共查询到20条相似文献,搜索用时 0 毫秒
1.
The schlieren method is applied to visualizing the sound scattering ofa cylinder immersed in the liquids.Images of the echoes,caused by normal andoblique incidence from a cylinder,are obtained for two kinds of liquids:(1)theliquid is composed of a transparent liquid;and(2)the liquid is composed of twonon-mixable transparent liquids.It is found experimentally that the echo canbe caused by the discontinaites in the shadow zone.This fact is utilized to dem-onstrate the locus of the helical surface wave creeping along the surface of thecylinder.For such cases the three-dimensional image can be described by thismethod and has not to use the system with special appliances and complexalgorithm. 相似文献
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Schwarz A Liebmann M Kaiser U Wiesendanger R Noh TW Kim DW 《Physical review letters》2004,92(7):077206
By visualization of the Barkhausen effect using magnetic force microscopy we are able to provide detailed information about the physical principles that govern the magnetization reversal of a granular ferromagnetic thin film with perpendicular anisotropy. Individual Barkhausen volumes are localized and distinguished as either newly nucleated or grown by domain wall propagation. The Gaussian size distribution of nucleated Barkhausen volumes indicates an uncorrelated random process, while grown Barkhausen volumes exhibit an inverse power law distribution, which points towards a critical behavior during domain wall motion. 相似文献
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In this report, a new rendering method of a moving sound with the Doppler effect is proposed. In the conventional rendering method of moving sound, Head Related Impulse Responses (HRIRs) are simply changed according to a sound position. However, the Doppler effect cannot be added to a sound in this method. The pitch of a sound object must be controlled using some other rendering method when a sound object moves at high speed. In our method, each HRIR is divided into two components, such as an initial delay and a main wave form. Two initial delays of both right and left ears are recalculated, respectively, based on relative speeds and a propagation path. These new initial delays are used in rendering. Therefore, the Doppler effect is added to a sound automatically only when a sound position is set in this algorithm. Details related to this algorithm are discussed in this report. 相似文献
5.
Seth Putterman 《Physica A》1978,94(2):361-364
The previous results for the scattered field of two plane monochromatic sound waves is shown to possess a singularity as the wave vectors become equal. A new solution which removes this singularity is presented. 相似文献
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S. Huang K. J. M. Moriarty E. Myers J. Potvin 《Zeitschrift fur Physik C Particles and Fields》1991,50(2):221-236
We present an initial study of the thermodynamics of hot lattice QCD using the “density of states” method, which we describe in detail. The raw data were generated from a Monte Carlo simulation of pureSU(3) gauge theory on 83×N t lattices, withN t =2,4,8, at several values of the gauge coupling β. These data, taken at up to eight values of β, are then used to reconstruct the “density of states” as a function of the action and one additional observable. When combined with the proper Boltzmann weight this yieldscurves of quantities of interest as functions of the coupling constant β. These curves then yield the equation of state in a range of temperature, and the corresponding velocity of sound is obtained through appropriate derivatives. We also discuss in detail the errors, limitations, and advantages of the density of states method in its general application to QCD. 相似文献
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声波多普勒效应综合实验 总被引:2,自引:2,他引:2
利用运动物体反射声波与原声波合成后产生拍,用数字存储示波器测定拍频,从而测定空气中的声速或运动物体的速度,并给出了相应的实验装置、实验方法。 相似文献
8.
The channelled spectrum phenomenon combined with a white-light imaging method yields image spectrograms giving access, under special conditions, to absolute path differences in a wide range of measurements (from one micron to several millimetres). Their interpretation is discussed through several applications: optical mapping, measurement of longitudinal displacement, evaluation of temperature and visualization of gas flow. 相似文献
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The knowledge of the reflection properties of open end jet ducts is important for different applications, where the flow and high temperature conditions are involved and add complexity to the problem. In this paper, the magnitude of the reflection coefficients together with the respective end-corrections is experimentally determined for hot flow duct openings. A Mach number range up to 0.3 for cold jets and up to 0.12 for a jet temperature of 200 °C is treated. The experimental results are compared with the numerical model proposed by Munt (Acoustic transmission properties of a jet duct with subsonic jet flow: 1. The cold jet reflection coefficient, Journal of Sound and Vibration 142 (1990) 413–436) and a good correlation in plane-wave region is demonstrated. To reduce experimental uncertainty, the sound reflection properties at the duct opening are obtained by using an overdetermined two-microphone technique with the implementation of a three pressure transducer array. By introducing a modified multistep version of the stepped sine excitation, the accuracy of data acquisition process is improved without compromising the measurement time. 相似文献
10.
