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291.
《Photonics and Nanostructures》2014,12(5):527-539
We present a refination method based on a cyclic cellular automaton (CCA) that simulates a crystallization-like process, aided with a heuristic evolutionary method called differential evolution (DE) used to perform an ordered search of full photonic band gaps (FPBGs) in a 2D photonic crystal (PC). The solution is proposed as a combinatorial optimization of the elements in a binary array. These elements represent the existence or absence of a dielectric material surrounded by air, thus representing a general geometry whose search space is defined by the number of elements in such array. A block-iterative frequency-domain method was used to compute the FPBGs on a PC, when present. DE has proved to be useful in combinatorial problems and we also present an implementation feature that takes advantage of the periodic nature of PCs to enhance the convergence of this algorithm. Finally, we used this methodology to find a PC structure with a 19% bandgap-to-midgap ratio without requiring previous information of suboptimal configurations and we made a statistical study of how it is affected by disorder in the borders of the structure compared with a previous work that uses a genetic algorithm. 相似文献
292.
293.
本文研究了热传导方程初边值问题的半离散化差分格式直接解算法.分别从Dirichlet和Neumann边界条件出发,直接由空间差分格式导出与时间相关的一阶常微分方程组,随后通过正/余弦变换获得了原方程的半解析解,并给出了相关收敛性分析.并对中心差分格式和紧差分格式的精度差异,通过矩阵特征值理论给出了相关原因分析.另外,对于二维热传导方程初边值问题,应用矩阵张量积运算,该直接解算法可直接演变成二重正(余)弦变换.该方法由于不涉及时间上的离散,从而具有较好的计算效率. 相似文献
294.
Fredrick Oluoch Nyamwala 《Mathematische Nachrichten》2015,288(8-9):1009-1027
We have studied the absolutely continuous spectrum of a selfadjoint subspace extension generated by a three‐term fourth order difference equation with bounded coefficients using subspace theory. In particular, we have shown that the absolutely continuous spectrum exists outside a certain bounded interval. In addition, we have computed the spectral multiplicity as well as the location of absolutely continuous spectrum of selfadjoint subspace extension under certain asymptotic conditions. 相似文献
295.
Fernando C. Silva 《Linear and Multilinear Algebra》1999,46(1):117-138
Consider a matrix D=[Di,j] partitioned in submatrices Di,j where the submatrices Di,iare square. This paper studies the possible eigenvalues of D, when the blocks Di,j, with i≤j, are fixed, and the other blocks vary. The result obtained generalizes twotheorems already known. 相似文献
296.
Ana Paula Santana Jo¯ o Filipe Queir Educardo Marques De S 《Linear and Multilinear Algebra》1999,46(1):1-23
We study a connectionvia group representation theory, between the problem of describing the invariant factors of a product of two matrices over a principal ideal domain and the problem of describing the spectrum of a sum of two Hermitian matrices. 相似文献
297.
本文研究形如(1.1)的第二特征上界问题,得到了定理1 和定理2,其中定理1 的估计系数与[a,b]无关,定理2 的结果在一定条件下比定理1 好. 相似文献
298.
We study the Lyapunov stability of the periodic generalized Camassa–Holm equation in terms of the periodic/anti-periodic eigenvalues and the associated spectral intervals. Moreover, we establish a Lyapunov-type stability criterion based on the Floquet theory and a Lyapunov-type inequality. 相似文献
299.
《Journal of Functional Analysis》2023,284(1):109651
In this corrigendum, we address some closability issues that were ignored in [1]. 相似文献