An upper limb kinematic model for the examination of cricket bowling: A case study of Mutiah Muralitharan

We show how biomechanics can be used to accurately assess spin-bowling techniques (offspin, legspin and topspin) in cricket, under controlled conditions, when the player is suspected of throwing. A 50 Hz six-camera Vicon Motion Analysis system was used to record the movements of markers strategically placed on the upper limb during each of the above bowling actions. A kinematic model of the upper limb, created using Vicon BodyBuilder® software, enabled the movements of the upper arm and forearm to be described during each delivery. Selected physical characteristics of the upper limb were also measured. The present 'no ball' law in cricket with reference to throwing states that 'the arm should not be straightened in the part of the delivery that immediately precedes ball release'. The bowler, Mutiah Muralitharan, was shown to maintain a relatively constant elbow angle in the 0.06 s before ball release. Furthermore, this angle changed little from the time that the upper arm was angled vertically downward until ball release during the three spin-bowling actions.     

The measurement of shoulder alignment in cricket fast bowling

The aim of this study was to compare thoracic spine alignment with two-and three-dimensional calculations of shoulder alignment (defined as a line joining the acromion processes of the right and left scapula) when all measures were projected onto the transverse plane. A six-camera Vicon system was used to reconstruct three markers positioned on the plane of the thorax such that the orthogonal vector to the thoracic spine, projected onto the transverse plane, was used as a virtual shoulder alignment during cricket fast bowling. This same measurement system was used to calculate the three-dimensional line between the acromion processes projected onto the transverse plane. These acromion markers were also used to calculate the two-dimensional transverse plane alignment of the shoulders from images recorded by a video camera positioned above ball release. All cameras operated at 50 Hz. A significant association was recorded between thorax alignment and the three- (0.97) and two-dimensional (0.87) shoulder alignment estimations at back-foot impact. The strength of association remained at front-foot impact, when correlations of 0.89 (three-dimensional) and 0.84 (twodimensional) were recorded. However, at ball release, non-significant associations of 0.58 (three-dimensional) and 0.41 (two-dimensional), representing shoulder alignment differences of approximately 10°, were recorded. The 95% limits of agreement comparisons for shoulder alignment at back-foot impact, front-foot impact and ball release produced mean random errors for the two comparisons of 9.5°, 11.7° and 22.5° respectively. Three- and two-dimensional transverse plane projections of shoulder alignment are reasonable estimates of thorax alignment at back-foot impact and front-foot impact but not at ball release.     

Q methodology in learning,design, and technology: an introduction

Educational technology research and development - An important element of good design, instructional or otherwise, is awareness of and being empathetic to the needs, wants, interests, values, and...     

在图像处理上做高性能离散傅立叶变换

我们介绍了一种利用高性能GPU来进行傅立叶变换的算法,包括级联式混合维数数FFT算法,无论是2的次幂大小或非2的次幂大小的。我们的级联式嘴法采用Stocldaam公式有效地利用了GPU的共享内存。我们通过把装置转换成基于块的多肿算法从而减小了内存装置的开销。对于非2次幂大小的情况,我们综合利用了小质数混合基FFr和Bluestein算法。     

Memory Binding in Early Childhood: Evidence for a Retrieval Deficit

Previous research has suggested that performance for items requiring memory-binding processes improves between ages 4 and 6 ( J. Sluzenski, N. Newcombe, & S. L. Kovacs, 2006 ). The present study suggests that much of this improvement is due to retrieval, as opposed to encoding, deficits for 4-year-olds. Four- and 6-year-old children ( N  = 48 per age) were given objects, backgrounds, and object + background combinations to remember. Younger children performed equivalently to 6-year-olds during a working memory task for all types of memory questions but were impaired during a long-term memory task for the object + background combinations. Furthermore, this deficit was completely due to differences in false alarm rates, suggesting that separate analyses of hits and false alarms may be preferable to corrected recognition scores when studying memory development.     

The implications of changing educational and family circumstances for children's grade progression in rural Pakistan: 1997–2004

We assess factors affecting primary and middle school dropout in rural Punjab and NorthWest Frontier Province over 6 years (1997–2004). These data are unique in a developing-country setting in longitudinally tracking changes in both school and household environments. While grade retention has improved, girls’ dropout rates remain fairly high. Results suggest the importance of both household and school factors. For girls, arrival in the family of an unwanted birth in the last 6 years and enrollment in a government (not private) primary school significantly increase the likelihood of dropout, whereas availability of post-primary schooling, having a mother who attended school, and living in a better-off household reduce the probability of dropout. For boys, school quality, measured by the percent of residential teachers in the primary school, and living in a more developed community significantly reduce the probability of dropping out; loss of household remittances significantly increases the likelihood of dropout.     

Evaluation of wireless bat swing speed sensors

Batter swing speed is an important parameter in understanding the performance of baseball and softball players. A number of swing speed sensors have recently been introduced and are commercially available. The aim of this study was to compare three wireless swing sensors with high speed video. Swing speed from high speed video was measured by differentiating the position coordinates of tracking markers on the bat barrel. On average, the wireless bat swing sensors reported speeds 8% slower than that found from video tracking. The agreement was better at low swing speeds, suggesting that the current generation of wireless sensors is best suited for developing players. Spatial measures, such as swing angle, were not in good agreement with video tracking.     

An audit of injuries in six english professional soccer academies

Regulations now state that professional academies in the United Kingdom are required to substantially increase the volume of soccer training. This study assessed the current injury occurrence, providing an update to reports published prior to the introduction of the Elite Player Performance Plan (EPPP). 608 soccer players aged 11–18 years from six professional soccer clubs were prospectively monitored, recording injuries during the 2014–2015 season. An injury rate of 1.32 injuries per player/season was indicated with a mean time loss of 21.9 days per injury. The greatest time loss per injury was in the U14s-U15s, and the highest rate of severe injuries in the U15s. Strains and sprains were the most common injury type, with the knee and ankle the most frequently injured anatomical sites. Seasonal variation indicated two peaks in injury incidence, occurring in September and January. In comparison to a published audit prior to the inception of the EPPP, this study indicates that academy soccer players are three-times more likely to experience an injury. Given that time loss and injury severity also increased during periods that typically follow rapid growth, these players should be considered an important group for training load monitoring and injury prevention strategies.