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   

Active recovery of the finger flexors enhances intermittent handgrip performance in rock climbers     

Jiří Baláš  David Giles  Jan Kodejška  Michaela Panáčková  Simon Fryer 《European Journal of Sport Science》2016,16(7):764-772

This study aimed to (1) evaluate the effect of hand shaking during recovery phases of intermittent testing on the time–force characteristics of performance and muscle oxygenation, and (2) assess inter-individual variability in the time to achieve the target force during intermittent testing in rock climbers. Twenty-two participants undertook three finger flexor endurance tests at 60% of their maximal voluntary contraction until failure. Performances of a sustained contraction and two intermittent contractions, each with different recovery strategies, were analysed by time–force parameters and near-infrared spectroscopy. Recovery with shaking of the forearm beside the body led to a significantly greater intermittent test time (↑ 22%, P?P?P?相似文献   

Determining optimal cadence for an individual road cyclist from field data     

Robert Reed  Simon Adrian Jobson  Louis Passfield 《European Journal of Sport Science》2016,16(8):903-911

The cadence that maximises power output developed at the crank by an individual cyclist is conventionally determined using a laboratory test. The purpose of this study was two-fold: (i) to show that such a cadence, which we call the optimal cadence, can be determined using power output, heart-rate, and cadence measured in the field and (ii) to describe methodology to do so. For an individual cyclist's sessions, power output is related to cadence and the elicited heart-rate using a non-linear regression model. Optimal cadences are found for two riders (83 and 70 revolutions per minute, respectively); these cadences are similar to the riders’ preferred cadences (82–92?rpm and 65–75?rpm). Power output reduces by approximately 6% for cadences 20?rpm above or below optimum. Our methodology can be used by a rider to determine an optimal cadence without laboratory testing intervention: the rider will need to collect power output, heart-rate, and cadence measurements from training and racing sessions over an extended period (>6 months); ride at a range of cadences within those sessions; and calculate his/her optimal cadence using the methodology described or a software tool that implements it.  相似文献   

Perianal findings in prepubertal children selected for nonabuse: a descriptive study   总被引：6，自引：0，他引：6  

J McCann  J Voris  M Simon  R Wells 《Child abuse & neglect》1989,13(2):179-193

The results of the perianal portion of a project designed to collect normative data of the anogenital anatomy from a representative sample of prepubertal children is presented. A total of 318 children were examined by three physicians from a child sexual abuse evaluation program. After screening for the onset of puberty and the possibility of undetected abuse, 267 subjects remained. The sample included 161 girls and 106 boys ranging in age from 2 months to 11 years. The perianal findings that were encountered with the greatest frequency included erythema (41%), increased pigmentation (30%), and venous engorgement (52%) after two minutes in the knee-chest position. Wedge-shaped smooth areas in the midline, with or without depressions, were found both anterior and posterior to the anus in 26% of the children. Anal skin tags/folds were discovered anterior to the anus in 11%. In 49% of the children there was some dilatation of the anus which opened and closed intermittently in 62%. Flattening of the anal verge and rugae occurred during dilatation by the midpoint of the examination in 44% and 34%, respectively. Perianal findings that were found infrequently in all subgroups included skin tags/folds (0%) and scars (1%) outside the midline, anal dilatation greater than 20 mm without the presence of stool in the rectal ampulla (1.2%), irregularity of the anal orifice after complete dilatation (3%), and prominence of the anal verge (3%). No abrasions, hematomas, fissures, or hemorrhoids were encountered. Less commonly detected findings within specific subgroups included perianal erythema in girls (32%) as compared to boys (57%), pigmentation in the lighter skinned white children (22%) when compared to black (53%) and Hispanic (58%) children, and venous congestion at the beginning of the examination (7%) when compared to the same findings after four minutes in the knee-chest position (73%). There were no perianal skin tags/folds found in the boys. The relatively high incidence of perianal soft tissue changes that were found in this study, when compared to the frequency of similar observations in children suspected of having been sexually abused, reemphasizes the caution medical examiners must exercise in rendering an opinion as to the significance of medical findings.  相似文献   

Making sense of learner and learning Big Data: reviewing five years of Data Wrangling at the Open University UK     

