388 research outputs found
Sparse machine learning methods with applications in multivariate signal processing
This thesis details theoretical and empirical work that draws from two main subject areas: Machine
Learning (ML) and Digital Signal Processing (DSP). A unified general framework is given for the application
of sparse machine learning methods to multivariate signal processing. In particular, methods that
enforce sparsity will be employed for reasons of computational efficiency, regularisation, and compressibility.
The methods presented can be seen as modular building blocks that can be applied to a variety
of applications. Application specific prior knowledge can be used in various ways, resulting in a flexible
and powerful set of tools. The motivation for the methods is to be able to learn and generalise from a set
of multivariate signals.
In addition to testing on benchmark datasets, a series of empirical evaluations on real world
datasets were carried out. These included: the classification of musical genre from polyphonic audio
files; a study of how the sampling rate in a digital radar can be reduced through the use of Compressed
Sensing (CS); analysis of human perception of different modulations of musical key from
Electroencephalography (EEG) recordings; classification of genre of musical pieces to which a listener
is attending from Magnetoencephalography (MEG) brain recordings. These applications demonstrate
the efficacy of the framework and highlight interesting directions of future research
Bandwidth Allocation Mechanism based on Users' Web Usage Patterns for Campus Networks
Managing the bandwidth in campus networks becomes a challenge in recent years. The limited bandwidth resource and continuous growth of users make the IT managers think on the strategies concerning bandwidth allocation. This paper introduces a mechanism for allocating bandwidth based on the users’ web usage patterns. The main purpose is to set a higher bandwidth to the users who are inclined to browsing educational websites compared to those who are not. In attaining this proposed technique, some stages need to be done. These are the preprocessing of the weblogs, class labeling of the dataset, computation of the feature subspaces, training for the development of the ANN for LDA/GSVD algorithm, visualization, and bandwidth allocation. The proposed method was applied to real weblogs from university’s proxy servers. The results indicate that the proposed method is useful in classifying those users who used the internet in an educational way and those who are not. Thus, the developed ANN for LDA/GSVD algorithm outperformed the existing algorithm up to 50% which indicates that this approach is efficient. Further, based on the results, few users browsed educational contents. Through this mechanism, users will be encouraged to use the internet for educational purposes. Moreover, IT managers can make better plans to optimize the distribution of bandwidth
Dimension-reduction and discrimination of neuronal multi-channel signals
Dimensionsreduktion und Trennung neuronaler Multikanal-Signale
Surface motion prediction and mapping for road infrastructures management by PS-InSAR measurements and machine learning algorithms
This paper introduces a methodology for predicting and mapping surface motion beneath road pavement structures caused by environmental factors. Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) measurements, geospatial analyses, and Machine Learning Algorithms (MLAs) are employed for achieving the purpose. Two single learners, i.e., Regression Tree (RT) and Support Vector Machine (SVM), and two ensemble learners, i.e., Boosted Regression Trees (BRT) and Random Forest (RF) are utilized for estimating the surface motion ratio in terms of mm/year over the Province of Pistoia (Tuscany Region, central Italy, 964 km2), in which strong subsidence phenomena have occurred. The interferometric process of 210 Sentinel-1 images from 2014 to 2019 allows exploiting the average displacements of 52,257 Persistent Scatterers as output targets to predict. A set of 29 environmental-related factors are preprocessed by SAGA-GIS, version 2.3.2, and ESRI ArcGIS, version 10.5, and employed as input features. Once the dataset has been prepared, three wrapper feature selection approaches (backward, forward, and bi-directional) are used for recognizing the set of most relevant features to be used in the modeling. A random splitting of the dataset in 70% and 30% is implemented to identify the training and test set. Through a Bayesian Optimization Algorithm (BOA) and a 10-Fold Cross-Validation (CV), the algorithms are trained and validated. Therefore, the Predictive Performance of MLAs is evaluated and compared by plotting the Taylor Diagram. Outcomes show that SVM and BRT are the most suitable algorithms; in the test phase, BRT has the highest Correlation Coefficient (0.96) and the lowest Root Mean Square Error (0.44 mm/year), while the SVM has the lowest difference between the standard deviation of its predictions (2.05 mm/year) and that of the reference samples (2.09 mm/year). Finally, algorithms are used for mapping surface motion over the study area. We propose three case studies on critical stretches of two-lane rural roads for evaluating the reliability of the procedure. Road authorities could consider the proposed methodology for their monitoring, management, and planning activities
Digital Image Processing
This book presents several recent advances that are related or fall under the umbrella of 'digital image processing', with the purpose of providing an insight into the possibilities offered by digital image processing algorithms in various fields. The presented mathematical algorithms are accompanied by graphical representations and illustrative examples for an enhanced readability. The chapters are written in a manner that allows even a reader with basic experience and knowledge in the digital image processing field to properly understand the presented algorithms. Concurrently, the structure of the information in this book is such that fellow scientists will be able to use it to push the development of the presented subjects even further
Hyperspectral Image Classification for Remote Sensing
This thesis is focused on deep learning-based, pixel-wise classification of hyperspectral images (HSI) in remote sensing. Although presence of many spectral bands in an HSI provides a valuable source of features, dimensionality reduction is often performed in the pre-processing step to reduce the correlation between bands. Most of the deep learning-based classification algorithms use unsupervised dimensionality reduction methods such as principal component analysis (PCA).
