Theory of electromagnetic wave propagation in a plasma-filled corrugate waveguide immersed in a finite magnetized field

The linear theory of electromagnetic radiation from a high-power backward-wave-oscillator (BWO), travelling-wave-tube (TWT) with plasma-filled, sinusoidally corrugate waveguide driven by an intense relativistic electron beam (IREB) has been derived and analysed numerically. A general dispersion relation is presented for analysing a plasmafilled corrugate waveguide immersed in magnetized plasma in this paper. It is shown that the linear theory developed here is in good agreement with the previous work.     

Optical dielectric waveguide analysis,based on the modified finite element and integral equation methods

Efficient versions of the finite element and integral equation methods have been developed to analyse the guided (surface) modes of an arbitrary shaped optical fibre. The first approach is based on the replacement of the open waveguide by the screen guide structure with an artificial impedance wall. The integral equation is solved by the adaptive collocation technique. The methods are used to calculate the dispersion characteristics of the elliptical fibre modes and their cut-off frequencies. The results obtained are compared with those calculated by other methods.     

A spectral finite element for analysis of wave propagation in uniform composite tubes

A spectral finite element model (SFEM) for analysis of coupled broadband wave propagation in composite tubular structure is presented. Wave motions in terms of three translational and three rotational degrees of freedom at tube cross-section are considered based on first order shear flexible cylindrical bending, torsion and secondary warping. Solutions are obtained in wavenumber space by solving the coupled wave equation in 3-D. An efficient and fully automated computational strategy is developed to obtain the wavenumbers of coupled wave modes, spectral element shape function, strain-displacement matrix and the exact dynamic stiffness matrix. The formulation emphasizes on a compact matrix methodology to handle large-scale computational model of built-up network of such cylindrical waveguides. Thickness and frequency limits for application of the element is discussed. Performance of the element is compared with analytical solution based on membrane shell kinematics. A map of the distribution of vibrational modes in wavelength and time scales is presented. Effect of fiber angle on natural frequencies, phase and group dispersions are also discussed. Numerical simulations show the ease with which dynamic responses can be obtained efficiently. Parametric studies on a clamped-free graphite-epoxy composite tube under short-impulse load are carried out to obtain the effect of various composite configurations and tube geometries on the response.     

有限磁场作用下等离子体圆柱波导中的线性理论

 考虑了有限磁场的作用,利用“匹配场法”推导出填充环形等离子体时圆柱波导的色散方程,并较详细地讨论了等离子体的厚度、密度, 以及所加磁场强度对色散特性的影响。尤其讨论了等离子体厚度对增长率的影响并得出：对应最大的增长率有一最佳的等离子体厚度。     

The finite element method for calculating the propagation constant in a rectangular chiral waveguide

The problem of finding the propagation constant of a rectangular chiral waveguide is solved using the finite element method. The method proved to be highly accurate and can be used for solving similar problems.     

“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.     

An analysis of wave phenomena in a dielectric waveguide with periodic metal strips

An analysis of a dielectric waveguide periodically loaded with metal strips is presented. Numerical results are obtained from the formulation based on Galerkin's procedure in a space-harmonic domain. Experimental studies are conducted to correlate with theoretical results and to study the effect of finite length of the grating.This work was supported by Office of Naval Research under Contract N00014-79-C-0553.     

有限磁场作用下等离子体背景中的切伦可夫不稳定性研究

较高密度的相对论电子束注入等离子体中将会形成离子通道,在考虑了离子通道的影响下,推导出圆柱波导中更普遍的色散方程,并计算出考虑离子通道和不考虑离子通道效应时的色散关系及电磁波的增长率。     

有限磁场作用下等离子体背景中的切伦可夫不稳定性研究

 较高密度的相对论电子束注入等离子体中将会形成离子通道，在考虑了离子通道的影响下，推导出圆柱波导中更普遍的色散方程，并计算出考虑离子通道和不考虑离子通道效应时的色散关系及电磁波的增长率。     

A finite element analysis for the vibration modes of a bladed disc

The coupled vibration modes of a rotating blade-disc system are calculated by a finite element method. It is assumed that a large number of identical blades are present, such that the resulting blade loadings on the disc can be considered continuously distributed around the rim of the disc. The disc may have arbitrary profile, and the blades may be tapered and twisted, thus closely representing practical axial flow turbomachine configurations. The effects of rotation, thermal stress, and transverse shear and rotatory inertia in discs of moderately thick profile are readily incorporated into the finite element model. Calculated values of frequencies are compared with experimental data obtained on non-rotating models, and the convergence of the solution is examined by comparison with exact solutions, which can be obtained for configurations of simple geometry. Excellent agreement with experimental data is obtained when using remarkably few elements in the mathematical model, and convergence of the solution is extremely rapid.     

有限磁场作用下填充环形等离子体波导中功率流密度的计算

 在考虑有限磁场的作用下,得到了填充等离子体的圆柱光滑波导中各场分量的表达式,然后导出了功率流密度的计算式。通过计算得出等离子体的密度和厚度对功率流密度有极大的影响,并分析了其机理。     

有限磁场作用下填充环形等离子体波导中功率流密度的计算

在考虑有限磁场的作用下,得到了填充等离子体的圆柱光滑波导中各场分量的表达式,然后导出了功率流密度的计算式。通过计算得出等离子体的密度和厚度对功率流密度有极大的影响,并分析了其机理。     

A finite element analysis of the reactive element effect in oxidation of chromia-forming alloys

In many situations, failures such as spallation or cracking occur when chromia-forming alloys are subjected to high-temperature thermal treatment. On the other hand, a small amount of reactive element addition can remarkably increase the adherence between chromia scales and alloys. A two-dimensional finite element model has been developed to analyze the effects of reactive elements on the selective oxidation of chromia scale-forming binary alloys. The quantitative relation between the diffusivities of chromium ions and the activities of reactive element (yttrium) has been derived for the first time and has been incorporated with a continuum thermodynamic model accounting for stress–diffusion interaction in the oxidation of Cr–Fe alloys. The model predicts that the diffusivities of Cr ions are affected by the activities of reactive element compounds, which eventually leads to a decrease of the interfacial spallation driving force, as well as an increase of the interfacial adherence.     

One-dimensional finite motion of a particle in the field of a weak gravitational wave

The Hamiltonian formalism of classical mechanics can be used effectively to describe the motion of a particle (including a massless one) along a segment of material that is in a nonsteady gravitational field. The problem of applying this formalism to the detection of gravitational waves using a Michelson or Fabry—Perot interferometer is considered. The existence of a phase shift of an electromagnetic wave due to the interaction of the electromagnetic and gravitational fields is noted. Moscow State Aviation Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 13–17, August, 1997.     

A combined three-dimensional finite element and scattering matrix method for the analysis of plane wave diffraction by bi-periodic,multilayered structures

A three-dimensional finite element method (FEM) for the analysis of plane wave diffraction by a bi-periodic slab is described and implemented. A scattering matrix formalism based on the FEM allows the efficient treatment of light reflection and transmission by multilayer bi-periodic structures, and the computation of Bloch modes of three-dimensional arrays. Numerical simulations, which show the accuracy and flexibility of the FEM, are presented.