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Sub-diffraction needle beams with high intensity, sub-diffraction focal size, and long depth of focus (DOF) have attracted many researchers' attention. However, the traditional methods for needle beam generation typically require many devices, such as phase elements, amplitude filters, and lens, which leads to a complex and bulky system and unfavorable for their integration. To address these challenges, we use a single multifunctional transmissive metasurface to convert a linearly polarized plane wave into a needle beam in the microwave range. The guided wave inspired unit cells of the proposed metasurface is designed to simultaneously and independently modulate the polarization and phase of transmitted waves. By imposing the desired polarization and phase distributions on the metasurface, the proposed multifunctional transmissive metasurface can efficiently generate a needle beam with subdiffraction size and extended DOF at 10 GHz when it is illuminated by an x-polarized wave. The proposed metasurface is fabricated, and a sub-diffraction needle beam with good performance is obtained in our measurements. In addition, a proof-of-concept of a high-resolution nondestructive testing experiment based on our designed metasurface is accomplished. Our work is expected to have potential applications in nondestructive testing of materials and structures. [ABSTRACT FROM AUTHOR]

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]

Pyrochlore oxides, specifically G d 2 Z r 2 O 7 , have been a subject of interest due to their unique structural, physical, and magnetic properties. These properties make pyrochlore oxides potential candidates for various technological applications, including magnetocaloric refrigeration. Magnetocaloric refrigeration is a promising alternative to conventional refrigeration methods, as it is more energy-efficient and environmentally friendly. By studying the magnetocaloric effect of pyrochlore oxides like G d 2 Z r 2 O 7 , researchers can gain a deeper understanding of the underlying mechanisms and potential applications of these materials in magnetocaloric refrigeration systems. By employing advanced computational methods such as Monte Carlo simulations and first-principles calculations based on the full-potential linearized augmented plane wave (FP-LAPW) a technique is employed to examine the magnetic structure, researchers can investigate the magnetocaloric effect of pyrochlore oxides with high accuracy and precision. This information has the potential to aid in the advancement of more effective magnetocaloric systems materials and ultimately lead to the design and optimization of advanced magnetocaloric refrigeration systems. [ABSTRACT FROM AUTHOR]

This study uses the triple-phase lag model to investigate how higher-order fractional order and memory-dependent derivatives affect reflection at the free surface of an orthotropic piezo-thermoelastic medium. The performance of both kinds of derivatives is studied using the normal mode analysis technique. Four different types of coupled reflected plane waves are identified and explore the impact of various parameters, fractional order parameter, kernel function, the higher-order time differential fractional, and memory-dependent heat conduction parameters on energy distribution with respect to the angle of incidence. The results are presented graphically, providing numerical data for reflected waves, amplitude, and energy ratios. [ABSTRACT FROM AUTHOR]

In this study, a simplified model for the pile-type composite ground, namely, the periodic pile-type composite ground (PPCG) model is proposed. The PPCG in this study is assumed to be periodic in the horizontal directions and finite in the vertical direction. For investigation of the dynamic response of the PPCG to a harmonic concentrated load, a plane wave finite element (PWFE) method for the PPCG under the load is developed in this study. To develop the method, the concentrated load is decomposed into its wavenumber domain components by the 2D Fourier transform first. The response of the PPCG to a wavenumber domain load component is represented by a set of plane waves, and the variables associated with each plane wave are discretized via the FEM along the vertical direction of the PPCG. The finite element equations for each plane wave of the PPCG are developed via the virtual work principle. To obtain the overall dynamic response of the PPCG to the concentrated load by synthesizing the responses due to all load components effectively, the mode superposition method is used to construct the response of the PPCG to the load component, and the polar coordinate system-based inverse Fourier transform method is developed for the inversion of the 2D Fourier transform with respect to the wavenumber. With the developed method, some numerical results about the dynamic response of the PPCG to the concentrated load are presented. [ABSTRACT FROM AUTHOR]

The exact solutions for the Navier–Stokes–Fourier equations in the case of plane shock waves for dilute monatomic gases with constant transport coefficients were found by Becker in 1922. The solutions obtained are limited for a Prandtl's number given by Pr=3/4$Pr=3/4$. Besides the solutions for the speed and temperature, profiles were given in an implicit way. In this paper, we consider Becker's model to find some exact explicit solutions for dilute polyatomic gases. [ABSTRACT FROM AUTHOR]

