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In this manuscript, we will apply the regularized meshless method, coupled with an error estimation technique, to tackle the challenge of modeling oblique incident waves interacting with multiple cylinders. Given the impracticality of obtaining an exact solution in many real engineering problems, we introduce an error estimation technique designed to achieve reliable solutions. This technique excels in providing dependable solutions that closely approximate analytical solutions. An additional advantage is its capacity to identify the optimal number of points for both source and collocating points, thereby enhancing computational efficiency. The validity of the proposed method will be demonstrated through three numerical cases, presenting results that exhibit substantial agreement. [ABSTRACT FROM AUTHOR]

In this manuscript, we will apply the regularized meshless method, coupled with an error estimation technique, to tackle the challenge of modeling oblique incident waves interacting with multiple cylinders. Given the impracticality of obtaining an exact solution in many real engineering problems, we introduce an error estimation technique designed to achieve reliable solutions. This technique excels in providing dependable solutions that closely approximate analytical solutions. An additional advantage is its capacity to identify the optimal number of points for both source and collocating points, thereby enhancing computational efficiency. The validity of the proposed method will be demonstrated through three numerical cases, presenting results that exhibit substantial agreement.

The problem of reflection of longitudinal and transverse waves from the boundary of a half-plane is considered. It is assumed that boundary conditions are a generalization the sliding contact and assume that the tangential stresses do not vanish, but obey the law of dry friction. Analytical expressions are obtained for the ratios of the amplitudes of reflected waves to the amplitude of an incident longitudinal or transverse wave. A numerical analysis of the dependence of these ratios on the wave incidence angle, friction coefficient, and Poisson's ratio is carried out. It is shown that when the direction of the boundary shear stresses and the direction of propagation of the incident both longitudinal and transverse waves coincide, there are critical angles of incidence at which the amplitudes of the reflected waves become infinite. [ABSTRACT FROM AUTHOR]

An inverse unsteady boundary value problem of a plane oblique pressure wave diffraction on a convex surface in the form of a parabolic cylinder is considered. At the same time, approximate models of the interaction of a wave with a rigid obstacle in a liquid are constructed, based on the hypothesis of a thin layer, which makes it possible to obtain fundamental solutions in a closed-form. To obtain an analytical solution for the direct problem, a non-stationary diffraction problem for an acoustic medium is solved using the transient function of the obstacle surface influence. The operational method is used. In the inverse problem, the angle of the front of the oblique wave is determined based on the measured pressure in the reflected and incident waves on the body surface using the least squares method. Among the results of the study, an algorithm was proposed for solving the inverse boundary value problem of diffraction of a plane oblique pressure wave on a rigid obstacle in the form of a parabolic cylinder by determining the angle of the oblique wave front. [ABSTRACT FROM AUTHOR]

If the octet truss core, which is a space filling structure of half regular octahedrons and regular tetrahedrons, has excellent sound insulation characteristics, the possibility of using the octet truss core is sufficiently widened. From this fact, we have studied to obtain sound insulation characteristics of the flat plate and the plate with single core using acoustic tube by the finite element method (FEM) with high accuracy. The calculation of sound insulation performance by FEM was limited to the qualitative study so far. For example, the correction is required due to the difference from the theoretical value, and the magnitudes of the correction values differ depending on the test pieces. In this study, we considered the incident wave and compared the sound insulation calculation result by the FEM calculation using the non-reflective boundary at the rear end of the sound receiving room with the theoretical calculation. As a result, both calculation values were almost the same. Therefore, it can be said that when the magnitudes of the incident wave and the reflective wave are almost equal, a quantitative study is possible. Taking advantage of this fact, in this paper the sound insulation characteristics of the plate with single core are compared with that of flat plate, and the effects of the sound insulation characteristics by the aspect ratio of the core are examined.

