交会法测定像控点的测角精度     

夏尚坤 《华东地质学院学报》1987,(3)

本文主要讨论1:1.6万航空像片测制1:2000地形图时,用交会法测定像控点的精度问题.按现行规范的规定不能满足1:2000测图精度要求。为保证连测的像控点精度的可靠性,本文提出了按交会基线长度和交会图形强度,增加适当测回数,提高测角精度的方法。  相似文献   

Uplift capacity of single piles: predictions and performance   总被引：4，自引：0，他引：4  

K. Shanker  P. K. Basudhar  N. R. Patra 《Geotechnical and Geological Engineering》2007,25(2):151-161

The paper pertains to the development of a simple semi-empirical model for predicting the uplift capacity of piles embedded in sand. Various pile and soil parameters such as length (L), diameter (d) of the pile and angle of friction (ϕ), soil–pile friction angle (δ) and unit weight (γ) of the soil which have direct influence on the uplift capacity of the pile are incorporated in the analysis. A comparative assessment of the ultimate uplift capacity of piles predicted by using the proposed theory and some of the available theories are made with respect to each other and with reference to the measured values obtained from model tests in the laboratory. For this purpose experimental data have been collected from the literature and also from model tests conducted as a part of the present investigation. The study shows the proposed model has an excellent potential in predicting the uplift capacity of piles embedded in sand that are consistent with model pile test results.  相似文献   

基于光谱角匹配预测的高光谱图像无损压缩   总被引：1，自引：0，他引：1  

陈亮  刘代志  黄世奇 《地球物理学报》2007,50(6):1894-1898

在地表信息获取方面，高光谱遥感是对地观测技术的主要方法，观测同时产生了海量高光谱图像的存贮与传输问题.研究发现，高光谱图像具有独特的光谱上下文特征，可从光谱维分析高光谱图像的光谱相关性，并用光谱角来度量相邻像素间的光谱相似性的差异，探测水平或垂直光谱边界，由此提出了基于光谱角匹配预测(SAMP)的无损压缩算法.实验表明，SAMP算法的预测效果好于已有文献中提出的一些优秀算法，且具有低复杂性.  相似文献   

STABILITY ANALYSIS OF RIVERBANK SUBJECT TO SEEPAGE     

Yan LU Yongjun LU Xingnong ZHANG 《国际泥沙研究》2007,22(4):282-291

The stability of riverbanks subject to seepage is studied experimentally and theoretically in this paper. By including seepage in a 3-dimensional theoretical analysis, the study first shows how the critical slope or angle of repose of a cohesionless material is related to the ratio of the hydraulic gradient of seepage to its critical value under the fluidization condition. The critical stable slope is shown to be related to not only the hydraulic gradient but also the seepage direction. Measured laboratory data reasonably fit well with the theoretical relationship for the case of injection and suction. The data reveal that the slope is reduced with injection and increased with suction, respectively. Additionally, the study identifies the seepage direction which results in a minimum critical stable slope for a certain hydraulic gradient of seepage.  相似文献   

Direct measurement of crustalP-velocities in the norsar area     

K. A. Berteussen 《Pure and Applied Geophysics》1977,115(3):707-719

Using simulated data, it is demonstrated that one may estimate the body wave velocity in the crust by measuring the angle of incidence ofP-waves provided only the very first part of the signal is used. This angle has been measured for a set ofP-waves at the NORSAR long period instrument sites. Combining these observations with measurements of apparent velocities, we find that the data indicates a crust velocity of 6.1±0.4 km/sec. While it is somewhat uncertain to what depth the value is representative, the observations are in obvious disagreement with previous authors who concluded that long periodP-waves were not affected by the earth's crust. Because of difficulties in separating the effects of real velocity variations from measurement errors, the details of the observedP-wave variation across the array are difficult to interpret. The consistent behavior of the data does, however, indicate that variations of approximately 3% must exist in the crustalP-wave velocity across the array.  相似文献   

地形对碎屑流冲出的影响作用(英文)     

苏志满  鵜飼惠三  杨情情  蔡飞  徐林荣 《地震工程学报》2011,33(Z1)

传统的碎屑流冲出预测经验模型主要基于冲出物体积与冲出物到达角的假设关系式,并没有考虑地形的影响,其中到达角指滑坡后壁顶点与堆积体末端点连线的角度。本文通过小尺寸模型槽实验研究不同地形条件对碎屑流冲出的影响,发现冲出路径上的缓地形将增加到达角,对近期的两个地震诱发型碎屑流场点的调查结果也表明了缓地形对到达角的影响。还发现冲出物受地形限制而改变冲出方向时可能增加冲出角。考虑上述两种地形约束作用的冲出距离预测值将小于传统的预测方法。  相似文献   

