261,742 research outputs found
Searching for Effects of Spatial Noncommutativity via Chern-Simons' Processes
The possibility of testing spatial noncommutativity in the case of both
position-position and momentum-momentum noncommuting via a Chern-Simons'
process is explored. A Chern-Simons process can be realized by an interaction
of a charged particle in special crossed electric and magnetic fields, in which
the Chern-Simons term leads to non-trivial dynamics in the limit of vanishing
kinetic energy. Spatial noncommutativity leads to the spectrum of the orbital
angular momentum possessing fractional values. Furthermore, in both limits of
vanishing kinetic energy and subsequent vanishing magnetic field, the
Chern-Simons term leads to this system having non-trivial dynamics again, and
the dominant value of the lowest orbital angular momentum being ,
which is a clear signal of spatial noncommutativity. An experimental
verification of this prediction by a Stern-Gerlach-type experiment is
suggested.Comment: 18 page
Morphological characterization of shocked porous material
Morphological measures are introduced to probe the complex procedure of shock
wave reaction on porous material. They characterize the geometry and topology
of the pixelized map of a state variable like the temperature. Relevance of
them to thermodynamical properties of material is revealed and various
experimental conditions are simulated. Numerical results indicate that, the
shock wave reaction results in a complicated sequence of compressions and
rarefactions in porous material. The increasing rate of the total fractional
white area roughly gives the velocity of a compressive-wave-series.
When a velocity is mentioned, the corresponding threshold contour-level of
the state variable, like the temperature, should also be stated. When the
threshold contour-level increases, becomes smaller. The area increases
parabolically with time during the initial period. The curve goes
back to be linear in the following three cases: (i) when the porosity
approaches 1, (ii) when the initial shock becomes stronger, (iii) when the
contour-level approaches the minimum value of the state variable. The area with
high-temperature may continue to increase even after the early
compressive-waves have arrived at the downstream free surface and some
rarefactive-waves have come back into the target body. In the case of energetic
material ... (see the full text)Comment: 3 figures in JPG forma
Local density of states of a d-wave superconductor with inhomogeneous antiferromagnetic correlations
The tunneling spectrum of an inhomogeneously doped extended Hubbard model is
calculated at the mean field level. Self-consistent solutions admit both
superconducting and antiferromagnetic order, which coexist inhomogeneously
because of spatial randomness in the doping. The calculations find that, as a
function of doping, there is a continuous cross over from a disordered ``pinned
smectic'' state to a relatively homogeneous d-wave state with pockets of
antiferromagnetic order. The density of states has a robust d-wave gap, and
increasing antiferromagnetic correlations lead to a suppression of the
coherence peaks. The spectra of isolated nanoscale antiferromagnetic domains
are studied in detail, and are found to be very different from those of
macroscopic antiferromagnets. Although no single set of model parameters
reproduces all details of the experimental spectrum in BSCCO, many features,
notably the collapse of the coherence peaks and the occurence of a low-energy
shoulder in the local spectrum, occur naturally in these calculations.Comment: 9 pages, 5 figure
Macroscopic tunneling of a membrane in an optomechanical double-well potential
The macroscopic tunneling of an optomechanical membrane is considered. A
cavity mode which couples quadratically to the membranes position can create
highly tunable adiabatic double-well potentials, which together with the high
Q-factors of such membranes render the observation of macroscopic tunneling
possible. A suitable, pulsed measurement scheme using a linearly coupled mode
of the cavity for the verification of the effect is studied.Comment: 5 pages, 5 figure
Novel method for refinement of retained austenite in micro/nano-structured bainitic steels
A comparative study was conducted to assess the effects of two different heat treatments on the amount and morphology of the retained austenite in a micro/nano-structured bainitic steel. The heat treatments used in this work were two-stage bainitic transformation and bainitic-partitioning transformation. Both methods resulted in the generation of a multi-phase microstructure containing nanoscale bainitic ferrite, and/or fresh martensitic phases and much finer retained austenite. Both heat treatments were verified to be effective in refining the retained austenite in micro/nano-structured bainite and increasing the hardness. However, the bainitic transformation followed by partitioning cycle was proved to be a more viable approach than the two-stage bainitic transformation due to much shorter processing time, i.e. ∼2 h compared to ∼4 day, respectively
Hardcore bosons on the dual of the bowtie lattice
We study the zero temperature phase diagram of hardcore bosons on the dual of
the bowtie lattice. Two types of striped diagonal long-range order (striped
order I and striped order II) are discussed. A state with type-II striped order
and superfluidity is found, even without nearest-neighbor repulsion. The
emergence of such a state is due to the inhomogeneity and the anisotropy of the
lattice structure. However, neither the translational symmetry nor the symmetry
between sublattices of the original lattice is broken. In this paper, we
restrict a 'solid state' of lattice bosons as a diagonal long-range ordered
state breaking either the translational symmetry of the original lattice or the
symmetry of different sublattices. We thus name such a phase a striped
superfluid phase (SSF). In the presence of a nearest-neighbor repulsion, we
find two striped charge density wave phases(SCDW I and II) with boson density
(with striped order I) and (with striped order II)
respectively, when the hopping amplitude is small compared with the repulsion.
The SCDW I state is a solid, in which the translational symmetry of the
original lattice is broken. We observe a rather special first-order phase
transition showing an interesting multi-loop hysteresis phenomenon between the
two SCDW phases when the hopping term is small enough. This can be accounted
for by the special degeneracy of the ground states near the classical limit.
The SSF re-appears outside the two SCDW phases. The transition between the SCDW
I and SSF phases is first order, while the transition between SCDW II and SSF
phases is continuous. We find that the superfluid stiffness is anisotropic in
the SSF states with and without repulsion. In the SSF with repulsion, the
superfluid stiffness is subject to different types of anisotropy in the region
near half filling and above 2/3-filling.Comment: 10 figure
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Automatic affective dimension recognition from naturalistic facial expressions based on wavelet filtering and PLS regression
Automatic affective dimension recognition from facial expression continuously in naturalistic contexts is a very challenging research topic but very important in human-computer interaction. In this paper, an automatic recognition system was proposed to predict the affective dimensions such as Arousal, Valence and Dominance continuously in naturalistic facial expression videos. Firstly, visual and vocal features are extracted from image frames and audio segments in facial expression videos. Secondly, a wavelet transform based digital filtering method is applied to remove the irrelevant noise information in the feature space. Thirdly, Partial Least Squares regression is used to predict the affective dimensions from both video and audio modalities. Finally, two modalities are combined to boost overall performance in the decision fusion process. The proposed method is tested in the fourth international Audio/Visual Emotion Recognition Challenge (AVEC2014) dataset and compared to other state-of-the-art methods in the affect recognition sub-challenge with a good performance
Exciton states in cylindrical nanowires
The exciton ground state and excited state energies are calculated for a
model system of an infinitely long cylindrical wire. The effective Coulomb
potential between the electron and the hole is studied as function of the wire
radius. Within the adiabatic approximation, we obtain `exact' numerical results
for the effective exciton potential and the lowest exciton energy levels which
are fitted to simple analytical expressions. Furthermore, we investigated the
influence of a magnetic field parallel to the nanowire on the effective
potential and the exciton energy.Comment: 9 pages, 9 figures. Submitted for publication to PRB. Figures must be
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