Speeding up the combination of multiple descriptors for different boundary conditions

Content-based complex data retrieval is becoming increasingly common in many types of applications. The content of these data is represented by intrinsic characteristics, extracted from them which together with a distance function allows similarity queries. Aimed at reducing the “semantic gap”, characterized by the disagreement between the computational representation of the extracted low-level features and how these data are interpreted by the human perception, the use of multiple descriptors has been the subject of several studies. This paper proposes a new method to carry out the combination of multiple descriptors for different boundary conditions in which the balancing is carried out in pairs, starting by the best candidate descriptor. In the experiments, the proposed method achieved computational cost up to 3650 times smaller than the exhaustive search for the best linear combination of descriptors, keeping almost the same average precision, with variations lower than 0.9%.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Multidimensional Particle Swarm Optimization for Machine Learning

Particle Swarm Optimization (PSO) is a stochastic nature-inspired optimization method. It has been successfully used in several application domains since it was introduced in 1995. It has been especially successful when applied to complicated multimodal problems, where simpler optimization methods, e.g., gradient descent, are not able to find satisfactory results. Multidimensional Particle Swarm Optimization (MD-PSO) and Fractional Global Best Formation (FGBF) are extensions of the basic PSO. MD-PSO allows searching for an optimum also when the solution dimensionality is unknown. With a dedicated dimensional PSO process, MD-PSO can search for optimal solution dimensionality. An interleaved positional PSO process simultaneously searches for the optimal solution in that dimensionality. Both the basic PSO and its multidimensional extension MD-PSO are susceptible to premature convergence. FGBF is a plug-in to (MD-)PSO that can help avoid premature convergence and find desired solutions faster. This thesis focuses on applications of MD-PSO and FGBF in different machine learning tasks.Multiswarm versions of MD-PSO and FGBF are introduced to perform dynamic optimization tasks. In dynamic optimization, the search space slowly changes. The locations of optima move and a former local optimum may transform into a global optimum and vice versa. We exploit multiple swarms to track different optima.In order to apply MD-PSO for clustering tasks, two key questions need to be answered: 1) How to encode the particles to represent different data partitions? 2) How to evaluate the fitness of the particles to evaluate the quality of the solutions proposed by the particle positions? The second question is considered especially carefully in this thesis. An extensive comparison of Clustering Validity Indices (CVIs) commonly used as fitness functions in Particle Swarm Clustering (PSC) is conducted. Furthermore, a novel approach to carry out fitness evaluation, namely Fitness Evaluation with Computational Centroids (FECC) is introduced. FECC gives the same fitness to any particle positions that lead to the same data partition. Therefore, it may save some computational efforts and, above all, it can significantly improve the results obtained by using any of the best performing CVIs as the PSC fitness function.MD-PSO can also be used to evolve different neural networks. The results of training Multilayer Perceptrons (MLPs) using the common Backpropagation (BP) algorithm and a global technique based on PSO are compared. The pros and cons of BP and (MD-)PSO in MLP training are discussed. For training Radial Basis Function Neural Networks (RBFNNs), a novel technique based on class-specific clustering of the training samples is introduced. The proposed approach is compared to the common input and input-output clustering approaches and the benefits of using the class-specific approach are experimentally demonstrated. With the class-specific approach, the training complexity is reduced, while the classification performance of the trained RBFNNs may be improved.Collective Network of Binary Classifiers (CNBC) is an evolutionary semantic classifier consisting of several Networks of Binary Classifiers (NBCs) trained to recognize a certain semantic class. NBCs in turn consist of several Binary Classifiers (BCs), which are trained for a certain feature type. Thanks to its topology and the use of MD-PSO as its evolution technique, incremental training can be easily applied to add new training items, classes, and/or features.In feature synthesis, the objective is to exploit ground truth information to transform the original low-level features into more discriminative ones. To learn an efficient synthesis for a dataset, only a fraction of the data needs to be labeled. The learned synthesis can then be applied on unlabeled data to improve classification or retrieval results. In this thesis, two different feature synthesis techniques are introduced. In the first one, MD-PSO is directly used to find proper arithmetic operations to be applied on the elements of the original low-level feature vectors. In the second approach, feature synthesis is carried out using one-against-all perceptrons. In the latter technique, the best results were obtained when MD-PSO was used to train the perceptrons.In all the mentioned applications excluding MLP training, MD-PSO is used together with FGBF. Overall, MD-PSO and FGBF are indeed versatile tools in machine learning. However, computational limitations constrain their use in currently emerging machine learning systems operating on Big Data. Therefore, in the future, it is necessary to divide complex tasks into smaller subproblems and to conquer the large problems via solving the subproblems where the use of MD-PSO and FGBF becomes feasible. Several applications discussed in this thesis already exploit the divide-and-conquer operation model

