First-order reversal curve diagrams and thermal relaxation effects in magnetic particles   总被引：3，自引：0，他引：3  

Christopher R. Pike  rew P. Roberts  Kenneth L. Verosub 《Geophysical Journal International》2001,145(3):721-730

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The Fourier transform of controlled-source time-domain electromagnetic data by smooth spectrum inversion   总被引：1，自引：0，他引：1  

Yuji Mitsuhata  Toshihiro Uchida  Yutaka Murakami  Hiroshi Amano 《Geophysical Journal International》2001,144(1):123-135

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Fixed-Domain Asymptotics for Variograms Using Subsampling     

Montserrat Fuentes 《Mathematical Geology》2001,33(6):679-691

The variogram is a measure of the local variation in space of a random field. For large geostatistical data sets, the traditional empirical variogram may be hard to compute. This article presents, for processes with a fixed domain, the effect of using a subsample of the available data on the performance of the empirical variogram. The motivation of this work, apart from the saving on computation, is to study how dense the observations need to be in the bounded sampling region to obtain most of the information we would get from continuous observations in the fixed domain.  相似文献   

Effective multidimensional resistivity inversion using finite-element techniques   总被引：2，自引：0，他引：2  

Christopher C. Pain  Jörg V. Herwanger  Michael H. Worthington  Cassiano R. E. de Oliveira 《Geophysical Journal International》2002,151(3):710-728

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热带内外地区环流季内变化的相互作用特征──Ⅱ．数值试验研究     

余斌  黄荣辉 《大气科学》1996,(4)

在本研究第Ｉ部分工作的基础上，本文建立了一个二层非线性动力学谱模式，并对它实施了一组数值试验，进而从数值试验角度探讨了季内低频域中的环流、热带对流以及低频波流之间的相互作用特征。模式大气结果进一步证实了我们在本研究第三部分中提出的结论：热带地区低频热力作用对于热带内外地区环流间的相互影响起重要的衔接作用。  相似文献   

用功率谱时间函数识别地震前兆异常     

刘允秀  关华平 《地震》1996,16(4):337-346

多年的前净观测和地震预报实践表明，与前兆观测资料的噪声水平相比，中强地震的前兆信息多属弱信息，信息识别较为困难，用功率谱分析方法，将前兆观测时间函数分解为不同周期的谱密度随时间变化的多个时间函数，通过震例分析，探讨在强干扰背景下识别中强地震前兆信息的可能性。从识别中短期地震前兆这一基本目的出发，采用“数据窗”滑动采样的计算方法，满足不同周期对样本长度的要求，实现了频率域的计算结果在时间域具有一定密  相似文献   

塔里木盆地北部中新生代陆相沉积盆地层序地层特征     

张希明 《新疆地质》1996,(4)

塔里木盆地北部中新生代陆相沉积盆地层序的发育具有以下特点：构造活动控制了沉积层序的发育，层序具明显的旋回性；层序发育受构造运动影响完整性差；盆地边缘与腹地层序特征差异明显；海侵（泛）事件使层序内部结构更加复杂化。根据其特征建立了层序地层格架，共划分出４５个地震及测井层序。详细描述了层序的展布及结构特征，分析了体系域发育与储盖组合关系。  相似文献   

应用时域反射仪测定农田土壤水分   总被引：23，自引：0，他引：23       下载免费PDF全文

龚元石  李子忠 《水科学进展》1997,8(4):329-334

介绍了时域反射仪(TDR)测定农田土壤水分的方法及其应用,包括测定农田根系层土壤含水量和一定深度范围内土体贮水量,TDR自动、连续监测土壤水分,用TDR实测土壤水分来估算作物不同生长发育期内农田实际蒸散量以及用于探讨农田水分空间变异性。还对TDR、中子仪和土钻法测定的土壤含水量进行了比较,结果表明,应用TDR测定农田土壤水分要优于中子仪和土钻法。  相似文献   

Time domain scattering of acoustic plane waves by vertical faults     

Edson E. S. Sampaio  Mikhail M. Popov 《Pure and Applied Geophysics》1996,148(1-2):95-112

Acoustic plane wave scattering at a vertical fault structure represents the simplest two-dimensional model of geophysical exploration that can be investigated by analytical techniques. The exact and complete solution, in the time domain, for the scattering of the pressure field of an acoustic plane wave normally incident on a vertical fault structure is determined adapting previous results given for the frequency domain. The wave form of the pressure field of the incident plane wave is expressed by a causal time function that decays exponentially with time at every point above the fault (z<0). The zero-order term of the scattered pressure field has been computed above the fault. This zero-order term consists of an inverse Fourier transform which reduces to a closed expression forx=0, and contains an integral of a Hankel function forx#0. The high frequency part of the inverse Fourier transform forx#0 is computed employing asymptotic expressions for the Hankel function. The integral of the asymptotic expression of the Hankel function reduces to: (i) a Fresnel integral which contains a plane wave term for |x||z|; and (ii) a stationary point plane wave term plus an upper limit term for |x|=O(|z|). For the latter case the plane wave term cancels, leaving a cylindrical wave emanated from the edge of the fault. The wave front is well defined in shape, in phase and in amplitude. The amplitude of the scattered field is discontinuous atx=0, presents a jump and is well defined for |x| small and is rather smooth for |x| large.  相似文献   

A comparative linear and nonlinear ship motion study using 3-D time domain methods     

S.P. Singh  Debabrata Sen   《Ocean Engineering》2007,34(13):1863-1881

This paper reports on 3D time domain seakeeping computations at different level of modeling of nonlinear effects. Four successively improved levels of computations are considered: (i) a linear computation, (ii) Froude-Krylov nonlinear computation, (iii) body nonlinear computation where the perturbation potential is computed based on the instantaneous hull under the mean free-surface, and finally (iv) the body-exact nonlinear computation, where the perturbation potential is determined based on the wetted hull under the incident wave profile after suitable mapping of the hull into a computational domain. Computations are carried out for a Wigley hull (having less ‘geometric’ nonlinearity due to vertical sides), and a S175 hull at different forward speeds. The results are obtained for both regular and irregular waves.  相似文献