6,561 research outputs found
Modeling Task Effects in Human Reading with Neural Attention
Humans read by making a sequence of fixations and saccades. They often skip
words, without apparent detriment to understanding. We offer a novel
explanation for skipping: readers optimize a tradeoff between performing a
language-related task and fixating as few words as possible. We propose a
neural architecture that combines an attention module (deciding whether to skip
words) and a task module (memorizing the input). We show that our model
predicts human skipping behavior, while also modeling reading times well, even
though it skips 40% of the input. A key prediction of our model is that
different reading tasks should result in different skipping behaviors. We
confirm this prediction in an eye-tracking experiment in which participants
answers questions about a text. We are able to capture these experimental
results using the our model, replacing the memorization module with a task
module that performs neural question answering
Centering in-the-large: Computing referential discourse segments
We specify an algorithm that builds up a hierarchy of referential discourse
segments from local centering data. The spatial extension and nesting of these
discourse segments constrain the reachability of potential antecedents of an
anaphoric expression beyond the local level of adjacent center pairs. Thus, the
centering model is scaled up to the level of the global referential structure
of discourse. An empirical evaluation of the algorithm is supplied.Comment: LaTeX, 8 page
It's a Bird, It's a Plane: Some Remarks on the Airbus Appellate Body Report (EC and Certain Member States – Large Civil Aircraft, WT/DS316/AB/R)
The emergence of Airbus transformed the market structure of the LCA industry into a duopoly of similar-sized full-range manufacturers. The financing of Airbus's upfront investment expenditures came in a significant proportion from public funds, which violated, in the US's opinion the SCM Agreement. While the Appellate Body follows this view of things to a large extent, it does so in a measured way: the category of per se illegal export subsidies is interpreted with a view to the manipulation of normal market conditions; the distortion on competitive conditions matters, not the increase of exports as such. Other aspects of subsidies law clarified are the relationship between effect and subsidy. They are closely related but not identical; rightly, the report operates from the premise that the SCM Agreement's regime focuses on the effect, and not on the subsidy as such, which is a manifestation of a political choice by a sovereign Member state. The Appellate Body affirms that a subsidy has a ‘life’, a shorthand for a beginning and an end: it follows that the effect of a subsidy is not bound to be permanent but is bound to terminate. It is to be regretted that the Appellate Body avoided clarifying to what extent partial privatization, hence sale of assets at market prices to private investors, ‘extinguish’ subsidies
News from FormCalc and LoopTools
The FormCalc package automates the computation of FeynArts amplitudes up to
one loop including the generation of a Fortran code for the numerical
evaluation of the squared matrix element. Major new or enhanced features in
Version 5 are: iterative build-up of essentially arbitrary phase-spaces
including cuts, convolution with density functions, and uniform treatment of
kinematical variables. The LoopTools library supplies the one-loop integrals
necessary for evaluating the squared matrix element. Its most significant
extensions in Version 2.2 are the five-point family of integrals, and complex
and alternate versions.Comment: 5 pages, to appear in the proceedings of the 7th International
Symposium on Radiative Corrections (RADCOR05), Shonan Village, Japan, 200
Observational Quantification of the Energy Dissipated by Alfv\'en Waves in a Polar Coronal Hole: Evidence that Waves Drive the Fast Solar Wind
We present a measurement of the energy carried and dissipated by Alfv\'en
waves in a polar coronal hole. Alfv\'en waves have been proposed as the energy
source that heats the corona and drives the solar wind. Previous work has shown
that line widths decrease with height in coronal holes, which is a signature of
wave damping, but have been unable to quantify the energy lost by the waves.
This is because line widths depend on both the non-thermal velocity v_nt and
the ion temperature T_i. We have implemented a means to separate the T_i and
v_nt contributions using the observation that at low heights the waves are
undamped and the ion temperatures do not change with height. This enables us to
determine the amount of energy carried by the waves at low heights, which is
proportional to v_nt. We find the initial energy flux density present was 6.7
+/- 0.7 x 10^5 erg cm^-2 s^-1, which is sufficient to heat the coronal hole and
acccelerate the solar wind during the 2007 - 2009 solar minimum. Additionally,
we find that about 85% of this energy is dissipated below 1.5 R_sun,
sufficiently low that thermal conduction can transport the energy throughout
the coronal hole, heating it and driving the fast solar wind. The remaining
energy is roughly consistent with what models show is needed to provide the
extended heating above the sonic point for the fast solar wind. We have also
studied T_i, which we found to be in the range of 1 - 2 MK, depending on the
ion species.Comment: Accepted for the Astrophysical Journa
Evidence for Wave Heating of the Quiet Sun Corona
We have measured the energy and dissipation of Alfvenic waves in the quiet
Sun. A magnetic field was used to infer the location and orientation of the
magnetic field lines along which the waves are expected to travel. The waves
were measured using spectral lines to infer the wave amplitude. The waves cause
a non-thermal broadening of the spectral lines, which can be expressed as a
non-thermal velocity v_nt. By combining the spectroscopic measurements with
this magnetic field model we were able to trace the variation of v_nt along the
magnetic field. At the footpoints of the quiet Sun loops we find that waves
inject an energy flux in the range of 1.2-5.2 x 10^5 erg cm^-2 s^-1. At the
minimum of this range, this amounts to more than 80% of the energy needed to
heat the quiet Sun. We also find that these waves are dissipated over a region
centered on the top of the loops. The position along the loop where the damping
begins is strongly correlated with the length of the loop, implying that the
damping mechanism depends on the global loop properties rather than on local
collisional dissipation.Comment: Submitted to the Astrophysical Journa
Inferring the Coronal Density Irregularity from EUV Spectra
Understanding the density structure of the solar corona is important for
modeling both coronal heating and the solar wind. Direct measurements are
difficult because of line-of-sight integration and possible unresolved
structures. We present a new method for quantifying such structure using
density-sensitive EUV line intensities to derive a density irregularity
parameter, a relative measure of the amount of structure along the line of
sight. We also present a simple model to relate the inferred irregularities to
physical quantities, such as the filling factor and density contrast. For quiet
Sun regions and interplume regions of coronal holes, we find a density contrast
of at least a factor of three to ten and corresponding filling factors of about
10-20%. Our results are in rough agreement with other estimates of the density
structures in these regions. The irregularity diagnostic provides a useful
relative measure of unresolved structure in various regions of the corona.Comment: Submitted to the Astrophysical Journa
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