The fractional volatility model : no-arbitrage, leverage and completeness

When the volatility process is driven by fractional noise one obtains a model which is consistent with the empirical market data. Depending on whether the stochasticity generators of log-price and volatility are independent or are the same, two versions of the model are obtained with different leverage behaviors. Here, the no-arbitrage and completeness properties of the models are rigorously studied

Teacher and school determinants of perceived classroom discipline: a multilevel analysis of TALIS 2013

Published online: 21 January 2021Classroom discipline is a significant concern in most educational systems and a critical element of an effective learning environment. In this article, we present a multilevel analysis of teachers' perceived classroom discipline (PCD) in Portugal, using data from the TALIS 2013. Portuguese teachers perceived slightly more classroom discipline problems than the mean of OECD countries, with classroom variables explaining PCD much better than school-related variables. The percentage of low achievers in the classroom, teacher's self-efficacy, and teacher's need for training in classroom management were the best predictors of PCD. Still, student-related factors (e.g., low achievement) were better predictors of PCD than teacher-related factors (e.g., teacher experience or teacher gender)

Human Dynamics: The Correspondence Patterns of Darwin and Einstein

While living in different historical era, Charles Darwin (1809-1882) and Albert Einstein (1879-1955) were both prolific correspondents: Darwin sent (received) at least 7,591 (6,530) letters during his lifetime while Einstein sent (received) over 14,500 (16,200). Before email scientists were part of an extensive university of letters, the main venue for exchanging new ideas and results. But were the communication patterns of the pre-email times any different from the current era of instant access? Here we show that while the means have changed, the communication dynamics has not: Darwin's and Einstein's pattern of correspondence and today's electronic exchanges follow the same scaling laws. Their communication belongs, however, to a different universality class from email communication, providing evidence for a new class of phenomena capturing human dynamics.Comment: Supplementary Information available at http://www.nd.edu/~network

The mechanical properties of wood and the design of Neolithic stone axes

Despite the importance of wooden tools for early man, and the development of woodworking in the Mesolithic and Neolithic culture, there has been surprisingly little research on how wood can be worked by stone tools or how wooden handles for composite tools were designed. This paper outlines an approach based on an understanding of the structure and mechanical properties of wood. The cell arrangement in wood makes it far less stiff, strong and tough across the grain, especially tangentially. This makes it hard to harvest wood or break it into lengths because it splits down its centre rather than breaking right across. Fortunately, this also makes wood easy to split along the grain, especially radially through its centre into sections and planks. A model of the splitting process predicted that wood is best split using blunt, broad but smooth wedges, as these would use less energy and would be less likely to get stuck in the wood. The predictions were verified in tests in which hazel coppice poles were split using wedges of contrasting angle, width and surface texture. The results help explain the change from the flaked flint Mesolithic tranchet axes to the broader polished stone Neolithic axe and adze heads. However, further experiments are also needed cutting wood obliquely to test this hypothesis. The splitting model also helps to understand the design of socketed axe hafts. Failure usually occurs when the handles split at the distal and proximal ends of the socket. To prevent this, handles are best designed with the growth rings parallel to the socket, and with an expanded head, especially with flanges on the distal and proximal ends of the socket. These designs are seen in some of the Neolithic axe handles that have been found in Britain, including the Etton, Ehenside and Shulishader axes. More experimental research is needed to understand the optimal way of hafting axe heads

Determinantes escolares y de los estudiantes en el rendimiento lector: un análisis multinivel con estudiantes portugueses

Available online 10 June 2021Reading is crucial for learning, in general. Starting right with reading in primary grades is, therefore, vital for school achievement. The present study aims to test whether students’ factors best predict reading performance than school factors and determine what student and school factors predict reading performance. The study sample includes 4,118 fourth-grade students participating in IEA PIRLS 2016. Three questionnaires were used to collect data: one for school principals, one for students, and one for parents. Hierarchical linear modeling was used to study the relation of school and student-level variables to students’ reading performance. Students’ confidence in reading and home resources for learning are the best predictors of reading performance at the student level. At the school level, school emphasis on academic success is the best predictor of reading performance. The results provide clues as to what schools might do to improve reading results.La lectura es fundamental para el aprendizaje en general. Empezar con la lectura en educación primaria es, por tanto, vital para el rendimiento académico. El presente estudio tiene como objetivo probar si los factores de los estudiantes predicen mejor el rendimiento en lectura que los factores escolares y determinar qué factores del alumnado y de la escuela predicen el rendimiento en lectura. La muestra del estudio incluye 4.118 estudiantes de cuarto curso de educación primaria que participan en el Progress in International Reading Literacy Study (PIRLS), 2016. Han sido utilizados tres cuestionarios para recopilar datos: un cuestionario para directores de escuela, un cuestionario para estudiantes y un cuestionario para padres. Se ha utilizado un modelo lineal jerárquico para estudiar la relación de las variables al nivel de la escuela y del alumnado con el rendimiento de los estudiantes en lectura. La confianza de los estudiantes en la lectura y los recursos del hogar para el aprendizaje son los mejores predictores del rendimiento lector. Al nivel escolar, el mejor indicador del rendimiento lector es el énfasis de la escuela en el éxito académico. Los resultados proporcionan pistas sobre lo que podrán hacer las escuelas para mejorar los resultados de lectura

