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The emergence of the Internet of Things and the interconnection of systems and machines enables the idea of Industry 4.0, a new industrial paradigm with a strong focus on interaction and communication between physical and digital entities, leading to the creation of cyber-physical systems. The digital twin and the standard for the Asset Administration Shell are concepts derived from Industry 4.0 that exploit the advantages of connecting the physical and virtual domains, improving the management and display of the collected data. Furthermore, the increasing availability of data has enabled the implementation of data-driven approaches, such as machine and deep learning models, for predictive maintenance in industrial and automotive applications. This paper provides a two-dimensional review of the Asset Administration Shell and data-driven methods for predictive maintenance, including fault diagnosis and prognostics. Additionally, a digital twin architecture combining the Asset Administration Shell, predictive maintenance and data-driven methods is proposed within the context of the WaVe project. [ABSTRACT FROM AUTHOR]

Establishing an energy harvesting device to supply sustainable energy to deep sea sensors is a challenging task due to the complex subsea marine phenomenon. To overcome this, we propose a two-magnet KMC energy harvester hanging on the cabin of the ship with a spherical bearing. The magnets connected with springs move vertically up and down when the ship is periodically actuated by surface waves, generating electricity to power the deep sea sensors through a cable. We present a case study using wave speed (Uow = 2.0 m/s), wave amplitude (Ho = 0.4 m), and wave length (λ = 4.0 m) to demonstrate the efficacy of the two-magnet energy harvester. Before optimizing the energy harvester, a sensitivity analysis is conducted on the electrical power with respect to marine parameters and the energy harvester's geometric parameters. To maximize the electrical power, we adopt a Cuckoo Search Algorithm as an optimizer. By using the objective function of root-mean-square electrical power in conjunction with the Cuckoo Search, we obtain optimal electrical power. Simulations reveal that the energy harvester produces 0.1497 Watts of power. [ABSTRACT FROM AUTHOR]

Better understanding the effects of hurricane waves and storm surges on barrier-island breaching is important for both scientific research and coastal hazard mitigations. In this study, the 2D non-hydrostatic Xbeach model has been applied to investigate interactions of hurricane wave, storm surge, and morphological processes in the case study of St. Joseph Peninsula during Category 5 Hurricane Michael. Model validations show a 2.45% average error and the 0.88 skill score between modeled and observed high water marks and bed elevations, respectively. Analysis of spatial distributions of currents and water levels indicates that a narrow area was overtopped at peak storm surge and wave. The gap was then quickly enlarged as the breaching area by wave-surge actions. By investigating foredune and peak dune along the central axis of breaching area, it shows that the foredune erosion on the ocean-side by wave-surge-current directly lead to the breach of the peak dune area in the barrier island. The Froude number shows a strong correlation with quick erosion of the barrier, indicating wave-surge supercritical flow is one of the major factors causing the barrier breaching. Results of cross sections of bed elevations and instantaneous surge-wave profiles at different storm surge stages reveal the evolution of the barrier-island breach. Results from this study provide valuable references for coastal hazard mitigation and resilience communities. Highlights: Application of non-hydrostatic Xbeach model reveals barrier-island breaching process and wave-surge-barrier interactions. Model validations show a 2.45% average error and the 0.88 skill score for high water marks and bed elevations, respectively. The breach started with a narrow gap overtopped in the peak of storm surge and was then quickly enlarged by wave-surge actions. Wave-surge induced supercritical flow is one of the major factors accelerating the barrier breaching. Foredune erosion by wave-surge-current is another factor that accelerates the breach of the barrier island. [ABSTRACT FROM AUTHOR]

Chinese satellite carrying synthetic aperture radar (SAR) with spatial resolution up to 1 m, denoted as 1mC-SAR, is the successor of Gaofen-3 (GF-3). The main purpose of this study is to conduct the preliminary analysis of wind and wave retrieval from more than 400 1mC-SAR images acquired in quad-polarization stripmap (QPS), which are located at China coastal waters on April 2023. The co-polarized (vertical−vertical [VV] and horizontal−horizontal [HH]) geophysical model function (GMF), denoted as CSARMOD-GF, is employed for wind speed retrieval from those images taking prior information on wind directions from European Centre for Medium-Range Weather Forecasts (ECMWF). Validation against the wind products from Haiyang-2 (HY-2) (2B/2C/2D) scatterometers yields a 1.78/1.91 m/s root mean squared error (RMSE) with a 0.22/0.23 scatter index (SI) for SAR retrievals at VV/HH polarization channels. Moreover, the accuracy of SAR-derived winds at spatial resolution of 2 km for QPS-I and 6 km for QPS-II is relatively higher than that achieved from the retrievals at spatial resolution of 4 km for QPS-I and 12 km. The wave slop spectrum is inverted from co-polarized image by polarimetric technique, in which the term of wind speed is included in the model transfer function (MTF) of tilt modulation. Significant wave height (SWH) retrievals are compared with the simulations by the third-generation numeric wave model, denoted as WAVEWATCH-III (WW3), showing a 0.53 m RMSE with a 0.36 SI. This behavior is also confirmed as comparing with SAR-derived wave spectra and WW3-simulated wave spectra, i.e. a 0.79 correlation coefficient (Cor) and a 0.92 squared error (Err). The variation of bias in wind speed and SWH indicates an increasing tendency with the growth of sea state, meaning that calibration is a heedful issue for 1mC-SAR. [ABSTRACT FROM AUTHOR]

As the global pursuit of renewable energy intensifies and the demand for offshore wind turbines rises, a comprehensive understanding of the coupling response characteristics of offshore monopiles, seabed, and waves in various sea conditions has become increasingly crucial. This paper reports on a wave flume experiment and seeks to contribute valuable insights by examining the coupling response of offshore monopiles, seabed, and waves exerting a relentless influence. The experimental results indicate that the impact of waves on monopiles is significant: there is greater pressure on the wave facing surface of the offshore piles than the other faces, and the pressure increases with increased wave height as well as the height of the monopile. The wave impact also gives rise to pile motion, squeezing the soil near the monopile and causing gradual pore water pressure around the monopile, and when the wave impact is strong enough, the monopile loses stability. Finally, the experimental results indicate significant differences in the coupling response characteristics of an offshore monopile, the seabed, and waves in various sea conditions. When the wave height was small, the pore water pressure attenuated quickly in the direction of the depth of the seabed; however, as the height and period of waves increased, when the test wave height was more than 18.6 cm and the period was more than 1.63 s, the dynamic pore water pressure around the monopile first decreased and then increased along the depth direction, which, generated by the wave impact, led to vibration and squeezing of the soil near the monopile leg. This indicates that the closer the pile bottom, the more intense the squeezing. By investigating this development across different sea conditions, this study provides a nuanced understanding that can inform the design of offshore monopiles in the face of various marine environmental challenges. [ABSTRACT FROM AUTHOR]

