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171.
172.
变形体的变形模式确定的情况下,应用灵敏度准则进行监测网的设计;根据Tayor展式,导出了监测网顾及灵敏度准则的二类设计模型,并对其解算及模拟算例加以说明。 相似文献
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王仲锋 《测绘与空间地理信息》1998,(2)
本文结合参数平差和主成分估计理论,导出了误差方程中含多重共线性时未知参数的求解公式,并以定理的形式,证明了主成分估计的解是极小范数解。由此,将主成分估计推广到秩亏网平差中,同时导出了未知参数估值之协因数阵的计算公式,同时,证明了自由网平差的传统特性。 相似文献
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176.
Ghassem Habibagahi 《Soil Dynamics and Earthquake Engineering》1998,17(1):53-56
Estimation of the magnitude of reservoir induced seismicity is essential for seismic risk analysis of dam sites. Different geological and empirical methods dealing with the mechanism or magnitude of such earthquakes are available in the literature. In this study, a method based on an artificial neural network utilizing radial basis functions (RBF network) was employed to analyze the problem. The network has only two input neurons, one representing the maximum depth of the reservoir and the other being a comprehensive parameter representing reservoir geometry. Magnitudes of the induced earthquakes predicted using the RBF network were compared with the actual recorded data. Compared with the conventional statistical approach, the proposed method gives a better prediction, both in terms of coefficients of correlation and error rates. 相似文献
177.
The analysis of drainage network composition 总被引:1,自引:0,他引:1
J. S. Smart 《地球表面变化过程与地形》1978,3(2):129-170
The Horton method of analyzing drainage network composition is reviewed, with the conclusion that it has not been very effective either in improving understanding or in developing useful methods of characterizing drainage basins. New methods which are based on the link rather than the Horton (or Strahler) stream are described. A number of detailed examples of the application of these new methods to the topologic and geometric properties of networks are provided. The results are compared with the predictions of the random model. Data used in the analysis were obtained from 1:24,000 U.S.G.S. topographic maps of eastern Kentucky. Thirty drainage basins were selected and their channel networks were outlined first by the contour-crenulation (CC) method and then by another, more objective, method (SC) in which stream sources were identified by a quantitative slope criterion. The CC and SC samples comprise about 8,700 and 1,700 links, respectively. The three most important results of the analysis are: (1) the channel networks are slightly but significantly more elongated than predicted by the random model, (2) there are fewer second magnitude links than predicted, and (3) the length distribution for interior links depends upon the kind of link (interior or exterior) joined downstream. These features are found in both CC and SC networks. 相似文献
178.
The random model of drainage basin composition is founded on the assumptions that (a) natural channels are topologically random in the absence of geological controls and (b) for channel networks developed in similar environments, the exterior and interior link lengths are independent random variables with a common distribution for each type. The effectiveness of this model in estimating the values of geomorphic variables and in explaining and predicting geomorphic relationships is illustrated by several examples. The data required for these examples were obtained from map studies of 30 channel networks, comprising a total of about 8700 links, in eastern Kentucky. A common factor in the success of all three applications of the model is the way in which the planimetric features of drainage basins are determined by their underlying topologic structure. 相似文献
179.
Diffuse sediment pollution impairs water quality, exerts a key control on the transfer and fate of nutrients and contaminants and causes deleterious impacts on freshwater ecology. A variety of catchment sediment sources can contribute to such problems. Sediment control strategies and effective targeting of mitigation options therefore require robust quantitative information on the key sources of the sediment problem at catchment scale. Recent observations by Catchment Sensitive Farming Officers (CSFO's) in England have highlighted road verges damaged and eroded by passing vehicles, particularly large farm machinery, and livestock herd movement as visually important potential sources of local sediment problems. A study was therefore undertaken to assess the relative importance of damaged road verges as a suspended sediment source in three sub‐catchments of the Hampshire Avon drainage basin, southern UK. Road verge sediment contributions were apportioned in conjunction with those from agricultural topsoils and channel banks/subsurface sources. Time‐integrating isokinetic samplers were deployed to sample suspended sediment fluxes at the outlets of two control sub‐catchments drained by the Rivers Chitterne and Till selected to characterize areas with a low road network density and limited visual evidence of verge damage, as well as the River Sem sub‐catchment used to represent areas where road verge damage is more prevalent. The findings of a sediment source fingerprinting investigation based on a combination of intermittent sampling campaigns spanning the period 22/5/02–27/4/08 suggested that the respective overall mean relative sediment contributions from damaged road verges were 5 ± 3%, 4 ± 2% and 20 ± 2%. Relative inputs from damaged road verges for any specific sampling period in the River Sem sub‐catchment were as high as 33 ± 2%. Reconstruction of historical sources in the same sub‐catchment, based on the geochemical record stored in a floodplain depth profile, suggested that the significance of damaged road verges as a sediment source has increased over the past 15–20 years. The findings provide important information on damaged road verges as a primary source of suspended sediment and imply that catchment sediment control strategies and mitigation plans should consider such verges in addition to those agricultural and channel sources traditionally taken into account when attempting to reduce sediment pressures on aquatic resources. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
180.
The impact of road‐generated runoff on the hydrological response of a zero‐order basin was monitored for a sequence of 24 storm events. The study was conducted in a zero‐order basin (C1; 0·5ha) with an unpaved mountain road; an adjacent unroaded zero‐order basin (C2; 0·2 ha) with similar topography and lithology was used to evaluate the hydrological behaviour of the affected zero‐order basin prior to construction of the road. The impact of the road at the zero‐order basin scale was highly dependent on the antecedent soil‐moisture conditions, total storm precipitation, and to some extent rainfall intensity. At the beginning of the monitoring period, during dry antecedent conditions, road runoff contributed 50% of the total runoff and 70% of the peak flow from the affected catchment (C1). The response from the unroaded catchment was almost insignificant during dry antecedent conditions. As soil moisture increased, the road exerted less influence on the total runoff from the roaded catchment. For very wet conditions, the influence of road‐generated runoff on total outflow from the roaded catchment diminished to only 5·4%. Both catchments, roaded and unroaded, produced equivalent amount of outflow during very wet antecedent conditions on a unit area basis. The lag time between the rainfall and runoff peaks observed in the unroaded catchment during the monitoring period ranged from 0 to 4 h depending on the amount of precipitation and antecedent conditions, owing mainly to much slower subsurface flow pathways in the unroaded zero‐order basin. In contrast, the lag time in the roaded zero‐order basin was virtually nil during all storms. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献