7,155 research outputs found
AT-GIS: highly parallel spatial query processing with associative transducers
Users in many domains, including urban planning, transportation, and environmental science want to execute analytical queries over continuously updated spatial datasets. Current solutions for largescale spatial query processing either rely on extensions to RDBMS, which entails expensive loading and indexing phases when the data changes, or distributed map/reduce frameworks, running on resource-hungry compute clusters. Both solutions struggle with the sequential bottleneck of parsing complex, hierarchical spatial data formats, which frequently dominates query execution time. Our goal is to fully exploit the parallelism offered by modern multicore CPUs for parsing and query execution, thus providing the performance of a cluster with the resources of a single machine. We describe AT-GIS, a highly-parallel spatial query processing system that scales linearly to a large number of CPU cores. ATGIS integrates the parsing and querying of spatial data using a new computational abstraction called associative transducers(ATs). ATs can form a single data-parallel pipeline for computation without requiring the spatial input data to be split into logically independent blocks. Using ATs, AT-GIS can execute, in parallel, spatial query operators on the raw input data in multiple formats, without any pre-processing. On a single 64-core machine, AT-GIS provides 3× the performance of an 8-node Hadoop cluster with 192 cores for containment queries, and 10× for aggregation queries
An overview of the communications technology satellite project: Executive summary
An overview of the Communications Technology Satellite (CTS) project, a joint venture between NASA and the Canadian Department of Communications is given. A brief technical description of the CTS spacecraft and its cognate hardware and operations, a history of the CTS project, and a list of the CTS experiments and demonstrations conducted during the course of the project are given
Katabasis and the serpent
If one descends to the Underworld, one can expect to encounter δράκοντες there (Aristophanes affirms this point explicitly, but already in the Odyssey Odysseus fears that Persephone may confront him with a Gorgon-head). This is not surprising. Under some circumstances the dead can mutate into δράκοντες. The δράκων Typhon is born in the earth and emerges therefrom to threaten the gods, and is then trapped within it again by them. In art Cerberus, the guard-dog of the Underworld, often possesses multiple δράκων heads, and it because of his nature of a δράκων that his spittle contains the venom that creates the aconite. Just as snakes live in holes in the ground, so too the great δράκοντες of myth live in caves, and these caves can be assimilated to or identified as Underworld entrances. Beyond this, Underworld entrances can in turn be assimilated to the pestilential gaping maws of great δράκοντες
Polaritonic characteristics of insulator and superfluid phases in a coupled-cavity array
Recent studies of quantum phase transitions in coupled atom-cavity arrays
have focused on the similarities between such systems and the Bose-Hubbard
model. However, the bipartite nature of the atom-cavity systems that make up
the array introduces some differences. In order to examine the unique features
of the coupled-cavity system, the behavior of a simple two-site model is
studied over a wide range of parameters. Four regions are identified, in which
the ground state of the system may be classified as either a polaritonic
insulator, a photonic superfluid, an atomic insulator, or a polaritonic
superfluid.Comment: 7 pages, 9 figures, 1 table, REVTeX 4; published versio
Spacelab mission dependent training parametric resource requirements study
Training flows were developed for typical missions, resource relationships analyzed, and scheduling optimization algorithms defined. Parametric analyses were performed to study the effect of potential changes in mission model, mission complexity and training time required on the resource quantities required to support training of payload or mission specialists. Typical results of these analyses are presented both in graphic and tabular form
Foot and Mouth Epidemic Reduces Cases of Human Cryptosporidiosis in Scotland.
In Scotland, rates of cryptosporidiosis infection in humans peak during the spring, a peak that is coincident with the peak in rates of infection in farm animals (during lambing and calving time). Here we show that, during the outbreak of foot and mouth disease (FMD) in 2001, there was a significant reduction in human cases of cryptosporidiosis infection in southern Scotland, where FMD was present, whereas, in the rest of Scotland, there was a reduction in cases that was not significant. We associate the reduction in human cases of cryptosporidiosis infection with the reduction in the number of young farm animals, together with restrictions on movement of both farm animals and humans, during the outbreak of FMD in 2001. We further show that, during 2002, there was recovery in the rate of cryptosporidiosis infection in humans throughout Scotland, particularly in the FMD-infected area, but that rates of infection remained lower, though not significantly, than pre-2001 levels
The Common Shrew (Sorex araneus): A neglected host of tick-borne infections?
Although the importance of rodents as reservoirs for a number of tick-borne infections is well established,
comparatively little is known about the potential role of shrews, despite them occupying similar habitats. To
address this, blood and tick samples were collected from common shrews (Sorex araneus) and field voles
(Microtus agrestis), a known reservoir of various tick-borne infections, from sites located within a plantation
forest in northern England over a 2-year period. Of 647 blood samples collected from shrews, 121 (18.7%)
showed evidence of infection with Anaplasma phagocytophilum and 196 (30.3%) with Babesia microti. By comparison,
of 1505 blood samples from field voles, 96 (6.4%) were positive for A. phagocytophilum and 458 (30.4%)
for Ba. microti. Both species were infested with the ticks Ixodes ricinus and Ixodes trianguliceps, although they had
different burdens: on average, shrews carried almost six times as many I. trianguliceps larvae, more than twice as
many I. ricinus larvae, and over twice as many nymphs (both tick species combined). The finding that the
nymphs collected from shrews were almost exclusively I. trianguliceps highlights that this species is the key
vector of these infections in this small mammal community. These findings suggest that common shrews are a
reservoir of tick-borne infections and that the role of shrews in the ecology and epidemiology of tick-borne
infections elsewhere needs to be comprehensively investigated
Dynamics in a coupled-cavity array
The dynamics of a system composed of two coupled optical cavities, each
containing a single two-level atom, is studied over a wide range of detuning
and coupling values. A description of the field in terms of delocalized modes
reveals that the detuning between the atoms and these modes is controlled by
the coupling between the cavities; this detuning in turn governs the nature of
the dynamics. If the atoms are highly detuned from both delocalized field
modes, the dynamics becomes dispersive and an excitation may be transferred
from the first atom to the second without populating the field. In the case of
resonance between the atoms and one of the delocalized modes, state transfer
between the atoms requires intermediate excitation of the field. Thus the
interaction between the two atoms can be controlled by adjusting the coupling
between the cavities.Comment: 11 pages, 3 figure
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