5,426 research outputs found
Overview of Swallow --- A Scalable 480-core System for Investigating the Performance and Energy Efficiency of Many-core Applications and Operating Systems
We present Swallow, a scalable many-core architecture, with a current
configuration of 480 x 32-bit processors.
Swallow is an open-source architecture, designed from the ground up to
deliver scalable increases in usable computational power to allow
experimentation with many-core applications and the operating systems that
support them.
Scalability is enabled by the creation of a tile-able system with a
low-latency interconnect, featuring an attractive communication-to-computation
ratio and the use of a distributed memory configuration.
We analyse the energy and computational and communication performances of
Swallow. The system provides 240GIPS with each core consuming 71--193mW,
dependent on workload. Power consumption per instruction is lower than almost
all systems of comparable scale.
We also show how the use of a distributed operating system (nOS) allows the
easy creation of scalable software to exploit Swallow's potential. Finally, we
show two use case studies: modelling neurons and the overlay of shared memory
on a distributed memory system.Comment: An open source release of the Swallow system design and code will
follow and references to these will be added at a later dat
Singular vectors for the algebras
In this paper, we use free field realisations of the A-type principal, or
Casimir, algebras to derive explicit formulae for singular vectors in
Fock modules. These singular vectors are constructed by applying screening
operators to Fock module highest weight vectors. The action of the screening
operators is then explicitly evaluated in terms of Jack symmetric functions and
their skew analogues. The resulting formulae depend on sequences of pairs of
integers that completely determine the Fock module as well as the Jack
symmetric functions.Comment: 18 page
The origin of IRS 16: dynamically driven inspiral of a dense star cluster to the Galactic center?
We use direct N-body simulations to study the inspiral and internal evolution
of dense star clusters near the Galactic center. These clusters sink toward the
center due to dynamical friction with the stellar background, and may go into
core collapse before being disrupted by the Galactic tidal field. If a cluster
reaches core collapse before disruption, its dense core, which has become rich
in massive stars, survives to reach close to the Galactic center. When it
eventually dissolves, the cluster deposits a disproportionate number of massive
stars in the innermost parsec of the Galactic nucleus. Comparing the spatial
distribution and kinematics of the massive stars with observations of IRS 16, a
group of young He I stars near the Galactic center, we argue that this
association may have formed in this way.Comment: 15 pages, Accepted for publiction in Ap
Star Cluster Ecology: VII The evolution of young dense star clusters containing primordial binaries
We study the first 100Myr of the evolution of isolated star clusters
initially containing 144179 stars, including 13107 (10%) primordial hard
binaries. Our calculations include the effects of both stellar and binary
evolution. Gravitational interactions among the stars are computed by direct
N-body integration using high precision GRAPE-6 hardware. The evolution of the
core radii and central concentrations of our simulated clusters are compared
with the observed sample of young (about 100Myr) star clusters in the large
Magellanic cloud. Even though our simulations start with a rich population of
primordial binaries, core collapse during the early phase of the cluster
evolution is not prevented. Throughout the simulations, the fraction of
binaries remains roughly constant (about 10%). Due to the effects of mass
segregation the mass function of intermediate-mass main-sequence stars becomes
as flat as in the central part of the cluster (where the initial
Salpeter mass function had ). About 6--12% of the neutron stars
were retained in our simulations; the fraction of retained black holes is
40--70%. In each simulation about three neutron stars become members of close
binaries with a main-sequence companion. Such a binary will eventually become
an x-ray binary, when the main-sequence star starts to fill its Roche lobe.
Black holes are found more frequently in binaries; in each simulated cluster we
find about 11 potential x-ray binaries containing a black hole. Abstract
abbreviated....Comment: MNRAS in pres
Preliminary results from an investigation of AIS-1 data over an area of epithermal alteration: Plateau, Northern Queensland, Australia
Airborne Imaging Spectrometer-1 (AIS-1) data were flown over undifferentiated sequences of acid to intermediate volcanics and intrusives; meta-sediments; and a series of partially lateritized sedimentary rocks. The area exhibits a considerable spectral variability, after the suppression of striping effects. Log residual, and Internal Average Relative Reflectance (IARR) analytical techniques were used to enhance mineralogically related spectral features. Both methods produce similar results, but did not visually highlight mineral absorption features due to processing artifacts in areas of significant vegetation cover. The enhancement of mineral related absorption features was achieved using a hybrid processing approach based on the relative reflectance differences between vegetated and non-vegetated surfaces at 1.2 and 2.1 micron. The result is an image with little overall contrast, but which enhances the more subtle spectral features believed to be associated with clays and epidote. The AIS data was subject to interactive analysis using SPAM. Clear separation of clay and epidote related absorption features was apparent, and the identification of kaolinite was possible despite detrimental spectral effects
Maavis@School
Managed Access to Audio, Visual and Information Services (Maavis) was launched as an open source beta release application in September 2008. Maavis was developed by the authors with the participation of older people using a prototype called ‘SIMWIN’ which showed proof of concept and indicated beneficial outcomes1-3. The concepts behind Maavis, which partially were guided by human computer interfacing for people with dementia4, were always recognised as beneficial to other populations5. During 2008 these concepts, summarised as use of IT without understanding it or extreme simplification of the interface, were evaluated with four school pupils with varying physical and learning impairments. Again this work indicated beneficial outcomes6. This lead to the authors adding features to Maavis to make it suitable for use in the special needs school environment, eg being network friendly and single switch scanning access. This was achieved through brainstorming and consultations with staff within three schools. These developments will be tested during the autumn term 2009 in the same three schools. The details of the developments and their success so far in the classroom will be reported.
In June 2009 Maavis was adopted by JISC’s OSS Watch as a ‘strategic’ project that will significantly address accessibility issues of IT and the web for groups who struggle with standard IT and/or are e-isolated. The aim is to establish an active open development community by the first half of 2010. Links with others in the adult education field and with UK and international care providers are already initiated
Constraints on dark and visible mass in galaxies from strong gravitational lensing
We give a non-exhaustive review of the use of strong gravitational lensing in
placing constraints on the quantity of dark and visible mass in galaxies. We
discuss development of the methodology and summarise some recent results.Comment: To appear in proceedings of IAU Symposium 244, 'Dark Galaxies and
Lost Baryons', 25th - 29th June 2007. Nine pages, five figures. Version 2
updates bibliograph
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