208 research outputs found
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 CoS: influence of spin orbit coupling
Electronic structure calculations were performed on the compound CoS, 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
many-body perturbation theory to perform state-of-the-art 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- superconductivity in the parent compounds
already. However, it remains marginal in the sense that it cannot explain the
record 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
Polymorphism in Ruddlesden-Popper : Discovery of a Hidden Phase with Distinctive Layer Stacking
We report the discovery of a novel form of Ruddlesden-Popper (RP) oxide,
which stands as the first example of long-range, coherent polymorphism in this
class of inorganic solids. Rather than the well-known, uniform stacking of
perovskite blocks ubiquitously found in RP phases, this newly discovered
polymorph of the bilayer RP phase adopts a novel stacking
sequence in which single and trilayer blocks of octahedra alternate
in a 1313 sequence. Crystals of this new polymorph are described in space group
Cmmm, although we note evidence for a competing Imcm variant. Transport
measurements at ambient pressure reveal metallic character with evidence of a
charge density wave transition with onset at T = 134 K, which lies intermediate
between that of the standard 2222 polymorph of (space group
Amam) and the trilayer RP phase, . The discovery of such
polymorphism could reverberate to the expansive range of science and
applications that rely on RP materials, particularly the recently reported
signatures of superconductivity with as high as 80 K above 14 GPa in
bilayer .Comment: 37 pages, 10 figure
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