波动方程偏移速度建模:一种直接反演方法   总被引：1，自引：1，他引：0       下载免费PDF全文

张江杰  张剑锋 《地球物理学报》2011,54(3):835-844

基于炮域波动方程叠前深度偏移所产出的角道集,发展了不需要多次迭代的波动方程偏移速度建模方法.文中分析了炮域波动方程偏移生成角道集的方法,给出了非均匀介质中角道集同相轴曲率与速度误差的定量关系,发展了基于同相轴曲率的速度模型直接更新算法.在初始模型较合理的情况下,应用一次炮域波动方程偏移计算,即可得到较准确的速度模型.这...  相似文献   

Angle gathers in wave‐equation imaging for transversely isotropic media     

Tariq Alkhalifah  Sergey Fomel 《Geophysical Prospecting》2011,59(3):422-431

In recent years, wave‐equation imaged data are often presented in common‐image angle‐domain gathers as a decomposition in the scattering angle at the reflector, which provide a natural access to analysing migration velocities and amplitudes. In the case of anisotropic media, the importance of angle gathers is enhanced by the need to properly estimate multiple anisotropic parameters for a proper representation of the medium. We extract angle gathers for each downward‐continuation step from converting offset‐frequency planes into angle‐frequency planes simultaneously with applying the imaging condition in a transversely isotropic with a vertical symmetry axis (VTI) medium. The analytic equations, though cumbersome, are exact within the framework of the acoustic approximation. They are also easily programmable and show that angle gather mapping in the case of anisotropic media differs from its isotropic counterpart, with the difference depending mainly on the strength of anisotropy. Synthetic examples demonstrate the importance of including anisotropy in the angle gather generation as mapping of the energy is negatively altered otherwise. In the case of a titled axis of symmetry (TTI), the same VTI formulation is applicable but requires a rotation of the wavenumbers.  相似文献   

Shear wave splitting in the Isparta angle,southwestern Turkey: Anisotropic complexity in the mantle     

Aslihan Şapaş  Aysun Boztepe-Güney 《Journal of Earth System Science》2009,118(1):71-80

This study presents shear wave splitting analysis results observed at ISP (Isparta) broadband station in the Isparta Angle, southwestern Turkey. We selected 21 good quality seismic events out of nearly 357 earthquakes and calculated splitting parameters (polarization direction of fast wave, ϕ and delay time between fast and slow waves, δt) from mainly SKS and a few SKKS phases of the selected 21 seismic events. Then, we compared calculated splitting parameters at ISP station (56° ≤ ϕ ≤ 205°; 0.37 s ≤ δt ≤ 4 s) with those previously calculated at ANTO (Ankara) and ISK (İstanbul) stations (27° ≤ ϕ ≤ 59°; 0.6 s ≤ δt ≤ 2.4 s and 26° ≤ ϕ ≤ 54°; 0.6 s ≤ δt ≤ 1.5 s) which are located at 230 and 379 km away from ISP station in central and northwestern Turkey, respectively. The backazimuthal variations of the splitting parameters at ISP station indicate a different and complex mantle polarization anisotropy for the Isparta Angle in southwestern Turkey compared to those obtained for Ankara and İstanbul stations.  相似文献   

抚仙湖流域不同农业模式砾质土壤环境质量及其氮磷流失风险评估   总被引：3，自引：2，他引：1  

夏天翔  李文朝  潘继征 《湖泊科学》2008,20(1):110-116

于2006年8月分层采集抚仙湖流域有机及传统农业农田砾质土壤,对土壤样品的机械组成、重金属含量、养分剖面积累进行测定分析;通过室内降雨模拟,对不同土壤样品氮磷流失风险进行评估.结果表明:①有机及传统农业模式下,砾质土壤机械组成发生明显变化,0-20cm土层砂粒含量明显降低:②除传统农业土壤Cd为二级标准,其他土壤重金属含量均符合国家土壤环境质量(GB/15618-1995)一级标准:③有机及传统农业模式下0-20cm土层有机质、全氮养分明显积累,但不同农业模式问无明显差异:有机农业土壤全磷、水溶性氮磷积累程度显著高于传统农业土壤;④有机农业土壤在780mm模拟降雨条件下,氮、磷流失风险更大,氮、磷流失总量分别是传统农业土壤的1.9倍、19.8倍.  相似文献