High Frequency Waves Research Articles

Solar Orbiter’s first Venus flyby

Context. The induced magnetosphere of Venus is caused by the interaction of the solar wind and embedded interplanetary magnetic field with the exosphere and ionosphere of Venus. Solar Orbiter entered Venus’s magnetotail far downstream, > 70 Venus radii, of the planet and exited the magnetosphere over the north pole. This offered a unique view of the system over distances that had only been flown through before by three other missions, Mariner 10, Galileo, and BepiColombo. Aims. In this study, we study the large-scale structure and activity of the induced magnetosphere as well as the high-frequency plasma waves both in the magnetosphere and in a limited region upstream of the planet where interaction with Venus’s exosphere is expected. Methods. The large-scale structure of the magnetosphere was studied with low-pass filtered data and identified events are investigated with a minimum variance analysis as well as combined with plasma data. The high-frequency plasma waves were studied with spectral analysis. Results. We find that Venus’s magnetotail is very active during the Solar Orbiter flyby. Structures such as flux ropes and reconnection sites were encountered, in addition to a strong overdraping of the magnetic field downstream of the bow shock and planet. High-frequency plasma waves (up to six times the local proton cyclotron frequency) are observed in the magnetotail, which are identified as Doppler-shifted proton cyclotron waves, whereas in the upstream solar wind, these waves appear just below the proton cyclotron frequency (as expected) but are very patchy. The bow shock is quasi-perpendicular, however, expected mirror mode activity is not found directly behind it; instead, there is strong cyclotron wave power. This is most likely caused by the relatively low plasma-β behind the bow shock. Much further downstream, magnetic hole or mirror mode structures are identified in the magnetosheath.

High-frequency radio wave electrocautery in modified Hotz operations for epiblepharon correction

To report the experience and advantageous effects of high-frequency radio wave electrocautery in modified Hotz operations for epiblepharon, We reviewed the records of all pediatric patients who underwent a modified Hotz operation with the use of high-frequency radio wave electrocautery (Ellman Surgitron Dual Frequency RF S5; Ellman International, Inc, Hewlett, NY) for epiblepharon between March 2016 and September 2019 at Korea University Guro Hospital. We evaluated the success rate, complications, recurrence rate and degree of satisfaction of our technique. Information from the medical records was collected, including demographics, ocular symptoms, severity of keratopathy, operation time, success/recurrence rate, and complications. 133 patients (98.52%) showed good correction of epiblepharon without complications or unpleasant cosmetic problems during 3 months of median follow-up period. Two patients (1.48%) showed recurrent corneociliary touch, but the degree was very mild and re-operation was not performed. One patient showed mild ectropion on his left lower eyelid, but the patient recovered well without operation. For complications, suture abscess and granulation were the most common, 3 cases in each, but all of those were temporary and resolved with conservative management. The approach with electrocautery for epiblepharon allows precise and fast incision of the lower eyelid, little bleeding, and minimal scarring. Surgical outcomes associated with the modified Hotz operation with electrocautery were consistent with previous studies.

Attenuation of long period multiple using F-k filter and surface-related multiple elimination methods on 2D broadband seismic data from Morowali Waters, Sulawesi

Wide range frequency bandwidth on seismic data is a necessity due to its close relation to resolution and depth of target. High-frequency seismic waves provide high-resolution imaging that defines thin bed layers in shallow sediment, while low-frequency seismic waves can penetrate into deeper target depth. As a result of broadband seismic technology, its wide range of frequency bandwidth is a suitable geophysical exploration method in the oil and gas industry. A major obstacle that is frequently found in marine seismic data acquisition is the existence of multiples. Short period multiple and reverberation are commonly attenuated by the predictive deconvolution method on prestack data. Advanced methods are needed to suppress long period multiple in marine seismic data. The 2D broadband marine seismic data from deep Morowali Waters, Sulawesi, contains both short and long period multiples. The predictive deconvolution, which is applied to the processing sequences, successfully eliminates short period multiple on prestack data. The combination of F-k filter and Surface Related Multiple Elimination (SRME) methods are successful in attenuating long period multiple of the 2D broadband marine seismic data. The Prestack Time Migration section shows fine resolution of seismic images.

