基质折射率对反常色散散射体散射特性的影响

基于Mie散射理论,给出了散射强度、散射截面及吸收截面的计算公式,并对不同基质中碳化硅材料在反常色散区中的散射特性进行了数值计算与理论分析。结果表明,在反常色散区中,随着基质折射率的增大,散射强度的峰位发生红移,峰值增大;散射截面和吸收截面的峰位发生红移,峰值减小,这为该材料在反常色散区中的光学理论、实验及应用方面提供了理论参考。     

极大子群的性质对有限群结构的影响

设H为有限群G的一个子群。称H在G中是s-半正规的,若对任意的素数p||G|,只要(p,|H|)=1,就有PH=HP,其中P∈Sylp(G);称H在G中是c-可补的,若存在G的子群N,使得G=HN且H∩N≤HG=CoreG(H)。证明了下面定理设F是一个包含超可解群类U的饱和群系,H△G,且G/H∈F。则G∈F,若下列条件之一成     

Classification of torsion-free genus zero congruence groups

We study and classify all torsion-free genus zero congruence subgroups of the modular group.

     

Theoretical analysis of abnormal grain growth in HCP-polycrystalline thin films on rigid substrates

In this paper, the effects of grain orientation on preferred abnormal grain growth in HCP-polycrystalline thin films have been analysed with respect to strain energy. The calculated results showed that C_hkl, the average values of the orientation factor, decreased with increase of 1 for the same h and k and increased with increase of h or/and k for constant 1. Where (hkl) denoted a particular grain orientation, that is, the grains with (hkl) planes oriented parallel to the film surface. This is preannounced that, considering the strain energy solely, the grains with higher 1 and lower h and k should be favorable in HCP-polycrystalline thin films on rigid substrates after annealing.     

Rank Tests Based on Exceeding Observations

Rank tests based on the maximum number of exceeding observations for several standard nonparametric hypotheses are proposed. An approach to constructing nonparametric rank tests via metrics on the permutation group is used. The test statistics are based on a metric induced by Chebyshev's norm.     

On Quasiconvex Subgroups of Word Hyperbolic Groups

We prove that a quasiconvex subgroup H of infinite index of a torsion free word hyperbolic group can be embedded in a larger quasiconvex subgroup which is the free product of H and an infinite cyclic group. Some properties of quasiconvex subgroups of word hyperbolic group are also discussed.     

改进三帧差分算法在移动物体检测中的应用

移动物体监控系统利用检测算法识别监控区域的移动物体,并进行实时异常信息存储,检测算法中的传统三帧差分法中的阈值是固定的,因此重叠部分无法准确检测出来,存在空洞现象,可能发生误判。针对这些问题,对已有的三帧差分法进行改进,结合图像边缘提取和自适应的迭代阈值计算方法来提高移动物体检测的准确性,并对异常信息进行选择性存储,由实验结果可知,应用平台采用改进后的移动物体检测算法,较好的提高了移动物体检测的灵敏度,增强了检测系统的实时性和准确性,若仅存储异常信息,可节省视频存储空间,并在定位异常动态信息时节省查找时间。     

Cuccia定理的一个推广

For a finite group G,let S(G)be the set of minimal subgroups of odd order of G which are complemented in G.It is proved that if every minimal subgroup X of odd order of G which does not belong to S(G),C_G(X)is either subnormal or abnormal in G.Then G solvable.     

Fully Invariant Subgroups of Abelian p-Groups with Finite Ulm–Kaplansky Invariants

We study primary groups containing proper fully invariant subgroups isomorphie to the group. The admissable sequence of Ulm–Kaplansky invariants for primary groups is introduced. Using these sequences, If-groups are described in the classes of seperable and periodically complete groups.     

On clique relaxation models in network analysis

Increasing interest in studying community structures, or clusters in complex networks arising in various applications has led to a large and diverse body of literature introducing numerous graph-theoretic models relaxing certain characteristics of the classical clique concept. This paper analyzes the elementary clique-defining properties implicitly exploited in the available clique relaxation models and proposes a taxonomic framework that not only allows to classify the existing models in a systematic fashion, but also yields new clique relaxations of potential practical interest. Some basic structural properties of several of the considered models are identified that may facilitate the choice of methods for solving the corresponding optimization problems. In addition, bounds describing the cohesiveness properties of different clique relaxation structures are established, and practical implications of choosing one model over another are discussed.