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991.
Chein‐Shan Liu 《Numerical Methods for Partial Differential Equations》2007,23(5):1083-1109
We consider an inverse problem for estimating the two coefficient functions c and k in a parabolic type partial differential equation c(u)ut = ?[k(u)ux]/?x with the aid of the measurements of u at two different times. The first‐ and second‐order one‐step group preserving schemes are developed. Solving the resultant algebraic equations with a closed‐form, we can estimate the unknown temperature‐dependent thermal conductivity and heat capacity. The new methods possess threefold advantages: they do not require any a priori information on the functional forms of thermal conductivity and heat capacity; no initial guesses are required; and no iterations are required. Numerical examples are examined to show that the new approaches have high accuracy and efficiency, even there are rare measured data. When the measured temperatures are polluted by uniform or normal random noise, the estimated results are also good. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
992.
Boonlert Srihirun Sergey V. Meleshko Eckart Schulz 《Communications in Nonlinear Science & Numerical Simulation》2007,12(8):1379-1389
A new definition of an admitted Lie group of transformations for stochastic differential equations involving Brownian motion is presented. The transformation of the dependent variables involves time as well, and it is proved that Brownian motion is transformed to Brownian motion. Applications to a variety of stochastic differential equations are presented. 相似文献
993.
Jonas Sjöstrand 《Journal of Combinatorial Theory, Series A》2007,114(7):1182-1198
We characterise the permutations π such that the elements in the closed lower Bruhat interval [id,π] of the symmetric group correspond to non-taking rook configurations on a skew Ferrers board. It turns out that these are exactly the permutations π such that [id,π] corresponds to a flag manifold defined by inclusions, studied by Gasharov and Reiner.Our characterisation connects the Poincaré polynomials (rank-generating function) of Bruhat intervals with q-rook polynomials, and we are able to compute the Poincaré polynomial of some particularly interesting intervals in the finite Weyl groups An and Bn. The expressions involve q-Stirling numbers of the second kind, and for the group An putting q=1 yields the poly-Bernoulli numbers defined by Kaneko. 相似文献
994.
One of the most interesting questions about a group is whether its word problem can be solved and how. The word problem in the braid group is of particular interest to topologists, algebraists, and geometers, and is the target of intensive current research. We look at the braid group from a topological point of view (rather than a geometric one). The braid group is defined by the action of diffeomorphisms on the fundamental group of a punctured disk. We exploit the topological definition in order to give a new approach for solving its word problem. Our algorithm, although not better in complexity, is faster in comparison with known algorithms for short braid words, and it is almost independent of the number of strings in the braids. Moreover, the algorithm is based on a new computer presentation of the elements of the fundamental group of a punctured disk. This presentation can be used also for other algorithms. 相似文献
995.
Tree-connected peer group situations and peer group games 总被引:2,自引:0,他引:2
996.
997.
We prove local finiteness for the groups generated by a conjugacy class of order 3 elements whose every pair generates a subgroup that is isomorphic to Z 3, A 4, A 5, SL 2(3), or SL 2(5). 相似文献
998.
We construct a Hartree-Fock (self-consistent)-like algorithm with renormalization group (RG) approach to calculate the anomalous dimension in a nonlinear diffusion equation. We find that our result improves the original RG work because we include the effect of Heaviside function. 相似文献
999.
顾琼 《应用数学与计算数学学报》1997,(2)
对于群体决策问题,本文给出一个新的带参数的ακ-较多规则,并且讨论了在此规则下个体选优解和群体选优解的关系。此外,还论证了相应的ακ-较多规则满足Arrow公理的情况。 相似文献
1000.
GAN DANYAN 《数学年刊B辑(英文版)》1994,15(1):123-127
ON THE SHEAF OF GENERALIZED FUNDAMENTAL GROUP AND COVERING SPACE¥GANDANYANAbstract:Theauthorconstructsthesheafofgeneralizedfu... 相似文献