Wave Conversion Research Articles

Porous-Solid Metaconverters for Broadband Underwater Sound Absorption and Insulation

Existing solid composite structures composed of several viscoelastic materials and metals mainly exploit diverse resonances, damping, and scattering to realize underwater acoustic wave functionalities. However, low-frequency broadband underwater sound absorption and insulation are still hard to capture with an acoustic coating possessing subwavelength thickness and lightweight nature simultaneously. This paper reports the systematic simulated and experimental validations of a porous-solid underwater metaconverter, consisting of a rubber layer and a topology-optimized elastic metasurface to exhibit broadband functionalities of sound absorption and insulation caused by the strong reflective and transmitted longitudinal-to-transverse wave conversion, while sustaining broadband impedance matching. Various results confirm the predicted capabilities of underwater broadband high-efficiency sound absorption (>80%) or insulation (20 dB) within the range of 2–10 kHz for a large- and limited-size sample, providing an estimate of the energy-converting effect and phenomenon. The present study provides possibilities for elastic wave energy dissipation, harvesting, and underwater acoustic stealth via metasurfaces.4 MoreReceived 9 December 2022Revised 3 February 2023Accepted 28 February 2023DOI:https://doi.org/10.1103/PhysRevApplied.19.044074© 2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAcoustic metamaterialsAcoustic wave phenomenaArchitectural acousticsCloakingMechanical & acoustical propertiesUnderwater acousticsPhysical SystemsPorous mediaTechniquesSound wave techniquesCondensed Matter, Materials & Applied Physics

Space-time exchanged symplectic integrator approach to temporal-mode selective optical three-wave mixing frequency conversion

A space-time exchanged symplectic integrator (SI) method is developed to solve the three-wave resonance interaction equations commonly used in describing a number of fundamental nonlinear optical phenomena, such as second harmonic generation, optical parametric amplification, etc. Exchanging the roles of the space and time coordinates allows us to solve these nonlinearly coupled equations with hard-wired boundary conditions using a highly accurate SI scheme instead of standard finite difference methods. The developed method is then applied to the optical three-wave mixing frequency conversion processes in which an input signal light is converted into an idler light guided by a strong pump pulse. The temporal-mode selectivity in the frequency conversion processes is examined by systematically varying system parameters and the results are summarized as contour maps of selectivity on the ‘group-slownesses’, defined by the inverse of the group velocities, of the signal pulse and of the idler pulse relative to that of the pump pulse. The areas showing the highest peaks on these undergo significant and characteristic changes in their positions as well as the heights for different values of the coupling strength γ. The observed trends are rationalized on the basis of the Schmidt modes obtained by decomposing the two-time transfer function that fully characterizes the dynamics of the signal–idler wave conversion.

Theoretical and experimental studies of effects of non-axisymmetric inner structures on vibration signatures of axisymmetric submarine hulls

A unified hybrid analytical-numerical method is proposed for vibration analysis of stiffened hulls coupled with non-axisymmetric internal structures. The coupled system is firstly decomposed into the submarine hull and internal structures. Then, the stiffened hull is further divided into ring stiffeners, bulkheads and shell segments, including conical and cylindrical shell segments. The shell strips and axisymmetric reinforcements are uniformly described by the Flügge formula and power series method. For non-axisymmetric interior structures, finite element method is utilized to establish the motion equations owing to their irregular shapes. To synthesize the shell and non-axisymmetric internal structures, the receptance functions at coupling nodes are respectively deduced by condensing the global stiff matrices of the hull and interior substructures. A precise coupling method fully considering all 6 DOFs at coupling nodes, rather than just 3 or 4 DOFs in previous literature, is proposed to synthesize the receptance functions. To verify the validity of this approach, a stiffened conical-cylindrical-spherical shell coupled with two foundations is manufactured and the forced vibration characteristics of this coupled model subjected to multiple types of excitations are tested. Results obtained by semi-analytical method are simultaneously compared with the ones measured from this experiment and calculated through finite element method (FEM). Effects of the inner structures and different external excitations on forced vibrations are discussed by experiment. Furthermore, how non-axisymmetric internal structures modify wave propagation and conversion characteristics of axisymmetric hulls is investigated through the present method.

