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The formation of laser-induced periodic surface structures (LIPSSs) on fused silica upon irradiation with plane wave, double pulse, spot processing, and scanning processing (pulse duration tp = 35 fs, center wavelength λ = 800 nm, low repetition rate ≈1 kHz) is studied theoretically with an improved three-dimensional finite-difference time-domain plasma model. The model covers both intrapulse feedback under single shot and interpulse feedback under multi-shots, thus enabling better prediction of transient responses during laser–material interaction and the evolution of the ablated morphology and accumulated defects' density with more shots. In simulations of a single plane wave, a double pulse can modulate LIPSS periodicity. In simulations of spot processing with Gaussian beam, an increase in the number of shots results in a noticeable ablation pattern where high-spatial-frequency LIPSS surrounds low-spatial-frequency LIPSS at a fluence of 2.8 J/cm2. Moreover, simulations of scanning processing with Gaussian beam showcase the broad applicability of this model, revealing that the orientation of the LIPSS depends on the polarization direction rather than the scanning path. This new model provides a powerful tool to simulate the formation of LIPSS on silica, particularly when temporally modulated laser is involved or predicting the evolution of morphology dependent on the number of shots. [ABSTRACT FROM AUTHOR]

Band structure and Dirac degeneracy are essential features of sonic crystals/acoustic metamaterials to achieve advanced control of exciting wave effects. In this work, we explore a deep learning approach for the design of phononic crystals with desired dispersion. A plane wave expansion method is utilized to establish the dataset relation between the structural parameters and the energy band features. Subsequently, a multilayer perceptron model trained using the dataset can yield accurate predictions of wave behavior. Based on the trained model, we further impose a re-learning process around a targeted frequency, by which Dirac degeneracy and double Dirac degeneracy can be embedded into the band structures. Our study enables the deep learning approach as a reliable design strategy for Dirac structures/metamaterials, opening up the possibilities for intriguing wave physics associated with Dirac cone. [ABSTRACT FROM AUTHOR]

Complementary acoustic metamaterials (CAMMs) have been proposed as a means of enhancing the transmission of acoustic imaging signals through aberrating layers. Aberrating layers with high impedance contrast compared to the surrounding material disrupt the acoustic field and hence distort acoustic images. However, conventional CAMMs are passive and thus unable to compensate for signal distortions associated with loss. This work presents an approach inspired by CAMMs that is not bound by the limits of passivity to compensate for both acoustic scattering and energy attenuation by augmenting a plane wave incident on a lossy material with monopolar and dipolar source fields to allow for perfect transmission, thus rendering the lossy medium acoustically transparent. We present a general approach to derive expressions for source magnitudes that are dimensionless with respect to frequency, system geometry, and the background medium. We validate these results with three-dimensional finite element simulations, where the appropriate monopolar and dipolar source fields are generated by prescribing velocities on finite-dimensional boundaries. We show the limitations of this approach with regard to frequency, system geometry, and lossy material characteristics via a parametric study. [ABSTRACT FROM AUTHOR]

The introduction of metasurfaces has renewed Snell's law, and the metasurfaces can manipulate sound waves flexibly. In this paper, a coding metasurface with a simple and adjustable coding unit for sound wave transmission is proposed. By changing the orientation of a movable part in a fixed structure, conversion is achieved between two types of units with a phase difference of 180° and high transmittance (>75%). By combining the two types of units, the phases of sound waves can be regulated dynamically. Structural simulations are performed using finite-element software, and the beam splitting of the transmitted sound wave is verified by theoretical analysis and experiments under plane wave incidence in the frequency range of 4.7–5.7 kHz. In addition, the two types of units are used to design a coding Fresnel lens, and its simulated focusing performance is verified by experiments at 4.7–5.7 kHz. [ABSTRACT FROM AUTHOR]

We construct correlation-consistent effective core potentials (ccECPs) for a selected set of heavy atoms and f elements that are currently of significant interest in materials and chemical applications, including Y, Zr, Nb, Rh, Ta, Re, Pt, Gd, and Tb. As is customary, ccECPs consist of spin–orbit (SO) averaged relativistic effective potential (AREP) and effective SO terms. For the AREP part, our constructions are carried out within a relativistic coupled-cluster framework while also taking into account objective function one-particle characteristics for improved convergence in optimizations. The transferability is adjusted using binding curves of hydride and oxide molecules. We address the difficulties encountered with f elements, such as the presence of large cores and multiple near-degeneracies of excited levels. For these elements, we construct ccECPs with core–valence partitioning that includes 4f subshell in the valence space. The developed ccECPs achieve an excellent balance between accuracy, size of the valence space, and transferability and are also suitable to be used in plane wave codes with reasonable energy cutoffs. [ABSTRACT FROM AUTHOR]

This paper reports the energies and charge and spin distributions of the low-lying excited states in singlet and triplet N2V defects in diamond from direct Δ-SCF calculations based on Gaussian orbitals within the B3LYP, PBE0, and HSE06 functionals. They assign the observed absorption at 2.463 eV, first reported by Davies et al. [Proc. R. Soc. London 351, 245 (1976)], to the excitation of a N(sp3) lone-pair electron in the singlet and triplet states, respectively, with estimates of ∼1.1 eV for that of the unpaired electrons, C(sp3). In both cases, the excited states are predicted to be highly local and strongly excitonic with 81% of the C(sp3) and 87% of the N(sp3) excited charges localized at the three C atoms nearest neighbor (nn) to the excitation sites. Also reported are the higher excited gap states of both the N lone pair and C unpaired electron. Calculated excitation energies of the bonding sp3 hybrids of the C atoms nn to the four inner atoms are close to that of the bulk, which indicates that the N2V defect is largely a local defect. The present results are in broad agreement with those reported by Udvarhelyi et al. [Phys. Rev. B 96, 155211 (2017)] from plane wave HSE06 calculations, notably for the N lone pair excitation energy, for which both predict an energy of ∼2.7 eV but with a difference of ∼0.5 eV for the excitation of the unpaired electron. [ABSTRACT FROM AUTHOR]

