Amorphous alloy sample Fe ₇₈Si ₉B ₁₃ is disposed by low frequency pulsating magnetic field and isothermic annealing, measuring magnetostriction coefficient by self-made magnetostriction coefficient measuring system. Results showed that both treatment process decreased the saturation magnetostriction coefficient λ _s of sample, λ _s is related with annealing time t and it reached minimal value 4.952×10 ^-5 when annealing under 300℃ for 40min. Saturation magnetostriction coefficient λs and low-frequency pulsed magnetic field strength Hp is nonlinear relationship, λ _s has a choice on the disposing parameters of pulsed magnetic field, λs reach minimal value 2.70×10 ^-5 when Hp equals to 19 900 A/m, pulsing frequency equals to 30Hz and processing time t equals to 240s. The impact of saturation magnetostriction coefficient by low frequency pulsed magnetic field is significantly greater than annealing.

As an information hide technology for implementing protection of multimedia copyright and content authentication, the digit watermark technology has become more and more useful and practical. But it is difficult to choose a suitable watermark for non-professional staff. For this reason, a fuzzy comprehensive evaluation model was designed. Based on robustness of digital watermarking the model used the methods of Delphi method and AHP (analytic hierarchy process). The experimental results show that fuzzy comprehensive evaluation model is convenient to choose watermark. The model is effective and practical.