基于DEM的黄土高原地貌分形美学图案研究

为进一步探索黄土高原千沟万壑、支离破碎的自然景观特征中蕴含的分形美学价值,本文基于黄土高原6个不同地貌类型区的数字高程模型,在分形图案设计软件Ultra Fractal中,利用多种标准化分形变换和Newton分形公式,设计并对比使用原始DEM数据提取出的地貌因子数据与不同分形变换集合得到的分形美学图案.结果 表明,对蕴...     

东海陆坡海底峡谷-扇体系沉积特征及物质搬运

利用多波束和高分辨率地震资料,分析了东海陆坡广泛发育的海底峡谷-扇体系的沉积地层结构,讨论了海底峡谷-扇体系内部主要的沉积物搬运方式、沉积特征和典型沉积环境.结果表明,海底峡谷是上陆坡沉积物质向下搬运的主要通道.海底峡谷段上部以侵蚀作用为主,局部堆积具丘状或透镜状外形的滑塌体或滑坡体;海底扇沉积开始于海底峡谷的出口,地...     

ESR,U-series and paleomagnetic dating of Gigantopithecus fauna from Chuifeng Cave,Guangxi, southern China

Several Gigantopithecus faunas associated with taxonomically undetermined hominoid fossils and/or stone artifacts are known from southern China. These faunas are particularly important for the study of the evolution of humans and other mammals in Asia. However, the geochronology of the Gigantopithecus faunas remains uncertain. In order to solve this problem, a program of geochronological studies of Gigantopithecus faunas in Guangxi Province was recently initiated. Chuifeng Cave is the first studied site, which yielded 92 Gigantopithecus blacki teeth associated with numerous other mammalian fossils. We carried out combined ESR/U-series dating of fossil teeth and sediment paleomagnetic studies. Our ESR results suggest that the lower layers at this cave can be dated to 1.92 ± 0.14 Ma and the upper layers can be dated to older than 1.38 ± 0.17 Ma. Correlation of the recognized magnetozones to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic, biostratigraphic and ESR data. The combined chronologies establish an Olduvai subchron (1.945–1.778 Ma) for the lowermost Chuifeng Cave sediments. We also analyzed the enamel δ¹³C values of the Gigantopithecus faunas. Our results show that southern China was dominated by C₃ plants during the early Pleistocene and that the Gigantopithecus faunas lived in a woodland-forest ecosystem.     

Comparison of rockfall susceptibility assessment at local and regional scale: a case study in the north of Beijing (China)

This study shows a rockfall susceptibility assessment at local scale in north Beijing of China, including the identification of rockfall sources onsite by terrain and rock discontinuities analysis and run-out distance prediction by Rocfall^? simulation. Two types of rockfall were defined including one type on the cliffs with long inclined slopes and another type on the road slopes with low height. Two historical rockfall events were used to back-calibrating the parameters used for run-out distance simulation. Based on the work, rockfall susceptibility map at local scale was created in GIS, which was compared with the map obtained at regional scale (entire Huairou district scale). Due to the difference of approaches applied, procedure of assessment and types of source data acquired, the two resulting rockfall susceptibility maps are proved to be different. Still, both of them are useful and could be used at different level’s decision for rockfall prevention and mitigation. Different types of uncertainties exist in the study of rockfall susceptibility assessment. To reduce the uncertainties, studies on both approaches and techniques are suggested.     

Groundwater use by plants in a semi-arid coal-mining area at the Mu Us Desert frontier

The hydrogen isotope (deuterium- $ \delta D $ ) composition at natural abundance levels of xylem water, soil water, groundwater, river water, and rainwater was used to evaluate whether adult plant species use groundwater and to detect seasonal shifts (dry/wet season) in water sources for plants growing in a semi-arid coal-mining area (located at the frontier of the Mu Us Desert). A direct inference approach and the IsoSource mixing model were used to estimate the contributions of different sources to the plant xylem water. The results showed that (1) the $ \delta D $ values of rainfall fluctuated considerably, while those of groundwater were generally constant during the experimental period; (2) the $ \delta D $ patterns in plant xylem water suggest that groundwater was a significant source of water for transpiration in the dry season, while all five selected species reduced dependence on groundwater sources in the wet season; and (3) soil water from the deep layer (50–100 cm) was used largely by adult species possibly because of interspecific competition. These results indicated that coal mining would significantly affect plant growth by reducing the water supply if it leads to a water table decrease. Therefore, it is necessary to protect groundwater resources during the coal mining operations in the region.     

