Modes Of Wave Propagation Research Articles

Wave analysis in porous thermoelastic plate with microtemperature

AbstractIn the current study, wave analysis in porous thermoelastic plates with microtemperature subject to insulated or isothermal boundaries is the main focus. The governing equations, after expressing for the two‐dimensional case, are converted into nondimensional quantities. For further simplification, potential functions have been used. The normal mode analysis technique is applied to solve the problem. This technique is an influential methodology that furnishes suitable solutions with no presumed limitations. For stress‐free insulated, or isothermal boundaries, the frequency equations for symmetric and skew‐symmetric modes of wave propagation are derived. The attributes of waves (phase velocity, attenuation coefficient, specific loss, and penetration depth) are computed numerically and presented graphically to show the impacts of porosity and microtemperature. Particular cases of porous thermoelastic plates and thermoelastic plates with microtemperatures are presented. The present problem provides a theoretical foundation for the design and development of new composite materials and surface acoustic devices.

Jeans Gravitational Instability of a Rotating Collisionless Magnetized Plasma with Anisotropic Pressure

The problem of self-gravitational instability of an astrophysical rotating plasma in a strong magnetic field with an anisotropic pressure tensor is studied on the basis of the Chew–Goldberger–Low (CGL) quasi-hydrodynamic equations modified by generalized polytropic laws. Using the general form of a dispersion relation obtained by the normal-mode perturbation method, a discussion is provided of the propagation of small-amplitude perturbation waves in an infinite homogeneous plasma medium for transverse, longitudinal, and oblique directions with respect to the magnetic field vector. It is shown that different polytropic indices and anisotropic pressures not only change the classical Jeans instability condition but also cause the appearance of new unstable regions. Modified Jeans instability criteria are obtained for isotropic MHD equations and anisotropic CGL equations owing to the influence of the polytropic indices on gravitational and firehose instabilities for astrophysical plasma. It is shown that in the case of a longitudinal mode of perturbation wave propagation, the Jeans instability criterion does not depend on uniform rotation. In the case of the transverse propagation regime, the presence of rotation reduces the critical wave number and exerts a stabilizing effect on the growth rate of the unstable regime.

Dispersion Characteristics of Low-Frequency Electron Waves in a Magnetoactive Plasma of Arbitrary Density

The article studies waves in a collisionless magnetoactive plasma with frequencies much lower than the electron cyclotron frequency at an arbitrary ratio between the electron plasma and cyclotron frequencies. A general dispersion relation is obtained for the wave frequency as a function of the wave vector and the ratio of the plasma frequency to the cyclotron frequency. This relation is a bicubic equation with respect to frequency. Based on this equation, the existence domains of various wave modes depending on the specified parameter, their group velocity, polarization, and energy density are studied. Special attention is paid to low-frequency whistler waves in a low-density plasma, since, among the propagating wave modes existing in the specified range of parameters, whistler waves have the highest refractive index and play an important role in theresonant interaction of waves and particles.

Time-dependent flexural gravity wave scattering due to uneven bottom in the paradigm of blocking dynamics

The present study investigates the scattering of flexural gravity waves due to uneven bottom topography in the context of wave blocking. Emphasis is given to analyzing the effects of multiple propagating wave modes on the solution procedures. The mathematical model is developed for two scenarios: a bottom step and a submerged rectangular breakwater. For the bottom step case, the complete solution in terms of the velocity potential is obtained using the eigenfunction expansion method. Subsequently, the solution associated with the wave transformation by the bottom step is extended to the case of a submerged rectangular breakwater using symmetry characteristics of the velocity potential. The energy balance relation is derived in both cases using the conservation of energy flux in the presence of multiple propagating wave modes. Wave blocking occurs for four different frequencies in both the cases of the bottom step and the submerged breakwater due to variations in water depth. This makes the problem more complex as, depending on the frequency, multiple propagating wave modes can exist in either the reflected region, the transmitted region, or both. The transmitted wave amplitude associated with the lower wavenumber within the blocking frequencies exceeds unity, and this excess energy is balanced by the corresponding energy transfer rate. Additionally, removable discontinuities are observed at the blocking frequencies in the scattering coefficients, where group velocity ceases. In the context of floating ice sheets, the deflection is analyzed in the time domain for frequencies within and outside the blocking limits.

