It is founded that the size of curvature difference envelopcurve can detect that of pre-stress losses.
发现可以通过模态曲率差的包络图面积，较好的反映出预应力损失程度的大小。
2
HHT has not been put forward for long time, so it contains some theoretical problems, such as envelop and mean curve fit, boundary effect, modes mix and so on.
HHT刚提出不久，其理论本身还存在不少问题，如包络线和均值曲线的拟合、边界效应和模态混叠等问题。
3
This model contains a series of governing variables to envelop the complicated hysteretic curve of steel braces and the governing variables can be calibrated by available test results.