A decomposition procedure based on approximate newton directions

The efficient solution of large-scale linear and nonlinear optimization problems may require exploiting any special structure in them in an efficient manner. We describe and analyze some cases in which this special structure can be used with very little cost to obtain search directions from decomposed subproblems. We also study how to correct these directions using (decomposable) preconditioned conjugate gradient methods to ensure local convergence in all cases. The choice of appropriate preconditioners results in a natural manner from the structure in the problem. Finally, we conduct computational experiments to compare the resulting procedures with direct methods, as well as to study the impact of different preconditioner choices

Retail competition with switching consumers in electricity markets

The ongoing transformations of power systems worldwide pose important challenges,both economic and technical, for their appropriate planning and operation. A key approach to improve the efficiency of these systems is through demand-side management, i.e., to promote the active involvement of consumers in the system. In particular, the current trend it to conceive systems where electricity consumers can vary their load according to real-time price incentives, offered by retailing companies.Under this setting, retail competition plays an important role as inadequate prices orservices may entail consumers switching to a rival retailer. In this work we consider a game theoretical model where asymmetric retailers compete in prices to increase their profits by accounting for the utility function of consumers. Consumer preferences for retailers are uncertain and distributed within a Hotelling line. We analytically characterize the equilibrium of a retailer duopoly, establishing its existence and uniqueness conditions. Furthermore, sensitivities of the equilibrium prices with respect to relevant model parameters are also provided. The duopoly model is extended to a multiple retailer case for which we perform an empirical analysis via numerical simulations. Results indicate that, depending on the retailer costs, loyalty rewards and initial market shares, the resulting equilibrium can range from complete competition to one in which a retailer have a leading or even a dominant position in the market, decreasing the consumers' utility significantly. Moreover, the retailer network configuration also plays an important role in the competitiveness of the systemAcknowledgements: The authors gratefully acknowledge financial support from the Spanish government through project MTM2013-

Efecto de los descansos activos físicos en la comprensión lectora de la lengua extranjera

The aim of the present study was to find out whether Active-Breaks (AB) improve the three levels of reading comprehension in a foreign language which could be a determining variable in the academic success of the implementation of CLIL programmes.  This study involved a total of 50 healthy students [n=25: Control Condition (CC), and n= 25: Active-Break Condition (ABC)] from one secondary school in the Region of Andalucía (Spain). To investigate the acute effects of an AB on reading comprehension in a foreign language, those in the CC were asked to maintain their ordinary routines, while those in the ABC modified their class by introducing ten minutes of exercise. After that both groups complete a reading comprehension test. Significant different were found in both question of literal comprehension, p=0.03, d=0.38, p=0.001, d=0.11, and in both question of inferential comprehension, p=.003, d=0.35, p=0.03, d=0.47. Crucially, in both question of evaluation, p=0.26, d=0.20, p=0.41, d=0.40, no significant difference was appreciated. The present study demonstrated that overall student’s reading comprehension in a foreign language improves after of AB of 10 min (compared with CC) and concretely, improve the efficiency in question of literal comprehension and inferential comprehension.El objetivo de la presente investigación fue el de averiguar si los descansos activos mejoran los niveles de comprensión lectora en una lengua extranjera, lo que podría ser una variable determinante en el éxito académico en la implementación de los programas AICLE. En este estudio participaron un total de 50 estudiantes sanos (n=25: Condición Control, and n= 25: Condición descanso activo) de un instituto de secundaria de Andalucía (España). Para investigar los efectos agudos de un descanso activo en la comprensión de lectura en un idioma extranjero, se les pidió a los estudiantes de Condición control que mantuvieran sus rutinas diarias, mientras que a los de la condición de descanso activo modificaron su clase introduciendo 10 minutos de ejercicio. Después de eso, ambos grupos completaron una prueba de comprensión lectora. Se encontraron diferencias significativas tanto en las preguntas de comprensión literal, p=0.03, d=0.38, p=0.001, d=0.11, como en las preguntas de comprensión inferencia, p=.003, d=0.35, p=0.03, d=0.47.  Hay que destacar que, en ambas cuestiones de evaluación, p=0.26, d=0.20, p=0.41, d=0.40, no se apreciaron diferencias significativas. El presente estudio demostró que la comprensión lectora general en un idioma extranjero mejoró después de un descanso activo de 10 minutos

Efecto de los descansos activos físicos en la comprensión lectora de la lengua extranjera

