5,958 research outputs found
Unsupervised Feature Selection with Adaptive Structure Learning
The problem of feature selection has raised considerable interests in the
past decade. Traditional unsupervised methods select the features which can
faithfully preserve the intrinsic structures of data, where the intrinsic
structures are estimated using all the input features of data. However, the
estimated intrinsic structures are unreliable/inaccurate when the redundant and
noisy features are not removed. Therefore, we face a dilemma here: one need the
true structures of data to identify the informative features, and one need the
informative features to accurately estimate the true structures of data. To
address this, we propose a unified learning framework which performs structure
learning and feature selection simultaneously. The structures are adaptively
learned from the results of feature selection, and the informative features are
reselected to preserve the refined structures of data. By leveraging the
interactions between these two essential tasks, we are able to capture accurate
structures and select more informative features. Experimental results on many
benchmark data sets demonstrate that the proposed method outperforms many state
of the art unsupervised feature selection methods
P3: Accurate modelling of the optics of high resolution liquid crystal devices including diffractive effects
Finite element based generalized impedance boundary condition for complicated em calculation
In this paper, a finite element based generalized impedance boundary condition (FEM-GIBC) is proposed to solve complicated electromagnetic (EM) problems. Complex structures with arbitrary inhomogeneity and shapes are modeled with the finite element method, and their scattering contributions are transformed to generalized impedance conditions on their boundaries. For each sub-domain, a special GIBC can be established and it is only related to the structures in this domain. Hence, for finite periodic structures, a representative GIBC can be formulated at the boundary of a unit cell. After the GIBC at each boundary is established, the electromagnetic coupling between each impedance boundary can be calculated by the boundary integral equations (BIE) and accelerated with the multilevel fast multipole algorithm (MLFMA). © 2011 IEEE.published_or_final_versionThe 2011 IEEE International Symposium on Antennas and Propagation (APSURSI), Spokane, WA., 3-8 July 2011. In IEEE APSURSI Digest, 2011, p. 2700-270
Evolution of In-Plane Magnetic Anisotropy In Sputtered FeTaN/TaN/FeTaN Sandwich Films
FeTaN/TaN/FeTaN sandwich films, FeTaN/TaN and TaN/FeTaN bilayers were
synthesized by using RF magnetron sputtering. The magnetic properties,
crystalline structures, microstructures and surface morphologies of the
as-deposited samples were characterized using angle-resolved M-H loop tracer,
VSM, XRD, TEM, AES and AFM. An evolution of the in-plane anisotropy was
observed with the changing thickness of the nonmagnetic TaN interlayer in the
FeTaN/TaN/FeTaN sandwiches, such as the easy-hard axis switching and the
appearing of biaxial anisotropy. It is ascribed to three possible mechanisms,
which are interlayer magnetic coupling, stress, and interface roughness,
respectively. Interlayer coupling and stress anisotropies may be the major
reasons to cause the easy-hard axis switching in the sandwiches. Whereas,
magnetostatic and interface anisotropies may be the major reasons to cause
biaxial anisotropy in the sandwiches, in which magnetostatic anisotropy is the
dominant one.Comment: 6 pages, 3 figure
An Evolutionary Algorithm to Generate Real Urban Traffic Flows
In this article we present a strategy based on an evolutionary algorithm to calculate the real vehicle ows in cities according to data from sensors placed in the streets. We have worked with a map imported from OpenStreetMap into the SUMO traffic simulator so that the resulting scenarios can be used to perform different optimizations with the confidence of being able to work with a traffic distribution close to reality. We have compared the results of our algorithm to other competitors and achieved results that replicate the real traffic distribution with a precision higher than 90%.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This research has been partially funded by project number 8.06/5.47.4142 in collaboration with the VSB-Technical University of Ostrava and Universidad de Málaga UMA/FEDER FC14-TIC36, programa de fortalecimiento de las capacidades de I+D+i en las universidades 2014-2015, de la Consejería de Economía, Innovación, Ciencia y Empleo, cofinanciado por el fondo europeo de desarrollo regional (FEDER). Also, partially funded by the Spanish MINECO project TIN2014-57341-R (http://moveon.lcc.uma.es). The authors would like to thank the FEDER of European Union for financial support via project Movilidad Inteligente: Wi-Fi, Rutas y Contaminación (maxCT) of the "Programa Operativo FEDER de Andalucía 2014-2020. We also thank all Agency of Public Works of Andalusia Regional Government staff and researchers for their dedication and professionalism. Daniel H. Stolfi is supported by a FPU grant (FPU13/00954) from the Spanish Ministry of Education, Culture and Sports
An extended view of the Pisces Overdensity from the SCUSS survey
SCUSS is a u-band photometric survey covering about 4000 square degree of the
South Galactic Cap, reaching depths of up to 23 mag. By extending around 1.5
mag deeper than SDSS single-epoch u data, SCUSS is able to probe much a larger
volume of the outer halo, i.e. with SCUSS data blue horizontal branch (BHB)
stars can trace the outer halo of the Milky Way as far as 100-150 kpc.
Utilizing this advantage we combine SCUSS u band with SDSS DR9 gri photometric
bands to identify BHB stars and explore halo substructures. We confirm the
existence of the Pisces overdensity, which is a structure in the outer halo (at
around 80 kpc) that was discovered using RR Lyrae stars. For the first time we
are able to determine its spatial extent, finding that it appears to be part of
a stream with a clear distance gradient. The stream, which is ~5 degrees wide
and stretches along ~25 degrees, consists of 20-30 BHBs with a total
significance of around 6sigma over the background. Assuming we have detected
the entire stream and that the progenitor has fully disrupted, then the number
of BHBs suggests the original system was similar to smaller classical or a
larger ultra-faint dwarf galaxy. On the other hand, if the progenitor still
exists, it can be hunted for by reconstructing its orbit from the distance
gradient of the stream. This new picture of the Pisces overdensity sheds new
light on the origin of this intriguing system.Comment: 8 pages, 4 figures, accepted by Ap
Finite-element-based generalized impedance boundary condition for modeling plasmonic nanostructures
The superior ability of plasmonic structures to manipulate light has propelled their extensive applications in nanophotonics techniques and devices. Computational electromagnetics plays a critical role in characterizing and optimizing the nanometallic structures. In this paper, a general numerical algorithm, which is different from the commonly used discrete dipole approximation, the finite-difference time-domain, and the surface integral equation (SIE) method, is proposed to model plasmonic nanostructures. In this algorithm, the generalized impedance boundary condition (GIBC) based on the finite element method (FEM) is formulated and converted to the SIE. The plasmonic nanostructures with arbitrary inhomogeneity and shapes are modeled by the FEM. Their complex electromagnetic interactions are accurately described by the SIE method. As a result, the near field of plasmonic nanostructures can be accurately calculated. The higher order basis functions, together with the multifrontal massively parallel sparse direct solver, are involved to provide a higher order accurate and fast solver. © 2011 IEEE.published_or_final_versio
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