Study of the Earth’s free core nutation by tidal gravity data recorded with international superconducting gravimeters   总被引：2，自引：0，他引：2  

Jianqiao Xu  Heping Sun  Shaocong Luo 《中国科学D辑(英文版)》2002,45(4):337-347

By stacking high-precision tidal gravity observations obtained with superconducting gravimeters at six stations in China, Japan, Belgium, France, Germany and Finland, the local systematical discrepancies in the parameter fitting, caused by atmospheric, oceanic tidal loading and the other local environmental perturbations, are eliminated effectively. As a result, the resonance parameters of the Earth’s free core nutation are accurately determined. In this study, the eigenperiod of free core nutation is given as 429.0 sidereal days, which is in agreement with those published in the previous studies. It is about 30 sidereal days less than those calculated in theoretical models (about 460 sidereal days), which confirms the real ellipticity of the fluid core of the Earth to be about 5% larger than the one expected in assumption of hydrostatic equilibrium. The quality factor (Q value) of free core nutation is given as about 9543, which, compared with those determined before based on the body tide observations, is much larger, but more close to those obtained using the VLBI observations. The complex resonance strength is also determined as (−6.10×10⁻⁴, −0.01 ×10⁻⁴)°/h, which can principally describe the deformation characteristics of an anelastic mantle.  相似文献   

山东月湖的沉积物分布特征及搬运趋势   总被引：12，自引：0，他引：12  

薛允传  贾建军  高抒 《地理研究》2002,21(6):707-714

1998年 11～ 12月和 1999年 8～ 9月各一个月对月湖进行的野外工作 ,共取得表层沉积物样品 131个 ,应用激光粒度仪并结合传统的筛分法对这些样品进行粒度分析 ,进行矩法计算获得粒度参数。采用Gao命名方法 ,将沉积物划分出 5种主要类型。利用Gao -Collins粒径趋势分析模型 ,计算该区沉积物粒径趋势所显示的沉积物净搬运方向 ,结果表明 ,沉积物从四周向湖中心搬运 ,同时显示湾顶的西部和北部、涨潮三角洲以及湖心等地貌单元是沉积的优势区域。  相似文献   

Groundwater regime and calculation of yield response in North China Plain: a case study of Luancheng County in Hebei Province     

Jia Jin-sheng  Yu Jing-jie  Liu Chang-ming 《地理学报(英文版)》2002,12(2):217-225

The groundwater table has been declining at a rate of 0.65 m/yr in Luancheng County since large scale groundwater extraction carried out in the 1960s. The drop of precipitation, substantial increase in agricultural output, variations of crop planting structure and construction of water conservancy projects in the headwater area all tie up with the decline of the groundwater table. On the basis of analyzing the hydrogeological conditions and the water resources utilization of Luancheng County, a three-dimensional groundwater flow model was developed to simulate the county’s groundwater flow through finite-difference method using Visual Modflow software. We divide the research field into four parts after analyzing the hydrogeological condition. Based on parameter calibration and adjustment using measured data, the hydraulic conductivity and specific yield were simulated. Using the calibrated model, we analyze the agricultural water saving potentiality and its influence on the groundwater. The results are as follows: (1) if we decrease the amount of water extracted by 0.14xl0⁸ m³, the average groundwater table of the five observation wells in December will rise by 0.33 m; (2) if we decrease the water by 0.29x 10⁸m³, the average groundwater table of the five observation wells in December will rise by 0.64 m; and (3) if we increase the water by 0.29 x 10⁸m³, the average groundwater table of the five observation wells in December will decline by 0.45 m. So we can draw a conclusion that controlling the agricultural water use is an important way to prevent the decline of groundwater table.  相似文献   

Source scaling of intermediate-depth Vrancea earthquakes   总被引：3，自引：0，他引：3  

A. Gusev  M. Radulian  M. Rizescu  G. F. Panza 《Geophysical Journal International》2002,151(3):879-889

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Comparison of Earth-tide parameters over a large latitude difference     

D. Arabelos 《Geophysical Journal International》2002,151(3):950-956

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Implementing spectral leakage corrections in global surface wave tomography     

Jesper Spetzler  Jeannot Trampert 《Geophysical Journal International》2003,155(2):532-538

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大兴安岭浅覆盖区生态地质评价方法初探——以1∶25万区调呼中镇幅为例   总被引：1，自引：0，他引：1       下载免费PDF全文

马江水李仰春  任凤和尤福珍 李清伟 《中国地质》2003,30(3):330-336

通过野外调查，在收集统计大量基础地质、经济地质、环境地质、旅游地质、农(林)业地质等数据信息的基础上，在GIS技术指导下，采用定量定性相结合的半定量分析评价方法，对森林浅覆盖区生态地质现状及各类资源的开发利用潜力进行了综合评价。在研究和探讨森林浅覆盖区生态地质综合评价方法的基础上，提出了森林浅覆盖区生态地质评价模型，确定了综合参数，划分了生态地质类型。  相似文献   

影响新生界"底含"发育的因素及含水层参数修正   总被引：5，自引：1，他引：5  

许光泉  严家平  桂和荣 《煤田地质与勘探》2003,31(2):40-42

分析了“底含”发育的主要影响因素，并以祁东煤矿为例，利用地下水动力学方法重新计算了“底含”的有关参数，对以往抽水试验参数进行修正，并成功地运用到邻近矿井。该研究表明，在富水性较强的古河道发育位置，要合理留设防水煤岩柱，才能保证煤矿安全生产。  相似文献   

软土大变形固结计算中参数识别的遗传算法     

吴振君  施斌  亓军强 《水文地质工程地质》2003,30(4):35-38

含水量很高的饱和软土在外荷载作用下沉降很大,小变形分析误差太大,必须通过大变形非线性固结计算来模拟。遗传算法是一种全局优化和搜索的仿生算法。近年来随着工程领域中复杂的大规模非线性系统的出现,遗传算法日益得到青睐,目前已经广泛应用到各个领域中。本文对遗传算法做了改进,主要体现在杂交算子的选取和轮盘赌模型的模拟退火拉伸,并将其用于饱和软土的大变形固结分析,解决其中的关键参数识别问题。研究表明该方法是行之有效的,值得进一步研究探索。  相似文献   

实现数据库管理震源参数的探索     

张哲  李川君  陈景华  曾令国 《地震地磁观测与研究》2003,24(4):69-74

就如何利用数据库，结合Java、XML等手段对震源参数管理进行了一些探索，并给出了一些在一个实际系统中实现了的例子。  相似文献