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11.
本文提出了从栅格数据直接建立拓扑关系的思想,用跟踪过程中容易获得的拓扑信息来优化拓扑生成的算法模型,借以提高拓扑生成的效率。本文还提出用连通性区域填充的方法处理各种任意复杂岛的思想。 相似文献
12.
详细讨论了利用联测IGS跟踪站提高GPS区域控制网起算数据精度的方法,并介绍了将区域控制网框架和国际地球参考框架ITRF2000相连的方法,探讨了联测IGS跟踪站时应注意的事项,并根据实例对采用联测IGS跟踪站后对GPS网起算点的精度影响进行分析. 相似文献
13.
累积危险度的动态演化及其与强震的关系 总被引：2，自引：0，他引：2
完善了累积危险度的强震危险地点跟踪预测方法,并对１９８９看以来首都圈及邻近地区累积危险度的演化进行了分析。结果表明,累积危险度的演化过程,反映了地震孕育及构造应力活动的过程;２次６级地震前,均出现累积危险度数值增大,震后扩散－消退;累积危险度高值区及其边缘地国可能发震地点。 相似文献
14.
Non-linear Technique for Abstracting the Non-metallic Pipeline Image from GPR Section 相似文献
15.
William Sidle 《Environmental Geology》2009,57(2):377-388
Recent identification of elevated excess 210Pb (≤302.6 mBq L−1) and 137Cs (≤111.3 mBq L−1) activity in drinking water wells up to 20 m depth indicates some transport of airborne radionuclide fallout beyond soils
in the Shaker Village catchment, Maine. Estimated airborne mass loading 210Pbex fluxes of about 0.9 mBq m−3, canvass this headwater catchment and may be sufficient to pose risks to unprotected shallow wells. Inventories of 210Pbex and 137Cs in pond sediments indicate maximum median activities of 943 mBq g−1 and 40.0 mBq g−1, respectively. Calculated 210Pbex fluxes in the catchment soils range from 0.62–0.78 Bq cm−2 year−1 and yield a mean residence time of near 140 years. Measured 137Cs activity up to 51.1 mBq g−1 occurs in sediments at least to 5 m depth. Assumed particle transport in groundwater with apparent 85Kr ages less than 5 years BP (2005) may explain the correlation between these particle-reactive radionuclides and elevated
activity in some drinking water wells. 相似文献
16.
地表温度是地质学、水文学和陆面过程研究中的重要参数.由于地表的三维结构和异质性,大部分不同类型陆地表面均存在不同程度热辐射方向性现象.总结了基于真实结构的地表热辐射方向性计算机模型研究进展,归纳了真实结构模型中蒙特卡罗光线追踪法和辐射度方法的理论基础,阐明了两种方法的区别和联系,并从理论和物理意义上分别推导和阐释了其与几何光学模型及辐射传输模型的关系,指出了真实结构模型在算法效率、非同温系统蒙特卡罗模拟、参数获取、模型反演和应用等方面存在的主要问题,并展望了其在未来的发展趋势. 相似文献
17.
Slovenia's main military training area at Poček is located in the mountainous Javorniki Watershed. This is a karstic district
without surface drainage or river valleys. The typical landscapes are conical hills and plateaus with many dolines. The lithology,
tectonic structure and speleological data indicate a typical karst aquifer with underground water moving rapidly through fissures
and conduits. Little attenuation occurs in such conditions and as a result there is a high risk of pollution. Tracer tests
have shown that a significant proportion of the water recharging the Malni and Vipava springs comes from the vicinity of the
military training area. As a result any polluting activities taking place within the military training area are likely to
affect the two springs. This is a very serious matter as the springs have been developed to provide the water supply for the
population of south-western Slovenia.
Received: 20 April 1998 · Accepted: 24 August 1998 相似文献
18.
Delineation of groundwater protection zones based on tracer tests and transport modeling in alluvial sediments 总被引：1，自引：0，他引：1
Regulations aiming to protect exploitable groundwater resources were edicted in Belgium a few years ago. Therefore, prevention
and protection zones are defined by law and must be determined practically around each pumping well or spring, based on local
hydrogeological conditions. The determination of hydrodynamic and hydrodispersive parameters, characterizing the local flow
and transport properties of the aquifer, requires pumping and tracing tests. The interpretation of these field experiments,
considering the heterogeneity of the geological layers, is performed through the use of numerical FEM simulations of the groundwater
flow and pollutant transport conditions in a deterministic framework. After calibration of the model on experimental measurements,
multiple simulations with contaminant injections at various points of the modeled domain allow the determination of the transfer
time of the pollutant in the studied aquifer whilst taking the updated heterogeneity into account. On the basis of the computed
transfer times in the saturated zone, the various prevention and protection areas can be assessed based on provisions of the
law.
Received: 27 June 1997 · Accepted: 29 July 1997 相似文献
19.
石墨Re-Os同位素分析及其在成矿年代学中的初步运用 总被引：4，自引：0，他引：4
本文探索性地对江西省铅山县长寿源铅锌共生的晶质石墨进行了Re-Os同位素分析。研究结果显示石墨的Re-Os同位素年龄为424±25Ma(n=7,MSWD=7.8),与该区二云二长花岗岩中锆石的年龄(433±9Ma)在误差范围内相一致,说明石墨的成因与区域上岩浆的侵入存在密切联系。Re的含量介于47×10-9～330×10-9之间,普通Os和187Os的含量分别为0.32×10-9～2.15×10-9和0.27×10-9～1.75×10-9,相对于Re、Os在地壳中的丰度显著富集,Os同位素初始比值187Os/188Os=1.69±0.29,表明石墨来源于富有机质沉积地层。通过测定石墨样品中的有机碳和固定碳,对Re、Os在石墨中的赋存状态进行了研究,表明Re、Os可能是以某种形式赋存在石墨的固定碳中,与其中有机质无关。从原理上解释了石墨的Re-Os同位素年龄反映的是使沉积地层中的炭质变质为石墨,并发生富集迁移的岩浆热变质事件的时期。研究表明石墨的Re-Os同位素分析技术不仅能够为变质作用时间的精确测定提供新的方法,而且对矿床成因的研究也具有重要意义。 相似文献
20.
Cheng Kueihsiang 《中国地震研究》2003,17(1):85-96
The data of earthquakes with M≥3.0 during the 7 years from September 21, 1993 to September 20, 2000 recorded by the Taiwan Central Weather Bureau (CWB) show that there were 6 types of clear characteristics of seismicity during the Chi-Chi strong earthquake swarm of September 21. These 6 types of characteristics are (1) foreshock types, (2) seismic gaps, (3) seismic bands, (4) clustering activity of foreshocks and signal shock, (5) quiescence before the main shock and (6) secondary aftershocks in the aftershock sequence. Using the procedures for analyzing the yearly strong earthquake tendency, further tracing based on the earthquake sequence characteristics, and taking the Chi-Chi earthquake sequence as an example, tracing analysis of the earthquake tendency was attempted using the shorter time range of monthly rather than in a yearly time scale. An attempt was made to establish the procedures for tracing analysis of shallow-focus earthquakes in the seismic belt of western Taiwan. It is hoped that this can provide an analystical method for approaching the short-imminent time scale of seismometry-based earthquake forecasting. 相似文献