Adapting feedback types according to students’ affective states

Affective states play a significant role in students’ learning behaviour. Positive affective states can enhance learning, while negative ones can inhibit it. This paper describes the development of an affective state reasoner that is able to adapt the feedback type according to students’ affective states in order to evoke positive affective states and as such improve their learning experience. The reasoner relies on a dynamic Bayesian network trained with data gathered in a series of ecologically valid Wizard-of-Oz studies, where the effect of feedback on students’ affective states was investigated

Experimental verification of the boundary conditions in the success of the Brazilian test with loading arcs. An uncertainty approach using concrete disks

The present work analyses the reliability of the Brazilian test with loading arcs. A new testing set up has allowed to determine in an effective way the real load of the failure initiation as this moment was not always or correctly detected by the universal testing machine. The instrumentation used is a simple and low-cost method that allows to know the possible pressure distribution in the contact zone as well as the final contact angle. It has been observed that the success of the test depends mainly on the surface finish of the parts involved, their geometric tolerances and the symmetry of the applied load. These boundary conditions have a direct effect in the contact pressure distribution. The possible failure modes observed experimentally have been simulated with the finite element methods. For this, the contact boundary condition has been changed and the possible stress distribution in term of Griffith equivalent stress has been obtained. The numerical analysis allows to study the influence of the initial contact condition on the success of the test and agrees with the experimental results. Furthermore, an uncertainty analysis in the expression of the tensile strength confirms that, when the test is valid, a crack appears suddenly in the central area of the disk, as observed experimentally, so there is no need to determine if the starting point is in the centre. Additionally, it has been observed that the initial crack length depends on the type of pressure distribution in the contact zone. Finally, a series of recommendations are given in order to minimize both the variability of the final contact angle and the risk of premature failure of the Brazilian disk

Early diagenesis in biogenic carbonates of temperate and shoal waters (Cadiz Bay and adjacent continental shelf)

Because of the chemical reactivity of biogenic carbonates in shallow waters, there is increasing interest in those early diagenesis processes that imply an alteration or variation of the composition of original material. This paper presents the preliminary results of a study concerning the compositional variations that have taken place in the skeletons or skeletal remains of bryozoans and echinoids. This variation, which includes an aragonite-calcite transformation, has been checked by means of the Rietveld method, using the Fullprof program. This transformation is caused by an in situ dissolution-recrystallisation process, due to aragonite's metastability. Moreover, the presence of specific authigenic minerals helps to delimit early diagenetic processes, which are, in turn, indicative of the path and the extension of the diagenetic reactions that take place in the sediment column.Debido a que los carbonatos biogénicos de aguas someras son químicamente muy reactivos, existe cada vez mayor interés por conocer los procesos de diagénesis temprana que conllevan una alteración o modificación de la composición del material original. En este trabajo se presentan los resultados iniciales sobre las variaciones de composición que han tenido lugar en los caparazones o restos del esqueleto de equinodermos y briozoos. Esa variación, incluida la transformación aragonito-calcita, ha sido chequeada mediante el método Rietveld, programa Fullprof. Dicha transformación ocurre por un proceso de disolución-recristalización debida a la metaestabilidad del aragonito. Además, la presencia de una asociación de minerales neoformados implica procesos diagenéticos tempranos indicativos de las reacciones que tienen lugar en la columna del sedimento.Instituto Español de Oceanografí

Coal pit lakes in abandoned mining areas in León (NW Spain): characteristics and geoecological significance

1-14 pMining activity introduces severe changes in landscapes and, subsequently, in land uses. One of the most singular changes is the existence of pit lakes, which occur in active and, more frequently, abandoned mines. Pit lakes are produced by water table interception when open-pit mines deepen. Their characteristics are highly variable, depending on the type of mine, the environment or the climate. In León province there is a long tradition of coal mining that dates back to the nineteenth century, and hundreds of open pits from the 1970s to 2018 have been opened, producing permanent landscape changes. This work analyses the main parameters, including morphological measurements, depth and pH values obtained from aerial photos and field work, of 76 coal pit lakes more than 30 m in length. The vast majority of these pit lakes were unknown until now and were not included in inventories or maps. The data obtained provide baseline knowledge that will allow, in the future, potential uses (storage of water for various uses, recreational use, wildlife habitat, and geological heritage sites) for these pit lakes and establish their importance as a new geoecological environment.S

Contribución al estudio del ácido nitrilotripropiónico. Estudio termodinámico de sus complejos con Mn(II), Ni(II), Cu(II) y Zn(II)

From direct calorimetric measurements we have obtained the molar enthalpies, free energies and entropies of the precess of formation of chelates of the nitrilotripropionic acid with Mn(II), Ni(II), Cu(II) and Zn(II). The molar enthalpies corrected for the differences between the stabilization energies of the complexes and the respective aquocations are a linear function of the inverse radius. The corrected ∆S values show, therefore, a linear variation in relation to the inverse radius. The both events are an indication of the contribution of the ligand field stabilization energy to the molar enthalpie and to the formation entropy of the chelates.A partir de medidas calorimétricas directas se han obtenido las entalpías molares, energías libres y entropías que acompañan al proceso de formación de los quelatos del ácido nitrilotripropiónico (NTP) con los iones Mn(ll), Ni(II), Cu(II) y Zn(II). Las entalpías molares corregidas en las diferencias entre las energías de estabilización de los quelatos y acuocationes respectivos son función lineal del radio recíproco. Los valores de ∆S corregidos guardan, asimismo, una variación lineal con el radio recíproco. Ambos hechos son indicativos de la contribución de la acción estabilizante del campo de los ligandos a la entalpía molar y a la entropía de formación de los complejos

Neural-network approach to modeling liquid crystals in complex confinement

Finding the structure of a confined liquid crystal is a difficult task since both the density and order parameter profiles are non-uniform. Starting from a microscopic model and density-functional theory, one has to either (i) solve a non-linear, integral Euler-Lagrange equation, or (ii) perform a direct multi-dimensional free energy minimisation. The traditional implementations of both approaches are computationally expensive and plagued with convergence problems. Here, as an alternative, we introduce an unsupervised variant of the Multi-Layer Perceptron (MLP) artificial neural network for minimising the free energy of a fluid of hard non-spherical particles confined between planar substrates of variable penetrability. We then test our algorithm by comparing its results for the structure (density-orientation profiles) and equilibrium free energy with those obtained by standard iterative solution of the Euler-Lagrange equations and with Monte Carlo simulation results. Very good agreement is found and the MLP method proves competitively fast, flexible and refinable. Furthermore, it can be readily generalised to the richer experimental patterned-substrate geometries that are now experimentally realisable but very problematic to conventional theoretical treatments

Estimating the bispectrum of the Very Small Array data

We estimate the bispectrum of the Very Small Array data from the compact and extended configuration observations released in December 2002, and compare our results to those obtained from Gaussian simulations. There is a slight excess of large bispectrum values for two individual fields, but this does not appear when the fields are combined. Given our expected level of residual point sources, we do not expect these to be the source of the discrepancy. Using the compact configuration data, we put an upper limit of 5400 on the value of f_NL, the non-linear coupling parameter, at 95 per cent confidence. We test our bispectrum estimator using non-Gaussian simulations with a known bispectrum, and recover the input values.Comment: 17 pages, 16 figures, replaced with version accepted by MNRAS. Primordial bispectrum recalculated and figure 11 change