Wave Transmission Research Articles

Hydrodynamic analysis of floating VLFS using multi-domain boundary element method

The present study emphasizes the investigation of rigid and flexible Very Large Floating Structures (VLFS) by analyzing the reflection and transmission coefficients, plate deflections and wave force on the floating structure. The study involves analyzing the hydrodynamic characteristics of a porous and rigid VLFS, and hydroelastic analysis of flexible VLFS. The analysis is performed using the coupled Multi-Domain Boundary Element Method (MDBEM) and Finite Difference Method (FDM) at finite water depth. The flexible VLFS is modelled based on the Euler–Bernoulli thin plate theory and the study is performed using small amplitude wave theory. The study evaluates the hydroelastic behaviour in terms of structural deflection and hydrodynamic parameters by varying the structural porosity. The reflection and transmission coefficients are analyzed to show the extent of wave propagation on the lee side and the seaside of the structure. The wave force coefficients obtained signify the importance of the structure's orientation for the oncoming waves. The numerical results are validated with the results available in the literature. The analysis is performed for different structural and material properties to obtain the minimal hydroelastic and hydrodynamic response to assess the optimum design criteria and suitability of the type of VLFS, thereby maintaining the stability of the structure for safer operations.

Quantitative Determination of High-Frequency Voltage Attenuation in an Electric-Pulse-Excited Stroboscopic Transmission Electron Microscope.

High-frequency electric pulse signals are often applied to stimulate functional materials in devices. To investigate the relationship between materials structure and dynamic behavior under high-frequency electric excitation, the stroboscopic imaging mode is widely used in a transmission electron microscope (TEM). From a technical point of view, it is crucial to quantitatively determine high-frequency attenuation in an electric-pulse-excited stroboscopic TEM. Here, we propose the quantitative method to evaluate the voltage attenuation by using magnification variation of defocused bright-field transmission electron microscopy images in a stroboscopic mode when applying high-frequency electric pulse signals onto a model system of two opposite tungsten tips. The negative voltage excitation possesses higher high-frequency voltage attenuation than the positive voltage excitation due to the possible nonreciprocal transmission of the triangle waves within the circuit between the biasing sample holder and the arbitrary waveform generator. Our approach of high-frequency attenuation determination provides the experimental foundation for quantitative analysis on the dynamic evolution of materials structure and functionality under electric pulse stimuli.

Enhancing transcranial ultrasound stimulation planning with MRI-derived skull masks: a comparative analysis with CT-based processing

Objective.Transcranial ultrasound stimulation (TUS) presents challenges in ultrasound wave transmission through the skull, affecting study outcomes due to aberration and attenuation. While planning strategies incorporating 3D computed tomography (CT) scans help mitigate these issues, they expose participants to radiation, which can raise ethical concerns. A solution involves generating skull masks from participants' anatomical magnetic resonance imaging (MRI). This study aims to compare ultrasound field predictions between CT-derived and MRI-derived skull masks in TUS planning.Approach.Five participants with a range of skull density ratios (SDRs: 0.31, 0.42, 0.55, 0.67, and 0.79) were selected, each having both CT and T1/T2-weighted MRI scans. Ultrasound simulations were performed using BabelBrain software with a single-element transducer (diameter = 50 mm,F# = 1) at 250, 500, and 750 kHz frequencies. CT scans were used to generate maps of the skull's acoustic properties. The MRI scans were processed using the Charm segmentation tool from the SimNIBS tool suite using default and custom settings adapted for better skull segmentation. Ultrasound was adjusted to target 30 mm below the skull's surface at 54 electroencephalogram (EEG) locations.Main Results.The custom setting in Charm significantly improved the Dice coefficient between MRI- and CT-derived masks when compared to the default setting (p< 0.001). The maximum pressure error significantly decreased in the custom setting compared to the default setting (p< 0.001). Additionally, the focus location error median across different SDRs averaged 2.32, 1.45, and 1.57 mm in default and 2.08, 1.38, and 1.44 mm in custom conditions for 250 kHz, 500 kHz, and 750 kHz respectively.Significance.MRI-derived skull masks offer satisfactory accuracy at many EEG sites, and using custom settings can further enhance this accuracy. However, significant errors at specific locations highlight the importance of carefully considering stimulation location when choosing between CT- and MRI-derived skull modeling.

