213 research outputs found
The VVV Templates Project. Towards an Automated Classification of VVV Light-Curves. I. Building a database of stellar variability in the near-infrared
Context. The Vista Variables in the V\'ia L\'actea (VVV) ESO Public Survey is
a variability survey of the Milky Way bulge and an adjacent section of the disk
carried out from 2010 on ESO Visible and Infrared Survey Telescope for
Astronomy (VISTA). VVV will eventually deliver a deep near-IR atlas with
photometry and positions in five passbands (ZYJHK_S) and a catalogue of 1-10
million variable point sources - mostly unknown - which require
classifications. Aims. The main goal of the VVV Templates Project, that we
introduce in this work, is to develop and test the machine-learning algorithms
for the automated classification of the VVV light-curves. As VVV is the first
massive, multi-epoch survey of stellar variability in the near-infrared, the
template light-curves that are required for training the classification
algorithms are not available. In the first paper of the series we describe the
construction of this comprehensive database of infrared stellar variability.
Methods. First we performed a systematic search in the literature and public
data archives, second, we coordinated a worldwide observational campaign, and
third we exploited the VVV variability database itself on (optically)
well-known stars to gather high-quality infrared light-curves of several
hundreds of variable stars. Results. We have now collected a significant (and
still increasing) number of infrared template light-curves. This database will
be used as a training-set for the machine-learning algorithms that will
automatically classify the light-curves produced by VVV. The results of such an
automated classification will be covered in forthcoming papers of the series.Comment: 12 pages, 16 figures, 3 tables, accepted for publication in A&A. Most
of the data are now accessible through http://www.vvvtemplates.org
Reconstructing discards profiles of unreported catches
In Portugal it has been estimated that unreported catches represent one third of total catches. Herein, information on landings and total unreported catches (discards) by commercial métier were disaggregated into high taxonomic detail using published scientific studies. Fish accounted for 93.5% (115493 t) of overall unreported catches per year, followed by cephalopods (2345 t, 1.9%) and crustaceans (1754 t, 1.4%). Sharks accounted for 1.3% of total unreported catches in weight (1638 t/y). Unreported taxa consisted mostly of the commercial landed fish species: Scomber colias, Boops boops, Trachurus picturatus, T. trachurus, Merluccius merluccius, Sardina pilchardus, Liza aurata and Micromesistius poutassou, which together accounted for 70% of the unreported discarded catches. The number of unreported/discarded species was highest in artisanal fisheries, followed by trawl and purse seine. In artisanal fisheries, L. aurata, S. colias, S. pilchardus, Trachinus draco and B. boops accounted for 76.4% of the unreported discards. B. boops, S. colias and S. pilchardus were also among the most discarded purse seine species, together with Belone belone accounting for 79% of the unreported catches. In trawl fisheries, T. picturatus (16%), M. merluccius (13%), S. colias (13%) and M. poutassou (13%) accounted for 55% of the trawl discarded unreported catches. The discarded species that most contribute to overall unreported catches are those that are most frequently landed and that most contribute to overall landings in weight.SFRH/BD/104209/2014 and SFRH/
BPD/108949/2015). This work received national funds
through the Foundation for Science and Technology
(FCT) through project UID/Multi/04326/2013. Karim
Erzini was supported by funding from the European
Commission’s Horizon 2020 Research and Innovation
Programme under Grant Agreement No. 634495 for
the project Science, Technology, and Society Initiative
to minimize Unwanted Catches in European Fisheries
(MINOUW)info:eu-repo/semantics/publishedVersio
Observation and abstract behaviour in specification and implementation of state-based systems
Classical algebraic specification is an accepted framework for specification. A criticism which applies is the
fact that it is functional, not based on a notion of state as most software development and implementation languages
are. We formalise the idea of a state-based object or abstract machine using algebraic means. In contrast to similar approaches we consider dynamic logic instead of equational logic as the framework for specification and implementation. The advantage is a more expressive language allowing us to specify safety and liveness conditions. It also allows a clearer distinction of functional and state-based parts which require different treatment in order to achieve behavioural abstraction when necessary. We shall in particular focus on abstract behaviour and observation. A behavioural notion of satisfaction for state-elements is needed in order to abstract from irrelevant details of the state realisation
Equivalence of call-by-name and call-by-need for lambda-calculi with letrec
We develop a proof method to show that in a (deterministic) lambda calculus with letrec and equipped with contextual equivalence the call-by-name and the call-by-need evaluation are equivalent, and also that the unrestricted copy-operation is correct. Given a let-binding x = t, the copy-operation replaces an occurrence of the variable x by the expression t, regardless of the form of t. This gives an answer to unresolved problems in several papers, it adds a strong method to the tool set for reasoning about contextual equivalence in higher-order calculi with letrec, and it enables a class of transformations that can be used as optimizations. The method can be used in different kind of lambda calculi with cyclic sharing. Probably it can also be used in non-deterministic lambda calculi if the variable x is "deterministic", i.e., has no interference with non-deterministic executions. The main technical idea is to use a restricted variant of the infinitary lambda-calculus, whose objects are the expressions that are unrolled w.r.t. let, to define the infinite developments as a reduction calculus on the infinite trees and showing a standardization theorem
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