692 research outputs found
Teaching case: Managing an IT carve out at a multi-national enterprise
Research on the information society and the policies and strategies for its creation has tended to
discuss them rationally as the national, and occasionally international or regional, responses to
changes in the competitive environment. The predominant notion of the information society in various
levels of governance has only rarely been critically examined. The paper provides a Foucauldian
analysis of the constitution of the information society as a political and policy imperative at the level
of the European Union and the multiple effects it had for its member states. Drawing on ideas on
governmentality and regimes of truth, I argue that the European Commission continually shaped the
rationality and identity of the information society it heralded, by managing to set itself as the
legitimate locus of policy for the information society. In revealing the dominant discursive truths
about the European information society, the research discusses how the truth claims about the
construction of a particular version of the information society and the legitimate loci of its government
shaped the degrees of freedom of the Greek policy makers through a range of disciplining and selfdisciplining practices
Millimeter-Wave Aperture Synthesis Imaging of Vega: Evidence for a Ring Arc at 95 AU
We present the first millimeter-wave aperture synthesis map of dust around a
main sequence star. A 3'' resolution image of 1.3 mm continuum emission from
Vega reveals a clump of emission 12'' from the star at PA 45 deg, consistent
with the location of maximum 850 micron emission in a lower resolution
JCMT/SCUBA map. The flux density is 4.0+/-0.9 mJy. Adjacent 1.3 mm peaks with
flux densities 3.4+/-1.0 mJy and 2.8+/-0.9 mJy are located 14'' and 13'' from
the star at PA 67 deg and 18 deg, respectively. An arc-like bridge connects the
two strongest peaks. There is an additional 2.4 +/-0.8 mJy peak to the SW 11''
from the star at PA 215 deg and a marginal detection, 1.4+/-0.5 mJy, at the
stellar position, consistent with photospheric emission. An extrapolation from
the 850 micron flux, assuming F_{1.3mm-0.85mm} proportional to lambda^{-2.8},
agrees well with the total detected flux for Vega at 1.3 mm, and implies a dust
emissivity index, beta, of 0.8. We conclude that we have detected all but a
very small fraction of the dust imaged by SCUBA in our aperture synthesis map
and that these grains are largely confined to segments of a ring of radius 95
AU.Comment: 4 pages, 1 figure, 1 table, accepted for publication in Astrophysical
Journal Letter
SENTINEL-1 DATA TO MAP FLOODED AREAS: THE ROLE OF INSAR COHERENCE AND POLARIMETRIC INFORMATION
Τα SAR δεδομένα παρατήρησης της Γης μπορούν να προσφέρουν χάρτες πλημμυρικής έκτασης και πληροφοριών υψηλής ποιότητας για την καλύτερη εκτίμηση του κινδύνου πλημμύρας κατά συνέπεια το σχεδιασμό, καθώς και για την υποστήριξη των πολιτικών αρχών υπέρ της προστασίας κατά τη φάση έκτακτης ανάγκης. Το πεδίο εφαρμογής του παρόντος εγγράφου είναι να δημιουργήσει χάρτες πλημμυρικής έκτασης από μια σειρά εικόνων SAR της λεκάνης του Έβρου, που αντιπροσωπεύει μια διασυνοριακή κοίτη πλημμυρών. Η μελέτη χρησιμοποιεί χρονολογικές σειρές εικόνων SAR του Copernicus δορυφορικού συστήματος Sentinel-1 που καλύπτει την περίοδο Οκτώβριος 2014-Μάιος 2015. Η μεθοδολογία προσπαθεί να προσδιορίσει την πλημμύρα που συμβαίνει σε τρεις κύριες κατηγορίες κάλυψης γης, όπως είναι οι αστικές περιοχές, γυμνά ή κακώς βλάστηση εδάφους και περιοχές με βλάστηση, εκμεταλλευόμενοι τα εναλλασσόμενη πόλωση SAR κανάλια backscattering, και τη συνάφεια συμβολομετρίας για τον καλύτερο χαρακτηρισμό του τοπίου. Χρησιμοποιώντας εναλλασσόμενη πόλωση SAR δεδομένα παρέχει την ευκαιρία να υπάρχει μια καλύτερη κατανόηση και ερμηνεία της ανίχνευσης πλημμύρας λόγω του διαφορετικού τρόπου που αντιδρά η κάλυψη γης σε διαφορετικές 1731 πολώσεις. Έτσι, με την εφαρμογή της εκτίμησης της συμβολομετρικής συνάφειας μπορούμε να επιτύχουμε ένα καλύτερη καταγραφή και γνώση των πλημμυρισμένων περιοχών, στη πάροδο του χρόνου, στη συγκεκριμένη περιοχή.SAR earth observation data can provide high quality flood maps and information to better assess the flood risk accordingly planning as well as to support civil protection authorities during emergency phase. The scope of this paper is to create flood extent maps from a series of SAR scenes of the Evros basin which represents a transboundary floodplain. The study uses