Suppression of DC-link voltage unbalance in three-level neutral-point clamped converters

Two different control approaches for suppressing DC-link voltage unbalance in Three-Level Neutral-Point Clamped Converters (NPCs) are presented in this paper. They both guarantee DC-link voltage equalization over any NPC operating conditions, i.e. when the NPC feeds or is supplied by the main AC grid at different active and/or reactive power rates. The proposed control approaches consist of either a hysteresis or a proportional regulator, each of which synthesizes the most suitable control action based on the actual DC-link voltage unbalance. Particularly, two different PWM techniques have been developed in order to achieve DC-link voltage equalization successfully, preserving NPC voltage and current waveforms at the same time. The performances achievable by means of both the proposed control approaches have been compared to each other through an extensive simulation study in order to highlight their most important advantages and drawbacks, as well as their effectiveness over any operating conditions. Particularly, both control approaches are validated in the Matlab-Simulink environment referring to DC-link voltage equalization of an NPC that represents the point of common coupling between a DC microgrid and the main AC grid.     

Writing and conceptual change. What changes?

This study was focused on elementary school students'processes of scientific understanding within aclassroom environment characterized as a community ofdiscourse. In particular, it explored the role ofwritten discourse both on the plane of knowledgedevelopment and the conceptualization and evaluationof the writing activity itself. The purposes of thestudy were: (a) to see whether students could use writingas a means to express and compare ideas, reason andreflect on them in the process of scientificunderstanding; (b) to see whether writing in the serviceof learning facilitated the understanding of the newtopic through conceptual change; (c) to see whetherwriting affected the conceptualization of the writingactivity itself. Thirty-six fourth graders divided intwo groups, experimental (writing) and control(no-writing), were involved in the implementation ofcurriculum units on plants, whose target concept wasphotosynthesis. The findings show that in theexperimental group the students reached a betterconceptual understanding of the target concept andmore advanced metaconceptual awareness of the changesin their own knowledge structures. Moreover, theconceptualization of the writing activity seemed tochange as well to some extent as writing in aconceptual change process affected the ways learnersviewed some functions of it.     

Effects of different physical education programmes on children’s skill- and health-related outcomes: a pilot randomised controlled trial

Aim of this study was to evaluate the effectiveness of two different 5-month physical education (PE) interventions conducted by a specialist PE teacher on primary school children’s skill- and health-related outcomes. About 230 children were randomly assigned to one of three intervention groups: experimental_1 group, experimental_2 group or control group (school curriculum given by the generalist teacher). Pre- and post-intervention tests assessed pupils’ fitness (pacer, curl-up, push-up, trunk lift, sit and reach tests) and gross motor coordination (shifting platforms, balance beam, jumping laterally, hopping on one leg over an obstacle tests). Both experimental groups significantly improved some fitness and coordinative tests after the intervention period when compared with control group. However, no differential changes on coordinative development were observed between the 2 experimental groups. Results of this study demonstrated that children benefitted from a well-structured PE intervention conducted and supervised by a specialist PE teacher improving their motor skills and fitness.     

Handwriting,spelling, and narrative competence in the fictional stories of Italian primary-school children

European Journal of Psychology of Education - Previous studies with English-speaking children showed that handwriting and spelling abilities played a critical role in the development of writing...     