For kinetic full wave analysis in hot plasmas, integral form of dielectric tensors has been formulated. Derivation of the kernel function in a uniform plasma is presented for elucidating the concept. Various applications in inhomogeneous plasmas are described and future extensions in progress are discussed. [ABSTRACT FROM AUTHOR]

Time domain finite difference methods have been widely used for wave‐equation modelling in exploration geophysics over many decades. When using time domain finite difference methods, it is desirable to use a larger time step so as to save numerical simulation time. The Lax–Wendroff method is one of the well‐known methods to allow larger time step without increasing the time grid dispersion. However, the Lax–Wendroff method suffers from more time consumption because there are more spatial derivatives required to be approximated by the finite difference operators. We propose a new finite difference scheme for the Lax–Wendroff method so as to reduce the numerical simulation time. Then we determine the finite difference operator coefficients and analyse the dispersion error of the proposed finite difference scheme for the Lax–Wendroff method. At last, we apply the proposed finite difference scheme for the Lax–Wendroff method to different velocity models. The numerical simulation results indicate that the proposed finite difference scheme for the Lax–Wendroff method can effectively suppress time grid dispersion and is more efficient compared to the traditional finite difference scheme for the Lax–Wendroff method. [ABSTRACT FROM AUTHOR]

In seismic frequency‐domain finite‐difference modelling, the affine mixed‐grid method effectively eliminates the spatial sampling restriction associated with square meshes of the rotated mixed‐grid method. Nevertheless, the affine mixed‐grid method makes a weighted average of the entire elastic wave equations, resulting in reduced accuracy compared to the average‐derivative method in the case of rectangular meshes. It is worth noting, however, that the average‐derivative method is presently inapplicable to free‐surface scenarios, whereas the affine mixed‐grid method is applicable. By performing weighted averages of the derivative terms instead of the entire elastic wave equations in Cartesian and affine rotated coordinate systems, we have developed an improved affine mixed‐grid method for elastic‐wave frequency‐domain finite‐difference modelling. The proposed improved affine mixed‐grid method 9‐point scheme overcomes the drawback that the accuracy of affine mixed‐grid method is lower than that of average‐derivative method for unequal directional grid intervals. Moreover, the improved affine mixed‐grid method 6‐point scheme provides much higher numerical accuracy than the affine mixed‐grid method 6‐point scheme at either equal or unequal directional grid intervals. On the other hand, the proposed improved affine mixed‐grid method simplifies the coding complexity for implementing free‐surface condition in elastic‐wave frequency‐domain finite‐difference modelling by modifying the elastic parameters of the free‐surface layer and thus constructing the impedance matrix containing the free‐surface condition directly. [ABSTRACT FROM AUTHOR]

Abstract As the global pursuit of renewable energy intensifies and the demand for offshore wind turbines rises, a comprehensive understanding of the coupling response characteristics of offshore monopiles, seabed, and waves in various sea conditions has become increasingly crucial. This paper reports on a wave flume experiment and seeks to contribute valuable insights by examining the coupling response of offshore monopiles, seabed, and waves exerting a relentless influence. The experimental results indicate that the impact of waves on monopiles is significant: there is greater pressure on the wave facing surface of the offshore piles than the other faces, and the pressure increases with increased wave height as well as the height of the monopile. The wave impact also gives rise to pile motion, squeezing the soil near the monopile and causing gradual pore water pressure around the monopile, and when the wave impact is strong enough, the monopile loses stability. Finally, the experimental results indicate significant differences in the coupling response characteristics of an offshore monopile, the seabed, and waves in various sea conditions. When the wave height was small, the pore water pressure attenuated quickly in the direction of the depth of the seabed; however, as the height and period of waves increased, when the test wave height was more than 18.6 cm and the period was more than 1.63 s, the dynamic pore water pressure around the monopile first decreased and then increased along the depth direction, which, generated by the wave impact, led to vibration and squeezing of the soil near the monopile leg. This indicates that the closer the pile bottom, the more intense the squeezing. By investigating this development across different sea conditions, this study provides a nuanced understanding that can inform the design of offshore monopiles in the face of various marine environmental challenges.

In harsh environments, an floating production storage and offloading (FPSO) is occasionally damaged by impact loads, such as bow flare slamming and green water. This study conducted an impact load measurement experiment on a model of an FPSO bow in a 2D wave tank. Three types of frequency-focused waves (steep, spilling, and plunging) were generated, and the speed and slope of the waves were measured. Seven wave probes were placed in a row, and the wave elevation was measured to determine the speed and slope of the waves. In addition, the side of the 2D wave tank was photographed with a high-speed camera. The speed and slope of the waves obtained from the wave probe array agreed well with those obtained from the photographs taken using a high-speed camera. In the case of a steep wave, wave runup occurred at the bow before the wave reached the bow of the FPSO, so no impact load was generated, and only hydrostatic pressure was measured. Impact loads were generated in the spilling and plunging waves, and the magnitude of impact loads using the Von Karman’s estimation formula and the impact loads measured in model tests showed similar values.

Aiming at the process of underwater vehicle crossing the water-air interface based on the computational fluid dynamics(CFD) method, integrating the volume of fluid(VOF) and dynamic fluid body interaction(DFBI) models, a numerical simulation method for the trans-media process in a wave environment was studied. The motion simulation method of underwater vehicle under the action of complex fluid environment was established. The simulation of the water-exit process of the underwater vehicle in a wave environment has been realized. The accuracy verification of the wave-making and trans-media processes has been completed. The hydrodynamic and kinematic characteristics of the vehicle during the water-exit process have been obtained. The influences of the wave phase and velocity on the force and motion characteristics of the underwater vehicle were obtained, which provides technical support for designing the unmanned vehicles.

