diffusivity

例句：

1. 1. The rate of diffusion is directly proportional to the concentration gradient.
   扩散速率与浓度梯度成正比。
2. 2. The dispersion coefficient of a gas in a given medium depends on its molecular weight and temperature.
   气体在给定介质中的分散系数取决于其分子量和温度。
3. 3. The diffusivity of a substance in a solid matrix can be influenced by factors such as porosity and crystallinity.
   物质在固体基质中的扩散性受到孔隙度和结晶度等因素的影响。