Robust self-triggered MPC with fast convergence for constrained linear systems

In this paper, a robust self-triggered model predictive control (MPC) scheme is proposed for linear discrete-time systems subject to additive disturbances, state and control constraints. To reduce the amount of computation on controller sides, MPC optimization problems are only solved at certain sampling instants which are determined by a novel self-triggering mechanism. The main idea of the self-triggering mechanism is to choose inter-sampling times by guaranteeing a fast decrease in optimal costs. It implies a fast convergence of system states to a compact set where it is ultimately bounded and a reduction of computation times to stabilize the system. Once the state enters a terminal region, the system can be stabilized to a robust invariant set by a state feedback controller. Robust constraint satisfaction is ensured by utilizing the worst-case set-valued predictions of future states in such a way that recursive feasibility is guaranteed for all possible realisations of disturbances. In the case where a priority is given to reducing communication costs rather than improvement in control performance in a neighborhood of the origin, a feedback control law based on nominal state predictions is designed in the terminal region to avoid frequent feedback. Performances of the closed-loop system are demonstrated by a simulation example.     

Difference score reliabilities within the RIAS-2 and WISC-V

Many prominent intelligence tests (e.g., Wechsler Intelligence Scale for Children, Fifth Edition [WISC-V] and Reynolds Intellectual Abilities Scale, Second Edition [RIAS-2]) offer methods for computing subtest- and composite-level difference scores. This study uses data provided in the technical manual of the WISC-V and RIAS-2 to calculate reliability coefficients for difference scores. Subtest-level difference score reliabilities range from 0.59 to 0.99 for the RIAS-2 and from 0.53 to 0.87 for the WISC-V. Composite-level difference score reliabilities generally range from 0.23 to 0.95 for the RIAS-2 and from 0.36 to 0.87 for the WISC-V. Emphasis is placed on comparisons recommended by test publishers and a discussion of minimum requirements for interpretation of differences scores is provided.     

New curve sprint test for soccer players: Reliability and relationship with linear sprint

ABSTRACT

The speed performance is involved not only in linear sprints, but also in a wide spectrum of multi-directional movements, such as curve sprinting. Curved sprint can be defined as sprint with gradual and continuous change of direction (COD). Although ~85% of the actions performed at maximum velocity in a professional soccer league are curvilinear sprints, there is not any specific test to assess this ability. This study aimed to analyse the reliability of a new curve sprint test, and compare its results with those obtained by soccer players in linear sprint. Forty experienced soccer players performed 3 attempts of curve sprint (using the penalty arc) to right and left side (17 m), and 3 linear sprints (17 m) in two different days. The ICCs (inter-session reliability) were 0.93 for sprint curve right side (CSRS) and 0.89 for sprint curve left side (CSLS), considered “acceptable”. The CVs (intra-session reliability) were 0.87% in CSRS and 1.15% in CSLS. The coefficient of determination (R²) between linear and curve sprinting was ~35%. The association between curve sides was “very large” (r = 0.878; p < 0.01). In summary, we showed that “curve sprint test” is highly reliable, and that curvilinear and linear sprints are different and independent actions.     

Comparison of 10 vs. 20 min neuromuscular training for the prevention of lower extremity injuries in male youth football: A cluster randomised controlled trial

ABSTRACT

The aim of this study was to compare the effects of 20 min neuromuscular training with a programme of 10 min in youth football players. 342 (15.4 ± 1.7 years) male football players from 18 teams were included, and cluster-randomized by team into two intervention groups. Both groups performed an injury prevention programme twice a week over five months using the same exercises but a different duration. The first intervention group (INT10, n = 175) performed the programme for 10 min, the second intervention group (INT20, n = 167) for 20 min. Primary outcomes were lower extremity (LE) injuries. Secondary outcomes were injury type, severity, mechanism and compliance to the intervention. 13 teams with 185 players were included for final analysis. No significant group difference was found between INT10 (6.37 per 1000 h) and INT20 (7.20 per 1000 h) for the incidence rate ratio of the lower extremities (IRR = 1.03, 95% confidence interval 0.59, 1.79), nor for the distribution of injury location, type, severity or mechanism. The results show that performing preventive exercises for 10 min is no less effective than 20 min in youth football players. Shorter training sessions can, therefore, be effectively used for injury prevention.     

Initial Validity and Reliability of the Portuguese Borg Rating of Perceived Exertion 6-20 Scale

ABSTRACT

The aims of this study were to perform the cross-cultural adaptation of the Borg Rating of Perceived Exertion (RPE) 6–20 Scale to Brazilian Portuguese language and to start testing its validity and reliability. After performing the cross-cultural adaptation of the Scale, concurrent and discriminative validity, and reliability were determined on a treadmill in young (18–30 years) and older adult women (60–75 years). Considering young and older adult women, RPE presented high and moderate positive correlation with heart rate and high and low positive correlation with oxygen consumption, respectively. Older adult women presented RPE (11 ± 2) significantly higher than young ones (8 ± 1) exercising at the same absolute intensity. Intraclass coefficient correlation was excellent for RPE to young and older adult women. The Scale presented concurrent validity only to young adult women, whereas it presented discriminative validity between such groups of women. Moreover, the scale is reliable to young and older adult women.     

Children's experience of violence in China and Korea: a transcultural study

OBJECTIVE: There were two aims: First, to compare children's rates of being battered in home, by peers, and by teachers among students between China and Korea, and second, to identify particular risk factors for such violence. METHODS: Children in grades four through six in Shanghai (238 cases) and Yanji (245 cases) in China and Seoul (248 cases) and Kimpo (241 cases) in Korea were surveyed by questionnaire method. They were asked to complete the Straus' Conflict Tactics Scale and their frequencies in the three situations respectively, and other demographic items. RESULTS: Family violence during the last 1 year was experienced in 70.6% (minor 42.2%; serious 22.6%) of the children in China and 68.9% (minor 9.4%; serious 51.3%) of those in Korea. Experience rates of violence by peers were 42.7% (minor 25.7%; serious 13.7%) in China and 26.0% (minor 11.5%; serious 14.3%) in Korea. Finally, rates of corporal punishment by teachers were 51.1% (minor 28.0%; serious 4.1%) in China and 62.0% (minor 8.8%; serious 43.8%) in Korea. The most important and common risk factor for violence in one situation was the presence of violence in another situation. CONCLUSIONS: The findings indicate that the differences in children's overall experience rates were not particularly striking. However, Korean children experienced more severe forms of violence from family members and from teachers. Findings of risk factors clearly imply that there are children vulnerable to violence from multiple sources.