Wave Technology Research Articles

Microcrack localization using nonlinear Lamb waves and cross-shaped sensor clusters

Using the nonlinear interaction effect between ultrasonic Lamb waves and microcracks to detect and locate microcracks has the advantages of fast detection speed and high sensitivity. In this paper, a method for microcrack localization based on cross-shaped sensor clusters in a plate is proposed by combining nonlinear ultrasonic Lamb wave technology and time difference of arrival (TDOA) technology. The antisymmetric (A0) mode at low frequency is chosen as the primary Lamb wave to simplify the complication of the dispersion and multi-mode properties of Lamb waves. The selected mode pair (A0-s0) weakens the influence of the cumulative growth effect of higher harmonics induced by the inherent material nonlinearity on the microcrack characteristic signals. Pulse inversion technique and cross correlation function are used to extract the TDOAs of the nonlinear characteristic signals including microcrack information. The cross-shaped sensor clusters approach proposed for the first time can achieve reliable and fast microcrack localization without being affected by the duration of the excitation signal, and a priori knowledge of group velocities of primary wave modes or generated harmonics. Experimental and numerical results validate the proposed method in isotropic and anisotropic plates. This paper provides a new idea for nonlinear ultrasonic nondestructive evaluation and structural health monitoring of microcracks in plates.

Performance analysis of congestion control protocols over 5G mmWave links

Millimeter wave technology is an important basic technology in 5G applications. It has higher bandwidth and lower delay. But high dynamics of the channel poses a major challenge to the design of congestion control protocols. Based on ns3, this paper conducts extensive experiments on the TCP congestion control protocols, and analyzes the transmission performance of different protocols over 5G millimeter wave links in detail. It will lay a foundation for further research on congestion control protocols suitable for 5G millimeter wave communications.

Analysis and Enhancement of Q-Factor in Thin-Film Bulk Acoustic Wave Resonator (FBAR)

In MEMS technology, MEMS Resonators has shown high potential applications in wireless communications such as Bluetooth and WIFI range. The Bulk Acoustic Wave (BAW) Resonator is a device which has more potential to meet the needs of today’s wireless technology. The Acoustic wave technology has attracted more attention and it’s an effective solution for achieving high-performance RF filters applications due to its low cost and small size of the device. The performance analysis of thin film bulk acoustic resonator (FBAR) by varying different piezoelectric material, piezoelectric material’s thickness and electrode materials is demonstrated in this paper. It is understood that the Quality factor is considerable higher for AlN as compared to ZnO and LiNbO3. Among all the materials, Aluminium electrode achieved maximum quality factor. As the thickness of piezo material decreases, it is found that the resonant frequency and Quality factor increases. Along with the Quality Factor, the top and bottom electrode thickness has a significant impact on the resonant frequency.

Nonreciprocity and Faraday Rotation at Time Interfaces.

Nonreciprocity is critically important in modern wave technologies, yet its general principles and practical implementations continue to raise intense research interest, in particular in the context of broken reciprocity based on spatiotemporal modulation. Abrupt changes in time of the electromagnetic properties of a material have also been shown to replace spatial boundaries, supporting highly unusual wave-matter interactions in so-called time metamaterials. Here, we introduce nonreciprocity for temporal boundaries, demonstrating Faraday polarization rotation in a magnetoplasma with material properties abruptly switched in time. Our findings open new opportunities for time metamaterials, yielding new avenues for nonreciprocity with broad applicability for wave engineering.

