Field and laboratory measurements of softball player swing speed and bat performance   总被引：1，自引：1，他引：0  

Lloyd Smith  Jeff Kensrud 《Sports Engineering》2014,17(2):75-82

The swing speed of the bat is one of the most important factors affecting the hit-ball speed. Most field studies tend to focus on measuring ball speed, which is easier to measure and quantify than bat speed. For this reason, relatively little data exist describing bat motion in field conditions. The following describes a relatively large swing speed field study involving bats of the same model with nearly constant weight and varying inertia. The study was conducted using right-handed batters on a regulation outdoor field with a live pitcher. Swing speed was measured by tracking markers on the bat with two high-speed video cameras so that the bat markers could be traced in three-dimensional space. The ball motion was tracked using the same high-speed video cameras and a three-dimensional Doppler radar system. Bat swing speed was observed to be proportional to the batter skill level and the normalised swing speed increased with decreasing bat inertia. The bat centre of rotation during impact was close to the knob of the bat. The bats were tested under controlled laboratory conditions using a standardised performance test. The field and laboratory results showed good agreement including the hit-ball speed and the subtle effect of bat inertia on the maximum performance location. The vibrational response of the bats was considered using modal analysis. The maximum performance location was correlated with the node of the first vibrational mode.  相似文献   

The Cambridge Companion to Horseracing     

James Williams 《Sport in History》2014,34(2):378-382

  相似文献   

A two-stage proxy variable approach to estimating movie box office receipts     

Frederick W. Derrick  Nancy A. Williams  Charles E. Scott 《Journal of Cultural Economics》2014,38(2):173-189

This paper advances the ongoing discussion of methods for predicting movie box office revenues with two contributions to the methodology and an out-of-sample test of the model. The first innovation is the development of a two-stage model using publicly available pre-release indicators to predict (1) initial week and (2) subsequent run box office revenues. To incorporate the experience-good nature of movies, the second stage is estimated by incorporating a proxy variable for box office success during the first week relative to predicted first week success. The second contribution is an empirical test of De Vany and Walls’ (J Econ Dyn Control 28:1035–1057, 2004) finding that the distribution of movie revenues has “heavy tails” and follows a non-Gaussian stable distribution with infinite variance. We estimate the two-stage model of a movie’s box office success on all general release movies in 1 year with both the Gaussian and stable distribution with heavy tails and infinite variance and find no evidence for the stable distribution in either stage of the estimation. This two-stage model is validated by comparing all general release movies in 3 future years (out-of-sample data) to the model’s predictions.  相似文献   

Campaign ‘76: Agenda setting during the New Hampshire primary     

Wenmouth Williams Jr.  William Semlak 《广播与电子媒介杂志》2013,57(4):531-540

  相似文献   

Report: The entebbe mathematics project     

Grace Alele Williams 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》1971,17(2):210-214

  相似文献   

Building Trust Through Culturally Reciprocal Home-School-Community Collaboration from the Perspective of African-American Parents     

Ereka R. Williams  Ceola Ross Baber 《Multicultural Perspectives》2013,15(2):3-9

This article presents findings of an instrumental case study that examined the perceptions held by African-American parents on the efficacy of schools in meeting the needs of African-American learners in a North Carolina community. A theme of distrust emerged and evidenced the need for teachers, administrators, and teacher educators to reconsider approaches used with African-American parents, particularly where building culturally reciprocal home-school-community relationships is concerned.  相似文献   

RESEARCH PARTNERS: A NEW LOOK AT COLLABORATION OF FACULTY AND CLASSROOM TEACHERS     

Cleta Booth  Dr. Karen Cachevki Williams 《Journal of Early Childhood Teacher Education》2013,34(3):285-292

  相似文献   

Compressive strength of portland cement mortars and concretes     

R.J. Wig  G.M. Williams  E.R. Gates 《Journal of The Franklin Institute》1915,180(5):608-613

  相似文献   

Leadership and inclusion: a special school perspective     

Robin Attfield  & Chris Williams 《British Journal of Special Education》2003,30(1):28-33

In July 2002, the National College for School Leadership (NCSL) held a 'Leading Edge' seminar focused on the contribution that leaders in special schools can make to the development of Inclusive policies and practices. The day gave colleagues working in specialist contexts an opportunity to share examples and experiences of current initiatives and to speculate about future trends and developments in inclusive education. In this article, Robin Attfield and Chris Williams, Assistant Directors in Programmes and Research respectively at the NCSL, explore the context in which the seminar took place and some of the themes and issues that emerged from discussion on the day. At the end of their paper, they summarise the key messages that the special school leaders who attended the seminar wished to communicate to a wider audience and articulate a further role for leaders in special schools in the development of inclusion.  相似文献   

Justice in the process,not in the results     

Walter E. Williams 《Academic Questions》1996,9(4):76-79

  相似文献