Aprendizaje basado en problemas y en comparación de soluciones en un contexto semipresencial

Este trabajo propone un método de evaluación continua, no presencial e implementable a través de entornos de aprendizaje en línea. En una primera fase, el profesor propone un problema y define una fecha de entrega, antes de la cual los alumnos deberán enviar sus soluciones (resultado A). Cumplido este plazo, el profesor publica una solución correcta. En una segunda fase, los alumnos comparan sus soluciones con la del profesor, y elaboran un informe de autoevaluación (resultado B). De la entrega A se evalúa corrección y optimalidad, mientras que de B se valora la capacidad del alumno para realizar un análisis crítico de los errores y singularidades de su solución. Como evaluación global del ejercicio se propone una media ponderada de las notas de ambos resultados, A y B.SUMMARY -- This paper proposes a method of continuous assessment that can be implemented through online learning environments. In a first phase, the teacher poses a problem and sets a deadline for students to submit their individual solutions (outcome A), after which a correct solution is published. In a second phase, students will compare their solutions with that of the teacher, and write a self-assessment report (outcome B). The outcome A is evaluated based on its correctness and optimality, while B is assessed considering students' ability to detect their errors and to make a reasoned defense of their solutions. The overall evaluation is intended as a weighted average of the notes of both deliverables, A and B.Peer Reviewe

On the Complementarity of Face Parts for Gender Recognition

This paper evaluates the expected complementarity between the most prominent parts of the face for the gender recognition task. Given the image of a face, five important parts (right and left eyes, nose, mouth and chin) are extracted and represented as appearance-based data vectors. In addition, the full face and its internal rectangular region (excluding hair, ears and contour) are also coded. Several mixtures of classifiers based on (subsets of) these five single parts were designed using simple voting, weighted voting and other learner as combiners. Experiments using the FERET database prove that ensembles perform significantly better than plain classifiers based on single parts (as expected)

The Role of Face Parts in Gender Recognition

This paper evaluates the discriminant capabilities of face parts in gender recognition. Given the image of a face, a number of subimages containing the eyes, nose, mouth, chin, right eye, internal face (eyes, nose, mouth, chin), external face (hair, ears, contour) and the full face are extracted and represented as appearance-based data vectors. A greater number of face parts from two databases of face images (instead of only one) were considered with respect to previous related works, along with several classification rules. Experiments proved that single face parts offer enough information to allow discrimination between genders with recognition rates that can reach 86%, while classifiers based on the joint contribution of internal parts can achieve rates above 90%. The best result using the full face was similar to those reported in general papers of gender recognition (>95%). A high degree of correlation was found among classifiers as regards their capacity to measure the relevance of face parts, but results were strongly dependent on the composition of the database. Finally, an evaluation of the complementarity between discriminant information from pairs of face parts reveals a high potential to define effective combinations of classifiers

Aprendizaje basado en problemas y en comparación de soluciones en un contexto semipresencial

Este trabajo propone un método de evaluación continua, no presencial e implementable a través de entornos de aprendizaje en línea. En una primera fase, el profesor propone un problema y define una fecha de entrega, antes de la cual los alumnos deberán enviar sus soluciones (resultado A). Cumplido este plazo, el profesor publica una solución correcta. En una segunda fase, los alumnos comparan sus soluciones con la del profesor, y elaboran un informe de autoevaluación (resultado B). De la entrega A se evalúa corrección y optimalidad, mientras que de B se valora la capacidad del alumno para realizar un análisis crítico de los errores y singularidades de su solución. Como evaluación global del ejercicio se propone una media ponderada de las notas de ambos resultados, A y B.This paper proposes a method of continuous assessment that can be implemented through online learning environments. In a first phase, the teacher poses a problem and sets a deadline for students to submit their individual solutions (outcome A), after which a correct solution is published. In a second phase, students will compare their solutions with that of the teacher, and write a self-assessment report (outcome B). The outcome A is evaluated based on its correctness and optimality, while B is assessed considering students' ability to detect their errors and to make a reasoned defense of their solutions. The overall evaluation is intended as a weighted average of the notes of both deliverables, A and B.Este trabajo ha sido parcialmente financiado por el Vicerrectorado de Ordenación Académica y Profesorado de la Universitat Jaume I de Castelló

A Kinect-Based Interactive System for Home-Assisted Active Aging

Virtually every country in the world is facing an unprecedented challenge: society is aging.Assistive technologies are expected to play a key role in promoting healthy lifestyles in the elderly.This paper presents a Kinect-based interactive system for home-assisted healthy aging, which guides,supervises, and corrects older users when they perform scheduled physical exercises. Interactionstake place in gamified environments with augmented reality. Many graphical user interface elementsand workflows have been designed considering the sensory, physical and technological shortcomingsof the elderly, adapting accordingly the interaction methods, graphics, exercises, tolerance margins,physical goals, and scoring criteria. Experiments involved 57 participants aged between 65 and 80who performed the same physical routine six times during 15 days. After each session, participantscompleted a usability survey. Results provided significant evidence that support (1) the effectivenessof the system in assisting older users of different age ranges, (2) the accuracy of the system inmeasuring progress in physical achievement of the elderly, and (3) a progressive acceptance ofthe system as it was used. As a main conclusion, the experiments verified that despite their poortechnological skills, older people can adapt positively to the use of an interactive assistance tool foractive aging if they experience clear benefits

