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On 15 January 2022, the largest eruption of the Hunga‐Tonga volcano in recorded history produced a plume registered by multi‐parametric instruments around the world. However, the far‐field hydrogeological responses to Lamb waves from this eruption remain underexplored. We studied the responses of groundwater to the volcanic eruption in the far‐field over 8,700 km, including 274 wells. Results show that the Lamb waves with a speed of 316 m/s affects the groundwater system, leading to similar fluctuations in well water level (WL) and opposite phase fluctuation in borehole strain. Different wells exhibit diverse responses in WL amplitudes, possibly for heterogeneities in local aquifer systems. Gain values of 5 wells that simultaneously measure atmospheric pressure, borehole air pressure, borehole strain and WL are consistent with results obtained through cross‐power spectrum estimation. This work demonstrates a novel response in far‐field groundwater systems induced by Lamb waves and expects application for aquifer parameter estimation. Plain Language Summary: The massive eruption of the Hunga‐Tonga volcano on 15 January 2022 generated shock waves in the Earth's atmospheric layer, known as Lamb waves, which propagated at the boundary of air and the solid Earth. While many studies reported multi‐parameter responses during or after the eruption, the response of the groundwater system has not been studied. In this study, we found that Lamb waves from the volcano eruption induced similar phase responses in the water levels of 256 wells within the 274‐well network and opposite phase responses in borehole strain in mainland China. Additionally, the Lamb wave induced a possible time lag in the response of well water level (WL) and horizontal strain, which may be caused by different hydraulic properties of the wells. In the five wells with common observations, the calculated atmosphere pressure sensitivity is consistent with previous studies. The response of well WL to the Lamb wave is obviously different compared to that observed during co‐seismic events and Earth tides. Key Points: The Lamb wave from the Hunga‐Tonga volcano eruption induces similar phase responses in the water level (WL) of 256 wells in the far fieldResponses of well WL and borehole strain to the Lamb wave show a possible time‐delay relative to that of atmosphere pressureThe incorporation of the WL parameter and horizontal transverse strain is recommended to calibrate the appropriate models [ABSTRACT FROM AUTHOR]

A general expression for the magnetostatic field generated by mechanical deformations to a ferromagnetic material in the continuum description is derived. Linearization with respect to the displacement vector is shown to be well defined. To demonstrate the use of the formulation, two examples are discussed. First, a complete derivation of the magneto‐rotation coupling for a uniformly magnetized film is given. Second, the lowest asymmetric mode of Lamb waves propagating through a magnetic vortex is shown to induce an in‐plane magnetostatic field localized around the vortex core. [ABSTRACT FROM AUTHOR]

Manipulating terahertz (THz) polarization in an efficient and broadband manner is of great significance to facilitating THz applications, including communications, imaging, defense, and homeland security. In this work, a dispersion compensation scheme is proposed for high‐efficiency and ultra‐broadband THz polarization manipulation using an anisotropic dielectric‐metal hybrid metadevice. The operating bandwidth is broadened by dispersion compensation, where the dielectric grating provides an artificial birefringence with a phase dispersion of positive slope and the metallic grating provides a phase dispersion of negative slope. Experimental results show that the device achieves two ultra‐broadband dispersion compensation, corresponding to the achromatic quarter‐wave plate in the lower frequency band (QWP: 0.5–2.0 THz, PCR >0.95) and the achromatic half‐wave plate in the higher frequency band (HWP: 1.0–2.1 THz, PCR >0.9), respectively. Theoretically, the bandwidth of QWP can be further improved to 2.6 THz by optimizing the grating dispersion, which brings huge application space to cover most of the THz radiation. This hybrid metadevice configuration offers a versatile platform for engineering electromagnetic waves, and the strategy of phase compensation can be generalized to extend the bandwidth of the metadevice in imaging and communications. [ABSTRACT FROM AUTHOR]

Ice shelves are assumed to flow steadily from their grounding lines to the ice front. We report the detection of ice‐propagating extensional Lamb (plate) waves accompanied by pulses of permanent ice shelf displacement observed by co‐located Global Navigation Satellite System receivers and seismographs on the Ross Ice Shelf. The extensional waves and associated ice shelf displacement are produced by tidally triggered basal slip events of the Whillans Ice Stream, which flows into the ice shelf. The propagation velocity of 2,800 m/s is intermediate between shear and compressional ice velocities, with velocity and particle motions consistent with predictions for extensional Lamb waves. During the passage of the Lamb waves the entire ice shelf is displaced about 60 mm with a velocity more than an order of magnitude above its long‐term flow rate. Observed displacements indicate a peak dynamic strain of 10−7, comparable to that of earthquake surface waves that trigger ice quakes. Plain Language Summary: Ice shelves normally flow steadily toward their boundaries with the open ocean at the ice front. However, seismographs and Global Navigation Satellite System receivers deployed on the Ross Ice Shelf record guided elastic plate waves traveling in the ice as well as permanent displacement of the ice shelf. The elastic waves and ice shelf displacement originate from basal slip events of the Whillans Ice Stream, which flows into the Ross Ice Shelf. The velocity of the elastic waves is about 2,800 m/s, as expected for guided plate waves propagating in an ice shelf. During the passage of the elastic waves, the entire ice shelf with an area of 500,000 square kilometers is displaced about 60 mm in a direction away from the Whillans Ice Stream. These observations show that the strain imparted to the ice shelf by the once or twice daily Whillans Ice Stream basal slip events is sufficient to trigger ice quakes and perhaps enhance the deformation of the ice shelf. Key Points: Extensional Lamb waves propagate across the Ross Ice Shelf, radiated from slip events at the base of the Whillans Ice StreamDuring the passage of the Lamb waves, the entire ice shelf is displaced about 60 mm, with a velocity an order of magnitude above its long‐term flow rateThe displacement pulses produce a peak dynamic strain of 10−7, suggesting that they could trigger icequakes in the ice shelf [ABSTRACT FROM AUTHOR]

Compact circularly‐polarized (CP) light sources are important for chirality‐based applications at the chip level. The CP light is conventionally generated by passing the linearly‐polarized (LP) one through quarter wave plates which are too thick for packed integrations. In this work, the in‐plane submicron phase shifter substitutes the quarter‐wave plate in the creation of CP light. After the lasing field of a holed microdisk is coupled into the nearby waveguide and phase shifter, it is guided into two grating couplers that output orthogonally LP waves vertically. The two LP waves are phase‐shifted by π/2$\pi /2$ and combine into the coherent CP radiation in the far‐field zone. Experimentally, the fabricated devices exhibit a degree of circular polarization as high as 74%. This device scheme is simple and effective in that it relies on no extrinsic materials, large‐area auxiliary structures, or specialized operation conditions critical for CP radiation. The compatibility issues for integrated photonic systems are of less concern in such schemes. [ABSTRACT FROM AUTHOR]

This study presents the observation and evaluation of a meteotsunami in the Indian Ocean triggered by the Hunga‐Tonga volcanic eruption. The event was detected through tide gauges and bottom‐pressure recordings across the Indian Ocean, with an amplitude of 10–15 cm, lasting for a few days. A numerical model was used to understand the ocean's response to meteotsunami and evaluate the dynamics behind it. The model results show that the sea‐level oscillations result from the ocean waves generated by a propagating Lamb wave. In addition to interaction with bathymetry, refracted and reflected waves also determine the sea‐level variability. Our analysis shows that bathymetric slope plays a vital role in near‐shore processes. The spectral and spatial characteristics of the meteotsunami were reminiscent of seismic tsunamis. Our research on this rare event elucidates the unresolved issues and eventually leads to designing a blueprint for future observation and modeling of meteotsunamis and seismic tsunamis. Plain Language Summary: This study evaluates the observation of a rare meteotsunami event that occurred in the Indian Ocean. An atmospheric pressure wave generated by the eruption of the Hunga‐Tonga volcano in the Pacific Ocean caused the meteotsunami. The signatures of this event were captured by tide gauges installed along the coast and pressure recorders moored at the ocean floor. We demonstrate using a numerical model that fast‐moving atmospheric pressure waves, Lamb waves, caused the sea‐level oscillations. Interactions with bathymetry further influenced sea‐level variability in the basin, reflected waves, and refracted waves. The vulnerable areas showed a striking resemblance to the area impacted by the tsunami that hit the Indian Ocean in 2004. This research eventually helps to identify and incorporate observational and modeling issues associated with seismic tsunamis and meteotsunami. Key Points: We present the first comprehensive evaluation of meteotsunami in the Indian Ocean using observation and modelingA forced wave to free wave transformation happens on the continental slope, and the bathymetry slope is crucial to near‐shore processesThe meteotsunami exhibits a spectral and spatial similarity to seismic tsunamis that previously occurred in the Indian Ocean [ABSTRACT FROM AUTHOR]

