Regional debris flow susceptibility analysis based on principal component analysis and self-organizing map: a case study in Southwest China

A method was developed to analyze the susceptibilities of 541 regional basins affected by debris flows at the Wudongde Dam site in southwest China. Determining susceptibility requires information on source material quantity and occurrence frequency. However, the large number of debris flows can hinder the individual field investigation in a each small basin. Factors that may trigger debris flows can be identified using remotely sensed interpretation information. Susceptibility analysis can then be conducted based on these factors. In this study, SPOT5 satellite imagery, digital elevation models (DEM), a lithology distribution map, and rainfall monitoring data were used to identify 12 debris flow trigger factors: basin relief ratio, slope gradient in the initiation zone, drainage density, downslope curvature of the main channel, vegetation coverage, main channel aspect, topographic wetness index, Melton’s ruggedness number, lithology, annual rainfall, form factor, and cross-slope curvature of the transportation zone. Principal component analysis was used to obtain the eight principal components of these factors that contribute to susceptibility results. Then, a self-organizing map method was adopted to analyze the principal components, which resulted in a debris flow susceptibility classification. Field validation of 26 debris flow basins was used to evaluate the errors of the susceptibility classification, as well as assess the causes of such errors. The study found that principle component analysis and self-organizing map methodologies are good predictors of basin susceptibility to debris flows.     

Radar-based collision avoidance for unmanned surface vehicles

Unmanned surface vehicles (USVs) have become a focus of research because of their extensive applications. To ensure safety and reliability and to perform complex tasks autonomously, USVs are required to possess accurate perception of the environment and effective collision avoidance capabilities. To achieve these, investigation into realtime marine radar target detection and autonomous collision avoidance technologies is required, aiming at solving the problems of noise jamming, uneven brightness, target loss, and blind areas in marine radar images. These technologies should also satisfy the requirements of real-time and reliability related to high navigation speeds of USVs. Therefore, this study developed an embedded collision avoidance system based on the marine radar, investigated a highly real-time target detection method which contains adaptive smoothing algorithm and robust segmentation algorithm, developed a stable and reliable dynamic local environment model to ensure the safety of USV navigation, and constructed a collision avoidance algorithm based on velocity obstacle (V-obstacle) which adjusts the USV’s heading and speed in real-time. Sea trials results in multi-obstacle avoidance firstly demonstrate the effectiveness and efficiency of the proposed avoidance system, and then verify its great adaptability and relative stability when a USV sailing in a real and complex marine environment. The obtained results will improve the intelligent level of USV and guarantee the safety of USV independent sailing.     

Paratacamite from Gypsum Veins in Sandstones of the Kuqa Basin,Xinjiang, China: Implications for a New Epigenetic Cu Enrichment Mechanism

The Kuqa Basin filled with Paleogene evaporite series is located in the northeast of the Tarim Basin, Xinjiang, China. It is famous for sandstone‐hosted Cu deposits formed by synsedimentary processes. However, our recent studies reveal that there has been another Cu mineralization mechanism in this basin. Field investigations show that there is a close relationship among faults, salt domes, and brine. Cu deposits are mainly located in two east–west‐trending anticlinal belts in the basin, adjacent to salt domes in the belts. Cu minerals in gypsum veins of the Jidike and Kangcun formations have been investigated by SEM, EDS, and X‐ray diffraction methods. The occurrence of paratacamite in gypsum veins has been reported to coexist with glauberite and halite in the joint planes of sandstones. In addition, it occurs accompanying residual crystal salt encrustation in limestone fractures, or in sandstones in dendritic form. These features indicate that the surface‐Cu enrichment in the Kuqa Basin might have originated from Cu‐bearing brine in the underlying evaporite units, which migrated upward along fractures. In addition, the presence of H₂S in the east–west fault belt in the Kuqa Basin, and the discovery of surface sulfur, calcium carbonate, and covellite, suggest thermochemical sulfate reduction near salt domes in the deeper parts of the rock units. This process resulted in the generation of reduced brine and provided a favorable environment for Cu enrichment. Therefore, the surface‐Cu mineralization near salt domes is interpreted to be the result of Cu‐bearing brine migrating upward to the surface along faults (or joints) following the intrusion of deep salt domes. The geological evidence indicates the presence of reducing brine and Cu‐bearing brine near the salt dome in the deeper rocks of the Kuqa Basin, thus making the intrusive contact zone of the salt dome a favorable site for the epigenetic enrichment of Cu. Our study demonstrates that Cu enrichment in the Kuqa Basin resulted not only from synsedimentary deposition but also through epigenetic enrichment associated with salt dome intrusion and brine‐rich fluids.     

Non-capacity transport of non-uniform bed load sediment in alluvial rivers

Rivers often witness non-uniform bed load sediment transport. For a long time, non-uniform bed load transport has been assumed to be at capacity regime determined exclusively by local flow. Yet whether the capacity assumption for non-uniform bed load transport is justified remains poorly understood. Here, the relative time scale of non-uniform bed load transport is evaluated and non-capacity and capacity models are compared for both aggradation and degradation cases with observed data. As characterized by its relative time scale, the adaptation of non-uniform bed load to capacity regime should be fulfilled quickly. However, changes in the flow and sediment inputs from upstream or tributaries hinder the adaptation. Also, the adaptation to capacity regime is size dependent, the finer the sediment size the slower the adaptation is, and vice versa. It is shown that the capacity model may entail considerable errors compared to the non-capacity model. For modelling of non-uniform bed load, noncapacity modelling is recommended, in which the temporal and spatial scales required for adaptation are explicitly appreciated.     

青海省祁连县大拉洞柏杨沟矿区煤岩层对比研究

通过研究太原组的沉积特征及聚煤变化规律,采用了标志层、煤岩层组合特征、层间距、测井曲线形态等方法,对矿区内煤层、岩层进行了综合对比。确定了该区主要煤层的赋存层位、形态、分布及变化特征,对周边地区找煤工作具有一定的指导作用。