1,546 research outputs found
Existence and Vanishing of the Breathing Mode in Strongly Correlated Finite Systems
One of the fundamental eigenmodes of finite interacting systems is the mode
of {\em uniform radial expansion and contraction} -- the ``breathing'' mode
(BM). Here we show in a general way that this mode exists only under special
conditions: i) for harmonically trapped systems with interaction potentials of
the form or , or ii) for
some systems with special symmetry such as single shell systems forming
platonic bodies. Deviations from the BM are demonstrated for two examples:
clusters interacting with a Lennard-Jones potential and parabolically trapped
systems with Yukawa repulsion. We also show that vanishing of the BM leads to
the occurence of multiple monopole oscillations which is of importance for
experiments
Ground state of a confined Yukawa plasma
The ground state of an externally confined one-component Yukawa plasma is
derived analytically. In particular, the radial density profile is computed.
The results agree very well with computer simulations on three-dimensional
spherical Coulomb crystals. We conclude in presenting an exact equation for the
density distribution for a confinement potential of arbitrary geometry.Comment: 5 pages, 4 figure
Self-Diffusion in 2D Dusty Plasma Liquids: Numerical Simulation Results
We perform Brownian dynamics simulations for studying the self-diffusion in
two-dimensional (2D) dusty plasma liquids, in terms of both mean-square
displacement and velocity autocorrelation function (VAF). Super-diffusion of
charged dust particles has been observed to be most significant at infinitely
small damping rate for intermediate coupling strength, where the
long-time asymptotic behavior of VAF is found to be the product of and
. The former represents the prediction of early theories in
2D simple liquids and the latter the VAF of a free Brownian particle. This
leads to a smooth transition from super-diffusion to normal diffusion, and then
to sub-diffusion with an increase of the damping rate. These results well
explain the seemingly contradictory scattered in recent classical molecular
dynamics simulations and experiments of dusty plasmas.Comment: 10 pages 5 figures, accepted by PR
Lifetime Extension, Repowering or Decommissioning? Decision Support for Operators of Ageing Wind Turbines
In Germany, more than one third of the installed wind energy capacity will leave the feed-in tariff funding between 2021 and 2025. Operators of affected turbines are therefore increasingly concerned with the design of profitable end-of-funding strategies. This requires feasibility analyses of both lifetime extension and repowering options and entails the subsequent challenge to determine the optimal lifetime extension and corresponding repowering timing. To support operators and other stakeholders dealing with wind turbines' end-of-life issues, this study presents a geographic information system that permits evaluating optimal end-of-funding strategies at different spatial scales reaching down to detailed analyses on individual turbine level. The decision support system processes topographic, wind, turbine, and finance data in an integrated system of resource simulations, spatial planning analyses and economic viability assessments. Case-study results show that a uniform end-of-funding strategy cannot be applied to all ageing turbines. Conducted sensitivity analyses rather indicate that the best strategy highly depends on various turbine-specific aspects, especially the location, type and maintenance costs as well as exogenous factors, including the developments of electricity spot market prices and tendered feed-in premiums. In light of latest trends regarding the exogenous factors, lifetime extension and repowering potentials increase. However, the results also indicate that dismantling, disposal and recycling of numerous ageing turbines will become a major challenge for the wind energy sector in the next decade. © 2019 Published under licence by IOP Publishing Ltd
Wave spectra of 2D dusty plasma solids and liquids
Brownian dynamics simulations were carried out to study wave spectra of
two-dimensional dusty plasma liquids and solids for a wide range of
wavelengths. The existence of a longitudinal dust thermal mode was confirmed in
simulations, and a cutoff wavenumber in the transverse mode was measured.
Dispersion relations, resulting from simulations, were compared with those from
analytical theories, such as the random-phase approximation (RPA),
quasi-localized charged approximation (QLCA), and harmonic approximation (HA).
An overall good agreement between the QLCA and simulations was found for wide
ranges of states and wavelengths after taking into account the direct thermal
effect in the QLCA, while for the RPA and HA good agreement with simulations
were found in the high and low temperature limits, respectively.Comment: 26 pages, 9 figure
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