Model analysis
We observed how ESV (Y) responded to the change in each influence factor (X) by sampling continuously in the range of each input X. In the course of the concrete analysis, other factors were kept as the mean of samples, and the values of the target factors were changed by adopting control variables. In addition, the range of target X was regarded as its definition domain, called the sampling domain. The range of ESV is called the response domain. The influence intensity of every X factor can be judged according to the corresponding response domain, and the influence mode and potential mechanism can be judged according to the variation trend of the function.
Results and discussion