21,895 research outputs found
Large-scale Hierarchical Alignment for Data-driven Text Rewriting
We propose a simple unsupervised method for extracting pseudo-parallel
monolingual sentence pairs from comparable corpora representative of two
different text styles, such as news articles and scientific papers. Our
approach does not require a seed parallel corpus, but instead relies solely on
hierarchical search over pre-trained embeddings of documents and sentences. We
demonstrate the effectiveness of our method through automatic and extrinsic
evaluation on text simplification from the normal to the Simple Wikipedia. We
show that pseudo-parallel sentences extracted with our method not only
supplement existing parallel data, but can even lead to competitive performance
on their own.Comment: RANLP 201
Exporting Hyperinflation: The Long Arm of Chiang Kai-shek
As mainland China's inflationary spiral accelerated in 1947-1949 there was a massive outflow of funds to the island of Taiwan. The exporting of China's hyperinflation was facilitated by the fixed, overvalued, exchange rate between the mainland Chinese currency and the Taiwanese currency that was adopted in August 1948. Empirical tests offer support for the importance of the 1948 monetary policy reform and suggest a substantial impact of capital inflows and excess money growth in mainland China on inflationary pressures in Taiwan. We find no independent role for Taiwanese money growth in the inflation process.
Character-level Chinese-English Translation through ASCII Encoding
Character-level Neural Machine Translation (NMT) models have recently
achieved impressive results on many language pairs. They mainly do well for
Indo-European language pairs, where the languages share the same writing
system. However, for translating between Chinese and English, the gap between
the two different writing systems poses a major challenge because of a lack of
systematic correspondence between the individual linguistic units. In this
paper, we enable character-level NMT for Chinese, by breaking down Chinese
characters into linguistic units similar to that of Indo-European languages. We
use the Wubi encoding scheme, which preserves the original shape and semantic
information of the characters, while also being reversible. We show promising
results from training Wubi-based models on the character- and subword-level
with recurrent as well as convolutional models.Comment: 7 pages, 3 figures, 3rd Conference on Machine Translation (WMT18),
201
Significant g-factor values of a two-electron ground state in quantum dots with spin-orbit coupling
The magnetization of semiconductor quantum dots in the presence of spin-orbit
coupling and interactions is investigated numerically. When the dot is occupied
by two electrons we find that a level crossing between the two lowest many-body
eigenstates may occur as a function of the spin-orbit coupling strength. This
level crossing is accompanied by a non-vanishing magnetization of the
ground-state. Using first order perturbation theory as well as exact numerical
diagonalization of small clusters we show that the tendency of interactions to
cause Stoner-like instability is enhanced by the SO coupling. The resulting
g-factor can have a significant value, and thus may influence g-factor
measurements. Finally we propose an experimental method by which the predicted
phenomenon can be observed.Comment: 7+ pages, 7 figure
Eigenvalue bounds for a class of singular potentials in N dimensions
The eigenvalue bounds obtained earlier [J. Phys. A: Math. Gen. 31 (1998) 963]
for smooth transformations of the form V(x) = g(x^2) + f(1/x^2) are extended to
N-dimensions. In particular a simple formula is derived which bounds the
eigenvalues for the spiked harmonic oscillator potential V(x) = x^2 +
lambda/x^alpha, alpha > 0, lambda > 0, and is valid for all discrete
eigenvalues, arbitrary angular momentum ell, and spatial dimension N.Comment: 10 pages (plain tex with 2 ps figures). J.Phys.A:Math.Gen.(In Press
The stellar mass-accretion rate relation in T Tauri stars and brown dwarfs
Recent observations show a strong correlation between stellar mass and
accretion rate in young stellar and sub-stellar objects, with the scaling
holding over more than four orders of magnitude
in accretion rate. We explore the consequences of this correlation in the
context of disk evolution models. We note that such a correlation is not
expected to arise from variations in disk angular momentum transport efficiency
with stellar mass, and suggest that it may reflect a systematic trend in disk
initial conditions. In this case we find that brown dwarf disks initially have
rather larger radii than those around more massive objects. By considering disk
evolution, and invoking a simple parametrization for a shut-off in accretion at
the end of the disk lifetime, we show that such models predict that the scatter
in the stellar mass-accretion rate relationship should increase with increasing
stellar mass, in rough agreement with current observations.Comment: 4 pages, 2 figures. Accepted for publication in ApJ Letter
Pacific Ocean Forcing and Atmospheric Variability are the Dominant Causes of Spatially Widespread Droughts in the Contiguous United States
The contributions of oceanic and atmospheric variability to spatially widespread summer droughts in the contiguous United States (hereafter, pan-CONUS droughts) are investigated using 16-member ensembles of the Community Climate Model version 3 (CCM3) forced with observed sea surface temperatures (SSTs) from 1856 to 2012. The employed SST forcing fields are either (i) global or restricted to the (ii) tropical Pacific or (iii) tropical Atlantic to isolate the impacts of these two ocean regions on pan-CONUS droughts. Model results show that SST forcing of pan-CONUS droughts originates almost entirely from the tropical Pacific because of atmospheric highs from the northern Pacific to eastern North America established by La Nia conditions, with little contribution from the tropical Atlantic. Notably, in all three model configurations, internal atmospheric variability influences pan-CONUS drought occurrence by as much or more than the ocean forcing and can alone cause pan-CONUS droughts by establishing a dominant high centered over the US montane West. Similar results are found for the Community Atmosphere Model version 5 (CAM5). Model results are compared to the observational record, which supports model-inferred contributions to pan-CONUS droughts from La Nias and internal atmospheric variability. While there may be an additional association with warm Atlantic SSTs in the observational record, this association is ambiguous due to the limited number of observed pan-CONUS. The ambiguity thus opens the possibility that the observational results are limited by sampling over the 20th-century and not at odds with the suggested dominance of Pacific Ocean forcing in the model ensembles
Honeycomb lattice polygons and walks as a test of series analysis techniques
We have calculated long series expansions for self-avoiding walks and
polygons on the honeycomb lattice, including series for metric properties such
as mean-squared radius of gyration as well as series for moments of the
area-distribution for polygons. Analysis of the series yields accurate
estimates for the connective constant, critical exponents and amplitudes of
honeycomb self-avoiding walks and polygons. The results from the numerical
analysis agree to a high degree of accuracy with theoretical predictions for
these quantities.Comment: 16 pages, 9 figures, jpconf style files. Presented at the conference
"Counting Complexity: An international workshop on statistical mechanics and
combinatorics." In celebration of Prof. Tony Guttmann's 60th birthda
Magnetorotational Instability in Liquid Metal Couette Flow
Despite the importance of the magnetorotational instability (MRI) as a
fundamental mechanism for angular momentum transport in magnetized accretion
disks, it has yet to be demonstrated in the laboratory. A liquid sodium
alpha-omega dynamo experiment at the New Mexico Institute of Mining and
Technology provides an ideal environment to study the MRI in a rotating metal
annulus (Couette flow). A local stability analysis is performed as a function
of shear, magnetic field strength, magnetic Reynolds number, and turbulent
Prandtl number. The later takes into account the minimum turbulence induced by
the formation of an Ekman layer against the rigidly rotating end walls of a
cylindrical vessel. Stability conditions are presented and unstable conditions
for the sodium experiment are compared with another proposed MRI experiment
with liquid gallium. Due to the relatively large magnetic Reynolds number
achievable in the sodium experiment, it should be possible to observe the
excitation of the MRI for a wide range of wavenumbers and further to observe
the transition to the turbulent state.Comment: 12 pages, 22 figures, 1 table. To appear in the Astrophysical Journa
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