1,221,410 research outputs found
LISA as a dark energy probe
Recently it was shown that the inclusion of higher signal harmonics in the
inspiral signals of binary supermassive black holes (SMBH) leads to dramatic
improvements in parameter estimation with the Laser Interferometer Space
Antenna (LISA). In particular, the angular resolution becomes good enough to
identify the host galaxy or galaxy cluster, in which case the redshift can be
determined by electromagnetic means. The gravitational wave signal also
provides the luminosity distance with high accuracy, and the relationship
between this and the redshift depends sensitively on the cosmological
parameters, such as the equation-of-state parameter of dark energy. With a single binary SMBH event at having
appropriate masses and orientation, one would be able to constrain to
within a few percent. We show that, if the measured sky location is folded into
the error analysis, the uncertainty on goes down by an additional factor of
2-3, leaving weak lensing as the only limiting factor in using LISA as a dark
energy probe.Comment: 11pages, 1 Table, minor changes in text, accepted for publication in
Classical and Quantum Gravity (special issue for proceedings of 7th LISA
symposium
Applications of Internet of Things
This book introduces the Special Issue entitled âApplications of Internet of Thingsâ, of ISPRS International Journal of Geo-Information. Topics covered in this issue include three main parts: (I) intelligent transportation systems (ITSs), (II) location-based services (LBSs), and (III) sensing techniques and applications. Three papers on ITSs are as follows: (1) âVehicle positioning and speed estimation based on cellular network signals for urban roads,â by Lai and Kuo; (2) âA method for traffic congestion clustering judgment based on grey relational analysis,â by Zhang et al.; and (3) âSmartphone-based pedestrianâs avoidance behavior recognition towards opportunistic road anomaly detection,â by Ishikawa and Fujinami. Three papers on LBSs are as follows: (1) âA high-efficiency method of mobile positioning based on commercial vehicle operation data,â by Chen et al.; (2) âEfficient location privacy-preserving k-anonymity method based on the credible chain,â by Wang et al.; and (3) âProximity-based asynchronous messaging platform for location-based Internet of things service,â by Gon Jo et al. Two papers on sensing techniques and applications are as follows: (1) âDetection of electronic anklet wearersâ groupings throughout telematics monitoring,â by Machado et al.; and (2) âCamera coverage estimation based on multistage grid subdivision,â by Wang et al
Coherent Bayesian analysis of inspiral signals
We present in this paper a Bayesian parameter estimation method for the
analysis of interferometric gravitational wave observations of an inspiral of
binary compact objects using data recorded simultaneously by a network of
several interferometers at different sites. We consider neutron star or black
hole inspirals that are modeled to 3.5 post-Newtonian (PN) order in phase and
2.5 PN in amplitude. Inference is facilitated using Markov chain Monte Carlo
methods that are adapted in order to efficiently explore the particular
parameter space. Examples are shown to illustrate how and what information
about the different parameters can be derived from the data. This study uses
simulated signals and data with noise characteristics that are assumed to be
defined by the LIGO and Virgo detectors operating at their design
sensitivities. Nine parameters are estimated, including those associated with
the binary system, plus its location on the sky. We explain how this technique
will be part of a detection pipeline for binary systems of compact objects with
masses up to 20 \sunmass, including cases where the ratio of the individual
masses can be extreme.Comment: Accepted for publication in Classical and Quantum Gravity, Special
issue for GWDAW-1
The INTEGRAL IBIS/ISGRI System Point Spread Function and Source Location Accuracy
The imager on board INTEGRAL (IBIS) presently provides the most detailed sky
images ever obtained at energies above 30 keV. The telescope is based on a
coded aperture imaging system which allows to obtain sky images in a large
field of view 29deg x 29deg with an angular resolution of 12'. The System Point
Spread Function of the telescope and its detailed characteristics are here
described along with the specific analysis algorithms used to derive the
accurate point-like source locations. The derived location accuracy is studied
using the first in-flight calibration data on strong sources for the IBIS/ISGRI
system. The dependence of the calibrated location accuracy with the signal to
noise ratio of the sources is presented. These preliminary studies demonstrate
that the IBIS/ISGRI telescope and the standard scientific analysis software
allow source localizations with accuracy at 90% confidence level better than 1'
for sources with signal to noise ratios > 30 over the whole field of view, in
agreement with the expected performances of the instrument.Comment: 5 pages, 5 figures, accepted for publication in A&A Lett (INTEGRAL
special issue
Beyond Rhetoric: How Context Influences Education Policy Advocatesâ Success
This article discusses findings from a study of a 22-year campaign to change special education assessment policy in Ontario by the advocacy organization People for Education (P4E) and explains how dominant discourses enabled the government to leave the issue unresolved. Based on a rhetorical analysis of 58 documents, the article identifies strategies used by P4E to persuade Ontarioâs government and citizens to view studentsâ uneven access to educational assessments as a problem. Further, since this problem differently impacts children by class and geographical location, it perpetuates inequities. Despite using strategies deemed effective in other change efforts, arguments mobilized by P4E have not been persuasive in a neoliberal context that champions responsibilized individualism, meritocracy, human capital development, and reduced funding of public services
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