从托福听力背景材料中学单词—沙子是固体还是液体(11)

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从托福听力背景材料中学单词—沙子是固体还是液
体?(11)
本篇文章主要讲的是颗粒物质可以阻碍导弹。这些颗粒物质比如湿润的沙子像固体，
而你把它拿在手里就又变成了流动的。科学家就这一现象解释一些现象。下面前程百利
小编带大家一块看一下这篇托福听力背景材料中出现的生词，希望能给正在备考托福听
力的同学带来帮助。
·Ever run along wet sand, and it hardens up (使坚硬)almost like concrete(混
凝土) under your feet? But pick up that same sand and it drizzles(毛毛细雨般)
through your fingers? "So that's the essence of (真髓)why granular materials(颗
粒物质) are interesting...” Yale physicist Abe Clark. “?sometimes they can
behave like solids(固体)." And other times like fluids(流体). Understanding the
transitions(过渡时期) between liquid and solid, "that's really nontrivial(非
凡的)."
Grains—of sand or otherwise—are Clark’s specialty(专业). He and his
colleagues recently investigated(研究) how a bucket (桶)of beads(玻璃粉)
responds when another object falls into them. It's analogous to (与什么类
比)dropping a stone on sand, and then observing how the stone's force
transfers(转移到) to the grains. "The top grain is contacted by the intruder|(侵
入者), and then it tells a friend, and it tells a friend and so forth, and it
moves along(往里走) a little chain. So what this looks like is basically little
lightning bolts(闪电球) of force shooting off (发射)the intruder(侵入者)."
But the faster that impact gets—think meteor(流星) or missile (导
弹)strike—the more extensive that chain-like (链状)network between the
grains(谷粒) becomes, meaning the grains behave more like a solid. Which in some
cases made the intruding(挤硬) projectiles (落弹数)bounce(跳) right off.
The work was funded in part by the Defense Threat Reduction Agency, part
of the DoD, so of course some of the applications(应用) are military. Granular
materials(颗粒材料) might be the perfect thing to thwart (挫败)a missile attack,
for example. And on a smaller scale, "well if I was gonna go build sandbags for
the military I'd tell them to use little rubber(涂橡胶于) pellets(芯块) to fill
their sandbags with, instead of sand. " Because he says rubber beads (玻璃粉)would
create a stronger, longer-lasting repellent(防护剂) force against bullets. But
remember, Abe and his colleagues are physicists. "I've seen a couple crazy blogs
or something saying, you know, 'scientists are building bunker(沙坑) busters'(堵