排序方式: 共有127条查询结果,搜索用时 15 毫秒
91.
92.
93.
富含细节、纹理和边缘的图像中,重要信息大量集中在中、高频部分,基于小波变换的压缩方法只对低频信息进行多次分解.针对这个问题,以SPIHT算法为基础,研究了基于小波包分解的图像压缩算法.仿真结果表明,采用小波包分解的SPIHT算法与传统SPIHT算法相比,在同压缩比情况下,峰值信噪比提高了0.35~1dB,适用于纹理丰富的图像的压缩. 相似文献
94.
研究了一类向量型时滞脉冲微分方程系统的振动性问题,通过作变最变换,将常系数脉冲微分方程系统变为变系数非脉冲微分方程系统,得到了模型非振动解的渐近性态和方程任意解振动的充分条件,利用留数理论,得到了方程广义振动和广义非振动的充分条件。 相似文献
95.
96.
97.
TiO2-coated sericite powders were prepared by the chemical deposition method starting from lamellar sericite and TiCl4 in the presence of La3+. After calcination at 900 ℃ for 1 h, the resultant TiO2 nanoparticles on the sericite surfaces exist in anatase phase. The light scattering indexes of the TiO2-coated lamellar sericite powders are dozens of times higher than those of the naked lamellar sericite powders, varying with different contents of La3+. The presence of La3+ in the deposition solution is beneficial to the formation of the small-sized anatase TiO2 nanoparticles. The presence of La3+ also favors the formation of the dense and uniform island-like TiO2 coating layers in a large range of the mass ratio of TiO2 to sericite from 5% to 20%. XPS analysis shows that when La3+ is absent in the reaction solution, TiO2 coating layers anchor on the sericite surface via Ti-O-Si and Ti-O-Al bonds. The presence of La3+ causes the formation of Si-O-La and Al-O-La bonds on the sericite surface and Ti-O-La bond on the surface of TiO2 coating layers. 相似文献
98.
99.
100.