Rotary inverted pendulum with magnetically external perturbations as a source of the pendulum’s base navigation commands     

Gisela Pujol-Vazquez  Leonardo Acho  Saleh Mobayen  Amelia Nápoles  Vega Pérez 《Journal of The Franklin Institute》2018,355(10):4077-4096

The main objective of this paper is to drive a rotary inverted pendulum by following a desired navigation instruction. This navigation is commanded by the user through a new electromagnetic device which is allowed to perturb the pendulum from its upright position. This apparatus consists of an electronic magnetic driving circuit to introduce commands and realized via two operated magnetic coils. So, the external programmed magnetic perturbation can be seen as external commandments. Therefore, the control problem statement is solved via a modified regulation control implementation, to maintain the pendulum on its upright position and giving free manipulation of the base of the rotary inverted pendulum. Hence, by using the corresponding H_∞-linear matrix inequality technique, a static state controller is designed and tested experimentally so supporting our findings.  相似文献   

A numerically robust blind equalization scheme applied to MIMO communication systems     

Flávio R.  M. Pavan  Magno T.  M. Silva  Maria D. Miranda 《Journal of The Franklin Institute》2018,355(1):596-624

In this paper, we propose a numerically robust blind equalization scheme to mitigate cochannel and intersymbol interferences and separate signals from a convolutive mixture in multiple-input multiple-output (MIMO) communication systems. The robustness of the proposed scheme is achieved through a particular dual-mode operation applied to a constant-modulus-based space-time algorithm that corrects phase rotations. In the first mode of operation, the consistency in the nonlinear estimates of the transmitted signals is ensured. In the second mode, the Euclidean norms of the equalizer coefficient vectors decrease along the iterations, which allows the algorithm to return to the first mode of operation, where the estimation of the transmitted signals really occurs. In particular, we apply this scheme to a multimodulus version of the multiuser Shalvi-Weinstein algorithm (MU-SWA). By means of a deterministic stability analysis assuming the persistence of excitation condition, we show that the dual-mode MU-SWA does not diverge.  相似文献   

Assessing perceived need support and need satisfaction in physical education: adaptation and validation with English students     

David Sánchez-Oliva  Florence-Emilie Kinnafick  Nathan Smith  Andreas Stenling 《Measurement in physical education and exercise science》2018,22(4):332-342

This study aimed to validate an English version of Basic Psychological Needs Support Questionnaire (BPNSQ) and the Basic Psychological Needs in Physical Education Scale (BPN-PE) in the physical education context. Participants included 453 students aged between 12 and 17 years. For the BPNSQ, the hypothesized three-factor solution displayed high interfactor correlations (rs > 1), and a follow-up analysis indicated that the items were represented by a single need-support factor. For the BPN-PE, hypothesized three-factor solution was supported. Both scales were found invariant across gender, and the nomological validity was also demonstrated through the associations between factors of both scales. This study provides initial support for the use of the BPN-PE to assess psychological need satisfaction within the physical education context among English-speaking adolescents. The hypothesized three-factor structure of the BPNSQ was not supported and more research is needed to evaluate the English version in the physical education context.  相似文献   

A qualitative analysis of the factors determining the quality of relations between a novice physical education teacher and his students’ families: implications for the development of professional identity     

Gustavo González-Calvo 《Sport, Education and Society》2018,23(5):491-504

The purposes of this study were: (a) to analyze the factors determining the quality of relationships between a novice physical education (PE) teacher and his students’ families and (b) understand the implications of these relationships for his professional identity. The data stemmed from detailed teacher’s diaries written by the participant throughout his first five years of teaching. The data analysis followed several rounds of cyclical inductive-deductive processes in order to identify and classify the patterns related to the aforementioned purposes. The results, presented in two sections, show two distinct sets of factors, which, respectively, had very different implications for the development of the teacher’s professional identity. On the one hand, in the first three years of teaching, there appeared 11 specific ‘struggle factors’ (6 socio-cultural and structural factors and 5 family prejudices toward PE) that threatened the teacher’s initial pedagogical passion and lead to a great deal of hesitation and discouragement on his part; on the other hand, in the fourth and fifth years, due to the teacher’s ongoing commitment and (self-)reflective practice, there emerged eight ‘success factors’ (one from the families and seven from the teacher) that transformed his previous discouragement into hope and self-confidence. Besides the detailed analysis of all these factors and their implications, some additional recommendations for PE teacher education programs and further research are provided.  相似文献   