Corrugated plate mist eliminators are commonly employed in industrial processes to eliminate liquid droplets from gas flows. Engineering a mist eliminator with excellent separation performance including high removal efficiency and low pressure drop and is a primary consideration in industrial processes. This study focuses on the separation of tiny droplets reinforced by the generation of transverse vortices with the help of curved wings. The Euler–Lagrange model is developed to predict the behavior of droplets in gas streams, and velocity distributions and particle trajectories on the demisters were derived. And the prediction equations of the curved wing structure sizes on the efficiency and pressure drop of the mist eliminator are established. The results demonstrated that the grade separation efficiency of 10~20 μm droplet was significantly improved by 25.7%~66.51%. Moreover, for the total removal efficiency, it could be improved from.8 to.92 at 5.5 m s−1, and the accompanying resistance factor was as low as 2.7. Among the proposed arrangements, the double‐row single‐column array arrangement was characterized by higher demisting efficiency and lower pressure drop. Overall, compared to other optimization methods, this proposed optimization approach by means of transverse vortices yielded a higher demisting efficiency and less pressure drop. [ABSTRACT FROM AUTHOR]

The strongest volcanic eruption since the 19th century occurred on 15 January 2022 at Hunga Tonga‐Hunga Ha'apai, generating unprecedented atmospheric waves not seen before in observations. We used satellite microwave observations from (a) Advanced Technology Microwave Sounder (ATMS) on board the National Oceanic and Atmospheric Administration (NOAA)‐20 and the Suomi‐National Polar‐orbiting Partnership (SNPP) and (b) Advanced Microwave Sounding Unit (AMSU)‐A on board Meteorological operational satellite (MetOp)‐B/MetOp‐C to study these waves in the stratosphere immediately after the eruption. The NOAA Microwave Integrated Retrieval System (MiRS) was applied to these microwave observations to produce atmospheric temperature profiles. The atmospheric Lamb wave and fast‐traveling gravity waves are clearly revealed in both the brightness temperatures and the MiRS retrieved temperatures, revealing their vertical phase structures. This study is the first attempt to perform a detailed analysis of the stratospheric impact of the Tonga eruption on operational satellite microwave observations and the corresponding MiRS retrievals. Plain Language Summary: The strongest volcanic eruption since the 19th century occurred on 15 January 2022 at Hunga Tonga‐Hunga Ha'apai. The microwave instruments onboard the currently operational satellites observed the area in the vicinity of the eruption. The eruption impacts were most obvious at high altitudes (the stratosphere) in the observed microwave brightness temperatures. Additionally, atmospheric temperature profiles have been retrieved using the satellite measured microwave brightness temperatures. The retrieved atmospheric temperature fields also show the impacts of the volcanic eruption in the stratosphere. This study is the first attempt to perform a detailed analysis of the impact of the Tonga volcanic eruption using operational satellite microwave observations and the corresponding retrievals. Key Points: Microwave observations from multiple satellites capture stratospheric waves from the Tonga eruption, including Lamb and gravity wavesMiRS atmospheric temperature retrievals also resolve wave perturbations in the stratosphere after the eruptionThe Lamb wave and the lead gravity wave show no apparent phase change with height, whereas the trailing gravity waves do [ABSTRACT FROM AUTHOR]

The use of metamaterials in terahertz (THz) polarization wave plates is widespread. Metallic metamaterials, however, typically operate within a constrained bandwidth and have a large ohmic loss. All‐dielectric metamaterials could address these issues. To achieve an ultrawide‐band at THz frequencies, a multilayered silicon metasurface with elliptical or rectangular pillars has been employed. According to simulations, the achromatic relative bandwidth of the dielectric metamaterial can remain flat within a broadband with the appropriate structural parameters. Additionally, a scoring system with error analysis is added to help with choosing the geometry of terahertz polarization wave plates with various layers of metasurface. Due to its flexible polarization control capability, the proposed multilayer metasurface may open the door for arbitrary phase delays of incident waves. [ABSTRACT FROM AUTHOR]

Intense eruptions of the Tonga volcano activated prominent traveling atmospheric disturbances (TADs) at 04:05UT on 15 January 2022. Himawari‐8 satellite images depict that TADs of the tropospheric Lamb wavefront propagate with a speed of 315 m/s and arrive in Taiwan at 11:30UT. Networks of 98 barometers, 28 tide gauges, an ionosonde, and 10 magnetometers are used to study the responses of magnetic fields to TADs in Taiwan. The horizontal components in magnetic field changes of the Taiwan magnetometers all point toward and away from the Tonga volcano at 11:00–12:00UT upon the tropospheric Lamb wavefront arrival and at 22:00–23:00UT when the thermospheric Lamb wavefront with speeds of 487 m/s coming, respectively. Analyses of the raytracing and beamforming techniques on the horizontal components in magnetic field changes of 69 INTERMAGNET magnetometers show that both tropospheric and thermospheric Lamb waves efficiently activate traveling ionospheric disturbances and modify ionospheric currents of the globe. Plain Language Summary: At 04:05UT on 15 January 2022, intense Tonga volcanic eruptions induce prominent atmospheric disturbances and tsunami waves. Himawari‐8 meteorological satellite images depict the induced upper‐level tropospheric disturbances with horizontal speeds of about 315 m/s at 8.2 km altitude in the Lamb wave mode travel worldwide. Upon the traveling atmospheric disturbances (TADs) of the tropospheric Lamb wavefront arriving in Taiwan at 11:30UT, 98 ground‐based barometers register increases and reach peaks at about 11:50UT in the atmospheric pressure; 28 tide gauges record enhancements and maximums of sea level fluctuations at about 14:30–17:30UT; and a local ionosonde observes that the ionosphere reaches the highest altitude at 14:30UT. The changes of the horizontal component of the Earth's magnetic fields measured by 10 Taiwan magnetometers almost all point exactly toward the Tonga volcano upon the tropospheric Lamb wavefront arrival at 11:00–12:00UT, and away from the volcano at 22:00–23:00UT, which suggests a 487 m/s TAD (or thermospheric Lamb wavefront) at about 130 km altitude also being activated. The horizontal components in magnetic field changes of 69 INTERMAGNET magnetometers show that both tropospheric and thermospheric Lamb waves triggered by Tonga volcanic eruptions are very powerful, and can induce intense dynamo currents and electric fields on the globe. Key Points: Tropospheric and thermospheric Lamb waves of the Tonga volcanic eruption activate dynamo currents and electric fieldsTraveling atmospheric disturbances of the Tonga volcanic eruption significantly uplift the ionosphereTropospheric Lamb waves of the Tonga volcanic eruption modulate ground‐based air pressures and sea levels [ABSTRACT FROM AUTHOR]

In 2022, the Hunga volcano eruption in Tonga generated atmospheric pressure waves that propagated globally and produced tsunamis in all the world's oceans. The largest pressure wave, with an amplitude of several hundred pascals, is the Lamb wave. Standard Lamb wave models, incorporating the sound‐speed as a function of temperature, satisfactorily explain observations in the near‐field but not in the far‐field. We show that an augmented Lamb wave model that includes the effects of wind and topography accurately reproduces the wavefronts observed by satellites and barometers, including those close to the antipode. Winds, first suggested to explain the travel times of Lamb waves from Krakatau in 1883, are now shown to also play a major role in shaping their waveforms; temperature and topography play smaller, but still detectable, roles. Our augmented model provides a significant advance for the development of early warning and hazard assessments for the meteotsunamis these waves produce. Plain Language Summary: The January 2022 explosive eruption of the Hunga volcano in Tonga produced a pressure wave (of a type known as a Lamb wave) in the atmosphere, which was detected worldwide. This wave circled the Earth more than once, and generated tsunami in unexpected times and places. We have derived a mathematical description that allows us to quickly and accurately model the observations of this atmospheric wave. The description includes the effects of winds, temperature, and topography. The wave modeled using this description reproduces satellite and ground observations much better than simpler models, notably the complex pattern of the wave near the antipode of the eruption. Our model clearly identifies global winds as the crucial influence on global‐scale Lamb‐wave propagation, and provides modeling tools for possible future occurrences of such waves and the global tsunamis created by them. Key Points: A augmented model is proposed to simulate the propagation of planetary scale Lamb waves, incorporating wind, temperature and topographyWinds play a primary role shaping Lamb waves in the far field, especially near the antipode of the sourceThe augmented Lamb wave model will help better assess far‐field volcanic tsunami hazards [ABSTRACT FROM AUTHOR]