Bandwidth Enhancement of Epsilon‐Near‐Zero Supercoupling with Inverse‐Designed Metamaterials

AbstractEpsilon‐near‐zero (ENZ) materials exhibit unique electromagnetic properties that enable efficient wave transmission through channels of arbitrary geometry, which is known as ENZ supercoupling or tunneling. However, the supercoupling effect is typically confined to an inherent narrow bandwidth, which significantly restrict its practical applications. In this paper, a feasible method is proposed that enhanced the bandwidth of ENZ supercoupling. By optimizing the structure of an inverse‐designed pixel metamaterial inserted into the ENZ channel, multiple Fabry‐Perot (FP) modes are properly regulated and coupled, facilitating multimode superposition to enhance the bandwidth for high‐efficiency signal transmission in ENZ channels with arbitrary geometry. Furthermore, a prototype is constructed at microwave frequency to validate the performance of the proposed method, which opens new avenues for the development of broadband and geometry‐independent electromagnetic devices with the benefit of ENZ materials.

Tunable optical nonreciprocity in double-cavity optomechanical system with nonreciprocal coupling

We propose a double-cavity optomechanical system with nonreciprocal coupling to realize tunable optical nonreciprocity that has the prospect of making an optical device for the manipulation of information processing and communication. Here we investigate the steady-state dynamic processes of the double-cavity system and the transmission of optical waves from opposite cavity directions. The transmission spectrum of the probe field is presented in detail and the physical mechanism of the induced transparency window is analyzed. It is found that the nonreciprocal response of the probe field transmission appears at two different coupling strengths between two cavities, which breaks the spatial symmetry to lead to optical nonreciprocal transmission. In addition, through analytical calculations, we have given the conditions for nonreciprocal effects, and the optimally nonreciprocal effects can be controlled by adjusting both the coupling strengths and the dissipation rates of cavity fields. Due to the simplicity of the device, this study may provide promising opportunities to realize nonreciprocal structures for optical wave transmission.

Electromagnetic performance and loss mechanism decoding of 3D woven composite metamaterials through physical and computational models

Abstract Electromagnetic metamaterials regulated the directional transmission of electromagnetic waves to optimize the electromagnetic characteristics of electronic devices, but the facile lamination failure limited the wider application. The introduction of 3D weaving technology significantly enhanced the structural integrity and anti-delamination capabilities of metamaterials. However, due to their unique buckling structures and discrete fiber morphologies, traditional metamaterial theories struggled to explain the electromagnetic mechanisms of 3D woven metamaterials. In this study, the physical and computational models for 3D woven composite metamaterials were developed to decode the in-phase reflection and electromagnetic loss mechanism. The input impedance and reflection phase of metamaterials with different patch sizes and different weaving density were calculated by physical and computational models. The models calculated the resonant frequency difference of less than 0.4 GHz, with in-phase reflection bandwidth agreement of 80.4%. Furthermore, the computational model revealed the mechanism of energy loss caused by the increase of the surface current of the patches due to the decrease of the weaving density. The experimental results of the reflection phase for metamaterials with different patch sizes and different weaving density closely matched the calculated outcomes, confirming the model’s reliability. This study provided a crucial theoretical foundation for electromagnetic mechanisms of fabric metamaterials.

Robust terahertz on-chip topological pathway with single-mode and linear dispersion.

Terahertz on-chip pathway is crucial for next-generation wireless communication, terahertz integrated circuits, and high-speed chip interconnections, yet its development is impeded by issues like channel crosstalk and disordered scattering. In this study, we propose and experimentally demonstrate a terahertz on-chip topological pathway that exhibits exceptional transmission robustness, unaffected by structural curvature. The pathway is constructed using a subwavelength structure that combines the benefits of topological properties, such as broadband single-mode transmission and linear dispersion, with the field localization effects of periodic metal structures. By integrating topological protection into radio frequency circuits through metal microstructures, the device maintains efficient terahertz wave transmission even in the presence of scattering or structural defects while minimizing signal interference. These findings hold significant potential for applications in radio frequency device transmission and chip interconnection, particularly within the terahertz frequency range.

Wave Transmission Analysis of Timoshenko Beam Junction with Mindlin Plates Connected in the Same Plane

Wave Transmission Analysis of Timoshenko Beam Junction with Mindlin Plates Connected in the Same Plane

Symmetry Breaking as a Basis for Characterization of Dielectric Materials.