This work is funded by General Directorate of Teacher Training and Educational Innovation of the Andalusian Ministry of Education (Resolution: august 31, 2020) under the project “The inclusion of physical activity for foreign language learning in the CLIL classroom through the learning-HITT program”.The aim of the present study was to find out whether Active-Breaks (AB) improve the three levels of reading comprehension in a foreign language which could be a determining variable in the academic success of the implementation of CLIL programmes. This study involved a total of 50 healthy students [n=25: Control Condition (CC), and n= 25: Active-Break Condition (ABC)] from one secondary school in the Region of Andalucía (Spain). To investigate the acute effects of an AB on reading comprehension in a foreign language, those in the CC were asked to maintain their ordinary routines, while those in the ABC modified their class by introducing ten minutes of exercise. After that both groups complete a reading comprehension test. Significant different were found in both question of literal comprehension, p=0.03, d=0.38, p=0.001, d=0.11, and in both question of inferential comprehension, p=.003, d=0.35, p=0.03, d=0.47. Crucially, in both question of evaluation, p=0.26, d=0.20, p=0.41, d=0.40, no significant difference was appreciated. The present study demonstrated that overall student’s reading comprehension in a foreign language improves after of AB of 10 min (compared with CC) and concretely, improve the efficiency in question of literal comprehension and inferential comprehension, contributing to enhancement of quality of education.El objetivo de la presente investigación fue el de averiguar si los descansos activos mejoran los niveles de comprensión lectora en una lengua extranjera, lo que podría ser una variable determinante en el éxito académico en la implementación de los programas AICLE. En este estudio participaron un total de 50 estudiantes sanos (n=25: Condición Control, and n= 25: Condición descanso activo) de un instituto de secundaria de Andalucía (España). Para investigar los efectos agudos de un descanso activo en la comprensión de lectura en un idioma extranjero, se les pidió a los estudiantes de Condición control que mantuvieran sus rutinas diarias, mientras que a los de la condición de descanso activo modificaron su clase introduciendo 10 minutos de ejercicio. Después de eso, ambos grupos completaron una prueba de comprensión lectora. Se encontraron diferencias significativas tanto en las preguntas de comprensión literal, p=0.03, d=0.38, p=0.001, d=0.11, como en las preguntas de comprensión inferencia, p=.003, d=0.35, p=0.03, d=0.47. Hay que destacar que, en ambas cuestiones de evaluación, p=0.26, d=0.20, p=0.41, d=0.40, no se apreciaron diferencias significativas. El presente estudio demostró que la comprensión lectora general en un idioma extranjero mejoró después de un descanso activo de 10 minutos en comparación con el Grupo Control y en concreto, mejoró de manera eficiente en términos de comprensión literal e inferencial, contribuyendo a mejorar la calidad de la educación.Andalusian Ministry of Education (Resolution: august 31, 2020

A Partial parametric path algorithm for multiclass classification

The objective functions of Support Vector Machine methods (SVMs) often includeparameters to weigh the relative importance of margins and training accuracies.The values of these parameters have a direct effect both on the optimal accuraciesand the misclassification costs. Usually, a grid search is used to find appropriatevalues for them. This method requires the repeated solution of quadraticprograms for different parameter values, and it may imply a large computationalcost, especially in a setting of multiclass SVMs and large training datasets. Formulti-class classification problems, in the presence of different misclassificationcosts, identifying a desirable set of values for these parameters becomes evenmore relevant. In this paper, we propose a partial parametric path algorithm, basedon the property that the path of optimal solutions of the SVMs with respect tothe preceding parameters is piecewise linear. This partial parametric path algorithmrequires the solution of just one quadratic programming problem, and anumber of linear systems of equations. Thus it can significantly reduce the computationalrequirements of the algorithm. To systematically explore the differentweights to assign to the misclassification costs, we combine the partial parametricpath algorithm with a variable neighborhood search method. Our numerical experimentsshow the efficiency and reliability of the proposed partial parametricpath algorithm

A projection method for multiobjective multiclass SVM

Support Vector Machines (SVMs) have become a very popular technique in the machine learning field for classification problems. It was originally proposed for classification of two classes. Various multiclass models with a single objective have been proposed mostly based on two families of methods: an all-together approach and a one-against-all approach. However,most of these single-objective models consider neither the different costs of misclassification nor the user's preferences. To overcome these drawbacks, multiobjective models have been proposed.In this paper we rewrite the different approaches that deal with the multiclass SVM using multiobjective techniques. These multiobjective techniques can give us weakly Pareto-optimal solutions. We propose a multiobjective technique called Projected Multiobjective All-Together(PMAT), which works in a higher-dimension space than the object space. With this technique, we can theoretically characterize the Pareto-optimal solution set. For these multiobjective techniques we get approximate sets of the Pareto-optimal solutions. For these sets, we use hypervolume and epsilon indicators to evaluate different multiobjective techniques. From the experimental results, we can see that (PMAT) outperfoms the other multiobjective techniques. When facing classification problems with very large numbers of classes, we suggest combininga tree method and multiobjective technique

Eigenvectors of a kurtosis matrix as interesting directions to reveal cluster structure

In this paper we study the properties of a kurtosis matrix and propose its eigenvectors as interesting directions to reveal the possible cluster structure of a data set. Under a mixture of elliptical distributions with proportional scatter matrix, it is shown that a subset of the eigenvectors of the fourth-order moment matrix corresponds to Fisher's linear discriminant subspace. The eigenvectors of the estimated kurtosis matrix are consistent estimators of this subspace and its calculation is easy to implement and computationally efficient, which is particularly favourable when the ratio n/p is large.Publicad