Piezothermoelasticity and wave interaction studies hold immense significance in designing functional devices ranging from transducers to sensors for a variety of purposes like energy harvesting and structural health monitoring. These applications catalyze interest in this article which addresses the problem of reflection of plane wave at the boundary of piezothermoelastic half-space. Through this study, the effect of impedance parameter on amplitude and energy ratios of the reflected waves is studied. Four wave modes are indicated upon reflection and a linear system of equations is formed to obtain a closed-form expression for amplitude and energy ratios. These equations are solved by suitable mathematical tools leading to expression for amplitude ratios as a function of incidence angle. For a suitable piezothermoelastic medium, the ratios are plotted against incidence angle and the findings are compared for two well-known theories of thermoelasticity, namely, Lord–Shulman (LS theory) and Green–Lindsay (GL theory). The analytical outcomes suggest approximate values of impedance and incidence angle for preferred energy division between reflected waves. It is recognized that adding impedance increases the amplitude of the quasi-longitudinal (qP) wave and decreases that of the quasi-transverse wave, making it suitable for devices that require a more robust qP wave signal detection. [ABSTRACT FROM AUTHOR]

The optical properties of TiO2 are changed while doped with impurity atoms. This paper made a systematical calculation of the bandgap, the density-of-states (DOS), the optical properties for pure TiO2, and Bi-doped anatase TiO2 according to the first-principles plane wave ultrasoft pseudopotential method which is primarily based on the density functional theory (DFT). The calculation results exhibit that the bandgap decreased after doping, and the impurity energy level is produced into the bandgap of Bi-doped TiO2, which makes red-shift for the absorption band edge of Bi-doped TiO2 and the absorption is enhanced more in the visible light range. [ABSTRACT FROM AUTHOR]

In this study, we are analyzing the effect of the Hilbert Transform (HT) on diffraction of a plane wave by an oscillating half-plane. Both the incident wave and oscillating half-plane have different oscillating frequencies. After the necessary mathematical computations for several types of time-dependent oscillating functions, it is verified graphically that the HT induces a shift of 90 ∘ , which can be observed from the flipping effect in the magnitude of the sinusoidal components occurring in their respective diffracted fields. Graphical illustrations presenting the effects of the HT are presented and discussed. [ABSTRACT FROM AUTHOR]

The optical properties of TiO2 are changed while doped with impurity atoms. This paper made a systematical calculation of the bandgap, the density-of-states (DOS), the optical properties for pure TiO2, and Bi-doped anatase TiO2 according to the first-principles plane wave ultrasoft pseudopotential method which is primarily based on the density functional theory (DFT). The calculation results exhibit that the bandgap decreased after doping, and the impurity energy level is produced into the bandgap of Bi-doped TiO2, which makes red-shift for the absorption band edge of Bi-doped TiO2 and the absorption is enhanced more in the visible light range. [ABSTRACT FROM AUTHOR]

Considering the significant impact of anisotropy on forward and inversion results, this paper presents a research study on tensor controlled-source audio magnetotellurics (CSAMT) forward modeling in axis anisotropic media. In this study, the tensor resistivity of axis anisotropic medium is introduced according to the control equation of electric field with sources. The total electric field is decomposed into primary and secondary fields, with the primary field obtained using Key's algorithm and the secondary field calculated using the finite difference method. This approach enables three-dimensional (3D) modeling of tensor CSAMT in axis anisotropic media. The correctness of the algorithm is verified by comparing it with the results obtained using a two-dimensional (2D) finite element algorithm. Several sets of axis anisotropic 3D models are designed, and the response characteristics of anisotropic target bodies to plane waves and non-plane waves are summarized. The findings indicate that the Cagniard resistivity and tipper are sensitive to changes in the X and Y directions of the anomaly, but not sensitive to changes in resistivity in the Z direction. Additionally, in the near region, non-plane wave CSAMT signals may cause distortion in the Cagniard resistivity. The results highlight that tensor CSAMT has the capability to detect changes in resistivity in two-axis directions (X and Y), providing greater exploration advantages compared to scalar CSAMT. This study provides a foundation for the forward modeling and inversion of tensor CSAMT in arbitrary anisotropic media. [ABSTRACT FROM AUTHOR]

In the context of the triple-phase lag model, comparison studies are conducted between the memory-dependent derivative and fractional order derivative on the propagation of plane waves in a half-space of initially stressed transversely isotropic piezothermoelastic material. The coupled governing equations of the considered model involving relaxation time, time delay, fractional order parameter, and kernel function are selected according to specific problems and solved using the normal mode analysis technique and obtaining the analytical expression. The non-dimensional temperature, displacement, electrical displacements, and stresses at different values of the fractional order parameter and time delay factor are obtained graphically. [ABSTRACT FROM AUTHOR]

