7,226 research outputs found
Ab initio study of shock compressed oxygen
Quantum molecular dynamic simulations are introduced to study the shock
compressed oxygen. The principal Hugoniot points derived from the equation of
state agree well with the available experimental data. With the increase of
pressure, molecular dissociation is observed. Electron spin polarization
determines the electronic structure of the system under low pressure, while it
is suppressed around 30 50 GPa. Particularly, nonmetal-metal transition
is taken into account, which also occurs at about 30 50 GPa. In
addition, the optical properties of shock compressed oxygen are also discussed.Comment: 5 pages, 5 figure
Extracting and Stabilizing the Unstable State of Hysteresis Loop
A novel perturbation method for the stabilization of unstable intermediate
states of hysteresis loop (i.e. S-shaped curve) is proposed. This method only
needs output signals of the system to construct the perturbation form without
delay-coordinate embedding technique, it is more practical for real-world
systems. Stabilizing and tracking the unstable intermediate branch are
demonstrated through the examples of a bistable laser system and delay feedback
system. All the numerical results are obtained by simulating each of the real
experimential conditions.Comment: 6 pages, REVTEX, 4 ps figure
Exceptional Points in a Non-Hermitian Topological Pump
We investigate the effects of non-Hermiticity on topological pumping, and
uncover a connection between a topological edge invariant based on topological
pumping and the winding numbers of exceptional points. In Hermitian lattices,
it is known that the topologically nontrivial regime of the topological pump
only arises in the infinite-system limit. In finite non-Hermitian lattices,
however, topologically nontrivial behavior can also appear. We show that this
can be understood in terms of the effects of encircling a pair of exceptional
points during a pumping cycle. This phenomenon is observed experimentally, in a
non-Hermitian microwave network containing variable gain amplifiers.Comment: 7 pages, 7 figures. The first author did the experiment, and the
second author did the theoretical stud
Perceptions of Machine Translation and Computer-Aided Translation by Professionals and the General Public: A Survey Study Based on Articles in Professional Journals and in the Media
This article examines perceptions of MT and CAT among translation professionals and the general public by surveying 124 articles published in the professional journals of ITI Bulletin and MultiLingual and in the Chinese media between 2017 and 2019. Through framing analysis, the following frames about MT and CAT are identified: progress, quality, threat, limitation, cooperation, economic factors, and ethics. Through qualitative analysis of prominent frames, it is also found that attitudes vary between the professional journals and the media about the role of MT as related to human translators. While ITI Bulletin holds a generally conservative attitude, MultiLingual takes a more positive stance towards the applications of MT, and the Chinese media generally hype MT as a potential threat to HT but promote human-machine cooperation as the way out. This study also shows that the ethical and legal issues involving MT and CAT have not been addressed adequately
Pseudo-magnetoexcitons in strained graphene bilayers without external magnetic fields
The structural and electronic properties of graphene leads its charge
carriers to behave like relativistic particles, which is described by a
Dirac-like Hamiltonian. Since graphene is a monolayer of carbon atoms, the
strain due to elastic deformations will give rise to so-called `pseudomagnetic
fields (PMF)' in graphene sheet, and that has been realized experimentally in
strained graphene sample. Here we propose a realistic strained graphene bilayer
(SGB) device to detect the pseudo-magnetoexcitons (PME) in the absence of
external magnetic field. The carriers in each graphene layer suffer different
strong PMFs due to strain engineering, which give rise to Landau quantization.
The pseudo-Landau levels (PLLs) of electron-hole pair under inhomogeneous PMFs
in SGB are analytically obtained in the absence of Coulomb interactions. Based
on the general analytical optical absorption selection rule for PME, we show
that the optical absorption spectrums can interpret the corresponding formation
of Dirac-type PME. We also predict that in the presence of inhomogeneous PMFs,
the superfluidity-normal phase transition temperature of PME is greater than
that under homogeneous PMFs.}Comment: 16 pages, 6 figure
Summertime Tropospheric Ozone Columns from Aura OMI/MLS Measurements Versus Regional Model Results Over the United States
[1] Ozone columns below 147 hPa are derived over the United States from September 2004 to August 2005 from the differences between clear-sky Aura OMI columns and coincident MLS columns. The mean difference from coincident ozonesonde measurements at four USA sites is 0.3 DU with an rms difference of 10.1 DU and a correlation coefficient of 0.67. Semimonthly patterns of the columns over the USA for the summer of 2005 have been produced. The observed columns, as well as Regional Air Quality Forecast (RAQAST) model columns, show high values over the southeastern USA and its surrounding oceans. Changes of these columns exceeding 6 DU in many places were observed between June 17–30 and July 1–16 and the changes reversed in the following two-week period. Comparisons against calculations from the RAQAST model, as well as correlations with geopotential height changes at 147 hPa, indicate that these changes were primarily related to dynamics
Orbital magnetization and its effect in antiferromagnets on the distorted fcc lattice
We study the intrinsic orbital magnetization (OM) in antiferromagnets on the
distorted face-centered-cubic lattice. The combined lattice distortion and spin
frustration induce nontrivial -space Chern invariant, which turns to result
in profound effects on the OM properties. We derive a specific relation between
the OM and the Hall conductivity, according to which it is found that the
intrinsic OM vanishes when the electron chemical potential lies in the Mott
gap. The distinct behavior of the intrinsic OM in the metallic and insulating
regions is shown. The Berry phase effects on the thermoelectric transport is
also discussed.Comment: 18 pages, 6 figure
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