5,677 research outputs found
Multi-Entity Dependence Learning with Rich Context via Conditional Variational Auto-encoder
Multi-Entity Dependence Learning (MEDL) explores conditional correlations
among multiple entities. The availability of rich contextual information
requires a nimble learning scheme that tightly integrates with deep neural
networks and has the ability to capture correlation structures among
exponentially many outcomes. We propose MEDL_CVAE, which encodes a conditional
multivariate distribution as a generating process. As a result, the variational
lower bound of the joint likelihood can be optimized via a conditional
variational auto-encoder and trained end-to-end on GPUs. Our MEDL_CVAE was
motivated by two real-world applications in computational sustainability: one
studies the spatial correlation among multiple bird species using the eBird
data and the other models multi-dimensional landscape composition and human
footprint in the Amazon rainforest with satellite images. We show that
MEDL_CVAE captures rich dependency structures, scales better than previous
methods, and further improves on the joint likelihood taking advantage of very
large datasets that are beyond the capacity of previous methods.Comment: The first two authors contribute equall
Current-Voltage Curves for Molecular Junctions Computed Using All-Electron Basis Sets
We present current-voltage (I-V) curves computed using all-electron basis
sets on the conducting molecule. The all-electron results are very similar to
previous results obtained using effective core potentials (ECP). A hybrid
integration scheme is used that keeps the all-electron calculations cost
competitive with respect to the ECP calculations. By neglecting the coupling of
states to the contacts below a fixed energy cutoff, the density matrix for the
core electrons can be evaluated analytically. The full density matrix is formed
by adding this core contribution to the valence part that is evaluated
numerically. Expanding the definition of the core in the all-electron
calculations significantly reduces the computational effort and, up to biases
of about 2 V, the results are very similar to those obtained using more
rigorous approaches. The convergence of the I-V curves and transmission
coefficients with respect to basis set is discussed. The addition of diffuse
functions is critical in approaching basis set completeness
Inclinations and black hole masses of Seyfert 1 galaxies
A tight correlation of black hole mass and central velocity dispersion has
been found recently for both active and quiescent galaxies. By applying this
correlation, we develop a simple method to derive the inclination angles for a
sample of 11 Seyfert 1 galaxies that have both measured central velocity
dispersions and black hole masses estimated by reverberation mapping. These
angles, with a mean value of 36 degree that agrees well with the result
obtained by fitting the iron K lines of Seyfert 1s observed with ASCA,
provide further support to the orientation-dependent unification scheme of AGN.
A positive correlation of the inclinations with observed FWHMs of H line
and a possible anti-correlation with the nuclear radio-loudness have been
found. We conclude that more accurate knowledge on inclinations and broad line
region dynamics is needed to improve the black hole mass determination of AGN
with the reverberation mapping technique.Comment: 12 pages including 4 figures, accepted for publication in The
Astrophysical Journal Letter
Electronic structure of the Au/benzene-1,4-dithiol/Au transport interface: Effects of chemical bonding
We present results of electronic structure calculations for well-relaxed
Au/benzene-1,4-dithiol/Au molecular contacts, based on density functional
theory and the generalized gradient approximation. Electronic states in the
vicinity of the Fermi energy are mainly of Au 5d and S 3p symmetry, whereas
contributions of C 2p states are very small. Hybridization between C 2p
orbitals within the benzene substructure is strongly suppressed due to S-C
bonding. In agreement with experimental findings, this corresponds to a
significantly reduced conductance of the molecular contact.Comment: 7 pages, 5 figures, accepted by Chemical Physics Letter
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