The creation of a sink in a lossless wave‐bearing medium is achieved using complex frequency signals—harmonic excitations that exponentially grow in time. The wave sink, where incident waves are confined to a point, has attracted interest for imaging and sensing since it may lead to arbitrarily small hotspots that surpass the diffraction limit. However, most methods of creating sinks require careful tuning, such as by impedance matching the sink to free space through the inclusion of loss, which imposes constraints on emerging applications. An alternative method, proposed here, relies on complex frequency excitations, bypassing the need to modify the scattering system by instead shaping the input signal. Eigenvalue zeros derived from a scattering formalism extended to the complex frequency plane reveal operating conditions that induce complete energy trapping under steady‐state conditions in a framework generally applicable to 2D and 3D media. To support the developed theory, an experiment is performed where a sink is realized using elastic waves on a plate with a circular cutout. These findings may lead to imaging and sensing applications relying on subwavelength focal points and nonlinear wave generation due to the high amplitudes achieved over short timescales. [ABSTRACT FROM AUTHOR]

The aim of this work is to propose a numerical methodology based on the finite element (FE) method to study the propagation mechanisms of transmitted, converted, and reflected guided waves in stiffened fiber‐reinforced polymeric (FRP) composite structures. The dispersion curves of such modes can help designers to improve the damage detection sensitivity of Lamb waves based structural health monitoring (SHM) systems. Using a FE model, whose accuracy is demonstrated against semi‐analytical data in a previous work, the phenomena of scattering and mode conversion in composite panels characterized by a structural discontinuity, such as a stiffener, are investigated. In particular, the behavior of guided waves is analyzed using stiffeners of different shapes, C and Omega shaped. The research activity makes it possible to highlight conversion of modes and reflected waves at stiffeners, providing new observations compared to the state of the art. The morphological complexities of the structure (thickness steps, multiple boundaries, stiffeners) can be used to redirect guided waves and to allow monitoring of a specific area. Wave reflections interacting with stiffeners, therefore, can be analyzed to improve diagnostics or design new detection strategies. [ABSTRACT FROM AUTHOR]

Recently Lamb wave devices have originated as an alternate acoustic device for high‐frequency wireless sensing applications. Their potential for sensing devices, including biomedical diagnostics and environmental monitoring as a wireless and passive device, calls for further analysis of the device with higher sensitivity. ZnO‐based sensor has always been of research interest due to its biocompatibility, sensing abilities, and yet cost‐effectivity. A Lamb wave device based on ZnO/SiO2/Si membrane has been theoretically simulated using finite element analysis method (FEM) to study the higher modes, as higher working frequency leads to higher sensitivity of the device toward sensing applications. Optimized properties are identified and utilized for the fabrication of Lamb wave devices. It is observed that for optimized parameters of ZnO/SiO2/Si Lamb device, higher antisymmetric modes are not only advantageous for high sensitivity applications but also more stable within the given operating conditions. Experimentally obtained results indicate close matching with theoretical results. [ABSTRACT FROM AUTHOR]

On 15 January 2022, the Hunga volcano produced a massive explosion that generated perturbations in the entire atmosphere. Nonetheless, signatures in the mesosphere and lower thermosphere (MLT) have been challenging to identify. We report MLT horizontal wind perturbations using three multistatic specular meteor radars on the west side of South America (spanning more than 3,000 km). The most notorious signal is an exceptional solitary wave with a large vertical wavelength observed around 18 UT at all three sites, with an amplitude of ∼50 m/s mainly in the westward direction. Using a customized analysis, the wave is characterized as traveling at ∼200 m/s, with a period of ∼2 hr and a horizontal wavelength of ∼1,440 km in the longitudinal direction, away from the source. The perturbation is consistent with an L1 Lamb wave mode. The signal's timing coincides with the arrival time of the tsunami triggered by the eruption. Plain Language Summary: The eruption of the Hunga volcano in January 2022 had a widespread impact on the atmosphere, affecting various layers. We describe a perturbation in horizontal winds caused by the event, which was observed over the west coast of South America by three different meteor radar systems separated by more than 3,000 km between them. The perturbation behaved similarly in the altitude range of 80–100 km, and the wave parameters observed were consistent with high‐order Lamb wave solutions from simulations carried out using the Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension. This finding complements other studies that have explored the impacts of the eruption on different atmospheric levels. Overall, this study provides valuable insights into the complex and far‐reaching effects of volcanic eruptions on the atmosphere. Key Points: Hunga eruption generated extreme horizontal wind perturbations at 80–100 km of altitude over South AmericaThe signal was detected almost simultaneously by three multistatic meteor radar systems spanning more than 3,000 kmThe perturbation had a period of ∼2 hr, a horizontal phase velocity of ∼200 m/s, and a horizontal wavelength of ∼1,440 km [ABSTRACT FROM AUTHOR]

High‐resolution Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension is used to simulate the responses to the Hunga‐Tonga volcano eruption on 15 January 2022. Global propagation of the Lamb wave L'0 and L'1 pseudomodes are reproduced in the simulation, with the exponential growth of wave amplitudes with altitudes. The wavefront is vertical up to the lower thermosphere, and tilts outward above. These features are consistent with theoretical results. With simulated surface pressure perturbation agreeing with observations (∼100–250 Pa), thermospheric wind perturbations over 100 ms−1 are comparable with reported satellite and ground‐based observations. Traveling ionospheric disturbances in the total electron contents from the simulation show good agreement with observations, including magnitude and propagating speed and evidence of conjugacy in the first 1–2 hr after eruption. Conjugacy in E × B drift, on the other hand, is more persistent. Plain Language Summary: As one of the most powerful volcano eruptions on record, the Hunga Tonga‐Hunga Ha'apai Volcano produces waves that ripple through the atmosphere and near‐space environment. These wave signals have been recorded by observations from instruments on the ground and from satellites, and they propagate around the Earth multiple times. This event provides a rare opportunity to study the strong and direct connection of the whole atmosphere system. The challenge is for a model to be able to represent the key processes in the whole atmosphere system and to have sufficient spatial and temporal fidelity to gain a realistic global picture of the event. This is achieved in the study by using the high‐resolution Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension. The model is able to simulate the global propagation of the waves, and the model results compare favorably with observations from the surface to the thermosphere and ionosphere. Key Points: High‐resolution Whole Atmosphere Community Climate Model with thermosphere/ionosphere extension simulation of Hunga eruption shows whole atmosphere responsesSimulated wave amplitude growth and phase structure are consistent with the theoretical predictionSimulation results are comparable with thermospheric and ionospheric observations [ABSTRACT FROM AUTHOR]

We investigate the oceanic and ionospheric response in New Caledonia‐New Zealand and Chile‐Argentina to the 15 January 2022 Hunga‐Tonga volcanic eruption. For the first time, we highlight a reversed response in the oceans and in the ionosphere in terms of the amplitudes. The sea‐surface fluctuations due to the passage of the atmospheric Lamb wave (i.e., air‐sea wave) were not remarkable while the related ionospheric perturbation was considerable. Reversely, the eruption‐induced tsunami ("regular" tsunami) caused major variations in sea‐surface heights (∼1 m near the volcano and ∼2 m along the Chilean coastline), whereas the associated ionospheric perturbation was quite small. The observed large‐amplitude ionospheric response due to Lamb waves propagation is difficult to explain, and the coupling between the Lamb wave and the ionosphere is not well‐understood yet. For the first time, we estimate the delay between the Lamb waves and their signatures in the ionosphere to be ∼12–20 min. Plain Language Summary: The eruption of Hunga‐Tonga volcano produced a variety of atmospheric and tsunami waves recorded all over the world. We study the impacts of the eruption together on the oceans and in the ionosphere in New Caledonia‐New Zealand (near the volcano) and Chile‐Argentina (far from the volcano). At the sea surface, we observe two phenomena causing sea‐height variations. The first is a small tsunami (air‐sea wave) created by the Lamb wave: the high‐pressure atmospheric wave triggered by the eruption. The second is the tsunami induced by the eruption itself. Spectacularly, at 300 km altitude, in the ionosphere, we observe perturbations in the electron content caused by the Lamb wave and by the regular tsunami. We are the first to report on the reversed amplitude of the two phenomena in the oceans and in the ionosphere. The sea‐surface perturbation caused by the Lamb wave was not significant, while ionospheric perturbation was considerable. In contrast, the regular tsunami wave produced major variations. For the first time, we estimate the time delay between the Lamb wave and its signature in the ionosphere. Key Points: Joint study of oceanic and ionospheric response in New Caledonia‐New Zealand and Chile‐Argentina to the 15 January 2022 volcanic eruptionNear‐surface propagating Lamb wave caused a small tsunami in the ocean (air‐sea wave) and unusually strong disturbances in the ionosphereInversely, the eruption‐generated tsunami showed significant wave heights in the ocean and much smaller response in the ionosphere [ABSTRACT FROM AUTHOR]