Effects of cerium doping on the microstructure, mechanical properties, thermal conductivity, and dielectric properties of ZrP2O7 ceramics

A two-step method, combined with cold isostatic pressing, was used to prepare CeO2-doped ZrP2O7 ceramics, and their microstructure, mechanical properties, thermal conductivities, and dielectric properties were determined. It was found that CeO2 doping could increase the Zr–P and P–O bond lengths, which in turn decreased the thermal conductivity of the ZrP2O7 matrix. Doping with 12 wt% CeO2 simultaneously reduced the sintering temperature and improved the mechanical properties of the ZrP2O7 ceramics, while retaining its low thermal conductivity and good dielectric properties. The maximum cold modulus of rupture of a sample at 1250 °C was 75.91 MPa, which met most conditions for use at room temperature. A COMSOL model was used to predict the thermal conductivity, based on the microstructure, with a relatively high degree of accuracy. The thermal conductivity of the CeO2-doped samples was lower than 1.083 W/(m·K). The dielectric constant was in the range of 5.93–6.52 at 20–40 GHz, and the dielectric loss was less than 4 × 10−3. The ZrP2O7-doped ceramics have potential for application in millimetre wave technology, satellite communication, and vehicle radar fields, because they can meet the high thermal insulation requirements for these applications.

2D materials-enabled optical modulators: From visible to terahertz spectral range

Two-dimensional (2D) materials with layered structures have a variety of exceptional electronic and optical attributes for potentially developing basic functions of light wave technology from light-emitting to -modulating and -sensing. Here, we present state-of-the-art 2D materials-enabled optical intensity modulators according to their operation spectral ranges, which are mainly determined by the optical bandgaps of the 2D materials. Leveraging rich electronic structures from different 2D materials and the governed unique light–matter interactions, the working mechanisms and device architectures for the enabled modulators at specific wavelength ranges are discussed. For instance, the tunable excitonic effect in monolayer transition metal dichalcogenides allows the modulation of visible light. Electro-absorptive and electro-refractive graphene modulators could be operated in the telecom-band relying on their linear dispersion of the massless Dirac fermions. The bendable electronic band edge of the narrow bandgap in few-layer black phosphorus promises the modulation of mid-infrared light via the quantum-confined Franz–Keldysh or Burstein–Moss shift effect. Electrically and magnetically tunable optical conductivity in graphene also supports the realizations of terahertz modulators. While these modulators were demonstrated as proof of concept devices, part of them have great potential for future realistic applications, as discussed with their wavelength coverage, modulation depth, insertion loss, dynamic response speed, etc. Specifically, benefiting from the well-developed technologies of photonic chips and optical fibers in telecom and datacom, the 2D materials-based modulators integrated on these photonic structures are expected to find applications in fiber and chip optical communications. The free-space mid-infrared and terahertz modulators based on 2D materials can expect application in chemical bond spectroscopy, free-space communications, and environment/health sensing.

Balanced-ternary-inspired reconfigurable vortex beams using cascaded metasurfaces

Abstract Electromagnetic vortex carries the orbital angular momentum, one of the most fundamental properties of waves. The order of such vortex can be unbounded in principle, thus facilitating high-capability wave technologies for optical communications, photonic integrated circuits and others. However, it remains a key challenge to generate the high-order vortex beams in a reconfigurable, broadband and cost-effective manner. Here, inspired by the balanced-ternary concept, we demonstrate the reconfigurable generation of order-controllable vortices via cascaded N-layer metasurfaces. We theoretically showed that 3 N − 1 ${3}^{N}-1$ different vortex modes can be generated by cascading N metasurfaces, each one serving as an individual vortex beam generator for the order of 3 k ${3}^{k}$ (k = 0,1,2 …, N − 1 $N-1$ ). As a proof-of-concept demonstration, a reconfigurable generation of 26 different vortex beams, with orders from 1 to 13 and from −1 to −13, is showcased in a broad millimeter-wave region by a cascade of 3 metasurfaces. Our method can be easily extended to vortex beam generator of arbitrary orders in a reconfigurable and easily implementable manner, paving a new avenue towards tremendous practical applications.

Terahertz biophotonics poised to provide an alternative to conventional medical diagnostics

Biomedical applications harness the effectiveness of promising wave technology.

Ability of matrix metalloproteinase-8 biosensor, IFMA, and ELISA immunoassays to differentiate between periodontal health, gingivitis, and periodontitis.

