基于移动开窗法协方差估计和方差分量估计的自适应滤波   总被引：8，自引：1，他引：8  

杨元喜  徐天河 《武汉大学学报(信息科学版)》2003,28(6):714-718

基于移动窗口协方差估计和方差分量估计，提出了一种新的自适应Kalman滤波技术。计算结果证实，该方法能有效地控制观测异常和载体状态扰动异常对动态系统参数估值的影响。  相似文献   

Principal axes of M-DOF structures Part Ⅱ: Dynamic loading     

Zach Liang  George C.Lee 《地震工程与工程振动(英文版)》2003,2(1)

This paper is the second in a two-part series that discusses the principal axes of M-DOF structures subjected to static and dynamic loads. The primary purpose of this series is to understand the magnitude of the dynamic response of structures to enable better design of structures and response modification devices/systems. Under idealized design conditions, the structural responses are obtained by using single direction input ground motions in the direction of the intended response modification devices/systems, and by assuming that the responses of the structure is decoupleable in three mutually perpendicular directions. This standard practice has been applied to both new and retrofitted structures using various seismic protective systems. Very limited information is available on the effects of neglecting the impact of directional couplings (cross effects of which torsion is a component) of the dynamic response of structures. In order to quantify such effects, it is necessary to examine the principal axes of structures under both static and dynamic loading. In this two-part series, the first paper is concerned with static loading, which provides definitions and fundamental formulations, with the conclusion that cross effects of a statically loaded M-DOF structure resulting from the lack of principal axes are of insignificant magnitude. However, under dynamic or earthquake loading, a relatively small amount of energy transferred across perpendicular directions is accumulated, which may result in significant enlargement of the structural response. This paper deals with a formulation to define the principal axes of M-DOF structures under dynamic loading and develops quantitative measures to identify cross effects resulting from the non-existence of principal axes.  相似文献   

A process‐based conversion model for caesium‐137 derived erosion rates on agricultural land: an integrated spatial approach     

K. Van Oost  G. Govers  W. Van Muysen 《地球表面变化过程与地形》2003,28(2):187-207

There is increasing recognition that ¹³⁷Cs data remain one of the few sources of spatially distributed information concerning soil erosion. However, many of the conversion models that have been used to convert ¹³⁷Cs data into soil redistribution rates failed to account for some of the key factors affecting the redistribution of ¹³⁷Cs in agricultural landscapes. The conversion model presented in this paper aims to overcome some of the limitations associated with existing models and therefore to provide more realistic estimates of soil erosion rates on agricultural land. The conversion model aims at coupling soil redistribution processes directly with ¹³⁷Cs redistribution. Emphasis is placed on the spatial representation of soil redistribution processes and the adequate simulation of tillage processes. The benefits of the presented model arise from the two‐dimensional spatial integration of mass balance models with soil erosion models. No a priori assumptions about the intensity of any soil redistribution process are necessary and the level of agreement between observed and simulated ¹³⁷Cs inventories enables us to evaluate the performance of the model. The spatial implementation and the use of fuzzy parameter sets also allow us to assess the uncertainties associated with soil erosion estimates. It was shown that an adequate simulation of tillage processes is necessary and that simplified tillage models may lead to erroneous estimates of soil redistribution. The model was successfully applied to a study site in the Belgian Loam Belt and the results indicated that tillage is the dominant process. Furthermore, the uncertainties associated with the estimation of water erosion rates were much higher than those associated with tillage, especially for depositional areas. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

A MODEL FOR QUANTITATIVELY ESTIMATING SHORT-RANGE PRECIPITATION BASED ON GMS DIGITALIZED CLOUD MAPS—PART Ⅱ:ASSESSMENT OF RESULTS FROM THE MODEL FOR SATELLITE-IMAGE QUANTITATIVELY ESTIMATING PRECIPITATION          下载免费PDF全文

LUO Changrong  ZHANG Mingxi  ZOU Yan  HUANG Yongyu 《Acta Meteorologica Sinica》2003,17(2):245-256

This is Part Ⅱ of this series.It introduces the technique for recognizing MαCS phased properties and its precipitation center or centers by means of dynamic digitalized cloud maps and presents the assessment of the effectiveness of the model proposed in Part Ⅰ as to its fitting and forecasting accuracy.  相似文献   