Noninvasive detection of elevated ICP using spontaneous tympanic membrane pulsation

Neurological conditions such as traumatic brain injury (TBI) and hydrocephalus may lead to intracranial pressure (ICP) elevation. Current diagnosis methods rely on direct pressure measurement, while CT, MRI and other expensive imaging may be used. However, these invasive or expensive testing methods are often delayed because symptoms of elevated ICP are non-specific. Invasive methods, such as intraventricular catheter, subdural screw, epidural sensor, lumbar puncture, are associated with an increased risk of infection and hemorrhage. On the other hand, noninvasive, low-cost, accurate methods of ICP monitoring can help avoid risks and reduce costs while expediting diagnosis and treatment. The current study proposes and evaluates a novel method for noninvasive ICP monitoring using tympanic membrane pulsation (TMp). These signals are believed to be transmitted from ICP to the auditory system through the cochlear aqueduct. Fifteen healthy subjects were recruited and TMp signals were acquired noninvasively while the subjects performed maneuvers that are known to change ICP. A custom made system utilizing a stethoscope headset and a pressure transducer was used to perform these measurements. Maneuvers included head-up-tilt, head-down-tilt and hyperventilation. When elevated ICP was induced, significant TMp waveform morphological changes were observed in each subject (p < 0.01). These changes include certain waveform slopes and high frequency wave features. The observed changes were reversed by the maneuvers that decreased ICP (p < .01). The study results suggest that TMp waveform measurement and analysis may offer an inexpensive, noninvasive, accurate tool for detection and monitoring of ICP elevations. Further studies are warranted to validate this technique in patients with pathologically elevated ICP.

Were recently reported MHz events planet mass primordial black hole mergers?

A bulk acoustic wave cavity as high frequency gravitational wave antenna has recently detected two rare events at 5.5MHz. Assuming that the detected events are due to gravitational waves, their characteristic strain amplitude lies at about h_capprox 2.5 times 10^{-16}. While a cosmological signal is out of the picture due to the large energy carried by the high frequency waves, the signal could be due to the merging of two planet mass primordial black holes (approx 4times 10^{-4} M_odot ) inside the Oort cloud at roughly 0.025 pc (5300 AU) away. In this short note, we show that the probability of one such event to occur within this volume per year is around 1:10^{24}, if such Saturn-like mass primordial black holes are 1% of the dark matter. Thus, the detected signal is very unlikely to be due the merger of planet mass primordial black holes. Nevertheless, the stochastic background of saturn mass primordial black holes binaries might be seen by next generation gravitational wave detectors, such as DECIGO and BBO.

High-frequency Wave Power Observed in the Solar Chromosphere with IBIS and ALMA

Abstract We present observational constraints on the chromospheric heating contribution from acoustic waves with frequencies between 5 and 50 mHz. We use observations from the Dunn Solar Telescope in New Mexico, complemented with observations from the Atacama Large Millimeter Array collected on 2017 April 23. The properties of the power spectra of the various quantities are derived from the spectral lines of Ca ii 854.2 nm, H i 656.3 nm, and the millimeter continuum at 1.25 and 3 mm. At the observed frequencies, the diagnostics almost all show a power-law behavior, whose particulars (slope, peak, and white-noise floors) are correlated with the type of solar feature (internetwork, network, and plage). In order to disentangle the vertical versus transverse Alfvénic plasma motions, we examine two different fields of view: one near disk center, and the other close to the limb. To infer the acoustic flux in the middle chromosphere, we compare our observations with synthetic observables from the time-dependent radiative hydrodynamic RADYN code. Our findings show that acoustic waves carry up to about 1 kW m−2 of energy flux in the middle chromosphere, which is not enough to maintain the quiet chromosphere. This is in contrast to previous publications.

