Wave Transmission Research Articles

Research on the effect of thin tungsten patch on the fracture behaviour of steel shells under detonation

Abstract To achieve controlled fragmentation of the shell, a pre-control method was designed, which involved adhering high-impedance thin tungsten patches to the outer wall of the shell according to specific rules. Based on the transmission and reflection characteristics of shock waves at different interfaces, the effect of waves on shell fracture was analyzed, revealing that the shell at the gap between the patches fractured first. Through numerical simulation studies, it was found that adhering thin tungsten sheets externally could effectively control the fragmentation of the shell, with shear fracture being the prior mechanism for shell fragmentation. When using rectangular patches, there were fewer connected fragments, and the effective fragment generation rate reached 67.90%, higher compared to the other two patch methods. Comparison revealed that the effective length χ was directly proportional to the effective mass of the fragment when using a rectangular patch, and χ=1.3 resulted in a pure shear fracture mode, forming the most uniform fragments. The velocity distribution along the axial direction was consistent under different patches, with the highest fragment velocity occurring at a distance of 3/4 from the initiation point. When rhombus patches were used, the average fragment velocity was higher than that of the other two patch methods.

Comparison of mechanical response of head structure with different brain material models under impact

Abstract Brian material models and mechanical properties are very important for pressure evolution experiments and numerical simulations in head structure under impact. A simplified head structure with core-shell finite element model was established, and the motion, skull stress, skull deformation, and brain stress were numerically simulated with different soft tissue material models. The equivalence of the material model in stress propagation simulation was discussed. In the present work, it showed that when the head with impact velocity of 1m/s, the head structure rebound with a velocity of 0.6 m/s ∼ 0.8m/s, and occurred between 600μs and 1000μs due to different material models, at this time, the stress wave oscillation propagated in the skull underwent 3-5 repeated loads. The positive pressure on the impact side of brain tissue could reach 400kPa ∼ 800kPa, the negative pressure on the opposite side was between −150 kPa to −385kPa, the skull strain was between −1.8 ‰ to −3.7 ‰, and the skull stress was between 25.3MPa ∼ 41.2MPa. In a larger range of impact velocities, material models with strain rate effect have more advantages in stress wave transmission and pressure changing within the core-shell structure. The strain rate effect characterized only by creep and relaxation has limited effects on impact simulation, and directly introducing different strain rate mechanical property interpolation for hyperelastic model simulation is more effective.

Numerical calculation and analysis of anti-penetration of ultra-high strength bullet shielding layer

Abstract This research deals with the numerical investigation of ballistic protection proided by a combination of steel and reinforced concrete. Firstly, the parameters of the material model were calibrated based on the experimental data, and numerical simulations were carried out with existing experiments to verify the rationality of the material model and numerical simulation methods. Subsequently, the numerical simulation of the penetration of a typical ground-penetrating projectile into the G50/RC composite target at a velocity of 350m/s was carried out to analyze the stress wave transmission and ballistic performance during the penetration process, and the critical penetration depth was obtained. Finally, by changing the steel type and the number of steel plate layers, the best composite target combination is obtained. The simulation results show that the G50/RC composite target can effectively withstand the impact of conventional ground-penetrating warheads, and make them break or explode outside the shielding layer. At a projectile velocity of 350 m/s, the critical penetration thickness of BLU-109/B, BLU-122 and BLU-137 prototypes is 16, 17 and 19cm, respectively. Under the penetration of BLU-137, 40cm 45# steel can achieve the same protection effect as 19cm G50; The double steel plate composed of 12cm G50 steel and 12cm 45# steel has excellent penetration resistance. By comprehensive analysis, the same composite target using double steel plate can greatly increase the anti-penetration performance of the bomb shield and reduce the cost of engineering construction.

Design of a novel high-speed tensile method for testing the high strain rate tensile behavior of aluminum alloys.

The high-strain rate mechanical behavior of aluminum alloys is crucial for the stability of electromagnetic launch systems. However, current high-strain rate testing methods are not suitable for large-scale screening of materials needed in electromagnetic launch systems due to their low precision and high cost. In this paper, a novel method for high-strain rate tensile testing of aluminum alloys based on magnetic pulse driving was proposed. The method can generate a fast-rising edge and adjustable stress pulses to enable uniaxial tensile deformation, reaching a target strain rate quickly and keeping it constant. Based on the theory of stress wave transmission, a single-point method for measuring stress-strain relationship of the specimen combining digital image correlation (DIC) technology is proposed. Finite element simulations using the explicit finite element software LS-DYNA demonstrate a good agreement between the strains and strain rate with experimental values. Tensile tests were conducted on AA7075 in the strain rate range of 1000-3000s-1, the stress-strain relationship obtained from DIC agrees well with the results of traditional Hopkinson bar experiments.

