Because of the high similarity between the gradient magnitudes of low-contrast edge and noise,the conventional Canny algorithm for detection,which is based on the double-threshold to detect and connect edges,damages partly the low-contrast edge though it suppresses noise.

The image s gradient magnitude mean and the variance of every pixel in the image relative to the gradient magnitude mean are calculated according to the method proposed in the paper.

Using knowledge which has been known beforehand in Grads Range,this paper proposes an image segmentation method which can solve the problem.

For measurement of lateral vibration acceleration of railway bridges,necessary technical measures should be taken to ensure that the data collecting will not be mixed and overlaid,and setting of the data sampling frequency should also meet the requirements for amplitude precision.

Given reasonable gain margin (GM), response of setting point and load disturbance for the first order plus dead-time process were considered integrated to search optimal phase margin (PM) and tune PI parameters under ISE (Integral Square Error) performance index.

Based on a graphical stability criterion in parameter spacet,he stabilizing region of PI parameters was discussed for first-order processes with dead-timea,nd this kind of design method was extended to the case of achieving the given phase and gain margins.