Science Letters：Visual odometry for road vehicles —— feasibility analysis

Estimating the global position of a road vehicle without using GPS is a challenge that many scientists look forward to solving in the near future. Normally, inertial and odometry sensors are used to complement GPS measures in an attempt to provide a means for maintaining vehicle odometry during GPS outage. Nonetheless, recent experiments have demonstrated that computer vision can also be used as a valuable source to provide what can be denoted as visual odometry. For this purpose, vehicle motion can be estimated using a non-linear, photogrametric approach based on RAndom SAmple Consensus (RANSAC). The results prove that the detection and selection of relevant feature points is a crucial factor in the global performance of the visual odometry algorithm. The key issues for further improvement are discussed in this letter.     

Relationship between physical activity,physical fitness and multiple metabolic risk in youths from Muzambinho's study

Negative associations between physical activity (PA), physical fitness and multiple metabolic risk factors (MMRF) in youths from populations with low PA are reported. The persistence of this association in moderately-to highly active populations is not, however, well established. The aim of the present study was to investigate this association in a Brazilian city with high frequency of active youths. We assessed 122 subjects (9.9?±?1.3 years) from Muzambinho city. Body mass index, waist circumference, glycaemia, cholesterolaemia, systolic and diastolic blood pressures were measured. Maximal handgrip strength and one-mile walk/run test were used. Leisure time PA was assessed by interview. Poisson regression was used in the analysis. The model explained 11% of the total variance. Only relative muscular strength and one-mile walk/run were statistically significant (p?相似文献   

Acute effects of exercise and active video games on adults’ reaction time and perceived exertion

The purpose of the present study was to examine the acute effects of resting, aerobic exercise practised alone, and aerobic exercise with active video games (AVG), on complex reaction time (CRT) and the post-exercise acute rate of perceived exertion (RPE) in young healthy adults. The experimental group was composed of 92 healthy young adults, 78 males and 13 females (age M?=?21.9?±?2.7 years) who completed two sessions, A and B. In session A, participants rode 30?min on an ergometer, while in session B they exercised for 30?min on an ergometer while playing an AVG on a Wii. The control group was composed of 30 young adults, 26 males and 4 females (age M?=?21.4?±?2.9 years) who rested for 30?min. In each session, a CRT task was performed before and after exercising or resting, and post-exercise global RPE was noted. Repeated measures general linear model (GLM) and Wilcoxon tests were performed. (1) Both aerobic exercise alone and aerobic exercise combined with AVG improved CRT, while resting did not; (2) aerobic exercise combined with AVG did not improve CRT more than aerobic exercise only; and (3) RPE was lower after aerobic exercise combined with AVG compared with aerobic exercise only. In young adults, exercise produces acute benefits on CRT, and practising exercise with AVG helps to decrease RPE.     

Effects of an intervention programme with teachers on the development of positive behaviours in Spanish physical education classes

Background: The physical education (PE) context has been emphasised as an ideal environment for developing positive behaviours among students. Under the Positive Youth Development paradigm, various initiatives have been conducted with the aim of promoting personal and social responsibility among adolescents. Self-Determination Theory has been widely used to analyse students’ motivational processes during PE classes.

Purpose: This study aimed to measure the effects of a multidisciplinary intervention with teachers on the development of positive behaviours in PE classes.

Participants: Twenty PE teachers participated in the study (M_age?=?35 years; SD?=?2.32) along with 777 of their students (M_age?=?12.81 years; SD?=?.93). The teachers (male?=?16; female?=?4) were between the ages of 29 and 48 years (M?=?35.2 years; SD?=?2.32). The students who participated in this study (male?=?377; female?=?400) were divided into 52 classes and were between the ages of 12 and 16 years (M?=?12.81; SD?=?.93).

Research design: A quasi-experimental design was used that consisted of a control group and three groups in which an intervention was developed. In the control group, the teachers did not receive any type of intervention; in the second group, the teachers received a training programme to develop strategies for supporting basic psychological needs and promoting positive behaviours; in the third group, the teachers received a didactic unit to promote positive behaviours; and in the last group the teachers received a combination of the two previous interventions.

Data analysis: A repeated-measures ANCOVA (analysis of covariance) was used for every dependent variable included in the study to analyse the effect of Group?×?Time interaction, including Gender and Grade Level as covariates. The fixed effects caused by Intercept, Group, Time, and the Group?×?Time interaction were calculated using compound symmetry as the type of covariance and restricted maximum likelihood as the estimation method.

