Influence of long‐period filter cut‐off on elastic spectral displacements     

Sinan Akkar  Julian J. Bommer 《地震工程与结构动力学》2006,35(9):1145-1165

The effect of the long‐period filter cut‐off, T_c, on elastic spectral displacements is investigated using a strong ground‐motion database from Europe and the Middle East. The relation between the filter and oscillator responses is considered to observe the influence of T_c for both analogue and digital records, and the variations with site classification, magnitude, filter order and viscous damping. Robust statistics are derived using the re‐processed European data to generalize the effects of the long‐period filter cut‐off on maximum oscillator deformation demands as a function of these seismological and structural features. Statistics with a 95% confidence interval are derived to suggest usable period ranges for spectral displacement computations as a function of T_c. The results indicate that the maximum period at which spectral displacements can be confidently calculated depend strongly on the site class, magnitude and filter order. The period range where reliable long‐period information can be extracted from digital accelerograms is twice that of analogue records. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

The use of riparian vegetated filter strips to reduce river sediment loads: an overestimated control measure?   总被引：1，自引：0，他引：1  

Gert Verstraeten  Jean Poesen  Katleen Gillijns  Gerard Govers 《水文研究》2006,20(20):4259-4267

The spatially distributed soil erosion and sediment delivery model WATEM/SEDEM was used to simulate the impact of riparian vegetated filter strips (RVFSs) on river sediment delivery at different spatial scales. For a field plot with a straight slope, sediment reduction by the RVFSs is comparable to results obtained through experimental set‐ups elsewhere (i.e. >70%). However, at the scale of an entire catchment, sediment reduction is much less (i.e. ±20%) due to (1) overland flow convergence, which reduces the sediment trapping efficiency of an RVFS, and (2) because part of the sediment bypasses the RVFSs through ditches, sewers and road surfaces. These results suggest that, at the catchment scale, RVFSs should be accompanied with other conservation techniques that are more appropriate for reducing river sediment loads, and that also reduce on‐site soil erosion. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

高效纤维束过滤器去除黄河水浊度的应用     

付宏峰 《地下水》2006,28(1):71-72

简要介绍了纤维束过滤器的工作原理,针对原水水质及用户对水质的要求,设计了用纤维束过滤器去除黄河水浊度的处理工艺,提出了纤维束过滤器的运行参数,分析了纤维束过滤器对黄河水浊度的去除效果.  相似文献   

Wavelet filter analysis of atmospheric pressure effects in the long-period seismic mode band   总被引：2，自引：0，他引：2  

X.-G. Hu  L.-T. Liu  H.T. Hsu 《Physics of the Earth and Planetary Interiors》2006,154(1):70-84

The importance of the reduction of atmospheric pressure effects becomes very clear when investigating seismic normal-mode spectra below 1.5 mHz. The usual simple correction method consists in subtracting a term converted from local atmospheric pressure (pressure multiplied by a frequency-independent admittance) from the gravity record in time domain. Thus, estimating an efficient admittance is the key for an improved correction. Band-pass filters derived from dyadic orthogonal wavelet transform, having narrow pass-bands with good frequency response but without Gibbs phenomenon and causing no phase lag, are very helpful to estimate an efficient admittance, which is both time and frequency-dependent. Processing of high quality superconducting gravimeter (SG) records for the great Sumatra earthquake (Mw = 9.3, Dec 26, 2004) with wavelet filters reveal the three very well resolved splitting singlets of overtone ₂S₁ with a single gravity record after correction with time-dependent and frequency-dependent admittances. We also observe all coupled toroidal modes below 1.5 mHz, except ₀T₅, ₀T₇ and ₁T₁, with good signal-to-noise ratio (SNR); moreover, toroidal modes ₁T₂ and ₁T₃ are for the first time unambiguously revealed in vertical components.  相似文献   

