Equivalent Source Method Approachto Compositely Postsina Rectangular Waveguide

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A Design Analysis of Split-folded Waveguide Slow-wave Structure†

A design analysis of the split-folded waveguide structure for high power M-type tubes is presented. The theory predicts the existence of two slow-wave modes that are corroborated experimentally. A scheme of modifying the slow-wave structure is presented that eliminates the unwanted upper band and increases the bandwidth of the lower band considerably.     

An Improved Version of Split-folded Waveguide Slow-wave Structure†

An improved version of split-folded waveguide slow-wave structure for crossed-field tubes is described. The equivalent capacitance type analysis is given that predicts the dispersion characteristics of the structure accurately. The experimental slow-wave structure demonstrates a usable band from 1·4 to 3·1 Gc (bandwidth 2·25 : 1), The interaction impedance of the modified structure being reasonably largo, allows the use of fundamental backward or first forward-wave harmonics over wide bandwidths.     

Analysis and Simulation of S-shaped Waveguide in Silicon-on-insulator

The simulation and analysis of S-shaped waveguide bend are presented.Bend radius larger than 30 mm assures less than 0.5 dB radiation loss for a 4-μm-wide silicon-on-insulator waveguide bend with 2-μm etch depth.Intersection angle greater than 20° provides negligible crosstalk (<-30 dB) and very low insertion loss.Any reduction in bend radius and intersection angle is at the cost of the degradation of characteristics of bent waveguide and intersecting waveguide, respectively.     

Dispersion Equation in Non—uniform Optical Waveguide

We study the WKB dispersion equation in non-uniform optical wave-guide.There are three methods given in this paper；(1)method of Airy function；（2）method of connection formula；and（3） method of phase shift.At last we make some re-marks.     

Electron Attachment in Oxygen†

Processes of electron detachment in Townsend discharges in oxygen ore discussed and, it is suggested, are negligible for pressures greater than very approximately 1OO—200 mm Hg in the range of values of the parameter E/P(≯E/P～50 v/cm/mm Hg) used in the experiments. At lower pressures, in agreement with Frommhold's recent work, detachment becomes important particularly at higher values of E/p.     

Realization of Tapered Waveguide by Stretching the Rod Waveguide

By stretching the rod waveguide with different velocities in opposite directions, the tapered waveguide can be fabricated. In condition of taking no account of volume expansion caused by heating and under the assumptions of volume conservation,the rod waveguide can be stretched freely in the heated region without being stretched outside of the heated region. A model,which shows the relation of the transition shape and the two factors, that is the ratio of two velocity and the heated region length, is presented for the shape of the taper transition through mathematic deduction. Based on this model, a desired tapered waveguide can be fabricated. The tapered waveguide are widely used for fabricating tapered fiber couplers and sensors. In addition, the conclusion can be used for fabricating fused fiber coupler.     

Design of Polarization-independent Wavelength-interleave Coupler in Fluorinated Polyimide Waveguide

Based on the measurement of dispersion characteristic and birefractive index of the fluorinated polyimide film,a statistical optimum design method is proposed and used to realize the design of 32-and 36-wavelengths optical waveguide wavelength-interleave coupler (i,e.,interleaver) with the optimization of polarization fluctuation and wavelength interval of 0.8nm at 1550nm. The largest cross coupling ratios of the two interleavers are respectively less than 1.8% and 3.5%, while the least through coupling ratios are respectively greater than 98. 2% and 96. 5%. The output differences due to polarization fluctuation are less than 1.7% and 3.2%     

Moving Striations in Iodine Vapour†

Striations have been observed in the positive column of a discharge through an electronegative gas, iodine, moving from anode towards cathode with speeds between 3 × 10² and 5 × 10³ cm see^?1. Compared to those commonly observed in electropositive gases, these striations have up to order of magnitude lower velocities and wavelengths. A semi-quantitative theory of electronegative striations is approached in three ways, each taking account of the presence of negative ions : (i) comparing the striations to plasma ion waves, (ii) assuming control by lateral diffusion, and (iii) assuming control by ion-ion volume recombination.     

Electrical Transport in nGe-pGaAs Heterojunctions†

A multi-step recombination-tunnelling model, similar to that used to describe the excess current in tunnel diodes, is developed to explain the observed electrical characteristics of nGe-pGaAs heterodiodes. Two different, but quite similar models are used to qualitatively describe the observed forward and reverse characteristics. Quantitative agreement with the experimental characteristics of the many devices presented is obtained by an empirical modification of the resulting equations. The lack of minority carrier injection in these devices is in agreement with the proposed model.     

Design of a 300 GHz Band TWT with a Folded Waveguide Fabricated by Microelectromechanical Systems

For future broadband wireless links, we have designed a 300 GHz band traveling wave tube (TWT) with a folded waveguide fabricated by microelectromechanical systems (MEMS). The TWT operates at a beam voltage of 12 kV and a beam current of 8.3 mA. The classical large signal simulation code predicts the output power greater than 1 W and gain larger than 20 dB over the bandwidth from 280 to 300 GHz.     