This article presents a planar Vivaldi array antenna based on a power divider structure. A half‐loop defected ground structure (DGS) is performed to decrease the mutual coupling between antennas in the bottom layer of the substrate. The proposed Vivaldi antenna has a 1 × 8 power divided microstrip line structure and performs well in antenna gain and beam directivity. To validate the design, the proposed high‐gain planar Vivaldi array antenna was manufactured, and the measured results were very similar to the simulated one. The size of the proposed antenna is 67 × 44 mm2, the application band is 25–27.3 GHz, and the measured peak gain is 12.6 dBi. The antenna is simulated with an electromagnetic power density (PD) of 28.5 W/m2 at 1 cm2 and 7.27 W/m2 at 4 cm2, which are in compliance with the FCC regulations. Therefore, this antenna is suitable for wearable devices and is applied to n257, n258, and n261. [ABSTRACT FROM AUTHOR]

The nearshore wind stress, u∗2 ${u}_{\ast }^{2}$, is examined using machine‐learning models for air‐ocean data collected via new flux buoys deployed across four experiments. Consistent with prior nearshore studies, existing open‐ocean models predict nearshore u∗2 ${u}_{\ast }^{2}$ with a large error of 0.0152 m2/s2. Gaussian Process Regression (GPR) for nearshore u∗BM2 ${u}_{\ast \text{BM}}^{2}$ is developed, reducing errors to 0.0108 m2/s2. Nearshore air‐sea parameterizations are examined with wind speed (61%) and the wind‐wave frequency of encounters (16%) being the most important. A simpler nearshore, GPR‐derived, wind‐dependent‐only model (u∗NSU2 ${u}_{\ast \text{NSU}}^{2}$) is developed, with errors of 0.0135 m2/s2. GPRs, evaluated using identical variables, were applied to nearshore observations, and these observations modeled with open‐ocean formulations for an initial comparison of parameterizations between these two regimes. The parameterizations are similar, though with subtle nonlinear differences. The new nearshore data set and machine‐learning models enhance the accuracy of predictions and understanding of differences from the open‐ocean. Plain Language Summary: Understanding and accurately parameterizing wind stress on the ocean surface is crucial for modeling oceanic and atmospheric phenomena. Despite its significance, nearshore wind stress and its influencing factors remain inadequately understood due to limited in situ observations and the complexity of the problem. To address this gap, ten shallow‐water air‐sea buoys were developed and deployed alongside directional wave buoys in four field experiments, yielding a substantial data set of nearshore wind stress and associated variables. Discrepancies between nearshore and open‐ocean models were observed, with open‐ocean models exhibiting large errors. Machine‐learning models enhance the accuracy of predictions and understanding of the input variables. A new data‐informed machine‐learning model for nearshore wind stress significantly reduced the error by 30%. Each variable parameterization is described, and a simple model for wind stress based solely on wind speed is provided. Furthermore, an examination of wind stress parameterizations revealed similarities and differences between nearshore and open‐ocean, primarily attributed to wind speeds. These findings significantly enhance the accuracy of weather and ocean forecasts, particularly for nearshore regions. Key Points: Ten air‐sea buoys for winds and fluxes, deployed with wave buoys in four experiments, improve nearshore wind stress observation gapsSupervised machine learning enhances nearshore wind stress predictions, yielding parameterized variable responses without preconceptionsNearshore wind stress parameterizations relative to the open‐ocean have similar variable responses though with small nonlinear differences [ABSTRACT FROM AUTHOR]

In this work, conceptual approximations of the Boussinesq equation were introduced and analyzed, resulting into a very accurate and well-applicable model for horizontal unconfined aquifers during the pure drainage phase, without any recharge and zero-inflow conditions. The model was constructed by employing a variety of methods that included wave solution, variable separation, and series expansion, and its analysis and performance against the Boussinesq equation, at early and later times, providing fruitful insights enlightening the main mechanisms and physical characteristics of the drainage phase. The modeled non-linear forms were finally linearized, concluding with explicit analytical expressions that accurately incorporated most of the basic characteristics regarding the evolution of the water table and the outflow from the exact Boussinesq equation under different initial conditions. The endeavors of this work can be utilized for theoretical and modeling purposes related to this problem. [ABSTRACT FROM AUTHOR]

We present a numerical method to simulate seismic wave propagation in coupled fluid and porous media. We developed a numerical finite element–based algorithm to approximate solutions to viscoacoustic and Biot's equations, considering the open pore conditions at the interfaces between both media. The algorithm architecture allows to simulate arbitrary distributions of viscoacoustic and poroelastic regions, facilitating the modelling of heterogeneous systems involving complex geometries. The algorithm includes a double parallelization scheme whose efficiency in terms of computing time and memory requirements was tested for different core distributions and mesh sizes. We validate our proposal by performing a comparison between its results and those obtained with a well‐known freely available code. We test its capabilities by studying two different scenarios with geophysical interest: a lake with an irregular bottom and a fractured porous medium. [ABSTRACT FROM AUTHOR]

In this study, the parameterization of the drag coefficient is improved using remotely sensed wind and wave products during tropical cyclones (TCs) and implemented for wave simulation using a third-generation numeric model, namely, WAVEWATCH-III (WW3). The significant wave height and peak wavelength from SWIM(Surface Waves Investigation and Monitoring) measured wave spectra are collocated with wind speeds derived from the Haiyang-2 (HY-2) constellation, Soil Moisture Active–Passive (SMAP) radiometer, and Advanced Microwave Scanning Radiometer-2 (AMSR2) in 2019 − 2023. Cyclonic winds at a spatial resolution of 0.25° and intervals of 6 h are obtained by fusion remotely sensed winds from the HY-2 scatterometers and radiometers from SMAP and AMSR2. The parameterization of the drag coefficient during TCs is improved using a matching dataset for 100 TCs consisting of fusion winds and SWIM-measured wave spectra. The significant wave height (SWH) is simulated by WW3 using the optimized parameterization in the several input/dissipation source terms, i.e., ST2, ST3, ST4 and ST6. It is found that the accuracy of simulated SWH using optimized parameterization in switch ST2, ST3 and ST4 is worse than that using optimized parameterization in switch ST6. Moreover, taking two parameterizations in switch ST6 of WW3, validation against the measurements from altimeters and the SWH calculated by SWIM-measured wave spectrum during other 20 TCs yields a root mean square error (RMSE) of 0.60 m, and a correlation coefficient (COR) of 0.85 by optimized parameterization, which are better than the 0.68 m RMSE, and 0.80 COR obtained using existing parameterization. Furthermore, the variation in the bias (altimeter minus WW3) shows that the larger bias (> 2 m) at wind speed > 20 m/s or SWH > 6 m is significantly improved using the optimized parameterization formula and fusion remotely sensed winds. [ABSTRACT FROM AUTHOR]

