Numerical analysis of a rib optical waveguide with trapezoidal cross section

Dispersion relations and field distributions in rib optical waveguides with several sizes of trapezoidal cross sections are investigated by using a new highly accurate numerical method, which is based on the Rayleigh principle and on the least-squares method.     

The scattering cross section of a resonator in a multimode waveguide

The scattering of sound by a single monopole-dipole resonator in a multimode pipe is investigated. The resonator has the form of a Helmholtz resonator connected through a small bar to the pipe wall. In fact, this resonator is a combination of a monopole resonator and a dipole one positioned at the same point. The scattered fields of these resonators are orthogonal to each other. The scattering cross sections of the monopole and dipole resonators in a multimode pipe are calculated. The scattering cross section of the monopole-dipole resonator is determined as the sum of the scattering cross sections of the monopole and the dipole resonators. The friction in a resonator (the monopole or dipole resonator) reduces its scattering cross section by a factor of (1 + β)², where β is the ratio between the friction resistance and the radiation resistance of this resonator.     

Dipole-exchange spin wave spectrum in an anisotropic ferromagnetic waveguide with a rectangular cross section

A theory has been constructed that strictly describes the spectrum of dipole-exchange spin waves in an arbitrarily magnetized anisotropic ferrite waveguide with a rectangular cross section. The theory takes into account the spatial inhomogeneity of the internal magnetic field in the waveguide cross section. The influence of parameters of the ferrite waveguide on the distribution of the internal magnetic field in the waveguide cross section is analyzed. The dispersion characteristics of two waveguide types most widely used in practice are investigated. The dipole-exchange spin wave spectra calculated for a transversely magnetized waveguide are presented and the distributions of the dynamic magnetization in the waveguide cross section for several types of volume and localized spin-wave modes are constructed.     

梯形截面脊形介质波导导模的分析

本文给出用分区分离变量法计算梯形截面脊形介质波导传插特性与场分布的近似方法.所导出的数学表达式形式简单,物理图象清晰,可用袖珍计算器进行计算,计算工作量较小,所得结果与精确数值计算结果符合较好.     

Viscoplastic flows in channels with variable cross section and deformable walls

A longitudinal axially symmetric Shvedov-Bingham medium flow in a deformable vessel is studied. A formulation of the problem in terms of the integral characteristics of the channel cross section (radius, flow rate, rigid core radius in the cross section, core velocity, and average pressure in the cross section) is pro- posed. The problem of a steady flow in a confuser and the problem of medium acceleration in a cylinder are solved using the integral method.     

Analysis of dielectric waveguide structure of arbitrary cross section

A class of dielectric waveguide structures of arbitrary cross section in conjuction with one or more layer dielectrics is ana lysis with the Method of Lines(MOL). This leads to an eigenvalue problem where the nonphysical and spurious modes do not appear. Dispersion characteristic examples are calculated for structures suitable for mm waves and optical integrated circuits. Such as ridge guides, guide, and so on. The numerical examples are verified by results available from other methods.     

Propagation of an ultrashort laser pulse in a waveguide of rectangular cross section

The propagation of a spikelike ultrashort laser pulse in a mirror waveguide of rectangular cross section with perfectly conducting walls is considered. An algorithm for the calculation of the propagation of a field pulse in such a waveguide is designed. The general approach is illustrated by calculation of the propagation of a p-polarized field pulse shorter than the dimensions of the waveguide cross section.     

Theory of gyro-backward wave oscillators with tapered magneticfield and waveguide cross section

A theory is developed which describes gyro-backward wave oscillators (gyro-BWO's) with arbitrarily relativistic electron beams and tapered external magnetic field and waveguide wall radius. For the case of linear tapering the optimal parameters are found that correspond to highly efficient operation. The frequency tunability as the function of magnetic field and voltage deviations has been analyzed. It is shown how to use the results given in terms of normalized parameters for designing concrete gyro-BWO's. For one concrete design the effect of electron velocity spread on the efficiency has been studied     

Electron scattering cross section measurements in a variable pressure scanning electron microscope

Scattering of the incident electron beam in the variable pressure scanning electron microscope (VPSEM) affects the ability to perform quantitative chemical measurements. However, the manner in which the sum of the elastic and inelastic scattering cross sections varies as a function of gas type and accelerating voltage in the VPSEM is not well understood. A dual Faraday cup was constructed to measure the scattered fraction of the primary beam as a function of gas pressure, working distance, and accelerating voltage in air, water vapor, and argon environments. Experimentally measured values of the scattering cross section agree with previous experimental work, and agree within a factor of two with those values calculated carefully from theory.     

Dynamics of detonation waves in a channel with variable cross section and filled with bubbly fluid

The flow of bubbly fluid comprising a mixture of bubbles filled with explosive and inert gases, which is driven through a converging channel, was studied. Depending on the velocity of the hummer hitting the bubbly fluid boundary, the flow may be accompanied by the development of detonation waves which compress the bubbles with inert gas.     

Generation of pure single-photon states via spontaneous four-wave mixing in nanofibers with a variable cross section

A theory of single-photon sources of light is developed on the basis of spontaneous four-wave mixing in optical nanofibers. The spectral amplitude of the biphoton field is calculated with allowance for the real geometry of a nanofiber manufactured from standard optical fiber by heating and stretching. It is shown that by selecting pump parameters, we can simultaneously obtain the high spectral brightness and low frequency correlation of generated biphoton states in a nondegenerate mode of four-wave mixing that corresponds to single-photon states with the high purity.     

Seismic response of underwater members of variable cross section

This paper is concerned with a method for solving seismic response problems of a pile of variable cross section with a tip inertia subjected to a sea bottom seismic displacement. The analysis developed here is based on an elastodynamic theory in which the effects of the continuously distributed mass and rigidity of the pile are included. The method includes use of Fourier series expansion, the Laplace transform, the transfer matrix method and the residue theorem in order to deal with the complex seismic displacement and arbitrarily shaped piles; considerable simplification of the calculations is thus achieved. The theoretical results given are applicable to seismic response problems for a pile of arbitrary shape with a tip inertia, excited by arbitrary displacements. As an application of the present theoretical results, the dynamic response has been calculated for hollow piles of curved conical shape with tip inertias and double taper beams subjected to seismic displacements.     

Study of turbulent swirling flow in a rotating separation element of variable cross section

In the present study, the distribution of circumferential velocity components of carrier flow in separation elements of air-centrifugal classifiers of powder materials has been experimentally examined. The study was carried out for variously contoured separation channels, and also for various conditions of a carrying agent (air) input in a separation zone. Optimal conditions for particle separation throughout the whole volume of the separation element can be organized by making the channel contour diverging towards the center of rotation. The experimental data gained in this study supplement the mathematical model for the aerodynamics of turbulent carrier flow in the shaped rotating separation elements of air-centrifugal classifiers and make an analysis of the separation-zone flow possible.     

On the quantization of a kinetic energy with variable inertia

It is shown that fundamental properties of kinetic energy determine its operator in wave mechanics almost completely: The part containing differential operators is unequivocally given by the Laplacian calculated for the metric which is defined by the classical kinetic energy. The only remaining ambiguity is an additive scalar function proportional to ?². Invariance properties with respect to infinitesimal transformations may reduce the number of coordinates on which this function depends. In certain cases it must be constant.