Effect of wetted surface area on friction,pressure, wave and total drag of a kayak

Using theoretical principles, the components of drag (friction D _F, pressure D _PR and wave D _W) of a single-seat kayak were analysed. The purpose was to examine the effect of changes in wetted surface area due to changes in kayaker’s weight and the relative contribution of D _F, D _PR and D _W to the total passive drag as function of velocity. The total passive drag values were based on experimental data collected in a single-seat kayak. Three different kayaker simulated weights were tested – 65, 75 and 85 kg. D _F was the drag component that contributed the greatest percentage (between 60 and 68% at 5.56 m/s the top velocity tested) to the total passive drag for all the velocities tested and simulated weights. D _W was the most affected by the increase in kayaker’s simulated weight, mainly when comparing 65/75 to 85 kg. Results support the importance of a kayak design selection that minimises the kayak’s drag for the individual weight of the kayaker. Also, the results suggest that the path for better hydrodynamic kayak performance should seek changes that can reduce D _F, D _PR and D _W with D _F offering the most potential to reduce passive drag.     

Sodium bicarbonate ingestion increases glycolytic contribution and improves performance during simulated taekwondo combat

Purpose: To investigate the effect of sodium bicarbonate (NaHCO₃) on performance and estimated energy system contribution during simulated taekwondo combat. Methods: Nine taekwondo athletes completed two experimental sessions separated by at least 48?h. Athletes consumed 300?mg/kg body mass of NaHCO₃ or placebo (CaCO₃) 90?min before the combat simulation (three rounds of 2 min separated by 1 min passive recovery), in a double-blind, randomized, repeated-measures crossover design. All simulated combat was filmed to quantify the time spent fighting in each round. Lactate concentration [La^?] and rating of perceived exertion (RPE) were measured before and after each round, whereas heart rate (HR) and the estimated contribution of the oxidative (W_OXI), ATP (adenosine triphosphate)-phosphocreatine (PCr) (W_PCR), and glycolytic (W_{[ La^? ]}) systems were calculated during the combat simulation. Results: [La^?] increased significantly after NaHCO₃ ingestion, when compared with the placebo condition (+14%, P?=?0.04, d?=?3.70). NaHCO₃ ingestion resulted in greater estimated glycolytic energy contribution in the first round when compared with the placebo condition (+31%, P?=?0.01, d?=?3.48). Total attack time was significantly greater after NaHCO₃ when compared with placebo (+13%, P?=?0.05, d?=?1.15). W_OXI, W_PCR, VO₂, HR and RPE were not different between conditions (P?>?0.05). Conclusion: NaHCO₃ ingestion was able to increase the contribution of glycolytic metabolism and, therefore, improve performance during simulated taekwondo combat.     

A tool-kit to help students from low socioeconomic status background: a school-based self-regulated learning intervention

European Journal of Psychology of Education - Socioeconomic status has been a long-time discussed topic due to its impact on children’s school paths. However, despite extant research...     

Teacher and school determinants of perceived classroom discipline: a multilevel analysis of TALIS 2013

Learning Environments Research - Classroom discipline is a significant concern in most educational systems and a critical element of an effective learning environment. In this article, we present a...     

University entrepreneurial performance: A Fuzzy Set Qualitative Comparative Analysis

As key players in innovation and entrepreneurial ecosystems, Higher Education Institutions (HEI) assume a position as catalysts in creating and disseminating knowledge with repercussions in the societal, economic, political and innovation environments. In this scenario, HEI are facing the need to balance the performance of their traditional missions—teaching and research—with the pursuit of entrepreneurial performance. This brings awareness of the need to pay particular attention to HEI entrepreneurial performance (HEIEP) and how to measure it. Based on HEInnovate, a self-assessment tool resulting from a joint effort of the European Community and the OECD, this study aims to explore the benefits of university entrepreneurial metrics, analysing HEIEP as a discriminant function of the HEInnovate dimensions complemented with a qualitative approach using Fuzzy Set Qualitative Comparative Analysis (fsQCA). The analysis provides valuable details, presenting recipes based on the HEInnovate dimensions or combinations of dimensions to achieve a mission legitimation. This research brings awareness to the use of the HEInnovate scale, where it is possible to highlight the importance of the digital transformation and capability dimension to entrepreneurial performance (EP) and university mission legitimation.