PWM Control of a Buck Converter with an Amorphous Core Coil

Pulse-width modulation is widely used to control electronic converters. One of the most topologies used for high DC voltage/low DC voltage conversion is the Buck converter. It is obtained as a second order system with a LC filter between the switching subsystem and the load. The use of a coil with an amorphous magnetic material core instead of air core lets design converters with smaller size. If high switching frequencies are used for obtaining high quality voltage output, the value of the auto inductance L is reduced throughout the time. Then, robust controllers are needed if the accuracy of the converter response must not be affected by auto inductance and load variations. This paper presents a robust controller for a Buck converter based on a state space feedback control system combined with an additional virtual space variable which minimizes the effects of the inductance and load variations when a not-toohigh switching frequency is applied. The system exhibits a null steady-state average error response for the entire range of parameter variations. Simulation results are presented

Using the Own Flexibility of a Climbing Robot as a Double Force Sensor

Force sensors are used when interaction tasks are carried out by robots in general, and by climbing robots in particular. If the mechanics and electronics systems are contained inside the own robot, the robot becomes portable without external control. Commercial force sensors cannot be used due to limited space and weight. By selecting the links material with appropriate stiffness and placing strain gauges on the structure, the own robot flexibility can be used such as force sensor. Thus, forces applied on the robot tip can be measured without additional external devices. Only gauges and small internal electronic converters are necessary. This paper illustrates the proposed algorithm to achieve these measurements. Additionally, experimental results are presented

Economy and Environmental Problems in the Mexican Coastal States

A canonical correspondence analysis (CCA) for environmental and economic variables was performed for 17 Mexican coastal states. The ordination method allowed us to identify three groups, namely hydroelectric energy generation (I), pollution (II) and harbours (III), which were associated to different human activities. Furthermore, CCA is efficient to help us generate hypotheses for future research. It is therefore advised that CCA should be used for routine analyses into economics.Coastal States of Mexico, Canonical Correspondence Analysis, Diversity Index, Economic Development, Environmental Variables.

Laser Shock Microformingof Thin Metal Sheets with ns Lasers

Continuous and long-pulse lasers have been used for the forming of metal sheets in macroscopic mechanical applications. However, for the manufacturing of micro-electromechanical systems (MEMS), the use of ns laser pulses provides a suitable parameter matching over an important range of sheet components that, preserving the short interaction time scale required for the predominantly mechanical (shock) induction of deformation residual stresses, allows for the successful processing of components in a medium range of miniaturization without appreciable thermal deformation.. In the present paper, the physics of laser shock microforming and the influence of the different experimental parameters on the net bending angle are presented

GNUsmail: Open framework for on-line email classification

Real-time classification of massive email data is a challenging task that presents its own particular difficulties. Since email data presents an important temporal component, several problems arise: emails arrive continuously, and the criteria used to classify those emails can change, so the learning algorithms have to be able to deal with concept drift. Our problem is more general than spam detection, which has received much more attention in the literature. In this paper we present GNUsmail, an open-source extensible framework for email classification, which structure supports incremental and on-line learning. This framework enables the incorporation of algorithms developed by other researchers, such as those included in WEKA and MOA. We evaluate this framework, characterized by two overlapping phases (pre-processing and learning), using the ENRON dataset, and we compare the results achieved by WEKA and MOA algorithms

Impact assessment of mechanical harvest on fruit physiology and consequences on oil physicochemical and sensory quality from ‘Manzanilla de Sevilla’ and ‘Manzanilla Cacereña’ super-high-density hedgerows. A preliminary study

BACKGROUND Super-intensive cultivation facilitates olive mechanized harvesting, allowing substantial savings in the production cost of virgin olive oil (VOO). However, the number of varieties adapted to this type of cultivation is small. This study explores the impact that harvesting with a grape straddle harvester of ‘Manzanilla de Sevilla’ and ‘Manzanilla Cacereña’ olives grown in super-intensive cultivation has on the physiology of the fruit and the quality of the oil subsequently extracted. RESULTS For both cultivars, fruits harvested mechanically showed higher respiration and ethylene production and lower firmness than fruits harvested by hand. Their oils exhibited lower phenol contents, lower oxidative stability and lower presence of positive sensory attributes. However, in these oils the values of parameters used to assess the level of quality of VOO remained within the limits required for the best commercial category. CONCLUSION Mechanical harvesting of ‘Manzanilla de Sevilla’ and ‘Manzanilla Cacereña’ super-high-density hedgerows induced physiological alterations in the fruits and a reduction in the contents of natural antioxidants and flavour components in the oils, though it did not result in a loss of the ‘Extra’ level of quality. © 2014 Society of Chemical IndustryThis work was funded by the research project AGL2011-30371-C02-02 of the Spanish State Secretary for Research and by the FEDER program. Special thanks are due to Elaia SA for providing facilities for this study and to Alejandro Trigo (technical assistant of Elaia SA), María del Carmen Martínez, Cristina Rodríguez and Antonio Montero for technical assistance.Peer Reviewe

