The amount that comes in minus the amount that goes out,

进入系统的质量减去流出系统的质量
plus any molecules that are generated inside,

加上系统内产生的分子质量
minus any molecules that are consumed inside the system

减去系统内消耗的分子质量
In - out + gen - cons = acc

进入-流出+产生-消耗=净增加量
has to be equal to accumulation.

必须等于系统中该分子质量的净增加量
Accumulation is just the rate of change of concentration.

净增加量就是浓度的变化
If molecules are accumulating inside the vessel

如果一种分子在导管内的质量增加
that means their concentration is either going up or down,

这就意味着浓度不是上升就是下降
and so accumulation is the

因此净增加量就是
rate of change with time of the total number of molecules inside the vessel:

在一定时间内导管中分子总数量的变化
If we went through this analysis for the system that I drew up here,

如果继续分析我们设计出来的这个系统
and the particular circumstance,

并考虑一个特定条件