Information-governing dynamics of attacker–defender interactions in youth rugby union     

Pedro Passos  Duarte Araújo  Keith Davids  Luis Gouveia  João Milho  SidóNio Serpa 《Journal of sports sciences》2013,31(13):1421-1429

Abstract

Previous work on dynamics of interpersonal interactions in 1 vs. 1 sub-phases of basketball has identified changes in interpersonal distance between an attacker and defender as a potential control parameter for influencing organizational states of attacker–defender dyads. Other studies have reported the constraining effect of relative velocity between an attacker and defender in 1 vs. 1 dyads. To evaluate the relationship between these candidate control parameters, we compared the impact of both interpersonal distance and relative velocity on the pattern-forming dynamics of attacker–defender dyads in the sport of rugby union. Results revealed that when interpersonal distance achieved a critical value of less than 4 m, and relative velocity values increased or were maintained above 1 m · s^?1, a successful outcome (i.e. clean attempt) for an attacker was predicted. Alternatively, when values of relative velocity suddenly decreased below this threshold, at the same critical value of interpersonal distance, a successful outcome for the defender was predicted. Data demonstrated how the coupling of these two potential, nested control parameters moved the dyadic system to phase transitions, characterized as a try or a tackle. Observations suggested that relative velocity increased its influence on the organization of attacker–defender dyads in rugby union over time as spatial proximity to the try line increased.  相似文献   

Velocity and acceleration before contact in the tackle during rugby union matches     

Sharief Hendricks  David Karpul  Fred Nicolls  Michael Lambert 《Journal of sports sciences》2013,31(12):1215-1224

Abstract

The velocity and acceleration at which the ball-carrier or tackler enters the tackle may contribute to winning the contest and prevailing injury free. Velocity and acceleration have been quantified in controlled settings, whereas in match-play it has been subjectively described. The purpose of this study was to determine the velocity and acceleration of the ball-carrier and tackler before contact during match-play in three competitions (Super 14, Varsity Cup, and Under-19 Currie Cup). Using a two-dimensional scaled version of the field, the velocity and acceleration of the ball-carrier and tackler were measured at every 0.1 s to contact for 0.5 s. For front-on tackles, a significant difference (P < 0.05) between the ball-carrier (4.6 ± 1 m · s^–1) and tackler (7.1 ± 3.5 m · s^–1) was found at the 0.5 s time to contact interval in the Varsity Cup. For side-on tackles, differences between the two opposing players were found at 0.5 s (ball-carrier: 4.6 ± 1.7 m · s^–1; tackler: 3.1 ± 1.2 m · s^–1) and 0.4 s (ball-carrier: 6.3 ± 2.3 m · s^–1; tackler: 3.7 ± 1.6 m · s^–1) at Under-19 level. After 0.4 s, no significant differences (P > 0.05) were evident. Also, the ball-carrier's velocity over the 0.5 s was relatively stable compared with that of the tackler. Results suggest that tacklers adjust their velocity to reach a suitable relative velocity before making contact with the ball-carrier.  相似文献   

本质集的邻域并和无爪图的哈密尔顿性     

徐新萍 《东南大学学报》2002,18(2)

设G是一个图 ,G的独立集Y称为本质集 ,如果存在 {y1,y2 } Y ,使得dist(y1,y2 ) =2 .本文利用插点方法 ,给出了关于k或 (k + 1)连通 (k≥ 2 )无爪图G是哈密尔顿的或 1哈密尔顿的统一的证明 .2个结果的充分条件是关于 ∑ki=0N(Yi) 与n(Y)的不等式 ,这里Y是图G的任一本质集 ,对于i∈ { 0 ,1,… ,k} ,Yi={y1,yi- 1,… ,yi- (b- 1) } Y(yj 的下标将取模k + 1) ;b是一个整数 ,且 0 相似文献