El concepto de infinito en el proceso de enseñanza de la Matemática

En el presente trabajo de investigación, se estudia la evolución histórica del concepto de infinito, desde la antigua Grecia hasta la actualidad. Se expone la presencia del concepto de infinito en distintas áreas de la matemática tales como la geometría, el cálculo y la teoría de números. Posteriormente se estudia el concepto de infinito matemático o infinito actual a través de la teoría de conjuntos en donde se presentan definiciones y se demuestran algunas propiedades relacionadas a dicho concepto. Se analiza la presencia del concepto de infinito en los programas de estudios de la asignatura de Matemática en los niveles de premedia y media de la educación panameña. Finalmente se presentan algunas situaciones didácticas relacionadas con el concepto de infinito que sirven de base para la comprensión de diversos temas en las distintas ramas de la matemática

La formación matemática del docente de educación primaria, un factor influyente en el desempeño de los alumnos al resolver problemas matemáticos

This study aims to identify whether the mathematical training of primary school teachers influences the performance of students in solving mathematical problems. This is a descriptive, quantitative research, with a non-experimental, cross-sectional design. The survey and a test were used as a data collection instrument, which was applied to teachers and students. 5 schools from the Cabecera district were selected and a probabilistic sample was applied with a confidence level of 95%. The sample consisted of 99 teachers and 340 students. The sample consisted of 99 teachers and 340 students. The statistical analysis of the collected data made it possible to describe the weaknesses that primary level teachers present in terms of their mathematical training in the areas of arithmetic, geometry, statistics and measurement systems.El presente estudio pretende identificar si la formación matemática del docente de educación primaria influye en el desempeño de los alumnos en la resolución de problemas matemáticos. Se trata de una investigación descriptiva, cuantitativa con diseño no experimental, transversal. Se empleó como instrumento de recolección de datos, la encuesta y una prueba, la cual se aplicó a docentes y estudiantes. Se seleccionaron 5 escuelas del distrito cabecera y se aplicó un muestreo probabilístico con un 95% de confianza.  La muestra consistió en 99 docentes y 340 estudiantes. El análisis estadístico de los datos recopilados permitió describir las debilidades que presentan los docentes del nivel primario en cuanto a su formación matemática en las áreas de aritmética, geometría, estadística y sistemas de medidas

An Ontology for Modeling Cultural Heritage Knowledge in Urban Tourism

Urban tourism information available on Internet has been of enormous relevance to motivate the tourism in many countries. There exist many applications focused on promoting and preserving the cultural heritage, through urban tourism, which in turn demand a well-defined and standard model for representing the whole knowledge of this domain, thus ensuring interoperable and flexible applications. Current studies propose the use of ontologies to formally model such knowledge. Nonetheless, most of them only represent partial knowledge of cultural heritage or are restrictive to an indoor perspective (i.e., museum ontologies). In this context, we propose the ontology CURIOCITY ( Cultural Heritage for Urban Tourism in Indoor/Outdoor environments of the CITY ), to represent the cultural heritage knowledge based on UNESCO’s definitions. CURIOCITY ontology has a three-level architecture (Upper, Middle, and Lower ontologies) in accordance with a purpose of modularity and levels of specificity. In this paper, we describe in detail all modules of CURIOCITY ontology and perform a comparative evaluation with state-of-the-art ontologies. Additionally, to demonstrate the suitability of CURIOCITY ontology, we show several touristic services offered through a framework supported in the ontology. The framework includes an automatic population process, that allows transforming a museum data repository (in CSV format) into RDF triples of CURIOCITY ontology to automatically populate the CURIOCITY repository, and facilities to develop a set of tourism applications and services, following the UNESCO’s definitions

Conductive paint-filled cement paste sensor for accelerated percolation

Cementitious-based strain sensors can be used as robust monitoring systems for civil engineering applications, such as road pavements and historic structures. To enable large-scale deployments, the fillers used in creating a conductive material must be inexpensive and easy to mix homogeneously. Carbon black (CB) particles constitute a promising filler due to their low cost and ease of dispersion. However, a relatively high quantity of these particles needs to be mixed with cement in order to reach the percolation threshold. Such level may influence the physical properties of the cementitious material itself, such as compressive and tensile strengths. In this paper, we investigate the possibility of utilizing a polymer to create conductive chains of CB more quickly than in a cementitious-only medium. This way, while the resulting material would have a higher conductivity, the percolation threshold would be reached with fewer CB particles. Building on the principle that the percolation threshold provides great sensing sensitivity, it would be possible to fabricate sensors using less conducting particles. We present results from a preliminary investigation comparing the utilization of a conductive paint fabricated from a poly-Styrene-co-Ethylene-co-Butylene-co-Styrene (SEBS) polymer matrix and CB, and CB-only as fillers to create cementitious sensors. Preliminary results show that the percolation threshold can be attained with significantly less CB using the SEBS+CB mix. Also, the study of the strain sensing properties indicates that the SEBS+CB sensor has a strain sensitivity comparable to the one of a CB-only cementitious sensor when comparing specimens fabricated at their respective percolation thresholds

