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Loren Z. F. Chiu Torstein E. Dæhlin 《Measurement in physical education and exercise science》2020,24(1):25-32
ABSTRACTMales (n = 29) and females (n = 34) performed vertical jumps. Jump height was estimated from force platform data using five numerical methods and compared using intraclass correlation (ρ), and linear and rank regression standard error of estimate (SEE). Take-off velocity plus center of mass height at take-off and mechanical work methods were identical (ρ = 1.000) with small linear (SEE < 0.0001 cm) and rank order (SEE = 0) error. Integrating acceleration to displacement was nearly identical (ρ > 0.999), with small linear (SEE = 0.1 cm) and rank order (SEE < 1) errors compared to the above methods. Take-off velocity (ρ = 0.517) and flight time (ρ = 0.573) estimates were less than all other methods and had large linear (SEE ≥ 2.1 cm) and rank order (SEE > 4) errors. Take-off velocity and flight time methods should be avoided due to systematic and random error. 相似文献
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灰雁是最常见的欧亚代表种,分为2个亚种,即指明亚种（西方亚种）A．a．anser和东方亚种A．a．rubrirostris。于2009年2月13日,在拉萨市达孜县境内的塔杰湿地记录到了灰雁东方亚种。塔杰湿地位于东经91°26’北纬29°44’,海拔3719m;被318国道分割为南北两个部分,北面的面积较大,仍具有天然湿地的生态学特性,南面的大部分已开垦为农田。本记录是西藏自治区境内的首次有关灰雁的报道,为西藏鸟类资源增添了一个新成员;更重要的是扩大了灰雁在我国乃至世界的分布范围。 相似文献
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ABSTRACTPrevious research suggests that landing mechanics may be affected by the mechanics of the preceding jump take-off. The purpose of the present study was to investigate whether jump take-off mechanics influence the subsequent landing mechanics. Female volleyball (n = 17) and ice hockey (n = 19) players performed maximal vertical jumps with forefoot and heel take-off strategies. During forefoot and heel jumps, participants were instructed to shift their weight to their forefoot or heel, respectively, and push through this portion of the foot throughout the jump. Jump mechanics were examined using 3D motion analysis, where lower extremity net joint moment (NJM) work, NJM, and segment angles were compared between forefoot and heel jumps using multivariate ANOVA. During jump take-off, participants performed more positive ankle plantar flexor and knee extensor NJM work in forefoot compared to heel jumps (P < 0.05). From initial foot contact to foot flat, participants performed more negative ankle plantar flexor and hip extensor NJM work during heel compared to forefoot jumps (P < 0.05). The present results demonstrate that using a heel take-off strategy results in a different distribution of lower extremity NJM work and NJM during landing compared to landings following forefoot jumps. 相似文献
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Torstein Rekkedal 《Distance Education》1983,4(2):231-258
An essential feature in correspondence education is the two‐way communication between teacher and student and a central feature of this is the written assignments. Even if the postal services are quick, the handling of the assignments, correcting and commenting on them is bound to take some time. Studies by Sloan in 1965 and Saxe et al in 1966 suggested that the time element involved in the communication between teacher and student might be one of the main reasons for loss of interest and, ultimately, drop‐out.
The main purpose of the experiment reported here was to examine the effect of reducing the turn‐around time. Some statistical analyses in the original have been omitted in this translation. The approach cannot be taken as being representative of what the author's views on the subject would be a decade later. 相似文献
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Recent research on distance education in Norway 总被引：1，自引：1，他引：0
Torstein Rekkedal 《Open Learning》2013,28(1):32-37