraction, a rather turbulent clumpy ISM,
the absence of an old stellar population, a moderate metallicity and star
formation efficiency. The MUSE spectra allow us to determine the physical
conditions within the various complex substructures revealed by the deep
optical images, and to scrutinize at unprecedented spatial resolution the
ionization processes at play in this specific medium. Starburst age, extinction
and metallicity maps of the TDG and surrounding regions were determined using
the strong emission lines Hbeta, [OIII], [OI], [NII], Halpha and [SII] combined
with empirical diagnostics. Discrimination between different ionization
mechanisms was made using BPT--like diagrams and shock plus photoionization
models. Globally, the physical conditions within the star--forming regions are
homogeneous, with in particular an uniform half-solar oxygen abundance. At
small scales, the derived extinction map shows narrow dust lanes. Regions with
atypically strong [OI] emission line immediately surround the TDG. The [OI] /
Halpha ratio cannot be easily accounted for by photoionization by young stars
or shock models. At larger distances from the main star--forming clumps, a
faint diffuse blue continuum emission is observed, both with the deep FORS
images and MUSE data. It does not have a clear counterpart in the UV regime
probed by GALEX. A stacked spectrum towards this region does not exhibit any
emission line, excluding faint levels of star formation, nor stellar absorption
lines that might have revealed the presence of old stars. Several hypotheses
are discussed for the origin of these intriguing features.Comment: 13 pages, 15 figures, accepted for publication in A&
H I Recycling: Formation of Tidal Dwarf Galaxies
Original paper can be found at: http://www.astrosociety.org/pubs/cs/222-252.html--Copyright Astronomical Society of the PacificGalactic collisions trigger a number of phenomena, such as transportation inward of gas from distances of up to kiloparsecs from the center of a galaxy to the nuclear region, fueling a central starburst or nuclear activity. The inverse process, the ejection of material into the intergalactic medium by tidal forces, is another important aspect and can be studied especially well through detailed HI observations of interacting systems. These studies have shown that a large fraction of the gaseous component of colliding galaxies can be expelled. Part of this tidal debris might fall back, be dispersed throughout the intergalactic medium or re-condense to form a new generation of galaxies: the so-called tidal dwarf galaxies. The latter are nearby examples of galaxies in formation. The properties of these recycled objects, and different ways to identify them, are reviewed here
Molecular Gas in Tidal Dwarf Galaxies: On-going Galaxy Formation
We investigate the process of galaxy formation as can be observed in the only
currently forming galaxies -- the so-called Tidal Dwarf Galaxies, hereafter
TDGs -- through observations of the molecular gas detected via its CO (Carbon
Monoxide) emission. Molecular gas is a key element in the galaxy formation
process, providing the link between a cloud of gas and a {\it bona fide}
galaxy. We have now detected CO in 9 TDGs with an overall detection rate of
80%, showing that molecular gas is abundant in TDGs, up to a few . The CO emission coincides both spatially and kinematically with the
HI emission, indicating that the molecular gas forms from the atomic hydrogen
where the HI column density is high. A possible trend of more evolved TDGs
having greater molecular gas masses is observed, in accord with the
transformation of HI into H. Although uncertainties are still large for
individual objects as the geometry is unknown, we find that the "dynamical"
masses of TDGs, estimated from the CO line widths, do not seem to be greater
than the "visible" masses (HI + H + a stellar component), i.e., TDGs
require no dark matter. We provide evidence that TDGs are self-gravitating
entities, implying that we are witnessing the ensemble of processes in galaxy
formation: concentration of large amounts of gas in a bound object,
condensation of the gas, which is atomic at this point, to form molecular gas
and the subsequent star formation from the dense molecular component.Comment: 8 pages 4 figures, to be published in: Proceedings of the IAU
Symposium 217: Recycling Intergalactic and Interstellar Matte
High-field irreversible moment reorientation in the antiferromagnet FeTe
Magnetization measurements have been performed on single-crystalline
FeTe in pulsed magnetic fields up to 53 T
and temperatures from 4.2 to 65 K. At K, a non-reversible reorientation
of the antiferromagnetic moments is observed at T as the pulsed
field is on the rise. No anomaly is observed at during the fall of the
field and, as long as the temperature is unchanged, during both rises and falls
of additional field pulses. The transition at is reactivated if the
sample is warmed up above the N\'{e}el temperature K and cooled
down again. The magnetic field-temperature phase diagram of FeTe in
is also investigated. We present the temperature
dependence of , as well as that of the antiferromagnetic-to-paramagnetic
borderline in temperatures above 40 K.Comment: 5 pages, 4 figure
Is there really a case for Off-Site Manufacturing?
The solution often suggested to mitigate poor time, cost and quality in construction is to produce buildings in an automated and industrialised environment. To date, use of Off-Site Manufacturing (OSM) in Australia has enjoyed extremely limited success. Distilling the variables in the success and failure of OSM in other places and applying relevant variables to the Australian context, enables a better response for OSM. The purpose of the paper is therefore to examine whether or not OSM techniques are viable in the Australian housing market. The paper uses a detailed and critical analysis of the literature to examine OSM of housing in various countries, seeking to establish the major reasons for successful and unsuccessful models. The findings are then contrasted with the Australian context seeking criteria to inform successful introduction of OSM into Australia. Among other things, findings indicate the catalyst for the introduction of OSM of housing is almost universally a result of major events such as wars and natural disasters. Innovation has also played a role in encouraging change to construction methods. Whilst the countries addressed have diverse economies and climates compared to each other and Australia, certain common criteria have been found from those examples to assist in modelling an OSM solution in Australia. The implications of this work revolve around the provision of a more efficient, less wasteful and more responsive housing production environment which will potentially improve affordability in the market place
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