霍金提出：大质量天体的坍缩不足以形成黑洞，而形成比典型中子星有较小的半径和较大的密度的天体叫作灰洞。
重点讨论在AODV协议下的黑洞攻击和灰洞攻击，并根据攻击的特点，提出了一种利用虫洞原理防御的策略。
The black hole attack and the gray hole attack on the networks running under the AODV protocol are discussed.
外喷的气体将大量的灰尘和火山灰带入空中。数以吨计的火山灰，在地球的这个洞的周围，形成一个锥体。
The out-rushing gases carry up into the air huge amounts of dust and ashes. The tons of ashes form a cone around the hole in the earth.
由于地下水潜蚀、化学溶蚀等作用，灰岩地区溶洞、土洞较为发育，给桩基施工带来较大困难。
By the action of groundwater erosion and chemolysis, cavities are well developed in limestone area, which causes many problems for pile foundation construction.
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