المؤلفون: Falletta, S., Monegato, G., Scuderi, L.

المصدر: AIP Conference Proceedings; 2024, Vol. 3094 Issue 1, p1-4, 4p

مصطلحات موضوعية: ELASTIC wave propagation, ELASTODYNAMICS, BOUNDARY element methods, FINITE element method, ELASTIC scattering, COLLOCATION methods, INTEGRAL representations

مستخلص: We consider the decomposition into scalar potentials for the simulation of transient 2D soft scattering elastic wave propagation problems in unbounded isotropic homogeneous media. The vector elastodynamic equation is reformulated in terms of two scalar wave equations, that are coupled by the Dirichlet boundary conditions. These are successively solved by using their associated space-time Boundary Integral Equation (BIE) representations. The corresponding Boundary Element Method (BEM) is obtained by combining a time convolution quadrature formula with a classical space collocation method. Then, the same boundary integral representation and its discretization are used to define a non-reflecting condition to be imposed on an artificial boundary delimiting the exterior computational domain of interest. In this latter a Finite Element Method (FEM) is applied. [ABSTRACT FROM AUTHOR]

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المؤلفون: Pomerleau-Perron, Patrick, Rankin, Gary W.

المصدر: AIP Conference Proceedings; 2024, Vol. 3094 Issue 1, p1-4, 4p

مصطلحات موضوعية: MACH number, ACOUSTIC wave propagation, FREQUENCIES of oscillating systems, SURFACE pressure, NAVIER-Stokes equations, ATMOSPHERIC turbulence

مستخلص: A numerical model is used to explain the high-frequency surface pressure fluctuations experimentally observed during the transient impact of a supersonic jet onto a substrate. The observations are made during experiments associated with the Shockwave-Induced Spray Process. Various approximations of the experimental arrangement and operating conditions are made to simplify the model and maintain a reasonable computational cost. The model geometry is axially symmetric, and a single mean jet Mach number value is used. The selected Mach number corresponds to the transient value that occurs during the high-frequency oscillation. The steady Reynolds-Averaged Navier-Stokes equations are first solved to establish the mean velocity field, followed by an unsteady Reynolds-Averaged Navier-Stokes solution to resolve the fluctuations. Due to the presence of acoustic wave propagation, non-reflecting boundary conditions are employed on the atmospheric boundaries of the solution domain. The numerical results indicate that the substrate pressure fluctuations are due to an instability of the bow shockwave that forms ahead of the substrate. The shock experiences an axially pulsing oscillation which is consistent with that previously described in the literature. The predicted frequency of oscillation however does not agree with the experiment. This is explained by the differences in the current model geometry compared to that of the actual experimental equipment. [ABSTRACT FROM AUTHOR]

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المؤلفون: Manelil, Neeraj Paul, Knoblauch, Jan, Höning, Leo, Theron, Johannes Nicolaas, Stoevesandt, Bernhard

المصدر: AIP Conference Proceedings; 2024, Vol. 3094 Issue 1, p1-4, 4p

مصطلحات موضوعية: WIND shear, WIND turbines, VERTICAL wind shear, ACOUSTIC wave propagation, WIND turbine blades, SOUND pressure

مستخلص: Acoustics from wind turbines is a cause of annoyance to neighbors. The low-frequency noise that travels to the far-field is an increasing concern with growing numbers of onshore wind turbines. This work discusses the noise generation and propagation from a wind turbine under four vertical atmospheric wind shear conditions. Firstly, the flow characteristics (specifically the trailing-edge boundary layer thickness) around a NACA0012 aerofoil are determined using CFD simulations for an angle of attack of 6°. These results are used in the BPM model to estimate the trailing-edge noise generated from the blades. The resulting broadband noise signal is then propagated to the far-field using a ray model. The sound pressure level for distances up to 5km in the downwind direction is evaluated, and the spectral distribution of the noise at different locations analyzed using Fourier Transform. Low-frequency fluctuations are observed to persist even at large distances from the wind turbine blades. The spatial locations corresponding to constructive and destructive interference of the acoustic signals appear to be strongly influenced by the vertical wind shear profile. [ABSTRACT FROM AUTHOR]

: Copyright of AIP Conference Proceedings is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Naveen, Kanne, Kumbhare, Amol

المصدر: AIP Conference Proceedings; 2024, Vol. 2971 Issue 1, p1-10, 10p

مصطلحات موضوعية: SYNCHRONIZATION, AUTONOMOUS underwater vehicles, SENSOR networks, ACOUSTIC wave propagation, SUBMERSIBLES, INFORMATION networks, ENERGY consumption, RADAR in aeronautics