ObjectiveThe aim of this study was to determine the diagnostic utility of an MMP‐8 biosensor assay in differentiating periodontal health from gingivitis and periodontitis and compare it with an established time‐resolved immunofluorescence assay (IFMA) and enzyme‐linked immunosorbent assay (ELISA).BackgroundCurrently available antibody‐based assays display a wide variability in their ability to accurately measure matrix metalloproteinase‐8 (MMP‐8) levels in saliva.MethodsSalivary MMP‐8 levels were analyzed in 189 systemically healthy participants using an antibody‐based biosensor prototype that operates using a surface acoustic wave technology and compared with IFMA and ELISA antibody assays. Participants were categorized into 3 groups: periodontal health (59), gingivitis (63), and periodontitis (67). A sub‐population of participants (n = 20) with periodontitis received periodontal treatment and were monitored for 6 months.ResultsAll the assays demonstrated significantly higher salivary MMP‐8 concentrations in participants with periodontitis versus gingivitis, periodontitis versus health, and gingivitis versus health (all p < .05). The biosensor data demonstrated significant correlations with IFMA (r = .354, p < .001) and ELISA (r = .681, p < .001). Significant reductions in salivary MMP‐8 concentrations were detected by the biosensor (p = .030) and IFMA (p = .002) in participants with periodontitis 6 months after non‐surgical periodontal treatment. IFMA had the best sensitivity (89.2%) for detecting periodontitis and gingivitis versus health and 96.6% for detecting periodontitis versus health and gingivitis. The biosensor had an AUC value of 0.81 and diagnostic accuracy of 74.2% for differentiating periodontitis and gingivitis from health; an AUC value of 0.86 and diagnostic accuracy of 82.8% for periodontitis versus health and gingivitis.ConclusionsThe biosensor, IFMA, and ELISA assays differentiated between periodontal health, gingivitis, and periodontitis based on salivary MMP‐8 levels. Only the biosensor and, particularly, IFMA identified an effect of periodontal treatment in the participants with periodontitis. Our findings support the potential utility of salivary oral fluid aMMP‐8‐based point‐of‐care technology in the future of periodontal diagnostics.

Electric field sensing characteristics of ZnO/SiO2/Si surface acoustic wave devices

Existing microelectro mechanical systems (MEMSs) electric field sensors have movable parts and electronic components. The movable parts are susceptible to external vibration, and the electronic components distort the distribution of the measured electric field. Therefore, we proposed a novel MEMS electric field sensor based on surface acoustic wave (SAW) technology. The SAW electric field sensor is a delay line device with an interdigital transducer and a reflector. The substrate of the device is a ZnO/SiO2/Si multilayer structure. The ZnO piezoelectric layer is not only used as the propagation medium of SAW, but also used as the sensing film of the external electric field. Then, the external electric field could be detected by analyzing the change of the eigenfrequency of the SAW. The multilayer structure of the substrate was prepared by MEMS process. The interdigital transducer and the reflector are fabricated by the lift-off process. The SAW sensor is characterized at different external electric field strengths by a network analyzer. The sensitivity of the sensor was 0.23 kHz/(kV m−1) and the nonlinearity was 6.8%.

