基于小波变换和数学形态学的潮沟提取方法研究

潮沟是潮滩的主要地貌类型之一,潮沟信息的检测对湿地生态环境的监测和保护有着重要意义。本文以长江口九段沙下沙北部发育比较复杂的潮沟为研究对象,使用2016年1月26日Landsat8全色波段数据,采用了一种融合小波变换、最大类间方差法和数学形态学的方法对潮沟边缘信息进行了检测。小波变换中通过减小高层小波系数,达到弱化潮滩灰度变化的目的;通过增大低层小波系数,达到增强潮沟信息的目的;利用数学形态学和图像之间的几何(加减乘)运算,完成潮沟的提取;最后,分别在原始数据和检测结果相应的位置取样进行精度验证,样方潮沟面积一致性精度平均为92.1%。     

岬湾海滩剖面中长期变化特征及其控制因素——以青岛石老人海滩为例

了解海滩剖面变化可以更好地理解海滩动态过程。利用2007年5月~2014年12月近8 a青岛石老人海滩剖面的实测资料,计算剖面各段单宽体积变化量及后滨宽度,结合交叉小波和小波相干分析方法,探讨海滩剖面中长期淤蚀变化特征及其控制因素。结果表明,近8 a来海滩剖面表现为侵蚀状态,不同岸段侵蚀程度不同。剖面1岸段侵蚀明显,剖面2和剖面3岸段轻微侵蚀。剖面的变化过程可划分为平稳期、剧变期和微调期3个时期。各时期剖面的季节性变化较复杂,平稳期具冬蚀夏淤的交替变化特征,整体淤蚀量较小;剧变期剖面呈阶段性蚀退,变化幅度相对较大,微调期剖面可能仍处于剧变期的恢复阶段,季节性变化不明显。剧变期和微调期的小波交叉谱和相干谱分析显示,波浪和前滨单宽体积相干性较好,尤其当大于2 m的波高达到10%以上,海滩地形可以和波高变化产生同周期的变化。因此波高变化基本控制了剖面的季节变化。而海滩长周期变化主要受控于风暴潮作用及其漫长的恢复期,沿岸输沙和海平面变化则一定程度上导致了剖面长期侵蚀格局的形成。     

基于遗传小波神经网络的海底声学底质识别分类

分割海底声纳探测图像,提取单元特征向量进行主成份分析,选取均值、标准差、对比度、相关系数、能量及同质性作为训练特征向量,构建小波神经网络。利用遗传算法优化小波神经网络的初始权值及小波参数,对砂、礁石、泥3种底质类型分别进行训练,并得到3种底质的测试精度都在90%以上,优于单独利用小波神经网络进行训练时的测试精度,克服了小波神经网络训练时易陷入局部极小的固有缺陷,表明基于遗传算法的小波神经网络可有效用于海底底质声纳图像的识别和分类。     

基于静态小波变换改进邻域系数法的遥感图像滤波

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.     

A novel technique in analyzing non-linear wave-wave interaction

During wave growth non-linear wave–wave interactions cause transfer of some wave energy from lower to higher wave periods as the spectrum grows. Wavelet bicoherence, which is a new technique in the analysis of wind–wave and wave–wave interactions, is used to analyze non-linear wave–wave interactions. A selected record of wind wave that contains the maximum wave height observed during 6 h of wave generation is divided into five segments and wavelet bicoherence is computed for the whole record, and for all divided segments. The study shows that the non-linear wave–wave interaction occurs at different bicoherence levels and these levels are different from one segment to another due to the non-stationarity feature of the examined data set.     

多功能水合物沉积物三轴试验系统的研制与应用

研制了新型多功能水合物沉积物三轴试验系统,系统由供-排气模块、应力加载模块、温控模块、数据采集模块和辅助模块组成。利用泵驱动高压液体施加围压和轴压,加载方式有恒压、恒流、梯度增压、跟踪气压模式,可以实现不同条件下的水合物合成、三轴剪切。围压跟踪气压的功能使水合物生成过程中净围压不变,保证了试样初始条件一致性。根据围压液体积变化测量试样体积变形,通过设置回压泵压力变化方式控制水合物气压,可以模拟不同降压速率条件下的水合物沉积物分解变形。以泥质粉细砂和二氧化碳为材料制作了三轴试样,进行了水合物合成、三轴剪切和降压分解试验,检验了仪器的可靠性。     

基于EMD小波阈值滤波的地磁数据去噪分析

采用小波阈值滤波、经验模态分解滤波和基于经验模态分解的小波阈值滤波3种方法,对磁通门磁力仪观测数据进行去噪,有效去除或抑制郫县地震台地磁数据的地电干扰.     

基于复数小波变换的遥感图像融合新算法

提出了一种基于复数小波变换的影像融合新算法，用以融合全色影像和多光谱影像。试验结果表明，谊算法可以取得比传统的实数小波变换融合算法更好的效果。     

位场小波变换研究进展

小波变换的具有多尺度分析的特点,在位场资料分析中得到了广泛应用.本文总结了位场小波变换的理论基础及应用现状,介绍了位场小波基函数的概念.小波分析可以应用于位场分离、去噪、反演及综合地质解释等分析.文中从小波的数学性质和物理意义等角度讨论了位场资料处理中小波基函数的选取问题.     

Shear-tensile crack as a tool for reliable estimates of the non-double-couple mechanism: West Bohemia-Vogtland earthquake 1997 swarm

Shear-tensile crack is a model for an earthquake mechanism that is more constrained than the moment tensor but that can still describe a non-shear focus. As such, the shear-tensile crack model is more robust than the moment tensor model and yields more reliable estimates for the earthquake mechanism. Such an advantage verifies the credibility of the non-double-couple component found for some events of the 1997 West Bohemia-Vogtland earthquake swarm. As expected, in several cases, a significantly resolved non-double-couple component was obtained where the moment tensor approach failed. Additionally, for non-shear sources, the shear-tensile crack model offers optimization of the Poisson number within the focus, concurrently with retrieval of the mechanism. However, results obtained for the joint inversion of the 1997 swarm indicate that resolution is low. A series of synthetic experiments indicated that limited observations during 1997 were not the cause. Rather, hypothetical experiments of both very good and extremely poor network configurations similarly yielded a low resolution for the Poisson number. Applying this method to data for recent swarms is irrelevant because the small non-double-couple components detected within the inversion are spurious and, thus, the events are pure double-couple phenomena.