Wave Propagation In Media Research Articles

Possibility of diagnostics of layered media with interferometric side-view sonar

A method is considered and an algorithm is developed that makes it possible to identify the layered structure of the propagation medium of a probing signal based on strip survey data from an interferometric side-scan sonar (ISSS) with antennas located in a vertical plane. Using the example of mathematical modeling of phase-difference measurements of ISSS for multilayer scattering planes, the capabilities of the proposed algorithm to determine their spatial position are demonstrated in the wave propagation medium. An analysis of the accuracy of calculating the position of scattering layers at heights (depths) and with different slopes was performed. The effectiveness of the method and algorithm for diagnosing the structure of layered media has been confirmed. The effectiveness of the method was tested on experimental data obtained using ISSS.

On the electromagnetic wave interaction with subluminal, luminal, and superluminal mirrors

As predicted by A. Einstein [Ann. Phys. (Leipzig) 17, 891 (1905)], the electromagnetic wave reflected at a moving mirror is frequency-upshifted and intensified as high as the mirror velocity is close to the speed of light in vacuum. However, at this limit the mirror reflectivity vanishes, because the higher the wave frequency the more transparent matter is. To resolve this paradox, we analyse the electromagnetic wave propagation in medium where the refractive index modulation moves at the speed of light in vacuum. Although the luminal and superluminal modulations are unconditionally transparent for the incident radiation, they both can reflect. We find the new type of the electromagnetic wave reflection with the increasing in time frequency inside the luminal mirror. If the modulation disappears the high frequency radiation is released as a short wavepacket.

Simulations of the optical diffraction patterns produced by the pressure field of a clinical shock wave source

Today, shock waves are used to treat a wide variety of ailments. Consequently, there is a need to develop efficient methodologies for comparing and evaluating the pressure fields generated by different equipment. Hydrophones are commonly utilized for accurate pressure measurements although they can be damaged by pitting due to acoustic cavitation. Furthermore, the range of measurement is limited by the position of the device. Optical methods have also been proposed since the presence of a disturbing device in the wave propagation medium is not necessary, and they provide a broader registering field. Nevertheless, these methods do not provide accurate measurements compared with those obtained with polyvinylidene difluoride or fiber-optic hydrophones. Herein, an optical method for shock wave characterization based on diffraction analysis, that can lead to more precise results, is proposed. The phase fluctuations of a light wave produced when it traverses the shock wave pressure field are calculated. The diffraction patterns produced by this perturbed wave at an observation plane at different propagation distances are presented. Considering the state of the art of high-speed cameras, we conclude that an experimental setup, based on the results reported here, can contribute to the evaluation and comparison of shock wave generators for medical applications.

Azimuth anisotropy prediction and correction of wide-azimuth seismic data

For seismic wave propagation in media with horizontal transverse isotropy (HTI), kinematic and dynamic attributes are anisotropic. P waves propagate slower in perpendicular to fracture azimuth than parallel to it, whereas reflection strength and frequency vary with azimuth. The azimuthal effects on reflection coefficients and seismic wave velocities in an HTI medium are quantitatively analyzed. The resulting theory-based and real-world azimuth gathers demonstrate the anisotropic nature of such media. The fitting of the ellipse is used to quantitatively predict the direction and strength of anisotropy in the study area, which is consistent with that obtained by the S-wave splitting prediction method. In wide-azimuth data processing, measures are taken to eliminate the influence of azimuthal anisotropy, and the coherent spectrum pickup method is used to accurately calculate the azimuthal velocity of underground HTI media and perform azimuthal anisotropy correction processing, which eliminates the time difference between fast and slow wave caused by azimuthal anisotropy. The achieved results provide support for subsequent high-resolution imaging.

Recent Advancements in Modern Antenna Design for Wearable Devices

The rapid growth of wearable technologies within wireless body area networks (WBANs) has increased the demand for advanced wearable antennas. The human body's presence creates significant challenges for these antennas since it behaves differently as a wave propagation medium. It is necessary to prioritize specific requirements for antenna design, such as size, frequency, efficiency, wideband and multiband operation, because of body interaction and signal attenuation. The development of novel methodologies, the use of state-of-the-art fabrication methods, and the advancement of antenna designs have been the main areas of attention for researchers in this field in recent years. This research investigates contemporary advancements in wearable antennas, particularly emphasizing utilizing recent materials, fabrication processes, and new techniques. It also highlights the unique applicability of these antennas in advanced WBAN systems.

