正负折射率的一维圆形受限光子晶体特性研究

对正负折射率材料构成的一维光子晶体,在横向圆形受限的条件下,推出了光波在其中传播时模式所满足的条件,并利用特征矩阵法研究了正负折射率绝对值相同时,光波在不同模式和不同介质厚度可见光能实现透射波和零反射。正负折射率绝对值不等时,得出介质厚度为半波长时透射波出现在中心波长处;随着模式数即入射角增大,透射波曲线向短波方向移动;介质折射率差的绝对值越大、周期数增加都使透射波谱宽度变窄。     

抗阵风载荷的小型无人飞行器设计及相关风洞舵效比较

本文目的在于探索验证微小型飞行器的气动布局与抗突风载荷能力的关系,结合风洞试验验证了结果并进行了数据分析。在低雷诺数条件下采用大边条、小展弦比非常规的气动布局设计,根据性能指标要求对飞行器的机翼面积、翼展、翼型等相关参数进行了分析设计;运用数值模拟等手段对全机简化模型进行了气动力计算,对结果进了行初步的定性分析,为初始的设计提供了验证;结合实际的靶机制作得到了实际飞机的风洞验证缩比模型,对其进行了风洞的常规测力实验。根据风洞试验结果对飞机升降舵舵面与副翼舵面偏转0°、±15°、±30°的气动性能进行了评估,为进一步的理论分析提供依据。结合实际外场飞行实验情况得出飞行器的实际气动性能,并对大量相关风洞试验数据进行了分析;探索性地给出了一条适用于微小型飞行器进行的新设计方法和设计流程,为设计适应于阵风载荷等恶劣气候条件下微小的型飞行器提供了参考新思路。     

Kernels by monochromatic paths in digraphs with covering number 2

We call the digraph D an k-colored digraph if the arcs of D are colored with k colors. A subdigraph H of D is called monochromatic if all of its arcs are colored alike. A set N⊆V(D) is said to be a kernel by monochromatic paths if it satisfies the following two conditions: (i) for every pair of different vertices u,v∈N, there is no monochromatic directed path between them, and (ii) for every vertex x∈(V(D)?N), there is a vertex y∈N such that there is an xy-monochromatic directed path. In this paper, we prove that if D is an k-colored digraph that can be partitioned into two vertex-disjoint transitive tournaments such that every directed cycle of length 3,4 or 5 is monochromatic, then D has a kernel by monochromatic paths. This result gives a positive answer (for this family of digraphs) of the following question, which has motivated many results in monochromatic kernel theory: Is there a natural numberlsuch that if a digraphDisk-colored so that every directed cycle of length at mostlis monochromatic, thenDhas a kernel by monochromatic paths?     

Counting lattice chains and Delannoy paths in higher dimensions

Lattice chains and Delannoy paths represent two different ways to progress through a lattice. We use elementary combinatorial arguments to derive new expressions for the number of chains and the number of Delannoy paths in a lattice of arbitrary finite dimension. Specifically, fix nonnegative integers n₁,…,n_d, and let L denote the lattice of points (a₁,…,a_d)∈Z^d that satisfy 0≤a_i≤n_i for 1≤i≤d. We prove that the number of chains in L is given by where . We also show that the number of Delannoy paths in L equals Setting n_i=n (for all i) in these expressions yields a new proof of a recent result of Duchi and Sulanke [9] relating the total number of chains to the central Delannoy numbers. We also give a novel derivation of the generating functions for these numbers in arbitrary dimension.     

Segments and Hilbert schemes of points

Using results obtained from a study of homogeneous ideals sharing the same initial ideal with respect to some term order, we prove the singularity of the point corresponding to a segment ideal with respect to a degreverse term order (as, for example, the degrevlex order) in the Hilbert scheme of points in Pⁿ. In this context, we look into the properties of several types of “segment” ideals that we define and compare. This study also leads us to focus on the connections between the shape of generators of Borel ideals and the related Hilbert polynomial, thus providing an algorithm for computing all saturated Borel ideals with a given Hilbert polynomial.     

GLOBAL STABILITY OF AN SVIR EPIDEMIC MODEL WITH VACCINATION

In this paper, an SIR epidemic model with vaccination for both the newborns and susceptibles is investigated, where it is assumed that the vaccinated individuals have the temporary immunity. The basic reproduction number determining the extinction or persistence of the infection is found. By constructing a Lyapunov function, it is proved that the disease free equilibrium is globally stable when the basic reproduction number is less than or equal to one, and that the endemic equilibrium is globally stable wh...     

Bounding the sum of powers of the Laplacian eigenvalues of graphs

For a non-zero real number α, let s _α (G) denote the sum of the αth power of the non-zero Laplacian eigenvalues of a graph G. In this paper, we establish a connection between s _α (G) and the first Zagreb index in which the Hölder’s inequality plays a key role. By using this result, we present a lot of bounds of s _α (G) for a connected (molecular) graph G in terms of its number of vertices (atoms) and edges (bonds). We also present other two bounds for s _α (G) in terms of connectivity and chromatic number respectively, which generalize those results of Zhou and Trinajsti? for the Kirchhoff index [B Zhou, N Trinajsti?. A note on Kirchhoff index, Chem. Phys. Lett., 2008, 455: 120–123].     

带启动时间的Geom/Geom/1多重工作休假排队

本文中研究了一个带有启动时间的Geom/Geom/1多重工作休假排队模型。服务台在休假期间,不停止服务,而是以较低的服务率为顾客提供服务。运用拟生灭过程和矩阵几何解的方法,给出了该模型的稳态队长分布,并求出了平均队长以及顾客的平均逗留时间。     

知识型员工行为能力的构成要素与评价研究

行为能力对于解释员工绩效具有重要意义.本文以知识型员工为研究对象,通过规范的实证研究获得了知识型员工行为能力的构成要素,以此为基础构建了知识型员工行为能力的评价指标体系.根据指标模糊性的特点,将三角模糊数理论与FAHP的融合,提出了一种基于三角模糊数的FAHP评价方法.以DR公司招聘某岗位的知识型员工为实例,说明了本文提出的方法在知识型员工行为能力评价中的适用性.     

高校创新型科研团队行为模式研究——以生命科学部高校国家重点实验室为例

国家重点实验室作为高校创新型科研团队的"国家队",是我国基础研究的核心力量和重大创新成果的摇篮,更是培养高层次科技人才的基地.研究高校创新型科研团队组织分布、管理结构、团队成员组成、科研、学术交流等具体行为模式特征,将是进一步发展和完善高校创新型科研团队的有力切入点,也将为相关科研政策的改进和完善提供参考依据.