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141.
This paper presents an approximate analytical model of the dynamics of a tapered fly line during a standard overhead cast.
During casting, the line forms a nonlinear propagating wave that is frequently referred to as a ‘loop’ by fly casters. The
geometry of the loop is described by three distinct parts: a straight bottom segment (attached to a stationary fly rod), a
semi-circular segment that is propagating (i.e. the loop), and a straight top segment that is also propagating, (i.e. the
traveling line). A fly (particle) is attached at the end of the traveling line. A work-energy balance yields the velocity
of the fly as a function of the length of the traveling line. For a uniform fly line (level line), a closed-form solution
is found, while for a tapered fly line, the solution is obtained by quadrature. A critical loop diameter arises in the analysis,
and it determines whether the final velocity of the fly is greater or lesser than the initial velocity of the traveling line.
The analytical solutions are critically compared against numerical solutions of a general model for fly line dynamics that
relaxes many of the assumptions employed in the analytical model. The agreement between the two solutions remains close during
the loop propagation phase, provided a significant amount of fly line remains in the traveling line. However, as the traveling
line vanishes and the loop ‘turns over’, the two solutions diverge abruptly due to the many simplifying assumptions employed
in the analytical model. 相似文献
142.
143.
Pierre Touzard Richard Kulpa Benoit Bideau Bernard Montalvan Caroline Martin 《European Journal of Sport Science》2019,19(6):765-773
Waiter’s serve (WS) is a specific tennis serve posture frequently observed in young players, and commonly considered as a technical error by tennis coaches. However, biomechanical impact of WS is unknown. The aims of this study were to identify the potential consequences of WS in young elite players relating to performance and injury risk, and to explain the kinematic causes of WS. Serve of 18 male junior elite players (Top 10 national French ranking, aged 12–15 years) was captured with a 20 camera, 200?Hz VICON MX motion analysis system. Depending on their serve technique, the players were divided into two groups (WS versus Normal Serve [NS]) by experienced coaches. Injury data were collected for each player during a 12-month-period following the motion capture. Normalized peak kinetic values of the dominant arm were calculated using inverse dynamics. In order to explain WS posture, upper limb kinematics were calculated during the cocking and the acceleration phases of the serve. Shoulder internal rotation torque, wrist proximal and anterior forces (P?.05) and elbow varus torque (P?.01) were significantly higher in WS group, with no difference from NS group concerning serve velocity. Moreover, significant lower shoulder abduction and higher wrist extension (P?.05) were observed for WS players during the cocking phase. Even if no significant difference was found between groups concerning injuries, higher upper limb joint loads suggested WS could be considered as pathomechanical in young elite players and could lead to upper limb joint injuries. 相似文献
144.
Recent experiments on the ski simulator produced ambiguous results and raised unanswered questions concerning the true nature of "novice" behavior and the occurrence of behavioral changes during learning. The aim of the present experiment was to analyze the evolving behavior of three beginners during six practice sessions on a ski simulator The position of the apparatus platform was recorded as time series and used for constructing dynamical models, including stiffness and damping functions. The results showed that novices tended to exploit a Rayleigh damping behavior during the first trials and then transition toward a van der Pol damping. These results replicate previous observations by Nourrit, Delignieres, Caillou, Deschamps, and Lauriot (2003) and suggest the transition to the expert behavior could arise early in practice, when the task is of moderate difficulty. The discussion focuses on the properties of the observed learning dynamics and proposes a global conceptualization for acquiring complex motor skills. 相似文献
145.
146.
Andrew Burn Sue Brindley James Durran Carol Kelsall Jane Sweetlove Caroline Tuohey 《English in Education》2001,35(2):34-48
This article is an interim report on a small action research project being carried out by a group of teachers into digital editing. The authors focus on a critical evaluation of a ‘conceptual framework’ for editing digitised moving images, devised as part of the research project. The body of the article is concerned with observations of students carrying out editing, with the framework being used to structure the observations. 相似文献
147.
Sawers C 《Health information and libraries journal》2005,22(Z1):31-37
The Medical Library Bulletin of the Thames Regions reflected the development of health-service libraries over the 20 years it existed. Originally begun as a practical aid to improving services by encouraging co-operation, improving communication and giving instructive advice, it charted the work of health-service librarians and the growth of their services. The articles contained in it covered professional developments and wider political issues as they occurred, and illustrated the extension of the librarians' knowledge and skills. Leslie Morton, Library Adviser to the British Postgraduate Medical Federation, edited almost every issue, starting at a time when there was little guidance or professional literature available for health-service librarians. 相似文献
148.
PURPOSE: To develop and evaluate a programme of information skills training for social-care practitioners and health-care librarians. SETTING: Two one-day training courses run separately for 13 social-care practitioners and 10 health-care librarians in the Trent geographic region within Northern England. METHODOLOGY: Qualitative and quantitative feedback collected through questionnaires supplemented by participant observation. RESULTS: While generally feedback was favourable, the courses were overly ambitious. More training sessions of shorter duration would offer participants opportunities to practise and use the skills they have acquired. Social-care practitioners responded more positively to skills associated with appraising qualitative research than with randomised controlled trials. Librarians appreciated the opportunity to learn about unfamiliar social-care resources. Both practitioners and health-care librarians reported that they acquired skills to support evidence-based social care as a result of the training intervention. DISCUSSION/CONCLUSION: Involvement of a multi-disciplinary team and support from a social-care information provider maximized the impact of this experimental training intervention. 相似文献
149.
This study compares the demographic characteristics of 142 nursing students in hospital programs and 365 nursing students in higher education programs in Queensland. Data were collected on a questionnaire distributed to students during lecture times by a contact person in each institution. No significant difference was found in the gender and age of entry variable. Males from Catholic schools and enrolled nurses were more likely to enter higher education programs than hospital programs. There was no significant difference in the geographic location of the school attended by students between the two institutional sub-groups which suggests that the national transfer of nurse education to higher education institutions will not be a disadvantage to country students. 相似文献
150.