Diffraction-free beams with large depth-of-field have a lot of potential in the field of acoustics, such as imaging, sensing, and particle manipulation. In this study, an acoustic Bessel-like beam is produced using an axicon-sonic crystal lens. The sonic crystal is created using cylindrical glass rods arranged in a triangular shape with a centered square lattice configuration. The numerical simulation between 4 and 8 kHz indicates that the axicon-sonic crystal converts the plane acoustic wave into a Bessel-like beam. The analysis of the beam indicates that the depth of field of this beam depends on the size and periodicity (lattice parameter) of the sonic crystal. The axicon lens also displays variable focal lengths at different frequencies. A graded index layer was implemented to mitigate the reflection caused by the significant impedance mismatch. Experimental validation of acoustic Bessel-like beam formation is also reported for the working frequencies. At 8 kHz, the measured range to the 50 % on-axis intensity was 34 λ , while the focus width at the same frequency was measured to be 2 λ. The integration of three distinct design strategies—axicon shape, sonic crystal, and graded index—expands the possibilities for sound focusing applications. [ABSTRACT FROM AUTHOR]

We have developed and implemented an implicit electrolyte model in the Vienna Ab initio Simulation Package (VASP) that includes nonlinear dielectric and ionic responses as well as a nonlocal definition of the cavities defining the spatial regions where these responses can occur. The implementation into the existing VASPsol code is numerically efficient and exhibits robust convergence, requiring computational effort only slightly higher than the original linear polarizable continuum model. The nonlinear + nonlocal model is able to reproduce the characteristic "double hump" shape observed experimentally for the differential capacitance of an electrified metal interface while preventing "leakage" of the electrolyte into regions of space too small to contain a single water molecule or solvated ion. The model also gives a reasonable prediction of molecular solvation free energies as well as the self-ionization free energy of water and the absolute electron chemical potential of the standard hydrogen electrode. All of this, combined with the additional ability to run constant potential density functional theory calculations, should enable the routine computation of activation barriers for electrocatalytic processes. [ABSTRACT FROM AUTHOR]

When a vacancy is created in an inner-valence orbital of a dimer of atoms or molecules, the resulting species can undergo interatomic/intermolecular Coulombic decay (ICD): the hole is filled through a relaxation process that leads to a doubly ionized cluster with two positively charged atoms or molecules. Since they are subject to electronic decay, inner-valence ionized states are not bound states but electronic resonances whose transient nature can only be described with special quantum-chemical methods. In this work, we explore the capacity of equation-of-motion coupled-cluster theory with two techniques from non-Hermitian quantum mechanics, complex basis functions and Feshbach–Fano projection with a plane wave description of the outgoing electron, to describe ICD. To this end, we compute the decay rates of several dimers: Ne2, NeAr, NeMg, and (HF)2, among which the energy of the outgoing electron varies between 0.3 and 16 eV. We observe that both methods deliver better results when the outgoing electron is fast, but the characteristic R−6 distance dependence of the ICD width is captured much better with complex basis functions. [ABSTRACT FROM AUTHOR]

Kohn–Sham density functional theory (DFT) is nowadays widely used for electronic structure theory simulations, and the accuracy and efficiency of DFT rely on approximations of the exchange-correlation functional. By including the kinetic energy density τ, the meta-generalized-gradient approximation (meta-GGA) family of functionals achieves better accuracy and flexibility while retaining the efficiency of semi-local functionals. For example, the strongly constrained and appropriately normed (SCAN) meta-GGA functional has been proven to yield accurate results for solid and molecular systems. We implement meta-GGA functionals with both numerical atomic orbitals and plane wave bases in the ABACUS package. Apart from the exchange-correlation potential, we also discuss the evaluation of force and stress. To validate our implementation, we perform finite-difference tests and convergence tests with the SCAN, rSCAN, and r2SCAN meta-GGA functionals. We further test water hexamers, weakly interacting molecules from the S22 dataset, as well as 13 semiconductors using the three functionals. The results show satisfactory agreement with previous calculations and available experimental values. [ABSTRACT FROM AUTHOR]

We investigate the role of Compton ionization in ultrafast non-resonant x-ray scattering using a molecular model system, which includes the ionization continuum via an orthonormalized plane wave ansatz. Elastic and inelastic components of the scattering signal, as well as coherent-mixed scattering that arises from electron dynamics, are calculated. By virtue of a near-quantitative distinction between scattering related to electronic transitions into bound and continuum states, we demonstrate how Compton ionization contributes to the coherent-mixed component. Analogous to inelastic scattering, the contribution to the coherent-mixed signal is significant and particularly manifests at intermediate and high-momentum transfers. Strikingly, for molecules with inversion symmetry, the exclusion of bound or continuum transitions may lead to the prediction of spurious coherent-mixed signals. We conclude that qualitative and quantitative accuracies of predicted scattering signals on detectors without energy resolution require that elements of the two-electron density operator are used. This approach inherently accounts for all accessible electronic transitions, including ionization. [ABSTRACT FROM AUTHOR]

Train vibrations are the primary concern in environmental engineering and civil engineering. It is significantly imperative to find new methods for reducing and isolating vibrations. The locally resonant metamaterials (LRMs) propose a novel method and concept for reducing train vibration. However, the accurate and quick design structures of LRMs based on vibration characteristics are still an issue. Thus, this study presents a novel inverse design model of three-component locally resonant metamaterial barriers (LRMBs) for vibration reduction based on deep learning. The bandgap characteristics and vibration modes of the LRMB are investigated by using the improved plane wave expansion (IPWE) and finite element method (FEM). Besides, the gradient-combined LRMBs are proposed based on time–frequency features of measured vibration caused by trains and the novel inverse design model, and a two-dimensional finite element model coupling with infinite element boundaries is established to study the reduction efficiency of the gradient-combined LRMBs. And the performances of different LRMBs are fully analyzed in time and frequency domains. The results show that the novel inverse design model can be successfully used to design the LRMB based on vibration features. Moreover, the gradient-combined LRMBs have better isolation performance. [ABSTRACT FROM AUTHOR]

The attenuation zones (AZs) of periodic pile barriers can be used to mitigate ambient vibration. To identify pile structures with optimal vibration isolation performance and minimal concrete consumption, this study adopts a multi-objective topology optimization (MOTO) procedure to optimize the periodic pile units for the isolation of plane waves. The optimized pile structures are presented, and the most cost-effective one is suggested. The effects of the AZ orders, the elastic modulus and the density of soil on the optimization results are investigated. By establishing numerical models, the vibration reduction performance of the optimized pile barriers in the frequency domain and time domain is verified. [ABSTRACT FROM AUTHOR]

