非稳态雾赋能网络中的在线任务卸载方法

为充分发掘分布在不同位置上的雾节点的计算资源,任务卸载被寄予众望。在雾计算场景下,以尽可能减少任务卸载的长期成本为目标,试图寻找一个高效的在线任务卸载方法。为此,这一问题被建模成一个随机规划问题,该问题中系统参数所对应的随机变量的期望会在未知时刻突变,系统参数相关信息只能在任务完成后的反馈中获得。基于非稳态多臂老虎机模型,提出一个高效的算法来解决这一具有挑战性的随机优化问题,给出理论分析证明该算法的渐进最优性。数值实验证明了该算法的优越性。     

Motivation counteracts fatigue-induced performance decrements in soccer passing performance

Recent theories suggest that negative effects of fatigue on performance are determined by perception of effort and motivation rather than being directly caused by reaching physiological limits. In the current experiment, the influence of motivation on fatigue-induced decrements in soccer performance was experimentally investigated. Sixty amateur soccer players performed a validated soccer-passing test before and after a fatigue protocol. Results showed that players’ motivation and performance decreased after the fatigue protocol for players in the control group. In contrast, players in the motivation group (i.e., with motivation experimentally induced after the fatigue protocol) were able to uphold their motivation and increase their performance. These results indicate that motivation plays a crucial role in performance under fatigue, as fatigue-induced decrements in soccer passing performance can be counteracted by high levels of motivation. Future research may explore the limits of this counteracting effect and extend findings to other relevant performance aspects.     

体育院校高水平运动队成员关系对团队冲突的影响

摘要：近些年来,团队成员关系变化对团队冲突影响越来越多,相关问题也得到了学者们的热切关注。体育团队作为较为特殊的团队形式具有与常规团队区别的差异特征,团队成员关系与团队冲突的关系更加值得深入探讨。本研究目的在于：通过对团队成员关系的阐述,解释成员关系特征对团队冲突的影响,由此找到合理激发任务冲突、控制关系冲突和任务冲突向关系冲突转化的办法,为提升体育团队绩效提供支持。为此,运用文献分析法、问卷调查法、案例分析法等研究方法,以沈阳体育学院板球院队为测量对象,研究了体育院校高水平运动队成员关系对对团队冲突的影响。通过研究,结果表明：1）体育院校高水平运动团队成员关系深刻影响着团队冲突,一般说来,团队成员关系越亲密,团队冲突就越少;2）团队成员工具性关系对团队冲突没有影响;3）团队成员情感关系对冲突具有积极的影响作用,成员关系越亲密,团队冲突就越少;4）关键事件通过影响团队成员关系来深刻影响团队冲突。     

The effects of localised fatigue on upper extremity jump shot kinematics and kinetics in team handball

Team handball is a popular sport worldwide that requires numerous throws to be made throughout the course of a game. Because of the upper extremity demands of repetitive throwing, it is possible that fatigue can alter the mechanics of a shot. The purpose of this study was to determine the influence of localised fatigue on jump shot kinematics and kinetics. Eleven male team handball players (23.1 ± 3.1 years; 185.1 ± 8.3 cm; 89.7 ± 12.2 kg) volunteered. An electromagnetic tracking system was used to examine the jump shot prior to and following localised fatigue. The fatiguing protocol consisted of throwing a 2.2 kg medicine ball into a rebounder until volitional fatigue. No significant kinematic or kinetic differences were observed following fatigue. Shoulder external rotation was ?74.8 ± 14.9° prior to and ?79.0 ± 14.7° following fatigue at MER. Scapula, external rotation at ball release (BR) prior to fatigue was ?2.2 ± 7.0° and ?3.2 ± 11.1° following fatigue. Scapular internal rotation, at maximum shoulder internal rotation (MIR), changed from 18.4 ± 11.2° to 20.4 ± 11.8°. Ball velocity decreased from19.8 m · s^–1 to 18.8 m · s^–1 (P = 0.12). Accuracy percentage in the pre-fatigue trials was 60.8 ± 14.1% and 52.8 ± 12.7% following fatigue (P = 0.20). While no significant changes were observed, it is possible that other fatiguing protocols that more closely represent the aerobic and throwing demands of the sport may have a greater effect on the kinematics and kinetics of the jump shot.     

