La modelización matemática para iniciar la construcción de conjunto generador y espacio generado

Este estudio exploratorio se fundamenta en la necesidad de que la investigación en Educación Matemática a nivel universitario, de acuerdo con Selden y Selden (2001), posea un rol activo y contribuya al desarrollo del currículum. Aquí se presentan los resultados del primer ciclo de experimentación de una investigación de diseño más extensa cuyo objetivo es construir una teoría de instrucción local para los conceptos específicos de Álgebra Lineal: conjunto generador y espacio generado

Residual-based stabilization of the finite element approximation to the acoustic perturbation equations for low Mach number aeroacoustics

This is the peer reviewed version of the following article: [Guasch, O., Sánchez-Martín, P., Pont, A., Baiges, J., and Codina, R. (2016) Residual-based stabilization of the finite element approximation to the acoustic perturbation equations for low Mach number aeroacoustics. Int. J. Numer. Meth. Fluids, 82: 839–857. doi: 10.1002/fld.4243], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/fld.4243/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The acoustic perturbation equations (APE) are suitable to predict aerodynamic noise in the presence of a non-uniform mean flow. As for any hybrid computational aeroacoustics approach, a first computational fluid dynamics simulation is carried out from which the mean flow characteristics and acoustic sources are obtained. In a second step, the APE are solved to get the acoustic pressure and particle velocity fields. However, resorting to the finite element method (FEM) for that purpose is not straightforward. Whereas mixed finite elements satisfying an appropriate inf–sup compatibility condition can be built in the case of no mean flow, that is, for the standard wave equation in mixed form, these are difficult to implement and their good performance is yet to be checked for more complex wave operators. As a consequence, strong simplifying assumptions are usually considered when solving the APE with FEM. It is possible to avoid them by resorting to stabilized formulations. In this work, a residual-based stabilized FEM is presented for the APE at low Mach numbers, which allows one to deal with the APE convective and reaction terms in its full extent. The key of the approach resides in the design of the matrix of stabilization parameters. The performance of the formulation and the contributions of the different terms in the equations are tested for an acoustic pulse propagating in sheared-solenoidal mean flow, and for the aeolian tone generated by flow past a two-dimensional cylinder.Peer ReviewedPostprint (author's final draft

Moradebrichthys vilasecae gen. et sp. nov., a new perleidid (Actinopterygii: Osteichthyes) from the Middle Triassic of Catalonia (NE Iberian Peninsula)

A new actinopterygian, Moradebrichthys vilasecae gen. et sp. nov., from the Middle Triassic (Late Ladinian) of Móra d'Ebre-Camposines (Catalonia, NE Iberian Peninsula) is erected on the basis of several, almost complete, articulated and well-preserved specimens. It is referred to the controversial family Perleididae based on the presence of a combination of features such as paried nasals, presence of rostral, vertical suspensorium, absence of interopercle, lack of coronoid in the mandible, basal and fringing fulcra on fins developed to different extents and an almost symmetrical caudal fin with epaxial fin rays. Comparisons to other well-known taxa usually assigned to the Perleididae family reveals that the new taxon presents many similarities with the genera Perleidus, Peltoperleidus, Aetheodontus and Meridensia, rather than other perleidids. Moreover, additional morphological characters, not shared with any of these genera are: a big half moon shaped infraorbital-2 and one elongate infraorbital-1, a narrow vertical preopercle with a prominent and pointed anterior maxillary process, a dentary covered by horizontally arranged ridges, a very big opercle and a much smaller subopercle, and the high level of lepidotrichia branching in the caudal fin. A comparison of Catalan Middle Triassic actinopterygian assemblages with other ones from Central European basins of coeval age (particularly Italian and Swiss localities) suggest some faunal similarities, being of special interest the potential correlation with the Besano Formation

Muestreador sumergible de materia orgánica disuelta y particulada en medios acuáticos

