大口径光束高效三倍频理论和实验研究

根据三颗耦合波方程,研究了基波与谱波能量比,晶体长度、功率密度、角失配量和匹配类型等诸因素对三倍频最大可获转换效率的影响.大口径光束三倍频实验结果与理论计算相一致.用类型IIKDP晶体三倍频,在中等功率密度下,获得了43%的能量转换效率.     

On the Divergence of Collocation Solutions in Smooth Piecewise Polynomial Spaces for Volterra Integral Equations

In this paper we present a characterization of those smooth piecewise polynomial collocation spaces that lead to divergent collocation solutions for Volterra integral equations of the second kind. The key to these results is an equivalence result between such collocation solutions and collocation solutions in slightly smoother spaces for initial-value problems for ordinary differential equations. For the latter problems Mülthei (1979/1980) established a complete divergence (and convergence) theory. Our analysis can be extended to furnish divergence results for smooth collocation solutions to Volterra integral equations of the first kind. AMS subject classification (2000) 65R20, 65L20, 65L60.Received May 2004. Accepted September 2004. Communicated by Tom Lyche.Hermann Brunner: This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).     

A Set of Exact Solutions for Singular Integral Equation and a Divergence Pcreoblem of 1D Hydrogen Atom in Moment Represent

The divergence problem in momentum representation of some singular potentials in Schrodinger equation is discussed. A set of exact solutions for a singular integral equation and the criteria determining the solutions in momentum space are obtained. The problems on Loudon's symmetric solutions and counter example of nondegeneracy theorem are solved.     

Further Study on U(1) Gauge Invariance Restoration

To further investigate the applicability of the projection scheme for eliminating the unphysical divergence s/m_e² due to U(1) gauge invariance violation, we study the process e^- + W⁺ → e^- + t + b which possesses advantages of simplicity and clearness. Our study indicates that the projection scheme can indeed eliminate the unphysical divergence s/m_e² caused by the U(1) gauge invariance violation and the scheme can be applied to very high energy region.     

A pressure correction method for fluid–particle interaction flow: Direct‐forcing method and sedimentation flow

A direct‐forcing pressure correction method is developed to simulate fluid–particle interaction problems. In this paper, the sedimentation flow is investigated. This method uses a pressure correction method to solve incompressible flow fields. A direct‐forcing method is introduced to capture the particle motions. It is found that the direct‐forcing method can also be served as a wall‐boundary condition. By applying Gauss's divergence theorem, the formulas for computing the hydrodynamic force and torque acting on the particle from flows are derived from the volume integral of the particle instead of the particle surface. The order of accuracy of the present method is demonstrated by the errors of velocity, pressure, and wall stress. To demonstrate the efficiency and capability of the present method, sedimentations of many spherical particles in an enclosure are simulated. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparison of some tests for convergence of positive series

In this survey, aimed at professors and students of undergraduate analysis courses, two hierarchies of tests are considered. The first is originated from the ratio test and the second from the root test. The test construction techniques are exposed and relations between the tests in each family are discussed. The examples of convergent and divergent series clarify the range of application for each of the introduced tests and situations when they are not conclusive. The behaviour of the partial sums of these series is illustrated geometrically and the level of complexity of each series is evaluated in terms of the rate of its convergence or divergence.     

拉贝判别法的推广

建立了判别正项级数敛散性的几个方法,并运用其中一个方法证明了拉贝判别法及其极限形式的等价形式,改进了最近一篇文献中的结果,同时给出了应用的例子.     

On Bartlett correctability of empirical likelihood in generalized power divergence family

Baggerly (1998) showed that empirical likelihood is the only member in the Cressie–Read power divergence family to be Bartlett correctable. This paper strengthens Baggerly’s result by showing that in a generalized class of the power divergence family, which includes the Cressie–Read family and other nonparametric likelihood such as Schennach’s (2005, 2007) exponentially tilted empirical likelihood, empirical likelihood is still the only member to be Bartlett correctable.     

基于K-L散度与光谱可分性距离的波段选择算法

波段选择是高光谱降维的常用手段,文中从波段选择应遵循的3个原则出发设计了一种基于信息散度与光谱可分性距离的波段选择算法。将高光谱数据中每个波段的光谱分量看作一个一维向量,使用K-L散度表示其相互之间的信息量,选出信息量大且相似性最小的波段组合;根据每个波段中不同地物光谱可分性距离的计算,得到可分性较大的波段组合;将两组波段组合取交集,即得到最优组合波段。为了验证算法的有效性,将选出的最佳3个波段进行伪彩色合成,对其进行光谱角制图分类,分类精度达到922%,Kappa系数为088.     

能见度仪探测光束平行度检测方法

为实现能见度计算中消光系数的正确测量,论述了光源平行度在能见度测量中的重要作用,设计了探测光束发散角检测方法与测量装置。该装置包括定焦成像系统和移动光源的直线系统,利用成像关系与空间几何关系推导了发散角表达式。以紫外LED作为实验光源,设计完成了测量系统成像装置与控制软件,计算得到水平方向与垂直方向发散角,利用所得发散角分析探测光束。实验结果表明,紫外LED光源的光束发散角水平与垂直方向分别为78°和69°,经比较得到未加入平行度的能见度与加入后的比值为051。该方法测得的能见度值更接近于实际值。