Current Issue : January-March Volume : 2024 Issue Number : 1 Articles : 5 Articles
For enhanced energy concentration with improved flexibility for object manipulation, a focused acoustic vortex (FAV) is designed using a sector planar piston transducer array and acoustic lens that can produce the effective concentration of the acoustic field to perform the focusing function. Compared to the Gaussian beam, which tends to cause the object to deviate from the axis of acoustic propagation, FAVs can form a central valley region to firmly bind the objects, thus preventing offtarget effects. The heat energy in the paraxial region is transferred to the vortex center in the form of heat transfer so that the temperature-sensitive liposomes captured can quickly release drugs, which has a good effect on targeted drug administration. The focused acoustic wave stopped acting on the tissue (gel) for 2 s, the temperature of the vortex center continued to rise, reaching 41.5 ◦C at the moment of 3.7 s, at which point the liposomes began to release the drug. The FAVs capture the drug and use its thermal effect to achieve accurate and rapid treatment. The simulation results show that the drug release temperature of temperature-sensitive liposomes can be achieved by controlling the action time of the vortices. This study provides a reliable theoretical basis for the clinical application of targeted drugs....
The intensification of the global energy crisis has led to an increasing demand for coal. China is a major coal-producing country in the world and also the country with the most severe coal and gas outburst disasters. Thus, the coal and gas outburst experiment was conducted, and the following results were obtained: the whole outburst process was divided into three stages, namely the outburst preparation stage, the outburst gestation stage, and the outburst development stage. The gas pressure and acoustic emission signals show significant changes in all three stages, while the variation patterns are different. The gas pressure changes were strongest and the acoustic emission signals were highest during the development stage. Therefore, the outburst development stage was further subdivided into four phases, and the correlation between acoustic emission and gas pressure in each phase was analyzed in detail. Furthermore, the acoustic emission signals in three stages were compared and analyzed. The peak values of acoustic emission count and energy reached 285 times·s−1 and 245 V in the preparation stage and reached 265 times·s−1 and 231 V in the gestation stage, respectively, only 1.66%~1.78% and 2.19%~2.32% of the development stage, namely 15,980 times·s−1 and 10,566 V. Moreover, it was found that the cumulative count and cumulative energy showed a parabolic relationship with the development time of the outburst. Based on the above experimental results, during the production process in coal mines, the dangerous state of outbursts can be monitored through gas pressure changes in the outburst preparation stage and gestation stage. Once in the development stage, more sensitive signals of acoustic emission and their fitting results are used for outburst hazard monitoring and early warning. Monitoring and warning of outbursts of combined gas pressure and acoustic emission signals can effectively improve the safety level of coal mine production....
The effects of nonextensive electrons on nonlinear ion acoustic waves in dusty negative ion plasmas with ion–dust collisions are investigated. Analytical results show that both solitary and shock waves are supported in this system. The wave propagation is governed by a Korteweg–de Vries Burgers-type equation. The coefficients of this equation are modified by the nonextensive parameter q. Numerical calculations indicate that the amplitude of solitary wave and oscillatory shock can be obviously modified by the nonextensive electrons, but the monotonic shock is little affected....
The acoustic emission (AE) technique has been widely investigated for its ability to locate damage in structures. However, the selection of the arrival point of AE signals and the existence of nonhomologous AE signals can significantly affect the location accuracy of damages. The synchrosqueezed wavelet transform (SWT) was used in our previous research to pick the accurate arrival point, but the existence of the nonhomologous signals was neglected in the picking process. To address this limitation, the synchrosqueezed wavelet transform coherence (SWTC) method is proposed to improve the accuracy by recognizing homologous signals and suppressing the spectral leakage in this paper. Compared with the wavelet transform coherence (WTC) method previously used, the SWTC method using the squeezing wavelet coefficients obtained by the SWTcan constitute a more explicit coherence graph of AE signals. This clear coherence graph can help reduce the effect of subjective factors in observing the coherence and improve the recognition accuracy of homologous signals. The effectiveness of the proposed method is experimentally verified on a steel pipe and a concrete beam.Theresults demonstrate that the SWTC accurately identifies homologous AE signals and effectively improves the localization accuracy across different signal densities, localization distances, and materials....
This paper presents an underwater biomimetic covert acoustic communication system that achieves high covertness and a high data rate by mimicking dolphin group whistles. The proposed method uses combined time–frequency shift keying modulation with continuous varying carrier frequency modulation, which mitigates the interference between two overlapping multiple whistles while maintaining a high data rate. The data rate and bit error rate (BER) performance of the proposed method were compared with conventional underwater covert communication through an additive white Gaussian noise channel, a modeled underwater channel, and practical ocean experiments. For the covertness test, the similarity of the proposed multiple whistles was compared with the real dolphin group whistles using the mean opinion score test. As a result, the proposed method demonstrated a higher data rate, better BER performance, and large covertness to the real dolphin group whistles....
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