A study of airfoil parameterization,modeling, and optimization based on the computational fluid dynamics method

An excellent airfoil with a high lift-to-drag ratio may decrease oil consumption and enhance the voyage. Based on NACA 0012, an improved airfoil is explored in this paper. The class/shape function transformation has been proved to be a good method for airfoil parameterization, and in this paper it is modified to improve imitation accuracy. The computational fluid dynamics method is applied to obtain numerically the aerodynamic parameters of the parameterized airfoil, and the result is proved credible by comparison with available experimental data in the open literature. A polynomial-based response surface model and the uniform Latin hypercube sampling method are employed to decrease computational cost. Finally, the nonlinear programming by quadratic Lagrangian method is utilized to modify the multi-island genetic algorithm, which has an improved optimization effect than the method used on its own. The obtained result shows that the modified class/shape function transformation method produces a better imitation of an airfoil in the nose and tail regions than the original method, and that it will satisfy the tolerance zone of the model in a wind tunnel. The response surface model based on the uniform Latin hypercube sampling method gives an accurate prediction of the lift-to-drag ratio with changes in the design variables. The numerical result of the flow around the airfoil shows reasonable agreement with the experimental data graphically and quantitatively. Ultimately, an airfoil with better capacity than the original one is acquired using the multi-island genetic algorithm based nonlinear programming by quadratic Lagrangian optimization method. The pressure contours and lift-to-drag ratio along with the attack angle have been compared with those of the original airfoil, and the results demonstrate the strength of the optimized airfoil. The process for exploring an improved airfoil through parameterization to optimization is worth referencing in future work.     

Chinese middle school teachers’ preferences regarding performance evaluation measures

Teacher performance evaluation currently is receiving unprecedented attention from policy makers, scholars, and practitioners worldwide. This study is one of the few studies of teacher perceptions regarding teacher performance measures that focus on China. We employed a quantitative dominant mixed research design to investigate Chinese teachers’ preferences for teacher performance measures and the possible reasons for their preferences. Considering the quantitative results, the surveyed Chinese teachers identified fulfillment of additional roles, collaboration with faculty and staff, and students’ test scores as the most important measures for performance evaluation. Qualitatively, the most important measures that the surveyed teachers reported were the teacher’s morality, workload, and students’ test scores.     

Discriminating talent-identified junior Australian football players using a video decision-making task

This study examined if a video decision-making task could discriminate talent-identified junior Australian football players from their non-talent-identified counterparts. Participants were recruited from the 2013 under 18 (U18) West Australian Football League competition and classified into two groups: talent-identified (State U18 Academy representatives; n = 25; 17.8 ± 0.5 years) and non-talent-identified (non-State U18 Academy selection; n = 25; 17.3 ± 0.6 years). Participants completed a video decision-making task consisting of 26 clips sourced from the Australian Football League game-day footage, recording responses on a sheet provided. A score of “1” was given for correct and “0” for incorrect responses, with the participants total score used as the criterion value. One-way analysis of variance tested the main effect of “status” on the task criterion, whilst a bootstrapped receiver operating characteristic (ROC) curve assessed the discriminant ability of the task. An area under the curve (AUC) of 1 (100%) represented perfect discrimination. Between-group differences were evident (P < 0.05) and the ROC curve was maximised with a score of 15.5/26 (60%) (AUC = 89.0%), correctly classifying 92% and 76% of the talent-identified and non-talent-identified participants, respectively. Future research should investigate the mechanisms leading to the superior decision-making observed in the talent-identified group.     

Bedingungen der Bindungswirkung inkrementeller Normen in Fußballvereinen

Sports clubs depend on the pooling of resources by their members. The supportive distribution of the resources within a club is facilitated in particular by the effectiveness of incremental standards. A basic prerequisite for a fair distribution of resources is a minimum of community spirit among the members. Based on a nationwide survey of football clubs and an ordinal logistic regression model, factors were determined that reflect the extent of the community spirit within a club. The opening up of the club by payment to players and perceived problems with acquiring and binding of volunteers are associated with a reduction of community spirit. In contrast, the perception that the club activities can be continued in the long term shows a positive correlation to a highly developed community spirit.     

A channel distortion model for video over lossy packet networks

Error-resilient video communication over lossy packet networks is often designed and operated based on models for the effect of losses on the reconstructed video quality. This paper analyzes the channel distortion for video over lossy packet networks and proposes a new model that, compared to previous models, more accurately estimates the expected mean-squared error distortion for different packet loss patterns by accounting for inter-frame error propagation and the correlation between error frames. The accuracy of the proposed model is validated with JVT/H.264 encoded standard test sequences and previous frame concealment, where the proposed model provides an obvious accuracy gain over previous models.     

Centralising space: the physical education and physical activity experiences of South Asian,Muslim girls

This paper explores the physical education (PE) and physical activity experiences of a group of South Asian, Muslim girls, a group typically marginalised in PE and physical activity research. The study responds to ongoing calls for research to explore across different spaces in young people's lives. Specifically, I draw on a ‘middle-ground’ approach, using Hill Collins' matrix of domination and the notion of intersectionality. These concepts offer the possibility to explore the kinds of settings (physical, social and cultural) in which girls undertake PE and physical activity, how these spaces influence experience and how the girls navigate these spaces. The study is based in a large, urban, co-educational, secondary school in Yorkshire, England (95% of the students are from minority ethnic communities, 91% are Muslim and 63% live in the top 10% most deprived neighbourhoods in the country). Data generation involved three phases: observations, creating research artefacts in focus groups and in-depth interviews. The findings reveal the diverse ways the girls are physically active. They also demonstrate a complexity to their involvement which is contingent upon space, discourses and people. For example, discourses of competition, ability and peers are more significant within PE; whilst family, religion and culture feature beyond this context. The paper concludes by acknowledging the girls' heterogeneity and agency in the ways they strategically navigate spaces in their quest to be physically active on their terms.     