On Improving Generalization of CNN-Based Image Classification with Delineation Maps Using the CORF Push-Pull Inhibition Operator

Deployed image classification pipelines are typically dependent on the images captured in real-world environments. This means that images might be affected by different sources of perturbations (e.g. sensor noise in low-light environments). The main challenge arises by the fact that image quality directly impacts the reliability and consistency of classification tasks. This challenge has, hence, attracted wide interest within the computer vision communities. We propose a transformation step that attempts to enhance the generalization ability of CNN models in the presence of unseen noise in the test set. Concretely, the delineation maps of given images are determined using the CORF push-pull inhibition operator. Such an operation transforms an input image into a space that is more robust to noise before being processed by a CNN. We evaluated our approach on the Fashion MNIST data set with an AlexNet model. It turned out that the proposed CORF-augmented pipeline achieved comparable results on noise-free images to those of a conventional AlexNet classification model without CORF delineation maps, but it consistently achieved significantly superior performance on test images perturbed with different levels of Gaussian and uniform noise

Generative Adversarial Network (GAN) for Medical Image Synthesis and Augmentation

Medical image processing aided by artificial intelligence (AI) and machine learning (ML) significantly improves medical diagnosis and decision making. However, the difficulty to access well-annotated medical images becomes one of the main constraints on further improving this technology. Generative adversarial network (GAN) is a DNN framework for data synthetization, which provides a practical solution for medical image augmentation and translation. In this study, we first perform a quantitative survey on the published studies on GAN for medical image processing since 2017. Then a novel adaptive cycle-consistent adversarial network (Ad CycleGAN) is proposed. We respectively use a malaria blood cell dataset (19,578 images) and a COVID-19 chest X-ray dataset (2,347 images) to test the new Ad CycleGAN. The quantitative metrics include mean squared error (MSE), root mean squared error (RMSE), peak signal-to-noise ratio (PSNR), universal image quality index (UIQI), spatial correlation coefficient (SCC), spectral angle mapper (SAM), visual information fidelity (VIF), Frechet inception distance (FID), and the classification accuracy of the synthetic images. The CycleGAN and variant autoencoder (VAE) are also implemented and evaluated as comparison. The experiment results on malaria blood cell images indicate that the Ad CycleGAN generates more valid images compared to CycleGAN or VAE. The synthetic images by Ad CycleGAN or CycleGAN have better quality than those by VAE. The synthetic images by Ad CycleGAN have the highest accuracy of 99.61%. In the experiment on COVID-19 chest X-ray, the synthetic images by Ad CycleGAN or CycleGAN have higher quality than those generated by variant autoencoder (VAE). However, the synthetic images generated through the homogenous image augmentation process have better quality than those synthesized through the image translation process. The synthetic images by Ad CycleGAN have higher accuracy of 95.31% compared to the accuracy of the images by CycleGAN of 93.75%. In conclusion, the proposed Ad CycleGAN provides a new path to synthesize medical images with desired diagnostic or pathological patterns. It is considered a new approach of conditional GAN with effective control power upon the synthetic image domain. The findings offer a new path to improve the deep neural network performance in medical image processing

Medical Image Analysis using Deep Relational Learning

In the past ten years, with the help of deep learning, especially the rapid development of deep neural networks, medical image analysis has made remarkable progress. However, how to effectively use the relational information between various tissues or organs in medical images is still a very challenging problem, and it has not been fully studied. In this thesis, we propose two novel solutions to this problem based on deep relational learning. First, we propose a context-aware fully convolutional network that effectively models implicit relation information between features to perform medical image segmentation. The network achieves the state-of-the-art segmentation results on the Multi Modal Brain Tumor Segmentation 2017 (BraTS2017) and Multi Modal Brain Tumor Segmentation 2018 (BraTS2018) data sets. Subsequently, we propose a new hierarchical homography estimation network to achieve accurate medical image mosaicing by learning the explicit spatial relationship between adjacent frames. We use the UCL Fetoscopy Placenta dataset to conduct experiments and our hierarchical homography estimation network outperforms the other state-of-the-art mosaicing methods while generating robust and meaningful mosaicing result on unseen frames.Comment: arXiv admin note: substantial text overlap with arXiv:2007.0778

