<abstract> <p>Aiming at the problem of easy tampering and difficult integrity authentication of paper text documents, this paper proposes a robust content authentication method for printed documents based on text watermarking scheme resisting print-and-scan attack. Firstly, an authentication watermark signal sequence related to content of text document is generated based on the Logistic chaotic map model; then, the authentication watermark signal sequence is embedded into printed paper document by using a robust text watermarking scheme; finally, the watermark information is extracted from scanned image of paper document, and compared with the authentication watermark information calculated in real time by the text document content obtained by OCR technology, thereby performing content integrity authentication of the paper text documents. Experimental results show that our method can achieve the robust content integrity authentication of paper text documents, and can also accurately locate the tampering position. In addition, the document after embedding the watermark information has a good visual effect, and the text watermarking scheme has a large information capacity.</p> </abstract>

The spectroscopic and electrochemical behavior of the complex of tetraalkylurea ligands with uranyl(VI) and europium(III) in ionic liquid 1-butyl-3-methylimidazolium bis(tri-fluoromethylsulfonyl)imide ([Bmim][NTf 2 ]) was studied. As the steric hindrance of the substituent increases, the number of ligands in the [UO 2 (L) n ] 2+ complex decreases, however, Eu(III) maintains 8-coordinated complexes [Eu(L) 8 ] 3+ . The effect of urea ligands on the redox potential of Eu(III) is significantly greater than that of UO 2 2+ . Tetrabutylurea can better stabilize the low-valence Eu(II) and improve the redox reversibility of UO 2 2+ .

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