隐写分析是信息安全的重要内容.为提高JPEG图像隐写的检测能力,建立了散度矩阵的特征谱,提出了一种对载体和含密图像的训练特征进行变换的新方法.首先根据特征谱的分布规律进行建模,划分为3个区域:特征值下降区、平稳区、特征值为零的区...隐写分析是信息安全的重要内容.为提高JPEG图像隐写的检测能力,建立了散度矩阵的特征谱,提出了一种对载体和含密图像的训练特征进行变换的新方法.首先根据特征谱的分布规律进行建模,划分为3个区域:特征值下降区、平稳区、特征值为零的区域,然后通过白化处理得到白化特征向量,进而对处于3个不同区域的特征向量使用自适应正则化方法.经这几步处理得到特征转移矩阵,也就是输入特征的变换矩阵,最后取变换后特征的前t个向量完成特征选择.并将这些特征数据Fisher线性判决(Fisher linear discriminant,FLD)集成分类器进行训练.结果表明,通过对图像特征进行排序、正则化和选择,FLD集成分类器对JPEG图像隐写的识别准确率得到了提升.展开更多
The eigenspectrum and eigenvectors of the ^(2)F_(7/2) ground multiplets of two structural isomer coordination complexes,Yb(trenovan)(H_(3)trenovan=tris(((3-methoxysalicylidene)amino)ethyl)amine)and Yb(trenpvan)(H_(3)t...The eigenspectrum and eigenvectors of the ^(2)F_(7/2) ground multiplets of two structural isomer coordination complexes,Yb(trenovan)(H_(3)trenovan=tris(((3-methoxysalicylidene)amino)ethyl)amine)and Yb(trenpvan)(H_(3)trenpvan=tris(((5-methoxysalicylidene)amino)ethyl)amine),were determined by use of magnetometry,electron paramagnetic resonance and luminescence spectroscopies.The two 4f complexes crystallise in the trigonal P3space group,have identical chemical formulas and differ only in the placement of the methoxy group on the aromatic ring of salicylaldehyde,with it being either ortho,Yb(trenovan),or para,Yb(trenpvan),to the phenoxo group.This structural isomerism is found to have a profound influence on the solid state static and dynamic magnetic properties of the complexes.In the bulk,both isomers display a combination of direct and Raman magnetisation relaxation proccesses,however,at vastly different rates.Magnetic dilution in an isostructural diamagnetic host supresses the occurrence of the direct process suggesting that the direct process observed in the bulk originates from Yb_((III))centres coupled by magnetic dipole interactions.The eigenspectrum,eigenvectors and spin lattice relaxation of Yb(trenpvan)are found to be closer to the ones found in Yb(trensal)(H_(3)trensal=tris(((salicylidene)amino)ethyl)amine)where the methoxy group is substituted by an H atom,than to those of Yb(trenovan)where the methoxy group is in the ortho position.Thus,the position of chemical modifications has a tremendous influence on the static and dynamic solid state magnetic properties of 4f coordination complexes.Our detailed study on single crystals,demonstrates that the rarely studied effect of modifications of the position of second coordination sphere chemical groups on the dynamic magnetic properties can in fact be used to chemically tune the magnetisation dynamics of 4f spin systems.展开更多
文摘隐写分析是信息安全的重要内容.为提高JPEG图像隐写的检测能力,建立了散度矩阵的特征谱,提出了一种对载体和含密图像的训练特征进行变换的新方法.首先根据特征谱的分布规律进行建模,划分为3个区域:特征值下降区、平稳区、特征值为零的区域,然后通过白化处理得到白化特征向量,进而对处于3个不同区域的特征向量使用自适应正则化方法.经这几步处理得到特征转移矩阵,也就是输入特征的变换矩阵,最后取变换后特征的前t个向量完成特征选择.并将这些特征数据Fisher线性判决(Fisher linear discriminant,FLD)集成分类器进行训练.结果表明,通过对图像特征进行排序、正则化和选择,FLD集成分类器对JPEG图像隐写的识别准确率得到了提升.
基金Novo Nordisk Foundation for research grant NNF20OC0065610 under the Natural and Technical Sciences programme.
文摘The eigenspectrum and eigenvectors of the ^(2)F_(7/2) ground multiplets of two structural isomer coordination complexes,Yb(trenovan)(H_(3)trenovan=tris(((3-methoxysalicylidene)amino)ethyl)amine)and Yb(trenpvan)(H_(3)trenpvan=tris(((5-methoxysalicylidene)amino)ethyl)amine),were determined by use of magnetometry,electron paramagnetic resonance and luminescence spectroscopies.The two 4f complexes crystallise in the trigonal P3space group,have identical chemical formulas and differ only in the placement of the methoxy group on the aromatic ring of salicylaldehyde,with it being either ortho,Yb(trenovan),or para,Yb(trenpvan),to the phenoxo group.This structural isomerism is found to have a profound influence on the solid state static and dynamic magnetic properties of the complexes.In the bulk,both isomers display a combination of direct and Raman magnetisation relaxation proccesses,however,at vastly different rates.Magnetic dilution in an isostructural diamagnetic host supresses the occurrence of the direct process suggesting that the direct process observed in the bulk originates from Yb_((III))centres coupled by magnetic dipole interactions.The eigenspectrum,eigenvectors and spin lattice relaxation of Yb(trenpvan)are found to be closer to the ones found in Yb(trensal)(H_(3)trensal=tris(((salicylidene)amino)ethyl)amine)where the methoxy group is substituted by an H atom,than to those of Yb(trenovan)where the methoxy group is in the ortho position.Thus,the position of chemical modifications has a tremendous influence on the static and dynamic solid state magnetic properties of 4f coordination complexes.Our detailed study on single crystals,demonstrates that the rarely studied effect of modifications of the position of second coordination sphere chemical groups on the dynamic magnetic properties can in fact be used to chemically tune the magnetisation dynamics of 4f spin systems.
