Identificando algunas causas del fracaso en el aprendizaje de la recursividad: análisis experimental en las asignaturas de programación

La recursividad es una herramienta muy potente para la solución de problemas complejos, sin embargo constituye uno de los conceptos más difíciles de entender por los alumnos cuando están aprendiendo a programar. En este artículo se describe una experiencia desarrollada en las asignaturas de Fundamentos de Programación I y de Metodología de la Programación en la Escuela Superior de Informática en Ciudad Real, que tenía como objetivo identificar las necesidades del alumnado a la hora de enfrentarse a la asimilación del concepto de recursividad. El hecho de haber realizado la experiencia en distintos cursos nos ha servido para identificar empíricamente los aspectos que más dificultades les suponen en distintas etapas de su aprendizaje. El estudio que se presenta en este artículo nos ha permitido contrastar la opinión y experiencia de los distintos grupos de estudiantes. Las conclusiones de esta experiencia y las lecciones aprendidas permitirán diseñar en el futuro una herramienta para la visualización de la recursividad que se adapte a las distintas necesidades del alumno, dependiendo de la etapa de aprendizaje en la que se encuentre.SUMMARY -- Recursion is a powerful tool for solving complex problems but it really is one of the most difficult concepts for students to understand when learning to program. This article describes the experience developed in the subjects of Fundamentals of Programming I and Programming Methodology in the School of Informatics in Ciudad Real in order to identify the needs of students when faced with the assimilation of recursion. The fact that the experience has been carried out in different courses has allowed us to identify empirically those aspects more difficult for the understanding of recursive algorithms at different stages of the learning. The study presented in this article allows us to contrast the opinion and experience of different groups of students. The conclusions of this experience and the lessons learned will enable design a tool for visualization of recursion to suit different needs depending on the student's learning stage

6-D manipulation with aerial towed-cable system

We propose a new approach for the reliable 6-dimensional quasi-static manipulation of an aerial towed-cable system. The novelty of this approach lies in the combination of results deriving from the static analysis of cable-driven manipulators with the application of a cost-based motion-planning algorithm to solve manipulation queries. Using this approach, we can ensure that the produced paths are feasible and do not approach dangerous configurations that could provoque the malfunction of the system. The approach has been simulated on the FlyCrane, consisting of a platform attached to three flying robots using six fixed-length cables. The obtained results show the success and the suitability of the approach.Postprint (author’s final draft

First paleomagnetic results of mid-to late Holocene sediments from Lake Issyk-Kul (Kyrgyzstan): Implications for paleosecular variation in central Asia

We present new paleomagnetic and rock magnetic data from mid and late Holocene sediments recovered in two gravity cores (C087 and C142a) from Lake Issyk-Kul (central Asia), for which independent radiocarbon-based age models are available. Our results indicate that sediments from core C087 are characterized by fine (pseudo single domain) magnetite grains and are reliable recorders of Holocene geomagnetic paleosecular variation (PSV) in central Asia, which is a region with poor data coverage. Similarity is found between the core C087 PSV record, which spans the last 5700 years, and the Lake Baikal PSV record, which is the only published Holocene central Asian PSV record of comparable length with an independent radiocarbon-based chronology. Our new results represent a step forward in constructing a reference PSV curve for central Asia that can be used to date sedimentary sequences. These results can also be used to improve the reliability and accuracy of global geomagnetic field models. We have not been able to disentangle past environmental changes in the Lake Issyk-Kul region based on rock magnetic properties, probably because the magnetite and hematite in the studied sediments have a mixed (fluvial and eolian) terrigenous origin. Copyright 2012 by the American Geophysical Union.Financial support for this research was provided through a CSIC JAE-Doc post-doctoral research contract (MGP), the GRACCIE (Spanish Consolider-Ingenio CSD2007-00067), APELIK (EU ICA2-CT-2000-10003), CGL2008-02203/BTE, and PALEONAO (CGL2010-15767/BTE) research projects.Peer Reviewe

