The influence of moment of inertia on baseball/softball bat swing speed   总被引：1，自引：1，他引：0  

Keith?KoenigEmail author  Nan?Davis?Mitchell  Thomas?E.?Hannigan  J.?Keith?Clutter 《Sports Engineering》2004,7(2):105-117

The speed at which a player can swing a bat is central to the games of baseball and softball, determining, to a large extent, the hit speed of the ball. Experimental and analytical studies of bat swing speed were conducted with particular emphasis on the influence of bat moment of inertia on swing speed. Two distinct sets of experiments measured the swing speed of colege baseball and fast-pitch softball players using weighted rods and modified bats. The swing targets included flexible targets, balls on a tee and machine pitched balls. Internal mass alterations provided a range of inertial properties. The average measured speeds, from 22 to 31 m s⁻¹, are consistent with previous studies. Bat speed approximately correlates with the moment of inertia of the bat about a vertical axis of rotation through the batter's body, the speed generally decreasing as this moment of inertia increases. The analytical model assumes pure rotation of the batter/bat system about a vertical axis through the batter's body. Aerodynamic drag of the batter's arms and the bat is included in the model. The independent variable is bat moment of inertia about the rotation axis. There is reasonable agreement between the model and the measured speeds. Detailed differences between the two suggest the importance of additional degrees of freedom in determining swing speed.  相似文献   

对体育教师实施"能本管理"的研究     

邱启国 《体育成人教育学刊》2004,20(2):93-94

科学管理体育师资队伍,充分发挥每个体育教师的工作潜能,是全面提高学校素质教育质量的重要保证。从怎样培养体育教师的工作能力、激发体育教师工作的潜力及发挥好他们的聪明才智三方面论述了“能本管理”的概念、模式及对现实的重要意义。  相似文献   

道家哲学思想对太极拳理论的影响   总被引：12，自引：1，他引：11  

陈青山  胡来东 《体育成人教育学刊》2004,20(2):31-32

武术是中国的传统化,其中太极拳理论的形成是以道家哲学思想为基础,其拳理拳论、风格特点和价值取向,处处体现道家“依乎天理,顺其自然”的哲学思想和“虚静,守寂不争,为而不持”的精神境界及“贵柔守雌,柔弱胜刚强”的道家风度。道家哲学思想是太极拳哲理的理论基础。  相似文献   

Price Indices for Artists – A Proposal     

Guido?Candela  Paolo?Figini  Antonello?E.?ScorcuEmail author 《Journal of Cultural Economics》2004,28(4):285-302

This paper proposes a price index for artists adjusted for the quality of the paintings, based on the ratio between the average market price and the average pre-sale estimate for paintings. We apply this methodology to a group of selected artists and schools presented in auctions worldwide in the period 1990–2001. A comparison with quality unadjusted and hedonic indices is also conducted.JEL Classification: C10, Z11  相似文献   

ONIX: Is there a return on investment for all publishers?     

Endre?L.?BekyEmail author 《Publishing Research Quarterly》2004,20(2):3-8

Summary What will be the future of ONIX? Some argue that wider industry acceptance will lead to increased efficiencies in the transfer of book data, which will ultimately benefit book sales. ONIX still has to overcome many challenges: its implementation cost is high, whole-salers and aggregators are still using different spreadsheets and information sources. Furthermore, MS Excel as an alternative solution is widely available and accepted by the industry. Small publishers need more education and a straightforward demonstration of ONIX’s return on investment. An outreaching of the helping hand of professional organizations is strongly suggested to foster the adoption process among small players. It is the role of the AAP and BISG to get their memberships to think about what is good for all members as a whole throughout the industry. As an organization BISG can recommend, educate, and promote the standard. It cannot, however, bring pressure or demand organizations use it. Publishers, retailers, and wholesalers make those decisions for themselves and quite apparently the majority do not yet see the rewards. Market players need to determine the cost versus benefit and as long as distributors and retailers agree on receiving other formats, ONIX will never take a strong hold in the marketplace. After all, publishers should compete against each other with good books and not with multiple computer codes.  相似文献   

Grey literature in the life of GESAMP,an international marine scientific advisory body     

Bertrum?H.?MacDonaldEmail author  Ruth?E.?Cordes  Peter?G.?Wells 《Publishing Research Quarterly》2004,20(1):25-41

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Capturing academic grey literature—Starting at home     

Gretta?E.?SiegelEmail author 《Publishing Research Quarterly》2004,20(1):62-69

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The New Yorker: Aftermath     

Calvin Tomkins  June L. Orton 《Annals of dyslexia》1964,14(1):94-94

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Mother-child interaction and the socialization process     

J S Hatfield  L R Ferguson  R Alpert 《Child development》1967,38(2):365-414

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Judgments of vocal attributes in normal and schizophrenic children     

E Sass 《Exceptional children》1967,33(9):645-646

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