时滞广义时变系统的渐近稳定与镇定     

毕淑慧  高存臣 《中国海洋大学学报(自然科学版)》2006,36(Z1):212-214

研究了时滞广义时变系统的渐近稳定和镇定问题。首先利用相关不等式,通过建立Lyapunov方程,给出了1个时滞广义时变系统无脉冲、渐近稳定性的充分条件。然后,基于这一工作,利用Riccati方程,进一步研究了时滞广义时变系统的镇定问题。最后,举例说明该结论的可行性。  相似文献   

初值影响下误差分配的微观结构     

何珊  陈锴  李婷  鹿荻 《测绘科学》2012,37(2):123-125

测量数据处理中,初值对平差结果存在很大的影响,其机理影响设计矩阵的数值特征,进而影响误差的分配结构。本文着力于大地测边控制网的模拟分析,研究初值如何影响误差分配。结果表明,在奇异的网形结构下,初值越靠近真实值,对随机误差的放大作用越大。初值对线性化误差存在影响,在图形最弱方向上,线性化误差影响最大,且误差影响随初值靠近真值而减小。平差结果是随机误差的放大倍率与线性化误差的综合作用的结果,其准确度取决于线性化误差与随机误差的平衡性。  相似文献   

Potential Predictability of Sea Surface Temperature in a Coupled Ocean--Atmosphere GCM     

YAN Li  WANG Panxing  YU Yongqiang  LI Lijuan  WANG Bin 《大气科学进展》2010,27(4):921-936

Using the Flexible Global Ocean--Atmosphere--Land System model (FGOALS) version g1.11, a group of seasonal hindcasting experiments were carried out. In order to investigate the potential predictability of sea surface temperature (SST), singular value decomposition (SVD) analyses were applied to extract dominant coupled modes between observed and predicated SST from the hindcasting experiments in this study. The fields discussed are sea surface temperature anomalies over the tropical Pacific basin (20^oS--20^oN, 120^oE--80^oW), respectively starting in four seasons from 1982 to 2005. On the basis of SVD analysis, the simulated pattern was replaced with the corresponding observed pattern to reconstruct SST anomaly fields to improve the ability of the simulation. The predictive skill, anomaly correlation coefficients (ACC), after systematic error correction using the first five modes was regarded as potential predictability. Results showed that: 1) the statistical postprocessing approach was effective for systematic error correction; 2) model error sources mainly arose from mode 2 extracted from the SVD analysis---that is, during the transition phase of ENSO, the model encountered the spring predictability barrier; and 3) potential predictability (upper limits of predictability) could be high over most of the tropical Pacific basin, including the tropical western Pacific and an extra 10-degrees region of the mid and eastern Pacific.  相似文献   

INGULAR CROSS SPECTRUM APPLIED ON DIAGNOSTIC ANALTSIS OF AIR-SEA INTERACTION     

朱艳峰  丁裕国  何金海 《热带气象学报(英文版)》1999,5(2):163-170

The Singular Cross Spectrum Analysis(SCSA) method was employed to investigate the coupled-periods of air-sea/mid-low circulation interaction using 1951-1993 500-hpa geopotential heights and the sea surface temperature(SST)in the Northern Hemisphere. Results show that air-sea correlation is noticeable on the 3-7 year scale which is similar to ENSO circle. In this sense, ENSO is a Strong signal. Quasi-ten/quasi-four year periods are prominent in the mid-low interaction, and quasi-if our year oscillation is uniform with the ENSO circle.Studies indicate that the mid-low interaction possess quasi-ten year oscillation beside being affected by ENSO.  相似文献   

A New Temperature Channel Selection Method Based on Singular Spectrum Analysis for Retrieving Atmospheric Temperature Profiles from FY-4A/GIIRS     

