45,059 research outputs found
Exploring roles and relationships in the production of the built environment
Given the number of different agencies and the complexity of institutional and professional relationships in the production, management and regulation of the built environment, many students entering built environment professions leave university education to take up work placements or employment without a sufficient understanding of the different actors and the formal and informal interactions and social relationships between them. Furthermore, destructive stereotypes may form during the educational process as students construct their own professional identity, in part learnt from their teachers and peers, and naturalised by the academic and professional institutions that form the context of their education – a process of enculturation termed ‘professional socialization’ by social scientists (Cuff, 1991: 118). These stereotypes may lead ultimately to inter-professional tensions and hostilities. Innovations in practice often involve challenges to established roles or joined-up thinking which breaches institutional structures, for all of which graduates may be ill-prepared
The Parsec-Scale Jets of the TeV Blazars H 1426+428, 1ES 1959+650, and PKS 2155-304: 2001-2004
We present Very Long Baseline Array (VLBA) observations of the TeV blazars H
1426+428, 1ES 1959+650, and PKS 2155-304 obtained during the years 2001 through
2004. We observed H 1426+428 at four epochs at 8 GHz, and found that its
parsec-scale structure consisted of a ~17 mJy core and a single ~3 mJy jet
component with an apparent speed of 2.09 +/- 0.53c. The blazar 1ES 1959+650 was
observed at three epochs at frequencies of 15 and 22 GHz. Spectral index
information from these dual-frequency observations was used to definitively
identify the core of the parsec-scale structure. PKS 2155-304 was observed at a
single epoch at 15 GHz with dual-circular polarization, and we present the
first VLBI polarimetry image of this source. For 1ES 1959+650 and PKS 2155-304,
the current observations are combined with the VLBA observations from our
earlier paper to yield improved apparent speed measurements for these sources
with greatly reduced measurement errors. The new apparent speed measured for
component C2 in 1ES 1959+650 is 0.00 +/- 0.04c (stationary), and the new
apparent speed measured for component C1 in PKS 2155-304 is 0.93 +/- 0.31c. We
combine the new apparent speed measurements from this paper with the apparent
speeds measured in TeV blazar jets from our earlier papers to form a current
set of apparent speed measurements in TeV HBLs. The mean peak apparent pattern
speed in the jets of the TeV HBLs is about 1c. We conclude the paper with a
detailed discussion of the interpretation of the collected VLBA data on TeV
blazars in the context of current theoretical models for the parsec-scale
structure of TeV blazar jets.Comment: 16 pages, Astrophysical Journal, in pres
Local Spin-Gauge Symmetry of the Bose-Einstein Condensates in Atomic Gases
The Bose-Einstein condensates of alkali atomic gases are spinor fields with
local ``spin-gauge" symmetry. This symmetry is manifested by a superfluid
velocity (or gauge field) generated by the Berry phase of the
spin field. In ``static" traps, splits the degeneracy of the
harmonic energy levels, breaks the inversion symmetry of the vortex nucleation
frequency , and can lead to {\em vortex ground states}. The
inversion symmetry of , however, is not broken in ``dynamic"
traps. Rotations of the atom cloud can be generated by adiabatic effects
without physically rotating the entire trap.Comment: Typos in the previous version corrected, thanks to the careful
reading of Daniel L. Cox. 13 pages + 2 Figures in uuencode + gzip for
VLBA Polarization Observations of Markarian 421 After a Gamma-Ray High State
We present four high dynamic range, dual-circular polarization, Very Long
Baseline Array (VLBA) observations at 22 GHz of Markarian 421, taken throughout
the year following the source's unprecedented gamma-ray high state in early
2001. These four new VLBA observations are combined with data from our earlier
1999 paper and archival VLBA data-sets that have become available since 1999 to
produce a combined 28 epoch VLBA data-set on Mrk 421 spanning the years 1994 to
2002. No new component associated with the 2001 flares was seen on the total
intensity images, but the combined data-set allowed precise measurements of the
apparent speeds of the existing components. The peak measured apparent speed
was for component C5, which has an apparent speed of 0.1 +/- 0.02 c (H_0=71 km
s^{-1} Mpc^{-1}, Omega_m=0.27, and Omega_Lambda=0.73). No counterjet is seen
with a limit on the jet to counterjet brightness ratio J >~ 100. These observed
VLBI properties of Markarian 421 are consistent with a jet with a bulk Lorentz
factor of about 2 and an angle to the line-of-sight of about 1 degree,
suggesting a jet that decelerates between the gamma-ray producing region and
the parsec scale. The VLBI core and inner jet (component C7) have fractional
polarizations of about 5%, and an electric vector position angle (EVPA) aligned
with the jet axis. Component C5 (at 1.5 mas from the core) has a higher
fractional polarization of about 15%, and an EVPA nearly orthogonal to the jet
axis. Significant variability is detected in the EVPA of component C6, which at
two of the four epochs shows an EVPA aligned with the jet axis, possibly a sign
of propagating disturbances that are only visible on the polarization images.