Project-based learning: a university experience

La finalidad de nuestra experiencia de innovación ha sido introducir en nuestras aulas universitarias la metodología de Aprendizaje Basado en Proyectos (ABP), la cual consideramos una estrategia de enseñanza en la que los estudiantes planifican, implementan y evalúan proyectos que tienen aplicaciones en el mundo real y que va más allá de lo que sucede en las aulas universitarias. Esta innovación puesta en práctica con 107 estudiantes de segundo curso del Grado de Educación Infantil de la Universidad de Sevilla (España) ha tenido como meta fomentar y desarrollar una variedad de competencias relacionadas no solo con el trabajo en equipo, sino también con habilidades y estrategias de gestión, localización, búsqueda y evaluación de información a partir de fuentes documentales electrónicas, acercándolos a la reflexión de sus propias investigaciones y la construcción de conocimientos. Aunque el ABP es una metodología difícil de aplicar en Educación Superior, los resultados obtenidos ponen de manifiesto las ventajas que ofrece este tipo de metodología y el alto nivel de satisfacción de los estudiantes participantes. Ha ofrecido interacciones óptimas entre profesores y estudiantes, se ha creado un ambiente positivo de aprendizaje en el aula facilitando la comunicación y permitiendo un mejor proceso de enseñanza y aprendizaje.The purpose of our experience of innovation has been introduced in our university classrooms teaching methodology based on project (PBL), which we consider a teaching strategy in which students plan, implement and evaluate projects that have real-world applications and that goes beyond ofwhat happens in university classrooms. This innovation implementation 140 students's Degree in Early Childhood Education at the University of Seville (Spain) has been aimed to encourage and develop a variety of skills related not only teamwork, but also with the skills and management strategies, locating, searching and evaluating information from electronic documentary sources, bringing them closer to the reflection of their own research and knowledge building. Although the PBL is a difficult methodology applied in higher education, the results show the advantages of this type of methodology and the high level of satisfaction of participating students. It has offered optimal interactions between teachers and students, it has created a positive learning environment in the classroom facilitating communication and enabling better teaching and learning proces

Augmented Reality in Primary Education: effects on learning

El uso de Realidad Aumentada (RA) lleva a investigar los efectos de su utilización en los entornos educativos, si modifica y facilita la adquisición de conocimientos, la atención y la motivación, así como el rendimiento académico del alumnado, y las percepciones que tenían tras el uso de este novedosa tecnología. La muestra del estudio la formaron 46 alumnos de dos aulas de 6º de educación primaria de un colegio de la provincia de Sevilla (España), asignados a un grupo control de 22 alumnos y a un grupo experimental de 24 alumnos, con el cual se utilizó herramientas de RA. El diseño cuasi-experimental llevó a utilizar herramientas que recogieron datos de forma cuantitativa y cualitativa. Para la realización de este estudio utilizamos contenidos de RA durante cinco semanas, periodo necesario para impartir el tema seleccionado para el que se crearon contenidos específicos. Su uso reveló una mejora significativa en el proceso de aprendizaje y la adquisición de conocimientos por los alumnos. Se puede apreciar una mejora de las calificaciones, la adquisición de conocimientos y la mejora en el rendimiento que es deseable y beneficiosa. La percepción por parte del alumnado y el profesorado de esta tecnología es positiva y les parece incentivadora, motivadora y capaz de propiciar una mejora en el proceso de enseñanza y aprendizaje.The use of Augmented Reality (AR) leads to investigate the effects of its use in educational environments, if it modifies and facilitates the acquisition of knowledge, attention and motivation, as well as the academic performance of students, and the perceptions they had The use of this new technology. The sample of the study was formed by 46 students from two classrooms of 6º of primary education of a school of the province of Seville (Spain), assigned to a control group of 22 students and to an experimental group of 24 students, with which tools were used of AR. The quasi-experimental design led to the use of tools that collected data in a quantitative and qualitative way. To carry out this study we used AR content for five weeks, a period necessary to impart the selected topic for which specific contents were created. Its use revealed a significant improvement in the learning process and the acquisition of knowledge by students. It is possible to appreciate an improvement of the qualifications, the acquisition of knowledge and the improvement in the performance that is desirable and beneficial. The perception by the students and teachers of this technology is positive and seems encouraging, motivating and capable of promoting an improvement in the teaching and learning process.peerReviewe

Networks in education: from a global perspective to a nodal approach

En este artículo nos aproximamos a la implantación de la internet en el ámbito global y como ha influido en la sociedad. Su influencia en las empresas, los centros de enseñanza y en las personas, siendo tanto una herramienta de trabajo como un medio de comunicación y de negocios. Apreciación de los aspectos positivos, negativos, el análisis de diversas observaciones sobre la conveniencia de que ha de estar más dirigida al individuo, su formación y beneficio. Creando entornos seguros y estables en los crear relaciones y aportar conocimientos