diffusivity theory的用法和样例：
例句
- Many of the above-mentioned trends can be rationalized in terms of quasi-steady diffusion theory.
上述的许多问题可用准稳态扩散理论加以推理。 - According to the need for study on methane movement law in fully mechanizedsublevl caving stopes,the methane rising and pressure diffusion theory is put forward.
依研究综放采场瓦斯运移规律的需要，提出矿井瓦斯气体浮升与压强扩散理论。
