Congressional oversight of security classification policy

Security classification policy is generally established by the President through an executive order. Although Congress has no formally established oversight role on security classification issues, there has been fairly regular and systematic congressional oversight of security classification policy. However, the nature of the classification process makes it very difficult for Congress to monitor the way in which classification policy is applied in practice.     

鬼节快乐？

一个狂野的圣诞形象凶神恶煞般地回归了。克朗普斯的名字来自“claw”（爪子）这个单词，是会把淘气的孩子抓走装在麻袋里的魔鬼。几世纪以前在阿尔卑斯山的村落中很是流行，克朗普斯把孩子们吓得够呛——血红长舌让恐惧升级——教导孩子们恶魔会在好的事物前屈服。     

自然界的平衡

自然界的平衡是一种十分精密复杂而又敏感脆弱的抑制与反抑制体系，它总是随着气候条件的变化，随着新的生物体的形成，和随着动植物蔓延入新的地区而持续不断地变化着。可是，在过去．这些变化大部分是很缓慢的。而自从文明人出现以后，变化的速度便增大了很多倍。用以测量它们的时间标度，已经从适用于自然演化过程的、以一万年或十万年为计量单位的时间标度．转变成人类所使用的、以几百年甚至几十年为计量单位的时间标度。     

放手

莎士比亚说：再好的东西都有失去的一天。再深的记忆也有淡忘的一天。再相爱的人，也有放手的一天。爱不能成为牵绊，所以要选择放手，从容的让彼此走出彼此的世界。其实爱过，就会懂。     

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.