HYDRODYNAMICS OF A DUAL-CHAMBER OWC WAVE ENERGY CONVERTER IN HEAVING MOTION

The oscillating water column (OWC) wave energy conversion device have been recognized as the most promising wave energy conversion technology due to the advantages of its simple structure, convenient assembly and easy maintenance. A heave-only dual-chamber OWC device was numerically investigated by a well-developed open source software OpenFOAM coupled with a wave generation and absorption toolbox Waves2Foam. The volume of fluid (VOF) method tracking the water-air interface and the six-degree-freedom (6DOF) Dynamic Mesh solver duplicating the heave motion of the OWC device were employed to examine the influences of the relative width of the front and rear chambers and the spring elastic coefficient on the energy capture width ratio and hydrodynamic characteristics of the device under the actions of different incident regular waves. Through comparing the present results with the existing ones of a fixed dual-chamber OWC wave energy converter, and examining the free-decay motion of a cylinder, the rationality and effectiveness of the present numerical model has been revealed. The results show that the wider rear chamber can make for the extraction of wave energy of the dual-chamber OWC in heave motion. The heave-only dual-chamber OWC device can improve the device performance as the relative width ratio of the front and rear chambers is 1/2, and the rear chamber has larger capture width ratio in the middle and high frequency wave bands, compared with that of the fixed one. Multiple-peak values of the relative water surface elevation and the relative pressure occur in the whole test wave frequency bands due to the phase gap between the dual-chamber OWC device and the water columns in the front and rear chambers. In addition, it is found that by adjusting the spring stiffness coefficient, the wave-frequency bandwidth of high-efficiency can be significantly broadened and larger energy capture width ratio can be achieved.

Hydrodynamic effects on the energy transfer from dipoles to metal slab.

A systematic study of nonlocal and size effects on the energy transfer of a dipole (e.g., a molecule or a quantum dot) induced by the proximity of a metal slab is presented. Nonlocal effects are accounted for using the hydrodynamic model (HDM). We derive a general relation that connects the energy transfer rate to the linear charge density-density response function of the slab. This function is explicitly evaluated for the HDM and the local Drude model. We show that a thin metal slab can support a series of higher-frequency surface plasma wave (SPW) modes in addition to the normal SPW modes, thanks to the nonlocal effects. These modes markedly alter the response and the energy transfer process, as revealed in the structure of the energy transfer rate in the parameter space. Our findings are important for applications such as the recently developed metal-induced energy transfer imaging, which relies on accurate modeling of the energy transfer rate.

Online measurements of material flow compositions using acoustic emission: Case of gypsum and anhydrite

In this study, acoustic emission technology (AE), an established technology in various applications, has been investigated for its suitability for material flow characterization of bulk material. High-frequency waves generated during impact processes are recorded as acoustic emission signals to be used as a suitable measurement technology. By analysing the acoustic emission signals of known material flow compositions, suitable parameters and algorithms can be developed. Based on AE technology, the study focused on determining the gypsum and anhydrite content of an unknown material flow with the aim of building an online measuring system that could be integrated into the process of gypsum mining and processing. If successful, this approach could partly replace current offline analysis methods and enable real-time process control in the gypsum industry. The AE application was tested in laboratory experiments on a custom-built circulation test bench as well as in gypsum processing plants. Online measurements of the gypsum content were successfully achieved with an accuracy of 2.5% and an update rate of every five seconds.

