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针对JPEG压缩,提出一种自嵌入的半脆弱内容认证水印方法.采用离散小波分解提取原始图像的稳态特征并映射成水印信息,在密钥控制下生成混沌序列对水印信息进行加密;将水印嵌入到离散余弦变换的量化系数中,最后进行逆量化和逆离散余弦变换变换得到含水印图像.当图像的内容需要认证时,可以区分正常的压缩和恶意篡改,而且还可以进行篡改定位.实验结果表明,该方法对JPEG有损压缩具有较好的鲁棒性、安全性和良好的不可见性. 相似文献
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智能性是智能教学系统最重要的特性之一。为提高智能教学系统的智能水平,研究了利用具有较强自学习能力的人工神经网络来构建智能教学系统。从因材施教,准确反映学生学习状态、特征的角度出发,分析了学生学习过程中的影响因素,提出将学生的学习方式、学习习惯等因素纳入学生模型构建中,并对学生模型进行了设计。 相似文献
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《Ceramics International》2015,41(6):7916-7920
The corrosive wear behavior of chromium carbide coatings deposited by air plasma spraying was studied, through wet pin-on-disk wear experiments. During the wear tests, the samples were immersed in corrosive environments consisting of watery hydrochloric acid with the acid concentrations of 5, 10 and 15 vol%. The wear tests were performed at both room temperature and 80 °C. The results showed that the wet environment significantly increased the wear rate. In addition, the increase of the acid concentration and temperature considerably deteriorated the wear resistance of the coated samples. It was also realized that, compared to the dry condition, the wear mechanism changed from abrasive to adhesive in the wet environment where a tribochemical wear was observed. 相似文献
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