Analysis of characteristics of time-frequency correlations between runoff, tidal range and salinity in the Changjiang Estuary   总被引：2，自引：0，他引：2  

FEI Yuejun  XU Lili  DU Panjun  GUAN Qinle  KANG Xing  XIAO Wenjun 《海洋学报(英文版)》2011,30(5):84-93

Power spectrum and cross-wavelet transform analysis was adopted to study the time-frequency characteristics and multiscale correlations between runoff, tidal range and salinity in the Changjiang Estuary based on the runoff data collected at the Datong Station, the tidal range measured at the Baozhen Station, and the salinity at the Baogang Station from 2008 to 2009. The variations of the salinity showed significant periodicity at scales of 2-3, 7-8, 14-15 and 26-30 d. The correlation between the salinity and the runoff and the tidal range were found to be significantly related to shock at scales of 5-7, 14-15, 26-30 d and 0.5 a. The correlation between the runoff and the salinity was mainly in the same phase, while the correlation between the tidal range and the salinity was in the antiphase. Different frequency bands were related to different degrees, and their relevance increased as the resonance frequency decreased. In addition, changes of the seasonal runoff were obvious. Specifically, a point of discontinuity was reached in early June with a cycle of 7-8 d, which coincided with the periodicity of plum rains in the Changjiang-Huaihe region. High-frequency changes (8-16 d period) of the salinity corresponded to the time domain in January-April 2008, February-April 2009 and October-December 2009 and exhibited an approximately 0.5 a (184 d) long frequency oscillation. Short-period changes were found to be stronger than long-period changes. Cross-wavelet transforms for the salinity, the runoff and the tidal range revealed local features in the time domain, while the significant levels of different periodic oscillations were observed in the frequency domain. The correlation characteristics of the salinity and the runoff were significant in the 80-90 d frequency domain, indicating that the major impact of the runoff on the salinity was reflected in seasonal changes. The tidal range on the small scale of 14-15 and 30-32 d was more obvious than the runoff.  相似文献   

基于Contourlet变换的海底声纳图像特征提取与分类   总被引：2，自引：1，他引：1  

李庆武  石丹  霍冠英 《海洋学报》2011,33(5):163-168

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Spectral wave transformation model for simulating refraction-diffraction with strongly reflecting coastal structures   总被引：1，自引：0，他引：1  

ZHENG Jinhai  NGUYEN Viet Thanh  ZHANG Chi 《海洋学报(英文版)》2011,30(2):25-32

On the basis of the wave action balance equation which incorporates refraction, diffraction, reflection and wave-current interaction, a directional spectral wave transformation model WABED is developed for predicting the irregular wave refraction-diffraction with strongly reflecting structures in coastal regions. In the model, diffraction is taken into account by introducing a term formulated from a parabolic approximation wave equation, and reflection is calculated through a back-marching numerical approach at the reflecting boundary. Two experimental data sets are used to examine the performance of present model with regard to wave characteristics around reflecting coastal structures. One is from a physical experiment at idealized inlet with parallel jetties, while the other is from a laboratory study on a coastal project of the concave breakwater. Reasonably good agreements are found for both cases, revealing the applicability of the present model for predicting combined wave refraction-diffraction processes with strongly reflecting coastal structures.  相似文献   

爆心距对爆破震动信号频谱的影响分析     

毕卫国  田岗  燕永峰 《岩土工程技术》2011,25(6):304-306

结合临沂某一隧洞工程,利用matlab分析软件分析了不同爆心距下的爆破震动信号的频谱变化情况。得出：在爆破中近区,震动信号的主频在垂直方向的分量较水平方向大,随着爆心距的增加地面震动峰值速度的主震方向会由水平方向向垂直方向转化,总体呈衰减趋势,震动主频趋向于低频;在爆破参数和爆区特征类似于本工程的工程爆破现场其中低频震动信号在水平方向上的分量所占能量比例高于垂直分量的能量比例,在距爆源较远的位置也不能忽略爆破震动对建筑结构的影响,尤其是要加强水平方向的抗震设防。  相似文献   

