Aproximaciones socioculturales a la modelación en Educación Matemática. Aportes de una comunidad latinoamericana

La modelación matemática es un dominio de investigación dentro de la Educación Matemática (Blum, Galbraith, Henn, y Niss, 2007). Su grado de consolidación se observa en la cantidad de eventos académicos, revistas científicas y colecciones de libros especializados que centran su interés en la temática. Este interés se fundamenta en la relevancia que tienen los contextos y conexiones en la producción de significados matemáticos, así como en el desarrollo de competencias, habilidades, visiones y para la participación ciudadana. Este documento ofrece un panorama de las comprensiones y aportes que un conjunto de investigadores latinoamericanos tienen sobre la modelación matemática en una aproximación sociocultural

Searching for BcB_c mesons in the ATLAS experiment at LHC

We discuss the feasibility of the observation of the signal from $B_c$ mesons in the ATLAS experiment of the LHC collider at a luminosity of ${\approx}\ 10^{33}$cm$^{-2}$s$^{-1}$. In particular we address the decay mode$B_c{\rightarrow}J/\psi \pi$followed by the leptonic decay$J/\psi{\rightarrow}\mu^+\mu^-$, which should permit an accurate measurement of the$B_c$mass. We performed a Monte Carlo study of the signal and background concluding that a precision of$40$MeV for the$B_c$ mass could be achieved after one year of running.Comment: Latex,7 pages including 3 uuencoded Postscript figures appended at the end of the latex fil

Tailoring the microstructure by a proper electric current control in flash sintering: The case of barium titanate

Flash sintering is arousing growing interest because high-density ceramics can be obtained at lower temperatures and shorter dwell times than conventional sintering. However, not only temperature and dwell times should be controlled during flash sintering but also parameters such as the electric field and electric current should be considered. Controlling all the parameters during the processing allows comprehensive control of the microstructure and, consequently, functional properties can be improved. In this work, it is evidenced that an exhaustive control of the flash electric current is a crucial factor for tailoring the microstructure of BaTiO3 ceramics. The results reveal that the most suitable way to control the sintering process is by using nonlinear current profiles because better densification and improved grain growth is achieved. Although the results focus on BaTiO3, this work offers a new pathway to tailor the microstructure of flash sintered ceramics, which may be extended to other materials

Particle size effect on the microstructure and the aging process of flash-sintered barium titanate from micro and nanopowders

Flash sintering is a novel sintering technique that allows high-density ceramics to be obtained at lowtemperatures and using short dwell times, thus providing an energy-efficient alternative to conventionalsintering. The microstructure of flash-sintered samples can be fine-tuned by a proper control ofelectrical parameters such as current density, electric field, and current profile, yielding significantimprovements of functional properties. The starting powder should also be carefully selected sincebetter sintering results are reported for smaller green grain sizes. However, this work evidences timeevolution of electrical properties of flash-sintered BaTiO3 ceramics from submicron powders. Theresults reveal that these transformations greatly depend on powder grain size and can be furtheradjusted with an adequate selection of electric power profiles. This work provides new insights intoongoing phenomena during field-assisted sintering, such as grain growth and defect formationdynamics. Although the results focus on BaTiO3, it offers a new pathway to tailor the microstructure offlash-sintered ceramics, which may be extended to other electronic materials

A semi-supervised Teacher-Student framework for surgical tool detection and localization

Surgical tool detection in minimally invasive surgery is an essential part of computer-assisted interventions. Current approaches are mostly based on supervised methods requiring large annotated datasets. However, labelled datasets are often scarce. Semi-supervised learning (SSL) has recently emerged as a viable alternative showing promise in producing models retaining competitive performance to supervised methods. Therefore, this paper introduces an SSL framework in the surgical tool detection paradigm, which aims to mitigate training data scarcity and data imbalance problems through a knowledge distillation approach. In the proposed work, we train a model with labelled data which initialises the Teacher-Student joint learning, where the Student is trained on Teacher-generated pseudo-labels from unlabelled data. We also propose a multi-class distance with a margin-based classification loss function in the region-of-interest head of the detector to segregate the foreground-background region effectively. Our results on m2cai16-tool-locations dataset indicates the superiority of our approach on different supervised data settings (1%, 2%, 5% and 10% of annotated data) where our model achieves overall improvements of 8%, 12%, and 27% in mean average precision on 1% labelled data over the state-of-the-art SSL methods and the supervised baseline, respectively. The code is available at https://github.com/Mansoor-at/Semi-supervised-surgical-tool-detection

Growth and physical properties of highly oriented La-doped (K,Na)NbO3 ferroelectric thin films

Lead-free (K,Na)NbO3 (KNN) and La doped (K,Na)NbO3 (KNN-La) thin films were grown on SrTiO3 substrates by chemical solution deposition method. The effect of adding different amounts of Na and K excess (0-20 mol%) has been investigated. The results confirm the necessity to add 20 mol% excess amounts of Na and K precursor solutions in order to avoid the formation of the secondary phase, K4Nb6O17, as is confirmed by X-ray diffraction and Raman spectroscopy. Moreover, when adding a 20 mol% of alkaline metal excess the thin films are highly textured with out-of-plane preferential orientation in the [100] direction following the [100] orientation of the substrate. Doping with lanthanum resulted in the decrease in the leakage current density at low electric field, and an increase in the dielectric permittivity across all the temperatures range (80-380 K). Although the (100)-oriented KNN and KNN-La films exhibited rounded hysteresis loops, at low temperature the films showed the typical ferroelectric hysteresis loops