1,409 research outputs found
Application of probabilistic modeling and automated machine learning framework for high-dimensional stress field
Modern computational methods, involving highly sophisticated mathematical
formulations, enable several tasks like modeling complex physical phenomenon,
predicting key properties and design optimization. The higher fidelity in these
computer models makes it computationally intensive to query them hundreds of
times for optimization and one usually relies on a simplified model albeit at
the cost of losing predictive accuracy and precision. Towards this, data-driven
surrogate modeling methods have shown a lot of promise in emulating the
behavior of the expensive computer models. However, a major bottleneck in such
methods is the inability to deal with high input dimensionality and the need
for relatively large datasets. With such problems, the input and output
quantity of interest are tensors of high dimensionality. Commonly used
surrogate modeling methods for such problems, suffer from requirements like
high number of computational evaluations that precludes one from performing
other numerical tasks like uncertainty quantification and statistical analysis.
In this work, we propose an end-to-end approach that maps a high-dimensional
image like input to an output of high dimensionality or its key statistics. Our
approach uses two main framework that perform three steps: a) reduce the input
and output from a high-dimensional space to a reduced or low-dimensional space,
b) model the input-output relationship in the low-dimensional space, and c)
enable the incorporation of domain-specific physical constraints as masks. In
order to accomplish the task of reducing input dimensionality we leverage
principal component analysis, that is coupled with two surrogate modeling
methods namely: a) Bayesian hybrid modeling, and b) DeepHyper's deep neural
networks. We demonstrate the applicability of the approach on a problem of a
linear elastic stress field data.Comment: 17 pages, 16 figures, IDETC Conference Submissio
Evaluation and implementation of an auto-encoder for compression of satellite images in the ScOSA project
The thesis evaluates the efficiency of various autoencoder neural networks for image compression regarding satellite imagery. The results highlight the evaluation and implementation of autoencoder architectures and the procedures required to deploy neural networks to reliable embedded devices. The developed autoencoders evaluated, targeting a ZYNQ 7020 FPGA (Field Programmable Gate Array) and a ZU7EV FPGA
Evaluation and implementation of an auto-encoder for compression of satellite images in the ScOSA project
The thesis evaluates the efficiency of various autoencoder neural networks for image compression regarding satellite imagery. The results highlight the evaluation and implementation of autoencoder architectures and the procedures required to deploy neural networks to reliable embedded devices. The developed autoencoders evaluated, targeting a ZYNQ 7020 FPGA (Field Programmable Gate Array) and a ZU7EV FPGA
Machine Learning for Fluid Mechanics
The field of fluid mechanics is rapidly advancing, driven by unprecedented
volumes of data from field measurements, experiments and large-scale
simulations at multiple spatiotemporal scales. Machine learning offers a wealth
of techniques to extract information from data that could be translated into
knowledge about the underlying fluid mechanics. Moreover, machine learning
algorithms can augment domain knowledge and automate tasks related to flow
control and optimization. This article presents an overview of past history,
current developments, and emerging opportunities of machine learning for fluid
mechanics. It outlines fundamental machine learning methodologies and discusses
their uses for understanding, modeling, optimizing, and controlling fluid
flows. The strengths and limitations of these methods are addressed from the
perspective of scientific inquiry that considers data as an inherent part of
modeling, experimentation, and simulation. Machine learning provides a powerful
information processing framework that can enrich, and possibly even transform,
current lines of fluid mechanics research and industrial applications.Comment: To appear in the Annual Reviews of Fluid Mechanics, 202
A survey of outlier detection methodologies
Outlier detection has been used for centuries to detect and, where appropriate, remove anomalous observations from data. Outliers arise due to mechanical faults, changes in system behaviour, fraudulent behaviour, human error, instrument error or simply through natural deviations in populations. Their detection can identify system faults and fraud before they escalate with potentially catastrophic consequences. It can identify errors and remove their contaminating effect on the data set and as such to purify the data for processing. The original outlier detection methods were arbitrary but now, principled and systematic techniques are used, drawn from the full gamut of Computer Science and Statistics. In this paper, we introduce a survey of contemporary techniques for outlier detection. We identify their respective motivations and distinguish their advantages and disadvantages in a comparative review
Design and Real-World Application of Novel Machine Learning Techniques for Improving Face Recognition Algorithms
Recent progress in machine learning has made possible the development of real-world face recognition applications that can match face images as good as or better than humans. However, several challenges remain unsolved. In this PhD thesis, some of these challenges are studied and novel machine learning techniques to improve the performance of real-world face recognition applications are proposed.
Current face recognition algorithms based on deep learning techniques are able to achieve outstanding accuracy when dealing with face images taken in unconstrained environments. However, training these algorithms is often costly due to the very large datasets and the high computational resources needed. On the other hand, traditional methods for face recognition are better suited when these requirements cannot be satisfied. This PhD thesis presents new techniques for both traditional and deep learning methods. In particular, a novel traditional face recognition method that combines texture and shape features together with subspace representation techniques is first presented. The proposed method is lightweight and can be trained quickly with small datasets. This method is used for matching face images scanned from identity documents against face images stored in the biometric chip of such documents. Next, two new techniques to increase the performance of face recognition methods based on convolutional neural networks are presented. Specifically, a novel training strategy that increases face recognition accuracy when dealing with face images presenting occlusions, and a new loss function that improves the performance of the triplet loss function are proposed. Finally, the problem of collecting large face datasets is considered, and a novel method based on generative adversarial networks to synthesize both face images of existing subjects in a dataset and face images of new subjects is proposed. The accuracy of existing face recognition algorithms can be increased by training with datasets augmented with the synthetic face images generated by the proposed method. In addition to the main contributions, this thesis provides a comprehensive literature review of face recognition methods and their evolution over the years.
A significant amount of the work presented in this PhD thesis is the outcome of a 3-year-long research project partially funded by Innovate UK as part of a Knowledge Transfer Partnership between University of Hertfordshire and IDscan Biometrics Ltd (partnership number: 009547)
Modular Deep Learning
Transfer learning has recently become the dominant paradigm of machine
learning. Pre-trained models fine-tuned for downstream tasks achieve better
performance with fewer labelled examples. Nonetheless, it remains unclear how
to develop models that specialise towards multiple tasks without incurring
negative interference and that generalise systematically to non-identically
distributed tasks. Modular deep learning has emerged as a promising solution to
these challenges. In this framework, units of computation are often implemented
as autonomous parameter-efficient modules. Information is conditionally routed
to a subset of modules and subsequently aggregated. These properties enable
positive transfer and systematic generalisation by separating computation from
routing and updating modules locally. We offer a survey of modular
architectures, providing a unified view over several threads of research that
evolved independently in the scientific literature. Moreover, we explore
various additional purposes of modularity, including scaling language models,
causal inference, programme induction, and planning in reinforcement learning.
Finally, we report various concrete applications where modularity has been
successfully deployed such as cross-lingual and cross-modal knowledge transfer.
Related talks and projects to this survey, are available at
https://www.modulardeeplearning.com/
Modularity and Neural Integration in Large-Vocabulary Continuous Speech Recognition
This Thesis tackles the problems of modularity in Large-Vocabulary Continuous Speech Recognition with use of Neural Network
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