If these propagating disturbances are linked to the 2001 gamma-ray high state,
then their inferred apparent speed is between 1 and 3 c.Comment: 11 pages, accepted to Ap
Channel, tube, and Taylor-Couette flow of complex viscoelastic fluid models
We show how to formulate two-point boundary value problems to compute laminar channel, tube, and Taylor-Couette flow profiles for some complex viscoelastic fluid models of differential type. The models examined herein are the Pom-Pom Model [McLeish and Larson 42:81-110, (1998)] the Pompon Model [Öttinger 40:317-321, (2001)] and the Two Coupled Maxwell Modes Model (Beris and Edwards 1994). For the two-mode Upper-Convected Maxwell Model, we calculate analytical solutions for the three flow geometries and use the solutions to validate the numerical methodology. We illustrate how to calculate the velocity, pressure, conformation tensor, backbone orientation tensor, backbone stretch, and extra stress profiles for various models. For the Pom-Pom Model, we find that the two-point boundary value problem is numerically unstable, which is due to the aphysical non-monotonic shear stress vs shear rate prediction of the model. For the other two models, we compute laminar flow profiles over a wide range of pressure drops and inner cylinder velocities. The volumetric flow rate and the nonlinear viscoelastic material properties on the boundaries of the flow geometries are determined as functions of the applied pressure drop, allowing easy analysis of experimentally measurable quantitie
End to end distance on contour loops of random gaussian surfaces
A self consistent field theory that describes a part of a contour loop of a
random Gaussian surface as a trajectory interacting with itself is constructed.
The exponent \nu characterizing the end to end distance is obtained by a Flory
argument. The result is compared with different previuos derivations and is
found to agree with that of Kondev and Henley over most of the range of the
roughening exponent of the random surface.Comment: 7 page
Approach to the Continuum Limit of the Quenched Hermitian Wilson-Dirac Operator
We investigate the approach to the continuum limit of the spectrum of the
Hermitian Wilson-Dirac operator in the supercritical mass region for pure gauge
SU(2) and SU(3) backgrounds. For this we study the spectral flow of the
Hermitian Wilson-Dirac operator in the range . We find that the
spectrum has a gap for and that the spectral density at zero,
, is non-zero for . We find that and, for
(exponential in the lattice spacing) as one goes to
the continuum limit. We also compute the topological susceptibility and the
size distribution of the zero modes. The topological susceptibility scales well
in the lattice spacing for both SU(2) and SU(3). The size distribution of the
zero modes does not appear to show a peak at a physical scale.Comment: 19 pages revtex with 9 postscript figures included by eps
Statistical comparison of pooled nitrogen washout data of various altitude decompression response groups
This analysis was done to determine whether various decompression response groups could be characterized by the pooled nitrogen (N2) washout profiles of the group members, pooling individual washout profiles provided a smooth time dependent function of means representative of the decompression response group. No statistically significant differences were detected. The statistical comparisons of the profiles were performed by means of univariate weighted t-test at each 5 minute profile point, and with levels of significance of 5 and 10 percent. The estimated powers of the tests (i.e., probabilities) to detect the observed differences in the pooled profiles were of the order of 8 to 30 percent
Nucleon structure from mixed action calculations using 2+1 flavors of asqtad sea and domain wall valence fermions
We present high statistics results for the structure of the nucleon from a
mixed-action calculation using 2+1 flavors of asqtad sea and domain wall
valence fermions. We perform extrapolations of our data based on different
chiral effective field theory schemes and compare our results with available
information from phenomenology. We discuss vector and axial form factors of the
nucleon, moments of generalized parton distributions, including moments of
forward parton distributions, and implications for the decomposition of the
nucleon spin.Comment: 68 pages, 47 figures. Main revision points: improved discussion of
chiral fits and systematic uncertainties, several minor refinements. Accepted
for publication in Phys.Rev.
Scanning laser source and scanning laser detection techniques for different surface crack geometries
Standard test samples typically contain simulated defects such as slots machined normal to the surface. However, real defects will not always propagate in this manner; for example, rolling contact fatigue on rails propagates at around 25º to the surface, and corrosion cracking can grow in a branched manner. Therefore, there is a need to understand how ultrasonic surface waves interact with different crack geometries. We present measurements of machined slots inclined at an angle to the surface normal, or with simple branched geometries, using laser ultrasound. Recently, Rayleigh wave enhancements observed when using the scanning laser source technique, where a generation laser is scanned along a sample, have been highlighted for their potential in detecting surface cracks. We show that the enhancement measured with laser detector scanning can give a more significant enhancement when different crack geometries are considered. We discuss the behaviour of an incident Rayleigh wave in the region of an angled defect, and consider mode-conversions which lead to a very large enhancement when the detector is close to the opening of a shallow defect. This process could be used in characterising defects, as well as being an excellent fingerprint of their presence
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