Coordination of aproximations in secondary school students’ understanding of limit concept

The aim of this research is to characterize the coordination of the processes of approximation related to the understanding of the limit of a function. We analyze the answers of 64 post-secondary school students to 7 problems considering the dynamic and metric conception of limit of a function. Results indicate that the metric understanding of the limit in terms of inequality supports that the student is capable of coordinating the approximations in the domain and in the range when lateral approximations coincide. However, the student is not capable of this coordination when lateral approximations do not coincide. This indicates that the metric understanding of the limit begins with the previous construction of the dynamic conception in case of coincidence of the lateral approximations in the range.

Towards a model-driven engineering approach of data mining

Nowadays, data mining is based on low-level specications of the employed techniques typically bounded to a specic analysis platform. Therefore, data mining lacks a modelling architecture that allows analysts to consider it as a truly software-engineering process. Here, we propose a model-driven approach based on (i) a conceptual modelling framework for data mining, and (ii) a set of model transformations to automatically generate both the data under analysis (via data-warehousing technology) and the analysis models for data mining (tailored to a specic platform). Thus, analysts can concentrate on the analysis problem via conceptual data-mining models instead of low-level programming tasks related to the underlying-platform technical details. These tasks are now entrusted to the model-transformations scaffolding.

Integrating the development of data mining and data warehouses via model-driven engineering

Data mining is one of the most important analysis techniques to automatically extract knowledge from large amount of data. Nowadays, data mining is based on low-level specifications of the employed techniques typically bounded to a specific analysis platform. Therefore, data mining lacks a modelling architecture that allows analysts to consider it as a truly software-engineering process. Bearing in mind this situation, we propose a model-driven approach which is based on (i) a conceptual modelling framework for data mining, and (ii) a set of model transformations to automatically generate both the data under analysis (that is deployed via data-warehousing technology) and the analysis models for data mining (tailored to a specific platform). Thus, analysts can concentrate on understanding the analysis problem via conceptual data-mining models instead of wasting efforts on low-level programming tasks related to the underlying-platform technical details. These time consuming tasks are now entrusted to the model-transformations scaffolding. The feasibility of our approach is shown by means of a hypothetical data-mining scenario where a time series analysis is required.

Use of subpixel techniques in pocket cameras to measure vibrations and displacements

Presentación oral SPIE Photonics Europe, Brussels, 16-19 April 2012.

Measurement of wide frequency range structural microvibrations with a pocket digital camera and sub-pixel techniques

Analysis of vibrations and displacements is a hot topic in structural engineering. Although there is a wide variety of methods for vibration analysis, direct measurement of displacements in the mid and high frequency range is not well solved and accurate devices tend to be very expensive. Low-cost systems can be achieved by applying adequate image processing algorithms. In this paper, we propose the use of a commercial pocket digital camera, which is able to register more than 420 frames per second (fps) at low resolution, for accurate measuring of small vibrations and displacements. The method is based on tracking elliptical targets with sub-pixel accuracy. Our proposal is demonstrated at a 10 m distance with a spatial resolution of 0.15 mm. A practical application over a simple structure is given, and the main parameters of an attenuated movement of a steel column after an impulsive impact are determined with a spatial accuracy of 4 µm.

La historia de la química: Pequeña guía para navegantes. Parte II: Libros, revistas, sociedades, centros de investigación y enseñanza

Este trabajo pretende ser una guía de las investigaciones en historia de la química. Consta de dos partes muy relacionadas entre sí. En la primera parte se ha descrito el desarrollo de la historia de la química como área de investigación, desde sus orígenes hasta el siglo XX. En esta segunda parte se ofrece una lista ordenada de fuentes de información indispensables para trabajar en historia de la química. También se describen las características de las principales instituciones europeas dedicadas a la historia de la química, a partir de una encuesta recientemente realizada por la sociedad europea de sociedades químicas. Información bibliográfica adicional se ofrece en .

Washcoated Pd/Al2O3 monoliths for the liquid phase hydrodechlorination of dioxins

The catalytic activity and durability of 2 wt.% Pd/Al2O3 in powder and washcoated on cordierite monoliths were examined for the liquid phase hydrodechlorination (LPHDC) of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs), also known as dioxins. NaOH was employed as a neutralizing agent, and 2-propanol was used as a hydrogen donor and a solvent. Fresh and spent powder and monolith samples were characterized by elemental analysis, surface area, hydrogen chemisorption, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), and transmission electron microscopy/energy dispersive X-ray spectroscopy (TEM/EDX). Three reactor configurations were compared including the slurry and monolith batch reactors as well as the bubble loop column resulting in 100, 70, and 72% sample toxicity reduction, respectively, after 5 h of reaction. However, the slurry and monolith batch reactors lead to catalyst sample loss via a filtration process (slurry) and washcoat erosion (monolith batch), as well as rapid deactivation of the powder catalyst samples. The monolith employed in the bubble loop column remained stable and active after four reaction runs. Three preemptive regeneration methods were evaluated on spent monolith catalyst including 2-propanol washing, oxidation/reduction, and reduction. All three procedures reactivated the spent catalyst samples, but the combustion methods proved to be more efficient at eliminating the more stable poisons.

La calidad de vida de los ancianos: revisión de literatura

Se trata de una revisión de la literatura que investigó la producción científica en la calidad de vida de los ancianos. Los artículos fueron recogidos en la base de datos SciELO y se identificaron las siguientes variables: los temas más estudiados, el año y el enfoque metodológico de las publicaciones. Se identificaron 56 artículos, 23 de los cuales la calidad de vida relacionada a los indicadores de salud, el mejor año de publicación fue 2011 y el enfoque cuantitativo era frecuente en la muestra. Los estudios llevaron a aprehender que la evaluación de la calidad de vida deberían fusionarse en enfermería vislumbrando la optimización de la salud física y mental de los ancianos.

