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491.
通过对焦家金矿田地球化学异常的分析,并以此为基础设计隶属函数,进而建立了模糊模式。根据隶属函数计算的各个元素信息变量的模糊数,把它作为模糊判别指标,然后用贴近度的度量方法与预测区内待识别的模糊判别指标进行识别。应用此方法对水系沉积物中Au、Ag、Cu、Pb四种元素进行模糊模式识别与处理,并在胶东7800km2范围内进行了金矿预测,其中有些贴近度(T)异常已经得到验证,获得了较好的效果。 相似文献
492.
The surface reflectance properties of the irregular outer planets satellites are probed for evidence for the presence of aqueous alteration products on their surfaces using the strong correlation between the 3.0-μm water of hydration absorption feature and the 0.7-μm Fe2+ → Fe3+ oxidized iron feature seen in low-albedo asteroid reflectances, in an effort to expand our understanding of the composition of the precursor bodies from which the dynamical satellite clusters are derived. Equations converting Johnson V and Kron-Cousins RI photometry to Eight Color Asteroid Survey v (0.550 μm), w (0.701 μm), and x (0.853 μm) photometry are derived from relationships defined by Howell (1995, Ph.D. thesis), and coupled with an algorithm previously defined to detect the presence of the 0.7-μm absorption feature in ECAS asteroid photometry [Vilas, F., 1994. Icarus 111, 456-467]. Broadband VRI photometry of Ch-class Asteroid 19 Fortuna acquired during 2004 confirms the efficacy of this method of identifying the presence of the 0.7-μm feature. Photometric observations of many recently discovered irregular outer jovian, saturnian, uranian, and neptunian satellites, coupled with limited asteroid spectroscopy, were examined for the presence of aqueous alteration. The dynamical clusters of outer irregular jovian satellites are mixed between objects that do and do not show this absorption feature. Multiple observations of some objects test both positively and negatively, similar to the surface variegation that has been observed among many C-class asteroids in the main asteroid belt. Evidence for aqueous alteration on these jovian satellites augers for an origin in or near the same location as the asteroids now occupying the aqueous alteration zone (2.6-3.5 AU), at heliocentric distances internal to Jupiter's orbit. Among the saturnian irregular satellites, only S IX Phoebe shows limited evidence of aqueous alteration from ground-based observations. The other satellites show no sign of this feature, and have general reflectance properties very similar to the D-class asteroids, supporting an origin for their precursor bodies in the outer Solar System, perhaps the Centaur region. Only two uranian satellites were tested: U XVII Caliban tests positively for the feature. The differences in surface reflectance properties support the idea that Caliban and U XVI Sycorax derive from separate parent bodies. One observation of neptunian satellite N II Nereid shows no sign of this absorption feature. 相似文献
493.
In order to reduce the maintenance costs of ballasted railway track and improve passenger comfort, the railway ballast particle breakage and its effect on track settlement need to be better understood. The failure process of individual railway ballast loaded between flat platens is simulated using the discrete element method, considering its irregular shape with the incorporation of parallel bonds. The tensile strength, the stress of a survival probability of 37% of samples, is obtained and compared with laboratory results from published literature for the verification of DEM simulations. The evolution to failure of the particle is understood from the stress-strain curve and progressive failure modes. The internal breakage mechanisms are analysed by tracking the accumulation of bond breakage number and the contact force distributions. 相似文献
494.
Laboratory study of the nonlinear transformation of irregular waves over a mild slope 总被引:1,自引:0,他引:1
This paper considers the nonlinear transformation of irregular waves propagating over a mild slope (1:40). Two cases of irregular waves, which are mechanically generated based on JONSWAP spectra, are used for this purpose. The results indicate that the wave heights obey the Rayleigh distribution at the offshore location; however, in the shoaling region, the heights of the largest waves are underestimated by the theoretical distributions. In the surf zone, the wave heights can be approximated by the composite Weibull distribution. In addition, the nonlinear phase coupling within the irregular waves is investigated by the wavelet-based bicoherence. The bicoherence spectra reflect that the number of frequency modes participating in the phase coupling increases with the decreasing water depth, as does the degree of phase coupling. After the incipient breaking, even though the degree of phase coupling decreases, a great number of higher harmonic wave modes are also involved in nonlinear interactions. Moreover, the summed bicoherence indicates that the frequency mode related to the strongest local nonlinear interactions shifts to higher harmonics with the decreasing water depth. 相似文献
495.
