共查询到20条相似文献,搜索用时 359 毫秒
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同时利用两个振源,在液体表面上产生两列低频表面波,实现了多振源条件下表面声光效应,观察到清晰、稳定、反衬度高的声光衍射条纹.当引起两列表面波的两个振源频率具有倍数关系时,声光衍射条纹的极大值位置与较小频率的振源单独存在时所产生表面波的极大值位置相同,与较大频率的振源单独存在时所产生表面波的极大值位置部分相同.当引起两列表面波的两个振源频率不具备倍数关系时,不仅观察到单振源的衍射条纹,而且也观察到了双振源的干涉条纹.理论上得到多振源衍射光场和表面波波长、振幅之间的解析表达式,理论规律与实验结果吻合较好. 相似文献
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通过采用将入射光掠入射到频率为几百赫兹的衰减低频液体表面波上,观察到了清晰的间距分布具有明显非对称性的衍射条纹。当入射光掠入射到低频液体表面上时,衍射图样非对称分布具有普遍性。理论上得到了考虑表面波衰减影响后观察屏处衍射光强分布的解析表达式。理论结果表明:衍射图样的这种非对称分布与衍射级次、入射光波波长、液体表面波波长及表面波衰减系数有关;正负级次衍射亮条纹距离中央零级亮条纹的间距体现表面波衰减信息;正衍射级次之间以及负衍射级次之间的条纹间距体现表面波波长信息。利用所提出的方法实现了对几百赫兹液体表面波的衰减系数的实时便捷测量。 相似文献
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运用MATLAB软件平台设计了等厚干涉图样模拟的程序。使用者可通过命令窗口输入相关参数的值,运行程序得到等厚干涉图样。本文通过改变相关参数的值,分析薄膜夹角、介质折射率、入射光波长、入射角度对等厚干涉条纹间距的影响。此外,还研究了非单色光对等厚干涉条纹可见度的影响。 相似文献
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Gwal A. K. Misra K. D. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1977,5(3):146-150
Mode conversion and collisionless absorption of electromagnetic wave at the cyclotron harmonic frequencies in an inhomogeneous non-Maxwellian magnetoplasma have been studied. Under suitable energy transfer condition the converted electrostatic wave (plasma wave) either grows or damps. The expressions for the growth/damping rates of this wave have been derived and studied at the cyclotron harmonic frequencies. The effect of the temperature anisotropy on the growth/damping rate of the electrostatic wave at the second cyclotron harmonic frequency has been shown. Growth of such electrostatic waves at ionospheric heights may explain the observed upper hybrid resonance (UHR) echoes and noise bands at the second cyclotron harmonic frequency. 相似文献
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M R Stinson 《The Journal of the Acoustical Society of America》1990,88(4):1773-1778
An improved analysis procedure has been applied to standing wave patterns measured previously [B. W. Lawton and M. R. Stinson, J. Acoust. Soc. Am. 79, 1003-1009 (1986)] in human ear canals. Revised acoustic energy reflection coefficients, at the eardrum, are obtained for 20 ears for frequencies between 3 and 13 kHz. The new analysis addresses anomalous features of the standing wave patterns, apparent at frequencies above 8 kHz, due primarily to the curvature of the ear canal. Much better agreement is now found, at these higher frequencies, between the theoretical form assumed for the standing wave patterns and the experimental data. The revised values of eardrum reflectance are somewhat smaller, especially for frequencies above 11 kHz. The reflectance rises from about 0.25 at 4 kHz up to 0.7 at 8 kHz, falls to a minimum of 0.5 at 11 kHz, then rises to 0.6 at 13 kHz. Considerable intersubject variability in the results is noted. 相似文献
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Electro-magneto-acoustic SH waves propagating oblique to the periodic layered piezoelectric structures are studied under the coupling of the acoustic wave and the electromagnetic wave. Band structures of the so-called piezoelectric superlattice and phononic/photonic crystal are given both at acoustic frequencies and at optical frequencies. For the periodic layered piezoelectric structures, phonon-polaritons (the coupling modes of the phonons and photons) are found not only happening near the center of the Brillouin zone (in the long-wavelength limit) at acoustic frequencies, but also being able to appear in the whole Brillouin zone at optical frequencies. Appearing of these phonon-polaritons may provide a way to design a new type of acousto-optic devices. 相似文献
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Nonlinear phenomena that arise during the propagation of spin waves in thin ferromagnetic films under conditions of the simultaneous existence of three-wave and four-wave parametric processes have been investigated. Investigations have been performed for single-frequency and double-frequency regimes of excitation of intense spin waves. The spontaneous modulation instability of the monochromatic running spin wave has been revealed for the first time at frequencies at which three-wave decay processes are allowed. The pronounced generation of a periodic sequence of bright spin wave solitons has been observed under excitation of two monochromatic spin waves at the same frequencies. 相似文献
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Beam shaping technique for generating flattop beam has long been used in optics, and there are many methods to design flattop-beam
shapers in optics. Flattop beam is also important in some applications at millimeter wavelengths such as in the quasi-optical
power divider, however, there are few design method for the flattop-beam shaper used at millimeter wave frequencies and the
