印刷带状偶极子天线与经典三维柱状偶极子天线的等效理论研究

相对于传统的柱状偶极子,印制偶极子天线更适合应用于现代通讯系统.本文通过引入边缘场效应,对传统的基于感应电动势法的柱状电偶极子辐射阻抗公式进行修正,并在此基础上将其推广至印制偶极子天线中.此外,本文还采用合成渐进法,基于物理概念,推导出平面偶极子天线的谐振频率及谐振频率处辐射电阻的两个计算机辅助计算公式.数值计算及验证表明,两个公式的精度均在2%以内,可以用于指导工程设计.     

On the Pesin set of expansive geodesic flows in manifolds with no conjugate points

In this paper, we show that the Pesin set of an expansive geodesic flow in compact manifold with no conjugate points and bounded asymptote coincides a.e with an open and dense set of the unit tangent bundle. We also show that the set of hyperbolic periodic orbits is dense in the unit tangent bundle.     

一种分析有限金属厚度和有限电导率的共面波导结构的有效方法

采用分区直线法与渐近拟合阻抗边界条件相结合的方法,对一种具有限金属厚度和有限电导率的共面波导结构的相对介电常数和损耗特性进行了分析,这是一种全波分析方法,并且可以适用于趋肤深度与金属厚度之比为任意数值的情况。计算实例证明了该方法的正确性和有效性。     

Improved Steplength by More Practical Information in the Extragradient Method for Monotone Variational Inequalities

The extragradient method uses only the values of the function in the variational inequality to solve it. In many real-life problems, the functions do not have explicit expressions and their evaluations are expensive. Therefore, it is important and practical to reduce the number of function evaluations used in these problems. In order to do this, we present some modifications to one existing extragradient method. First, we analyze the limit of the projection along a direction onto a closed convex set. Then, using the obtained result, we give a horizontal asymptotic property of an estimated function to the one measuring the progress in each iteration. From this property, a Newton search as well a self-adjusted relaxation procedure are introduced with an improved steplength into the extragradient method. Besides the theoretical background, numerical results are given to show the progress of the modified method. This work was supported by National Natural Science Foundation of China 10571083 and Doctoral Fund of Ministry of Education of China 20060284001.     

二次曲线局部与整体的关系

用射影几何知识讨论欧氏平面上二次曲线局部与整体的关系,讨论如何通过二次曲线的一些已知点与切线判断它的类型,作出它的对称轴,渐近线,焦点与准线.     

煤油和空气的混合流体水平管内沸腾换热实验研究

以煤油为介质,在高不凝气体含量下对水平管内的沸腾换热进行了实验研究,得到了在不同的不凝气体含量范围内,沸腾换热系数随不凝气体含量增加而降低的规律．实验结果表明了不凝气体的加入使得煤油的分压降低,泡点温度降低,在较低的混合流体温度下就产生了沸腾,但不凝气体对核态沸腾换热存在抑制现象．采用渐进逼近模型给出了含不凝气体的煤油管内沸腾换热的实验关联式。     

Polynomial asymptotes

This note develops and implements the theory of polynomial asymptotes to (graphs of) rational functions, as a generalization of the classical topics of horizontal asymptotes and oblique/slant asymptotes. Applications are given to hyperbolic asymptotes. Prerequisites include the division algorithm for polynomials with coefficients in the field of real numbers and the elementary limit theorems from calculus. This note could be used as enrichment material in courses ranging from Calculus to Real Analysis to Abstract Algebra.     

非对称侧边耦合带线特性参数提取的研究

通过模糊电磁理论中的"合成渐近"法得到了非对称侧边耦合带状线单位长度奇偶模电容和奇偶模特性阻抗的计算公式。运用数值分析方法矩量法(MoM)进行了以上特性参数的算法分析,所得公式计算结果与矩量法分析结果相比,其平均误差均小于2%。给出并描述了奇偶模特性阻抗随耦合带线耦合间距S变化曲线。这些研究数据为实际工作中相关微波无源电路的设计提供了帮助。     

求代数曲线斜渐近线的一种新方法

根据对渐近线的定义的理解,给出了求代数曲线斜渐近线的一种新方法．     

求平面曲线渐近线的一种新方法

利用曲线割线的极限得到曲线的渐近线,给出了求渐近线的一种新方法.这种方法直观性强,有助于培养学生的创新能力.