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61.
Machar Reid Bruce Elliott 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(1):47-68
The study investigated differences in the one‐ (SH) and two‐handed (DH) backhands when hit flat, across‐court (AC) and down‐the‐line (DL), and with heavy topspin DL (TDL). The ability to disguise each of these backhands when hitting the above strokes was also assessed. Eighteen college‐level male tennis players, identified as having a high performance topspin SH (n = 6) or DH (n = 12) backhand drive, participated in the study. Players were required to hit three AC, DL and TDL backhands from the baseline with their preferred technique, while being filmed with two high‐speed video cameras operating at 200 Hz. The highest horizontal velocity backhand for each stroke was analysed. Results indicated that the sequential coordination of five body segments (hips, shoulder, upper arm, forearm, and hand/racquet rotations) was required for the execution of the SH stroke. The same number of segments were generally coordinated in the DH stroke (hips, shoulders, and varying degrees of upper arm and forearm rotations followed by hand/racquet movement). Mature players produced comparable racquet horizontal velocities 0.005 s prior to impact using either the SH or DH backhand technique. The SH backhand was characterised by a more rotated shoulder alignment than the DH stroke (SH: 119.1°; DH: 83.4°) at the completion of the backswing. At impact the ball was impacted further in front (SH: 0.59 m; DH: 0.40 m) and a similar distance to the side of the body (SH: 0.75 m; DH: 0.70 m). Players using the DH backhand technique delayed the horizontal acceleration of the racquet towards the ball (SH: 0.13 s; DH: 0.08 s prior to impact) and thus were capable of displaying a similar hitting motion closer to impact than players with a SH technique. 相似文献
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John Elliott 《Cambridge Journal of Education》1981,11(2):146-166
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ABSTRACT: A simple laboratory experiment, based on the Maillard reaction, served as a project in Introductory Statistics for undergraduates in Food Science and Technology. By using the principles of randomization and replication and reflecting on the sources of variation in the experimental data, students reinforced the statistical concepts and techniques introduced to them in lectures before the experiment. The experiment was run simultaneously by several student groups, using the same materials. Comparing the results of their analyses of variance, students became aware of the difference between P values and significance levels in making statistical decisions. In the experiment, the complete randomized design was applied; however, it is easy to adjust the experiment to teach students simple regression and randomized block designs. 相似文献
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Support is needed to promote problem-based learning (PBL) and to enhance critical thinking skills in discussion-based Internet forums. By advancing the capabilities of chat room and forum software, problem-based discussions for learning can be supported further in online learning environments. In this paper, the authors report on MALESAbrain, an intelligent learning tool. The model is built on the notions of threshold and knowledge weight from the discipline of machine learning. The model encourages learners to judge or critically evaluate the solutions posted by others before exploring further knowledge content. The system then sums up the judgment scores as its knowledge weight to pass the thresholds setup for ranking/arranging the learning issues. This constraint design, therefore, becomes a mechanism for critical thinking in a problem-based learning activity. MALESAbrain as a model helps transform the forum and chat room into rich learning discussion environments. 相似文献
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Julian G Elliott Neil Hufton Leonid Illushin Wayne Willis 《Cambridge Journal of Education》2001,31(2):179-204
Comparative studies of attitudes in different countries have resulted in the claim that parents in the USA and England tend to have unrealistically positive views of their children's schools and academic performance. Low expectations, together with a belief in the importance of natural ability, it has been argued, lead to low standards and reduce striving to succeed. The present study builds upon earlier investigations of children's attitudes, beliefs and behaviours in Sunderland, Eastern Kentucky and St Petersburg by surveying parental perspectives. Findings from these three regions reinforce earlier findings about English and American complacency and the more demanding nature of the Russian context. In line with our earlier studies, and contrary to the suggestion of a number of writers, an emphasis upon effort, rather than ability, was a strong feature of the English and American responses, although it is pointed out that such beliefs may not actually result in high work rates. The paper concludes by suggesting that the important role of parents in instilling important attitudes and behaviours in their children is undermined by the current emphasis upon schools as fundamentally responsible for ensuring high levels of achievement. 相似文献
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