The lOW frequency characteristic of the ultrasound reflection spectrum from the structure of two equal-thickness aluminum plates bonded by a thin adhesive layer are studied theoretically and experimentally, the low-frequency here implying that the frequency of the interrogating ultrasound is much less than the resonance frequency of the adhesive layer. The possibility of the inversion of the spring stiffness in the spring model from the shift of “right peaks” of resonance frequency in weak bonded structure is indicated.
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From Alaska to the snowy peaks of the Andes the world is heating up right now, and fast.
从阿拉斯加到安第斯山脉的雪峰,世界正在迅速升温。
Right now, about 90 percent of the circulating flu is H1N1, although seasonal flu, which typically peaks in winter, has also been detected.
目前,尽管已探测到了通常在冬季才达到顶峰的季节流感,但90%正在传播的流感是H1N 1流感。
In the north (right), the cloud cover is less uniform, with scattered clouds creating jagged peaks in the profile.
在北方(图中右侧),云盖更加凌乱,云的散射使大气廓线中的峰值参差不齐。
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