Wave Applications Research Articles

The effect of the barrier thickness on DC and RF performances of AlGaN/GaN HEMTs on silicon

In this study, the effect of barrier thickness on the DC and RF performances of AlGaN/GaN high-electron mobility transistors (HEMTs) on silicon for millimeter wave applications is experimentally investigated. GaN HEMT devices with different barrier thicknesses were fabricated and characterized. While the device with the thinnest barrier exhibited the highest extrinsic transconductance (gm) resulting from the shortest gate-to-channel distance, such configuration suffered from the lowest unit current-gain cut-off frequency (fT) due to the increase of the total gate capacitance. Moreover, degradation in the output power was observed for devices with thinner barriers. Such degradation was related to the severe knee walkout as evidenced from drain-lag characterization.

Ultrashort wave alleviates oxygen-glucose deprivation/reoxygenation injury via up-regulation of SPCA1 expression in N2a cells.

Application of ultrashort wave (USW) to rats with cerebral ischemia and reperfusion injury could inhibit the decrease of expression of secretory pathway Ca2+-ATPase 1 (SPCA1), an important participant in Golgi stress, reduce the damage of Golgi apparatus and the apoptosis of neuronal cells, thereby alleviating cerebral ischemia-reperfusion injury. This study aims to investigate the effect of USW on oxygen-glucose deprivation/reperfusion (OGD/R) injury and the expression of SPCA1 at the cellular level. N2a cells were randomly divided into a control (Con) group, an OGD/R group, and an USW group. The cells in the Con group were cultured without exposure to OGD. The cells in the OGD/R group were treated with OGD/R. The cells in the USW group were treated with USW after OGD/R. Cell morphology was observed under the inverted phase-contrast optical microscope, cell activity was detected by cell counting kit-8 (CCK-8), apoptosis was detected by flow cytometry, and SPCA1 expression was detected by Western blotting. Most of the cells in the Con group showed spindle shape with a clear outline and good adhesion. In the OGD/R group, cells were wrinkled, with blurred outline, poor adhesion, and lots of suspended dead cells appeared; compared with the OGD/R group, the cell morphology and adherence were improved, with clearer outlines and fewer dead cells in the USW group. Compared with the Con group, the OGD/R group showed decreased cell activity, increased apoptotic rate, and down-regulating SPCA1 expression with significant differences (all P<0.001); compared with the OGD/R group, the USW group showed increased cell activity, decreased apoptotic rate, and up-regulating SPCA1 expression with significant differences (P<0.01 or P<0.001). USW alleviates the injury of cellular OGD/R, and its protective effect may be related to its up-regulation of SPCA1 expression.

Mutual Coupling Reduction Using 8x8 MIMO Antenna for MM Wave Applications

A 8x8 multiple input multiple output antenna is developed for the applications of MM wave. this proposed model has 8 ports on the single structure of antenna system. The proposed design gives a triple bands k-band (14.6 at-22dB), ku-band (19.6 at -28dB) and ka-band (27.6 at -27dB) which this ka-band wii be act as mm wave band for the applications of MM wave. The proposed antenna having the dimensions of 64mm x 32mm x 1.6 mm having thickness 1.6mm and the Fr4 substrate has been used for designing. The proposed antenna is designed, measured and tested

A compact quad‐band circular cavity backed substrate integrated waveguide antenna for millimeter wave applications

AbstractIn this letter, a compact circular cavity‐backed, circularly polarized substrate integrated waveguide (SIW) multiband antenna is proposed. In the outer circular cavity, an array of two periodic metal slots, tilted at an angle, resonate at 25.32, 26.44, and 28.83 GHz, and the inner circular cavity's periodic slots radiate at 28.01 GHz. Two concentric SIW cavities are structured in such a distinct manner that no loss due to leakage takes place thus, achieving a maximum isolation of −43.8 dB at 28.83 GHz. The miniaturized antenna has dimensions of 2.2λo × 2.2λo × 0.1λo where λo is the operating wavelength. It achieves a maximum gain of 9.1 dBi at 26.44 GHz, and VSWR &lt; 2 is achieved at all frequency bands. The antenna is circularly polarized at 26.44 and 28.01 GHz as well. The design results are plotted in the Ansys high‐frequency structure simulator version EM19.2 tool. The proposed antenna is fabricated and tested using an Anritsu Vector Network Analyzer version v4.0 with an anechoic chamber setup.

