Vertical Wave Research Articles

New Ultrasonic Tip for Root Canal Filling of the Mesial Canals of Mandibular Molars with Isthmus: A Laboratory Evaluation Using Computed Microtomography

IntroductionThe obturation quality of the mandibular molar mesial canals and isthmuses with two thermoplastic techniques, ultrasonic vertical condensation (UVC) and continuous wave of condensation (CWC), was evaluated using computed microtomography (μCT). MethodsThirty-six human mandibular molars had been previously scanned and analyzed using μCT for mesial roots with morphologically similar isthmuses for this study. Coronal access and confirmation of foraminal patency were performed, and the actual length of the teeth was established using a clinical microscope (40X magnification). The canals were prepared using ProTaper Gold instruments up to #F3, with 2.5% sodium hypochlorite as the irrigant solution, followed by a passive ultrasonic irrigation protocol. The specimens were randomly divided into the UVC and CWC groups based on the obturation technique to be used. Obturation was performed with #F3 gutta-percha cones cemented using AH Plus Jet sealer. The μCT scans were performed after 15 days, and the images were evaluated by a calibrated examiner blinded to the experimental groups to determine the filling rate of the entire canal area, including the main canal and isthmus. Student's t-test was used for statistical analysis; P values ≤0.05 were considered significant. ResultsNeither of the thermoplastic obturation techniques achieved complete filling of the canals (86.3% for UVC and 91.4% for CWC), with a statistically significant difference between them (P = .029). Conclusions:Under the conditions of the study, it can be concluded that none of the techniques completely filled the canal/isthmus of the mandibular molars; however, the CWC exhibited better performance.

Analytical study on an oscillating buoy integrated with a perforated structure with a quadratic pressure drop condition: A case study on a WEC-perforated breakwater integration system

A general analytical method for solving the linear wave interactions with the integration systems comprising an oscillating buoy and perforated structure is presented, with a quadratic pressure drop condition on the perforated surface. Using the method of variable separation and eigenfunction expansion, the motion response of the buoy and total velocity potential can be solved using a two-loop iterative method. The method is validated against the published results. The integration system with a heaving WEC arranged inside a perforated breakwater was investigated particularly. Under the quadratic pressure drop condition, the symmetry of the hydrodynamic coefficients and Haskind relation, are found no longer satisfied, and the dissipation through the perforated wall also contribute to the damping coefficient. Effects of the damping of the power take-off system, front wall porosity, wave amplitude, and position of the WEC are investigated in particular. It was found that the horizontal and vertical wave forces on the WEC increase significantly as wave amplitude increases; however, the hydrodynamic efficiency decreases. When the WEC is near the solid rear wall, the horizontal wave forces on the WEC and solid rear wall increase significantly at the frequencies of piston mode gap resonance and heave motion resonance.

Wave Propagation Characteristics and Compaction Status of Subgrade during Vibratory Compaction.

Vibratory compaction status has a significant influence on the construction quality of subgrade engineering. This study carried out field experiments to study the propagation characteristics of the vertical vibration wave in the soil field along the traveling direction of the vibratory roller. The propagation coefficients of the peak acceleration at different positions and compacting rounds are compared in both the time and frequency domains. The compaction status is estimated in the form of dynamic modulus of deformation (Evd) obtained by plate load tests. The experiment results show that the propagation coefficient of peak acceleration is affected by the traveling speed, excitation amplitude, and frequency of the vibratory roller, as well as the compacting rounds. An exponential relationship between the wave amplitudes of the fundamental mode and higher-order modes is revealed. The amplitude of the fundamental wave is maximum at the speed of 3 km/h, whereas the amplitudes of higher-order waves have a maximum of 1.5 km/h. The influences of compaction rounds on the average value of Evd are also investigated to provide a practical reference for engineering construction.

Experimental and theoretical study of internal solitary wave loads on a submerged slender body

Based on the extended Korteweg de Vries (eKdV) theory and Morison's equation, a theoretical model of internal solitary wave (ISW) loads on a submerged slender body is investigated, and experimental measurements are further carried out in a large stratified fluid flume. The results show that the theoretical results are in good agreement with the experimental results. The horizontal force of the ISW on the slender body is consists of the horizontal dynamic pressure force and the friction force, in which the horizontal dynamic pressure force plays a dominant role. The vertical force includes the vertical wave force and the reduced gravity during the interaction between a slender body and an ISW. The magnitude of the force increases with increasing ISW amplitude, while its direction remains unchanged, and the force is closely related to the submerged depth of the slender body in the density pycnocline, which affects both the magnitude and the direction of the force.