The electronic, magnetic and optical properties of the double perovskites Ca2NiOsO6 and Fe-doped derivative were calculated using the full potential linearized augmented plane wave technique through the GGA + U with PBE exchange correlation functionals. The calculations show that both of the systems are half-metallic with Fe-doped system as a ferromagnet, whereas the undoped system shows the ferrimagnetic ordering. Additionally, the study is extended for calculating the Mott parameters through dynamical mean field theory (DMFT) with the maximum entropy model (MEM). It is found that the MIT model parameters (U, β) for Ca2NiOsO6 and Ca2Fe 0. 5 0 Ni 0. 5 0 OsO6 systems are (5.7 eV, 6.0 (eV) − 1 ) and (6.0 eV, 6.0 (eV) − 1 ), respectively. Furthermore, the calculations agree with optical Drude peak analysis. The optical conductivity, reflectivity, absorptivity, ELOSS function, dielectric function refractive index and sum-rule are also explored in relation to the photoinduced behaviors of the materials. [ABSTRACT FROM AUTHOR]

Last December 27th, 2023, Ebru Cavlak Aslan et al. have published the article in the Journal "Optical and Quantum Electronics" the article titled "Analysing of different wave structures to the dissipative NLS equation and modulation instability" (Opt Quantum Electron 56:254, 2024. https://doi.org/10.1007/s11082-023-06035-6) where they tried to present analytical solutions of a dissipative nonlinear Schrödinger equation and study the modulational instability of the continuous wave solution of that equation. After analyzing their results, we found a number of shortcomings about both the modulational instability study and the analytical solutions. For analytical solutions, we found that all their found exact solutions were about the standard nonlinear Schrödinger equation and may contain errors/mistakes since at least one of their found dark soliton solutions was done in the region of modulational instability of the standard nonlinear Schrödinger equation. We also found that all their results about the modulational instability were obtained on an erroneous plane wave solution of their model equation, leading thus to obsolete results. It is the aim of the present comment to correct all shortcomings found in that study on the modulational instability. [ABSTRACT FROM AUTHOR]

Acoustical parameter estimation is a routine task in many domains. The performance of existing estimation methods is affected by external uncertainty, yet the methods provide no measure of confidence in the estimates. Hence, it is crucial to quantify estimate uncertainty before real-world deployment. Conformal prediction (CP) generates statistically valid prediction intervals for any estimation model using calibration data; a limitation is that calibration data needed by CP must come from the same distribution as the test-time data. In this work, we propose to use CP to obtain statistically valid uncertainty intervals for acoustical parameter estimation using a data-driven model or an analytical model without training data. We consider direction-of-arrival estimation and localization of sources. The performance is validated on plane wave data with different sources of uncertainty, including ambient noise, interference, and sensor location uncertainty. The application of CP for data-driven and traditional propagation models is demonstrated. Results show that CP can be used for statistically valid uncertainty quantification with proper calibration data. [ABSTRACT FROM AUTHOR]

Using finite element simulation, we study the main features of rotating wave solutions of the cubic complex Ginzburg–Landau equation. To focus on the characteristics of the waves themselves, we have used a circular domain to avoid the effects of irregular boundaries; we have inhibited the formation of defects using an Archimedean wave centered at the origin as the initial condition, and we have chosen a domain size long enough to contain several spiral arms but not so long as to promote long-wave instabilities. This allows us to focus on the geometric features of the solutions often overlooked in traditional works with random initial conditions in large domains. We show with our simulations that the convective and absolute stabilities differ from those predicted for plane waves. Likewise, we show that the appearance of spirals and anti-spirals can occur in any of the quadrants of the parameter space and depends fundamentally on the initial conditions. Finally, regarding the stability of spiral waves against sideband disturbances, we show that the persistence of two-dimensional spiral waves, if fulfilled, does not correspond to the Eckhaus criterion. Our simulations allow us to corroborate the idea that two-dimensional spirals depend on the size of the domain and that they require new analytical results whose trends are identified in this work. [ABSTRACT FROM AUTHOR]

