difference between peak and valley的用法和样例：
- The Difference between Peak and Valley of the Northeast Power Pool and Hydropower Planning and Development
- Discussion on balance of ratio between peak and valley period on generation-side in Hunan power grid
- He did not give the remote trace, just stood out the vigor of grand verve and wavy peak and valley of the mountain.
- The RF carrier is the classic sinusoid;its frequency counts the number of cycles (each peak and valley) per second.
- the difference of peak and valley