496.
J.D. Jansen 《Computational Geosciences》2002,6(2):195-206
This paper concerns the computation of near-well flow in numerical reservoir simulation with unstructured grids. In particular, it uses spherical trigonometry to derive analytical expressions for the flow towards a well modeled as either a number of point sources or a constant-flux line source. The expression for the point source representation is based on projections of the grid block boundaries on spheres with unit radius around the sources. The expression for the line source is based on projection on a prolate spheroid. The computation of the surface area is done through transformation to prolate spheroidal coordinates and subsequent projection on a sphere at infinity. The point source expression for a single source is exact for grid block boundaries with straight edges; the line source expression is an approximation. Both representations are fully volume conserving, such that the sum of the fluxes through the grid block boundaries surrounding a source adds up exactly to the total source flow rate. Both representations can be used to accurately model complicated wells in the form of segments. The point source representation is simpler to implement and not necessarily less accurate than the line source representation. 相似文献
497.
Yumin Chen Qiming Zhou Sheng Li Fanrui Meng Xiaomei Bi John P. Wilson 《International journal of geographical information science》2014,28(11):2242-2260
This paper proposes a flow-path network (FPN) model to simulate complex surface flow based on a drainage-constrained triangulated irregular network (TIN). The TIN was constructed using critical points and drainage lines extracted from a digital terrain surface. Runoff generated on the surface was simplified as ‘water volumes’ at constrained random points that were then used as the starting points of flow paths (i.e. flow source points). The flow-path for each ‘water volume’ was constructed by tracing the direction of flow from the flow source point over the TIN surface to the stream system and then to the outlet of the watershed. The FPN was represented by a set of topologically defined one-dimensional line segments and nodes. Hydrologic variables, such as flow velocity and volume, were computed and integrated into the FPN to support dynamic surface flow simulation. A hypothetical rainfall event simulation on a hilly landscape showed that the FPN model was able to simulate the dynamics of surface flow over time. A real-world catchment test demonstrated that flow rates predicted by the FPN model agreed well with field observations. Overall, the FPN model proposed in this study provides a vector-based modeling framework for simulating surface flow dynamics. Further studies are required to enhance the simulations of individual hydrologic processes such as flow generation and overland and channel flows, which were much simplified in this study. 相似文献
498.
针对单一无人机影像无法有效地提取高郁闭度林分树高的问题,该文提出一种结合无人机影像数据和全站仪测量的地形数据获取高郁闭度林分树高的方法。①利用搭载数码相机的小型无人机平台,以50m航高获取实验区局部高精度林分影像,利用全站仪获取实验区的地形数据;②利用无人机影像处理软件对影像进行处理,通过初步的几何校正以及空三加密过程得到整个实验区的高分辨率DEM和DOM模型;③采用局部最大值算法探测单株林木的树冠中心点坐标,利用自然生长算法和高程差值公式得到树冠中心对应的树根高程;④以树冠中心点高程以及树根高程的差值作为单木树高的估计值。通过实验得出:结合无人机影像与全站仪数据能够准确快速地获取高郁闭度林分树高,本文提出的方法可以为森林可持续经营提供数据基础。 相似文献
499.
500.
不规则重磁测线网误差模型的约束最小二乘平差 总被引:5,自引:1,他引:5
传统实用的海洋重力、磁力测线网平差方法主要为规则测线网设计,并只就线偏差进行调整,用于处理航次数据之间的拼接时效果不理想。为了解决重磁测线数据拼接和建库工作中碰到的误差难以调平的问题,设计、建立了不规则海洋重磁测线网的任意复杂误差模型的最小二乘平差方法,将线偏差纳入到任意复杂(如非线性和周期性)的误差模型中,归纳出最小二乘条件方程系数矩阵的直接构制法。针对可能出现的解不稳定,放弃不易实用的权矩阵,引入两种解决方法:先验确定部分测线误差分布的固定测线法和视误差大小实施系数矩阵对角线微扰动的泛约束法。 相似文献