We analyze the Sommerfeld solution to the stationary diffraction by a half‐plane. We prove that this solution is the limiting amplitude for time‐dependent scattering of incident plane waves with a broad class of the profile functions. We also show that this solution is the asymptotics of the limiting amplitudes of solutions to time‐dependent scattering problem with narrow wedges when the angle of the wedge tends to zero. [ABSTRACT FROM AUTHOR]

One of the most promising wave energy converter type is Oscillating Water Column (OWC) system. Fluctuation amounts and the motion behavior of the water column inside the chamber are very important parameters effecting the energy extraction. Therefore, predicting these parameters with respect to varying wave characteristics and geometric design parameters is of great importance. In this study, physical experiments are conducted for a bottom-fixed OWC system with seven different sizes of opening heights under various regular wave series. Average fluctuations inside the chamber are measured. It is found that there is a critical relative opening height ratio (α) that makes the fluctuations maximum regardless of wave parameters used. Exponential and linear relationships are found between average fluctuations and dimensionless parameters ‘dimensionless wave frequency’ and ‘captured wavelength’ defined, respectively. Mathematical models are developed to predict water column fluctuations under varying relative opening heights and wave parameters. The results of mathematical models indicated good aggrement with experimental data. Also chamber water surface profiles are observed and related to defined dimensionless wave parameters. Another factor (named as excessive harmful energy) is determined which also induces sloshing motion inside the chamber after the critical ratio value α is exceeded. It is found that under all wave series, the highest relative average column water surface fluctuations occur at relative opening height α is equal to 0.67 which is a unique value. It can be concluded that mathematical models can be used to estimate water column fluctuations from relative opening height and wave parameter data in the chamber. [ABSTRACT FROM AUTHOR]

• The BEM-FEM coupled equations of PSFS were solved numerically in the frequency domain. • Hydroelastic of floating structure response was mitigated due to pneumatic effect. • Hydroelastic performance of PSFS was the most effective as the incident waves. • The PSFS platforms can outperform the pontoon type as far as hydroelastic response. Pneumatically supported floating structures, which utilize an aircushion below the structural bottom, have been suggested to remedy the excessive hydroelastic response of the conventional pontoon-type floating structures. This paper presents an analytical study to examine the hydroelastic responses of the pneumatically supported floating structures. For the hydroelastic analysis, the fluid was modeled as a 2D-strip of finite depth seawater, whilst the floating structure was modeled as a beam with zero-draft. A direct coupled model was then constructed by using the boundary integral formulation for the fluid and FEM for the structure and by incorporating a pneumatic factor at the fluid-structure interface to consider the compressibility of the aircushion. Additionally, hydroelastic responses of the pneumatically supported type were compared for the pontoon-type for a wide range of pneumatic factors and regular waves. As a result, the pneumatic supports could significantly reduce the hydroelastic responses in most cases and that the response reduction may be markedly enhanced when the pneumatic factor was taken as small for a relatively short incident wave. Substantially, the analytical technique used in the present study can examine the design conditions, as being essential for practical applications of the pneumatically supported floating structures. [ABSTRACT FROM AUTHOR]

• In this paper, an incident wave inversion model based on substation components is proposed, which realizes the accurate inversion of incident wave signal in substation. • A denoising and extraction method of mixed wave based on improved EMD and FFT was proposed to filter noise out and obtain the power frequency signal under the noise with a signal-to-noise ratio above 10 dB. The proposed method is capable of extracting mixed waves; • Using the equivalent circuit of multiple outgoing lines, bus-to-ground stray capacitances, transformers, and line traps in the substation, we established an inversion model of incident wave based on substation component parameters. The inversion calculation of the incident wave in the complex frequency domain effectively avoids the difficulty of solving high-order differential equations. • We then solved the parameter optimization model based on the PSO to ensure that the population is always distributed in the feasible region where we modified the particle swarm position update formula. This method accurately identifies the parameters of the substation's equivalent circuit components. In substations, the fault signal at the measuring point includes a variety of signal aliasing. This is partly due to the short length of the substation lines and the exitance of multiple types of equipment that cause the reflection and refraction of the traveling waves. Compared with the incident wave, the distortion in the fault signal is often significant hence interfering with the fault identification and location. To address this issue, we propose an inversion method of the incident wave. To do this, we first investigate the impact of multiple outlets of the substation bus, equivalent stray capacitance of the bus to the ground, transformers, line trap, and other types of equipment on traveling wave transmission. Modeling the aliasing effect of the traveling wave measuring point signal we then propose a fault signal filtering algorithm based on the improved Empirical Mode Decomposition (EMD) and Fast Fourier Transform (FFT). Using this algorithm we then formulate an incident wave inversion model based on substation component parameters. The component parameters in the equivalent circuit model of substation are then accurately identified to achieve an accurate inversion of the incident waves. Identification of parameters is based on an optimization model of substation component parameters based on the Particle Swarm Optimization algorithm (PSO). Our results show that compared with the measured mixed wave signal, the fault characteristics of the inverted incident waves are more accurate, hence improving the fault location accuracy. [ABSTRACT FROM AUTHOR]

