5,526 research outputs found
Stochastic Gravitational Wave Measurements with Bar Detectors: Dependence of Response on Detector Orientation
The response of a cross-correlation measurement to an isotropic stochastic
gravitational-wave background depends on the observing geometry via the overlap
reduction function. If one of the detectors being correlated is a resonant bar
whose orientation can be changed, the response to stochastic gravitational
waves can be modulated. I derive the general form of this modulation as a
function of azimuth, both in the zero-frequency limit and at arbitrary
frequencies. Comparisons are made between pairs of nearby detectors, such as
LIGO Livingston-ALLEGRO, Virgo-AURIGA, Virgo-NAUTILUS, and EXPLORER-AURIGA,
with which stochastic cross-correlation measurements are currently being
performed, planned, or considered.Comment: 17 pages, REVTeX (uses rcs, amsmath, hyperref, and graphicx style
files), 4 figures (8 eps image files
Economic Standards for Pedestrian Areas for Disabled People: Results from Observation Work
1.1.1 The Institute for Transport Studies was invited by the
Transport and Road Research Laboratory to submit a research
proposal, with costs, aimed at establishing suitable "Ergonomic
Standards for Pedestrian Areas for Disabled People". The project
commenced on 1st July, 1986 and was split into two parts, with
part one involving four months' work over the period to 31st
December, 1986 and part two finishing on 30th April, 1988.
1.1.2
The -objectives of the study laid down in the design
brief by the Transport and Road Research Laboratory were:
a) To produce a guide to good practice for the design and
maintenance of footways and pedestrianised areas;
b) To provide, where possible, recommended standards for design
and maintenance.
The good practice guide and the recommended standards were to be
primarily aimed at disabled people and the elderly, but the
requirements of the able-bodied were also to be considered, as
were conflicts between the needs of different groups of user.
The economic implications of implementation and maintenance were
also to be detailed.
(Continues..
Economic Standards for Pedestrian Areas for Disabled People: Results of the Initial and Main Interview
1.1.1
The Institute for Transport Studies was invited by the
Transport and Road Research Laboratory to submit a research
proposal, with costs, aimed at establishing suitable llErgonomic
Standards for Pedestrian Areas for Disabled People". The project
commenced on 1st July, 1986 and was split into two parts, with
part one involving four monthso work over the period to 31st
December, 1986 and part two finishing on 30th April, 1988.
1.1.2
The main objectives of the Study laid down in the design
brief by the Transport and Road Research Laboratory were:
a) To produce a guide to good practice for the design and
maintenance of footways and pedestrianised areas;
b) To provide, where possible, recommended standards for design
and maintenance.
The good practice guide and the recommended standards were to be
primarily aimed at disabled people and the elderly, but the
requirements of the able-bodied were also to be considered, as
were conflicts between the needs of different groups of user.
The economic implications of implementation and maintenance were
also to be detailed
Ergonomic Standards for Pedestrian Areas for Disabled People: Results from Observation Work
1.1.1 The Institute for Transport Studies was invited by the
Transport and Road Research Laboratory to submit a research
proposal, with costs, aimed at establishing suitable "Ergonomic
Standards for Pedestrian Areas for Disabled People". The project
commenced on 1st July, 1986 and was split into two parts, with
part one involving four months' work over the period to 31st
December, 1986 and part two finishing on 30th April, 1988.
1.1.2
The -objectives of the study laid down in the design
brief by the Transport and Road Research Laboratory were:
a) To produce a guide to good practice for the design and
maintenance of footways and pedestrianised areas;
b) To provide, where possible, recommended standards for design
and maintenance.
The good practice guide and the recommended standards were to be
primarily aimed at disabled people and the elderly, but the
requirements of the able-bodied were also to be considered, as
were conflicts between the needs of different groups of user.
The economic implications of implementation and maintenance were
also to be detailed.
(Continues..