Hybrid precoding algorithm for massive MIMO system with imperfect channel knowledge

Millimeter wave MIMO system offers orders of magnitude high data rate due to the excess bandwidth available then conventional MIMO system. But, at the cost of excessive free space losses that highly influence the transmission at very high millimeter wave frequencies. The resulting small Wavelength at the millimeter wave frequency can overcome the path losses using beam forming gain offered by the massive antennas which is known as pre-coding. In millimeter wave massive MIMO system, hybrid pre-coding is the technique that combines analog pre-coding and digital pre-coding to reduce the requirement of high number of RF chains and thus energy consumption. Hybrid beam forming uses number of RF chains equal to the number of simulations users being served rather than using separate RF chains in the case of digital pre-coding. In designing analog and digital pre-coders, large number of calculations that uses complex mathematical process such as block diagonalization, SVD for channel matrix inversion required for the computation of pre-coder weight vector computation. In this paper, we propose low complexity hybrid pre-coding algorithm using simple linear approximation algorithms for matrix inversion operations. We first used the simple inversion algorithm in the computation of analog beam forming matrix without any SVD or direct inversion of matrices. Then, the same is being used in digital pre-coding matrix. In the proposed algorithm, there is no need for the complicated operations as SVD as in traditional pre coding algorithms.

Excitation of airwaves by bubble bursting in suspensions : regime transitions and implications for basaltic volcanic eruptions

Basaltic magma becomes more viscous, solid-like (elastic), and non-Newtonian (shear-thinning, non-zero yield stress) as its crystal content increases. However, the rheological effects on bubble bursting and airwave excitation are poorly understood. Here we conduct laboratory experiments to investigate these effects by injecting a bubble of volume V into a refractive index-matched suspension consisting of non-Brownian particles (volumetric fraction phi) and a Newtonian liquid. We show that depending on phi and V, airwaves with diverse waveforms are excited, covering a frequency band of f = {mathcal {O}}(10-10^4) Hz. In a suspension of phi le 0.3 or in a suspension of phi = 0.4 with a V smaller than critical, the bubble bursts after it forms a hemispherical cap at the surface and excites a high-frequency (HF) wave (f sim 1-2 times 10^4 Hz) with an irregular waveform, which likely originates from film vibration. However, in a suspension of phi = 0.4 and with a V larger than critical, the bubble bursts as soon as it protrudes above the surface, and its aperture opens slowly, exciting Helmholtz resonance with f = {mathcal {O}}(10^3) Hz. Superimposed on the waveform are an HF wave component excited upon bursting and a low-frequency (f = {mathcal {O}}(10) Hz) air flow vented from the deflating bubble, which becomes dominant at a large V. We interpret this transition as a result of the bubble film of a solid-like phi = 0.4 suspension, being stretched faster than the critical strain rate such that it bursts by brittle failure. When the Helmholtz resonance is excited by a bursting bubble in a suspension whose surface level is further below the conduit rim, an air column (length L) resonance is triggered. For L larger than critical, the air column resonance continues longer than the Helmholtz resonance because the decay rate of the former becomes less than that of the latter. The experiments suggest that a bubble bursting at basaltic volcanoes commonly excites HF wave by film vibration. The Helmholtz resonance is likely to be excited under a limited condition, but if detected, it may be used to track the change of magma rheology or bubble V, where the V can be estimated from its frequency and decay rate.

INFORMATION EXTRACTION FROM LAPAN SATELLITE AIS DATABASE FOR SHIP CLASSIFICATION IN THE INDONESIAN TERRITORIAL WATERS

Automatic Identification System (AIS) is a system used to monitor ship activity by sending ship information via Very High Frequency (VHF) waves. Information sent by ships around the world is recorded by AIS receivers carried by the LAPAN-A2 and LAPAN-A3 satellites along their orbital trajectories. The AIS data recorded by the satellite will then be acquired and stored at the LAPAN earth station. This study focuses on extracting information from the LAPAN satellite AIS database to obtain information on the number of vessels based on a unique Maritime Mobile Service Identity (MMSI) grouped according to the type of vessel entering Indonesian waters with coordinates 95BT / 141BT, -11LS / 6LU every month. in the period January to December 2019. The results of extracting the information are in the form of the number of ships based on unique MMSI which are grouped according to the type of ship in the territory of Indonesia with that region and time period

