Piston acoustic radiator in an impedance screen of a Pekeris waveguide

A model problem of seismic hydroacoustics is studied for a piston radiator inserted in an impedance screen that coincides with the lower boundary of a Pekeris waveguide. The radiation resistance of the piston is numerically calculated as a function of the screen type and parameters of the radiator and the waveguide.     

The field of an equivalent multipole composite radiator in a waveguide

The possibility of replacing a spatially extended volume low-frequency sound source, which forms a three-dimensional directional field in the far-field zone, by an equivalent multipole source is considered. Developing the ideas of L.M. Brekhovskikh, who obtained the solution for a monopole, exact and simplified models of the source field are constructed in the form of superpositions of multipoles of various orders. The models are considered in the integral, mode, and ray approximations applied to the unbounded space and homogeneous and plane-layered waveguides. The results of computations are presented, and the conclusion is made that the contribution of the vertical dipole and quadrupole components to the interference structure of the field amplitude in a waveguide decreases with an increase in the distance from the source. The phase structure is found to be stable regardless of the type of the complex multipole source.     

Spherical dielectric resonator in near zone of waveguide radiator

The results of an experimental study of the electric field near a dielectric resonance sphere located at the open end of a rectangular waveguide or in the near zone are presented. The field distributions at the resonance frequencies of reflection and transmission and far from resonance are studied. The results are compared with the case of an unloaded waveguide radiator.Khar'kov State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 5, pp. 451–457, May, 1992.     

Waves trapped by a thin curved screen in a waveguide with rigid walls

The conditions are derived for the existence of waves trapped by a symmetrical thin rigid screen in a two-dimensional waveguide with rigid walls. Asymptomatic formulas are found for the corresponding eigenvalues, while the asymptomatic structures differ from those pertaining to the eigenvalues of problems in bounded domains. Various generalizations of the results are discussed, and open questions are formulated.     

Investigation of a highly saturated soft X-ray amplification in a capillary discharge plasma waveguide

The characterization of the laser beam intensity distribution of a highly saturated 46.9-nm soft X-ray laser excited by capillary discharges is reported. The laser produces a total output energy of 300 J/pulse by amplification in plasma channels having lengths up to 0.45 m. A regime of laser amplification, which is almost free from the effect of the refraction defocusing, is experimentally determined. This regime produces a soft X-ray laser beam with an intense sub-milliradiant component. In the longer active medium the laser intensity distribution reaches the divergence of 0.6 mrad, which approaches the limit of diffraction. A comparison of the experimental results with the simulations performed with a ray-tracing code shows that the small divergence of the beam could be attributed to the effect of a weak index waveguiding of the laser beam through the long plasma channels. PACS 42.55.Vc; 42.60.Jf     

Loss in a rectangular optical waveguide induced by the crossover of a second waveguide

We calculate the loss induced in a single-mode rectangular optical waveguide by the presence of a second waveguide, perpendicular to the first, which crosses over the first waveguide at a variable distance d. Our calculation is applied to the analysis of several doped silica waveguides of practical importance for optical circuit design.     

Null-broadening in a waveguide

Null-broadening, introduced in plane wave beamforming, is extended to an ocean waveguide in the context of matched field processing. The method is based on the minimum variance processor with white noise constraint and the distribution of fictitious sources using the theory of waveguide invariants. The proposed method is demonstrated in simulation as well as with data collected during the SWellEx-96 experiment. As another application, it is shown that the width of a null can be controlled in an adaptive time reversal mirror with a source-receive array.     

Axion electrodynamics in a waveguide

The interaction of axion and electromagnetic waves is studied in the presence of a magnetic field threading a waveguide. This interaction, which vanishes in free space, is found to induce transverse magnetic waves with frequency spectra associated with transverse electric waves in the absence of the axion.     

Unruh effect in a waveguide

Here we demonstrate that photons launched into a specially designed metamaterial waveguide act as massive quasi-particles, which experience strong acceleration. Laser light propagating through such a waveguide may be used as a thermometer which would measure the Unruh temperature. Moreover, the metamaterial waveguide design may be approximated by a tapered optical waveguide.     

Self-consistent oscillations of the charge in a waveguide

Small oscillations of the charge in a rectangular waveguide are considered. The electromagnetic field generated by these oscillations and its effect on the charge are investigated. It is found that at a certain frequency there is a self-consistent regime of oscillations wherein the charge oscillates under the influence of its self-field in the absence of external forces. The combination of such a charge and the self-consistent alternating field has the property of a quasiparticle, which is named an electromagneton. Zh. Tekh. Fiz. 67, 120–121 (November 1997)     

On the cyclotron maser instability in a waveguide

The cyclotron maser instability is conventionally treated as a pure electromagnetic instability⁽⁵⁾. Waveguide modes can'be equivalent to plane waves reflected slantingly upon the two sides of the waveguide. According to the principles of plasma physics(⁶) the electromagnetic and the electrostatic modes can't be decoupled when the wave vector isn't strictly perpendicular or parallel to the d-c magnetic field. Therefore the conventional treatment is incomplete and invalid in the case of intense beams.Vlasov kinetic theory of the cyclotron maser instability taking into account the space-charge wave is presented. It is found that the respective couplings between the negative-energy cyclotron mode and the RHCP waveguide mode as well as the fast space-charge mode are responsible for the wave-guide maser instability.     

矩形辐射器压电多频超声换能器的研究

研究了一种具有多个共振频率的矩形辐射器夹心式超声换能器,换能器由圆柱形后盖板、压电陶瓷晶堆及矩形六面体辐射器前盖板组合而成。利用表观弹性法和一维近似理论给出了多频换能器横向及纵向理论共振频率方程。对一种特殊情况下的此类换能器进行了有限元及实验分析,给出了各自的频率输入导纳曲线。对理论和实验结果进行分析后表明,此类矩形辐射器夹心式超声换能器可以在不同的振动模态上工作,具有多个共振频率.     

换能器前辐射头与轴向相平行方向的弯曲振动

复合棒型换能器前面的变截面组件在工作时常伴有弯曲振动现象，这在一定程度上会影响换能器的工作性能；利用复合棒型换能器的纵向振动基频与前辐射头弯曲振动的恰当耦合，可展宽换能器的频带。本文用有限元法，研究了前辐射头在声换能器组成中的弯曲振动问题，与测试结果相吻合。