青海东昆仑哈西哇金多金属矿地质特征及找矿前景     

周兵  李双江 《四川地质学报》2020,40(1):51-55

研究区内广布的富金元古宇地层是金矿集中区形成的基础,多期次的强烈岩浆活动为金矿集中区的形成提供了极为丰富的成矿流体和矿质来源,脆韧性剪切带为矿液流通和汇聚提供了有利空间。在区内的脆韧性剪切带中分布有Ⅰ矿带和Ⅱ矿带,带内发育硅化、绢云母化、黄铁矿化、绿泥石化、碳酸盐化、纤闪石化、高岭土化蚀变,金多金属矿化主要与硅化、绢云母化、绿泥石化、黄铁矿化关系密切。目前已提交金资源量约8.94t,银金属量约247.02t,铅金属量约6.45万t,锌金属量约5.23万t。综合分析该区地质矿化特征和控矿因素认为,研究区成矿条件优越,找矿潜力巨大,通过开展进一步勘查工作有望达到大型金多金属矿床规模。  相似文献   

APPARENT STRESS VARIATION CHARACTERISTICS BEFORE AND AFTER BADONG EARTHQUAKE IN THE THREE GORGES RESERVOIR AREA          下载免费PDF全文

DAI Miao  WU Gui-ju  LIU Jian  SHEN Chong-yang  SHEN Xue-lin  SHEN Xue-lin  WEI Gui-chun 《地震地质》2017,39(4):837-852

The causes of earthquakes in the Three Gorges reservoir area are complex. In order to study the cause of earthquakes happening in the region, we calculated the source parameters of 394 M_L ≥ 2.0 earthquakes occurring in Three Gorges reservoir area based on waveform data observed by the regional seismic network of Hubei Province and Three Gorges, obtained the apparent stress spatial-temporal variation map of Three Gorges reservoir area, and analyzed apparent stress spatial-temporal variation characteristics before and after the main earthquakes in the Three Gorges reservoir area. The results show that:1)Before the Badong M_L5.5, Zigui M_L4.7 and Zigui M_L5.1 earthquake, high apparent stress of earthquakes with different magnitudes is concentrated in Xinhua-Shuitianba Fault and Gaoqiao Fault. The distribution of high value area shows the high degree of synergism before the earthquake and the scattering after the earthquake, which indicates that the area accumulated a high stress before the earthquake, and the fault was in a locked state; 2)In the study area, the apparent stress before and after the earthquake showed significant rise in the first and then decline, the earthquake occurred in the process of rising; 3)Apparent stress depth profiles show that apparent stress at different depths has a positive correlation with the size of magnitude of earthquake, and the phenomenon of "small magnitude and strong apparent stress" did not appear. The small earthquakes occurring after the major earthquakes in the study area belong to low strain release under the background of low stress release, and there are no new apparent stress anomaly concentration areas appearing, this indicates that the Badong-Gaoqiao Fault, Zhoujiashan-Niukou Fault and Zigui Xiannushan Fault have been effective in releasing after the Badong earthquake and Zigui earthquakes and the probability of destructive earthquake is small on these faults.  相似文献   

Application of Structure‐from‐Motion photogrammetry to river restoration          下载免费PDF全文

Baptiste Marteau  Damià Vericat  Chris Gibbins  Ramon J. Batalla  David R. Green 《地球表面变化过程与地形》2017,42(3):503-515

Structure‐from‐Motion (SfM) photogrammetry is now used widely to study a range of earth surface processes and landforms, and is fast becoming a core tool in fluvial geomorphology. SfM photogrammetry allows extraction of topographic information and orthophotos from aerial imagery. However, one field where it is not yet widely used is that of river restoration. The characterisation of physical habitat conditions pre‐ and post‐restoration is critical for assessing project success, and SfM can be used easily and effectively for this purpose. In this paper we outline a workflow model for the application of SfM photogrammetry to collect topographic data, develop surface models and assess geomorphic change resulting from river restoration actions. We illustrate the application of the model to a river restoration project in the NW of England, to show how SfM techniques have been used to assess whether the project is achieving its geomorphic objectives. We outline the details of each stage of the workflow, which extend from preliminary decision‐making related to the establishment of a ground control network, through fish‐eye lens camera testing and calibration, to final image analysis for the creation of facies maps, the extraction of point clouds, and the development of digital elevation models (DEMs) and channel roughness maps. The workflow enabled us to confidently identify geomorphic changes occurring in the river channel over time, as well as assess spatial variation in erosion and aggradation. Critical to the assessment of change was the high number of ground control points and the application of a minimum level of detection threshold used to assess uncertainties in the topographic models. We suggest that these two things are especially important for river restoration applications. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

将微粒群和支持向量机用于耕地驱动因子选择的研究   总被引：2，自引：0，他引：2  

杨柳  刘艳芳 《武汉大学学报(信息科学版)》2010,(2)

结合微粒群算法(PSO)具有执行速度快、受问题维数变化影响小的优点及支持向量机算法(SVM)结构风险最小化原理,构建了基于离散二进制微粒群(BPSO)与支持向量机的耕地驱动力因子选择方法,使用特征子集中确定的特征来训练支持向量回归机,用适应度函数来评价回归机的性能,指导BPSO的搜索。实验表明,该方法能有效地提取出耕地驱动因子的特征子集,从而降低了指标的维数,保留了关键信息,以获得知识的最小表达。  相似文献   

