Dynamic stiffness matrix of a poroelastic multi-layered site and its Green＇s functions   总被引：3，自引：1，他引：2  

梁建文  尤红兵 《地震工程与工程振动(英文版)》2004,3(2):273-282

Few studies of wave propagation in layered saturated soils have been reported in the literature. In this paper, a general solution of the equation of wave motion in saturated soils, based on one kind of practical Biot‘s equation,was deduced by introducing wave potentials. Then exact dynamic-stiffness matrices for a poroelastic soil layer and halfspace were derived, which extended Wolf‘s theory for an elastic layered site to the case of poroelasticity, thus resolving a fundamental problem in the field of wave propagation and soil-structure interaction in a poroelastic layered soil site. By using the integral transform method, Green‘s functions of horizontal and vertical uniformly distributed loads in a poroelastic layered soil site were given. Finally, the theory was verified by numerical examples and dynamic responses by comparing three different soil sites. This study has the following advantages: all parameters in the dynamic-stiffness matrices have explicitly physical meanings and the thickness of the sub-layers does not affect the precision of the calculation which is very convenient for engineering applications. The present theory can degenerate into Wolf‘s theory and yields numerical results approaching those for an ideal elastic layered site when porosity tends to zero.  相似文献   

Building extraction from DSM acquired by airborne 3D image     

YOU Hongjian LI Shukai 《地球空间信息科学学报》2003,6(3):25-31

1　IntroductionAutomaticbuildingextractionistheresearchfocustoobtainthree dimensional (3D)informationofcity .Therearetwomainapproachestoextractbuildingsbyremotesensing :oneisbasedonaerialphotosandtheotherisbasedonstereophotosordigitalsurfacemodels (DSM) .Man madebuildingsgenerallyhavesuchcharacteristicsaslimitedarea ,evidentandregularboundary ,heightdifferencebetweenbuildingandground ,etc .Somemethodsareproposedtoextractbuildingsbyusingremotesensingbasedonthesecharacteristics .Inthe 1 980s ,…  相似文献   

知识创新工程重大项目在大庆油田的技术成果要览   总被引：13，自引：8，他引：5  

李幼铭 《地球物理学进展》2003,18(1):5-18

在国家自然科学基金委员合和大庆油田的长期支持与资助下,我国陆相油储地球物理历经十余年的广泛探索,在理论认识上取得长足进步。据此,中国科学院第一批知识创新工程重大项目启动时,就以“油气勘探二次创业的前导研究”为题,列项研究。本文着重介绍在该重大项目推动下,近三年来参于大庆油气储量探到实践过程中,所摧熟的若干地球物理关键技术及软件系统功能。  相似文献   

Scattering of SV waves by a canyon in a fluid-saturated, poroelastic layered half-space, modeled using the indirect boundary element method     

Jianwen Liang  Hongbing You  Vincent W. Lee   《Soil Dynamics and Earthquake Engineering》2006,26(6-7):611-625

The scattering of SV waves by a canyon in a fluid-saturated, poroelastic layered half-space is modeled using the indirect boundary element method in the frequency domain. The free-field responses are calculated to determine the displacements and stresses at the surface of the canyon, and fictitious distributed loads are then applied at the surface of the canyon in the free field to calculate the Green's functions for displacements and stresses. The amplitudes of the fictitious distributed loads are determined from the boundary conditions, and the displacements arising from the waves in the free field and from the fictitious distributed loads are summed to obtain the solution. The effects of fluid saturation, boundary conditions, porosity, and soil layers on the surface displacement amplitudes and phase shifts are discussed, and some useful conclusions are obtained. It is shown that the surface displacement amplitudes due to saturation and boundary conditions, different porosities, or the presence of a soil layer can be very dissimilar, and large phase shifts can be observed. The resulting wavelengths for an undrained saturated poroelastic medium are slightly longer than those for a drained saturated poroelastic medium; and are longer for a drained saturated poroelastic medium than those for a dry poroelastic medium. As porosity increases, the wavelengths become longer; and a layered half-space produces longer wavelengths than a homogeneous half-space.  相似文献   

基于离散小波变换的油气检测技术   总被引：2，自引：2，他引：2  

周游  胡远来  王茂芝  王兰图 《物探化探计算技术》2006,28(2):98-100

小波变换的时频双重局部化特性，是处理非平稳地震信号的有效方法。尝试利用离散小波变换提取地震道信号的特征参数。并根据提取的小波参数，寻求其变化规律，从而直接进行油气检测。首先，在选择不同的小波母函数的基础上，对给定的地震道数据进行小波特征参数提取；最后对小波参数值进行分析、比较以优选油气识别的小波特征参数；然后进行小波特征参数的综合；再根据已知井位的油气属性，确定归类门槛值。通过研究认为，该方法具有可行性。  相似文献   