A space decomposition method for path planning of loop linkages

This paper introduces box approximations as a new tool for path planning of closed-loop linkages. Box approximations are finite collections of rectangloids that tightly envelop the robot's free space at a desired resolution. They play a similar role to that of approximate cell decompositions for open-chain robots - they capture the free-space connectivity in a multi-resolutive fashion and yield rectangloid channels enclosing collision-free paths - but have the additional property of enforcing the satisfaction of loop closure constraints frequently arising in articulated linkages. We present an efficient technique to compute such approximations and show how resolution-complete path planners can be devised using them. To the authors' knowledge, this is the first space-decomposition approach to closed-loop linkage path planning proposed in the literature.This work has been partially supported by the Spanish Ministryof Education and Science through the contract DPI2004-07358, by the“Comunitat de Treball dels Pirineus” under contract 2006ITT-10004, andby Ram ́on y Cajal and I3 programme funds.Peer ReviewedPostprint (author's final draft

Landscape-scale effects of irrigation on a dry cereal farmland bird community

Landscape modification and habitat fragmentation are one of the major current threats to biodiversity. The main source of habitat fragmentation is the loss of focal habitat area, but changes in the composition of the surrounding landscape also have a direct effect on biodiversity. These changes may lead to the loss of some species but also may favor species replacement. Farmland birds in Europe are affected by landscape changes due to farmland intensification, such as the spread of irrigation, which may occur at different spatial scales. As irrigation is expected to increase in the coming years, which may affect protected areas, it is necessary to evaluate its potential consequences over focal biodiversity. In this study we assess the relationship between the increase of irrigated land at different spatial scales and changes in a dry cereal farmland bird community, bird abundance and species richness, using generalized linear models. We used a dry cereal farmland affinity index to describe the level of community specificity for dry cereal farmland. The increase in irrigated tree orchards produced an increase in species richness up to 500 m away from the irrigated area, which had a negative effect on the dry cereal farmland bird community, by triggering a replacement of specialist by generalist species. Our results show the importance of landscape-scale effects of irrigation occurring outside protected areas on the farmland bird community inside Natura 2000 sites, as well as how these effects are detected even at long distances from the disturbance source.Departament d’Agricultura, Ramaderia, Pesca i Alimentació and Infraestructures de la Generalitat de Catalunya S.A.U. have funded a relevant part of the field work and data acquisition

A space decomposition method for path planning of loop linkages

This paper introduces box approximations as a new tool for path planning of closed-loop linkages. Box approximations are finite collections of rectangloids that tightly envelop the robot's free space at a desired resolution. They play a similar role to that of approximate cell decompositions for open-chain robots - they capture the free-space connectivity in a multi-resolutive fashion and yield rectangloid channels enclosing collision-free paths - but have the additional property of enforcing the satisfaction of loop closure constraints frequently arising in articulated linkages. We present an efficient technique to compute such approximations and show how resolution-complete path planners can be devised using them. To the authors' knowledge, this is the first space-decomposition approach to closed-loop linkage path planning proposed in the literature.Peer Reviewe

Passive acoustic monitoring for estimating human-wildlife conflicts: The case of bee-eaters and apiculture

In human-wildlife conflicts, it is crucial to develop accurate protocols for the reliable verification of the causative species and its relationship with potential damage claims. One of such conflicts is that occurring between apiarists and bee-eaters. In this work, we aim to assess the utility of passive acoustic monitoring (PAM) as an efficient methodology to measure European bee-eater (Merops apiaster) predation pressure at beehives and its impact on honeybees foraging activity. Using Autonomous Recording Units (ARUs) in apiaries, coupled to automated recognition methods for bee-eater calls identification, we found a positive relationship between Vocal Activity Rate (VAR) index and number of bee-eaters hunting attempts on honeybees. We also found that VAR varied over time, showing a lower predation pressure during midday hours and higher during the post-breeding migratory period. Honeybees flying activity was negatively associated with VAR and this relationship was conditioned by the hour of the day. Our study offers a new application of PAM and acoustic derived indices for the evaluation of potential damages caused by wildlife. We focused on the interaction between honeybees and the European bee-eater, but we expect PAM might be useful also to remotely monitor impacts to human activities produced by other vocally active species.European bee-eater monitoring was funded by the Department of Territory and Sustainability of the Generalitat de Catalunya. ARUs conception and design were partially supported by Programa de Investigación y Conservación del Zoo de Barcelona within the project ‘Nuevas tecnologías para viejos trabajos. Uso de grabadores automáticos para la detección y censo de especies raras y amenazadas. El caso de la alondra ricotí en Lleida y otras poblaciones pequeñas’. CPG acknowledges the support from Ministerio de Educación y Formación Profesional through the Beatriz Galindo Fellowship (Beatriz Galindo – Convocatoria 2020)