مستخلص: The time synchronization algorithm of Underwater Sensor Network (UWSN) is studied. Aiming at the problems of time synchronization caused by the prolonged sound signal propagation time and node mobility in the underwater environment, a distributed time synchronization algorithm (NU-Sync) is proposed based on the Doppler principle, which solves the problem by calculating the relative speed. Node movement leads to the problem of uncertain propagation delay. Autonomous underwater vehicles are used as beacon nodes to calculate clock frequency skew by continuously broadcasting time information to save network energy consumption. Simulation experiments show that compared with existing algorithms, NU-Sync can achieve higher synchronization accuracy. [ABSTRACT FROM AUTHOR]

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المؤلفون: Goncharenko, Yu. Yu., Kartsan, I. N., Zhukov, A. O.

المصدر: AIP Conference Proceedings; 2024, Vol. 2969 Issue 1, p1-7, 7p

مصطلحات موضوعية: SPEECH, ACOUSTIC wave propagation, MATHEMATICAL models, SURFACE of the earth, RADON transforms, AUTOMATIC speech recognition, ACOUSTIC models

مستخلص: The paper proposes a variant of describing the propagation of speech signals under ideal conditions using the mathematical apparatus of Radon in the interests of their subsequent identification. The task of describing the propagation of speech signals has been formulated and it has been shown that the main goal of its solution is to develop a universal mathematical apparatus based on a generalized mathematical model of acoustic wave propagation, which is considered as a spherically symmetric function from the distance to the wave source, described by the Radon transform, which provides automation identification and increases the efficiency of the removal of speech information. The concept of ideal conditions for the propagation of speech signals is described, under which it is necessary to have a point omnidirectional sound source, the constancy of the parameters of acoustic receiving devices, a homogeneous unlimited environment limited only by a flat earth's surface and described by a mathematical model with the Radon transform, where the Fourier transform is understood as the corresponding equivalent norm. A variant of describing the propagation of speech signals under ideal conditions using the mathematical apparatus of Radon is proposed, which makes it possible to identify the received signals, in which all the properties and features of the emitted speech signals that determine their belonging to a fixed object of generation of these signals, propagating under ideal conditions for unlimited distances before registration receiving devices retain all these properties and features. The presence in the database and knowledge of mappings of these properties and features, accumulated and replenished during the execution of applied tasks for the removal of speech information, makes it possible to automate the identification of received signals and fixed objects of their generation. [ABSTRACT FROM AUTHOR]

: Copyright of AIP Conference Proceedings is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Zhuravleva, L. M., Levshunov, V. V., Ryzhkov, D. A.

المصدر: AIP Conference Proceedings; 2023, Vol. 2624 Issue 1, p1-7, 7p

مصطلحات موضوعية: TELECOMMUNICATION, WIRELESS communications, RADIO wave propagation, COMMUNICATION of technical information, ELECTRIC networks, RAILROAD tunnels, ROLLING stock, ROAMING (Telecommunication)

مستخلص: The results of an experiment on measuring the characteristics of a radio signal at the input of mobile base stations of local Wi-Fi networks of an electric train on the railway are presented. The analysis of the results of the experiment carried out in the laboratory of MaximaTelecom JSC using Channel Emulator CH01 (RadioGigabit) device, together with the base stations Fruidmesh 4800. The analysis of the qualitative characteristics of signals at the entrance of the train base stations in tunnels and in open areas is given. Based on the obtained graphs, it is concluded that it is necessary to study the effect of the handover on the decrease in the input signal level, an increase in the probability of error (BER), as well as the number of retransmissions and a decrease in the channel speed. Significant fluctuations of the channel velocity in open areas due to the phenomenon of multipath propagation of radio waves are noted. All these factors create time delays for transmission of information and negatively affect the efficiency of train traffic management. The methods of reducing duration of the handover and reducing the influence of multipath are offered. [ABSTRACT FROM AUTHOR]

: Copyright of AIP Conference Proceedings is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Szczepaniak, Zenon, Susek, Waldemar, Rogala, Tomasz, Suchorab, Zbigniew, Tabiś, Krzysztof

المصدر: AIP Conference Proceedings; 2023, Vol. 2801 Issue 1, p1-6, 6p

مصطلحات موضوعية: CONSTRUCTION materials, MOISTURE measurement, ELECTROMAGNETIC wave propagation, CONSTRUCTION cost estimates, MICROWAVE measurements, HUMIDITY, HYGROTHERMOELASTICITY, MICROWAVES