The usual gravitational wave memory effect can be understood as a change in the separation of two initially comoving observers due to a burst of gravitational waves. Over the past few decades, a wide variety of other, 'persistent' observables which measure permanent effects on idealized detectors have been introduced, each probing distinct physical effects. These observables can be defined in (regions of) any spacetime where there exists a notion of radiation, such as perturbation theory off of a fixed background, nonlinear plane wave spacetimes, or asymptotically flat spacetimes. Many of the persistent observables defined in the literature have only been considered in asymptotically flat spacetimes, and the perturbative nature of such calculations has occasionally obscured deeper relationships between these observables that hold more generally. The goal of this paper is to show how these more general results arise, and to do so we focus on two observables related to the separation between two, potentially accelerated observers. The first is the curve deviation, which is a natural generalization of the displacement memory, and also contains what this paper proposes to call drift memory (previously called 'subleading displacement memory') and ballistic memory. The second is a relative proper time shift that arises between the two observers, either at second order in their initial separation and relative velocity, or in the presence of relative acceleration. The results of this paper are, where appropriate, entirely non-perturbative in the curvature of spacetime, and so could be used beyond leading order in asymptotically flat spacetimes. [ABSTRACT FROM AUTHOR]

In the present paper, we consider the problem of plane wave reflection and transmission at the boundary of two different transversely isotropic microstretch elastic half-spaces. The main purpose of this problem is to examine the effect of microstretch elasticity, microrotation and transverse isotropy on wave propagation. Four reflected and four transmitted waves are produced when a plane wave is incident at the boundary between two different half-spaces. The relations for Amplitude ratios and Energy ratios of reflected and transmitted waves are derived which depends upon the material parameters and angle of propagation. The Amplitude ratios and square root of Energy ratios are plotted against the angle of propagation using MATLAB Software to observe the effect of microstretch elasticity, microrotation and transverse isotropy. Theoretical and numerical results show the significant dependence of microstretch fields, microrotation and transverse isotropy on wave propagation. [ABSTRACT FROM AUTHOR]

Nonlinear effects can enrich the propagation of elastic waves in mechanical metamaterials, which makes it possible to extend classical phenomena and functions in linear systems to nonlinear ones. In this work, rather than monochromatic waves in similar linear structures, the negative refraction is realized by mixing waves which are generated in nonlinear elastic wave metamaterials. Based on the stiffness matrix and plane wave expansion methods, dispersion curves of in–plane modes resulting from the collinear and non–linear mixings of two longitudinal waves are calculated. In the frequency spectrum, two propagating modes coalesce at exceptional points due to the coupling of in–plane modes, and those points at which the refraction type changes are also exceptional ones. Two kinds of negative refraction can be found in the mixing modes near exceptional points, but each of them needs to be induced in a specific configuration. Moreover, experiments are performed to support the pure negative refraction and beam splitting of the nonlinear elastic waves. Particularly, the parallel configuration is able to separate and extract the nonlinear mode when the single–mode negative refraction occurs, which shows the possibility to design elastic wave device by the negative refraction of nonlinear mixing waves. [ABSTRACT FROM AUTHOR]

The radiation shielding properties of different samples of borate-tellurite glass were investigated using WO3 modifiers. Geometric optimization and modification of pristine borate-tellurite with WO3 were carried out based on density functional theory calculations using plane wave basis sets and pseudo-potentials. It was observed that the changes in the physical properties of the white box testing glass (WBTG) systems were determined by WO3 content. Analysis of the linear attenuation coefficient of the sampled glasses, which yielded a value of 7.43 cm for WBTG1 at 20 keV, indicated that WBTG1 was able to stop gamma radiation from Cs-137 and Th-237 sources. Both the µ and µm values were zero above 0.15 MeV, indicating that the WBTG composite was only able to attenuate low-energy photons such as gamma rays. It was found that the characteristic behavior of the WBTG was generally determined primarily by oxygen content, which is in good agreement with theoretical and experimental data. [ABSTRACT FROM AUTHOR]

In this paper, electronic properties of Janus MSX monolayers (M = Mo, W; X = Se or Te), including electron energy loss near edge structures (ELNES), as K and L2,3 edge spectra of sulfur atoms, have been calculated using a full potential scheme and the augmented plane wave plus local orbitals (APW+lo) method in the framework of density functional theory (DFT). Due to the lack of experimental results, the obtained spectra are compared with the corresponding spectra of MoS2 monolayer. The band structure analysis shows that the Janus MoSSe and WSSe monolayers are direct bandgap semiconductors, while the Janus MoSTe and WSTe monolayers are indirect bandgap semiconductors. In comparison to MoS2, the main structures of the K edge ELNES spectra of sulfur atoms in Janus monolayers occur at lower energies, due to the structural change and increased bond length. The relative reduction of intensities in the main structures predicts the possibility of reducing the number of partial densities of states (PDOS), that is, the reduced p PDOS for the K edge in the corresponding energy range. In the K (L2,3) edge ELNES spectra of the sulfur atom in Janus monolayers and MoS2 monolayers, the main structures are due to the electron transfer to the unoccupied px+py and pz states (3s of sulfur and 4d states of the transition metal). [ABSTRACT FROM AUTHOR]

In the present paper, we propose an asymptotic form at infinity in the configuration space for the quantum scattering problem solution of three three-dimensional like-charged particles, including the description of single and double rescattering, also in domains where one of Jacobi pair coordinates proves to be bounded. [ABSTRACT FROM AUTHOR]