Low‐symmetry van der Waals materials are promising candidates for the next generation of polarization‐sensitive on‐chip photonics since they do not require lattice matching for growth and integration. Due to their low‐symmetry crystal behavior, such materials exhibit anisotropic and polarization‐dependent optical properties for a wide range of optical frequencies. Here, depolarization characteristics of orthorhombic α‐MoO3 is studied in the visible range. Using polarizers and analyzers, it is demonstrated that α‐MoO3 has negligible loss and that birefringence values as high as 0.15 and 0.12 at 532 nm and 633 nm, respectively, are achievable. With such a high birefringence, quarter‐ and half‐wave plate actions are demonstrated for a 1400 nm α‐MoO3 flake at green (532 nm) and red (633 nm) wavelengths, and polarizability as high as 90% is reported. Furthermore, a system of double α‐MoO3 heterostructure layer is investigated that provides the possibility of tuning polarization as a function of rotation angle between the α‐MoO3 layers. These findings pave the way to the promising future of on‐chip photonic heterostructures and twist‐optics that can dictate the polarization state of light. [ABSTRACT FROM AUTHOR]

The explosive 2022 Tonga submarine volcanic eruption produced a globally propagated atmospheric disturbance. A leading Lamb wave pulse was recorded as a pressure pulse worldwide. A weather‐station network in Japan recorded the pressure pulse together with temperature and wind conditions during the passage of the pulse. Individual temperature and wind records indicate little simultaneous change. However, after alignment of records at the time of pressure pulse arrivals and stacking, clear temperature and wind changes synchronized with the pressure change are evident. Assuming Lamb wave propagation, the synthesized temperature and wind changes from the pressure record show a good match with the observed waveforms. The observed wind speed and pressure change of the Lamb pulse yielded a total energy transported by the pulse of 4.2 × 1016 J. Plain Language Summary: Atmospheric disturbance caused by the violent 2022 Tonga volcanic eruption was recorded by multiple types of sensors on the ground. The leading pressure signals, of about 20 min duration and about 2 hPa amplitude, were observed in a nationwide weather network in Japan as an anomaly that stands out from the background atmospheric pressure trend. Other meteorological sensors such as temperature and wind components were also in operation, but expected changes are on the order of 0.15 K and 0.5 m/s over the 20 min signal duration, too small to be detected in individual records. Using a pressure signal as a time mark for data alignment, we averaged all temperature and wind components parallel to the direction from Tonga toward Japan recorded by the network. Such averaging steps greatly reduced the spatially incoherent background noise and enhanced the signals coherent with the arrival of the pressure pulse. The resultant temperature and wind changes are comparable to the theoretically predicted ones. The measured temporal changes of atmospheric pressure and air flow enable direct estimation of the energy flow transported by the pressure pulse. The estimated total energy transported by the pressure pulse is between (3.8–4.6) × $\times $ 1016 J. Key Points: Stacking nationwide weather network records reveals temporal changes in temperature and wind flow synchronized with the Lamb pressure pulseObserved temporal variations are close to the adiabatic air compression and Lamb wave flow models expected from the pressure pulseAnalysis of observed wind speed and pressure changes reveals that the total energy transported by the Lamb pulse was 4.2 × 1016 J [ABSTRACT FROM AUTHOR]

Flexible and wearable sensors are highly desired for health monitoring, agriculture, sport, and indoor positioning systems applications. However, the currently developed wireless wearable sensors, which are communicated through radio signals, can only provide limited positioning accuracy and are often ineffective in underwater conditions. In this paper, a wireless platform based on flexible piezoelectric acoustics is developed with multiple functions of sensing, communication, and positioning. Under a high frequency (≈13 MHz) stimulation, Lamb waves are generated for respiratory monitoring. Whereas under low‐frequency stimulation (≈20 kHz), this device is agitated as a vibrating membrane, which can be implemented for communication and positioning applications. Indoor communication is demonstrated within 2.8 m at 200 bps or 4.2 m at 25 bps. In combination with the sensing function, real‐time respiratory monitoring and wireless communication are achieved simultaneously. The distance measurement is achieved based on the phase differences of transmitted and received acoustic signals within a range of 100 cm, with a maximum error of 3 cm. This study offers new insights into the communication and positioning applications using flexible acoustic wave devices, which are promising for wireless and wearable sensor networks. [ABSTRACT FROM AUTHOR]

In this contribution, the thermoelastic Lamb waves in the homogeneous, transversely isotropic, plate with voids have been investigated in the context of classical and non‐classical theories of thermoelasticity. To investigate the problem, the fundamental governing equations have been developed in a unified way. On the solutions of these governing equations, the thermal and mechanical stress‐free boundary conditions, as well as constraints due to voids, have been imposed. The solutions of governing equations indicate that there exists a coupled system of wave motion called thermal waves (T‐mode), void wave motion (V‐mode), and elastic waves (E‐mode). However, the shear horizontal component of elastic wave decouples from the system is unaffected by elasto‐poro‐thermal coupling. For the symmetric and anti‐symmetric families of vibrations, the secular equation for the wave motion along with its special cases has been derived. To discover the wave characteristics, the secular equation has been solved using the numerical‐functional iteration method in MATLAB software, and the findings have been manifested by plotting the graphs. It has been concluded that the presence of voids affects the magnitudes of phase velocity, attenuation coefficient, and specific loss. This work may be helpful for geophysicists and engineers in the field of earthquake engineering. The developers of modern facilitating things such as acoustic touch screens, liquid viscosity sensors, etc. which are based on Lamb‐type wave propagation may also get benefitted. [ABSTRACT FROM AUTHOR]

The previous published work by Othmani et al. invites a further useful discussion on how the viscoelastic rheological model affects the second harmonic and single modes of guided waves. However, this paper has two main objectives. The first objective is to establish a simple relationship between the Rayleigh waves velocity (VR), fundamental Lamb modes (A0 and S0), and the shear wave velocity (VS) in unidirectional viscoelastic carbon–epoxy at high frequency. The second objective is to study the second harmonic Lamb modes. Numerical codes based on Legendre polynomial and Newton–Raphson methods are developed and implemented to predict dispersion and attenuation curves. The second harmonic generation was investigated with the hysteretic and Kelvin–Voigt viscoelastic models. Results showed that rheological models have a much larger effect on the attenuation curves than the ones on the dispersion trajectories. Additionally, the optimal angles of Lamb and SH modes in unidirectional carbon–epoxy under Snell‐Descartes law was investigated. The present numerical results may render as a useful message for the rheological community. [ABSTRACT FROM AUTHOR]

On 15 January 2022, Tonga's Hunga Tonga‐Hunga Ha'apai (HTHH) volcano violently erupted, generating a tsunami that killed three people. Acoustic‐gravity waves propagated by the eruption and tsunami caused global complex ionospheric disturbances. In this paper, we study the nature of these perturbations from Global Navigation Satellite System observables over the southwestern Pacific. After processing data from 818 ground stations, we detect supersonic acoustic waves, Lamb waves, and tsunamis, with filtered magnitudes between 1 and 7 Total Electron Content units. Phase arrivals appear superpositioned up to ∼1,000 km from HTHH and are distinct by ∼2,200 km. Within ∼2,200 km, signals have an initial low‐frequency pulse that transitions to higher frequencies. We note the presence of a faster perturbation generated 1 hr post‐eruption which crosses the tsunami disturbance ∼3,000 km from HTHH, potentially contributing to premature land arrivals. Lastly, the arrival of tsunami‐generated disturbances coincides with deep‐ocean observations. Plain Language Summary: The 15 January 2022 volcanic eruption of Hunga Tonga‐Hunga Ha'apai and subsequent tsunamis sent powerful energy waves into the ionosphere (a layer of Earth's atmosphere that is deformed by energy emitted from events like volcanic eruptions, tsunamis, earthquakes, tornadoes, hurricanes, and large man‐made explosions). These waves can provide valuable information about different phases of the event, such as the powerful explosion, sound wave, and tsunami. Using Global Positioning Systems data, we measure these ionospheric signals over the southwestern Pacific Ocean to examine which phases of the event contributed to each ionospheric disturbance. We successfully detect all three event phases in the ionosphere and determine the distance at which these signals separate from one another. Furthermore, we validate our data by comparing tsunami signals in the ionosphere against direct ocean‐based observations of tsunami activity. Of particular note is our observation of a faster ionospheric signal that forms an hour after the eruption and catches up to the tsunami's disturbance. Our work supports the hypothesis that others have proposed in which high‐energy waves from the eruption escalated tsunami speeds and wave heights. This, in turn, supports the observation of early tsunami arrivals that were reported along many Pacific coastlines. Key Points: We see distinct phase arrivals in the ionosphere for a supersonic wave, Lamb wave, and tsunami (the latter is validated by ocean sensors)Phase arrivals begin to separate at ∼1,000 km from Tonga and are fully separated by ∼2,200 kmWe highlight a faster disturbance that propagates 1 hr post‐eruption and meets the tsunami perturbation ∼3,000 km from the volcano [ABSTRACT FROM AUTHOR]

