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1.
Kirchhoff beam migration is a beam migration method, which focuses on rapid imaging of geological structures. Although this imaging method ignores the amplitude information in the calculation process, it can calculate multi-arrival traveltime. This migration method takes into account both imaging accuracy and computational efficiency. Kirchhoff beam migration employs coarse grid techniques in several key steps such as traveltime calculation, weight function calculation, and imaging calculation. The selection of the coarse mesh size has an important influence on the computational efficiency and imaging accuracy of the migration imaging method. This paper will analyze this influence and illustrate the analysis results by the Marmousi data sets.  相似文献   

2.
Prestack elastic reverse time migration ( RTM) requires multicomponent seismic data .But for multi-component elastic Kirchhoff migration , there is a limitation that ray theory no longer applies if thegeology be-comes complicated .In this paper, the authors have created a new 2D migration context for isotropic , elastic RTM, which included decomposition of the elastic source and receiver wavefields into P and S wave vectors by decoupled elastodynamic extrapolation , which retained the same stress and particle velocity components as the input data .Then we appliedsource-normalized crosscorrelation imaging condition in elastic reverse time migra-tion to compensate the energy of deep strata .We found that the resulting images were nearly identical to the ve-locity model , and the resolution has been improved .Our method is a wavefielddecomposition based on vector , and we can alsoavoid the problem of polarity reversal of converted shear wave imaging .It proved the applicabili-ty of the method proposed in our paper .  相似文献   

3.
基于GPU并行加速的叠前逆时偏移方法   总被引：1，自引：1，他引：0  
为了提高复杂地下介质的成像精度和偏移算法的计算效率,提出可高效对地下复杂构造进行准确成像的GPU加速叠前逆时偏移方法.该方法采用双程声波方程进行波场延拓,突破倾角限制,借助于高阶有限差分方法实现叠前逆时偏移成像;利用GPU(Graphic Processing Unit)并行加速技术对波场延拓和成像进行计算,相比于传统算法,其计算效率有较大提高,可以解决叠前逆时偏移算法计算量过大问题;在获取波场信息过程中,也采用随机边界条件,实施以计算换存储策略,解决逆时偏移计算中的海量存储问题.模型测试结果表明,该方法能够高效和高精度地对地下复杂地质体成像.  相似文献   

4.
With the increasing complexity of prospecting objectives,reverse time migration (RTM)has attracted more and more attention due to its outstanding imaging quality.RTMis based on two-way wave equation,so it can avoid the limits of angle in traditional one-way wave equation migration,image reverse branch,prism waves and multi-reflected wave precisely and obtain accurate dynamic information.However,the huge demands for storage and computation as well as low frequency noises restrict its wide application.The normalized cross-correlation ima-ging conditions based on wave field decomposition are derived from traditional cross-correlation imaging condition, and it can eliminate the low-frequency noises effectively and improve the imaging resolution.The practical proce-dure includes separating source and receiver wave field into one-way components respectively,and conducting cross-correlation imaging condition to the post-separated wave field.In this way,the resolution and precision of the imaging result will be promoted greatly.  相似文献   

5.
国内生产总值（GDP）是衡量地区经济发展水平的重要指标,GDP的空间化可以为灾害风险分析等多学科交叉研究提供基础数据。空间化代用数据的选择是社会经济统计数据空间化的关键,本文以京津冀地区作为研究区,将夜间灯光、全球人口密度（LandScan）和亚洲人口密度（AsiaPop）空间分布信息作为代用数据,将市级GDP统计数据空间展布到栅格单元,以绝对误差、相对误差和均方根误差为指标,利用县级统计数据对展布结果进行误差分析,并对比3种数据对GDP空间模拟的表达效果。结果表明：相对于夜间灯光和LandScan数据,AsiaPop模拟得到的综合误差最小;基于夜间灯光和LandScan的GDP空间展布误差格局比较接近,即存在经济较发达的市辖区GDP值被低估、市郊区县GDP被高估的误差“两极区”倾向,而基于AsiaPop的GDP空间展布误差格局与经济发展水平关系不密切。因此,利用单一代用数据很难合理地反映经济活动的空间分布,综合夜间灯光、人口密度、道路和建筑物等多源空间数据是提高GDP空间展布精度的发展趋势。  相似文献   