Puppet play as interactive approach in drug abuse prevention

The national strategies of drug abuse prevention across Europe have come to recognise that the drugs abuse problem presents a complex set of issues of which there is no simple solution. There is a considerable increase in investment in prevention, treatment and harm-reduction activities and increased focus on supply reduction. School settings are the focus of most attempts to implement effective prevention programmes. Prevention in schools does not only focus on drugs alone, but also includes personal and social skills, often with family involvement and involvement of local community. The school is an ideal setting for drug abuse prevention and development of active and responsible attitudes against drug abuse. Successful school drug-prevention programmes include personal skills training （decision-making, coping and goal-setting）, social skills training （assertiveness, resisting peer-pressure）, drug education （knowledge about drugs and the consequences of taking them） and developing attitudes （especially correcting misconceptions about peer group drug use）. Effective drug education programmes incorporate a range of activities which provide students with relevant factual information, the opportunity to consider their attitudes and values, and the values of others. For effective delivery of prevention programmes, interactive teaching is better than didactic teaching alone. In that sense, the puppet play could be used as an interactive technique. Puppets help the students engage actively in communicating their emotions, opinions and experiences, and learn about the drug abuse problem. By the means of puppetry and dramatic play, the students may learn about drugs and the consequences of taking them.     

Renaissance Science and Literature: Benedetti,Ovid and the Transformations of Phaeton’s Myth after Copernicus

This paper aims at showing the close ties between Renaissance literature and science as emerge from the use and the transformation, in a post-Copernican context, of the myth of Phaeton—according to Greek mythology: the boy who tried to conduct the chariot of the Sun and died in this attempt. G.B. Benedetti’s analysis and criticism of Ovid’s Metamorphoses, book two, provides an insight into this literary and scientific issue. Astronomical poems and variations of Phaeton’s myth by other illustrious Renaissance men—including T. Brahe and King James of Scotland and England—are taken into account, as well.     

The impact of funding on research collaboration: Evidence from a developing country

In this paper we evaluate the impact of research grants on the amount of collaboration among scientific researchers in Argentina. We find a positive and significant impact of funding on collaboration which is measured in terms of the number of co-authors for publications in peer-reviewed journals. Our identification strategy is based on comparing collaboration indicators for researchers with financially supported projects with those of a control group of researchers who submitted projects that were accepted in terms of quality, but not supported because of shortage of funds. We obtain consistent results by using different non-experimental techniques including difference-in-differences models combined with propensity score matching algorithms.     

The terracotta modelli of Palazzo Venezia in Rome: Investigation of the constituent materials for fundamental knowledge and to aid conservation decisions

This work presents the results of the investigation carried out on a group of terracotta sculptures (modelli) (sixteenth to eighteenth century) belonging to the extraordinary collection of Palazzo Venezia in Rome. The study, the diagnostic analysis, and the conservation work, were possible thanks to the grant supplied by the Getty Foundation of Los Angeles and by the bank Intesa San Paolo. The terracotta modelli had a practical function as they were of great use as sketches to the creation of the final masterpieces or as models for restoration. As a consequence, the terracotta models allow reconstructing the creative process of artists and restorers, fundamental to outlining the ancient workshop production. X-ray fluorescence spectroscopy, micro-stratigraphic investigation, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy were chosen as useful techniques to study the morphology and composition of the surface-painted layers. Usually the surfaces were painted in order to simulate the materials of the sculpture for which the model was created, for example lead white was used to obtain a white surface simulating marble. But, often the models were re-painted to make them more attractive for the antique trade. So, several pigments have been found on the surfaces such as zinc white, Prussian blue, chrome yellow, and mono-azo pigment. In some cases, the characterization of the surface paintings was particularly important to the final decision about removing or leaving the surface paint in place.     

Topic Knowledge,Text Coherence,and Interest: How They Interact in Learning From Instructional Texts

The effects of topic knowledge, text coherence, and topic interest on learning from text were examined. One hundred sixty high school students participated in 1 of 4 groups according to their levels of topic knowledge and interest. Participants read 1 of 3 versions of a scientific text: minimally coherent, locally coherent, and locally and globally coherent. Text comprehension was examined by tasks aimed at tapping both textbase and situation-model levels. The contribution of topic interest seemed to increase according to the quantity of learners' topic knowledge. High-knowledge and high-interest students performed significantly better than those in the other 3 groups in all tasks. Text version differentiated students' performance on all measures but 1. The expected Group x Version interactions did not emerge.