25,628 research outputs found
Semantic multimedia remote display for mobile thin clients
Current remote display technologies for mobile thin clients convert practically all types of graphical content into sequences of images rendered by the client. Consequently, important information concerning the content semantics is lost. The present paper goes beyond this bottleneck by developing a semantic multimedia remote display. The principle consists of representing the graphical content as a real-time interactive multimedia scene graph. The underlying architecture features novel components for scene-graph creation and management, as well as for user interactivity handling. The experimental setup considers the Linux X windows system and BiFS/LASeR multimedia scene technologies on the server and client sides, respectively. The implemented solution was benchmarked against currently deployed solutions (VNC and Microsoft-RDP), by considering text editing and WWW browsing applications. The quantitative assessments demonstrate: (1) visual quality expressed by seven objective metrics, e.g., PSNR values between 30 and 42 dB or SSIM values larger than 0.9999; (2) downlink bandwidth gain factors ranging from 2 to 60; (3) real-time user event management expressed by network round-trip time reduction by factors of 4-6 and by uplink bandwidth gain factors from 3 to 10; (4) feasible CPU activity, larger than in the RDP case but reduced by a factor of 1.5 with respect to the VNC-HEXTILE
Numerical Studies of the Compressible Ising Spin Glass
We study a two-dimensional compressible Ising spin glass at constant volume.
The spin interactions are coupled to the distance between neighboring particles
in the Edwards-Anderson model with +/- J interactions. We find that the energy
of a given spin configuration is shifted from its incompressible value, E_0, by
an amount quadratic in E_0 and proportional to the coupling strength. We then
construct a simple model expressed only in terms of spin variables that
predicts the existence of a critical value of the coupling above which the
spin-glass transition disappears.Comment: REVTeX, 4 pages, 4 figures. Submitted to Phys. Rev. Let
An observational study of children interacting with an augmented story book
We present findings of an observational study investigating how young children interact with augmented reality story books. Children aged between 6 and 7 read and interacted with one of two story books aimed at early literacy education. The books pages were augmented using animated virtual 3D characters, sound, and interactive tasks. Introducing novel media to young children requires system and story designers to consider not only technological issues but also questions arising from story design and the design of interactive sequences. We discuss findings of our study and implications regarding the implementation of augmented story books
Monitoring and Discovering X-ray Pulsars in the Small Magellanic Cloud
Regular monitoring of the SMC with RXTE has revealed a huge number of X-ray
pulsars. Together with discoveries from other satellites at least 45 SMC
pulsars are now known. One of these sources, a pulsar with a period of
approximately 7.8 seconds, was first detected in early 2002 and since discovery
it has been found to be in outburst nine times. The outburst pattern clearly
shows a period of 45.1 +/- 0.4 d which is thought to be the orbital period of
this system. Candidate outburst periods have also been obtained for nine other
pulsars and continued monitoring will enable us to confirm these. This large
number of pulsars, all located at approximately the same distance, enables a
wealth of comparative studies. In addition, the large number of pulsars found
(which vastly exceeds the number expected simply by scaling the relative mass
of the SMC and the Galaxy) reveals the recent star formation history of the SMC
which has been influenced by encounters with both the LMC and the Galaxy.Comment: 5 pages, 4 figures, AIP conference proceedings format. Contribution
to "X-ray Timing 2003: Rossi and Beyond." meeting held in Cambridge, MA,
November, 200
A search for X-ray emission from rich clusters, extended halos around clusters, and superclusters
The all-sky data base acquired with the HEAO A-2 experiment was searched for X-ray emission on a variety of metagalactic size scales which were either predicted or previously detected. Results in the 0.2-60 keV energy range are presented. The optically richest clusters, including those from which a microwave decrement were observed, appear to be relatively underluminous in X-rays. Observations of Abell 576 show its luminosity to be less than earlier estimates, and moreover less than the luminosity predicted from its microwave decrement, unless the intracluster gas is a factor of approximately 10 hotter than in typical clusters. Near SC0627 there are two X-ray sources, and the identification of the dominant source with SCO627 is probably incorrect. New spectral observations of Abell 401 and 2147, possible superclusters, reveal that they have typical cluster spectra with iron line emission
Interpreting the extended emission around three nearby debris disc host stars
Cool debris discs are a relic of the planetesimal formation process around
their host star, analogous to the solar system's Edgeworth-Kuiper belt. As
such, they can be used as a proxy to probe the origin and formation of
planetary systems like our own. The Herschel Open Time Key Programmes "DUst
around NEarby Stars" (DUNES) and "Disc Emission via a Bias-free Reconnaissance
in the Infrared/Submillimetre" (DEBRIS) observed many nearby, sun-like stars at
far-infrared wavelengths seeking to detect and characterize the emission from
their circumstellar dust. Excess emission attributable to the presence of dust
