带状电子束的空间电荷场

 利用理论分析和数值计算的方法研究了矩形波导内均匀电流密度的带状电子束模型的空间电荷场,给出了该带状电子束模型的空间电荷场的解析表达式,并研究了空间电荷场随带状电子束的几何参数和物理参数的变化规律。研究表明：在不改变电流密度的前提下,更宽的电子束可以传输更强的束流,而空间电荷场并不随束宽度的增大而增大,但是增加电子束厚度会使空间电荷场显著增强,从而不利于高流强电子束的传输;对于相同电流的带状电子束,保持电子束厚度不变,增大电子束宽度,相应地降低电流密度是降低空间电荷场的一个很好的途径,而保持电子束的宽度不变,增大束厚度,相应地降低电流密度只会使沿着电子束截面宽度方向的电场减小,而沿着电子束截面厚度方向的电场基本不变;对于相同电流和电流密度的带状电子束,更宽、更薄的电子束横截面尺寸能使沿着电子束截面宽度方向的电场降到更低,而沿着电子束截面厚度方向的电场只是略有减小。     

Darboux Transformation and Soliton Solutions for Inhomogeneous Coupled Nonlinear Schrodinger Equations with Symbolic Computation

With the aid of computation, we consider the variable-coefficient coupled nonlinear Schrodinger equations with the effects of group-velocity dispersion, self-phase modulation and cross-phase modulation, which have potential applications in the long-distance communication of two-pulse propagation in inhomogeneous optical fibers. Based on the obtained nonisospectral linear eigenvalue problems （i.e. Lax pair）, we construct the Darboux transformation for such a model to derive the optical soliton solutions. In addition, through the one- and two-soliton-like solutions, we graphically discuss the features of picosecond solitons in inhomogeneous optical fibers.     

SINGULAR LIMITS FOR INHOMOGENEOUS EQUATIONS OF ELASTICITY

Based on the framework introduced in [4] or [5], the singular limits of stiff relaxation and dominant diffusion for the Cauchy problem of inhomogeneous equations of elasticity is studied. We are able to reach equilibrium even though the nonlinear stress term is not strictly increasing.     

A NUMERICAL STUDY OF UNIFORM SUPERCONVERGENCE OF LDG METHOD FOR SOLVING SINGULARLY PERTURBED PROBLEMS

In this paper, we consider the local discontinuous Galerkin method （LDG） for solving singularly perturbed convection-diffusion problems in one- and two-dimensional settings. The existence and uniqueness of the LDG solutions are verified. Numerical experiments demonstrate that it seems impossible to obtain uniform superconvergence for numerical fluxes under uniform meshes. Thanks to the implementation of two-type different anisotropic meshes, i.e., the Shishkin and an improved grade meshes, the uniform 2p ＋ i-order superconvergence is observed numerically for both one-dimensional and twodimensional cases.     

全局非均匀积性语言评估标度

提出了两种全局非均匀积性语言评估标度, 在决策过程中, 决策者可以根据实际需要调节这两种标度中相邻语言术语之间的偏差, 从而表明它们具有较好的灵活性. 最后给出了积性语言评估标度和加性语言评估标度之间的转换关系.     

First exit distribution and path continuity of Hunt processes

This paper gives a characterization of a Hunt process path by the first exit left limit distribution. It is also showed that if the first exit left limit distribution leaving any ball from the center is a uniform distribution on the sphere, then the Levy Processes are a scaled Brownian motion.     

一个Erds问题的新证明及其在球面的猜想

著名的数学家P.Erds在给殷涌泉教授的一封信中曾经提到过一个几何概率问题,张景中、杨路、张伟年用初等几何方法证明了Erds的这个猜想[1]。本文利用线集测度理论给出一个更直接的新证明,并讨论在球面上的推广问题,它可形象地描述成如何用＂绷带＂均匀缠球的问题。     

基于超球面支持向量机的综合传动状态判别

以油液光谱分析数据为基础,建立了基于超球面支持向量机的综合传动状态判别模型。利用主成分分析法,对油液光谱分析数据进行预处理,并进行主成分提取的研究分析。研究了参数的变化和异常样本对模型性能的影响。实验研究表明,基于超球面支持向量机的状态判别模型准确可行,能实现综合传动的状态判别。     

节理巷道变形非均匀性与锚杆支护优化

采用UDEC数值模拟软件,分析了不同节理倾角下巷道围岩的变形破坏特点,并对锚杆均匀支护方案和非均匀支护方案进行了对比分析。模拟结果表明:节理巷道变形及锚杆受力存在严重的不均匀性。随着节理倾角的增大,巷道围岩变形值及破坏范围逐渐增大,最大变形值发生的位置由顶底板中部向左肩和右底角逐渐转移。锚杆支护应根据节理角度不同实行非均匀支护,即锚杆安装角度应大致沿节理法线方向,节理影响严重的部位应加长锚杆。非均匀支护不仅能显著减小围岩变形,也明显改善了锚杆受力状况,使锚杆受力趋于均匀,有利于各锚杆加固作用的充分发挥及围岩自身稳定性的提高。     

浅议如何利用统计学技术进行能力验证样品均匀性、稳定性评价

能力验证样品的均匀性和稳定性评价是能力验证活动中最基础的一个环节,用单因素方差分析法判定均匀性和t检验法判定稳定性是两种最常见的方法。本文从统计学的角度对两种判定方法进行了解释,希望对能力验证组织实施有一定的借鉴指导作用。