Staggered circular nanoporous graphene converts electromagnetic waves into electricity

Harvesting largely ignored and wasted electromagnetic (EM) energy released by electronic devices and converting it into direct current (DC) electricity is an attractive strategy not only to reduce EM pollution but also address the ever-increasing energy crisis. Here we report the synthesis of nanoparticle-templated graphene with monodisperse and staggered circular nanopores enabling an EM–heat–DC conversion pathway. We experimentally and theoretically demonstrate that this staggered nanoporous structure alters graphene’s electronic and phononic properties by synergistically manipulating its intralayer nanostructures and interlayer interactions. The staggered circular nanoporous graphene exhibits an anomalous combination of properties, which lead to an efficient absorption and conversion of EM waves into heat and in turn an output of DC electricity through the thermoelectric effect. Overall, our results advance the fundamental understanding of the structure–property relationships of ordered nanoporous graphene, providing an effective strategy to reduce EM pollution and generate electric energy.

Wave Conversion, Decay, and Heating in a Partially Ionized Two-fluid Magneto-atmosphere

A ray-theoretic phase-space description of linear waves in a two-fluid (charges and neutrals) magnetized plasma is used to calculate analytic decay rates and mode transmission and conversion coefficients between fast and slow waves in two dimensions due to finite ion–neutral collision frequencies at an arbitrary ionization fraction. This is relevant to partially ionized astrophysical plasmas, in particular solar and stellar atmospheres. The most important parameter governing collisional effects is the ratio of the wave frequency to the neutral–charges collision frequency, ϵ = ω/ν nc, with secondary dependence on ionization fraction and wave attack angle. Comparison is made to the one-fluid magnetohydrodynamic case, and it is found that acoustic-to-acoustic and magnetic-to-magnetic transmission through the Alfvén-acoustic equipartition layer is decreased by a term of relative to one-fluid (infinite collision frequency), and correspondingly acoustic-to-magnetic and magnetic-to-acoustic conversion is increased. The neutral-acoustic mode is shown to dissipate rapidly as ν nc → ∞. Away from the mode conversion region, dissipative decay along the remaining magneto-acoustic rays scales as and is found to be much more effective on magnetically dominated rays compared to acoustically dominated rays. This produces a steep jump in dissipation in mode conversion regions, where the rays change character, and can produce localized heating there and beyond. Applications to the solar chromosphere are discussed.

Tunable metasurfaces for seismic Love wave manipulation: A theoretical study

Seismic Love waves are horizontally polarized surface waves propagating within an overlying layer, which have been shown to pose potential hazards to infrastructures. In this study, we propose an original analytical formulation to investigate the interaction between seismic Love waves and a metasurface that is composed of a cluster of tunable anti-plane resonators. The formulation utilizes the Green's function of a layered half-space subjected to a surface SH source, to describe both the source-induced incident field and the resonator-excited scattered field. Based on the multiple scattering theory, we obtain the total wavefield of the layered half-space equipped with surface resonators by coupling the incident field and the scattered field. Besides, a closed-form dispersion relation governing the hybrid Love waves is derived by utilizing the effective medium approximation. We demonstrate the capabilities of our analytical formulation by modelling Love waves propagating across a pair and a cluster of resonators, evidenced by some complex phenomena (e.g., surface-to-bulk wave conversion and higher-order hybridized surface modes). The hybridization features of different Love modes and metasurface resonances are clearly revealed. We anticipate the proposed tunable metasurface and the formulation can shed light on versatile control of Love wave propagation.

Dynamic Performance and Stress Wave Propagation Characteristics of Parallel Jointed Rock Mass Using the SHPB Technique

To investigate the effects of joint number on dynamic compressive strength, crushing effect, stress wave propagation, stress wave conversion, and energy evolution of rock masses, SHPB and LS-DYNA were used to conduct impact experiments and numerical simulations, respectively. The results demonstrate that the dynamic strength of a multi-jointed (two- and three-jointed) rock are 11.1 and 25.1% lower, respectively, compared with that of a single-jointed rock. The weak surface near the joint causes the rock mass to crack first. The rock cracking time advances significantly as the joints number increases. The reflection coefficient falls as the number of joints increases, because the wave impedance of the joint differs from that of the rock. The transmission coefficient, however, is exactly the reverse. When the P wave strikes the specimen, the vibration direction of the particles is deflected at the joint, resulting in a shear wave. P waves are reflected and superimposed between joints, increasing the strength of shear waves and resulting in more transverse cracks in multi-jointed rock masses under dynamic loading. Meanwhile, the total energy consumed by a bedrock under dynamic loading is obviously larger than that of joints. However, the total energy absorbed by joints exceeds that of the bedrock when the joints number increases. The results further enrich the dynamic basis of jointed rock masses.

