1,810 research outputs found
Site-selective particle deposition in periodically driven quantum lattices
We demonstrate that a site-dependent driving of a periodic potential allows
for the controlled manipulation of a quantum particle on length scales of the
lattice spacing. Specifically we observe for distinct driving frequencies a
near depletion of certain sites which is explained by a resonant mixing of the
involved Floquet-Bloch modes occurring at these frequencies. Our results could
be exploited as a scheme for a site-selective loading of e.g. ultracold atoms
into an optical lattices
Disorder-induced regular dynamics in oscillating lattices
We explore the impact of weak disorder on the dynamics of classical particles
in a periodically oscillating lattice. It is demonstrated that the disorder
induces a hopping process from diffusive to regular motion i.e. we observe the
counterintuitive phenomenon that disorder leads to regular behaviour. If the
disorder is localized in a finite-sized part of the lattice, the described
hopping causes initially diffusive particles to even accumulate in regular
structures of the corresponding phase space. A hallmark of this accumulation is
the emergence of pronounced peaks in the velocity distribution of particles
which should be detectable in state of the art experiments e.g. with cold atoms
in optical lattices
Symmetries and transport in site-dependently driven quantum lattices
We explore the quantum dynamics of particles in a spatiotemporally driven
lattice. A powerful numerical scheme is developed, which provides us with the
Floquet modes and thus enables a stroboscopic propagation of arbitrary initial
states. A detailed symmetry analysis represents the cornerstone for an
intricate manipulation of the Floquet spectrum. Specifically, we show how exact
crossings can be converted into avoided ones, while the width of these
resulting avoided crossings can be engineered by adjusting parameters of the
local driving. Asymptotic currents are shown to be controllable over a certain
parameter range
Identification of a competing risks model with unknown transformations of latent failure times
This paper is concerned with identification of a competing risks model with unknown
transformations of latent failure times. The model in this paper includes, as special
cases, competing risks versions of proportional hazards, mixed proportional hazards,
and accelerated failure time models. It is shown that covariate effects on latent failure
times, cause-specific link functions, and the joint survivor function of the disturbance
terms can be identified without relying on modelling the dependence between latent
failure times parametrically nor using an exclusion restriction among covariates. As a
result, the paper provides an identification result on the joint survivor function of the
latent failure times conditional on covariates
Analysis of interface conversion processes of ballistic and diffusive motion in driven superlattices
We explore the non-equilibrium dynamics of non-interacting classical
particles in a one-dimensional driven superlattice which is composed of domains
exposed to different time-dependent forces. It is shown how the combination of
directed transport and conversion processes from diffusive to ballistic motion
causes strong correlations between velocity and phase for particles passing
through a superlattice. A detailed understanding of the underlying mechanism
allows us to tune the resulting velocity distributions at distinguished points
in the superlattice by means of local variations of the applied driving force.
As an intriguing application we present a scheme how initially diffusive
particles can be transformed into a monoenergetic pulsed particle beam whose
parameters such as its energy can be varied
Adolescents' postural control learning according to the frequency of knowledge of process
Feedback is one of the most influential factors for motor skills learning. Physical Education teachers commonly use verbal cues to provide knowledge of process (KP) when teaching motor skills, but the ideal presentation frequency for KP in adolescents is unclear. The aim of this study was to compare the effectiveness of the frequency of KP (i.e., 100%, 67%, 0%) on dynamic balance. Thirty adolescents, age 14-15 years, participated in the study. Performance on a stabilometer platform was used to assess dynamic balance. Participants received feedback after each trial (100%), in two out of three trials (67%), or no feedback during 12 30-s trials of practice. Adolescents who received feedback (67% or 100%) required lower mean velocity to maintain similar dynamic balance performance (i.e., root mean square). Moreover, adolescents receiving 100% feedback had a higher α-scaling than those who did not received it. During the post-test and the retention, both 67% and 100% KP frequencies were effective at improving postural control, compared to the no feedback control
Dynamics of a thin liquid film with surface rigidity and spontaneous curvature
The effect of rigid surfaces on the dynamics of thin liquid films which are
amenable to the lubrication approximation is considered. It is shown that the
Helfrich energy of the layer gives rise to additional terms in the
time-evolution equations of the liquid film. The dynamics is found to depend on
the absolute value of the spontaneous curvature, irrespective of its sign. Due
to the additional terms, a novel finite wavelength instability of flat rigid
interfaces can be observed. Furthermore, the dependence of the shape of a
droplet on the bending rigidity as well as on the spontaneous curvature is
discussed.Comment: 4 pages, 5 figure
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