المؤلفون: Hao Qin¹, Xingqi Zhang^1,2 xingqi.zhang@ucd.ie

المصدر: IET Microwaves, Antennas & Propagation (Wiley-Blackwell). Feb2024, Vol. 18 Issue 2, p59-72. 14p.

مصطلحات موضوعية: *TELECOMMUNICATION systems, RADIO wave propagation, TUNNELS, COMPARATIVE studies, ELECTROMAGNETIC wave propagation

مستخلص: Radio wave propagation modelling in railway environments is of fundamental importance in designing reliable train communication systems. Parabolic equation (PE) methods have been widely applied to the modelling of wave propagation in tunnels due to their high computational efficiency and fidelity. The finite-difference parabolic equation (FDPE) and the split-step parabolic equation (SSPE) methods are two commonly used approaches to solve PE numerically. However, the relevant literature is still missing a comprehensive study of their performance, including the selection of parameters such as discretisation steps and the tradeoffs involved in terms of their accuracy and efficiency, especially as current wireless systems shift to high frequencies. In this study, a systematic analysis of the error and computational complexity of the FDPE and SSPE methods for radio wave propagation modelling in tunnels is provided. Guidelines for the choice of their parameters are provided, and their performance is demonstrated through both numerical examples and experimental measurements in actual tunnel cases. [ABSTRACT FROM AUTHOR]

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المؤلفون: Islam, S. M. Rayhanul¹ (AUTHOR) rayhanulmath@yahoo.com

المصدر: Scientific Reports. 5/19/2024, Vol. 14 Issue 1, p1-16. 16p.

مصطلحات موضوعية: *ELASTIC wave propagation, *HAMILTON'S principle function, *NONLINEAR waves, *EQUATIONS

مستخلص: The doubly dispersive (DD) equation finds extensive utility across scientific and engineering domains. It stands as a significant nonlinear physical model elucidating nonlinear wave propagation within the elastic inhomogeneous Murnaghan's rod (EIMR). With this in mind, we have focused on the integration of the DD model and the modified Khater (MK) method. Through the wave transformation, this model is effectively converted into an ordinary differential equation. In this paper, the goal of our work is to explore new wave solutions to the DD model by using the MK scheme. These solutions provide extremely helpful insights into the operation of the system. The three-dimensional (3D) plot and two-dimensional (2D) combined plot via the impacts of the parameters are provided for various parameters in this manuscript. We also discussed the dynamical properties of the model, which are accomplished through the bifurcation analysis, and also found the Hamiltonian function. This research makes a substantial contribution to the area by increasing our understanding of wave solutions in the DD, introducing novel investigation tools, and carrying out an in-depth investigation of the bifurcation and stability aspects of the system. As a direct result of this research, novel openings have been uncovered for further investigation and application in the various disciplines of science and engineering. [ABSTRACT FROM AUTHOR]

المؤلفون: Ziaja, Dominika¹ (AUTHOR) dziaja@prz.edu.pl, Jurek, Michał¹ (AUTHOR)

المصدر: Materials (1996-1944). May2024, Vol. 17 Issue 9, p2160. 14p.

مصطلحات موضوعية: *ACOUSTIC surface waves, *ELASTIC wave propagation, *ELASTIC waves, *GLUE, *STRUCTURAL engineering, *CIVIL engineering

مستخلص: In this article, the practical issues connected with guided wave measurement are studied: (1) the influence of gluing of PZT plate actuators (NAC2013) on generated elastic wave propagation, (2) the repeatability of PZT transducers attachment, and (3) the assessment of the possibility of comparing the results of Laser Doppler Vibrometry (LDV) measurement performed on different 2D samples. The consideration of these questions is crucial in the context of the assessment of the possibility of the application of the guided wave phenomenon to structural health-monitoring systems, e.g., in civil engineering. In the examination, laboratory tests on the web of steel I-section specimens were conducted. The size and shape of the specimens were developed in such a way that they were similar to the elements typically used in civil engineering structures. It was proved that the highest amplitude of the generated wave was obtained when the exciters were glued using wax. The repeatability and durability of this connection type were the weakest. Due to this reason, it was not suitable for practical use outside the laboratory. The permanent glue application gave a stable connection between the exciter and the specimen, but the generated signal had the lowest amplitude. In the paper, the new procedure dedicated to objective analysis and comparison of the elastic waves propagating on the surface of different specimens was proposed. In this procedure, the genetic algorithms help with the determination of a new coordinate system, in which the assessment of the quality of wave propagation in different directions is possible. [ABSTRACT FROM AUTHOR]