A review of tennis racket performance parameters

The application of advanced engineering to tennis racket design has influenced the nature of the sport. As a result, the International Tennis Federation has established rules to limit performance, with the aim of protecting the nature of the game. This paper illustrates how changes to the racket affect the player-racket system. The review integrates engineering and biomechanical issues related to tennis racket performance, covering the biomechanical characteristics of tennis strokes, tennis racket performance, the effect of racket parameters on ball rebound and biomechanical interactions. Racket properties influence the rebound of the ball. Ball rebound speed increases with frame stiffness and as string tension decreases. Reducing inter-string contacting forces increases rebound topspin. Historical trends and predictive modelling indicate swingweights of around 0.030–0.035 kg/m² are best for high ball speed and accuracy. To fully understand the effect of their design changes, engineers should use impact conditions in their experiments, or models, which reflect those of actual tennis strokes. Sports engineers, therefore, benefit from working closely with biomechanists to ensure realistic impact conditions.     

Synchronized lower limb kinematics with pelvis orientation achieves the non-rotational shot

A non-rotational (NR) shot is now a well-known scoring move in soccer. To execute the NR shot, it is necessary to deprive the ball of any rotational forces during the impact phase. To execute the NR shot, it is natural that the force vector acting from the foot would pass through the ball’s center of gravity; however, the coordinated motion of the lower limb joint’s angular displacement and the pelvis is still unclear. The aim of this study is to estimate the coordinated leg and pelvis motion during the NR shot as compared to that during instep kicking. Four right-leg dominant college league players were asked to perform a NR shot and an instep kick a total of 10 times each. Hip, knee, and ankle joint angular displacements in the sagittal plane and pelvis yaw and roll rotational motions during both types of kicks were calculated with 14 IR reflective markers using a 3D real-time motion analysis system with a 250-Hz sampling. The Euclidean distances of the joint space of the NR shot and the instep kick were also calculated to detect similarities in the coordinated motion of the lower limb. The results showed that the lower limb joint motions in the sagittal plane were not different; however, the pelvis roll and yaw motions were apparently different, and these phenomena could simulate a pendulum motion with changes in both the vertical and horizontal displacements. These results suggest that the coordinated motion of the lower limb joint’s angular displacement shows high similarity between the NR shot and the instep kick, and the pelvis roll and yaw synchronized orientation is essential for achieving the NR shot.     

Elite wheelchair rugby: a quantitative analysis of chair configuration in Australia

Limited recommendations of wheelchair configurations for court sports have been identified in the published literature. To accommodate the wide range of impairments in wheelchair rugby, players are given a point score that reflects their impairment. Players have regularly been grouped as high-, mid-, or low-point players in research, with high-point players having greater levels of muscle function compared with other classifications. This research documented the wheelchair configurations of elite Australian wheelchair rugby players across classification groups. Significant differences (p < 0.05) were found for increased seat height and decreased seat depth for high-point players compared with low- and mid-point groups, respectively. Low-point players displayed reduced wheelchair mass compared with high- and mid-point players, as well as increased frame length. Camber angles showed no significant differences across the classification groups. The incorporation of anthropometric measures, such as the elbow angle at the top dead center, was also investigated. While elbow angle showed no significant differences, seat height-to-total arm length ratio was higher for high-point players. Participants also completed surveys detailing their perception of the effect of altering wheelchair configurations. It is suggested that wheelchair configurations should consider an individual’s anthropometrics, impairment, training history, and court role to promote optimal performance, with predictive modeling having the potential to reduce the associated time and cost.     

Direct skeletal attachment prosthesis for the amputee athlete: the unknown potential

Lower limb amputees often experience complications with the use of conventional socket-type prostheses, which further reduce their already compromised ability to perform the activities of daily living, or to participate in sporting activities. During the last two decades, a new technology of direct skeletal attachment (osseointegration) of prosthesis to the femoral residuum has been developed. The aim of this research was to assess the implant design, surgery protocols, and functional testing of this new technology on the first 100 patients using the Integral Leg Prosthesis procedure. This new knowledge can guide future engineering developments of osseointegration within the sporting arena. Between 1999 and 2013, direct skeletal implantation was performed on 112 amputees, from two centres in Germany and Australia. From the experience of the surgical team, modifications were made to the implant design. This re-engineering of the implant has reduced the surgical revisions due to infection from 29 % with the early implant design down to 7 %. The functional testing of the 34 Australian cases were assessed pre- and 12 months post-implant with significant improvements of one complete K-scale; the Q-TFA measures increased (50.9–86.7), whilst the Timed Up and Go decreased significantly (12.43 s ± 3.89 to 8.03 s ± 2.80), and the 6 min walk increased (304.0–383.9 m). From these findings, osseointegration technology is realistically the way of the future for amputee athletes. Further refinement of the implant design and sports-specific functional testing are required to define the potential of this technology.