variable-density system

例句：

1. 1. Thevariable density system is used to control the flow of gases and liquids in industrial processes.
   变量密度系统用于工业过程中控制气体和液体的流动。
2. 2.In this variable density system, the temperature and pressure can be adjusted to optimize the performance of the process.
   在这个可变密度系统中，温度和压力可以被调整以优化过程的性能。
3. 3.The variable density system has been widely used in various industries due to its ability to accurately measure the concentration of chemicals in a sample.
   由于其能够准确测量样品中化学物质的浓度，可变密度系统在各个行业中得到了广泛应用。