Дослідження методів боротьби із шкідниками на зерносховищах та продуктових базах на прикладі підприємств системи держрезерву України

At present, the enterprises of the State Reserve system have a long-term storage of a large number of wheat and other cereals, as well as a significant range of food products. Recently, due to the violation of the organizational and economic method of storage of grain crops and the system of technological operations during their cultivation, the amount of grain damaged by pests and pathogens has increased, as a result, it gets to the elevators of low quality. This facilitates access to such grain during storage of collar pests. There is another important factor in enhancing the negative effects of collar pests - warm, with a short frosty winter, which only stimulates their reproduction. For these reasons, up to 100% of the crop can be lost during storage. Poor preparation of the granary for storage, moisture, and high grain temperature can also be the reason. The article is devoted to the essence and content of such a problem as the control of various pests in granaries and food bases. The article provides a brief overview of the main existing pest species and methods of pest control. As a result of research for the enterprises of the State Reserve system of Ukraine the most effective method, ozonation and ultrasonic loading is chosen. The technology of decontamination of warehouses is given, the advantages and disadvantages of this method are shown. The article also presents an effective method of rodent control in granaries and food warehouses with the help of ultrasonic waves and electromagnetic radiation, the technology of application of ultrasonic frequencies to repel rodents is proposed. The article presents the method of research using industrial ozonator, shows its technical characteristics and also presents the results of research and the main parameters of ozonation of the warehouse (ozone concentration and duration of treatment). Recently, ozonation of premises has become widespread in pest control. Ozonation - a technology for decontamination of premises, based on the use of ozone gas - a strong oxidant. Special installation - ozonator produces ozone from oxygen contained in atmospheric air. The approximate required capacity of the ozonator is 3 - 5 g/h per 100 m3 of room volume. Large granaries and food warehouses require additional fans to mix the air. Ozonation is carried out in the absence of people. People should not enter for 1.5 - 2 hours after switching off the ozonator, while ozone decomposes into oxygen, if necessary, you can enter in an ozone respirator or a respirator with a carbon filter. An effective method of combating rodents and insects in granaries and food warehouses is deterrence by ultrasonic waves and electromagnetic radiation. Ultrasonic deterrent generates sound waves of high frequency and high volume, electromagnetic generates pulses that are transmitted through electrical wiring. These devices create an uncomfortable environment for rodents and insects, forcing them to leave the room. To avoid rodents getting used to ultrasonic radiation, the devices automatically change the range of emitted ultrasonic frequencies. Ultrasonic waves are reflected from solid materials and coatings (wood, glass, concrete, etc.) and are absorbed by soft materials (curtains, carpets, products stored in bags, etc.).

Elastic and viscoelastic flexural wave motion in woodpecker-beak-inspired structures

This paper comprehensively investigates elastic and viscoelastic flexural wave propagation in structures that are inspired by the unique suture configurations present in a woodpecker’s beak, in order to understand their ability to attenuate velocity amplitudes and wave speeds. Waveguides characterized by sinusoidal depth variations, both plain and variously graded along the length, mimicking the suture geometry, are considered in this work. Elastic and viscoelastic wave propagation analyses, along with prior static and free vibration studies, are carried out using a novel superconvergent finite element formulation. In elastic wave propagation analysis, firstly the attenuation characteristics are appraised in relation to the high amplitude and frequency waves of three different plain waveguides with differing depth profile orientations. This prompted us to next consider waveguides of hybrid configurations derived from them. Further, waveguides with lengthwise graded sinusoidal segments, as observed in nature, are studied for better wave attenuation properties compared to plain waveguides. This is followed by viscoelastic wave propagation analysis. Regarding the important role of the suture geometry, which is the focus of this work, the results from the elastic analyses revealed the nature of the reduction in wave speeds and amplitudes, both qualitatively and quantitatively, in such waveguides, and their dependence on the orientation and magnitude of the sinusoidal depth variation. Some waveguide configurations with remarkable wave attenuation characteristics, in terms of both wave speeds and amplitudes, are presented, along with their implications regarding impact mitigation applications.

