The principle and method of the adaptive filter and the filtering with wavelet transform were analyzed, and the model and method of adaptive filtering with wavelet transforms for the transient signal was established. The separated noise of signal by the multi-scale decomposition of wavelet transforms, was the input signal of adaptive filter, and accordingly the optimal filtering method of signal-noise decomposition was realized. By the adaptive filter grou Pbased on the wavelet transform, the optimal filtering to the multi-noise of signal is achieved at the same time, and the method presented in this paper has the excellent filtering capability. Examples of application demonstrate that this method presented is excellent to realize the optimal estimate to the valuable signal and noise of the transient signal in the same frequency segment. 相似文献
Transferring ecological information across scale often involves spatial aggregation, which alters information content and
may bias estimates if the scaling process is nonlinear. Here, a potential solution, the preservation of the information content
of fine-scale measurements, is highlighted using modeled net ecosystem exchange (NEE) of an Arctic tundra landscape as an
example. The variance of aggregated normalized difference vegetation index (NDVI), measured from an airborne platform, decreased
linearly with log(scale), resulting in a linear relationship between log(scale) and the scale-wise modeled NEE estimate. Preserving
three units of information, the mean, variance and skewness of fine-scale NDVI observations, resulted in upscaled NEE estimates
that deviated less than 4% from the fine-scale estimate. Preserving only the mean and variance resulted in nearly 23% NEE
bias, and preserving only the mean resulted in larger error and a change in sign from CO2 sink to source. Compressing NDVI maps by 70–75% using wavelet thresholding with the Haar and Coiflet basis functions resulted
in 13% NEE bias across the study domain. Applying unique scale-dependent transfer functions between NDVI and leaf area index
(LAI) decreased, but did not remove, bias in modeled flux in a smaller expanse using handheld NDVI observations. Quantifying
the parameters of statistical distributions to preserve ecological information reduces bias when upscaling and makes possible
spatial data assimilation to further reduce errors in estimates of ecological processes across scale. 相似文献
Stress wavelet properties are inherently involved in the process of the drop-shatter method of assessment on soil structural characteristics. The analogies between wavelet analysis and the drop-shatter process are based on two factors: scale and resolution. By carefully following the requirements of wavelet analysis, a standard procedure of soil fragmentation and sieving is described. Following this procedure, a set of equations can be derived from which surface contacting energy between soil aggregates of a specific scale can be calculated. The resultant values in fact mirror the multi-resolutions of wavelets.
Natural soil clods as well as artificial structured soil cores were used for fragmentation. Though the experiment can do well on natural soil clods, and it is precise enough in predicting structural state of a sub-dimensional clods of 8 mm, its use on artificial soil cores produced a set of data that was quite chaotic. The unique behavior experienced in the process of fragmentation of artificial soil structure indicates that there is no distinct stage between mother soil clods (cores) and its constituent primary particles. Such a state should result from an excessively large impact energy (too low a resolution in the wavelet analysis) for each drop stroke impact.
With an ultimate goal for soil process simulation, the construction of the experiment for artificial structured soil core preparation brings the traditional methods of sample preparation a step forward further by creating an environment much nearer to the field conditions experienced in natural soils. Still, extensive refinements are needed, especially for the mode of water application, cycle and intensity of management. 相似文献