现如今，这种乌托邦空想已经过时了，我们对所面临的威胁有了更深刻的认识，从彗星撞击到流行感冒，再到气候变化。
Now utopia has grown unfashionable, as we have gained a deeper appreciation of the range of threats facing us, from asteroid strike to epidemic flu and to climate change.
如果这是事实。那北美洲应该是进入现代人类时代以来，第一个遭受到来自于地球外物体撞击并造成翻天覆地变化的地方。
If that were true, North America would have suffered the first world-changing impact of an extraterrestrial object in the era of modern man.
但由于近地面风风向会跟随地形变化，在山坡，这便意味着风会以一定角度撞击涡轮，而不是正面撞击。
But on a hillside that means the wind (which tends to follow the ground when it is close to the surface) hits the blades of the turbines at an Angle, instead of face on.
但上个月情况发生了变化，当美国航天局向月球恒久背阴面发射了一颗卫星，撞击产生的一缕尘埃里就有水分。
This changed last month, when NASA shot a satellite into a permanently Shadowed region on the Moon's surface, throwing a plume of material containing water up out of the shadow.
在撞击过程中，动量的变化是突然的，但非瞬时的。
In a crash, momentum changes abruptly but not instantaneously.
锤(3)与活塞(5)的质量匹配产生更高的效率、撞击能量的更小的角度变化和更轻的重量。
Matching the mass of the mallet (3) to the plunger (5) yields higher efficiency, less angular variation of the impact energy and lighter weight.
根据一维应力波传播理论，提出了圆柱壳受轴向撞击破坏的简化模型，分析了这一破坏过程中的能量变化。
Based on the one dimensional wave propagation theory, a simple dynamic model was presented to analyze the failure process and energy absorption of the shells under impact loading.
本文介绍了投梭转子与投梭鼻之间撞击的动力学分析，包括速度变化、动能转换及弹性冲击的分析等。
The article makes a dynamic analysis of the impact between the picking bowl and the nose, including the speed variable, the energy transfer and elastic impact.
主要观察指标：不同的角度撞击时下颌骨各部分的应力和应变变化。
MAIN OUTCOME MEASURES: The stress and stress changes of mandible when impacted from different angles.
根据一维应力波传播的理论，提出了圆柱壳受轴向撞击破坏的简化模型，分析了这一破坏过程中的能量变化。
Based on the one-dimensional wave propagation theory, a simplified dynamic model was presented to analyze the failure and energy absorption of the tubes under impact load.
四喷嘴工况的撞击火焰噪声的标准偏差值要大于两喷嘴，但标准偏差随工况的变化小于两喷嘴，说明四喷嘴撞击火焰燃烧剧烈但稳定。
The standard deviation of four-nozzle impinging flame noise was greater than that of the two-nozzle impinging flame noise, but the change of the standard deviation was the reverse.
这对于分析和改进对这类碰撞的预报，确定撞击时刻和撞击点位置，以及今后研究撞击黑斑的变化，都有一定的意义。
This is meaningful for analysis and improvement of the impact prediction. As well as for researching variations of the impact sites.
对一些板和梁进行了撞击试验，测量了撞击力随时间变化的波形及其频谱。
The wave form and the spectrum of impact force as well as the variation in sound exposure level (SEL) at a fixed point were measured which representing the relative changes of the ringing noise.
对一些板和梁进行了撞击试验，测量了撞击力随时间变化的波形及其频谱。
The wave form and the spectrum of impact force as well as the variation in sound exposure level (SEL) at a fixed point were measured which representing the relative changes of the ringing noise.
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