28,048 research outputs found
Field Induced Positional Shift of Bloch Electrons and its Dynamical Implications
We derive the field correction to the Berry curvature of Bloch electrons,
which can be traced back to a positional shift due to the interband mixing
induced by external electromagnetic fields. The resulting semiclassical
dynamics is accurate to second order in the fields, in the same form as before,
provided that the wave packet energy is derived up to the same order. As
applications, we discuss the orbital magnetoelectric polarizability and predict
nonlinear anomalous Hall effects
SCMA with Low Complexity Symmetric Codebook Design for Visible Light Communication
Sparse code multiple access (SCMA) is attracting significant research
interests currently, which is considered as a promising multiple access
technique for 5G systems. It serves as a good candidate for the future
communication network with massive nodes due to its capability of handling user
overloading. Introducing SCMA to visible light communication (VLC) can provide
another opportunity on design of transmission protocols for the communication
network with massive nodes due to the limited communication range of VLC, which
reduces the interference intensity. However, when applying SCMA in VLC systems,
we need to modify the SCMA codebook to accommodate the real and positive signal
requirement for VLC.We apply multidimensional constellation design methods to
SCMA codebook. To reduce the design complexity, we also propose a symmetric
codebook design. For all the proposed design approaches, the minimum Euclidean
distance aims to be maximized. Our symmetric codebook design can reduce design
and detection complexity simultaneously. Simulation results show that our
design implies fast convergence with respect to the number of iterations, and
outperforms the design that simply modifies the existing approaches to VLC
signal requirements
DC-Informative Joint Color-Frequency Modulation for Visible Light Communications
In this paper, we consider the problem of constellation design for a visible
light communication (VLC) system using red/green/blue light-emitting diodes
(RGB LED), and propose a method termed DC-informative joint color-frequency
modulation (DCI-JCFM). This method jointly utilizes available diversity
resources including different optical wavelengths, multiple baseband
subcarriers, and adaptive DC-bias. Constellation is designed in a high
dimensional space, where the compact sphere packing advantage over lower
dimensional counterparts is utilized. Taking into account multiple practical
illumination constraints, a non-convex optimization problem is formulated,
seeking the least error rate with a fixed spectral efficiency. The proposed
scheme is compared with a decoupled scheme, where constellation is designed
separately for each LED. Notable gains for DCI-JCFM are observed through
simulations where balanced, unbalanced and very unbalanced color illuminations
are considered.Comment: submitted to Journal of Lightwave Technology, Aug. 5th 201
The possible molecular state and its radiative decay
Recently, several exotic bosons have been confirmed as multi-quark states,
but there are violent disputes about their inner structures, namely if they are
molecular states or tetraquarks, or even mixtures of the two structures. It
would be interesting to experimentally search for non-strange four-quark states
with open charm or bottom which are lighter than or .
Reasonable arguments indicate that they are good candidates of pure molecular
states or because pions are the lightest boson. Both and
bound states do not decay via strong interaction. The molecule
may decay into by radiating a photon, whereas molecule can only
decay via weak interaction. In this paper we explore the mass spectra of
molecular statesby solving the corresponding B-S equation. Then the rate of
radiative decay is calculated
and our numerical results indicate that the processes can be measured by the
future experiment. We also briefly discuss the case, due to the
constraint of the final state phase space, it can only decay via weak
interaction.Comment: 12 pages, 3 figures, 3 table
Application of deep learning neural network for classification of TB lung CT images based on patches
In this work, convolutional neural network (CNN) is applied to classify the five types of Tuberculosis (TB) lung CT images. In doing so, each image has been segmented into rectangular patches with side width and high varying between 20 and 55 pixels, which are later normalised into 30x30 pixels. While classifying TB types, six instead of five categories are distinguished. Group 6 houses those patches/segments that are common to most of the other types, or background. In this way, while each 3D dataset only has less than 10% distinguishable volumes that are applied to perform the training, the rest remains part of the learning cycle by participating to the classification, leading to an automated process to differentiation of five types of TB. When tested against 300 datasets, the Kappa value is 0.2187, ranking 5 among 23 submissions. However, the accuracy value of ACC is 0.4067, the highest in this competition of classification of TB types
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