高分辨率遥感图像最近邻模糊分类器的研究及实现     

朱国龙  汪云甲  乔浩然  刘乐乐  赵一清 《测绘科学》2010,35(6):96-98

本文针对高分辨率遥感影像快速高效萃取有用信息这一遥感技术应用的热点问题,探讨了一种适合于组合特征识别的遥感图像最近邻模糊分类器。该分类器首先把待识别目标的组合特征与训练模板中的组合特征样本的平均值一一进行比较,从而得到了一个特征差矩阵。用模糊分布函数在同类特征差之间进行处理,生成一个隶属度矩阵,然后用算术平均法对隶属度矩阵进行处理,并用最大隶属度准则来进行分类判决。以新疆和静县的SPOT5图像为例,应用此方法对其进行分类试验。结果表明:利用此分类方法对SPOT5遥感图像进行分类,不仅使分类结果具有丰富的语义信息,而且克服了由于特征选择的不稳定性对分类结果的影响,分类精度也得到了显著的提高。  相似文献   

基于小波包分解的结构自振特征提取及多路径误差分离     

吴继忠  花向红  高俊强 《武汉大学学报(信息科学版)》2010,(4)

为了准确获取结构自振特性,通过分析多路径误差和结构振动的频率特征,采用小波包分解和频谱分析相结合的方法,在不同尺度下进行特定成分的提取,再作频率特性分析。实验结果表明,小波包能够有效地分离多路径误差,实现结构振动特征的提取,GPS测定的结构自振频率与理论值吻合较好,并且具有很好的稳定性。  相似文献   

Geomorphic process from topographic form: automating the interpretation of repeat survey data in river valleys          下载免费PDF全文

Alan Kasprak  Joshua Caster  Sara G. Bangen  Joel B. Sankey 《地球表面变化过程与地形》2017,42(12):1872-1883

The ability to quantify the processes driving geomorphic change in river valley margins is vital to geomorphologists seeking to understand the relative role of transport mechanisms (e.g. fluvial, aeolian, and hillslope processes) in landscape dynamics. High‐resolution, repeat topographic data are becoming readily available to geomorphologists. By contrasting digital elevation models derived from repeat surveys, the transport processes driving topographic changes can be inferred, a method termed ‘mechanistic segregation.’ Unfortunately, mechanistic segregation largely relies on subjective and time consuming manual classification, which has implications both for its reproducibility and the practical scale of its application. Here we present a novel computational workflow for the mechanistic segregation of geomorphic transport processes in geospatial datasets. We apply the workflow to seven sites along the Colorado River in the Grand Canyon, where geomorphic transport is driven by a diverse suite of mechanisms. The workflow performs well when compared to field observations, with an overall predictive accuracy of 84% across 113 validation points. The approach most accurately predicts changes due to fluvial processes (100% accuracy) and aeolian processes (96%), with reduced accuracy in predictions of alluvial and colluvial processes (64% and 73%, respectively). Our workflow is designed to be applicable to a diversity of river systems and will likely provide a rapid and objective understanding of the processes driving geomorphic change at the reach and network scales. We anticipate that such an understanding will allow insight into the response of geomorphic transport processes to external forcings, such as shifts in climate, land use, or river regulation, with implications for process‐based river management and restoration. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

An improved segmentation approach for planar surfaces from unstructured 3D point clouds     

Tarek M.  Awwad  Qing  Zhu  Zhiqiang  Du  Yeting  Zhang 《The Photogrammetric Record》2010,25(129):5-23

The extraction of object features from massive unstructured point clouds with different local densities, especially in the presence of random noisy points, is not a trivial task even if that feature is a planar surface. Segmentation is the most important step in the feature extraction process. In practice, most segmentation approaches use geometrical information to segment the 3D point cloud. The features generally include the position of each point (X, Y and Z), locally estimated surface normals and residuals of best fitting surfaces; however, these features could be affected by noisy points and in consequence directly affect the segmentation results. Therefore, massive unstructured and noisy point clouds also lead to bad segmentation (over-segmentation, under-segmentation or no segmentation). While the RANSAC (random sample consensus) algorithm is effective in the presence of noise and outliers, it has two significant disadvantages, namely, its efficiency and the fact that the plane detected by RANSAC may not necessarily belong to the same object surface; that is, spurious surfaces may appear, especially in the case of parallel-gradual planar surfaces such as stairs. The innovative idea proposed in this paper is a modification for the RANSAC algorithm called Seq-NV-RANSAC. This algorithm checks the normal vector (NV) between the existing point clouds and the hypothesised RANSAC plane, which is created by three random points, under an intuitive threshold value. After extracting the first plane, this process is repeated sequentially (Seq) and automatically, until no planar surfaces can be extracted from the remaining points under the existing threshold value. This prevents the extraction of spurious surfaces, brings an improvement in quality to the computed attributes and increases the degree of automation of surface extraction. Thus the best fit is achieved for the real existing surfaces.  相似文献   

基于物理特征的平面流场拓扑简化算法     

秦勃  李兵  王庆江 《中国海洋大学学报(自然科学版)》2010,40(2)

基于网格合并思想实现的平面流场拓扑简化,存在物理特征被忽略和并行实现困难的问题,难以满足远程可视化的要求。文中提出1种基于物理特征的平面流场拓扑简化算法。算法通过计算生成平面流场的物理特征参数图像,利用图像分割提取平面流场的特征区域达到流场简化的目的。实验结果表明,算法能从物理特征和宏观的角度出发快速、准确描述平面流场的拓扑结构,为平面流场可视化提供了1种新方法。  相似文献   

1∶10000 DLG矢量数据符号化的制作过程初探     

李杰 《东北测绘》2010,(5):192-194

初探综合运用Geoway软件和AutoCAD2007软件对1∶10000 DLG矢量数据符号化的制作过程,对作业过程中一些关键步骤的做法进行详细描述,为以后的测绘作业提供参考。  相似文献