U正交函数系有良好的数据逼近性能,而全相位数字滤波器具有零相位特性,文中把二者结合起来,构造出了基于三次U系统的全相位双正交U变换(APBUT3,All Phase Bi-orthogo-nal U Transform Based on 3-Degree U System),用APBUT3矩阵作为列...U正交函数系有良好的数据逼近性能,而全相位数字滤波器具有零相位特性,文中把二者结合起来,构造出了基于三次U系统的全相位双正交U变换(APBUT3,All Phase Bi-orthogo-nal U Transform Based on 3-Degree U System),用APBUT3矩阵作为列率变换矩阵代替离散余弦变换(DCT,Discrete Cosine Transform)对图像进行变换编码,提出了基于APBUT3的图像编码算法.由于APBUT3能有效地抑制图像的高频成分,编码时,可以用均匀的量化间隔对变换系数进行量化,也可以预处理变换矩阵代替编码的量化过程,简化了图像编码.该算法与DCT对比,当码率较大时,其编码效果与DCT基本相同;当码率较小时,用16×16的APBUT3编码的方块效应没有DCT明显,用均值滤波器对块边界像素进行平滑处理后,其方块效应可以基本消除.展开更多
Given the conflicts over the proposed formation mechanisms of Xiashu loess, the question of the provenance of sediments comprising the Xiashu loess in the Yangtze River Delta has not been satisfactorily resolved. In t...Given the conflicts over the proposed formation mechanisms of Xiashu loess, the question of the provenance of sediments comprising the Xiashu loess in the Yangtze River Delta has not been satisfactorily resolved. In this study, the provenance of aeolian sediments of the Yangtze River Delta, China was examined by applying the detrial zircon U–Pb dating technique, Sr–Nd isotopic and trace element compositional analysis. U-Pb dating analysis was conducted on the Xiashu loess at three locations over the Yangtze River Delta, including Huangnishan(HNS) hill, Shengshan(SS) island and the Xuancheng(XC) area. The Xiashu loess and the sediments of the Yangtze River Valley share considerable similarity in their zircon U-Pb age spectra with the same main age peak and comparable age distribution. By contrast, significant differences in the age spectra, existbetween the Xiashu loess and loess deposits of Chinese Loess Plateau(CLP). Coarse grains of the Yangtze River Delta loess may have a proximal material source identical to the sediments from the Yangtze River valley. Sr–Nd isotopic values of the Xiashu loess match those from the northern margin of the Tibetan Plateau. Rare earth element ratios independent of grain size illustrate that the values from loess of the Yangtze River Delta mostly overlap with those of CLP loess. This feature implies that loess from the Yangtze River Delta has a dominant source of distant material similar as the CLP loess. As such, we conclude that multi-proxy analysis of sediments can shed new light on tracing the provenance of aeolian loess in the Yangtze River Delta.展开更多
文摘U正交函数系有良好的数据逼近性能,而全相位数字滤波器具有零相位特性,文中把二者结合起来,构造出了基于三次U系统的全相位双正交U变换(APBUT3,All Phase Bi-orthogo-nal U Transform Based on 3-Degree U System),用APBUT3矩阵作为列率变换矩阵代替离散余弦变换(DCT,Discrete Cosine Transform)对图像进行变换编码,提出了基于APBUT3的图像编码算法.由于APBUT3能有效地抑制图像的高频成分,编码时,可以用均匀的量化间隔对变换系数进行量化,也可以预处理变换矩阵代替编码的量化过程,简化了图像编码.该算法与DCT对比,当码率较大时,其编码效果与DCT基本相同;当码率较小时,用16×16的APBUT3编码的方块效应没有DCT明显,用均值滤波器对块边界像素进行平滑处理后,其方块效应可以基本消除.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41371032, 41671003, 41601189, 41672349)
文摘Given the conflicts over the proposed formation mechanisms of Xiashu loess, the question of the provenance of sediments comprising the Xiashu loess in the Yangtze River Delta has not been satisfactorily resolved. In this study, the provenance of aeolian sediments of the Yangtze River Delta, China was examined by applying the detrial zircon U–Pb dating technique, Sr–Nd isotopic and trace element compositional analysis. U-Pb dating analysis was conducted on the Xiashu loess at three locations over the Yangtze River Delta, including Huangnishan(HNS) hill, Shengshan(SS) island and the Xuancheng(XC) area. The Xiashu loess and the sediments of the Yangtze River Valley share considerable similarity in their zircon U-Pb age spectra with the same main age peak and comparable age distribution. By contrast, significant differences in the age spectra, existbetween the Xiashu loess and loess deposits of Chinese Loess Plateau(CLP). Coarse grains of the Yangtze River Delta loess may have a proximal material source identical to the sediments from the Yangtze River valley. Sr–Nd isotopic values of the Xiashu loess match those from the northern margin of the Tibetan Plateau. Rare earth element ratios independent of grain size illustrate that the values from loess of the Yangtze River Delta mostly overlap with those of CLP loess. This feature implies that loess from the Yangtze River Delta has a dominant source of distant material similar as the CLP loess. As such, we conclude that multi-proxy analysis of sediments can shed new light on tracing the provenance of aeolian loess in the Yangtze River Delta.