Selection of Higher Order Lamb Wave Mode for Assessment of Pipeline Corrosion

Hidden corrosion defects can lead to dangerous accidents such as leakage of toxic materials causing extreme environmental and economic consequences. Ultrasonic guided waves showed good potential detecting distributed corrosion in pipeline networks at sufficiently large distances. To simplify signal analysis, traditional guided wave methods use low frequencies where only fundamental modes exist; hence, the small, localized defects are usually barely detectable. Novel techniques frequently use higher order guided wave modes that propagate around the circumference of the pipe and are more sensitive to the localized changes in the wall thickness. However current high order mode guided wave technology commonly uses either non-dispersive shear modes or higher order mode cluster (HOMC) waves that are mostly sensitive to surface defects. As the number of application cases of high order modes to corrosion detection is still limited, a huge potential is available to seek for other modes that can offer improved resolution and sensitivity to localized corrosion type defects. The objective of this work was to investigate higher order modes for corrosion detection and to determine the most promising ones in sense of excitability, leakage losses, propagation distance, and potential simplicity in the analysis. The selection of the proper mode is discussed with the support of phase and group velocity dispersion curves, out of plane and in plane distributions over the thickness and on surface of the sample, and leakage losses due to water load. The analysis led to selection of symmetric S3 mode, while the excitation of it was demonstrated through finite element simulations, taking into account the size of phased array aperture and apodization law and considering two-sided mode generation. Finally, theoretical estimations were confirmed with experiments, demonstrating the ability to generate and receive selected mode. It was shown that S3 mode is a good candidate for corrosion screening around the circumference of the pipe, as it has sufficient propagation distance, can be generated with conventional ultrasonic (UT) phased arrays, has sufficiently high group velocity to be distinguished from co-existing modes, and is sensitive to the loss of wall thickness.

SWELT – technology of wave enhanced transportaion of viscous and ultra-viscous oil via pipelines

SWELT – technology of wave enhanced transportaion of viscous and ultra-viscous oil via pipelines

Combination of local sea winds/land breezes and nearshore wave energy resource: Case study at MaRELab (Naples, Italy)

Co-located offshore wind turbines and wave energy converters are of great interests as several studies established that combined power productions are more predictable, less-fluctuating and more continuous than when wind and wave technologies are working individually. However, what happens at nearshore locations with special focus to thermal winds, has never been fully explained. The objective of the present work is to evaluate the effects of local sea winds and land breeze circulations on the wave-wind resources, proposing a method to estimate the quality of the co-exploitation by means of different multivariate techniques. The research is illustrated through a case study at the novel Marine Renewable Energy Laboratory (MaRELab, Italy), analyzing a 42-year hindcast dataset. While the bulk of the power is provided by southwest waves, the wind mostly blows from two widespread sectors, west and east-northeast, having frequencies of occurrence almost the same (i. e. 50.2% vs 49.2%). Clusters referring meteo-climatic conditions that should be dominant to maximize the advantage to combine wind and wave sources, have a total occurrence of 54.1% in sea breeze time series and 72.8% in land breeze dataset. In these situations, the combined production would be more available and less variable, leading the combined nearshore wave-wind farm more interesting.

Preoperative apnea-hypopnea index predicts increased postoperative intrathoracic pressure during sleep in patients who underwent endoscopic nasal surgery

ObjectiveRespiratory condition could worsen during sleep in patients with nasal packing following endoscopic nasal and sinus surgery (ESS) under general anesthesia. Recently, a noninvasive intrathoracic pressure estimation sensor was developed that uses photoplethysmographic pulse wave technology. The purpose of this study was to noninvasively evaluate the effect of bilateral nasal packing on respiration during sleep, using a photoplethysmographic pulse wave sensor in perioperative patients who underwent ESS under general anesthesia. MethodsIn this observational cross-sectional case-control study, estimated intrathoracic pressure and SpO2 were noninvasively measured during sleep with a wristband-type photoplethysmographic pulse wave sensor and a pulse oximeter in 43 patients with chronic sinusitis, nasal allergy, or septal deviation who underwent bilateral ESS under general anesthesia. Measurements were taken preoperatively, at postoperative day 1 (POD1) with bilateral nasal packing in place, and at POD5 after the nasal packing was removed. Based on the preoperative obstructive apnea-hypopnea index (AHI) score determined by overnight polysomnography, patients were classified into those with moderate to severe obstructive sleep apnea (OSA) (AHI ≥ 15/h) and those with mild or non-OSA (AHI ≤ 15/h). ResultsSignificant changes were noted in estimated intrathoracic pressure, but not in SpO2 nadir, between time points. Estimated intrathoracic pressure decreased the most at POD1 with bilateral nasal packing in place in patients with OSA after ESS. Multivariate stepwise regression revealed the relative incidence of increased estimated intrathoracic pressure on POD1 was independently predicted by preoperative AHI, but not by age, body mass index, total nasal resistance, or preoperative SpO2 nadir. ConclusionUse of the photoplethysmographic pulse wave sensor to noninvasively measure intrathoracic pressure detected changes in perioperative respiratory effort that pulse oximetry did not. Attention should be paid to the use of postoperative bilateral nasal packing in patients with moderate to severe OSA who undergo ESS under general anesthesia. Our results support the concept of using less, short-term, or no nasal packing after ESS.

