排序方式: 共有39条查询结果,搜索用时 46 毫秒
11.
12.
13.
探讨了以氡为主的断层气测量结果与断层活动性的关系;并讨论了土质、土壤、含水量、取样深度等对断层气氡测量的影响。 相似文献
14.
边坡变形受地质、水文、气候、突发因素(如暴雨、地震)、人工活动(如开挖或防护)等各种因素的影响,这些因素与变形之间一般不是确定的定量关系。本文介绍了不同影响因素与位移量的模糊关系及位移量的模糊近似推论,在此基础上应用模糊人工神经网络进行位移量预报,并以一个边坡监测资料为例说明了具体的应用方法。 相似文献
15.
太湖沉积物微量元素特征和变化:自然与人类活动的影响 总被引:7,自引:1,他引:7
通过对太湖沉积物微量元素的测定,分析了沉积物的元素含量特征及变化趋势,指出了重金属元素的分布特点。沉积物和岩石微量元素的上地壳标准化值显示,它们的曲线存在明显的区别,反映了物质在风化和沉积过程中不同的性质差异。重金属在太湖北部地区较高,在南部地区较低,特别是As、Hg、Cu、Zn、Ni。对照背景值,探讨了重金属元素的富集程度,并运用地累积指数评估了沉积物的污染程度。根据1987年和2000年的数据,计算了重金属的累积速率。最后,讨论了自然作用和人类活动对微量元素的影响。 相似文献
16.
According to the principle of the eruption of debris flows, the new torrent classification techniques are brought forward.
The torrent there can be divided into 4 types such as the debris flow torrent with high destructive strength, the debris flow
torrent, high sand-carrying capacity flush flood torrent and common flush flood by the techniques. In this paper, the classification
indices system and the quantitative rating methods are presented. Based on torrent classification, debris flow torrent hazard
zone mapping techniques by which the debris flow disaster early-warning object can be ascertained accurately are identified.
The key techniques of building the debris flow disaster neural network (NN) real time forecasting model are given detailed
explanations in this paper, including the determination of neural node at the input layer, the output layer and the implicit
layer, the construction of knowledge source and the initial weight value and so on. With this technique, the debris flow disaster
real-time forecasting neural network model is built according to the rainfall features of the historical debris flow disasters,
which includes multiple rain factors such as rainfall of the disaster day, the rainfall of 15 days before the disaster day,
the maximal rate of rainfall in one hour and ten minutes. It can forecast the probability, critical rainfall of eruption of
the debris flows, through the real-time rainfall monitoring or weather forecasting. Based on the torrent classification and
hazard zone mapping, combined with rainfall monitoring in the rainy season and real-time forecasting models, the debris flow
disaster early-warning system is built. In this system, the GIS technique, the advanced international software and hardware
are applied, which makes the system’s performance steady with good expansibility. The system is a visual information system
that serves management and decision-making, which can facilitate timely inspect of the variation of the torrent type and hazardous
zone, the torrent management, the early-warning of disasters and the disaster reduction and prevention. 相似文献
17.
太平湖水库的底栖动物 总被引:8,自引:3,他引:5
研究了太平湖水库底栖动物群落组成(1992-1993年)定量样品出现26种(属),主要是寡毛类和摇蚊科幼虫,软体动物只有1种,现存量有明显的季节差异,本次调查结果与1985-1986年资料比较,种类数减少,现存量显著增加,生物量由0.562g/m^2增加到3.90g/m^3生物多样性指数偏低,底栖动物的参数与环境因素进行了相关分析,寡毛类的密度和生物量与总氮,总磷正相关,水生昆虫的密度和生理量与水 相似文献
18.
Major advances in studies of the physical geography and living environment of China during the past 70 years and future prospects 总被引:2,自引:0,他引:2
Chen Fahu Fu Bojie Xia Jun Wu Duo Wu Shaohong Zhang Yili Sun Hang Liu Yu Fang Xiaomin Qin Boqiang Li Xin Zhang Tingjun Liu Baoyuan Dong Zhibao Hou Shugui Tian Lide Xu Baiqing Dong Guanghui Zheng Jingyun Yang Wei Wang Xin Li Zaijun Wang Fei Hu Zhenbo Wang Jie Liu Jianbao Chen Jianhui Huang Wei Hou Juzhi Cai Qiufang Long Hao Jiang Ming Hu Yaxian Feng Xiaoming Mo Xingguo Yang Xiaoyan Zhang Dongju Wang Xiuhong Yin Yunhe Liu Xiaochen 《中国科学:地球科学(英文版)》2019,62(11):1665-1701
The natural environment provides material essentials for human survival and development. The characteristics,processes, regional differentiation and forcing mechanisms of the elements of the natural environment(e.g. geomorphology,climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective. 相似文献
19.
排桩冻结法深基坑施工监测与反馈分析 总被引:5,自引:0,他引:5
对于润扬大桥南锚碇排桩冻结法深大基坑,冻结作用使基坑的受力过程变得更为复杂,根据排桩冻结法基坑结构和场地工程地质条件,建立了大型安全监测系统。本文介绍了润扬大桥南锚碇场地工程地质条件、排桩冻结法基坑的结构和南锚碇基坑监测方案、分析了南锚排桩冻结法深基坑各项监测数据的变化规律,包括侧向土压力、内支撑轴力、排桩钢筋应力和排桩水平位移随时间变化规律,并基于施工监测进行了反馈分析,保障了南锚碇排桩冻结法深基坑的安全与稳定。监测结果分析表明,排桩冻结法是基坑工程的一种可行的施工工法,润扬大桥南锚碇排桩冻结法深大基坑的成功实践为今后类似工程的建设积累了宝贵经验。 相似文献
20.
Streamflow changes and its influencing factors in the mainstream of the Songhua River basin,Northeast China over the past 50 years 总被引:1,自引:3,他引:1
The Songhua River plays a key role in the national development of China, owing to its unique natural condition and resources.
Recent changes in the streamflow in the Songhua River are important with regard to local sustainable development and management
under the background of global warming and aggravating soil erosion. In order to detect changes in the streamflow, two streamflow
series from 1955 to 2004 (observed at the Harbin and Jiamusi stations) in the mainstream of Songhua River basin were obtained,
and methods of statistical analysis, wavelet transform, and double mass analysis were employed to analyze the data. Reasons
for the changes to the streamflow are discussed with respect to natural and man-made drivers. The results show the following:
(1) From 1955 to 2004, the streamflow series present obvious declining trends. (2) The streamflow series followed the pattern
of a wet–dry–wet–dry cycle pattern over the past 50 years. In the mainstream of Songhua River, wet years mainly occurred during
the periods of 1955–1966 and 1984–1993, while dry years mainly occurred in the 1970s and after 2000. (3) Within the 50-year
scale, the streamflow series appeared in the main periods of circa 33-, 13- and 4-year, in which the 33-year periodicity is
the strongest. (4) Precipitation and temperature directly influenced the streamflow in the mainstream of the basin. The discharge
was positively correlated with the precipitation and negatively correlated with the temperature. In addition, human activity
was another important driving factor for streamflow change. (5) In the mainstream of Songhua River basin, the influences on
streamflow can be divided into three periods: 1955–1976, 1977–1997, and 1998–2004. In the first period climate change played
a dominant role, and during the latter two periods human influences were enhanced significantly. 相似文献