Utilizing the characteristics of the human visual system , we embed a digital signal into the average value of the four adjacent wavelet coefficients since the average value has better stability than single wavelet coefficient . this method need n ' t original image when the watermark is extracting . experiment results show the effectiveness of this method which is robust to common image process and fragile to malicious attack , i . e . this method can detect the tampered portions 因此，本文利用小波系数均值来嵌入水印，提出了一种基于小波域的图像完整性验证的半脆弱水印算法，在鲁棒性和脆弱性方面达到了很好的平衡，对非恶意攻击有很强的鲁棒性，而对于恶意的篡改操作有很强的识别和定位能力。
To improve the precision of the piezoelectric stage further , a scanning close loop system based on the mathematical model is studied and designed . experiments are also desinged to prove the precision of the close loop system . the experimental results demonstrate that the positional error of the system reduces to 0 . 1 % , and the close loop system has high dynamic performance and position precision 为进一步提高工作台的定位精度,本文建立了基于迟滞模型的闭环扫描控制系统,并对系统的定位能力进行了实验,实验结果表明,系统最大定位误差减小至0 . 1 % ,该控制系统兼顾了系统的动态响应和高定位精度。
Trenchless technology given rised to the 20 centuries in abroad 70 ' s empress period , as an new construction technique in paving underground tube line . directional drilling come into being the most potential method because it achieve accuracy designed - area on trenchless technology , so it bring great benefit , especially in complexity pipe line area of city 非开挖铺设地下管线施工技术(简称非开挖铺管技术)是国外二十世纪七十年代后期发展起来的一项管道施工新技术，定向钻进非开挖铺管技术因其高精度的定位能力而成为非开挖四大工法之中最具潜力的技术，在城市管网极为复杂的地区，是其它施工方法难以代替的，社会经济效益尤为突出。