The Detection Scheme and Applications of Gravitational Waves

In recent years, gravitational waves have already attracted attention as the gateway to a new era in physics since they were first directly detected and observed. This paper summarizes the development of gravitational waves from the first proposed to the present and the main observation methods, as well as the main uses and significance of the detection of them. To be specific, in this paper, the most popular laser interferometer technique for the detection based on Michelson interferometer is discussed, and several purposes of the detection of gravitational waves are given. The detection signatures are available to adopt to the analysis of the collision of binary star systems. Gravitational radiation or primordial gravitational radiation can carry more information about black holes or the Big Bang than electromagnetic waves. The gravitational wave astronomy created by gravitational waves has opened a new horizon for astronomers to explore the universe, and the detection of them is an integral part of the future development of physics and astronomy. To sum up, these results shed light on guiding further exploration of gravitational waves detection as well as applications of them.

Possibilities of Applying Acoustic Method and Electrical Engineering for Acoustic Wave Flame Extinguishing based on the Latest European Research: Benefits, Development Prospects and Limitations

The article analyzes the possibilities of using acoustic technology for extinguishing flames from various sources. Advantages as well as disadvantages of acoustic technology are presented. The structure of this article shows different approaches, methods, as well as application of acoustic waves for fire extinguishing. In the light of the latest research, the state of the art is presented (literature review) and the prospects for the development of technology using low cost intelligent sensors are shown. The second aspect of fire management is fire detection. In practice, the use of a subdiscipline of machine learning, in which the learning process is carried out in an unsupervised way – deep learning, is a modern alternative to flame detection in relation to classical temperature or smoke sensors. In this case, it is possible to benefit from the advantages of technologies described in this article by combining the use of these techniques.

Acoustofluidics: A Versatile Tool for Micro/Nano Separation at the Cellular, Subcellular, and Biomolecular Levels

AbstractSeparation of micro/nanoparticles, such as cellular, subcellular and biomolecular, has attracted increasing attention because of their remarkable potential applications in various fields, including chemistry, physics, medicine, etc. Among different micro/nanoparticle separation methods, acoustofluidics, which combines acoustics and microfluidics, has drawn the interest of researchers due to its biocompatibility, high efficiency and free labeling. In this review, the basic constitutions, mechanisms, and materials of acoustofluidics are described. Subsequently, sorts of delicately designed acoustofluidic devices, including diverse bulk acoustic wave (BAW) microfluidics and surface acoustic wave (SAW) microfluidics, are discussed, covering principles, advantages, limitations and applications in separation. Besides the introduction of advances of micro/nanoparticle separation in the BAW microfluidics, the SAW microfluidics are elaborated in detail with a focus on various configurations of interdigital transducers (IDTs), comprising straight IDT, slanted‐finger IDT, chirped IDT and focused IDT. Microfluidic systems of the acoustofluidics involve the forms of straight channels, serpentine channels, and droplets. Additionally, besides simply structured acoustofluidics, acoustofluidics integrated with other structures are also mentioned. Finally, the prospects and limitations of acoustofluidics in micro/nanoparticle separation are also discussed. The acoustofluidics reviewed here is envisioned as a versatile tool for micro/nanoparticle separation at the cellular, sub‐cellular, and biomolecular levels.

Fabrication of SiCN(Fe)/Al2O3 wave-absorbing ceramics with enhanced electromagnetic performance

The SiCN(Fe)/Al2O3 composite ceramics containing C, α-Fe, and Al4C3 were designed by impregnating and pyrolysis polysilazane adding iron(III) acetylacetonate (FeAA) to porous alumina matrix. This composite material can absorb over 90% of electromagnetic wave in the range of 9–13 GHz with a thickness of 3.5 mm. The minimum reflectivity was −18 dB at 12 GHz with the addition of 3 wt% FeAA, demonstrating over 99% electromagnetic wave absorption at this frequency. Additionally, a circular metamaterial structure was designed and its wave absorption performance was simulated. The reflection coefficient of the sample in the range of 4.7–18 GHz is above 90%, and the electromagnetic absorption rate at 7.152 GHz is nearly 100%. This paper presents a novel porous alumina ceramic loaded with SiCN(Fe) composite material with excellent wave absorption performance. It also analyzes the loss and absorption mechanisms of electromagnetic wave at different frequencies, providing an experimental and theoretical basis for the practical application of porous ceramic matrix composite wave absorbing materials.