Smart Concrete for Enhanced Nondestructive Evaluation

The authors recently investigated the use of conductive concrete to enhance nondestructive evaluation (NDE) capa- bilities. Preliminary results have shown that a conductive concrete can facilitate the utilization of an eddy current technique, where damages in a conductive specimen were easier to detect compared with a non-conductive substrate. While such results demonstrated the promise of using conductive concrete to facilitate and potentially accelerate the NDE process, the fabrication of an homogeneous conductive concrete is technically or economically challenging, depending on the conductive filler used in the process. In this paper, we propose a new cementitious composite to accelerate NDE. The composite uses inexpensive carbon black particles (CB) and a block-copolymer. The purpose of the block co-polymer, a styrene-ethylene-butylene-styrene (SEBS), is to facilitate the creation of conductive chains, therefore reducing the necessary concentration of conductive filler required to achieve electrical percolation. Several cementitious composite specimens of various concentrations of CB are fabricated, and results show that the utilization of SEBS reduces the electrical percolation threshold by approximately 50% with a gain on electrical conductivity relative to a non-conductive specimen mix of approximately 33%. Strain-sensing tests also demonstrate that SEBS-based specimens have good sensing properties, but lag behind those of conductive concrete specimens fabricated with CB only

Neonatal cranial ultrasound abnormalities in LBW infants: Relation to cognitive outcomes at age six

bjective: To assess the independent relation of neonatal cranial ultrasound (US) abnormalities in low birth weight (LBW) infants to cognitive outcomes at 6 years of age.Design: Prospective cohort study.Sample and Methods: Six-year follow-up data were obtained on a regional birth cohort of LBW infants (\u3c 2 kg) systematically screened as neonates with serial US. US abnormalities were dichotomized into isolated germinal matrix/intraventricular hemorrhage (GM/IVH) and parenchymal lesions/ventricular enlargement (PL/VE). Global cognitive outcomes (mental retardation, borderline intelligence, and normal intelligence) and selected specific cognitive abilities were assessed at 6 years of age with standardized instruments. Multivariate techniques were used to assess the effects of US independent of maternal social disadvantage at birth and other perinatal and neonatal risk factors.Results: The sample as a whole had a significantly elevated rate of mental retardation (MR; 5%), almost all moderate to profound in severity. PL/VE was independently related to MR (odds ratio [OR], 65.8; confidence interval [CI], 19.1 to 22.4) and borderline intelligence (OR, 3.7; CI, 1.3 to 10.8); isolated GM/IVH was more modestly related to MR (OR, 4.6; CI, 1.2 to 18.6) but not related to borderline intelligence. Approximately half of the cases of MR were attributable to PL/VE independent of other factors. Of non-US factors, the number of days receiving mechanical ventilation increased the risk for MR. Maternal social disadvantage increased the risk for borderline intelligence but not MR. Among children of normal intelligence, those with PL/VE, but not isolated GM/IVH, performed more poorly than those without US abnormalities on tests of visual perceptual organization but not on tests of language, memory, or quantitative skills.Conclusion: Prevention of white matter injury would substantially improve cognitive outcomes for LBW infants

Acceleration of percolation for cementitious sensors using conductive paint filler

Structural health monitoring has emerged as an important branch of civil engineering in recent times, with the need to automatically monitor structural performance over time to ensure structural integrity. More recently, the advent of smart sensing materials has given this field a major boost. Research has shown that smart sensing materials fabricated with conductive filler at a concentration close to the percolation threshold results in high sensitivity to strain due to the piezoresistive effect. Of particular interest to this research are cementitious sensors fabricated using carbon black fillers. Carbon black is considered because of its widespread availability and low cost over other conductive fillers such as carbon nanotubes and carbon nanofibers. A challenge in the fabrication of these sensors is that cementitious materials require a significant amount of carbon black to percolate, resulting in a loss in mechanical properties. This research investigates a new method to accelerate percolation of the materials, enabling cementitious sensors with fewer carbon black particles. A carbon black-based conductive paint that allows earlier percolation by facilitating conducting networks in cementitious sensors is used. The conductive paint consists of a block copolymer, SEBS (styrene-co-ethylene-co-butylene-co-styrene), filled with carbon black particles. The percolation thresholds of sensors fabricated both with and without conductive paint are, as well as their strain sensing characteristics and compressive strength. The study found that SEBS could successfully reduce the percolation threshold by 42%, and that samples with SEBS showed better electrical responses in dynamic conditions. Despite showing lower compressive strength, cementitious sensors fabricated with this novel conductive paint show promise for real time health monitoring applications.</p