A subsampling method for the computation of multivariate estimators with high breakdown point

All known robust location and scale estimators with high breakdown point for multivariate sample's are very expensive to compute. In practice, this computation has to be carried out using an approximate subsampling procedure. In this work we describe an alternative subsampling scheme, applicable to both the Stahel-Donoho estimator and the estimator based on the Minimum Volume Ellipsoid, with the property that the number of subsamples required is substantially reduced with respect to the standard subsampling procedures used in both cases. We also discuss some bias and variability properties of the estimator obtained from the proposed subsampling process

Fuentes primarias, objetos y artefactos en la interpretación de la historia. Diseño y evaluación de un taller de numismática en Educación Secundaria

Este trabajo presenta el diseño y evaluación de una experiencia de innovación para la enseñanza de la historia, basada en el uso de un taller de numismática en la unidad didáctica sobre el Antiguo Régimen. Se incide principalmente en los aspectos metodológicos de la experiencia, y en el uso de diferentes fuentes para desarrollar la interpretación y argumentación histórica en el alumnado. La experiencia se realizó en tres cursos consecutivos. La valoración de la experiencia se realizó a través de un cuestionario cerrado con una escala de estimación tipo Likert (1-5), donde el alumnado debía valorar tanto la actividad, como el proceso de enseñanza y el aprendizaje adquirido. Los resultados fueron positivos a lo largo de los tres años.This paper presents the design and evaluation of an innovative experience to teach history based on the use of a numismatic workshop in the teaching unit on the Old Regime. We deepen mainly on methodological aspects of the experience, and the use of different sources to develop the interpretation and historical argument in students. The experience was carried out in three consecutive courses. The assessment of the experience was carried out through a closed questionnaire with a Likert scale (1-5), where students should assess both the activity and the process of teaching and learning acquired. The results were positive over the three years

Coupling hydro-geo-chemical and isotopic approaches to assess the main factors controlling karst development in a fissure-dominated carbonate aquifer system (s-Spain)

Sierra Tejeda, Almijara and Albuñuelas mountains comprise a large outcrop (750 km² ca) of Triassic marbles in between of Málaga and Granada provinces in S Spain. They constitute a large entity carbonate aquifer system providing strategic groundwater resources for drinking water supply in sparse urban settlements and crops irrigation. The present research aims to refine the current hydrogeological knowledge of large-scale fissure-dominated carbonate aquifers regarding flow mechanisms and geochemical processes defining observed groundwater quality. To this, a two-year monitoring program of aquifer dynamics have been conducted in three selected discharge points (Fájara, Cijancos and Maro springs) showing characteristic spring responses. A combined approach based on the analysis of spring discharge and time series of selected hydrochemical and isotopic tracers (Na+, Ca+2, Mg+2, TA, TOC, Cl-, SO4-2 and δ13CTDIC) and on the geochemical calculations from the chemical signature of spring waters have been followed. The results indicate that the more bicarbonate enriched waters and the lowest hydrochemical variability of Cijancos spring, practically in all analyzed solutes, denotes a fissure type dominant flow system, while the larger variations in meteoric/soil tracers (Cl- and TOC) observed in Fajara spring chemograph as consequence of rainfall inputs characterize a karst drainage from a better hierarchized fracture-enlarged flow system. Maro spring waters are rich in Na+, Ca+2, Cl- and SO4-2, have higher δ13CTDIC amplitude and the temporal variations of major ions display marked dilutions after rainfall events followed by rapid recoveries of pre-event concentrations, evidence a complex flow system and variable groundwater source contribution. The chemical reactions deduced from the molar ratios of spring water chemistry are commonly CO2 dissolution and calcite dissolution, but also salt evapoconcentration in soil layer and gypsum dissolution in the case of Maro spring.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

THE IMPACT OF USING SMARTPHONES AS STUDENT RESPONSE SYSTEMS ON PROSPECTIVE TEACHER EDUCATION TRAINING: A CASE STUDY. EL IMPACTO DE LOS DISPOSITIVOS MÓVILES COMO SISTEMAS DE RESPUESTA PERSONAL EN LA ENSEÑANZA DE FUTUROS MAESTROS: UN ESTUDIO DE CASO. doi 10.20420/GUIN.2014.0066

-Higher education classrooms have long suffered from a lack of interactivity. At Universidad Rey Juan Carlos, some instructors actively seek technologic interventions that can increase interactivity in large classes. This study explored the learningeffectiveness and engagement appeal of using Socrative as a Student Response System (SRS), known as clicker, and also reports results from a formal implementation of the system in K-12 prospective teachers higher education classrooms. A questionnaire based survey was conducted to inquire into students’ perceptions on their use, and data collected from 70 students was examined. As the data reveal, Socrative can much better engage students in the learning process, promoting collaboration and encouragingparticipation. However, some problems related to the use of SRSs were revealed such as the off-task use of the smartphones in the classroom. Recommendations were provided with respect to the use of SRSs in higher education.--Las metodologías interactivas han estado tradicionalmente ausentes de las aulas de educación superior. Este artículo presenta un estudio de caso basado en una experiencia llevada a cabo en la práctica docente en los grados de educación de la Universidad Rey Juan Carlos. Este estudio exploró la eficacia del aprendizaje interactivo y la implicación del alumnado al utilizar Socrative como Sistema de Respuesta Personal (SRP), o clicker. Se realizó una encuesta para conocer las percepciones de 70 estudiantes sobre su uso. Los resultados obtenidos muestran que Socrative permite una mayor implicación y más compromiso de los estudiantes en el proceso de aprendizaje, además de favorecer la colaboración y fomentar la participación. Sin embargo, se descubrieron algunos problemas relacionados con el uso de los SRP como el abuso de los dispositivos móviles en el aula. Por último, el estudio propone varias recomendaciones sobre la utilización de los SRP en la educación superior.DOI 10.20420/GUIN.2014.006

Using angles to identify concentrated multivariate outliers

This article describes a procedure for the detection of multivariate outliers based on the analysis of certain angular properties of the observations. The method is simple, exploratory in nature, and particularly well suited for the detection of concentrated contamination patterns, in which the outliers appear to form a cluster, separated from the sample. It is shown that it presents good properties for the identification of contaminations on high-dimensional sample spaces and for high contamination levels, including some cases in which methods based on robust estimators (the minimum covariance determinant and minimum volume ellipsoid estimators, the Stahel–Donoho estimator, or other recent proposals) may fail. The use of the procedure is illustrated through several examplesPublicad

Generic Battery Model based on a Parametric Implementation

Batteries are a common element used in many electronic applications. Therefore, the analysis and simulation of these applications requires a battery model in order to validate the behavior of the whole system. Since batteries are based on different technologies, a modeling approach valid for any technology is a potential good alternative. Since there are similarities among the different technologies, it is possible to address the modeling of batteries as generic energy storage elements with particular differences. This work presents a battery model valid for different technologies based on a parametric implementation