Forward Modeling of Gravity, Gravity Gradients, and Magnetic Anomalies due to Complex Bodies

On the basis of the results of improved analytical expression of computation of gravity anomalies due to a homogeneous polyhedral body composed of polygonal facets, and applying the forward theory with the coordinate transformation of vectors and tensors, we deduced both the analytical expressions for gravity gradient tensors and for magnetic anomalies of a polygon, and obtained new analytical expressions for computing vertical gradients of gravity anomalies and vertical component of magnetic anomalies caused by a polyhedral body. And also we developed explicitly the complete unified expressions for the calculation of gravity anomalies, gravity gradient, and magnetic anomalies due to the homogeneous polyhedron. Furthermore, we deduced new analytical expressions for computing vertical gradients of gravity anomalies due to a finite rectangular prism by applying the newly obtained expressions for gravity gradient tensors due to a polyhedral target body. Comparison with forward calculation of models shows the correctness of these new expressions. It will reduce forward calculation time of gravity-magnetic anomalies and improve computational efficiency by applying our unified expressions for joint forward modeling of gravity-magnetic anomalies due to homogeneous polyhedral bodies.     

The development of stochastic space transformation and diagrammatic perturbation techniques in subsurface hydrology

This paper develops concepts and methods to study stochastic hydrologic models. Problems regarding the application of the existing stochastic approaches in the study of groundwater flow are acknowledged, and an attempt is made to develop efficient means for their solution. These problems include: the spatial multi-dimensionality of the differential equation models governing transport-type phenomena; physically unrealistic assumptions and approximations and the inadequacy of the ordinary perturbation techniques. Multi-dimensionality creates serious mathematical and technical difficulties in the stochastic analysis of groundwater flow, due to the need for large mesh sizes and the poorly conditioned matrices arising from numerical approximations. An alternative to the purely computational approach is to simplify the complex partial differential equations analytically. This can be achieved efficiently by means of a space transformation approach, which transforms the original multi-dimensional problem to a much simpler unidimensional space. The space transformation method is applied to stochastic partial differential equations whose coefficients are random functions of space and/or time. Such equations constitute an integral part of groundwater flow and solute transport. Ordinary perturbation methods for studying stochastic flow equations are in many cases physically inadequate and may lead to questionable approximations of the actual flow. To address these problems, a perturbation analysis based on Feynman-diagram expansions is proposed in this paper. This approach incorporates important information on spatial variability and fulfills essential physical requirements, both important advantages over ordinary hydrologic perturbation techniques. Moreover, the diagram-expansion approach reduces the original stochastic flow problem to a closed set of equations for the mean and the covariance function.     

南京地磁台地铁干扰特征分析与抑制处理

地铁运行时产生的漏电流而形成的附加磁场会对附近的地磁观测造成严重干扰。通过对地铁供电系统的模拟分析得出了地铁干扰的一些基本特征。选取了2008年5月1日到30日南京地磁台受地铁干扰的日变数据和泉州参考地磁台日变数据,利用Welch功率谱估计法进行功率谱对比分析,发现地铁干扰主要对地磁场的Z分量、D分量的功率谱的高频部分造成影响,并且影响的频带范围几乎一致,主要集中在0．004-0．03Hz范围,而对H分量的影响比较微弱。在此基础上,通过小波变换对受干扰数据的Z分量和D分量进行干扰抑制处理,处理结果表明该方法能够有效抑制地铁造成的地磁场干扰。因此本文研究也提供了地磁台站干扰抑制的一种方法。     

用EDAS-3型数据采集器对倾斜仪进行数字化改造

用EDAS-3型16位地震数据采集器和MDS-2710数传电台对克拉玛依地震台井下摆倾斜仪进行数字化遥测改造.结合改造实例,详细介绍了新观测系统的实现方法和应用效果,提出一套完整的解决方案.改造后的新观测系统的工作范围、采样率和测量精度均高于国家行业标准,工作稳定可靠.     

Derivation and assessment of a bivariate IDF relationship using paired rainfall intensity–duration data

A procedure is presented for developing a rainfall intensity–duration–frequency (IDF) relationship that is consistent with bivariate normal distribution modeling. The Box–Cox transformation was used to derive the relation and two methods of determining the parameters of this transformation were evaluated. To assess the uncertainty of the parameters, a confidence interval was constructed and verified with the non-parametric bootstrap method. Additionally, the effect of sample size on the bivariate normality assumption was examined. Case studies, based on data from significant gauge stations in Korea, were performed. The result shows that the use of the bivariate normal model as an IDF relationship is particularly recommended when the available data size is small.     

