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281.
在频率域,利用地震记录反卷积恢复地面运动,由于FFT运算导致的谱泄漏与系统传递函数对高频与低频的放大效果会导致地面运动恢复失败,本研究采用重叠加窗方式,可避免单一加窗的时域失真,并减小频域谱泄漏。结果表明,恢复地面运动取得了较好效果。 相似文献
282.
Introduction Since 1920s, with increasing awareness of disaster prevention and reduction in various as-pects and gradually deepened development of International Decade for Natural Disaster Reduction (IDNDR) activities in China, the role and position of disaster risk analysis and risk management work are increasingly prominent. In the final report of the IDNDR activities in 1999, the Science and Technology Committee of IDNDR had presented 5 challenge fields, which the international dis… 相似文献
283.
Tao Zhen Shen ChengDe Gao QuanZhou Sun YanMin Yi WeiXi Li YingNian 《中国科学D辑(英文版)》2007,50(7):1103-1114
High-resolution sampling, measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau, and application
of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic carbon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm−2 to 30.75×104 kg C hm−2 in the alpine meadow ecosystems, with an average of 26.86×104 kg C hm−2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of
years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m−2 a−1 to 254.93 gC m−2 a−1, with an average of 191.23 g C m−2 a−1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m−2 a−1 to 181 g C m−2 a−1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%281.23% of total CO2 emitted from organic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming, the storage, volume of flow and fate of the soil organic carbon in the alpine meadow
ecosystem of the Tibetan Plateau will be changed, which needs further research.
Supported by the National Natural Science Foundation of China (Grant Nos. 40231015, 40471120 and 40473002) and the Guangdong
Provincial Natural Science Foundation of China (Grant No. 06300102) 相似文献
284.
通过实地考察、槽探和浅层地震探测等手段以及对地质构造和地下水超采环境的分析,详细地研究了大同铁路分局地裂缝带的三维构造特征,指出现今处于发展中的地裂缝带是由东向西扩展的,扩展速率为260~520m/a,地裂缝带两侧的差异升降运动速率达22.1~24.4mm/a,主地裂缝带的水平拉张速率约1.11~11.6mm/a,垂直错动速率0.2~8.57mm/a,左旋错动速率1.87~3.57mm/a。地裂缝带的活动方式为无震蠕滑型,扩展中的地裂缝是一种无震的地质灾害 相似文献
285.
Short-range prediction of a heavy precipitation event by assimilating Chinese CINRAD-SA radar reflectivity data using complex cloud analysis 总被引:5,自引:0,他引:5
Summary With the ARPS (Advanced Regional Prediction System) Data Analysis System (ADAS) and its complex cloud analysis scheme, the
reflectivity data from a Chinese CINRAD-SA Doppler radar are used to analyze 3D cloud and hydrometeor fields and in-cloud
temperature and moisture. Forecast experiments starting from such initial conditions are performed for a northern China heavy
rainfall event to examine the impact of the reflectivity data and other conventional observations on short-range precipitation
forecast.
The full 3D cloud analysis mitigates the commonly known spin-up problem with precipitation forecast, resulting a significant
improvement in precipitation forecast in the first 4 to 5 hours. In such a case, the position, timing and amount of precipitation
are all accurately predicted. When the cloud analysis is used without in-cloud temperature adjustment, only the forecast of
light precipitation within the first hour is improved.
Additional analysis of surface and upper-air observations on the native ARPS grid, using the 1 degree real-time NCEP AVN analysis
as the background, helps improve the location and intensity of rainfall forecasting slightly. Hourly accumulated rainfall
estimated from radar reflectivity data is found to be less accurate than the model predicted precipitation when full cloud
analysis is used. 相似文献
286.
Sediment and pore water samples have been collected from the coastal tidal flat in the Shuangtaizi estuary, China, in order to investigate the geochemical behavior of iron, cadmium, and lead during diagenesis and to assess the degree of contamination. The calculated enrichment factors and geoaccumulation indices for separate elements show that anthropogenic activities have had no significant influence on the distribution of Fe and Pb in the study area, whereas the distribution of Cd has been closely influenced in this way. The high percentage of exchangeable Cd (average of 56.34%) suggests that Cd represents a potential hazard to benthic organisms in the estuary. The calculated diffusive fluxes of metals show that the most mobilized metal is Fe (9.22 mg m?2 a?1), followed by Cd (0.54 mg m?2 a?1) and Pb (0.42 mg m?2 a?1). Low Fe2+ contents in surface pore water, alongside high chromium-reducible sulfur contents, and low acid-volatile sulfur, and elemental sulfur contents at 0–25 cm depth in sediments show that Fe2+ is formed by the reduction of Fe oxides and is transformed first to a solid phase of iron monosulfides (FeS) and eventually to pyrite (FeS2). The release of adsorbed Pb due to reductive dissolution of Fe/Mn oxides during early diagenesis could be a source of Pb2+ in pore water. From the relatively low total organic carbon contents measured in sediments (0.46–1.28%, with an average of 0.94%) and the vertical variation of Cd2+ in pore water, sulfide or Fe/Mn oxides (instead of organic matter) are presumed to exert a significant influence on carrying or releasing Cd by the sediments. 相似文献
287.
过去2000年以来地磁偶极子的长期变化 总被引:1,自引:0,他引:1
利用地磁场模型资料,计算和分析了公元0~2000年的地磁场偶极子磁矩和地磁北极位置的长期变化。结果表明:过去2000年中,地磁场的偶极子磁矩并非一直减小,有近400年的时间是持续增长的。地磁北极位置的移动并不均匀,在纬度方向的变化范围只有10°左右,经度方向变化有255°。 相似文献
288.
二轴晶光率体光性正负有两种判别方法:一种是根据光轴角(2V)的锐角平分线(Bxa)与Ng一致还是与Np一致来判别,其临界点是2y=90°;另一种是根据三个主拆射率的相对大小来判别.由于二轴晶光率体为三轴椭球体,在其临界点Ng一Nm=Nm一Np时,光轴角并不等于90°。就是说,两种判别方法的临界点不一致。本文从光率体几何特性研究入手,通过几何及数学方法,着重讨论上述两种判别方法在其临界点时的相对关系,并结合实际例证,认为二轴晶光率体光性正负的临界点不能只确定为一个点,而应限定在一个范围,即2V=90°到Ng-Nm=Nm-Np之间。 相似文献
289.
290.