proportional-action coefficient

例句：

1. 1.The relationship between temperature and humidity is proportional to the amount of rain.
   温度和湿度之间的关系与降雨量成正比。
2. 2. The growth rate of the plant is proportional to the amount of sunlight it receives.
   植物的生长速率与其接收到的阳光量成正比。
3. 3.The speed of sound is proportional to the density of the medium it travels through.
   声音的速度与其通过的介质密度成正比。