In this study, we report observations of propagating radial carpet beams (RCBs) through a turbulent atmosphere at ground level with a 120 m path length. RCBs are a class of nondiffracting, accelerating, self-healing, and self-amplifying beams, and generated in the diffraction of a plane wave from amplitude/phase radial gratings having different spoke numbers. Observations were made at different times of the day. The intensity profile of an RCB becomes complicated when the number of grating spokes used to generate the beam is large, and includes high intensity spots, called main intensity spots (MISs), which are symmetrically placed at the central area around the beam axis and whose number is equal to (twice) the number of spokes of the amplitude (phase) grating used to generate the beam. With the aid of a telescope and a CCD camera, successive frames of the intensity pattern of the RCBs having different levels of structural complexity are recorded at the end of the path. For the data recorded at different times of the day, we calculate the variance of displacements of MISs along the radial direction. We observe that displacements of the MISs increase with increasing mean temperature of the air; on the other hand, as the complexity of the beam intensity pattern increases, the displacements of the MISs decrease. In order to compare the resilience of different RCBs and a well-known structured beam against atmospheric turbulence, we investigate deformation of the intensity profiles of a Laguerre–Gaussian (LG) beam having a topological charge 20 and different RCBs at the end of the path. It is shown that under the same turbulence condition, highly complex RCBs are more resilient to the destructive effects of the atmospheric turbulence. In particular, for the RCBs generated with gratings having 30 spokes and more, the number of MISs of the received intensity patterns is changed by less than 1% even when the turbulence strength is high. But for the LG beam, its intensity ring is clearly broken in different places, which makes it impossible to follow its maximum intensity in the radial direction [ABSTRACT FROM AUTHOR]

The diffuse field sound absorption coefficient (SAC) of a sound absorber can be obtained from an average over the incidence angles of the oblique incidence plane wave SAC. The plane wave SAC can be derived from the plane wave complex-valued reflection coefficient defined as the ratio of the reflected sound pressure at a given point on the material surface to the incident sound pressure at the same point. In practice, the material is excited by a monopole, and the reflection coefficient becomes a local quantity which is a function of the source height and the radial distance from the source. This local reflection coefficient obtained at various points on the material surface is commonly used to approximate the oblique incidence plane wave reflection coefficient. The error in estimating the diffuse field SAC introduced by this approximation has not been explored in the literature. This paper investigates this error as a function of the material extent, thickness, and source height using an analytical approach to calculate the local reflection coefficient. The calculation is based on Allard's model which describes the sound propagation above an infinite lateral extent porous material backed by a rigid wall and excited by a monopole. Using finite element simulations as a reference, the analytical model is shown to provide a good approximation of the diffuse field sound absorption performance of sufficiently large material areas. The diffuse field SAC calculated from plane wave reflection coefficients and local reflection coefficient are compared. The limitations inherent in deriving diffuse field SACs from local reflection measurements obtained with a monopole are highlighted. [ABSTRACT FROM AUTHOR]

We analyzed electrostatic electron cyclotron harmonic waves observed by the interferometry observation mode of the Arase satellite. It is found that the magnitude of the phase difference varies with the satellite spin. The spin dependence of this phase difference was investigated by examining the trend of the spin dependence for the 84 events of interferometry observation of ECH waves. We found that they are divided into two categories. One is that the phase difference tends to show sinusoidal variations as a function of the angle γ B between the ambient magnetic field projected on the spin plane and the electric field sensor. The other is that the phase difference is close to zero and does not depend on γ B . A numerical model of interferometry observation of single plane wave is constructed to explain the observed phase differences. We performed the numerical calculations when the background magnetic field was oriented in the direction often observed in the Arase satellite. The result of the calculations shows the wave vector direction relates to the spin angle with the maximum phase difference. Using this relation, we show that it may be possible to estimate the wave vector direction of ECH waves from one-dimensional interferometry data. This is expected to enable more accurate estimates of phase velocity. [ABSTRACT FROM AUTHOR]

Automotive antennas are gaining importance due to their increasingly important role for autonomous driving with the development of the Internet of Vehicles. However, over‐the‐air testing on automotive antennas is difficult owing to its large volume and complex body structure. Plane wave generators can approximate uniform plane waves in the near field of the device under test, which can greatly reduce the measurement distance and thereby decreasing the cost compared with direct far‐field solutions. This letter designs three plane wave generators for three quiet zone sizes selected according to the vehicle structure at 5.9 GHz, achieving quiet zone sizes of 1.45 m ×0.23$\times 0.23$ m, 2.9m ×0.56$\times 0.56$ m, and 3.9 m ×1.27$\times 1.27$ m, respectively. Within the three quiet zones, amplitude deviations of 0.82, 0.34, and 0.34 dB and phase deviations of 9.4∘${9.4^\circ }$, 6.72∘${6.72^\circ }$ and 1.42∘${1.42^\circ }$ are realized, respectively, according to the numerical simulations. Uncertainty analysis is further implemented to investigate the robustness of the designed PWGs proposed in this letter. [ABSTRACT FROM AUTHOR]

There has been a considerable number of studies on the reflection and transmission of plane waves in anisotropic elastic half-spaces. However, the obtained formulas of the reflection and transmission coefficients are implicit, and the numbers of reflected and transmitted waves are undetermined. In this paper, the reflection of qP waves from an orthotropic elastic layer overlying an orthotropic elastic half-space is considered. It has been proved that an incident qP wave always creates two reflected waves, one qP wave and one qSV wave, and the reflection angle of the reflected qP wave is equal to the incident angle. Based on this fact, formulas for the reflection coefficients have been derived by using the transfer matrix method along with the effective boundary condition technique. It should be noted that, different from the previously obtained implicit formulas, these formulas are totally explicit functions of the incident angle, the (dimensionless) layer thickness and the material parameters of the half-space and the layer. Since the obtained formulas are totally explicit, they will be useful in various practical applications, especially in nondestructively evaluating the mechanical properties of deposited layers. [ABSTRACT FROM AUTHOR]

