周期和振幅相结合检测地震方法研究     

张念印苏文  张志俊 《大地测量与地球动力学》2007,27(F06):133-135

分析了单纯用地震波振幅作为报警阈值的缺点,通过数字地震仪与模拟地震仪报警机制的对比,提出用检测周期和振幅相结合的方法来实现地震报警。  相似文献   

大气和极移的高频变化比较     

王保卫  顾震年  金文敬 《天文学报》2001,42(3):278-286

采用从1988－1999年的现代技术测定的高精度极移序列EOP（IERS97C04）推导出激发函数χ^m）和美国国家环境预测中心和美国国家大气研究中心（CNEP／NCAR）提供的大气角动量激发函数χp和χib^p，使用几种数据分析方法，分析了大气对极移高频振荡（12－42cpy)激发贡献，复数小波变换和功率谱分析表明，χ^m和χ^p序列在高频段内呈现比较强的谱峰，它们具有相似的谱特征，比较而言，χib^p在这个频率段内比χ^p要弱些，χ^m和χ^p之间的相关系数分别为0．75（逆向）和0．6（顺向），两个序列之间的平方相关谱的估计值分别在0．5－0．9之间（负频）和0．4－0．6（正频），相位谱表明χ^p(AAM)超前x^m一天左右，这些大气是极移高频变化的主要激发源，特别是在逆向运动上具有更大的贡献，由于它们之间位相差和振幅变化的不稳定性，说明可能存在AAM以外的其他激发源，这个问题有待进一步深入研究。χ  相似文献   

Footprints of the weak s-process in the carbon-enhanced metal-poor star ET0097     

Guochao Yang  Hongjie Li  Nian Liu  Wenyuan Cui  Yanchun Liang  Bo Zhang 《Astrophysics and Space Science》2016,361(9):317

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多沙河流河口泥沙淤积自生性过程试验研究          下载免费PDF全文

罗优  简鸿福  罗琳  邓亮  周念 《水科学进展》2018,29(3):348-356

多沙河流河口输沙不平衡带来的淤积演变过程,动态调整着上游河道控制基面,影响通航和防洪安全等。开展水槽试验,控制上游水沙条件和下游水位不变,研究河口三角洲自生性过程的形成机理、波动性和趋势性演变特征。试验中观测到淤积朵体迁移、溯源冲淤和河道摆动等自生性调整现象,其中朵体发育和迁移起控制作用。研究结果表明:自生性过程具有内在临界性,不同水沙条件下淤积朵体临界尺度不同,相应的水位波动周期、溯源波能量、水位涨落规律和三角洲形态亦有所差异。结合试验成果探讨了自生性过程形成的内在动力、临界性及其与三角洲形态的内在联系。  相似文献   

Research Progress of Relative Humidity and Its Changing Annual Cycle     

Da Nian  Qimin Deng  Zuntao Fu 《地球科学进展》2018,33(7):762-774

Studies on the characteristics of relative humidity annual cycle change include the frequency, phase, and amplitude of the time series and their changes. The effective diagnosis of the relative humidity annual cycle can provide important help in the monitoring and regulation of seasonal haze, the spatial distribution of epidemic outbreaks and their prevention and control, and the real-time forecasting and decision-making of monsoon precipitation. Different from studies on the trend of the relative humidity, the diagnosis in the annual cycle is scarce. This paper summarized the research status of relative humidity and its annual cycle, introduced several current methods for extracting common signals, and evaluated the feasibility of these methods for extracting annual cycle signals. Due to the time-varying characteristics of the annual cycle of relative humidity and complex structures such as asymmetric triangular waves, square-like waves, and state transients, harmonic-based extraction methods are difficult to succeed. The nonlinear signal extraction method with high noise immunity will solve this problem. At present, the relative humidity annual cycle studies urgently need to be improved and improve the quality of relative humidity observation data, accurately extract and quantify the time-varying characteristics and complex structure of the annual cycle. Moreover, combining the dynamic process and statistical analysis, we also need to study the physical mechanism of the change of relative humidity annual cycle (frequency, phase, amplitude, etc.) in China.  相似文献   

The Deep Geophysical Structure of the Middle Section of the Longmen Mountains Tectonic Belt and its Relation to the Wenchuan Earthquake   总被引：1，自引：0，他引：1  

YU Nian  WANG Xuben  HU Xiangyun  CAI Xuelin  KAN Aike  ZHAO Ning 《《地质学报》英文版》2014,88(2):483-497

