Current Issue : April - June Volume : 2017 Issue Number : 2 Articles : 6 Articles
In this work, we study the existence of coupled bandgaps for corrugated plate structures\nand acoustic channels. The study is motivated by the observation that the performance of traditional\nbandgap structures, such as periodic plates, may be compromised due to the coupling to a\nsurrounding acoustic medium and the presence of acoustic resonances. It is demonstrated that\ncorrugation of the plate structure can introduce bending wave bandgaps and bandgaps in the\nacoustic domain in overlapping and audible frequency ranges. This effect is preserved also when\ntaking the physical coupling between the two domains into account. Additionally, the coupling is\nshown to introduce extra gaps in the band structure due to modal interaction and the appearance of\na cut-on frequency for the fundamental acoustic mode....
In this paper, acoustic tweezers which use beam forming performed by a Fresnel zone plate\nare proposed. The performance has been demonstrated by finite element analysis, including the\nacoustic intensity, acoustic pressure, acoustic potential energy, gradient force, and particle distribution.\nThe acoustic tweezers use an ultrasound beam produced by a lead zirconate titanate (PZT) transducer\noperating at 2.4 MHz and 100 Vpeak-to-peak in a water medium. The design of the Fresnel lens\n(zone plate) is based on air reflection, acoustic impedance matching, and the Fresnel half-wave band\n(FHWB) theory. This acoustic Fresnel lens can produce gradient force and acoustic potential wells\nthat allow the capture and manipulation of single particles or clusters of particles. Simulation results\nstrongly indicate a good trapping ability, for particles under 150 �¼m in diameter, in the minimum\nenergy location. This can be useful for cell or microorganism manipulation....
AE technology,an advanced fault diagnosis technique,is impacted by environmental noise during\nmonitoring equipment. The occurrence of interfere noise,the fashion of interfere and the effect to the system in the AE\nautomatic online monitoring system is analyzed. At present, most of the acoustic emission signal transmission by\ncable, this way of transmission has a limited transmission distance, shortcomings and so on signal easily disturbed. Is\nproposed in this paper based on the optical fiber transmission technology, designed and developed a information\ncollection system based on optical fiber acoustic emission monitoring.This way has the advantages of long distance\ntransmission, strong anti-jamming capability....
Research has shown that the soundboard plays an increasingly important role compared to the sound hole, back plate, and the bridge\nat high frequencies. The frequency spectrumof investigation can be extended to 5 kHz. Design of bracings and their placements on\nthe soundboard increase its structural stiffness as well as redistributing its deflection to nonbraced regions and affecting its loudness\nas well as its response at low and high frequencies. This paper attempts to present a review of the current state of the art in guitar\nresearch and to propose viable alternatives that will ultimately result in a louder and better sounding instrument. Current research\nis an attempt to increase the sound level with bracing designs and their placements, control of natural frequencies using scalloped\nbraces, aswell as improve the acoustic radiation of this instrument at higher frequencies by deliberately inducing asymmetricmodes\nin the soundboard using the concept of ââ?¬Å?splitting board.ââ?¬Â Variousmathematicalmethods are available for analysing the soundboard\nbased on the theory of thin plates. Discrete models of the instrument up to 4 degrees of freedom are also presented. Results from\nfinite element analysis can be utilized for the evaluation of acoustic radiation....
This paper reports on the design, fabrication and preliminary test results of a novel\nmicroelectromechanical systems (MEMS) deviceââ?¬â?the acoustic gyroscope. The unique operating\nmechanism is based on the ââ?¬Å?acoustic versionââ?¬Â of the Sagnac effect in fiber-optic gyros. The device\nmeasures the phase difference between two sound waves traveling in opposite directions, and\ncorrelates the signal to the angular velocity of the hosting frame. As sound travels significantly\nslower than light and develops a larger phase change within the same path length, the acoustic gyro\ncan potentially outperform fiber-optic gyros in sensitivity and form factor. It also promises superior\nstability compared to vibratory MEMS gyros as the design contains no moving parts and is largely\ninsensitive to mechanical stress or temperature. We have carried out systematic simulations and\nexperiments, and developed a series of processes and design rules to implement the device....
Typical railway wheelsets consist of wheels, axle and axle bearings. Faults can develop on any of the aforementioned\ncomponents, but the most common are related to wheel and axle bearing defects. The continuous increase in train\noperating speeds means that failure of an axle bearing can lead to serious derailments, causing loss of life and severe disruption\nin the operation of the network, damage to the track and loss of confidence in rail transport by the general public.\nThe rail industry has focused on the improvement of maintenance and remote condition monitoring of rolling stock\nto reduce the probability of failure as much as realistically possible. Current wayside systems such as hot axle box detectors\nand acoustic arrays may fail to detect defective bearings. This article discusses the results of wayside high-frequency\nacoustic emission measurements performed on freight rolling stock with artificially induced damage in axle bearings in\nLong Marston, UK. Time spectral kurtosis is applied for the analysis of the acoustic emission data. From the results\nobtained, it is evident that time spectral kurtosis is capable of distinguishing the axle bearing defects from the random\nnoises produced by different sources such as the wheelââ?¬â??rail interaction, braking and changes in train speed....
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