Millimetre wave antenna for biomedical applications-a review

Terahertz represents the portion of electromagnetic wave between the microwave and IR region. Recent research has been focused on the application of Terahertz waves in biomedical applications such as cancer detection. The current diagnostic methods in cancer treatment involve imaging to MRI and biopsy. Due to the low photon energy that terahertz possess, there are no health threats caused in contrast to traditional methods. Cancer cells can be detected by monitoring the blood supply to the affected tissues and water level in the local tissues. This can be diagnosed using Terahertz imaging. THz radiation can be generated and detected using various commercialized systems. On analysis of various literatures, it is observed that Meta material antennas will be the suitable candidate to enhance the existing terahertz spectroscopy techniques since it has better focusing capabilities. This paper reviews the various implementation techniques of an antenna in THz range. The design and properties of the antenna are also investigated.

Channel Tracking for RIS-Aided mmWave Communications Under High Mobility Scenarios

The emerging reconfigurable intelligent surface (RIS) technology is promising for applications in the millimeter wave (mmWave) communication systems to effectively compensate for propagation loss or tackle the blockage issue. Considering the high mobility of users in realistic scenarios, it is essential to adjust the phase shifts in real time to align the beam towards the mobile users, which requires to frequently estimate the channel state information. Hence, it is imperative to design efficient channel tracking schemes to avoid the complex channel estimation procedure. In this paper, we develop a novel channel tracking scheme with two advantages over conventional schemes. First, our tracking scheme is based on the cascaded angles at the RIS instead of the accurate angle values, which is more practical. Second, it can be employed under a more general setting where the noise can be non-Gaussian. Simulation results show the high tracking accuracy of our proposed scheme, and validate the superiority to the existing EKF-based tracking scheme.

Terahertz Schottky Barrier Diodes Based on Aligned Carbon Nanotube Arrays

Carbon nanotubes (CNTs) with superior electrical characteristics are among the most promising candidate materials for constructing millimeter wave and terahertz wave electronic devices. However, the reported Schottky barrier diodes (SBDs) based on CNTs usually exhibited high series resistance and severe mismatch to lower impedance external circuits, which limits the devices for high frequency applications. In this work, CNT SBDs of lateral structure with a rectify current density of -0.78 mA/μm and a short circuit current responsivity of 6.8 A/W are demonstrated based on aligned carbon nanotube arrays (A-CNTs) with high-density and high-semiconducting purity on a quartz substrate. The A-CNT SBD with a width of 10 μm and an L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ch</sub> of 50 nm under zero bias exhibits an ultra-low intrinsic capacitance of 2.5 fF and an intrinsic cutoff frequency <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> of up to 840 GHz, which suggests that CNT-based SBDs are promising for millimeter wave and terahertz wave applications.

A Comprehensive Review of the Effects of Extracorporeal Shock Wave Therapy on Stroke Patients: Balance, Pain, Spasticity.

Stroke remains a leading cause of disability worldwide, with survivors often experiencing impairments in balance, pain, spasticity, and control that limit their ability to perform daily living activities. Extracorporeal shock wave therapy (ESWT) has emerged as a potential treatment modality to improve these outcomes in stroke patients. This review aims to provide a comprehensive examination of the effects of ESWT on stroke patients, focusing on the theoretical background, balance, pain reduction, muscle spasticity and control, and upper and lower extremities. This study reviewed the use of ESWT in treating balance, pain, and spasticity in stroke patients, focusing on articles published in PubMed between January 2003 and January 2023. Systematic reviews related to stroke were used to provide an overview of stroke, and a total of 33 articles related to balance, pain, and spasticity were selected. ESWT has several shock wave generation methods and application methods, and it has been shown to have positive therapeutic effects on various aspects of rehabilitation for stroke patients, such as improving balance, reducing pain, decreasing muscle spasticity and increasing control, and enhancing functional activities of the upper and lower extremities. The efficacy of ESWT may vary depending on the patient's condition, application method, and treatment area. Therefore, it is important to apply ESWT according to the individual characteristics of each patient in clinical practice to maximize its potential benefits.

One-way collinear wave mixing in solids with cubic nonlinearity based on Murnaghan’s potential

Ultrasonic wave mixing is a powerful new nondestructive evaluation technique for accessing hidden subtle imperfections in materials. First, this paper derives the resonance conditions of one-way collinear mixing with cubic nonlinearity. The results show that the mixing of two collinear longitudinal waves can generate a resonant longitudinal wave, the mixing of two transverse waves can generate a resonant transverse wave, and the resonant longitudinal wave and transverse wave can be generated, respectively, when two primary longitudinal and transverse waves satisfy different resonance conditions. This is different from the case with quadratic nonlinearity. Furthermore, we obtain the analytical solutions of resonant waves generated by the mixing of harmonic longitudinal and transverse pulses. The waveforms are approximate hexagonal shapes according to the analysis of the envelopes. Finally, the numerical simulation results conducted on material aluminum prove the correctness of the analytical solution. Compared with quadratic nonlinearity, the resonant wave is more sensitive to material constants for some materials when considering one-way collinear mixing of primary longitudinal and transverse pulses based on cubic nonlinearity. The results provide new opportunities on mixing wave applications in nondestructive evaluation.

