315 research outputs found
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" . 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 . Here we
use black hole perturbation theory to compute instability rates and decay
widths for generic values of , and we show that this leads to much
larger cloud depletion estimates when . 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
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