was identified from around 20% of stars. Herschel's high angular
resolution ( 7" FWHM at 100 m) provided the capacity for resolving
debris belts around nearby stars with radial extents comparable to the solar
system (50 to 100 au). As part of the DUNES and DEBRIS surveys, we obtained
observations of three debris disc stars, HIP 22263 (HD 30495), HIP 62207 (HD
110897), and HIP 72848 (HD 131511), at far-infrared wavelengths with the
Herschel PACS instrument. Combining these new images and photometry with
ancilliary data from the literature, we undertook simultaneous multi-wavelength
modelling of the discs' radial profiles and spectral energy distributions using
three different methodologies: single annulus, modified black body, and a
radiative transfer code. We present the first far-infrared spatially resolved
images of these discs and new single-component debris disc models. We
characterize the capacity of the models to reproduce the disc parameters based
on marginally resolved emission through analysis of two sets of simulated
systems (based on the HIP 22263 and HIP 62207 data) with the noise levels
typical of the Herschel images. We find that the input parameter values are
recovered well at noise levels attained in the observations presented here.Comment: 13 pages, 5 figures, 5 tables, accepted for publication in A&
Short gamma-ray bursts within 200 Mpc
We present a systematic search for short-duration gamma-ray bursts (GRBs) in the local Universe based on 14âyr of observations with the Neil Gehrels Swift Observatory. We cross-correlate the GRB positions with the GLADE catalogue of nearby galaxies, and find no event at a distance âČ100 Mpc and four plausible candidates in the range 100âMpc âČ DââČ 200âMpc. Although affected by low statistics, this number is higher than the one expected for chance alignments to random galaxies, and possibly suggests a physical association between these bursts and nearby galaxies. By assuming a local origin, we use these events to constrain the range of properties for X-ray counterparts of neutron star mergers. Optical upper limits place tight constraints on the onset of a blue kilonova, and imply either low masses (â âČ10â3Mââ ) of lanthanide-poor ejecta or unfavorable orientations (Ξ_(obs) âł 30 deg). Finally, we derive that the all-sky rate of detectable short GRBs within 200 Mpc is 1.3^(+1.7)_(â0.8) yrâ»Âč (68 perâcent confidence interval), and discuss the implications for the GRB outflow structure. If these candidates are instead of cosmological origin, we set a upper limit of âČ2.0 yrâ»Âč (90 perâcent confidence interval) to the rate of nearby events detectable with operating gamma-ray observatories, such as Swift and Fermi
Intraflagellar transport particle size scales inversely with flagellar length: revisiting the balance-point length control model
Chlamydomonas reinhardtii IFT particle trains, important for flagella maintenance and assembly, are observed to decrease in size as a function of cilia length
A Morphological and Multicolor Survey for Faint QSOs in the Groth-Westphal Strip
Quasars representative of the populous faint end of the luminosity function
are frustratingly dim with m~24 at intermediate redshift; moreover groundbased
surveys for such faint QSOs suffer substantial morphological contamination by
compact galaxies having similar colors. In order to establish a more reliable
ultrafaint QSO sample, we used the APO 3.5-m telescope to take deep groundbased
U-band CCD images in fields previously imaged in V,I with WFPC2/HST. Our
approach hence combines multicolor photometry with the 0.1" spatial resolution
of HST, to establish a morphological and multicolor survey for QSOs extending
about 2 magnitudes fainter than most extant groundbased surveys. We present
results for the "Groth-Westphal Strip", in which we identify 10 high likelihood
UV-excess candidates having stellar or stellar-nucleus+galaxy morphology in
WFPC2. For m(606)<24.0 (roughly B<24.5) the surface density of such QSO
candidates is 420 (+180,-130) per square degree, or a surface density of 290
(+160,-110) per square degree with an additional V-I cut that may further
exclude compact emission line galaxies. Even pending confirming spectroscopy,
the observed surface density of QSO candidates is already low enough to yield
interesting comparisons: our measures agree extremely well with the predictions
of several recent luminosity function models.Comment: 29 pages including 6 tables and 7 figures. As accepted for
publication in The Astronomical Journal (minor revisions
Discovery of a Second Millisecond Accreting Pulsar: XTE J1751-305
We report the discovery by the RXTE PCA of a second transient accreting
millisecond pulsar, XTE J1751-305, during regular monitoring observations of
the galactic bulge region. The pulsar has a spin frequency of 435 Hz, making it
one of the fastest pulsars. The pulsations contain the signature of orbital
Doppler modulation, which implies an orbital period of 42 minutes, the shortest
orbital period of any known radio or X-ray millisecond pulsar. The mass
function, f_x = (1.278 +/- 0.003) x 10^{-6} M_sun, yields a minimum mass for
the companion of between 0.013 and 0.017 M_sun, depending on the mass of the
neutron star. No eclipses were detected. A previous X-ray outburst in June,
1998, was discovered in archival All-Sky Monitor data. Assuming mass transfer
in this binary system is driven by gravitational radiation, we constrain the
orbital inclination to be in the range 30-85 deg, and the companion mass to be
0.013-0.035 M_sun. The companion is most likely a heated helium dwarf. We also
present results from the Chandra HRC-S observations which provide the best
known position of XTE J1751-305.Comment: Astrophysical Journal Letters, Accepted, (AASTeX
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