Parametric Reduced Order Models for wave propagation in 1D media containing defects

This paper presents analyses of reduced order models (ROM) for wave propagation in media containing material defects. Parametric ROMs based on POD (Proper Orthogonal Decomposition) are used here to take into account parameters that characterize local defects such as center position, extension and magnitude (localized loss of stiffness). Local and adaptive (based on the Grassmann interpolation) POD strategies are used. Sequential analyses regarding parametric dependence with one, two and three parameters are performed along with accuracy and speed up as a function of model order. Furthermore, the accuracy of ROMs is also investigated for uncertainty quantification analyses. Our results show that the choice of ROM technique is not straightforward and the best solution, which is case dependent, is not always the most complex one.

A coupling analysis method of foundation soil dynamic responses induced by metro train based on PDEM and stochastic field theory

Foundation soil is an important medium for vibration wave propagation in the running of metro train. The spatial variability of soil properties has an important influence on vibration response. The parameters of foundation soil are often determined. Based on the probability density evolution method (PDEM) and stochastic field theory, a coupling model of the metro train-track-shield tunnel-foundation soil is established. The stochastic field is expressed by the series of stochastic variables and deterministic space functions by the Karhunen-Loeve Expansion (KLE) method. The stochastic parameters of the cross-section of tunnel-foundation soil are specified to simulate the stochastic field of foundation soil. Based on PDEM, the environmental vibration caused by metro trains in shield tunnels is studied. The results of ground surface vibration displacement under different metro train speeds are analyzed, and the upper and lower limits and probability density information of ground surface vibration displacement are obtained. The results show that the probability density distribution of ground vibration displacement at each time is approximately normal due to the stochastic field of foundation soil. The peak and valley of the vibration displacement curve at the inverted arch of the tunnel are caused by the wheel distance of the metro train. The probability density distribution of velocity and acceleration is more sensitive to the stochastic field of velocity foundation soil and the change in metro train speed. The maximum Z vibration level results under different metro train speeds all meet the requirements of vibration allowable limits in the specification.

Numerical wave propagation aided by deep learning

We propose a deep learning approach for wave propagation in media with multiscale wave speed, using a second-order linear wave equation model. We use neural networks to enhance the accuracy of a given inaccurate coarse solver, which under-resolves a class of multiscale wave media and wave fields of interest. Our approach involves generating training data by the given computationally efficient coarse solver and another sufficiently accurate solver, applied to a class of wave media (described by their wave speed profiles) and initial wave fields. We find that the trained neural networks can approximate the nonlinear dependence of the propagation on the wave speed as long as the causality is appropriately sampled in training data. We combine the neural-network-enhanced coarse solver with the parareal algorithm and demonstrate that the coupled approach improves the stability of parareal algorithms for wave propagation and improves the accuracy of the enhanced coarse solvers.

Intensity fluctuations in biological tissues at any turbulence strength

This study investigates the intensity fluctuations of the optical plane and spherical waves in biological tissue that experience any strength of turbulence. Biological tissue is a random and complex medium for optical wave propagation, having a power spectrum reflecting the turbulent characteristics that depend on the structural parameters. It is important to accurately determine the strength of turbulence and classify turbulence regimes for the correct modeling of the behavior of the optical wave propagation. To classify weak, moderate and strong turbulent regimes, closed-form expressions of modified Rytov variances are obtained. Based on the modified Rytov variance that involves the large-scale and small-scale variations, the intensity fluctuations specified by the metric of scintillation index, are calculated versus various parameters such as the propagation distance, refractive index, characteristic length of heterogeneity, small length-scale factor, wavelength, fractal dimension and strength of the refractive index fluctuations. Behavior of optical plane and spherical waves in different turbulent regimes and the comparison of intensity fluctuations in different specimens of human and animal tissues are shown.