المؤلفون: De Piante, Marco¹ (AUTHOR) marco.depiante@uniud.it, Midrio, Michele¹ (AUTHOR) michele.midrio@uniud.it, Rinaldo, Roberto¹ (AUTHOR) roberto.rinaldo@uniud.it, Scagnetto, Ivan² (AUTHOR) ivan.scagnetto@uniud.it, Specogna, Ruben¹ (AUTHOR) francesco.trevisan@uniud.it, Trevisan, Francesco¹ (AUTHOR)

المصدر: Sensors (14248220). Apr2024, Vol. 24 Issue 8, p2582. 21p.

مصطلحات موضوعية: *RADIO wave propagation, *DEW point, *DATA transmission systems, *MARINE communication, *AREA measurement

مستخلص: This paper focuses on the characterization of radio propagation, and data communication in a marine environment. More specifically, we consider signal propagation when three different sub-gigahertz industrial, scientific, and medical (ISM) bands, i.e., 169 MHz, 434 MHz, and 868 MHz, are used. The main focus of the paper is to evaluate the path loss (PL), i.e., the power loss that a propagation radio wave would experience when communication occurs between a sail boat and a buoy. We describe the measurement results obtained performing three different radio power measurement campaigns, at the three different aforementioned ISM sub-gigahertz bands. We also want to correlate the radio propagation quality with the weather conditions present in the measurement areas. The obtained results show that higher distances are achieved by transmitting at lower frequencies, i.e., 169 MHz, and, on average, the propagation is directly dependent from the dew point index. [ABSTRACT FROM AUTHOR]

المؤلفون: Wen, Xiaomin¹ (AUTHOR) eeiwxm@163.com, Fang, Shengliang² (AUTHOR) eeifsl@163.com, Fan, Youchen² (AUTHOR)

المصدر: Sensors (14248220). Apr2024, Vol. 24 Issue 8, p2523. 20p.

مصطلحات موضوعية: *GRAPH neural networks, *RADIO wave propagation, *DEEP learning, *TASK performance, *RADIO technology

مستخلص: The graph neural network (GNN) has shown outstanding performance in processing unstructured data. However, the downstream task performance of GNN strongly depends on the accuracy of data graph structural features and, as a type of deep learning (DL) model, the size of the training dataset is equally crucial to its performance. This paper is based on graph neural networks to predict and complete the target radio environment map (REM) through multiple complete REMs and sparse spectrum monitoring data in the target domain. Due to the complexity of radio wave propagation in space, it is difficult to accurately and explicitly construct the spatial graph structure of the spectral data. In response to the two above issues, we propose a multi-source domain adaptive of GNN for regression (GNN-MDAR) model, which includes two key modules: (1) graph structure alignment modules are used to capture and learn graph structure information shared by cross-domain radio propagation and extract reliable graph structure information for downstream reference signal receiving power (RSRP) prediction task; and (2) a spatial distribution matching module is used to reduce the feature distribution mismatch across spatial grids and improve the model's ability to remain domain invariant. Based on the measured REMs dataset, the comparative results of simulation experiments show that the GNN-MDAR outperforms the other four benchmark methods in accuracy when there is less RSRP label data in the target domain. [ABSTRACT FROM AUTHOR]

المؤلفون: Faktorová, Dagmar¹ (AUTHOR) dagmar.faktorova@tnuni.sk, Stanciu, Mariana Domnica² (AUTHOR) mariana.stanciu@unitbv.ro, Krbata, Michal¹ (AUTHOR) michal.krbata@tnuni.sk, Savin, Adriana^2,3 (AUTHOR) mariana.stanciu@unitbv.ro, Kohutiar, Marcel¹ (AUTHOR) marcel.kohutiar@tnuni.sk, Chlada, Milan⁴ (AUTHOR) chlada@it.cas.cz, Năstac, Silviu Marian^2,5 (AUTHOR)

المصدر: Polymers (20734360). Mar2024, Vol. 16 Issue 6, p753. 17p.