This paper presents a low‐scattering 1 × 2 patch array antenna combining resistive and coding metasurfaces (MSs) for the reduction of wideband‐backscatter. An artificial magnetic conductor technology is used to validate the proposed technique, which is fundamentally based on scattering, phase cancellation, and absorptive property of the MS. By integration of coding MS elements and an absorbent unit cell, three different array blocks are utilized to significantly reduce the monostatic and bistatic backscattered energy level from 6.5 to 16.5 GHz, as well as overall reduction from 5 to 22 GHz. Under the incidence of plane waves, various reflection phases have been observed. The diffusion of the scattering energy from the surface can be achieved by carefully choosing the phase distributions for the reflected waves. Additionally, the bistatic backscattered energy level of the prototype is realized at various frequency points. This technique is validated using artificial magnetic conductors, which uniquely combine the effects of scattering, phase cancellation, and absorption in the MS's hybrid unit cells. Further, antenna array parameters are optimized for frequency, polarization, and angular diversity, S‐parameters, radiating efficiency, reducing radar cross section (RCS) in the wideband range and ensuring robust performance. The experimental results were substantiated by simulations of the reference and proposed prototypes suggesting that the proposed prototype can be a good candidate for applications that require a low monostatic and bistatic RCS platform. [ABSTRACT FROM AUTHOR]

In this letter, the realization of minimizing the scattering of the Ku band is investigated by designing a two-dimensional gradient-index metasurface to control the propagation of the incident waves. Through the gradient phase design, the maximum RCS reduction was observed at 14 GHz, the x-polarized plane wave exhibits an RCS reduction of 15.43 dB, while the y-polarized plane wave shows an RCS reduction of 13.13 dB compared to the same size of PEC. The proposed metasurface with low backward RCS shows the capability to scatter the incident plane wave in different directions at both normal and oblique incidence. According to equation 2, by calculating the variable phase distribution of large-scale arrays at different frequencies, the maximum reduction of RCS can be obtained at any frequencies. Therefore, this work effectively designs and suggests the research of low RCS metasurface at different frequencies. [ABSTRACT FROM AUTHOR]

Context and results: The structure, mechanical, electronic, vibration, and hydrogen bonding properties of a novel high-energy and low-sensitivity 5, 5′-dinitroamino-3, 3′-azo-oxadiazole 4, 7-diaminopyridazino [4, 5-c] furoxan salt have been studied by density functional theory. The calculated vibrational properties show that the low-frequency mode is mainly contributed by the vibration of the -NO2 group, and the high-frequency mode is mainly contributed by the vibration of the -NH2 group and the N7-H3 bond which protonates the cation. In addition, it is analyzed that the first bond to break may be the N-NO2 bond. The calculated hydrogen bond properties indicate that the hydrogen bond between water molecules and cations is N7-H3... O5 (1.563 Å), which is the shortest hydrogen bond among all hydrogen bonds. The presence of this exceptionally short hydrogen bond renders the N7-H3 and H6-O5 bonds resistant to disruption at high frequencies, underscoring the pivotal role of hydrogen bonding in stabilizing the structure of energetic materials. Given the absence of experimental and theoretical data on the electronic, mechanical, and vibrational properties of the material thus far, our calculations offer valuable theoretical insights into the ionic salts of high energy and low sensitivity. Computational methods: All calculations have been carried out based on density functional theory (DFT) and implemented in the CASTEP code. The mode-conserving pseudopotential is utilized to describe the plane wave expansion function, while the PBE functional within the generalized gradient approximation (GGA) is employed to characterize the exchange–correlation interaction. Additionally, dispersion correction is applied using Grimme's DFT-D method. [ABSTRACT FROM AUTHOR]

The second-order gradient theory is reliable to predict the behavior of mechanical phenomena such as wave scattering, vibration, and buckling in nano/micro-structures. This theory incorporates size-dependent effects including strain-gradient elasticity and micro-inertia, crucial for constitutive modeling of piezomagnetic-flexomagnetic crystals. These small-scale size effects can have significant impact on the sensing mechanism of nanoscale transducers used in structural health monitoring (SHM) and nondestructive testing (NDT). In this article, we address the scattering of a plane wave (P-type longitudinal wave) in a piezomagnetic-flexomagnetic solid halfspace after it reflects from an open surface. The secular equation of quasi plane (qP) wave and multiple wave modes generated after reflection have been obtained analytically using non-classical governing equations. Impedance boundary conditions have been considered and conventional stress-free boundary conditions have been obtained as its case. Unlike a conventional piezomagnetic medium, five different wave modes have been traced after reflection (two different surface wave modes are present due to the gradient elasticity and micro-inertia effect). Closed expressions of amplitude ratios and energy flux ratios of reflected waves have been formulated from the system of linear equations. By taking a suitable numerical example, amplitude ratios and energy flux ratios for reflected waves have been plotted with respect to incidence angle. Detailed discussions have been made to understand the influence of impedance boundary and flexomagnetic effect on those ratios. The numerical results have been validated by energy conservation law. This investigation may provide necessary guidelines to understand the plane wave characteristics in micro-structural smart solid structures. [ABSTRACT FROM AUTHOR]