Ultrasonic Battery Management System for Lamb wave mode tracking on Lithium-ion pouch cells

During charging and discharging, lithium-ion secondary batteries (LIBs) change their mechanical properties due to intercalation and deintercalation of lithium-ions in the electrodes. In this work, a novel ultrasonic battery management system (UBMS) with dedicated FPGA hard- and software has been developed that can track these mechanical changes by using ultrasonic sensors. In particular, the group velocity of the fundamental Lamb mode A0 is tracked and compared with the proposed simulation model. Previous studies have shown that the Young’s modulus of the anode coating changes significantly during cycling. By incorporating this information into the simulation, a change in this value will drastically affect the group velocity of the propagating wave mode A0, which can also be seen in the measurements carried out. To represent a realistic use case, the behaviour of the Lamb mode A0 is measured at different temperatures, which have a big influence on the group velocity of the propagating wave mode. The collected ultrasonic BMS data was further used to develop a state-of-charge (SOC) and temperature estimator. The accuracy of this novel method is discussed. With the addition of the ultrasonic sensors, the BMS can have a larger and better database that can be used to provide a more accurate estimate of the mechanical properties of LIBs and their SOC and temperature.

Lamb Wave-Based Structural Damage Detection: A Time Series Approach Using Cointegration.

Although Lamb waves have found extensive use in structural damage detection, their practical applications remain limited. This limitation primarily arises from the intricate nature of Lamb wave propagation modes and the effect of temperature variations. Therefore, rather than directly inspecting and interpreting Lamb wave responses for insights into the structural health, this study proposes a novel approach, based on a two-step cointegration-based computation procedure, for structural damage evaluation using Lamb wave data represented as time series that exhibit some common trends. The first step involves the composition of Lamb wave series sharing a common upward (or downward) trend of temperature. In the second step, the cointegration analysis is applied for each group of Lamb wave series, which represents a certain condition of damage. So, a cointegration analysis model of Lamb wave series is created for each damage condition. The geometrical and statistical features of Lamb wave series and cointegration residual series are used for detecting and distinguishing damage conditions. These features include the shape, peak-to-peak amplitude, and variance of the series. The validity of this method is confirmed through its application to the Lamb wave data collected from both undamaged and damaged aluminium plates subjected to temperature fluctuations. The proposed approach can find its application not only in Lamb wave-based damage detection, but also in other structural health monitoring (SHM) systems where the data can be arranged in the form of sharing common environmental and/or operational trends.

Fast and slow magnetosonic shock waves in non-Maxwellian plasmas

Obliquely propagating nonlinear fast and slow magnetosonic wave modes in a hot non-Maxwellian dissipative plasma are investigated in the current work. Modified temperatures have been derived for the non-extensive Q- and (r,q)-distributions that correspond to the physical properties of such non-Maxwellian plasmas. The reductive perturbation technique has been employed to derive the linear dispersion relation (LDR) and Kadomstev-Petvashvilli-Burgers (KPB) equation for slow and fast magnetosonic wave modes in two dimensions. We then investigated the effect of non-extensive parameter Q, spectral indices (r,q) and kinematic viscosity ν on the LDR and nonlinear propagation of KPB shock profiles for both the slow and fast mode magnetosonic waves. We found that linear and nonlinear propagation of fast and slow magnetosonic wave modes have been considerably modified in such non-Maxwellian plasmas. The results presented here would depict a realistic picture of the propagation of linear and nonlinear fast and slow magnetosonic wave modes in non-Maxwellian plasmas.