6.
This is an empirical paper that measures and interprets the position of Chinese cities in the world city network in 2010. Building on a specification of the world city network as a′interlocking network′in which business services firms play the crucial role in city network formation, information is gathered about the presence of global service firms in cities. This information is converted into data to provide the′service value′of a city for a firm′s provision of corporate services in a 526(cities)×175(firms) matrix. These data are then used as the input to the interlocking network model in order to measure cities′connectivity and its predominant geographical orientation. Here we focus on the position of some key Chinese cities in this regard, and discuss and interpret results in the context of the urban dimensions of the′opening up′of the Chinese economy.  相似文献   

7.
密度大于水的重非水液相（DNAPLs）有机污染物在重力作用下向地下介质深部迁移从而增加污染范围。前人通过一维砂柱和二维砂箱试验发现利用密度调节技术可降低DNAPLs向下迁移的风险，但目前缺乏微观尺度上密度调节影响DNAPLs迁移的定量观测。本研究试验模拟丁醇注入微空隙调节四氯乙烯（PCE）的密度，通过建立非水相中染色PCE浓度、密度与灰度的定量关系，监测注入丁醇后空隙介质中非水相密度的动态变化，基于空隙中代表性非水相PCE受力情况分析其运移状态，揭示空隙尺度介质性质和密度调节程度对DNAPLs迁移的影响。试验结果表明:丁醇注入后，PCE浓度和密度迅速下降，离散状PCE与丁醇有效接触面积大且起效快；当非水相密度降至略大于水相密度时，非水相受毛细力和摩擦力的影响停止向下迁移；当非水相密度小于水相密度时，非水相才在注入压力与浮力的作用下克服毛细力、重力和摩擦力向上迁移；注入压力、摩擦力、毛细力、浮力与重力影响着空隙中非水相的迁移行为，空隙半径越大，毛细力对调节PCE向上迁移的影响越小；密度比水小的丁醇注入介质后向上迁移，因此丁醇从DNAPLs下端注入可提高修复效率。试验证实了向空隙介质中注入丁醇能够显著减小DNAPLs的密度从而降低其向下迁移的风险，为实际场地DNAPLs修复方案的制定提供微观机制方面的信息。   相似文献   

8.
To study the bubble plume’s seismic response characteristics, the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theory based on an analysis of both the acoustic characteristics of a bubble-contained water body and the actual features of a plume. The finite difference method is used for forward modelling, and the single-shot seismic record exhibits the characteristics of a scattered wave field generated by a plume. A meaningful conclusion is obtained by extracting seismic attributes from the pre-stack shot gather record of a plume. The values of the amplitude-related seismic attributes increase greatly as the bubble content goes up, and changes in bubble radius will not cause seismic attributes to change, which is primarily observed because the bubble content has a strong impact on the plume’s acoustic velocity, while the bubble radius has a weak impact on the acoustic velocity. The above conclusion provides a theoretical reference for identifying hydrate plumes using seismic methods and contributes to further study on hydrate decomposition and migration, as well as on distribution of the methane bubble in seawater.  相似文献   

9.
国产高分卫星6号（简称GF6）具有高分辨率、宽覆盖、高质量和高效成像等特点,可为农业资源遥感监测提供可靠的数据支撑。本研究以GF6卫星影像为主要数据源,综合利用遥感技术理论和方法开展对夏津县棉花种植面积的提取研究,利用同时相的哨兵2号（简称Sentinel2）影像解译结果进行对比分析。研究结果表明：基于GF6卫星的夏津县棉花种植面积提取方案高效、准确,提取精度明显优于Sentinel2卫星,进一步证明了新增了红边波段的GF6卫星能够显著增强作物的识别能力,其在大规模作物种植信息提取方面具有广阔的应用潜力。  相似文献   

