共查询到20条相似文献,搜索用时 140 毫秒
1.
2.
《数学的实践与认识》2015,(9)
首先给出二维土壤溶质输运问题时间二阶精度的Crank-Nicolson(CN)时间半离散化格式,然后直接从CN时间半离散化格式出发,建立具有时间二阶精度的全离散化CN有限元格式,并给出CN有限元解的误差分析,最后用数值例子验证全离散化CN有限元格式的优越性.这种方法提高了时间离散的精度,并极大地减少时间方向的迭代步,从而减少实际计算中截断误差的积累,提高计算精度和计算效率.而且方法绕开对空间变量半离散化有限元格式的讨论,使得理论研究更简便. 相似文献
3.
4.
5.
6.
7.
8.
一类非线性抛物型方程的广义Galerkin方法 总被引:1,自引:0,他引:1
李潜 《高等学校计算数学学报》1986,(2)
本文研究一类非线性二维二阶抛物型方程混合问题的广义Galerkin方法(即广义差分法)讨论了半离散化和全离散化方程的收敛性和稳定性,并得到与有限元方法相同的最佳收敛阶。 相似文献
9.
半导体器件数值模拟的混合有限元方法 总被引:1,自引:0,他引:1
本文就半导体器件中载流子运动方程组的混合初边值问题提出了一种全离散的混合有限元逼近格式,考虑到混合边界条件下解的光滑性较差,我们在分数阶Sobolev空间中研究了逼近格式,得到了误差估计。 相似文献
10.
11.
宏观因素影响下的系统中元件重要性研究 总被引:9,自引:0,他引:9
为研究复杂系统在工作环境中其组成元件对系统安全运行的重要性,将汪培庄先生的因素空间理论与笔者提出的空间事故树理论相结合,构造了一套元件重要性研究方法.构建系统T={U,C,D},将元件作为研究对象集合U,系统工作的宏观环境作为因素集C,元件重要性排序集作为D.对宏观环境中的工作时间a1和温度a_2进行划分形成不同的状态区域S_q,计算在S_q中元件xj的失效权重γ(AS_q(x_j))和在S_q中系统T的失效权重δ(AS_q(T))),从而得到x_j在S状态下的等效失效权重Z(AS_q(x_j)),研究状态S_q下的原件重要性排序D_η,及元件x_j失效性对a_1及a_2的敏感性.使用一个实际的电气系统维修情况统计资料,使用上述方法进行了研究,结果表明:不同工作环境下元件对系统的重要程度是不同的.元件对温度和使用时间是敏感的,并得到了在1030°且5030°且5075d环境下工作系统可靠性是最高的结论.在给定工作环境下,重要性大的元件多储备,重要性小的元件少储备,以满足系统维修需要,并指导实际工程. 相似文献
12.
Paolo Albano 《Nonlinear Analysis: Theory, Methods & Applications》2010,73(2):458-1425
We show that if the Hamiltonian is locally semiconvex with respect to the state variables and strictly convex with respect to the gradient then every viscosity solution of the eikonal equation is locally semiconcave. Furthermore, in the 1D case, we show that every viscosity solution of the eikonal equation is semiconcave if and only if the Hamiltonian is Lipschitz continuous with respect to the state variable. 相似文献
13.
Khaled Omrani 《Numerical Methods for Partial Differential Equations》2004,20(4):527-551
In this article an error bound is derived for a piecewise linear finite element approximation of an enthalpy formulation of the Stefan problem; we have analyzed a semidiscrete Galerkin approximation and completely discrete scheme based on the backward Euler method and a linearized scheme is given and its convergence is also proved. A second‐order error estimates are derived for the Crank‐Nicolson Galerkin method. In the second part, a new class of finite difference schemes is proposed. Our approach is to introduce a new variable and transform the given equation into an equivalent system of equations. Then, we prove that the difference scheme is second order convergent. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2004 相似文献
14.
Hirotugu Akaike 《Statistics & probability letters》1982,1(2):75-78
By using the direct and inverse binomial experiments it is shown that there is a situation where Birnbaum's basic axiom of mathematical equivalence and the likelihood principle is a tautology. This observation disqualifies Birnbaum's proof of the likelihood principle based on the axioms of mathematical equivalence and conditionality. The implication of this disproof of Birnbaum's argument for Bayesian statistics is briefly discussed. 相似文献
15.
Marc J. G. van Eijs 《Mathematical Methods of Operations Research》1994,39(3):289-304
This paper considers the well-known class of can-order policies. This type of coordinated replenishment policies accounts for a joint set-up cost structure, where a major set-up cost is incurred for any order and an individual minor set-up cost is charged for each item in the replenishment. Recent comparative studies have pointed out that the performance of the optimal can-order policy is poor, compared to other coordinated replenishment strategies, when the major set-up cost is high. This paper shows that it is the approximate decomposition method to calculate the optimal canorder parameters which performs bad in such situations and not the policy itself. Attention is focused to a subclass of can-order policies, which is close to the optimal can-order policy for high major set-up costs. A solution procedure is developed to calculate the optimal control parameters of this policy. It is shown that a properly chosen combination of the solution procedures to calculate can-order parameters leads to a can-order strategy which performs as well as other coordinated replenishment policies. 相似文献
16.
17.
When the Laplace transform is inverted numerically, the original function is sought in the form of a series in the Laguerre polynomials. To accelerate the convergence of this series, the Euler-Knopp method is used. The techniques for selecting the optimal value of the parameter of the transform on the real axis and in the complex plane are proposed. 相似文献
18.
In this paper the numerical analysis of the drawing process with the blankholder is presented. The influence of the value of the blankholder force on the value of the drawing force and drawpiece height is examined. A different friction coefficient of the sheet metal for die and blankholder is considered. A defect at the lack of the blankholder is presented. The analysis in the system ANSYS/LS-DYNA is passed. The material model with the mixed hardening, isotropic and isothermal is used. Technological parameters of the sheet-metal to drawing, the die, the stamp and the blankholder from the literatures are chosen. Examples results of computer simulations are presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
王志龙 《数学的实践与认识》2007,37(14):212-219
气象部门将6小时的降雨按降雨量划分为无雨、小雨、中雨、大雨、暴雨、大暴雨及特大暴雨七个级别进行预报,这与公众感受认可这些降雨量级别的程度是有差异的.即使气象部门预报的很准,这种差异有可能使公众感受到降雨级别的程度和预报的级别不符,从而认为预报得不准确,用模糊数学的方法对公众的感受度进行了刻划,给出了计算预报数据与公众感受度差异的数值公式及方法. 相似文献
20.
If N is a hyperbolic 3-manifold with finitely generated fundamental group, then the nearest point retraction is a proper homotopy equivalence from the conformal boundary of N to the boundary of the convex core of N. We show that the nearest point retraction is Lipschitz and has a Lipschitz homotopy inverse and that one may bound the Lipschitz constants in terms of the length of the shortest compressible curve on the conformal boundary. 相似文献