59,067 research outputs found
The Iray Light Transport Simulation and Rendering System
While ray tracing has become increasingly common and path tracing is well
understood by now, a major challenge lies in crafting an easy-to-use and
efficient system implementing these technologies. Following a purely
physically-based paradigm while still allowing for artistic workflows, the Iray
light transport simulation and rendering system allows for rendering complex
scenes by the push of a button and thus makes accurate light transport
simulation widely available. In this document we discuss the challenges and
implementation choices that follow from our primary design decisions,
demonstrating that such a rendering system can be made a practical, scalable,
and efficient real-world application that has been adopted by various companies
across many fields and is in use by many industry professionals today
Constraints on Blazar Jet Conditions During Gamma-Ray Flaring from Radiative Transfer Modeling
As part of a program to investigate jet flow conditions during GeV gamma-ray
flares detected by Fermi, we are using UMRAO multi-frequency, centimeter-band
total flux density and linear polarization monitoring observations to constrain
radiative transfer models incorporating propagating shocks orientated at an
arbitrary angle to the flow direction. We describe the characteristics of the
model, illustrate how the data are used to constrain the models, and present
results for three program sources with diverse characteristics: PKS 0420-01, OJ
287, and 1156+295. The modeling of the observed spectral behavior yields
information on the sense, strength and orientation of the shocks producing the
radio-band flaring; on the energy distribution of the radiating particles; and
on the observer's viewing angle with respect to the jet independent of VLBI
data. We present evidence that, while a random component dominates the jet
magnetic field, a distinguishing feature of those radio events with an
associated gamma-ray flare is the presence of a weak but non-negligible ordered
magnetic field component along the jet axis.Comment: 6 pages, 4 figures. To appear in the proceedings of "The Innermost
Regions of Relativistic Jets and Their Magnetic Fields", Granada, Spai
The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing
The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV
solar telescope on board ESA's Project for Onboard Autonomy 2 (PROBA2) mission
launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm
and provides images of the low solar corona over a 54x54 arcmin field-of-view
with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is
designed to monitor all space-weather-relevant events and features in the low
solar corona. Given the limited resources of the PROBA2 microsatellite, the
SWAP telescope is designed with various innovative technologies, including an
off-axis optical design and a CMOS-APS detector. This article provides
reference documentation for users of the SWAP image data.Comment: 26 pages, 9 figures, 1 movi
Collaborative Storage Management In Sensor Networks
In this paper, we consider a class of sensor networks where the data is not
required in real-time by an observer; for example, a sensor network monitoring
a scientific phenomenon for later play back and analysis. In such networks, the
data must be stored in the network. Thus, in addition to battery power, storage
is a primary resource: the useful lifetime of the network is constrained by its
ability to store the generated data samples. We explore the use of
collaborative storage technique to efficiently manage data in storage
constrained sensor networks. The proposed collaborative storage technique takes
advantage of spatial correlation among the data collected by nearby sensors to
significantly reduce the size of the data near the data sources. We show that
the proposed approach provides significant savings in the size of the stored
data vs. local buffering, allowing the network to run for a longer time without
running out of storage space and reducing the amount of data that will
eventually be relayed to the observer. In addition, collaborative storage
performs load balancing of the available storage space if data generation rates
are not uniform across sensors (as would be the case in an event driven sensor
network), or if the available storage varies across the network.Comment: 13 pages, 7 figure
The ALADIN Interactive Sky Atlas
The Aladin interactive sky atlas, developed at CDS, is a service providing
simultaneous access to digitized images of the sky, astronomical catalogues,
and databases.
The driving motivation is to facilitate direct, visual comparison of
observational data at any wavelength with images of the optical sky, and with
reference catalogues.
The set of available sky images consists of the STScI Digitized Sky Surveys,
completed with high resolution images of crowded regions scanned at the MAMA
facility in Paris.
A Java WWW interface to the system is available at:
http://aladin.u-strasbg.fr/Comment: 8 pages, 3 Postscript figures; to be published in A&
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