DEVELOPMENT AND EVALUATION OF ENVELOPE, SPECTRAL AND TIME ENHANCEMENT ALGORITHMS FOR AUDITORY NEUROPATHY

Auditory neuropathy (AN) is a hearing disorder that reduces the ability to detect temporal cues in speech, thus leading to deprived speech perception. Traditional amplification and frequency shifting techniques used in modern hearing aids are not suitable to assist individuals with AN due to the unique symptoms that result from the disorder. This study proposes a method for combining both speech envelope enhancement and time scaling to combine the proven benefits of each algorithm. In addition, spectral enhancement is cascaded with envelope and time enhancement to address the poor frequency discrimination in AN. The proposed speech enhancement strategy was evaluated using an AN simulator with normal hearing listeners under varying degrees of AN severity. The results showed a significant increase in word recognition scores for time scaling and envelope enhancement over envelope enhancement alone. Furthermore, the addition of spectral enhancement resulted in further increase in word recognition at profound AN severity

A numerical study on turbulence generation and decay in a suddenly stopped Taylor Couette flow

In this study are presented the numerical results obtained when simulating the abruptly stoppage of the outer cylinder in a Taylor-Couette system where the inner cylinder is static. The results are compared with the experimental observations published in the Journal of Fluid Mechanics.En este estudio se presentan los resultados numéricos obtenidos al simular un sistema Taylor-Couette en el cual el cilindro exterior se para mientras que el cilindro interior está estático. Los resultados se comparan con las observaciones experimentales ya publicas en el Journal of Fluid MechanicsEn aquest estudi es presenta els resultats numèrics quan es simula un sistema Taylor-Couette en el qual es para el cilindre exterior de cop, tenint el cilindre interior sempre estàtic. Els resultats es comparan amb les observacions experimentals ja obtingudes anteriorment, publicades al Journal of Fluid Mechanics

Setting the quantum integrand of M-theory

In anomaly-free quantum field theories the integrand in the bosonic functional integral--the exponential of the effective action after integrating out fermions--is often defined only up to a phase without an additional choice. We term this choice ``setting the quantum integrand''. In the low-energy approximation to M-theory the E(8)-model for the C-field allows us to set the quantum integrand using geometric index theory. We derive mathematical results of independent interest about pfaffians of Dirac operators in 8k+3 dimensions, both on closed manifolds and manifolds with boundary. These theorems are used to set the quantum integrand of M-theory for closed manifolds and for compact manifolds with either temporal (global) or spatial (local) boundary conditions. In particular, we show that M-theory makes sense on arbitrary 11-manifolds with spatial boundary, generalizing the construction of heterotic M-theory on cylinders.Comment: 52 pages; revised version for publication in Commun. Math. Phys. corrects a few typo

Automatic Computation of Potential Tumor Regions in Cancer Detection using Fractal analysis techniques

Radiology is one of the most active and technologically advanced fields in medicine. It was born from the most advanced physics concepts, and it became a reality thanks to the state-of-the art of electronics and computer science. The advances of medical imaging have made possible the early detection and diagnosis of multiple affections that were not at our reach just some years ago. However, progress comes with a price. The raise of imaging machinery has implied that the number and complexity of technical parameters have grown in the same proportion, and the amount of information generated by the imaging devices is much larger. In spite of technical progress, medical imaging supply chain invariantly finalizes at the same point: a human being, typically the radiologist or medical practitioner in charge to interpret the obtained images. At the end, it is not unusual that human operators check one by one two hundred slices of a Computer Tomography coming from a single routine control scanner. It is not surprising if some tiny detail is missed when searching for “something wrong”, especially after some hours of continuous visualization, or due to insufficient time budgets. One of the milestones of this work is providing the reader with an overview of the field of volumetric medical imaging, in order to achieve a sufficient understanding of the problematic involving this discipline. This master thesis is mainly an exercise of exploration of a set of techniques, based on fractal analysis, aimed to provide any sort of computational help to the personal in charge of the interpretation of volumetric medical images. Fractal analysis is a set of powerful tools which have been applied successfully in multiple fields. The thesis goal has been to apply these techniques within the scope of tumor detection on liver tissues and evaluate their efficiency and adequateness

Estimation of future extreme rainfall in Barcelona (Spain) under monofractal hypothesis