Heat transfer enhancement using 40 kHz ultrasound and metal foams inside a horizontal mini-channel

The aim of this experimental and numerical study using COMSOL Multiphysics is to analyze the effects of the metal foam and the acoustic streaming generated by ultrasonic waves of 40 kHz on heat transfer in forced convection over a heated plate. The results of the literature show that the metallic foam, and the ultrasonic acoustic streaming, improve heat transfer independently. For this purpose, we carried out a comparative study of different configurations. In the first configuration, aluminum foam occupies the entire surface of the heating body and the cooling fluid passes through it. However, in the second configuration, two aluminum foams of 10 mm thickness, spaced 10 mm apart, arranged in a manner that a quantity of air passes above and the other through its pores. Flow regime is maintained laminar for velocities ranging between 0.2 and 1 m/s. A heat flux of 50 W is kept constant in the bottom of test section.The results revealed that the insertion of aluminum foams improved the heat transfer by a factor of 227% and 125% respectively for a fully and partially porous channel, compared to an empty channel for equal flow velocities. While an enhancement factor of 42% was obtained by the acoustic streaming effect generated by ultrasonic waves of 40 kHz in an empty channel. The coupling of these two intensifying methods showed a slight increase in heat exchange coefficient in a partially porous channel configuration with an enhancement factor of 7% compared to a flow without ultrasound, Otherwise, no ultrasound influence on heat transfer in a fully porous channel configuration, this is explained by the impedance of wave propagation medium which attenuates the acoustic streaming effect.

Measurement of the Magnetic Monopole Charge, the Missing Link in Quantum Mechanics, Aether and the Dark Energy

Charge conservation in the theory of elementary particle physics is one of the best-established principles ‎in physics. As such, if ‎there are magnetic monopoles in the universe, the magnetic charge will most likely be a ‎conserved quantity like electric ‎charges. If neutrinos are magnetic monopoles, as physicists have reported ‎the possibility, the Earth should show signs of ‎having a magnetic monopole charge on a macroscopic scale ‎since neutrons must also have a magnetic monopole charge if ‎the general charge conservation principle is valid. ‎To test this hypothesis, experiments were performed to detect the collective ‎effect of the magnetic monopole ‎charge of neutrons on the earth's equator using two balanced high-strength neodymium rod ‎magnets. We ‎were able to identify the non-zero magnetic monopole charge of the individual neutrons from the experiments. ‎‎The presence of individual magnetic monopole charges in the universe prompted the proposition of the new ‎symmetric form ‎of Maxwell's equations. Based on the theoretical investigation of the new Maxwell's ‎equations, we conclude that magnetic ‎monopole neutrinos are the cause of the origin of quantum ‎mechanical uncertainty, dark energy, and the medium for ‎electromagnetic wave propagation in space.‎‎

Multiscale and multiphysics FEA simulation and materials optimization for laser ultrasound transducers

The relationship between the nanocomposite design and the laser ultrasound transducer (LUT) characteristics was investigated through simulations in multiple scale levels for material behavior, device response, and acoustic wave propagation in media. First, the effects of the nanoparticle size and concentration on the effective properties of composites were quantitatively investigated with the finite element analysis (FEA) method. Second, the effective properties of the nanocomposite were assigned to the layer, which is modeled as a homogeneous material, in the FEA for the LUT simulating the energy conversion from the incident laser to the acoustic wave. Finally, the ultrasound propagation in the water was calculated by a theoretical wave propagation model. The FEA-based prediction was compared with the experimental data in the literature and a theoretical analysis for LUT based on Thermal-Acoustic coupling. As a result, the ultrasound waves on the transducer surface and at a distance in the water could be predicted. Based on the hierarchically integrated prediction procedure, the optimal conditions of the photoacoustic nanocomposites were investigated through the parametric study with the particle size and concentration as variables. The results guide the material designs optimized for different device characteristics, such as high pressure and broad bandwidth.

Deformation Response of Tunnel Lining in Geological Area of Coal Seam Group Caused by Explosion Stress Wave

Abstract To study the influence of drilling and blasting on the deformation of the tunnel lining in a multimedium surrounding rock section, this paper constructs the deformation calculation theory of the explosion stress wave of the tunnel lining. We select single-medium surrounding rock, multimedium surrounding rock, different explosion accelerations, and different surrounding rock grades as research variables and analyse in depth the causes of the deformation response of the tunnel lining. It is found that the stress wave causes more damage to the surrounding rock closer to the explosion point, and the disturbance to the surrounding rock increases with the increase of the acceleration of the explosion stress wave. And the better the surrounding rock grade, the more obvious the creep effect formed by the explosion stress wave, and the more damaging the stress wave propagation is to the tunnel lining. After the stress wave propagation medium changes from soft to hard, the energy will produce a “nest effect” at the interface between the two media, and the energy will accumulate briefly at the interface. When a certain amount of energy has accumulated, it propagates into the hard medium in an excited state, which causes large vibration of the tunnel lining in the soft medium area. The stress wave propagation medium changes from hard to soft, and the excessive energy in the hard medium produces huge vibration only at the junction of the hard–soft media, and there is no “nest effect.”

