Suppression Of Waves Research Articles

Ground roll wave suppression based on wavelet frequency division and radial trace transform

Ground roll waves interfere with seismic data. The suppression of ground roll waves based on the division of wavelet frequencies considers the low-frequency characteristics of ground roll waves. However, this method will not be effective when the ground roll wave and the effective signal have the same frequency bands because of overlapping. The radial trace transform (RTT) considers the apparent velocity difference between the effective signal and the ground roll wave to suppress the latter, but affects the low-frequency components of the former. This study proposes a ground roll wave suppression method by combining the wavelet frequency division and the RTT based on the difference between the ground roll wave velocity and the effective signal and their energy difference in the wavelet domain, thus making full use of the advantages of both methods. First, we decompose the seismic data into different frequency bands through wavelet transform. Second, the RTT and low-cut filtering are applied to the low-frequency band, where the ground roll waves are appearing. Third, we reconstruct the seismic record without ground roll waves by using the inverse RTT and the remaining frequency bands. The proposed method not only improves the ground roll wave suppression, but also protects the signal integrity. The numerical simulation and real seismic data processing results suggest that the proposed method has a strong ability to denoise while preserving the amplitude.

Effective Suppression of Arrhythmogenic Ca Waves by Flecainide in Ventricular Myocytes from Casq2 -/- Mice Depends on CaMKII Activity

Effective Suppression of Arrhythmogenic Ca Waves by Flecainide in Ventricular Myocytes from Casq2 -/- Mice Depends on CaMKII Activity

Internal Gravity Waves in the Magnetized Solar Atmosphere. I. Magnetic Field Effects

Abstract Observations of the solar atmosphere show that internal gravity waves are generated by overshooting convection, but are suppressed at locations of magnetic flux, which is thought to be the result of mode conversion into magnetoacoustic waves. Here, we present a study of the acoustic-gravity wave spectrum emerging from a realistic, self-consistent simulation of solar (magneto)convection. A magnetic field free, hydrodynamic simulation and a magnetohydrodynamic (MHD) simulation with an initial, vertical, homogeneous field of 50 G flux density were carried out and compared with each other to highlight the effect of magnetic fields on the internal gravity wave propagation in the Sun’s atmosphere. We find that the internal gravity waves are absent or partially reflected back into the lower layers in the presence of magnetic fields and argue that the suppression is due to the coupling of internal gravity waves to slow magnetoacoustic waves still within the high-β region of the upper photosphere. The conversion to Alfvén waves is highly unlikely in our model because there is no strongly inclined magnetic field present. We argue that the suppression of internal waves observed within magnetic flux concentrations may also be due to nonlinear breaking of internal waves due to vortex flows that are ubiquitously present in the upper photosphere and the chromosphere.

Effects of silicone rubber and aerogel blanket-walled tubes on H2/Air gaseous detonation

The experimental study of hydrogen-air detonation was performed in a 6.3-m-long circular cross-section tube, the rear section of which was walled by silicone or aerogel material. Mixtures of 25% or 29.6% hydrogen with air by volume with an initial pressure of 0.1 MPa and temperature of 293 K were used in the experiments. A short Shchelkin spiral was fixed at the tube head to accelerate the deflagration-to-detonation transition. The flame and pressure wave propagation velocities were measured by ion probes and pressure transducers, respectively. The detonation regimes and velocities of flame propagation in walled tubes of different materials were compared. It was found that it is difficult for a silicone rubber-walled tube to reduce the intensity of the detonation wave. In this case, for the stoichiometric mixture, a reduction in the propagation velocity by 5% and the pressure peak by 12% was recorded in order to compare those parameters in a stainless smooth tube. An aerogel blanket wall has a strong ability to reduce the intensity of the detonation wave with the peak pressure decreased by 35% for the stoichiometric hydrogen-air mixture. The attenuation of the steady detonation wave can occur in the aerogel blanket-walled tube under the present experimental conditions. This is because of the effective suppression of transverse waves by interaction with the aerogel wall; then, the generation of stable detonation cells is no longer possible, and thus, the shock wave and flame front are decoupled, and detonation is suppressed.

