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321.
常规高阶和时空域高阶有限差分方法广泛应用于三维标量波动方程的数值模拟,这两种差分方法仅利用笛卡尔坐标系中的坐标轴网格点构建三维Laplace差分算子,相应的差分离散波动方程本质上仅具有2阶差分精度,模拟精度低.本文将三维笛卡尔坐标系中非坐标轴网格点分为两类：坐标平面内的非坐标轴网格点和坐标平面外的非坐标轴网格点,系统推导出了两类非坐标轴网格点构建三维Laplace差分算子的方法,进而提出了一种利用坐标轴网格点和非坐标轴网格点共同构建三维Laplace差分算子的混合网格有限差分方法,并利用时空域频散关系和泰勒展开建立差分系数方程,推导出了差分系数的通解.相比常规高阶和时空域高阶差分格式的2阶差分精度,时空域混合网格差分离散波动方程理论上能够达到任意偶数阶差分精度,模拟精度显著提高,同时稳定性更强.频散分析表明：相比常规高阶和时空域高阶差分格式,在计算效率基本相同时,时空域混合网格差分格式能更有效地减小数值频散,减弱数值各向异性,模拟精度更高;在模拟精度基本相当时,混合网格差分格式能采用更大的时间采样间隔,计算效率更高.数值模拟实例进一步验证了混合网格差分格式在提高模拟精度和计算效率方面的先进性,也验证了其普遍适用性.
相似文献322.
致密油气层的物性（孔隙度和渗透率）较差.针对致密储层,目前常用的氦气法孔隙度测量方法存在两个不足：器壁压变性参数G定义不明确;膨胀前压力设置普遍偏小.本次基于氦气法孔隙度测量装置岩心室的应力应变力学分析和不确定度理论分析,开发了一种面向致密储层的氦孔隙度测量方法.本次提出的方法给出了器壁压变性参数G的解析式,并基于G的解析式推导出了新的孔隙度计算公式,将刻度系数减少到1个,简化了刻度过程.其次,基于不确定度理论得到的孔隙度测量不确定度表明：氦气法测量致密储层孔隙度的膨胀前压力大于2 MPa基本可以将孔隙度绝对误差控制在0.5%以内.与高压压汞法孔隙度测量结果对比发现,该方法测量孔隙度的相对偏差在14%以内,远低于常规氦气法测量孔隙度的相对偏差（50%）.
相似文献323.
DAI Xiao-ai LIU Chao LI Nai-wen WANG Mei-lian YANG Yu-wei YANG Xing-ping ZHANG Shi-qi HE Xu-wei YANG Zheng-li LU Heng LI Jing-zhong WANG Ze-kun 《山地科学学报》2021,276(6):1630-1645
As one of the key parameters for characterizing crop canopy structure, Leaf Area Index (LAI) has great significance in monitoring the crop growth and estimating the yield. However, due to the nonlinearity and spatial heterogeneity of LAI inversion model, there exists scale error in LAI inversion result, which limits the application of LAI product from different remote sensing data. Therefore, it is necessary to conduct studies on scale effect. This study was based on the Heihe Oasis, Zhangye city, Gansu province, China and the following works were carried out: Airborne hyperspectral CASI (Compact Airborne Spectrographic Imager) image and LAI statistic models were adopted in muti-scale LAI inversion. The overall difference of muti-scale LAI inversion was analyzed in an all-round way. This was based on two aspects, 相似文献
324.
Tibetan Plateau (TP) lakes are important water resources, which are experiencing quick expansion in recent decades. Previous researches mainly focus on analyzing the relationship between terrestrial water storage (TWS) change and lake water storage (LWS) change in the total inner TP, it is still lack of researches about the spatial difference and the characteristic of sub-region in the inner TP. In this study, we estimated the area change of 34 lakes by using Landsat images in the northeastern TP during 1976-2013, and LWS change by using the Shuttle Radar Topography Mission (SRTM). The results suggested that LWS had shrunk from 1976 to 1994, and then expanded quickly until 2013. LWS had a serious decrease by 13.6 Gt during 1976-1994, and then it increased quickly by 35.4 Gt during 1994-2013. We estimated TWS change, soil moisture change, and permafrost degradation based on the satellite data and related models during 2003-2013. The results indicated that their changing rates were 1.86 Gt/y, 0.22 Gt/y, and -0.19 Gt/y, respectively. We also calculated the change of groundwater based on the mass balance with a decreasing trend of -0.054 Gt/y. The results suggested that the cause of TWS change was the increase of LWS. We analyzed the cause of lake change according to water balance, and found that the primary cause of lake expansion was the increasing precipitation (80.7%), followed by glacier meltwater (10.3%) and permafrost degradation (9%). The spatial difference between LWS change and TWS change should be studied further, which is important to understand the driving mechanism of water resources change. 相似文献
325.
