Distributed Correlation-Based Feature Selection in Spark

CFS (Correlation-Based Feature Selection) is an FS algorithm that has been successfully applied to classification problems in many domains. We describe Distributed CFS (DiCFS) as a completely redesigned, scalable, parallel and distributed version of the CFS algorithm, capable of dealing with the large volumes of data typical of big data applications. Two versions of the algorithm were implemented and compared using the Apache Spark cluster computing model, currently gaining popularity due to its much faster processing times than Hadoop's MapReduce model. We tested our algorithms on four publicly available datasets, each consisting of a large number of instances and two also consisting of a large number of features. The results show that our algorithms were superior in terms of both time-efficiency and scalability. In leveraging a computer cluster, they were able to handle larger datasets than the non-distributed WEKA version while maintaining the quality of the results, i.e., exactly the same features were returned by our algorithms when compared to the original algorithm available in WEKA.Comment: 25 pages, 5 figure

Un modelo de los niveles de comprensión de la propiedad conmutativa de la adición

En esta investigación se analiza el desarrollo y comprensión de la propiedad conmutativa de la suma. Para ello tres grupos de niños de Educación Infantil (EI), lº y 2° de Educación Primaria (EP) realizaban tres tareas de conmutatividad: Construir, Encontrar y Comparar equivalencias. Asimismo, se tiene en cuenta el tamaño de los pares conmutados para analizar su incidencia en la comprensión de la conmutatividad. Los resultados indican que existen diferencias significativas entre los grupos y las distin­ tas tareas. En general, los datos obtenidos a partir del análisis de los errores y estrategias de los niños confirman de diverso modo los cinco niveles del modelo hipotético propuesto por Bermejo y Rodr{guez (1993) sobre la comprensión de la propiedad conmutativa: (1) no equivalencia, (2) equivalencia perceptiva, (3) equivalencia basada en el cómputo del resultado, (4) equivalencia práctica y (5) conmutatividad formal

Experimental validation of a SAR-Based RFID localization technique exploiting an automated handling system

The synthetic aperture radar (SAR) approach has attracted a considerable interest in the context of phase-based techniques for the localization of UHF-RFID passive tags. In this letter, the results of an extensive experimental activity are presented, when the reader antenna is moved in front of a set of static passive UHF-RFID tags by means of a planar handling system. Measured performance is evaluated with respect to several system parameters: tag number and typology, tag reciprocal distance and orientation, trajectory and speed of the moving reader antenna. It is shown that the SAR processing can guarantee an accurate two-dimensional localization of multiple tags, with a localization error comparable to the size of typical commercial tags, by using a single reader antenna and without the need for any reference tag

Risk Perception: the case of Microplastics. A discussion of enviornmental risk perception focused on the microplastics issue.

publishedVersio

Drought influence over radial growth of Mexican conifers inhabiting mesic and xeric sites

Drought is a major constraint of forest productivity and tree growth across diverse habitat types. In this study, we investigated the drought responses of four conifer species growing within two locations of differing elevation and climatic conditions in northern Mexico. Two species were selected at a mesic site (Cupressus lusitanica Mill., Abies durangensis Martínez) and the other two species were sampled at a xeric site (Pinus engelmannii Carr., Pinus cembroides Zucc.). Using a dendrochronological approach, we correlated the radial-growth series of each species and the climatic variables. All study species positively responded to wet-cool conditions during winter and spring. Despite the close proximity of species at a mesic site, A. durangensis had high responsiveness to hydroclimatic variability, but C. lusitanica was not responsive. At the xeric site, P. engelmannii and P. cembroides were very responsive to drought severity, differentiated only by the longer time scale of the response to accumulated drought of P. engelmannii. The responsiveness to hydroclimate and drought of these tree species seems to be modulated by site conditions, or by the functional features of each species that are still little explored. These findings indicate that differentiating between mesic and xeric habitats is a too coarse approach in diverse forests with a high topographic heterogeneity.Fil: Pompa García, Marín. Universidad Juárez; MéxicoFil: González Cásares, Marcos. Universidad Juárez; MéxicoFil: Acosta Hernández, Andrea C.. Universidad Juárez; MéxicoFil: Camarero, Jesús Julio. Instituto Pirenaico de Ecología; EspañaFil: Rodriguez Catón, Milagros Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

The nonlinear wave loading and dynamic response of a freely-floating two-dimensional box

This thesis concerns the nonlinear loading and dynamic response of a rectangular box in two dimensions. A fully-nonlinear potential flow model and a series of experimental procedures are employed to describe the nonlinearities governing the floating-body behaviour. Adopting this twin-track approach, nonlinear forcing components are found to make major contributions to both the excitation problem and the motion response. Two main sources of nonlinearity are established: a first associated with higher-order wave-structure interactions, and a second associated with viscous dissipation. The main advance of the present work lies in the quantification of the relative influence of these two sources. The first source, prevalent in steep wave conditions, is particularly significant in the diffraction regime and leads to significant excitation force amplifications. In deep water, these nonlinearities are primarily driven by interactions between the incident and the reflected wave components. The second source, due to viscosity, plays a minor role in the excitation problem, but has a major influence on the motion response. Viscous effects are critically important when the structure exhibits large motions, particularly at resonance. The relative importance of both types of nonlinearity is discussed in regular waves, focused wave groups and random seas. The first two cases are included to gain a clear physical description of the problem, whilst the random sea states are chosen to relate to practical ocean conditions. Experimental data is provided for sea states comprising in excess of 150,000 individual waves, presenting one of the most substantial data sets of this kind to date. In considering this random sea data, the two sources of nonlinearity are found to approximately balance in heave, with a load amplification due to wave-structure interactions and a motion reduction due to viscous dissipation. In roll, viscous dissipation dominates the overall response. Setting the work into its wider context, practical engineering approaches are also offered. A time-domain simulation, building upon a linear hydrodynamic description and a quadratic Morison’s type drag term, is generally found to lead to a good agreement with the experimental data. An approach of this type is computationally very efficient, and hence suitable to day-to-day engineering practice.Open Acces

The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: a tomographic analysis of structure growth and expansion rate from anisotropic galaxy clustering

We perform a tomographic analysis of structure growth and expansion rate from the anisotropic galaxy clustering of the combined sample of Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12, which covers the redshift range of $0.2<z<0.75$. In order to extract the redshift information of anisotropic galaxy clustering, we analyse this data set in nine overlapping redshift slices in configuration space and perform the joint constraints on the parameters $(D_V, F_{\mathrm{AP}}, f\sigma_8)$ using the correlation function multipoles. The analysis pipeline is validated using the MultiDark-Patchy mock catalogues. We obtain a measurement precision of $1.5\%-2.9\%$ for $D_V$, $5.2\%-9\%$ for $F_{\mathrm{AP}}$ and $13.3\%-24\%$ for $f \sigma_8$, depending on the effective redshift of the slices. We report a joint measurement of $(D_V, F_{\mathrm{AP}}, f\sigma_8)$ with the full covariance matrix in nine redshift slices. We use our joint BAO and RSD measurement combined with external datasets to constrain the gravitational growth index $\gamma$, and find $\gamma=0.656 \pm 0.057$, which is consistent with the $\Lambda$CDM prediction within 95\% CL.Comment: 8 pages, 8 figures, 2 tables, accepted for publication MNRAS. The measured results including the full covariance matrices are made available at https://github.com/ytcosmo/TomoBAORSD and tomographic clustering data used in this work is available at https://sdss3.org//science/boss_publications.ph