Showing papers by "Miguel Ferrer published in 2005"

Offline geometric parameters for automatic signature verification using fixed-point arithmetic

Abstract: This paper presents a set of geometric signature features for offline automatic signature verification based on the description of the signature envelope and the interior stroke distribution in polar and Cartesian coordinates. The features have been calculated using 16 bits fixed-point arithmetic and tested with different classifiers, such as hidden Markov models, support vector machines, and Euclidean distance classifier. The experiments have shown promising results in the task of discriminating random and simple forgeries.

Floater survival affects population persistence. The role of prey availability and environmental stochasticity

Abstract: We develop two individual-based models using a large and detailed data set (information gathered over more than a century) on a population of a longlived and territorial predator, the Spanish imperial eagle. We investigated the relationship between survival and predator pressure, prey behaviour and patch availability (i.e. settlement areas). Survival of dispersing individuals was highly dependent on the number of available settlement areas, mediated by prey availability. Changes in prey behaviour due to predation pressure (e.g. shifting from diurnal to nocturnal activity) can decrease their availability for predators even if the density significantly exceeds the predator needs. Environmental stochasticity had a strong influence on population viability when it occurred in a synchroneous way between breeding and settlement areas, and an increase in floater mortality negatively influenced stability and dynamics of the breeding segment of populations in reproductive areas. Our simulations demonstrated the link between the dynamics in settlement and breeding areas: factors affecting floater survival also influence whole population dynamics. Moreover, model outputs provided insights into the relationship between environmental stochasticity and population dynamics.

Environmental stochasticity in dispersal areas can explain the ‘mysterious’ disappearance of breeding populations

Abstract: We present the results of an individual-based simulation model, showing that increasing the mortality of non-breeding dispersers within settlement areas can lead to the extinction of species and (meta)populations in a subtle way. This is because the areas where dispersers settle are generally unknown or difficult to detect. Consequently, fewer efforts are devoted to the conservation of these sites than to the conservation of breeding territories. Additionally, high mortality rates affecting the floater sector of a population become evident in the breeding sector only after several of years, when it is too difficult or too late to halt the decline. As a result, because most conservation projects on endangered species and populations mainly focus on breeding areas, many current efforts may be wasted in locations other than those in which conservation would be really necessary and effective.

Unidades de cuidados respiratorios intermedios: Definición y características

Abstract: 1. Cuando se iniciaron los cuidados intensivos en España los neumólogos españoles, aún anclados en la tisiología, no tuvieron una visión estratégica de futuro. Este hecho fue radicalmente diferente en cardiología: los cardiólogos reclamaron y asumieron la responsabilidad de las unidades coronarias. 2. Históricamente, ha habido poco interés por parte de los(as) neumólogos(as) y de la especialidad de neumología para implicarse en el cuidado del paciente respiratorio crítico. 3. Los especialistas en medicina intensiva han defendido lógicamente su especialidad y evitado la entrada de otras2.

A Bird and Small Mammal BACI and IG Design Studies in a Wind Farm in Malpica (Spain)

Abstract: Wind farms have shown a spectacular growth during the last 10 years. As far as we know, this study is the first where the relationship between wind power and birds and small mammals have been considered. Before–after control impact (BACI) study design to birds and Impact Gradient (IG) study design to small mammals to test the null hypothesis of no impact of a wind farm were used. In the BACI model Windfarm Area and a Reference Area were considered. Distance from turbines was considered in the IG model. Windfarm installations did not clearly affect bird and small mammal populations. Flight height of nesting and no nesting birds did not show a clear tendency. Small mammals populations suffered high variations in numbers through times by intrinsic population factors. There are many practical problems of detection of human influence on abundances of populations so sampling in the long run can be suggested.

Humans act against the natural process of breeder selection: A modern sickness for animal populations?

Abstract: We present a new idea about the possible effects of human-induced mortality on different age cohorts (i.e., breeders vs. juveniles) in long-lived animals. Our hypothesis is based on Curio’s idea on the effect of natural selective processes on cohorts to explain age-related increases in fecundity (selection hypothesis). We believe that negative human pressure may modify such contribution to reproduction of good versus low quality phenotypes, altering the genetic structure of the population. Ecologists and environmental managers in general should be aware of how stochastic events provoked by humans may induce changes in the genetic structure of populations.

Using hand knuckle texture for biometric identifications

Abstract: In this paper is proposed a first approach of a novel and simple biometric verification system based on the texture of the hand knuckles. A knuckle image with scale, rotation and translation invariance is isolated from the hand recorded image with digital image processing techniques. The wrinkle of the knuckle images are extracted to a black and white image which is used as biometric feature. A hidden Markov model and a support vector machine are proposed as verifiers. A similar equal error rate of 0.094 is reached by both classifiers with our preliminary database consisting of 8 samples of 20 people hand.

