Online drawings for dementia diagnose: in-air and pressure information analysis

In this paper we present experimental results comparing on-line drawings for control population (left and right hand) as well as Alzheimer disease patients. The drawings have been acquired by means of a digitizing tablet, which acquires time information angles and pressures. Experimental measures based on pressure and in-air movements appear to be significantly different for both groups, even when control population performs the tasks with the non-dominant hand

Automatic Analysis of Archimedes’ Spiral for Characterization of Genetic Essential Tremor Based on Shannon’s Entropy and Fractal Dimension

Among neural disorders related to movement, essential tremor has the highest prevalence; in fact, it is twenty times more common than Parkinson's disease. The drawing of the Archimedes' spiral is the gold standard test to distinguish between both pathologies. The aim of this paper is to select non-linear biomarkers based on the analysis of digital drawings. It belongs to a larger cross study for early diagnosis of essential tremor that also includes genetic information. The proposed automatic analysis system consists in a hybrid solution: Machine Learning paradigms and automatic selection of features based on statistical tests using medical criteria. Moreover, the selected biomarkers comprise not only commonly used linear features (static and dynamic), but also other non-linear ones: Shannon entropy and Fractal Dimension. The results are hopeful, and the developed tool can easily be adapted to users; and taking into account social and economic points of view, it could be very helpful in real complex environments.This research was partially funded by the Basque Goverment, the University of the Basque Country by the IT1115-16 project-ELEKIN, Diputacion Foral de Gipuzkoa, University of Vic-Central University of Catalonia under the research grant R0947, and the Spanish Ministry of Science and Innovation TEC2016-77791-C04-R

An Online writer recognition system based on in-air and on-surface trajectories

The main motivation of this dissertation is the exploration of the field of online text-dependent writer recognition, in order to provide evidence of the usefulness of short sequences of text to perform identification and verification, which are the two tasks involved in recognition. From this motivation stem its main goals and contributions: an exploration performed from a practical perspective, thus requiring the development of a recognition system, and the gathering of evidence concerning the discriminative power of in-air trajectories (the trajectories described while not exerting any pressure on the writing surface, when the hand moves in the air while transitioning from one stroke to the next), i.e. their ability to discriminate among writers. In-air and on-surface trajectories have been analyzed from the perspective of information theory and the results yielded by this analysis show that, except for pressure, they contain virtually equal amounts of information and are notably non-redundant. This suggests that in-air trajectories may have a considerable discriminative power and that they may help improve the overall recognition performance when combined with on-surface trajectories. An innovative writer recognition system that fulfils the abovementioned practical goal has been devised. It follows an allographic approach, that is, it does not take into account the global characteristics of the text but focuses on character and character-fragment shapes. Strokes are considered the structural units of handwriting and any piece of text is regarded as two separate sequences, one of pen-up and one of pen-down strokes. The system relies on a pair of catalogues of strokes, built in an unsupervised manner by means of self-organizing maps, which allow mapping sequences of strokes into sequences of integers. The latter sequences, much simpler than the original ones, can be effectively compared by means of dynamic time warping, which takes advantage of the neighbouring properties exhibited by self-organizing maps. Measures obtained from each sequence can be combined in a later step. The recognition system has been experimentally tested using 16 uppercase words from the BiosecurID database, which contains 4 executions of each word donated by 400 writers. The experimental results obtained clearly sustain the claim that online words have a notable recognition potential and show the suitability of the allographic approach to perform writer recognition in the online text-dependent context. Regarding identification, the system compares positively to other word-based identification schemas. As for verification, the accuracy levels attained do not lie much below the accuracies reported for today¿s state-of-the-art signature verification methods. Furthermore, the results obtained from in-air trajectories have substantiated what the information analysis had already suggested: their considerable recognition power and their notable non-redundancy with respect to on-surface trajectories. Finally, a new method to generate synthetic samples of online words from real ones has been proposed. This method is based on the recognition system previously described, takes advantage of its main characteristics and can be seamlessly integrated into it. Synthetic samples are used to enlarge the enrolment sets, which has the effect of substantially improving the recognition accuracy of the system.La principal motivació d’aquesta dissertació és la investigació en el camp del reconeixement d’escriptors en la modalitat online depenent del text, amb intenció de proporcionar evidències que avalin la utilitat de les seqüències curtes per a la identificació i la verificació, que són les dues tasques compreses en el reconeixement. D’aquesta motivació se’n deriven els seus objectius més rellevants: una exploració feta des d’una perspectiva pràctica que requereix, doncs, el desenvolupament d’un sistema de reconeixement; i la recerca d’evidència relacionada amb la potència discriminant de les trajectòries en l’aire (aquelles que són executades sense que l’estri d’escriptura exerceixi pressió sobre la superfície, en les transicions entre traços), això és, la seva capacitat per a reconèixer escriptors. Les trajectòries en l’aire i sobre la superfície han estat analitzades des de la perspectiva de la teoria de la informació. Els resultats obtinguts d’aquesta anàlisi mostren que, llevat de la pressió, ambdós tipus de trajectòries contenen quantitats d’informació pràcticament idèntiques, amb un nivell notable de no redundància. Això suggereix que les trajectòries en l’aire potser posseeixen una potència discriminant considerable i que la capacitat global de reconeixement pot millorar si es combinen amb les trajectòries sobre la superfície. S’ha desenvolupat un sistema de reconeixement innovador que representa l’assoliment de l’objectiu pràctic. Aquest sistema està basat en una aproximació al•logràfica, això és, no té en compte les característiques globals del text sinó que està focalitzat en les formes dels caràcters i dels seus fragments. Els traços són considerats la unitat estructural bàsica de l’escriptura i qualsevol fragment de text és entès com un parell de seqüències separades, una de traços en superfície i una de traços elevats. El sistema treballa en base a un parell de catàlegs de traços, construïts de manera no supervisada amb l’ajut de mapes autoorganitzats, que li permeten transformar les seqüències de traços en seqüències de números enters. Aquestes darreres seqüències, molt més simples que no pas les originals, poden ser comparades, de manera efectiva, mitjançant el dynamic time warping (alineament temporal dinàmic) el qual treu profit de les propietats de veïnatge característiques dels mapes autoorganitzats. Les mesures que s’obtenen de cada seqüència poden ser combinades en un pas posterior. El sistema de reconeixement ha estat provat experimentalment fent ús de les 16 paraules en majúscules de la base de dades BiosecurID, la qual en conté 4 realitzacions de cadascuna donades per 400 persones. Els resultats experimentals que s’han obtingut recolzen clarament l’afirmació que les paraules online presenten una potència discriminant notable i avalen l’adequació de l’aproximació al•logràfica per a dur a terme reconeixement d’escriptors en el context online depenent del text. Quant a la identificació, el sistema es compara favorablement amb altres mètodes basats en paraules. I, pel que fa a la verificació, els nivells de precisió obtinguts no es troben gaire lluny dels nivells assolits pels mètodes de verificació de signatura representatius de l’estat de l’art actual. És més, els resultats que s’obtenen de les trajectòries en l’aire han corroborat allò que havia estat suggerit per l’anàlisi de la informació: la seva considerable potència discriminant i la seva substancial manca de redundància respecte de les trajectòries sobre la superfície. Finalment, s’ha proposat un nou sistema de generació de mostres sintètiques de paraules online. Aquest mètode està basat en el sistema de reconeixement abans descrit, n’aprofita les característiques principals i s’hi pot integrar amb facilitat. Les mostres sintètiques s’utilitzen per engrandir els conjunts d’inscripció (enrolment sets), la qual cosa té com a efecte una millora substancial de la precisió del sistema