Pattern Recognition

A wealth of advanced pattern recognition algorithms are emerging from the interdiscipline between technologies of effective visual features and the human-brain cognition process. Effective visual features are made possible through the rapid developments in appropriate sensor equipments, novel filter designs, and viable information processing architectures. While the understanding of human-brain cognition process broadens the way in which the computer can perform pattern recognition tasks. The present book is intended to collect representative researches around the globe focusing on low-level vision, filter design, features and image descriptors, data mining and analysis, and biologically inspired algorithms. The 27 chapters coved in this book disclose recent advances and new ideas in promoting the techniques, technology and applications of pattern recognition

Políticas de Copyright de Publicações Científicas em Repositórios Institucionais: O Caso do INESC TEC

A progressiva transformação das práticas científicas, impulsionada pelo desenvolvimento das novas Tecnologias de Informação e Comunicação (TIC), têm possibilitado aumentar o acesso à informação, caminhando gradualmente para uma abertura do ciclo de pesquisa. Isto permitirá resolver a longo prazo uma adversidade que se tem colocado aos investigadores, que passa pela existência de barreiras que limitam as condições de acesso, sejam estas geográficas ou financeiras. Apesar da produção científica ser dominada, maioritariamente, por grandes editoras comerciais, estando sujeita às regras por estas impostas, o Movimento do Acesso Aberto cuja primeira declaração pública, a Declaração de Budapeste (BOAI), é de 2002, vem propor alterações significativas que beneficiam os autores e os leitores. Este Movimento vem a ganhar importância em Portugal desde 2003, com a constituição do primeiro repositório institucional a nível nacional. Os repositórios institucionais surgiram como uma ferramenta de divulgação da produção científica de uma instituição, com o intuito de permitir abrir aos resultados da investigação, quer antes da publicação e do próprio processo de arbitragem (preprint), quer depois (postprint), e, consequentemente, aumentar a visibilidade do trabalho desenvolvido por um investigador e a respetiva instituição. O estudo apresentado, que passou por uma análise das políticas de copyright das publicações científicas mais relevantes do INESC TEC, permitiu não só perceber que as editoras adotam cada vez mais políticas que possibilitam o auto-arquivo das publicações em repositórios institucionais, como também que existe todo um trabalho de sensibilização a percorrer, não só para os investigadores, como para a instituição e toda a sociedade. A produção de um conjunto de recomendações, que passam pela implementação de uma política institucional que incentive o auto-arquivo das publicações desenvolvidas no âmbito institucional no repositório, serve como mote para uma maior valorização da produção científica do INESC TEC.The progressive transformation of scientific practices, driven by the development of new Information and Communication Technologies (ICT), which made it possible to increase access to information, gradually moving towards an opening of the research cycle. This opening makes it possible to resolve, in the long term, the adversity that has been placed on researchers, which involves the existence of barriers that limit access conditions, whether geographical or financial. Although large commercial publishers predominantly dominate scientific production and subject it to the rules imposed by them, the Open Access movement whose first public declaration, the Budapest Declaration (BOAI), was in 2002, proposes significant changes that benefit the authors and the readers. This Movement has gained importance in Portugal since 2003, with the constitution of the first institutional repository at the national level. Institutional repositories have emerged as a tool for disseminating the scientific production of an institution to open the results of the research, both before publication and the preprint process and postprint, increase the visibility of work done by an investigator and his or her institution. The present study, which underwent an analysis of the copyright policies of INESC TEC most relevant scientific publications, allowed not only to realize that publishers are increasingly adopting policies that make it possible to self-archive publications in institutional repositories, all the work of raising awareness, not only for researchers but also for the institution and the whole society. The production of a set of recommendations, which go through the implementation of an institutional policy that encourages the self-archiving of the publications developed in the institutional scope in the repository, serves as a motto for a greater appreciation of the scientific production of INESC TEC