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991.
The convective instability of a horizontal liquid layer confined in an annular Hele–Shaw cell subject to a constant rotation and submitted to a centrifugal gradient of temperature is investigated. Using a linear stability analysis, we study the effects of both Coriolis forces and curvature aspect on the stationary convective threshold when the Prandtl number is of the order of unity or larger than unity. We show that the Coriolis forces have a stabilizing effect, and the wave number is independent of these forces. However, a multicellular regime in the radial direction is observed for small Ekman numbers. The results related to the influence of the curvature are also shown. To cite this article: S. Ramezani et al., C. R. Mecanique 330 (2002) 633–640. 相似文献
992.
In this paper new integration algorithms based on the Magnus expansion for linear differential equations up to eighth order are obtained. These methods are optimal with respect to the number of commutators required. Starting from Magnus series, integration schemes based on the Cayley transform an the Fer factorization are also built in terms of univariate integrals. The structure of the exact solution is retained while the computational cost is reduced compared to similar methods. Their relative performance is tested on some illustrative examples. 相似文献
993.
Karen A. Chandler 《Compositio Mathematica》2002,134(3):269-282
We present an elementary proof that given a general collection of d points in Pn the linear system of cubics singular on each point has the expected codimension except when n=4 and d=7. In that case the cubic is unique. This, together with previous work of the author, gives a proof of the Alexander–Hirschowitz interpolation theorem. 相似文献
994.
Evald Übi 《Central European Journal of Mathematics》2007,5(2):373-385
The system of inequalities is transformed to the least squares problem on the positive ortant. This problem is solved using
orthogonal transformations which are memorized as products. Author’s previous paper presented a method where at each step
all the coefficients of the system were transformed. This paper describes a method applicable also to large matrices. Like
in revised simplex method, in this method an auxiliary matrix is used for the computations. The algorithm is suitable for
unstable and degenerate problems primarily.
相似文献
995.
记Q(X)为双曲黎曼曲面X上所有具有有限L^1-模的全纯二次微分所组成的Banach空间.本文讨论由V(φ)=|φ|/φ所定义的映射V:Q(x)→Q*(X)及其逆映射V^-1的连续性,并得到一些关于Teichmiiller空间几何的Lakic-型结果. 相似文献
996.
夏登俊 《数学的实践与认识》2004,34(1):7-12
首先提出了电阻网络电流分配的能量损耗最小原理 ,接着用此原理对一个电阻网络建立了二次规划数学模型 .求解此模型得到了各个支路上的电流值 .此电流值和由基尔霍夫定律计算出的电流值一致 ,同时由此原理推导出基尔霍夫电压定律 ,从而得出结论 :电阻网络电流分配的能量损耗最小原理是正确的 .最后 ,讨论了此原理在电路分析理论中的地位 . 相似文献
997.
非参数计量经济联立模型的局部线性两阶段最小二乘变窗宽估计 总被引:2,自引:0,他引:2
叶阿忠 《数学的实践与认识》2004,34(1):13-18
联立方程模型在经济政策制定、经济结构分析和经济预测方面起重要作用 .本文在随机设计 (模型中所有变量为随机变量 )下 ,提出了非参数计量经济联立模型的局部线性两阶段最小二乘变窗宽估计并利用概率论中大数定理和中心极限定理在内点处研究了它的大样本性质 ,证明了它的一致性和渐近正态性 .它在内点处的收敛速度达到了非参数函数估计的最优收敛速度 . 相似文献
998.
In this paper, we propose a nested simple incomplete LU decomposition (NSILU) method for preconditioning iterative methods for solving largely scale and sparse ill-conditioned hnear systems. NSILU consists of some numerical techniques such as simple modification of Schur complement, compression of ill-condition structure by permutation, nested simple ILU, and inner-outer iteration. We give detailed error analysis of NSILU and estimations of condition number of the preconditioned coefficient matrix, together with numerical comparisons. We also show an analysis of inner accuracy strategies for the inner-outer iteration approach. Our new approach NSILU is very efficient for linear systems from a kind of two-dimensional nonlinear energy equations with three different temperature variables, where most of the calculations centered around solving large number of discretized and illconditioned linear systems in large scale. Many numerical experiments are given and compared in costs of flops, CPU times, and storages to show the efficiency and effectiveness of the NSILU preconditioning method. Numerical examples include middle-scale real matrices of size n = 3180 or n = 6360, a real apphcation of solving about 755418 linear systems of size n = 6360, and a simulation of order n=814080 with structures and properties similar as the real ones. 相似文献
999.
Baskakov算子也是一类很重要的正线性算子,在其它领域(如概率及其它学科)都应用很广,本文利用多元分解技巧和已有的一元的结论得出多元Baskakov算子的等价一致逼近定理. 相似文献
1000.