Acoustic logging is an important method used to determine formation velocities near boreholes. However, in practice, determining accurate formation velocities from acoustic logging data is challenging because of the presence of various noise interferences. Accordingly, a method to increase the amplitudes of refracted waves in open boreholes is proposed herein on the basis of the directional radiation technology of pulse compression signal–driven linear phased array acoustic transmitters. The waveforms generated by a Ricker monopole acoustic transmitter, linear frequency modulation monopole acoustic transmitter and pulse compression signal–driven linear phased array acoustic transmitter in a fluid‐filled open borehole are numerically simulated by employing the finite‐difference method. The effects of the pulse compression signal–driven linear phased array parameters on the amplitudes of the refracted compressional and shear waves are studied. Results show that borehole mode waves with the same velocities and dispersion characteristics can be determined using the pulse compression signal–driven linear phased array acoustic and Ricker monopole acoustic transmitters in fluid‐filled open boreholes. Pulse compression signal–driven linear phased array acoustic transmitters leverage the advantages of pulse compression and phased array technologies, ensuring that a single element can radiate more acoustic energy, whereas pulse compression signal–driven linear phased array parameters can be modulated to further increase the amplitudes of the refracted compressional and shear waves. Compared with Ricker and linear frequency modulation monopole acoustic transmitters, pulse compression signal–driven linear phased array acoustic transmitters can provide downhole received waveforms of better quality and improved a signal‐to‐noise ratio of the mode wave dispersion curves obtained using the downhole received waveforms. Because pulse compression signal–driven linear phased array acoustic transmitters use linear frequency modulation drive signals of longer duration, the recording time required for the received waveforms is also longer and the amount of data generated is larger, presenting new challenges for downhole data processing and high‐speed data transmission. [ABSTRACT FROM AUTHOR]

Multicomponent seismic technology utilizes the kinematic and dynamic characteristics of reflected P‐waves and converted S‐waves to reduce ambiguity in seismic exploration. The imaging and inversion accuracy of P‐SV‐converted waves are important in determining whether multicomponent seismic exploration can achieve higher exploration accuracy than conventional P‐wave exploration. Pre‐stack inversion of P‐SV‐converted waves requires precise input of P‐SV‐converted wave angle‐domain common‐image gathers. Consequently, the P‐SV‐converted wave angle‐domain common‐image gather extraction accuracy will significantly affect the P‐SV‐converted wave inversion accuracy. However, existing methods for extracting P‐SV‐converted wave angle‐domain common‐image gathers are constrained by issues such as the P‐ and S‐wave crosstalk artefacts, low‐frequency noises and inaccurate calculation of P‐wave incident angles, leading to poor imaging accuracy. We study an angle‐domain cross‐correlation imaging condition and address three key issues based on this condition: the decoupling of P‐ and S‐waves, the separation of up‐going and down‐going waves and the precise calculation of P‐wave incident angles. Our strategies facilitate high‐precision extraction of P‐SV‐converted wave angle‐domain common‐image gathers using elastic wave reverse‐time migration. In this paper, first, we employ the first‐order velocity‐dilatation‐rotation elastic wave equations to decouple P‐ and S‐waves automatically during source and receiver wavefield extrapolations. Second, we calculate the optical flow vectors of P‐ and S‐waves to ensure stable calculations of wave propagation directions. Based on this, we obtain up‐going and down‐going waves of P‐ and S‐waves. Meanwhile, we calculate the incident angle of the source P‐wave using geometric relations. Lastly, we apply the angle‐domain imaging condition to achieve high‐precision extraction of P‐SV‐converted wave angle‐domain common‐image gathers. Model examples demonstrate the effectiveness and advantages of the proposed method. [ABSTRACT FROM AUTHOR]

Full waveform inversion stands at the forefront of seismic imaging technologies, pivotal in retrieving high‐resolution subsurface velocity models. Its application is especially profound when imaging complex geologies such as salt bodies, which are regions notoriously challenging, yet essential given their hydrocarbon potential. However, with the power of full waveform inversion comes the intrinsic challenge of estimating the associated uncertainties. Such uncertainties are crucial in understanding the reliability of subsurface models, particularly in terrains like subsalt regions. Addressing this, we advocate for a nuanced approach employing the Stein variational gradient descent algorithm. Through a judicious use of a limited number of velocity model particles and the integration of random field‐based perturbations, our methodology provides a local representation of the uncertainties inherent in full waveform inversion. Our evaluations, based on the Marmousi model, showcase the robustness of the proposed technique. Yet, it is our exploration into salt‐intensive terrains, leveraging data from the Sigsbee 2A synthetic model and the Gulf of Mexico, that emphasizes the method's versatility. Findings indicate pronounced uncertainties along salt boundaries and in the deeper subsalt sediments, contrasting the minimal uncertainties in non‐salt terrains. However, anomalies like salt canyons present unique challenges, potentially due to the interplay of multi‐scattering effects. Emphasizing the scalability and cost‐effectiveness of this approach, we highlight its potential for large‐scale industrial applications in full waveform inversion, while also underscoring the necessity for prudence when integrating these uncertainty insights into subsequent seismic‐driven geological and reservoir modelling. [ABSTRACT FROM AUTHOR]

Marsh lateral expansion and retreat are often attributed to sediment availability, but a causal link is difficult to establish. To shed light on this problem, we analyzed changes in salt marsh area along the ~ 200-km-long Georgia coast (USA) from the 1850s to 2010s in relation to total suspended sediment (TSS) and to proxies for river sediment input and local sediment resuspension. Marsh area is characterized by large gains and losses (up to 200 m2/m/yr), but relatively small net change (-50 to 50 m2/m/yr or -0.1 to 0.1%/yr). This has resulted in a general loss of marsh area, except close to the mouths of major rivers, where there is net gain. Net expansion rates decreased in the Savannah Estuary but increased in the Altamaha Estuary from the 1850s–1930s period to the 1930s–2010s period, which are consistent with observed decreases and likely increases in sediment discharge in the two estuaries, respectively. To explain the spatial patterns in the 1930s–2010s marsh area change, we estimated TSS from satellite measurements (2003 to 2020). Along the northern part of the Georgia coast, net marsh gain is positively correlated to the average TSS within the estuarine region. However, this correlation breaks down in more southern areas (Cumberland Sound). Coast-wide, there is a better correlation between TSS associated with new input from the rivers, estimated as the TSS difference between high-discharge (Jan–Mar) and low-discharge (Sept–Nov) months. To identify the effect of wave resuspension in the nearshore, we consider the TSS difference between high-wave, low-discharge (Sept–Nov) and low-wave, low-discharge periods (Jun–Aug). Wave resuspension is relatively uniform along the coast and does not explain spatial patterns of marsh area change. Sediment input from the nearshore is likely contributing to the estuarine sediment budget in Georgia, but it is not sufficient to prevent marsh lateral retreat. To identify the role of tidal resuspension and advection, we consider differences in TSS between low and high tide. This differential is relatively constant along most of the coast, but it is much lower in the southern part of the coast, suggesting a lower tidal action in this region. Sediment resuspended by tides is likely originating from internal recycling (i.e., erosion) within the estuary, and thus does not contribute to marsh lateral expansion. The proposed approach to partition TSS is a general demonstration and could be applied to other coastal regions. [ABSTRACT FROM AUTHOR]