The authors report a waveform‐selective metasurface that operates at 2.4 GHz band, i.e. one of ISM (Industrial, Scientific and Medical) bands. This structure gives us an additional degree of freedom to control electromagnetic waves and absorbs a particular waveform or pulse width of an incident wave at the same frequency band, while transmitting others. This unique capability is demonstrated using either ideal sinusoidal waves or Wi‐Fi signals as a more practical waveform in wireless communications. Especially, this Letter shows how the waveform‐selective metasurface interacts with realistic wireless communication signals from the viewpoint of communication characteristics, such as error vector magnitude, bit error rate, and phase error. Thus, the authors' Letter paves the way for extending the concept of waveform selectivity from a fundamental electromagnetic research field to a more realistic wireless communication field to, for instance mitigate electromagnetic interference occurring at the same frequency band without significantly degrading communication characteristics. [ABSTRACT FROM AUTHOR]

The authors demonstrate two types of non‐reciprocal waveform‐selective metasurfaces that control the level of reflectance, depending not only on the direction of the incident wave but also on the waveform, namely, on the pulse width. A capacitor‐based waveform‐selective metasurface exhibits strong reflectance for a short pulse compared to that for a continuous wave (CW) at the same frequency. In contrast, an inductor‐based waveform‐selective metasurface more strongly reflects a CW than a pulse. The difference between them is demonstrated to be more than 50% but is reduced for a wave propagating in the other direction. The concept of the authors' structures is expected to offer an additional degree of freedom with which to design non‐reciprocal devices and applications. [ABSTRACT FROM AUTHOR]

The testing of structural metals at high strain rates is a subject of great interest in many modern technological areas. The split Hopkinson tension bar (SHTB) allows to investigate the ductile failure at nominal strain rates between 102 and some thousands of s−1. The tensile wave in SHTBs can be generated in various ways, but the simpler one from the viewpoint of its realisation is that of pre-tensioning a partial length of the input bar with an hydraulic cylinder and an opportune clamping device, and then suddenly releasing the clamp. So, a tensile stress wave is originated which travels towards the unstressed free end of the bar and towards the output bar through the specimen, breaking it. In this work a special clamping system is developed, integrating a Shape Memory Alloy actuator which allows the breaking of a fragile pin and initiating the rapid release of the input bar, without the need of a secondary hydraulic cylinder which is usually adopted in these devices. The clamp developed is much lighter than the standard clamping systems, and does not require the large centring and orientation efforts typical of heavier frame-fixed clamps. [ABSTRACT FROM AUTHOR]

A numerical method for the fully distributed modeling of Field Effect Transistor (FET) excited by an incident electromagnetic field using a Finite-Difference Time-Domain (FDTD) method is described. The transistor is modeled using the fully distributed model which consists of a configuration of the conventional equivalent circuit of the transistor and three coupled lines as each distributed element. The distributed source terms represent the coupling with an electromagnetic field in the equation which can be used in the Electromagnetic Interference (EMI) analysis. As a numerical example, the method is applied to a GaAs MESFET and the time domain results are presented. [ABSTRACT FROM AUTHOR]