Searching for Galactic White Dwarf Binaries in Mock LISA Data using an F-Statistic Template Bank
We describe an F-statistic search for continuous gravitational waves from
galactic white-dwarf binaries in simulated LISA Data. Our search method employs
a hierarchical template-grid based exploration of the parameter space. In the
first stage, candidate sources are identified in searches using different
simulated laser signal combinations (known as TDI variables). Since each source
generates a primary maximum near its true "Doppler parameters" (intrinsic
frequency and sky position) as well as numerous secondary maxima of the
F-statistic in Doppler parameter space, a search for multiple sources needs to
distinguish between true signals and secondary maxima associated with other,
"louder" signals. Our method does this by applying a coincidence test to reject
candidates which are not found at nearby parameter space positions in searches
using each of the three TDI variables. For signals surviving the coincidence
test, we perform a fully coherent search over a refined parameter grid to
provide an accurate parameter estimation for the final candidates. Suitably
tuned, the pipeline is able to extract 1989 true signals with only 5 false
alarms. The use of the rigid adiabatic approximation allows recovery of signal
parameters with errors comparable to statistical expectations, although there
is still some systematic excess with respect to statistical errors expected
from Gaussian noise. An experimental iterative pipeline with seven rounds of
signal subtraction and re-analysis of the residuals allows us to increase the
number of signals recovered to a total of 3419 with 29 false alarms.Comment: 29 pages, 11 figures; submitted to Classical and Quantum Gravit
Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217
As the number of observed brown dwarf outflows is growing it is important to
investigate how these outflows compare to the well studied jets from young
stellar objects. A key point of comparison is the relationship between outflow
and accretion activity and in particular the ratio between the mass outflow and
accretion rates (/). The brown dwarf candidate
ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric
study of brown dwarfs, to be driving an asymmetric outflow with the
blue-shifted lobe having a position angle of 20. The aim here
is to further investigate the properties of ISO-ChaI 217, the morphology and
kinematics of its outflow, and to better constrain
(/). The outflow is spatially resolved in the
lines and is detected out to 1\farcs6
in the blue-shifted lobe and ~ 1" in the red-shifted lobe. The asymmetry
between the two lobes is confirmed although the velocity asymmetry is less
pronounced with respect to our previous study. Using thirteen different
accretion tracers we measure log() [M/yr]= -10.6
0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI
217 outflow was derived for a range of values of A, up to
a value of A = 2.5 mag estimated for the source extinction. The logarithm
of the mass outflow () was estimated in the range -11.7 to -11.1
for both jets combined. Thus / [\Msun/yr] lies
below the maximum value predicted by magneto-centrifugal jet launching models.
Finally, both model fitting of the Balmer decrements and spectro-astrometric
analysis of the H line show that the bulk of the H I emission comes
from the accretion flow.Comment: accepted by Astronomy & Astrophysic
New Coordinates for the Amplitude Parameter Space of Continuous Gravitational Waves
The parameter space for continuous gravitational waves (GWs) can be divided
into amplitude parameters (signal amplitude, inclination and polarization
angles describing the orientation of the source, and an initial phase) and
phase-evolution parameters. The division is useful in part because the
Jaranowski-Krolak-Schutz (JKS) coordinates on the four-dimensional amplitude
parameter space allow the GW signal to be written as a linear combination of
four template waveforms with the JKS coordinates as coefficients. We define a
new set of coordinates on the amplitude parameter space, with the same
properties, which is more closely connected to the physical amplitude
parameters. These naturally divide into two pairs of Cartesian-like coordinates
on two-dimensional subspaces, one corresponding to left- and the other to
right-circular polarization. We thus refer to these as CPF (circular
polarization factored) coordinates. The corresponding two sets of polar
coordinates (known as CPF-polar) can be related in a simple way to the physical
parameters. We illustrate some simplifying applications for these various
coordinate systems, such as: a calculation of Jacobians between various
coordinate systems; an illustration of the signal coordinate singularities
associated with left- and right-circular polarization, which correspond to the
origins of the two two-dimensional subspaces; and an elucidation of the form of
the log-likelihood ratio between hypotheses of Gaussian noise with and without
a continuous GW signal. These are used to illustrate some of the prospects for
approximate evaluation of a Bayesian detection statistic defined by
marginalization over the physical parameter space. Additionally, in the
presence of simplifying assumptions about the observing geometry, we are able
to explicitly evaluate the integral for the Bayesian detection statistic, and
compare it to the approximate results.Comment: REVTeX, 18 pages, 8 image files included in 7 figure
Sensitivity of predicted bioaerosol exposure from open windrow composting facilities to ADMS dispersion model parameters
Bioaerosols are released in elevated quantities from composting facilities and are associated with negative health effects, although dose-response relationships are not well understood, and require improved exposure classification. Dispersion modelling has great potential to improve exposure classification, but has not yet been extensively used or validated in this context. We present a sensitivity analysis of the ADMS dispersion model specific to input parameter ranges relevant to bioaerosol emissions from open windrow composting. This analysis provides an aid for model calibration by prioritising parameter adjustment and targeting independent parameter estimation. Results showed that predicted exposure was most sensitive to the wet and dry deposition modules and the majority of parameters relating to emission source characteristics, including pollutant emission velocity, source geometry and source height. This research improves understanding of the accuracy of model input data required to provide more reliable exposure predictions
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