A collisionless nonmagnetized e-p-i plasma consisting of quantum-degenerate gases of ions, electrons, and positrons at nonzero temperatures is considered. The
dispersion equation for isothermal ionic sound waves is derived and analyzed, and an exact expression is obtained for the
linear velocity of ionic sound. Analysis of the dispersion equation has made it possible to determine the ranges of parameters
in which nonlinear solutions in the form of solitons should be sought. A nonlinear theory of isothermal ionic sound waves
is developed and used for obtaining and analyzing the exact solution to the system of initial equations. Analysis has been
carried out by the method of the Bernoulli pseudopotential. The ranges of phase velocities of periodic ionic sound waves and
soliton velocities are determined. It is shown that in the plasma under investigation, these ranges do not overlap and that
the soliton velocity cannot be lower than the linear velocity of ionic sound. The profiles of physical quantities in a periodic
wave and in a soliton are constructed, as well as the dependences of the velocity of sound and the critical velocity on the
ionic concentration in the plasma. It is shown that these velocities increase with the ion concentration. 相似文献
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Simultaneous temporal characterization of telecommunication optical pulses and modulators by use of spectrograms 总被引:1,自引:0,他引:1
We demonstrate a simple technique for simultaneous and complete characterization of the optical pulses and temporal modulators commonly used in telecommunication. The electric field of a pulse and the response of a modulator are obtained from the analysis of the two-dimensional spectrogram of the pulse gated by the modulator. The measurement sensitivity is greatly improved compared with the conventional nonlinear optical techniques. Trains of picosecond pulses as weak as 10(-17)J are accurately characterized with an electroabsorption modulator as the temporal gate. The time-resolved transmission and phase of the modulator are also presented. 相似文献
12.
We report an experimental study of the scattering of sound by sound in the vicinity of the liquid-vapor critical point of carbon dioxide. We measure the amplitude of the scattered difference frequency wave generated by acoustic bulk nonlinearities. We observe that it is strongly increased in the vicinity of the critical point. 相似文献
13.
This letter reports a novel way of imaging the acoustic power carried in a sound beam by using either +1 or −1 order of Raman-Nath diffraction of light. 相似文献
14.
Two computational methods for pruning a reassigned spectrogram to show only quasisinusoidal components, or only impulses, or both, are presented mathematically and provided with step-by-step algorithms. Both methods compute the second-order mixed partial derivative of the short-time Fourier transform phase, and rely on the conditions that components and impulses are each well-represented by reassigned spectrographic points possessing particular values of this derivative. This use of the mixed second-order derivative was introduced by Nelson [J. Acoust. Soc. Am. 110, 2575-2592 (2001)] but here our goals are to completely describe the computation of this derivative in a way that highlights the relations to the two most influential methods of computing a reassigned spectrogram, and also to demonstrate the utility of this technique for plotting spectrograms showing line components or impulses while excluding most other points. When applied to speech signals, vocal tract resonances (formants) or glottal pulsations can be effectively isolated in expanded views of the phonation process. 相似文献
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声波多普勒效应演示实验 总被引:2,自引:2,他引:2
利用声波多普勒效应导致声强变化的特性,设计了声波多普勒效应实验装置,该装置将声音信号转变成电信号,并用信号大器进行放大,驱动发光二极管发光演示了声波的多普勒效应. 相似文献
17.
The number of helicopter operations has rapidly increased during the last 20 years in Japan. Helicopter noise sounds different from other aircraft; the waveform of the sound pressure is impulsive and the signal duration is relatively long. The Environmental Agency of Japan implemented new guidelines for evaluating noise exposure around small airports, including heliports, in 1990. This study was executed in connection with the development of provisional guidelines. Psychoacoustic experiments were carried out to identify an evaluation index for helicopter noise. In order to examine the effect of duration independently, we not only used original sound recordings, but also synthesized sound signals. The durations of these sound signals were time compressed or expanded without degrading the quality of the original sound recording. The test results show that the effect of duration is significant, and that the A-weighted sound exposure level is a better index than the maximum A-weighted sound pressure level for the evaluation of helicopter noise. 相似文献
18.
Dobrucki AB 《The Journal of the Acoustical Society of America》2003,113(3):1207-8; author reply 1209
19.
We describe a new and simple method to aid in the analysis of retrieved pulses from inverted frequency-resolved optical gating (FROG) traces. The analysis can separate noise from distortion and shows that distortion is more deleterious to the retrieved pulse than is pure noise. The analysis relies on the fact that FROG traces can be constructed from a single outer product of two vectors, whereas distortion and noise require the sum of a series of outer products. 相似文献