The wave reflection and transmission (R/T) coefficients in fluid-saturated porous media with the effect of effective pressure are rarely studied, despite the ubiquitous presence of in situ pressure in the subsurface Earth. To fill this knowledge gap, we derive exact R/T coefficient equations for a plane wave incident obliquely at the interface between the dissimilar pressured fluid-saturated porous half-spaces described by the theory of poro-acoustoelasticity (PAE). The central result of the classic PAE theory is first reviewed, and then a dual-porosity model is employed to generalize this theory by incorporating the impact of nonlinear crack deformation. The new velocity equations of generalized PAE theory can describe the nonlinear pressure dependence of fast P-, S- and slow P-wave velocities and have a reasonable agreement with the laboratory measurements. The general boundary conditions associated with membrane stiffness are used to yield the exact pressure-dependent wave R/T coefficient equations. We then model the impacts of effective pressure on the angle and frequency dependence of wave R/T coefficients and synthetic seismic responses in detail and compare our equations to the previously reported equations in zero-pressure case. It is inferred that the existing R/T coefficient equations for porous media may be misleading, since they lack consideration for inevitable in situ pressure effects. Modeling results also indicate that effective pressure and membrane stiffness significantly affect the amplitude variation with offset characteristics of reflected seismic signatures, which emphasizes the significance of considering the effects of both in practical applications related to the observed seismic data. By comparing the modeled R/T coefficients to the results computed with laboratory measured velocities, we preliminarily confirm the validity of our equations. Our equations and results are relevant to hydrocarbon exploration, in situ pressure detection and geofluid discrimination in high-pressure fields. [ABSTRACT FROM AUTHOR]

The focus of the present study is to analyze the reflection and refraction of plane-P-wave at the interface between a nonlocal transversely isotropic poroelastic medium (excluding fluid nonlocal effects) and a nonlocal transversely isotropic thermoelastic half-space. The incidence of the plane P (P 1) wave generates three reflected and three transmitted waves in the respective media. Generalized governing equations for the two media are solved assuming plane wave solutions for displacement components and temperature field. The calculation of theoretical expressions for reflection and transmission coefficients involves a system of six non-homogeneous linear equations, based on boundary constraints and are computed utilizing Cramer's rule. The findings demonstrate a significant influence of incidence angle and nonlocal parameter on the amplitude ratios of each reflected and refracted wave. Graphical representations explore the impact of material parameters of both poroelastic medium (porosity, Biot's parameter, and tortuosity), and thermoelastic medium (temperature and thermal relaxation time) on amplitude ratios of waves. Propagation characteristics for different boundary constraints (permeable/impermeable, and thermally insulated/isothermal) are numerically compared. In addition, variations of velocities of all reflected and transmitted waves showing the impact of nonlocal parameter and incidence angle are shown graphically. This study enhances the comprehension of wave behavior in anisotropic nonlocal materials, with potential applications in geophysics, seismology, and material science. Understanding these interactions can improve the design and performance of devices, systems, and structures utilizing poroelastic and thermoelastic materials. [ABSTRACT FROM AUTHOR]

The problem of reflection and transmission of inhomogeneous plane waves caused by incident quasi-longitudinal (qP) and quasi-shear vertical (qSV) waves at the interface between a fiber-reinforced thermoelastic solid under magnetic field and a fiber-reinforced thermoelastic solid is examined mathematically using Lord-Shulman theory. The impact of magnetic intensity on the phase speeds has been discussed. The boundary conditions are taken at the plane interface of the two half-spaces and the amplitude and the energy ratios are derived. Two plane waves, qP wave and qSV wave are modeled to incident at the plane interface which result in three reflected waves in one of the half-spaces and three transmitted waves in the other half-space. The effect of magnetic field on the amplitude ratios, the bulk energy ratios and the interacting energy ratios are analyzed numerically and the results are illustrated graphically. [ABSTRACT FROM AUTHOR]

The research article deals with the reflection of plane waves in a micropolar thermoelastic diffusion solid half-space with voids in the context of Lord-Shulman theory of thermoelasticity. The governing equations are formulated to obtain two velocity equations. The plane wave solution of these velocity equations indicate the existence of six plane waves, a set of four coupled longitudinal displacement waves and a set of two coupled transverse displacement wave namely coupled longitudinal displacement wave $ (LD - 1) $ (LD − 1) , coupled thermal wave $ (LD - 2) $ (LD − 2) , coupled mass diffusion wave $ (LD - 3) $ (LD − 3) , coupled longitudinal void volume fraction wave $ (LD - 4) $ (LD − 4) and coupled transverse displacement wave $ (TD - 1) $ (TD − 1) , coupled transverse micro-rotational wave $ (TD - 2) $ (TD − 2). A reflection of the plane wave from a stress-free thermally insulated surface is studied to obtain the reflection coefficients and energy ratios of reflected waves. The reflection coefficients and energy ratios of the reflected waves are computed for a particular material and the variations of the reflection coefficients and energy ratios against the angle of incidence are shown graphically. [ABSTRACT FROM AUTHOR]

Aiming at the problem of error in deep-sea DOA (Direction of Arrival, DOA) estimation based on plane wave sound field model, this paper establishes the array signal model of deep-sea DOA estimation under multipath channel based on ray theory. The characterization method of deep-sea multipath ray propagation time and adjacent array element ray propa- gation delay difference are also derived. Compared with the propagation delay difference expression of adjacent array elements in the traditional plane wave model, the propagation delay difference expression of adjacent array elements derived in this pa- per is more universal. Combined with the decoherence DOA estimation algorithm, the performance of deep-sea DOA estima- tion is improved, and the effectiveness of the algorithm is verified by simulation. The research shows that the time delay difference between adjacent array elements is not only related to the distance between array elements and the target azimuth, but also related to the depth of the sound source and the horizontal distance from the sound source to each array element. The construction of the steering vector in DOA estimation should consider the influence of these factors. At this time, DOA esti- mation is a multi-dimensional parameter optimization problem. Fully considering the acoustic propagation characteristics of the ocean sound field can fundamentally solve the error problem of deep-sea DOA estimation. [ABSTRACT FROM AUTHOR]

Dynamics and properties of breathers for the modified Korteweg–de Vries equations with negative cubic nonlinearities are studied. While breathers and rogue waves are absent in a single component waveguide for the negative nonlinearity case, coupling can induce regimes of modulation instabilities. Such instabilities are correlated with the existence of rogue waves and breathers. Similar scenarios have been demonstrated previously for coupled systems of nonlinear Schrödinger and Hirota equations. Both real- and complex-valued modified Korteweg–de Vries equations will be treated, which are applicable to stratified fluids and optical waveguides, respectively. One special family of breathers for coupled, complex-valued equations is derived analytically. Robustness and stability of breathers are studied computationally. Knowledge of the growth rates of modulation instability of plane waves provides an instructive prelude on the robustness of breathers to deterministic perturbations. A theoretical formulation of the linear instability of breathers will involve differential equations with periodic coefficient, i.e., a Floquet analysis. Breathers associated with larger eigenvalues of the monodromy matrix tend to suffer greater instability and increased tendency of distortion. Predictions based on modulation instability and Floquet analysis show excellent agreements. The same trend is obtained for simulations conducted with random noise disturbances. Linear approaches like modulation instabilities and Floquet analysis, thus, generate a very illuminating picture of the nonlinear dynamics. [ABSTRACT FROM AUTHOR]

