65,228 research outputs found
Generic Connectivity-Based CGRA Mapping via Integer Linear Programming
Coarse-grained reconfigurable architectures (CGRAs) are programmable logic
devices with large coarse-grained ALU-like logic blocks, and multi-bit
datapath-style routing. CGRAs often have relatively restricted data routing
networks, so they attract CAD mapping tools that use exact methods, such as
Integer Linear Programming (ILP). However, tools that target general
architectures must use large constraint systems to fully describe an
architecture's flexibility, resulting in lengthy run-times. In this paper, we
propose to derive connectivity information from an otherwise generic device
model, and use this to create simpler ILPs, which we combine in an iterative
schedule and retain most of the exactness of a fully-generic ILP approach. This
new approach has a speed-up geometric mean of 5.88x when considering benchmarks
that do not hit a time-limit of 7.5 hours on the fully-generic ILP, and 37.6x
otherwise. This was measured using the set of benchmarks used to originally
evaluate the fully-generic approach and several more benchmarks representing
computation tasks, over three different CGRA architectures. All run-times of
the new approach are less than 20 minutes, with 90th percentile time of 410
seconds. The proposed mapping techniques are integrated into, and evaluated
using the open-source CGRA-ME architecture modelling and exploration framework.Comment: 8 pages of content; 8 figures; 3 tables; to appear in FCCM 2019; Uses
the CGRA-ME framework at http://cgra-me.ece.utoronto.ca
Does perceived organisational support influence career intentions?:The qualitative stories shared by UK early career doctors
Our thanks to all those FP2 doctors who participated in the interviews. Our thanks also to the Foundation Programme Directorate staff in the Scotland Deanery, NHS Education for Scotland, for sending out the email correspondence to the two regions involved in the interviews. No patients or any members of the public were involved in this study. Funding: Our thanks go to NHS Education for Scotland for funding Gillian Scanlan’s programme of work through the Scottish Medical Education Research Consortium (SMERC) and for funding the open-access fee for this paper.Peer reviewedPublisher PD
The case for a cold dark matter cusp in Draco
We use a new mass modelling method, GravSphere, to measure the central dark
matter density profile of the Draco dwarf spheroidal galaxy. Draco's star
formation shut down long ago, making it a prime candidate for hosting a
'pristine' dark matter cusp, unaffected by stellar feedback during galaxy
formation. We first test GravSphere on a suite of tidally stripped mock
'Draco'-like dwarfs. We show that we are able to correctly infer the dark
matter density profile of both cusped and cored mocks within our 95% confidence
intervals. While we obtain only a weak inference on the logarithmic slope of
these density profiles, we are able to obtain a robust inference of the
amplitude of the inner dark matter density at 150pc, . We show that, combined with constraints on the density profile at larger
radii, this is sufficient to distinguish a Cold Dark Matter
(CDM) cusp that has from alternative dark matter models
that have lower inner densities. We then apply GravSphere to the real Draco
data. We find that Draco has an inner dark matter density of , consistent with a CDM cusp. Using a velocity independent
SIDM model, calibrated on SIDM cosmological simulations, we show that
Draco's high central density gives an upper bound on the SIDM cross section of
at 99% confidence. We conclude that
the inner density of nearby dwarf galaxies like Draco provides a new and
competitive probe of dark matter models.Comment: 19 pages, 11 Figures. Final version accepted for publication in MNRA
Use of Skylab EREP data in a sea-surface temperature experiment
The author has identified the following significant results. A sea surface temperature experiment was studied, demonstrating the feasibility of a procedure for the remote measurement of sea surface temperature which inherently corrects for the effect of the intervening atmosphere without recourse to climatological data. The procedure was applied to Skylab EREP S191 spectrometer data, and it is demonstrated that atmospheric effects on the observed brightness temperature can be reduced to less than 1.0 K
Use of Skylab EREP Data in a Sea Surface Temperature Experiment
There are no author-identified significant results in this report
Use of Skylab EREP data in a sea surface temperature experiment
There are no author-identified significant results in this report
Dark matter heats up in dwarf galaxies
Gravitational potential fluctuations driven by bursty star formation can
kinematically 'heat up' dark matter at the centres of dwarf galaxies. A key
prediction of such models is that, at a fixed dark matter halo mass, dwarfs
with a higher stellar mass will have a lower central dark matter density. We
use stellar kinematics and HI gas rotation curves to infer the inner dark
matter densities of eight dwarf spheroidal and eight dwarf irregular galaxies
with a wide range of star formation histories. For all galaxies, we estimate
the dark matter density at a common radius of 150pc, . We find that our sample of dwarfs falls into two
distinct classes. Those that stopped forming stars over 6Gyrs ago favour
central densities , consistent with cold dark matter cusps, while those with more
extended star formation favour , consistent with shallower dark matter cores. Using
abundance matching to infer pre-infall halo masses, , we show that
this dichotomy is in excellent agreement with models in which dark matter is
heated up by bursty star formation. In particular, we find that steadily decreases with increasing stellar mass-to-halo
mass ratio, . Our results suggest that, to leading order, dark
matter is a cold, collisionless, fluid that can be kinematically 'heated up'
and moved around.Comment: 22 pages, 10 Figures. Final version accepted for publication in MNRA
Use of Skylab EREP data in a sea surface temperature experiment
There are no author-identified significant results in this report
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