87 research outputs found
Combination Strategies for Semantic Role Labeling
This paper introduces and analyzes a battery of inference models for the
problem of semantic role labeling: one based on constraint satisfaction, and
several strategies that model the inference as a meta-learning problem using
discriminative classifiers. These classifiers are developed with a rich set of
novel features that encode proposition and sentence-level information. To our
knowledge, this is the first work that: (a) performs a thorough analysis of
learning-based inference models for semantic role labeling, and (b) compares
several inference strategies in this context. We evaluate the proposed
inference strategies in the framework of the CoNLL-2005 shared task using only
automatically-generated syntactic information. The extensive experimental
evaluation and analysis indicates that all the proposed inference strategies
are successful -they all outperform the current best results reported in the
CoNLL-2005 evaluation exercise- but each of the proposed approaches has its
advantages and disadvantages. Several important traits of a state-of-the-art
SRL combination strategy emerge from this analysis: (i) individual models
should be combined at the granularity of candidate arguments rather than at the
granularity of complete solutions; (ii) the best combination strategy uses an
inference model based in learning; and (iii) the learning-based inference
benefits from max-margin classifiers and global feedback
Informal Persian Universal Dependency Treebank
This paper presents the phonological, morphological, and syntactic distinctions between formal and informal Persian, showing that these two variants have fundamental differences that cannot be attributed solely to pronunciation discrepancies. Given that informal Persian exhibits particular characteristics, any computational model trained on formal Persian is unlikely to transfer well to informal Persian, necessitating the creation of dedicated treebanks for this variety. We thus detail the development of the open-source Informal Persian Universal Dependency Treebank, a new treebank annotated within the Universal Dependencies scheme. We then investigate the parsing of informal Persian by training two dependency parsers on existing formal treebanks and evaluating them on out-of-domain data, i.e. the development set of our informal treebank. Our results show that parsers experience a substantial performance drop when we move across the two domains, as they face more unknown tokens and structures and fail to generalize well. Furthermore, the dependency relations whose performance deteriorates the most represent the unique properties of the informal variant. The ultimate goal of this study that demonstrates a broader impact is to provide a stepping-stone to reveal the significance of informal variants of languages, which have been widely overlooked in natural language processing tools across languages. © European Language Resources Association (ELRA), licensed under CC-BY-NC-4.0.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Visualization of novel flux dynamics in YBa2Cu3O7-x thin films with antidots.
Using magneto-optical visualization, individual 2 μm diameter antidots (circular holes) in YB
The ab-anisotrophy of twinfree YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> films above and below T<sub>c</sub>
High quality twin-free c-axis oriented YBa2Cu3O7 films were grown by pulsed laser deposition on NdGaO3. We find resistive anisotropies between 1 < a/b < 1.6. The resistive anisotropy above Tc appears to be correlated to the anisotropy in the critical current below Tc. The normal state properties of the chains along b seem to have a significant influence on the superconducting properties of YBa2Cu3O7
Flux front penetration in disordered superconductors
We investigate flux front penetration in a disordered type II superconductor
by molecular dynamics (MD) simulations of interacting vortices and find scaling
laws for the front position and the density profile. The scaling can be
understood performing a coarse graining of the system and writing a disordered
non-linear diffusion equation. Integrating numerically the equation, we observe
a crossover from flat to fractal front penetration as the system parameters are
varied. The value of the fractal dimension indicates that the invasion process
is described by gradient percolation.Comment: 5 pages, 4 figures, to appear in Phys. Rev. Let
Magneto-optical imaging of magnetic flux patterns in superconducting films with antidots
Superconducting YBaCuO thin films were equipped with a special arrangement of
antidots (holes) of 1 micron radius in order to guide the stream of magnetic
flux moving in (or out of) the sample. The flux distribution and its dynamics
were visualized using real-time magneto-optical imaging. It is clearly
demonstrated that one-dimensional antidot arrays strongly facilitate
propagation of magnetic flux. We also demonstrate a possibility to alter the
direction of flux motion in a controlled way by special arrangement of
intercepting antidot arrays. Our resolution was sufficient for observation of
flux in particular antidots, which allows a more detailed dynamic analysis of
such systems.Comment: 4 pages, 5 figures, submitted to Physica C, Proc. of VORTEX-IV
Workshop on Crete-200
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