南京地区雷暴活动强度潜势预报

利用江苏省2008、2009和2010年6 8月闪电定位资料对雷暴活动的强度进行了分级,并使用同一时段的探空资料计算了47个代表南京地区 环境层结特征的对流参数,利用其与雷暴活动强度的相关性选取预报因子.在此基础上,采用Bayes分类法和Logistic 回川归分析法,结合逐步选择法进一步筛选预报因子,分别建立了两种雷暴强度的预报模型.通过检验独立样本对比分析两种模型的预报效果,结果表明,Logistic回归分析法的Hedike技巧评分为0.396,并能识别出30％的强雷暴,而Bayes分类法的Hedike技巧评分为0.370,只能识别出5％的强雷暴.Logistic回归分析法对雷暴强度的潜势预报具有较好的指示意义.进一步分析进入预报模型的9个对流参数,表明雷暴活动越强时,低层空气越暖湿,中层空气越干冷,高低层的风切变越大.     

2007年3月4～5日黑龙江省暴雪天气过程诊断分析

本文在分析大气环流及物理量场特征基础上,结合卫星云图资料对2007年3月4～5日黑龙江东南部地区一次暴霄天气过程成因进行了探讨,发现本次暴雪出现在强烈上升的饱和湿区,水汽主要来自于低层输入,是高空南北锋区合并、低空暖式切变、地面低压人海加强东移北上等高低空系统相互作用的结果,同时分析还表明本次暴雪过程也具有中小尺度特征。     

江苏省地闪密度及雷电流幅值分布

从雷电防护中重点关心的地闪密度和雷电流幅值两个方面进行分析,引入时间权重法结合人工观测雷暴日资料和闪电定位仪资料,给出地闪密度分布情况并依此绘制江苏省雷区分布图,对照Anderson经验公式拟合雷电流幅值概率分布情况.结果表明:江苏省地闪密度的分布趋势是南部比北部多,西部比东部多;洪泽湖周边、太湖和宁镇丘陵周边是江苏省雷电防护重点区域.江苏省雷电流幅值概率分布符合Anderson经验公式,幅值主要在20～40kA范围内变化.     

降雨对土质边坡稳定性影响分析

从降雨对土体抗剪强度的影响、降雨对土体重度的影响、降雨形成的水压力及降雨对土体的化学作用四个方面分析了降雨对边坡稳定性的影响。并通过一个因降雨而失稳的滑坡实例介绍其整治措施。     

Environmental emigration stress of slope farmland in the Three Gorges area

The project of 'grain for green', to restore woodland and grass by retreating from slope farmland, as a fundamental measure of eco-environmental rehabilitation, is being conducted in the reservoir area of the Three Gorges gradually. However, the de-farming of slope farmland will reduce the amount of farmland in de-farmed areas, especially in the areas with concentrated slope farmland, which would cause the problems of environmental emigration. The people who cannot regain enough farmland by relocating farmlands within village after de-farming and have to emigrate to other places are called environmental emigrants or ecological emigrants. In the research, a de-farming stress index model and an environmental emigration model are developed based on GRID data, and the potential amount of environmental emigration caused by de-farming of slope farmland in the reservoir area is simulated aided with GIS. The simulation indicates that the potential emigration amount caused by de-farming is quite large. When the de-farming stress index reaches 40%, the amount is as large as 890,000 people, which is equivalent to the emigrants caused by the submergence of the Three Gorges reservoir. So it should be considered as a big problem during the eco-environmental rehabilitation in this area. Some suggestions are raised to tackle the problem. Firstly, the emigration plan should be included in the de-farming plan. Secondly, some provinces, especially those located in the lower reaches of the Yangtze River, should accommodate part of the environmental emigrants.