In order to improve the attack efficiency of the New FORK-256 function, an algorithm based on Grover's quantum search algorithm and birthday attack is proposed. In this algorithm, finding a collision for arbitrary...In order to improve the attack efficiency of the New FORK-256 function, an algorithm based on Grover's quantum search algorithm and birthday attack is proposed. In this algorithm, finding a collision for arbitrary hash function only needs O(2m/3) expected evaluations, where m is the size of hash space value. It is proved that the algorithm can obviously improve the attack efficiency for only needing O(2 74.7) expected evaluations, and this is more efficient than any known classical algorithm, and the consumed space of the algorithm equals the evaluation.展开更多
Motion estimation is an important part of the MPEG- 4 encoder, due to its significant impact on the bit rate and the output quality of the encoder sequence. Unfortunately this feature takes a significant part of the e...Motion estimation is an important part of the MPEG- 4 encoder, due to its significant impact on the bit rate and the output quality of the encoder sequence. Unfortunately this feature takes a significant part of the encoding time especially when the straightforward full search(FS) algorithm is used. In this paper, a new algorithm named diamond block based gradient descent search (DBBGDS) algorithm, which is significantly faster than FS and gives similar quality of the output sequence, is proposed. At the same time, some other algorithms, such as three step search (TSS), improved three step search (ITSS), new three step search (NTSS), four step search (4SS), cellular search (CS) , diamond search (DS) and block based gradient descent search (BBGDS), are adopted and compared with DBBGDS. As the experimental results show, DBBGDS has its own advantages. Although DS has been adopted by the MPEG- 4 VM, its output sequence quality is worse than that of the proposed algorithm while its complexity is similar to the proposed one. Compared with BBGDS, the proposed algorithm can achieve a better output quality.展开更多
In this paper, a three-dimensional quantitative structure-activity relationships(3 D-QSAR) study for 20 HIV-1 reverse transcriptase(RT) inhibitors was established using Topomer Co MFA. The models were built based on d...In this paper, a three-dimensional quantitative structure-activity relationships(3 D-QSAR) study for 20 HIV-1 reverse transcriptase(RT) inhibitors was established using Topomer Co MFA. The models were built based on different fragment cutting models, with the most effective model of the multiple correlation coefficients of fitting(r^2) to be 0.920, cross-validation(q^2) of 0.575, and external validation(Q_(ext)~2) being 0.701. The results indicated that the model obtained has both favorable estimation stability and good prediction capability. Topomer Search was used to search R-group from ZINC database. As a result, a series of R-groups with relatively high activity contribution was obtained. By No. 6 molecule filtering, 3 R_1 and 15 R_2 groups were selected, and employed to alternately substitute for the R_1 and R_2 of sample 6. Finally, 45 new compounds were designed, and the Topomer CoMFA model was used to predicate the biological activity, so the Topomer Search is effective in screening and can guide the design of new HIV/AIDS drugs. The molecular docking method was also used to study the interactions of these drugs by docking the ligands into HIV-1 RT active site, which revealed the likely bioactive conformations. This study showed that there are extensive interactions between the 1,3,4-thiazolidinone revertase inhibitors and His84, Asp145, Lys33 and Leu83 residues in the active site of HIV-1 RT. These results provide useful insights for the design of potent new inhibitors of RT.展开更多
基金Supported by the National High Technology Research and Development Program(No.2011AA010803)the National Natural Science Foundation of China(No.U1204602)
文摘In order to improve the attack efficiency of the New FORK-256 function, an algorithm based on Grover's quantum search algorithm and birthday attack is proposed. In this algorithm, finding a collision for arbitrary hash function only needs O(2m/3) expected evaluations, where m is the size of hash space value. It is proved that the algorithm can obviously improve the attack efficiency for only needing O(2 74.7) expected evaluations, and this is more efficient than any known classical algorithm, and the consumed space of the algorithm equals the evaluation.
文摘Motion estimation is an important part of the MPEG- 4 encoder, due to its significant impact on the bit rate and the output quality of the encoder sequence. Unfortunately this feature takes a significant part of the encoding time especially when the straightforward full search(FS) algorithm is used. In this paper, a new algorithm named diamond block based gradient descent search (DBBGDS) algorithm, which is significantly faster than FS and gives similar quality of the output sequence, is proposed. At the same time, some other algorithms, such as three step search (TSS), improved three step search (ITSS), new three step search (NTSS), four step search (4SS), cellular search (CS) , diamond search (DS) and block based gradient descent search (BBGDS), are adopted and compared with DBBGDS. As the experimental results show, DBBGDS has its own advantages. Although DS has been adopted by the MPEG- 4 VM, its output sequence quality is worse than that of the proposed algorithm while its complexity is similar to the proposed one. Compared with BBGDS, the proposed algorithm can achieve a better output quality.
基金supported by the National Natural Science Foundation of China(21475081,21275094)the Graduate Innovation Fund of Shaanxi University of Science and Technology
文摘In this paper, a three-dimensional quantitative structure-activity relationships(3 D-QSAR) study for 20 HIV-1 reverse transcriptase(RT) inhibitors was established using Topomer Co MFA. The models were built based on different fragment cutting models, with the most effective model of the multiple correlation coefficients of fitting(r^2) to be 0.920, cross-validation(q^2) of 0.575, and external validation(Q_(ext)~2) being 0.701. The results indicated that the model obtained has both favorable estimation stability and good prediction capability. Topomer Search was used to search R-group from ZINC database. As a result, a series of R-groups with relatively high activity contribution was obtained. By No. 6 molecule filtering, 3 R_1 and 15 R_2 groups were selected, and employed to alternately substitute for the R_1 and R_2 of sample 6. Finally, 45 new compounds were designed, and the Topomer CoMFA model was used to predicate the biological activity, so the Topomer Search is effective in screening and can guide the design of new HIV/AIDS drugs. The molecular docking method was also used to study the interactions of these drugs by docking the ligands into HIV-1 RT active site, which revealed the likely bioactive conformations. This study showed that there are extensive interactions between the 1,3,4-thiazolidinone revertase inhibitors and His84, Asp145, Lys33 and Leu83 residues in the active site of HIV-1 RT. These results provide useful insights for the design of potent new inhibitors of RT.
