Cartographic techniques for mapping the geochemical data of stream sediments: the “Sample Catchment Basin” approach

The Sample Catchment Basin (SCB) mapping technique extends the representativeness of the geochemical features of stream sediments to the surface of the whole upstream drainage basin. SCB boundaries clash with the water divides traced from each sampling point and are limited upstream by the presence of further SCBs. They are also assumed to represent the elementary map unit. The rank of SCBs can be defined counting the number of upstream SCBs along the branches of a fluvial network. The presence of low rank SCBs minimizes the statistical redundancy of measures. The SCB technique is particularly suitable for the geochemical mapping of mountainous or hilly areas and to correctly display the information into a morphological context. This approach can be also valuable in the case of low sampling density, inhomogeneous sampling schemes, and especially when very accurate evaluations of the spatial distribution of chemicals (with natural or anthropogenic origin) are required.     

Properties of iron at the Earth's core conditions

Summary. The phase diagram of iron up to 330 GPa is solved using the experimental data of static high pressure (up to 11 GPa) and the experimental data of shock wave data (up to 250 GPa). A solution for the highest triple point is found ( P = 280 GPa and T = 5760 K) by imposing the thermodynamic constraints of triple points. This pressure of the triple point is less than the pressure of the inner core–outer core boundary of the Earth. These results indicate that the density of iron at the inner core–outer core boundary pressure is close to 13 g cm⁻³, which lies close to the seismic solutions of the Earth at that pressure. It is thus concluded that the Earth's inner core is very likely to be virtually pure iron in its hexagonal close packed (hcp) phase.
It is shown that four properties of the Earth's inner core determined from seismology are close in value to the corresponding properties of hcp iron at inner core conditions: density, bulk modulus, longitudinal velocity, and Poisson's ratio. The density–pressure profile of hcp iron at inner core conditions matches the density–pressure profile of the inner core as determined by seismic methods, within the spread of values given by recent seismic models.
This indicates that the Earth is slowly cooling, the Earth's inner core is growing by crystallization, and the impurities of the core are concentrated in the outer core. The calculated temperature at the Earth's centre is 6450 K.     

Hierarchical community detection and functional area identification with OSM roads and complex graph theory

An in-depth analysis of the urban road network structure plays an essential role in understanding the distribution of urban functional area. To concentrate topologically densely connected road segments, communities of urban roads provide a new perspective to study the structure of the network. In this study, based on OpenStreetMap (OSM) roads and points-of-interest (POI) data, we employ the Infomap community detection algorithm to identify the hierarchical community in city roads and explore the shaping role roads play in urban space and their relation with the distribution of urban functional areas. The results demonstrate that the distribution of communities at different levels in Guangzhou, China reflects the urban spatial relation between the suburbs and urban centers and within urban centers. Moreover, the study explored the functional area characteristics at the community scale and identified the distribution of various functional areas. Owing to the structure information contained in the identification process, the detected community can be used as a basic unit in other urban studies. In general, with the community-based network, this study proposes a novel method of combining city roads with urban space and functional zones, providing necessary data support and academic guidance for government and urban planners.     

抽汲地下水引起地面沉降的水-土耦合三维有限元数值模拟

建立了抽汲地下水非稳定流定解问题的三维数学模型,利用现有承压含水层非稳定流定解问题数值方程求解,重点讨论了源汇项的具体数学表达式.根据土的有效应办原理和压密原理推导出抽水沉降非线性弹性压密方程,结合武汉新业大厦水文地质与工程地质条件,利用已研制的三维有限元计算程序LCYXY3D.F90对该环境岩土工程问题进行了分析和评价,计算结果与实测结果符合较好.     

随机扩散水质模型研究

考虑湖泊中影响总磷沉积过程的众多生态因子的变化过程,假定湖泊中总磷沉积过程由标准布朗运动驱动,建立了一个总磷浓度的随机扩散方程,推广确定性富营养化Vollenweider水质模型为随机扩散模型,获得了总磷浓度过程的解析解,进而求出了总磷浓度过程的均值和方差,指出了一种依据沉积系数调控湖泊中总磷浓度的方法。模型被应用于巢湖总磷浓度过程的模拟。     

双平方根单程波动方程叠前τ偏移方法

本文将常规双平方根（DSR）单程波动方程从深度域变换到双程垂直走时（τ）域,由此推导出可从数学上实现“沉降观测”的单程波DSR传播算子. 其递归波场延拓算法包含波数域针对常速背景的相移处理和空间域针对横向速度扰动的相位校正,可以应对上覆地层速度横向变化对构造成像的影响. 结合零炮检距、零时间成像条件,提出了在τ域进行波场延拓与成像的DSR方程叠前偏移新方法. 为了克服其全三维偏移算法在实际应用中可能面临的困难,本文采用稳相近似,在crossline常炮检距偏移理论基础上推导了实用的共方位角叠前τ偏移方法. 数值试验表明,DSR方程叠前τ偏移在强横向非均匀介质中的成像精度与分辨率优于传统的时间域成像技术.     

基于脉冲频响函数的MATLAB动力方程求解方法

提出一种基于脉冲频响函数并利用MATLAB求解的方法，由于脉冲频响函数利用卷积公式进行动力微分方法计算，因此，从理论上讲，它适合于任意外力下的动力方程求解，同时，MATAL又提供了卷积函数conv，所以，在MATLAB下求解动力方程将变得十分容易。     

自由场典型液化特征数值模拟试验

应用FLAOD实现自由场液化数值模拟试验.试验结果验证了砂土液化典型特征:超静孔隙水压升高,有效应力降低,体积压缩积累增大.证实了液化的隔振作用:砂土在液化状态变为流体,不能传递剪力,液化时砂土位移、速度、加速度振幅显著降低,剪应力降低,动水向上渗流,土体向下沉降,水平残留不可恢复位移.球压应力、有效压应力、动水压力满...