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991.
992.
应用数学分析的方法递归地表示了三角域上有理Bernstein多项式的所有方向导数,并给出了一种高效的求值方法,该方法在效果上比前人有明显的改进。 相似文献
993.
Calculation of electromagnetic sensitivities in the time domain 总被引:1,自引:0,他引:1
Andreas Hördt 《Geophysical Journal International》1998,133(3):713-720
The speed of calculating sensitivities for 3-D conductivity structures for time- domain electromagnetic methods is significantly improved by applying the reciprocity theorem directly in the time domain. The sensitivities are obtained by convolving the electric field in the subsurface due to a transmitter at the surface with the electric field impulse response due to another transmitter, which replaces the original receiver. The acceleration compared to the classical perturbation method is approximately P/R , where P is the number of model parameters and R is the number of receiver positions. If the sensitivity has to be calculated very close to the receiver, approximate sensitivities can be obtained using an integral condition. Comparisons with the classical perturbation approach show that the method gives accurate results. Examples using transmitter–receiver configurations from a long-offset transient electromagnetics survey demonstrate the usefulness of sensitivities for the evaluation of resolution properties. 相似文献
994.
Micromagnetic modelling with a Monte Carlo method was performed to obtain 2-D micromagnetic structures of pseudo-single-domain (PSD) magnetite (0.2–2.5 μm). Cubic model grains were subdivided into a 2-D array with a maximum of 100×100 cells. In order to find an appropriate cell size, the variation of the self-consistency parameter ( S ) with cell size was examined. We regard solutions with S >0.95, which corresponds to cell sizes ≤0.03 μm, as representing realistic micromagnetic structures. For saturation remanence states, we found vortex structures for small PSD grains (≤0.25 μm) and closure domain structures for larger PSD grains (0.6–2.5 μm). Between 0.25 and 0.6 μm, structures remained chaotic even after a very large number of Monte Carlo steps. In grains with a closure domain structure, domain walls were usually subdivided into several segments with opposite polarities of magnetization rotation. 相似文献
995.
996.
997.
时空多元协同克立格的理论研究 总被引:11,自引:0,他引:11
本文结合地质统计学的最新成果,在空间协同区域化理论的基础上,对时空域中多元信息的协同克立格(STCOK)理论进行了较为详细的研究。主要研究内容有:(1)STCOK中的互变异函数与互协方差函数;(2)STCOK方程组及求解估值权因子的三种方法:①传统普通协同克立格法(STTOCOK),②标准普通协同克立格法(STSOCOK),③简单协同克立格法(STSCOK);(3)排列协同克立格(STCOLCOK);(4)指示协同克立格(STIKCOK)。 相似文献
998.
Numerical solutions for the hydroelastic problems of bodies are studied directly in the time domain using Neumann–Kelvin formulation. In the hydrodynamic part of problem, the exact initial boundary value problem is linearized using the free stream as a basis flow, replaced by the boundary integral equation applying Green theorem over the transient free surface Green function. The resultant boundary integral equation is discretized using quadrilateral elements over which the value of the potential is assumed to be constant and solved using the trapezoidal rule to integrate the memory or convolution part in time. In the structure part of the problem, the finite element method is used to solve the hydroelastic problem. The Mindlin plate as a bending element, which includes transverse shear effect and rotary inertia effect are used. The present numerical results show acceptable agreement with experimental, analytical, and other published numerical results. 相似文献
999.
This paper investigates latching type control on a floating wave energy converter in deep water. An on-board, actively controlled motion-compensated platform is used as a reference (‘active reference’) for power absorption and latching. A variational formulation is used to evaluate an optimal control sequence in the time domain. Time domain simulation results are presented for a heaving buoy in small-amplitude waves. Results are compared with an equivalent system where latching and power absorption are from a sea-bottom-fixed reference. 相似文献
1000.
基于物元分析的登陆台风次数预报 总被引:1,自引:0,他引:1
利用前期的预后因子进行计算,使物元分析具有了预报功能,通过反复调整各因子的等级分界值(经典域和节域), 可以使登陆台风次数计算等级和实际等级的历史拟合率达到最大,其结果是比较好的,这对沿海地区的防台减灾具有重要的现实意义。 相似文献