Regression relationships for conversion of body wave and surface wave magnitudes toward Das magnitude scale, Mwg

A reliable and standardized estimation of earthquake size is a fundamental requirement for all tectonophysical and engineering applications. Several investigations raised questions about the determinations of smaller and intermediate earthquakes using Mw scale. Recent investigations (Das et al. in Bull Seismol Soc Am 108(4):1995–2007, 2018b) show that the moment magnitude scale Mw is not applicable for lower and intermediate ranges throughout the world and does not efficiently represent the seismic source potential due to its dependence on surface wave magnitudes; therefore, an observed seismic moment (M0)-based magnitude scale, Mwg, which smoothly connects seismic source processes and highly correlates with seismic-radiated energy (Es) compared to the Mw scale is suggested. With the goal of constructing a homogeneous data set of Mwg to be used for earthquake-related studies, relationships for body wave (mb) and surface wave magnitudes (Ms) toward Mwg have been developed using regression methodologies such as generalized orthogonal regression (GOR) (GOR1: GOR relation is expressed in terms of the observed independent variable; and GOR2: GOR relation is used inappropriately in terms of theoretical true point of GOR line) and standard least-square regression (SLR). In order to establish regression relationships, global data have been considered during 1976–2014 for mb magnitudes of 524,790 events from the International Seismological Centre (ISC) and 326,201 events from the National Earthquake Information Center (NEIC), Ms magnitudes of 111,443 events from ISC along with 41,810 Mwg events data from the Global Centroid Moment Tensor (GCMT). Scaling relationships have been obtained between mb and Mwg for magnitude range 4.5 ≤ mb ≤ 6.2 for ISC and NEIC events using GOR1, GOR2 and SLR methodologies. Furthermore, scaling relationships between Ms and Mwg have been obtained for magnitude ranges 3.0 ≤ Ms ≤ 6.1 and 6.2 ≤ Ms ≤ 8.4 using GOR1, GOR2 and SLR procedures. Our analysis found that GOR1 provides improved estimates of dependent variable compared to GOR2 and SLR on the basis of statistical parameters (mainly uncertainty on slope and intercept, RMSE and Rxy) as reported in Das et al. (2018b). The derived global scaling relationships would be helpful for various seismological applications such as seismicity, seismic hazard and Risk assessment studies.

Terahertz Receiver based on Room-Temperature Rydberg-Atoms

Realization of practical terahertz wireless communications still faces many challenges. The receiver with high sensitivity is important for THz wireless communications. Here we demonstrate a terahertz receiver based on the cesium Rydberg atoms in a room-temperature vapor cell. The minimum detectable THz electric field is calibrated. With this receiver, the phase-sensitive conversion of amplitude-modulated or frequency-modulated terahertz waves into optical signals is performed. The results show that the atomic receiver has many advantages due to its quantum properties. Particularly, the long distance THz wireless communications is achievable using this receiver. Furthermore, the atomic receiver can be used in the THz wireless-to-optical link.

Dual-band valley topological refraction materials for bulk elastic waves manipulation

Valley topological refraction material (TRM) of elastic wave and its direction signal transmittance with robustness against structural disturbance is crucial for various applications such as communication, navigation and detection devices for medical and industrial purpose. However, the existing TRM is limited by the single topological band, which obviously hinders the exploration of the multi-band topological ultrasonic devices to guarantee its efficiency and stability. Here, we demonstrate the dual-band valley TRM for elastic waves, in which the valley edge states and their robustness are investigated. Furthermore, the topological refractions of the valley edge states from the interface into the free space at zigzag termination in two frequency bands are explored, where the mode conversion of the bulk elastic wave occurs at interface termination. Interestingly, the full mode conversion from longitudinal to transverse waves is revealed in the low frequency band while the non-full mode conversion between the longitudinal and transverse takes place in the high frequency band. The researched dual-band elastic TRM could facilitate the potential applications in multi-band and multi-directional devices.

