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951.
952.
三峡库区白家包滑坡变形特征与影响因素分析 总被引:3,自引:0,他引:3
针对三峡库区阶跃型滑坡,以白家包滑坡为例,统计分析滑坡位移、变形速率和裂缝监测数据。显示滑坡在2007年6月之前为蠕动变形初期,受降雨和库水位等外界因素的作用,6月滑坡发生剧烈变形,之后一直保持约75°方向滑动。滑坡体中前部位移速率大于后缘,其变形具有牵引式特点。滑体上裂缝与变形位移具有一致性,位移量越大的区域裂缝越发育。将位移速率与降雨、库水位和地下水进行影响机制分析,建立滑坡变形与外界动态影响因素之间的响应关系。结果表明降雨量和库水位变化是引起滑坡季节性变形的主要因素,其中降雨强度、库水位下降及下降速率是导致滑坡位移速率波动大小的关键因子。 相似文献
953.
954.
High-resolution monitoring of nitrate variations in a typical subterranean karst stream, Chongqing, China 总被引:1,自引:0,他引:1
Junbing Pu Daoxian Yuan Qiufang He Zhijun Wang Zhiyong Hu Pengfei Gou 《Environmental Earth Sciences》2011,64(7):1985-1993
Globally, it is possible that up to 25% of the world’s population depends on karst water supplies. In karst areas, a high
degree of groundwater and surface water linkage often results in the direct recharge of groundwater with polluted run-off
following rainfall. In order to reveal the hydrochemical variations after rainfall, especially real-time variation of pollutants,
high-resolution auto-monitoring techniques were used at the outlet of Qingmuguan subterranean stream (QSS), which is influenced
by agricultural activities. In addition to rainfall, high-resolution measurements of pH, water level, electrical conductivity
(Ec) and NO3
− concentration were recorded in the monsoon season and fertilizer application period using a data logger with time intervals
of 15 min. In the six observed rainfall events, the pH value was mainly controlled by acidic rainfall inputs. The pH showed
sharp decline after the rainfall event, and then increased. The Ec was impacted by the rainfall chemistry, dilution effect
of rainfall and agricultural wastewater. NO3
− derived from agricultural activities was less impacted by rain chemistry; and its variations were mainly affected by the
dilution effect of rainfall and agricultural wastewater. Under the influences of the R1 rainfall, the rapid changes of Ec
and NO3
− were opposite in direction. As the rain continued, both the Ec and NO3
− rapidly changed in synchronization within the shortest period of 5 h and the longest of 27 h because of the impact of the
agricultural wastewater. The groundwater quality changed due to the influx of agricultural wastewater over the entire monitoring
period. According to the National Groundwater Quality Standard, People’s Republic of China (GB/T14848-9), the groundwater
quality of the QSS moved through the following grades during the monitoring period: Grade III → Grade IV → Grade V → Grade
IV → Grade V → Grade IV → Grade V → Grade IV → Grade III. Traditional sampling methods did not reveal accurate hydrochemistry
changes of the QSS, and even generated misleading results. Consequently, the high-resolution auto-monitoring technique is
necessary for the future protection and sustainable use of karst aquifer in Southwest China. 相似文献
955.
956.
随着现代科学技术的发展,水声探测浮标系统也向着高灵敏度、高集成度、高可靠性方向发展,其对浮标系统的电磁兼容性能的要求越来越高.结合电磁干扰的形成因素及电磁干扰的传播途径等理论,分析了水声探测浮标系统在测量过程中出现的毛刺、尖刺等影响系统正常工作的干扰现象形成原因,提出了电磁兼容的改进措施,根据浮标系统结构等设计特点,主... 相似文献
957.
针对4类持续性、灾害性天气,利用集合平均、离散度、概率以及盒须图等方法对T213集合预报的数据进行再加工,得到其中期概率预报,包括全国范围的持续性降水、南方春季持续低温(重度低温)、南方春季低温(重度低温)连阴雨、江淮梅雨。其结果表明:(1)对于全国范围内的持续性降水过程,各类图都能很好的反映集合预报中不同量级的降水预报在10天之内的落区变化以及持续情况,并与实况对应较好。(2)对于南方低温和低温连阴雨,集合平均、离散度和概率图都能明显的反映出实际天气过程和范围的变化。(3)对于江淮梅雨这5个指标站的盒须图,能明显看出各集合成员在15个集合成员中的相对位置,以及数据的分布情况。同时还能看出集合成员与集合平均数之间的关系。梅雨日概率图则能直观的反映出10天之内每天达到梅雨日标准的概率,更有利于判断梅雨天气。 相似文献
958.