10.
The vertical cable method for acquiring and processing pre-stack 3-D marine seismic data is based on the technology developed by the US Navy for antisubmarine warfare. In order to achieve the maximum utilization of vertical cable field data, a new separation method of the up-going and down-going wave fields of the vertical cable data processing was developed in this paper, which is different from the separation of the down-going and up-going wave fields of normal VSP data processing. In tests with synthetic modeling data andactual field data, this newly developed method performs well and is also computationally simpler without pre-assumption conditions.  相似文献   

11.
Strong fluctuation of seabed, abrupt variation in depth and dip of seabed bring seismic imaging problems, such as irregular reflection waves, obvious multiple waves, serious lateral wave development, poor imaging on base surface and depression structure, low signal-to-noise ratio of middle and deep layers. In this paper, Gaussian beam migration imaging method is used to analyze the imaging effect of rugged seabed in deep water area, and the ray tracing method of wavefront construction method is used to analyze the kinematic characteristics of seismic waves. By improving the design of seismic data acquisition and observation system, imaging quality of fine structures is improved.  相似文献   

12.
The spatialization of population of counties in China is significant.Fistly,we can gain the estimated val-ues of population density adaptive to different kinds of regions.Secondly,we can integrate effectively population data with other data including natural resources,environment,society and economy,build 1km GRIDs of natural resources re-serves per person,population density and other economic and environmental data,which are necessary to the national manage-ment and macro adjustment and control of natural resources and dynamic monitoring of population.In order to establish population information system serving national decision-making,three steps ought to be followed:1)establishing complete geographical spatial data foundation infrastructure including the establishment of electric map of residence with high resolu-tion using topographical map with large scale and high resolution satellite remote sensing data,the determination of at-tribute information of housing and office buildings,and creating complete set of attribute database and rapid data update-ing;2) establishing complete census systems including improving the transformation efficiency from census data to digital database and strengthening the link of census database and geographical spatial database,meanwhile,the government should attach great importance to the establishment and integration o population migration database;3)considering there is no GIS software specially seving the analysis and management of population data,a practical approach is to add spe-cial modules to present software system,which works as a bring actualizing the digitization and spatialization of popula-tion geography research.  相似文献   

13.
Ecological migration is the process of increasing the population density in the immigration area and transferring the ecological pressure from emigration area to immigration area. This process may result in significant changes in land use and land cover in the area of immigration and have an important effect on ecosystem services. Therefore, scientifically revealing the effects and differentiation mechanisms of ecological migration on ecosystem services is becoming an important issue related to the implementation of the national ecological migration strategy in China. This study employed the Hongsibu District as a typical example of ecological migration. Hongsibu District is located in the central Ningxia steppe and desert steppe areas. Remote sensing data covering five periods from the period before ecological migration in 1995 and after migration in 2000, 2005, 2010, and 2015 was used to measure the value of ecosystem services(ESV). A geographical detector model and the value of ecosystem services model were used to diagnose the dynamic mechanism of the effects of land use change on ecosystem services. The results showed that: 1) The development of large-scale ecological resettlement has caused the area of cultivated land and urbanized land area to increase significantly in the area of immigration, while the grass area decreased significantly. 2) The overall value of the Hongsibu ecosystem services increased in a form of a ‘V'. Among them, during the period of 1995–2005, the overall ESV decreased and had an annual rate of change of-0.67%. During the period of development 2005–2015, the ESV increased steadily, with an annual rate of change of 0.79%. 3) The proportion and total ESV in soil formation and protection, waste treatment, and biodiversity conservation of the Hongsibu District decreased from 57.61% in 1995 to 56.17% in 2015, indicating that the region's ecological regulation function slightly decreased. 4) The ESV in the Hongsibu District, showed a low distribution pattern of ecosystem services increasing from northeast to southwest, and the capacity of three townships, Hongsibu, Taiyangshan, and Liuquan, to provide ecosystem services gradually declined over time. The ecological service function of Xinzhuangji Township and Dahe Township gradually improved. 5) The sensitivity index of the ESV of each land use type was less than 1, indicating that the environment lacks flexibility in providing a strong ESV index in Hongsibu, which shows that the research results are reliable and believable. 6) During the study period, the decisive force of the change of land use on ecosystem services in Hongsibu District was: grassland(0.9934), climate regulation(0.9413), soil formation and protection(0.9321) and waste treatment(0.9241).  相似文献   

