6,382 research outputs found
Identifying functional regions of interest within the speech motor control neural network
Towards an Ashtekar formalism in eight dimensions
We investigate the possibility of extending the Ashtekar theory to eight
dimensions. Our approach relies on two notions: the octonionic structure and
the MacDowell-Mansouri formalism generalized to a spacetime of signature 1+7.
The key mathematical tool for our construction is the self-dual (antiself-dual)
four-rank fully antisymmetric octonionic tensor. Our results may be of
particular interest in connection with a possible formulation of M-theory via
matroid theory.Comment: 15 pages, Latex, minor changes, to appear in Class. Quantum Gra
Quimismo de un sedimento clástico formador de esmectita y sus implicaciones en la transformación esmectita-ilita
3 páginas, 1 figura.-- Trabajo presentado en la XX Reunion de la Sociedad Española de MineralogÃa, La Coruña (2000).Prior to the development of "in-situ"
analysis techniques, data on the chemical
composition of minerals was derived
exclusively from whole rocks using
monomineral samples or from assemblages in
which the separation of minerals was possible.
Therefore, knowledge concerning the real
composition of smectites in soils and
sediments was significantly delayed, and it
was assumed that the typical smectite
composition was that of materials in which
they were the only phase or easily separated.
Recently, Analytical Electron Microscopy
(AEM) analyses have demonstrated that
smectites forming sediments or sedimentary
rocks can also be analysed in spite of their
small size and their defective nature. Smectites
play an important role in the geological cycle.
They are the basic material for the smectiteillite
transformation during the diagenesis of
sedimentary materials giving rise to illitebearing
sedimentary rocks.Financial support was supplied by
Research Project nº PB96-1383 of the
Spanish Ministry of Education and
Research Group RNM-0179 of the Junta
de AndalucÃa.Peer reviewe
Quimismo de un sedimento clástico formador de esmectita y sus implicaciones en la transformación esmectita-ilita
3 páginas, 1 figura.-- Trabajo presentado en la XX Reunion de la Sociedad Española de MineralogÃa, La Coruña (2000).Prior to the development of "in-situ"
analysis techniques, data on the chemical
composition of minerals was derived
exclusively from whole rocks using
monomineral samples or from assemblages in
which the separation of minerals was possible.
Therefore, knowledge concerning the real
composition of smectites in soils and
sediments was significantly delayed, and it
was assumed that the typical smectite
composition was that of materials in which
they were the only phase or easily separated.
Recently, Analytical Electron Microscopy
(AEM) analyses have demonstrated that
smectites forming sediments or sedimentary
rocks can also be analysed in spite of their
small size and their defective nature. Smectites
play an important role in the geological cycle.
They are the basic material for the smectiteillite
transformation during the diagenesis of
sedimentary materials giving rise to illitebearing
sedimentary rocks.Financial support was supplied by
Research Project nº PB96-1383 of the
Spanish Ministry of Education and
Research Group RNM-0179 of the Junta
de AndalucÃa.Peer reviewe
Influence of the Ground-State Topology on the Domain-Wall Energy in the Edwards-Anderson +/- J Spin Glass Model
We study the phase stability of the Edwards-Anderson spin-glass model by
analyzing the domain-wall energy. For the bimodal distribution of bonds, a
topological analysis of the ground state allows us to separate the system into
two regions: the backbone and its environment. We find that the distributions
of domain-wall energies are very different in these two regions for the three
dimensional (3D) case. Although the backbone turns out to have a very high
phase stability, the combined effect of these excitations and correlations
produces the low global stability displayed by the system as a whole. On the
other hand, in two dimensions (2D) we find that the surface of the excitations
avoids the backbone. Our results confirm that a narrow connection exists
between the phase stability of the system and the internal structure of the
ground-state. In addition, for both 3D and 2D we are able to obtain the fractal
dimension of the domain wall by direct means.Comment: 4 pages, 3 figures. Accepted for publication in Rapid Communications
of Phys. Rev.
