387 research outputs found
TIMME: Twitter Ideology-detection via Multi-task Multi-relational Embedding
We aim at solving the problem of predicting people's ideology, or political
tendency. We estimate it by using Twitter data, and formalize it as a
classification problem. Ideology-detection has long been a challenging yet
important problem. Certain groups, such as the policy makers, rely on it to
make wise decisions. Back in the old days when labor-intensive survey-studies
were needed to collect public opinions, analyzing ordinary citizens' political
tendencies was uneasy. The rise of social medias, such as Twitter, has enabled
us to gather ordinary citizen's data easily. However, the incompleteness of the
labels and the features in social network datasets is tricky, not to mention
the enormous data size and the heterogeneousity. The data differ dramatically
from many commonly-used datasets, thus brings unique challenges. In our work,
first we built our own datasets from Twitter. Next, we proposed TIMME, a
multi-task multi-relational embedding model, that works efficiently on
sparsely-labeled heterogeneous real-world dataset. It could also handle the
incompleteness of the input features. Experimental results showed that TIMME is
overall better than the state-of-the-art models for ideology detection on
Twitter. Our findings include: links can lead to good classification outcomes
without text; conservative voice is under-represented on Twitter; follow is the
most important relation to predict ideology; retweet and mention enhance a
higher chance of like, etc. Last but not least, TIMME could be extended to
other datasets and tasks in theory.Comment: In proceedings of KDD'20, Applied Data Science Track; 9 pages, 2
supplementary page
Two-dimensional Massless Dirac Fermions in Antiferromagnetic AFe2As2 (A = Ba, Sr)
We report infrared studies of AFeAs (A = Ba, Sr), two
representative parent compounds of iron-arsenide superconductors, at magnetic
fields (B) up to 17.5 T. Optical transitions between Landau levels (LLs) were
observed in the antiferromagnetic states of these two parent compounds. Our
observation of a dependence of the LL transition energies, the
zero-energy intercepts at B = 0 T under the linear extrapolations of the
transition energies and the energy ratio ( 2.4) between the observed LL
transitions, combined with the linear band dispersions in two-dimensional (2D)
momentum space obtained by theoretical calculations, demonstrates the existence
of massless Dirac fermions in antiferromagnetic BaFeAs. More
importantly, the observed dominance of the zeroth-LL-related absorption
features and the calculated bands with extremely weak dispersions along the
momentum direction indicate that massless Dirac fermions in
BaFeAs are 2D. Furthermore, we find that the total substitution of
the barium atoms in BaFeAs by strontium atoms not only maintains 2D
massless Dirac fermions in this system, but also enhances their Fermi velocity,
which supports that the Dirac points in iron-arsenide parent compounds are
topologically protected.Comment: Magneto-infrared study, Landau level spectroscopy, DFT+DMFT
calculation
- …