We present waveguide cavity measurements used to evaluate several thin materials for use in radomes. In addition to the data on the materials, we show how these measurements can be performed with common laboratory equipment and simple calculations. We sought an approach that allowed candidate materials to be readily evaluated to deal with formerly selected materials becoming unavailable or cost-prohibitive. We used lengths of standard waveguide (WR650 and WR137 here) with readily manufactured irises and a vector network analyzer (Keysight N5225B here). To select the iris size and determine the limits of the simplifications in the equations used, we employed a full-wave 3D electromagnetic simulator (CST Microwave Studio). The equations required to calculate the dielectric properties of samples and their contribution to the equivalent system noise temperature from unloaded and loaded resonant frequencies and Q factors are shown. While these formulations can be found elsewhere, we did not find these assembled as conveniently in other studies in the literature. We also show that orienting the sample down the length of the cavity allows for higher-order modes to be fully utilized. We did not find this straightforward adaptation of the common cross-guide orientation in other works. Overall, the results allowed us to recommend three fabrics for use at the frequencies tested (1.7 and 5.6 GHz). The complete process is outlined to assist others in performing these measurements themselves. [ABSTRACT FROM AUTHOR]

In order to investigate the hydrodynamic performances of semi-submersible type floating offshore wind turbines (FOWTs), particularly the effect of body-wave-current interaction, the OC4 FOWT is considered in the presence of co-existing regular wave and uniform current fields. The wind loads are not considered at this stage. The problem is treated in the framework of potential-flow theory in the frequency domain, assuming waves of small steepness, and the solution is obtained by using a perturbation expansion method for the diffraction potential with respect to the normalized current speed. Analytical and numerical formulations have been used to treat the inhomogeneous free-surface boundary condition involved in the hydrodynamic problem formulation for the derivation of the associated perturbation potential. The hydrodynamic loads were obtained after evaluating the pressure field around the multi-body configuration using three different computer codes. The results from the three computer codes compare very well with each other and with the numerical predictions of other investigators. Finally, the mean second-order drift forces are calculated by superposing their zero-current values with the corresponding current-dependent first-order corrections, with the latter being evaluated using a 'heuristic' approach. [ABSTRACT FROM AUTHOR]

Purpose: To study the additional value of FRONSAC encoding in 2D and 3D wave sequences, implementing a simple strategy to trajectory mapping for FRONSAC encoding gradients. Theory and Methods: The nonlinear gradient trajectory for each voxel was estimated by exploiting the sparsity of the point spread function in the frequency domain. Simulations and in‐vivo experiments were used to analyze the performance of combinations of wave and FRONSAC encoding. Results: Field mapping using the simplified approach produced similar image quality with much shorter calibration time than the comprehensive mapping schemes utilized in previous work. In‐vivo human brain images showed that the addition of FRONSAC encoding could improve wave image quality, particularly at very high undersampling factors and in the context of limited wave amplitudes. These results were further supported by g‐factor maps. Conclusion: Results show that FRONSAC can be used to improve image quality of wave at very high undersampling rates or in slew‐limited acquisitions. Our study illustrates the potential of the proposed fast field mapping approach. [ABSTRACT FROM AUTHOR]

Saltwater intrusion occurs frequently in the Yangtze Estuary during winter, when the river discharges are low along with strong wind and waves. However, the influence of wind and waves on saltwater intrusion in the Yangtze Estuary remains unclear. This study uses a coupled wind‐wave‐current numerical model based on Delft3D to investigate the impacts of wind and waves on saltwater intrusion in the Yangtze Estuary. The results show that the strong northerly wind alone enhances saltwater intrusion in the estuary by inducing a counterclockwise circulation and reducing the stratification. However, with the combined effect from wind and waves, it is found that stratification is reduced in the outer North Channel, but enhanced in the inner North Channel, which results in an increase of salt transport in the estuary by approximately 40%. The results highlight the fact that saltwater intrusion in the Yangtze Estuary could be significantly underestimated without considering waves. Plain Language Summary: The effect of wind on saltwater intrusion in estuaries has been widely reported. However, strong wind can generate strong waves, but relatively few studies explore the combined effect of wind and waves on saltwater intrusion. This study uses a strong wind event that occurred in the Yangtze Estuary in 2014 with a coupled computer model to demonstrate such an effect. We found that the peak salt transport can be significantly underestimated without considering waves, as they play an important role in salt transport during strong wind events. Therefore, it is necessary to consider the combined influence from wind and waves in studying saltwater intrusion in estuaries to ensure the safety of the freshwater supply. Key Points: Strong northerly winds have considerable effects on the saltwater intrusion in the Yangtze EstuaryCombined wind and waves effects further increase the estuarine salt transportWave radiation stress enhances the stratification in the North Channel under northerly winds [ABSTRACT FROM AUTHOR]

Under the action of waves, a small unmanned surface vehicle (USV) will experience continuous oscillation, significantly impacting its photovoltaic power generation system. This paper proposes a USV photovoltaic power generation simulation model, and the efficiency of photovoltaic MPPT control under wave action is studied. A simulation model for solar irradiance on solar panels of USV under wave action is established based on CFD and solar irradiation models. The dynamic changes in irradiance of USV solar panels under typical wave conditions are analyzed. The MPPT efficiency of USV photovoltaic power generation devices under continuously changing irradiance conditions is studied on this basis. The simulation research results indicate that waves and solar altitude angles significantly impact the instantaneous irradiation energy of USV photovoltaic devices. However, the impact of waves on the average irradiance is relatively tiny. The sustained oscillation of irradiance poses certain requirements for the Maximum Power Point Tracking (MPPT) control frequency of USV photovoltaic systems; a disturbance control frequency of no less than 50 Hz is proposed. [ABSTRACT FROM AUTHOR]