design method of optics are not suitable to the beam shaper at millimeter wave frequencies, so a design method for the flattop-beam
shaper at millimeter wave frequencies is presented in this paper. Several flattop-beam shapers in the form of diffractive
element have been designed and simulation results are presented. 相似文献
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《Waves in Random and Complex Media》2013,23(3):543-555
We consider the intensity fluctuation patterns produced beyond a deeply modulated phase changing screen when two plane waves, each with a different frequency, are incident on the same screen. The spatial frequency spectrum corresponding to the cross-correlation between these two different intensity fluctuation patterns is derived. This spectrum has two distinct regions, one of low spatial frequencies which is independent of the incident wave frequencies, and another at high spatial frequencies which is wave frequency dependent. As the difference between the incident wave frequencies increases the upper cut-off spatial frequency of the spectrum decreases. The corresponding cross-scintillation index is also considered and it is shown that this is independent of the incident wave frequencies close to the phase screen and including the focal region where there is a peak in the index. In the far field the scintillation index approaches unity as the distance from the screen increases in the monochromatic case. However, for different incident wave frequencies the far-field scintillation index falls off both with distance from screen and with increasing wave frequency difference. 相似文献
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A. A. Nazarova S. V. Dmitriev A. I. Pshenichnyuk R. R. Mulyukov 《Physics of the Solid State》2010,52(12):2490-2495
The dynamics of an infinite edge-dislocation wall and fragments of this wall in their interaction with a monochromatic sound
wave with a nonzero wave vector has been investigated taking into account the mass of dislocations. It has been shown that
the drift velocities of the wall fragments significantly increase when the sound wave frequency approaches the natural frequencies
of small-amplitude vibrations, including zero frequency. For the infinite wall, a similar increase in the drift velocity is
observed for low frequencies and for frequencies close to half the maximum frequency of small-amplitude vibrations of the
edge-dislocation wall. The resonance increase in the drift velocity at low frequencies of the sound wave can be important
for practical applications. 相似文献
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Alok Kumar Rastogi A. K. Tiwari R. P. Shrivastava 《International Journal of Infrared and Millimeter Waves》1993,14(7):1445-1453
The dielectric optical wave guide is finding growing attention at millimeter wave frequencies. However the dielectric optical waveguide radiates at bends and thus transmission loss increases. These radiations are in the outword direction of bends. This output radiation at output bends arises due to change in phase velocities of the propagating wave at the centre of the dielectric guide and the phase velocity at the outer surface of the dielectric guide. A unique methiod is suggested to avoid these radiation losses.Experimental results are also shown at microwave frequencies. 相似文献
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H.K. Avetissian 《Physics letters. A》1978,67(2):101-104
The quantum modulation of an electron beam in the field of opposite electromagnetic waves, at a frequency equal to the difference of the wave frequencies, and its harmonics, is obtained. The depth of the modulation becomes of order one at relatively small intensities of the laser fields (including a real spreading of the beam). In the case of equal frequencies of the waves (when the Kapitza-Dirac effect occurs particles form a beam. An experiment for obtaining a modulated beam of particles at the frequencies of the laser radiation, and its harmonics, as well as for bunching of particles in the field of a standing wave is suggested. 相似文献
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Manheimer W.M. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(6):1389-1397
Cyclotron wave amplifiers at the harmonics of the electron cyclotron frequency are investigated. Since the waves on the beam are electrostatic, harmonics are strongly excited in nonrelativistic beams if they are rotating rather than filamentary. These modes at the harmonics can couple to input Cuccia couplers, and pump fields which drive parametric amplification, in very much the same way as they do on filamentary beams at the cyclotron frequency. Harmonic cyclotron wave amplifiers have the possibility of giving rise to a new class of devices at millimeter wave frequencies 相似文献