332 research outputs found
Three-dimensional localized coherent structures of surface turbulence. III Experiment and model validation
The paper continues a series of publications devoted to the 3D nonlinear
localized coherent structures on the surface of vertically falling liquid
films. The work is primarily focussed on experimental investigations. We study:
(i) instabilities and transitions leading to 3D coherent structures; (ii)
characteristics of these structures. Some nonstationary effects are also
studied numerically. Our experimental results, as well as the results of other
investigators, are in a good agreement with our theoretical and numerical
predictions.Comment: 42 pages, 15 figure
Strong interference effects in the resonant Auger decay of atoms induced by intense X-Ray fields
The theory of resonant Auger decay of atoms in a high intensity coherent
X-ray pulse is presented. The theory includes the coupling between the ground
state and the resonance due to an intense X-ray pulse, taking into account the
decay of the resonance and the direct photoionization of the ground state, both
populating the final ionic states coherently. The theory also considers the
impact of the direct photoionization of the resonance state itself which
typically populates highly-excited ionic states. The combined action of the
resonant decay and of the direct ionization of the ground state in the field
induces a non-hermitian time-dependent coupling between the ground and the
'dressed' resonance stats. The impact of these competing processes on the total
electron yield and on the 2s2p3p P spectator and
2s2p S participator Auger decay spectra of the Ne 1s3p
resonance is investigated. The role of the direct photoionization of the ground
state and of the resonance increases dramatically with the field intensity.
This results in strong interference effects with distinct patterns in the
electron spectra, different for the participator and spectator final states.Comment: 31 pages, 6 figure
Linear and Nonlinear Evolution and Diffusion Layer Selection in Electrokinetic Instability
In the present work fournontrivial stages of electrokinetic instability are
identified by direct numerical simulation (DNS) of the full
Nernst-Planck-Poisson-Stokes (NPPS) system: i) The stage of the influence of
the initial conditions (milliseconds); ii) 1D self-similar evolution
(milliseconds-seconds); iii) The primary instability of the self-similar
solution (seconds); iv) The nonlinear stage with secondary instabilities. The
self-similar character of evolution at intermediately large times is confirmed.
Rubinstein and Zaltzman instability and noise-driven nonlinear evolution to
over-limiting regimes in ion-exchange membranes are numerically simulated and
compared with theoretical and experimental predictions. The primary instability
which happens during this stage is found to arrest self-similar growth of the
diffusion layer and specifies its characteristic length as was first
experimentally predicted by Yossifon and Chang (PRL 101, 254501 (2008)). A
novel principle for the characteristic wave number selection from the
broadbanded initial noise is established.Comment: 13 pages, 8 figure
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