The characteristics of ‘abrupt wave front’ floods on Pennine catchments, northern England, and their transmission downstream

Abstract Visible flood waves, described as abrupt wave front events (AWF), have been identified on rivers in northern England rising in the Pennines, from both historical and recent gauged data. The focus of this paper is on the characteristics of two gauged AWF events on the Rivers Wear and Tees in 1983 and their comparison to ‘normal’ floods. The description and analysis is based on contemporaneous photographs and observations and on digital level and flow records. The rapid 15-min rise in these events is compared with the maximum rate of rise in annual maximum peak floods by comparing flood hydrographs. The propagation of the flood wave downstream is illustrated. The 15-min increase in discharge is compared in relation to the peak flow for AWF and normal floods at different gauged locations down the catchments showing striking differences. The character of the AWF response in the vertical or near-vertical wave front and rapid increase in both level and discharge points to the occurrence of kinematic shock waves.

Fast prediction of turbine energy acquisition capacity under combined action of wave and current based on digital twin method

ABSTRACT Due to the strong nonlinear interaction between the flow field and blades, the prediction of turbine energy acquisition capacity is still quite complex, the traditional methods take too long time to evaluate. In this article, the digital twin model + CFD simulation + monitor data are used for turbine energy efficiency assessment. A self-designed vertical wave flow turbine (VWFT) is taken as the research object, the prediction takes into account the coupling of the VWFT for motion and blade rotation, which is in good agreement with the monitor data at sea. The simulations show that the torque, thrust force and lateral force flow rate data can be loaded from the database into the digital model. If those data are not in the database, the interpolation method is used along with deep learning of recurrent neural network to obtain the energy harvesting parameters, all the error is no more than 10%.

Research on direct-drive motor for wave energy conversion based on Halbach array

In this paper, an improved Halbach array structure of a direct-drive linear motor for wave energy conversion is proposed, and its magnetic circuit structure is modeled and the induced electromotive force (EMF) generated by vertical wave energy conversion is deduced. Then, using the internal and external parameters of the wave energy conversion direct-drive motor, that is, four internal parameters of the magnetic circuit topology and two external parameters of the mover motion, the influence of these parameters on the induced EMF of the direct-drive motor in the wave energy conversion is analyzed. Since the theoretical analysis results of the model are consistent with the results of the two kinds of permanent magnet materials analyzed by the finite element method (FEM), the model and analysis method of the direct drive motor are correct. The investigation show that the modeling method proposed in this paper can be used to optimize the energy conversion of the direct-drive motor from two aspects: the internal parameters of the magnetic circuit topology of the direct-drive motor and the external parameters of the mover motion.

The local stratification preconditions the marine heatwaves in the Yellow Sea

Vertical stratification preconditions marine heat wave (MHW) events in marginal seas. The major events since 1982 in the marginal sea area west and south of the Korean Peninsula have been led by abnormally strong stratification in the vicinity, which was detected at least two months in advance. This robust coincidence provides substantial control over mid-summer events through local stratification in early summer. Such heatwave-leading stratification can be attributed to various oceanic factors during early summers, including anomalous sea surface temperature, freshwater flux, and wind mixing. Knockout-style experiments using a 1-dimensional ocean model revealed that the upper ocean stratification in the preceding months, mostly through wind mixing, is capable of regulating MHWs. Meanwhile, in the longer historical records, gradual decreases in the intensity and frequency of the daily wind gusts were found, possibly as a mixed result of anthropogenically induced climate change and strong natural variability of the midlatitudes. This might have dominated in enhancing the occurrence of MHWs, combined with the rising background surface temperature.

