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81.
We study the chromatic polynomials for m×n square-lattice strips, of width 9m13 (with periodic boundary conditions) and arbitrary length n (with free boundary conditions). We have used a transfer matrix approach that allowed us also to extract the limiting curves when n. In this limit we have also obtained the isolated limiting points for these square-lattice strips and checked some conjectures related to the Beraha numbers. 相似文献
82.
If (Xi, i
) is a strictly stationary process with marginal density function f, we are interested in testing the hypothesis H0: {f=f0}, where f0 is given. We consider different test statistics based on integrated quadratic forms measuring the proximity between fn, a kernel estimator of f, and f0, or between fn and its expected value computed under H0. We study the asymptotic local power properties of the testing procedures under local alternatives. This study generalizes to the multidimensional case in a context of dependence the corresponding one made by P. J. Bickel and M. Rosenblatt in 1973 (Ann. Statist.1, 1071–1095). 相似文献
83.
Let G be a finite group written multiplicatively and k a positive integer. If X is a non-empty subset of G, write X
2 = |xy | x, y X . We say that G has the small square property on k-sets if |X
2| < k
2 for any k-element subset X of G. For each group G, there is a unique m = m
G
such that G has the small square property on (m + 1)-sets but not on m-sets. In this paper we show that given any positive integer d, there is a finite group G with m
G
= d. 相似文献
84.
85.
采用平面波法(PWM)计算一维光子晶体的带隙结构。分别就构造一维光子晶体结构的高低折射膜层的介电常数及填充比(高折射膜层的厚度与晶体周期长度的比值)对禁带带隙宽度的影响作出分析。通过最小二乘曲线和曲面拟合得到带宽与介电常数或带宽与填充比的函数关系图,以确定最佳的禁带带宽,从而设计一维光子晶体的周期结构。对高低折射膜层为GaAs/空气组成的一维光子晶体,介电常数比约为13/1,当填充比为0.16时,计算得禁带带宽为0.2564×2πc/Λ,禁带的中心频率为0.3478×2πc/Λ,与实验数据吻合。 相似文献
86.
根据密度泛函理论,用自洽迭代的方法求解二维方形量子点中有杂质时电子(N=1~12)的薛定谔方程,对绝对零度情况下处于基态电子的总能量进行了数值计算,并讨论了杂质对量子点中电子基态能量的影响,得出了方形量子点中多电子系统基态的一些性质. 相似文献
87.
The present study evaluates the growth kinetics of the boride layer Fe2B in AISI 1045 steel, by means of neural networks and the least square techniques. The Fe2B phase was formed at the material surface using the paste boriding process. The surface boron potential was modified considering different boron paste thicknesses, with exposure times of 2, 4 and 6 h, and treatment temperatures of 1193, 1223 and 1273 K. The neural network and the least square models were set by the layer thickness of Fe2B phase, and assuming that the growth of the boride layer follows a parabolic law. The reliability of the techniques used is compared with a set of experiments at a temperature of 1223 K with 5 h of treatment time and boron potentials of 2, 3, 4 and 5 mm. The results of the Fe2B layer thicknesses show a mean error of 5.31% for the neural network and 3.42% for the least square method. 相似文献
88.
Abstract Numerous studies have demonstrated the importance to include pressure as a kinetic parameter in the elucidation of inorganic reaction mechanisms. These studies have specially led to a better understanding and a systematic classification of solvent exchange and ligand substitution reactions of octahedral complexes of transition metal elements. The mechanistic picture for substution reactions on square planar complexes is well established and involves a concurrent bimolecular attack by solvent and the nucleophile on the substrate with a considerable discrimination among different entering groups. The search for factor promoting the conversion of the normal associative mode of activation into a dissociative process has then attracted much attention. Two attempts to induce dissociation, as studied by high-pressure NMR, are presented: one is to prevent the formation by means of sterically hindered ligands, the other one is to promote bond weakening at the leaving group. 相似文献
89.
The concept of minimized integrated exponential error for low dispersion and low dissipation schemes
We devise two novel techniques to optimize parameters which regulate dispersion and dissipation effects in numerical methods using the notion that dissipation neutralizes dispersion. These techniques are baptized as the minimized integrated error for low dispersion and low dissipation (MIELDLD) and the minimized integrated exponential error for low dispersion and low dissipation (MIEELDLD) . These two techniques of optimization have an advantage over the concept of minimized integrated square difference error (MISDE) , especially in the case when more than one optimal cfl is obtained, out of which only one of these values satisfy the shift condition. For instance, when MISDE is applied to the 1‐D Fromm's scheme, we have obtained two optimal cfl numbers: 0.28 and 1.0. However, it is known that Fromm's scheme satisfies shift condition only at r=1.0. Using MIELDLD and MIEELDLD , the optimal cfl of Fromm's scheme is computed as 1.0. We show that like the MISDE concept, both the techniques MIELDLD and MIEELDLD are effective to control dissipation and dispersion. The condition ν2>4µ is satisfied for all these three techniques of optimization, where ν and µ are parameters present in the Korteweg‐de‐Vries‐Burgers equation. The optimal cfl number for some numerical schemes namely Lax–Wendroff, Beam–Warming, Crowley and Upwind Leap‐Frog when discretized by the 1‐D linear advection equation is computed. The optimal cfl number obtained is in agreement with the shift condition. Some numerical experiments in 1‐D have been performed which consist of discontinuities and shocks. The dissipation and dispersion errors at some different cfl numbers for these experiments are quantified. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
90.
Digital image correlation (DIC) has received a widespread research and application in experimental mechanics. In DIC, the performance of subpixel registration algorithm (e.g., Newton-Raphson method, quasi-Newton method) relies heavily on the initial guess of deformation. In the case of small inter-frame deformation, the initial guess could be found by simple search scheme, the coarse-fine search for instance. While for large inter-frame deformation, it is difficult for simple search scheme to robustly estimate displacement parameters and deformation parameters simultaneously with low computational cost. In this paper, we proposed three improving strategies, i.e. Q-stage evolutionary strategy (T), parameter control strategy (C) and space expanding strategy (E), and then combined them into three population-based intelligent algorithms (PIAs), i.e. genetic algorithm (GA), differential evolution (DE) and particle swarm optimization (PSO), and finally derived eighteen different algorithms to calculate the initial guess for qN. The eighteen algorithms were compared in three sets of experiments including large rigid body translation, finite uniaxial strain and large rigid body rotation, and the results showed the effectiveness of proposed improving strategies. Among all compared algorithms, DE-TCE is the best which is robust, convenient and efficient for large inter-frame deformation measurement. 相似文献