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Learning dictionaries for sparse signal representation
Ettl, Ondřej ; Jirgl, Miroslav (referee) ; Mihálik, Ondrej (advisor)
This thesis focuses on examining data from measurements on a pressure mattress that uses a 30 × 11. sensor grid to collect. This data will be used to train and test learners dictionaries that are built using sparse signal representation. Applied learning methods include the method of optimal direction (MOD) and K-SVD, which uses singular decomposition. The resulting dictionaries for different numbers of iterations or atoms are then used to classify and reconstruction of the test data. Cross-validation determined the true positive ratio of the models, which was then compared with conventional classifiers. These models included Decision trees, KNNs and SVMs. Finally, the ability of the learning dictionaries was verified to filter the error in the corrupted image.
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Sparse Representation of Signals
Mesárošová, Michaela ; Arm, Jakub (referee) ; Jirgl, Miroslav (advisor)
People who are immobile or lie for long periods are at high risk of developing pressure ulcers and require additional care. Therefore, it is necessary to monitor the condition of such persons as simply and efficiently as possible. In this work, we focus on processing the signals provided by a pressure mattress with a 30x11 sensor grid on which a person lays and the possibilities of its use after conversion into sparse representation coefficients. Redundant dictionaries, also known as frames, enable non-orthogonal representation of signals, which leads to a sparse representation of coefficients. Since this approach provides many advantageous properties and is being used in various applications, such as denoising, segmentation, robust transformations, quantum theory, and others, we verified the possibility of classifying a person’s lying position based on a sparse representation. The results were compared with other traditional classification methods, which were found to be less suitable for the classification problem, with the best-achieved result of 92.41 % for CNN, but with high demands on time, design and complexity. The success rate of the classification reached 92.76 %, with fewer demands on design and implementation complexity. The possibilities of classification and reconstruction of an image containing occlusions were also investigated, where the sparse representation proved to be an effective method to remove these defects.
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