Evaluation of Electromagnetic Fields of Extremely Low-Frequency Horizontal Electric Dipoles at Sea–Air Boundaries

The technologies of undersea detection and communication, seabed sensor networks, and geophysical detection using electromagnetic waves have emerged as research focal points within the field of marine science and engineering. However, most studies have focused on the propagation of electromagnetic fields over long distances within the shallow “sea-seabed” environment. This paper introduces a quasi-static approximation method to address the Sommerfeld numerical integration challenge within the near-field region, employing the horizontal electric dipole (HED) as a model. It derives the Sommerfeld numerical integral expressions under conditions where the wave-number ratio at the “seawater-air” boundary does not adhere to the requirement of |k0/k1| << 1 (where subscripts 0 and 1 denote seawater and air media, respectively). Building upon this, the paper simplifies the Bessel-Fourier infinite integral term within the integral expression to obtain Sommerfeld numerical integral approximations for the propagation of electromagnetic fields in the near region of extremely low frequency (ELF) within seawater. The study further conducts simulations and calculations to determine amplitude variations in electromagnetic field intensity generated by an ELF HED at different frequencies, dipole heights, and observation point depths. It concludes with an analysis of electromagnetic field propagation characteristics at the seawater-air boundary. Experimental findings highlight the lateral wave as the primary mode of electromagnetic wave propagation at this interface.

Feasibility study of eigenmode propagation through 2D models of vegetation

PurposeThis study aims to model and investigate low-loss wave-propagation modes across random media. The objective is to achieve better channel properties for applying radio links through random vegetation (e.g. forest) using a beamforming approach. Thus, obtaining the link between the statistical parameters of the media and the channel properties.Design/methodology/approachA beamforming approach is used to obtain low-loss propagation across random media constructed of long cylinders, i.e. a simplified two dimensional (2D) model of agroforests. The statistical properties of the eigenmode radio wave propagation are studied following a Monte Carlo method. An error quantity is defined to represent the robustness of an eigenmode, and it is shown that it follows a known Lognormal statistical distribution, thereby providing a base for further statistical investigations.FindingsIn this study, it is shown that radio wave propagation eigenmodes exist based on a mathematical model. The algorithm presented can find such modes of propagation that are less affected by the statistical variation of the media than the regular beams used in radio wave communication techniques. It is illustrated that a sufficiently chosen eigenmode waveform is not significantly perturbed by the natural variation of the tree trunk diameters.Originality/valueAs a new approach to obtain low-loss propagation in random media at microwave frequencies, the presented mathematical model can calculate scattering-free wave-propagation eigenmodes. A robustness quantity is defined for a specific eigenmode, considering a 2D simplified statistical forest example. This new robustness quantity is useful for performing computationally low-cost optimization problems to find eigenmodes for more complex vegetation models.

Numerical demonstration of a topologically-protected electroacoustic transistor

In this paper we conceptualize electroacoustic transistors based on topologically protected interface states in a reconfigurable valley-Hall topological insulator. Using piezoelectric media and active shunt circuits, we numerically model the spatial inversion symmetry breaking in a unit cell to produce topological bandgaps. These gaps are known to host robust modes for wave propagation along an interface. We use two such modes to design a transistor where the wave propagation in one topological channel switches on or off a second topological channel between a source and receiver elsewhere in the structure. Multiple such transistors may be combined to develop logic gates. Further, we develop and simulate the behavior of an electronic circuit which enables the transistor action. Our design opens a pathway to novel wave-based devices which may find applications in structure-based computing, as hybrid multiplexers in communication devices, and as structural switches or embedded sensors in robotics and internet of things.

Theoretical investigation on the elastic and mechanical properties of high-entropy alloys with partial replacement of Sc in Hf0.25Ti0.25Zr0.25Sc0.25−x Al x (x ≤ 15 %)

Abstract The theoretical assessment of mechanical and elastic properties is used to analyze the distinctive properties of high entropy alloys (HEAs) at room temperature. Using Lennard–Jones potential model, the second order elastic constants (SOECs) and third order elastic constants (TOECs) have been determined for the HEAs Hf0.25Ti0.25Zr0.25Sc0.25−x Al x (x ≤ 15 %) in their hexagonal close-packed (hcp) phases. SOECs have been used to calculate mechanical constants, Poisson’s ratio, Pugh’s ratio, Kleinman’s parameter. In order to determine the anisotropic behaviour of the selected HEAs, the elastic anisotropy has also been computed at room temperature. All the HEAs under consideration have anisotropy parameters that are not equal to one, indicating anisotropic behaviour. Later, the Grüneisen parameters were estimated for the chosen HEAs Hf0.25Ti0.25Zr0.25Sc0.25−x Al x (x ≤ 15 %) along longitudinal and shear modes of wave propagation. Analysis of the research results reveals the inherent properties of HEAs.