This paper introduces a novel method for measuring the dielectric permittivity of materials within the microwave and millimeter wave frequency ranges. The proposed approach, classified as a guided wave transmission system, employs a periodic transmission line structure characterized by mirror/glide symmetry. The dielectric permittivity is deduced by measuring the transmission properties of such structure when presence of the dielectric material breaks the inherent symmetry of the structure and consequently introduce a stopband in propagation characteristic. To explore the influence of symmetry breaking on propagation properties, an analytical dispersion equation, for both symmetries, is formulated using the Rigorous Coupled Wave Analysis (RCWA) combined with the matrix transverse resonance condition. Based on the analytical equation, an optimization procedure and linearized model for a sensing structure is obtained, specifically for X-band characterization of FR4 substrates. The theoretical results of the model are validated with full wave simulations and experimentally.

Based on an all-dielectric metamaterial sensing strategy to reveal the effect of acoustic AO effect on optical fiber transmission performance

Abstract Acousto-optic (AO) effect is an important factor affecting the transmission performance of optical fiber. Here, a metamaterial-based sensing scheme is proposed and applied to measure the AO effect resonance behaviors inside optical fibers due to sound wave transmission. This sensor scheme can obtain the effect of the amplitude and frequency of the sound wave on the optical fiber at the same time, which is different from the traditional photoelectric measurement scheme. The physical mechanism of the AO effect is revealed by measuring the amplitude and frequency of sound waves. The AO effect in the fiber is enhanced with the drive voltage of the sound wave generator increasing, which leads to the transmission performance of the fiber be suppressed. On the contrary, the attenuation coefficient and the group velocity of the fiber are basically stable. At the same time, the time for sound waves to enter and leave the AO effect zone is extended. Moreover, the AO effect is enhanced as the sound frequency gradually approached the resonant frequency. These measurements reveal the physical mechanism of the AO effect of optical fibers and validate the feasibility of this proposed metamaterial sensing scheme.

Approximation for reflection and transmission at a thin isotropic poroelastic bed between two isotropic elastic half‐spaces

AbstractSeismic responses from a horizontal poroelastic layer provide chances to detect fluids and characterize reservoirs. The poroelastic layer can be considered a thin poroelastic bed if the layer's thickness is less than about one‐eighth of the P‐wave wavelength. Most previous theoretical studies on the reflection and transmission of waves in a model containing a thin poroelastic bed employ fluid or poroelastic medium as the overlying media. Existing approximate formulas of PP‐wave reflection coefficients are given for P‐wave normal‐incidence. Thus, this paper derived the wave reflection and transmission approximate formulas of a thin poroelastic bed between two elastic half‐spaces with P‐wave oblique incident. First, we illustrated the exact reflection and transmission matrix equations for P‐wave incidents based on poroelasticity theory and the boundary conditions. Assuming the poroelastic bed's thickness is far less than wavelengths of S‐ and P‐waves, approximate reflection and transmission formulas are expanded in Taylor series centred at value of the parameter defined as the product of angular frequency, thickness and slowness. Numerical results show that the thinner the poroelastic layer, the closer the approximate reflection and transmission coefficients are to the exact ones. The approximate formulas are valid for small and medium angles. Approximated PP‐wave reflection and transmission coefficients are closer to the exact values than those of the converted waves, which is caused by the fact that P‐wave has a lower slowness than S‐wave.

Multiscale Finite Element Modeling of Human Ear for Acoustic Wave Transmission into Cochlea and Hair Cells Fatigue Failure.

Hearing loss is highly related to acoustic injuries and mechanical damage of ear tissues. The mechanical responses of ear tissues are difficult to measure experimentally, especially cochlear hair cells within the organ of Corti (OC) at microscale. Finite element (FE) modeling has become an important tool for simulating acoustic wave transmission and studying cochlear mechanics. This study harnessed multiscale FE models to investigate the mechanical behaviors of ear tissues in response to acoustic wave and developed a fatigue mechanical model to describe the outer hair cells (OHCs) failure. The three-dimensional multiscale FE models consisted a macroscale model of the ear canal, middle ear, and 3-chambered cochlea and a microscale OC model on a representative basilar membrane section, including the hair cells, membranes, and supporting cells. Harmonic Acoustic mode was used in the FE models for simulating various acoustic pressures and frequencies. The cochlear basilar membrane and the cochlear pressure induced by acoustic pressures were derived from the macroscale model and used as inputs for microscale OC model. The OC model identified the stress and strain concentrations in the reticular lamina at the root of stereocilia hair bundles and in the Deiter's cells at the connecting ends with OHCs, indicating the potential mechanical damage sites. OHCs were under cyclic loading and the alternating stress was quantified by the FE model. A fatigue mechanism for OHCs was established based on modeling results and experimental data. This mechanism would be used for predicting fatigue failure and the resulting hearing loss.