Short range electromagnetic interface using 0.35 μm CMOS blocks for temperature monitoring in isolated areas

IntroductionInfra-red (IR) and visible light (VL) based systems developed for transmission of information about physical quantities (e.g. humidity, temperature) out from closed areas, cannot be effectively employed in case of specific conditions in a targeted environment (because of fog or vapor for example). ObjectivesIn this work, we introduce a concept of wireless short-range transmitter and receiver to sense physical quantities, for instance temperature, with slow variation. The proposed concept is able to transmit analog-based information from isolated environments (e.g. aquariums or environments for plant growing) with high immunity against vapor and fog that limits standard optical (laser, IR band) methods of communication. MethodsIn this work, a new concept of short range radiofrequency (RF) communication device consisting of transmitting and receiving parts build from active devices fabricated in 0.35 μm I3T25 3.3 VCMOS process and ferrite antennas is selected. RF part uses medium-wave propagation within 10 mm distance at frequency 700 kHz. Such an approach offers minimal path loss of the radiated energy of a signal and low-gain amplification required for restoration of similar levels as available at the transmitting side. ResultsThe processing of base-band signals of simple (sine wave) and complex (electrocardiogram) character was verified experimentally through the system. Application example of temperature monitoring in a closed environment, based on a temperature sensor (thermistor), verifies operationability in temperature range from 10 °C up to 50 °C. ConclusionCompared to state-of-the-art solution, the presented concept has several advantages, for instance: less complexity; using of simpler type of modulation and demodulation; lower power consumption and significantly reduced issues caused by an environment with special transmission conditions (e.g. fog and vapor). The obtained results are in good agreement with expectations. Among others, the presented system brings beneficial performances for similar applications targeting on monitoring of low-frequency or slowly varying signals.

Simulation of Medium Wave Propagation in the Magnetosphere

A model of the medium of the ionosphere and magnetosphere, including the distributions of the concentrations and temperatures, collision frequencies, and magnetic field parameters, is described. The ray-tracing method was used to simulate the parameters of medium radio waves in this environment. The wave trajectories were calculated in the approximation of geometric optics. When the level of solar and geomagnetic activity and the location of the transmitter and the frequency are set, the parameters of the wave paths can be calculated. Numerical modeling of the characteristics of experimental echo signals has shown that the mechanism of magnetospheric propagation is of paramount importance. In this case, the main ionospheric trough turned out to be an unusual channel. Medium waves propagate inside the trough along the plasmapause. This is possible with sufficiently clear relationships between the positions of the trough, plasmapause, and transmitter. The considered effect of medium wave channeling can be used to diagnose the position of the trough and plasmapause.

Exact boundary controllability of the structural acoustic model with variable coefficients

We consider the boundary controllability of the structural acoustic model with variable coefficients. The structural acoustic model is a coupled partial differential equation, which comprises an acoustic wave equation in the interior domain, a Kirchoff plate equation on the boundary portion, with the coupling being accomplished across a boundary interface. In this model, the wave propagation medium and the plate material are all inhomogeneous. By the Riemannian geometry theory and the multiplier technique, our paper derives the exact controllability with two boundary controls under some checkable conditions and the exact–approximate boundary reachability with only one control for the boundary Kirchoff plate equation.

Research on Microseismic Source Location Method Based on Waveform Characteristics Monitored by Nanomaterial Sensor under the Background of Metal Oxide Polluted Environment.

