64 research outputs found
Resonant translational, breathing and twisting modes of pinned transverse magnetic domain walls
We study translational, breathing and twisting resonant modes of transverse
magnetic domain walls pinned at notches in ferromagnetic nanostrips. We
demonstrate that a mode's sensitivity to notches depends strongly on the
characteristics of that particular resonance. For example, the frequencies of
modes involving lateral motion of the wall are the ones which are most
sensitive to changes in the notch intrusion depth (especially at the narrower,
more strongly confined end of the domain wall). In contrast, the breathing
mode, whose dynamics are concentrated away from the notches is relatively
insensitive to changes in the notches' sizes. We also demonstrate a sharp drop
in the translational mode's frequency towards zero when approaching depinning
which is found, using a harmonic oscillator model, to be consistent with a
reduction in the local slope of the notch-induced confining potential at its
edge.Comment: 11 pages, 10 figures, additional data and analysi
Frequency-based nanoparticle sensing over large field ranges using the ferromagnetic resonances of a magnetic nanodisc
Using finite element micromagnetic simulations, we study how resonant
magnetisation dynamics in thin magnetic discs with perpendicular anisotropy are
influenced by magnetostatic coupling to a magnetic nanoparticle. We identify
resonant modes within the disc using direct magnetic eigenmode calculations and
study how their frequencies and profiles are changed by the nanoparticle's
stray magnetic field. We demonstrate that particles can generate shifts in the
resonant frequency of the disc's fundamental mode which exceed resonance
linewidths in recently studied spin torque oscillator devices. Importantly, it
is shown that the simulated shifts can be maintained over large field ranges
(here up to 1T). This is because the resonant dynamics (the basis of
nanoparticle detection here) respond directly to the nanoparticle stray field,
i.e. detection does not rely on nanoparticle-induced changes to the magnetic
ground state of the disk. A consequence of this is that in the case of small
disc-particle separations, sensitivities to the particle are highly mode- and
particle-position-dependent, with frequency shifts being maximised when the
intense stray field localised directly beneath the particle can act on a large
proportion of the disc's spins that are undergoing high amplitude precession.Comment: 9 pages, 9 figures. Updated version from 31.7.2016 includes minor
changes in introduction and sections III.C and III.D (additional information
linking the results to real-world bio-sensing devices
Social Media and Collective Intelligence: Ongoing and Future Research Streams
The tremendous growth in the use of Social Media has led to radical paradigm shifts in the ways we communicate, collaborate, consume, and create information. Our focus in this special issue is on the reciprocal interplay of Social Media and Collective Intelligence. We therefore discuss constituting attributes of Social Media and Collective Intelligence, and we structure the rapidly growing body of literature including adjacent research streams such as Social Network Analysis, Web Science, and Computational Social Science. We conclude by making propositions for future research where in particular the disciplines of artificial intelligence, computer science, and information systems can substantially contribute to the interdisciplinary academic discourse
A Visualization System for Correctness Proofs of Graph Algorithms
In this paper we describe a system for visualizing correctness proofs of graph algorithms. The system has been demonstrated for a greedy algorithm. Prim\u27s algorithm for finding a minimum spanning tree of an undirected, weighted graph. We believe that our system is particularly appropriate for greedy algorithms, though much of what we discuss can guide visualization of proofs in other contexts. While an example is not a proof, our system provides concrete examples to illustrate the operation of the algorithm. These examples can be referred to by the user interactively and alternatively with the visualization of the proof where the general case is portrayed abstractly
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