9,685 research outputs found
Anisotropic transport in quantum wires embedded in (110) plane
We investigate theoretically the effects of the Coulomb interaction and
spin-orbit interactions (SOIs) on the anisotropic transport property of
semiconductor quantum wires embedded in (110) plane. The anisotropy of the dc
conductivity can be enhanced significantly by the Coulomb interaction for
infinite-long quantum wires. But it is smeared out in quantum wires with finite
length, while the ac conductivity still shows anisotropic behavior, from which
one can detect and distinguish the strengths of the Rashba SOI and Dresselhaus
SOI.Comment: 3 pages,3 figure
Simultaneous Amplitude and Phase Measurement for Periodic Optical Signals Using Time-Resolved Optical Filtering
Time-resolved optical filtering (TROF) measures the spectrogram or sonogram
by a fast photodiode followed a tunable narrowband optical filter. For periodic
signal and to match the sonogram, numerical TROF algorithm is used to find the
original complex electric field or equivalently both the amplitude and phase.
For phase-modulated optical signals, the TROF algorithm is initiated using the
craters and ridges of the sonogram.Comment: 10 pages, 5 figure
Scars in Dirac fermion systems: the influence of an Aharonov--Bohm flux
Time-reversal (-) symmetry is fundamental to many physical
processes. Typically, -breaking for microscopic processes requires
the presence of magnetic field. However, for 2D massless Dirac billiards,
-symmetry is broken automatically by the mass confinement, leading
to chiral quantum scars. In this paper, we investigate the mechanism of
-breaking by analyzing the local current of the scarring
eigenstates and their magnetic response to an Aharonov--Bohm flux. Our results
unveil the complete understanding of the subtle -breaking
phenomena from both the semiclassical formula of chiral scars and the
microscopic current and spin reflection at the boundaries, leading to a
controlling scheme to change the chirality of the relativistic quantum scars.
Our findings not only have significant implications on the transport behavior
and spin textures of the relativistic pseudoparticles, but also add basic
knowledge to relativistic quantum chaos.Comment: 37 pages, 11 figure
First-principles study the electronic and structural properties of chromium arsenide
We systematically study chromium arsenide in various crystal structures in
order to investigate the structural, magnetic and electronic properties for
real applications. The calculations are performed within the density functional
framework using the projected augmented plane wave method as employed in VASP
code. Using the generalized gradient approximation (GGA) for exchange
correlation energy functional, we have calculated the lattice parameters, bulk
modulus and cohesive energy. Here we show the structural parameters and
magnetic properties of CrAs in six different structures. The density of states
are calculated and differences are compared. Our results for structural and
electronic properties are compared with the experimental and other theoretical
results wherever these are availableComment: 14, 6 figure
Gaussian Filter in CRF Based Semantic Segmentation
Artificial intelligence is making great changes in academy and industry with
the fast development of deep learning, which is a branch of machine learning
and statistical learning. Fully convolutional network [1] is the standard model
for semantic segmentation. Conditional random fields coded as CNN [2] or RNN
[3] and connected with FCN has been successfully applied in object detection
[4]. In this paper, we introduce a multi-resolution neural network for FCN and
apply Gaussian filter to the extended CRF kernel neighborhood and the label
image to reduce the oscillating effect of CRF neural network segmentation, thus
achieve higher precision and faster training speed.Comment: 11 pages, 9 figures, 2 table
A note on self-improving sorting with hidden partitions
We study self-improving sorting with hidden partitions. Our result is an
optimal algorithm which runs in expected time O(H(\pi(I)) + n), where I is the
given input which contains n elements to be sorted, \pi(I) is the output which
are the ranks of all element in I, and H(\pi(I)) denotes the entropy of the
output.Comment: 4page
Asymptotic Analysis for Low-Resolution Massive MIMO Systems with MMSE Receiver
The uplink achievable rate of massive multiple- input-multiple-output (MIMO)
systems, where the low-resolution analog-to-digital converters (ADCs) are
assumed to equip at the base station (BS), is investigated in this paper. We
assume that only imperfect channel station information is known at the BS. Then
a new MMSE receiver is designed by taking not only the Gaussian noise, but also
the channel estimation error and quantizer noise into account. By using the
Stieltjes transform of random matrix, we further derive a tight asymptotic
equivalent for the uplink achievable rate with proposed MMSE receiver. We
present a detailed analysis for the number of BS antennas through the
expression of the achievable rates and validate the results using numerical
simulations. It is also shown that we can compensate the performance loss due
to the low-resolution quantization by increasing the number of antennas at the
BS.Comment: 7 pages, 3 figure
Vanishing contact structure problem and convergence of the viscosity solutions
This paper is devoted to study the vanishing contact structure problem which
is a generalization of the vanishing discount problem. Let
be a family of Hamiltonians of contact type with parameter and
converges to . For the contact type Hamilton-Jacobi equation with
respect to , we prove that, under mild assumptions, the associated
viscosity solution converges to a specific viscosity solution
of the vanished contact equation. As applications, we give some
convergence results for the nonlinear vanishing discount problem
On the origin of the Extreme-Ultraviolet late phase of solar flares
Solar flares typically have an impulsive phase that followed by a gradual
phase as best seen in soft X-ray emissions. A recent discovery based on the EUV
Variability Experiment (EVE) observations onboard the Solar Dynamics
Observatory (SDO) reveals that some flares exhibit a second large peak
separated from the first main phase peak by tens of minutes to hours, which is
coined as the flare's EUV late phase. In this paper, we address the origin of
the EUV late phase by analyzing in detail two late phase flares, an M2.9 flare
on 2010 October 16 and an M1.4 flare on 2011 February 18, using multi-passband
imaging observations from the Atmospheric Imaing Assembly (AIA) onboard SDO. We
find that: (1) the late phase emission originates from a different magnetic
loop system, which is much larger and higher than the main phase loop system.
(2) The two loop systems have different thermal evolution. While the late phase
loop arcade reaches its peak brightness progressively at a later time spanning
for more than one hour from high to low temperatures, the main phase loop
arcade reaches its peak brightness at almost the same time (within several
minutes) in all temperatures. (3) Nevertheless, the two loop systems seem to be
connected magnetically, forming an asymmetric magnetic quadruple configuration.
(4) Further, the footpoint brightenings in UV wavelengths show a systematic
delay of about one minute from the main flare region to the remote footpoint of
the late phase arcade system. We argue that the EUV late phase is the result of
a long-lasting cooling process in the larger magnetic arcade system.Comment: 12 figure
Detect overlapping and hierarchical community structure in networks
Clustering and community structure is crucial for many network systems and
the related dynamic processes. It has been shown that communities are usually
overlapping and hierarchical. However, previous methods investigate these two
properties of community structure separately. This paper proposes an algorithm
(EAGLE) to detect both the overlapping and hierarchical properties of complex
community structure together. This algorithm deals with the set of maximal
cliques and adopts an agglomerative framework. The quality function of
modularity is extended to evaluate the goodness of a cover. The examples of
application to real world networks give excellent results.Comment: 7 pages, 5 figure
- …