Climate change effects on subdaily rainfall (from 5¿min to a few hours) can hardly be measured in mid-latitude climates due to the high natural variability of the precipitation patterns and their effects on local topography. The goal of this study was to obtain change projections of intensity–duration–frequency (IDF) curves, for up to 2-h precipitation events, comparing two approaches that use the daily outputs of the downscaled Coupled Model Intercomparison Project Phase 5 (CMIP5) multi-model projections: (a) direct scaling of the expected probable precipitation, from 2-year to 500-year return periods of daily rainfall and (b) a new semi-stochastic approach, built by combining the physically forced outputs of climate models (on a daily scale) and stochastic simulation given by the probability distribution of a concentration index (n-index) for individual rainfall events (on a subdaily scale). The approaches were applied to a set of 27 stations located around Barcelona, Spain, including a long reference series (with 5-min rainfall records since 1927), representing the highly variable Mediterranean climate. The validation process showed a systematic error (bias) generally smaller than 10%, especially for rainfall extreme events with durations of less than 2¿h. The concentration n-index and IDF curves were projected by 10 downscaled CMIP5 climate models under 2 emission scenarios (RCP4.5 and RCP8.5), obtaining a consensual increase in both relative concentration and absolute intensities in Barcelona. Ensemble projection of rainfall concentration (n-index) showed an increase up to 10% by 2071–2100 and about 20% (15%–30% range) for maximum intensities of 2-year to 500-year return periods. Results provide robustness in decision-making regarding the design of stormwater management infrastructure at a local scale.This study has been partially developed under the ‘RESilience to cope with Climate Change in Urban arEas’ (RESCCUE) project, funded by the European Union's Horizon 2020 Research and Innovation Program (Grant agreement number: 700174) and under the ‘Improving ClimAte Resilience of crItical Assets’ (ICARIA) project, funded by the European Union's Horizon Europe, Cluster 5—Climate, Energy and Mobility (EC Project Code: 101093806). The work is also supported by the Ministry for the Ecological Transition and the Demographic Challenge (MITECO) of the Spanish Government under the two phases of the ‘IMpacts of climate change on wetlands Affected by GroUndwAter (IMAGUA)’ project. Finally, the authors would like to thank the reviewers for their thoughtful comments.Peer ReviewedPostprint (published version

Coherency analysis between SGs at BFO and Strasbourg

The twin satellite GRACE mission has provided high-precision, spaceborne measurements of the Earth time-varying gravity field. Independent validation of the GRACE derived gravity field models using superconducting gravimeters (SGs) has been discussed controversially in the literature, since SGs provide gravity observations at a stationary point with high-precision and low instrumental drift. To evaluate whether ground based gravity observations can be used to validate GRACE gravity field models we compare 3 years of continuous SG data from the Strasbourg Observatory (ST) and the Black Forest Observatory (BFO). These two stations are only 57.5 km apart which is twelve times smaller than the shortest resolved wavelength (about 700 km) in the weekly GRACE gravity field models. Thus, since GRACE derived models predict essentially the same temporal gravity field variations for both ST and BFO we require high correlation between ST and BFO at periods longer than one week. A lack of correlation at these long periods would point to more local sources of these gravity variations and would make a GRACE validation impossible, if BFO and ST are representatives of typical GGP stations. The coherence between the residuals of the two stations ranges from 0.65 to 0.9 at periods from 15 days to 30 days. We further investigate the local hydrology of the SG stations which may not be embodied in the GRACE predictions. Local hydrological signals are known to be a major signal in gravity residuals at period longer than 1 day. We inspect locally recorded precipitation and global hydrological models data in this context. The difference of residuals between the two stations is enlarged after correcting for the local hydrological effects. Correcting for the local hydrological effects using GLDAS model or ERA-interim does not improve the coherence from 15 days to 30 days significantly. The trends of SG residual variations before correcting for local hydrology agree well with GRACE predictions. We suggest more sophisticated measuring and modelling of local hydrology to better estimate the hydrological effect