On Calculation of the Amplitude–Phase Distribution of the Field Radiated from an Open End of a Rectangular Dielectric Waveguide

The problem of calculating the amplitude–phase distribution of the field radiated from an open end of a rectangular dielectric waveguide expanding along one of its sides (a plane dielectric horn) is considered. The problem of diffraction on the junction of a feed dielectric waveguide and the horn is solved by the domain decomposition method using a model in the form of a screened dielectric waveguide. The amplitude–phase distributions over the distance from the end of the radiator are studied. The possibility of using the screened model for solving the problem of radiation from the open end of a dielectric horn is shown.     

Local field in small metallic particles†

The local electric field governing the emission of electrons and phonons by island metallic films subject to CO₂ laser irradiation is treated in an approximation which allows for the depolarization due to neighbouring particles.     

Fast transfer processes in organic molecules†

In organic compounds constituted of several smaller molecules it is possible that the subunits keep their 'identity’. This behaviour results in absorption lines observed both in the subunits as well as unchanged in the whole molecule and can be explained by the existence of states being localized predominantly on the subunits. The coupling of these states to molecular vibrations may lead to an intersection of adiabatic potential curves of states with totally different localization behaviour and therefore to a fast transition between these states. Using such a transfer mechanism allows experimentally observed excitation spectra to be explained and the time constant to be predicted for energy transfers from initial states localized on one end of the molecule to final states localized on the other side of the same molecule.     

Note on dust in positive columns†

Some improved and extended calculations on this subject are reported briefly.     

Bound Waves in Compressible Plasma Gaps†

It is shown that a planar gap in a plasma medium is an appropriate idealized model for studying electromagnetic and plasma waves in a variety of situations, including plasma sheaths and ionospheric layers. A uniform, isotropic, lossless, warm plasma gap is investigated and is found to support both surface and interface waves which consist of an electromagnetic mode coupled to a plasma pressure mode. The surface waves are fast and they occur primarily at frequencies below the plasma frequency, whereas the interface waves are slow and are present at all frequencies ; in both cases, the waves may be either of the forward- or backward-travelling variety. In addition, the presence of leaky waves of the spectral type is demonstrated at frequencies above the plasma frequency. Dispersion curves are calculated for o large range of the parameters involved and the results are compared to those for surface waves along a dielectric slab which, in certain respects, represents a configuration analogous to the plasma gap if pressure effects are neglected.     

Knowledge Creation Systems in Seven-Eleven Japan

Japanese convenience store chain Seven-Eleven Japan (hereinafter "SEJ") has been profitable for 30 years by constantly anticipating changing trends regardless of the severe business environment. In this paper, the knowledge creation process and its supportive systems in SEJ to examine how information system can support knowledge creation are described. Using case study method, the knowledge creation theory is applied to SEJ, and the results show that facilitating "dialogue" and reinforcing "creative routine" might be the most important functions of information system to support knowledge creation.     

Beam-Plasma Interaction in a Warm Plasma†

Theoretical studies of electron beam-plasma interactions have predicted the occurrence of amplifying waves having growth rates maximizing near to the electron plasma frequency. For the special case of an infinite beam interacting with a cold infinite plasma, an infinite growth rate is expected at the plasma frequency. In practice, the theoretical gain becomes finite if factors such as collisions or non-zero electron temperature are taken into account, or if the beam and plasma ore not both infinite. In this paper, beam-plasma interaction is investigated in planar geometry for both finite and infinite beams in an infinite, uniform, warm plasma. In the finite beam case, the question of appropriate boundary conditions to use at the beam edge arises. For cold plasmas, the Hahn approximation involving postulatian of an equivalent surface charge at the beam edge is usually applied. In the case of a warm plasma, it is unlikely that this approximation would describe accurately the plasma behaviour, though it may still be appropriate for the beam. Suitable boundary conditions are suggested, and computed curves are presented comparing the complex solutions of the resulting dispersion relation with the cold plasma solutions for the same geometry. For typical experimental conditions a substantial reduction of gain is indicated when non-zero electron temperature is taken into account.     

Application of a New Numerical Method in Calculation of Optical Waveguide

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The Plasma Capacitor in a Magnetic Field†

This paper extends previous work on the impedance of a parallel plate capacitor, filled with warm plasma, to take account of a static magnetic field. Computations are presented for parallel plate and coaxial cylinder geometries and indicate series of resonances occurring at, and between, the electron cyclotron frequency harmonies. It is suggested that if the theoretical results were confirmed experimentally, plasma admittance measurements would form the basis of a simple and powerful diagnostic technique for measuring plasma parameters such as electron density and temperature in the laboratory and in the ionosphere.