25,709 research outputs found
Average power density spectrum of long GRBs detected with BeppoSAX/GRBM and with Fermi/GBM
From past experiments the average power density spectrum (PDS) of GRBs with
unknown redshift was found to be modelled from 0.01 to 1 Hz with a power-law,
f^(-alpha), with alpha broadly consistent with 5/3. Recent analyses of the
Swift/BAT catalogue showed analogous results in the 15-150 keV band. We carried
out the same analysis on the bright GRBs detected by BeppoSAX/GRBM and
Fermi/GBM. The BeppoSAX/GRBM data, in the energy range 40-700 keV and with 7.8
and 0.5-ms time resolutions, allowed us to explore for the first time the
average PDS at very high frequencies (up to 1 kHz) and reveal a break around
1-2 Hz, previously found in CGRO/BATSE data. The Fermi/GBM data, in the energy
band 8-1000 keV, allowed us to explore for the first time the average PDS
within a broad energy range. Our results confirm and extend the energy
dependence of the PDS slope, according to which harder photons have shallower
PDS.Comment: 13 pages, 9 figures, accepted to MNRA
Holistic corpus-based dialectology
This paper is concerned with sketching future directions for corpus-based dialectology. We advocate a holistic approach to the study of geographically conditioned linguistic variability, and we present a suitable methodology, 'corpusbased dialectometry', in exactly this spirit. Specifically, we argue that in order to live up to the potential of the corpus-based method, practitioners need to (i) abandon their exclusive focus on individual linguistic features in favor of the study of feature aggregates, (ii) draw on computationally advanced multivariate analysis techniques (such as multidimensional scaling, cluster analysis, and principal component analysis), and (iii) aid interpretation of empirical results by marshalling state-of-the-art data visualization techniques. To exemplify this line of analysis, we present a case study which explores joint frequency variability of 57 morphosyntax features in 34 dialects all over Great Britain
Foreground and background text in retrieval
Our hypothesis is that certain clauses have foreground functions in text,
while other clauses have background functions and that these functions are
expressed or reflected in the syntactic structure of the clause.
Presumably these clauses will have differing utility for automatic
approaches to text understanding; a summarization system might want to
utilize background clauses to capture commonalities between numbers of
documents while an indexing system might use foreground clauses in order to
capture specific characteristics of a certain document
The Infrared Spectrograph on the Spitzer Space Telescope
The Infrared Spectrograph (IRS) is one of three science instruments on the
Spitzer Space Telescope. The IRS comprises four separate spectrograph modules
covering the wavelength range from 5.3 to 38micron with spectral resolutions, R
\~90 and 600, and it was optimized to take full advantage of the very low
background in the space environment. The IRS is performing at or better than
the pre-launch predictions. An autonomous target acquisition capability enables
the IRS to locate the mid-infrared centroid of a source, providing the
information so that the spacecraft can accurately offset that centroid to a
selected slit. This feature is particularly useful when taking spectra of
sources with poorly known coordinates. An automated data reduction pipeline has
been developed at the Spitzer Science Center.Comment: Accepted in ApJ Sup. Spitzer Special Issue, 6 pages, 4 figure
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