Construction of core-shell structured SiO2@MoS2 nanospheres for broadband electromagnetic wave absorption

Herein, core-shell structured SiO2@MoS2 nanospheres were made via hydrothermal method, with MoS2 nanosheets growing irregularly on the outside surface of SiO2. The microstructure and EM wave absorption properties of the prepared SiO2@MoS2 nanospheres were explored. SiO2@MoS2 achieved a minimum reflection loss (RLmin) value of − 49.35 dB with a thickness of 2.8 mm, and an effective absorption bandwidth (EAB) of 7.44 GHz. The remarkable EM wave absorption performance of SiO2@MoS2 nanospheres could be attributed to interfacial polarization originating from the designed core-shell structure and the multiple reflections on MoS2 ultrathin nanosheets. Meanwhile, impedance matching was regulated effectively by combination of SiO2 and MoS2, which provided a synergistic effect and enhanced EM wave dissipation. Therefore, the core-shell structured SiO2@MoS2 could be a great potential candidate material in the application of high-performance EM wave absorbing area.

Design and Fabrication of Waveguide Slot Antenna Using 3D Printing for 5G Application

This research constructs a 26 GHz waveguide slot antenna with decent gain. The application of millimeter-wave requires high bandwidth and gain to increase the traffic and users for millimeter-wave and 5G technology. The application of millimeter waves requires a high gain and bandwidth to achieve the requirements of traffic and users increasing for 5G technology and existing millimeter-wave. High-gain and power handling are provided by waveguide slot antennas. Three waveguide structures which are two waveguide antennae and a waveguide horn have been simulated by using CST and fabricated by a 3D printer. The tilt technique has been used with a waveguide to increase the bandwidth and gain of an antenna. A waveguide with broad wall tilt slots has one diction beam while a waveguide with broad and narrow wall tilt slots has two direction beams, each length of the wall enough to distribute six symmetric tilt slots. The gain of 14.3 dB and 1.9 GHz bandwidth are recorded for an antenna with broad wall tilt slots with one beam. While the waveguide with broad and narrow wall tilt slots achieved a gain of 13.9dB and a bandwidth of 1.9 GHz. The proposed antenna is a decent candidate for use with millimeter waves.

Manipulation of Impedance Matching toward 3D-Printed Lightweight and Stiff MXene-Based Aerogels for Consecutive Multiband Tunable Electromagnetic Wave Absorption

Highly conductive MXene material exhibits outstanding dissipation capability of electromagnetic (EM) waves. However, the interfacial impedance mismatch due to high reflectivity restricts the application of MXene-based EM wave absorbing materials. Herein, a direct ink writing (DIW) 3D printing strategy to construct lightweight and stiff MXene/graphene oxide aerogels (SMGAs) with controllable fret architecture is demonstrated, exhibiting tunable EM wave absorption properties by manipulating impedance matching. Noteworthy, the maximum reflection loss variation value (ΔRL) of SMGAs is -61.2 dB by accurately modulating the width of the fret architecture. The effective absorption region (fE) of SMGAs exhibits consecutive multiband tunability, and the broadest tunable fE (Δf) is 14.05 GHz, which could be continuously tuned in the whole C- (4-8 GHz), X- (8-12 GHz), and Ku-bands (12-18 GHz). Importantly, the hierarchical structures and the orderly stacking of filaments endow lightweight SMGAs (0.024 g cm-3) with a surprising compression resistance, which can withstand 36 000 times its own weight without obvious deformation. Finite element analysis (FEA) further indicates that the hierarchical structure facilitates stress dispersion. The strategy developed here provides a method for fabricating tunable MXene-based EM wave absorbers that are lightweight and stiff.

High stability with low polarization and confinement loss based new structure of photonic crystal fiber waveguide profile

Abstract Nowadays ethanol is broadly used chemical item in various industrial purpose. So, detection of this organic chemical has become very important task in industrial basis. In this paper, a hexagonal core PCF has constructed in which silica is used as base material. A finite element method is applied and mesh analysis has been done for investigating boundary conditions of proposed PCF sensor. After simulation, 59.48 % sensitivity and an ignorable loss of confinement which is 8·956020 × 10−13 cm−1 at 2.5 THz frequency has been gained. Focusing on easy construction of fiber, conventional fabrication procedures are attainable. Having satisfactory waveguiding attributes, the proposed sensor can be applicable effectively for sensing ethanol and also polarization-based applications of terahertz waves.