Flexural-gravity wave scattering due to a crack in a floating ice sheet in the perspective of wave blocking in a three-layer fluid

Flexural-gravity wave blocking is demonstrated in a three-layer fluid having a floating ice-covered surface in the water of finite depth. The study reveals that wave blocking occurs for higher values of compressive force in either of the modes, which depends on the density ratio and the wave frequency. Two (three) roots of the dispersion relation coalesce at the blocking (saddle) frequencies. Further, within the blocking frequencies, the dispersion relation possesses five propagating wave modes, of which three are affiliated with the layer where blocking occurs, whilst the other two modes are connected with the wave motion propagating in the respective layers. Dead water analogue is established due to the propagation of internal waves along the interface when the thickness of an individual layer is either thin or the density of two consecutive layers is close to each other. Subsequently, the role of blocking dynamics on the flexural-gravity wave scattering by a linear crack in an ice sheet floating in a three-layer fluid is studied. The canonical energy balance relation is generalized to account for multiple propagating wave modes. The velocity potentials are expanded in terms of a scattering matrix to account for the multiple incidents and scattered wave modes within the blocking frequencies. The study depicts the occurrence of removable/jump discontinuities in the scattering coefficients, both at the points where blocking/mode conversion takes place. Irregularities in the ice sheet's deflection and interface elevations are due to the superposition of multiple propagating wave modes within the blocking frequencies.

Flexural gravity wave interaction with an articulated heterogeneous plate within the paradigm of blocking dynamics

Surface gravity waves interact with the flexural waves to generate the flexural gravity waves whose characteristics are triggered for higher values of lateral compressive stress to generate multiple propagating wave modes. This investigation examines the scattering of obliquely incident flexural gravity waves due to articulation in two semi-infinite heterogeneous floating elastic plates in finite water depth within a blocking dynamics regime. The dispersion curve demonstrates the existence of three propagating wave modes within the blocking limits. The canonical eigenfunction expansion method used for a single propagating mode is generalized to account for multiple propagating wave modes within the limits of blocking periods. The energy relation is established using the conservation of wave energy flux and Snell's law of refraction, which depends upon the angles and amplitude of the scattered waves along with the wave energy transfer rates. The amplitude of scattering coefficients (energy transfer rate) goes beyond the unit, where the corresponding energy transfer rate (scattering coefficients) diminishes for specific wave periods. Subsequently, complete wave reflection occurs for oblique waves beyond a critical angle of incidence for a fixed period and prior to a critical angle of incidence at a higher angle of incidence. Removable discontinuities occur at the blocking and saddle points, while a jump discontinuity appears due to a change in the incident wave mode in the scattering coefficients. Surface plots reveal the irregular pattern of plate deflection for the period within the blocking limits. Linear time-dependent plate displacement is simulated in two and three dimensions.

Lower-temperature fabrication of airbridges by grayscale lithography to increase yield of nanowire transmons in circuit QED quantum processors

Quantum hardware based on circuit quantum electrodynamics makes extensive use of airbridges to suppress unwanted modes of wave propagation in coplanar-waveguide transmission lines. Airbridges also provide an interconnect enabling transmission lines to cross. Traditional airbridge fabrication produces a curved profile by reflowing resist at elevated temperature prior to metallization. The elevated temperature can affect the coupling energy and even yield of pre-fabricated Josephson elements of superconducting qubits, tunable couplers, and resonators. We employ grayscale lithography to enable reflow and thereby reduce the peak temperature of our airbridge fabrication process from 200 to 150 °C and link this change to a substantial increase in the physical yield of transmon qubits with Josephson elements realized using Al-contacted InAs nanowires.

