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931.
朱玉扬 《数学的实践与认识》2008,38(4):142-148
记平面边长为1的正m边形为S_m,将S_m剖分成n块:S_(m1),S_(m2),…,S_(mn),这样的剖分称S_m的n剖分,并以T(m,n)表示.以d_(mi)表示区域S_(mi)(i=1,2,…,n)的直径(即区域S_(mi)任意两点之间距离的最大者).记D(m,n)=max{d_(m1),d_(m2),…,d_(mn)}及Ψ(m,n)=■{D(m,n)}.本文将估计Ψ(m,n)的上下界.证明Ψ(6,3)=3/2,Ψ(6,4)=3-3~(1/2),Ψ(6.6)=1,Ψ(6,7)=3/2,估计Ψ(6,n)的渐进性.提出几个猜想. 相似文献
932.
In this paper, a class of second order discrete Hamiltonian systems without any periodicity assumptions are considered. Base
on the critical point theory, some sufficient conditions for the existence of homoclinic orbits are obtained. The results
obtained extend the results in [2006] by relaxing the assumptions on the sign of the potential.
相似文献
933.
Hong-Shun Li 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,92(2):153-173
On the basis of the discrete ordinate scheme with (an) infinitely small weight(s), an easy-to-use and comprehensive method, named multi-rays method, is developed to calculate total, direct and medium intensities in arbitrarily specified directions. In doing this, for each of the specified directions, three identical discrete directions with infinitely small weights are employed to represent the three intensities. The new method is verified with two standard test problems, and is used to compute the intensities in two anisotropically scattering problems. 相似文献
934.
A. Alsaad A. Ahmad 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):151-156
First-principles calculations are performed to compute the e33
piezoelectric coefficients of GaN, ScN and (ScxGa1-xN) alloys
exhibiting an alternation of hexagonal GaN, with hexagonal ScN along the c-axis. For Sc compositions larger than 50%, each atom has nearly five nearest
neighbors (i.e., the ground state exhibits a phase that is five-fold
coordinated). On the other hand, Sc-deficient (Sc, Ga) N alloys adopt a
ground-state that is four-fold coordinated). The magnitude of e33 in
the Sc-deficient ideally ordered (Sc0.25Ga0.75N) is found to be larger
than the magnitude of the corresponding e33 coefficients resulting from
the compositional weighted average over the hexagonal (h-ScN) and the wurtzite (w-GaN) parent compounds. On the other hand, the e33 coefficients of the Sc-rich
ordered (Sc0.75Ga0.25N) is found to be negligibly small. In addition, e33
piezoelectric coefficients in ordered (Sc0.5Ga0.5N) exhibit quite
large magnitudes, due to the nonpolar to polar transition occurs at Sc composition x = 0.5, and thus can bridge the corresponding coefficients of (Ga, In) N and
ferroelectric alloys. The microscopic origins for this huge enhancement in
the piezoelectric behavior in Sc-low and Sc-intermediate alloys and the role
of each atom are revealed and discussed. 相似文献
935.
936.
应用固体经验电子理论,并联系 G.Inden 的有序转变温度与原子间作用能的关系式,计算了 CuZnAl 记忆合金的 A_2到 B_2,B_2到 DO_3两种有序转变温度随合金元素变化的规律。计算得出的变化趋势与实验结果符合得相当好,表明所采用的理论模型可以说明 CuZnAl 合金的记忆性能和用来指导探索新的记忆合金。 相似文献
937.
Y. Wardi 《Journal of Optimization Theory and Applications》1990,64(3):615-640
A stochastic approximation algorithm for minimax optimization problems is analyzed. At each iterate, it performs one random experiment, based on which it computes a direction vector. It is shown that, under suitable conditions, it a.s. converges to the set of points satisfying necessary optimality conditions. The algorithm and its analysis bring together ideas from stochastic approximation and nondifferentiable optimization. 相似文献
938.
By reexamining the analysis of Basu and Biswas, based on the stereographic projection method of Fock and Levy, it is shown
that the general solution of the Wick-Cutkosky model in the instantaneous approximation, hitherto unreported, involves only
one quantum number; this is contrasted with the well-known solution which involves two quantum numbers, but for which the
spectrum is degenerate with respect to one of them. The latter situation is shown to hold under a rather special circumstance. 相似文献
939.
We consider the application of semiclassical approximation to relativistic potentials for massless particles where the kinetic
energy is a nontrivial, nonlocal operator. Quantization rules are derived for an arbitrary confining potential and compared
to some exact results forS-waves. These results admit of a partial generalization to smalll values. 相似文献
940.