Flexible horizontal piezoelectric energy generator for sea wave applications

Energy harvesting from the environment becomes a valuable technology, especially for sea wave applications, in which it usually ends up wasted despite its potential to be harvested. Due to its wide availability and high energy density, piezoelectric energy harvesting (PEH) is becoming popular for flexible energy harvesting. This paper presents a flexible horizontal piezoelectric (FHP) energy harvester to harvest energy from the surface of sea wave. The harvester is made of bimorph piezoelectric devices; they are utilised to amplify and convert the collected mechanical vibrations into electrical power. A finite element model is established from ANSYS simulations to solve the iteration method by generating resonance frequency (fr). Then, Taguchi method, SN ratio and the ANOVA approach were used by considering the input variable of fr to estimate the optimum performance through control factors; number of blade, length and thickness. From the performance test result, it is proven that the higher numbers of blade including length, and minimum numbers of thickness significantly improve the significant level, α = 0.05% of ANOVA. Three prototypes are developed with approximate body dimensions through the resonance frequency perform and generate a 160.3 Hz on blade dimensions of 10 × 300 × 0.2 mm, with a piezoelectric (PZT) on its surface. This particular study shows that the potential of output power is generated from sea wave surface through a significant relationship between length, thickness, and blade design. This research develops a novelty for energy harvesting from flexible piezoelectric generator on sea wave application that could be easily install on offshore platform.

A Ka-Band SLM Printed Filtering Divider-Fed Magnetoelectric Dipole Antenna Array Using Embedded Gap Waveguide

In this letter, a filtering divider-fed magnetoelectric (ME) dipole antenna array using embedded gap waveguide (GW) is investigated. The antenna array is fed by a 5th-order all-resonator 1-to-4 filtering power divider. 4 × 4 ME dipole antennas are excited with the same amplitude and in phase. The selective laser melting (SLM) and embedded GW technology are employed to reduce fabrication complexity. The measured results show that the proposed antenna array achieves an impedance bandwidth of 27.3 - 30.8 GHz ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$|S_{11}| &lt; -10$</tex-math></inline-formula> dB). The gain of the antenna array varies from 19.5 to 20.6 dBi with stable radiation patterns. The advantages of the proper filtering function together with high gain, high efficiency, large power capacity and compact size in the proposed design ensure a promising future in its applications for millimeter wave (mm-Wave) radars and communication systems.

Direct Simulation of the Surface Manifestation of Internal Gravity Waves with a Wave–Current Interaction Model

Abstract Internal solitary waves in the ocean are characterized by the surface roughness signature of smooth and rough bands that are observable in synthetic aperture radar satellite imagery, which is caused by the interaction between surface gravity waves and internal wave–induced surface currents. In this work, we study the surface signature of an internal wave packet in deep water over a large range of spatial scales using an improved wave–current interaction model that supports a moving surface current corresponding to a propagating internal gravity wave. After validating the model by comparison to previously published numerical results by Hao and Shen, we investigate a realistic case based on a recent comprehensive field campaign conducted by Lenain and Pizzo. Distinct surface manifestation caused by internal waves can be directly observed from the surface waves and the associated surface wave steepness. Consistent with observations, the surface is relatively rough where the internal wave–induced surface current is convergent (∂U/∂x &lt; 0), while it is relatively smooth where the surface current is divergent (∂U/∂x &gt; 0). The spatial modulation of the surface wave spectrum is rapid as a function of along-propagation distance, showing a remarkable redistribution of energy under the influence of the propagating internal wave packet. The directional wavenumber spectra computed in the smooth and rough regions show that the directional properties of the surface wave spectra are also rapidly modulated through strong wave–current interactions. Good agreement is found between the model results and the field observations, demonstrating the robustness of the present model in studying the impact of internal waves on surface gravity waves. Significance Statement The purpose of this study is to better understand the physical processes leading to the bands of rough and smooth surface waves arising from internal gravity waves. The surface manifestation of internal gravity waves allows them to be measured remotely via surface imagery, which can provide insight into their nonlinear behavior and sources and fate and which can ultimately inform the local stratification for assimilation into larger-scale models. Our results highlight the application of wave–current interaction models to the study of the interaction of surface waves with internal gravity waves and indicate strong modulation of the surface wave spectra over relatively short time scales despite the long time scales associated with the internal wave propagation.