Physical model test is an effective way to unveil the dynamic response of a slope under seismic condition. The similarity design is the key of physical model test. An isolated similarity design method for shaking table tests was proposed and verified in this work. In this method, the relevant physical quantities were divided into several subsystems and subcharacteristic equations for each subsystem were then established based on the Buckingham similarity theory. Large-scale shaking table tests on a reinforced slope were adopted herein to illustrate the application of the proposed isolated similarity design method. The similarity system for the studied slope was divided into four parts in the process of similarity design. The geometrical dimension L, density ρ and gravity g were selected as fundamental quantities for the similarity design, and four subcharacteristic equations were established for each subsystem. The dynamic responses of the recorded acceleration and axis force show that the seismic waves propagate well in the model slope. The proposed isolated similarity design method solves the conflict between the similarity requirement for all relevant physical quantities and the difficulty of test model fabrication to satisfy all similarity relations. 相似文献
326.
HUANG Xiao-rong ZHOU Xing-yu YOU Jin-jun YANG Qing WANG Yan-jun MA Kai 《山地科学学报》2021,56(11):2971-2982
The Dujiangyan Project, located at the junction of the upstream of the Minjiang River and Chengdu Plain, Sichuan Province, China, is an irrigation system project as important as the Great Wall in the history of China. Without dam structures, this project has been continuously playing its crucial role in diverting water for irrigation, separating sediments, and controlling flood for 2275 years. In this study, the predicaments of the Dujiangyan Project under the background of rapid urbanization and social economic development were summarized by conducting the field research and using the Indicators of Hydrological alteration (IHA) method: excessive diversion of water, disruption of hydrological pulses, erosion and deposition imbalance and conflicts between power generation and water supply. These contradictions have led to the weakening of the function of automatic water diversion and sand removal in the Dujiangyan Project. Considering the influence of climate change and strong human activities, we pointed out the challenges faced by the millennium ancient weir in balancing human and environmental water usage and project operation and management based on the simulation results of the hydrological model. The corresponding suggestions about strengthening agricultural water saving, generating artificial flood peak were provided to protect and continue to maintain the function of the Dujiangyan Project. 相似文献
327.
袁长征;周成涛;王大涛 《测绘地理信息》2018,43(3):108-111
在介绍SENTINEL-1TOOLBOX(S1TBX)软件的主要功能和特点的基础上,对采用该软件进行InSAR(interferometicsyntheticapertureradar)数据处理的具体流程及相关原理进行了详细说明。以意大利西西里岛的埃特纳(Etna)火山地区的两景ERS-1/2影像为例,验证了S1TBX软件在InSAR数据处理中的可行性。 相似文献
328.
针对球形全景的匹配问题,提出了基于本质矩阵鲁棒估计的匹配方法。首先构建了球形全景的投影模型,通过推导球形全景的对极几何关系,得到本质矩阵的估计模型和对极线求解算法,再利用SIFT(scaleinvariantfeaturetransform)算法进行特征提取和匹配,最后采用RANSAC(randomsampleconsensus)算法,以改进的Sampson距离算子设置阈值,对本质矩阵进行鲁棒估计并剔除误匹配。实验结果表明,该方法切实可行,可提高球形全景匹配的精度。 相似文献
329.
利用三维地理信息技术、遥感技术建立数字地球模型,采用专题制图仪影像与三维高分辨率遥感影像结合方式进行遥感地质解译,描述了地质遥感影像特征,确定出山东省的旅游地质资源分布范围和具有开发远景的旅游地质资源十多处。建立了旅游地质资源管理信息系统,实现了三维多功能一体化管理与应用。为山东省旅游地质资源保护与开发及科学研究提供了详实可靠的参考依据。 相似文献
330.
熊朝晖;姚宜斌;袁德宝;刘磊;王亚 《测绘地理信息》2018,43(4):20-23
对于特定频率电磁波,电离层时间延迟与电子含量成正比,对电离层时间延迟建模即对电子密度建模。基于薄层模型假设,选用15阶球谐函数,将电离层划分为经度分辨率为5°、纬度分辨率5°的网格建模,反演格网电子密度,同时与CODE(centerorbitdeterminationEurope)产品比较,统计残差、评定精度。除此之外,分时间段统计2016-01海洋测高卫星Jason-2数据与模型数据间关联以求得相似比例因子k ,进而评估模型精度。电离层;时间延迟;总电子含量;海洋测高卫星 相似文献