地震孕育过程的物理学研究展望   总被引：4，自引：0，他引：4  

安镇文 《国际地震动态》1999,(5):12-15

综述了地震孕育过程的研究展望,提出了多尺度地震系统研究的复杂性及其新的探索方法,讨论了其演化过程的非线性机理和当前科学水平上地震虚报的必然性。  相似文献   

中国地级城市建成区蓝绿空间时空格局及其气候影响因素分析     

张歆越  高晓路  柴琪  宋敦江 《地球信息科学学报》2023,25(1):190-207

蓝绿空间是城市生态安全的重要保障。本文通过谷歌地球引擎（GEE）提取2005、2010、2015与2020年的植被与水体指数数据,构建了包含272个地级城市建成区的蓝绿空间数据库。运用蓝绿空间覆盖率、300 m服务半径覆盖率、分维数与分离度4个指标分析其时空格局与演化模式,并进一步探讨其气候影响因素。结果表明：(1)地级城市建成区蓝绿空间整体呈现为“南高北低”的格局,且南方“西高东低”、北方“东高西低”,但环渤海地区为蓝绿空间覆盖率“洼地”;时间格局为“总体增长、局部降低”,华中地区呈下降趋势的城市最多;(2)就分区而言,西南地区城市建成区蓝绿空间覆盖率最高（平均高于65%）、分离度最低（平均低于0.60）,西北地区覆盖率分异较大,华北地区覆盖率最低（平均10%～30%）且分离度最高（平均约0.98）;(3)采用多尺度地理加权回归模型所得R2为0.85（校正R2为0.83）,其中,降水量对城市建成区蓝绿空间的影响最显著,降水量变化成正相关,气温则成负相关;整体上气候影响与比人为影响相当,但在某些时段间更大。  相似文献   

Recent changes in the sediment regime of the Pearl River (South China): Causes and implications for the Pearl River Delta   总被引：1，自引：0，他引：1       下载免费PDF全文

Feng Liu  Shuai Hu  Xiaojuan Guo  Xiangxin Luo  Huayang Cai  Qingshu Yang 《水文研究》2018,32(12):1771-1785

Riverine sediments have played an important role in the morphological evolution of river channels and river deltas. However, the sediment regime in the many world's rivers has been altered in the context of global changes. In this study, temporal changes in the sediment regime of the Pearl River were examined at different time scales, that is, annual, seasonal, and monthly time scales, using the Mann–Kendall test. The results revealed that precipitation variability was responsible for monthly and seasonal distribution patterns of the sediment regime and the long‐term changes in the water discharge; however, dam operation has smoothed the seasonal distribution of water discharge and resulted in decreasing trends in the annual, wet‐season, and dry‐season sediment load series since the 1950s. Due to the different regulation magnitudes of dam operation, differences were observed in sediment regime changes among the three tributaries. In addition, human activities have altered the hysteresis of seasonal rating curves and affected hysteresis differences between increasing and decreasing water discharge stages. Sediment supply is an important factor controlling river channel dynamics, affecting channel morphology. From the 1950s to the 1980s, siltation was dominant in river channels across the West River and North River deltas in response to the sediment increases; however, scouring occurred in the East River deltas due to sediment reduction. Significant erosion occurred in river channels in the 1990s, which was mostly due to downcutting of the river bed caused by sand excavations and partly because of the reduced sediment load from upstream. Although sand excavations have been banned and controlled by authority agencies since 2000, the erosion of cross sections was still observed in the 2000s because of reduced sediment caused by dam construction. Our study examines the different effects of human activities on the sediment regime and downstream channel morphology, which is of substantial scientific importance for river management.  相似文献   

GPU ray casting method for visualizing 3D pipelines in a virtual globe     

Zhaocong Wu  Jie Shao  Guohui Deng 《International Journal of Digital Earth》2019,12(4):428-441

Pipelines are an important part of urban infrastructure development. As part of a virtual globe (VG), the high-efficiency and high-quality visualization of 3D large-scale and high-density urban pipelines is of great importance. This paper proposes a GPU-based pipeline ray casting method for the visualization of urban-scale pipelines in the framework of a VG. The method involves the initial partitioning of the pipeline data into tiles, based on the relationship between the pipeline layer scale and the discrete global grid system (DGGSs). The pipeline centerline in each tile is then segmented and encoded, and a coarser pipeline bounding volume is subsequently constructed using a geometry shader. Finally, the fine 3D pipeline is rendered using a pixel shader. The results of the experimental implementation of the proposed method show that it satisfies the requirements for the multiscale visualization of pipelines in a VG. Moreover, compared with the traditional polygon-based method, the method facilitates a 20% increase in rendering frame rate for the same pixel level accuracy display effect. It also enables the visualization of the thickness of the 3D pipeline without any obvious effect on the rendering efficiency.  相似文献   

Network-constrained bivariate clustering method for detecting urban black holes and volcanoes     

Qiliang Liu  Zhihui Wu  Wenkai Liu  Yaolin Liu 《International journal of geographical information science》2020,34(10):1903-1929