Approximation of Vertical Short Waves of Small Amplitude in the Atmosphere Taking into Account the Average Wind

Approximation of Vertical Short Waves of Small Amplitude in the Atmosphere Taking into Account the Average Wind

Evanescent waves in hybrid poroelastic metamaterials with interface effects

The propagation of evanescent waves in hybrid poroelastic metamaterials is investigated by considering interface effects. Hybrid metamaterials consist of a single-phased (acoustic or elastic) medium and a poroelastic medium. To establish the finite element model of elastic/poroelastic and fluid/poroelastic interfaces, weak integral forms of wave equations for elastic, fluid, and poroelastic media and boundary conditions at the interfaces between different media are first given. Next, the expressions for displacement and pressure in the frame of Bloch’s theorem are substituted into the dynamical equations to obtain general forms suitable for periodic metamaterials, from which the complex band structure and the frequency response of hybrid metamaterials are calculated. The influence of geometrical and material parameters, as well as the viscosity of the pore fluid on the propagation of elastic waves are discussed. The results and discussions show that flat bands and narrow locally resonant band gaps appear for elastic/poroelastic metamaterials. A quasi-resonance Bragg band gap is formed in the case of an elastic inclusion in a poroelastic matrix. Furthermore, a transition from an avoided crossing to a wave-number band gap is obtained by adjusting the geometrical and material parameters of the elastic inclusion. For the case of fluid inclusion in a poroelastic matrix with the open-pore interface, a cut-off frequency for the fast longitudinal wave is observed. However, only an avoided crossing is produced for the sealed-pore interface. For both cases, the phase velocity of the shear vertical (SV) wave decreases faster than that of the slow longitudinal wave as the radius of the inclusion increases. When the viscosity of the pore fluid is considered for elastic inclusion in a poroelastic matrix, the transmission dip at the ‘quasi-resonance Bragg’ band gap disappears. However, the transmission dip in the locally resonant band gap of the SV wave becomes slightly shallower and smoother than in the inviscid case. This study is relevant to practical applications of hybrid single-phased and poroelastic metamaterials, e.g., for coastal engineering and civil engineering.

Conditional sea surface statistics and their impact on geophysical sea surface parameters retrieved from SAR altimetry signals

In this study we present an analytical formulation of synthetic-aperture radar (SAR) altimetry signals including narrow banded nonlinear wave fields and conditional statistics between wave elevation displacements, horizontal wave slopes and vertical wave particle velocities. Considering the wave elevation displacements coskewness with respect to horizontal slopes leads to an analytical formulation of the electromagnetic bias within a SAR-mode altimeter stack. This formulation can be either parametrized by the significant wave height (SWH) and mean wave steepness, or in terms of the variance of vertical wave velocities. The effect of conditional vertical wave particle velocity variances with respect to the observed horizontal wave slopes close to nadir incidence angles leads to an effective reduction of the azimuth blurring of SAR-mode stacks. We present here a formulation of this effect by examining JONSWAP ocean wave spectra. In most cases this effect reduces the azimuth blurring by 10% to 30%. Additionally we investigate the effect of a nonlinear wave elevation displacement probability density function (PDF) on estimated geophysical parameters. We were able to show that including an elevation displacement skewness of 0.13 improves significantly the SWH consistency between altimetry and ECMWF Reanalysis v5 ERA5 results.All of these effects are validated with respect to ERA5 model data in the North East Atlantic region and in situ data located in the German Bight and Baltic Sea.The developed model can be used in both SAR and conventional altimetry retrackers.

P/SVAmplitude Ratios of Shallow Isotropic Explosions and Earthquakes Could Be Indistinguishable at Local Distances: Insights from Single-Station Waveform Simulations

AbstractShear waves play a key role in seismic discrimination between explosions and earthquakes due to their different source mechanisms. However, shear waves are often observed in field explosions with unexpectedly large amplitude, and their generation mechanism is still a significant unresolved question in seismology. Many explanations have been proposed, including the asymmetry of explosive sources, and heterogeneity and/or anisotropy of the Earth’s subsurface. However, it has not been well understood whether source or velocity structure can independently and sufficiently explain the shear waves generated by explosions. Theoretically, tangential SH waves can be converted and scattered from vertical and radial SV waves due to anisotropy and heterogeneity. Thus, it is essential to understand the generation of SV waves by explosions. In this study, we utilize the frequency–wavenumber algorithm and 1D layered velocity models to simulate waveforms of isotropic explosions and double-couple earthquakes at local distances (<20 km). Our results suggest that explosions and earthquakes may generate comparable SV waves if both occurred within a near-surface velocity gradient zone. The earliest SV waves by explosions appear to originate from the near-source region. It implies that P/SV amplitude ratios of explosions and earthquakes could be indistinguishable under certain circumstances.