The persistence of malachite green (MG), and its metabolite leucomalachite green (LMG), in fish tissues is still unclear, leading to many trade disputes. In this research, we established and evaluated an HPLC method that could detect MG and LMG simultaneously, and then investigated the persistence of these two toxins in the tissues of juvenile perch (Lateolabrax japonicus) post sub-chronic MG exposure at 1.0 mg/L. Exposure lasted for 2 h everyday and was repeated six times. The perch were then placed in MG-free seawater for 100 d to eliminate the toxins. Results show that MG accumulated in the tissues, including the gills, liver, muscle, blood and viscera, and then was metabolized rapidly to LMG. The concentrations of these two toxins increased significantly with the accumulation process. In general, the highest concentrations of MG and LMG in all tissue exceeded 1 000 μg/kg, except for MG in the muscle. The order of accumulation levels (highest to lowest) of MG was gill>blood>liver>viscera>muscle, while that of LMG was liver>blood>gill>viscera>muscle. High levels of MG or LMG could persist for several hours but decreased rapidly during the elimination process. The concentration of LMG was much higher than that of MG during the experiment, especially in the gill, liver and blood. Therefore, the three tissues play important roles in toxin accumulation, biotransformation, and elimination. Although the MG and LMG concentrations in muscle were much lower than in other tissues, the content still exceeded the European minimum required performance limit (MRPL), even after 2 400 h (100 d) of elimination. This demonstrates that it is extremely difficult to eliminate MG and LMG from tissues of perch, and therefore use of these toxins is of concern to public health. 相似文献
959.
传感器大气顶层波段平均太阳辐照度(Band-Averaged Extraterrestrial Solar Irradiance,BAESI)是表观反射率和星上辐亮度之间转换的重要因子,为了针对FY-4A/AGRI有关通道较为准确地计算这一数值,分别以韩国COMS/GOCI、美国GEOS-16/ABI、日本Himawari-8/9/AHI传感器为例,利用国际上常用的6条太阳光谱曲线与传感器光谱响应函数参与计算BAESI,并与各传感器BAESI标准值进行比较。结果表明,Kurucz计算结果平均绝对误差与均方根误差均最小,是最理想的太阳光谱曲线,此外,Kurucz计算值与各传感器各波段BAESI标准值的最大偏差均小于4.5%,最大偏差百分比及对应波段分别为-2.39%(GOCI-band3)、1.49%(ABI-band6)、4.28%(AHI-08-band6)、4.42%(AHI-09-band6)。因此选择Kurucz太阳光谱曲线参与计算FY-4A/AGRI传感器各波段BAESI值,给出相应结果,并分析了计算值的不确定性,解决了将表观反射率转换为辐射亮度的困难。 相似文献
960.
The Variability of Spring Sand-Dust Storm Frequency in Northeast
Asia from 1980 to 2011 总被引:1,自引:0,他引:1
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YANG Yuanqin WANG Jizhi NIU Tao ZHOU Chunhong CHEN Miao LIU Jiyan 《Acta Meteorologica Sinica》2013,27(1):119-127
The characteristic distributions of regional sand-dust storm(SDS) weather processes over Northeast Asia from 1980 to 2011 were investigated using the shared WMO surface station meteorological data,atmospheric sounding data,China high density weather data,NCEP/NCAR reanalysis data,as well as the archived original weather maps of China.The concentration-weighted trajectory(CWT) method was used to calculate the SDS frequency from the discrete station data and to track the large-scale regional SDS weather processes in Northeast Asia.A spline trend analysis method was employed to investigate the variability of the SDS weather systems.The results show that during 1980-2011,the SDS weather processes exhibit both a historical persistence and abrupt transitions with an approximate 10-yr high-low occurrence oscillation.Through composite analysis of atmospheric circulation during high and low SDS years,it is found that the SDS occurrences are closely related to the anomalies of arctic vortex and midlatitude westerly,and the circulation patterns around the Lake Baikal.During the high frequency years,the meridianal flows in the upper and mid troposphere above the high SDS corridor in East Asia(from the Lake Balkhash along Northwest and North China,Korean Peninsula,and Japan Islands) are apparently stronger than the meridianal flows during the low SDS frequency years,favoring the development and transport of SDSs in the midlatitude regions. 相似文献