Inclusive education in Portugal: teachers’ professional development, working conditions, and instructional efficacy

Inclusive education policies thin the boundaries of special and regular education as well as teachers’ roles and competencies. The present study, using data from TALIS 2018, aims to find out whether Portuguese teachers working in classes directed entirely or mainly to special education needs students (SENS) differ from teachers working in classes with few or no SENS in the following areas: (a) professional development needs in special education; (b) perceived barriers to professional development; and (c) teaching and work features related to SENS. The results show small but significant differences between teachers working and teachers not working entirely or mainly with SENS in professional development needs, perceived opportunities for professional development, and stress involved in modifying SENS lessons. No other significant differences were found. Still, the results show that both groups of teachers perceive significant professional development needs and barriers to professional development but are optimistic about the quality of professional development, job satisfaction, and self-efficacy in instruction. However, teachers of both groups are pessimistic about professional collaboration, a key element of inclusive education. Overall, it seems that some critical elements of inclusive education are still to be implemented in Portuguese schools

In-season internal and external training load quantification of an elite European soccer team

Elite soccer teams that participate in European competitions need to have players in the best physical and psychological status possible to play matches. As a consequence of congestive schedule, controlling the training load (TL) and thus the level of effort and fatigue of players to reach higher performances during the matches is therefore critical. Therefore, the aim of the current study was to provide the first report of seasonal internal and external training load that included Hooper Index (HI) scores in elite soccer players during an in-season period. Nineteen elite soccer players were sampled, using global position system to collect total distance, high-speed distance (HSD) and average speed (AvS). It was also collected session rating of perceived exertion (s-RPE) and HI scores during the daily training sessions throughout the 2015-2016 in-season period. Data were analysed across ten mesocycles (M: 1 to 10) and collected according to the number of days prior to a one-match week. Total daily distance covered was higher at the start (M1 and M3) compared to the final mesocycle (M10) of the season. M1 (5589m) reached a greater distance than M5 (4473m) (ES = 9.33 [12.70, 5.95]) and M10 (4545m) (ES = 9.84 [13.39, 6.29]). M3 (5691m) reached a greater distance than M5 (ES = 9.07 [12.36, 5.78]), M7 (ES = 6.13 [8.48, 3.79]) and M10 (ES = 9.37 [12.76, 5.98]). High-speed running distance was greater in M1 (227m), than M5 (92m) (ES = 27.95 [37.68, 18.22]) and M10 (138m) (ES = 8.46 [11.55, 5.37]). Interestingly, the s-RPE response was higher in M1 (331au) in comparison to the last mesocycle (M10, 239au). HI showed minor variations across mesocycles and in days prior to the match. Every day prior to a match, all internal and external TL variables expressed significant lower values to other days prior to a match (p<0.01). In general, there were no differences between player positions. Conclusions: Our results reveal that despite the existence of some significant differences between mesocycles, there were minor changes across the in-season period for the internal and external TL variables used. Furthermore, it was observed that MD-1 presented a reduction of external TL (regardless of mesocycle) while internal TL variables did not have the same record during in-season match-day-minus.: The authors state that there were no salaries’ fund from a tobacco company. Also, the authors are not aware of any competing interests. This project was supported by the National Funds through FCT—Portuguese Foundation for Science and Technology (UID/DTP/04045/2013)—and the European Fund for Regional Development (FEDER) allocated by European Union through the COMPETE 2020 Programme (POCI-01-0145- FEDER-006969)—competitiveness and internationalization (POCI). All funding received for this work from any of the following organizations: National Institutes of Health (NIH); Welcome Trust; Howard Hughes Medical Institute (HHMI). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio

A multi-criteria decision support system for a routing problem in waste collection

Autor proofThis work presents a decision support system for route planning of vehicles performing waste collection for recycling. We propose a prototype system that includes three modules: route optimization, waste generation prediction, and multiple-criteria decision analysis (MCDA). In this work we focus on the application of MCDA in route optimization. The structure and functioning of the DSS is also presented. We modelled the waste collection procedure as a routing problem, more specifically as a team orienteering problem with capacity constraints and time windows. To solve the route optimization problem we developed a cellular genetic algorithm. For the MCDA module, we employed three methods: SMART, ValueFn and Analytic Hierarchy Process (AHP). The decision support system was tested with real-world data from a waste management company that collects recyclables, and the capabilities of the system are discussed.FCT Fundação para a Ciência e Tecnologia, Project Scope: PEst-OE/EEI/UI0319/2

Character education in Portugal

Around the world, children who can exercise their right to attend school spend a significant part of their lives within the education environment. Therefore, schools have a great deal of influence on children’s development beyond the academic realm. Given this accessibility to children, schools have opportunities to help children develop positive character traits. Each community must determine what role schools will play in providing character education and what content would be delivered through character education programs. This article explores these issues associated with character education within Portugal, including who should be responsible for providing character education and how it can best be transmitted.(undefined