4,490 research outputs found
Spatiotemporal Chaos, Localized Structures and Synchronization in the Vector Complex Ginzburg-Landau Equation
We study the spatiotemporal dynamics, in one and two spatial dimensions, of
two complex fields which are the two components of a vector field satisfying a
vector form of the complex Ginzburg-Landau equation. We find synchronization
and generalized synchronization of the spatiotemporally chaotic dynamics. The
two kinds of synchronization can coexist simultaneously in different regions of
the space, and they are mediated by localized structures. A quantitative
characterization of the degree of synchronization is given in terms of mutual
information measures.Comment: 6 pages, using bifchaos.sty (included). 7 figures. Related material,
including higher quality figures, could be found at
http://www.imedea.uib.es/PhysDept/publicationsDB/date.html . To appear in
International Journal of Bifurcation and Chaos (1999
Adam through a Second-Order Lens
Research into optimisation for deep learning is characterised by a tension
between the computational efficiency of first-order, gradient-based methods
(such as SGD and Adam) and the theoretical efficiency of second-order,
curvature-based methods (such as quasi-Newton methods and K-FAC). We seek to
combine the benefits of both approaches into a single computationally-efficient
algorithm. Noting that second-order methods often depend on stabilising
heuristics (such as Levenberg-Marquardt damping), we propose AdamQLR: an
optimiser combining damping and learning rate selection techniques from K-FAC
(Martens and Grosse, 2015) with the update directions proposed by Adam,
inspired by considering Adam through a second-order lens. We evaluate AdamQLR
on a range of regression and classification tasks at various scales, achieving
competitive generalisation performance vs runtime.Comment: 28 pages, 15 figures, 4 tables. Submitted to ICLR 202
Series of Hessian-Vector Products for Tractable Saddle-Free Newton Optimisation of Neural Networks
Despite their popularity in the field of continuous optimisation,
second-order quasi-Newton methods are challenging to apply in machine learning,
as the Hessian matrix is intractably large. This computational burden is
exacerbated by the need to address non-convexity, for instance by modifying the
Hessian's eigenvalues as in Saddle-Free Newton methods. We propose an
optimisation algorithm which addresses both of these concerns - to our
knowledge, the first efficiently-scalable optimisation algorithm to
asymptotically use the exact (eigenvalue-modified) inverse Hessian. Our method
frames the problem as a series which principally square-roots and inverts the
squared Hessian, then uses it to precondition a gradient vector, all without
explicitly computing or eigendecomposing the Hessian. A truncation of this
infinite series provides a new optimisation algorithm which is scalable and
comparable to other first- and second-order optimisation methods in both
runtime and optimisation performance. We demonstrate this in a variety of
settings, including a ResNet-18 trained on CIFAR-10.Comment: 36 pages, 10 figures, 5 tables. Submitted to TMLR. First two authors'
order randomise
La Teología del Pseudo Aristóteles (Kitab Utülüylya li-Aristü) y la estructuración del neoplatonismo islámico.
The Theology of the Pseudo Aristotle has played an important role in the structure of Islamic Neoplatonism, and, therefore, in the formation of muslim philosophy and mysticism. His arabic text has numerous correspondences with the Enneads IV, V & VI of Plotinus, by that which it can be concluded that it is not only a free and fragmentary translation of the last three Enneads, but also that it constitutes an attempt to explain the text, leaving aside some conflictive points for a believer
Dynamics of localized structures in vector waves
Dynamical properties of topological defects in a twodimensional complex
vector field are considered. These objects naturally arise in the study of
polarized transverse light waves. Dynamics is modeled by a Vector Complex
Ginzburg-Landau Equation with parameter values appropriate for linearly
polarized laser emission. Creation and annihilation processes, and
selforganization of defects in lattice structures, are described. We find
"glassy" configurations dominated by vectorial defects and a melting process
associated to topological-charge unbinding.Comment: 4 pages, 5 figures included in the text. To appear in Phys. Rev.
Lett. (2000). Related material at http://www.imedea.uib.es/Nonlinear and
http://www.imedea.uib.es/Photonics . In this new version, Fig. 3 has been
replaced by a better on
The Effect of Cranio-Cervical Position on Core Muscle Activation during the Prone Plank Exercise
This study aimed to investigate the influence of head position on the electromyographical activity of the core muscles during the prone plank exercise. Twenty healthy participants were enrolled in this study. Muscle activation was registered using surface electromyography in the rectus abdominis, external oblique, internal oblique, and the lumbar portion of erector spinae. Three plank conditions were randomly evaluated, varying the position of the cranio-cervical segment during the plank performance (neutral, flexion and extension). The activation of each individual examined muscle and the overall core muscle activity (Total Intensity), as well as the ratings of perceived exertion were analysed with statistical significance set at p 0.90). The rectus abdominis presented larger activation in flexion compared to the other variations (p 0.70). Flexion elicited a greater response for both sides of external oblique when compared to neutral and extension, and also for both sides of internal oblique compared to the other conditions (p 0.70). Both flexion and extension reported higher exertion rating values compared to neutral (p 0.90). Head position influenced the electromyographical activation of core musculature, showing highest values when performing the plank in a head flexion.This research was funded by Consellería de Educación, Investigación, Cultura y Deporte de la Generalitat Valenciana, and European Social Fund (European Union), Grant Project Number ACIF/2016/048
Solución Abierta de Barrido y Pulsación en Dispositivos Móviles Accesible para Personas con DFiscapacidad Física
Este trabajo de investigación tiene como objetivo esencial ofrecer una solución de accesibilidad a los dispositivos móviles táctiles para personas con discapacidad física con afección en los miembros superiores. El diseño, desarrollo y validación de la solución detallada está basado en una plataforma abierta y de bajo coste como Android que, mediante la interconexión de conmutadores comerciales y el uso de un sistema de barrido con realimentación por voz sintetizada, permite al usuario acceder a todas las funciones básicas de la telefonía móvil.
El análisis de los requisitos de usuario es un eje central de este trabajo para lo cual se ha contado con la participación de la Asociación de Lesionados Medulares y Grandes Discapacitados Físicos (ASPAYM), de la Asociación de Padres de Alumnos Minusválidos (APAM) y del Centro de Referencia Estatal de Atención al Daño Cerebral (CEADAC). El sistema resultante preserva las expectativas de autonomía personal y privacidad demandadas
Sample treatments prior to capillary electrophoresis-mass spectrometry
Sample preparation is a crucial part of chemical analysis and in most cases can become the bottleneck of the whole analytical process. Its adequacy is a key factor in determining the success of the analysis and, therefore, careful selection and optimization of the parameters controlling sample treatment should be carried out. This work revises the different strategies that have been developed for sample preparation prior to capillary electrophoresis-mass spectrometry (CE-MS). Namely, the present work presents an exhaustive and critical revision of the different samples treatments used together with on-line CE-MS including works published from January 2000 to July 2006Authors are grateful to the AGL2005-05320-C02-01 Project (Ministerio de Educacion y Ciencia) and the ALIBIRD-S-505/AGR-0153 Project (CAM) for financial support of this work.Peer reviewe
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