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731.
Z. X. Liu L. M. Wang H. He W. Y. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(2):179-184
We study the propagation of electromagnetic wave in piezoelectric
period-doubling superlattices with using the generalized 4 ×
4 transfer matrix method, and the dynamics of electromagnetic wave
and acoustic wave is treated on equal footing. The band-gap
structure trifurcates, which is understood within the framework of
perturbation theory under periodic boundary condition. The uncoupled
phononic branch of field distributions is Bloch-wave-like. For the
coupled polaritonic branch, the lattice-like field distributions,
for which Thue-Morse sequence is famous, also manifest in this
piezoelectric period-doubling system and coexist with critical
states. They can be characterized as extended if the superlattice
size considered is large enough. In fact, our study suggests that
such lattice-like field distributions are common phenomena in
piezoelectric superlattices irrespective of lattice types and depend
only on the frequency and domain widths, they reflect the intrinsic
symmetry of the transfer matrices for the particular domain setting
and frequency. 相似文献
732.
Joint influence of heterogeneous stochastic factors on bit-error rate of ground-to-ground free-space laser communication systems 总被引:1,自引:0,他引:1
Research methods for the formation of BER in the ground-to-ground Free-Space Laser Communication Systems (Free-Space Optics – FSO) with increased analytical effectiveness have been suggested. They correspond to physically rightful approximations with approbated quantity effectiveness. The methods have been used to study the influence of heterogeneous stochastic factors, such as: quantum noises, atmospheric transmittance fluctuations, mechanical vibrations of the transmitting laser antenna, atmospheric turbulence, on BER of FSO.
An algorithm for quantity estimation of the joint influence of all stochastic factors has been created. Numerical examples, illustrated by graphic material, have been shown. 相似文献
733.
M. V. Korolevich S. G. Kirillova V. N. Piottukh-Peletskii V. M. Andrianov 《Journal of Structural Chemistry》2009,50(1):41-51
A detailed assignment of absorption bands in IR spectra of methyl 3,4-anhydro-α-D-talo-hexapyranoside and methyl 2,3-anhydro-4-deoxy-α-D-ribo-hexapyranoside is first made based on the complete calculation of frequencies and absolute intensities of normal vibrations of molecules and their comparison with the corresponding experimental values. The effect of the epoxy group on the bands characteristic of the pyranose ring is analyzed. The charactericity of spectral features of oxymethyl substitution for the hydroxyl group and the oxirane ring is studied. 相似文献
734.
Problems of forced nonaxisymmetric vibrations of ellipsoidal shells under nonstationary loads are formulated. A numerical
algorithm to solve them is developed. The solutions obtained are analyzed
Translated from Prikladnaya Mekhanika, Vol. 44, No. 9, pp. 73–84, September 2008. 相似文献
735.
This paper aims to provide a review and critical analysis of the state of the art concerning crowd-structure interaction phenomena on footbridges. The problem of lateral vibrations induced by synchronised pedestrians, namely the Synchronous Lateral Excitation, is specifically addressed. Due to the multi-physic and multi-scale nature of the complex phenomenon, several research fields can contribute to its study, from structural engineering to biomechanics, from transportation engineering to physics and applied mathematics. The different components of the overall coupled dynamical system – the structure, the crowd and their interactions – are separately analysed from both a phenomenological and modelling point of view. A special attention is devoted to those models, which explicitly account for the interaction between mechanical and living systems. 相似文献
736.
Kh. Sh. Abdulov 《Journal of Applied Spectroscopy》2007,74(2):188-193
A method is proposed for assigning absorption bands in IR spectra of polyatomic molecules. An algorithm is developed and a
Fortran program is written based on this method. The method is illustrated for the example of the toluene molecule.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 169–173, March–April, 2007. 相似文献
737.
Spectroscopic features of oxymethyl substituents in β-D-glucopyranosides and their characteristicity
M. V. Korolevich V. N. Piottukh-Peletskii M. R. Zhbankova 《Journal of Structural Chemistry》2008,49(1):31-41
In this paper we studied whether the spectral features of the oxymethyl group in methyl-β-D-glucopyranoside with an additional oxymethyl substituent are characteristic. We also investigated the possibilities of using these features in spectral analysis. This study was based on our complete calculations of the frequencies and forms of the normal vibrations and the absolute intensities of the IR absorption bands of the 4-O-methyl-β-methyl-D-glucopyranoside molecule and comparison of the results and the theoretical absorption curve of this compound with the corresponding data for methyl-β-D-glucopyranoside, 2,3-, 2,6-, and 3,6-di-O-nitromethyl-β-D-glucopyranoside, and 4-O-methyl-2,3-di-O-nitromethyl-β-D-glucopyranoside. 相似文献
738.
This paper presents a semi‐analytical investigation of a fluid–structure system. Both isotropic and composite cylindrical shells filled with or subjected to a flowing fluid have been considered in this study. The structure may be uniform or non‐uniform in the circumferential direction. The hybrid finite element approach, shearable shell theory and velocity potential flow theory have been combined to establish the dynamic equations of the coupled system. The set of matrices describing their relative contributions to equilibrium is determined by exact analytical integration of the equilibrium equations. The linear potential flow theory is applied to describe the fluid effects that lead to the inertial, centrifugal and Coriolis forces. The axisymmetric, beam‐like and shell modes of vibrations in both cases of uniform and non‐uniform cylindrical shells are investigated. Fluid elastic stability of a structure subjected to a flowing fluid is also studied. This theory yields the high and the low eigenvalues and eigenmodes with comparably high accuracy. Reasonable agreement is found with other theories and experiments. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
739.
The article presents an analysis of a model describing lateral vibrations of a pipe induced by fluid flow velocity pulsation. The motion has been described with a set of two non-linear partial differential equations with periodically variable coefficients. In the analysis Galerkin method has been applied using orthogonal polynomials as shape function. To determine instability regions Floquet theory has been employed. The effect of selected parameters on parametric resonance ranges and regions of increased vibration level has been investigated. The character and form of vibrations have been investigated indicating the possibility of excitation of sub-harmonic and quasi-periodic vibrations in the combination resonance ranges. 相似文献
740.
Theoretical and experimental non-linear vibrations of thin rectangular plates and curved panels subjected to out-of-plane harmonic excitation are investigated. Experiments have been performed on isotropic and laminated sandwich plates and panels with supported and free boundary conditions. A sophisticated measuring technique has been developed to characterize the non-linear behavior experimentally by using a Laser Doppler Vibrometer and a stepped-sine testing procedure. The theoretical approach is based on Donnell's non-linear shell theory (since the tested plates are very thin) but retaining in-plane inertia, taking into account the effect of geometric imperfections. A unified energy approach has been utilized to obtain the discretized non-linear equations of motion by using the linear natural modes of vibration. Moreover, a pseudo arc-length continuation and collocation scheme has been used to obtain the periodic solutions and perform bifurcation analysis. Comparisons between numerical simulations and the experiments show good qualitative and quantitative agreement. It is found that, in order to simulate large-amplitude vibrations, a damping value much larger than the linear modal damping should be considered. This indicates a very large and non-linear increase of damping with the increase of the excitation and vibration amplitude for plates and curved panels with different shape, boundary conditions and materials. 相似文献