We simulated coastal waves and wave absorbers in a lab-scale wave flume. The goal of this study was to observe and optimize a typical ocean environment and to reduce the wall reflection in the wave flume. In order to generate ocean waves in the wave flume, a combination of a flat-type wave generator and wave absorbers was installed in the channel. Two probes for measuring the wave heights, i.e., level gauges, were used to observe the temporal variation of the wave surface as well as the phase difference and maximum (crest) and minimum (trough) points between the propagating waves. In order to optimize the shape and size of the propagating waves, several absorption methods were proposed. Apart from an active wave absorption method, we used methods that involved vertical, porous plates; horizontal, punching plates; and sloping-wall-type wave absorbers. For obtaining the best propagating waves, the sloping-wall-type wave absorbers were chosen and tested in terms of the constitutive filling materials and the location and shape of the plate. This study also focused on the theoretical prediction of the wave surface, separating them into incident and reflective components. From the results, it is evident that the wave absorber comprised a hard filling material exhibits a better performance than the absorber comprised soft material; i.e., the wave absorber can be a strong sink to control the energy of the oncoming wave. In addition, larger wave absorbers corresponded to lower reflectance because the larger volume can remove the oncoming wave energy better. Therefore, with constant absorber conditions, the reflectance increases as the wave period increases. Finally, the reflectance of the wave was controlled to be less than 0.1 in this study so that the wave flume could be applied to simulate the offshore environment. [ABSTRACT FROM AUTHOR]

Abstract: UHF method to detect partial discharge phenomenon has been proven to be an effective way. Many types of UHF antennas have been developed in order to achieve a better sensitivity and accuracy in certain bandwidth (300MHz – 3.0GHz) for detecting the ultra-high frequencies generated by partial discharge. Bowtie antenna is one type of broadband antenna proven to be sensitive, accurate and easily designed and fabricated. This paper focused on the bowtie antenna characteristics both the measurement using vector network analyzer and simulation. The finite-difference time-domain (FDTD) technique is applied to model and confirm the antenna under observation in this research and later on modify to enhance the better performance. Simulation has proven, antenna achieves the optimum angle at flare angle of 60° as per simulation within the frequency range over 913MHz –3.0GHz as per measurement. The simulation results are used to construct the new modified antenna which showed the better sensitivity in the frequency bandwidth of partial discharge. The Gigahertz transverse electromagnetic (GTEM) like environment also used to simulated the sensitivity of antenna as compared to the calibration value approximately 11.0mm. [Copyright &y& Elsevier]

Construction of electromagnetic wave propagation model in layered pavement structure is a key problem for applying ground penetrating radar (GPR) to the road quality detection. A first-order explicit symplectic Euler method with Higdon absorbing boundary condition is presented to simulate GPR wave propagation in 2-D pavement structure. The incident wave is considered as line source and plane wave source, respectively. The total-field/scatter-field technique is used to simulate plane wave excitation. Numerical examples are provided to verify the accuracy and efficiency of the proposed algorithm. It can be observed that the symplectic Euler method achieves almost the same level of accuracy as the finite-difference time-domain scheme, while saving CPU time considerably. [ABSTRACT FROM AUTHOR]

When studying the harbor water tranquility, cases are often confronted as that the verification point is not located on the generation line or that the angle between the generation line and the isobath is so large that the differences of the wave climates along the generation line can not be ignored. For these cases, the incident boundary conditions are difficult to evaluate. In order to solve this problem, a combined wave model is developed in the present paper based on the Boussinesq equation and the wave action balance equation. Instead of the one-line wave generation method, a multi-line generation method is proposed for the combined model. Application of this method is given to a case that the harbor is designed with two entrances and the angle between the generation line and the isobath is large and the results are shown reasonable. We suggest that the wave generation method on multi-lines might also be introduced to the wave physical model as the replacement for the one-line generation method. [ABSTRACT FROM AUTHOR]

This paper presents a broadband circularly polarized patch antenna using an artificial ground (AG) structure with rectangular unit cells as a reflector. The AG structure changes the reflection phase in accordance with the polarization state of the incident wave. By properly combining the transmitted wave from the antenna and the reflected wave from the AG structure, broadband circular polarization can be obtained. The AG structure and the antenna are simulated using a full-wave solver and the results show a 10 dB return loss bandwidth of 48.6% and a 3 dB axial ratio bandwidth of 20.4%. The measured results are in good agreement with the simulated results. The radiation characteristics of the antenna are almost the same as those for an antenna with a PEC reflector. [ABSTRACT FROM PUBLISHER]