Effects of viscosity and induced magnetic fields on weakly nonlinear wave transmission in a viscoelastic tube using physics-informed neural networks

This study presents an advanced deep learning methodology that utilizes physics-informed neural networks (PINNs), to analyze the transmission of weakly nonlinear waves in a prestressed viscoelastic arterial tube. Using the long wave approximation, a mathematical model is constructed to replicate the propagation of weakly nonlinear waves in a viscoelastic arterial tube filled with viscous nanofluid, taking into account the influence of an induced magnetic field. The perturbed Burger, perturbed Korteweg–de Vries, and perturbed Korteweg–de Vries-Burgers equations are formulated based on the combined effects of nanofluid viscosity and the applied magnetic field using the reductive perturbation technique. Semi-supervised physics-informed neural network models are utilized to solve these perturbed evolutionary equations, trained on a limited dataset within their rectangular domain of definition. Gaussian process-based Bayesian optimization is used to determine the hyperparameters of the neural network, ensuring optimal model is performance. The effectiveness of the optimal models is evaluated by calculating the residual losses associated with the perturbed partial differential equations (PDEs). Visual representations of weakly non-linear wave propagation, considering nanofluid viscosity and induced magnetic fields, enhance the comprehension of dissipative effects in the cardiovascular system. These insights aid in obtaining precise measurements of pulse wave velocity for cardiovascular health monitoring. Consequently, the application of PINN proves to be a valuable tool for solving real-world PDEs and highlights its importance in advancing medical machine learning fields.

Transformasi Gelombang Reguler Akibat Pemecah Gelombang Tiang Pancang Dua Baris Selang-Seling

Hydraulic experiments in a two-dimensional physical laboratory were conducted to evaluate the performance of pile breakwaters in reducing wave energy. The piles on the breakwater were arranged in a staggered pattern in two rows. A total of seventy-two simulation scenarios were run based on variations in the incoming wave height and period, and the spacing between the piles, using a 1:10 model scale. The data from the hydraulic tests were then processed using a spectral method that could separate the energy spectra of reflected and transmitted waves. These changes result in reflected and transmitted waves. The laboratory test data were used to estimate the values of the transmission coefficient and reflection coefficient. Both coefficients were then used to validate semi-empirical formulas for the two coefficients. The semi-empirical formulas for the two coefficients were developed based on a model for estimating the spatial porosity of pile breakwaters. The porosity estimation model takes into account the dimensions of the piles and the dimensional components of the breakwater, including the arrangement, number of rows, and spacing between the piles. The validation results of the semi-empirical formulas with the laboratory test data showed a coefficient of determination of 0.917 and a root mean square of 0.077. The staggered arrangement improves the effectiveness of the breakwater in reducing the transmission wave height. The developed semi-empirical model can be used to design the pile dimensions to achieve optimal reflected and transmitted wave heights for coastal protection. Keywords: pile breakwater, coastal protection, hydraulic experiment, physical wave simulation, wave transmission new formula

Four-band tunable narrowband optical absorber built on surface plasmonically patterned square graphene

The square and ring-shaped graphite four-band ultra-narrow-band absorber in this paper achieve perfect absorption. Therefore, the four waves of perfect transmission in the middle infrared band have been achieved, and there are four common values at λ1 = 2471.33 nm, λ2 = 2553.81 nm, λ3 = 2588.4 nm and λ4 = 2661.9 nm. Their ultra-high reflectors are 99.95 %, 96.65 %, 92.87 %, and 97.65 %, respectively, and the average reflective rate is 96.78 %. This is achieved in the graphene array structure of the pattern. Single-layer graphene is due the near-field enhancement has achieved almost perfect absorption. From the characteristics of graphene, a single variable is used to compare the effects of each variable on the efficiency of the absorber. From the perspective of incident light, it can be understood that the absorber can work within a wide range of incident angle to achieve a high absorption rate. The results obtained from the changes in environmental refractive index are more interesting. The structural model in this chapter has a high FOM (Figure of Merit) and can act as a atmospheric refractive index sensor.