مصطلحات موضوعية: *ACOUSTIC wave propagation, *SPEED of sound, *LAMB waves, *VARNISH & varnishing, *ANISOTROPY, *WOOD, *RESONANCE

مستخلص: The objective of the study was to analyze the influence of coating treatments on sound propagation speeds in thin boards, along the longitudinal and radial directions of resonance wood. The samples studied were thin boards made of spruce and maple wood with dimensions of 240 mm × 80 mm × 4 mm (length × width × thickness) subjected to different coating treatments (oil-based varnish and alcohol varnish) as well as unvarnished samples, exposed to radiation UV, and specimens treated in the saline fog. The test method consisted of evaluating the propagation speeds of Lamb waves applied to thin plates, according to a semicircular test model, so that the results highlighted both the acoustic response in the longitudinal and radial directions as well as the variation in the anisotropy of the samples with the change in the sound propagation direction relative to wood fibers. Based on the statistical analysis, sound propagation speed profiles were obtained in each of the 38 directions analyzed for all wood samples. The results highlighted that the oil-based varnish led to a decrease in the speed of propagation in the radial direction, compared to the alcoholic varnish, whose major effect was in the longitudinal direction, on the spruce wood. On maple wood, increasing the number of varnish layers, regardless of the type of varnish, led to a decrease in the anisotropy ratio between the longitudinal and radial directions. [ABSTRACT FROM AUTHOR]

المؤلفون: Jiang, Hongwei¹ (AUTHOR), Zhao, Xin² (AUTHOR) 6120160101@bit.edu.cn

المصدر: AIP Advances. Mar2024, Vol. 14 Issue 3, p1-11. 11p.

مصطلحات موضوعية: *AIR ducts, *ACOUSTIC wave propagation, *COMPUTER simulation, *NAVIER-Stokes equations, *HELMHOLTZ resonators, *IDEAL gases, *AIR flow

مستخلص: Noise reduction structures are important for the vibration and noise reduction design of aerospace engines. The design of noise-reducing structures often needs to be quickly evaluated via numerical simulations. Hence, the simulation results of the corresponding system are very important for guiding the design of noise-reducing structures. High temperature is one of the key environmental factors that need to be considered when evaluating the sound attenuation process via numerical methods. In this study, numerical simulations of acoustic wave propagation on an acoustic liner structure considering air temperature variations are carried out by using compressible Navier–Stokes equations and the ideal gas equation of state. The results showed that the effect of temperature on sound attenuation under grazing flow conditions is complex. Moreover, an increase in temperature will reduce the transmission loss of the acoustic liner in the grazing flow at high air speed. [ABSTRACT FROM AUTHOR]

المؤلفون: Zhang, Yiwei^1,2 (AUTHOR), Guo, Chengcheng² (AUTHOR), Huang, Yahui² (AUTHOR), Zhang, Ruizhi² (AUTHOR), Zhang, Jian² (AUTHOR), Luo, Guoqiang^1,2 (AUTHOR) luogq@whut.edu.cn, Shen, Qiang^1,2 (AUTHOR)

المصدر: Materials (1996-1944). Feb2024, Vol. 17 Issue 3, p643. 12p.