Chaotic dynamics analysis and control of iterative procedure of capacity spectrum method

The capacity spectrum method (CSM), capable of predicting the demands of forces and deformations of the inelastic system, has been applied in the ATC and FEMA guidelines. The deformation of an inelastic system is solved iteratively by using the equivalent linearization for CSM, which actually forms a nonlinear map or discrete dynamical system. However, the iterative procedure of CSM did not converge for some inelastic systems, and the complicated dynamical phenomena for the solutions such as the periodic oscillation, period-doubling bifurcation and chaos may occur, which were shown in the bifurcation plots of iterative map of the simplified CSM in ATC40 and FEMA440. This paper presents a novel method to analyze and control the non-convergence of the iterative procedure of CSM from the perspective of chaotic dynamics. The Lyapunov exponent of the dynamical system is employed to identify the evolutional state and stability of solutions. Finally, the stability transformation method as a simple, versatile and effective chaos feedback control approach is applied to control the convergent failure of CSM in ATC40 and FEMA440. The numerical results illustrate that the stability transformation method can capture the desired fixed points of the dynamical system and obtain the stable convergent solutions of CSM.     

智能互联重塑中国能源体系

随着第五代移动通信(5G)技术的突破、推广与应用,世界逐渐进入智能互联时代.在此背景下,本研究以能源系统分析模型(G C A M)为基础,设计和模拟基准与智能互联情景,探索在智能互联技术加快突破的情况下我国能源转型发展道路.研究发现,与基准情景比较,智能互联情景下能源结构更加清洁,能源系统更加高效,2050年一次能源消...     

浅谈延庆地震台地电阻率观测系统改造

分析了延庆地震台地电阻率观测中存在的干扰因素，以此说明观测系统进行改造的必要性，介绍了电极和外线路改造的过程和技术环节，通过改造前后观测资料的对比分析对改造的效果进行了评价。     

青藏高原水体碳源汇过程的重新认知与挑战

陆地-大气和陆地-水体的碳输送与碳交换共同决定了陆地生态系统的碳平衡,但长期以来青藏高原水体由于缺乏有效的观测数据,导致青藏高原水体一直是全球碳循环研究中被忽视的碳汇功能区。本研究聚焦青藏高原水体,重新认知水体碳侵蚀与碳沉积对青藏高原固碳的重要作用,系统分析河湖库-大气间的碳运移与交换时空格局与驱动机制。通过归纳总结发现:(1)青藏高原河流岩石风化速率以及CO₂消耗速率较高,强烈的侵蚀作用对地球系统吸收和平衡CO₂浓度起着重要的调控作用;(2)青藏高原湖泊是内陆生态系统的重要碳库,12 ka以来湖泊沉积物碳储量约为73 kg C/m²;(3)青藏高原湖泊浮游植物和水生植物影响内陆水体C沉积,年均初级生产力达(553±36) mg C/(m²·d)。(4)青藏高原湖泊目前为“碳源”,碳排放量约为2.27 Tg C/a。此外,本文还阐明青藏高原水体碳源汇过程评估的不确定性,以及从方法学角度分析如何加强其水体的碳循环研究,厘清全球变化下青藏高原水体的碳源汇机制,并展望了青藏高原水体碳源汇功能未来研究所面临...     

利用数字化速度记录仿真加速度时程与合成场地设计地震波

研究利用测震台网数字化宽频带速度型记录仿真加速度时程,并通过提取其相位信息和拟合场地设计反应谱(目标谱)的方法来获得场地设计地震波的有关技术途径与应用实例,所提供的具体算式采用便于编程和利用快速傅氏变换(FFT)技术进行计算的离散化傅氏正逆变换的复数表达式。有关研究结果可拓宽现有地震观测资料的使用价值,减少地面运动模拟中人造地震波与原始地震记录存在的差异,并可使所合成的设计地震波满足给定的目标谱,且能较好地反映其非平稳性特征,因此在地震工程中具有实际的应用价值。