海洋波导中三维可穿透目标的快速声学成像

研究了用声传播远场分布信息来成像海洋波导环境中三维可穿透目标的反问题.建立了求解这类反问题的远场方程,基于内透射边界值问题的分析,讨论了远场方程解的唯一性和可解性,证明了总能找到远场方程的一个在最小平方意义下的近似解,其模在可穿透目标内部的取值是小的,而在外部的取值是大的,进而发展了一种快速成像可穿透目标的一种指示器样本方法.数值试验表明了这种方法是有效的,即使在有限孔径测量方式的情况,也能够得到未知目标的一个理想成像,而且不需要先验知道可穿透目标的任何几何与物理信息.     

非均匀介质中声波的远场分布的性质

本文运用泛函分析和积分方程的方法,讨论了非均匀介质中声波的远场分布的性质,并应用Тихонов正则化方法讨论了不适定的逆散射问题.     

实数若干性质的证明及其应用

本文介绍实数的阿基米德性、稠密性等性质的证明及其应用,同时也推广了已有文献的相关结论.     

多目标决策非凸锥Λ－有效点的存在性与控制性质

本文提出了多目标决策偏好及最优解的一般概念和集诱导偏好的概念．给出了判断ρ－完备集的一系列条件，从而指出了ρ－完备集是十分广泛的集类．得到了集合的Λ－有效点的存在性定理和ρ－下闭集与截面的Λ－有效点的性质．通过引入函数Λ－下半连续的概念，得到了多目标决策一般集诱导偏好最优解的存在性定理．在这些结果的基础上，最后得到了集合Ｙ关于Λ和多目标决策问题的控制性质．     

T-IPH分布的若干性质及其在排队论中的应用

本文讨论T-IPH分布的一些重要性质,其中T-IPH表示可数状态离散时间吸收生灭链吸收时间的分布.对该分布,首先给出了其概率生成函数(PGF),在此基础上,进~步给出了计算分布概率分布律以及阶乘矩数值结果的迭代公式.另外,还讨论了T-IPH分布在排队论中的一个应用.     

T分布族对数似然方程根的大样本性质

对一类具体的分布族——T分布族中的参数θ,证明了存在θ的一个强相合且最优渐近正态估计θn*,它以概率1当n充分大时是对数似然方程的根.     

Gumbel分布最大吸引场的次序统计量的精致渐近性

得到一类Gumbel分布最大吸引场的随机容量样本的次序统计量的精致渐近性,揭示了收敛速度、权函数、边界函数及极限状态之间的联系.这类吸引场真包含了全体(γ),γ>0分布族.     

Scattering of an incident acoustic wave by an infinite elastic cylinder in a shallow sea

The scattering of sound waves by an isotropic elastic circular cylinder of infinite extent in a water of finite depth is investigated taking into account the shear waves that can exist in addition to compressional waves in scatterers of solid material. The axis of the cylinder is parallel to the water level. The reflected and transmitted energies are plotted for the various values of the radius of the cylinder, and the farfield scattered pressure is obtained for various depth and presented in a graphical form. Copyright © 2008 John Wiley & Sons, Ltd.     

双空间指示函数方法在三维柱面对称波导中电磁波的反散射问题的推广

给出了双空间指示函数方法在三维柱面对称波导中电磁波的反散射问题的推广.基于这个观察:当Green函数的点源在障碍物内部时,那么远域数据的赋权积分可以很好地近似估计Green函数,但是当Green函数的点源在障碍物外部时,那么远域数据的赋权积分就不能很好地近似估计Green函数.建立一个积分方程:它的右边是点源在所重构区域的Green函数,那么我们可以知道这个积分方程的解的范数在未知障碍物的内部有极大值,而这些取得极大值的点所围成的区域恰好就是所重构的障碍物区域.方法最显著的优势在于它不依赖于未知障碍物的边界条件.     

Relation Between a Pole of the Scattering Matrix and the Transmission and Reflection Coefficients in Scattering in a Quantum Waveguide

We use an example to illustrate how a pole with a small imaginary part can affect the transmission and reflection coefficients in the scattering in a quantum waveguide.     

ANALYSIS OF TWO-DIMENSIONAL ELECTROMAGNETIC SCATTERING BY A PERFECTLY CONDUCTING OBSTACLE IN A HOMOGENEOUS CHIRAL ENVIRONMENT

The time-harmonic electromagnetic plane waves incident on a perfectly conducting obstacle in a homogeneous chiral environment are considered.A two-dimensional direct scat- tering model is established and the existence and uniqueness of solutions to the problem are discussed by an integral equation approach.The inverse scattering problem to find the shape of scatterer with the given far-field data is formulated.Result on the uniqueness of the inverse problem is proved.     

Diffraction of the Fundamental Waveguide Wave on an Inductive Cylinder in a Rectangular Waveguide

Computational Mathematics and Modeling - We apply the integral equation method to the diffraction of a waveguide wave on an impedance inductive cylinder in a rectangular waveguide. The...     

一类单位逼近所定义的卷积函数的边界分形性质

我们研究一类单位逼近与具有重分形分解的测度的卷积所定义的函数，给出测度的局部Ｌｉｐｓｃｈｉｔｚ指数与函数的奇异边界增长性质的关系．特别应用于Ｐｏｉｓｏｎ核和Ｇａｕｓ Ｗｅｉｅｒｓｔｒａｓ核，得出正调和函数和（抛物）热函数的某些分形性质     

Analysis of a Degenerate Obstacle Problem on an Unbounded Set Arising in the Environment

We study a class of optimization dynamics problems related to investment under uncertainty. The general model problem is reformulated in terms of an obstacle problem associated to a second-order elliptic operator which is not in divergence form. The spatial domain is unbounded and no boundary conditions are a priori specified. By using the special structure of the differential operator and the spatial domain, and some approximating arguments, we show the existence and uniqueness of a solution of the problem. We also study the regularity of the solution and give some estimates on the location of the coincidence set.     

Analysis of a Degenerate Obstacle Problem on an Unbounded Set Arising in the Environment

We study a class of optimization dynamics problems related to investment under uncertainty. The general model problem is reformulated in terms of an obstacle problem associated to a second-order elliptic operator which is not in divergence form. The spatial domain is unbounded and no boundary conditions are a priori specified. By using the special structure of the differential operator and the spatial domain, and some approximating arguments, we show the existence and uniqueness of a solution of the problem. We also study the regularity of the solution and give some estimates on the location of the coincidence set.     

Scattering of an incident acoustic wave by an elastic sphere in a shallow water

The scattering of acoustic waves by an elastic sphere in a shallow ocean wave guide is investigated taking into account the shear waves which can exist in addition to compressional waves in scatterers of solid material. Expressions for the scattered waves are given. Numerical values for a quantity called the farfield form function for various depth are presented in graphical forms.      

Mathematical Justification of an Obstacle Problem in the Case of a Plate

In this paper the modeling of a thin plate in unilateral contact with a rigid plane is properly justified.Starting from the three-dimensional nonlinear Signorini problem,by an asymptotic approach the convergence of the displacement field as the thickness of the plate goes to zero is studied.It is shown that the transverse mechanical displacement field decouples from the in-plane components and solves an obstacle problem.