Analysis and experimentation of lamb wave transmission characteristics in the stiffened plates

ABSTRACT Ultrasonic Lamb wave technology holds extreme significance in the structural health monitoring of integral metal wall plates. However, its application is limited due to complex Lamb wave transmission characteristics caused by stiffeners. In the study, the transmission characteristics of Lamb waves in common types of stiffener cross sections (I-type and Γ-type) of large wall plates were investigated. A 2D-FFT (Two-Dimensional Fast Fourier Transform) calculation method was developed to accurately analyse the transmission characteristics of Lamb waves in stiffened plates with different stiffener cross-sections. The stiffener structure could be considered as a comb filter through the experimental and simulation results. Theoretical and experimental evidence shows that the characteristics of the filter are mainly affected by the dimensions of the height direction of the stiffeners. The variations of comb filtering characteristics of Lamb waves with stiffener geometry were deeply analysed. In addition, the formation mechanism of the comb-filtering effect of the stiffeners on the transmitted wave has been validated through experimental measurement. This study provides the basis for the reasonable frequency selection of Lamb waves for detecting the stiffened plate structure, and it significantly advances the application of Lamb waves in the structural health monitoring of integral metal wall plates.

Full-space programmable circularly polarized metasurface for space-multiplexing wireless communications

The programmable metasurface has been proved to be an effective tool to dynamically tailor electromagnetic (EM) waves. However, how to achieve real-time and independent controls of circularly polarized (CP) waves in the transmission and reflection spaces is still a challenge. To address this problem, we propose a full-space programmable CP metasurface, which can independently manipulate the CP waves in transmission and reflection spaces in real time by controlling the bias voltage. The polarization states of reflected and transmitted CP waves can be independently customized through elaborate meta-atom design. As a proof of concept, we designed, fabricated, and measured a full-space programmable CP metasurface that can realize copolarized reflection for right-handed circularly polarized (RCP) waves and cross-polarized transmission for left-handed circularly polarized (LCP) waves. Simulated and measured results verify that the wavefronts of reflected and transmitted CP waves can be independently manipulated in real time by reprogramming the reflection and transmission phase coding sequences. Based on the full-space programmable CP metasurface, a space-multiplexing wireless communication scheme is established, successfully delivering two different images along preset reflection and transmission channels.

Study on the influence of submergence depth on the hydrodynamic and wave load characteristics of semi-submersible structures induced by a solitary wave

The submergence depth directly affects the safety of semi-submersible marine structures due to that the submergence depth significantly impacts on the hydrodynamic characteristics and wave loads of structures excited by extreme wave. This paper studies the influence of submergence depth on the hydrodynamic and wave load characteristics of semi-submersible structures by establishing a numerical model of the interaction between solitary waves and semi-submersible structures based on the SPH model and Rayleigh theory. Furthermore, equations for transmission coefficient, reflection coefficient, and wave load are fitted. The calculated wave heights of solitary wave propagation test case are in good agreement with the theoretical values. The maximum relative error of the wave peak is 8.4%. The calculated wave loads of submerged horizontal plates test case has a consistent trend with the experimental data. The maximum relative error of wave load peak and valley is 54% (absolute error 0.37 N). Furthermore, the interaction between solitary waves and structures with different submergence depths is investigated by using the meshless numerical model. It is found that the reflection coefficient first increases and then decreases with increasing submergence depth, and reaching a maximum value of 0.39 at the submergence depth equal to 0.0 m. On the contrary, the transmission coefficient decreases first and then increases with the increase of submergence depth. The minimum value of transmission coefficient is 0.36 with the submergence depth of 0.3 m. As the submergence depth increased, the horizontal wave load peak of the structure gradually increases, and the maximum value of 0.13 is obtained at the submergence depth of 0.7 m. The peak of vertical wave load rapidly increases with the increase of submergence depth and then gradually decreases while the trough gradually decreases with increasing submergence depth.

A study on solutions of fractional order equal-width equation using novel approach

The time-fractional equal-width equation plays a vital role in plasma physics, serving as an essential tool for elucidating the dynamics of hydromagnetic waves in cold plasma, a critical component for the comprehensive understanding of plasma-related phenomena. Furthermore, this equation finds application in fluid mechanics, which models the transmission of nonlinear waves across shallow waters. In this study, we employ an innovative technique to solve time-fractional equal-width equation, demonstrating the q-homotopy analysis transform technique. This considered technique was implemented to find the effective approximated solution of the considered equations. The obtained results are discussed through the 3D plots and graphs that express the physical representation. The results derived from the q-homotopy analysis transform method are presented in a series form, exhibiting swift convergence and capturing the behavior of the equal-width equation’s solution with minimal error, and the convergence analysis and uniqueness of the solution using the projected method have been secured using the fixed-point theory. The projected method we used does not require linearization, perturbations, or discretization, which significantly reduces computations. The results disclose that the proposed technique is highly effective, methodical, and easy to apply for complex and nonlinear systems, helping us to capture the associated behavior of diverse classes of phenomena. The numerical simulations presented ensure higher accuracy and are compared with other techniques to evaluate approximate errors. In comparison with other techniques, the considered method is a competent tool to get an analytical solution of an considered equation and the methodology employed herein for the considered equation is demonstrated to be both efficient and dependable, marking a significant advancement in the field.

