Ambientes, territorios y subsistencia en el Paleolítico Medio de PortugaL

Sin resume

Current-driven skyrmion motion along disordered magnetic tracks

The motion of skyrmions along ferromagnetic strips driven by current pulses is theoretically analyzed by means of micromagnetic simulations. Analytical expressions describing the skyrmion dynamics during and after the current pulse are obtained from an extended rigid skyrmion model, and its predictions are compared with full micromagnetic simulations for perfect samples with a remarkable agreement. The dynamics along realistic samples with random disorder is also studied by both models. Our analysis describes the relevant ingredients behind the current-driven skyrmion dynamics, and it is expected to be useful to understand recent and future experimental.Comment: Micromagnetic simulations and analytical expressions describing the dynamics of skyrmions under current-pulses along realistic strip

Current-driven domain wall motion along ferromagnetic strips with periodically-modulated perpendicular anisotropy

The dynamics of magnetic domain walls along ferromagnetic strips with spatially modulated perpendicular magnetic anisotropy is theoretically studied by means of micromagnetic simulations. Ferromagnetic layers with a periodic sawtooth profile of the anisotropy depict a well-defined set of energy minima where the walls are pinned in the absence of external stimuli, and favor the unidirectional propagation of domain walls. The performance of the current-driven domain wall motion along these ratchet-like systems is compared to the field-driven case. Our study indicates that the current-driven domain wall motion exhibits significant improvements with respect to the field-driven case in terms of bit shifting speed and storage density, and therefore, it is suggested for the development of novel devices. The feasibility of these current-driven ratchet devices is studied by means of realistic micromagnetic simulations and supported by a one-dimensional model updated to take into account the periodic sawthooth anisotropy profile. Finally, the current-driven domain wall motion is also evaluated in systems with a triangular modulation of the anisotropy designed to promote the bidirectional shifting of series of walls, a functionality that cannot be achieved by magnetic fields.Comment: 32 pages, 11 figure

Ultralight boson cloud depletion in binary systems

Ultralight scalars can extract rotational energy from astrophysical black holes through superradiant instabilities, forming macroscopic boson clouds. This process is most efficient when the Compton wavelength of the boson is comparable to the size of the black hole horizon, i.e. when the "gravitational fine structure constant" $\alpha\equiv G \mu M/\hbar c\sim 1$. If the black hole/cloud system is in a binary, tidal perturbations from the companion can produce resonant transitions between the energy levels of the cloud, depleting it by an amount that depends on the nature of the transition and on the parameters of the binary. Previous cloud depletion estimates considered binaries in circular orbit and made the approximation $\alpha\ll 1$. Here we use black hole perturbation theory to compute instability rates and decay widths for generic values of $\alpha$, and we show that this leads to much larger cloud depletion estimates when $\alpha \gtrsim 0.1$. We also study eccentric binary orbits. We show that in this case resonances can occur at all harmonics of the orbital frequency, significantly extending the range of frequencies where cloud depletion may be observable with gravitational wave interferometers.Comment: 12 pages, 6 figures. v2: references added, matches published versio

Simulation of a milk run material transportation system in the semiconductors industry

This paper deals with a project that consisted in the implementation of a Milk Run Lot Transportation System in Qimonda Porto Test Area, done by a multidisciplinary team formed by Qimonda Porto's workers, and the development of the corresponding simulation model. The first part of the study concerns an industrial engineering assessment of the test area, which identified sources of waste and improvement possibilities, and the implementation process of a Milk Run system in this area. Secondly, the results of the system implementation are discussed, and the construction of a simulation model in Arena® is presented. The purpose of the simulation exercise is to test different system configurations that may allow the improvement of the real-world system. Finally, some information about the simulation results and further steps to be taken regarding the improvement of the system is presented. The target of the project, framed in a Lean approach, was to reduce waste, namely transportation waste, thus optimizing the utilization of the test area human resources.info:eu-repo/semantics/publishedVersio

Saul Steinberg. Palabras sobre el pensamiento dibujado

[EN] Today seems like a good day to write, and show in this article, some of the research that has been done, over many years, on the drawings of Saul Steinberg, and which we would like to share with you our attempt to understand and naively master the thoughts of Saul Steinberg, without being able to do so (Figs. 1 and 2).Steinberg’s sharp eye will always infiltrate the lines and colours with which a cartoonist tries to capture life. Somehow, seduced by his images, we recognize ourselves on many occasions trying to emulate the subtle languages of Saul Steinberg.[ES] Hoy parece un buen día para escribir, y mostrar en este artículo, algo de lo investigado durante muchos años sobre los dibujos de Saul Steinberg, y que quisiéramos compartir con ustedes, en nuestro intento de comprender e ingenuamente dominar los pensamientos de Saul Steinberg, posiblemente sin poder conseguirlo (Figs. 1 y 2).La aguda mirada de Steinberg siempre se infiltrará entre las líneas y los colores con los que un dibujante intenta capturar la vida. De alguna manera, seducidos por sus imágenes, nos reconocemos en multitud de ocasiones intentando emular los sutiles lenguajes de Saul Steinberg.García Gil, L.; Raposo Grau, JF. (2021). Saul Steinberg. Words on the drawn thought. EGA Expresión Gráfica Arquitectónica. 26(42):204-221. https://doi.org/10.4995/ega.2021.15884OJS204221264