Terminating spiral wave and spatiotemporal chaos in cardiac tissues by using late sodium current

Most Na+ channels open transiently upon depolarization of cardiac cell membrane and then are quickly inactivated. However, some Na+ channels remain active, which generate the late sodium current during the action potential plateau. So far, late sodium current has been regarded as a relevant contributor to arrhythmias and its inhibition can suppress re-entrant and multifocal ventricular fibrillation so that its inhibition may become a novel therapeutic strategy to treat cardiac arrhythmias in the future. Therefore, how to inhibit late sodium current has received special attention. Since both the late sodium current and defibrillation shocks can lead to the increase of action potential duration, the late sodium current can be used to terminate ventricular fibrillation. However, the suppression of spiral wave and spatiotemporal chaos in cardiac tissues via late sodium current has been neglected. In this paper, we use the model of human heart to study the suppression of spiral wave and spatiotemporal chaos in two-dimensional cardiac tissue by generating late sodium current. We suggest that such a control strategy to induce late sodium current. The slow inactivation gate of sodium channel is clamped to 0.7 while the threshold voltage of corresponding fast inactivation gate is real-timely modulated. We first reduce the threshold voltage from 71.55 mV to 50.55 mV within the time interval T1, and then increase it from 50.55 mV to 71.55 mV within the time interval T2. When the threshold voltage returns to 71.55 mV, the changes of the relevant inactivation gates of sodium channel go back to normal dynamic state. Numerical simulation results show that when the control parameters are properly chosen, the control-induced late sodium current can effectively suppress spiral wave and spatiotemporal chaos even if there are some cardiac cells with spontaneous late sodium current. The advantage of the control scheme is that the control-induced late sodium current is small. The control duration is short because the spiral wave and spatiotemporal chaos disappear mainly due to the conduction obstacle. In a few cases, the spatiotemporal chaos disappears through the transition from spiral wave to target wave. We hope that these results may provide a new strategy to treat heart disease.

Suppression of bulk waves in surface acoustic wave filter

Introduction. One of the dominant second order effects in devices based on surface acoustic waves (SAW) is the excitation of parasitic bulk acoustic waves (BAW). Attention is drawn to the lack of effectiveness of traditional BAW suppression ways. Traditional ways of suppressing the bulk acoustic waves. Provides an overview of how suppression of parasitic BAW to SAW filters. One way allows to reach a record level of BAW suppression (−65 dB) due to the significant mechanical weakening of the acoustic line of the filter. Narrowband surface acoustic wave filter. It is found that in the SAW filter with an extremely high level of out-of-band suppression (−72 dB) traditional ways do not provide the required level of suppression of BAW. Wave heterogeneity of special shape. Tested the effectiveness of the authors proposed way of BAW suppression in a narrow-band SAW filter with an extremely high level of out-of-band suppression. A deep closed groove which is cut in the lower surface of the acoustic line of filter reduces the level of BAW to −70 dB, and the strength of the acoustic line of filter is almost not reduced. The dependence of suppression the bulk acoustic waves from the parameters of the wave heterogeneity. The dependence of the relative level (B) of suppression the slow quasi-shear bulk acoustic waves from the depth of the closed groove was investigated. It was found a monotonic increase in the level of B with increasing groove depth. Level B = −70 dB was obtained when the thickness of the gap between the bottom of the groove and the working surface of the acoustic line was (for different filter samples). Conclusion. The effectiveness of the authors proposed way of suppression the slow quasi-shear BAW in SAW filters is proved. A deep closed groove which is cut into the bottom surface of the acoustic line of filter can suppress slow quasi-shear BAW to a level of −70 dB.