UPCSCHEMEv2.0 : un intèrpret de SCHEME amb continuacions de primer ordre : master thesis

This work describes and justifies a new approach to the implementation model of the evaluation process of LISP-like languages. The new model possibilities are studied, mainly those related with the implementation of capture and invocation mechanisms for first class continuations. In addition, macroexpansion and timing mechanisms are implemented too, to serve the double purpose of providing the UPCSCHEMEv.2.0 interpreter with them and allowing further research on the possibilities and limitations of the new evaluator implementation model.Aquest treball descriu i justifica un nou plantejament en el model d'implementació del procés d'avaluació en llenguatges funcionals de la familia LISP. S'estudien les possibilitats d'aquest nou model, principalment pel que fa a la implementació de mecanismes de captura i invocació de continuacions de primera classe. Per altra banda, s'implementen també mecanismes de macroexpansió i temporització amb el doble propòsit de dotar l'intèrpret UPCSCHEMEv2.0 amb aquests serveis i continuar la tasca d'estudi de les possibilitats i limitacions que ofereix el nou model d'implementació de l'avaluador pel que fa a les seves futures ampliacions.Preprin

Lògica, febrer 2011

Material docent de la Universitat Oberta de Catalunya.Material docente de la "Universitat Oberta de Catalunya".Learning material of the "Universitat Oberta de Catalunya"

Biometric Applications Related to Human Beings: There Is Life beyond Security

The use of biometrics has been successfully applied to security applications for some time. However, the extension of other potential applications with the use of biometric information is a very recent development. This paper summarizes the field of biometrics and investigates the potential of utilizing biometrics beyond the presently limited field of security applications. There are some synergies that can be established within security-related applications. These can also be relevant in other fields such as health and ambient intelligence. This paper describes these synergies. Overall, this paper highlights some interesting and exciting research areas as well as possible synergies between different applications using biometric information

Selection of Entropy Based Features for Automatic Analysis of Essential Tremor

Biomedical systems produce biosignals that arise from interaction mechanisms. In a general form, those mechanisms occur across multiple scales, both spatial and temporal, and contain linear and non-linear information. In this framework, entropy measures are good candidates in order provide useful evidence about disorder in the system, lack of information in time-series and/or irregularity of the signals. The most common movement disorder is essential tremor (ET), which occurs 20 times more than Parkinson’s disease. Interestingly, about 50%–70% of the cases of ET have a genetic origin. One of the most used standard tests for clinical diagnosis of ET is Archimedes’ spiral drawing. This work focuses on the selection of non-linear biomarkers from such drawings and handwriting, and it is part of a wider cross study on the diagnosis of essential tremor, where our piece of research presents the selection of entropy features for early ET diagnosis. Classic entropy features are compared with features based on permutation entropy. Automatic analysis system settled on several Machine Learning paradigms is performed, while automatic features selection is implemented by means of ANOVA (analysis of variance) test. The obtained results for early detection are promising and appear applicable to real environments