40,213 research outputs found
Jointly Modeling Topics and Intents with Global Order Structure
Modeling document structure is of great importance for discourse analysis and
related applications. The goal of this research is to capture the document
intent structure by modeling documents as a mixture of topic words and
rhetorical words. While the topics are relatively unchanged through one
document, the rhetorical functions of sentences usually change following
certain orders in discourse. We propose GMM-LDA, a topic modeling based
Bayesian unsupervised model, to analyze the document intent structure
cooperated with order information. Our model is flexible that has the ability
to combine the annotations and do supervised learning. Additionally, entropic
regularization can be introduced to model the significant divergence between
topics and intents. We perform experiments in both unsupervised and supervised
settings, results show the superiority of our model over several
state-of-the-art baselines.Comment: Accepted by AAAI 201
Two Solar Tornadoes Observed with the Interface Region Imaging Spectrograph
The barbs or legs of some prominences show an apparent motion of rotation,
which are often termed solar tornadoes. It is under debate whether the apparent
motion is a real rotating motion, or caused by oscillations or
counter-streaming flows. We present analysis results from spectroscopic
observations of two tornadoes by the Interface Region Imaging Spectrograph.
Each tornado was observed for more than 2.5 hours. Doppler velocities are
derived through a single Gaussian fit to the Mg~{\sc{ii}}~k~2796\AA{}~and
Si~{\sc{iv}}~1393\AA{}~line profiles. We find coherent and stable red and blue
shifts adjacent to each other across the tornado axes, which appears to favor
the interpretation of these tornadoes as rotating cool plasmas with
temperatures of K- K. This interpretation is further supported by
simultaneous observations of the Atmospheric Imaging Assembly on board the
Solar Dynamics Observatory, which reveal periodic motions of dark structures in
the tornadoes. Our results demonstrate that spectroscopic observations can
provide key information to disentangle different physical processes in solar
prominences.Comment: 14 figures, accepted by Ap
Electronic, mechanical, and thermodynamic properties of americium dioxide
By performing density functional theory (DFT) + calculations, we
systematically study the electronic, mechanical, tensile, and thermodynamic
properties of AmO. The experimentally observed antiferromagnetic
insulating feature [J. Chem. Phys. 63, 3174 (1975)] is successfully reproduced.
It is found that the chemical bonding character in AmO is similar to that
in PuO, with smaller charge transfer and stronger covalent interactions
between americium and oxygen atoms. The valence band maximum and conduction
band minimum are contributed by 2 hybridized and 5 electronic states
respectively. The elastic constants and various moduli are calculated, which
show that AmO is less stable against shear forces than PuO. The
stress-strain relationship of AmO is examined along the three low-index
directions by employing the first-principles computational tensile test method.
It is found that similar to PuO, the [100] and [111] directions are the
strongest and weakest tensile directions, respectively, but the theoretical
tensile strengths of AmO are smaller than those of PuO. The phonon
dispersion curves of AmO are calculated and the heat capacities as well
as lattice expansion curve are subsequently determined. The lattice thermal
conductance of AmO is further evaluated and compared with attainable
experiments. Our present work integrally reveals various physical properties of
AmO and can be referenced for technological applications of AmO
based materials.Comment: 23 pages, 8 figure
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