Findings: By examining the differences between pre-test and post-test, it was determined that in comparison with the students in the control group, the students from the three experimental groups had generally improved scores on the variables related to positive behaviours, such as perceptions of the teacher's support, as well as the development of the targeted behaviours.

Conclusions: These results provide information about the efficacy of an intervention programme with teachers that consists of strategies for developing positive behaviour and support for basic psychological needs to promote the development of positive student behaviour.     

Yo-Yo Intermittent Endurance Test-Level 1 to monitor changes in aerobic fitness in pre-pubertal boys

The present study aimed to examine the performance and heart rate responses during the Yo-Yo Intermittent Endurance Test-Level 1 (Yo-Yo IE1) in children under the age of 10. One hundred and seven male children (7–9 years) performed the Yo-Yo IE1 at the beginning (M₁), middle (M₂) and end (M₃) of the school year. Data from individual heart rate curves of the Yo-Yo IE1 were analysed in order to detect the inflection point between an initial phase of fast rise in heart rate values and a second phase in which the rise of the heart rate values is much smaller. The distance covered in the Yo-Yo IE1 improved from M₁ to M₃ (884 ± 496 vs. 1032 ± 596 m; p < 0.05; d = 0.27), with intermediate values for M₂ (962 ± 528 m). Peak heart rate (HR_peak) decreased from M₁ to M₂ and M₃ (204 ± 9, 202 ± 9 and 200 ± 9 bpm, respectively; p < 0.05; d = 0.25–0.42). The 7th shuttle of the test (280 m), corresponding to 2.5 min, was identified as the inflection point between the two phases. Also, absolute heart rate at the 7th shuttle decreased progressively throughout the year (185 ± 9, 183 ± 10, and 179 ± 10 bpm; p < 0.05; d = 0.31–0.61). The present study provides evidence of the usefulness of a maximal as well as a submaximal version of Yo-Yo IE1 as a tool to monitor changes in aerobic fitness in pre-pubertal children.     

Evolution in Freedom? The Meanings of ‘Free School’ in Chile

This article examines the background in which enterprises called free schools, as well as complementary educational activities, have taken root in Chile. Two kinds of recently burgeoning free schools are identified; one supplementing regular schooling with a social justice focus, and another that is a fully fledged alternative to other schooling. The history of freedom itself in Chile is explored from a historical perspective, contrasting somewhat with freedom as it is understood in more developed countries. Parallels to Anglophone free schools such as AS Neill’s Summerhill are also discussed, as well as the sociopolitical context in which Chilean free schools continue to develop.     

Three concepts or one? Students’ understanding of basic limit concepts

In many mathematics curricula, the notion of limit is introduced three times: the limit of a sequence, the limit of a function at a point and the limit of a function at infinity. Despite the use of very similar symbols, few connections between these notions are made explicitly and few papers in the large literature on student understanding of limit connect them. This paper examines the nature of connections made by students exposed to this fragmented curriculum. The study adopted a phenomenographic approach and used card sorting and comparison tasks to expose students to symbols representing these different types of limit. The findings suggest that, while some students treat limit cases as separate, some can draw connections, but often do so in ways which are at odds with the formal mathematics. In particular, while there are occasional, implicit uses of neighbourhood notions, no student in the study appeared to possess a unifying organisational framework for all three basic uses of limit.     

The impact of the university context on European students' learning approaches and learning environment preferences

This article describesexperiences of 610 Dutch students and 241students from other European countries whostudied at least three months abroad within theframework of an international exchange program.The Dutch students went to a university inanother European country and the foreignstudents went to a Dutch university. By meansof a questionnaire students' perceptions ofthree main characteristics of the universitylearning environment were measured concerningthe home university, the host university andthe ideal learning environment. The studentswere also asked about their way of learning atthe home university and at the host university,in particular about the extent of constructivelearning and reproductive learning. Evidencewas found for the influence of aspects of thelearning environment on the two learningapproaches; e.g., a learning environmentcharacterized as student-oriented discouragesreproductive learning and promotes constructivelearning, especially when conceptual andepistemological relations within the learningdomain are stressed. The learning environmentpreferences of the students were partly relatedto their learning orientations at the homeuniversity, but they were strikingly similarfor students from different countries. Therewas a strong preference for those learningenvironment aspects that promote constructivelearning.     

