A PI controller configuration for robust control of a class of nonlinear systems

The PI control configuration for stabilization and signal tracking of nonlinear systems is investigated. Semiglobal asymptotic stability and semiglobal practical signal tracking of the controlled system are proven using results from the theory of nonlinear singularly perturbed systems.     

Are practical activities and ICTs important？ Thoughts and practice of a physics teacher

The influence of teachers＇ beliefs in curriculum implementation has been explored in a number of contexts. With the aim of describing curricular beliefs about practical activities in laboratory and 1CT （information and communication technology） resources, and the relationship between thinking and practice, the author has carried out the case study of a physics teacher, both in his classroom activities and those in laboratory. The sources of information include field notes, questionnaire, interviews, planning and class observation. The results indicate that, what teachers believe is not the same as what they do, appearing more constructive in thinking and more traditional in practice. For example, they believe that ICT must be used to teach science, however, in practice, the most utilized resource is the textbook. The author considers that, taking into account this kind of incoherence is essential in order to reflect about teachers＇ knowledge of sciences, practices and the relationship between these.     

Encounters of the Traditional Kind: Reflections on the In‐Service Teacher Training of Traditional Filipino Arts

This article presents the second segment of a qualitative study on the integration of traditional arts in tertiary level art and design education in the Philippines. It is focused on the experience of artist‐teachers as participants in an in‐service teacher training programme that aimed to prepare the teachers for the trial integration of traditional Filipino arts in art and design courses. Taking the view of the participants, journals written by the artist‐teachers were sourced for their reflections about their encounter with traditional Filipino artists during field visits. This phase of the study takes the form of action research as it involves the participants in gathering data that could inform the methods and content of the learning of traditional Filipino arts in the schools of art and design. The findings reveal that artist‐teachers acknowledge the traditional artist as a valuable source of traditional knowledge and expertise. They also recognise their own essential role in the transmission of learning between the traditional artists and the students. The prerequisites of the course take the artist‐teachers beyond teaching in the classroom and extend their tasks to research.     

Hierarchical linear dynamical systems for unsupervised musical note recognition

In this paper we develop a new framework for time series segmentation based on a Hierarchical Linear Dynamical System (HLDS), and test its performance on monophonic and polyphonic musical note recognition. The center piece of our approach is the inclusion of constraints in the filter topology, instead of on the cost function as normally done in machine learning. Just by slowing down the dynamics of the top layer of an augmented (multilayer) state model, which is still compatible with the recursive update equation proposed originally by Kalman, the system learns directly from data all the musical notes, without labels, effectively creating a time series clustering algorithm that does not require segmentation. We analyze the HLDS properties and show that it provides better classification accuracy compared to current state-of-the-art approaches.     

Relationship between exchange block time in swim starts and final performance in relay races in international championships

Abstract

The purpose of this study was to investigate the association between relay exchange block time and final performance in 4 × 100-m and 4 × 200-m freestyle and 4 × 100-m medley relays as a function of sex (men and women) and classification (medallists and non-medallists) in international competitions. Nineteen international competitions covering a 13-year period (2000–2012) were analysed retrospectively. The data corresponded to a total of 827 team relay histories (407 men, 420 women). Kruskal–Wallis and Mann–Whitney tests were performed to determine any differences by sex, classification, and event. Similarly, the relationship between the exchange block times and final performance was examined by means of a Pearson correlation analysis. In the three events, the men’s exchange block times were shorter than those of the women (η² = 0.049–0.109; P < 0.001). The exchange block time was especially relevant for the women’s relay medallists in the 4 × 100-m freestyle (r = 0.306, P = 0.021) and 4 × 100-m medley (r = 0.385, P = 0.011), while for men the relationship was clearer for the non-medallists. These results suggest that the exchange block time should be considered as one of the performance parameters of swimming relay starts, and thus should be included explicitly as part of training. In particular, the coach could design training targeted at standardising an optimal exchange block time equal to or less than that expected for other teams in the competition.     

