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481.
将一种基于混沌退火的Hopfield神经网络(ACHN)应用到储层聚类分析中。这里主要阐述了ACHN聚类的基本原理、混沌神经元的标定、ACHN聚类的策略、先验信息的约束以及混沌退火搜索。实际砂砾岩储层聚类分析表明:这种网络能克服普通Hopfield网络陷入局部最优的不足,得到更准确、精细的聚类结果。 相似文献
482.
利用测井数据中的自然伽玛、中子、声波和密度测井曲线所蕴含的岩性信息,用模糊聚类算法实现岩性的自动划分。该方法识别准确度高,可靠性强。通过对川西坳陷十八口井的实际应用,此方法在低孔低渗的致密碎屑岩岩性划分中取得了良好的效果。 相似文献
483.
For the Fiji-Tonga-Kermadec area and for the period from January 1977 to July 2003, the Harvard CMT catalogue lists 1022 shallow,
410 intermediate and 633 deep earthquakes of moment magnitude from 4.9 to 8.0. The magnitude threshold, above which the catalogue
is complete, is 5.3–5.4, and the number of earthquakes of magnitude above this value is 691 for shallow, 329 for intermediate
and 476 for deep events, respectively. The proportion of earthquakes associated with doublets and multiplets against the total
number of earthquakes is approximately the same in both data sets and therefore all earthquake pairs were considered regardless
of their magnitude. We investigated all the pairs of earthquakes that occurred at a centroid distance of less than 40, 60
or 90 km from each other and within a time interval of 200, 300 or 450 days, depending on their magnitude. We found 208 pairs
of shallow, 31 of intermediate and 92 of deep events. To ascertain whether these earthquakes in pairs are not connected by
chance, the possibility of their occurrence in an uncorrelated Poissonian catalogue was considered. It was assumed that in
such a catalogue the inter-event time is exponentially distributed, the earthquake magnitude follows the Gutenberg-Richter
relation, and the distribution of centroid distances between the events in pairs is controlled by its non-parametric kernel
estimate. The probability of the appearance of the observed proportion of doublets of shallow earthquakes in the Poissonian
catalogue was found to be very low. The low probability of occurrence in a semi-random catalogue, created by randomising centroid
locations in the actual data set, also indicates major importance of the distance criterion used for a doublet specification.
In general, shallow earthquakes tend to form pairs at shorter distances and within shorter time intervals than deep earthquakes.
Both the distance and the time intervals do not depend on the magnitude of involved events. The largest number of pairs of
deep earthquakes is observed at a depth of about 600 km, and the proportion of deep events associated with doublets against
the number of all events increases with depth. From comparison of the focal mechanism of earthquakes in pairs, measured by
the 3-D rotation angle, it follows that deep earthquakes forming pairs have a more diverse focal mechanism than shallow events;
the rotation angle for three quarters of shallow pairs and only for about one third of deep pairs is reasonably small. The
azimuth between two events forming a doublet is in about 60–65% of cases close to the strike of one of nodal planes of the
first or the second event. 相似文献
484.
This study proposes an inverse solution algorithm through which both the aquifer parameters and the zone structure of these parameters can be determined based on a given set of observations on piezometric heads. In the zone structure identification problem fuzzy c-means (FCM) clustering method is used. The association of the zone structure with the transmissivity distribution is accomplished through an optimization model. The meta-heuristic harmony search (HS) algorithm, which is conceptualized using the musical process of searching for a perfect state of harmony, is used as an optimization technique. The optimum parameter zone structure is identified based on three criteria which are the residual error, parameter uncertainty, and structure discrimination. A numerical example given in the literature is solved to demonstrate the performance of the proposed algorithm. Also, a sensitivity analysis is performed to test the performance of the HS algorithm for different sets of solution parameters. Results indicate that the proposed solution algorithm is an effective way in the simultaneous identification of aquifer parameters and their corresponding zone structures. 相似文献
485.
景益鹏 《中国天文和天体物理学报》1989,(1)
本文对D≤4,R≥0的Abell团样品和整个R≥3的Abell团样品的空间两点相关函数做了统计分析,结果表明R≥0,R=0和R≥3的Abell团的相关函数分别为175r~(-1.8),150r~(-1.8)和1900r~(-1.8)利用已有的R≥1和R≥2团的相关函数的统计结果,我们得到了Abell团的相关性幅度α与富度N之间的关系:α∝N~(1.6)。在相关性幅度的统计误差所允许的范围内,α与N之间的关系可以在宇宙弦理论中得到解释。 相似文献
486.
487.
基于MRF随机场和广义混合模型的遥感图像分级聚类 总被引:3,自引:0,他引:3
有限混合模型FM的分级聚类已广泛应用于不同领域,然而,它的计算复杂度与观测数据的平方成正比,因此,在海量数据方面的应用就受到了限制。另一方面,多光谱图像数据中同时包含有空间和光谱两类信息,但大多数基于像素的多光谱图像聚类方法,仅使用了其频谱信息而忽视了空间信息。本文提出了一种新的基于广义有限混合模型GFM的分级聚类方法,该算法把MRF随机场和GFM模型结合在一起,分类数可以通过PLIC准则自动确定。算法在执行过程中,采用K均值聚类方式获得过分类图像,分级聚类从过分类图像开始,代替原来从单点类开始的方式,这样可以方便获取GFM模型成分密度的初始参数。最后,采用由Gibbs采样器生成的仿真测试图对算法的精度进行了定量评价,通过与K均值聚类和FM聚类的比较说明了本文算法的优越性,同时用荷兰Flevoland农业地区的极化SAR图像验证了本文算法的有效性。 相似文献
488.
Zhenhong Du Yuhua Gu Chuanrong Zhang Feng Zhang Renyi Liu Jean Sequeira 《International Journal of Digital Earth》2018,11(6):609-634
Spatiotemporal clustering is one of the most advanced research topics in geospatial data mining. It has been challenging to discover cluster features with different spatiotemporal densities in geographic information data set. This paper presents an effective density-based spatiotemporal clustering algorithm (DBSTC). First, we propose a method to measure the degree of similarity of a core point to the geometric center of its spatiotemporal reachable neighborhood, which can effectively solve the isolated noise point misclassification problem that exists in the shared nearest neighbor methods. Second, we propose an ordered reachable time window distribution algorithm to calculate the reachable time window for each spatiotemporal point in the data set to solve the problem of different clusters with different temporal densities. The effectiveness and advantages of the DBSTC algorithm are demonstrated in several simulated data sets. In addition, practical applications to seismic data sets demonstrate the capability of the DBSTC algorithm to uncover clusters of foreshocks and aftershocks and help to improve the understanding of the underlying mechanisms of dynamic spatiotemporal processes in digital earth. 相似文献
489.
490.
道路识别是无人驾驶、机器导航等领域的关键问题之一。本文利用局部特征约束方法进行点云的预处理分割,基于多尺度聚类方法实现道路要素的点云提取,并在结构化道路实例的识别中进行应用。结果表明,该方法效果良好,是一种合理有效的道路识别手段。 相似文献