排序方式: 共有35条查询结果,搜索用时 46 毫秒
11.
D. Wagner M. Thumm W. Kasparek 《International Journal of Infrared and Millimeter Waves》1999,20(4):567-581
Using a scattering matrix formalism the relative TE/TM eigenmode contents of hybrid modes in oversized corrugated rectangular waveguides has been calculated. The influences of slot depth and corrugation period on the eigenmode mixture have been examined. 相似文献
12.
Analytic approach to dielectric optical bent slab waveguides 总被引:1,自引:0,他引:1
K. R. Hiremath M. Hammer R. Stoffer L. Prkna J. Čtyroký 《Optical and Quantum Electronics》2005,37(1-3):37-61
A rigorous classical analytic frequency domain model of confined optical wave propagation along 2D bent slab waveguides and curved dielectric interfaces is investigated, based on a piecewise ansatz for bend mode profiles in terms of Bessel and Hankel functions. This approach provides a clear picture of the behaviour of bend modes, concerning their decay for large radial arguments or effects of varying bend radius. Fast and accurate routines are required to evaluate Bessel functions with large complex orders and large arguments. Our implementation enabled detailed studies of bent waveguide properties, including higher order bend modes and whispering gallery modes, their interference patterns, and issues related to bend mode normalization and orthogonality properties. 相似文献
13.
P. Sanchis J. Martí B. Luyssaert P. Dumon P. Bienstman R. Baets 《Optical and Quantum Electronics》2005,37(1-3):133-147
A rigorous analysis and design of efficient coupling from photonic crystal (PhC) waveguides into conventional dielectric waveguides is reported. Closed-form expressions for the reflection and transmission matrices that completely characterize the scattering that occurs at the interface are derived based on an eigenmode expansion technique and a Bloch basis. Analytic expressions are used to analyze the reflection into PhC waveguides. We obtain that negligible reflection can be achieved by choosing a certain interface within a PhC unit cell. Furthermore, analytic expressions are used to design a novel and compact coupler structure in order to achieve high coupling efficiency when broad dielectric waveguides are considered. Thereby, transmission efficiencies near 100 from the fundamental guided Bloch mode into the fundamental waveguide mode are achieved. 相似文献
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In order to realise the full potential of eigenmode expansion models, advanced boundary conditions are required that can absorb
the radiation impinging on the walls of the discretisation volume. In this paper, we will discuss and compare a number of
these boundary conditions, like perfectly matched layers (PMLs), open (leaky mode) boundary conditions and transparent boundary
conditions (TBCs). We will also introduce the case of PMLs with infinite absorption and discuss its relation to leaky mode
expansion, leading to a deeper insight into the physics of PML. 相似文献
16.
Alfvnic gap eigenmode(AGE) can eject energetic particles from confinement and thereby threaten the success of magnetically controlled fusion. A low-temperature plasma cylinder is a promising candidate to study this eigenmode, due to easy diagnostic access and simple geometry, and the idea is to arrange a periodic array of magnetic mirrors along the plasma cylinder and introduce a local defect to break the field periodicity. The present work validates this idea by reproducing a clear AGE inside a spectral gap, and more importantly details the influence of the number and depth(or modulation factor)of magnetic mirror on the characteristics of AGE. Results show that AGE is suppressed by other modes inside the spectral gap when the number of magnetic mirrors is below a certain value, which leads to a weakened Bragg's effect. The structure and frequency of AGE remain unchanged for a decreased number of magnetic mirrors, as long as this number is enough for the AGE formation. The width of spectral gap and decay constant(inverse of decay length) of AGE are linearly proportional to the depth of magnetic mirror, implying easier observation of AGE through a bigger mirror depth. The frequency of AGE shifts to a lower range with the depth increased, possibly due to the unfrozen plasma with field line and the invalidity of small-perturbation analysis. Nevertheless, it is exciting to find that the depth of field modulation can be increased to form AGE for a very limited number of magnetic mirrors. This is of particular interest for the experimental implementation of AGE on a low-temperature plasma cylinder with limited length. 相似文献
17.
利用 AMC 程序获取了不同最小安全因子( qmin )情况下反剪切阿尔芬本征模频率(RSAE)的变化特征:
当最小安全因子 qmin >1 时,RSAE 频率随着 qmin 增大而增大;当 qmin <1 时,RSAE 频率随着 qmin 减小而增大。这
与简化 RSAE 色散关系给出的频率相符。在 HL-2A 电流爬升期间和锯齿期间分别发现了 qmin >1 和 qmin <1 情况下
缓慢向上扫频的模。这些模的频率介于环向阿尔芬本征模和比压阿尔芬本征模之间,与 AMC 得到的 RSAE 模频
率一致,模的径向结构由单一极向谐波组成,并且高度局域在 qmin 附近,具有典型的 RSAE 特征。 相似文献
18.
从弗拉索夫方程出发,导出了托卡马克等离子体中漂移不稳定性的回旋动理学二维本征模积分方程组。该方程组保留了离子的动理学效应,包括沿磁场的运动、磁场梯度和曲率漂移以及有限拉莫半径效应。与传统的采用气球模表象得到的一维回旋动理学方程(其只能给出不稳定模沿磁场线的结构)不同,该方程组不仅能给出托卡马克等离子体中漂移不稳定模的径向结构,同时还考虑了由离子的环形性漂移引起的相邻极向模之间的线性耦合,进而得到模的极向结构。该结果为相应的数值模拟研究提供了理论基础。 相似文献
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Gary Froyland Simon Lloyd Naratip Santitissadeekorn 《Physica D: Nonlinear Phenomena》2010,239(16):1527-1700
We describe a mathematical formalism and numerical algorithms for identifying and tracking slowly mixing objects in nonautonomous dynamical systems. In the autonomous setting, such objects are variously known as almost-invariant sets, metastable sets, persistent patterns, or strange eigenmodes, and have proved to be important in a variety of applications. In this current work, we explain how to extend existing autonomous approaches to the nonautonomous setting. We call the new time-dependent slowly mixing objects coherent sets as they represent regions of phase space that disperse very slowly and remain coherent. The new methods are illustrated via detailed examples in both discrete and continuous time. 相似文献