某大型火电站解决汽轮机喷油试验不成功问题的实践

文章根据人机材料方法环境,分析在中国北方的大型火力发电站失败的几个蒸汽涡轮机燃油喷射试验,同时阐述如何解决。     

两种速度训练方法新探--弹簧式反弹练习和超速训练

速度的提高是一个复杂的过程,提高速度的方法有多种,但速度训练一定要有针对性.本文通过借鉴国外学者的一些研究,对两种提高速度的训练方法进行探讨,以期对教练员和运动员有所启发和帮助.     

Effects of modified-implement training on fast bowling in cricket

The effects of training with overweight and underweight cricket balls on fast-bowling speed and accuracy were investigated in senior club cricket bowlers randomly assigned to either a traditional (n = 9) or modified-implement training (n = 7) group. Both groups performed bowling training three times a week for 10 weeks. The traditional training group bowled only regulation cricket balls (156 g), whereas the modified-implement training group bowled a combination of overweight (161?-?181 g), underweight (151?-?131 g) and regulation cricket balls. A radar gun measured the speed of 18 consecutive deliveries for each bowler before, during and after the training period. Video recordings of the deliveries were also analysed to determine bowling accuracy in terms of first-bounce distance from the stumps. Bowling speed, which was initially 108?±?5 km?·?h^?1 (mean?±?standard deviation), increased in the modified-implement training group by 4.0 km?·?h^?1 and in the traditional training group by 1.3 km?·?h^?1 (difference, 2.7 km?·?h^?1; 90% confidence limits, 1.2 to 4.2 km?·?h^?1). For a minimum worthwhile change of 5 km?·?h^?1, the chances that the true effect on bowling speed was practically beneficial/trivial/harmful were 1.0/99/<?0.1%. For bowling accuracy, the chances were 1/48/51%. This modified-implement training programme is not a useful training strategy for club cricketers.