8,216 research outputs found
Novel Radiation-induced Magnetoresistance Oscillations in a Nondegenerate 2DES on Liquid Helium
We report the observation of novel magnetoresistance oscillations induced by
the resonant inter-subband absorption in nondegenerate 2D electrons bound to
the surface of liquid helium. The oscillations are periodic in 1/B and
originate from the scattering-mediated transitions of the excited electrons
into the Landau states of the first subband. The structure of the oscillations
is affected by the collision broadening of the Landau levels and by
many-electron effects.Comment: 4 figure
Collisional energy transfer in two-component plasmas
The friction in plasmas consisting of two species with different temperatures
is discussed together with the consequent energy transfer. It is shown that the
friction between the two species has no effect on the ion acoustic mode in a
quasi-neutral plasma. Using the Poisson equation instead of the
quasi-neutrality reveals the possibility for an instability driven by the
collisional energy transfer. However, the different starting temperatures of
the two species imply an evolving equilibrium. It is shown that the relaxation
time of the equilibrium electron-ion plasma is, in fact, always shorter than
the growth rate time, and the instability can thus never effectively take
place. The results obtained here should contribute to the definite
clarification of some contradictory results obtained in the past
EEG Signal Processing and Classification for the Novel Tactile-Force Brain-Computer Interface Paradigm
The presented study explores the extent to which tactile-force stimulus
delivered to a hand holding a joystick can serve as a platform for a brain
computer interface (BCI). The four pressure directions are used to evoke
tactile brain potential responses, thus defining a tactile-force brain computer
interface (tfBCI). We present brain signal processing and classification
procedures leading to successful interfacing results. Experimental results with
seven subjects performing online BCI experiments provide a validation of the
hand location tfBCI paradigm, while the feasibility of the concept is
illuminated through remarkable information-transfer rates.Comment: 6 pages (in conference proceedings original version); 6 figures,
submitted to The 9th International Conference on Signal Image Technology &
Internet Based Systems, December 2-5, 2013, Kyoto, Japan; to be available at
IEEE Xplore; IEEE Copyright 201
Dynamics of the vortex-particle complexes bound to the free surface of superfluid helium
We present an experimental and theoretical study of the 2D dynamics of
electrically charged nanoparticles trapped under a free surface of superfluid
helium in a static vertical electric field. We focus on the dynamics of
particles driven by the interaction with quantized vortices terminating at the
free surface. We identify two types of particle trajectories and the associated
vortex structures: vertical linear vortices pinned at the bottom of the
container and half-ring vortices travelling along the free surface of the
liquid
Dynamics of fine particles due to quantized vortices on the surface of superfluid He
Peculiar dynamics of a free surface of the superfluid 4He has been observed
experimentally with a newly established technique utilizing a number of
electrically charged fine metal particles trapped electrically at the surface
by Moroshkin et al. They have reported that some portion of the particles
exhibit some irregular motions and suggested the existence of quantized
vortices interacting with the metal particles. We have conducted calculations
with the vortex filament model, which turns out to support the idea of the
vortex-particle interactions. The observed anomalous metal particle motions are
roughly categorized into two types; (1) circular motions with specific
frequencies, and (2) quasi-linear oscillations. The former ones seem to be
explained once we consider a vertical vortex filament whose edges are
terminated at the bottom and at a particle trapped at the surface. Although it
is not yet clear whether all the anomalous motions are due to the quantum
vortices, the vortices seem to play important roles for the motions.Comment: 7 pages, 10 figure
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