A review of tennis racket performance parameters     

Tom Allen  Simon Choppin  Duane Knudson 《Sports Engineering》2016,19(1):1-11

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.  相似文献   

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

Taishu Nakamura  Tasuku Miyoshi  Motoki Takagi  Yasuhisa Kamada 《Sports Engineering》2016,19(2):71-79

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.  相似文献   

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

David S. Haydon  Ross A. Pinder  Paul N. Grimshaw  William S. P. Robertson 《Sports Engineering》2016,19(3):177-184

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.  相似文献   

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

Munjed Al Muderis  Horst Heinrich Aschoff  Belinda Bosley  Guy Raz  Ludger Gerdesmeyer  Brendan Burkett 《Sports Engineering》2016,19(3):141-145

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.  相似文献   

Validation of the Microsoft Kinect® camera system for measurement of lower extremity jump landing and squatting kinematics     

Moataz Eltoukhy  Adam Kelly  Chang-Young Kim  Hyung-Pil Jun  Richard Campbell 《Sports biomechanics / International Society of Biomechanics in Sports》2016,15(1):89-102

Cost effective, quantifiable assessment of lower extremity movement represents potential improvement over standard tools for evaluation of injury risk. Ten healthy participants completed three trials of a drop jump, overhead squat, and single leg squat task. Peak hip and knee kinematics were assessed using an 8 camera BTS Smart 7000DX motion analysis system and the Microsoft Kinect® camera system. The agreement and consistency between both uncorrected and correct Kinect kinematic variables and the BTS camera system were assessed using interclass correlations coefficients. Peak sagittal plane kinematics measured using the Microsoft Kinect® camera system explained a significant amount of variance [Range_hip = 43.5–62.8%; Range_knee = 67.5–89.6%] in peak kinematics measured using the BTS camera system. Across tasks, peak knee flexion angle and peak hip flexion were found to be consistent and in agreement when the Microsoft Kinect® camera system was directly compared to the BTS camera system but these values were improved following application of a corrective factor. The Microsoft Kinect® may not be an appropriate surrogate for traditional motion analysis technology, but it may have potential applications as a real-time feedback tool in pathological or high injury risk populations.  相似文献   

In Search of Staff Development: A study of academic staff appraisal     

Richard James 《高等教育研究与发展》1995,14(2):185-199

The academic award restructuring of 1991 established a trial period for academic staff appraisal for the purposes of staff development. The trend in Australia towards more formal performance management for academics has occurred during a period of substantial change to the structure of higher education and institutional management, and brought debate on whether appraisal, for either summative purposes (where performance assessment is for remuneration or promotion purposes) or formative purposes (where the emphasis is on planning personal development), is appropriate for academic staff. Arguments have been put forward for the benefits of appraisal processes with primarily developmental intent. Thus far there have been reports of the characteristics and processes of appraisal schemes, but less data on outcomes; in particular, little evidence to indicate the extent to which schemes lead to worthwhile staff development. This paper reports selected findings of a study of the evolving appraisal scheme of The University of Melbourne. The study was conducted after the scheme's second year of operation by the Centre for the Study of Higher Education which played an advisory role in an internal review of the scheme. The findings reveal some uncertainty among staff about the intentions of the scheme, and tensions between summative and formative purposes, perhaps not surprising given the contentious issue which staff appraisal has been in higher education. Nevertheless, positive outcomes were identified, but possibly too few to claim that the scheme was fully achieving a developmental objective. These findings raise questions about the effectiveness of academic staff appraisal nationally and suggest that it is time to reconsider the policy linkage between appraisal and staff development.  相似文献   

Effect of blended learning and learners’ characteristics on students’ competence: An empirical evidence in learning oriental music     

Chamila Nishanthi Edward  David Asirvatham  Md. Gapar Md. Johar 《Education and Information Technologies》2018,23(6):2587-2606

