Inverse dynamics control in terms of unnormalized quasi-velocities

In this paper a proposition of inverse dynamics control for a manipulator using the unnormalized quasi-velocities (UQV) is presented. These quasi-velocities introduced by Jain and Rodriguez (IEEE Trans. Robotics Automat,16, 2000, 517; 11, 1995, 571) are used here to show some performance obtained from the controller. It is shown that for a two d.o.f. planar manipulator one can assume UQV which are integrable with respect to time. The introduced controller in terms of UQV is exponentially convergent. As a consequence of using UQV inverse dynamics control, one can notice some interesting properties in comparison with the classical controller. Additionally, some geometrical interpretation based on Riemannian geometry is given.     

The effect of peer group stability on achievements: Evidence from Poland

This article reports on a study using data from nation-wide standardised examinations in Poland. We analysed the extent to which grade 9 student achievements have depended on the stability of their peer group over the course of middle school. We controlled for the fixed effects of schools attended by the students, as well as for individual achievements prior to middle school enrolment. To mitigate the risk for endogeneity, analysis was informed by a consideration of the fact that middle schools operate in different institutional relations with nearby primary schools. This also allowed us to distinguish between the effect related to peer group stability and the one connected to the stability of the learning environment in general. The results of our analysis show that instability significantly reduces students' expected performance in mathematics and science. The impact of peer group stability on test achievements varies strongly across the student ability distribution. Very low-performing students and top performers were most affected. The average students were largely unaffected. One category of students that seems to benefit from the change when moving to middle school are students from very competitive primary schools who have average skills.     

Translating Key Competences into the School Curriculum: lessons from the Polish experience

Over the last 20 years, Poland has gone through a major transition process in which the challenges for education in terms of new approaches to learning and teaching have been compounded by broader changes such as the democratisation of structures and processes and the major economic and social changes. This article is a case study that examines the early stages of significant shifts in the learning and teaching process, the stepped approach that was taken and the different international influences. It was decided to focus on the top-down, policy level actions in order to trace how influences have shaped current policy on outcomes-based approaches and key competences, which are increasingly implemented in schools today. The Polish education and training system has been through a complex series of reforms, many simultaneously. The introduction of outcome-based approaches and key competences is part of much broader reforms that have affected mindsets and attitudes by having addressed the structure of the system (e.g. the length of compulsory education), school governance, the roles of principals and teachers, teacher training, etc. Parents' expectations have evolved and students are growing up in a much more connected environment with Internet and social networks and an exponential development of access to ICT and the need for digital competences and a range of key competences for lifelong learning and work (Gordon et al., 2009). Although change has taken place at all levels and in all sub-sectors of the system, this article focuses on general education in primary and secondary schools.     

Choosing the Future: Economic Preferences for Higher Education Using Discrete Choice Experiment Method

Research in Higher Education - This study illustrates how respondents’ stated choices (the discrete choice experiment method) combined with the random utility framework can be used to model...     

Relevance matters. Eighteen-month-olds’ use of relevant informative pointing as a predictor of two-year-olds’ language abilities / La relevancia es importante. El uso de gestos deícticos relevantes e informativos por parte de niños de año y medio como factor predictor de las capacidades lingüísticas a los dos años

Abstract

The significance of pointing gestures in the development of linguistic communication is linked to their referential character and formation of common ground in use of gestures and speech. Our longitudinal study aimed to define the nature of this relationship more precisely and to explore whether the relevance vs lack of relevance of a child’s pointing gestures is related to development of language abilities. We developed a special protocol to measure relevant and irrelevant pointing gestures in 18-month-olds, sampled production of spontaneous speech and measured their language comprehension at two years of age. A group of 343 children was tested, and using structural equation modelling we showed that relevant gestures predict the level of development of language production and comprehension. As predicted, this association was not applied to irrelevant gestures. It is likely that a child’s more frequent use of relevant pointing gestures helps the caregiver to recognize the child’s communicative intentions and to comment on his/her behaviour appropriately. The identified developmental/predictive relationship is valid in both mentalistic and teleological interpretation of early communicative development.     

Oculomotor dynamics in skilled soccer players: The effects of sport expertise and strenuous physical effort

The ability to quickly locate objects within the visual field has a significant influence on athletic performance. Saccades are conjugate eye movements responsible for the rapid shift that brings a new part of the visual field into foveal vision. The aim of this study was to investigate the effects of sport expertise and intense physical effort on saccade dynamics during a free-viewing visual search task in skilled soccer players. Two groups of male subjects participated in this study: 18 soccer players and 18 non-athletes as the control group. Two sessions of visual search tasks without a sport-specific design were employed. Eye movements during the visual search tasks were recorded binocularly. Between pre- and post-test sessions, athletes performed a maximal incremental treadmill test. Cardiorespiratory parameters were measured continuously. Capillary lactate samples were collected. Pre-test findings indicated that athletes, in comparison to non-athletes, achieve higher values of the following characteristics of saccades (1) average acceleration, (2) acceleration peak, (3) deceleration peak, and (4) average velocity. An increase in post-test saccade duration and a decrease in post-test saccade velocity was observed in athletes due to the strenuous physical effort in relation to the pre-test state. Athletes may transfer high saccadic function efficiency to non-specific visual stimuli. The findings partially confirm that physical exertion can reduce oculomotor efficiency in athletes.     

Distribution of the AMPD1 C34T polymorphism in Polish power-oriented athletes

The aims of this study were to determine the distribution of the AMPD1 genotype among groups of high-level Polish power-oriented athletes, and to investigate potential associations between genetic polymorphism in exon 2 of the AMPD1 gene and power-oriented athlete status. Altogether, 158 male Polish power-oriented athletes were genotyped by PCR-RFLP. The genetic control group comprised 160 unrelated male volunteers. We observed significant differences in genotype distribution when all 158 athletes (89.25% CC, 10.75% CT, 0.00% TT; P = 0.0025) were compared with controls (75.00% CC, 23.75% CT, 1.25% TT). A significant deficiency of the T allele was noted in all subgroups (short-distance runners: 5.21%, P = 0.032; short-distance swimmers: 5.56%, P = 0.031; weightlifters: 5.36%, P = 0.024) compared with controls (13.13%), while this trend was even stronger when the frequency of the T allele was compared between controls and all 158 athletes (5.38%, P = 0.0007). Our results indicate a lower frequency of the AMPD1 exon 2 T34 allele in elite Polish power-oriented athletes. Our data suggest that the C allele may help athletes to attain elite status in power-oriented sports.     

Future climate-induced pressures on painted wood

A broad category of cultural heritage objects are multilayer structures composed of organic, humidity-sensitive materials – wood, animal glue, paper, leather, bone or paints. They respond to variations in relative humidity (RH) in their environment by cyclically gaining and losing moisture, and consequently swelling and shrinking. Differences in the moisture response of the materials induce internal stresses in the individual layers of the structures, which cause objects to deform and crack. Polychrome wood is examined in detail. The cumulative physical damage of the design layer on wood due to repeated RH variations is quantified in terms of their magnitude and number of times they occur. The climatological risk index for accumulated, ‘fatigue’ damage is established, using a procedure to reduce irregular real-world climate histories into simple RH cycles of known damage impact. Using output from the Hadley Model (HadCM3) and simple transfer functions predicting indoor temperature and RH from outdoor climate, changes in the indoor climate through to 2100 were forecast for unheated buildings. European maps highlighting the areas in which painted wood may be significantly affected by climate change are presented.