167 research outputs found
Universal Indexes for Highly Repetitive Document Collections
Indexing highly repetitive collections has become a relevant problem with the
emergence of large repositories of versioned documents, among other
applications. These collections may reach huge sizes, but are formed mostly of
documents that are near-copies of others. Traditional techniques for indexing
these collections fail to properly exploit their regularities in order to
reduce space.
We introduce new techniques for compressing inverted indexes that exploit
this near-copy regularity. They are based on run-length, Lempel-Ziv, or grammar
compression of the differential inverted lists, instead of the usual practice
of gap-encoding them. We show that, in this highly repetitive setting, our
compression methods significantly reduce the space obtained with classical
techniques, at the price of moderate slowdowns. Moreover, our best methods are
universal, that is, they do not need to know the versioning structure of the
collection, nor that a clear versioning structure even exists.
We also introduce compressed self-indexes in the comparison. These are
designed for general strings (not only natural language texts) and represent
the text collection plus the index structure (not an inverted index) in
integrated form. We show that these techniques can compress much further, using
a small fraction of the space required by our new inverted indexes. Yet, they
are orders of magnitude slower.Comment: This research has received funding from the European Union's Horizon
2020 research and innovation programme under the Marie Sk{\l}odowska-Curie
Actions H2020-MSCA-RISE-2015 BIRDS GA No. 69094
Megabenthic decapod crustacean assemblages on the Galician continental shelf and upper slope (north-west Spain)
The original publication is avaliable at www.springerlink.comThe structure of megabenthic decapod crustacean
assemblages on the Galician (north-west Spain)
continental shelf (100 to 200 depth) and upper slope (200
to 500 m) was analyzed based on surveys carried out in
autumn and spring, from 1980 to 1987. Forty species
belonging to 19 families were caught. The portunid crab
"Polybius henslowii", a species with pelagic phases, was the
most abundant species, but displayed strong spatial and
temporal fluctuations. Other dominant species were the
Norway lobster "Nephrops norvegicus", the portunid "Liocarcinus
depurator", the galatheids "Munida intermedia" and
"M. sarsi", and the shrimps "Solenocera membranacea",
"Plesionika heterocarpus", "Pasiphaea sivado" and "Dichelopandalus
bonnieri". Total abundance and biomass (average
values excluding Polybius henslowii = 255 individuals
and 2.06 kg/30 min tow) and species richness
and diversity, Ht (6.85 species and Ht = 1.45 per tow)
displayed a significant positive correlation with depth,
and strong interannual fluctuations. The factors determining
community organization were depth and, to a
lesser extent, spatial structure. There was clear evidence
of bathymetric zonation, differentiating between species
characteristic of the slope ("D. bonnieri" and "Pasiphaea
sivado"), shelf-slope edge ("Macropipus tuberculatus", "Pontophilus
spinosus", "Munida sarsi", "S. membranacea", "Processa
spp.") and shelf ("L. depurator", "Macropodia tenuirostris",
"Paguridae" and "Chlorotocus crassicornis"). The
spatial zonation was related to changes in oceanography
and sediment along the continental margin. "Goneplax rhomboides", "N. norvegicus", "C. crassicornis" and "Alpheus
glaber" are benthic species which generally exhibit burrowing
behaviour, and they were found mainly in the
southern area where there are fine sediments due to the
outwelling from the RÃas Baixas. Different benthopelagic
shrimps ("Pontophilus spinosus", "Plesionika heterocarpus",
"Processa spp." and "Pasiphaea sivado") were typical of the
zone just north of Fisterra, characterized by a convergence
of water masses bringing about an increase in
productivity due to upwelling. The benthic anomuran
and brachyuran crabs "Munida intermedia", "M. sarsi",
"L. depurator" and "Macropipus tuberculatus" were characteristic
of the northwestern zone between Fisterra and
Estaca, where the infauna reaches high biomass despite
coarser sediments with a lower concentration of organic
material than in the southern area. Lastly, both the
"Paguridae" and "Macropodia tenuirostris" were species typically
found in the waters in the northern shelf. Based
on interannual changes in assemblage structure, two
periods could be distinguished: between 1980 and 1984,
when "Polybius henslowii", "D. bonnieri" and "Pasiphaea sivado"
had abundance peaks; and another period from
1985 to 1987 when "L. depurator", "Munida intermedia",
"M. sarsi" and "Macropipus tuberculatus" increased in
abundanc
Algunas situaciones problemáticas en las aulas y las pautas de actuación correspondientes
Este trabajo contempla algunas situaciones problemáticas que se pueden dar en las aulas de primaria en
el dÃa a dÃa. Comienza tratando los fenómenos más comunes, para posteriormente introducirnos en casos