Моделирование магнитоэлектрического материала для антенн

The paper is devoted to the modeling of magnetoelectric material for antennas. The effect observed in magnetoelectric gradient structures is discussed. Gradient magnetoelectric structures are a new type of composite structures consisting of a magnetoelectric material and an artificial dielectric. A new principle of controlling the antenna wave properties based on the geometric displacement of the excitation point due to the application of an external electric field is being considered. The use of an artificial dielectric in a multiferroid structure will make it possible to more flexibly control the areas of conversion of a magnetostatic surface wave into an electromagnetic wave, which in practical terms will give new opportunities for controlling the characteristics of antennas. The conclusion about the possibility of controlled conversion of a magnetostatic surface wave into an electromagnetic wave was obtained as a result of calculations based on the developed model by selecting the values of stationary magnetic and electric fields, and the values of the permittivity of the artificial dielectric layer

Conversion of Waves Under Different Gravitational Field Intensity Area

Natural disturbances in the gravitational field cause light, infrared, x-ray, and other waves. We define a complete wave as ‎having two parts: a crest and a trough. A complete wave represents a single frequency. Every wave is initially powered at the ‎source along with its wavelength and amplitude, which all vary with the gravitational field intensity in subsequent steps. A/λ ‎has a significant impact on the wave's power. A gravitational wave is a converted wave, because of its changing power due to ‎the changing intensity of the gravitational field.‎

Controllable wavelength conversion based on soliton dynamics in mid-infrared fiber

We provide a convenient way to actively control the wavelength conversion of probe waves based on the soliton dynamics in the As2S3 fibers. In this paper, it is found by numerical calculation that wavelength conversion occurs in the frequency domain due to the existence of refractive index barrier. By adjusting the collision position of pump pulse and probe pulse to realize the conversion of probe pulse wavelength, the effect of the power and the incident wavelength of the probe wave on the wavelength conversion are also discussed. This frequency domain conversion is of great use in the mid-infrared region, for example, all-optical conversion switches.

NON-REFLECTIVE INCIDENCE OF P-POLARIZED ELECTROMAGNETIC WAVES ON THE SOLID-STATE STRUCTURE "UNIAXIAL PLASMONIC METASURFACE — DIELECTRIC LAYER — METAL"

Subject and Purpose. The solid-state structures involving metasurfaces can be used to effectively control some of the basic properties of electromagnetic waves, like amplitude, phase and polarization. The present work is aimed at analyzing the new effects that may appear during incidence of p-polarized electromagnetic waves upon a solid-state structure involving a uniaxial plasmonic metasurface, a dielec- tric interlayer, and a layer of metal. Methods and Methodology. The conditions suitable for identifying the effects that result from the reflection of a p-polarized electro- magnetic wave incident upon a solid-state structure of the above described type have been sought for via numerical simulation. That has allowed finding the magnitudes of the essential parameters, such as angles of incidence and frequencies of the electromagnetic waves, as well as thicknesses of the dielectric interlayer, that could stipulate appearance of novel electromagnetic effects. Results. It has been shown that the solid-state structure involving a uniaxial plasmonic metasurface, a dielectric interlayer, and a layer of metal is capable, under certain conditions, to fully absorb an incident electromagnetic wave of p-polarization. Moreover, a new effect has been predicted, specifically that of full conversion of the incident p-polarized electromagnetic wave into a reflected wave of s-polariza- tion. The necessary condition is that the plane of incidence of the electromagnetic wave were at an acute angle to the principal symmetry axis of the plasmonic metasurface. Conclusions. The solid-state structures of the type involving a uniaxial plasmonic metasurface, a dielectric interlayer, and a layer of metal are characterized by unique reflective properties. They are capable of fully absorbing, under certain conditions, the p-polarized electromagnetic waves incident upon them. Such structures can be used for creating optical and nanoelectronic devices of new types.

Amplification and Frequency Conversion of Spin Waves Using Acoustic Waves

Amplification and Frequency Conversion of Spin Waves Using Acoustic Waves

Quantitative phase reconstruction method based on an infrared-like single wave conversion in dual-wavelength phase-shift digital holography

Dual-wavelength digital holography has recently become a promising tool for achieving higher axial measurement ranges in microscopy. However, digital filtering, such as Fourier transform, or a separate hologram acquisition process is essential for retrieving the quantitative phase information of each respective wavelength. In this paper, a quantitative phase reconstruction method based on an infrared-like single wave conversion in dual-wavelength phase-shift digital holography, which does not require any of the processes mentioned above, has been proposed. Based on the proposed method, the quantitative phase information on the axial measurement specimen was simply obtained by only a phase-shift of a quarter of an infrared-like single wave which has the same magnitude of the synthetic wavelength. This approach simplifies not only the hologram acquisition process but also the numerical reconstruction process. The newly proposed theory is verified and evaluated using simulations and experimental validation.

