closed system的用法和样例：
例句
- People were not necessary for a closed ecosystem to run once stable, but they might be helpful in stabilizing it.
封闭系统一旦进入稳定运行，人类就不是必不可少的部分，不过，他们可能会有助于其稳定。 - Dowling points out that excess ink is recirculated within the sealed system, reducing consumption and contamination from lint, dust or dampener fluid.
道林指出，过剩的墨水循环的封闭系统，减少消耗和污染皮棉，尘埃或沮丧液。