In recent years, the monitoring range of source location technology has developed from being one-dimensional and two-dimensional to being three-dimensional. However, due to the complexity and nonuniformity of the seismic wave propagation medium and the uncertainty of the propagation law, there will be large errors in the source location results. Therefore, the analysis of vibration signal has become the key problem of current research. This paper designs a microseismic monitoring system based on Internet of Things sensors, which can monitor the vibration wave characteristics of vibration signals. In order to test the positioning accuracy of the system, this paper introduces three positioning methods: target positioning method based on time difference, time delay estimation method based on EMD, and source target positioning method based on the characteristic frequency of vibration signal. The purpose of this paper is to find the most accurate method from the three source location methods. Through these three methods, the vibration source generated by a single person walking in situ can be located in the vibration positioning experiment of human walking. The error between the actual position and the measurement source position is compared. The results show that the time delay estimation method based on empirical mode decomposition has the highest positioning accuracy. In addition, in the microseismic experiment, it is proved that the positioning accuracy of EMD using L1 norm statistical criterion is higher than that using L2 norm statistical criterion.

Interaction of circularly polarized light with an absorptive electromagnetic conductor sphere – Radiation force and spin torque

The concept of a perfect electromagnetic conductor (PEMC) material, which is a class of a magneto-electric metamaterial, has been recently examined in the context of the optical radiation force theory [J. Quant. Spectr. Rad. Transfer, 233 (2019) 21–28; ibid 256 (2020) 107280], with particular emphasis on the rotary polarization effect and the contribution of the cross-polarized waves to the transfer of linear momentum, assuming an illumination of linearly-polarized plane progressive waves. The present investigation shows that additional cross-interference factors, which cannot be ignored, contribute to the time-averaged optical radiation force exerted on an absorptive electromagnetic conductor (AEMC) sphere when the incident field becomes circularly-polarized. Moreover, the analysis is extended to investigate the co-polarized, cross-polarized and cross-interference components of the time-averaged optical spin radiation torque. The multipole series expansion method in spherical coordinates is utilized to derive exact mathematical partial-wave series for the co-polarized, cross-polarized and cross-interference components of the radiation force and torque based on the integration of Maxwell’s radiation stress tensor and its moment over a spherical surface of large radius enclosing the sphere suspended in a lossless medium of wave propagation. Numerical results for the radiation force and spin torque efficiencies and their corresponding co-polarized, cross-polarized and cross-interference components illustrate the analysis with emphasis on the size parameter of the sphere ka, its electromagnetic admittance M as well as its imaginary part amounting to absorption. The computations are of importance from the standpoint of the fundamentals of the linear and angular momenta of circularly-polarized electromagnetic waves transferred to an AEMC and related applications in optical tweezers and particle manipulation of objects exhibiting circular dichroism.

An overset-grid finite-difference algorithm for simulating elastic wave propagation in media with complex free-surface topography

We have developed an overset-grid algorithm to simplify the difficulty of curvilinear grid (CG) generation and increase the computational efficiency for seismic wavefield modeling by using the finite-difference method in areas with complex surface topography. The overset grid comprises a Cartesian grid block and an approximately orthogonal CG block. The Cartesian grid covers most of the simulation domain, whereas the CG discretizes the near-surface topography. The Cartesian grid and the CG overlap each other arbitrarily. We use sixth-order explicit Lagrangian interpolation to exchange data between the Cartesian grid and the CG, which is shown to be sufficiently accurate. We also find that spatially smoothing the source term is important for reducing strong artificial reflections when the source is near the overlapping zone. Finally, numerical tests are performed to verify that the proposed overset grid is well suited for effective numerical simulation of seismic wave propagation.

Uncertainty Quantification and Global Sensitivity Analysis for Transient Wave Propagation in Pressurized Pipes

AbstractAccurate simulation of pipe transient wave is crucial for the design, reliability assessment, and defect detection of water supply systems. However, this is a difficult task since the wave propagation media in pipeline systems are often highly complex and involve a range of uncertainties. Experimental data show that key parameters such as valve closure time, wave speed, and pipe material coefficients are strongly uncertain and stochastic that may vary in a wide range. To analyze the transient behavior in such complex environments, surrogate models are built to realize the fast computation of uncertainty propagation. Three surrogate modeling methods, i.e., the polynomial‐chaos‐expansion, ordinary‐Kriging, and polynomial‐chaos‐Kriging, are tested and compared in terms of transient wave forecast accuracy. The global sensitivity is then analyzed via the Sobol index method, by which the most influential uncertainty sources on various transient signal features are identified.