提高武术选项课教学质量有效途径的探讨

文章采用文献资料法和访问调查法,对提高武术选项课教学质量的有效途径进行了探讨。认为抓好武术基本功教学是提高武术选项课教学质量的基础;按武术攻防技击性特点教学是关键;采用灵活多样的教学方法是前提;熟悉教材、编写好教案是重要环节。     

Describing the plastic deformation of aluminium softball bats

Hollow aluminium bats were introduced over 30 years ago to provide improved durability over wooden bats. Since their introduction, however, interest in hollow bats has focused almost exclusively around their hitting performance. The aim of this study was to take advantage of the progress that has been made in predicting bat performance using finite elements and apply it to describe bat durability. Accordingly, the plastic deformation from a ball impact of a single-wall aluminum bat was numerically modelled. The bat deformation from the finite-element analysis was then compared with experiment using a high-speed bat test machine. The ball was modelled as an isotropic, homogeneous, viscoelastic sphere. The viscoelastic parameters of the ball model were found from instrumented, high-speed, rigid-wall ball impacts. The rigid-wall ball impacts were modelled numerically and showed good agreement with the experimentally obtained response. The strain response of the combined bat-ball model was verified with a strain-gauged bat at intermediate ball impact speeds in the elastic range. The strain response of the bat-ball model exhibited positive correlation with the experimental measurements. High-speed bat-ball impacts were performed experimentally and simulated numerically at increasing impact speeds which induced correspondingly increased dent sizes in the bat. The plastic deformation from the numerical model found good agreement with experiment provided the aluminium work hardening and strain rate effects were appropriately described. The inclusion of strain rate effects was shown to have a significant effect on the bat deformations produced in the finite-element simulations. They also helped explain the existence of high bat stresses found in many performance models.     

未经训练成年男性急性运动性疲劳的电刺激研究

运用电刺激的方法研究未经训练成年男性的急性运动性疲劳机制。结果表明:在疲劳性伸膝运动后,最大随意收缩力下降17±15%(p<0.001),中枢激活水平从88±7%下降到84±6%(p=0.001),M波波幅基本不变,但电刺激诱发的最大颤搐张力和最大张力上升速度明显降低,半舒张时间延长,激活后增强效应(postactivation potentiation)下降19%(p<0.001)。疲劳过程中平均肌电图-力矩比值升高。结论:在未经训练成年男性间歇性大负荷运动导致疲劳过程中,中枢神经系统及肌肉本身均参与了运动性疲劳的形成,肌肉的兴奋性未发生明显变化,但收缩能力减弱。     

海杜克建筑人文主义精神

作为“纽约 5”的一员 ,海杜克始终在研究建筑的语言逻辑 ,并力求在其作品中体现人文主义关怀。对于海杜克而言 ,现代建筑的问题不在于逻辑的贫乏 ,而在于过多的逻辑 ,以致于缺少了对人的尊敬。海杜克的研究则注重在建筑中体现人文主义的精神。