Parasympathetic activity delayed after self-paced exercise     

Lucas Rosiello Trojbicz  Mayara Vieira Damasceno  Leonardo Alves Pasqua  Arthur Fernandes Gáspari  Adriano Eduardo Lima-Silva 《European Journal of Sport Science》2018,18(6):842-850

The main purpose of this study was to compare the effect of the constant load and self-paced exercise with similar total work on autonomic control after endurance exercise. Ten physically active men were submitted to (i) a maximal incremental exercise test, (ii) a 4-km cycling time trial (4-km TT), and (iii) a constant workload test with identical total external work performed at 4-km TT. Gas exchange was measured throughout the tests, while blood lactate, heart rate, and heart rate variability (HRV) were measured during the passive recovery. Power output measured at the last lap (i.e. 3600–4000?m) of 4-km TT (316?±?89?W) was statistically higher than power output measured at the end of the constant workload exercise (211?±?42?W). The 4-km TT produced higher values of blood lactate concentration (8.8?±?2.1?mmol?L^?1) than the constant workload test (7.8?±?2.1?mmol?L^?1). The heart rate recovery measured at 60?s (constant workload: 37?±?7?bpm; 4-km TT: 30?±?6) and 120?s (constant workload: 57?±?9?bpm; 4-km TT: 51?±?9?bpm) were higher in the constant workload than in the self-paced exercise. The HRV (i.e. RMSSD30s) was statistically higher in the constant load exercise measured at 120, 420, 450, 480, 540, and 570?s than the self-paced exercise. These findings suggest that the autonomic control responses were dependent of the endurance exercise modalities, with parasympathetic activity being delayed after self-paced exercise, as evidenced by post-exercise heart rate indices.  相似文献   

Effects of different percentages of body weight support on spatiotemporal step characteristics during running     

Luis E. Roche-Seruendo  Isabel Auria-Martin  Ana V. Bataller-Cervero  Pedro A. Latorre Román  Victor M. Soto -Hermoso 《Journal of sports sciences》2018,36(13):1441-1446

This study aimed to determine the effect of different percentages of body weight support (BWS) on spatiotemporal step characteristics during running. 26 endurance runners (age: 37 ± 9 years) completed a running treadmill protocol consisting of 6 different conditions (BWS combinations: 0–50%), with velocity maintained at 12 km/h. Each condition lasted 1 minute. Step angle, ground contact time (CT), flight time (FT), step length (SL) and frequency (SF), and duration of phases during stance time (phase1: initial contact; phase2: midstance; phase3: propulsion) were measured for every step during the test using a photoelectric cell system. Compared with the baseline condition (100% BW), FT was longer, CT was shorter, SL was longer, SF was lower, and the step angle was higher with each increase in BWS (p < 0.05). Also, some changes were observed in the duration of phases during stance time: phase1 did not experience changes across experimental conditions (p = 0.096), phase2 decreased and phase3 increased as BW was supported (p < 0.05). These results indicate that as BW was supported, runners showed longer FT and SL, shorter CT, lower SF, and greater step angle as well as some changes in the phases during the ground contact. Therefore, this study highlights the effect of different percentages of BWS on spatiotemporal parameters.  相似文献   

Influence of different attentional focus on EMG amplitude and contraction duration during the bench press at different speeds     

Joaquin Calatayud  Jonas Vinstrup  Markus D. Jakobsen  Emil Sundstrup  Juan Carlos Colado  Lars L. Andersen 《Journal of sports sciences》2018,36(10):1162-1166

The purpose of this study was to investigate whether using different focus affects electromyographic (EMG) amplitude and contraction duration during bench press performed at explosive and controlled speeds. Eighteen young male individuals were familiarized with the procedure and performed the one-maximum repetition (1RM) test in the first session. In the second session, participants performed the bench press exercise at 50% of the 1RM with 3 different attentional focuses (regular focus on moving the load vs contracting the pectoralis vs contracting the triceps) at 2 speed conditions (controlled vs maximal speed). During the controlled speed condition, focusing on using either the pectoralis or the triceps muscles increased pectoralis normalized EMG (nEMG) by 6% (95% CI 3–8%; p = 0.0001) and 4% nEMG (95% CI 1–7%; p = 0.0096), respectively, compared with the regular focus condition. Triceps activity was increased by 4% nEMG (95% CI 0–7%; p = 0.0308) at the controlled speed condition during the triceps focus. During the explosive speed condition, the use of different focuses had no effect. The different attentional focus resulted in comparable contraction duration for the measured muscles when the exercise was performed explosively. Using internal focus to increase EMG amplitude seems to function only during conditions of controlled speed.  相似文献   