A laboratory investigation concerning the superharmonic free wave suppression in shallow and intermediate water conditions

This paper concerns laboratory wavemaking in shallow and intermediate water conditions. A comparison is made between two wave generation techniques, a first based on controlling the wavemaker displacement, and a second based on controlling the wavemaker force. Nonlinear wave generation in position control is well understood, and many laboratories rely on established second-order or Stream-function inputs. In deep water, using flap-type wavemakers, a force-control approach based on a linear demand signal was recently shown to offer benefits in terms of wave quality. The shallow water operation of such force-control strategies is less certain, which motivates the present study.To investigate the influence of the water depth on this type of control, a range of generation scenarios is considered, including small amplitude and large amplitude regular waves. Adopting both supporting calculations and experimental evidence, the work demonstrates that first-order force-based wave generation in shallow water suffers from similar limitations as first-order position control. This principally concerns the contamination of the testing area due to unwanted free waves, where the present focus is placed on the superharmonic range.The main advance of the work lies in the solutions it offers to overcome this free wave contamination. A number of nonlinear wave solutions upon which force-based generation can be based are discussed, and a suitable methodology is proposed and validated for each case. The developed methodology allows for high quality wave generation, whilst maintaining the benefit of active wave absorption. The work is timely in the sense that is responds to two recent developments. First, the majority of wavemaking facilities commissioned over the past two decades are computer controlled, and active absorption has become commonplace. The work presented offers solutions highly relevant to such installations. Second, developments particularly in offshore wind, have seen many new structures placed in relatively shallow-water depth. It is essential that the model testing of such structures adequately accounts for the issues and solutions presented herein.

Relativistic Second-Harmonic Gyrotron With a Selective Quasi-Regular Cavity

A typical problem of gyrotrons operating at the second harmonic of the electron cyclotron frequency is the suppression of parasitic near-cutoff waves excited at the fundamental harmonic. In this paper, we discuss the possibility for the selective excitation of two different second-harmonic waves in a relativistic millimeter-wavelength gyrotron by means of the use of a method for a significant improvement of the selectivity of this system. This method is based on the use of a quasi-regular cavity with a short irregularity providing different effects on the interaction of the electron beam with the operating second-harmonic wave and the spurious fundamental-harmonic wave.

Wave propagation in nonlinear metamaterial multi-atomic chains based on homotopy method

This paper studies the dispersion properties and wave propagation in the tetratomic nonlinear acoustic metamaterial chain based on the homotopy analysis method (HAM). We perform a comparison between HAM and Perturbation approach, harmonic balance method (HBM) and equivalent method. Results indicate that HAM can filter the unstable multiple periodic solutions fined by HBM and be more accurate. The succinct equivalent formulas can estimate the bandgaps. There is a limit of the dispersion solution when the nonlinearity tends to infinity. Analyses demonstrate that the energy dispersion in spectrum replaces the linear energy localization because of the hyperchaos that is induced by period-doubling bifurcations. The hyper-chaotic phenomena are demonstrated with frequency spectra, bifurcation diagram and Lyapunov Exponents. This paper further proves the chaotic bands can significantly expand the bandwidth for wave suppression. Enhancing the nonlinearity will vary the behavior of nonlinear bandgaps from independent state to coupling state and then experience a transition. Approaches to manipulate bands are elucidated. The strong nonlinearity is beneficial to expand the total width about 6 times. Moreover, lightweight, low-frequency and broadband characteristics are compatible so can be achieved simultaneously for nonlinear acoustic metamaterial.

Broadband and tunable one-dimensional strongly nonlinear acoustic metamaterials: Theoretical study.

This paper focuses on the dispersion properties and mechanism of the one-dimensional strongly nonlinear acoustic metamaterials (NAMMs) based on the homotopy method. The local bifurcation mechanism, which is different from conventional local resonance, is found. It is demonstrated that the local period-doubling bifurcation of multiple cells will induce chaotic bands in the NAMMs, which can significantly expand the bandwidth for wave suppression. The saddle-node bifurcation leads the system state jumping to the chaotic branch. Furthermore, the amplitude-dependent dispersion properties enable NAMMs to manipulate elastic waves externally. Study of broadband tunable abilities reveals that stronger nonlinearity (larger nonlinear coefficient or higher amplitude) presents a broader nonlinear band gap and larger transmission loss. Moreover, with less attached mass, a low frequency and broadband are achievable simultaneously. This research may provide useful approaches for elastic wave control.