Resonant surface waves in an oscillating periodic tank with a submerged hill

Experimental studies on the sloshing of fluid layers are usually performed in rectangular tanks with fixed boundaries. In contrast, the present study uses a 4.76-m-long circular channel, a geometry with open periodic boundaries. Surface waves are excited by means of a submerged hill that, together with the tank, performs a harmonic oscillation. Laboratory measurements are made using 18 ultrasonic probes, evenly distributed over the channel to track the wave propagation. It is shown that a two-dimensional long-wave numerical model derived via the Kármán–Pohlhausen approach reproduces the experimental data as long as the forcing is monochromatic. The sloshing experiments imply a highly complex surface wave field. Different wave types such as solitary waves, undular bores and antisolitary waves are observed. For order one $\delta _{hill} = h_{hill}/h_0$ , where $h_0$ is the mean water level and $h_{hill}$ the obstacle's height, the resonant reflections of solitary waves by the submerged obstacle give rise to an amplitude spectrum for which the main resonance peaks can be explained by linear theory. For smaller $\delta _{hill}$ , wave transmissions lead to major differences with respect to the more common cases of sloshing with closed ducts having fully reflective ends for which wave transmission through the end walls is not possible. This ultimately results in more complex resonance diagrams and a pattern formation that changes rather abruptly with the frequency. The experiments are of interest not only for engineering applications but also for tidal flows over bottom topography.

Spin wave linear response of three-dimensional structures calculated in the frequency domain

A theory is presented for calculating the spin wave response of a three-dimensional damped magnetic system to an external excitation, in the frequency domain. The equation of motion, written in the Hamiltonian formalism, is discretized within a finite-element method, and the corresponding large system of equations is first linearized and then solved with well-established techniques of linear algebra, leading directly to the spectral response. This approach is therefore particularly suitable for interpreting the results of all-electric microwave measurements of magnonic crystals. The response of a three-dimensional structure, composed of a portion of a square array of circular dots placed in close proximity of a magnetic substrate, is then investigated. A prominent, narrow feature with a large rejection ratio is observed in the spin wave transmission spectrum, making this structure useful as a narrowband notch filter.

Developing a Virtual Model of the Rhesus Macaque Inner Ear.

A virtual model of the rhesus macaque inner ear was created in the present study. Rhesus macaques have been valuable in cochlear research; however, their high cost prompts a need for alternative methods. Finite Element (FE) analysis offers a promising solution by enabling detailed simulations of the inner ear. This study employs FE analysis to create a virtual model of the rhesus macaque's inner ear, reconstructed from MRI scans, to explore how cochlear implants (CIs) impact residual hearing loss. Harmonic-acoustic simulations of sound wave transmission indicate that CIs have minor effects on the displacement of the basilar membrane and thus minimally impact residual hearing loss post-implantation, but stiffening of the round window membrane worsens this effect. While the rhesus macaque FE model presented in this study shows some promise, its potential applications will require further validation through additional simulations and experimental studies.

Research on the wave transmission characteristics of a flexible chamber inserted in the fluid-filled elastic pipeline

In the acoustic calculations of pneumatic pipeline systems, it is commonly assumed that the walls of the pipeline are rigid. It leads to the development of various acoustic theories based on rigid wall. However, in situations involving high-density fluids or thin-walled structures, the propagation of waves in the pipeline becomes complex due to the strong vibroacoustic coupling. In such cases, the wave transmission characteristics calculation methods based on the rigid wall assumption are no longer applicable. This paper employs the pipeline waveguide theory to estimate the wave transmission characteristics in the presence of complex wave behavior within the pipeline. Once the accuracy of the proposed method has been verified, the wave responses of a flexible chamber inserted in the fluid-filled elastic pipeline are analyzed. The analysis shows that the lowest-order fluid-type waves and the lowest-order longitudinal extension waves are found to propagate in the pipeline. The incident lowest-order fluid-type wave and its transmitted wave of the same mode can be successfully separated from other waves. The elasticity of the pipe wall can significantly affect the acoustic characteristics of an expansion chamber. Nevertheless, significant disparities in the wave amplitudes and limited sampling pose challenges to accurate calculations of the transmission loss.