The target scattering characteristics in microwave band are necessary to be researched for Orbital‐Angular‐Momentum (OAM) wave‐based radar applications. A theoretical description of electromagnetic (EM) scattering from a typical target by OAM waves is proposed in this paper. First, OAM waves are decomposed into plane waves in the spectral domain with different elevation and azimuth angles. Then, the scattering form of each decomposed plane wave is determined through coordinate system transformation and physical optics approximation. Formulas and numerical results are presented for OAM‐based radar scattering cross section of a perfect electric conductor and dielectric plate and a cylinder. Unlike the conventional results of EM plane wave scattering, the scattering properties of OAM waves from plate and cylinder are analysed with particular emphasis on OAM mode influence. The results provide insights into OAM wave‐matter interactions and may find important applications in wave propagation and OAM wave‐based radar detection and imaging. [ABSTRACT FROM AUTHOR]

The 2022 volcanic eruption in Tonga caused an unusually large tsunami around the Pacific. It travels with a faster apparent velocity and has larger amplitudes at long distances than what would be expected from a conventional tsunami from the volcanic source. This tsunami was generated by the moving atmospheric Lamb wave and traveled at the speed of the Lamb wave (0.31 km/s). Japanese data showed the amplitude of this first tsunami becomes small when approaching the coast, due to the weaker air‐sea coupling at the shallow depth. This wave split when passing the continental slope, and traveled at the speed of the ocean gravity wave. Therefore, the tsunami observed at the coast is delayed by thousands of seconds from the passage of the Lamb wave. Tsunamis generated by this atmospheric mechanism have not been previously observed by modern digital recording systems and should be considered in the tsunami warning systems. Plain Language Summary: A tsunami is usually generated by the sudden changes of the water heights, and caused by offshore earthquakes, coastal landslides, and submarine volcanic eruptions. The generated vertical displacement of the water propagates as a very long wave, and the tsunami waves become compressed with increased heights as they approach the coast. The 2022 volcanic eruption in Tonga caused an unusually large tsunami, which cannot be explained by conventional sources. The speed and amplitude are very different from theoretical values: the speed is about 0.31 km/s, whereas the average tsunami speed in the Pacific is 0.2 km/s. These data suggest that the tsunami from the Tonga eruption was excited by a pulse of atmospheric pressure as it traveled from the volcano. This source of the tsunami in the atmosphere needs to be considered for the tsunami warning system in the future. Key Points: Lamb wave produced by the volcanic eruption excites the sea surface as it travels across the Pacific and generates a tsunami pulseThe effect of the air‐sea coupling becomes weaker as the Lamb wave approaches the coastThe tsunami wave splits when passing the continental slope of Japan causing more complex waves [ABSTRACT FROM AUTHOR]

Transparent thin‐film piezoelectric transducers are attractive for haptic displays. However, for their widespread use in consumer electronics, innovative and cost‐effective processing methods need to be developed. In this contribution the effectiveness of the deposition of lead zirconate titanate thin films by inkjet printing for the fabrication of haptic devices is demonstrated. The 1,3‐propanediol solvent is used to prepare effective inkjet‐printing inks from chemical solution deposition solutions. The printed thin‐film structures on fused silica glass substrates are 900 nm thick and strongly {100} oriented perovskite phase is detected in X‐ray diffraction patterns. To fabricate devices, interdigitated capacitors and SU‐8 insulation layers are deposited on top of the printed lead zirconate titanate. Dimensions of the final device are 15.7 × 3.4 mm2. A standing antisymmetric Lamb wave is observed at 63.3 kHz, with out‐of‐plane displacement reaching 2 µm at an applied voltage of 100 V. This value exceeds the limit at which the texture rendering function can be induced in the device. Good functional performance of the device is linked with good electromechanical properties of the printed piezoelectric, with permittivity ε ′ and piezoelectric coefficient e33,f values of 1000 and 7.7 C m−2, respectively, which are comparable to films prepared by standard spin‐coating process. [ABSTRACT FROM AUTHOR]

The Legendre polynomial series approach (LPSA) has been widely used to solve guided wave propagation in various structures since 1999. The LPSA directly introduces the boundary conditions into the control equations through the rectangular window function. However, in the solving process, the Legendre polynomial series, the rectangular window function, and their derivatives are introduced into the integral kernel functions, which results in a lot of CPU time on the abundant numerical integration calculations. To overcome this defect, an analytical integration Legendre polynomial series approach (AILPSA) is presented and is used to solve the Lamb waves in fractional order thermoelastic multilayered plates. Coupled wave equations and heat conduction equation are solved by the AILPSA and the LPSA, respectively. Comparison between two approaches indicates the computational efficiency of the AILPSA is improved by more than 90%. In addition, a backward error estimation is given in the convergency analysis to make up for the deficiency of the numerical experiments. Finally, the influence of fractional order on the thermoelastic Lamb wave is discussed. [ABSTRACT FROM AUTHOR]

This study reports different properties of ionospheric perturbations detected to the west and south of the Korean Peninsula after the Hunga‐Tonga volcanic eruption on 15 January 2022. Transient wave‐like total electron content (TEC) modulations and intense irregular TEC perturbations are detected in the west and south of the Korean Peninsula, respectively, about 8 hr after the eruption. The TEC modulations in the west propagate away from the epicenter with a speed of 302 m/s. Their occurrence time, propagation direction and velocity, and alignment with the surface air pressure perturbations indicate the generation of the TEC modulations by Lamb waves generated by the eruption. The strong TEC perturbations and L band scintillations in the south are interpreted in terms of the poleward extension of equatorial plasma bubbles (EPBs). We demonstrate the association of the EPBs with the volcanic eruption using the EPB occurrence climatology derived from Swarm satellite data. Plain Language Summary: A massive eruption of Hunga Tonga–Hunga Ha'apai volcano on 15 January 2022 left its footprint as various perturbations in the atmosphere and ionosphere. We report the detection of different types of ionospheric perturbations in the south and west of the Korean Peninsula. One is a transient wave‐like perturbation detected to the west, and the other is a more substantial one detected to the south, including L band scintillation. Both disturbances occurred about 8 hr after the eruption. This study demonstrates that the ionospheric perturbations in the two regions are generated by different mechanisms. The former is associated with the modulation of the ionospheric height by atmospheric waves, but the latter is attributed to the plasma instabilities triggered by atmospheric waves. The consistent behavior of atmospheric and ionospheric perturbations and the development of severe storms in the low latitude ionosphere support these interpretations. Key Points: Moderate and intense total electron content perturbations are detected to the west and south of Korea about 8 hr after eruptionPerturbations to the west are consistent with surface air pressure perturbations and propagate away from the epicenter at 302 m/sIntense perturbations to the south are associated with the poleward extension of equatorial plasma bubbles triggered by the eruption [ABSTRACT FROM AUTHOR]