Suppression of seismic surface waves based on adaptive weighted super-virtual interferometry

For land seismic surveys, the surface waves are the dominant noises that mask the effective signals on seismograms. The conventional methods isolate surface waves from the effective signals by the differences in frequencies or apparent velocities, but may not perform well when these differences are not obvious. Since the original seismic interferometry can only predict inter-receiver surface waves, we propose the use of super-virtual interferometry (SVI), which is a totally data-driven method, to predict shot-to-receiver surface waves, since this method relieves the limitation that a real shot should collocate with one of the receivers for adaptive subtraction. We further develop the adaptive weighted SVI (AWSVI) to improve the prediction of dispersive surface waves, which may be generated from heterogeneous media at the near surface. Numerical examples demonstrate the effectiveness of AWSVI to predict dispersive surface waves and its applicability to the complex near surface. The application of AWSVI on the field data from a land survey in the east of China improves the suppression of the residual surface waves compared to the conventional methods.

An aperture coupled metamaterial mushroom antenna for operation at WLAN frequency

ABSTRACTA proposed aperture coupled metamaterial mushroom antenna with inherent surface wave suppression at resonance (5.8 GHz) demonstrates over 5.41% higher measured impedance bandwidth of 8.8% and over 3.79 dBi higher gain of 5.46 dBi compared with a similar sized typical aperture coupled microstrip patch antenna, similarly fabricated. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2692–2696, 2016

Shock Wave Refraction at Gas Media Interface

Background/Objectives: This article discusses the problem of refraction of the shock wave with finite amplitude at contact discontinuity between two ideal gases is non-linear, and can be solved numerically for both stationary two-dimensional and transient one-dimensional cases. Methods/Statistical Analysis: Here considered the problem of interaction of one dimensional shock wave (weak and strong) with the contact surface dividing two different gases with different chemical composition and temperature. The interface surface is considered parallel to the shock wave surface. Findings: The sound speed maximal increase in the layer after the contact discontinuity by means of the gas selection with minimal molar mass and its heating seems to be the most satisfying technical solution for the shock wave suppression. Applications/Improvements: This work can be used for both solution of the problem of the intense explosion shock wave attenuation, and the problem of optimal organisation of detonation combustion, where the wave attenuation at the interface should be minimal.

Novel, direct observations of ice on Lake Superior during the high ice coverage of winter 2013–2014

Abstract During the 2013–2014 winter, the Lake Superior basin experienced record-low air temperatures and record-high ice cover. We present observations from three subsurface moorings which provided a novel view of the ice cover during this extreme winter. Each mooring carried a set of thermistors, and two sites had ADCPs, providing a rare glimpse into the subsurface characteristics and behavior of a large, partially ice-covered lake, including ice drift velocity, keel size and abundance, surface gravity wave suppression, and passive acoustics below the ice sheet. Ice drift velocities were well correlated with nearby wind velocities, with ice speeds approximately 4% of the wind speed and 20° to the right of the wind direction. Passing ice keels displaced the top subsurface float at the western mooring to depths of 6 m on a regular basis, and up to 11 m during one event. Anomalously large signal return strength at two ADCPs occurred sporadically at roughly the same time at two geographically separate locations, but only during periods of ice cover. The distribution of signal strength with depth suggests that these events are actually sounds from the ice cover itself, rather than reflectors in the water. Broadly speaking, ice cover on Lake Superior has more in common with oceanic ice cover than with ice cover on small lakes.

A Novel Rough - Surface Direct Wave Suppression Algorithm based on Energy Adaptive Analysis

A Novel Rough - Surface Direct Wave Suppression Algorithm based on Energy Adaptive Analysis

Flexural wave suppression by an acoustic metamaterial plate

A new acoustic metamaterial plate is presented for the purpose of suppressing flexural wave propagation. The metamaterial unit cell is made of a plate with a lateral local resonance (LLR) substructure which consists of a four-link mechanism, two lateral resonators and a vertical spring. The substructure presents negative Young’s modulus property in certain frequency range. We show theoretically and numerically that two large low-frequency band gaps are obtained with different formation mechanisms. The first band gap is due to the elastic connection with the foundation while the second is induced by the lateral resonances. Besides, four-link mechanisms can transform the flexural wave into the longitudinal vibration which stimulates the lateral resonators to vibrate and to generate inertial forces for absorbing the energy and thus preventing the wave propagation. Frequency response function shows that damping from the vertical spring has little influence on the band gaps, although the damping can smooth the variation of frequency response (see the dotted line in Figs. 10 and 11). Increasing the damping of the lateral resonators may broaden the second band gap but deactivate its effect. This study provides guidance for flexibly tailoring the band characteristics of the metamaterial plate in noise and vibration controls.