Wave transformation in transmission lines with rapid connection and disconnection of reactive elements

Rapid switching of transmission line parameters has emerged as a way to manipulate signals and as a testbed for various electromagnetic processes in time-varying media, including metamaterials. In general, the switching results in wave reflection and transmission similar to that for a spatial interface but at new frequencies. Here, various realizations of parameter switching are studied: connection and disconnection of reactive elements (capacitors and inductors) in series and in parallel. The temporal boundary conditions for the current and voltage distributions are derived rigorously based on the telegrapher’s equations that explicitly model additional elements, instead of taking the equivalent values. It is shown that the temporal boundary conditions depend not only on the parameter values before and after switching but on its specific realization. Connecting or disconnecting reactive elements always involves energy losses. When new elements are added, two types of losses are identified. The first type is related to the creation of static magnetic and electric fields in the elements after switching. The second type is related to a very rapid energy dissipation during switching even for a vanishingly small resistivity in the line. When elements are removed, their energy is also removed from the waves. The effects of finite switching times are discussed. This study defines some serious constraints in using switchable transmission lines for the realization of photonic time crystals and efficient wave manipulation without externally added energy. The results are also applicable to wave propagation phenomena in other media with time-varying parameters.

The Influence of mangrove arrangement on wave transmission using smoothed particle hydrodynamics

Mangroves have been proven for their role as a natural barrier to various environmental risks such as abrasion and erosion. It helped improve water quality, reducing storms and providing habitat for marine species. Not only playing an essential role in maintaining the water surface, Mangroves have a crucial role in several aspects such as ecology, economy, and socio-culture. This study aims to understand the effects of the arrangement and length of mangrove trees in wave transmission. The present study is performed on the mesh-free CFD method, i.e., the smoothed particle hydrodynamics (SPH), which was developed for free surface flow problems and complex interactions. Three variations of mangrove trees are used,i.e., uniform 0.3 m, random 0.3 m, and random 0.15 m. The piston wavemaker is based on a previous study that has been validated with experiments. The simulation results indicate 0.15 m variations in a gap for the transverse line on the longitudinal provide maximum wave transmission reduction. The wave transmission value produced by the mangrove forest is relatively small. Additionally, the wave energy result decreased significantly after passing through the mangroves.

Wave transmission through the megaregolith as a mechanism for lunar cold spot formation

Wave transmission through the megaregolith as a mechanism for lunar cold spot formation

Robust Integrated Ag/PP-PP/Ag Hollow Waveguide for Low-Loss and Low-Dispersion Transmission of Low-Frequency Terahertz Waves: Design, Fabrication and Performances

Robust Integrated Ag/PP-PP/Ag Hollow Waveguide for Low-Loss and Low-Dispersion Transmission of Low-Frequency Terahertz Waves: Design, Fabrication and Performances

A retrospective study of zoonotic tuberculosis among livestock farmers of Lahore district using one health approach

Objectives: Tuberculosis (TB) affects humans and animals regardless of species type, causing huge economic losses and deaths worldwide. However, the mechanisms and risk factors of zoonotic transmission are not well known in Pakistan. The current study aimed to identify the potential risk factors associated with TB in farmers and their animals, particularly exposure to infected animals in Lahore District, Pakistan. Materials and Methods: The study consisted of two components utilizing the concept of One Health. In the first component, a retrospective case-control study of human subjects (cases = 25, control = 25) was conducted from December 2021 to July 2022. In the second component, a cross-sectional analysis of the cattle owned by selected participants (TB cases and healthy controls) was completed in the Lahore district. A single intradermal tuberculin skin test was used to determine TB infection in cattle. Results: A total of 25 TB cases and 25 healthy controls were enrolled. Males in cases were found (OR = 0.01, 95% CI: 0.0002–0.29, p = 0.014) less likely to get TB, cases older than 35 years (OR = 1.13 (95% CI: 1.05–1.24, p = 0.004), unmarried cases (OR = 32.20, 95% CI: 2.92–819.03, p = 0.014), being a smoker (OR = 21.87, 95% CI: 2.80–395.82, p = 0.011), and keeping animals inside the home (OR = 9.92, 95% CI: 1.29–134.61, p = 0.047) were identified as significant predictors of TB in humans in the final multivariable logistic regression. Out of 175 tested animals, 3/65 animals belonging to the cases and 1/110 animals belonging to the controls were found positive. The animals belonging to the TB cases were (OR = 7.76, 95% CI; 0.79–76.02) more likely to have a positive Single Comparative Intradermal Tuberculin Test. The prevalence of bTB in animals belonging to the cases was 4.6% (95% CI, 1.26–12.58) compared to 0.9% (95% CI, 0.04–4.67) in animals of the control group. Conclusion: This study identified potential risk factors that could contribute to the complex wave of TB transmission between humans and animals. Our findings could provide data to inform policy-making and intervention strategies to reduce TB’s burden in both populations. Embracing a holistic One Health perspective is imperative to effectively combat this shared health threat.

