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.     

CO2加富对塔玛亚历山大藻叶绿素荧光参数及产毒的影响

由大气中CO_2浓度升高引起的海洋酸化,是全球性的重大环境问题之一。本研究采用实验生态学的方法,以塔玛亚历山大藻(Alexandrium tamarense)为研究对象,分析其在CO_2加富条件下叶绿素荧光动力学参数及产毒特征的变化。调制叶绿素荧光结果显示,CO_2加富对塔玛亚历山大藻的PSⅡ最大光化学量子产量(Fv/Fm)、最大相对电子传递效率(r ETRmax)有显著影响(P0.05),且随着培养时间的增长Fv/Fm、r ETRmax均降低,对半饱和光强(Ik)、快速光曲线初始斜率(α)却无显著影响(P0.05)。结果说明CO_2加富能促进塔玛亚历山大藻的PSⅡ最大光化学量子产量,提高其最大光能转换效率和相对最大电子传递效率。高效液相色谱法分析结果显示,该株塔玛亚历山大藻主要产漆沟藻毒素1(GTX1)、漆沟藻毒素4(GTX4)、N-磺酰氨甲酰基毒素(C1)及N-磺酰氨甲酰基毒素(C2)四种PSTs毒素,CO_2加富不改变主要麻痹性贝毒(PSTs)的种类组成,但能显著提高氨基甲酸酯类毒素(GTX1、GTX4)产量(P0.05),而降低N-磺酰氨甲酰基类毒素(C1、C2)产量(P0.05),说明加富能使塔玛亚历山大藻所产毒素发生转化,进而影响藻细胞的整体毒性。     

天津市滨海新区芦苇湿地恢复适宜性评价

利用综合评价模型,结合地理信息系统技术的空间分析功能,以土地利用、土壤类型、坡度、降雨量和人类干扰活动作为评价因子,对天津滨海新区芦苇湿地恢复进行了适宜性评价。结果表明,较适宜开展湿地恢复的比例为21.46%,一般适宜比例为21.87%,不适宜比例占56.68%,其中较适宜湿地恢复的区域集中分布在北大港湿地自然保护区周边、独流减河下游、北塘入海口以及沿海滩涂,海河流域两侧也有零星分布。在适宜性评价基础上,对未来芦苇湿地恢复与建设的重点区域进行了成效预评估,芦苇对TC、TN、TP的年吸收通量约为1.3935×104、0.0258×104、0.0017×104t,能有效地减少入海排污压力和污染物对近岸海域环境质量的影响。研究结论可为天津湿地治理与生态恢复、土地利用结构调整、景观优化等提供理论依据和科学参考。     

Image-aided platform orientation determination with a GNSS/low-cost IMU system using robust-adaptive Kalman filter

The availability of miniaturized sensors with enhanced capabilities, new methods for image processing, and easy access to small and low-weight airborne platforms for data acquisition, including unmanned vehicles, opens new possibilities for geodetic navigation applications and developing new developments in sensor fusion. In this context, the development of efficient methods, based on low-cost sensors, to extract precise georeferenced information from digital cameras is of utmost interest. We present a method to improve the performance of the integration of GNSS/low-cost IMU by exploiting the orientation changes retrieved from digital images. In this work, a robust-adaptive Kalman filter is also introduced to further improve the performance of the method deployed. The adaptive factor and the robust factor accomplished are determined by innovation information and the threshold value of orientation changes between consecutive images. Results from airborne tests used to assess the performance of the method are presented. The results show that using a non-metric camera, the Euler angle estimation accuracy of the GNSS/low-cost IMU integration can be improved to be close to 0.5 degree and an additional improvement, which can reach 59%, can be achieved after using the robust-adaptive Kalman filter.     

Study on failure mechanism of a plain irrigation reservoir soil bank slope under wind wave erosion

Natural Hazards - The wind wave erosion is one of the main factors of the soil bank slope retreat in plain irrigation reservoirs, which plays an important role in the bank profile evolution and...     

Failure and Acoustic Emission Characteristics of Jointed Rock Masses with Different Joint Inclination Angles and Combination Mode

Geotechnical and Geological Engineering - In order to analyze the characteristics of the mechanical property, failure mode and acoustic emission of the columnar jointed rock masses,...     

杭锦旗北部牧草引种试验

利用在内蒙古杭锦旗北部进行牧草引种试验的数据,结合产量效益分析了4个牧草品种对当地土壤与气候条件的适应性,初步得出适应杭锦旗北部气候、生态条件的牧草品种,并通过产量效益分析,确定了适合当地的牧草间、混作模式,为当地建立人工饲草基地发展生态畜牧业提供决策参考。     

提高地面气象测报质量的思考

地面气象测报工作是地面气象观测站的基本工作之一,地面气象测报数据质量直接影响着天气预报的准确性。地面气象测报人员必须严肃、认真、负责地做好这项工作。