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1.
首先介绍了地理信息系统（GIS）网络分析的发展概况;其次在已有GIS最佳遍历分析存在问题的基础上,提出了一种最佳多路遍历分析算法。并在ArcEngine环境下,以某县交通网为例,利用C#.net及ArcEngine二次开发类库实现了其最佳多路灾情巡视路线分析。算法适用范围广,可以推广到很多同类的地理网络问题。 相似文献
2.
就地壳及其动力学过程的复杂性，结合地震预报与机理的研究现状和方法，提出了个人的看法，简介了非线性动态有限元方法。 相似文献
3.
Estimating Variogram Uncertainty 总被引：10，自引：0，他引：10
The variogram is central to any geostatistical survey, but the precision of a variogram estimated from sample data by the method of moments is unknown. It is important to be able to quantify variogram uncertainty to ensure that the variogram estimate is sufficiently accurate for kriging. In previous studies theoretical expressions have been derived to approximate uncertainty in both estimates of the experimental variogram and fitted variogram models. These expressions rely upon various statistical assumptions about the data and are largely untested. They express variogram uncertainty as functions of the sampling positions and the underlying variogram. Thus the expressions can be used to design efficient sampling schemes for estimating a particular variogram. Extensive simulation tests show that for a Gaussian variable with a known variogram, the expression for the uncertainty of the experimental variogram estimate is accurate. In practice however, the variogram of the variable is unknown and the fitted variogram model must be used instead. For sampling schemes of 100 points or more this has only a small effect on the accuracy of the uncertainty estimate. The theoretical expressions for the uncertainty of fitted variogram models generally overestimate the precision of fitted parameters. The uncertainty of the fitted parameters can be determined more accurately by simulating multiple experimental variograms and fitting variogram models to these. The tests emphasize the importance of distinguishing between the variogram of the field being surveyed and the variogram of the random process which generated the field. These variograms are not necessarily identical. Most studies of variogram uncertainty describe the uncertainty associated with the variogram of the random process. Generally however, it is the variogram of the field being surveyed which is of interest. For intensive sampling schemes, estimates of the field variogram are significantly more precise than estimates of the random process variogram. It is important, when designing efficient sampling schemes or fitting variogram models, that the appropriate expression for variogram uncertainty is applied. 相似文献
4.
This work is part of an attempt to quantify the relationship between the permeability tensor (K) and the micro-structure of natural porous media. A brief account is first provided of popular theories used to relate the micro-structure toK. Reasons for the lack of predictive power and restricted generality of current models are discussed. An alternative is an empirically based implicit model whereinK is expressed as a consequence of a few pore-types arising from the dynamics of depositional processes. The analytical form of that implicit model arises from evidence of universal association between pore-type and throat size in sandstones and carbonates. An explicit model, relying on the local change of scale technique is then addressed. That explicit model allows, from knowledge of the three-dimensional micro-geometry to calculateK explicitly without having recourse to any constitutive assumptions. The predictive and general character of the explicit model is underlined. The relevance of the change of scale technique is recalled to be contingent on the availability of rock-like three-dimensional synthetic media. A random stationary ergodic process is developed, that allows us to generate three-dimensional synthetic media from a two-dimensional autocorrelation functionr(
x
,
y
) and associated probability density function
measured on a single binary image. The focus of this work is to ensure the rock-like character of those synthetic media. This is done first through a direct approach:n two-dimensional synthetic media, derived from single set (
,r(
x
,
y
)) yieldn permeability tensorsK
i-1,n
i
(calculated by the local change of scale) of the same order. This is a necessary condition to ensure thatr(
x
,
y
) and
carry all structural information relevant toK. The limits of this direct approach, in terms of required Central Process Unit time and Memory is underlined, raising the need for an alternative. This is done by comparing the pore-type content of a sandstone sample andn synthetic media derived fromr(
x
,
y
) and
measured on that sandstone-sample. Achievement of a good match ensures that the synthetic media comprise the fundamental structural level of all natural sandstones, that is a domainal structure of well-packed clusters of grains bounded by loose-packed pores. 相似文献
5.