This paper proposes a quick and straightforward technique for estimating the insertion loss (IL) of earplugs measured on an acoustical test fixture (ATF) using a commercial impedance tube. In this method, the earplug's acoustic properties (i.e., its transmission loss and the reflection coefficient of its medial surface) are determined from its transfer matrix measured using the three-microphones impedance tube method modified here for the current application. The IL is then estimated using a one-dimensional analytical model of open and occluded earcanals based on the wavefield decomposition theory. The method is evaluated numerically and experimentally from 50 Hz to 6.5 kHz. The numerical study allows for verifying the accuracy of the proposed approach in comparison to a simplified model of an ATF earcanal excited by normal incidence plane wave and diffuse field excitation. The experimental evaluation, which involves six earplugs (including five commercially available ones) representing various earplug families, demonstrates the accuracy of the estimation method, yielding results with a maximum difference of 3 dB compared to ATF measurements, on average, among the tested earplugs. [ABSTRACT FROM AUTHOR]

In this paper, an ultrasound beamforming method for plane wave (PW) imaging based on modified sidelobe blanking (MSLB) is proposed to improve image resolution and contrast ratio (CR). In this framework, PWs from various angles were designed to create main and auxiliary beamformer signals. Specifically, the PW signals from all angles were first coherently combined to serve as the main beamformer output signals. To prevent excessive clutter and noise, output signals in the main beamformer were weighted by the generalized coherence factor. Subsequently, the PW signals were split into positive and negative angles to perform a subtraction, creating the auxiliary beamformer. Finally, signals in the main beamformer were compared with the signals in the auxiliary beamformer point by point to further eliminate the noises and clutters. Compared with the delay and sum, full width at half maximum of the MSLB for point targets was reduced by an average of 54.17% and 51.65% in simulations and experiments, respectively; and the corresponding CR was improved by 55.38% and 18.40% on average. The MSLB method provided better imaging quality in human carotid arteries. In conclusion, the proposed method can effectively improve image resolution and CR with low computational complexity. [ABSTRACT FROM AUTHOR]

The enhancement of scattered field from cylindrical structures in the presence of SPP waves is analyzed. The SPP waves are excited using the Turbadar-Kretschmann-Raether (TKR) configuration and a cylindrical wave approach (CWA) is implemented to obtain the scattered field. Different arrangements such as a corner reflector and a strip are simulated by means of multiple circular cylinders. It is noted that the back-scattered field from the strip is very strong and can be one of the main challenges in plasmonic communication. Moreover, the simulations give the idea that what combination of structure size and distance from the interface does not produce significant scattering for both the strip and corner reflector. To better understand the phenomenon, and to provide a good insight, two-dimensional near zone field maps are generated to observe field in the vicinity of the object. In the presence of SPP waves, simulations show strong field near the edges like dipole field which is contrary to usual scattering in the absence of SPP waves for a plane wave illumination. [ABSTRACT FROM AUTHOR]

While using the subway brings people convenient transportation, The low frequency vibration caused by metro is one of the factors that seriously threaten the physical and mental health of human beings and the working environment. Phononic crystals structure and elastic metamaterials have been favored for the past few years because of their excellent low frequency vibration control properties. In this paper, based on local resonance theory, an elastic metamaterial thick plate structure is designed to attenuate low frequency vibration. Through plane wave expansion method and numerical simulation, the dispersion curve and reduced vibration effect of the thick plate structure are simulated and analyzed, and it is proved that the elastic metamateric thick plate structure opens the bend wave band gap range of 36–110 Hz within the limits of lower frequency below 150 Hz. Finally, a kind of new lower frequency vibration isolation thick plate barrier is designed to minish the effect of low-frequency vibration, which has a potential engineering application foreground in the field of low-frequency vibration control and isolation of subway. [ABSTRACT FROM AUTHOR]

This paper studies the characteristics of internal waves induced by the motion of a submerged body through a combination of experimental and numerical methods. First, by deploying an array of conductivity probes in an experiment, the temporal evolution of the internal wave at the plane of the conductivity probe array is obtained and compared with numerical simulation results based on the Navier–Stokes equations, thereby validating the accuracy of the Computational Fluid Dynamics (CFD) model. Subsequently, utilizing CFD calculations, further exploration is conducted on the spatiotemporal distribution characteristics of the internal wave, encompassing its generation and evolution, velocity field distribution, wake angle, and wave profile features. Finally, the variation of the internal wave with the Froude number (Fr) is investigated, revealing that it varies apparently with Fr, including the wave component, wave mode, wake length, wake angle, wave amplitude, and so on. It is found that when Fr is large, the internal wave converges toward the centerline behind the body, until forming a line. The wave magnitude changes with Fr in four stages, i.e., increasing with Fr from zero in the first stage, reaching a peak and decreasing thereafter in the second stage, then changing little in the third stage, and finally increasing approximately linearly in the fourth stage. [ABSTRACT FROM AUTHOR]

Passive source detection is a challenging problem in the shadow zone, where the sound is contributed primarily by bottom‐bounce rays. The conventional beamforming detector (CBFD), which utilises the sound energy from a single direction, suffers potential significant performance degradation in the multipath‐signal scenario. The matched field detector (MFD) offers optimal performance by exploiting full‐wave field characteristics but is limited due to its reliance on prior ocean environmental knowledge. The authors demonstrate that the incident sound on a near‐surface vertical line array in the shadow zone can be approximated as a coherent sum of two plane waves that share a symmetric arrival angle about the horizontal. This leads to the signal subspace depending only on the arrival angle, which the authors call the bottom‐bounce ray angle subspace (BRAS). With generalised likelihood ratio test theory, the authors further derive the BRAS detector (BRASD). It can utilise the full signal energy under the premise of weak environmental knowledge requirements and is generally superior to the CBFD. Simulation results in a typical deep‐water channel under different source‐position and array configuration conditions demonstrate the effectiveness of the BRASD and suggest that it can even offer a performance comparable to that of the MFD under specific conditions. [ABSTRACT FROM AUTHOR]