Exfoliation of metal-organic framework nanosheets using surface acoustic waves

Two-dimensional (2D) metal–organic framework (MOF) nanosheets have recently received extensive attention due to their ultra-thin thickness, large specific surface area, chemical and functional designability. In this study, an unconventional method using surface acoustic wave (SAW) technology is proposed to exfoliate large quantities and uniform layers of 2D MOF-Zn2(bim)4 nanosheets in a microfluidic system. We successfully demonstrated that the thickness of 2D MOF is effectively and accurately controlled by optimizing the SAW parameters. The mechanisms for the efficient exfoliation of 2D MOF nanosheets is attributed to both the electric and acoustic fields generated by the SAWs in the liquid. The electric field ionizes the methanol to produce H+ ions, which intercalate Zn2(bim)4 sheets and weaken the interlayer bonding, and the strong shear force generated by SAWs separates the MOF sheets. A yield of 66% for monolayer MOFs with a maximum size of 3.5 μm is achieved under the combined effect of electric and acoustic fields. This fast, low-energy exfoliation platform has the potential to provide a simple and scalable microfluidic exfoliation method for production of large-area and quantities of 2D MOFs.

Hierarchically assembled carbon microtube@SiC nanowire/Ni nanoparticle aerogel for highly efficient electromagnetic wave absorption and multifunction

Efficient electromagnetic wave (EMW) absorption is of great significance to enjoy the service of electromagnetic wave technologies safely. Compared with powder-based EMW absorption materials, aerogels with 3D continous and highly porous network structure have demonstrated to have coordinate impedance matching and attenuation characteristics. Further introducing multicomponent to fabricate aerogels with synergetic conductive/dielectric/magnetic properties are expected to achieve efficient EMW absorption property but still remain challenging. Herein, we report the preparation and properties of a carbon microtube (as conductive network), SiC nanowires (as dielectric network), and Ni nanoparticles (as magnetic network) assembled aerogel with hierarchically network structure that is assembled by. The carbon microtube@SiC nanowire/Ni nanoparticle aerogel displays low density (∼5 mg/cm3), broad absorption bandwidth (10.1 GHz) and strong reflection loss (−51.3 dB). The unique synergistic magnetic/dielectric/conductive coupling attenuation mechanisms contribute to the good EMW absorption performance. This study opens a pathway for using 3D hierarchically network structure with conductive/dielectric/magnetic components to achieve excellent EMW absorption for promising applications.

Photonic Label-Free Biosensors for Fast and Multiplex Detection of Swine Viral Diseases.

In this paper we present the development of photonic integrated circuit (PIC) biosensors for the label-free detection of six emerging and endemic swine viruses, namely: African Swine Fever Virus (ASFV), Classical Swine Fever Virus (CSFV), Porcine Reproductive and Respiratory Syndrome Virus (PPRSV), Porcine Parvovirus (PPV), Porcine Circovirus 2 (PCV2), and Swine Influenza Virus A (SIV). The optical biosensors are based on evanescent wave technology and, in particular, on Resonant Rings (RRs) fabricated in silicon nitride. The novel biosensors were packaged in an integrated sensing cartridge that included a microfluidic channel for buffer/sample delivery and an optical fiber array for the optical operation of the PICs. Antibodies were used as molecular recognition elements (MREs) and were selected based on western blotting and ELISA experiments to ensure the high sensitivity and specificity of the novel sensors. MREs were immobilized on RR surfaces to capture viral antigens. Antibody–antigen interactions were transduced via the RRs to a measurable resonant shift. Cell culture supernatants for all of the targeted viruses were used to validate the biosensors. Resonant shift responses were dose-dependent. The results were obtained within the framework of the SWINOSTICS project, contributing to cover the need of the novel diagnostic tools to tackle swine viral diseases.