The eruption of the Hunga Tonga‐Hunga Ha'apai volcano on 15 January 2022 triggered atmospheric waves at all altitudes. The National Aeronautics and Space Administration Ionospheric Connection Explorer (ICON) and European Space Agency Swarm satellites were well placed to observe its impact on the ionospheric wind dynamo. After the Lamb wave entered the dayside, Swarm A observed an eastward and then westward equatorial electrojet (EEJ) on two consecutive orbits, each with magnitudes exceeding the 99.9th percentile of typically observed values. ICON simultaneously observed the neutral wind (90–300 km altitude) at approximately the same distance from Tonga. The observed neutral winds were also extreme (>99.9th percentile at some altitudes). The covariation of EEJ and winds is consistent with recent theoretical and observational results, indicating that the westward electrojet is driven by strong westward winds in the Pedersen region (∼120–150 km). These observations imply that the dynamo is a key mechanism in the ionospheric response to the Tonga disturbance. Plain Language Summary: The January 2022 Tonga volcanic eruption caused atmospheric impacts around the world. As a natural experiment, it can be used to test our understanding of how the lower atmosphere affects space weather. Researchers are only beginning to document the chain of events post‐eruption, and this paper focuses on its impact on the generator that drives electric fields in near‐Earth space, a key part of space weather. This generator is driven by the atmosphere pushing charged particles across Earth's magnetic field. This usually creates a strong eastward current above the equator. When the Swarm A satellite coincided with the wave from Tonga, it observed that this current strengthened dramatically, then reversed. Although reversals are not unusual, this was the strongest reversal observed by Swarm since its 2013 launch, except for one large geomagnetic storm in 2015. Another satellite, the Ionospheric Connection Explorer, was luckily at the right time and place to observe related motions of the upper atmosphere, which were similarly extreme. These observations are shown to be consistent with our theoretical understanding of the generator. This study is important because it represents a critical test of atmosphere‐space interactions and implies that the Tonga eruption caused a major space weather event. Key Points: Extreme thermospheric winds and ionospheric currents were observed in coordinated space/ground‐based measurements, 10 hours post‐eruptionThe westward electrojet current when the Lamb wave reaches the dayside is consistent with recent studies of the wind‐driven electrojetObservations of linked dynamo processes provide direct evidence of the space‐weather impacts of acute lower atmospheric forcing [ABSTRACT FROM AUTHOR]

The explosive eruption of the Hunga‐Tonga volcano in the southwest Pacific at 0415UT on 15 January 2022 triggered gigantic atmospheric disturbances with surface air pressure waves propagating around the globe in Lamb mode. In space, concentric traveling ionosphere disturbances (CTIDs) are also observed as a manifestation of air pressure waves in New Zealand ∼0500UT and Australia ∼0630UT. As soon as the air pressure waves reached central Australia ∼0800UT, conjugate CTIDs appeared almost simultaneously in the northern hemispheres through interhemispheric coupling, much earlier than the arrival of the surface air pressure waves to Japan after 1100UT. Combining observations over Australia and Japan between 0800 and 1000UT, both direct and conjugate CTIDs show similar horizontal phase velocities of 320–390 m/s, matching with the dispersion relation of Lamb mode. The arrival of atmospheric Lamb wave to Japan later created in situ CTIDs showing the same Lamb mode characteristics as the earlier conjugate CTIDs. Plain Language Summary: The Hunga‐Tonga volcano eruption on 15 January 2022 has created the impulsive Lamb wave propagation on the surface air pressure that has been observed globally. The Lamb wave, typically moving near the ground at the sound speed of ∼340 m/s, traveled 6 hr to reach Japan. However, the Lamb wave signature in the Earth's ionosphere, the ionized component of the atmosphere, arrived 3‐hr earlier than expected, thanks to the property of the ionospheric plasma being controlled by the Earth's magnetic field. As soon as the surface Lamb wave reached Australia, the ionosphere above showed concentric wave shape of the traveling ionospheric disturbances (CTIDs), and the effect was mapped to Japan in the northern hemisphere along the conductive magnetic field lines. The much faster appearance of the ionosphere disturbances to the northern hemisphere through the magnetic field lines is beyond expectations. This is the first time such concentric waves from a volcanic eruption have been observed simultaneously in both hemispheres. Monitoring the ionospheric disturbances could be a robust early warning tool for diagnosing such explosive events on the planet Earth. Key Points: Concentric traveling ionospheric disturbances (CTIDs) driven by volcano excited Lamb wave are observed simultaneously in Australia and JapanDue to magnetic conjugate effect, the northern hemisphere CTIDs appear 3‐hr prior to the arrival of the surface Lamb waveBoth direct and conjugate CTIDs match with the theoretical dispersion relation of the atmospheric Lamb and gravity modes [ABSTRACT FROM AUTHOR]

The major eruption of volcano Hunga Tonga‐Hunga Ha'apai in Tonga on 15 January 2022 generated atmospheric Lamb waves that propagated over the world. This seemed the first volcanic Lamb wave event that was clearly captured by the state‐of‐the‐art geostationary meteorological satellites. This paper provides visualization of the waves using thermal infrared images from geostationary satellite Himawari‐8. The second time derivatives of 10‐min interval images clearly illustrated the waves propagating at about 310 m s−1. The waves could be tracked for more than a week while they propagated five times round the earth. Automated wavefront identification illustrated nonuniform propagation speed. The signals in the satellite images well matched the surface pressure observations in Japan. Plain Language Summary: The major eruption of volcano Hunga Tonga‐Hunga Ha'apai in Tonga on 15 January 2022 generated atmospheric pressure pulses that propagated over the world. This seemed the first event that was clearly captured by the state‐of‐the‐art geostationary meteorological satellites, such as Himawari‐8. Taking the time difference of Himawari‐8's 10‐min interval images twice, the waves that propagated at about 310 m s−1 could be tracked for more than a week while they propagated five times round the earth. This was not possible with the previous‐generation geostationary meteorological satellites. Visualized waves also illustrated how the propagation speed changes in space and time. The signals in the satellite images well matched the surface pressure observations in Japan. Key Points: Lamb waves from an eruption were clearly visualized by the second time derivative of satellite infrared images every 10 minThe waves could be tracked for more than a week while they propagated at least five times round the earth at a speed of about 310 m s−1The signals in the satellite images matched the surface pressure changes quantitatively [ABSTRACT FROM AUTHOR]

On 15 January 2022, around 4:30 UTC the eruption of the Hunga‐Tonga volcano, in the South Pacific Ocean, generated a violent underwater explosion. In addition to tsunami waves that affected the Pacific coasts, the eruption created atmospheric pressure disturbances that spread out in the form of Lamb waves. The associated atmospheric pressure oscillations were detected in high‐frequency in‐situ observations all over the globe. Here we take advantage of the similarities in the propagation and characteristics between atmospheric Lamb waves and long ocean waves and we use a 2DH ocean numerical model to simulate the phenomenon. We compare the outputs of the numerical simulation with in‐situ atmospheric pressure records and with remote satellite observations. The signal in the model matches the observed atmospheric pressure perturbations and reveals an excellent agreement in the wave arrival time between model and observations at hundreds of locations at different distances from the origin. Plain Language Summary: The underwater explosion of the Hunga‐Tonga volcano in the South Pacific Ocean generated atmospheric pressure disturbances, known as Lamb waves, that propagated and surrounded the globe several times. In this study, we exploit the similarities between atmospheric Lamb waves and long waves in the ocean (e.g., tsunamis) to simulate their propagation using an ocean numerical model. The comparison of our results with remote satellite data and in‐situ atmospheric pressure records reveals that our model correctly reproduces the propagation of the atmospheric disturbances generated by the volcano explosion. Key Points: The underwater Hunga‐Tonga volcano exploded generating Lamb waves that traveled around the Earth several timesWe simulate these waves using a hydrostatic shallow water equation oceanic modelThe results closely follow the observations of atmospheric pressure perturbations [ABSTRACT FROM AUTHOR]

Ability to generate and manipulate spin‐polarized electrons is the cornerstone of prospective energy‐efficient spin‐based information processing technologies. Here, we report a novel method of generating transient spin‐polarized electrons by two‐photon absorption (TPA) in all‐inorganic perovskite CsPbBr3 using circularly polarized light (CPL) excitation. The photo‐generated transient spin‐polarized current serves as a source for terahertz emission detected in our experiment that shows quadratic pump fluence dependence, consistent with our previous report under linear polarized light excitation. Density functional calculations confirm the experimental results and pinpoint the role of the spin−orbit coupling in enabling TPA of CPL in CsPbBr3. In addition, the maximum degree of spin‐polarization under excitation by the CPL is ~21.3% at room temperature and can be tuned by the polarization of the excitation light with a quarter wave plate. The technique developed in this work can be applied to the analysis of spin‐related properties of materials, making it an important analytical tool for the exploration of future spintronic technology based on inorganic perovskites. [ABSTRACT FROM AUTHOR]