青海龙羊峡超低频电磁辐射在中强震前的短期(短临)异常特征及单台预报效能     

马玉虎  马文静  李北海  都昌庭 《内陆地震》2003,17(4):337-342

根据青海龙羊峡电磁台自1991年9月以来的资料，对电磁波辐射在震前的异常特征进行了分析总结。地震往往发生在电磁波异常结束后，电磁波在一组异常中出现显著异常是地震进入短期(短临)异常的主要特征。显著异常判断指标是一次地震中异常幅度(产生的场强)最大的或异常持续时间最长的异常。通过对有震异常、无震异常和漏报的统计，龙羊峡电磁波辐射的预报效能并不高。  相似文献   

抗差理论及在水文学中的应用   总被引：11，自引：0，他引：11       下载免费PDF全文

包为民  嵇海祥  胡其美  瞿思敏  赵超 《水科学进展》2003,14(4):528-532

综述了国内外抗差理论的研究过程与发展趋势,介绍了抗差估计的理论基础、方法和特点,分析了抗差理论在水文学中的应用现状,提出了进一步研究的问题.  相似文献   

A New Damage Index     

Blong  Russell 《Natural Hazards》2003,30(1):1-23

A new damage index to estimate damage to buildings relies on construction costs per square metre, and a replacement ratio which approximates costs relative to the cost of replacing a median-sized family home. Building damage is estimated against a five-point scale with Central Damage Values at 0.02, 0.1, 0.4, 0.75 and 1.0 of the replacement cost.Damage is expressed as damage in House Equivalents (HE) = Replacement Ratio × Central Damage Value. The Damage Index = log₂ (HE) provides a simple 0–20 scale covering total damage of less than 1 HE to>1 million HE. For all natural hazard impacts in Australia DI is less than 12.Where the only damage data available are of lesser quality Generic or Qualitative Damage Indices (GDI and QDI) can be used. The various advantages and limitations of the Damage Index are discussed.  相似文献   

板状金矿体的资源/储量计算方法   总被引：1，自引：0，他引：1  

李树海  王迎春 《黄金地质》2003,9(4):63-68

为提高地质块段法在板状金矿体资源，储量计算中的准确性，结合实例着重对各项计算参数的确定方法进行了论述；介绍了块段投影面积的平行线计算法及坐标计算法；强调用加权平均法求得块段平均厚度及平均品位；提出块段体积的计算宜采用斜面积与投影厚度的乘积，以补偿波状起伏的矿体因投影而减少的体积。  相似文献   

Automatic Surface Reconstruction Based on the Fusion of Fuzzy Logic and Robust Estimation Techniques     

Farhad Samadzadegan  Ali Azizi  Caro Lucas  & Michael Hahn 《The Photogrammetric Record》2002,17(100):651-674

Automatic surface reconstruction by means of digital image matching essentially involves computation in both image and object spaces. In image space, image matching is performed according to certain radiometric and geometric similarity criteria for conjugate point determination. The matching operations may therefore be regarded as decision–making processes. In practice, however, the similarity criteria for conjugate point determination demonstrate non–deterministic behaviour. Thus, the nature of these decision–making processes is more compatible with fuzzy reasoning concepts. In object space, on the other hand, surface reconstruction procedures, which operate on the basis of previously determined conjugate points, are essentially deterministic in nature and hence demand rigorous geometric modelling. In this paper, a new approach for automatic surface modelling is proposed, based on two different mathematical treatments: a fuzzy logic reasoning method for the conjugate point determination in image space; and a robust finite elements approach for the surface modelling in object space. Tests carried out on real data demonstrate the high potential of the strategy proposed.  相似文献   

按分量加权的探测目标状态线性融合   总被引：2，自引：0，他引：2  

徐毓  李群  周焰  杨瑞娟 《武汉大学学报(信息科学版)》2002,27(4):420-423

给出了一种在使残差方差矩阵的迹最小化意义下的状态估计线性组合的最优融合准则和加权矩阵的计算公式，并给出了利用实际数据计算的试验结果。结果表明，利用本方法使融合后的目标轨迹与目标真实运动轨迹非常接近，能有效地提高雷达情报的综合质量。  相似文献