Using a free open source software to teach mathematics

We present the experience of the authors teaching mathematics to freshmen engineering students with the help of the open source computer algebra system Sage. We describe some teaching resources and present an ad hoc distribution of Sage used by the authors

Fermiology and transport properties of the half-metallic itinerant ferromagnet CoS2_2: influence of spin orbit coupling

Electronic structure calculations were performed on the compound CoS$_2$, an itinerant ferromagnet whose magnetic properties can be understood in terms of spin fluctuation theory. We have identified nesting features in the Fermi surface of the compound, active for long wavelength spin fluctuations. The electronic structure of the material is close to a half-metal. We show the importance of introducing spin-orbit coupling (SOC) in the calculations, that partially destroys the half-metallicity of the material. By means of transport properties calculations, we have quantified the influence of SOC in the conductivity at room temperature, with an important decrease comparing to the GGA alone conductivity. SOC also helps to understand the negative 0 of the material, whose conductivity varies by a few percent with the introduction of small perturbations in the states around the Fermi level.Comment: 8 pages, 8 figure

Quantifying phase transformation during the manufacturing process of AISI 430 ferritic stainless steel

The effect of ferrite to austenite transformation phenomenon on microstructure and annealing performance of AISI 430 (EN 1.4016) ferritic stainless steel 16%Cr-0.04%C and 17%Cr-0.02%C was studied by electron backscatter diffraction and X-ray diffraction. Hot-rolled and annealed specimens of each ferritic stainless steel were collected from manufacturing route, where different states were analysed. Chemical composition shift of AISI 430 is correlated to microstructural behaviour of each material, while annealing temperature impact over grain growth phenomena is discussed

Characterisation of High Temperature Oxidation Phenomena during AISI 430 Stainless Steel Manufacturing under a Controlled H-2 Atmosphere for Bright Annealing

Localised-in-the-edge oxidation of four AISI 430 alloys was investigated after an industrial bright annealing process. The oxidised surface of each specimen was characterised by X-ray photoelectron spectroscopy (XPS), Raman-spectroscopy and SEM. The results showed that the selective oxidation of Cr and Mn took place at the coil edges of AISI 430. This led to the formation of an oxide scale based on Cr2O3 and MnCr2O4. On the other hand, the formation of Cr(OH)(3) and MnOOH in the outer part of the oxide scale was related to the effect of the H-2-N-2 environment on the annealing furnace. The results concluded that the composition of Cr and Mn in the alloy determined the composition of the oxidation products. However, the effect of annealing time was minor in this oxidation mechanism, which slightly contributed to an increase in the cation diffusion from the steel to the oxide. Finally, the results obtained indicate that the colouration of the coil edges displayed in each studied material varies according to the alloy chemical composition and annealing time.This research was funded by the "Proyectos de I+D Individuales" programme, Centro para el Desarrollo Tecnologico Industrial (CDTI), Ministerio de Economia y Competitividad from the Spanish Government-project "FERRINOP"

Preempted phonon-mediated superconductivity in the infinite-layer nickelates

Nickelate superconductors are outstanding materials with intriguing analogies with the cuprates. These analogies suggest that their superconducting mechanism is similarly unconventional, although this fundamental question is currently under debate. Here, we scrutinize the role played by electronic correlations in enhancing the electron-phonon coupling in the infinite-layer nickelates and the extent to which this may promote superconductivity. Specifically, we use $ab$ $initio$ many-body perturbation theory to perform state-of-the-art $GW$ and Eliashberg-theory calculations. We find that the electron-phonon coupling is in effect enhanced compared to density-functional-theory calculations. This enhancement may lead to low-$T_c$ superconductivity in the parent compounds already. However, it remains marginal in the sense that it cannot explain the record $T_c$s obtained with doping. Conventional superconductivity then appears to be preempted by another mechanism in the infinite-layer nickelates.Comment: 6 pages, 4 figures, 1 table + Supplementary Informatio