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111.
This article presents the implementation and application, to two complex machines, of two holography methods called CIBNAH (Complex Intensity Based Near-field Acoustic Holography) and MRNAH (Multi Reference Near-field Acoustic Holography) based on residual spectra. The first is a newly developed method that uses complex sound intensity as its basis and hence bypasses the need for reference signals. Here, several approaches are presented to validate both methods and to investigate each method’s advantages and limitations. 相似文献
112.
The effect of finite energy of intravalley acoustic phonons on the electric field dependence of the temperature of the non-equilibrium carriers in a quantum surface has been studied here. The calculations have been made, for a rather pure material, at low lattice temperature. Numerical results are obtained for GaAs and Si. The results are interesting being significantly different from what one obtains by neglecting the phonon energy. 相似文献
113.
Zhigang Suo 《Acta Mechanica Solida Sinica》2010,23(6):549-578
In response to a stimulus, a soft material deforms, and the deformation provides a function. We call such a material a soft active material (SAM). This review focuses on one class of soft active materials: dielectric elastomers. When a membrane of a dielectric elastomer is subject to a voltage through its thickness, the membrane reduces thickness and expands area, possibly straining over 100%. The dielectric elastomers are being developed as transducers for broad applications, including soft robots, adaptive optics, Braille displays, and electric generators. This paper reviews the theory of dielectric elastomers, developed within continuum mechanics and thermodynamics, and motivated by molecular pictures and empirical observations. The theory couples large deformation and electric potential, and describes nonlinear and nonequilibrium behavior, such as electromechanical instability and viscoelasticity. The theory enables the finite element method to simulate transducers of realistic configurations, predicts the efficiency of electromechanical energy conversion, and suggests alternative routes to achieve giant voltage-induced deformation. It is hoped that the theory will aid in the creation of materials and devices. 相似文献
114.
The transient backscattering mechanisms of a dipole array with reflector have been investigated from different aspects: time-domain, frequency-domain, and combined time-frequency domain, using 4 × 8 dipole arrays with reflector as an example. The data of scattering from the arrays under the incidence of Gaussian pulses are obtained by finite differential time domain method. The influences of the array structural parameters, incident wave parameters, and incident angles on the waveforms, spectrum, and time-frequency representations of the backscattered fields of the arrays are analysed and conclusions are drawn. From these characteristics and conclusions, it is possible to deduce the array structure inversely from the backscattered field. 相似文献
115.
Neji Khelifi 《Journal of Russian Laser Research》2008,29(3):274-287
Adiabatic and diabatic study for all the states dissociating below the ionic limit [i.e., Na (3s, 3p, 4s, 3d, 4p, 5s, 4d,
and 4f) + H (1s)] in 1Σ+ and 3Σ+ symmetries are presented. Adiabatic results are also reported for 1,3Π and 1,3Δ symmetries. Pseudo-potential, operatorial core-valence correlation, and full valence CI approaches combined with an efficient
diabatization procedure are used in these ab initio calculations. Our vibrational-level spacings and spectroscopic constants
are in good agreement with the available experimental data for the low-lying states. Diabatic potentials and dipole moments
are analyzed, revealing the strong imprint of the ionic state in the 1Σ+ adiabatic states. The hydrogen electron affinity correction was taken into account by the use of the efficient diabatization
method. This leads to a better agreement with the available experimental data. Experimental suggestions are also given for
the higher excited states based on their unusual behavior. 相似文献
116.
Using the methods of molecular simulation and HyperChem v.5.0 programs (PM3 method), we carried out calculations of the principal spectroscopic characteristics and of the structure of the laurdan molecule in the ground and the first excited electronic states. The thermal static distribution of molecules over various possible orientations of the plane of methyl groups relative to the plane of the naphthalene bicycle was taken into account. The energies and dipole moments of these electronic states have been calculated as functions of the torsion angle of methyl groups. The existence of an additional mechanism of electronic spectrum broadening is shown; it is associated with thermal mismatch of the equilibrium orientations of the rotational fragment of the molecule and with the dependence of the electron transition frequency on the degree of deviation of the angle from the equilibrium value. The dependence of dipole moments on this angle has been found and calculated. This dependence is the strongest for the ground state. The maximum values of dipole moments in the ground and excited states are 4.0 and 7.6 D. 相似文献
117.
研究了超短光脉冲在GaAs表面激发相干亚毫米波振幅随入射角变化的规律,前后向辐射比值随入射角度变化的规律,实验测量了GaAs表面镀上极薄金属薄膜后产生的相干亚毫米波振幅对薄膜厚度的依赖关系,利用光生载子偶极辐射的理论模型成功地解释了实验得到的角度依赖关系和相干亚毫米波的偏振特性。 相似文献
118.
119.
XU Yong WANG Binglin 《声学学报:英文版》1993,(3)
The author has made tests for an artificial head transfer system whichis modelled on a Chinese male on its main physical behaviour such as frequencyresponses,frequency response differences between the front and the rear inci-dences,as will as on its important hearing behaviour such as localization,theperception of distance and room dimensions.The results verify that this kind ofartificial head transfer system can be used as one of effective tools of acousticevaluation researches for halls. 相似文献
120.
Epaminondas Sidiropoulos Christos Tzimopoulos Panagiotis Tolikas 《Applied Mathematical Modelling》1983,7(5):306-310
An indirect boundary element method using dipole distribution is employed in order to model discontinuities inside the flow region. The problem of flow under a dam is treated with a sheet-pile in its foundation. The discontinuity across the sheet-pile is demonstrated, a general boundary element procedure for a mixed problem is outlined and the coefficients of the linear system are given in analytical form. Very good agreement with existing analytical results is obtained. 相似文献