飞轮质量越重或其直径越大，其速度变化率就越小。
The heavier the flywheel or the larger its diameter the smaller will be the speed changes.
泵腔中心线处的速度变化率最大，两侧处的速度变化率最小；
The acceleration is maximum in the center line of pump, and the acceleration is minimum in the edge of pump.
在一些国家，变化的速度是惊人的：在伊朗，人口出生率从1984年的7减少到2006年2以下；在孟加拉，数字从1980年的6减少到2000年的3。
In some countries the speed of change has been breathtaking: in Iran, fertility fell from seven in 1984 to below two in 2006; in Bangladesh from six to three in 1980-2000.
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