Peipei YU  Chunxiang SHI  Ling YANG  Shuai SHAN 《大气科学进展》2020,37(7):735-750

Hyperspectral data have important research and application value in the fields of meteorology and remote sensing.With the goal of improving retrievals of atmospheric temperature profiles, this paper outlines a novel temperature channel selection method based on singular spectrum analysis(SSA) for the Geostationary Interferometric Infrared Sounder(GIIRS), which is the first infrared sounder operating in geostationary orbit. The method possesses not only the simplicity and rapidity of the principal component analysis method, but also the interpretability of the conventional channel selection method. The novel SSA method is used to decompose the GIIRS observed infrared brightness temperature spectrum(700-1130 cm~(-1)), and the reconstructed grouped components can be obtained to reflect the energy variations in the temperature-sensitive waveband of the respective sequence. At 700-780 cm~(-1), the channels selected using our method perform better than IASI(Infrared Atmospheric Sounding Interferometer) and Cr IS(Cross-track Infrared Sounder)temperature channels when used as inputs to the neural network retrieval model.  相似文献   

二维地层结构和速度的走时反演     

张文生  谢靖 《吉林大学学报(地球科学版)》1993,(4)

介绍了在倾斜均匀各向同性层状介质情况下,根据地震反射走时反演二维地层结构和地层速度的地震射线层析成像方法——走时反演。正演模型射线追踪是根据Fermat原理实现的,即求解满足该原理的非线性方程组得到射线与界面的交点,进而计算相应的走时。反演是先假设一初始模型,用最优化方法使射线追踪走时与观察走时的残差极小。最后计算了分辨矩阵和信息密度矩阵,以评价反演结果。对有噪情形也进行了反演。  相似文献   

SVD方法在场的定量预测中的应用     

张礼平  柯怡明  王康康 《热带气象学报》2004,20(4):383-390

经SVD分析,截取足够多的预报场和因子场时间系数,使其相互关系代表两场的大尺度联系,预报场时间系数与其奇异向量线性组合估计场能反映原场主要特征.利用最小二乘法得到数值上最接近原场的初值,借助最优化技术,确定合理的系数,建立预测公式,由因子场时间系数预测预报场时间系数,同时订正预报场时间系数a1,a2,……,aN本身的误差和反演过程中分析误差造成的场格点趋势预测的误差.最后将预测的预报场时间系数和对应奇异向量反演为整个场的预报.预报过程重点考虑可预报的大尺度变化,滤去不可预报的小扰动,依据两场主要耦合关系,预测预报场未来的主要变化.  相似文献   

基于奇异值分解和小波阈值方法的地震资料处理方法     

HAO Xue LI Yue YANG Bao-jun .College of GeoExploration Science  Technology  Jilin University  Changchun  China .College of Communicate Engineering  Jilin University  Changchun  China 《吉林大学学报(地球科学版)》2006,(Z2)

奇异值分解是一种基于代数特征值的提取方法,小波变换是一种时间频率域的去噪方法,两者在去噪方面各有特点。将奇异值分解和小波阈值去噪的方法有机地结合起来,用于消除地震勘探资料中的随机噪声。仿真实验显示对于较低信噪比资料仍有很好的处理效果。  相似文献   

一类常系数线性奇异积分方程的讨论     

蒋勇国 《南京气象学院学报》2002,25(5):706-710

在“矩形”主值的基础上,获得合成公式,并利用合成公式讨论了一类相应的常系数线性奇异积分方程。  相似文献   

A model for solar quiet day variation at low latitude from past observations using singular spectrum analysis     

S. K. Bhardwaj  G. K. Rangarajan 《Journal of Earth System Science》1998,107(3):217-224

Singular spectrum isolates significant principal components in a time series from the embedded noise. This tool-kit is used to reconstruct trend-free individual time series, formed by restricting the mean monthly hourly values of geomagnetic field to one hour at a time at a low latitude station Alibag (dipole latitude 9.5°N). Each reconstructed component is extrapolated over the next 12 values using an autoregressive model based on Burg’s maximum entropy algorithm. Details of a numerical approach to increase the reliability of extrapolation are highlighted. The extrapolated reconstructed components are then combined to generate predicted monthly values for each hour. The mean diurnal variation for any month obtained from the extrapolated individual hourly time series compares favorably with the observations. This approach to Sq(H) modelling incorporating both long and short term variations will be beneficial in the derivation of Dst index.  相似文献