3,511 research outputs found
A hybrid algorithm for Bayesian network structure learning with application to multi-label learning
We present a novel hybrid algorithm for Bayesian network structure learning,
called H2PC. It first reconstructs the skeleton of a Bayesian network and then
performs a Bayesian-scoring greedy hill-climbing search to orient the edges.
The algorithm is based on divide-and-conquer constraint-based subroutines to
learn the local structure around a target variable. We conduct two series of
experimental comparisons of H2PC against Max-Min Hill-Climbing (MMHC), which is
currently the most powerful state-of-the-art algorithm for Bayesian network
structure learning. First, we use eight well-known Bayesian network benchmarks
with various data sizes to assess the quality of the learned structure returned
by the algorithms. Our extensive experiments show that H2PC outperforms MMHC in
terms of goodness of fit to new data and quality of the network structure with
respect to the true dependence structure of the data. Second, we investigate
H2PC's ability to solve the multi-label learning problem. We provide
theoretical results to characterize and identify graphically the so-called
minimal label powersets that appear as irreducible factors in the joint
distribution under the faithfulness condition. The multi-label learning problem
is then decomposed into a series of multi-class classification problems, where
each multi-class variable encodes a label powerset. H2PC is shown to compare
favorably to MMHC in terms of global classification accuracy over ten
multi-label data sets covering different application domains. Overall, our
experiments support the conclusions that local structural learning with H2PC in
the form of local neighborhood induction is a theoretically well-motivated and
empirically effective learning framework that is well suited to multi-label
learning. The source code (in R) of H2PC as well as all data sets used for the
empirical tests are publicly available.Comment: arXiv admin note: text overlap with arXiv:1101.5184 by other author
Automatic speech feature extraction using a convolutional restricted boltzmann machine
A dissertation submitted to the Faculty of Science, University of
the Witwatersrand, in fulfillment of the requirements for the degree
of Master of Science
2017Restricted Boltzmann Machines (RBMs) are a statistical learning concept that can
be interpreted as Arti cial Neural Networks. They are capable of learning, in an
unsupervised fashion, a set of features with which to describe a data set. Connected
in series RBMs form a model called a Deep Belief Network (DBN), learning abstract
feature combinations from lower layers. Convolutional RBMs (CRBMs) are a variation
on the RBM architecture in which the learned features are kernels that are convolved
across spatial portions of the input data to generate feature maps identifying if a feature
is detected in a portion of the input data. Features extracted from speech audio data
by a trained CRBM have recently been shown to compete with the state of the art
for a number of speaker identi cation tasks. This project implements a similar CRBM
architecture in order to verify previous work, as well as gain insight into Digital Signal
Processing (DSP), Generative Graphical Models, unsupervised pre-training of Arti cial
Neural Networks, and Machine Learning classi cation tasks. The CRBM architecture
is trained on the TIMIT speech corpus and the learned features veri ed by using them
to train a linear classi er on tasks such as speaker genetic sex classi cation and speaker
identi cation. The implementation is quantitatively proven to successfully learn and
extract a useful feature representation for the given classi cation tasksMT 201
A Comprehensive Survey of Deep Learning in Remote Sensing: Theories, Tools and Challenges for the Community
In recent years, deep learning (DL), a re-branding of neural networks (NNs),
has risen to the top in numerous areas, namely computer vision (CV), speech
recognition, natural language processing, etc. Whereas remote sensing (RS)
possesses a number of unique challenges, primarily related to sensors and
applications, inevitably RS draws from many of the same theories as CV; e.g.,
statistics, fusion, and machine learning, to name a few. This means that the RS
community should be aware of, if not at the leading edge of, of advancements
like DL. Herein, we provide the most comprehensive survey of state-of-the-art
RS DL research. We also review recent new developments in the DL field that can
be used in DL for RS. Namely, we focus on theories, tools and challenges for
the RS community. Specifically, we focus on unsolved challenges and
opportunities as it relates to (i) inadequate data sets, (ii)
human-understandable solutions for modelling physical phenomena, (iii) Big
Data, (iv) non-traditional heterogeneous data sources, (v) DL architectures and
learning algorithms for spectral, spatial and temporal data, (vi) transfer
learning, (vii) an improved theoretical understanding of DL systems, (viii)
high barriers to entry, and (ix) training and optimizing the DL.Comment: 64 pages, 411 references. To appear in Journal of Applied Remote
Sensin
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