山东古代气候与海岸变迁     

毛晓平刘翠芝  卢友发 《河南气象》2006,(2):31-34

利用有关考古资料以及前人的研究成果,分析了山东地区气候与古代文化的关系以及气候对海岸变迁的影响。结果表明,距今8500~7500年,该地区曾经是气候温暖、水网密布的亚热带景观。这一时期,遗址附近有沼泽和大面积水域,山地有森林覆盖,反映为湿热的亚热带气候环境,其植被具有明显的草原特征。距今7500~6300年,气候较今日温暖湿润,山林灌木丛生,芦苇草地茂密,河谷湖泊发育,大致与现在长江流域的气候条件相似。距今6000~5500年,气候、地貌、自然景观与今日有别,气候温暖湿润,处于大西洋期,一般称之为气候最宜时期。气温高出现在4~5℃,降雨较目前多。植被以阔叶树种占优势,并含少量亚热带成分。森林茂密,草木繁茂,湖沼交错,水域面积较大。距今5000~4500年,气候温和略干,气温有所下降。距今4000年前后,总的气候趋势是向干凉方向发展,雨量减少,湖沼水域收缩,自然环境发生急剧变化,大规模的洪水和降温事件,使人类文明活动受到了极大的限制。这一显著变化,也说明自然环境对古代文化的形成、发展、消亡所产生的影响是十分巨大的。  相似文献   

邵武地磁新台建设磁场梯度跟踪测量     

李华  陈俊峰  陈宝根  游永平 《福建地震》2006,(Z1)

根据“地震及前兆数字观测技术规范”电磁部分的要求,在地磁台站建筑施工过程中,需用质子旋进磁力仪在现场对建筑物及周围磁场背景进行监测。本文介绍了邵武地磁新台建设过程中的一次磁场梯度跟踪测量情况。  相似文献   

Thickness and stable isotopic characteristics of modern seasonal climate-controlled sub-annual travertine laminas in a travertine-depositing stream at Baishuitai, SW China: implications for paleoclimate reconstruction   总被引：2，自引：0，他引：2  

Zaihua Liu  Hongchun Li  Chengfeng You  Naijung Wan  Hailong Sun 《Environmental Geology》2006,51(2):257-265

A continuous high-resolution (monthly) record of stable isotopes (δ¹³C and δ¹⁸O) in a well-laminated freshwater travertine deposited at Baishuitai, SW China from May 1998 to November 2001 was presented. The travertine exhibits clear annual bands with coupled brown/white color laminations. Throughout field investigation, it was found that the thin (1.5–2.2 mm), brown porous lamina was formed in the monsoonal rainy season from April to September, whereas the thick (5–8 mm), dense white lamina was formed in the dry season from October to March. The comparisons of lamina thickness and stable isotope signals in the travertine with the meteorological records allow us to constrain the relevant geochemical processes in the travertine formation under different climate conditions and to relate climate variables to their physicochemical proxies in the travertine record. Sympathetic variations in lamina thickness, δ¹³C and δ¹⁸O along the sampled profile reflect changes in hydrogeochemistry, showing that thin lamina and low δ¹³C and δ¹⁸O values occur in warm and rainy seasons. The decreased amount of calcite precipitation and low δ¹³C values during the warm and rainy seasons is caused by dilution of overland flow after rainfall. The low δ¹⁸O values are believed to be related to the rainfall amount effect in subtropical monsoonal regions. This process is thought to be markedly subdued whenever the amount of rainfall is lower than a given threshold. Accordingly, distinct minima in lamina thickness, δ¹³C and δ¹⁸O are interpreted to reflect events with above-average rainfall, possibly heavy floods, and vice versa. This study demonstrates the potential of freshwater travertine to provide valuable information on seasonal or even monthly rainfall variations.  相似文献   

交叉型报表技术在GIS中的应用     

万幼 《测绘信息与工程》2005,30(2):23-24

分析了交叉型报表模版单元的内部结构,探寻了将ＳＱＬ语句嵌入交叉型报表表模版的基本单元,实现了报表快速自动创建的技术。  相似文献   

Assessing the spatial distribution of crop areas using a cross-entropy method   总被引：1，自引：0，他引：1  

Liangzhi You  Stanley Wood 《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):310-323

While crop production statistics are reported on a geopolitical – often national – basis, we often need to know, for example, the status of production or productivity within specific sub-regions, watersheds, or agro-ecological zones. Such re-aggregations are typically made using expert judgments or simple area-weighting rules. We describe a new, entropy-based approach to the plausible estimates of the spatial distribution of crop areas. Using this approach tabular crop production statistics are blended judiciously with an array of other secondary data to assess the areas of specific crops within individual ‘pixels’—typically 25–100 km² in size. The information utilized includes crop production statistics, farming system characterization, satellite-based interpretation of land cover, biophysical crop suitability assessments, and population density. An application is presented in which Brazilian state level production statistics are used to generate pixel level crop area data for eight crops. To validate the spatial allocation we aggregated the pixel estimates to obtain synthetic estimates of municipality level areas in Brazil, and compared those estimates with actual municipality statistics. The approach produced extremely promising results. We then examined the robustness of these results compared to simplified approaches to spatializing crop production statistics and showed that, while computationally intensive, the cross-entropy method does provide more reliable spatial allocations.  相似文献