求解非稳定对流占优水质模型的非标准Galerkin有限元法     

王新民  崔学慧  陆祥安 《吉林大学学报(地球科学版)》2011,41(3):812-818

在求解非稳定地下水溶质运移模型时,若对流项占优,则模型表现出双曲方程的特性。针对这种特性,采用非标准Galerkin有限元方法进行求解是解决这类问题的有效途径。分别采用Wavelet-Galer-kin有限元方法、迎风有限元方法和特征有限元方法对强对流溶质运移模型进行了求解,并将其结果与标准Galerkin有限元和解析解进行对比。结果表明:标准Galerkin有限元方法会产生强烈的数值振荡;Wavelet-Galerkin有限元方法的时空定位效果好;迎风有限元方法能够有效降低数值振荡现象,但迎风因子对解的影响较大,而且会带来时间延迟;特征有限元方法能够提高解的精度,故可以认为特征有限元方法是求解强对流地下水溶质运移模型的首选方法。  相似文献   

减小离散误差的时频峰值滤波算法   总被引：1，自引：0，他引：1  

林红波  李月  徐学纯  马海涛 《吉林大学学报(地球科学版)》2011,41(2):572-578

提出减少时频峰值滤波分段点处阶跃误差的改进方法。经过研究时频峰值滤波在频率调制和时频平面峰值滤波时产生的离散误差以及尺度变换方式,发现分段点处阶跃误差与离散傅里叶变换的长度成反比,且与零点在尺度变换后产生的不确定值有关。提出基于定零点尺度变换的时频峰值滤波,在信号尺度变换时将零点变换到瞬时频率区间上的固定值,使各段时频峰值滤波零点偏移量一致,从而消除分段点处的阶跃误差。仿真实验和实际地震信号时频峰值滤波处理结果表明,改进的时频峰值滤波算法能够有效消减随机噪声,减少分段滤波在分段处的阶跃。  相似文献   

二维小波变换与中值滤波联合去噪方法研究     

张胤彬  张华  刘松 《中国煤炭地质》2011,(5):38-41,48

由于随机噪声是一种频带较宽的干扰波,因此依靠单一的去噪处理方式往往难以获得清晰反映目标体的地震信息。小波变换能够较好的去除高斯噪声,保留有效波中、高频成分,提高记录的信噪比,但去除脉冲噪声的效果却并不理想;中值滤波具有良好的边缘保持特性,虽低频去噪声效果有限,但去除脉冲噪声效果明显。因此可利用二维小波变换与中值滤波优势互补的方法,进行叠前去噪处理,达到去除宽频随机噪声的目的。首先运用二维小波变换的理论,采用自适应门限阀值方法进行去噪,同时结合中值滤波方法联合去噪。模型与实际数据的应用效果表明,联合去噪方法可有效压制噪声能量、保留高频有效信号、提高地震记录信噪比与分辨率。  相似文献   

消频散变换反演海底地声参数     

姚玉玲  高大治  任新敏 《中国海洋大学学报(自然科学版)》2011,(Z1):433-435

提出1种将消频散变换应用到海底地声参数反演的方法。对单一水听器接收声压信号进行消频散处理后,根据群延时差建立代价函数,反演得到主要海底参数,最后根据贝叶斯统计理论给出了待反演地声参数的边缘后验概率密度。对单层波导进行仿真证明这种新方法的有效性。  相似文献   

基于静态小波变换改进邻域系数法的遥感图像滤波     

武海洋  王慧  樊菊 《海洋测绘》2011,31(2):24-27

针对NeighShrink滤波算法存在的不足,提出了改进的阈值估计策略和系数收缩方案,并将改进算法与静态小波变换相结合进行图像滤波,取到了较好的滤波效果.实验验证了改进算法的有效性,以峰值信噪比PSNR作为客观评价指标,通过与经典方法的比较,对该算法的滤波性能做出了客观评价.  相似文献   

石羊河流域近50 a来日照时数的时空变化特征分析   总被引：2，自引：0，他引：2  

张克新  刘普幸  霍华丽  张锐  马亚兰 《中国沙漠》2011,31(2):517-520

 基于石羊河流域5个气象站点1959—2008年的日照时数资料,采用气候倾向率分析、Kriging空间插值、Mann-Kendall检验、小波分析等方法对石羊河流域日照时数的变化特征进行了分析。结果表明,近50 a来,石羊河流域年日照时数呈显著增加趋势,其变化倾向率为33.9 h/10a;四季日照时数均呈增加趋势,春季增加最显著,对年日照时数的贡献率最大,冬季次之。石羊河流域日照时数空间差异显著,表现为年日照时数自南向北递增。突变分析表明,1987年为日照时数的突变年。Morlet小波分析表明,石羊河流域年日照时数存在8 a的显著周期。  相似文献