14.
Transhumant pastoralism is an important activity in southern Morocco. Migration pattern of transhumant pastoralists can be affected by physical factors (e.g. droughts and diseases) or socioeconomic factors (e.g. schooling options for children and migration costs). We studied the spatio-temporal rangeland usage of the three tribes Ait Mgoun, Ait Zekri, and Ait Toumert in the south-central Atlas region with a two-fold approach. First, we tracked the migration movements of one representative transhumant herd using the Advanced Research and Global Observation Satellite (ARGOS) collars, which record coordinates from satellite signals. Second, we interviewed herders to obtain information about general grazing practices of the respective tribe and to gain more direct information on motivations underlying decisions. For each tribe we observed small-, medium- and large-scale movements. We found that the most important drivers of migration decisions were seasonal fodder availability and weather conditions in combination with herd-specific risk and cost assessment, as well as personal factors. In conclusion, general migration patterns vary in time, both between and within the tribes, but according to a regulatory framework. Moreover, it appears that both the customary rules and its flexible adaptation to physical constraints are generally beneficial in terms of conservation of the arid and semiarid rangeland resources.  相似文献   

15.
Air guns are important sources for marine seismic exploration. Far-field wavelet of air gun arrays, as a necessary parameter for pre-stack processing and source models, plays an important role during marine seismic data processing and interpretation. When an air gun fires, it generates a series of air bubbles. Similar to onshore seismic exploration, the water forms a plastic fluid near the bubble; the farther the air gun is located from the measurement, the more steady and more accurately represented the wavelet will be. In practice, hydrophones should be placed more than 100 m from the air gun; however, traditional seismic cables cannot meet this requirement. On the other hand, vertical cables provide a viable solution to this problem. This study uses a vertical cable to receive wavelets from 38 air guns and data are collected offshore Southeast Qiong, where the water depth is over 1000 m. In this study, the wavelets measured using this technique coincide very well with the simulated wavelets and can therefore represent the real shape of the wavelets. This experiment fills a technology gap in China.  相似文献   

16.
城市人口实时分布与动态变化特征是城市规划与综合治理的重要依据。受数据获取手段的局限性,准确地获取城市人口的实时分布状况一直是技术瓶颈,而移动通讯技术的迅速普及为这一问题的解决提供了技术途径。本文基于移动通讯信令的连续轨迹数据,实现了城市精细尺度人口分布时空估算的方法流程,并以上海市为研究区,对城市人口分布特征及时空移动过程进行了量化分析。研究表明：① 在数据方面,基于移动通讯信令数据估算城市人口分布的方式样本覆盖广、时空精度高、时效性较强且支持时空尺度灵活多变的应用研究需求,能够定量地描述城市人口分布时空动态特征且能推算城市真实人口规模;② 在人口分布时空特征方面,上海市在全市尺度上,各时段人口空间分布较为稳定且差异较小,而在中心城区日间人口较夜间人口呈现更为显著的空间集聚特征;③ 在人口移动时空特征方面,城市功能承载区与其它区域之间人口移动很少,早晚高峰期各城市功能承载区之间人口移动均体现为中心城区与其它新城之间的移动,且2个方向移动人数较为平衡;各城市功能承载区内均有超过半数的人口全天仅在其所在城区内部活动。本文的研究成果可为上海城市规划、应急管理、交通出行等提供更精准的科学依据。  相似文献   

17.
针对非开挖工程工勘资料缺乏,掘进地层岩性难以判别的问题,提出一种基于非开挖泥浆性能检测与弱监督机器学习结合的典型非开挖地层岩性识别方法。结合自主设计研发的非开挖泥浆性能检测系统工程现场应用,获取非开挖掘进导向段泥浆流变性能参数和密度等敏感参数的训练样本。利用部分有标签数据与K近邻（K Nearest Neighbors,KNN）算法对所有泥浆参数训练样本进行特征标签,采用核函数映射到高维空间支持向量机（Support Vector Machines,SVM）进行分类处理,建立了以上海地区典型非开挖地层分类为目标的分类模型。将该地层识别模型应用于上海地区非开挖工程,验证其有效性。结果表明,该方法能在非开挖实时钻进条件下快速识别钻进地层,识别正确率高达96%。研究成果通过采集导向段泥浆性能参数,识别非开挖掘进段地层岩性,为非开挖扩孔阶段钻具选型、泥浆设计等提供了重要地质信息保障。   相似文献   