STUDY OF WAVE TRANSFORMATION AT COASTLINE CHANGE IN MENDALOK, SUNGAI KUNYIT SUB-DISTRICT, MEMPAWAH REGENCY, WEST KALIMANTAN

As one of the coastal areas, Mendalok, Sungai Kunyit sub-District, Mempawah Regency faces problems caused by coastline changes such as administrative area changes and damage to the mangrove forest ecosystem in the region. The objective of this study is to determine the process of wave conversion leading to coastline changes and to determine the potential for coastline changes from 2021 to 2031. Coastline change modelling analysis is performed with the CEDAS-NEMOS application. The results showed that the wave movement pattern was dominated by the southwest and west with a significant wave height averaging 1.36 meters and the waves were broken with a wave angle of 208.09o. The result of the coastline change modelling shows that coastline changes are more dominant in the study area when experiencing abrasion with calibration values of K1 0.5 and K2 0.25. Predicting the coastline changes that will occur from 2021 to 2031 shows that the coast with the greatest abrasion value of 31.83 meters and some accretion is more dominant with the greatest accretion value of 11.21 meters.

STUDY OF WAVE TRANSFORMATION AT COASTLINE CHANGE IN MENDALOK, SUNGAI KUNYIT SUB-DISTRICT, MEMPAWAH REGENCY, WEST KALIMANTAN

As one of the coastal areas, Mendalok, Sungai Kunyit sub-District, Mempawah Regency faces problems caused by coastline changes such as administrative area changes and damage to the mangrove forest ecosystem in the region. The objective of this study is to determine the process of wave conversion leading to coastline changes and to determine the potential for coastline changes from 2021 to 2031. Coastline change modelling analysis is performed with the CEDAS-NEMOS application. The results showed that the wave movement pattern was dominated by the southwest and west with a significant wave height averaging 1.36 meters and the waves were broken with a wave angle of 208.09o. The result of the coastline change modelling shows that coastline changes are more dominant in the study area when experiencing abrasion with calibration values of K1 0.5 and K2 0.25. Predicting the coastline changes that will occur from 2021 to 2031 shows that the coast with the greatest abrasion value of 31.83 meters and some accretion is more dominant with the greatest accretion value of 11.21 meters.

Theoretical design of multilayered VO2-based switchable terahertz metasurfaces as broadband functional devices

In this paper, a switchable terahertz metasurface based on VO2 multilayer structure is raised, which utilizes the temperature phase-transition properties of VO2 to achieve the functions of switchable polarization conversion and reflection phase modulation for arbitrarily polarized waves at different temperatures. The simulation results show that at high-temperature and low-temperature, the metasurface develop a resonant system to achieve polarization conversion for circularly polarized (CP) and linearly polarized (LP) waves, respectively. For the conversion of the CP wave at high-temperature, the polarization conversion rate exceeds 90% in the terahertz frequency range of 1.01 ∼ 2.00 THz, and at low-temperature, the polarization conversion of the LP wave reaches a near-perfect polarization conversion rate at frequencies ν = 0.65, 1.07, and 1.50 THz. Arbitrary phase regulation can be achieved by rotating the VO2 strips and altering the geometry of the C-shaped split resonator ring (CSRR) to form a periodic array with a constant gradient phase. In order to verify that the device has the function of wavefront phase modulation, we use the device to simulate the abnormal reflection based on the generalized Snell’s law.Additionally, we generated a bifocal focused beam within a cross-channel in LP incidence mode using the propagation phase principle.

Full-space polarization conversion of electromagnetic waves at terahertz frequency based on metasurface

In this paper, a full-space electromagnetic wave polarization converter working in the terahertz frequency was put forward, and its physical mechanism was also analyzed. The polarization converter could realize the reflection cross-polarization conversion in the frequency range of 3.16–3.75 THz, with the Polarization Conversion Rate (PCR) of more than 90%. In the frequency range of 0.43–2.15 THz, it could realize transmission cross-polarization conversion, with the PCR close to 100%. In short, the designed metasurface polarization converter has a simple structure, realizes full-space manipulation of electromagnetic waves, facilitates the miniaturization and integration of the system, and has the potential applications in antennas, imaging systems, remote sensors, and radiometers.