Global real-time optimization by output-feedback extremum-seeking control with sliding modes

This paper addresses the design of a sliding mode based extremum-seeking controller for a class of single-input–single-output (SISO) uncertain nonlinear systems with unmatched and state-dependent strong nonlinearities. We demonstrate that it is possible to achieve an arbitrarily small neighborhood of the desired optimal point using only output-feedback. The key idea is the combination of a periodic switching function with a norm state observer. As an important advantage, we show that the proposed scheme achieves extremum-seeking for all initial conditions, i.e., the real-time optimization algorithm has global convergence properties. An application to a simple nonderivative optimizer illustrates the viability of the proposed approach.     

Understanding productivity dynamics: A task taxonomy approach

As job markets have been polarizing, firms have been changing their labor inputs. By using matched employer–employee data for Portugal, we examine whether labor market polarization has occurred within or across firms and how labor input upgrades have contributed to overall productivity growth. We develop a firm taxonomy based on worker's occupational data. Firms can be focused on one task – Abstract, Manual or Routine – on a combination of tasks, or none. Results show that Abstract firms are the most productive and their share has increased over time. Manual firms, the least productive, have had a stable share throughout the period. Routine firms have seen their share decline over time. The dynamic decomposition of the estimated productivity reveals that productivity growth is propelled by increased market shares of the most productive incumbents and exiting of the least productive, especially for Abstract firms. Notwithstanding these productivity growth drivers, they fail to avert the productivity stagnation observed in Portugal between 2004 and 2009 due to the overall decline in productivity of incumbent firms, especially Routine. We discuss the policy implications of our results which are relevant to other European economies also lagging behind in terms of knowledge and innovation capabilities.     

Trademarks as an indicator of innovation and industrial change

As innovation becomes an ever more central issue for the development of firms and world economies, so the need for improved assessments of innovative performance grows more urgent. This paper suggests that trademark analysis can contribute in capturing relevant aspects of innovation phenomena and the process of industrial change. We propose trademarks as a complementary indicator in the portfolio of available empirical tools of innovation studies and industrial dynamics. Our empirical exploration is based on a study of community trade marks (CTM), an intellectual property right granted in the European Union, and draws on recent research on trademarking trends in Portugal. Quantitative as well as qualitative data, including survey data from a representative sample of Portuguese manufacturing and services firms, are used to identify the advantages and limitations of this indicator.     

Analysis of the distances covered and technical actions performed by professional tennis players during official matches

The purpose of this study was to analyse the physical and technical performances of professional tennis players during official matches. The trajectories of eight players were obtained during matches, using an automatic tracking method. The distances covered and technical performances were analysed for the first and second sets. The athletes covered (mean ± standard deviation) a total of 1702.4 ± 448.2 m in the first set, 1457.6 ± 678.1 m in the second set and 3160.0 ± 880.1 in the entire match. No differences were found between the sets for the physical variables (lateral and forward displacements, distance covered per rally, per game and per set, and the percentage of time spent in each range of velocity). However, the distances covered by the athletes during the rallies in which they were serving (median = 5.2; interquartile range (IQR) = 6.7 m) were statistically smaller than when they were returning (median = 6.2; IQR = 7.7 m). Forehand ground stroke proficiency decreased from the first (mean ± standard deviation: 75.2 ± 4.11%) to the second set (mean ± standard deviation = 65.5 ± 14.3%). In conclusion, tennis players did not present reduced physical performance from the first to the second set.     