Finding an objective cost for sliceable flexgrid transponders

We analyze the objective cost of SBVTs as a function of the traffic conveyed by IP/MPLS-over-flexgrid networks. Optimal results show that cost increment with respect to BVTs is related to the aggregation level.Postprint (published version

Astrocytic IL-6 Influences the Clinical Symptoms of EAE in Mice

Interleukin-6 (IL-6) is a multifunctional cytokine that not only plays major roles in the immune system, but also serves as a coordinator between the nervous and endocrine systems. IL-6 is produced in multiple cell types in the CNS, and in turn, many cells respond to it. It is therefore important to ascertain which cell type is the key responder to IL-6 during both physiological and pathological conditions. In order to test the role of astrocytic IL-6 in neuroinflammation, we studied an extensively-used animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), in mice with an IL-6 deficiency in astrocytes (Ast-IL-6 KO). Results indicate that lack of astrocytic IL-6 did not cause major changes in EAE symptomatology. However, a delay in the onset of clinical signs was observed in Ast-IL-6 KO females, with fewer inflammatory infiltrates and decreased demyelination and some alterations in gliosis and vasogenesis, compared to floxed mice. These results suggest that astrocyte-secreted IL-6 has some roles in EAE pathogenesis, at least in females

Great challenges and the application of participatory tools in the planning of the informal city. The case of Makeni, Sierra Leone.

El siguiente artículo indaga sobre la definición de modelos de planificación y herramientas de gestión para ciudades con crecimientos expansivos y amplios sectores informales, utilizando como caso de estudio la experiencia desarrollada en la ciudad de Makeni, Sierra Leona. En un proceso de varios años que continua vivo, la Escuela de Arquitectura de la Universidad San Pablo CEU (USP-CEU) ha impulsado acciones de planeamiento urbano participativo, aportando experiencia técnica desde la colaboración con la Universidad de Makeni y con el Ayuntamiento de la ciudad. Avanzando en el conocimiento paulatino de una realidad específica llena de retos, se han abordado propuestas urbanas en dos líneas fundamentales. Por un lado, mediante el desarrollo de un Plan Espacial Estratégico para Makeni, destinado a la generación de propuestas para la ciudad y su territorio; y, por otro, con la implementación del Programa de Mejoramiento de Barrios, centrado en la ciudad existente. En relación a los resultados, en el territorio de Makeni, destacan el desarrollo de las capacidades formativas de los alumnos de la universidad local, la generación de metodologías e instrumentos de planeamiento básicos, el reforzamiento de los cuadros administrativos municipales, junto a la implicación y concienciación de la población local. A nivel global, hay que destacar la definición de un marco coherente y sistemático, factible de ser replicado en otras realidades urbanas con similares características. Un aporte que resulta especialmente válido en aquellos contextos urbanos desfavorecidos que, en sus procesos de crecimiento, afrontan el mayor reto futuro vinculado a la habitabilidad a nivel global.This article investigates the definition of planning models and management tools for cities with expansive growth and broad informal sectors using the experience of the city of Makeni, Sierra Leone as a case study. In an ongoing process over several years, the School of Architecture at the University San Pablo CEU (USP-CEU) has promoted participatory urban planning actions by providing technical experience through collaboration with the University of Makeni and the Makeni City Council. In the gradual advancement of knowledge about a specific reality full of challenges, urban proposals have been approached in two fundamental ways: on the one hand, through the development of a Strategic Spatial Plan for Makeni aimed at generating proposals for the city and its territory; and on the other, with the implementation of the Neighborhood Improvement Program focused on the existing city. On a local scale in the Makeni territory, notable results include: progress in the training and abilities of local university students, the generation of methodologies and basic planning tools, the strengthening of the municipal administrative cadres, and the involvement and increased awareness of the local population. At the global level, it is important to highlight the creation of a coherent and systematic framework, which can be replicated in other urban realities with similar characteristics. This contribution is especially appropriate in those disadvantaged urban contexts that, in their growth processes, face the greatest future challenge related to habitability at the global level