第28-32届奥运会投掷项目运动员年龄特征发展趋势研究

通过文献资料法、数理统计法、对比分析法以及个案分析法对第28-32届奥运会投掷项目前12名运动员的竞技年龄从结构、性别、年龄特征等角度进行对比分析。结果表明:(1)在28-32届奥运会投掷项目中,25-30岁年龄段运动员一直是奥运会投掷项目的主力军,在1-3名以及1-12名的人数占比中,一直呈增长趋势; 31岁以上年龄段运动员对奖牌仍具有较强的竞争力,在1-3名的人数占比中,整体呈现出增长的趋势。(2)在近5届奥运会中,投掷项目在整体上1-12名运动员平均年龄呈下降趋势;前3名运动员平均年龄发展呈现出增长趋势,女子运动员的平均年龄普遍低于男子运动员。(3)投掷运动员最佳竞技年龄表现出铁饼>链球>标枪>铅球(29> 28> 27.5> 27)的现象。(4)随着科技的助力以及科学的训练理念和方法的普及,国内外部分高水平投掷运动员能够较长时间的保持个人最佳竞技状态。     

Representative learning design in springboard diving: Is dry-land training representative of a pool dive?

Abstract

Two distinctly separate training facilities (dry-land and aquatic) are routinely used in springboard diving and pose an interesting problem for learning, given the inherent differences in landing (head first vs. feet first) imposed by the different task constraints. Although divers may practise the same preparation phase, take-off and initial aerial rotation in both environments, there is no evidence to suggest that the tasks completed in the dry-land training environment are representative of those performed in the aquatic competition environment. The aim of this study was to compare the kinematics of the preparation phase of reverse dives routinely practised in each environment. Despite their high skill level, it was predicted that individual analyses of elite springboard divers would reveal differences in the joint coordination and board-work between take-offs. The two-dimensional kinematic characteristics were recorded during normal training sessions and used for intra-individual analysis. Kinematic characteristics of the preparatory take-off phase revealed differences in board-work (step lengths, jump height, board depression angles) for all participants at key events. However, the presence of scaled global topological characteristics suggested that all participants adopted similar joint coordination patterns in both environments. These findings suggest that the task constraints of wet and dry training environments are not similar, and highlight the need for coaches to consider representative learning designs in high performance diving programmes.     

影响中国女子冰壶队投壶成功率因素分析

本文运用文献资料法、录像观察法和数理统计法,对影响中国女子冰壶队投壶成功率进行分析,结果表明：技战术水平高低是关键因素;心理素质是另一主要因素;魔鬼赛程是影响投壶成功率的另一障碍因素。     

对健美操专选大学生任务定向与自我定向的研究

通过对浙江省部分在校的大一、大二共3280名学生任务定向和自我定向自然实验的测试结果表明：大学生在体育运动中任务定向均值较高，而自我定向均值较低，但不同专项的学生在任务定向和自我定向中有着不同的差异。不了解体育项目之间的特点与内在性质上的差异，是造成大学生任务定向与自我定向均值高低不等的主要原因。     

论最后用力在掷标枪技术中的重要作用

标枪投掷中,最后用力的好坏直接影响到运动成绩,在分析了各环节的基础上提出了最后用力在标枪投掷中的重要作用。而在最后用力技术环节中,左侧支撑技术的好坏,直接影响力的传递和用力的效果,进而影响投掷成绩。     

The influence of pitch dimensions on performance during small-sided and conditioned soccer games

Abstract

This study examined the influence of pitch dimensions in small-sided soccer games in shaping opportunities for performers to maintain ball possession, pass to teammates and shoot at goal. Fifteen amateur standard male participants (M = 21.87, σ = 1.96 years) played 5 v 5 small-sided soccer games in three varying pitch conditions (28 m × 14 m, 40 m × 20 m and 52 m × 26 m). Thirty sequences of play in each condition were selected for digitisation using TACTO software, allowing the capture of bi-dimensional displacement coordinate data of all players and the ball. The values of interpersonal distance between all attackers and immediate defenders and the relative distances of defenders to intercept a shot and a pass were computed as dependent variables. Results showed existence of fewer opportunities to maintain ball possession on smaller pitches, compared to medium and larger pitches. Conversely, the different dimensions set to the pitch did not influence opportunities for players to shoot at goal, or to perform passes to other teammates. By examining the specific spatial–temporal relationships of players and key-task constraints, the data from this study explain how effects of manipulating pitch dimensions of small-sided games might enhance opportunities for acquiring specific movement and decision-making skills.