Design of α–alumina integrated ultrasound transducer for wireless power transmission system

Traditional ultrasound wireless power transmission (UWPT) technology often faces challenges such as low power transmission efficiency and safety concerns. This paper proposes a highly reliable α–alumina integrated ultrasound transducer–based ultrasound wireless power transmission (IUT–UWPT) system designed for metallic medium. The proposed system is capable of powering and communicating with embedded sensors inside metal–sealed tanks. An acoustic wave transmission model for the IUT–UWPT system is developed based on acoustic theory to optimize the thickness of the matching layer and bonding layers between piezoelectric ceramics and metallic medium. The effect of the α–alumina integrated ultrasound transducer on the input–output characteristics of the system is analyzed using the mason equivalent circuit method considering acoustic attenuation and finite element simulation. Experimental results show that, compared to traditional UWPT systems without α–alumina integrated ultrasound transducer, the IUT–UWPT system exhibits a broader frequency response range from 0.8 MHz to 1.2 MHz and achieves a 13.19 % increase in maximum output power. Notably, the insulating properties of the α–alumina integrated ultrasound transducer prevent electrical generation on the surface of the metal–sealed tank. This system is well–suited for health monitoring in storage facilities such as gas pipelines, liquid nitrogen tanks and nuclear waste containers.

Experimental realization of on-chip few-photon control around exceptional points

Non-Hermitian physical systems have attracted considerable attention in recent years for their unique properties around exceptional points (EPs), where the eigenvalues and eigenstates of the system coalesce. Phase transitions near exceptional points can lead to various interesting phenomena, such as unidirectional wave transmission. However, most of those studies are in the classical regime and whether these properties can be maintained in the quantum regime is still a subject of ongoing studies. Using a non-Hermitian on-chip superconducting quantum circuit, here we observe a phase transition and the corresponding exceptional point between the two phases. Furthermore, we demonstrate that unidirectional microwave transmission can be achieved even in the few-photon regime within the broken symmetry phase. This result holds some potential applications, such as on-chip few-photon microwave isolators. Our study reveals the possibility of exploring the fundamental physics and practical quantum devices with non-Hermitian systems based on superconducting quantum circuits.

Modeling hydrodynamic properties of oyster reefs

Understanding how the shape and size of oyster reefs affect pore pressure and wave transmission can help guide efforts to build coastal barriers.

Incidence of severe and non-severe SARS-CoV-2 infections in children and adolescents: a population-based cohort study using six healthcare databases from Italy, Spain, and Norway.

Severe COVID-19 was rare across databases, but up to 3 to 4 times higher in children with comorbidities during the predominance of Omicron BA.1-2 variant in winter 2021-2022. COVID-19 vaccination coverage was slightly lower in children with comorbidities in ARS (Tuscany) and SIDIAP (Catalonia) data sources. Our findings will inform future public policies aimedto protect the pediatric population, both within these countries and globally. • Pediatric population is susceptible to SARS-CoV-2 infection. • COVID-19 severity rates in children vary across study settings and context. • This study confirms the low severity rates of COVID-19 in the pediatric population based on a large cohort of children and adolescents residing in Spain, Italy, and Norway. • Incidence of severe COVID-19 in children and adolescents with comorbidities was up to 3 to 4 times higher than in the general pediatric population during the SARS-CoV-2 high transmission wave of Omicron BA.1-2 variant in winter 2021-2022 in Italy and Spain.

Investigation on the transmission of Love waves due to an impulsive line source in a heterogeneous double porous rock structure

The region around the reservoir sometimes encounters the seismic response of ground. The phenomena of Love waves propagation also caused by seismic activity which can further significantly influenced by an impulsive line source present in the rock structures of ground. The current study elucidates the propagation behavior of Love waves induced by an impulsive line source within the anisotropic layered heterogeneous double porous rock structures commonly found in proximity to the reservoir areas. The expression of the dispersion relation for the Love waves propagation due to an impulsive line source has been derived by using the Fourier transformation and Green’s function technique. The above-mentioned rock composite structure is consisted of two different portions: upper transversely isotropic double porous (TIDP) layer medium and lower heterogeneous isotropic double porous half-space (IDP) medium. In the aforesaid half-space medium, both types of heterogeneities viz. linear and quadratic have been considered. The impacts of heterogeneity parameters associated with the lower heterogeneous IDP half-space, porosity parameter (corresponds to both upper TIDP layer and lower IDP half-space) and anisotropic parameter of TIDP layer on Love waves phase velocity have also been studied. Some special outlines have also been depicted graphically.