However, in this thesis in order to take advantage of class discriminatory information in the dimensionality reduction step as well as power of deep neural network we propose a new method that combines a supervised dimensionality reduction technique, principal component discriminant analysis (PCDA) and deep learning.
Furthermore, in this thesis in order to overcome the common problem of inadequacy of labeled samples in remote sensing HSI classification, we propose a spectral perturbation method to augment the number of training samples and improve the classification results.
Since combining spatial and spectral information can dramatically improve HSI classification results, in this thesis we propose a new spectral-spatial feature vector. In our feature vector, based on their proximity to the dominant edges, neighbors of a target pixel have different contributions in forming the spatial information. To obtain such a proximity measure, we propose a method to compute the distance transform image of the input HSI. We then improved the spatial feature vector by adding extended multi attribute profile (EMAP) features to it. Classification accuracies demonstrate the effectiveness of our proposed method in generating a powerful, expressive spectral-spatial feature vector
Sparse and Redundant Representations for Inverse Problems and Recognition
Sparse and redundant representation of data enables the
description of signals as linear combinations of a few atoms from
a dictionary. In this dissertation, we study applications of
sparse and redundant representations in inverse problems and
object recognition. Furthermore, we propose two novel imaging
modalities based on the recently introduced theory of Compressed
Sensing (CS).
This dissertation consists of four major parts. In the first part
of the dissertation, we study a new type of deconvolution
algorithm that is based on estimating the image from a shearlet
decomposition. Shearlets provide a multi-directional and
multi-scale decomposition that has been mathematically shown to
represent distributed discontinuities such as edges better than
traditional wavelets. We develop a deconvolution algorithm that
allows for the approximation inversion operator to be controlled
on a multi-scale and multi-directional basis. Furthermore, we
develop a method for the automatic determination of the threshold
values for the noise shrinkage for each scale and direction
without explicit knowledge of the noise variance using a
generalized cross validation method.
In the second part of the dissertation, we study a reconstruction
method that recovers highly undersampled images assumed to have a
sparse representation in a gradient domain by using partial
measurement samples that are collected in the Fourier domain. Our
method makes use of a robust generalized Poisson solver that
greatly aids in achieving a significantly improved performance
over similar proposed methods. We will demonstrate by experiments
that this new technique is more flexible to work with either
random or restricted sampling scenarios better than its
competitors.
In the third part of the dissertation, we introduce a novel
Synthetic Aperture Radar (SAR) imaging modality which can provide
a high resolution map of the spatial distribution of targets and
terrain using a significantly reduced number of needed transmitted
and/or received electromagnetic waveforms. We demonstrate that
this new imaging scheme, requires no new hardware components and
allows the aperture to be compressed. Also, it
presents many new applications and advantages which include strong
resistance to countermesasures and interception, imaging much
wider swaths and reduced on-board storage requirements.
The last part of the dissertation deals with object recognition
based on learning dictionaries for simultaneous sparse signal
approximations and feature extraction. A dictionary is learned
for each object class based on given training examples which
minimize the representation error with a sparseness constraint. A
novel test image is then projected onto the span of the atoms in
each learned dictionary. The residual vectors along with the
coefficients are then used for recognition. Applications to
illumination robust face recognition and automatic target
recognition are presented
Density Preserving Sampling: Robust and Efficient Alternative to Cross-validation for Error Estimation
Estimation of the generalization ability of a classi-
fication or regression model is an important issue, as it indicates
the expected performance on previously unseen data and is
also used for model selection. Currently used generalization
error estimation procedures, such as cross-validation (CV) or
bootstrap, are stochastic and, thus, require multiple repetitions
in order to produce reliable results, which can be computationally
expensive, if not prohibitive. The correntropy-inspired density-
preserving sampling (DPS) procedure proposed in this paper
eliminates the need for repeating the error estimation procedure
by dividing the available data into subsets that are guaranteed to
be representative of the input dataset. This allows the production
of low-variance error estimates with an accuracy comparable to
10 times repeated CV at a fraction of the computations required
by CV. This method can also be used for model ranking and
selection. This paper derives the DPS procedure and investigates
its usability and performance using a set of public benchmark
datasets and standard classifier
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