aislados con diagnóstico, refiriéndonos a algunos trastornos de conducta. El trabajo busca proporcionar
información acerca de las pautas de actuación docente en estos casos. Se trata de un estudio de
investigación bibliográfica, donde se ha recabado información desde las áreas de educación, psicologÃa y
derecho.This project keeps in mind some potential issues that might appear in our classrooms. It
starts dealing with the most common events, and afterwards about more specific cases,
concerning to those whom needs to be diagnose. This work tries to supply some rigth
procedures in this cases. It´s a research of information from the departments of
education, psichology and law
Nuevas técnicas de inyección de fallos en sistemas embebidos mediante el uso de modelos virtuales descritos en el nivel de transacción
Mejor software y más rápido. Este es el desafÃo que se deriva de la necesidad de construir sistemas cada vez más inteligentes. En cualquier diseño embebido actual, el software es un componente fundamental que dota al sistema de una alta capacidad de configuración, gran número de funcionalidades y elasticidad en el comportamiento del sistema en situaciones excepcionales. Si además el desarrollo del conjunto hardware/software integrado en un System on Chip (SoC), forma parte de un sistema de control crÃtico donde se deben tener en cuenta requisitos de tolerancia a fallos, la verificación exhaustiva de los mismos consume un porcentaje cada vez más importante de los recursos totales dedicados al desarrollo y puesta en funcionamiento del sistema. En este contexto, el uso de metodologÃas clásicas de codiseño y coverificación es completamente ineficiente, siendo necesario el uso de nuevas tecnologÃas y herramientas para el desarrollo y verificación tempranos del software embebido. Entre ellas se puede incluir la propuesta en este trabajo de tesis, la cual aborda el problema mediante el uso de modelos ejecutables del hardware definidos en el nivel de transacción. Debido a los estrictos requisitos de robustez que imperan en el desarrollo de software espacial, es necesario llevar a cabo tareas de verificación en etapas muy tempranas del desarrollo para asegurar que los mecanismos de tolerancia a fallos, avanzados en la especificación del sistema, funcionan adecuadamente. De forma general, es deseable que estas tareas se realicen en paralelo con el desarrollo hardware, anticipando problemas o errores existentes en la especificación del sistema. Además, la verificación completa de los mecanismos de excepción implementados en el software, puede ser imposible de realizar en hardware real ya que los escenarios de fallo deben ser artificial y sistemáticamente generados mediante técnicas de inyección de fallos que permitan realizar campañas de inyección controlables, observables y reproducibles. En esta tesis se describe la investigación, desarrollo y uso de una plataforma virtual denominada "Leon2ViP", con capacidad de inyección de fallos y basada en interfaces SystemC/TLM2 para el desarrollo temprano y verificación de software embebido en el marco del proyecto Solar Orbiter. De esta forma ha sido posible ejecutar y probar exactamente el mismo código binario a ejecutar en el hardware real, pero en un entorno más controlable y determinista. Ello permite la realización de campañas de inyección de fallos muy focalizadas que no serÃan posible de otra manera. El uso de "\Leon2ViP" ha significado una mejora significante, en términos de coste y tiempo, en el desarrollo y verificación del software de arranque de la unidad de control del instrumento (ICU) del detector de partÃculas energéticas (EPD) embarcado en Solar Orbiter
An Efficient Representation of Enriched Temporal Trajectories
[Abstract] We present a novel representation of enriched trajectories of a mobile workforce management system. In this system, employees are tracked during their working day and both their routes and the tasks performed at each time instant are recorded. Our proposal tackles the representation of this information paying special attention to the space footprint without neglecting query time. We performed experiments using real and synthetic datasets where we show the compression effectiveness as well as the efficiency at query time. Our results showed that our proposal yields promising results in terms of the space needed to represent both users’ locations and activities while performing access queries to the original data within microseconds.Xunta de Galicia; ED431G 2019/01Xunta de Galicia; IG240.2020.1.185Xunta de Galicia; IN852A 2018/14Partially funded by the CITIC research center funded by Xunta/FEDER-UE 2014-2020 Program, grant ED431G 2019/01.
MICIU (PGE/ERDF) [Datos 4.0: TIN2016-78011-C4-1-R; STEPS: RTC-2017-5908-7; BIZDEVOPS: RTI2018-098309-B-C32].
IGAPE/Xunta (FEDER-UE) 2014-2020 [IG240.2020.1.185].
Xunta/GAIN (ERDF) [GEMA: IN852A 2018/14] and by FPI Program [BES-2017-081390].https://www.scitepress.org/ProceedingsDetails.aspx?ID=H6opWeZtwKs=&t=
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