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101.
Ali Reza Moghaddamfar 《Siberian Mathematical Journal》2006,47(5):911-914
The noncommuting graph ?(G) of a nonabelian finite group G is defined as follows: The vertices of ?(G) are represented by the noncentral elements of G, and two distinct vertices x and y are joined by an edge if xy ≠ yx. In [1], the following was conjectured: Let G and H be two nonabelian finite groups such that ?(G) ? ?(H); then ¦G¦ = ¦H¦. Here we give some counterexamples to this conjecture. 相似文献
102.
The degree distribution has attracted considerable attention from network scientists in the last few decades to have knowledge of the topological structure of networks. It is widely acknowledged that many real networks have power-law degree distributions. However, the deviation from such a behavior often appears when the range of degrees is small. Even worse, the conventional employment of the continuous power-law distribution usually causes an inaccurate inference as the degree should be discrete-valued. To remedy these obstacles, we propose a finite mixture model of truncated zeta distributions for a broad range of degrees that disobeys a power-law behavior in the range of small degrees while maintaining the scale-free behavior. The maximum likelihood algorithm alongside the model selection method is presented to estimate model parameters and the number of mixture components. The validity of the suggested algorithm is evidenced by Monte Carlo simulations. We apply our method to five disciplines of scientific collaboration networks with remarkable interpretations. The proposed model outperforms the other alternatives in terms of the goodness-of-fit. 相似文献
103.
In order to overcome the deficiency in classical method of low order spectral model, a new method for low order spectral model was advanced. Through calculating the multiple correlation coefficients between combinations of different functions and the recorded data under the least square criterion, the truncated functions which can mostly reflect the studied physical phenomenon were objectively distilled from these data. The new method overcomes the deficiency of artificially selecting the truncated functions in the classical low order spectral model. The new method being applied to study the inter-annual variation of summer atmospheric circulation over Northern Hemisphere, the truncated functions were obtained with the atmospheric circulation data of June 1994 and June 1998. The mechanisms for the two-summer atmospheric circulation variations over Northern Hemisphere were obtained with two-layer quasi-geostrophic baroclinic equation. 相似文献
104.
105.
106.
Consider the problem of scattering of electromagnetic waves by a doubly periodic Lipschitz structure. The medium above the structure is assumed to be homogenous and lossless with a positive dielectric coefficient. Below the structure there is a perfect conductor with a partially coated dielectric boundary. We first establish the well‐posedness of the direct problem in a proper function space and then obtain a uniqueness result for the inverse problem by extending Isakov's method. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
107.
In this paper we consider the transmission problem of viscoelastic waves. That is, we study the wave propagations over materials consisting of elastic and viscoelastic components. We show that for this types of materials the dissipation produced by the viscoelastic part is strong enough to produce exponential decay of the solution, no matter how small is its size. We also show that the linear model is well posed. 相似文献
108.
《Journal of Graph Theory》2018,89(3):350-360
Suzuki [Discrete Math. 310 (2010), 6–11] proved that for any orientable closed surface F2 other than the sphere, there exists an optimal 1‐planar graph which can be embedded on F2 as a triangulation. However, for nonorientable closed surfaces, the existence of such graphs is unknown. In this article, we prove that no optimal 1‐planar graph triangulates a nonorientable closed surface. 相似文献
109.
部分相干光学成像系统的光学传递函数和像质评价准则 总被引:2,自引:2,他引:2
根据光学成像理论,建立了部分相干成像光学系统的光学传递函数。该函数与非相干成像光学系统传递函数相同,因而部分相干成像和非相干成像两者的光学系统波面像差公差标准也是相同的。这一点解释了显微镜光学系统的光学设计惯用法则:镜头像差公差标准的选择,并不因为采用成像照明方式的不同而有所差异。 相似文献
110.
The concept of partially coherent nonparaxial modified Bessel--Gauss (MBG)
beams is proposed. Based on the generalized Rayleigh-Sommerfeld diffraction
integral, the analytical propagation equations of nonparaxial MBG beams in
free space are derived and analysed, and some special cases are discussed.
In particular, under the paraxial approximation our results reduce to the
corresponding paraxial ones. Numerical calculation examples are given to
illustrate the dependence of intensity and spectral degree of coherence on
the beam order $m$, \textit{$\xi $} and $f$ parameters, and to compare
the difference between the paraxial and nonparaxial results. 相似文献