In order to enhance the robustness of digital watermarking,to make the system possess the zoom resistance capability and to estimate the zoom resistance degree of the system,a difference feature point grid is constructed,and a zoom resistance embedding and extracting scheme of digital watermarking is designed.

A new difference grid of the finite-difference time-domain method(FDTD) is put forward;and the electric components are in the vertex of the grid;the magnetic components are in the center.

Based on the study of billet heating grid difference model and energy distribution model, a billet reheating furnace simulation system, by which all key parameters of furnace can be calculated, is designed and fulfilled in this paper.