Analytical computation of coupling coefficients in non-Poissonian media

As indicated by numerical tests, the computation of synthetic seismograms based on the modal summation technique, for 2-D or 3-D media, requires the computation of the transmission and reflection coupling coefficients, at sharp lateral heterogeneities, with a formulation that takes into account the possible non-Poissonian character of the media.     

Geophysical model of the dynamical flattening of the Earth in agreement with the precession constant

The dynamical flattening of the Earth, as observed by geodetic techniques, is different by about 1 per cent from the value associated with the PREM density profile with hydrostatic equilibrium. In this paper, we compute a new dynamical flattening H induced by PREM mean density with hydrostatic equilibrium, to which we add lateral heterogeneities associated with (1) seismic velocity variations observed by tomography and (2) internal boundary topographies. First, we compute mantle circulation associated with the density anomalies derived from a tomography model. The flow-induced boundary deformations are then converted into additional mass anomalies which are added to the tomography model for computing the associated perturbation to the Earth's inertia tensor. Finally, we show that it is possible to obtain a dynamical flattening from the total inertia tensor (i.e. the sum of the PREM inertia tensor and of the perturbation) in agreement with that observed.     

Electrochemical properties of solids at the aqueous–solid interface and heterogeneity of surfacePropriétés électrochimiques des solides à l'interface solide–eau et hétérogénéité de surface

In aqueous medium, solid surfaces are in general electrically charged. The induced electrical and chemical properties govern numerous phenomena, such as colloidal stability or transport of pollutants. Numerous industrial processes make use of these properties. The understanding of the underlying mechanisms at molecular level is of high importance in order to predict and master the behaviour of dispersed matter in the environment and in industrial processes. The present paper shows the evolution of theories and experimental methods, their recent developments and applications. To cite this article: F. Thomas et al., C. R. Geoscience 334 (2002) 633–648.     

地形通行性能的研究

本文从计算机地形分析的角度，研究了地形通行性能分析的方法与步骤，对涉及的地形因素，采用调研和试验得到的数据，建立了数学模型。     

Effect of waterwashing on light ends compositional heterogeneity

A number of experiments have been carried out to study in the laboratory the effects of waterwashing on light ends composition. The experimental data were then compared with the results of a simple numerical model. Both approaches confirm the fast removal of the light aromatics by the flushing water and the very slow alteration of the C₁₀₊ compounds. The experimental results also indicate that the normal paraffins are removed faster than the cycloalkanes which is not in agreement with their respective solubility data. the simulations show that, over geological time, compounds such as benzene and toluene should be completely absent in an oil column which is not the case. Therefore, it is likely that in nature oil-water interactions are not as effective as one could imagine, which has implications for oil migration, as well as for the understanding of hydrodynamism phenomena in oil pools.     

国家城市规模分布的时空演化特征及影响因素——基于LandScan的全球实证研究

洞悉世界各国城市规模分布规律有助于推动形成合理的城镇格局和促进国家经济高质量发展。论文基于2000—2018年LandScan等数据库,按照统一的人口集聚标准创新性地识别了全球各国的城市,分析了国家城市规模分布的时空演化特征、影响因素及其异质性。研究发现：全球各国城市规模分布在研究期间内呈波动均衡的态势。从空间演化来看,非洲、南美洲国家城市规模分布逐渐均衡,而亚洲、欧洲国家出现极化趋势;从现状比较来看,非洲国家城市规模分布的极化程度居于首位,欧洲国家则最为均衡。河流密度、城市人口密度以及工业化水平提高会促进城市规模分布均衡发展,而地形起伏度、国家不稳定程度增加则会强化其极化程度。相比于其他要素,社会经济要素(尤其是城市人口密度)对城市规模分布的影响在不同收入水平、产业结构和政府干预程度的国家间异质性最为明显。研究深化了对城市规模分布及其形成机理的规律性认知,为形成合理的城市规模分布提供了有力的实证支撑。未来中国应通过构建适度均衡的城市规模分布体系、扩大内外双向开放以及应用新一代信息技术,重塑国家经济地理格局。     

“求人”还是“求己”：多尺度知识溢出与企业出口产品演化

进口能为区域带来新知识,而这些知识在本地的溢出具有多尺度的特征。论文认为,进口知识首先能够在企业内部溢出,继而跨越企业边界在区域内部溢出。企业通过在企业内部和区域内部对进口知识进行搜寻,能够促进自身的出口产品演化。基于此,论文建立知识溢出的多尺度研究框架,并利用2002—2016年中国海关进出口贸易库数据,证实了上述现象的存在。同时,研究发现,一方面,对于出口产品演化来说,企业内部和区域内部知识溢出的效用是相互替代的;另一方面,知识溢出效应呈现距离衰减的特征。分样本回归结果表明,在市场化水平较高的地区,区域内部的知识溢出对促进企业出口产品演化更有效,企业为实现产品出口更倾向于“求人”;而在市场化水平较低的地区,企业出口产品演化则更依赖于企业内部的知识溢出,倾向于“求己”。论文一定程度上丰富了学界关于不同地理尺度下的知识溢出及其相互关系的讨论,同时完善了学界对于企业出口产品演化机制的认识,具有一定的理论和实际意义。