Resonant interaction of relativistic electrons with realistic electromagnetic ion\u2013cyclotron wave packets

We study the influence of real structure of electromagnetic ion-cyclotron wave packets in the Earth’s radiation belts on precipitation of relativistic electrons. Automatic algorithm is used to distinguish isolated elements (wave packets) and obtain their amplitude and frequency profiles from satellite observations by Van Allen Probe B. We focus on rising-tone EMIC wave packets in the proton band, with a maximum amplitude of 1.2–1.6 nT. The resonant interaction of the considered wave packets with relativistic electrons 1.5–9 MeV is studied by numerical simulations. The precipitating fluxes are formed as a result of both linear and nonlinear interaction; for energies 2–5 MeV precipitating fluxes are close to the strong diffusion limit. The evolution of precipitating fluxes is influenced by generation of higher-frequency waves at the packet trailing edge near the equator and dissipation of lower-frequency waves in the text {He}^+ cyclotron resonance region at the leading edge. The wave packet amplitude modulation leads to a significant change of precipitated particles energy spectrum during short intervals of less than 1 minute. For short time intervals about 10–15 s, the approximation of each local amplitude maximum of the wave packet by a Gaussian amplitude profile and a linear frequency drift gives a satisfactory description of the resonant interaction.

Variable-Frequency Pulse Width Modulation Circuits for Resonant Wireless Power Transfer

In this paper, we develop a variable-frequency pulse width modulation (VFPWM) circuit for input control of 6.78-MHz resonant wireless power transfer (WPT) systems. The zero-voltage switching control relies on the adjustments of both duty cycle and switching frequency for the class-E amplifier used in the WPT as the power transmission unit. High-frequency pulse wave modulation integrated circuits exist, but some have insufficiently high frequency or unfavorable resolution for duty cycle tuning. The novelty of this work is the VFPWM circuit design that we put together. A voltage-controlled oscillator (VCO) of radio frequency and capacitor-coupled difference amplifiers are used to simultaneously perform the frequency and duty cycle tuning required in resonant WPT applications. Different circuit topologies of VFPWM are compared analytically and numerically. The most favorable circuit topology, enabling independent control of the frequency and duty cycle, is employed in experiments. The experimental results demonstrate the validity of the novel VFPWM, which is capable of operating at 6.78-MHz and has a duty ratio adjustable from 20% to 45% of the range applicable in the resonant WPT applications.

Heat wave magnitude over India under changing climate: Projections from CMIP5 and CMIP6 experiments

AbstractAtmospheric warming is expected to increase the magnitude and frequency of extreme climatic events namely floods, droughts, heat waves, and so on. Thus, the present study attempts to answer the following research questions; (i) What are the possible implications on future heat wave events due to the projected temperature? (ii) What are the expected changes in heat wave properties under different classifications of heat wave events under different climate scenarios? (iii) Whether the future projection of heat wave events differ significantly under CMIP5 and CMIP6 experiments over India? To answer the above questions, the present study uses the bias‐corrected future projections of maximum temperature (Tmax) from 26 GCMs that is, 13 from CMIP5 and 13 from CMIP6 experiments. In addition, two RCPs (4.5 and 8.5) under CMIP5 and four SSPs (126, 245, 370, and 585) under CMIP6 scenarios are considered. The Heat Wave Magnitude Index (HWMI) is used to characterize the heat wave over India. The essential findings from the study indicate that the Tmax anomaly is likely to increase (SSP126 &lt; SSP245 &lt; SSP370 &lt; SSP585 and RCP4.5 &lt; RCP8.5) in future causing more intense, high frequency, and long duration heat wave events over India. Presently unaffected large regions of southern, northeast, and western parts are expected to be severely affected by heat wave events. More intense heat wave events are likely to occur under RCP8.5 scenario as compared to SSP585 scenario. The percentage of affected area is projected to increase significantly from SSP126 to SSP585 under extreme and very extreme heat wave events. Under RCP8.5 scenario, the average duration of heat wave events for very extreme, and super extreme classifications is significantly higher than SSP585 scenario. Our findings suggest the paramount necessity of adaptation strategies to address the adverse consequences of foreseen heat wave events.