مصطلحات موضوعية: *DEEP learning, *ELASTIC wave propagation, *DYNAMIC simulation, *YIELD strength (Engineering), *FINITE element method, *TEMPERATURE effect, *ELASTIC waves

مستخلص: Owing to the challenge of capturing the dynamic behaviour of metal experimentally, high-precision numerical simulations have become essential for analysing dynamic characteristics. In this study, calculation accuracy was improved by analysing the impact of constitutive models using the finite element (FE) model, and the deep learning (DL) model was employed for result analysis. The results showed that FE simulations with these models effectively capture the elastic-plastic response, and the ZA model exhibits the highest accuracy, with a 26.0% accuracy improvement compared with other models at 502 m/s for Hugoniot elastic limit (HEL) stress. The different constitutive models offer diverse descriptions of stress during the elastic-plastic response because of temperature effects. Concurrently, the parameters related to the yield strength at quasi-static influence the propagation speed of elastic waves. Calculation show that the yield strength at quasi-static of 6061 Al adheres to y = ax + b for HEL stress. The R-squared (R2) and mean absolute error (MAE) values of the DL model for HEL stress predictions are 0.998 and 0.0062, respectively. This research provides a reference for selecting constitutive models for simulation under the same conditions. [ABSTRACT FROM AUTHOR]

المؤلفون: Mousavi, Abbas, Berggren, Martin, Hägg, Linus, Wadbro, Eddie, 1981

المصدر: Journal of the Acoustical Society of America. 155(1):742-756

مصطلحات موضوعية: Acoustic wave propagation, Acoustics, Black holes, Conceptual design, Focusing, Gravitation, Navier Stokes equations, Stars, Topology, Acoustic black holes, Controlling waves, Design optimization, Focusing device, Focusing effect, Hole effects, Structural-acoustics, Topology optimisation, Viscothermal loss, Wave focusing, article, black hole, controlled study, drug development, simulation, Waveguides, Matematik, Mathematics

الوصف: The waveguide acoustic black hole (WAB) effect is a promising approach for controlling wave propagation in various applications, especially for attenuating sound waves. While the wave-focusing effect of structural acoustic black holes has found widespread applications, the classical ribbed design of waveguide acoustic black holes (WABs) acts more as a resonance absorber than a true wave-focusing device. In this study, we employ a computational design optimization approach to achieve a conceptual design of a WAB with enhanced wave-focusing properties. We investigate the influence of viscothermal boundary losses on the optimization process by formulating two distinct cases: one neglecting viscothermal losses and the other incorporating these losses using a recently developed material distribution topology optimization technique. We compare the performance of optimized designs in these two cases with that of the classical ribbed design. Simulations using linearized compressible Navier-Stokes equations are conducted to evaluate the wave-focusing performance of these different designs. The results reveal that considering viscothermal losses in the design optimization process leads to superior wave-focusing capabilities, highlighting the significance of incorporating these losses in the design approach. This study contributes to the advancement of WAB design and opens up new possibilities for its applications in various fields.

وصف الملف: electronic

الوصول الحر: https://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-98643Test
https://doi.org/10.1121/10.0024470Test
https://kau.diva-portal.org/smash/get/diva2:1841044/FULLTEXT01.pdfTest

المؤلفون: Shishlenin, Maxim^1,2 (AUTHOR) m.a.shishlenin@mail.ru, Kozelkov, Andrey^3,4,5 (AUTHOR) askozelkov@mail.ru, Novikov, Nikita^1,2 (AUTHOR) novikov-1989@yandex.ru

المصدر: Mathematics (2227-7390). Jan2024, Vol. 12 Issue 2, p212. 14p.

مصطلحات موضوعية: *THEORY of wave motion, *ACOUSTIC wave propagation, *SOUND waves, *ORGANS (Anatomy), *NAVIER-Stokes equations, *TOMOGRAPHY

مستخلص: The article aimed to show the fundamental possibility of constructing a computational digital twin of the acoustic tomograph within the framework of a unified physics–mathematical model based on the Navier–Stokes equations. The authors suggested that the size of the modeling area is quite small, sound waves are waves of "small" disturbance, and given that a person consists of more than 60% water, human organs can be modeled using a liquid model, taking into account their density. During numerical experiments, we obtained the pressure registered in the receivers that are located on the side walls of the tomograph. The differences in pressure values are shown depending on the configuration of inclusions in the mannequin imitating internal organs. The results show that the developed technology can be used to probe the human body in medical acoustic tomographs and determine the acoustic parameters of the human body to detect neoplasms. [ABSTRACT FROM AUTHOR]