Image processing techniques for braille writing recognition

Abstract: In this paper we present the development of BrailLector, a system able to speak from Braille writing. By means of dynamic thresholding, adaptive Braille grid, recovery dots techniques and TTS software (Text-To-Speech), BrailLector translates Braille scanned images into normal text, and not only that, it speaks the translated text. BrailLector is a robust application with innovative thersholding and Braille grid creation algorithms which detects and read Braille characters with 99.9% of correct symbols and an error variance below 0.012. The conversion time is only 26 secs for double-sided documents by MATLAB programming language.

Image processing techniques for braille writing recognition

Abstract: In this paper we present the development of BrailLector, a system able to speak from Braille writing. By means of dynamic thresholding, adaptive Braille grid, recovery dots techniques and TTS software (Text-To-Speech), BrailLector translates Braille scanned images into normal text, and not only that, it speaks the translated text. BrailLector is a robust application with innovative thersholding and Braille grid creation algorithms which detects and read Braille characters with 99.9% of correct symbols and an error variance below 0.012. The conversion time is only 26 secs for double-sided documents by MATLAB programming language.

Condition of large brood in Bonelli's Eagle Hieraaetus fasciatus

Abstract: Capsule Young body condition is affected by the interaction of environment (rainfall) and brood size. Aims To investigate factors affecting offspring condition using levels of urea in plasma. Methods We used generalized linear mixed models (GLMMs) with the levels of urea in plasma as the dependent variable and laying date, brood size, sex and year as the explanatory ones. Results Brood size had a significant effect on offspring condition only during a year of adverse weather (heavy rainfall). During this period, young from broods of two were in poor condition compared with single broods. Conversely, brood size had no effect in the other two years analysed. Neither sex nor laying date had a significant effect on young condition. Offspring condition was not related to first-year survival. Conclusion There is a trade-off between reproduction (brood size) and offspring condition only in years of adverse environmental conditions.

Biases in population diet studies due to sampling in heterogeneous environments: a case study with the Eagle Owl

Abstract: Many studies have reported variation in bird diet composition related to spatial variation in habitat quality and landscape heterogeneity. Most diet analyses involve collection of food items at a sub-sample of available sites. Because individuals at different sites may vary in their diet composition, the description of the diet of a population may depend on which sites are sampled. This potential bias associated with environmental heterogeneity has never been explicitly tested. We used dietary data from a long-term study of an owl population to simulate various scenarios of diet assessment in which the investigator samples food items from various sites without taking into account their variation in quality. The simulations showed that assessment of diet composition was highly dependent on the number and type of sites sampled for food items and that such bias caused by environmental heterogeneity disappeared when food samples were randomly collected at more than 60% of the available sites. Biases ...

Factors affecting the length of the post-fledging period in the bonelli's eagle Hieraaetus fasciatus

Abstract: We investigated factors associated with the length of the post-fledging dependence period in 28 radio-tagged young Bonelli's Eagles Hieraaetus fasciatus monitored from 1998 to 2000. Under the assumptions of the Resource Competition Hypothesis (RCH), we predicted that young hatched in high-quality territories would have longer post-fledging dependence periods than young hatched in low-quality territories. As an alternative, we tested the Ontogenetic Switch Hypothesis (OSH), which predicts a better body condition in early dispersing young. For this purpose we measured body condition of young through levels of urea in the blood plasma. We found a weak positive effect of natal habitat quality on the length of the post-fledging dependence period, but no effect of body condition. Siblings were dependent on their parents for a similar number of days, suggesting that habitat and/or parent quality might influence the length of the post-fledging dependence period. Young hatched in 1999 had shorter post-fledging dependence periods than young hatched in 1998 or 2000. The date of independence for young Bonelli's Eagles was correlated with the timing of breeding (laying date), but not with the length of the post-fledging dependence period. Neither brood size nor sex affected the length of this period.

Application of support vector machines and Gaussian mixture models for the detection of obstructive sleep apnoea based on the RR series

Abstract: In this paper we present the performances of two automatic statistical methods for the classification of the obstructive sleep apnoea syndrome based on the RR series obtained from the Electrocardiogram (ECG) We study the effect of working with Support Vector Machines (SVM) and compare its performance with a reference detector based on Gaussian Mixture Models (GMM) These classifications methods require two previous stages: preprocessing and feature extraction Firstly, we apply a preprocessing over the ECG for estimating the R instants which is previous to feature extraction Secondly, a power-ratio-based coefficient (PRC) and a Linear Frequency Cepstral Coefficients (LFCC) parameterization over the RR signal is applied to extract the relevant characteristics We fix the set of features for both classification methods

Slant estimation of handwritten characters by means of Zernike moments

Abstract: Slant estimation is an indispensable technique for handwritten analysis. Proposed is a novel method for slant estimation based on the average inclination of the Zernike reconstructed images for low moments. This method improves the linearity of the characteristic curve in comparison with a generalised chain code method.