Substrate Integrated Waveguide Based Leaky Wave Antenna for High Frequency Applications and IoT

Background &amp; Objective: Internet of things devices managed by wireless networks so that higher data rates can be achieved. With increase in demand of usage of Internet microwave signals are capable for delivering the demand. However these high frequency waves needs a waveguide to propagate otherwise they get affected due to atmospheric attenuation and rain fade. A modified structure of rectangular waveguide is used named as Substrate Integrated Waveguide (SIW). Methods: In this paper, the work has been carried out taking SIW and Leaky Wave Antenna. The dielectric substrate was taken as carbon. Modeling of SIW Leaky wave Antenna is done by making C shaped Slots. Design steps for modeling LWA were orderly pursued also optimized with various equations followed by Finite Element Method based modeling. A range of frequency as input is taken from 7 GHz to 11 GHz to take the analysis of design modeled. Results: The result shows the electric field intensity and radiation pattern is directly proportional with frequency while the return loss is acceptable for applied frequency range. Conclusion: The proposed antenna can radiate in omni directional radiation pattern hence can be used to connect devices with IoT.

Impact of the buoy geometry on power absorption of a point absorber with a cylindrical buoy under motion constraint

In this work, we studied the impact of the buoy geometry on power absorption of a point absorber consisting of a cylindrical buoy. The displacement volume of the buoy is fixed while the radius to draft ratio is adopted to completely define the buoy geometry. A motion constraint that prevents the buoy from jumping out of or being submerged by the water is applied so that the absorbed power is restrained at a reasonable range. The maximum power absorption ability under reactive control has been attained, and the most appropriate buoy geometry has been identified. Passive control is also investigated to find the possible condition where it can be used as an alternative to active control. Results show that the maximum absorbed power approaches the Budal limit at low wave frequencies, and gradually departs from this limit with the increasing wave frequency. The most attractive radius to draft ratio, which shows more absorbed power and wider bandwidth, is around 1.0 and decreases with the increasing wave amplitude. At high wave frequencies, the absorbed power is identically affected by the motion constraint for both passive and reactive control, hence passive control may be an alternative to reactive control in this condition due to simpler implementation.

Investigation of critical delamination characteristics in composite plates combining cubic spline piezo-layerwise mechanics and time domain spectral finite elements

The scope of the present work is to elucidate the reverberations of propagating guided waves through delaminated regions confined in composite plate structures. As it is well known, delamination between consequent plies is the most common type of damage in composite structures. A mean of investigation of delamination cracks is through guided wave propagation. It has been observed that either type of guided waves (antisymmetric or symmetric) has different repercussions inside and outside the delaminated area. Inside this work is used a well-established numerical tool developed by the authors. By making good use of its reported numerical capabilities, the authors used the Hermitian Cubic Splined Layerwise mechanics to incorporate the delamination and the physical presence of piezoelectric actuators. The two mentioned aspects were then integrated into a time domain spectral finite element. The outcome was the development of a multinode explicit layerwise finite element, able of modelling the physical presence of active piezoelectric sensors, the existence of delamination cracks through the thickness and the excitation of each fundamental wave mode separately (A0 &S0). The calculated semi-diagonal mass matrix, due to the collocation of the nodes with the grid points of Gauss–Lobatto–Legendre quadrature, boosts the speed of numerical time integration, while the use of high order polynomials as shape functions, conduce to a vast reduction of the mesh size, enabling the thorough investigation and simulation of high frequency wave propagation.