3,200 research outputs found
Understanding the patterns, characteristics and trends in the housing sector labour force-AHURI Final Report No.208
The focus of this study is the national policy problem of the gap between housing supply and demand, as identified and monitored by the National Housing Supply Council. Research to date has not focused upon the spatial distribution of labour supply and demand of the housing sector labour force (HSLF). Also research to date has not distinguished between labour engaged in building new dwellings and labour engaged in undertaking alterations and additions. In addressing this research gap, this Final Report presents the summative output of the AHURI research project entitled: Understanding the patterns, characteristics and trends in the housing sector labour force in Australia. It follows the publication of the Positioning Paper for the project (Dalton et al. 2011a).This chapter has presented a response to the secondary research question: What are the temporal dimensions of the HSLF as a whole and the new build and alterations and additions sub-sectors? It first described the categories, containing records of workers who worked in the housing industry, which were used to interrogate the census data. Using these categories, the data presented showed that, in aggregate, the size of the HSLF grew in the period 2001-06. In Victoria, the workforce grew from 72 000 to 89 000, an increase of 23 per cent in the five-year period 2001-06. The 44 per cent growth in the Queensland workforce was almost twice that of Victoria for the same period when it grew from 53 000 to 77 000. This aggregate data was then split to distinguish between workers who worked on 'new build' housing and those who worked on 'alterations and additions'. The results of this splitting showed that there had been growth in both sub-sectors. The rate of growth in the alterations and additions sub-sector was greater than for the new build sector, although this growth was from a lower base
Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula
We report the first detection of X-ray emission associated with the
Homunculus Nebula which surrounds the supermassive star Eta Carinae. The
emission is characterized by a temperature in excess of 100 MK, and is
consistent with scattering of the time-delayed X-ray flux associated with the
star. The nebular emission is bright in the northwestern lobe and near the
central regions of the Homunculus, and fainter in the southeastern lobe. We
also report the detection of an unusually broad Fe K fluorescent line, which
may indicate fluorescent scattering off the wind of a companion star or some
other high velocity outflow. The X-ray Homunculus is the nearest member of the
small class of Galactic X-ray reflection nebulae, and the only one in which
both the emitting and reflecting sources are distinguishable.Comment: 17 pages, 5 figures, accepted by Ap
A Coordinated X-ray and Optical Campaign of the Nearby Massive Binary Orionis Aa: II. X-ray Variability
We present time-resolved and phase-resolved variability studies of an
extensive X-ray high-resolution spectral dataset of the Orionis Aa
binary system. The four observations, obtained with Chandra ACIS HETGS, have a
total exposure time of ~479 ks and provide nearly complete binary phase
coverage. Variability of the total X-ray flux in the range 5-25 is
confirmed, with maximum amplitude of about +/-15% within a single ~125 ks
observation. Periods of 4.76d and 2.04d are found in the total X-ray flux, as
well as an apparent overall increase in flux level throughout the 9-day
observational campaign. Using 40 ks contiguous spectra derived from the
original observations, we investigate variability of emission line parameters
and ratios. Several emission lines are shown to be variable, including S XV, Si
XIII, and Ne IX. For the first time, variations of the X-ray emission line
widths as a function of the binary phase are found in a binary system, with the
smallest widths at phase=0.0 when the secondary Orionis Aa2 is at
inferior conjunction. Using 3D hydrodynamic modeling of the interacting winds,
we relate the emission line width variability to the presence of a wind cavity
created by a wind-wind collision, which is effectively void of embedded wind
shocks and is carved out of the X-ray-producing primary wind, thus producing
phase-locked X-ray variability.Comment: 36 pages, 14 Tables, 19 Figures, accepted by ApJ, one of 4 related
papers to be published togethe
Coherence in the Quasi-Particle 'Scattering' by the Vortex Lattice in Pure Type-II Superconductors
The effect of quasi-particle (QP) 'scattering' by the vortex lattice on the
de-Haas van-Alphen oscillations in a pure type-II superconductor is
investigated within mean field,asymptotic perturbation theory. Using a 2D
electron gas model it is shown that, due to a strict phase coherence in the
many-particle correlation functions, the 'scattering' effect in the asymptotic
limit () is much weaker than what is predicted
by the random vortex lattice model proposed by Maki and Stephen, which destroys
this coherence . The coherent many particle configuration is a collinear array
of many particle coordinates, localized within a spatial region with size of
the order of the magnetic length. The amplitude of the magnetization
oscillations is sharply damped just below because of strong
out of phase magnetic oscillations in the superconducting
condensation energy ,which tend to cancel the normal electron oscillations.
