9,556 research outputs found
BaFe2Se2O as an Iron-Based Mott Insulator with Antiferromagnetic Order
A new compound with a quasi-two-dimensional array of FeSe3O tetrahedra and an
orthorombic structure, namely BaFe2Se2O, has been successfully fabricated.
Experimental results show that this compound is an insulator and has an
antiferromagnetic (AF) transition at 240 K. Band structure calculation reveals
the narrowing of Fe 3d bands near the Fermi energy, which leads to the
localization of magnetism and the Mott insulating behavior. The large distances
between the Fe atoms perhaps are responsible for the characters. Linear
response calculation further indicates a strong in-plane AF exchange , this
can account for the enhanced magnetic susceptibility (which has a maximum at
about 450 K) above the Neel temperature.Comment: submitted to PRL on 2 May 2012, resubmitted to PRB on 31 May 2012,
and accepted by PRB on 5 July 201
Polygonal vortex beams in quasi-frequency-degenerate states
We originally demonstrate the vortex beams with patterns of closed polygons
[namely polygonal vortex beams (PVBs)] generated by a
quasi-frequency-degenerate (QFD) Yb:CALGO laser resonator with astigmatic
transformation. The PVBs with peculiar patterns of triangular, square, and
parallelogram shapes carrying large orbital angular momentums (OAMs) are
theoretically investigated and experimentally obtained in the vicinity of the
SU(2) degenerate states of laser resonator. The PVBs in QFD states are compared
with the vortex beams with patterns of isolated spots arrays located on the
triangle-, square-, and parallelogram-shaped routes [namely
polygonalspots-array vortex beams (PSA-VBs)] under normal SU(2) degenerate
states. Beam profile shape of PVB or PSA-VB and OAM can be controlled by
adjusting the cavity length and the position of pump spot. The simulated and
experimental results validate the performance of our method to generate PVB,
which is of great potential for promoting novel technologies in particle
trapping and beam shaping
OpinSummEval: Revisiting Automated Evaluation for Opinion Summarization
Opinion summarization sets itself apart from other types of summarization
tasks due to its distinctive focus on aspects and sentiments. Although certain
automated evaluation methods like ROUGE have gained popularity, we have found
them to be unreliable measures for assessing the quality of opinion summaries.
In this paper, we present OpinSummEval, a dataset comprising human judgments
and outputs from 14 opinion summarization models. We further explore the
correlation between 24 automatic metrics and human ratings across four
dimensions. Our findings indicate that metrics based on neural networks
generally outperform non-neural ones. However, even metrics built on powerful
backbones, such as BART and GPT-3/3.5, do not consistently correlate well
across all dimensions, highlighting the need for advancements in automated
evaluation methods for opinion summarization. The code and data are publicly
available at https://github.com/A-Chicharito-S/OpinSummEval/tree/main.Comment: preprint, included 2 more metrics compared with the previous
submissio
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