Investigation of the deep geophysical structure of the Longmen Mountains tectonic belt and its relation to the Wenchuan Earthquake is important for the study of earthquakes. By using magnetotelluric sounding profiles of the Luqu–Zhongjiang and Anxian–Suining; seismic sounding profiles of the Sichuan Maowen–Chongqing Gongtan, the Qinghai Huashi Gorge–Sichuan Jianyang, and the Batang–Zizhong; and magnetogravimetric data of the Longmen Mountains region, the deep geophysical structure of the Songpan–Ganzi block, the western Sichuan foreland basin, and the Longmen Mountains tectonic belt and their relation was discussed. The eastward extrusion of the Qinghai–Tibet Plateau thrusts the Songpan–Ganzi block upon the Yangtze block, which obstructs the eastward movement of the Qinghai–Tibet Plateau. The Maoxian–Wenchuan, Beichuan–Yingxiu, and Anxian–Guanxian faults of the Longmen Mountains fault belt dip to northwest with different dip angles and gradually converge in the deeper parts. Geophysical structure suggests that an intracrustal low-velocity, low-resistivity, and high-conductivity layer is common between the middle and upper crust west of the Longmen Mountains tectonic belt but not in the upper Yangtze block. The Sichuan Basin has a thick low-resistance sedimentary layer on a stable high-resistance basement; moreover, there are secondary paleohighs and depression structures at the lower part of the western Sichuan foreland basin with characteristic of high magnetic anomalies, whereas the Songpan–Ganzi block has a high resisitivity cover of upper crust and continues to a low-resistance layer. Considering the Longmen Mountains tectonic belt as the boundary, there are Bouguer gravity anomalies of "one belt between two zones." Thus, we infer that there is a corresponding relation between the inferred crystalline basement of the Songpan block and the underlying basin basement of the Longmen Mountains fault belt. Furthermore, there may be an extensive ancient Yangtze block, which is west of the Ruoergai block. In addition, the crust–mantle ductile shear zone under the Longmen Mountains tectonic belt is the main fault, whereas the Beichuan–Yingxiu and Anxian–Guanxian faults at the surface are earthquake faults. The Wenchuan Ms 8.0 earthquake might be attributed to the collision of the Yangtze block and the Qinghai–Tibet Plateau. The eastward obduction of the eastern edge of the Qinghai–Tibet Plateau and eastward subduction of its deeper part under the influence of the collision of the Indian, Pacific, and Philippine Plates with the Eurasia Plate might have caused the Longmen Mountains tectonic belt to cut the Moho and extend to the middle and upper crust; thus, creating high stress concentration and rapid energy release zone.  相似文献   

Problematic Soft Soil Improvement with Both Polypropylene Fiber and Polyvinyl Acetate Resin     

Esmaeil Masoumi  Seyed Mehdi Abtahi Forooshani  Farzad Abdi Nian 《Geotechnical and Geological Engineering》2013,31(1):143-149

Several methods are used to improve mechanical properties of loose soils including rewetting, soil replacement, compaction control, chemical additives, moisture control, thermal methods, and more recently, discrete fibers. All the methods are applied to soft soil to increase load bearing capacity and to improve other properties such as prevention of erosion and dust generation. In the present study, a new method of soil improvement using both discrete polypropylene (PP) fibers and polyvinyl acetate (PVAc) is introduced. The method is applied to improve load bearing capacity of a problematic sandy soil in both dry and saturated states. Based on the results from CBR tests on various specimens, it has been revealed that the combination of PP fiber and PVAc resin with weight percentages of 0.1 and 0.6 %, respectively, had the optimum effect in increasing the CBR value in both saturated and dry soil specimens. It should be mentioned that this method has caused a great increase in the CBR value in the saturated soil.  相似文献   

多极距地电场观测系统数据处理软件     

李伟  陈飞  徐年  王锋  皇甫德银 《地震地磁观测与研究》2012,33(Z1)

中国地震前兆台网数据处理系统针对传统的“L”型地电场布极方式而开发的数据处理软件,不能对南京地震台地电场数据有效处理,考虑到地电场的矢量特性,南京地震台取消斜道观测,布设同方向3个测道的多极距地电场观测系统.  相似文献   

中国性病疫情的时空差异与经济驱动机制     

杨振  王念  王宇 《热带地理》2016,36(5):761-766

综合采用变异系数、收敛性检验、分位数回归等方法考察中国2004―2014 年2 类经典性病（淋病、梅毒）疫情的时空差异特征与经济驱动机制,结果表明：1）2004 年以来,中国2 类性病的发病水平呈现“淋病降、梅毒升”的时序变化特征,病种结构发生转换,总体发病规模持续扩增;2）每年新发淋病数的地区差异略有增加,发病率差异持续降低,总体发病水平明显收敛,各地区预期会逐步趋同于某一较低水平,梅毒疫情预期将逐步趋同于某一较高水平;3）经济发展对低、中、高3 类发病水平的疫情变化均有显著的正向影响,部分地区存在明显的“经济越发展,疫情越严重”现象。  相似文献   

Elastic wave modelling method based on the displacement–velocity fields: an improving nearly analytic discrete approximation     

Dinghui Yang  Enru Liu  Guojie Song  Nian Wang 《Journal of Seismology》2009,13(2):209-217

In this paper, we present an improvement to our previously published nearly analytic discrete method (NADM) to solve acoustic and elastic wave equations. We compare the numerical errors of the improved NADM with the original NADM and also the fourth-order Lax–Wendroff correction and present examples of three-component wave fields in 2D transversely isotropic media with strong velocity contrasts. Comparing with the original NADM, we find that the improved method requires significantly less storage space and can increase the time accuracy from second order of the original NADM to fourth order, while the space accuracy remains the same as that of the original one. Theoretical analyses and numerical results suggest that our improved NADM is suitable for large-scale numerical modelling as it can effectively suppress numerical dispersion and source-generated noises caused by discretising wave equations when too-coarse grids are used.  相似文献