TOWARDS A UNIFORM CONCEPT FOR THE COMPARISON AND EXTRAPOLATION OF ROCKWALL RETREAT AND ROCKFALL SUPPLY 总被引：1，自引：0，他引：1
MICHAEL KRAUTBLATTER RICHARD DIKAU 《Geografiska Annaler: Series A, Physical Geography》2007,89(1):21-40
Rates of rockwall retreat and rockfall supply are fundamental components of sediment budgets in steep environments. However, the standard procedure of referencing rockwall retreat rates using only lithology is inconsistent with research findings and results in a variability that exceeds three orders of magnitude. The concept proposed in this paper argues that the complexity inherent in rockfall studies can be reduced if the stages of (i) backweathering, (ii) filling and depletion of intermediate storage on the rock face and (iii) final rockfall supply onto the talus slopes are separated as these have different response functions and controlling factors. Backweathering responds to preweathering and weathering conditions whereas the filling and depletion of intermediate storage in the rock face is mainly a function of internal and external triggers. The noise apparent in backweathering rates and rockfall supply can be reduced by integrating the relevant controlling factors in the response functions. Simple conceptual models for the three stages are developed and are linked by a time‐dependent ‘rockfall delivery rate’, which is defined as the difference between backweathering and rockfall supply, thus reflecting the specific importance of intermediate storage in the rock face. Existing studies can be characterized according to their ‘rockfall delivery ratio’, a concept similar to the ‘sediment delivery ratio’ used in fluvial geomorphology. Their outputs can be qualified as trigger‐dependent rockfall supply rates or backweathering rates dependent on (pre‐)weathering conditions. It is shown that the existing quantitative backweathering and rockfall supply models implicitly follow the proposed conceptual models and can be accommodated into the uniform model. Suggestions are made for how best to incorporate non‐linearities, phase transitions, path dependencies and different timescales into rockfall response functions. 相似文献
6.
为了解决传统的Theis配线法在求参过程中无法利用全部抽水试验数据、手动配线效率较低、求参过程受人为主观因素影响较大等问题,利用抽水试验数据,以Theis公式和叠加原理为理论基础,以理论计算降深与实测降深的Nach-Sutcliffe效率系数值达到最大为目标函数,基于Matlab软件编程,再利用遍历搜索算法对导水系数（T）、贮水系数（S）在其对应范围内进行遍历,实现了水文地质参数的自动精确求解。将遍历搜索算法应用于2个抽水试验实例的水文地质参数求解,并与传统求参方法的计算结果进行比较分析。结果表明：利用遍历搜索算法求参的计算结果与传统求参方法的计算结果相近,表明利用遍历搜索算法求解水文地质参数有效可靠;2个抽水实例利用遍历搜索算法得到的参数对应的理论计算降深与实测降深的Nach-Sutcliffe效率系数值分别为0.996 5、0.970 8,且相比传统的求参方法而言更接近1.000 0,说明其拟合程度更好。 相似文献
7.
在实测资料和前人研究的基础上,引入“空代时”假说,分析研究了丹江口建库后汉江下游河流再造床过程的时空演替现象。分析表明,河流再造床过程在冲刷延展、河床粗化、含沙量及其特征、岸滩侵蚀以及河型变化等方面具有较典型的时空演替现象。产生时空演替现象的根源在于河流自调整作用在同一变源下空间和时间响应的一致性,是过程的相似。输入水沙条件的变化、水库下游河道支流入汇、河床边界条件的变化以及因此导致的不同调整方式是引起时空演替复杂响应的主要原因。如能排除干扰、建立时空演替现象的数学模式将有助于水库下游河流调整的分析和预测。 相似文献
8.
Impact of the simulation algorithm, magnitude of ergodic fluctuations and number of realizations on the spaces of uncertainty of flow properties 总被引：1，自引：1，他引：0
P. Goovaerts 《Stochastic Environmental Research and Risk Assessment (SERRA)》1999,13(3):161-182
Geostatistical simulation algorithms are routinely used to generate conditional realizations of the spatial distribution
of petrophysical properties, which are then fed into complex transfer functions, e.g. a flow simulator, to yield a distribution
of responses, such as the time to recover a given proportion of the oil. This latter distribution, often referred to as the
space of uncertainty, cannot be defined analytically because of the complexity (non-linearity) of transfer functions, but
it can be characterized algorithmically through the generation of many realizations. This paper compares the space of uncertainty
generated by four of the most commonly used algorithms: sequential Gaussian simulation, sequential indicator simulation, p-field simulation and simulated annealing. Conditional to 80 sample permeability values randomly drawn from an exhaustive
40×40 image, 100 realizations of the spatial distribution of permeability values are generated using each algorithm and fed
into a pressure solver and a flow simulator. Principal component analysis is used to display the sets of realizations into
the joint space of uncertainty of the response variables (effective permeability, times to reach 5% and 95% water cuts and
to recover 10% and 50% of the oil). The attenuation of ergodic fluctuations through a rank-preserving transform of permeability
values reduces substantially the extent of the space of uncertainty for sequential indicator simulation and p-field simulation, while improving the prediction of the response variable by the mean of the output distribution. Differences
between simulation algorithms are the most pronounced for long-term responses (95% water cut and 50% oil recovery), with sequential
Gaussian simulation yielding the most accurate prediction. In this example, utilizing more than 20 realizations generally
increases only slightly the size of the space of uncertainty. 相似文献
9.
Random field characteristics of earthquake occurrence and test of earthquake occurrence rate 总被引：1，自引：0，他引：1
高孟潭 《地震学报(英文版)》1994,(Z1)
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10.