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991.
《Chinese Astronomy and Astrophysics》2013,37(3):315-327
In this paper, a method to calculate the inclination function with Jacobi polynomials is studied, the formulation of this method is very simple, it needs not to concern about whether k and l have the same parity, and to calcu- late the non-integral factorials, nor to concern about the conversion between the case of k < 0 and the case of k ≥ 0, and the recurrent formula can be the stan- dard recurrent formula for Jacobi polynomials. In addition, its computational accuracy and applicable order-numbers are equivalent to those of the Gooding method, but its calculating time is shorter than that of the Gooding method for 9%. 相似文献
992.
Two kinds of recursion relations of hypergeometric series were derived, and hereby the Gooding's recursion formula of inclination function. In addition, it was demonstrated that this recursion formula can be derived also on the basis of the recursion relation of Jacobi polynomials. Comparing with the hypergeometric series, the recursion process based on the Jacobi polynomials is much simpler, indicating that the Gooding's method is the recursion of Jacobi polynomials in essence. 相似文献
993.
From the point of view of the non-parametric statistics, a general estimation method of the accuracy and con?dence interval of preliminary orbit determination is proposed for the occasion without any other information but observational data. Based on the bootstrap method, the estimation relies only on the observational data and does not require the precise orbit determination as a reference, or the assumption of normal distribution of observational errors. Numerical experiments show that this method is very simple in implementa- tion, and may serve as an easy accuracy evaluation for the preliminary orbit determination and for the follow-up employments. 相似文献
994.
995.
决策者的经验和知识判断对实际洪水调度有着非常重要的影响,为此,将决策者预泄控制的实践经验和泄流状态持续性要求纳入模型约束条件中,提出了防洪优化调度多约束启发式逐步优化方法。该方法以最大削峰为控制目标,将水库泄流的一般操作原则概化为启发式信息,以洪水涨落和水位升降作为泄流增减的判别依据,与优化搜索相结合,采用启发式逐步优化算法求解。以水口水库为例,采用5个方案对所提方法进行了对比分析。结果表明,提出的方法可以充分考虑决策者的经验和知识判断,降低了预泄腾库水位过低造成的回蓄风险,避免了泄流过程的波动,得到符合实际洪水调度要求的计算结果。 相似文献
996.
997.
城镇土地集约利用研究 总被引:47,自引:1,他引:47
小城镇发展战略地位的确立,加速了城镇化进程,城镇化过程中的用地粗放与人均耕地锐减之间的矛盾,是提出城镇土地集约利用的依据。从城镇土地集约利用内涵界定入手,分析了城镇土地集约利用的必要性,探讨了城镇土地集约利用定量评价的原则,从城镇存量土地产出率、土地利用强度、土地投入强度和土地可持续度4个方面建立了城镇土地集约利用评价指标总系统。指出城镇发展与土地集约利用的途径。 相似文献
998.
《New Astronomy》2015
We have implemented open boundary conditions into the ANTARES code to increase the realism of our simulations of stellar surface convection. Even though we greatly benefit from the high accuracy of our fifth order numerical scheme (WENO5) the broader stencils needed for the numerical scheme complicate the implementation of boundary conditions. We show that the effective temperature of a numerical simulation cannot be changed by corrections at the lower boundary since the thermal stratification does only change on the Kelvin–Helmholtz time scale. Except for very shallow models this time scale cannot be covered by multidimensional simulations due to the enormous computational requirements. We demonstrate to what extent numerical simulations of stellar surface convection are sensitive to the initial conditions and the boundary conditions. An ill-conceived choice of parameters for the boundary conditions can have a severe impact. Numerical simulations of stellar surface convection will only be (physically) meaningful and realistic if the initial model, the extent and position of the simulation box and the parameters from the boundary conditions are chosen adequately. 相似文献
999.
1000.
In general, the accuracy of numerical simulations is determined by spatial and temporal discretization levels. In fractured porous media, the time step size is a key factor in controlling the solution accuracy for a given spatial discretization. If the time step size is restricted by the relatively rapid responses in the fracture domain to maintain an acceptable level of accuracy in the entire simulation domain, the matrix tends to be temporally over-discretized. Implicit sub-time stepping applies smaller sub-time steps only to the sub-domain where the accuracy requirements are less tolerant and is most suitable for problems where the response is high in only a small portion of the domain, such as within and near the fractures in fractured porous media. It is demonstrated with illustrative examples that implicit sub-time stepping can significantly improve the simulation efficiency with minimal loss in accuracy when simulating flow and transport in fractured porous media. The methodology is successfully applied to density-dependent flow and transport simulations in a Canadian Shield environment, where the flow and transport is dominated by discrete, highly conductive fracture zones. 相似文献