In this study, the influence of temperature and hydrostatic pressure on impurity states in InxGa1-xAs/GaAs quantum wells (QWs) with different shapes, including square, parabolic, and V-shaped, was investigated using the effective mass envelope function approximation and the plane wave expansion method. The results demonstrate that an increase in temperature leads to a decrease in the energy of the impurity states, while an increase in hydrostatic pressure causes the impurity state energy to rise. It was observed that the effect of hydrostatic pressure on the impurity states is more significant than that of temperature. Furthermore, the impact of temperature and hydrostatic pressure varies depending on the shape of the QWs. Additionally, as the In composition increases, the impurity states exhibit a gradual increasing trend. [ABSTRACT FROM AUTHOR]

Synthetic aperture interferometry (SAI) is a signal processing technique that mixes the signals collected by pairs of elementary antennas to obtain high-resolution images with the aid of a computer. This note aims at studying the effects of the distance between the synthetic aperture interferometer and an observed scene with respect to the size of the antenna array onto the imaging capabilities of the instrument. Far-field conditions and near-field ones are compared from an algebraic perspective with the aid of simulations conducted at microwave frequencies with the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS) onboard the Soil Moisture and Ocean Salinity (SMOS) mission. Although in both cases the signals kept by pairs of elementary antennas are cross-correlated to obtain complex visibilities, there are several differences that deserve attention at the modeling level, as well as at the imaging one. These particularities are clearly identified, and they are all taken into account in this study: near-field imaging is investigated with spherical waves, without neglecting any terms, whereas far-field imaging approximation is considered with plane waves according to the Van–Citter Zernike theorem. From an algebraic point of view, although the corresponding modeling matrices are both rank-deficient, we explain why the singular value distributions of these matrices are different. It is also shown how the angular synthesized point-spread function of the antenna array, whose shape varies with the distance to the instrument, can be helpful for estimating the boundary between the Fresnel region and the Fraunhofer one. Finally, whatever the region concerned by the aperture synthesis operation, it is shown that the imaging capabilities and the performances in the near-field and far-field regions are almost the same, provided the appropriate modeling matrix is taken into account. [ABSTRACT FROM AUTHOR]

It is demonstrated that single‐crystalline and highly doped GaAs membranes are excellent candidates for realizing infrared‐transparent shields of electromagnetic interference at millimeter frequencies. Measured optical transmittance spectra for the semiconductor membranes show resonant features between 750 and 2500 nm, with a 100% maximum transmittance. The shielding effectiveness of the membranes is extracted from measured scattering parameters between 65 and 85 GHz. Selected GaAs membranes and membranes/polyamide films exhibit shielding effectiveness ranging from 22 to 40 dB, which are suitable values to ensure the safe operation of infrared devices for commercial applications. Theoretical calculations based on a plane wave model show that the interplay of primary reflection and multiple internal reflections of the radio‐frequency waves results in broadband shielding capabilities of the membrane between 10 and 300 GHz. [ABSTRACT FROM AUTHOR]

The present article is concerned with the reflection of plane harmonic waves in a nonlocal micropolar thermoelastic medium having void pores in the context of dual-phase-lag and Lord-Shulman models. Two sets of coupled shear waves and three sets of coupled longitudinal waves are shown to exist. When a coupled longitudinal displacement wave is made incident, the reflection coefficients of the various reflected waves and their respective energy ratios are computed analytically and the numerical computation is carried out with the help of MATLAB software. For a particular model, the influence of nonlocal, voids and micropolar parameters on the variations of reflection coefficients and energy ratios of various reflected waves is presented graphically. It is verified that during reflection phenomenon, the sum of energy ratios is equal to unity at each angle of incidence. A comparison between the dual-phase-lag model and Lord-Shulman model is also depicted graphically. [ABSTRACT FROM AUTHOR]