Within the ideal 2D model used it is found, however, that because of the
relative smallness of the quartic and higher order terms in the expansion, the
oscillations amplitude at lower fields does not really damp to zero, but only
reverses sign and remains virtually undamped well below . This
conclusion may be changed if disorder in the vortex lattice, or vortex lines
motion will be taken into account. The reduced QP 'scattering' effect may be
responsible for the apparent crossover from a strong damping of the dHvA
oscillations just below to a weaker damping at lower fields observed
experimentally in several 3D superconductors.Comment: 26 pages, Revtex no Figure
A Coordinated X-ray and Optical Campaign on the Nearest Massive Eclipsing Binary, Delta Ori Aa: I. Overview of the X-ray Spectrum
We present an overview of four phase-constrained Chandra HETGS X-ray
observations of Delta Ori A. Delta Ori A is actually a triple system which
includes the nearest massive eclipsing spectroscopic binary, Delta Ori Aa, the
only such object which can be observed with little phase-smearing with the
Chandra gratings. Since the fainter star, Delta Ori Aa2, has a much lower X-ray
luminosity than the brighter primary, Delta Ori A provides a unique system with
which to test the spatial distribution of the X-ray emitting gas around Delta
Ori Aa1 via occultation by the photosphere of and wind cavity around the X-ray
dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for
the combined observation, having an exposure time of nearly 500 ksec and
covering nearly the entire binary orbit. Companion papers discuss the X-ray
variability seen in the Chandra spectra, present new space-based photometry and
ground-based radial velocities simultaneous with the X-ray data to better
constrain the system parameters, and model the effects of X-rays on the optical
and UV spectrum. We find that the X-ray emission is dominated by embedded wind
shock emission from star Aa1, with little contribution from the tertiary star
Ab or the shocked gas produced by the collision of the wind of Aa1 against the
surface of Aa2. We find a similar temperature distribution to previous X-ray
spectrum analyses. We also show that the line half-widths are about
the terminal velocity of the wind of star Aa1. We find a strong
anti-correlation between line widths and the line excitation energy, which
suggests that longer-wavelength, lower-temperature lines form farther out in
the wind. Our analysis also indicates that the ratio of the intensities of the
strong and weak lines of \ion{Fe}{17} and \ion{Ne}{10} are inconsistent with
model predictions, which may be an effect of resonance scatteringComment: accepted by ApJ; revised according to ApJ proo
Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core
With the XMM-Newton and Chandra observatories, we detected two extremely
embedded X-ray sources in the R Corona Australis (R CrA) star forming core,
near IRS 7. These sources, designated as XB and XA, have X-ray absorption
columns of ~3e23 cm-2 equivalent to AV ~180 mag. They are associated with the
VLA centimeter radio sources 10E and 10W, respectively. XA is the counterpart
of the near-infrared source IRS 7, whereas XB has no K-band counterpart above
19.4 mag. This indicates that XB is younger than typical Class I protostars,
probably a Class 0 protostar or in an intermediate phase between Class 0 and
Class I. The X-ray luminosity of XB varied between 29<log LX <31.2 ergs s-1 on
timescales of 3-30 months. XB also showed a monotonic increase in X-ray
brightness by a factor of two in 30 ksec during an XMM-Newton observation. The
XMM-Newton spectra indicate emission from a hot plasma with kT ~3-4 keV and
also show fluorescent emission from cold iron. Though the X-ray spectrum from
XB is similar to flare spectra from Class I protostars in luminosity and
temperature, the light curve does not resemble the lightcurves of magnetically
generated X-ray flares because the variability timescale of XB is too long and
because variations in X-ray count rate were not accompanied by variations in
spectral hardness. The short-term variation of XB may be caused by the partial
blocking of the X-ray plasma, while the month-long flux enhancement may be
driven by mass accretion.Comment: 26 pages, 8 figures, To be published in ApJ in April 200
Ginzburg-Landau-Gor'kov Theory of Magnetic oscillations in a type-II 2-dimensional Superconductor
We investigate de Haas-van Alphen (dHvA) oscillations in the mixed state of a
type-II two-dimensional superconductor within a self-consistent Gor'kov
perturbation scheme. Assuming that the order parameter forms a vortex lattice
we can calculate the expansion coefficients exactly to any order. We have
tested the results of the perturbation theory to fourth and eight order against
an exact numerical solution of the corresponding Bogoliubov-de Gennes
equations. The perturbation theory is found to describe the onset of
superconductivity well close to the transition point . Contrary to
earlier calculations by other authors we do not find that the perturbative
scheme predicts any maximum of the dHvA-oscillations below . Instead we
obtain a substantial damping of the magnetic oscillations in the mixed state as
compared to the normal state. We have examined the effect of an oscillatory
chemical potential due to particle conservation and the effect of a finite
Zeeman splitting. Furthermore we have investigated the recently debated issue
of a possibility of a sign change of the fundamental harmonic of the magnetic
oscillations. Our theory is compared with experiment and we have found good
agreement.Comment: 39 pages, 8 figures. This is a replacement of supr-con/9608004.
Several sections changed or added, including a section on the effect of spin
and the effect of a conserved number of particles. To be published in Phys.
Rev.
Absence of Persistent Magnetic Oscillations in Type-II Superconductors
We report on a numerical study intended to examine the possibility that
magnetic oscillations persist in type II superconductors beyond the point where
the pairing self-energy exceeds the normal state Landau level separation. Our
work is based on the self-consistent numerical solution for model
superconductors of the Bogoliubov-deGennes equations for the vortex lattice
state. In the regime where the pairing self-energy is smaller than the
cyclotron energy, magnetic oscillations resulting from Landau level
quantization are suppressed by the broadening of quasiparticle Landau levels
due to the non-uniform order parameter of the vortex lattice state, and by
splittings of the quasiparticle bands. Plausible arguments that the latter
effect can lead to a sign change of the fundamental harmonic of the magnetic
oscillations when the pairing self-energy is comparable to the cyclotron energy
are shown to be flawed. Our calculations indicate that magnetic oscillations
are strongly suppressed once the pairing self-energy exceeds the Landau level
separation.Comment: 7 pages, revtex, 7 postscript figure
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