Face recognition by means of advanced contributions in machine learning

Face recognition (FR) has been extensively studied, due to both scientific fundamental challenges and current and potential applications where human identification is needed. FR systems have the benefits of their non intrusiveness, low cost of equipments and no useragreement requirements when doing acquisition, among the most important ones. Nevertheless, despite the progress made in last years and the different solutions proposed, FR performance is not yet satisfactory when more demanding conditions are required (different viewpoints, blocked effects, illumination changes, strong lighting states, etc). Particularly, the effect of such non-controlled lighting conditions on face images leads to one of the strongest distortions in facial appearance. This dissertation addresses the problem of FR when dealing with less constrained illumination situations. In order to approach the problem, a new multi-session and multi-spectral face database has been acquired in visible, Near-infrared (NIR) and Thermal infrared (TIR) spectra, under different lighting conditions. A theoretical analysis using information theory to demonstrate the complementarities between different spectral bands have been firstly carried out. The optimal exploitation of the information provided by the set of multispectral images has been subsequently addressed by using multimodal matching score fusion techniques that efficiently synthesize complementary meaningful information among different spectra. Due to peculiarities in thermal images, a specific face segmentation algorithm has been required and developed. In the final proposed system, the Discrete Cosine Transform as dimensionality reduction tool and a fractional distance for matching were used, so that the cost in processing time and memory was significantly reduced. Prior to this classification task, a selection of the relevant frequency bands is proposed in order to optimize the overall system, based on identifying and maximizing independence relations by means of discriminability criteria. The system has been extensively evaluated on the multispectral face database specifically performed for our purpose. On this regard, a new visualization procedure has been suggested in order to combine different bands for establishing valid comparisons and giving statistical information about the significance of the results. This experimental framework has more easily enabled the improvement of robustness against training and testing illumination mismatch. Additionally, focusing problem in thermal spectrum has been also addressed, firstly, for the more general case of the thermal images (or thermograms), and then for the case of facialthermograms from both theoretical and practical point of view. In order to analyze the quality of such facial thermograms degraded by blurring, an appropriate algorithm has been successfully developed. Experimental results strongly support the proposed multispectral facial image fusion, achieving very high performance in several conditions. These results represent a new advance in providing a robust matching across changes in illumination, further inspiring highly accurate FR approaches in practical scenarios.El reconeixement facial (FR) ha estat àmpliament estudiat, degut tant als reptes fonamentals científics que suposa com a les aplicacions actuals i futures on requereix la identificació de les persones. Els sistemes de reconeixement facial tenen els avantatges de ser no intrusius,presentar un baix cost dels equips d’adquisició i no la no necessitat d’autorització per part de l’individu a l’hora de realitzar l'adquisició, entre les més importants. De totes maneres i malgrat els avenços aconseguits en els darrers anys i les diferents solucions proposades, el rendiment del FR encara no resulta satisfactori quan es requereixen condicions més exigents (diferents punts de vista, efectes de bloqueig, canvis en la il·luminació, condicions de llum extremes, etc.). Concretament, l'efecte d'aquestes variacions no controlades en les condicions d'il·luminació sobre les imatges facials condueix a una de les distorsions més accentuades sobre l'aparença facial. Aquesta tesi aborda el problema del FR en condicions d'il·luminació menys restringides. Per tal d'abordar el problema, hem adquirit una nova base de dades de cara multisessió i multiespectral en l'espectre infraroig visible, infraroig proper (NIR) i tèrmic (TIR), sota diferents condicions d'il·luminació. En primer lloc s'ha dut a terme una anàlisi teòrica utilitzant la teoria de la informació per demostrar la complementarietat entre les diferents bandes espectrals objecte d’estudi. L'òptim aprofitament de la informació proporcionada pel conjunt d'imatges multiespectrals s'ha abordat posteriorment mitjançant l'ús de tècniques de fusió de puntuació multimodals, capaces de sintetitzar de manera eficient el conjunt d’informació significativa complementària entre els diferents espectres. A causa de les característiques particulars de les imatges tèrmiques, s’ha requerit del desenvolupament d’un algorisme específic per la segmentació de les mateixes. En el sistema proposat final, s’ha utilitzat com a eina de reducció de la dimensionalitat de les imatges, la Transformada del Cosinus Discreta i una distància fraccional per realitzar les tasques de classificació de manera que el cost en temps de processament i de memòria es va reduir de forma significa. Prèviament a aquesta tasca de classificació, es proposa una selecció de les bandes de freqüències més rellevants, basat en la identificació i la maximització de les relacions d'independència per mitjà de criteris discriminabilitat, per tal d'optimitzar el conjunt del sistema. El sistema ha estat àmpliament avaluat sobre la base de dades de cara multiespectral, desenvolupada pel nostre propòsit. En aquest sentit s'ha suggerit l’ús d’un nou procediment de visualització per combinar diferents bandes per poder establir comparacions vàlides i donar informació estadística sobre el significat dels resultats. Aquest marc experimental ha permès més fàcilment la millora de la robustesa quan les condicions d’il·luminació eren diferents entre els processos d’entrament i test. De forma complementària, s’ha tractat la problemàtica de l’enfocament de les imatges en l'espectre tèrmic, en primer lloc, pel cas general de les imatges tèrmiques (o termogrames) i posteriorment pel cas concret dels termogrames facials, des dels punt de vista tant teòric com pràctic. En aquest sentit i per tal d'analitzar la qualitat d’aquests termogrames facials degradats per efectes de desenfocament, s'ha desenvolupat un últim algorisme. Els resultats experimentals recolzen fermament que la fusió d'imatges facials multiespectrals proposada assoleix un rendiment molt alt en diverses condicions d’il·luminació. Aquests resultats representen un nou avenç en l’aportació de solucions robustes quan es contemplen canvis en la il·luminació, i esperen poder inspirar a futures implementacions de sistemes de reconeixement facial precisos en escenaris no controlats.Postprint (published version