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.     

借助《说文解字》辨识中学文言文中的古今字、通假字、假借字和异体字

古书中的用字情况非常复杂。在阅读中学文言文的时候,我们常常会遇到古今字、通假字、假借字、异体字等不同的用字现象。古今字,就是古今同词异形而又有区别意义的一组词。古字包含今字的意义,今字是为古字的某项意义而造的。关于假借字和通假字,段玉裁说:"大抵假借之始,始于本无其字,及其后也,既有其字矣,而多为假借。"(《说文解字.叙》注)。异体字是音义完全相同,只形体有所不同,在任何情况下都可以互相代替的一组     

从府兵制与八旗制的比较看我国古代武术的发展

府兵制和八旗制都是我国历史上一种重要的兵民合一的军事制度,产生了重要的影响。文章将两者进行比较,认为府兵制和八旗兵制由于民族传统等原因并没有为我国军事武术的发展产生实质的推动作用,也没有实质上的促使我国民间武术的发展,更准确地说是没有促进武术技击性的发展。这是一种被高估了作用的制度。我国古代武术发展艰难的原因是封建统治者为了维护封建统治而对其进行抑制,并且武术的普及发展与兵器的进步有反向关系。