39,476 research outputs found
Geometrical resonance in spatiotemporal systems
We generalize the concept of geometrical resonance to perturbed sine-Gordon,
Nonlinear Schrödinger and Complex Ginzburg-Landau equations. Using this
theory we can control different dynamical patterns. For instance, we can
stabilize breathers and oscillatory patterns of large amplitudes successfully
avoiding chaos. On the other hand, this method can be used to suppress
spatiotemporal chaos and turbulence in systems where these phenomena are
already present. This method can be generalized to even more general
spatiotemporal systems.Comment: 2 .epl files. Accepted for publication in Europhysics Letter
Interplay of Coulomb and electron-phonon interactions in graphene
We consider mutual effect of the electron-phonon and strong Coulomb
interactions on each other by summing up leading logarithmic corrections via
the renormalization group approach. We find that the Coulomb interaction
enhances electron coupling to the intervalley A1 optical phonons, but not to
the intravalley E2 phonons
Lubrication of DLC Coatings with Two Tris(pentafluoroethyl)trifluorophosphate Anion-Based Ionic Liquids
The lubrication of a Cr-DLC coating with ethyl-dimethyl-2-methoxyethylammonium tris(pentafluoroethyl)trifluoropho-sphate [(NEMM)MOE][FAP] and 1-butyl-1-methylpyrro-lidinium tris(pentafluoroethyl)trifluorophosphate [BMP] [FAP] ionic liquids (ILs) as 1 wt% additives to a polyalphaolefin (PAO 6) was studied. Zinc dialkyldithiophosphate (ZDDP) was also used as reference in order to evaluate the effectiveness of the ILs. Reciprocating ball-on-plate tribological tests at loads of 20 and 40 N were performed. The results showed that both ILs exhibited a friction reduction, especially at the lowest load tested. Antiwear properties were also improved; the PAO 6 + 1% [BMP][FAP] mixture was slightly better, close to the values for PAO 6 + 1% ZDDP. Scanning electron microscopy (SEM) images and X-ray photoelectron spectroscopy (XPS) analysis indicated that the additive–surface interaction was responsible for the tribological improvement
From circular paths to elliptic orbits: A geometric approach to Kepler's motion
The hodograph, i.e. the path traced by a body in velocity space, was
introduced by Hamilton in 1846 as an alternative for studying certain dynamical
problems. The hodograph of the Kepler problem was then investigated and shown
to be a circle, it was next used to investigate some other properties of the
motion. We here propose a new method for tracing the hodograph and the
corresponding configuration space orbit in Kepler's problem starting from the
initial conditions given and trying to use no more than the methods of
synthetic geometry in a sort of Newtonian approach. All of our geometric
constructions require straight edge and compass only.Comment: 9 pages, 4 figure
Electron Confinement Induced by Diluted Hydrogen-like Ad-atoms in Graphene Ribbons
We report the electronic properties of two-dimensional systems made of
graphene nanoribbons which are patterned with ad-atoms in two separated
regions. Due to the extra electronic confinement induced by the presence of the
impurities, we find resonant levels, quasi-bound and impurity-induced localized
states, which determine the transport properties of the system. Regardless of
the ad-atom distribution in the system, we apply band-folding procedures to
simple models and predict the energies and the spatial distribution of those
impurity-induced states. We take into account two different scenarios: gapped
graphene and the presence of randomly distributed ad-atoms in a low dilution
regime. In both cases the defect-induced resonances are still detected. Our
findings would encourage experimentalist to synthesize these systems and
characterize their quasi-localized states employing, for instance, scanning
tunneling spectroscopy (STS). Additionally, the resonant transport features
could be used in electronic applications and molecular sensor devices.Comment: 12 pages, 11 figures, submitted (minor changes
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