Chinese satellite carrying synthetic aperture radar (SAR) with spatial resolution up to 1 m, denoted as 1mC-SAR, is the successor of Gaofen-3 (GF-3). The main purpose of this study is to conduct the preliminary analysis of wind and wave retrieval from more than 400 1mC-SAR images acquired in quad-polarization stripmap (QPS), which are located at China coastal waters on April 2023. The co-polarized (vertical−vertical [VV] and horizontal−horizontal [HH]) geophysical model function (GMF), denoted as CSARMOD-GF, is employed for wind speed retrieval from those images taking prior information on wind directions from European Centre for Medium-Range Weather Forecasts (ECMWF). Validation against the wind products from Haiyang-2 (HY-2) (2B/2C/2D) scatterometers yields a 1.78/1.91 m/s root mean squared error (RMSE) with a 0.22/0.23 scatter index (SI) for SAR retrievals at VV/HH polarization channels. Moreover, the accuracy of SAR-derived winds at spatial resolution of 2 km for QPS-I and 6 km for QPS-II is relatively higher than that achieved from the retrievals at spatial resolution of 4 km for QPS-I and 12 km. The wave slop spectrum is inverted from co-polarized image by polarimetric technique, in which the term of wind speed is included in the model transfer function (MTF) of tilt modulation. Significant wave height (SWH) retrievals are compared with the simulations by the third-generation numeric wave model, denoted as WAVEWATCH-III (WW3), showing a 0.53 m RMSE with a 0.36 SI. This behavior is also confirmed as comparing with SAR-derived wave spectra and WW3-simulated wave spectra, i.e. a 0.79 correlation coefficient (Cor) and a 0.92 squared error (Err). The variation of bias in wind speed and SWH indicates an increasing tendency with the growth of sea state, meaning that calibration is a heedful issue for 1mC-SAR.

Palipi Fishing Port is a fish landing port with the condition of the dock building facing directly to the open sea without any protection of the port pond. This causes fishermen to be afraid to anchor their ships at Palipi Harbor, especially during the west season. In addition, the condition of the soil bearing capacity at the seabed due to thick sediment deposits in the harbor water area makes it difficult to apply a pile-type breakwater. Therefore, in order to function optimally, Palipi Fishing Port needs to immediately have a breakwater that is suitable for its geographical conditions as a protection from ocean waves. Floating breakwater is the solution due to its floating structure and efficient in reducing waves. This research will identify the suitability between wave occurrence at Palipi Fishing Port and the effectiveness of using floating breakwater while still considering the ease of development so that it is expected that the port can function optimally for regional economic development.

Within the framework of constructing mega coastal ports in Egypt, this research aims to achieve coastal management sustainability in its surroundings by modeling the Longshore Sediment Transport 'LST'. The literature in the fields of modeling and sediment transport was reviewed and scrutinized. The model was calibrated by contrasting the calculated wave data against 2003 measured data at the Damietta Buoy. The model inputs were tuned to produce a result that was similar to the observed data. Moreover, the model results were validated against 2005 measured data at the Damietta Buoy. Likewise, MIKE21 SM was used to estimate 2011 bed levels within Damietta Port, where 2010 bathymetrical survey data were used. Confident with the model results, it was employed to synthesize transport data for 1940-2020 in terms of LST, Gross LST 'GLST' and Net LST 'NLST' while considering human intervention and implementing ERA5 wave data. Results were obtained and analyzed, and there was a significant correlation between the significant wave height 'Hs' and the wave period 'Tp' and GLST (i.e. R=0.91-0.79, respectively). The analyzed trend results highlighted that in the pre-construction phase of Damietta Port, increases in GLST and NLST were modest (1139.9 and 243.7 m3/year, respectively). However, in the post-construction phase of Damietta Port, they escalated between 4679.47 and 3962 m3/year. The analyzed results indicated that after introducing coastal protection, GLST and NLST decreased to 2978.1 and 2176 m3/year, respectively.

The article is devoted to the study of a little-known scroll by the 18th century Japanese artist Shiba Kōkan1 . The provenance of the scroll and the reasons for its poor study are considered. The main attention is paid to the analysis of the history of the scroll and the symbolism of three elements of images on it: wave, triad, and flame-fire. These three elements are important components of the Japanese cultural and artistic code, forming it since ancient times while changing over time and retaining their significance in contemporary culture. The multiple meanings of the symbolism of the images on the scroll allow us to propose at least two possibilities for its interpretation: as a separate and independent work and as an illustration of the artist’s diary-pamphlet written by him at the end of his life. In this article, we deal primarily with the first possibility. The duality of the perception of the wave and the sea in the cultural code is reflected in the scroll. The islanders realized the sea not only as a physically surmountable barrier, but also as a kind of translator of information. The central part of the scroll depicts a meeting at the table of three wise men from Japan, China and the West, which is analogous to the illustration of the famous Chinese parable Three Wise Men Tasting Vinegar. The article analyzes in detail the portraits of the three participants of the meeting, considers possible prototypes of the Japanese character and the collective images of the Chinese and the European ones, confirmed by the carefully studied symbolism of their appearance, as well as the objects spread out in front of them. The burning Buddhist pagoda depicted at the top of the scroll and the three groups of people trying to extinguish it seem to be an allegory for the gathering around the table. It is also seen in the use of different ways and means of extinguishing the fire by groups of Japanese, Chinese, and Europeans. It seems that the scroll also has Buddhist connotations. The image reflects the irony, mockery, and laughter, which are among the characteristics of Edo culture. The final part of the article speculates on the possible dating and authorship of the scroll.

Inborn errors of immunity (IEI) are a group of diseases in humans that typically present as increased susceptibility to infections, autoimmunity, hyperinflammation, allergy, and in some cases malignancy. Among newly identified genes linked to IEIs include 3 independent reports of 9 individuals from 7 independent kindreds with severe primary immunodeficiency disease (PID) and autoimmunity due to loss-offunction mutations in the NCKAP1L gene encoding Hematopoietic protein 1 (HEM1). HEM1 is a hematopoietic cell specific component of the WASp family verprolin homologous (WAVE) regulatory complex (WRC), which acts downstream of multiple immune receptors to stimulate actin nucleation and polymerization of filamentous actin (F-actin). The polymerization and branching of F-actin is critical for creating force-generating cytoskeletal structures which drive most active cellular processes including migration, adhesion, immune synapse formation, and phagocytosis. Branched actin networks at the cell cortex have also been implicated in acting as a barrier to regulate inappropriate vesicle (e.g. cytokine) secretion and spontaneous antigen receptor crosslinking. Given the importance of the actin cytoskeleton in most or all hematopoietic cells, it is not surprising that HEM1 deficient children present with a complex clinical picture that involves overlapping features of immunodeficiency and autoimmunity. In this review, we will provide an overview of what is known about the molecular and cellular functions of HEM1 and the WRC in immune and other cells. We will describe the common clinicopathological features and immunophenotypes of HEM1 deficiency in humans and provide detailed comparative descriptions of what has been learned about Hem1 disruption using constitutive and immune cell-specific mouse knockout models. Finally, we discuss future perspectives and important areas for investigation regarding HEM1 and the WRC. [ABSTRACT FROM AUTHOR]

