Bone mass density; Elderly people; Osteoporosis.

骨密度；老年人；骨质疏松。

youdao

Hence, the rest-mass of the neutrino being non-vanishing would influence greatly the mass density and further the evolution of the universe.

因此，中微子是否具有静止质量，将极大地影响着宇宙中的质量密度，从而影响着宇宙演化的进程。

youdao

The dynamic mass density can even be negative for the locally resonant sonic materials, as demonstrated both experimentally and theoretically.

实验和理论显示，对于局域共振声学材料而言，动态质量密度甚至还会变成是负的。

youdao

Ah, but density is mass over volume.

但密度是质量除以体积

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