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Numerical modeling of geothermal groundwater flow in karst aquifer system in eastern Weibei,Shaanxi Province,China

The quantitative assessment of geothermal water resources is important to the exploitation and utilization of geothermal resources. In the geothermal water systems the density of groundwater changes with the temperature, therefore the variations in hydraulic heads and temperatures are very complicated. A three-dimensional density-dependent model coupling the groundwater flow and heat transport is established and used to simulate the geothermal water flow in the karst aquifers in eastern Weibei, Shaanxi Province, China. The multilayered karst aquifer system in the study area is cut by some major faults which control the regional groundwater flow. In order to calibrate and simulate the effect of the major faults, each fault is discretized as a belt of elements with special hydrological parameters in the numerical model. The groundwater dating data are used to be integrated with the groundwater flow pattern and calibrate the model. Simulation results show that the calculated hydraulic heads and temperature fit with the observed data well.

     

Multi-directional transmitting boundaries for steady-state SH waves

The incident steady-state SH waves in the neighbourhood of a boundary node point are first expanded in terms of a few plane waves at different incident angles, the motion of the boundary point is then related to those of its adjacent node points to form the multi-directional transmitting boundary conditions, which reduce reflections from the boundary over the entire range of incident angles. This feature of the boundaries is demonstrated by finite element computations of SH motions of a layer fixed at its base, in which the incident wave may travel parallel to the boundary as the frequency of excitation approaches one of the natural frequencies of the system.     

辛算法在动力天文中的应用（Ⅲ）

文［１］和文［２］从哈密顿系统的整体结构保持一角度阐明了辛算法［３－６］的主要功能，本文将从定量的角度进一步表明辛算法的另一独特优点－可以控制天体运动沿迹误差的快速增长，并对可分离哈密顿系统的显式辛差分格式稍加改进，推广应用到一般动力系统，该系统含有小耗散项或小的不可分离项，计算结果表明，效果极佳，因此，辛算法与传统的数值解法相比，确有很多优点。     

地球自转动力学中的两个问题

介绍了地球自动力学中的两个目前正在研究的问题，1．Chandler摆动的随机激发，在分析Chandler摆动各种激发的可能性后，认为随机运动是最可能的激发源，在此基础,提出了一个Chandler摆动激发的动力学模型，并从理论和数值模拟两方面对此模型做了统计分析研究，描述了今后对此问题的研究思路，2．地球内部动力学是目前国际地球动力学界的一个热点研究课题，介绍了它的现状和最近的发展动态以及准备在这方面开展研究工作的打算。     

黄骅坳陷中区古近系东营组沉积特征及有利勘探区带预测*

综合岩心、钻井、地震等资料,运用层序地层学、现代沉积学的思路和方法,对黄骅坳陷中区古近系东营组的沉积体系特征进行了分析,指出东营组沉积时期处于盆地断—拗转化阶段,主要发育湖泊三角洲和湖泊体系,局部地区发育扇三角洲和浊积体系等。沉积体系的时空分布和演化特征受控于构造背景和层序结构样式的差异,表现为东三段层序（SQEd3）以低位域三角洲和范围扩大的高位域三角洲为主;东二段层序（SQEd2）、东一下段层序（SQEd1x）以板桥次凹等局部地区发育的低位域三角洲和普遍发育的高位域三角洲为主;东一上段层序（SQEd1s）低位域三角洲和高位域三角洲主要分布于歧南次凹和歧北次凹,总体形成了缓坡背景、断控斜坡背景和多级断阶背景下的3类沉积模式。基于上述研究,认为研究区发育5类有利圈闭区：坡折带附近的隐蔽圈闭区、越过凹陷中心的上超尖灭圈闭区、构造—岩性复合圈闭区、低位域和高位域浊积砂体形成的岩性圈闭区、下切谷充填岩性圈闭区,构成了6个有利的勘探区带,这对于指导研究区东营组的油气勘探具有重要意义。     

Variability of the currents in the Luzon Strait during spring of 2002 obtained from observations and satellite geostrophic currents and spectral analyses

The structure and variability of the currents in the Luzon Strait during spring of 2002 are studied, based on the current measurements at the average position of the mooring station (20°49′57"N, 120°48′12"E) from March 17 to April 15, 2002, satellite geostrophic currents in the Luzon Strait, and the spectral analyses, using the maximum entropy method. The subtidal currents at the mooring station show de-creased amplitudes downward with an anti-cyclonic rotation, suggesting that the currents enter and exit t...     

二维频率空间域25点优化系数差分格式弹性波数值模拟(英文)

频率空间域地震波数值模拟具有独特的优势:可以同时模拟多源的波传播、每个频率之间独立并行地计算、计算频带选择灵活、不存在累计误差、容易模拟粘弹性介质中地震波传播.但是该方法的最大瓶颈是对于计算机内存的巨大需求.我们使用压缩存储系数矩阵的方法,极大地减少了计算机内存的需求量.同时为了减少短筹分算子的数值频散,引用了频率空间域25点弹性波波动方程的差分格式,并使用了最小二乘意义下求出的优化差分系数.为了克服边界反射,采用了最佳匹配层吸收边界条件.数值模拟试验证明:用压缩存储系数矩阵及优化差分系数的频率空间域25点差分格式进行弹性波正演模拟,可以减少数值频散,提高计算精度.使用较大的网格间距,降低计算机内存需求,并保持较高的计算效率.该正演方法为后续弹性波偏移和弹性参数反演提供较好的基础.     

Convection in rotating annular channels heated from below. Part 3: Experimental boundary conditions

Results are presented from both linear stability analysis and numerical simulations of three-dimensional nonlinear convection in a Boussinesq fluid in an annular channel, under experimental boundary conditions, rotating about a vertical axis uniformly heated from below. The focus is placed on the Prandtl number Pr = 7.0, representing liquid water at room temperature. The linear analysis shows that, when the aspect ratio is sufficiently small, there exists only one stationary mode that occupies the whole fluid container. When the aspect ratio is moderate or large, however, there exist three different linear solutions: (i) the outer sidewall-localized traveling wave propagating against the sense of rotation; (ii) the inner sidewall-localized traveling wave propagating in the same sense as rotation; and (iii) both the counter-traveling waves occurring simultaneously. Guided by the result of the linear stability analysis, fully three-dimensional simulations are then performed for a channel with a moderate aspect ratio. It is found that neither the prograde nor the retrograde mode is physically realizable near threshold and beyond. The dynamics of nonlinear convection in a rotating channel are chiefly characterized by the interaction between the sidewall-localized waves and the interior convection cells/rolls, producing an interesting and unusual nonlinear phenomenon. In order to compare with the classical Rayleigh–Bénard problem without vertical sidewalls, we also study linear and nonlinear convection at exactly the same parameters but in an infinitely extended layer with periodic horizontal conditions. This reveals that both the linear instability and nonlinear convection in a rotating channel are characteristically different from those in a rotating layer with periodic horizontal conditions.