Coupled transport-reaction pathways and distribution patterns between siliciclastic-carbonate sediments at the Ria de Vigo

This paper examines the linkages between the space-distribution of grain sizes and the relative percentage of the amount of mineral species that result from the mixing process of siliciclastic and carbonate sediments at the Ria de Vigo (NW of Spain).The space-distribution of minerals was initially determined, starting from a detailed mineralogical study based on XRD-Rietveld analysis of the superficial sediments. Correlations between the maps obtained for grain sizes, average fractions of either siliciclastic or carbonates, as well as for individual-minerals, were further stabilised. From this analysis, spatially organized patterns were found between carbonates and several minerals involved in the siliciclastic fraction. In particular, a coupled behaviour is observed between plagioclases and carbonates, in terms of their relative percentage amounts and the grain size distribution.In order to explain these results a conceptual model is proposed, based on the interplay between chemical processes at the seawater–sediment interface and hydrodynamical factors. This model suggests the existence of chemical control mechanisms that, by selective processes of dissolution-crystallization, constrain the mixed environment's long-term evolution, inducing the formation of self-organized sedimentary patterns.     

Animal dynamics based approach for modeling pedestrian crowd egress under panic conditions

Collective movement is important during emergencies such as natural disasters or terrorist attacks, when rapid egress is essential for escape. The development of quantitative theories and models to explain and predict the collective dynamics of pedestrians has been hindered by the lack of complementary data under emergency conditions. Collective patterns are not restricted to humans, but have been observed in other non-human biological systems. In this study, a mathematical model for crowd panic is derived from collective animal dynamics. The development and validation of the model is supported by data from experiments with panicking Argentine ants (Linepithema humile). A first attempt is also made to scale the model parameters for collective pedestrian traffic from those for ant traffic, by employing a scaling concept approach commonly used in biology.     

基于非线性RSH方法的泥石流灾害预测预报

泥石流灾害系统是一种自组织临界性系统,这种系统的演化总是处在混沌的边缘,系统的演化过程是可以预测的。将改进的重标极差分析方法(RSH)引入泥石流灾害前兆观测资料的处理和分析中,并在计算赫斯特指数H时,定义1个涵盖序列历史和序列长时记忆信息的时间窗。应用该方法对云南蒋家沟泥石流总径流量观测数据进行研究表明:云南蒋家沟泥石流总径流量时间序列不仅具有持久相关性,而且在激增前赫斯特指数值要经历1个先降维,然后升维的过程。根据对云南蒋家沟泥石流总径流量时间序列赫斯特指数值及其变化的分析,提出了预测预报泥石流灾害的3种定性判据。