This manuscript studies the exact solitary wave profiles for the conformable Schrödinger–Poisson dynamical system. This system has a significant role in gravity's quantum state operation approximates the interaction between quantum mechanics and gravitation. The diverse exact solitary wave profiles are constructed by using the Khater method. The different closed-form solutions are obtained such as dark, singular, hyperbolic, periodic, and plane waves. Moreover, the modulation instability is also discussed for this dynamical system. To, show the physical significance of desired results we plot the 3D and 2D plots along with the related contour graphs, which are also drawn. The constraint criteria for the exact solutions are also exposed. [ABSTRACT FROM AUTHOR]

Relativistic electromagnetic plasma waves are described by a dynamical equation that can be solved not only in terms of plane waves, but also for several different accelerating wavepacket solutions. Depending on the spatial and temporal dependence of the plasma frequency, different kinds of accelerating solutions can be obtained, for example, in terms of Airy or Weber functions. Also, we show that an arbitrary accelerated wavepacket solution is possible, for example, for a system with a luminal plasma slab. [ABSTRACT FROM AUTHOR]

The selective control and manipulation of nanoparticles require developing and researching new methods for designing optical tweeters, mainly based on a photonic hooks (PHs) effect. This paper first proposes a tunable PH in which a structured beam illuminates an anisotropic cutting liquid crystal microcylinder based on the Finite-DifferenceTime-Domain (FDTD) method. The PHs generated by plane wave, Gaussian, and Bessel beam are analyzed and compared. The impact of beams and LC particle parameters on the PHs are discussed. Where the influence of the extraordinary refractive index ( n e ) on PHs is emphasized. Our results reveal that introducing birefringence can change the bending direction of PH. Besides, the maximum intensity of the PHs increases as n e increases regardless of the beam type. The PH generated by a plane wave has a higher maximum intensity and smaller FWHM than that generated by the Gaussian and Bessel beams. The smallest FWHM and maximum intensity of the PHs generated by the Gaussian falls between that generated by the plane wave and the Bessel beam. The PH generated by a Bessel beam has the minor maximum intensity and the largest FWHM. Still, it exceeds the diffraction limit and exhibits bending twice due to its self-recovery property. This paper provides a new way to modulate PH. This work offers novel theoretical models and the degree of freedom for the design of PHs, which is beneficial for the selective manipulation of nanoparticles. It has promising applications in Mesotronics and biomedicine. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to determine the optimum and fine values of the number and transmission angles of tilted plane waves for coherent plane‐wave compounding (CPWC)‐based high local pulse wave velocity (LPWV) estimation. Methods: A Verasonics system incorporating a linear array probe L14‐5/38 with 128 elements and a pulsatile pump, CompuFlow1000, were used to acquire radio frequency data of 3, 5, 7, and 9 tilted plane wave sequences with angle intervals from 0° to 12° with a coarse interval increment step of 1°, and the angle intervals from 0° to 2° with a fine interval increment step of 0.25° from a carotid vessel phantom with the LPWV of 13.42 ± 0.90 m/s. The mean value, standard deviation, and coefficients of variation (CV) of the estimated LPWVs were calculated to quantitatively assess the performance of different configurations for CPWC‐based LPWV estimation. Ten healthy human subjects of two age groups were recruited to assess the in vivo feasibility of the optimum parameter values. Results: The CPWC technique with three plane waves (PRF of 12 kHz corresponding to a frame rate of 4000 Hz) with an interval of 0.75° had LPWVs of 13.52 ± 0.08 m/s with the lowest CV of 1.84% on the phantom, and 5.49 ± 1.46 m/s with the lowest CV of 12.35% on 10 subjects. Conclusions: The optimum parameters determined in this study show the best repeatability of the LPWV measurements with a vessel phantom and 10 healthy subjects, which support further studies on larger datasets for potential applications. Access the CME test here and search by article title. [ABSTRACT FROM AUTHOR]

An epoxy-based metamaterial plate structure with local resonance is designed in this paper. The bandgap of the bending wave ranges from 36.46Hz to 110.55Hz. Through the optimization design of the oscillators in the plate structure, the starting bandgap moves to 19.79Hz, and the band gap width is 72Hz. The dispersion curve and frequency response function were calculated by finite element method (FEM). On this basis, the plane wave expansion method formula of the structural model was derived, and the equivalent model of spring-mass model was established. The results show that the calculation results of the three methods of the epoxide metamaterial plate structure were basically consistent, and the correctness of these methods was verified mutually. The methods derived in this paper bring great convenience and diversity to the application of plate structure. The article proposes a low-frequency wide bandgap thick plate structure model. [ABSTRACT FROM AUTHOR]

A number of previous papers have used the coupled-mode method to assess three-dimensional scattering by cylindrically symmetric anomalies (seamounts, hills) or anomalies which are invariant in a horizontal direction (wedges, ridges). This paper makes an extension to combinations of these two anomaly types. The upper and lower depth boundaries of the anomalies may be flat or irregular, and the sound source may be anywhere in the medium. After a discretization of the anomalies of the two types with laterally homogeneous rings and strips, respectively, an adaptation of the coupled-mode method yields the solution of the pertinent Helmholtz equation. The adaptation involves a combination of Fourier-series summations to handle the ring anomalies and adaptive wavenumber integrations to handle the strip structure. For each anomaly, recursively computed reflection matrices relate the expansion coefficients for incoming and outgoing normal modes. Iterative solution of a linear equation system for the amplitudes of the scattered cylindrical waves from the ring anomalies, involving formulas for transformation between plane and cylindrical waves, yields an expansion of the field. Related expansions allow isolation of partial waves, multiply scattered among the anomalies. The paper includes examples from underwater acoustics and atmospheric acoustics. [ABSTRACT FROM AUTHOR]

