运动表象的形成及其在背越式跳高教学中的运用

体育课教学中,教师针对动作的特点进行正确的讲解和示范,让学生对动作概念形成一个初步认识,并能使学生随着教师的讲解和示范去进行思维活动和反复练习,使得视觉表象与动觉表象有机的结合为一体。     

Comparison of step-by-step kinematics of resisted,assisted and unloaded 20-m sprint runs

This investigation examined step-by-step kinematics of sprint running acceleration. Using a randomised counterbalanced approach, 37 female team handball players (age 17.8 ± 1.6 years, body mass 69.6 ± 9.1 kg, height 1.74 ± 0.06 m) performed resisted, assisted and unloaded 20-m sprints within a single session. 20-m sprint times and step velocity, as well as step length, step frequency, contact and flight times of each step were evaluated for each condition with a laser gun and an infrared mat. Almost all measured parameters were altered for each step under the resisted and assisted sprint conditions (η² ≥ 0.28). The exception was step frequency, which did not differ between assisted and normal sprints. Contact time, flight time and step frequency at almost each step were different between ‘fast’ vs. ‘slow’ sub-groups (η² ≥ 0.22). Nevertheless overall both groups responded similarly to the respective sprint conditions. No significant differences in step length were observed between groups for the respective condition. It is possible that continued exposure to assisted sprinting might allow the female team-sports players studied to adapt their coordination to the ‘over-speed’ condition and increase step frequency. It is notable that step-by-step kinematics in these sprints were easy to obtain using relatively inexpensive equipment with possibilities of direct feedback.     

The effect of westward travel across five time zones on sleep and subjective jet-lag ratings in athletes before and during the 2015’s World Rowing Junior Championships

This study examined sleep-wake habits and subjective jet-lag ratings of 55 German junior rowers (n = 30 male, 17.8 ± 0.5 years) before and during the World Rowing Junior Championships 2015 in Rio de Janeiro, Brazil. Athletes answered sleep logs every morning, and Liverpool John Moore’s University Jet-Lag Questionnaires each evening and morning. Following an 11-h westward flight with 5-h time shift, advanced bedtimes (?1 h, P < .001, η_p² = 0.68), reduced sleep onset latency (P = .002, η_p² = 0.53) and increased sleep duration (P < .001, η_p² = 0.60) were reported for the first two nights. Jet-lag symptoms peaked upon arrival but were still present after 6 days. Sleep quality improved (P < .001, η_p² = 0.31) as well as some scales of the Recovery-Stress Questionnaire for Athletes. Participation was successful as indicated by 11 of 13 top 3 placings. Overall, the initial desynchronisation did not indicate negative impacts on competition performance. As travel fatigue probably had a major effect on perceptual decrements, sleep during travel and time to recover upon arrival should be emphasised. Coaches and practitioners should consider higher sleep propensity in the early evening by scheduling training sessions and meetings until the late afternoon.     

当前世界女子高低杠项目成套动作难度特征分析

以第39届世界体操锦标赛的女选手为研究对象，对新规则实施后世界女子高低杠发展特点进行研究。结果显示：成套动作的平均难度为6．638分，位居4项之首，仍有继续提高的空间；其中飞行动作的难度变化不大，连接价值提高；从低杠换握高杠大多以B组动作为主，从高杠换握低杠则以D组为主；上法开发了挺身跳起成低杠手倒立的D组难度，且有连接动作加难的趋势；下法动作继续呈现多样化特征：今后的主要任务是提高完成动作的成功率和动作质量，重点提高动作细节和下法的稳定性。     

武术腾空摆莲720°接马步的运动学分析

本文采用运动生物力学的三维摄像解析法对武术腾空摆莲720°接马步动作进行运动学分析,揭示该动作的运动学特征,为提高动作质量,改进动作技术提供参考。     

武术腾空飞脚动作的运动学分析

本文采用固定高速摄影及影片数字化研究方法,对武术腾空飞脚动作进行运动学分析。得出各分解动作的运动学数据,找到动作的运动学特征。     

空中乘务专业学生就业中的隐形劣势

空中乘务专业具有很强的行业特色。近几年,依托民航业的迅猛发展,本专业的就业率同比大幅高于其他专业。但是在良好的就业形势下,我们必须清晰地认识到目前大学生整体就业现状,应用科学方法有效分析空乘就业市场,深刻认识到本专业学生在就业过程中存在的隐形劣势,以确保学生就业工作的前瞻性。     

利用改进威胁模型的电势理论的三维飞行路径规划

用改进威胁模型规划后的电势理论划出实用的三维航迹.对有地形威胁和雷达、火力威胁的各种情况进行了分类、分析,并推出计算公式.通过限定搜索范围为包含起始点和目标点之间的矩形区域,不但减少了计算的复杂度,而且保证飞行路线收敛于目标点.用坡度限制平滑算法和用曲率限制平滑算法对上述航迹的法向加速度和曲率进行约束,得到符合飞行器机动性的飞行路线.     

人工免疫算法规划复杂环境下三维飞行航迹

应用人工免疫算法规划复杂地形和火力威胁环境下的三维飞行航迹.根据实际地形的特点提取在山岭横栏的地形和多火力威胁包围的复杂场景,利用人工免疫算法的3种情况分别进行飞行器的航线设计,同时根据飞机的机动性和适航性对上述规划出的航迹进行优化;并把免疫算法3种情况的模拟结果进行比较.仿真结果表明,与遗传算法相比,人工免疫算法在规划复杂环境下三维航迹是可行的,在时间上有一定的优势.     

浅析RNP AR技术的发展与应用实例

2020年6月24日,深航ZH9803航班的顺利落地,标志着RNP AR飞行程序在苏南硕放机场正式投入运行,苏南硕放机场周边空域环境复杂、军民航飞行矛盾突出,空域使用严重受限,但是通过实施RNP AR程序,成功地将传统需要降落的五边距离由17公里缩短到了3.7公里,使得苏南硕放机场成为国内采用最短五边实施RNP AR进近的机场。该文主要是基于RNP AR技术的发展以及如何通过RNP AR技术来解决苏南硕放机场空域限制的难题进行了阐述,目的是进一步推动我国民航事业的进步与发展。