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91.
将微粒群和支持向量机用于耕地驱动因子选择的研究 总被引:2,自引:0,他引:2
结合微粒群算法(PSO)具有执行速度快、受问题维数变化影响小的优点及支持向量机算法(SVM)结构风险最小化原理,构建了基于离散二进制微粒群(BPSO)与支持向量机的耕地驱动力因子选择方法,使用特征子集中确定的特征来训练支持向量回归机,用适应度函数来评价回归机的性能,指导BPSO的搜索。实验表明,该方法能有效地提取出耕地驱动因子的特征子集,从而降低了指标的维数,保留了关键信息,以获得知识的最小表达。 相似文献
92.
介绍了全国第二次土地调查项目中调绘底图生产、土地调查、田坎系数测定、农村宅基地调查等关键环节,结合实际生产,分析了各环节的重要性及实施情况。 相似文献
93.
94.
《水文科学杂志》2013,58(4)
Abstract The management of water excesses and deficits is a major task in semiarid Mediterranean regions, where the variability of rainfall inputs is high at different time and space scales. Thus intense hydrometeorological events, which generate both potential resource and hazards, are of major interest. A simple method is proposed, with the example of the Skhira basin (192 km2) in central Tunisia, to account for the event space–time variability of rainfall in a rainfall–runoff model, in order to check its influence on the shape, magnitude and timing of resulting hydrographs. The transfer function used is a geomorphology-based unit hydrograph with an explicit territorial significance. Simulations made for highly variable events show the relevance of this method, seen as the first step of a downward approach, and its robustness with respect to the quality and the density of rainfall data. 相似文献
95.
The Willyama Supergroup of the Broken Hill region in southern Australia consists of supracrustal sedimentary and magmatic rocks, formed between 1810 and 1600 Ma. A statistical analysis of nearly 2000 SHRIMP U–Pb zircon spot ages, compiled from published and unpublished sources, provides evidence for three distinct tectonostratigraphic successions and four magmatic events during this interval. Succession 1 includes Redan Geophysical Zone gneisses and the lower part of the Thackaringa Group (Cues Formation). These rocks were deposited after 1810 Ma and host granite sills of the first magmatic event (1710–1700 Ma). Succession 2 includes the upper Thackaringa Group (Himalaya Formation), the Broken Hill Group and the Sundown Group and was deposited between 1710 and 1660 Ma. These rocks all contain detrital zircons from the first magmatic event (1710–1700 Ma) and in some cases from the second magmatic event (1690–1680 Ma). The second magmatic event (1690–1680 Ma) was bimodal, resulted from crustal extension, and was coeval with deposition of the Broken Hill Group and deepening of the basin. With this event a mafic sill swarm focused in the Broken Hill Domain. Mafic sills lack any trace of inheritance, unlike the granitoids that commonly contain inherited zircons typical of the supracrustal sediments. Succession 3, the Paragon Group and equivalents were deposited after 1660 Ma, but before a regional metamorphic event at 1600 Ma. Metamorphism was closely followed by inversion of the succession into a fold‐and‐thrust belt, accompanied by a fourth late to post‐orogenic magmatic event (ca 1580 Ma) characterised by granite intrusion and regional acid volcanism (the local equivalents of the Gawler Range Volcanics in South Australia). 相似文献
96.
This article presents a method for the nonlinear analysis of laterally loaded rigid piles in cohesive soil. The method considers the force and the moment equilibrium to derive the system equations for a rigid pile under a lateral eccentric load. The system equations are then solved using an iteration scheme to obtain the response of the pile. The method considers the nonlinear variation of the ultimate lateral soil resistance with depth and uses a new closed‐form expression proposed in this article to determine the lateral bearing factor. The method also considers the horizontal shear resistance at the pile base, and a bilinear relationship between the shear resistance and the displacement is used. For simplicity, the modulus of horizontal subgrade reaction is assumed to be constant with depth, which is applicable to piles in overconsolidated clay. The nonlinearity of the modulus of horizontal subgrade reaction with pile displacement at ground surface is also considered. The validity of the developed method is demonstrated by comparing its results with those of 3D finite element analysis. The applications of the developed method to analyze five field test piles also show good agreement between the predictions and the experimental results. The developed method offers an alternative approach for simple and effective analysis of laterally loaded rigid piles in cohesive soil. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
97.
随着电磁探测的发展,三维精细勘探为复杂地质模型的分析提供了有效工具,为了更精细地研究大地介质的特性,利用三维矢量有限元模拟分析了三维异常模型的Ez、Hz分量的响应特征。Ez分量对界面异常敏感,在界面处存在突变;Hz分量则在界面处不存在突变,但界面处出现Hz分量极值,对异常体的变化也有一定的灵敏度。同时,进一步提出采用上下两个测点的数据比值进行归一化处理来获得稳定的传输函数。 相似文献
98.
The shortage of potassium salt seriously restricts the development of China's agriculture. Increasing the exploration and development of potash will help improve the self-sufficiency of potassium in China. With rich potassium salt resources, Sichuan basin is one of the most important research areas for potash exploration and development in China. Polyhalite is an important solid potassium salt mineral in Sichuan basin, often intercalated in rock minerals such as anhydrite, rock salt and dolomite. Aiming at the problem that conventional log interpretation methods are difficult to accurately identify polyhalites, this paper proposed a new Support Vector Machine (SVM) recognition method based on Particle Swarm Optimization (PSO) to classify polyhalites in Sichuan basin. Based on particle swarm optimization and support vector machine theory, combined with logging interpretation theory, the effective data sensitive to polyhalite logging response were selected as input samples to generate training sets and test sets randomly. The Radial Basis Function (RBF) parameters were optimized by particle swarm optimization, and the classification and prediction model of polyhalite was established. Compared with mud logging results, the recognition accuracy of SVM model based on particle swarm optimization reached 97.5758%, which is obviously better than that of SVM model optimized by cross validation method in recognition accuracy and speed. The results show that the model has broad application prospects in potash exploration in Sichuan basin. 相似文献
99.
在边坡稳定性分析中,滑面搜索方法对于得到边坡的稳定性系数至关重要。现今两种常用的边坡稳定性分析方法,极限平衡法以及强度折减法,可以得到极限应力状态下边坡的潜在滑面。而为了评价边坡在当前应力场下的稳定性,提出一种基于聚类分析概念的滑面搜索方法。这种方法综合考虑了边坡各点的位移以及点安全系数,采用K均值聚类法将具有相近性质的点进行分类,把边坡体分为潜在危险区以及稳定区。潜在危险区的边界即为边坡在当前应力状态下的潜在滑面,并运用矢量和方法计算得到其稳定性系数。采用上述方法对3个算例进行验算,并与极限平衡法以及强度折减法进行对比。结果表明:(1)基于聚类分析的边坡稳定性评价方法具有较好的合理性和可靠性;(2)当边坡处于临界状态附近,通过聚类分析得到的潜在滑面与其他两种方法得到的滑面基本一致;当边坡处于较稳定状态时,当前应力状态下的潜在滑面要比强度折减法得到的滑动带范围要更深更广,但求出的稳定性系数也较高;当存在软弱夹层时,矢量和计算出的滑面更为陡峻,稳定性系数比其他两种方法的结果要小。 相似文献
100.