24,393 research outputs found
Clockwise: a mixed-media file system
This paper presents Clockwise, a mixed-media file system. The primary goal of Clockwise is to provide a storage architecture that supports the storage and retrieval of best-effort and real-time file system data. Clockwise provides an abstraction called a dynamic partition that groups lists of related (large) blocks on one or more disks. Dynamic partitions can grow and shrink in size and reading or writing of dynamic partitions can be scheduled explicitly. With respect to scheduling, Clockwise uses a novel strategy to pre-calculate schedule slack time and it schedules best-effort requests before queued real-time requests in this slack tim
Minimizing the Dick Effect in an Optical Lattice Clock
We discuss the minimization of the Dick effect in an optical lattice clock.
We show that optimizing the time sequence of operation of the clock can lead to
a significant reduction of the clock stability degradation by the frequency
noise of the interrogation laser. By using a non-destructive detection of the
atoms, we are able to recycle most of the atoms between cycles and consequently
to strongly reduce the time spent capturing the atoms in each cycle. With
optimized parameters, we expect a fractional Allan deviation better than
2E-16 for the lattice clock.Comment: 6 pages, 10 figures. Submitted to IEEE Transactions on Ultrasonics,
Ferroelectrics, and Frequency Contro
Lightweight EDF scheduling with deadline inheritance
EDFI is a lightweight real-time scheduling protocol that combines EDF with deadline inheritance over shared resources. We will show that EDFI is flexible during a tasks admission control, efficient with scheduling and dispatching, and straightforward in feasibility analysis. The application programmer only needs to specify a tasks timing constraints (deadline, period, runtime) and resource needs, after which EDFI can execute admission control, scheduling, dispatching and resource synchronisation automatically. EDFI avoids gratuitous task switching and its programming overhead as well as runtime overhead is very low, which makes it ideal for lightweight and featherweight kernels. We will illustrate the elegance of the underlying theory and we will shortly discuss the implementation of EDFI in three different operating systems
Simple Finite Non-Abelian Flavor Groups
The recently measured unexpected neutrino mixing patterns have caused a
resurgence of interest in the study of finite flavor groups with two- and
three-dimensional irreducible representations. This paper details the
mathematics of the two finite simple groups with such representations, the
Icosahedral group A_5, a subgroup of SO(3), and PSL_2(7), a subgroup of SU(3).Comment: 42 pages, matches published version, references adde
The Alignment of the Magnetic Field and Collimated Outflows in Star-forming Regions: the Case of NGC 2071
The magnetic field is believed to play a crucial role in the process of star
formation. From the support it provides during the initial collapse of
molecular clouds to the creation of strong collimated jets responsible for
large mass losses, current theories predict its importance in many different
stages during the formation of stars. Here we report on observational evidence
which tests one aspect that can be inferred from these theories: the alignment
between the local magnetic field and collimated bipolar outflows in such
environments. There is good evidence of an alignment in the case of NGC 2071.Comment: 11 pages, 4 figure
Impact of ocean warming on sustainable fisheries management informs the Ecosystem Approach to Fisheries
Acknowledgements Serpetti N., Heymans J.J., and Burrows M.T. were funded by the Natural Environment Research Council and Department for Environment, Food and Rural Affairs under the Marine Ecosystems Research Programme (MERP) (grant No. NE/L003279/1). Baudron A. and Fernandes, P.G. were founded by Horizon 2020 European research projects MareFrame (grant No. 613571) and ClimeFish (grant No. 677039). Payne, B.L. was founded by the Natural Environment Research Council and Department for Environment under the ‘Velocity of Climate Change’ (grant No. NE/J024082/1).Peer reviewedPublisher PD
Molecular Carbon Chains and Rings in TMC-1
We present mapping results in several rotational transitions of HC3N, C6H,
both cyclic and linear C3H2 and C3H, towards the cyanopolyyne peak of the
filamentary dense cloud TMC-1 using the IRAM 30m and MPIfR 100m telescopes. The
spatial distribution of the cumulene carbon chain propadienylidene H2C3
(hereafter l-C3H2) is found to deviate significantly from the distributions of
the cyclic isomer c-C3H2, HC3N, and C6H which in turn look very similar. The
cyclic over linear abundance ratio of C3H2 increases by a factor of 3 across
the filament, with a value of 28 at the cyanopolyyne peak. This abundance ratio
is an order of magnitude larger than the range (3 to 5) we observed in the
diffuse interstellar medium. The cyclic over linear abundance ratio of C3H also
varies by ~2.5 in TMC-1, reaching a maximum value (13) close to the
cyanopolyyne peak. These behaviors might be related to competitive processes
between ion-neutral and neutral-neutral reactions for cyclic and linear
species.Comment: Accepted for publication in The Astrophysical Journal, part I. 24
pages, including 4 tables, 7 figures, and figure caption
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