ABSTRACT

Urban black holes and volcanoes are typical traffic anomalies that are useful for optimizing urban planning and maintaining public safety. It is still challenging to detect arbitrarily shaped urban black holes and volcanoes considering the network constraints with less prior knowledge. This study models urban black holes and volcanoes as bivariate spatial clusters and develops a network-constrained bivariate clustering method for detecting statistically significant urban black holes and volcanoes with irregular shapes. First, an edge-expansion strategy is proposed to construct the network-constrained neighborhoods without the time-consuming calculation of the network distance between each pair of objects. Then, a network-constrained spatial scan statistic is constructed to detect urban black holes and volcanoes, and a multidirectional optimization method is developed to identify arbitrarily shaped urban black holes and volcanoes. Finally, the statistical significance of multiscale urban black holes and volcanoes is evaluated using Monte Carlo simulation. The proposed method is compared with three state-of-the-art methods using both simulated data and Beijing taxicab spatial trajectory data. The comparison shows that the proposed method can detect urban black holes and volcanoes more accurately and completely and is useful for detecting spatiotemporal variations of traffic anomalies.  相似文献   

基于准连续介质方法模拟纳米多晶体Ni中裂纹的扩展   总被引：1，自引：0，他引：1  

邵宇飞  王绍青 《海洋学报》2010,32(10):7258-7265

通过准连续介质方法模拟了纳米多晶体Ni中裂纹的扩展过程.模拟结果显示:裂纹尖端的应力场可以导致晶界分解、层错和变形孪晶的形成等塑性形变;在距离裂纹尖端越远的位置,变形孪晶越少;在裂纹尖端附近相同距离处,层错要远多于变形孪晶.这反映了局部应力的变化以及广义平面层错能对变形孪晶的影响.计算了裂纹尖端附近区域原子级局部静水应力的分布.计算结果表明:裂纹前端晶界处容易产生细微空洞,这些空洞附近为张应力集中区,并可能促使裂纹沿着晶界扩展.模拟结果定性地反映了纳米多晶体Ni中的裂纹扩展过程,并与相关实验结果符合得很好  相似文献   

多源多尺度地图数据的组织与管理     

肖计划  孙群  刘海砚 《测绘学院学报》2009,(1)

多源多尺度地图数据的组织与管理是多源地图数据处理、数据融合以及地图制图综合的基础。首先对多源地图数据处理的主要方法和技术进行了总结;进而讨论了多源多尺度地图数据的组织与管理的两个关键技术,即多源多尺度地图数据引擎的设计和多图幅地图数据的内存管理技术。  相似文献   

重力数据的多尺度边缘分析及其应用(英文)     

汪海洪  罗志才  宁津生 《地球空间信息科学学报》2009,12(3):230-234

In order to improve the processing and interpretation of gravity data, multiscale edge theory in image processing is introduced into the study of gravity field. Multiscale edges of gravity anomaly are analyzed based on a special wavelet. It shows that the multiscale edges are the extrema points of the horizontal gravity gradient at different heights, which are related to the sharp discontinuities of underground sources. The applications of multiscale edge in downward continuation and gravity inversion are discussed. The simulated examples show that the multiscale edges can be applied to stabilize the downward continuation operator when the continuation height is low. The multiscale edges also have a convenient application to infer the geometry of the underground source. Moreover, the gravity inversion algorithm based on the multiscale edges has a good antinoise property. Supported by the National Natural Science Foundation of China(No.40704003), the National 973 Program of China(No.2007CB714405), the Open Research Fund from Key Laboratory of Geospace Environment and Geodesy(No.04-01-08).  相似文献   

测井多尺度分析方法用于准层序自动划分研究   总被引：6，自引：4，他引：2       下载免费PDF全文

房文静  范宜仁  邓少贵  谭茂金 《地球物理学进展》2007,22(6):1809-1814

多尺度分析方法实现了信号分析的时频局部化,是测井数据时频分析与地质解释恰当的数学工具.测井资料作为地层岩性、物性的反映,其中必然蕴含了大量与沉积地层旋回变化有关的信息.以胜坨油田某井为例,采用db4最佳小波基分别对自然伽马、自然电位和声波等测井曲线进行了多尺度分析,将一维测井数据拓展为二维深度-尺度空间,提取小波变换系数的时频色谱信息和能量信息,从而确定出测井曲线识别准层序界面的最佳尺度.依据最佳尺度下的小波系数幅度振荡特征和时频色谱信息实现了对准层序界面的自动划分,与传统方法所划分的界面基本一致.这些探索为层序地层的定量划分提供了一种新的思路.  相似文献   

诱发哈萨克斯坦夏季强降水的环流结构特征     

李如琦  李桉孛  王江  周雅蔓  魏娟娟 《沙漠与绿洲气象(新疆气象)》2024,18(5)

采用FNL1°×1°和CPC0.5°×0.5°再分析资料,通过对比分析夏季哈萨克斯坦不同区域的3次强降水过程的环流特征,揭示了诱发强降水的环流结构。结果表明：哈萨克斯坦各区域出现强降水时,西部和东部的强降水中心位于高空急流带入口区右侧,北部位于出口区左侧,辐散抽吸作用利于上升运动发展;强降水的影响系统主要为500 hPa低涡,强降水中心位于低涡槽线前部西南气流带上,中层温度平流对强降水发生有促进作用,西部和北部强降水中心位于低层冷平流大值区,东部则位于东北冷平流南侧的气旋性辐合区;除哈萨克斯坦东部强降水受地形影响地面系统尺度较小外,西部和北部强降水时地面有明显的冷锋,并存在气旋性的辐合切变,冷暖汇合形成的辐合线是强降水的主要中尺度触发系统;哈萨克斯坦强降水的水汽源地主要为地中海、黑海、波斯湾和北冰洋,经长途输送在强降水区形成强的水汽辐合,辐合值＞40×10-6 g?cm-1?s-1。  相似文献