Bart Rienties  Simon Cross  Vicky Marsh  Thomas Ullmann 《Open Learning》2017,32(3):279-293

Most distance learning institutions collect vast amounts of learning data. Making sense of this ‘Big Data’ can be a challenge, in particular when data are stored at different data warehouses and require advanced statistical skills to interpret complex patterns of data. As a leading institute on learning analytics, the Open University UK instigated in 2012 a Data Wrangling initiative. This provided every Faculty with a dedicated academic with expertise data analysis and whose task is to provide strategic, pedagogical and sense-making advice to staff and senior management. Given substantial changes within the OU (e.g. new Faculty structure, real-time dashboards, two large-scale adoptions of predictive analytics approaches, increased reliance on analytics), this embedded case study provides an in-depth review of lessons learned of five years of data wrangling. We will elaborate on the design of the new structure, its strengths and potential weaknesses, and affordances to be adopted by other institutions.  相似文献   

Why some teachers easily learn to use a new virtual learning environment: a technology acceptance perspective     

Bart Rienties  Bas Giesbers  Simon Lygo-Baker  Hoi Wah Serena Ma  Roger Rees 《Interactive Learning Environments》2016,24(3):539-552

After a decade of virtual learning environments (VLEs) in higher education, many teachers still use only a minimum of its affordances. This study looked at how academic staff interacted with a new and unknown VLE in order to understand how technology acceptance and support materials influence (perceived and actual) task performance. In an experimental design, 36 participants were split into a control (online help) and experimental (instructor video) condition and completed five common teaching tasks in a new VLE. In contrast to most technology acceptance model research, this study found that perceived usefulness of the VLE was not related to (perceived) task performance. Perceived ease of use was related to intentions and actual behaviour in the VLE. Furthermore, no significant difference was found between the two conditions, although the experimental condition led to a (marginal) increase in time to complete the tasks.  相似文献   

Inter-Parietal White Matter Development Predicts Numerical Performance in Young Children     

Cantlon JF  Davis SW  Libertus ME  Kahane J  Brannon EM  Pelphrey KA 《Learning and individual differences》2011,21(6):672-680

In an effort to understand the role of interhemispheric transfer in numerical development, we investigated the relationship between children's developing knowledge of numbers and the integrity of their white matter connections between the cerebral hemispheres (the corpus callosum). We used diffusion tensor imaging (DTI) tractography analyses to test the link between the development of the corpus callosum and performance on symbolic and non-symbolic numerical judgment tasks. We were especially interested in the interhemispheric connections of parietal cortex in 6-year-old children, because regions of parietal cortex have been implicated in the development of numerical skills by several prior studies. Our results revealed significant structural differences between children and adults in the fibers of the corpus callosum connecting the left and right parietal lobes. Importantly, these structural differences were predictive of individual differences among children in performance on numerical judgment tasks: children with poor numerical performance relative to their peers exhibited reduced white matter coherence in the fibers passing through the isthmus of the corpus callosum, which connects the parietal hemispheres.  相似文献   

Organizational effectiveness in education: Its measurement and enhancement     

Peter Coleman 《Interchange》1972,3(1):42-52

This study is concerned with the nature of organizational goals, and ways of measuring goal achievement. It is intended to provide administrators with some new ways of conceptualizing the evalution of effectiveness in educational systems. The paper points out the desirability of involving professionals in the setting of goals, proposes a three-tier system of goals for educational systems, and suggests some of the reasons for the frequent failure to achieve organizational goals. Additionally, a comprehensive approach to the goals of organizations, adapted from Gross's matrix of purposes, is proposed, on the grounds that only such an inclusive approach to organizational goals is entirely satisfactory. Finally, the paper takes issue with the notion that freedom for organization members equals absence of organizational controls. The sense of power for organization members increases with participation in control, as does effectiveness. Thus, particularly for organizations with large numbers of professionals as members, it is not absence of control but rather participation in control that is the vital factor in both freedom and effectiveness. The final conclusion of the paper is that attempts to improve the effectiveness of educational systems or institutions must be in the future more inclusive, and that the matrix of purposes approach is one possible line of development.

