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目前,对于可控源电磁法各向异性介质2.5维问题,主要采用一次场、二次场分离的方法消除场源奇异性并降低截断边界对计算区域的影响.该方法数值计算精度高,但是很难适用于复杂地形条件下的数值模拟.针对复杂地形问题,基于总场的有限元方法表现出一定的优越性,然而,这种方法存在场源奇异性问题和截断边界问题.本文采用基于总场计算的方法对带地形的可控源电磁法2.5维各向异性介质进行模拟研究,推导了考虑电导率和介电常数各向异性的2.5维控制方程;引入网格加密-收缩算法降低场源奇异性的影响范围,提升数值计算效率;引入行波分解边界条件降低截断边界的影响;提出任意采样反傅里叶变换方法,快速、高精度地计算出空间域电磁场分量.理论模型数值算例中:首先,验证了本文算法的有效性;其次,对任意各向异性倾角产生的可控源电磁响应规律进行研究;最后,采用山丘模型对各向异性介质电磁场的响应规律进行了模拟和分析. 相似文献
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A manual SPME method is presented for the analysis of organic compounds in industrial wastewater. 24 compounds commonly found in the wastewater of a chemical plant in northern Germany have been selected as reference compounds. Precision, linearity, and detection limits have been determined. Moreover, the effect of methanol content, pH value, salt content, and an excess of compounds on the extraction process have been studied. Several compounds have been investigated for their applicability as internal standards to quantify the compounds of interest. Since the method will later be transferred to a fully automated SPME-GC system, which will be operated directly on-site at an industrial wastewater purification plant, special attention has been paid to the analysis of real wastewater samples. In this context, the fibre stability has been studied by performing 53 extraction/desorption cycles from one wastewater sample. Neither a decrease in fibre performance nor in precision has been observed indicating that the proposed method is suitable for the analysis of real wastewater. 相似文献
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浅层地震勘探在工程勘察中的应用 总被引:3,自引:0,他引:3
根据地震波传播的基本理论,首先详细论述了各种波传播的特点,然后根据各种波的特点,论述了各种勘探方法--浅层反射波法、浅层折射波法、回折波剖面法及PS速度测井等方法的应用前提、应用范围及野外工作方法。并结合本单位近几年的工作成果,对一些应用实例进行了讨论。该方法在实际应用中解决了许多地质及工程问题,为城市地城小区划及建筑工程场地的选址提供了必要的参考资料,取得了较好的效果。 相似文献
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A. BurmanParsuram Nayak P. AgrawalDamodar Maity 《Soil Dynamics and Earthquake Engineering》2012,34(1):62-68
A time domain transient analysis of a concrete gravity dam and its foundation has been carried out in a coupled manner using finite element technique and the effect of Soil-Structure Interaction (SSI) has been incorporated using a simplified direct method. A two dimensional plane strain dam-foundation model has been used for the time history analysis to compute the stresses and displacements against earthquake loading considering the effect of soil-structure interaction. An effective boundary condition has been implemented by attaching dashpots to the vertical boundaries. The material damping effects have also been considered and the dam and foundation have both been modeled as linear, elastic materials. To achieve a greater degree of accuracy, the displacements and stresses calculated in the free-field analysis have also been added to those developed in the complete dam-foundation analysis. The proposed algorithm has been simulated for the case of two published problems and in both the cases the results have been found to be in close agreement. The proposed technique is quite simple and easy to implement in the computer code. The outcomes of the results show the efficacy of the developed method. 相似文献
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The decrease of density contrast in sedimentary strata may be approximated by a quadratic function. A sedimentary basin may be considered as a number of horizontal polygonal prisms of finite thickness placed one over the other. Equations for the gravity anomaly of ann-sided polygon prism have been derived using a quadratic density function. A method has been developed for inversion of the gravity anomalies using a polygonal prismatic model. An analytical method has been employed for evaluating the necessary derivatives as the computing time by this method is much slower than by a numerical method. Approximate equations have been derived for rapid calculation of the anomalies and derivatives. Efficient computer programs have been developed for calculation of the anomalies and derivatives by an appropriate use of the exact and approximate equations. The depths to the polygon prisms constituting the basin are iteratively adjusted by minimizing the sum of the squares of the differences between the observed and calculated anomalies. These methods have been applied to analyze the Bouguer anomaly map of the Los Angeles basin, California. 相似文献
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本文根据P波初动方向来判断在同一次地震群中,最大的一次地震发生后,有一次或几次地震的P波初动方向会改变,由此可以判断主震已过。此方法简单明了,在有感地震发生后能随时判断以后的P波初动方向,一旦方向改变说明不会再有大地震来了。在临震监测预报中具有一定意义。 相似文献
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Max Wyss R. E. Habermann P. Bodin Carl Kisslinger R. O. Burford F. W. Klein A. C. Johnson Zhengxiang Fu 《Pure and Applied Geophysics》1997,149(1):79-113
Conclusions Several cases of extremely strong quiescences have been investigated in great detail, and it was found that they are statistically highly significant and that they cannot be reasonably explained by catalog heterogeneity. Several additional cases of quantitatively measured quiescence have been documented. The method of measuring quiescence has progressed from using visual means to using a quantitative approach, and the understanding of the noise sources has significantly advanced during the last few years. Therefore I feel that quiescence is a real phenomenon and the method to detect it has matured to a point that is acceptable for the List of Significant Precursors, although considerably more work needs to be done to understand this parameter and its role in the earthquake generation process. 相似文献
