潮流能作为一种清洁无污染而且蕴藏丰富的可再生新能源,对其合理开发利用可以有效缓减能源短缺的问题。文中选用N A C A 644X X系列翼型,以得到较高捕能系数的水轮机为目标,基于叶素-动量(B EM)理论,给出了叶轮叶片设计的步骤,分别以翼...潮流能作为一种清洁无污染而且蕴藏丰富的可再生新能源,对其合理开发利用可以有效缓减能源短缺的问题。文中选用N A C A 644X X系列翼型,以得到较高捕能系数的水轮机为目标,基于叶素-动量(B EM)理论,给出了叶轮叶片设计的步骤,分别以翼型前缘和翼型最大厚度为基准设计出两种30 W的小型水平轴潮流能水轮机叶片;然后运用叶素理论和动量理论对叶轮捕能系数进行了理论计算,即运用C FD软件A N SY S C FX对设计出的叶轮模型捕能系数进行了数值模拟计算并与理论值进行了对比。结果表明以翼型前缘为基准设计出的叶片捕能效果更好,同时验证了叶素理论与动量理论的等效性以及运用叶素-动量理论进行叶片设计的有效性。展开更多
This study investigated changes in the complexity （magnitude and structure of variability） of the collective behaviours of association football teams during competitive performance. Raw positional data from an entir...This study investigated changes in the complexity （magnitude and structure of variability） of the collective behaviours of association football teams during competitive performance. Raw positional data from an entire competitive match between two professional teams were obtained with the ProZone tracking system. Five compound positional variables were used to investigate the collective patterns of performance of each team including： surface and geometrical centre. Analyses involve the coefficient （ApEn）, as well as the linear association between both area, stretch index, team length, team width, of variation （%CV） and approximate entropy parameters. Collective measures successfully captured the idiosyncratic behaviours of each team and their variations across the six time periods of the match. Key events such as goals scored and game breaks （such as half time and full time） seemed to influence the collective patterns of performance. While ApEn values significantly decreased during each half, the %CV increased. Teams seem to become more regular and predictable, but with increased magnitudes of variation in their organisational shape over the natural course of a match.展开更多
文摘潮流能作为一种清洁无污染而且蕴藏丰富的可再生新能源,对其合理开发利用可以有效缓减能源短缺的问题。文中选用N A C A 644X X系列翼型,以得到较高捕能系数的水轮机为目标,基于叶素-动量(B EM)理论,给出了叶轮叶片设计的步骤,分别以翼型前缘和翼型最大厚度为基准设计出两种30 W的小型水平轴潮流能水轮机叶片;然后运用叶素理论和动量理论对叶轮捕能系数进行了理论计算,即运用C FD软件A N SY S C FX对设计出的叶轮模型捕能系数进行了数值模拟计算并与理论值进行了对比。结果表明以翼型前缘为基准设计出的叶片捕能效果更好,同时验证了叶素理论与动量理论的等效性以及运用叶素-动量理论进行叶片设计的有效性。
基金supported by a grant of the Portuguese Foundation for Science and Technology(SFRH/BD/43994/2008)
文摘This study investigated changes in the complexity （magnitude and structure of variability） of the collective behaviours of association football teams during competitive performance. Raw positional data from an entire competitive match between two professional teams were obtained with the ProZone tracking system. Five compound positional variables were used to investigate the collective patterns of performance of each team including： surface and geometrical centre. Analyses involve the coefficient （ApEn）, as well as the linear association between both area, stretch index, team length, team width, of variation （%CV） and approximate entropy parameters. Collective measures successfully captured the idiosyncratic behaviours of each team and their variations across the six time periods of the match. Key events such as goals scored and game breaks （such as half time and full time） seemed to influence the collective patterns of performance. While ApEn values significantly decreased during each half, the %CV increased. Teams seem to become more regular and predictable, but with increased magnitudes of variation in their organisational shape over the natural course of a match.