Diving waves propagating in the subsurface are massive sources of low‐frequency information that can be used to constrain the kinematic component of the velocity model. Compared to reflected waves, less is known about the behaviour of diving waves, especially in the presence of azimuthal anisotropy. Anisotropy is needed to place the events to the correct depths and match travel times in synthetics with recorded data. Obtaining more insights into the influence of anisotropy on diving wave propagation can help to find parameters with a low trade‐off for inversion. Here, we derive equations for diving qP‐waves in an acoustic factorized anisotropic model with orthorhombic anisotropy. The effects of the anisotropic parameters in the acoustic factorized orthorhombic model are tested by perturbing ε1$\epsilon _1$, ε2$\epsilon _2$, η1$\eta _1$, η2$\eta _2$ and η3$\eta _3$ and observing differences in the ray paths, the effective vertical slowness and the relative geometrical spreading. The properties of diving waves in this model are also compared with those in an acoustic isotropic model and acoustic factorized anisotropic models with elliptical‐ and vertical transverse isotropic anisotropy. From our analysis, we found that perturbing ε1$\epsilon _1$ and ε2$\epsilon _2$ has the most significant influence on these characteristics. The η1$\eta _1$, η2$\eta _2$ and η3$\eta _3$ parameters were shown to induce minor changes. Compared with the other models, the acoustic factorized orthorhombic model had the most in common with the acoustic factorized anisotropic model with elliptical anisotropy. Although, in general, none of the other models could fully represent the effects of orthorhombic anisotropy. [ABSTRACT FROM AUTHOR]

The accurate numerical solution at an acoustic–elastic interface is important for offshore exploration. The solution requires careful implementation for the acoustic–elastic boundary conditions. In this work, we leverage a nodal discontinuous Galerkin method, in which the unstructured uniform triangular meshes are used for the model meshing and an explicit upwind numerical flux derived from the Riemann problem is adopted to handle the boundary conditions at the acoustic–elastic interface. Several numerical results are provided to assess the accuracy and convergence properties of this method. The convergence analysis is carried out in the coupled model with a flat interface, and the accuracy of the proposed method is verified in the curved interface coupled model. Finally, a more complex model with a salt dome, inspired by real geophysical applications, is carried out in this study. The numerical results demonstrate that the proposed nodal discontinuous Galerkin method is effective and accurate for dealing with the coupled acoustic–elastic media with complex geometries. [ABSTRACT FROM AUTHOR]

The reflection waveform inversion is a powerful technique to build a large‐scale velocity model of the subsurface by fitting the reflected recorded seismic waves. The reflection waveform inversion is designed based on the pillar concept of model and data‐scale separation. Therefore, its success is related to the ability of its forward modelling engine to separate reflected events distinctly from other propagation modes (diving waves, multiples, etc.). However, the standard Born modelling based on the two‐way wave equation may generate internal multiples in case of an insufficient smooth background model. These internal multiples may lead to a distorted sensitivity kernel, which adds more non‐linearity to the inverse problem. In addition, simulating the wave equation using two‐way propagators is still an overburden step of the algorithm especially in large three‐dimensional real surveys. In this proposal, we introduce an alternative to the two‐way wave equation by using a one‐way approach for the reflection waveform inversion. The Born modelling based on one‐way propagators significantly reduces the computational cost and I think it should be allows to relax the smooth background velocity model assumption by restricting the forward modelling to primary reflected waves. After a brief theoretical description of the one‐way waveform inversion, we present an application of the algorithm on the real marine dataset to review its promises and pitfalls. Our approach produces an acceptable large‐scale velocity model whose accuracy is confirmed by the migrated image and the offset gathers. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines (FOWTs) exhibit complex motion with multiple degrees of freedom due to the interaction of wind and waves. The aerodynamic performance and wake characteristics of these turbines are highly intricate and challenging to accurately capture. In this study, dynamic fluid body interaction (DFBI) and overset grid technology are employed to investigate the dynamic motion of a 5 MW FOWT. We use the volume of fluid (VOF) method and improved delayed detached eddy simulation (IDDES) model to investigate the aerodynamic performance and wake evolution mechanism for various wave periods and heights. According to the findings, the magnitude of the pitch motion increases with the period and height of the waves, leading to a decrease in both the power output and thrust; the maximum power was reduced by nearly 6.8% compared to a wind turbine without motion. The value of power and thrust reduction varies for different wave periods and heights, and is influenced by the relative speed and pitch angle, which play a crucial role. Wind–wave coupling has a significant impact on the evolution of both wake and vortex structures for FOWT. The wake shape downstream is also dynamically influenced by the waves. In the presence of wind and wave coupling, the interaction between the wind turbine and the wake is heightened, leading to the merger of two unstable vortex rings into a single, larger vortex ring. The research unveils a comprehensive picture of the offshore wind energy dynamics and wake field, which holds immense significance for the design of floating wind turbines and the optimization of wind farm layout. [ABSTRACT FROM AUTHOR]

Relating brain activity to cognition and behavior is the primary goal of cognitive neuroscience. Neuroscientists are increasingly summarizing the brain dynamics that underlie cognition and behavior in terms of brain states. Brain states have traditionally been defined as specific spatial patterns of activity or functional connectivity. We propose that brain states should be conceptualized as waves – recurring patterns of activity that sequentially propagate with different delay times. This definition emphasizes both the spatial and temporal patterns of brain activity. There is ample evidence of wave-like activity in the brain at multiple scales and levels. This emerging literature supports the broader adoption of a wave perspective of brain activity. Specifically, a brain state can be described as a set of recurring, sequential patterns of propagating brain activity, namely a wave. We examine a collective body of experimental work investigating wave-like properties. Based on these works, we consider brain states as waves using a scale-agnostic framework across time and space. Emphasis is placed on the sequentiality and periodicity associated with brain activity. We conclude by discussing the implications, prospects, and experimental opportunities of this framework. [ABSTRACT FROM AUTHOR]

To estimate the depth errors in a subsurface model obtained from the inversion of seismic data, the stationary‐phase approximation in a two‐dimensional constant‐velocity model with a dipped reflector is applied to migration with a time‐shift extension. This produces two asymptotic solutions: one is a straight line, and the other is a curve. If the velocity differs from the true one, a closed‐form expression of the depth error follows from the depth and apparent dip of the reflector as well as the position of the amplitude peak at a non‐zero time shift, where the two solutions meet and the extended migration image focuses. The results are compared to finite‐frequency results from a finite‐difference code. A two‐dimensional synthetic example with a salt diapir illustrates how depth errors can be estimated in an inhomogeneous model after inverting the seismic data for the velocity model. [ABSTRACT FROM AUTHOR]