Research on intragranular acicular ferrite inclusions has demonstrated that high-melting-point oxide MgAl2O4 cores and composite inclusions precipitated by Ti2O3 adhesion can be used as effective nucleation particles in oxide metallurgy. However, the microscopic mechanism underlying this adsorption behavior remains unclear. Hence, in this study, the adsorption and polymerization mechanisms of Ti2O3 on the MgAl2O4(100)Mg- and MgAl2O4(111)O3(Mg)-terminal surfaces in steel were studied using first-principles calculations based on density functional theory. The calculation based on the first principles of DFT and performed by the CASTEP code under plane wave basis set. The exchange correlation energy and correlation effects were described by generalized gradient approximation (GGA) using the Perdew–Burke–Ernzerhof (PBE) function. Spin polarization was considered in all calculation. Ultrasoft pseudopotentials (USPP) was employed to describe the electron-ion interactions. The energy cutoff for the plane wave basis was set at 620 eV in the current work. For the Brillouin zone sampling, we carried out 3 × 3 × 3 k-points mesh for MgAl2O4 bulk using the method of Monkhorst-Pack. A vacuum layer of 20.0 Å is added above the top surface of MgAl2O4 to eliminate the interaction of the normal periodic repetition of the surfaces. In all the surface calculations, the use of symmetry in bulk crystal was failed and k-point grids is set to 3 × 3 × 1. The results of this study revealed that when the most stable adsorption positions of Ti2O3 on the surface of MgAl2O4(100)Mg- and MgAl2O4(111)O3(Mg)-terminal are located at TAl and FMg, the adsorption energy is the highest and the most stable. The most stable adsorption configurations are located on vertical and parallel (P1) surfaces. Through comparative analysis, the best surface for Ti2O3 adsorption was found to be the MgAl2O4(111)O3(Mg)-terminal surface, and the adsorption behavior mainly occurred on the first layer of atoms on the surface. The best adsorption configuration was P1, and the best adsorption mode occurred when Ti2O3 formed three rings connected in pairs with the surface and embedded in the surface of the MgAl2O4(111)O3(Mg)-terminal. This study provides insights into the adsorption polymerization mechanisms of MgAl2O4–Ti2O3 complex inclusions in steel that could facilitate the fabrication of novel low-melting-point oxides and sulfides. [ABSTRACT FROM AUTHOR]

Landslides and landslide-generated tsunami waves arbitrarily happen and cause tremendous hazards to human lives worldwide. Among the recent landslide tsunami events, the rigid submarine landslide sources are becoming more and more concerned due to their mysteries. Dynamical properties of rigid submarine landslides (e.g., velocity) play an important role in the generated tsunami waves. In this study, an empirical velocity profile of rigid submarine landslide-generated waves on an inclined plane is proposed. This new velocity profile is suggested from the velocity profile in a physical experiment of the horizontal rigid submarine landslidegenerated waves. A new FLOW-3D HYDRO package is employed to conduct the rigid submarine landslidegenerated waves experiment. We first verified the chosen numerical model to the experimental data of rigid submarine landslides moving horizontally. Following the rigid velocity profile on the horizontal plane, we propose a new method to apply it on the inclined plane. The error norm technique is used to find out the empirical velocity profile among 10 critical velocity profiles applied. The novel empirical velocity profile of the critical case of m = 3 as well as critical velocity value of Vc = 0.82 m/s is used to generate tsunami waves, which are in good agreement with the experimental data and better than those of other similar three-dimensional numerical models. [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]

Computational simulations of cardiac electrophysiology provide detailed information on the depolarization phenomena at different spatial and temporal scales. With the development of new hardware and software, in silico experiments have gained more importance in cardiac electrophysiology research. For plane waves in healthy tissue, in vivo and in silico electrograms at the surface of the tissue demonstrate symmetric morphology and high peak-to-peak amplitude. Simulations provided insight into the factors that alter the morphology and amplitude of the electrograms. The situation is more complex in remodeled tissue with fibrotic infiltrations. Clinically, different changes including fractionation of the signal, extended duration and reduced amplitude have been described. In silico, numerous approaches have been proposed to represent the pathological changes on different spatial and functional scales. Different modeling approaches can reproduce distinct subsets of the clinically observed electrogram phenomena. This review provides an overview of how different modeling approaches to incorporate fibrotic and structural remodeling affect the electrogram and highlights open challenges to be addressed in future research. [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]

It is widely acknowledged that the effects of soil-structure interaction (SSI) can have substantial implications during periods of intense seismic activity; therefore, accurate quantification of these effects is of paramount importance in the design of earthquake-resistant structures. The analysis of SSI is typically conducted using either direct or substructure methods. Both of these approaches involve the use of numerical models with truncated or reduced-order computational domains. To ensure effective truncation, it is crucial to employ boundary representations that are capable of perfectly absorbing outgoing waves and allowing for the consistent application of input motions. At present, such capabilities are not widely available to researchers and practicing engineers. In order to address this issue, this study implemented the Domain Reduction Method (DRM) and Perfectly Matched Discrete Layers (PMDLs) in OpenSees. The accuracy and stability of these implementations were verified through the use of vertical and inclined incident SV waves in a two-dimensional problem. In terms of computational efficiency, PMDLs require a shorter analysis time (e.g., with PMDLs, the analysis concluded in 35 min as compared to 250 min with extended domain method) and less computational power (one processor for PMDLs against 20 processors for the extended domain method) thus offering a balance between accuracy and efficiency. Furthermore, illustrative examples of the aforementioned implemented features are presented, namely the response analysis of single-cell and double-cell tunnels exposed to plane waves inclined at an angle. [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]