Spiral and Project-Based Learning with Peer Assessment in a Computer Science Project Management Course

Different learning methods such as project-based learning, spiral learning and peer assessment have been implemented in science disciplines with different outcomes. This paper presents a proposal for a project management course in the context of a computer science degree. Our proposal combines three well-known methods: project-based learning, spiral learning and peer assessment. Namely, the course is articulated during a semester through the structured (progressive and incremental) development of a sequence of four projects, whose duration, scope and difficulty of management increase as the student gains theoretical and instrumental knowledge related to planning, monitoring and controlling projects. Moreover, the proposal is complemented using peer assessment. The proposal has already been implemented and validated for the last 3 years in two different universities. In the first year, project-based learning and spiral learning methods were combined. Such a combination was also employed in the other 2 years; but additionally, students had the opportunity to assess projects developed by university partners and by students of the other university. A total of 154 students have participated in the study. We obtain a gain in the quality of the subsequently projects derived from the spiral project-based learning. Moreover, this gain is significantly bigger when peer assessment is introduced. In addition, high-performance students take advantage of peer assessment from the first moment, whereas the improvement in poor-performance students is delayed.     

The recent process of decentralization and democratic management of education in Brazil

Brazilian society is beginning a new historical period in which the principle of decentralization is beginning to predominate over centralization, which held sway during the last 25 years. In contrast to recent Brazilian history, there is now a search for political, democratic and participatory decentralization more consonant with grass-roots aspirations. The first section of this article presents a brief analysis of some decentralization policies implemented by the military regime of 1964, and discusses relevant facts related to the resistance of civil society to state authoritarianism, and to the struggle for the democratization and organization of civil society up to the end of the 1970s. The second section analyzes some new experiences of democratic public school administration initiated in the 1970s and 1980s. The final section discusses the move toward decentralization and democratization of public school administration in the new Federal and State Constitutions, and in the draft of the new Law of National Education.

---

Zusammenfassung Die brasilianische Gesellschaft beginnt einen neuen Abschnitt in ihrer Geschichte, in dem das Prinzip der Dezentralisierung über die in den letzten 25 Jahren vorherrschende Zentralisierung dominiert. Im Gegensatz zur jüngsten brasilianischen Geschichte wird nunmehr eine politische, demokratische und partizipatorische Dezentralisierung gesucht, die mit den regionalen Bestrebungen besser vereinbar ist. Der erste Teil dieses Artikels enthält eine kurze Analyse einiger 1964 vom Militärregime eingeführter Dezentralisierungmaßnahmen und untersucht relevante Fakten, die mit dem Widerstand der zivilen Gesellschaft gegen die Staatsgewalt und mit dem Kampf um Demokratisierung und eine Organisation der zivilen Gesellschaft bis Ende der 70er Jahre zusammenhängen. Im zweiten Teil werden einige neue Erfahrungen den in der 70er und 80er Jahren eingeführten Verwaltung öffentlicher demokratischer Schulen analysiert. Im Schlußteil geht es um die Entwicklung zur Dezentralisierung und Demokratisierung der öffentlichen Schulverwaltung in den neuen Bundes- und Staatsverfassungen und im Entwurf des neuen Gesetzes zu Nationaler Bildung.

---

Résumé La société brésilienne entame une nouvelle ère historique caractérisée par une prédominance du principe de décentralisation sur celui de centralisation, qui a prévalu durant les 25 dernières années. Par comparaison à l'histoire brésilienne moderne, on vise actuellement une décentralisation politique, démocratique et fondée sur la participation, qui soit plus en harmonie avec les aspirations du peuple. La première partie du présent article contient une brève analyse des politiques de décentralisation appliquées par le régime militaire de 1964, et discute les faits pertinents relatifs à la résistance de la société civile à l'autoritarisme de l'Etat, et à la lutte pour la démocratisation et l'organisation de la société civile jusqu'à la fin des années 70. La deuxième partie analyse quelques expériences récentes concernant la démocratisation de l'administration de l'école publique, inaugurée dans les années 70 et 80. La dernière partie examine le passage à la décentralisation et à la démocratisation dans l'administration de l'école publique dans la nouvelle constitution fédérale et dans celles des Etats fédérés, ainsi que dans le nouveau projet de loi sur l'Education nationale.