---

Résumé Cette étude porte sur la nature des objectifs des plans d'organisation et des méthodes servant à mesurer le degré de réussite dans la poursuite de ces objectifs. L'auteur se propose de fournir aux administrateurs un certain nombre de nouveaux critères pour concevoir l'évaluation de l'efficacité des systèmes éducatifs. Soulignant l'opportunité de confier à des professionnels l'établissement des objectifs, cette étude propose un système à trois paliers et tente d'expliquer les échecs fréquents auxquels aboutissent les objectifs des plans d'organisation. Par ailleurs, en ce qui concerne les objectifs des organisations, elle propose une attitude globale adaptée de l'étude de Gross intitulée matrix of purposes (matrice des objectifs), étant donné qu'une telle attitude est la seule qui soit satisfaisante à tous points de vue. Enfin l'auteur dénonce la notion selon laquelle la liberté accordée aux membres des organisations équivaut à une absence de contrôle sur ces dernières. En participant au contrôle de leurs organisations, les membres prennent en effet de plus en plus conscience de leur pouvoir et l'efficacité s'en trouve accrue. C'est ainsi que lorsqu'il s'agit, en particulier, d'organisations comptant de nombreux membres des professions libérales, ce n'est pas l'absence de contrôle mais plutôt la participation au contrôle qui représente le facteur capital à la fois de la liberté et de l'efficacité. En conclusion finale, cette étude affirme qu'à l'avenir, les tentatives d'amélioration des systèmes éducatifs ou des institutions devront avoir un caractère plus global et que la matrice des objectifs représente l'une des méthodes possibles à adopter dans ce domaine.

  相似文献   

K S Krishnan’s 1948 perception of the sampling theorem     

Rajiah Simon 《Resonance》2002,7(2):20-25

K S Krishnan discovered in 1948 that the sum over samples of a band-limited function gives the value of the integral of the function exactly, provided the sampling interval does not exceed a threshold value. This result of Krishnan is shown to be equivalent to the Shannon sampling theorem.  相似文献   

Recruiting the graduate voice: informing higher education initiatives to underpin an emerging,veterinary paraprofession in Australia     

Patricia Clarke  Joerg Henning  Glen Coleman  Daniel Schull 《Journal of Vocational Education & Training》2019,71(1):126-152

In Australia, the inception of veterinary technology, as a higher education discipline underpinning an emerging, mid-tier paraveterinary field, reflected global trends for more highly educated veterinary paraprofessionals to meet changing societal demands. In this study, veterinary technology graduates were surveyed about their experiences in the workforce and reflections on their education. Seeking feedback on how well a new programme has prepared graduates for the workforce is a useful quality assurance tool. Clinical veterinary practice was the primary employment sector with the majority of respondents in full-time employment. Career advancement, professional recognition and salaries were identified as key career challenges. The important roles of the veterinary and veterinary nursing professions, the university, government and graduates in the development of this mid-tier, veterinary paraprofession were elucidated. Graduates’ feedback on criteria that underpinned ‘work-readiness’ revealed seven key domains: communication skills, research skills, knowledge, critical thinking/problem-solving, employability, practical skills and professionalism. Veterinary nursing skills, work placement, practice management and production animal health were flagged as areas for curricular improvement. This study illuminated facilitators and barriers critical to establishing a mid-tier veterinary paraprofession, bridging the divide between the vocational and higher education sectors in Australia.

Abbreviations: AUD: Australian dollar; AVA: Australian Veterinary Association; AVBC: Australasian Veterinary Boards Council; AVMA: American Veterinary Medical Association; BVNA: British Veterinary Nursing Association; CSU: Charles Sturt University; DAF: Department of Agriculture and Fisheries; FWC: Fair Work Commission; GCA: Graduate Careers Australia; HE: Higher Education; NHMRC: National Health and Medical Research Council; QLD: Queensland; RCVS: Royal College of Veterinary Surgeons; UK: United Kingdom; UQ: University of Queensland; VN: Veterinary nursing; VNCA: Veterinary Nurses Council of Australia; VSB: Veterinary Surgeons Board; VT: Veterinary technology; WIL: Work-integrated learning.  相似文献