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Search Results: 1 - 10 of 469013 matches for " Pablo A. Estevez "
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A review of learning vector quantization classifiers
David Nova,Pablo A. Estevez
Computer Science , 2015, DOI: 10.1007/s00521-013-1535-3
Abstract: In this work we present a review of the state of the art of Learning Vector Quantization (LVQ) classifiers. A taxonomy is proposed which integrates the most relevant LVQ approaches to date. The main concepts associated with modern LVQ approaches are defined. A comparison is made among eleven LVQ classifiers using one real-world and two artificial datasets.
An Information Theoretic Algorithm for Finding Periodicities in Stellar Light Curves
Pablo Huijse,Pablo A. Estevez,Pavlos Protopapas,Pablo Zegers,Jose C. Principe
Physics , 2012, DOI: 10.1109/TSP.2012.2204260
Abstract: We propose a new information theoretic metric for finding periodicities in stellar light curves. Light curves are astronomical time series of brightness over time, and are characterized as being noisy and unevenly sampled. The proposed metric combines correntropy (generalized correlation) with a periodic kernel to measure similarity among samples separated by a given period. The new metric provides a periodogram, called Correntropy Kernelized Periodogram (CKP), whose peaks are associated with the fundamental frequencies present in the data. The CKP does not require any resampling, slotting or folding scheme as it is computed directly from the available samples. CKP is the main part of a fully-automated pipeline for periodic light curve discrimination to be used in astronomical survey databases. We show that the CKP method outperformed the slotted correntropy, and conventional methods used in astronomy for periodicity discrimination and period estimation tasks, using a set of light curves drawn from the MACHO survey. The proposed metric achieved 97.2% of true positives with 0% of false positives at the confidence level of 99% for the periodicity discrimination task; and 88% of hits with 11.6% of multiples and 0.4% of misses in the period estimation task.
A Novel, Fully Automated Pipeline for Period Estimation in the EROS 2 Data Set
Pavlos Protopapas,Pablo Huijse,Pablo A. Estevez,Pablo Zegers,Jose C. Principe
Mathematics , 2014, DOI: 10.1088/0067-0049/216/2/25
Abstract: We present a new method to discriminate periodic from non-periodic irregularly sampled lightcurves. We introduce a periodic kernel and maximize a similarity measure derived from information theory to estimate the periods and a discriminator factor. We tested the method on a dataset containing 100,000 synthetic periodic and non-periodic lightcurves with various periods, amplitudes and shapes generated using a multivariate generative model. We correctly identified periodic and non-periodic lightcurves with a completeness of 90% and a precision of 95%, for lightcurves with a signal-to-noise ratio (SNR) larger than 0.5. We characterize the efficiency and reliability of the model using these synthetic lightcurves and applied the method on the EROS-2 dataset. A crucial consideration is the speed at which the method can be executed. Using hierarchical search and some simplification on the parameter search we were able to analyze 32.8 million lightcurves in 18 hours on a cluster of GPGPUs. Using the sensitivity analysis on the synthetic dataset, we infer that 0.42% in the LMC and 0.61% in the SMC of the sources show periodic behavior. The training set, the catalogs and source code are all available in http://timemachine.iic.harvard.edu.
Computational Intelligence Challenges and Applications on Large-Scale Astronomical Time Series Databases
Pablo Huijse,Pablo A. Estevez,Pavlos Protopapas,Jose C. Principe,Pablo Zegers
Computer Science , 2015, DOI: 10.1109/MCI.2014.2326100
Abstract: Time-domain astronomy (TDA) is facing a paradigm shift caused by the exponential growth of the sample size, data complexity and data generation rates of new astronomical sky surveys. For example, the Large Synoptic Survey Telescope (LSST), which will begin operations in northern Chile in 2022, will generate a nearly 150 Petabyte imaging dataset of the southern hemisphere sky. The LSST will stream data at rates of 2 Terabytes per hour, effectively capturing an unprecedented movie of the sky. The LSST is expected not only to improve our understanding of time-varying astrophysical objects, but also to reveal a plethora of yet unknown faint and fast-varying phenomena. To cope with a change of paradigm to data-driven astronomy, the fields of astroinformatics and astrostatistics have been created recently. The new data-oriented paradigms for astronomy combine statistics, data mining, knowledge discovery, machine learning and computational intelligence, in order to provide the automated and robust methods needed for the rapid detection and classification of known astrophysical objects as well as the unsupervised characterization of novel phenomena. In this article we present an overview of machine learning and computational intelligence applications to TDA. Future big data challenges and new lines of research in TDA, focusing on the LSST, are identified and discussed from the viewpoint of computational intelligence/machine learning. Interdisciplinary collaboration will be required to cope with the challenges posed by the deluge of astronomical data coming from the LSST.
