Goenaga-Jiménez, Miguel A.

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2006 - 200912010 - 20141
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    Spatially adaptive constrained non negative matrix factorization for hyperspectral unmixing
    (2014) Goenaga-Jiménez, Miguel A.; Hunt, Shawn D.; College of Engineering; Velez-Reyes, Miguel; Rodriguez, Domingo; Manian, Vidya; Chinea, J. Danilo; Department of Electrical and Computer Engineering; Santana, Samuel
    This dissertation proposes a spatially adaptive constrained Nonnegative Matrix Factorization (sacNMF) for unmixing of hyperspectral imagery. The image is decomposed into spectrally homogeneous regions using quadtree region partitioning. The constrained Nonnegative Matrix Factorization (cNMF) is applied to the individual image tiles to perform spectral endmember extraction. Spectral endmembers are clustered into endmember classes that better capture the endmember spectral variability across the image. Abundances are estimated using constrained least squares or sparse regression depending on the number of spectral endmembers. It is shown that by decomposing the image into spectrally homogeneous regions, the piecewise convex structure of the spectral cloud and the material mixing constraints imposed by the spatial relation between materials are better captured. A computational framework in MATLAB is developed to implement the proposed approach. The performance of sacNMF is evaluated using real hyperspectral data from the AVIRIS and the AISA sensor. Unmixing results are compared to available ground truth for the images and to results from standard unmixing algorithms, and some algorithms that use spatial information. Experimental results show that sacNMF outperforms the cNMF applied to the entire image (no spatial decomposition) and other standard unmixing algorithms that do not incorporate spatial information. Results also show that sacNMF performs equally or better than unmixing algorithms that incorporate spatial information.
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    An impermeable membrane design for hearing aid applications
    (2006) Goenaga-Jiménez, Miguel A.; Juan-García, Eduardo J.; College of Engineering; Beauchamp-Báez, Gerson; Toledo-Quiñones, Manuel; Department of Electrical and Computer Engineering; Vásquez-Urbano, Pedro
    A common problem when using a hearing aid is the accumulation of earwax, dust and water in the conduit that transmits the sound towards the ear. Hearing aids are damaged when unqualified people try to remove these foreign materials. An impermeable membrane can be placed at the opening of the hearing aid to avoid the entrance of dust or water and accumulation of earwax, without altering the frequency response of the hearing aid. The objective of this research project was to develop a tool to specify membrane mechanical properties and dimensions to achieve a specific frequency response that does not adversely affect the hearing aid’s performance. The frequency response for various types of impermeable membranes were measured experimentally and compared to computer simulations. We found that the membranes with similar output to that of the system without membrane were made of polypropylene and latex, agreeing with the data collected in the simulations made on the computer.