The purpose of this study is to analyze the features of a moving Griffith crack in an initially stressed infinitely long and finitely thick isotropic strip with moving parallel punches of constant load acting on its boundaries owing to plane wave propagation under point loading. Coupled singular integral equations and singularities of the Cauchy-type are used to formulate the present model, Dirac delta function is employed to analyze point load located at the moving crack edge, and Hilbert transformation properties are used for obtaining stress intensity factor (SIF) with constant point loading. Numerical simulations and graphical illustrations are performed to analyze the influences of the prevalent parameters, viz. initial stresses, punch pressure, distinct positions of point load, length and speed of the crack on the SIF for the considered isotropic material strip. [ABSTRACT FROM AUTHOR]

This paper presents simple numerical solutions for electromagnetic plane waves in spatially homogenous time varying medium. The solution is based on converting the resulting second order differential equation into two combined ordinary differential equations which are solved numerically by using the built-in ode113 function in Matlab. By using this method, the time domain responses of the electric and magnetic fields at fixed point in space are obtained. The proposed method is applied on two cases: linearly time varying medium and sinusoidally time varying medium. The corresponding frequency domain response is obtained by using inverse Fourier transformation of the obtained time domain response. The proposed method is compared with FDTD solution. It is found that the proposed method has the same accuracy of FDTD with much less computational time. [ABSTRACT FROM AUTHOR]

A horizontal towed linear coherent hydrophone array is often employed to estimate the spatial intensity distribution of incident plane waves scattered from the geological and biological features in an ocean acoustic waveguide using conventional beamforming. However, due to the physical limitations of the array aperture, the spatial resolution after conventional beamforming is often limited by the fat main lobe and the high sidelobes. Here, we propose a method originated from computer vision deblurring based on deep learning to enhance the spatial resolution of beamformed images. The effect of image blurring after conventional beamforming can be considered a convolution of beam pattern, which acts as a point spread function (PSF), and the original spatial intensity distributions of incident plane waves. A modified U-Net-like network is trained on a simulated dataset. The instantaneous acoustic complex amplitude is assumed following circular complex Gaussian random (CCGR) statistics. Both synthetic data and experimental data collected from the South China Sea Experiment in 2021 are used to illustrate the effectiveness of this approach, showing a maximum 700% reduction in a 3 dB width over conventional beamforming. A lower normalized mean square error (NMSE) is provided compared with other deconvolution-based algorithms, such as the Richardson–Lucy algorithm and the approximate likelihood model-based deconvolution algorithm. The method is applicable in various acoustic imaging applications that employ linear coherent hydrophone arrays with one-dimensional conventional beamforming, such as ocean acoustic waveguide remote sensing (OAWRS). [ABSTRACT FROM AUTHOR]

Various engineering equipments and devices use elastic vibrations and acoustic waves extensively for non-destructive testing and technical diagnostics of various materials and products. The propagation characteristics of plane and Rayleigh-type surface waves in an incompressible transversely isotropic diffusive material are investigated in context of nonlocal elasticity theory. The governing equations of motion for the medium are specialized in a plane and solved for time-harmonic solutions. A velocity equation for homogeneous plane wave is obtained which indicates the existence of two plane transverse waves. The two-dimensional equations are also solved for surface wave solutions and a Rayleigh characteristic equation is obtained. A numerical example is taken to illustrate graphically the effects of nonlocality, diffusion and material anisotropy parameters on the speeds of plane and Rayleigh surface waves. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the current manuscript is to investigate the reflection of plane waves in a rotating, two-dimensional homogeneous, initially stressed, nonlocal orthotropic thermoelastic solid half-space based on dual-phase-lag model. Design/methodology/approach: The reflection phenomenon has been utilized to study the effects of initial stress, rotation and nonlocal parameter on the amplitude ratios. During the reflection phenomenon three coupled waves, namely quasi displacement primary wave (qP), quasi thermal wave (qT) and quasi displacement secondary wave (qSV) have been observed in the medium, propagating with distinct velocities. After imposing the suitable boundary conditions, amplitude and energy ratios of the reflected waves are obtained in explicit form. Findings: With the support of MATLAB programming, the amplitude ratios and energy ratios are plotted graphically to display the effects of rotation, initial stress and nonlocal parameters. Moreover, the impact of anisotropy and phase lags is also observed on the reflection coefficients of the propagating waves. Originality/value: In the current work, we have considered rotation and nonlocality parameters in an initially stressed orthotropic thermoelastic half-space, which is lacking in the published literature in this field. The introduction of these parameters in a nonlocal orthotropic thermoelastic medium provides a more realistic model for these studies. The present work is valuable for the analysis of orthotropic thermoelastic problems involving rotation, initial stress and nonlocality parameters. [ABSTRACT FROM AUTHOR]

The objective of this empirical investigation is to explore the behavior of different waves reflected in a homogenous isotropic double porous structured micropolar thermoelastic medium with rotation and temperature‐dependent characteristics. Three‐phase‐lag theory of thermoelasticity is adopted to acquire the governing equations of the model. Six coupled plane waves have been found to propagate across the medium at distinct velocities. Derivation for energy and amplitude ratios of reflected waves were carried out by employing appropriate boundary conditions. For different angles of incidence, the outcomes for energy partition were determined numerically and displayed graphically. It is found that amplitude ratios associated with various reflected waves are affected by angular velocity, temperature‐dependent properties, micropolar parameter, and double porosity. Also, it has been discovered that throughout the reflection phenomena there is no dissipation of energy. Furthermore, this study concludes with a summary of the findings and subsequent observations. The current investigation has yielded inferences regarding specific cases that are of particular interest. [ABSTRACT FROM AUTHOR]

In this paper, we study a split-step Galerkin finite element (FE) method for the two-dimensional Riesz space-fractional coupled nonlinear Schrödinger equations (CNLSs). The proposed method adopts a second-order split-step technique to handle the nonlinearity and FE approximation to discretize the fractional derivatives in space, which avoids iteration at each time layer. The analysis of mass conservative and convergent properties for this split-step FE scheme is performed. To test its capability, some numerical tests and the simulation of the double solitons intersection and plane wave are carried out. The results and comparisons with the algorithm combined with Newton's iteration illustrate its effectiveness and advantages in computational efficiency. [ABSTRACT FROM AUTHOR]