Insectos acuáticos de la Meseta del Somuncura, Patagonia, Argentina. Inventario preliminar
Muzón,Javier; Spinelli,Gustavo R.; Pessacq,Pablo; Von Ellenrieder,Natalia; Estevez,Ana Lía; Marino,Pablo I.; Pérez Goodwyn,Pablo J.; Angrisano,Elisa B.; Díaz,Florentina; Fernández,Liliana A.; Mazzuconi,Silvia; Rossi,Gustavo; Salomón *****,Oscar D.;
Revista de la Sociedad Entomol?3gica Argentina , 2005,
Abstract: abstract. a preliminary inventory of the aquatic insects from the somuncura plateau and its area of influence (patagonia, argentina) is presented. it was done on the basis of the study of collections and previous records of species belonging to the orders ephemeroptera, odonata, hemiptera (heteroptera), trichoptera, diptera (families ceratopogonidae, culicidae, and psychodidae) and coleoptera. different kinds of environments were surveyed in 14 localities. seventy eigth species grouped in 51 genera and 26 families were registered, and 33 species are new records for the area. eighty three % of the registered genera are widely distributed (neotropical, american or cosmopolitan), while 41 % of the species exhibit patagonic or andean distribution.
Access to Barrier Perches Improves Behavior Repertoire in Broilers
Beth A. Ventura, Frank Siewerdt, Inma Estevez
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0029826
Abstract: Restriction of behavioral opportunities and uneven use of space are considerable welfare concerns in modern broiler production, particularly when birds are kept at high densities. We hypothesized that increased environmental complexity by provision of barrier perches would help address these issues by encouraging perching and enhancing use of the pen space across a range of stocking densities. 2,088 day-old broiler chicks were randomly assigned to one of the following barrier and density treatment combinations over four replications: simple barrier, complex barrier, or control (no barrier) and low (8 birds/m2), moderate (13 birds/m2), or high (18 birds/m2) density. Data were collected on focal birds via instantaneous scan sampling from 2 to 6 weeks of age. Mean estimates per pen for percent of observations seen performing each behavior, as well as percent of observations in the pen periphery vs. center, were quantified and submitted to an analysis of variance with week as the repeated measure. Barrier perches, density and age affected the behavioral time budget of broilers. Both simple and complex barrier perches effectively stimulated high perching rates. Aggression and disturbances were lower in both barrier treatments compared to controls (P<0.05). Increasing density to 18 birds/m2 compared to the lower densities suppressed activity levels, with lower foraging (P<0.005), decreased perching (P<0.0001) and increased sitting (P = 0.001) earlier in the rearing period. Disturbances also increased at higher densities (P<0.05). Use of the central pen area was higher in simple barrier pens compared to controls (P<0.001), while increasing density above 8 birds/m2 suppressed use of the central space (P<0.05). This work confirms some negative effects of increasing density and suggests that barrier perches have the potential to improve broiler welfare by encouraging activity (notably by providing accessible opportunities to perch), decreasing aggression and disturbances, and promoting more even distribution of birds throughout the pen space.
Differential Outcomes Effect in Four-year-old Children.
Estevez A. F.,Fuentes L. J.
Psicológica , 2003,
Abstract:
Darboux transformations for a Bogoyavlenskii equation in 2+1 dimensions
P. G. Estevez,G. A. Hernaez
Physics , 1999, DOI: 10.1063/1.532811
Abstract: We use the singular manifold method to obtain the Lax pair, Darboux transformations and soliton solutions for a (2+1) dimensional integrable equation.
Lax pair, Darboux Transformations and solitonic solutions for a (2+1) dimensional NLSE
P. G. Estevez,G. A. Hernáez
Physics , 1999,
Abstract: In this paper the Singular Manifold Method has allowed us to obtain the Lax pair, Darboux transformations and tau functions for a non-linear Schr\"odiger equation in 2+1 dimensions. In this way we can iteratively build different kind of solutions with solitonic behavior.
Discrete equations and the singular manifold method
P. G. Estevez,P. A. Clarkson
Physics , 1999,
Abstract: The Painleve expansion for the second Painleve equation (PII) and fourth Painleve equation (PIV) have two branches. The singular manifold method therefore requires two singular manifolds. The double singular manifold method is used to derive Miura transformations from PII and PIV to modified Painleve type equations for which auto-Backlund transformations are obtained. These auto-Backlund transformations can be used to obtain discrete equations.
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