time series SAR images of Sentnel-1 ESA’s Copernicus satellite system covering the period October 2014 to May 2015. The methodology tries to identify the flood that occurs in three main land cover classes, such as urban areas, bare or poorly vegetated soil and vegetated areas, taking advantage of co- and cross-polarized SAR backscattering channels, and the InSAR coherence to better characterize the landscape. Dual-pol SAR data provides the opportunity to have a better understanding and interpretation of flood detection due to way different land cover react to different polarizations. Thus, with the implementation of InSAR coherence estimation we may achieve a better record and knowledge of the flooded areas, over time, in the specific region.
Infrared to millimetre photometry of ultra-luminous IR galaxies: new evidence favouring a 3-stage dust model
Infrared to millimetre spectral energy distributions have been obtained for
41 bright ultra-luminous infrared galaxies. The observations were carried out
with ISOPHOT between 10 and 200 micron and supplemented for 16 sources with
SCUBA at 450 and 850 micron and with SEST at 1.3 mm. In addition, seven sources
were observed at 1.2 and 2.2 m with the 2.2 m telescope on Calar Alto.
These new SEDs represent the most complete set of infrared photometric
templates obtained so far on ULIRGs in the local universe.Comment: 23 pages, 11 figures, accepted for publication in Astronomy &
Astrophysic
High Mass Star Formation. II. The Mass Function of Submillimeter Clumps in M17
We have mapped an approximately 5.5 by 5.5 pc portion of the M17 massive
star-forming region in both 850 and 450 micron dust continuum emission using
the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk
Maxwell Telescope (JCMT). The maps reveal more than 100 dusty clumps with
deconvolved linear sizes of 0.05--0.2 pc and masses of 0.8--120 solar masses,
most of which are not associated with known mid-infrared point sources. Fitting
the clump mass function with a double power law gives a mean power law exponent
of alpha_high = -2.4 +/- 0.3 for the high-mass power law, consistent with the
exponent of the Salpeter stellar mass function. We show that a lognormal clump
mass distribution with a peak at about 4 solar masses produces as good a fit to
the clump mass function as does a double power law. This 4 solar mass peak mass
is well above the peak masses of both the stellar initial mass function and the
mass function of clumps in low-mass star-forming regions. Despite the
difference in intrinsic mass scale, the shape of the M17 clump mass function
appears to be consistent with the shape of the core mass function in low-mass
star-forming regions. Thus, we suggest that the clump mass function in
high-mass star-forming regions may be a scaled-up version of that in low-mass
regions, instead of its extension to higher masses.Comment: 33 pages, 6 figures, 3 tables. Accepted for publication in the
Astrophysical Journa
Radiometric calibration of the TreeTalker (TT+) spectrometer
Spectral raw data from the TreeTalker device are output as radiometrically uncalibratedand with the12 different spectral bandsnot directly comparableamong each other, hence hinderingthe retrieval of the real spectral signature from the observations. This report describes the methodology and results of experiments aimed at obtainingcustom calibration factors to convert the raw dataoutputfrom the TreeTalker spectrometer into values of radiative energy flux for each spectral band
Observations of T Tauri Disks at Sub-AU Radii: Implications for Magnetospheric Accretion and Planet Formation
We determine inner disk sizes and temperatures for four solar-type (1-2
M) classical T Tauri stars (AS 207A, V2508 Oph, AS 205A, and PX Vul)
using 2.2 m observations from the Keck Interferometer. Nearly
contemporaneous near-IR adaptive optics imaging photometry, optical photometry,
and high-dispersion optical spectroscopy are used to distinguish contributions
from the inner disks and central stars in the interferometric observations. In
addition, the spectroscopic and photometric data provide estimates of stellar
properties, mass accretion rates, and disk co-rotation radii. We model our
interferometric and photometric data in the context of geometrically flat
accretion disk models with inner holes, and flared disks with puffed-up inner
walls. Models incorporating puffed-up inner disk walls generally provide better
fits to the data, similar to previous results for higher-mass Herbig Ae stars.
