11,695 research outputs found
Two-level pipelined systolic array graphics engine
The authors report a VLSI design of an advanced systolic array graphics (SAG) engine built from pipelined functional units which can generate realistic images interactively for high-resolution displays. They introduce a structured frame store system as an environment for the advanced SAG engine and present the principles and architecture of the advanced SAG engine. They introduce pipelined functional units into this SAG engine to meet the performance requirements. This is done by a formal approach where the original systolic array is represented at bit level by a finite, vertex-weighted, edge-weighted, directed graph. Two architectures built from pipelined functional units are described. A prototype containing nine processing elements was fabricated in a 1.6-Âżm CMOS technolog
Adaptive Real Time Imaging Synthesis Telescopes
The digital revolution is transforming astronomy from a data-starved to a
data-submerged science. Instruments such as the Atacama Large Millimeter Array
(ALMA), the Large Synoptic Survey Telescope (LSST), and the Square Kilometer
Array (SKA) will measure their accumulated data in petabytes. The capacity to
produce enormous volumes of data must be matched with the computing power to
process that data and produce meaningful results. In addition to handling huge
data rates, we need adaptive calibration and beamforming to handle atmospheric
fluctuations and radio frequency interference, and to provide a user
environment which makes the full power of large telescope arrays accessible to
both expert and non-expert users. Delayed calibration and analysis limit the
science which can be done. To make the best use of both telescope and human
resources we must reduce the burden of data reduction.
Our instrumentation comprises of a flexible correlator, beam former and
imager with digital signal processing closely coupled with a computing cluster.
This instrumentation will be highly accessible to scientists, engineers, and
students for research and development of real-time processing algorithms, and
will tap into the pool of talented and innovative students and visiting
scientists from engineering, computing, and astronomy backgrounds.
Adaptive real-time imaging will transform radio astronomy by providing
real-time feedback to observers. Calibration of the data is made in close to
real time using a model of the sky brightness distribution. The derived
calibration parameters are fed back into the imagers and beam formers. The
regions imaged are used to update and improve the a-priori model, which becomes
the final calibrated image by the time the observations are complete
Implementation of a Direct-Imaging and FX Correlator for the BEST-2 Array
A new digital backend has been developed for the BEST-2 array at
Radiotelescopi di Medicina, INAF-IRA, Italy which allows concurrent operation
of an FX correlator, and a direct-imaging correlator and beamformer. This
backend serves as a platform for testing some of the spatial Fourier transform
concepts which have been proposed for use in computing correlations on
regularly gridded arrays. While spatial Fourier transform-based beamformers
have been implemented previously, this is to our knowledge, the first time a
direct-imaging correlator has been deployed on a radio astronomy array.
Concurrent observations with the FX and direct-imaging correlator allows for
direct comparison between the two architectures. Additionally, we show the
potential of the direct-imaging correlator for time-domain astronomy, by
passing a subset of beams though a pulsar and transient detection pipeline.
These results provide a timely verification for spatial Fourier transform-based
instruments that are currently in commissioning. These instruments aim to
detect highly-redshifted hydrogen from the Epoch of Reionization and/or to
perform widefield surveys for time-domain studies of the radio sky. We
experimentally show the direct-imaging correlator architecture to be a viable
solution for correlation and beamforming.Comment: 12 pages, 17 figures, 2 tables, Accepted to MNRAS January 24, 2014,
includes appendix diagram
Run 2 Upgrades to the CMS Level-1 Calorimeter Trigger
The CMS Level-1 calorimeter trigger is being upgraded in two stages to
maintain performance as the LHC increases pile-up and instantaneous luminosity
in its second run. In the first stage, improved algorithms including
event-by-event pile-up corrections are used. New algorithms for heavy ion
running have also been developed. In the second stage, higher granularity
inputs and a time-multiplexed approach allow for improved position and energy
resolution. Data processing in both stages of the upgrade is performed with
new, Xilinx Virtex-7 based AMC cards.Comment: 10 pages, 7 figure
The Blanco Cosmology Survey: Data Acquisition, Processing, Calibration, Quality Diagnostics and Data Release
The Blanco Cosmology Survey (BCS) is a 60 night imaging survey of 80
deg of the southern sky located in two fields: (,)= (5 hr,
) and (23 hr, ). The survey was carried out between
2005 and 2008 in bands with the Mosaic2 imager on the Blanco 4m
telescope. The primary aim of the BCS survey is to provide the data required to
optically confirm and measure photometric redshifts for Sunyaev-Zel'dovich
effect selected galaxy clusters from the South Pole Telescope and the Atacama
Cosmology Telescope. We process and calibrate the BCS data, carrying out PSF
corrected model fitting photometry for all detected objects. The median
10 galaxy (point source) depths over the survey in are
approximately 23.3 (23.9), 23.4 (24.0), 23.0 (23.6) and 21.3 (22.1),
respectively. The astrometric accuracy relative to the USNO-B survey is
milli-arcsec. We calibrate our absolute photometry using the stellar
locus in bands, and thus our absolute photometric scale derives from
2MASS which has % accuracy. The scatter of stars about the stellar locus
indicates a systematics floor in the relative stellar photometric scatter in
that is 1.9%, 2.2%, 2.7% and2.7%, respectively.
A simple cut in the AstrOmatic star-galaxy classifier {\tt spread\_model}
produces a star sample with good spatial uniformity. We use the resulting
photometric catalogs to calibrate photometric redshifts for the survey and
demonstrate scatter with an outlier fraction %
to . We highlight some selected science results to date and provide a
full description of the released data products.Comment: 23 pages, 23 figures . Response to referee comments. Paper accepted
for publication. BCS catalogs and images available for download from
http://www.usm.uni-muenchen.de/BC
Observing pulsars and fast transients with LOFAR
Low frequency radio waves, while challenging to observe,are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric âradio windowâ: 10â240 MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth.LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals.We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR
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