15,729 research outputs found
Using Multi-Sense Vector Embeddings for Reverse Dictionaries
Popular word embedding methods such as word2vec and GloVe assign a single vector representation to each word, even if a word has multiple distinct meanings. Multi-sense embeddings instead provide different vectors for each sense of a word. However, they typically cannot serve as a drop-in replacement for conventional single-sense embeddings, because the correct sense vector needs to be selected for each word. In this work, we study the effect of multi-sense embeddings on the task of reverse dictionaries. We propose a technique to easily integrate them into an existing neural network architecture using an attention mechanism. Our experiments demonstrate that large improvements can be obtained when employing multi-sense embeddings both in the input sequence as well as for the target representation. An analysis of the sense distributions and of the learned attention is provided as well
Estimativa de custo de produção de soja, nos sistemas plantio direto e convencional, safra 1999/2000.
bitstream/item/24905/1/Cot19992.pd
Estimativa de custo de produção de algodão, no sistema plantio convencional, safra 1999/2000.
bitstream/item/39711/1/COT-06-1999.pd
A brown dwarf companion to the intermediate-mass star HR6037
In the course of an imaging survey we have detected a visual companion to the
intermediate-mass star HR 6037. In this letter, we present two epoch
observations of the binary with NACO/VLT, and near-IR spectroscopy of the
secondary with ISAAC/VLT. The NACO observations allow us to confirm HR 6037B as
a co-moving companion. Its J and H band ISAAC spectra suggest the object has an
spectral type of M9+-1, with a surface gravity intermediate between that of 10
Myr dwarfs and field dwarfs with identical spectral type. The comparison of its
Ks-band photometry with evolutionary tracks allows us to derive a mass,
effective temperature, and surface gravity of 62+-20 MJup, Teff = 2330+-200 K,
and log g = 5.1+-0.2, respectively. The small mass ratio of the binary, -0.03,
and its long orbital period, -5000 yr, makes HR 6037 a rare and uncommon binary
system.Comment: (5 pages, 4 figures, accepted for publication in A&A Letters
Nonzero orbital angular momentum superfluidity in ultracold Fermi gases
We analyze the evolution of superfluidity for nonzero orbital angular
momentum channels from the Bardeen-Cooper-Schrieffer (BCS) to the Bose-Einstein
condensation (BEC) limit in three dimensions. First, we analyze the low energy
scattering properties of finite range interactions for all possible angular
momentum channels. Second, we discuss ground state () superfluid
properties including the order parameter, chemical potential, quasiparticle
excitation spectrum, momentum distribution, atomic compressibility, ground
state energy and low energy collective excitations. We show that a quantum
phase transition occurs for nonzero angular momentum pairing, unlike the s-wave
case where the BCS to BEC evolution is just a crossover. Third, we present a
gaussian fluctuation theory near the critical temperature (),
and we analyze the number of bound, scattering and unbound fermions as well as
the chemical potential. Finally, we derive the time-dependent Ginzburg-Landau
functional near , and compare the Ginzburg-Landau coherence length
with the zero temperature average Cooper pair size.Comment: 28 pages and 24 figure
Chemical abundances for the transiting planet host stars OGLE-TR-10, 56, 111, 113, 132 and TrES-1. Abundances in different galactic populations
We used the UVES spectrograph (VLT-UT2 telescope) to obtain high-resolution
spectra of 6 stars hosting transiting planets, namely for OGLE-TR-10, 56, 111,
113, 132 and TrES-1. The spectra are now used to derive and discuss the
chemical abundances for C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni,
Cu and Zn. Abundances were derived in LTE, using 1-D plane-parallel Kurucz
model atmospheres. For S, Zn and Cu we used a spectral synthesis procedure,
while for the remaining cases the abundances were derived from measurements of
line-equivalent widths. The resulting abundances are compared with those found
for stars in the solar neighborhood. Distances and galactic coordinates are
estimated for the stars. We conclude that besides being particularly
metal-rich, with small possible exceptions OGLE-TR-10, 56, 111, 113, 132 and
TrES-1 are chemically undistinguishable from the field (thin disk) stars
regarding their [X/Fe] abundances. This is particularly relevant for the most
distant of the targets, located at up to ~2 Kpc from the Sun. We also did not
find any correlation between the abundances and the condensation temperature of
the elements, an evidence that strong accretion of planetary-like material,
tentatively connected to planetary migration, did not occur.Comment: Accepted for publication in Astronomy & Astrophysics (June 2006
Search for associations containing young stars (SACY). VI. Is multiplicity universal? Stellar multiplicity in the range 3-1000 au from adaptive-optics observations
Context. Young loose nearby associations are unique samples of close (<150
pc), young (approx 5-100 Myr) pre-main sequence (PMS) stars. A significant
number of members of these associations have been identified in the SACY
collaboration. We can use the proximity and youth of these members to
investigate key ingredients in star formation processes, such as multiplicity.
Aims. We present the statistics of identified multiple systems from 113
confirmed SACY members. We derive multiplicity frequencies, mass-ratio, and
physical separation distributions in a consistent parameter space, and compare
our results to other PMS populations and the field.
Methods. We have obtained adaptive-optics assisted near-infrared observations
with NACO (ESO/VLT) and IRCAL (Lick Observatory) for at least one epoch of all
113 SACY members. We have identified multiple systems using co-moving
proper-motion analysis and using contamination estimates. We have explored
ranges in projected separation and mass-ratio of a [3-1000 au], and q [0.1-1],
respectively.
Results. We have identified 31 multiple systems (28 binaries and 3 triples).
We derive a multiplicity frequency (MF) of MF_(3-1000au)=28.4 +4.7, -3.9% and a
triple frequency (TF) of TF_(3-1000au)=2.8 +2.5, -0.8% in the separation range
of 3-1000 au. We do not find any evidence for an increase in the MF with
primary mass. The estimated mass-ratio of our statistical sample (with
power-law index gamma=-0.04 +/- 0.14) is consistent with a flat distribution
(gamma = 0).
Conclusions. We show further similarities (but also hints of discrepancies)
between SACY and the Taurus region: flat mass-ratio distributions and
statistically similar MF and TF values. We also compared the SACY sample to the
field (in the separation range of 19-100 au), finding that the two
distributions are indistinguishable, suggesting a similar formation mechanism.Comment: 16 Pages, accepted in A&A 28 May 201
- …