Body dissatisfaction in women’s artistic gymnastics: A longitudinal study of psychosocial indicators

Body dissatisfaction is prevalent in women’s artistic gymnastics (WAG). Cross-sectional research points to social and individual risk factors, however it does not account for potential changes in body dissatisfaction during an athletic season. This study aimed to determine how gymnasts’ body dissatisfaction, risk factors for eating disorders, media internalisation, perfectionism and mood state change during pre-competition, competition and post-competition seasons and to identify how these psychosocial indicators impact on body dissatisfaction during the athletic year. The sample consisted of 20 Brazilian elite women’s artistic gymnasts aged 10–16 years. Data were obtained from a 9-month study using: Body Shape Questionnaire (BSQ); Eating Attitude Test-26; Sociocultural Attitudes Towards Appearance Questionnaire-3 (SATAQ-3); Multidimensional Perfectionism Scale (MPS); Brunel Mood Scale (BRUMS) and triceps and subscapular skinfolds. Body dissatisfaction was higher during the competition season and disordered eating, perfectionism and vigour values were higher in the pre-competition season. Disordered eating has been found as the strongest predictor of body dissatisfaction during all seasons, and mood state partly contributed to body dissatisfaction in the competitive season. Stakeholders should understand that body dissatisfaction and the prevalence of disordered eating may change over time.     

Science curricula design: analysis of authors’ ideological and pedagogical principles

The study analyses the extent to which the sociological message transmitted by the Official Pedagogic Discourse of the curriculum for Portuguese middle schools contains the ideological and pedagogical principles of its authors. The research is epistemologically and sociologically grounded, placing particular emphasis on Bernstein theory of pedagogic discourse. The ideological principles underlie broad educational aims and the pedagogical principles underlie characteristics of the pedagogic practice. Data was obtained through a semi‐structured interview with the authors and documental analysis of their publications. The results suggest that the authors were distinct in the ideological and pedagogical principles they valued and that discontinuities were evident between those principles and the curriculum message. These results are discussed and their consequences in terms of scientific learning are explored.     

Nutritional intake of elite football referees

Abstract

There is a paucity of dietary data in football referees. In this study, 23 elite main and assistant referees (34.4 ± 5.6 years) completed a 7-day dietary record during the competitive season. No nutritional intake differences were observed between main and assistant referees. Referees’ mean daily energy intake (DEI) was 2819 ± 279 kcal. The intake of proteins (1.7 ± 0.2 g · kg^?1), carbohydrates (4.1 ± 0.8 g · kg^?1) and fats (1.4 ± 0.2 g · kg^?1) represented, respectively, 18.4 ± 1.5%, 44.4 ± 4.4% and 34.6 ± 4.1% of the DEI. Carbohydrate intakes before, during and after exercise were 66 ± 42, 7 ± 15 and 120 ± 62 g. Daily carbohydrate, fibre, polyunsaturated fat and water intakes were below recommendations, while fat, saturated fat, cholesterol and sodium intakes were above recommended values. The prevalence of inadequate intake was high for vitamin E (96%), folate (74%), vitamin A (61%), vitamin C (39%), magnesium (26%) and calcium (22%). Carbohydrate intake before, during and after exercise were far from achieving the minimum recommended values. Most referees demonstrated a negligent behaviour of hydration during exercise. Referees would benefit from dietary education in order to optimise performance and health.     

Unfairness in access to higher education: a 11 year comparison of grade inflation by private and public secondary schools in Portugal

Fairness in access to HE is unarguably a subject of paramount importance. Wherever a student’s secondary school scores are relevant for access to HE, grade inflation practices may jeopardize fair access. Pressures for high grading are common in the context of educational consumerism and competition between schools and students. However, they are not equally distributed across different types of schools, given that they have distinct relationships with the State and the market, and work with distinct populations. Specifically, the schools that are more subject to market pressures (namely private schools) are, in principle at least, the ones with more incentives to inflate their students’ grades. This paper presents an empirical study based on a large, 11 years database on scores in upper secondary education in Portugal, probing for systematic differences in grade inflation practices by four types of schools: public schools, government-dependent private schools, independent (fee-paying) private schools, and specially funded public schools in disadvantaged areas (TEIP schools). More than 3 million valid cases were analysed. Our results clearly show that independent private schools inflate their students’ scores when compared to the other types of schools. They also show that this discrepancy is higher where scores matter most in competition for HE access. This means that—usually wealthier—students from private independent schools benefit from an unfair advantage in the competition for the scarce places available in public higher education. We conclude discussing possible solutions to deal with such an important issue.