The biophysical properties of metoprolol are investigated by the full potential-linearized augmented plane wave method and molecular docking and molecular dynamic approaches. The exchange–correlation potentials are calculated by the Perdew–Burke–Ernzerhof generalized gradient approximation as implemented in the WIEN2k package. The electronic results show the insulator nature of metoprolol with the indirect bandgap of 3.74 eV between HOMO and LUMO states. In the density of state spectra, the p state of O, C, and N elements confirm the stability of metoprolol. Metoprolol exhibits a metallic behavior in the z direction, while it has a dielectric behavior in the x and y directions. The static refractive indices are obtained 1.49, 1.53, and 1.63 in the x, y, and z directions, respectively. It was found that the maximum reflectivity occurs at the ultraviolet region in the z-direction. The calculated absorption spectra also confirm the other's experimental results. The obtained results of molecular docking indicate the formation of hydrogen bonds between metoprolol and the beta-2 adrenergic receptors, and molecular dynamics showed a human beta-2 adrenoceptor either in its free state or in complex with a metoprolol molecule. The calculated binding energies of elements by molecular docking and the other biological properties of metoprolol by molecular dynamic are in close agreement with obtained Density Functional Theory (DFT) results for Pharmacia applications. [ABSTRACT FROM AUTHOR]

We perform the modulation instability analysis of the 2D and 3D nonlinear Klein–Gordon equation. The instability region depends on dispersion and wavenumbers of the plane wave. The N -breathers of the nonlinear Klein–Gordon equation are constructed directly from its 2 N -solitons obtained in history. The regularity conditions of breathers are established. The dynamic behaviors of breathers of the 2D nonlinear Klein–Gordon equation are consistent with modulation instability analysis. Furthermore, by means of the bilinear method together with improved long-wave limit technique, we obtain general high order rogue waves of the 2D and 3D nonlinear Klein–Gordon equation. In particular, the first- and second-order rogue waves and lumps of the 2D nonlinear Klein–Gordon equation are investigated by using their explicit expressions. We find that their dynamic behaviors are similar to the nonlinear Schrödinger equation. Finally, the first-order rational solutions are illustrated for the 3D nonlinear Klein–Gordon equation. It is demonstrated that the rogue waves of the 2D and 3D nonlinear Klein–Gordon equation always exist by choosing dispersion and wavenumber of plane waves. [ABSTRACT FROM AUTHOR]

The scattering phenomena can be realized in a variety of everyday situations, including the rainbow pattern after a rainstorm, the dispersion of raindrops, information and communication (ICT) systems, radar cross section (RCS) measurement, and remote sensing. Inspired by the electromagnetic scattering features, this study explores the scattering characteristics of orbital angular momentum (OAM) carried by Gaussian vortex beam (GVB) for perfect electromagnetic conductor (PEMC) sphere by utilizing the generalized Lorenz–Mie theory (GLMT). Stemming from the integral localized approximation (ILA) method, the beam‐shape coefficients (BSCs) representing the incident GVB are obtained. Vortex beams carry distinct unique optical characteristics as compared to the other beam types as these possess OAM. Computations for the efficiencies (scattering and extinction) for a focused GVB are conducted and discussed to analyze the scattering phenomena of the electromagnetic fields outside the PEMC sphere. To ensure the accuracy of the results, scattering efficiency for Gaussian beam and plane wave is computed and compared using the GLMT for PEMC sphere. The OAM mode index, beam waist radius, and the scalar admittance of GVB are chosen as parameters to investigate their impact on the scattering dynamics (i.e., scattering and extinction efficiency). The numerical results show that OAM mode index, beam waist radius, and PEMC admittance have greater impact on optical efficiencies. Nonetheless, the trend of the scattering efficiency decreases irrespective of the extinction efficiency i.e., increases for OAM mode index. [ABSTRACT FROM AUTHOR]