On the beamforming design of millimeter wave UAV networks: Power vs. capacity trade-offs

The millimeter wave (mmWave) technology enables unmanned aerial vehicles (UAVs) to offer broadband high-speed wireless connectivity in 5G/6G networks. However, the limited footprint of a single UAV implementing analog beamforming (ABF) requires multiple aerial stations to operate in swarms to provide ubiquitous network coverage, thereby posing serious constraints in terms of battery power consumption. A possible remedy is to investigate the concept of hybrid beamforming (HBF) transceivers, which use a combination of analog beamformers to achieve higher flexibility in the beamforming design. This approach permits multiple ground users to be served simultaneously by the same UAV, despite involving higher energy consumption than its ABF counterpart. This paper presents a tractable stochastic analysis to characterize the ergodic capacity and power consumption of UAV mmWave networks, focusing on the trade-off between ABF and HBF architectures. A multi-beam coverage model is derived as a function of several UAV-specific parameters, including the number of UAVs, the deployment altitude, the antenna configuration, and the beamforming design. Our results show that, while ABF achieves better ergodic capacity at high altitudes, an HBF configuration with multiple beams, despite the use of more individually power-hungry RF blocks, always consumes less total power with limited capacity degradation.

Characterization of Thickness Loss in a Storage Tank Plate with Piezoelectric Wafer Active Sensors

In terms of the structural health inspection of storage tanks by ultrasonic guided wave technology, many scholars are currently focusing on the tanks’ floor and walls, while little research has been conducted on storage tank roofs. However, the roof of a storage tank is prone to corrosion because of its complex structure and unique working environment. For this purpose, this paper proposes a reflection/transmission signal amplitude ratio (RTAR) coefficient method for corrosion depth assessment. We studied the relationship between the RTAR coefficient, the corrosion depth, and the guided wave frequency to establish a depth assessment model. More importantly, unlike the traditional reflection coefficient method, the characteristics of guided wave signals, including the propagation and attenuation, are introduced in this model for accurate assessment. To eliminate the interference of residual vibration and improve the detection accuracy of defects, we built a corrosion detection system by using piezoelectric sensors and carried out field tests to verify the performance of the proposed method. We demonstrate that corrosion defects with a minimum depth of 0.2 mm can be quantitatively evaluated.

Enhancing energy efficiency for cellular-assisted vehicular networks by online learning-based mmWave beam selection

Millimeter Wave (mmWave) technology has been regarded as a feasible approach for future vehicular communications. Nevertheless, high path loss and penetration loss raise severe questions on mmWave communications. These problems can be mitigated by directional communication, which is not easy to achieve in highly dynamic vehicular communications. The existing works addressed the beam alignment problem by designing online learning-based mmWave beam selection schemes, which can be well adapted to high dynamic vehicular scenarios. However, this kind of work focuses on network throughput rather than network energy efficiency, which ignores the consideration of energy consumption. Therefore, we propose an Energy efficiency-based FML (EFML) scheme to compensate for this shortfall. In EFML, the energy consumption is reduced as far as possible under the premise of meeting the basic data rate requirements of vehicle users, and the users requesting the same content in close proximity can be organized into the same receiving group to share the same mmWave beam. The simulation results demonstrate that, compare with the comparison method with best energy efficiency, the proposed EFML improves energy efficiency by 17–41% in different scenarios.