Variable training: effects on velocity and accuracy in the tennis serve

Abstract

Variable practice has been shown to be an effective strategy to improve open motor skills. However, the usefulness of this procedure in closed motor skills remains controversial. The following study has the objective of analysing the effects of variability practice in the improvement of a closed skill. The skill studied has been the tennis serve. Thirty young tennis players (13 ± 1.52 years), divided in two groups, took part in this study. One group practiced in variable conditions and the other group in consistency conditions. Both groups performed 12 training sessions (60 serves/session). The variable practice group improved their accuracy significantly compared with the consistency group (F_3.25 = 3.078; P = 0.035). The velocity of serve increased after training in both groups (F_3.25 = 15.890; P = 0.001). The practice in variable conditions seems to be effective in improving the performance of the tennis serve.     

Effects of mat characteristics on plantar pressure patterns and perceived mat properties during landing in gymnastics

Shock absorption and stability during landings is provided by both, gymnast ability and mat properties. The aims of this study were to determine the influence of different mat constructions on their energy absorption and stability capabilities, and to analyse how these properties affect gymnast's plantar pressures as well as subjective mat perception during landing. Six mats were tested using a standard mechanical drop test. In addition, plantar pressures and subjective perception during landing were obtained from 15 expert gymnasts. The different mats influenced plantar pressures and gymnasts' subjective perception during landing of gymnasts. Significant correlations between plantar pressures at the medial metatarsal and lateral metatarsal zones of the gymnasts' feet with the different shock absorption characteristics of the mats were found. However, subjective perception tests were not able to discriminate mat functionality between the six mats as no significant correlations between the mechanical mat properties with the subjective perception of these properties were found. This study demonstrated that plantar pressures are a useful tool for discriminating different landing mats. Using similar approaches, ideally including kinematics as well, could help us in our understanding about the influences of different mats upon gymnast-mat interaction.     

The interdependence of language and translational math skills among bilingual hispanic engineering students

The performance of 43 Hispanic engineering and science majors on a task that consists of reading a sentence describing a mathematical relationship between two variables, and then writing an equation describing the relationship, is investigated in both English and Spanish. Results are compared with grade point average and with language proficiency. Comparison of the bilingual group to a monolingual group consisting of 52 engineering and science students shows that performance, as measured by either the mathematical translation task or grade point average, is more strongly correlated with language proficiency for the bilingual group. Clinical interviews conducted with samples from each group reveal large differences in the interpretation of the mathematical task between Hispanics and monolinguals. Suggestions are made for the improvement of the technical education of Hispanics.     

The Evolution of the Concept of Capacitance Throughout the Development of the Electric Theory and the Understanding of Its Meaning by University Students

There are few didactic studies concerning the difficulties met by students inunderstanding the meaning of capacitance in a charged body. However, theunderstanding of capacitance can be a good indicator of the Students' learningof electrostatic theory in general. To describe Students' difficulties in learningthis concept we have considered, on the one hand, that individuals constructmental representations in order to help their understanding of the way a physicalsystem works under varied circumstances. On the other hand, a critical study ofthe history and epistemology of science is likely to enlighten us teachers andresearchers about the presence of qualitative leaps in the evolution of a concept.Thus, the consideration by teachers of these `discontinuities between meaningsfor the same concept, may lead them to understand Students' difficulties on learningit. We developed a historical study of the development of the capacitance conceptand an empirical study with students to identify historical and learning difficulties.The results obtained seem to show that most of the students who reason aboutaspects related to the charge of bodies and capacitance feel more comfortablewhen they talk in terms of charge than in terms of electric potential in a similarway to the first explanations of the early electric theories.     

Perceptual learning transfer in an appetitive Pavlovian task

In two experiments, rats were given intermixed or blocked preexposure to two similar compound stimuli, AX and BX. Following preexposure, conditioning trials took place in which AX (Experiment 1) or a novel compound stimulus NX (Experiment 2) was paired with a food-unconditioned stimulus in an appetitive Pavlovian preparation. Animals that were given alternated preexposure showed lower generalization from AX to BX (Experiment 1) and from NX to a new compound, ZX (Experiment 2), than animals that were given blocked preexposure, a perceptual learning and a perceptual learning transfer effect, respectively.