A breakwater is a structure designed to protect coastal areas by breaking and reducing the force of incoming waves. Waves that propagate through a wave dampening building will have some of their energy reflected (reflection), some of their energy transmitted (transmission), and some of their energy destroyed (dissipation). The effectiveness of wave-breaking structures in protecting coastal and harbor waters can be seen from how much wave energy the building can reduce. In this research, the performance of the wave breaker will be seen from the values of wave transmission (Kt) and wave reflection (Kr) with an inclined pile building structure. Reflection and transmission analysis of the results of 2D physical model testing of wave breakers with inclined pile structures are needed to optimize their use. Laboratory test results prove that this Inclined Pile Structure breakwater is quite effective in scenarios that have smaller Kt values and larger Kr values. In this experiment, testing was carried out with several parameters, namely the slope of the pile, the distance between the piles in one row (or distance between pillars), the distance between the tops of the piles (or distance between rows of piles), and the depth of the water. The Kt value in the model α=45°; D=1.69 cm; b=5 cm is 0.603 compared to the model α=60°; D=1.69cm; b=5 cm, Kt value is 0.652. This shows that the inclined pile structure of breakwater is more effective with a pile slope of 45° than with a pile slope of 60°. [ABSTRACT FROM AUTHOR]

The present study aimed to find the truth about the effect of ocean waves on the process of righting a capsized ship by employing common computational methods of marine salvage engineering. Mathematical models of ship stability and uprighting were developed to quantitatively evaluate the effects of wave encounter angle on the righting forces, bending moments and torques of the hull during the uprighting process. The results indicated that during the uprighting process, the maximum righting forces of the capsized ship were almost unchanged with a maximum difference of 1kN, when the ocean was calm or when the encounter angle of the waves varied. However, the righting force moment showed significant discrepancies under all conditions, with a maximum difference of 1177.5 kN m. When the wave encounter angle is at 0°, the shear force of some parts of the ship is 2–3 times that of the still water environment, and the shear force of some parts of the ship is 3–4 times that of the wave encounter angle at 300°. Remarkably, the bending moment varied by more than 200% at some particular locations under a particular wave encounter angle. Furthermore, the negative torque variation was relatively minor at a 300° wave encounter angle, and the uprighting process still needs relatively large righting forces. [ABSTRACT FROM AUTHOR]

Vehicular ad hoc networks (VANETs) use multiple channels to communicate using wireless access in vehicular environment (WAVE) standards to provide a variety of vehicle-related applications. The current IEEE 802.11p WAVE communication channel structure is composed of one control channel (CCH) and several service channels (SCHs). SCHs are used for non-safety data transmission, while the CCH is used for broadcasting beacons, control, and safety. WAVE devices transmit data that alternate between CCHs and SCHs, and each channel is active for a duration called the CCH interval (CCHI) and SCH interval (SCHI), respectively. Currently, both intervals are fixed at 50 ms. However, fixed-length intervals cannot effectively respond to dynamically changing traffic loads. Additionally, when many vehicles are simultaneously using the limited channel resources for data transmission, the network performance significantly degrades due to numerous packet collisions. Herein, we propose an adaptive resource allocation technique for efficient data transmission. The technique dynamically adjusts the SCHI and CCHI to improve network performance. Moreover, to reduce data collisions and optimize the network's backoff distribution, the proposed scheme applies reinforcement learning (RL) to provide an intelligent channel access algorithm. The simulation results demonstrate that the proposed scheme can ensure high throughputs and low transmission delays. [ABSTRACT FROM AUTHOR]

Talin (herein referring collectively to talin 1 and 2) couples the actomyosin cytoskeleton to integrins and transmits tension to the extracellular matrix. Talin also interacts with numerous additional proteins capable of modulating the actin-integrin linkage and thus downstream mechanosignaling cascades. Here, we demonstrate that the scaffold protein Caskin2 interacts directly with the R8 domain of talin through its C-terminal LD motif. Caskin2 also associates with the WAVE regulatory complex to promote cell migration in an Abi1-dependent manner. Furthermore, we demonstrate that the Caskin2-Abi1 interaction is regulated by growth factor-induced phosphorylation of Caskin2 on serine 878. In MCF7 and UACC893 cells, which contain an amplification of CASKIN2, Caskin2 localizes in plasma membrane-associated plaques and around focal adhesions in cortical microtubule stabilization complexes. Taken together, our results identify Caskin2 as a novel talin-binding protein that might not only connect integrin-mediated adhesion to actin polymerization but could also play a role in crosstalk between integrins and microtubules. [ABSTRACT FROM AUTHOR]

As one of wavefield separation methods in elastic reverse time migration, the decoupled wave equation succeeds to separate the particle velocity of P‐ and S‐wave without mode crosstalk. However, it fails to decouple the stress of P‐ and S‐wave which encounters with the problem of crosstalk. To overcome the crosstalk, the paper has proposed the quasi‐stress equations to decouple the stress tensor wavefields of P‐ and S‐wave based on the decoupled stress–strain relationship. Because P‐ and S‐wave stress wavefields are second‐order tensors, different from the imaging method of vector decoupled particle velocity wavefields, a double dot product imaging condition is proposed to obtain scalar images. Based on the total source‐stress tensor wavefields and separated receiver‐stress tensor wavefields, we obtain the scalar images of quasi‐PP and quasi‐PS from the stress information by the double dot product imaging condition. Several numerical examples are evaluated to demonstrate the effectiveness of the separation of P‐ and S‐wave stress and advantage of the proposed imaging condition from the second‐order stress tensor wavefields. [ABSTRACT FROM AUTHOR]

With the increasing maturity of ocean bottom seismometer technology in gas hydrate exploration, more and more researchers apply ocean bottom seismometer exploration technology for offshore oil exploration. However, due to the special observation mode of ocean bottom seismometer, it is impracticable to process ocean bottom seismometer data using traditional data processing methods, such as velocity analysis and pre‐stack time migration. This manuscript proposed a new velocity analysis method for ocean bottom seismometer data, which obtains more accurate root‐mean‐square velocity than the existing method. Then we deduced the Kirchhoff pre‐stack time migration formula for ocean bottom seismometer data. Two models demonstrate the correctness of the velocity analysis and migration methods. Finally, the two methods were applied to the actual ocean bottom seismometer data, and the obtained migration profile is consistent well with the profile of towed streamer data in the nearby area. [ABSTRACT FROM AUTHOR]