Growth,functional capacities and motivation for achievement and competitiveness in youth basketball: an interdisciplinary approach     

Humberto Moreira Carvalho  Carlos E Gonçalves  Dave Collins  Roberto R Paes 《Journal of sports sciences》2018,36(7):742-748

The interaction of multiple influences on the path to sport success is not yet fully understood by sport scientists. In this study, we examined variation in body size, functional capacities and motivation for achievement, competitiveness and deliberate practice of youth basketball players associated with differences in biological maturity status, chronological age and years of training experience. Reflecting the importance of interactive effects, we examined the relationships between the psychological variables and functional capacities. Fifty-eight male basketball players aged 9.5 to 15.5 years were considered. Variables included chronological age, estimated age at peak height velocity, stature, body mass and sitting height by anthropometry; the Work and Family Orientation and Deliberate Practice Motivation Questionnaires were also used. Finally, the Line Drill test and Yo-Yo Intermittent Recovery level 1 (Yo-Yo IR1) tests were used as functional capacities indicators for basketball. Variance components models derived from series of multilevel linear regression models revealed a substantial variation by maturity status for body size, functional capacities indicators, mastery and will to excel. The influence of estimated maturity status on mastery and will to excel was independent of age and years of experience. In contrast, no relationships were observed between psychological variables and functional capacities indicators. We conclude that growth-related changes are relevant to understanding players´ motivations for achievement, competitiveness and deliberate practice. This should be of interest to those involved in the selection and development of youth basketball players.  相似文献   

A cross-sectional and prospective analyse of reallocating sedentary time to physical activity on children’s cardiorespiratory fitness     

Diana A. Santos  Adilson Marques  Cláudia S. Minderico  Ulf Ekelund 《Journal of sports sciences》2018,36(15):1720-1726

Cardiorespiratory fitness (CRF) is associated with health benefits in children, improving cardiac morphology, cardiovascular disease risk factors, and biological outcomes. This study aimed to examine the substitution effects of displaying a fixed duration of sedentary time with a fixed duration of physical activity (PA) at different intensities on children’s CRF. A total of 315 children (136 boys) were assessed (age: 10.6 ± 0.6 years old). Outcomes at baseline and follow-up (16-months) were CRF determined using a maximal cycle test and sedentary time and PA measured with accelerometers. Data were analysed by isotemporal substitution analyses estimating the effect of reallocating 30 min/day of sedentary time by light (LPA), moderate (MPA) and vigorous physical activity (VPA) on CRF. VPA was positively and significantly associated with CRF cross-sectional (β = 0.026, p < 0.001) and prospectively (β = 0.010, p < 0.001). Reallocating 30 min/day of sedentary time into VPA was positively cross-sectionally (β = 0.780, p < 0.001) and prospectively (β = 0.303, p < 0.05) associated with CRF. Conversely, relocating 30-minutes of sedentary time into 30 minutes of LPA and MPA was not associated with CRF. These results suggest that reallocating an equal amount of time from sedentary into VPA is cross-sectional and prospectively associated with a favourable CRF.  相似文献   

Automatic evaluation of digital libraries with 5SQual     

Bárbara L. Moreira  Marcos André Gonçalves  Alberto H.F. Laender  Edward A. Fox 《Journal of Informetrics》2009,3(2):102-123

Digital libraries (DLs) are complex information systems which can present changes in their structure, content, and services. These complexities and dynamics make system maintenance a non-trivial task, since it requires periodical evaluation of the different DL components. Generally, these evaluations are customized per system and are performed only when problems occur and administrator intervention is required. This work aims to change the situation. We present 5SQual, a tool which provides ways to perform automatic and configurable evaluations of some of the most important DL components, among them, digital objects, metadata, and services. The tool implements diverse numeric indicators that are associated with eight quality dimensions described in the 5S quality model. Its generic architecture was developed to be applicable to various DLs and scenarios. In sum, the main contributions of this work include: (i) the design and implementation of 5SQual, a tool that validates a theoretical DL quality model; (ii) the demonstration of the applicability of the tool in several usage scenarios; and (iii) the evaluation (with usability specialists) of its graphical interface specially designed to guide the configuration of 5SQual evaluations. We also present the results of interviews conducted with administrators of real DLs regarding their expectations and opinions about 5SQual.  相似文献