等离子体填充波纹波导中低频模式特性分析

采用等离子体流体模型和线性场理论，导出了在强引导磁场下，一无限薄环形等离子体加载 波纹波导中电磁波传播的色散关系.数值计算并分析了在不同的等离子体填充密度下，低频 等离子体模式的色散特性和行波管的小信号增益.研究发现，低频等离子体模式可与相对论 电子束发生同步互作用使高频信号放大.同时，在无限薄环形等离子体填充条件下，波纹波 导中的低频等离子体模式严格满足Floquet定理所要求的周期性，其上截止频率不再受到等 离子体频率的限制，当密度较大时，等离子体模式还可与TM模式发生耦合. 关键词： 等离子体 波纹波导 色散关系 增益     

同轴相对论返波管高频特性的数值分析

提出一种数值分析周期慢波结构色散特性的模拟法，先采用时域有限差分法和离散傅里叶变换技术计算含周期慢波结构的谐振腔的谐振频率及谐振场分布，再基于周期慢波电路色散关系的周期性质，利用几个特殊色散点由数值组合技术获得周期慢波线的完整色散关系。数值计算了同轴波纹波导中ＴＭ０ｎ模式的色散关系，亦能用于分析计算任意复杂几何结构的周期慢波线的色散关系。     

“Cold” dispersion relation of corrugated waveguide filled with plasma immersed in a finite magnetic field

A general dispersion equation of a partially filled plasma corrugated waveguide immersed in a finite magnetic field is presented. When the guiding magnet B_0→∞ or 0, this equation can be reduced to the results obtained in previous works.     

Design and experiments for the waveguide to coaxial cable adapter of a cavity beam position monitor

The waveguide to coaxial cable adapter is very important to the cavity beam position monitor (CBPM) because it determines how much of the energy in the cavity could be coupled outside. In this paper, the waveguide to coaxial cable adapter of a CBPM is designed and experiments are conducted. The curve shapes of experiments and simulations are very similar and the difference in reflection is less than 0.1. This progress provides a reliable method for designing the adapter.     

基于波导模式变换的圆波导TE62模式激励器的研究

基于不规则波导模式匹配法以及缓变波导中电磁波模式耦合理论,研究了一种W波段圆波导TE₆₂模式激励器. 该波导模式激励器采用矩形波导TE₁₀模式通过侧壁耦合馈入同轴波导,利用同轴波导的选模特性激励TE₆₁模式;随后利用轴向半径周期微扰的圆波导实现TE₆₁–TE₆₂模式变换. 文中推导了矩形-同轴波导模式匹配理论,系统研究了波导结构缓变参数对模式变换效率的影响,完成了模式变换器的优化仿真设计,数值计算结果表明：中心频率处TE₆₂模式的转换效率为94.5%,纯度为98.16%,效率85%以上带宽达到1 GHz,能够满足回旋管冷测的要求. 关键词： 同轴波导 模式变换 耦合模理论 半径微扰     

TE10矩形波导中填充金属线阵和铁氧体合成的新型左手媒质

在TE₁₀矩形波导中填充金属线阵和铁氧体合成了一种新型的左手媒质结构.分别使用了转移函数矩阵方法以及全波仿真工具Ansoft HFSS对所提出的结构进行了分析.结果表明,在横向磁化铁氧体等效磁导率实部为负的频段范围内,该合成结构呈现左手通带特性并伴随着后向波的传播现象.由于横向磁化铁氧体的等效磁导率为负的频段范围可调,故所提出的结构具有左手通带范围可调的特性. 关键词： 左手媒质 10矩形波导')" href="#">TE₁₀矩形波导 金属线阵 铁氧体     

圆棒介质波导的电磁波传播特性

通过简单的数学分析,推导圆棒介质波导的导模传播条件及特征方程,讨论电磁波在圆棒介质波导中的传播特性。     

A new numerical solution for the MHD peristaltic flow of a bio-fluid with variable viscosity in a circular cylindrical tube via Adomian decomposition method

In this Letter, we considered a numerical treatment for the solution of the hydromagnetic peristaltic flow of a bio-fluid with variable viscosity in a circular cylindrical tube using Adomian decomposition method and a modified form of this method. The axial velocity is obtained in a closed form. Comparison is made between the results obtained by only three terms of Adomian series with those obtained previously by perturbation technique. It is observed that only few terms of the series expansion are required to obtain the numerical solution with good accuracy.     

A new technique for the measurement of the product CO/CO2 ratio at the surface of char particles burning in a fluidized bed

A new experimental technique is proposed to measure the product CO/CO₂ ratio at the surface of spherical char particles during fluidized bed combustion. It is based on the measurement of the burning rate of a single char particle under low oxygen concentration conditions and on the use of an accurate prediction of the particle Sherwood number. This technique was applied to spherical char particles obtained from a bituminous coal which is characterized by a low attrition and fragmentation propensity. The product CO/CO₂ ratio was measured at a bed temperature of 850 °C and at a fluidization velocity of 0.3 m/s in a lab-scale apparatus operated with a bed of 0.5–0.6 mm sand. The char particle size was varied between 2 and 7 mm and the inlet oxygen concentration between 0.1% and 2.0%. Results showed that under the experimental conditions investigated carbon was mostly oxidized to CO₂ within the particle boundary layer, with a maximum fraction of carbon escaping as CO of 10–20% at the lowest oxygen concentrations and largest particle sizes.