Evaluation of Telecommunications Electromagnetic Compatibility with the Use of Three-Dimensional Modeling Technology

Three-dimensional modeling is used as a new way of presenting information about the electromagnetic compatibility of telecommunications infrastructure equipment. We analyzed the problem of modeling of electromagnetic noise waves equipment and communication channels of telecommunications monitoring systems. Conducted the analysis of control problems of telecommunications equipment electromagnetic compatibility. Described the real conditions of installing the electronic equipment in computational complexes. Using tools of 3D-modeling was formed cable route, taking into account the suppression of noise waves, placement of telecommunication devices and checking whether the threshold value of cable susceptibility for all options of its gasket between devices was transcended. It is proposed to study the behavior of electromagnetic fields in the cable lines with shielding cable, electrostatic discharge, providing set of measures for electromagnetic compatibility, to convert created in a three-dimensional environment model in a specialized settlement package. The prospects of the use 4D-, 5D-, 6D-simulation for analysis of the implementation of projects, reduction of operating and electromagnetic compatibility costs.

Controlling formation and suppression of fiber-optical rogue waves.

Fiber-optical rogue waves appear as rare but extreme events during optical supercontinuum generation in photonic crystal fibers. This process is typically initiated by the decay of a high-order fundamental soliton into fundamental solitons. Collisions between these solitons as well as with dispersive radiation affect the soliton trajectory in frequency and time upon further propagation. Launching an additional dispersive wave at carefully chosen delay and wavelength enables statistical manipulation of the soliton trajectory in such a way that the probability of rogue wave formation is either enhanced or reduced. To enable efficient control, parameters of the dispersive wave have to be chosen to allow trapping of dispersive radiation in the nonlinear index depression created by the soliton. Under certain conditions, direct manipulation of soliton properties is possible by the dispersive wave. In other more complex scenarios, control is possible via increasing or decreasing the number of intersoliton collisions. The control mechanism reaches a remarkable efficiency, enabling control of relatively large soliton energies. This scenario appears promising for highly dynamic all-optical control of supercontinua.

Compact meandered‐shape electromagnetic bandgap structure using in a microstrip array antenna application

ABSTRACTIn this letter, a novel spiral shape for electromagnetic bandgap structure (EBG) is presented for array structure. By implementation of the spiral formation, the inductance of the EBG unit cell will be increased and the unit cells are compacted around 36% for 3.6 GHz in comparison to conventional EBG unit cells. The prototype model of unit cells is used for 2 × 2 element microstrip patch array antenna with slot feed for improving the radiation gain of the antenna by reducing the mutual coupling effect of the antenna. Suppression of surface waves using EBG has improved the gain about 1.2 dB. Finally, an antenna prototype was fabricated and tested. Good agreement between simulation and measurement is obtained that verified the performance of the proposed structure. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2084–2088, 2016

Sustainable zero liquid discharge desalination (SZLDD)

The main purpose of this study is to develop a sustainable zero liquid discharge desalination system. Direct contact membrane distillation unit is connected directly to salinity gradient solar pond (SGSP) to achieve zero liquid discharge desalination. The used system contains a hydrophobic microporous membrane module and a plastic pipe circulating all over the pond water surface to be used as a cooling system. The pipe also used as a wave suppression system as it is floating over the top of the pond water surface. The system is sourced by the hot and high concentrated saline water that is extracted from non-convective zone as a feed solution, then, the brine discharges at the lower convective zone of the solar pond. Therefore, if the saturated brine is used to produce salts, there will not be any brine left over which may lead to zero liquid discharge desalination. The system is modelled theoretically and solved by Matlab simulation program. It has been found that the system has the ability to deliver 52l/day of fresh water for m2 of membrane coupled with SGSP, consuming almost 11kW/m2 of thermal energy. Also, the trans-membrane coefficient of the used membrane is proved to be 0.001kg/m2/Pa/h. The results are analysed and the system performance is evaluated and presented in this paper.