6,916 research outputs found
Time-delayed feedback control of coherence resonance near subcritical Hopf bifurcation: theory versus experiment
Using the model of a generalized Van der Pol oscillator in the regime of
subcritical Hopf bifurcation we investigate the influence of time delay on
noise-induced oscillations. It is shown that for appropriate choices of time
delay either suppression or enhancement of coherence resonance can de achieved.
Analytical calculations are combined with numerical simulations and experiments
on an electronic circuit
A DC Programming Approach for Solving Multicast Network Design Problems via the Nesterov Smoothing Technique
This paper continues our effort initiated in [9] to study Multicast
Communication Networks, modeled as bilevel hierarchical clustering problems, by
using mathematical optimization techniques. Given a finite number of nodes, we
consider two different models of multicast networks by identifying a certain
number of nodes as cluster centers, and at the same time, locating a particular
node that serves as a total center so as to minimize the total transportation
cost through the network. The fact that the cluster centers and the total
center have to be among the given nodes makes this problem a discrete
optimization problem. Our approach is to reformulate the discrete problem as a
continuous one and to apply Nesterov smoothing approximation technique on the
Minkowski gauges that are used as distance measures. This approach enables us
to propose two implementable DCA-based algorithms for solving the problems.
Numerical results and practical applications are provided to illustrate our
approach
Search for solar axions produced by Compton process and bremsstrahlung using the resonant absorption and axioelectric effect
The search for resonant absorption of Compton and bremsstrahlung solar axions
by Tm nuclei have been performed. Such an absorption should lead to the
excitation of low-lying nuclear energy level: Tm Tm Tm (8.41 keV). Additionally the
axio-electric effect in silicon atoms is sought. The axions are detected using
a Si(Li) detectors placed in a low-background setup. As a result, a new model
independent restrictions on the axion-electron and the axion-nucleon coupling:
and the axion-electron
coupling constant: has been obtained. The
limits leads to the bounds 7.9 eV and 1.3 keV for the
mass of the axion in the DFSZ and KSVZ models, respectively ( C.L.).Comment: 6 pages, 3 figures, contributed to the 9th Patras Workshop on Axions,
WIMPs and WISPs, Mainz, June 24-28, 201
Transverse modulational instability of partially incoherent soliton stripes
Based on the Wigner distribution approach, an analysis of the effect of
partial incoherence on the transverse instability of soliton structures in
nonlinear Kerr media is presented. It is explicitly shown, that for a
Lorentzian incoherence spectrum the partial incoherence gives rise to a damping
which counteracts, and tends to suppress, the transverse instability growth.
However, the general picture is more complicated and it is shown that the
effect of the partial incoherence depends crucially on the form of the
incoherence spectrum. In fact, for spectra with finite rms-width, the partial
incoherence may even increase both the growth rate and the range of unstable,
transverse wave numbers.Comment: 5 pages, submitted to Phys. Rev.
Mixed Quantum/Classical Approach for Description of Molecular Collisions in Astrophysical Environments
An efficient and accurate mixed quantum/classical theory approach for computational treatment of inelastic scattering is extended to describe collision of an atom with a general asymmetric-top rotor polyatomic molecule. Quantum mechanics, employed to describe transitions between the internal states of the molecule, and classical mechanics, employed for description of scattering of the atom, are used in a self-consistent manner. Such calculations for rotational excitation of HCOOCH3 in collisions with He produce accurate results at scattering energies above 15 cm–1, although resonances near threshold, below 5 cm–1, cannot be reproduced. Importantly, the method remains computationally affordable at high scattering energies (here up to 1000 cm–1), which enables calculations for larger molecules and at higher collision energies than was possible previously with the standard full-quantum approach. Theoretical prediction of inelastic cross sections for a number of complex organic molecules observed in space becomes feasible using this new computational tool
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