2,952 research outputs found
Detecting synchronization of self-sustained oscillators by external driving with varying frequency
We propose a method for detecting the presence of synchronization of
self-sustained oscillator by external driving with linearly varying frequency.
The method is based on a continuous wavelet transform of the signals of
self-sustained oscillator and external force and allows one to distinguish the
case of true synchronization from the case of spurious synchronization caused
by linear mixing of the signals. We apply the method to driven van der Pol
oscillator and to experimental data of human heart rate variability and
respiration.Comment: 9 pages, 7 figure
Coulomb drag between one-dimensional conductors
We have analyzed Coulomb drag between currents of interacting electrons in
two parallel one-dimensional conductors of finite length attached to
external reservoirs. For strong coupling, the relative fluctuations of electron
density in the conductors acquire energy gap . At energies larger than
, where
is the impurity scattering rate, and for , where is the
fluctuation velocity, the gap leads to an ``ideal'' drag with almost equal
currents in the conductors. At low energies the drag is suppressed by coherent
instanton tunneling, and the zero-temperature transconductance vanishes,
indicating the Fermi liquid behavior.Comment: 5 twocolumn pages in RevTex, added 1 eps-Figure and calculation of
trans-resistanc
The -closure of a solvable permutation group is solvable
Let be a positive integer and let be a finite set. The
-closure of is the largest permutation
group on having the same orbits as in its induced action on the
Cartesian product . The -closure and -closure of a solvable
permutation group need not be solvable. We prove that the -closure of a
solvable permutation group is always solvable for
PdO impact on the activity of hydrocarbon oxidation with oxide catalysts
The palladium component influence on the catalytic activity of a catalyst was investigated based on transition-metal oxides deposited on α-Al2O3 carrier in the process of hydrocarbon catalytic thermal destruction. It has been determined that the value of surface concentrations of PdO deposited on Co3O4 doesn’t effect on the achievable conversion degree when using the obtained catalytic converter. It is suggested that PdO facilitates the interfacial diffusion of atomic oxygen on the catalyst oxide component due to support it in an oxidized state. Adsorbed on palladium oxygen migrates on cobalt oxide in the composition of this catalyst. At the expense of this process oxygen passivation of Pd-Co3O4/γ-Al2O3 catalyst is overcome and its high reaction activity is ensured. Our research is evidence that Co3O4 performs the role of active centers on a corundum carrier in the reaction of catalytic thermal hydrocarbon oxidation. Additionally injected PdO into the catalyst composition promotes to the cobalt phase enrichment by oxygen
Critical wind speed at which trees break
International audienceData from storms suggest that the critical wind speed at which trees break is constant (≃42m/s), regardless of tree characteristics. We question the physical origin of this observation both experimentally and theoretically. By combining Hooke's law, Griffith's criterion, and tree allometry, we show that the critical wind speed indeed hardly depends on the height, diameter, and elastic properties of trees
Transport properties of single channel quantum wires with an impurity: Influence of finite length and temperature on average current and noise
The inhomogeneous Tomonaga Luttinger liquid model describing an interacting
quantum wire adiabatically coupled to non-interacting leads is analyzed in the
presence of a weak impurity within the wire. Due to strong electronic
correlations in the wire, the effects of impurity backscattering, finite bias,
finite temperature, and finite length lead to characteristic non-monotonic
parameter dependencies of the average current. We discuss oscillations of the
non-linear current voltage characteristics that arise due to reflections of
plasmon modes at the impurity and quasi Andreev reflections at the contacts,
and show how these oscillations are washed out by decoherence at finite
temperature. Furthermore, the finite frequency current noise is investigated in
detail. We find that the effective charge extracted in the shot noise regime in
the weak backscattering limit decisively depends on the noise frequency
relative to , where is the Fermi velocity, the
Tomonaga Luttinger interaction parameter, and the length of the wire. The
interplay of finite bias, finite temperature, and finite length yields rich
structure in the noise spectrum which crucially depends on the
electron-electron interaction. In particular, the excess noise, defined as the
change of the noise due to the applied voltage, can become negative and is
non-vanishing even for noise frequencies larger than the applied voltage, which
are signatures of correlation effects.Comment: 28 pages, 19 figures, published version with minor change
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