11,495 research outputs found
Online Self-Indexed Grammar Compression
Although several grammar-based self-indexes have been proposed thus far,
their applicability is limited to offline settings where whole input texts are
prepared, thus requiring to rebuild index structures for given additional
inputs, which is often the case in the big data era. In this paper, we present
the first online self-indexed grammar compression named OESP-index that can
gradually build the index structure by reading input characters one-by-one.
Such a property is another advantage which enables saving a working space for
construction, because we do not need to store input texts in memory. We
experimentally test OESP-index on the ability to build index structures and
search query texts, and we show OESP-index's efficiency, especially
space-efficiency for building index structures.Comment: To appear in the Proceedings of the 22nd edition of the International
Symposium on String Processing and Information Retrieval (SPIRE2015
Finite Element Integration on GPUs
We present a novel finite element integration method for low order elements
on GPUs. We achieve more than 100GF for element integration on first order
discretizations of both the Laplacian and Elasticity operators.Comment: 16 pages, 3 figure
Quantum Molecular Dynamics Approach to the Nuclear Matter Below the Saturation Density
Quantum molecular dynamics is applied to study the ground state properties of
nuclear matter at subsaturation densities. Clustering effects are observed as
to soften the equation of state at these densities. The structure of nuclear
matter at subsaturation density shows some exotic shapes with variation of the
density.Comment: 21 pages of Latex (revtex), 9 Postscript figure
Noise-induced behaviors in neural mean field dynamics
The collective behavior of cortical neurons is strongly affected by the
presence of noise at the level of individual cells. In order to study these
phenomena in large-scale assemblies of neurons, we consider networks of
firing-rate neurons with linear intrinsic dynamics and nonlinear coupling,
belonging to a few types of cell populations and receiving noisy currents.
Asymptotic equations as the number of neurons tends to infinity (mean field
equations) are rigorously derived based on a probabilistic approach. These
equations are implicit on the probability distribution of the solutions which
generally makes their direct analysis difficult. However, in our case, the
solutions are Gaussian, and their moments satisfy a closed system of nonlinear
ordinary differential equations (ODEs), which are much easier to study than the
original stochastic network equations, and the statistics of the empirical
process uniformly converge towards the solutions of these ODEs. Based on this
description, we analytically and numerically study the influence of noise on
the collective behaviors, and compare these asymptotic regimes to simulations
of the network. We observe that the mean field equations provide an accurate
description of the solutions of the network equations for network sizes as
small as a few hundreds of neurons. In particular, we observe that the level of
noise in the system qualitatively modifies its collective behavior, producing
for instance synchronized oscillations of the whole network, desynchronization
of oscillating regimes, and stabilization or destabilization of stationary
solutions. These results shed a new light on the role of noise in shaping
collective dynamics of neurons, and gives us clues for understanding similar
phenomena observed in biological networks
Finite size effects on kaonic pasta structures
Non-uniform structures of mixed phases at the first-order phase transition to
charged kaon condensation are studied using a density functional theory within
the relativistic mean field model. Including electric field effects and
applying the Gibbs conditions in a proper way, we numerically determine density
profiles of nucleons, electrons and condensed kaons. Importance of charge
screening effects is elucidated and thereby we show that the Maxwell
construction is effectively justified. Surface effect is also studied to figure
out its effect on the density profiles
Hematopoietic Colony Forming Cells of Spleen
It was found that isologous spleen cells injected into heavily irradiated recipients produced spleen nodules. The number of nodules or colony-farming-units (CFU) varied with cell dose, and were presumably clonal descendants of a single progenitor cell. The properties of the spleen and bone marrow CFU were compared and it was found that although present in greatly differing concentration, the radiation response and morphological features were similar
Anisotropic Decay Dynamics of Photoexcited Aligned Carbon Nanotube Bundles
We have performed polarization-dependent ultrafast pump-probe spectroscopy of
a film of aligned single-walled carbon nanotube bundles. By taking into account
imperfect nanotube alignment as well as anisotropic absorption cross sections,
we quantitatively determined distinctly different photo-bleaching dynamics for
polarizations parallel and perpendicular to the tube axis. For perpendicular
polarization, we observe a slow (1.0-1.5 ps) relaxation process, previously
unobserved in randomly-oriented nanotube bundles. We attribute this slower
dynamics to the excitation and relaxation of surface plasmons in the radial
direction of the nanotube bundles.Comment: 4 pages, 3 figure
Online Pattern Matching for String Edit Distance with Moves
Edit distance with moves (EDM) is a string-to-string distance measure that
includes substring moves in addition to ordinal editing operations to turn one
string to the other. Although optimizing EDM is intractable, it has many
applications especially in error detections. Edit sensitive parsing (ESP) is an
efficient parsing algorithm that guarantees an upper bound of parsing
discrepancies between different appearances of the same substrings in a string.
ESP can be used for computing an approximate EDM as the L1 distance between
characteristic vectors built by node labels in parsing trees. However, ESP is
not applicable to a streaming text data where a whole text is unknown in
advance. We present an online ESP (OESP) that enables an online pattern
matching for EDM. OESP builds a parse tree for a streaming text and computes
the L1 distance between characteristic vectors in an online manner. For the
space-efficient computation of EDM, OESP directly encodes the parse tree into a
succinct representation by leveraging the idea behind recent results of a
dynamic succinct tree. We experimentally test OESP on the ability to compute
EDM in an online manner on benchmark datasets, and we show OESP's efficiency.Comment: This paper has been accepted to the 21st edition of the International
Symposium on String Processing and Information Retrieval (SPIRE2014
A dynamical description of neutron star crusts
Neutron Stars are natural laboratories where fundamental properties of matter
under extreme conditions can be explored. Modern nuclear physics input as well
as many-body theories are valuable tools which may allow us to improve our
understanding of the physics of those compact objects.
In this work the occurrence of exotic structures in the outermost layers of
neutron stars is investigated within the framework of a microscopic model. In
this approach the nucleonic dynamics is described by a time-dependent mean
field approach at around zero temperature. Starting from an initial crystalline
lattice of nuclei at subnuclear densities the system evolves toward a manifold
of self-organized structures with different shapes and similar energies. These
structures are studied in terms of a phase diagram in density and the
corresponding sensitivity to the isospin-dependent part of the equation of
state and to the isotopic composition is investigated.Comment: 8 pages, 5 figures, conference NN201
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