18.
出租车一直以来被看作公共交通的补充,但是以往研究多侧重于出租客流与公交客流的独立研究,对于二者的关联关系分析没有足够得到关注。预测出租车载客热点区域不仅能够实时的了解城市交通热点区域,还能够很好地指引出租车司机,帮助出租车司机快速寻客。出租车载客热点常发生在人流密集并且交通出行需求较高的区域,公交乘客IC卡数据能够实时的反映城市中的交通需求。因此,本文使用厦门岛出租车GPS轨迹数据与公共交通运输系统运营数据,利用核密度估计法和地理加权回归模型分析了早晚高峰时段出租车载客与公交上下车（OD）客流之间的时空分布关系。研究发现,出租乘客O点的核密度值在空间上存在分布不均衡性,聚集特征明显。在同一区域,公交乘客O点和公交乘客D点对出租乘客O点所产生的影响刚好相反;在不同区域,城市功能类型复杂的地区公交乘客O点对出租乘客O点产生负的影响,在城市功能类型单一的地区公交乘客O点对出租乘客O点产生正的影响,公交乘客D点则刚好相反。与普通线性回归模型相比,地理加权回归模型的拟合效果显著提高,早晚高峰拟合优度分别从0.13和0.11提升到了0.59和0.53。研究结果可为出租车载客数量的预测提供相关依据。  相似文献   

19.
导航大数据是大量与导航相关且具有泛在导航、定位、授时特征的数据集合。城市环境的特性影响居民的出行活动,而居民出行活动中产生的导航大数据则蕴含了城市环境的时空信息。热点区域空间分布以及热点区域之间的关联性特征是城市环境时空特性的重要组成部分,由客观的环境现状和主观的人为活动造成。通过挖掘导航大数据可以揭示这些特征。本文提出了利用导航大数据的城市热点区域关联性挖掘方法。首先,通过对居民出行的起点和终点坐标进行空间聚类,挖掘城市中的热点区域,并依据点的分布特点对城市热点区域进行离散化;然后,利用基于谱聚类和蚁群算法的方法分析居民出行特征,揭示城市中热点区域之间存在的关联性。本文提出的方法能够充分利用导航大数据对城市动态的感知能力。以上海市2007年2月20日的出租车轨迹数据为例进行分析,结果表明：利用导航大数据分析城市热点区域之间的关联性,可以得到具有紧密关联性的热点区域的空间分布特征;上海市居民出行活动频繁的热点区域被划分为15个内部紧密关联的子图,形成该分布特征的内在机制以及居民流通规律与上海市的土地资源利用及道路交通建设现状密切相关。分析方法和结果可为合理的城市功能区域规划,智慧城市建设等提供决策支持和参考信息。  相似文献   

20.
西安市城市边缘区空间识别与边界划分   总被引：2，自引：0，他引：2  
城市边缘区研究的首要任务是对城市边缘区进行空间识别和边界划分。针对现有研究存在的指标选取过于单一或繁杂、水陆分离导致划分间断等问题,利用西安市SPOT-5、Landsat TM遥感影像和社会统计数据,分别从物理、景观、人口3个视角出发,选定不透水面盖度与景观絮乱度作为主要判别指标,人口密度作为辅助指标,构建城市边缘区识别指标体系。运用信息熵法和突变检测法,量化并可视化西安市城市边缘区的空间范围。结果表明：① 所选取指标沿着城乡梯度表现出独特的空间信息,根据指标的城乡空间异质性特征可以识别出城市边缘区的空间范围,且方法更科学,界定结果更精确。② 西安市呈现出明显的城市核心区、城市边缘区、农村腹地的圈层结构特征。道路牵引与政策调控对城市边缘区的空间分布有重要影响。本研究可为城市边缘区其他相关研究提供科学参考和依据。  相似文献   

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