When dive teams drill through the frozen surface of the White Sea off the north-west coast of Russia, they are greeted by grinning belugas.
潜水团队钻透俄罗斯西北部白海冻结的海面，受到笑容可掬的白鲸欢迎。
Cold work: 'Buddy teams' dig out huge chunks of ice using a hand-powered drill to create dive holes in the White Sea, Russia.
钻冰洞：俄罗斯白海，“巴迪队”用手动钻挖出大块的冰，钻出潜水洞。
The results show that the input white noise can be substitute by pseudo-random signals in identifying the impulse response of a drill-string system.
研究了伪随机信号的特征及伪随机信号产生的方法，得出了用伪随机信号代替白噪声信号辨识钻柱系统脉冲响应的结论。
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