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81.
82.
S. BachaA. Bechiri F. BenmakhloufH. Allouache N. Bouarissa 《Physica B: Condensed Matter》2011,406(10):2021-2024
The investigation of optoelectronic properties of zinc-blende InPxSb1−x, semiconducting alloys by pseudopotential calculations is studied. The scheme uses the local empirical pseudopotential method, which involves the disorder effect into the virtual crystal approximation by introducing an effective potential disorder. Various quantities for the alloy of interest are calculated. The obtained results show a reasonable agreement with the available experimental data. Special attention has also been given to the compositional dependence of these studied quantities. 相似文献
83.
CHEN Guisheng 《声学学报:英文版》1993,(1)
This paper describes in detail an acoustical array structure with fourelements that have cosine directivity function over a certain frequency range.The acoustical axis directions of these elements are orthogonal to each other,sotheir beams cover all bearing angles within 360°.By use of the amplitude bear-ing method,it is easy to detect the bearing of incident acoustic signal.A specialsound reflection foam rubber is designed as a back baffle of the array.It hasbeen shown,in practice,that the constant beam-width has been obtained for amultiple frequency band of the ratio of 8:1.The paper also gives a mathematicalmodel for the array structure.The theoretical values are consistent with themeasured results. 相似文献
84.
85.
This study deals with the development of the approximate method to analyze the sound field around equally spaced finite obstacles, using the periodic boundary condition. First, on the assumption that the equally spaced finite obstacles are the periodically arranged obstacles, the sound field is analyzed by boundary integral equation method with a Green’s function which satisfies the periodic boundary condition. Furthermore, by comparing these results and the exact solution by using the fundamental solution as Green’s function, the validity of the approximate method is also investigated. Next, in order to evaluate the applicability of the approximate method, the simple formula using some parameters, i.e., the frequency, the period, and the number of obstacles, etc., is proposed. The results of the sound field analysis applied the formula are presented. 相似文献
86.
Propagation of sound and weak shock waves in gas-liquid foams is investigated theoretically and experimentally. An original
physical model is developed to describe the evolution of small perturbations in a foam of polyhedral structure. The model
developed takes into account both peculiarities of interface heat transfer in foam and liquid motion through the system of
Plateau-Gibbs borders which results in the appearance of an additional hydrodynamic dissipative force. The Rayleigh equation
analog, which takes into account the latter phenomenon, is obtained. Structure and dynamics of weak shock waves are investigated.
A vertical shock tube was constructed and used to measure the parameters of weak shock wave propagation in gas-liquid foams
of polyhedral structure. Spectral analysis of the data obtained shows that there are weak dispersion and strong dissipation
of the initial signal. Comparison of the evolution of experimental and theoretical profiles permits to conclude that the suggested
model allows to describe the peculiarities of acoustical perturbations in gas-liquid foam more precisely than it follows from
the standard models.
Received 15 September 1993 / Accepted 27 December 1993 相似文献
87.
A semi-analytical solution is presented for the virtual mass coefficient of an oblate-ellipsoidal bubble rising in liquid. The solution was found to be a function of Weber number. The present solution compared well with the numerical solution of the lattice Boltzmann method and the analytical solutions of other investigators. 相似文献
88.
Koichi Omori Hisayoshi Kojima Rajesh Kakani David H. Slavit Stanley M. Blaugrund 《Journal of voice》1997,11(1):40-47
This study investigates the relationship between rough voice and the presence of Subharmonics, which correspond to smaller yet distinct peaks located between two consecutive harmonic peaks in the power spectrum. Spectrum analysis was undertaken in 389 pathologic voices, of which 20 had subharmonics. Although all 20 voices had roughness perceptually, 8 had normal jitter and/or shimmer. The degree of roughness had a significant inverse relationship with the frequency of subharmonics. By digital signal processing, sound samples with various types of subharmonics were synthesized and perceptually analyzed. Power and frequency of subharmonics in the synthesized sound also had significant relationships with the degree of roughness. Rough voice is acoustically characterized not only by jitter and shimmer but also by the presence of subharmonics in the power spectrum. Subharmonics are important acoustic properties for objective evaluation of rough voices. 相似文献
89.
Manipulation of micro-objects have been playing an essential role in biochemical analysis or clinical diagnostics. Among the diverse technologies for micromanipulation, acoustic methods show the advantages of good biocompatibility, wide tunability, a label-free and contactless manner. Thus, acoustic micromanipulations have been widely exploited in micro-analysis systems. In this article, we reviewed the acoustic micromanipulation systems that were actuated by sub-MHz acoustic waves. In contrast to the high-frequency range, the acoustic microsystems operating at sub-MHz acoustic frequency are more accessible, whose acoustic sources are at low cost and even available from daily acoustic devices (e.g. buzzers, speakers, piezoelectric plates). The broad availability, with the addition of the advantages of acoustic micromanipulation, make sub-MHz microsystems promising for a variety of biomedical applications. Here, we review recent progresses in sub-MHz acoustic micromanipulation technologies, focusing on their applications in biomedical fields. These technologies are based on the basic acoustic phenomenon, such as cavitation, acoustic radiation force, and acoustic streaming. And categorized by their applications, we introduce these systems for mixing, pumping and droplet generation, separation and enrichment, patterning, rotation, propulsion and actuation. The diverse applications of these systems hold great promise for a wide range of enhancements in biomedicines and attract increasing interest for further investigation. 相似文献
90.
This paper is focused on the capabilities of gas–liquid foams to attenuate acoustic waves. It is postulated that the sound attenuation phenomenon in foams is largely governed by the hydrodynamic resistance of the Plateau-Gibbs channels (PGC) to the flow of liquid through them. It is shown that the addition of solid particles to gas–liquid foams has opposite effects depending on the concentration of the added solid particles. As long as the concentration of the added solid particles is smaller than a certain critical value the sound attenuation coefficient increases and as a result in the sound velocity decreases. However, if the concentration of the added solid particles becomes larger than this critical value the attenuation coefficient decreases and the sound velocity increases. When the concentration of the solid particles reaches some critical value, the particles block the Plateau-Gibbs channels and stop the filtration. As a result the attenuation coefficient of the sound wave decreases while the sound velocity, in such three-phase foams, increases. The point at which the sound wave stops attenuating and its velocity starts to increase is known as the point of self-clarification. Based on this postulate and on the results of our preliminary tests the present study provides a plausible explanation to the above-mentioned contradicting effect, and the self- clarification phenomenon. 相似文献