مستخلص: The paper comprises the presentation of non-invasive and non-contact microwave measurement method in order to estimate the humidity of building materials. The content of the paper covers information concerning the phenomena related to propagation of electromagnetic waves in building materials, introduction of non-invasive and non-contact measurement method with the use of wideband microwave signals and presentation of the exemplary moisture measurement results achieved by red brick examination. [ABSTRACT FROM AUTHOR]

: Copyright of AIP Conference Proceedings is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Raghib, R., Khalfi, H., Naciri, I., Elmaimouni, L., Yu, J., Belkassmi, Y., Maimouni, Lahcen. El

المصدر: AIP Conference Proceedings; 2023, Vol. 2761 Issue 1, p1-11, 11p

مصطلحات موضوعية: THEORY of wave motion, ACOUSTIC wave propagation, FUNCTIONALLY gradient materials, EQUATIONS of motion, FOURIER series, POWER law (Mathematics)

مستخلص: The study presented in this paper deals with the acoustic wave propagation modeling in a composite cylinders of infinite lengths, made of a functionally graded materials (FGM), using a semi-analytical method. The theory of three-dimensional elasticity is used to formulate this method. The effective material properties of FGM cylinders are supposed to change continuously in the radial direction accordance to the volume fraction's power-law distribution. The displacement components developed in a series of trigonometric functions, Legendre polynomials are embedded into the motion equations using elastic constants depending on the position, and the rectangular window function, with the advantage that the wave equation's solution is simplified to an eigenvalue/eigenvector problem. The dispersion curves in two types of FGM cylinders are calculated using a mathematical formula for longitudinal, torsional, and flexural modes. The dispersion curves with diverse graded index are depicted. These results imply that the graded-index has a major impact on the variations in material properties following the radial direction. Furthermore, the graded index has a considerable impact on the dispersion curves. The obtained numerical results are compared with those reported in theory in order to verify the efficiency and accuracy of this approach. [ABSTRACT FROM AUTHOR]

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المؤلفون: Mieloszyk, Eligiusz, Milewska, Anita, Wyroślak, Mariusz

المصدر: AIP Conference Proceedings; 9/4/2023, Vol. 2928 Issue 1, p1-8, 8p

مصطلحات موضوعية: FUZZY sets, SUBSOILS, LAND subsidence, ELASTIC wave propagation, SOIL ripping, BALLAST (Railroads), RAILROAD track maintenance & repair

مستخلص: The cause of the subsidence of the railway track is the subsidence of the track bed itself and it is often related to the subsidence of the subsoil. Such settlement leads to: uneven longitudinal railways and track twist. These phenomena have a negative impact on the comfort and safety of driving, and in extreme cases lead to a train derailment. It has been shown that the magnitude of these settlements is determined by many parameters characterizing the subgrade and subsoil as well as dynamic interactions (vibrations) generated by passing rail vehicles. The propagation of these vibrations in the subgrade and the subsoil is related to the propagation of the generated elastic waves as mechanical waves in the elastic medium which is the subgrade and further the subsoil. Fuzzy sets, operations on them and their properties were used to assess the subsidence of the subsoil under the railway surface. Using the created membership functions µXi, i=1, 2, ..., n their linear combination is determined. The coefficients of this combination are selected by the AHP method. Practical applications of the created linear combination (created models) were indicated. [ABSTRACT FROM AUTHOR]

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المؤلفون: Chertova, Nadezda

المصدر: AIP Conference Proceedings; 2023, Vol. 2899 Issue 1, p1-4, 4p

مصطلحات موضوعية: BODY fluids, LIQUID-liquid interfaces, SHEAR waves, STRAINS & stresses (Mechanics), REFLECTANCE, ELASTIC wave propagation, ELASTIC waves

مستخلص: The problem of elastic wave propagation through the interface of solid with ideal fluid is considered. In the framework of this problem the analytical expressions for the reflection and refraction coefficients, as well as strains components, at the boundary are obtained. The dependences of Fresnel coefficients and strains amplitudes on the incidence angle of the longitudinal and transverse waves are calculated and analyzed for contacting bodies with the different properties. The features of deformed state at the interface and at the boundary in a solid and in a fluid are identified. Changes of the elastic body strains at the interface with a fluid compared with strains on a free surface are studied. [ABSTRACT FROM AUTHOR]

: Copyright of AIP Conference Proceedings is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)