Wind loads analysis at the anchorages of the Talavera de la Reina cable stayed bridge
This paper describes wind tunnel tests performed on wind tunnel models of the Talavera de la Reina cable stayed bridge. The work describes the aeroelastic model construction and it is focused on the evaluation and analysis of the mean and peak wind loads at the tower foundation and the cable anchorages since these data can be very useful by the bridge manufacturer as a support for the bridge design. The work is part of a complete wind tunnel study carried out to analyze the aeroelastic stability of the bridge
A Practical Example for Model-Driven Web Requirements
The number of approaches for Web environments has grown very fast
in the last years: HDM, OOHDM, and WSDM were among the first, and now a
large number can be found in the literature. With the definition of MDA (Model-
Driven Architecture) and the acceptance of MDE (Model-Driven Engineering)
techniques in this environment, some groups are working in the use of metamodels
and transformations to make their approaches more powerful. UWE (UMLBased
Web Engineering) or OOWS (Object-Oriented Web Solutions) are only
some examples. However, there are few real experiences with Web Engineering in
the enterprise environment, and very few real applications of metamodels and
MDE techniques. In this chapter the practical experience of a Web Engineering
approach, NDT, in a big project developed in Andalusia is presented. Besides, it
shows the usability of metamodels in real environments
A Practical Environment to Apply Model-Driven Web Engineering
The application of a model-driven paradigm in the development of Web Systems has yielded very good research
results. Several research groups are defining metamodels, transformations, and tools which offer a suitable environment,
known as model-driven Web engineering (MDWE). However, there are very few practical experiences in real
Web system developments using real development teams. This chapter presents a practical environment of MDWE
based on the use of NDT (navigational development techniques) and Java Web systems, and it provides a practical
evaluation of its application within a real project: specialized Diraya.Ministerio de Educación y Ciencia TIN2007-67843-C06-03Ministerio de Educación y Ciencia TIN2007-30391-
ExoplANNET: A deep learning algorithm to detect and identify planetary signals in radial velocity data
The detection of exoplanets with the radial velocity method consists in
detecting variations of the stellar velocity caused by an unseen sub-stellar
companion. Instrumental errors, irregular time sampling, and different noise
sources originating in the intrinsic variability of the star can hinder the
interpretation of the data, and even lead to spurious detections. In recent
times, work began to emerge in the field of extrasolar planets that use Machine
Learning algorithms, some with results that exceed those obtained with the
traditional techniques in the field. We seek to explore the scope of the neural
networks in the radial velocity method, in particular for exoplanet detection
in the presence of correlated noise of stellar origin. In this work, a neural
network is proposed to replace the computation of the significance of the
signal detected with the radial velocity method and to classify it as of
planetary origin or not. The algorithm is trained using synthetic data of
systems with and without planetary companions. We injected realistic correlated
noise in the simulations, based on previous studies of the behaviour of stellar
activity. The performance of the network is compared to the traditional method
based on null hypothesis significance testing. The network achieves 28 % fewer
false positives. The improvement is observed mainly in the detection of
small-amplitude signals associated with low-mass planets. In addition, its
execution time is five orders of magnitude faster than the traditional method.
The superior performance exhibited by the algorithm has only been tested on
simulated radial velocity data so far. Although in principle it should be
straightforward to adapt it for use in real time series, its performance has to
be tested thoroughly. Future work should permit evaluating its potential for
adoption as a valuable tool for exoplanet detection.Comment: Accepted for publication; Corrected typos; Added section 6.1 with a
robustness analysis of the method; Added section 6.2 with tests on a real
time series; Added section 6.3 with a more detailed analysis of the caution
of the network around activity periods; Added other tested models to the
appendi
Hydrogen atom as an eigenvalue problem in 3D spaces of constant curvature and minimal length
An old result of A.F. Stevenson [Phys. Rev.} 59, 842 (1941)] concerning the
Kepler-Coulomb quantum problem on the three-dimensional (3D) hypersphere is
considered from the perspective of the radial Schr\"odinger equations on 3D
spaces of any (either positive, zero or negative) constant curvature. Further
to Stevenson, we show in detail how to get the hypergeometric wavefunction for
the hydrogen atom case. Finally, we make a comparison between the ``space
curvature" effects and minimal length effects for the hydrogen spectrumComment: 6 pages, v
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