Efficient Vertical Merger Waves with Heterogenous Suppliers

Efficient Vertical Merger Waves with Heterogenous Suppliers

Multi-directional extremely-low-frequency electromagnetic ocean wave energy harvester based on improved double pendulum structure

The study of ocean wave energy harvesting technology is of great importance in the field of distributed sensor energy supply. Aiming at the problems of insufficient output power, single direction of collecting vibration, restricted working frequency band and complex structure of traditional ocean wave energy harvesters of marine network nodes, a multi-directional extremely-low-frequency electromagnetic ocean wave energy harvester based on improved double pendulum structure is designed. The effect of different component parameters of the energy harvester on the output electrical performance is analyzed by simulation software and a constructed vibration test rig, and the relationship between output voltage and motion state is explored. After optimizing the structure, the ocean wave energy harvester has a minimum response frequency of about 0.25 Hz at a vertical wave height of 0.6 m and a minimum response flow speed of about 0.3 m/s in the horizontal direction. The peak output power is about 150 mW when the wave height is 0.6 m at a frequency of 1 Hz and about 110 mW when the horizontal speed is 0.9 m/s. Experimental results show that the energy harvester can better capture ocean wave energy and provide power for night lights and even IoT devices.

Random wave action on pile group foundations with complex geometry for sea-crossing bridges

To explore the mechanical properties of pile group foundations (PGFs) with complex geometry in sea-crossing bridges under ocean wave action, this study develops a numerical model for predicting wave loads on PGFs under multidirectional random wave action. Furthermore, an experimental model of the PGF composed of a quasi-elliptical pile cap and 13 tilted piles is designed and made based on the gravity similarity criterion. By performing model experiments and numerical analysis, the mechanical characteristics of the PGF model under random wave action, the effect of principal wave direction angle and random wave directionality, and the influence of the pile cap on wave loads of tilted piles are systematically investigated. The results show that the calculated results of the presented numerical model match well with the experimental data. The frequency characteristics of wave loads on the PGF model are mainly determined by the wave spectrum. The increase of the significant period improves the contribution of the pile group to the horizontal wave loads on the PGF. The effect of the principal wave direction on the vertical wave loads on the PGF is not obvious under the experimental wave conditions. Neglecting the wave directionality will overestimate the wave loads in the principal wave direction and vertical direction on the PGF. Under the influence of diffraction waves from the pile cap, the wave loads on the pile group and the piles where the wave finally acts are easily amplified when the wave number is small, but in the large wave number case, the wave loads on the pile group and the piles below the middle of the pile cap may be weakened.

Synthetic experimental and numerical investigation on the vertical seismic effect on underground structures

Seismic damage patterns of underground structures indicate unignorable effects of vertical seismic actions. To deal with this, this study distinguished the impact of the vertical seismic effect on the seismic safety of underground structures experimentally and theoretically and provides important shaking table test results for this topic. A typical shallow buried subway station-tunnel junction structure was designed by following the Buckingham similarity law, based on which the shaking table test was performed to investigate the vertical seismic effect on underground structures. The vertical wave propagation laws of the free field, the model structure, and the soil–structure interaction (SSI) system were comparatively analyzed. Numerical simulations considering the soil’s nonlinear behaviors under vertical loads were performed using the equivalent linear analysis method and were verified by the test records. By combining both the experimental and numerical results, it was found that the surrounding soils have very weak constraints on the structural vertical movements. By distinguishing lateral soil pressures from horizontal actions, the vertical seismic action is found to be mainly an inertia force that can stimulate high-frequency vibration modes of the system and cause considerable vertical relative deformations within the underground structure. Consistent with the observed structural damage at the Daikai station, the participation of high-frequency vibration modes is a rational approach that can explain the amplification effect of vertical ground motions on structural seismic responses. In addition, the equivalent linear method is generally satisfactory for simulating the soil compressional nonlinearity.