Clustering Big Data by Extreme Kurtosis Projections

Clustering Big Data is an important problem because large samples of many variables are usually heterogeneous and include mixtures of several populations. It often happens that only some of a large set of variables are useful for clustering and working with all of them would be very inefficient and may make more difficult the identification of the clusters. Thus, searching for spaces of lower dimension that include all the relevant information about the clusters seems a sensible way to proceed in these situations. Peña and Prieto (2001) showed that the extreme kurtosis directions of projected data are optimal when the data has been generated by mixtures of two normal distributions. We generalize this result for any number of mixtures and show that the extreme kurtosis directions of the projected data are linear combinations of the optimal discriminant directions if we knew the centers of the components of the mixture. In order to separate the groups we want directions that split the data into two groups, each corresponding to different components of the mixture. We prove that these directions can be found from extreme kurtosis projections. This result suggests a new procedure to deal with many groups, working in a binary decision way and deciding at each step if the data should be split into two groups or we should stop. The decision is based on comparing a single distribution with a mixture of two distribution. The performance of the algorithm is analyzed through a simulation study

Medición de la motivación para aprender inglés como lengua extranjera: Validación del LLOS-IEA. Diferencias de Sexo y Edad en las regulaciones emocionales

El objetivo de este estudio ha sido traducir al español, adaptar a un contexto AICLE y analizar las propiedades psicométricas de la escala LLOS-IEA; Escala de la orientación del aprendizaje de idiomas – Subescalas de Motivación Intrínseca, Motivación Extrínseca y desmotivación. La versión adaptada del LLOS-IEA fue administrada a 3355 estudiantes de Andalucía con edades comprendidas entre los 11 y los 17 años. Tras los procesos de traducción y adaptación, se realizaron análisis de los ítems y de la estructura interna con el fin de comparar los modelos de 5 y 7 factores. Esto dio lugar a análisis CFA, fiabilidad y validez que concluyeron el mejor ajuste del modelo de 5 factores. También se realizó un análisis de modelos multiniveles para estudiar la validez de constructo obteniendo resultados similares a otros estudios.The object of this research was to translate into Spanish and adapt to a CLIL context the Language Learning Orientation Scale-Intrinsic Motivation, Extrinsic Motivation and Amotivation Subscales (LLOS-IEA) analysing its psychometric properties. The LLOS-IEA adaptation was administered to a total of 3355 students from Andalusia aged from 11 to 17 years. After the translation and adaptation processes, item and internal structure analyses were conducted comparing the 5 and 7-factor models. This led to a CFA and to reliability and validity analyses, which concluded that the 5-factor performed the best fit. Other analyses have shown this instrument to be sex-invariant and to have convergent validity. A multi-level model analysis was also conducted in order to study the construct validity concluding with similar results from similar studies

Real situations in teaching as a learning strategy for the Initial Teacher Training in Secondary Education: The SIRECA Model

La formación del profesorado de Educación Secundaria, materializada en el Máster profesionalizante obligatorio de Educación Secundaria (MAES), está recibiendo diferentes críticas en los últimos tiempos. La más generalizada se focaliza en la distancia existente entre la formación teórica (dimensión sociológica, psicológica y pedagógica) y el desempeño práctico profesional. Como respuesta a ello en el Máster de Secundaria de la Universidad Pablo de Olavide, ha puesto en marcha un Modelo basado en las Situaciones REales en el Centro y en el Aula (SIRECA). Esta estrategia metodológica está haciendo más accesibles estas materias al alumnado que las visualizan, desde el inicio de su formación, como útiles y necesarias para su desarrollo profesional docente. El artículo recoge la evaluación del impacto del Modelo SIRECA, en el Máster. Para ello, se ha desarrollado una investigación bajo una metodología comparada, obteniendo como resultados principales un mayor grado de satisfacción del alumnado (subiendo de una media de 2,8, sobre 4, previo a la implementación del SIRECA; a un 3,13 tras su puesta en marcha). Las principales aportaciones de este Modelo radican en integrar las diferentes disciplinas teóricas en realidades propias del desempeño profesional, potenciando la coordinación docente, así como los elementos de evaluación del alumnado.Pre-service training for Secondary School and Vocational College teachers has been the subject of criticism recently from different areas. The most widespread criticism is aimed at the gap between theoretical training and practical professional performance. Hence, at the Universidad Pablo de Olavide, in Seville, an innovative methodology has been rolled out in order to respond to this need: the SIRECA Model (Real Situations in Schools and Classrooms). With this model, future secondary school teachers, in each of the disciplines that make up the generic module, are given different real situations, which they will have to deal with in the classroom with their students, in the day-to-day running of a school, and in relations with families and the socio-educational community. Hence, students on this Master’s Degree will have to put into practice the psyco-social-pedagogical knowledge acquired through the theoretical contents taught, as a tool in resolving the real situations proposed. It is when they transfer that knowledge and acquired competencies to the practical reality when the students are able to identify the utility of what they have learned during all sections of the Master’s Degree. Hence, with this model, we bring that practical reality of the secondary classroom into the university classroom, as a key element in the transfer of knowledge and competencies acquired by the students, through the generic Master’s module