Analysis of reservoir selection by wintering ospreys (Pandion haliaetus haliaetus) in Andalusia, Spain: A potential tool for reintroduction

Abstract: las Montafias Rocosas en las d6cadas de 1960 y 1970. En el afio 2004 revis6 15 de los 21 acantilados utilizados pot Falco peregrinus en el pasado en Colorado para determinat los cambios en la ocupaci6n yen las tasas de productividad. En el afio 2004, la tasa de ocupaci6n pot pareja fue de un 87% en comparaci6n con un 47% y un 40% entre 1963-65 y 1973-75, respectivamente. La tasa reproductiva basada en todas las parejas con territorios rue de 2.1 juveniles/pareja, en comparaci6n con una tasa de 1.2 y 0.7 para los periodos anteriores, respectivamente. Se estima que 136 parejas nidifican en unos 160 acantilados donde F. peregrinus estuvo presente en la filtima d& cada, pero el nfimero real es seguramente mayor y podria aumentar a 250-400 parejas dada la estimaci6n de la d•sponibilidad de h•bitat apropiado. [Traducci6n del equipo editorial]

Optimal size of time window in nonlinear features for voice quality measurement

Abstract: In this paper we propose the use of nonlinear speech features to improve the voice quality measurement. We have tested a couple of features from the Dynamical System Theory, namely: the Correlation Dimension and the largest Lyapunov Exponent. In particular, we have studied the optimal size of time window for this type of analysis in the field of the characterization of the voice quality. Two systems of automatic detection of laryngeal pathologies, one of them including these features, have been implemented with the purpose of validating the usefulness of the suggested nonlinear features. We obtain slight improvements with respect to a classical system.

Strategy for improving the reliability in the facial identification

Abstract: This paper presents a simple, robust and novel for errors detection in biometric system which is applied to the Olivetti Research Laboratory (ORL) face database (400 images). We have used as parameterisation different transformed dominions (Travieso et al., 2004; Faundez, 2003), and a support vector machine (SVM) (Burges, 1998; Cristianini and Shawe-Taylor, 2000) as classifier. This system has been adjusted with our experiments for obtaining a false identification rate (FIR) of 0%, with a success rate of 90.8% a rejected samples rate of 9.2%.

Recognition system for wooded species of Canary Laurisilva from its contour using kernel of Fisher

Abstract: In this work it has been developed a novel system of automatic recognition for trees leaves, based on a hybrid classification method by means of a Support Vector Machine (SVM), using the Fisher kernel, and calculated from a Hidden Markov Model (HMM). An angle sequence has been used as an element of parameterization, extracted from the leaves contour, making such sequence invariable by rotation, movements and size. The application of these algorithms has been focused on the implementation of a recogniser of leaves of endemic trees from the Canary Islands, in particular, 16 different species of Canary Laurisilva. Obtained successful rates have been higher than 99.9%, according to the number of employed leaves in the training process.

Characterization of a speaker from a telephone recording using speech quality measurements

Abstract: Starting from a telephone recording of a speaker, by means of subjective techniques based on the experience, it is possible to identify characteristics of the speaker like for example the linguistic origin, the cultural level, and the repetitive use of certain grammatical expressions. In this work, the preliminary results of applying techniques based on speech quality measurements for characterizing to a speaker are presented. This technique is objective and it is based on the behaviour of the fonator system. These techniques have been applied with success in the medical environment. In this paper, we propose the use speech features to improve the voice quality measurement, with the purpose of extracting characteristic of a speaker that allows the identification of the speaker. We have tested different measures based on voiced speech in the context of telephone recordings using healthy speakers (high voice quality) and with speakers which present laryngeal pathologies (low voice quality). The speakers used in the study are classified between healthy speakers or pathological speakers by mean an automatic classification with the purpose of justifying the effectiveness of the measures proposals.

Characterizationofa speakerfrom a telephonerecordingusing speechqualitymeasurements

Abstract: Starting fromatelephone recording ofaspeaker, bymeansof subjective techniques based ontheexperience, itispossible to identify characteristics ofthespeaker likeforexample the linguistic origin, thecultural level, andtherepetitive useof certain grammatical expressions. Inthis work, thepreliminary results ofapplying techniques basedon speechquality measurements forcharacterizing toaspeaker arepresented. Thistechnique isobjective anditisbased onthebehaviour of thefonator system. Thesetechniques havebeenapplied with success inthemedical environment. Inthis paper wepropose theusespeechfeatures toimprove thevoicequality measurement, withthepurpose ofextracting characteristic of aspeaker thatallows theidentification ofthespeaker. We havetested different measures based onvoiced speech inthe context oftelephone recordings using healthy speakers (high voicequality) andwithspeakers whichpresent laryngeal pathologies (lowvoicequality). Thespeakers usedinthe study areclassified between healthy speakers orpathological speakers bymeananautomatic classification withthepurpose ofjustifying theeffectiveness ofthemeasures proposals.