太阳活动变化的小波分析

结合太阳活动变化分析,介绍了Morlet小波变换方法在气象时间序列周期分析和突变分析中的应用,对太阳黑子活动得出了一些有意义的结果。分析发现,太阳活动存在14.5 a和106 a的变化周期,其中14.5 a周期最为显著。太阳活动强弱变化存在一定的阶段性,在近258 a发生过6次突变。     

一种基于小波包变换的盲数字水印算法

提出了一种基于小波包变换的盲数字水印算法,该算法首先对图像进行小波包分解,并根据视觉感知特性将作为水印的二值图像嵌入到分解后的高频分量中,再进行小波包重构得到嵌入水印的图像。实验结果表明,该算法添加水印后的图像对于压缩、噪声、中值滤波、几何裁剪等处理具有很强的稳健性。     

三分量地震检波器的转换公式及误差分析

54.74°型三分量检波器在某种环境下按置常发生偏差,本文研究在偏差情况下的信号转换公式及误差分析。     

A technique to improve the empirical mode decomposition in the Hilbert-Huang transform

The Hilbert-based time-frequency analysis has promising capacity to reveal the time-variant behaviors of a system. To admit well-behaved Hilbert transforms, component decomposition of signals must be performed beforehand. This was first systematically implemented by the empirical mode decomposition (EMD) in the Hilbert-Huang transform, which can provide a time-frequency representation of the signals. The EMD, however, has limitations in distinguishing different components in narrowband signals commonly found in free-decay vibration signals. In this study, a technique for decomposing components in narrowband signals based on waves’ beating phenomena is proposed to improve the EMD, in which the time scale structure of the signal is unveiled by the Hilbert transform as a result of wave beating, the order of component extraction is reversed from that in the EMD and the end effect is confined. The proposed technique is verified by performing the component decomposition of a simulated signal and a free decay signal actually measured in an instrumented bridge structure. In addition, the adaptability of the technique to time-variant dynamic systems is demonstrated with a simulated time-variant MDOF system.     

Research on scale effect of histogram

To describe the spatial relationship among the earth objects compactly, in this paper, we raised the concept of histo-variogram based on the analysis of the characteristics of other spatial analyzing methods such as variogram, information entropy. And we also raised a new spatial analysis method of histogram decomposition based on the definition of standing pixel and contour pixel. At the end of this paper, we demonstrated the characteristics of histo-variogram by two experiments, one for spatial analysis, the other for image fusion.     

磁异常数据处理方法的应用

文章以冀东一些铁矿区地面磁测成果为例,总结了磁异常转换、定量解释推断一些方法的应用及效果.     

堤坝管涌的室内试验与颗粒流细观模拟研究

本文对水流垂直方向的堤坝管涌现象分别进行了室内模型模拟和颗粒流模拟实验。在室内模型试验模拟中采用先进的数码成像跟踪设备在细观的尺度上对土样在管涌发生发展的全过程进行了观察和记录,为颗粒流细观模拟提供了必要的细观参数及宏观依据。提出的二维孔隙率与三维孔隙率转换的关系公式很好的将室内模型试验的孔隙率同颗粒流数值模拟结合,运用颗粒流程序采用固液耦合的分析模型对管涌现象作进一步的数值模拟分析。根据模拟结果,分析了管涌产生、发展在颗粒细观尺度的原因,对管涌产生发展中的试样细观变化规律及流速的变化规律进行了分析。这些结果为PFC2D在渗流和渗透破坏等方面的深入研究应用提供了一定的实用依据,同时也为在细观尺度上解释和分析管涌现象提供了一条新的途径。     

利用FHT法反演海洋重力

从快速 Hartley变换 (FHT)基本概念入手 ,给出了 Hotine核在平面近似、球面近似、Molodenskii近似下的反演模型。另对 FHT处理中所需的坐标转换以及边缘效应等问题加以讨论。同时 ,为了改善长波特性的重力场信息 ,利用 M阶次的参考重力场对上述 Molo-denskii模型进行了改化。