Blended learning emerged as the most popular instructional design strategy in the field of education since last decade to present date. In fact, it is well acknowledged that blended learning approach significantly elevate students’ engagement and competency in learning process. Despite immense potentiality, many countries are still lag behind adopting this instructional design, such as Sri Lanka. Therefore, the primary aims of this study are two fold, (a) to investigate the effect of blended learning and learners’ characteristics on students’ competence and (b) to investigate the effectiveness of blended learning in teaching Oriental Music. This study mainly carried out among the senior secondary schools students at Colombo, Sri Lanka. A mixed methods, experimental and survey, were carried out to test the effectiveness of blended learning and identifying the important factors for enhancing students’ competence in learning Oriental Music. Results of independent sample t-test confirmed that blended learning is effective in terms of improving students’ performance in learning Oriental Music. Similarly, regression analysis confirmed that attitude and motivation are the two most important determinants for improving students’ competence. This study fulfilled an existing research gap by utilizing blended learning to teach highly traditional abstract art. Results of the study contributes to the curriculum designing field with novel ideas to adapt in hybrid instructions to teach secondary level students effectively. The curriculum designers will make use of these findings during innovation and future researcher would be benefitted to overlook more possible platforms to deliver music instructions. It will help them to understand how their set objectives have been achieved in technology integrations and seek for improvement where necessary.  相似文献   

Improved fast intra prediction algorithm of H.264/AVC     

Liu Qiong  Hu Rui-min  Zhu Li  Zhang Xin-chen  Han Zhen 《浙江大学学报(A卷英文版)》2006,7(1):101-105

With advanced prediction modes of intra prediction, intra coding of H.264/AVC offers significant coding gains compared with previous video coding standards. It uses an important tool called Lagrangian rate-distortion optimization (RDO) technique to decide the best coding mode for a block, but the computational burden is extremely high. In this paper, we proposed an improved fast intra prediction algorithm including block type selection and mode decision algorithm based on analysis of edge feature of a block. Our algorithm filters out unlikely block type and candidate modes to reduce the RDO calculations. Experimental results showed that the proposed algorithm can reduce the computation complexity of intra prediction from 52.90% to 56.31%, with 0.04 dB PSNR degradation and 2% increase of bit rate.  相似文献   

STUDENTS' PERCEPTION OF THE MEDICAL SCHOOL LEARNING ENVIRONMENT: A PILOT STUDY INTO SOME DIFFERENCES AND SIMILARITIES BETWEEN CLINICAL SCHOOLS IN THE U.K.     

Richard E. Wakeford 《Assessment & Evaluation in Higher Education》1981,6(3):206-217

The importance of the ethos or learning environment of a training institution is increasingly being appreciated in terms of its effect on learning process and outcome. This paper reports upon the development of an inventory to measure medical students’ perceptions of their learning environment and upon its pilot use to contrast their experiences in five British medical schools. Broad similarities were found between the medical schools upon some dimensions of the questionnaire, but a number of substantial differences are also reported. It is concluded that it is by no means difficult to develop an instrument which can identify important differences between institutions’ learning milieux. However, reservations are expressed about making other than tentative conclusions from the details of the findings of similarities and differences: the desirability of conducting a more comprehensive study is emphasised.  相似文献   

Triadic interaction in clinical task-based interviews with mathematics teachers     

Boris Koichu  Guershon Harel 《Educational Studies in Mathematics》2007,65(3):349-365

A clinical task-based interview can be seen as a situation where the interviewer–interviewee interaction on a task is regulated by a system of explicit and implicit norms, values, and rules. This paper describes how documenting and mapping triadic interaction among the interviewer, the interviewee, and the knowledge negotiated can be used to increase procedural replicability of the interview and accuracy of drawn conclusions about the interviewee’s thinking process. Excerpts from interviews with 25 inservice mathematics teachers working on a task to make up a problem whose solution requires division of two fractions are discussed. The excerpts illustrate the relationship between methodological decisions taken by the interviewer during the interview and the applicability of the interview output to the research questions. A divergent analysis of the interviews with these teachers, which spanned over two years and were conducted by four interviewers, is used to offer a framework for analyzing data collected in clinical task-based interviews.  相似文献