Dual metal synergistic modulation of boron nitride for high-temperature wave-transparent metamaterials.

Electromagnetic metamaterials have demonstrated immense potential in the development of novel high-temperature wave-transparent materials, yet the requirements of their intricate structural design and strict stability pose dual challenges, particularly in high-speed radome applications. A strategy involving the synergistic modulation of boron nitride (BN) by dual metallic elements of Ca and Al (0.5Ca-0.5Al-BN) was proposed in this study, which elegantly integrates the advantages of metamaterial-like split ring resonator (SRR) features and h-BN's oxidation resistance enhancement. The highest wave transmittance at room temperature reaches 0.96 at 2-18 GHz. Notably, Al elements play a pivotal dual role in: (1) facilitating the solid solution of Ca to optimize the formation of metamaterial-like structures and (2) generating an amorphous Al2O3 protective layer to preferentially defend against surface oxidation. This further prevents the breakdown of metamaterial characteristics at high temperatures, thereby striking a dual balance between the preservation of metamaterial-like structures and the high temperature stability of BN. Notably, 0.5Ca-0.5Al-BN retains its metamaterial-like characteristics, with a low permittivity not exceeding 2 even after exposure to 1500 °C oxidation. The corresponding wave transmission rate remains above 0.7 in most frequency bands at incidence angles of 0°, 10°, and 30°, ensuring superior wave-transparent properties. Furthermore, 0.5Ca-0.5Al-BN exhibits great hydrophobicity, benefiting resistance to rain and snow erosion. By integrating the merits between fundamental materials and metamaterials, this work transcends the limitations of conventional metamaterial design and offers fresh insights and empirical support for developing high-speed aircraft radome materials.

Branching a benzoxazole-g-PBO fiber/cyanate ester resin composite with excellent wave transmission at high temperatures

Branching a benzoxazole-g-PBO fiber/cyanate ester resin composite with excellent wave transmission at high temperatures

Size-Dependent Effects in the Modified Green–Lindsay Thermoelasticity Model: Analysis of Ultrashort Pulse Interactions in the Presence of Electromagnetic Fields

Abstract This study provides a more detailed model for wave transmission and reflection in a complex thermodynamic framework. The governing equations are developed from multiphase electromagnetic size-dependent thermoelasticity models. The main focus here is on the development of the Modified-Green Lindsay nonlocal generalized thermoelasticity model that improves previous nonlocal approaches by incorporating additional strain and temperature rate terms. This study also examines how materials react to very short pulses and the effect of external electric and magnetic fields. The highly developed nonlinear equations in this study are solved using advanced programming techniques, including an iterative approach that combines finite element methods with a Newmark time-marching scheme. The results of this work established the nonlocal heat conduction theory of generalized thermoelasticity along with nonlocal continuum theory as a new improvement and progress in the field of thermoelasticity. This model shows that without considering thermal nonlocality interactions, predictions may miss essential aspects of wave behavior. The results show that the materials experience changes in mechanical properties, particularly an increase in hardness, when exposed to stronger magnetic fields. In addition, the results show that as the duration of laser pulses decreases, the speed of wave propagation increases. Shortening the pulse duration increases the wave propagation speed, which can create steep thermal gradients. In the case of pure metals heated by ultra-short pulse lasers, the fast electron heat conduction prevents the formation of significant thermal waves, while these pulses induce more intense and localized thermal stresses. Analysis of wave propagation also shows that the return time can exceed the forward time as the waves react to applied electric and magnetic fields.