62,796 research outputs found
Comparison between Oja's and BCM neural networks models in finding useful projections in high-dimensional spaces
This thesis presents the concept of a neural network starting from its corresponding biological model, paying particular attention to the learning algorithms proposed by Oja and Bienenstock Cooper & Munro. A brief introduction to Data Analysis is then performed, with particular reference to the Principal Components Analysis and Singular Value Decomposition.
The two previously introduced algorithms are then dealt with more thoroughly, going to study in particular their connections with data analysis. Finally, it is proposed to use the Singular Value Decomposition as a method for obtaining stationary points in the BCM algorithm, in the case of linearly dependent inputs
Mesh-based Autoencoders for Localized Deformation Component Analysis
Spatially localized deformation components are very useful for shape analysis
and synthesis in 3D geometry processing. Several methods have recently been
developed, with an aim to extract intuitive and interpretable deformation
components. However, these techniques suffer from fundamental limitations
especially for meshes with noise or large-scale deformations, and may not
always be able to identify important deformation components. In this paper we
propose a novel mesh-based autoencoder architecture that is able to cope with
meshes with irregular topology. We introduce sparse regularization in this
framework, which along with convolutional operations, helps localize
deformations. Our framework is capable of extracting localized deformation
components from mesh data sets with large-scale deformations and is robust to
noise. It also provides a nonlinear approach to reconstruction of meshes using
the extracted basis, which is more effective than the current linear
combination approach. Extensive experiments show that our method outperforms
state-of-the-art methods in both qualitative and quantitative evaluations
SOM-based algorithms for qualitative variables
It is well known that the SOM algorithm achieves a clustering of data which
can be interpreted as an extension of Principal Component Analysis, because of
its topology-preserving property. But the SOM algorithm can only process
real-valued data. In previous papers, we have proposed several methods based on
the SOM algorithm to analyze categorical data, which is the case in survey
data. In this paper, we present these methods in a unified manner. The first
one (Kohonen Multiple Correspondence Analysis, KMCA) deals only with the
modalities, while the two others (Kohonen Multiple Correspondence Analysis with
individuals, KMCA\_ind, Kohonen algorithm on DISJonctive table, KDISJ) can take
into account the individuals, and the modalities simultaneously.Comment: Special Issue apr\`{e}s WSOM 03 \`{a} Kitakiush
Machine Learning in Wireless Sensor Networks: Algorithms, Strategies, and Applications
Wireless sensor networks monitor dynamic environments that change rapidly
over time. This dynamic behavior is either caused by external factors or
initiated by the system designers themselves. To adapt to such conditions,
sensor networks often adopt machine learning techniques to eliminate the need
for unnecessary redesign. Machine learning also inspires many practical
solutions that maximize resource utilization and prolong the lifespan of the
network. In this paper, we present an extensive literature review over the
period 2002-2013 of machine learning methods that were used to address common
issues in wireless sensor networks (WSNs). The advantages and disadvantages of
each proposed algorithm are evaluated against the corresponding problem. We
also provide a comparative guide to aid WSN designers in developing suitable
machine learning solutions for their specific application challenges.Comment: Accepted for publication in IEEE Communications Surveys and Tutorial
Zeeman-Tomography of the Solar Photosphere -- 3-Dimensional Surface Structures Retrieved from Hinode Observations
AIMS :The thermodynamic and magnetic field structure of the solar photosphere
is analyzed by means of a novel 3-dimensional spectropolarimetric inversion and
reconstruction technique. METHODS : On the basis of high-resolution,
mixed-polarity magnetoconvection simulations, we used an artificial neural
network (ANN) model to approximate the nonlinear inverse mapping between
synthesized Stokes spectra and the underlying stratification of atmospheric
parameters like temperature, line-of-sight (LOS) velocity and LOS magnetic
field. This approach not only allows us to incorporate more reliable physics
into the inversion process, it also enables the inversion on an absolute
geometrical height scale, which allows the subsequent combination of individual
line-of-sight stratifications to obtain a complete 3-dimensional reconstruction
(tomography) of the observed area. RESULTS : The magnetoconvection simulation
data, as well as the ANN inversion, have been properly processed to be
applicable to spectropolarimetric observations from the Hinode satellite. For
the first time, we show 3-dimensional tomographic reconstructions (temperature,
LOS velocity, and LOS magnetic field) of a quiet sun region observed by Hinode.
The reconstructed area covers a field of approximately 12000 by 12000 km and a
height range of 510 km in the photosphere. An enormous variety of small and
large scale structures can be identified in the 3-D reconstructions. The
low-flux region (B_{mag} = 20G) we analyzed exhibits a number of "tube-like"
magnetic structures with field strengths of several hundred Gauss. Most of
these structures rapidly loose their strength with height and only a few larger
structures can retain a higher field strength to the upper layers of the
photosphere.Comment: accepted for A&A Letter
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