Our measured inner disk sizes are larger than disk truncation radii predicted
by magnetospheric accretion models, with larger discrepancies for sources with
higher mass accretion rates. We suggest that our measured sizes correspond to
dust sublimation radii, and that optically-thin gaseous material may extend
further inward to the magnetospheric truncation radii. Finally, our inner disk
measurements constrain the location of terrestrial planet formation as well as
potential mechanisms for halting giant planet migration.Comment: Accepted for publication in ApJ (May 1, 2005 issue
Line emission from circumstellar disks around A stars
The nature of the tenuous disks around A stars has raised considerable
controversy in the literature during the past decade. The debate whether or not
the disk around beta Pictoris contains gaseous molecular hydrogen is only the
most recent example. Since CO is in general a poor tracer for the gas content
of these low mass disks, we discuss here detailed emission line calculations
for alternative tracers like C and C+, based on recent optically thin disk
models by Kamp & van Zadelhoff (2001). The [CII] 157.7 mum line was searched
toward Vega and beta Pictoris -- the most prominent A stars with disks -- using
ISO LWS data, and a tentative detection is reported toward the latter object.
From a comparison with emission line observations as well as absorption line
studies of both stars, the gas-to-dust ratio is constrained to lie between 0.5
and 9 for beta Pictoris. For Vega the [CII] observations indicate an upper
limit of 0.2 M_Earth for the disk gas mass. Predicted line intensities of C+
and C are presented for a range of models and appear promising species to trace
the gas content in the disks around A stars with future instrumental
capabilities (SOFIA, Herschel, APEX and ALMA). Searches for CO emission should
focus on the J=3-2 line.Comment: 14 pages, to appear in A&A (accepted
Temperatura superficial de isolantes térmicos e cortinas para a produção animal.
Projeto: 03.07.09.049
A near-infrared survey of the entire R Corona Australis cloud
To understand low- to intermediate-mass star-formation in the nearby R CrA
molecular cloud, we try to identify the stellar content that is accessible with
near-infrared observations. We obtained a JHK band mosaic of 10 x 60 arcmin
square covering the entire RCrA molecular cloud with unprecedented sensitivity.
We present a catalogue of about 3500 near-infrared sources fainter than the
saturation limit K = 10 mag, reaching K = 18mag. We analysed the extended
sources by inspecting their morphology and point sources by means of
colour-colour and colour-magnitude diagrams. Additionally, we compared the
extinction inferred from the NIR data with the line-of-sight dust emission at
1.2 mm. Sources towards high dust emission but relatively low H-K show a
projected mm-exces; these sources are either immediately surrounded by cold
circumstellar material or, if too red to be a true foreground object, they are
embedded in the front layer of the 1.2 mm emitting dust cloud. In both cases
they are most likely associated with the cloud.Comment: 11 pages, 12 Figures, accepted by Astronomy and Astrophysic
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