Benalúa de Alicante: la identidad de un barrio transformado reconsiderada desde la actualidad

Se muestra el estudio de la evolución del barrio residencial de Benalúa, una de las áreas más singulares y valoradas de la ciudad de Alicante, España, que ha transformado completamente su imagen original. Se hace una lectura global cronológica desde su formación y primera consolidación (1883-1900) hasta el momento actual (2011) y, como conclusiones, se identifican y destacan las claves que han propiciado mantener su identidad en el complejo proceso de adaptación y cambio a las nuevas demandas y necesidades urbanas; cualidades que devienen, exclusiva y directamente, de la calidad urbanística y validez de su proyecto. Como base del análisis, se incluyen algunos de los materiales estudiados en el transcurso de la investigación, la mayoría inéditos y de amplio contenido gráfico, con especial interés en los proyectos de obra.

EDUTIC-WQ: de la herramienta de autor hacia la Web 2.0. Evolución en la creación, diseño, accesibilidad y publicación online de WebQuest

Utilizar Internet como medio de aprendizaje, donde se crean, comparten y encuentran infinidad de recursos destinados a la educación es una realidad que se consolida cada día. En este artículo presentamos la evolución, en cuanto a características, uso y difusión, de la plataforma para el aprendizaje on-line EDUTIC-WQ. Esta plataforma, que proporciona una aplicación online para crear, diseñar, compartir y consultar WebQuests, fue creada como herramienta de autor en 2004 en el seno del grupo de investigación EDUTIC-ADEI de la Universidad de Alicante y actualmente ha sido orientada hacia la filosofía de la Web 2.0. EDUTIC-WQ ha superado con creces todas las expectativas de uso y consulta: aproximadamente 4 millones de páginas consultadas en 2011 y ha servido 647 Gigabytes de información consultada por más de 1 millón de personas distintas.

Recommendation of RILEM TC 178-TMC: Testing and modelling chloride penetration in concrete

This RILEM Technical Recommendation intends to give a general description of methods of sampling for obtaining chloride concentration profiles in concrete, applicable both for laboratory cast concrete specimens, for concrete cores taken from structures and for testing on site. These sampling procedures may be applied for obtaining concentration profiles of any other chemical species present in concrete.

Effect of aspect ratio on strain sensing capacity of carbon fiber reinforced cement composites

The electrical resistivity of carbon fiber reinforced cement composites (CFRCCs) has been widely studied, because of their utility as multifunctional materials. The percolation phenomenon has also been reported and modeled when the electrical behavior of those materials had to be characterized. Amongst the multiple applications of multifunctional cement composites the ability of a CFRCC to act as a strain sensor is attractive. This paper provides experimental data relating self-sensing function and percolation threshold, and studying the effect of fiber aspect ratio on both phenomena. Higher fiber slenderness permitted percolation at lower carbon fiber addition, affected mechanical properties and improved strain-sensing sensitivity of CFRCC, which was also improved if percolation had not been achieved.

Feasibility of electrochemical chloride extraction from structural reinforced concrete using a sprayed conductive graphite powder–cement paste as anode

This article summarizes research on the application of a conductive cement paste as an anode in the now classical technique of electrochemical extraction of chlorides applied to a concrete structural element by spraying the paste on the surface of a concrete structural element, a pillar. Sprayed conductive cement paste, by adding graphite powder, is particularly useful to treat sizable vertical surfaces such are structural supports. Outcomes indicate that this kind of anode not only provides electrochemical chloride removal with similar efficiency, but also is able to retain moisture even without the use of a continuous dampening system.

Blending of industrial waste from different sources as partial substitution of Portland cement in pastes and mortars

Binary and ternary combinations of sewage sludge ash (SSA) with marble dust (MD), fly ash (FA) and rice husk ash (RHA) as replacement in Portland cement pastes, were assessed. Several tests were carried out at different curing ages: thermogravimetry, density, water absorption, ultrasonic pulse velocity and mechanical strengths. Pozzolanic effects of the mineral admixtures, densities similar to control sample and improved absorptions when combining waste materials were identified. In general, the compressive strength reaches or exceeds the cement strength class, and blending SSA, FA and RHA (30% cement replacement) increase of strength by 9%, compared to the control sample, was achieved.

Prevalencia de depresión en pacientes con cáncer de mama. Revisión de la literatura

1.- INTRODUCCIÓN: La depresión es una sintomatología muy frecuente en los pacientes diagnosticados con cáncer de mama y su tratamiento. Se plantea una revisión de la literatura para analizar la prevalencia de la depresión en personas con cáncer de mama. 2.- METODOS: Revisión sistemática. Bases de datos: EMBASE (1999-2010) PUBMED (1981-2010). Se incluyeron los artículos que relacionaban prevalencia y depresión en cáncer de mama. 3.- RESULTADOS: Se localizaron 49 estudios; sólo 12 cumplieron los criterios de inclusión, se encontró 7 estudios descriptivos y 5 analíticos. La prevalencia de depresión encontrada en los estudios oscila entre el 6%-57%. 4.- CONCLUSIONES: La disparidad de datos obtenidos conlleva a la falta de una evidencia empírica de la prevalencia de la depresión en personas con cáncer de mama.