Reconstruction of noisy signals by minimization of non-convex functionals

Non-convex functionals have shown sharper results in signal reconstruction as compared to convex ones, although the existence of a minimum has not been established in general. This paper addresses the study of a general class of either convex or non-convex functionals for denoising signals which combines two general terms for fitting and smoothing purposes, respectively. The first one measures how close a signal is to the original noisy signal. The second term aims at removing noise while preserving some expected characteristics in the true signal such as edges and fine details. A theoretical proof of the existence of a minimum for functionals of this class is presented. The main merit of this result is to show the existence of minimizer for a large family of non-convex functionals.The rst author gratefully acknowledges many helpful discussion with Professor H. Frid from IMPA. Also thanks the Promeps Project that support this work. The second author is grateful to the Spanish Ministry of Economy and Competitiveness for the grant TIN2013-46522-P, and to the Generalitat Valenciana for the grant PROMETEOII/2014/062

Face gender classification: A statistical study when neutral and distorted faces are combined for training and testing purposes

This paper presents a thorough study of gender classification methodologies performing on neutral, expressive and partially occluded faces, when they are used in all possible arrangements of training and testing roles. A comprehensive comparison of two representation approaches (global and local), three types of features (grey levels, PCA and LBP), three classifiers (1-NN, PCA + LDA and SVM) and two performance measures (CCR and d′) is provided over single- and cross-database experiments. Experiments revealed some interesting findings, which were supported by three non-parametric statistical tests: when training and test sets contain different types of faces, local models using the 1-NN rule outperform global approaches, even those using SVM classifiers; however, with the same type of faces, even if the acquisition conditions are diverse, the statistical tests could not reject the null hypothesis of equal performance of global SVMs and local 1-NNs

Vision-based gait impairment analysis for aided diagnosis

Gait is a firsthand reflection of health condition. This belief has inspired recent research efforts to automate the analysis of pathological gait, in order to assist physicians in decision-making. However, most of these efforts rely on gait descriptions which are difficult to understand by humans, or on sensing technologies hardly available in ambulatory services. This paper proposes a number of semantic and normalized gait features computed from a single video acquired by a low-cost sensor. Far from being conventional spatio-temporal descriptors, features are aimed at quantifying gait impairment, such as gait asymmetry from several perspectives or falling risk. They were designed to be invariant to frame rate and image size, allowing cross-platform comparisons. Experiments were formulated in terms of two databases. A well-known generalpurpose gait dataset is used to establish normal references for features, while a new database, introduced in this work, provides samples under eight different walking styles: one normal and seven impaired patterns. A number of statistical studies were carried out to prove the sensitivity of features at measuring the expected pathologies, providing enough evidence about their accuracy

Classification of high dimensional and imbalanced hyperspectral imagery data

The present paper addresses the problem of the classification of hyperspectral images with multiple imbalanced classes and very high dimensionality. Class imbalance is handled by resampling the data set, whereas PCA is applied to reduce the number of spectral bands. This is a preliminary study that pursues to investigate the benefits of using together these two techniques, and also to evaluate the application order that leads to the best classification performance. Experimental results demonstrate the significance of combining these preprocessing tools to improve the performance of hyperspectral imagery classification. Although it seems that the most effective order of application corresponds to first a resampling algorithm and then PCA, this is a question that still needs a much more thorough investigationPartially supported by the Spanish Ministry of Education and Science under grants CSD2007–00018, AYA2008–05965–0596–C04–04/ESP and TIN2009–14205–C04–04, and by Fundació Caixa Castelló–Bancaixa under grant P1–1B2009–0

Arm Swing Asymmetry Measurement from 2D Gait Videos

Arm swing during gait has been positively related to gait stability and gait efficiency, particularly in the presence of neurological disorders that affect locomotion. However, most gait studies have focused on lower extremities, while arm swing usually remains ignored. In addition, these studies are mostly based on costly, highly-specialized vision systems or on wearable devices which, despite their popularity among researchers and specialists, are still relatively uncommon for the general population. This work proposes a way of estimating arm swing asymmetry from a single 2D gait video. First, two silhouette-based representations that separately capture motion data from both arms were built. Second, a measure to quantify arm swing energy from such a representation was introduced, producing two side-dependent motion measurements. Third, an arm swing asymmetry index was obtained. The method was validated on two public datasets, one with 68 healthy subjects walking normally and one with 10 healthy subjects simulating different styles of arm swing asymmetry. The validity of the asymmetry index at capturing different arm swing patterns was assessed by two non-parametric tests: the Mann–Whitney U test and the Wilcoxon signed-rank test. The so-called physiological asymmetry was observed on the normal gait sequences of both datasets in a statistically similar way. The asymmetry index was able to fairly characterize the different levels of asymmetry simulated in the second set. Results show that it is possible to estimate the arm swing asymmetry from a single 2D gait video, with enough sensitivity to discriminate anomalous patterns from normality. This opens the door to low-cost easy-to-use mobile applications to assist clinicians in monitoring gait condition in primary care (e.g., in the elderly), when more accurate and specialized technologies are often not available