Flexural waves analysis and enhancement of bandgap properties of a periodic track structure

Periodic structures possess frequency bandgaps wherein the waves cannot pass through. Here, the propagation behaviour of vertical and lateral flexural waves and its control in a railway track supported on periodic sleeper blocks connected using fasteners is investigated. The dispersion relationships for two kinds of waves are derived through Floquet–Bloch theorem, and the ensuing band structures are validated from finite element (FE) models. The results demonstrate that a Bragg and a locally resonant (LR) bandgap evolve in the track for both types of waves in the examined frequency range. However, the bandwidth of these bandgaps is found to be very small. Thus, waves can freely propagate in the track for a large frequency range, causing vibration and noise. Subsequently, the dependence of transmission properties of waves on the number of unit cells is studied. It is observed that the attenuation in the bandgap is significantly improved on increasing the number of unit cells. Further, to tune the bandgap properties, a single-degree-of-freedom resonator (SDoF) is used in the middle of each unit cell of the track. Afterwards, the parametric influence of resonator properties, that is, mass, stiffness and damping, on bandgaps is investigated in depth. Moreover, the phenomenon of bandgaps coupling is demonstrated when the resonator is tuned near the Bragg bandgap. The results provided herein are promising to realize the characteristics of flexural waves and to design resonators for track structures.

Effect of gas density and surface tension on liquid film thickness in vertical upward disturbance wave flow

Gas–liquid annular flows, such as the flow attached to the fuel rods of boiling water reactors, is a prevalent occurrence in industrial processes. At the gas–liquid interface of such flows, disturbance waves with diverse heights commonly arise. Because the thin liquid film between two successive disturbance waves leads to the dryout on the heating surface and limits the performance of the heating components, complete knowledge of the film thickness and disturbance waves is crucial. The properties of the base film and disturbance waves have been studied extensively through experimental and analytical approaches. However, most experimental data and analysis available in the literature are limited to the near atmospheric condition, and the liquid–gas density ratio under near atmospheric conditions is much higher than in practical nuclear applications. In this study, we use nitrogen gas and water under the system pressures of 0.2 and 0.4 MPa, as well as HFC134a gas and water under the system pressure of 0.7 MPa. Therefore, the density ratio can be varied between 32 and 434. Based on our experimental data, we report a direct link between the film thickness, wave height, and dimensionless numbers. The analysis indicates the Weber number which represents the ratio of the drag force to the surface tension force is critical for the film thickness behavior. To examine this, we perform the experiments using nitrogen gas and 95% (v/v) of aqueous ethanol solution under the system pressure of 0.2 MPa. Finally, two models are proposed to predict the averaged film thickness and wave height, which are then compared with previous data.

Extending the Incidence Angle of Shear Vertical Wave Electromagnetic Acoustic Transducer with Horizontal Magnetization.

Angled shear vertical (SV) waves have been successfully employed in the non-destructive testing of welds, pipes, and railways. Non-contact meander-line coil electromagnetic acoustic transducers (EMAT) have many benefits in generating angled SV waves. The most important benefit is that the incidence angle of an SV wave can be controlled by the excitation frequency. However, the incidence angle of a traditional SV-wave EMAT is reported to be under 45 degrees in many cases. In this work, such cases are tested, and the problems of the received signal at large incidence angles are found to be due to wave interference and small signal amplitudes. An equivalent finite element (FE) model is established to analyze the problem, and the main reason is found to be the head wave. An alternative configuration of angled SV-wave EMAT with horizontal magnetization is proposed to reduce the influence of the head wave. Finally, the results from simulations and experiments show that the proposed EMAT has a larger signal amplitude and significantly reduced interference in large-incidence angle scenarios. Moreover, an incidence angle of an SV wave of up to 60 degrees can be achieved, which will help improve the performance and capability of nondestructive testing.

Numerical investigation on horizontal deformation of large diameter monopile under cyclic wave loading with local scour holes

Seabed liquefaction and local scour around the offshore wind turbine (OWT) monopile have significant effects on the horizontal bearing capacity of the foundation. The horizontal displacement of the monopile at the seabed mudline is one of important factors considered in the foundation design. In this study, the effects of local scour and soil liquefaction on the monopile horizontal displacement were investigated. The dynamic response of sandy seabed with various densities under wave loading was simulated by adopting the Cyclic Mobility (CM) model. The numerical model was compared with previous experimental results. Then, the effects of local scour and soil liquefaction on the monopile horizontal bearing capacity were discussed. The differences in the effects of local scour and liquefaction on the horizontal displacement of monopile in the case of sandy seabed with different densities were compared. Numerical results shown that the effect of soil liquefaction caused by the vertical cyclic wave loading on the monopile horizontal bearing capacity is more significant than that of local scouring and horizontal cyclic loading, especially in loose sandy seabed. For dense sandy seabed, the local scour of the seabed has a more significant impact on the horizontal bearing capacity of the foundation.