Fecha de presentación nacional 04-08-1988.-- Titular: Consejo Superior de Investigaciones científicas (CSIC).El equipo que se presenta permite el muestreo directo de los compuestos orgánicos disueltos y particulados en aguas profundas y el registro simultáneo de las caracteristícas de la masa de agua muestreada (volumen, profundidad, dirección e intensidad de la corriente salinidad, temperatura, etc...). El equipo es sumergible y se basa en la filtración "in situ" de grandes volúmenes de agua mediante una bomba impelente no contaminante y subsiguiente extracción de la fase disuelta mediante adsorción sobre un soporte polimérico. El sistema opera conectado por un cable eléctrico polifásico a un panel de mandos y recogida de datos. Los fi ltros y adsorbentes son posteriormente analizados en el laboratorio. El sistema es de aplicación en numerosos campos de actividad que requieren la investigación o control de masas de agua como la oceanografía, acuicultura, medio ambiente, etc.Peer reviewe

Mathematical modelling and the learning trajectory: tools to support the teaching of linear algebra

In this article we present a didactic proposal for teaching linear algebra based on two compatible theoretical models: emergent models and mathematical modelling. This proposal begins with a problematic situation related to the creation and use of secure passwords, which leads students toward the construction of the concepts of spanning set and span. The objective is to evaluate this didactic proposal by determining the level of match between the hypothetical learning trajectory (HLT) designed in this study with the actual learning trajectory in the second experimental cycle of an investigation design-based research more extensive. The results show a high level of match between the trajectories in more than half of the conjectures, which gives evidence that the HLT has supported, in many cases, the achievement of the learning objective, and that additionally mathematical modelling contributes to the construction of these linear algebra concepts.Peer ReviewedPostprint (author's final draft

Unified solver for fluid dynamics and aeroacoustics in isentropic gas flows

The high computational cost of solving numerically the fully compressible Navier–Stokes equations, together with the poor performance of most numerical formulations for compressible flow in the low Mach number regime, has led to the necessity for more affordable numerical models for Computational Aeroacoustics. For low Mach number subsonic flows with neither shocks nor thermal coupling, both flow dynamics and wave propagation can be considered isentropic. Therefore, a joint isentropic formulation for flow and aeroacoustics can be devised which avoids the need for segregating flow and acoustic scales. Under these assumptions density and pressure fluctuations are directly proportional, and a two field velocity-pressure compressible formulation can be derived as an extension of an incompressible solver. Moreover, the linear system of equations which arises from the proposed isentropic formulation is better conditioned than the homologous incompressible one due to the presence of a pressure time derivative. Similarly to other compressible formulations the prescription of boundary conditions will have to deal with the backscattering of acoustic waves. In this sense, a separated imposition of boundary conditions for flow and acoustic scales which allows the evacuation of waves through Dirichlet boundaries without using any tailored damping model will be presented.Peer ReviewedPostprint (author's final draft

La construcción de conceptos de álgebra lineal a través de los modelos emergentes

Álgebra lineal es un curso reconocido por sus dificultades tanto cognitivas como conceptuales. Para contribuir a minimizarlas se elaboró y evaluó un diseño instruccional innovador basado en los modelos emergentes y la modelización matemática para los conceptos de conjunto generador y espacio generado a través de la investigación de diseño con estudiantes universitarios. Los resultados sugieren que este tipo de diseño instruccional favorece la construcción de estos conceptos matemáticos, por tanto, podría ser utilizado como una alternativa, a la enseñanza tradicional, para estos y otros conceptos de álgebra lineal

La trayectoria hipotética de aprendizaje en matemática universitaria: un ejemplo para el curso de álgebra lineal

En la actualidad, el curso de álgebra lineal se incluye en la mayoría de los programas de estudios de las carreras universitarias enfocadas en el área de ciencia y tecnología. Sin embargo, su enseñanza en este nivel educativo, según señala Hillel (2000) es calificada universalmente como una experiencia frustrante tanto para los profesores como para los estudiantes. Con el objetivo de favorecer el aprendizaje y la enseñanza de este curso, en este trabajo se presenta una trayectoria hipotética de aprendizaje (THA) que tiene como finalidad apoyar a los estudiantes en la construcción de ciertos conceptos del álgebra lineal. En particular, se eligen los conceptos de conjunto generador y espacio generado. Esta THA se sustenta en la heurística de diseño instruccional de los modelos emergentes y la modelización matemática. La THA surge del análisis de los resultados de una investigación de diseño que constó de tres ciclos de experimentación en la que participaron estudiantes de primer año de la carrera de ingeniería. El análisis de los resultados da evidencias del potencial de esta THA para apoyar el aprendizaje de estos conceptos del álgebra lineal