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Researchonearthquakepredictionfromgeomagneticpulsation周军成,韩克礼,王培德,鲁跃Jun-ChengZHOU;Ke-LiHAN;Pei-DeWANGandYueLU(InstituteofGeop... 相似文献
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A geophysical interpretative method is proposed to depth, amplitude coefficient and geometrical shape factor determination
of a buried structure from an observed gravity anomaly related to a cylinder or a sphere-like structure.The method is based
on nonlinearly constrained mathematical modelling and also on stochastic optimization approaches. The proposed interpretative
method first has been tested on theoretical synthetic models with different random errors at a certain depth, where a very
close agreement has been observed between assumed and evaluated parameters. Subsequent field data have been considered for
which the interpreted results by other methods are available for comparison. The agreement between the obtained results by
the proposed technique and by other geophysical methods is good. A statistical analysis has been also carried out to demonstrate
the accuracy and the precision of the suggested interpretative method. 相似文献
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Non dynamite seismic energy sources have shown only limited success in difficult shallow-water or marsh prospect areas, and none have applicability to both environments. Recently, a method has been devised to adapt a marine pneumatic source for operation in abrasive surroundings. A system composed of four of these modified sources together with associated emplacement and retrieval mechanisms has been developed and has proven to be a reliable and efficient seismic energy source for both shallow-water and marsh applications. 相似文献
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Summary The magnetic phases of natural pyrrhotites were studied by the method of powder patterns, the chemism of the magnetic phases by means of the electron microprobe method, and the crystal phases by etching the polished sections. The method of powder patterns distinguished the ferrimagnetic and antiferromagnetic phases in the transition-type pyrrhotites. The method of absorbed electrons lead to the discovery that both phases have a different chemical composition and that the ferrimagnetic phase has a lower denisty and an average atomic number. The linear and point-by-point analysis disclosed that the ferrimagnetic phase has a lower weight content of Fe and a higher weight content of S than the antiferromagnetic phase. Both the magnetic phases displayed different properties when etched, and therefore they not only have a different chemical composition, but also a different crystal structure. The necessity of studying the image of the absorbed electrons and the image of the etched surface of the polycrystalline samples of pyrrhotites of the transition type separately on individual grains was pointed out. 相似文献
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利用小波变换方法可以把原始信号分解为一系列载有不同信息的子信号,每种子信号载有储层的特定信息,包括流体、岩性和孔隙结构等。我们开发出了基于小波变换的谱分析方法,利用该方法可以从这些子信号中提取出反映地层流体特性的子信号,通过对该子信号的处理识别出地层所含流体的特性。本文利用该流体识别新方法对某油田的实际测井资料进行了处理,处理结果与试油结果符合得很好,进一步证明了本方法的可靠性和实用性。 相似文献
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Pu Wang R. Kahawita Professor of Mechanics Lenzhou University Lanzhou China. Professor of Civil Ensineering Ecole Polytechnique de Montreal Canada. 《国际泥沙研究》1990,(1)
I. INTRODUCTIONNumerical models of estuaries incorporating simulation of the density induced circulation are consideredimPOrtant tools in the assessment of their dispersive characteristics. Most models to date have used finite difference approximations to the governing equations (see for example thericke and Hogan, 1977, Blumberg,1 977, Perrels and Karelse, 1978). A numeriCal model of estuarine circulation using a SADI (Spline Alternating Direction implicit) procedure together with a… 相似文献
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Vijay Kumar Kalyani Amalendu Sinha Pallavika Swapan Kumar Chakraborty N. C. Mahanti 《Acta Geophysica》2008,56(4):1074-1089
Reported in the present paper are the results of the study of propagation of SH waves in the plane of mirror symmetry of a monoclinic multilayered medium with displacement normal to the plane. Dispersion equation has been obtained analytically ussing Haskell’s matrix method, while the finite-difference method has been employed to model the SH-wave propagation to study its phase and group velocities. The stability analysis has been carried out to minimize the exponential growth of the error of finite difference approximation in order to make the finite difference method stable and convergent. Further, variations of phase velocity with respect to both wave number and dispersion parameter for different stability ratios in monoclinic media have been examined and shown graphically. The effect of change of stability ratio on the group velocity of the wave propagation has been also investigated. Likewise, the effects of change of dispersion parameter on phase velocity and the variation of frequency with increase of wave number have been graphically represented and discussed. 相似文献