Quantitative detection of crack depth in V-groove weld using laser-generated surface acoustic waves

Thick-walled structures are widely used in kinds of high-end equipment. As the most conventional method adopted to manufacture large-scale structures, multi-pass butt-welds are one of the most critical areas prone to defects. In this paper, we focus on the quantitative detection of crack depth in a V-groove weld using laser-generated surface acoustic waves. A two-dimensional finite-element method with Q345 steel is adopted to reveal the complicated propagation characteristics of laser-generated surface acoustic waves with surface cracks. The displacement fields are discussed to show the wave transmission, reflection, and mode-conversion phenomena. The main propagating wave modes—P, R, R′, R′r, and R′t waved—are distinguished with the help of the out-of-plane displacement under different crack depths in the time domain. It is found that R′r can be used to locate the cracks and R′t can be used to quantify the depth of the cracks.

Experimental and numerical study on wave characteristics by a moving submerged body in a two-layer fluid

Waves induced by an immersed moving body in a two-layer fluid were studied experimentally and numerically. Unmixed fluids (water and cooking oil) were used as the two-layer fluid. A submerged body was manufactured to move with a wire loop system connected to the motor. The measured data were compared with numerical results and theoretical solutions. Numerical calculations were performed using the computational fluid dynamics (CFD) program. The characteristics of the generated waves, such as wave patterns and wavelengths, were qualitatively similar to the numerical results and theoretical values. Of the two wave propagation modes in a two-layer fluid, the baroclinic mode was dominant when the immersed body moved at a low speed. In contrast, the barotropic mode became more prominent as the body velocity increased. Based on these characteristics, transverse waves dominated when the velocity of the body was low, and divergent waves became more distinct as the velocity increased. In addition, the fluid depth and the location of a submerged body can affect the characteristics of the wave patterns.

Retraction

This article refers to:RETRACTED ARTICLE: Convergence study on ultrasonic guided wave propagation modes in an axisymmetric cylindrical waveguide

An Efficient Wireless Propagation Loss Prediction Model Based on 3-D Terrain Features Extracted by Deep Learning

This paper proposes a path loss prediction method based on convolutional neural network (CNN) by extracting features such as terrain obstacles and building distribution. 20 prediction tasks are carried out for different configurations of wave propagation mode, the number and height distribution of buildings and whether there is blocking effect, and a good accuracy is achieved. Meanwhile, the prediction time cost of the CNN and that of ray tracing are comprehensively compared, and in general the CNN has stable and higher computing efficiency. It can be seen that the CNN has greater advantages when dealing with complex environments and multiple propagation mechanisms by processing topographic maps attributed to its better feature extraction and generalization capabilities.

Wave motion in homogeneous isotropic micropolar porous thermoelastic plate under memory-dependent Lord-Shulman and Green-Lindsay theories

The homogeneous isotropic micropolar porous thermoelastic plate under memory-dependent derivatives (MDD) has been taken into consideration to investigate the wave propagation regarding Lord-Shulman (LS) and Green-Lindsay (GL) theories. The governing equations are non-dimensionalized and solved using normal mode analysis. The dispersion equations for both symmetric and anti-symmetric modes of wave propagation are obtained in the assumed model. The comparisons between the variation of phase velocity and attenuation coefficient corresponding to LS and GL theories are shown graphically using MATLAB software. The amplitudes of dilatation, volume fraction, micro-rotation and temperature distribution are computed analytically and presented in the form of graphs for LS and GL theories in the presence of MDD. Various particular cases are discussed in detail.

Wave resonances and hydroelastic wave motion

Three different types of resonances, i.e. blocking, trapping and Bragg resonance, associated with flexural gravity wave motion in the presence of current and permeable bottom are discussed. Also, using the different modes of wave propagation, the interconnection among all these resonances is analysed. An uneven pattern in the plate deflection is seen inside the blocking resonance zone. The uniform convergence of the infinite series associated with the trapped mode is proved. We have found that the trapped mode does not exist if the magnitude of the opposing current is higher or whenever we move the cylinder away from the platecovered surface. It is also observed that two propagating modes within the blocking frequencies create the environment for the occurrence of trapped waves. At the same time, all three modes have a remarkable contribution to Bragg resonance. The Bragg reflection increases in the blocking zone and decreases outside of it. We have seen that the amplitude of the Bragg reflection increases with the increase in current speed and porosity parameter. Also, the discontinuities in Bragg reflection coefficients are seen at blocking frequencies. The model is also carefully validated numerically for trapped and Bragg resonances against the results available in the existing literature.