均方根信息滤波和平滑及其在低轨卫星星载GPS精密定轨中的应用     

赵齐乐  刘经南  葛茂荣  施闯 《武汉大学学报(信息科学版)》2006,31(1):12-15

从均方根信息滤波和平滑的基本原理出发．结合卫星定轨的实际特征．导出了其在精密定轨软件中实现的详细公式；针对均方根滤波的特点，提出了快速高效地探测和修复GPS观测数据中周跳的新方法。利用实测星载GPS数据验证了基于均方根滤波的质量控制算法的可靠性．得到了有益的结果。  相似文献   

UKF滤波器性能分析及其在轨道计算中的仿真试验   总被引：5，自引：0，他引：5  

蔡志武  赵东明 《武汉大学学报(信息科学版)》2006,31(2):180-183

讨论了UT（unscented transform）变换的性质，给出了一种新的扩展型卡尔曼滤波器UKF（unscented Kalman filter），它不仅具有较高的精度，而且不必计算偏导数阵。仿真分析的结果表明，UKF有良好的状态估计性能，使用简便，适合于非线性系统状态估计。  相似文献   

一种纹理特征融合分类算法     

赵银娣  张良培  李平湘 《武汉大学学报(信息科学版)》2006,31(3):278-281

分别利用多通道Gabor滤波器和马尔可夫随机场模型对纹理图像进行分析，得到两组特征影像。将上述两组特征影像进行融合，最后利用融合后的数据实现图像的分类。实验证明，基于上述方法的纹理特征融合分类算法大大提高了图像的分类精度。  相似文献   

Application of ensemble kalman filter to geophysical parameters retrieval in remote sensing:A case study of kernel-driven BRDF model inversion   总被引：2，自引：0，他引：2  

QIN Jun  YAN Guangjian  LIU Shaomin  LIANG Shunlin  ZHANG Hao  WANG Jindi  LI Xiaowen 《中国科学D辑(英文版)》2006,49(6):632-640

Remote sensing can provide multi-spatial resolution, multi-temporal resolution multi-spectral band and multi-angular data for the observation of land surface. At present, one of research focuses is how to make the best of these data to retrieve geophysical parameters in conjunction with their a priori knowledge and simul-taneously consider the influence of data uncertainties on inversion results[1-5]. The essence of remote sensing lies in inversion. It is difficult to precisely retrieve parame…  相似文献   

Wavelet filter analysis of splitting and coupling of seismic normal modes below 1.5 mHz with superconducting gravimeter records after the December 26, 2004 Sumatra earthquake     

Jacques Hinderer 《中国科学D辑(英文版)》2006,49(12):1259-1269

New generation superconducting gravimeters (SGs), which have been demonstrated to be better than the best seismometers STS-1 at frequencies below 1 mHz, can be accepted as the quietest vertical seismometers for observation of long-period earth free oscillations. Wavelet filtering with narrow band-pass frequency response as shown in this paper is very helpful in removing at- mospheric pressure effects from on gravity records in long-period seismic mode frequency bands. The processing of high quality SG records after the great Sumatra earthquake (Dec. 26, 2004) with wavelet filtering leads to clear observations of all coupled toroidal modes below 1.5 mHz except these for 0T5, 0T7 and 1T1; moreover 1T2 and 1T3 are, for the first time, unambiguously revealed in the vertical components of the free oscillations. The three well-resolved splitting singlets of overtones 2S1 are observed from a single SG record for the first time.  相似文献   

MT时间序列的FIR数字滤波分析   总被引：1，自引：0，他引：1  

李建华  林品荣  何畏  郑采君 《物探与化探》2007,31(Z1):24-28

大地电磁测深法(MT)野外观测得到的原始资料是包含多种频谱的时间序列,这种时间序列中常包含不需要的信息和50 Hz及其谐波的干扰。结合FIR数字滤波技术与MT时间序列的特征,提出了一种基于FIR数字滤波技术的MT时间序列去噪方法,讨论了FIR数字滤波器的原理和实现,分析了理论数据通过FIR数字滤波的带通和陷波处理,探讨了对实测时间序列的带通和陷波所取得的效果。  相似文献