In this study, the acoustic damping performances of the dual Helmholtz resonators were numerically evaluated using a 3D model. The grazing flow passes tangentially through the resonator neck, with a Mach number range of 0 ≤ Ma ≤ 0.1. The numerical model operates by solving the linearized Navier–Stokes equations. The current model is validated through a comparison with experimental data. The model is then utilized to explore the effects of the dual Helmholtz resonators on acoustic transmission loss performance in the presence of a grazing flow. Three key parameters are examined: 1) different implementation configurations of the dual Helmholtz resonators (including Models (b), (c), and (d)), 2) the mean temperature of the grazing flow, and 3) the axial distance between the dual Helmholtz resonators. For comparison, the acoustic damping performance of these dual Helmholtz resonators is compared to the single Helmholtz resonator case (Model (a)). The maximum transmission loss of Model (c) is significantly higher, recording values of 91%, 89.4%, and 92.5% than those observed for Model (a) at Ma = 0, Ma = 0.05, and Ma = 0.1, respectively. It is observed that the dual Helmholtz resonators dramatically increase the transmission loss. Model (c) is demonstrated to be associated with the most significant damping on the acoustic plane waves in comparison with that of Model (a). Additionally, the maximum transmission loss of Model (c) is 23.23 dB, 30.32 dB, and 34.58 dB at mean temperatures of 300 K, 600 K, and 900 K, respectively. Therefore, increasing the mean temperature is shown to be beneficial to enhance transmission losses in the presence of the grazing flow. Furthermore, under Ma = 0.1, the resonant frequency of Model (c) is 127 Hz, 152 Hz, and 172 Hz, corresponding to mean temperatures of 300 K, 600 K, and 900 K. It can be concluded that increasing the temperature has the effect of broadening the resonant frequency, especially at a high grazing flow Mach number. However, increasing the mean temperature results in a reduction of transmission loss in the absence of the grazing flow. In the case of Model (c), a 32 cm axial distance results in a 5.6% larger transmission loss at Ma = 0 and a 26.4% larger loss at Ma = 0.1 compared to a 16 cm axial distance. This indicates that increasing the axial distance between the dual Helmholtz resonators improves transmission loss. [ABSTRACT FROM AUTHOR]

For the wave equation with two nonlinear terms we consider the inverse problem consisting in recovering finitely supported coefficients of the nonlinear terms by using an information about the solutions corresponding to the plane waves coming from infinity and passing through inhomogeneity. The direction of propagation of plane waves is considered as a parameter of the problem, and the solution is measured at the boundary of the domain the interior of which contains the support of the unknown coefficients at time moments close to the arrival time of the wave front. The main result is that we reduce the inverse problem to the usual X-ray tomography problem for one of the coefficients at the nonlinear terms and a new integral geometry problem for the other coefficient. For the latter problem we derive the stability estimate for solutions. [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]

In this work, we present a novel approach to resolve the refractive indices of transparent and translucent liquids from straight interference fringes. The optical path difference between the two arms of the Mach–Zehnder interferometer is first derived by assuming a reference plane wave interfering with a plane wave passing through a rectangular cuvette. The analytic expressions for the liquid refractive indices are then deduced, describing how the refractive index is related to the fringe spacings, spatial frequencies, and directions. The structure coefficients in the above formulas are determined from the fringe spacings and directions of the interference patterns of the empty cuvette and the cuvette filled with a liquid of a known refractive index. The NaCl solution and Coca Cola are adopted as the test examples to show experimentally the validity of the proposed method. There is good agreement between the refractive indices obtained from the fringe spacings and direction of a single interference pattern. The sensitivity and resolution of this method are dependent on the structure of the experimental systems and thus can be adjusted in a controlled manner. The proposed method is simple to implement and can be easily extended to other high precision optical interferometer systems. [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]

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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 the bench method of tunnel excavation, the blasting impact from upper bench blasting poses significant risks to personnel and equipment. This study employed dynamic analysis software, ANSYS/LS-DYNA, and field testing to examine the propagation characteristics and attenuation behavior of tunnel shock waves. The findings revealed that, near the central axis of the tunnel, shock wave overpressure was lower compared to areas near the tunnel wall due to reflections from the wall. As the shock wave traveled a distance six times the tunnel diameter, it transitioned from a spherical wave to a plane wave. The attenuation coefficient for the plane wave ranged from 1.03 to 1.17. A fitting formula for shock wave overpressure attenuation, based on field test results, was proposed, and it showed good agreement with the numerical simulation results. This provided valuable theoretical insights for predicting shock wave overpressure during bench method tunnel excavation. [ABSTRACT FROM AUTHOR]