Artificial structures for controlling ultrasonic‐waves are attractive for developing superb functions in sensing‐imaging techniques. However, the complicated fabrication and fixed design associated with the particular wave limit the scalability. Herein, a versatile‐reversible ultrasonic‐wave engineering using programmable heating of local areas on thermoresponsive polymers is presented. As an abrupt shift of the elastic modulus occurs at selectively heated zones over the glass transition temperature, the drastic modulus change alters the S0 phase velocity of the Lamb wave within ultrasonic waves passing through the heated regimes. The modified wave propagation results in an active wavelength shift and wave refraction, which enables multifunctional programming of wave propagation pathways and wavefront shapes. Multiple functions such as reduced wavelength, wave steering, energy focusing and bifurcation are implemented in one nylon 6 thermoresponsive polymer, according to predesigned heating shapes. This work demonstrates the capability of temperature‐responsive wave engineering in bulk solid media with only a heating configuration. [ABSTRACT FROM AUTHOR]

Control of optical polarization is central to harnessing the properties of electromagnetic radiation for many applications, including 3D imaging and quantum computation. However, conventional optical polarizing components are typically bulky and static, that is, fixed in their degree of polarization control. Active metasurfaces have potential for versatile polarization control in a compact form factor by temporally modulating electromagnetic amplitudes and phase between orthogonal electric field components. Here, dynamic control of the polarization state of reflected light from an active metasurface is demonstrated. The metasurface uses indium tin oxide (ITO) as an active element in an array of aluminum nanoantennas operating in the telecom range. Applying an electrical bias between the ITO layer and the back reflector modulates the carrier concentration in ITO at the gate‐dielectric/ITO interface, resulting in complex refractive index modulation in the epsilon‐near‐zero condition. This index modulation alters the degree of excitation of plasmonic modes corresponding to the orthogonal polarization components, leading to polarization modulation. By suitably biasing the metasurface, linearly polarized incident light can be converted to cross‐polarized, circularly polarized or elliptically polarized light upon reflection. Dynamic control of the reflected polarization state has potentially wide applications in dynamic wave plates, spatial light modulators, and adaptive wavefront control. [ABSTRACT FROM AUTHOR]

Control of optical polarization is central to harnessing the properties of electromagnetic radiation for many applications, including 3D imaging and quantum computation. However, conventional optical polarizing components are typically bulky and static, that is, fixed in their degree of polarization control. Active metasurfaces have potential for versatile polarization control in a compact form factor by temporally modulating electromagnetic amplitudes and phase between orthogonal electric field components. Here, dynamic control of the polarization state of reflected light from an active metasurface is demonstrated. The metasurface uses indium tin oxide (ITO) as an active element in an array of aluminum nanoantennas operating in the telecom range. Applying an electrical bias between the ITO layer and the back reflector modulates the carrier concentration in ITO at the gate‐dielectric/ITO interface, resulting in complex refractive index modulation in the epsilon‐near‐zero condition. This index modulation alters the degree of excitation of plasmonic modes corresponding to the orthogonal polarization components, leading to polarization modulation. By suitably biasing the metasurface, linearly polarized incident light can be converted to cross‐polarized, circularly polarized or elliptically polarized light upon reflection. Dynamic control of the reflected polarization state has potentially wide applications in dynamic wave plates, spatial light modulators, and adaptive wavefront control. [ABSTRACT FROM AUTHOR]

The multiple scattering of flexural waves on an elastic plate with circular scatterers is analyzed in the frequency domain based on the Mindlin plate theory accounting for the rotary inertia and shear deformation of the plate. To this purpose, a semi‐analytical numerical method is formulated as an extension of the previous study based on the Kirchhoff plate theory. It consists of expressing the flexural wave field in terms of the superposition of the wave function expansion, and determining the expansion coefficients by a collocation technique. As demonstrative examples, the transmission of a plane flexural wave across a square array of circular through‐thickness holes or thin‐plate inclusions is analyzed using the proposed method. The comparison between the results based on the Mindlin and Kirchhoff theories is shown for the case of multiple holes. The analysis shows that the transmission amplitude of the flexural wave is reduced at certain frequencies due to the Bragg reflection by the inclusions. In the case of thin‐plate inclusions, the resonance of the inclusions also brings about a sharp decrease of the transmission amplitude. [ABSTRACT FROM AUTHOR]

An improved Legendre polynomial series approach (AILPSA) is presented to investigate the circumferential thermoelastic Lamb wave in a fractional order orthotropic cylindrical plate. In the AILPSA, the analytical integration is developed based on the orthogonality and recursive properties of the Legendre polynomial to simplify the integral computation involved in the solving progress. As a consequence, the computational efficiency is improved significantly. Results are compared with those from the previous article to confirm the validity of the introduced method. Using the AILPSA, guided wave characteristics in various fractional order orthotropic cylindrical plates are investigated by solving the eigenvalues and eigenvectors of the system of algebraic equations. The influences of fractional order and radius‐thickness ratio on dispersion curve and displacement, temperature amplitudes are illustrated. The results show that the fractional order almost has no effect on the phase velocities of quasi‐elastic wave modes, but has notable effect on their attenuations. A smaller fractional order means a smaller temperature amplitude for the quasi‐elastic wave mode, but means a larger temperature amplitude for the thermal wave mode. A smaller radius thickness ratio indicates a smaller attenuation and a larger temperature amplitude. [ABSTRACT FROM AUTHOR]

Coordinate‐transformation‐inspired optical devices have been mostly examined in the continuous‐wave regime: the performance of an invisibility cloak, which has been demonstrated for monochromatic excitation, is likely to deteriorate for short pulses. Here, pulse dynamics of flexural waves propagating in transformed plates is investigated. A practical realization of a waveshifter and a rotator for flexural waves based on the coordinate transformation method is proposed. Time‐resolved measurements reveal how the waveshifter deviates a short pulse from its initial trajectory, with no reflection at the bend and no spatial and temporal distortion of the pulse. Extending the strategy to cylindrical coordinates, a wave rotator is designed. It is demonstrated experimentally how a pulsed plane wave is twisted inside the rotator, while its wavefront is recovered behind the rotator and the pulse shape is preserved, with no extra time delay. The realization of the dynamical mirage effect is proposed, where an obstacle appears oriented in a deceptive direction. [ABSTRACT FROM AUTHOR]

In this large‐scale field study we use a prototype impact‐echo scanner to detect delaminations on a concrete bridge deck surveying in total over 17,000 m2. Delaminated bridge sections are known from manual sounding and coring. A large‐scale damage assessment is necessary to identify the need of repair work. Based on first results, two lanes of the bridge are repaired and in subsequent tests the bonding of fresh and old concrete is examined. It shows that delaminations found on the bridge deck surface are unevenly distributed with more defects on the southbound lanes. This indicates constructional problems during the concrete placement. The developed scanner excites stress waves by dropping steel solenoids on the surface and recording the impact‐echo frequency by air‐coupled microphone arrays. It is pushed at a speed of 600 m/h, hitting the surface 300 times per square meter. The recorded data is preprocessed on site with an automated delamination detection threshold implemented. Found delaminations are transferred to a bridge map to allow an overall damage assessment. [ABSTRACT FROM AUTHOR]

In the last years, a significant interest has been pointed out in the capability of ultrasonic guided waves as candidate tool for structural health monitoring (SHM), due to their high damage detection sensitivity and low power consumption. The monitoring of the structural health through the propagation of guided waves is complex: some wave phenomena, namely dispersion and slowness, together with boundary scattered waves, may mask the presence of damages. So, studying the dispersion phenomenon through the dispersion curves may be helpful in understanding the propagation mechanisms. As Lamb waves dispersion equations do not generally have analytical solutions, the development of a predictive finite element (FE) model can be a valuable tool for the improvement of SHM systems, avoiding the high cost of experimental campaigns. Thus, once calibrated with respect to an experimental test case, the developed FE model can be used to simulate and predict guided‐wave propagation mechanisms in a given structure. This leads to the possibility of employing such approach to identify and localize potential structural damages, that is the final aim of an SHM system. In this work, the FE method, together with an in‐house code, has been used to investigate guided wave dispersion phenomenon in plates for possible SHM applications. [ABSTRACT FROM AUTHOR]

In the current research the effect of the radius of a transducer, vibration frequency and anisotropic properties of the host structure on the occuring wave fields is analyzed. Semi‐analytical approach based on the Green's matrix representations and the Fourier transform is applied for calculation of dispersion curves and wave fields in two types of composite layups in a wide frequency‐thickness product range. The contribution of each wave mode in the excited wave field is analyzed. A method for decomposition of the Lamb waves is proposed and examined for the example of a combination of two ring‐shaped actuators. [ABSTRACT FROM AUTHOR]