The finite-difference time-domain (FDTD) method is an effective technique for computing wideband electrical parameters such as scattering parameters of waveguide structures. in the computations, a known incident is normally required and is usually obtained with a simulation of a long uniform structure. For a three-dimensional problem, simulation of a long structure can be very memory- and CPU time-intensive. In addition, effective absorbing boundary conditions are needed to effectively terminate the structure even at and below the cutoff frequencies. To address these issues, many one-dimensional FDTD methods and absorbing schemes were proposed. However, they all have dispersion characteristics different from those of the conventional FDTD method, leading to undesired errors or reflections. In this paper, a new one-dimensional scheme is developed that has numerical dispersion characteristics very similar to that of the conventional FDTD method. When used as the absorbing boundary condition, it generates reflections of less than -200 dB even at and below the cutoff frequencies for the considered modes. When used to obtain the incident wave, its results have difference of less than -200 dB from that produced by the conventional FDTD method. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, we have considered the reflection and refraction of a plane wave at an interface between two half-spaces. The lower half-spaces is composed of highly anisotropic triclinic crystalline material and the upper half-space is homogeneous and isotropic. It has been assumed that due to incidence of a plane quasi- P ( qP) wave, three types of waves, namely, quasi- P ( qP), quasi- SV ( qSV) and quasi- SH ( qSH), will be generated in the lower half space whereas P and S waves will be generated in the upper half space. The phase velocities of all the quasi waves have been calculated. It has been assumed that the direction of particle motion is neither parallel nor perpendicular to the direction of propagation. Some specific relations have been established between directions of motion and propagation, respectively. The expressions for reflection coefficients of qP, qSV, qSH and refracted coefficients of P and SV waves are obtained. Results of reflection and refraction coefficients are presented. [ABSTRACT FROM AUTHOR]

This paper explores the development of thin glass panels that can be controlled electronically so as to act as transmission preventers that block the propagation of sound. Small rare earth voice coil actuators are used to control glass panel vibrations. The development of the control system is based on the use of a wave separation algorithm that separates incident sound from reflected sound. The incident sound serves the important purpose of providing an acoustic reference that is unaffected by the action of the control system speaker. This reference signal is used in an adaptive feedforward control system to drive the transmitted sound to zero. Detailed experimental results are presented showing the efficacy of the algorithms in achieving real-time control of acoustic transmission. The glass panels are able to effectively block transmission of sound, reducing sound transmission by 20 dB in the case of tonal frequencies and by 10–15 dB in the case of broadband noise. The glass panels can potentially be of great value in the development of noise-blocking glass windows for homes close to airports and noisy highways. [Copyright &y& Elsevier]

Accurate evaluation of dynamic resistance provided by the surrounding soil is the key to determining the dynamic performance of the pile foundation, especially for long piles. A new method is proposed to evaluate the dynamic pile-side soil resistance (DPSR). A dynamic coupled model of the pile-soil system is established considering the three-dimensional nature of the surrounding soil. Analytical solutions are then deduced for the dynamic response of each point along the pile shaft. The derived analytical solutions are then used to investigate several characteristics of the DPSR by analyzing the attenuation of the incident wave propagating along the pile shaft. The results show that the effect of DPSR decreases gradually from the pile top to tip under low-strain dynamic loading conditions, and it increases as the shear wave velocity of the surrounding soil increases between points under consideration along the pile shaft. It is also found that energy dissipation is the most important mechanism of soil resistance during longitudinal vibration associated with low strain axial loading, and thus damping should be evaluated carefully. The findings from this study aid in understanding the dynamic pile-soil interaction and provide practical guidance for analyzing the effect of the DPSR in engineering practice. • Analytical solutions are deduced for the dynamic response of each point along the pile shaft. • A new method is proposed to evaluate the dynamic pile-side soil resistance (DPSR). • Distribution characteristics of DPSR under low-strain conditions are studied. • Energy dissipation is the most important mechanism of the DPSR under low-strain conditions. [ABSTRACT FROM AUTHOR]