Vacuum assisted resin infusion (VARI) has attracted more and more attentions in the aerospace field and the monitoring of the process variables has been one of the milestones for most aerospace companies. This study focuses on monitoring the flow front and curing degree of the resin in‐suit using a piezoelectric (PZT) sensor network. In the resin transfer stage, the propagation characteristics of Lamb waves were extracted from different paths to characterize the resin flow front, and the quadratic regression models of three variables were established. In the resin cure stage, the leaky Lamb waves and electromechanical impedance based on PZT sensors were simultaneously adopted to monitor the degree of cure of the resin globally and locally, respectively. The differential scanning calorimeter analysis was carried to see the compatibility among different methods for the curing degree. Experimental results demonstrated that it was feasible to monitor the flow front and curing degree of resin in VARI process using Lamb waves and electromechanical impedance based on a multifunctional piezoelectric sensor network. [ABSTRACT FROM AUTHOR]

Due to the limit of preparation technology, defects, such as cracks and inclusions, are inevitable in the functionally graded quasi‐crystal material. For the purpose of the guided wave non‐destructive testing on the functionally graded (FG) two‐dimensional(2‐D) hexagonal quasi‐crystal(QC) plates, Lamb and SH wave characteristics in the context of the Bak's model are investigated by means of the Legendre polynomial method. The convergence of the polynomial method applied on the FG 2‐D hexagonal QC plate is analyzed. Some new wave characteristics resulted from the phonon‐phason coupling effect are revealed. There are three Lamb‐like modes without cut‐off frequencies for the x‐y and y‐z QC plates, but four Lamb‐like modes without cut‐off frequencies for the x‐z QC plate. For phonon modes, phonon displacements and stresses are bigger than phason displacements and stresses. However, they are just opposite for phason modes. It can be utilized to distinguish phonon modes and phason modes. [ABSTRACT FROM AUTHOR]

Lamb wave based Structural Health Monitoring (SHM) is a well‐known approach in today's mechanical engineering [1, 2]. One possible approach to determine the behavior of Lamb waves experimentally lies in the use of a frequency‐based approach using a 2d Fourier transform (2d‐FT) [3–5]. A closer look at this approach reveals that it has been used to represent dispersion relationships in large frequency ranges, but its potential for high accuracy has not been fully exploited. In this work a measurement and evaluation system for the experimental determination of dispersion diagrams is developed. It is able to cover large frequency ranges and it additionally shows a high degree of automation and accuracy. This allows a broadband examination of influences, which have only a small effect on the wave propagation. To verify the accuracy of the developed measurement and data evaluation method, experimental results of an aluminum specimen are compared with those from analytical solutions. A good agreement is achieved. [ABSTRACT FROM AUTHOR]

Standing Lamb waves in vibrating plates enable haptic interfaces. If the out‐of‐plane displacement of these waves exceeds 1 µm at frequencies above 25 kHz, a silent friction modulation can be created between a human finger and a vibrating plate. A fully transparent friction‐modulation haptic device based on a piezoelectric thin film is demonstrated. The antisymmetric Lamb mode induced at 73 kHz allows for a functional performance that fulfills all conditions for practical use. Out‐of‐plane displacement reaches 2.9 µm when 150 V unipolar voltage is applied. The average transmittance of the whole transducer reaches 75%. The key points of this technology are: 1) a thin HfO2 layer between lead zirconate titanate film and substrate that prevents chemical reaction between them; 2) the efficient integration of transparent indium tin oxide electrodes and solution‐derived piezoelectric lead zirconate titanate thin film onto optical‐grade fused silica; and 3) the use of a transparent insulating layer made of SU‐8 photoresist. [ABSTRACT FROM AUTHOR]

Summary: Thirty‐two lambs were finished on a total mixed ration (TMR) pelleted alone (00SS) or including sunflower soap stock (SS): 15SS (15 g SS per kg TMR), 30SS (30 g SS per kg TMR) and 60SS (60 g SS per kg TMR). Lambs (8 per group) were slaughtered at 27 kg live weight. Colour evolution, lipid oxidation, microbial growth and detection of diarrhoeagenic Escherichia coli were studied in meat samples. SS in the diet reduced meat lipid oxidation (P < 0.05), but had no significant effect (P > 0.05) on the cholesterol oxidation products. Meat from 60SS and control animals (00SS) revealed greater discoloration (P < 0.05) than 15SS. SS supplementation did not affect the microbiological populations, whereas high doses of SS seemed to increase the proliferation of diarrhoeagenic E. coli on day 14 (P < 0.10). These results suggest that the rate of SS inclusion in the diet of fattening lambs should not be above 15 g SS per kg TMR. [ABSTRACT FROM AUTHOR]

The long‐term temperature induced errors caused by fiber λ/4 wave plate and the Verdet constant of sensing fiber in the all fiber current transformer (FOCT) are theoretically analyzed. A temperature related response of fiber λ/4 wave plate is adopted to compensate for the change caused by temperature related Verdet constant through choosing appropriate initial phase retardation of the λ/4 wave plate. The experimental results show high temperature‐cycle accuracy in this kind of FOCT with relative error within 0.6%. [ABSTRACT FROM AUTHOR]

Localization of signals is a widely applied technique used in different areas of science telecommunication, medicine, or seismology. In this work, we study microseismic emissions due to stick‐slip events during pneumatic fracture in a transparent setup at laboratory scale and apply a localization method "Estimated Source Energy Homogeneity." The seismic location results are compared with the image correlation results for displacement maps corresponding to the event times. We have observed (using optics and acoustics) that the movement starts inside the porous medium and progresses toward the channel tips, eventually causing channels to grow further. This finding could be of interest in understanding fluid‐induced earthquake nucleation processes. Similar to in‐site applications of pneumatic or fluid‐related fracturing, it shows that the area influenced extends beyond the fracture tips. This also shows why even after the end of pumping, we may get earthquakes, such as in the Basel case (Haring et al., 2008, https://doi.org/10.1016/j.geothermics.2008.06.002). Plain Language Summary: An uncompacted granular medium having a fixed grain size is placed between two glass plates as a very thin layer. Using air injection, this porous medium is compacted and fractured. This system is monitored using a camera capable of recording more than 100 images per second and accelerometers which can record vibrations in high frequencies. During this injection, earthquake‐like vibrations are generated by the system. Sources of these vibrations are located using acoustic recordings and image processing. We have observed that the channeling starts with a compaction inside the medium; this compaction propagates toward the channel tips and cause them to advance further inside the medium. Key Points: Pneumatic fracturing experiments in a Hele‐Shaw cell are monitored using accelerometers and a high‐speed cameraAcoustic emissions are localized using an energy‐based signal location method, and displacement maps are obtained from image correlationBy comparing the acoustic and the optical results, we observe that motion starts within porous medium and propagates toward the channel tips [ABSTRACT FROM AUTHOR]

Abstract: When a crack initiates and grows in a metal or composite structure, for example, due to high cycle fatigue, the crack propagation gives rise to acoustic emissions (AE)—ultrasonic waves travelling through the structure. Because the presence and rate of growth of any cracks are important pieces of information about the condition or health of the structure, the monitoring of AE activity using sensors mounted on its surface is a potentially useful technique of structural health monitoring. In tests, acoustic emissions are often simulated by breaking a pencil lead against the surface of the structure in a standardised way (a "Hsu‐Nielsen" source), but the forces that this imparts are not well understood at present. The current paper proposes a new evolutionary optimisation‐based approach to source characterisation. The principle is to introduce a parametrised representation of a general source and then identify the parameters that allow the source to best match responses measured elsewhere on the structure. The predicted responses are modelled using a local interaction simulation approach (LISA) algorithm to simulate the propagation of the ultrasonic waves. The approach is validated here using experiments on AE propagation in thin plate‐like structures, where the ultrasound propagates as Lamb waves. Three separate case studies are proposed here. In the first case, an idealised point source is simulated using laser‐generated ultrasound, and the optimisation algorithm uses a two‐dimensional LISA model. A differential evolution optimisation scheme is used to find the optimal profile of forcing to match the simulation with experiment. In the second case, the two‐dimensional LISA approach is used to characterise the forces associated with standard pencil lead breaks. The final study addresses the full three‐dimensional wave propagation. Because of the computational expense of the latter calculation, the LISA algorithm is implemented using a CUDA graphics card computer system. [ABSTRACT FROM AUTHOR]