Resonant Research Articles

A Novel Microwave Dielectric Ceramic LiSrVO4 for LTCC

Abstract LiSrVO4 (LSV) ceramics were prepared using the solid-state synthesis method, and their phase structure, morphology, sintering characteristics, and microwave dielectric properties were investigated. The LSV ceramics could be densified by sintering at 875–925 °C for 4 hours. XRD indicated that LSV ceramics sintered at 875–925 °C for 4 hours were singlephase ceramics with a monoclinic structure. With the increase in sintering temperature, the dielectric constant and quality factor of LSV ceramics first increased and then decreased, while the temperature coefficient of the resonant frequency gradually decreased. LSV ceramics sintered at 900 °C for 4 hours exhibited a εr of 10.92, a Q×f value of 21115 GHz, and a τf of -4 ppm/°C. LSV ceramics demonstrated good chemical compatibility with silver, showing promising potential in the field of Low-Temperature Co-fired Ceramics.

Design of Modified UWB Microstrip Antenna for UHF Partial Discharge Sensor

The development of printable ultrahigh-frequency (UHF) antennas as partial discharge (PD) sensors for high-voltage equipment has been extensively studied. However, achieving ultrawideband (UWB) UHF PD sensors frequently requires larger sizes, unsuitable for certain applications requiring compact sensors for dielectric windows in HV equipment. This research objective is to obtain PD sensors with a wider bandwidth (0.3–3 GHz) and a compact size fitting a less-than-100mm-length gas-insulated switchgear (GIS) dielectric window. A circular patch microstrip antenna (CPMA) was chosen for its small size and potential for UWB performance. This paper discusses the design modification of the CPMA to obtain a wider bandwidth for PD detection in GIS. Simulations and lab-scale experimental verifications were conducted to evaluate the optimized sensor. The modified sensor, with a size of 60 × 73 mm², achieved a bandwidth of 3.08–3.14 GHz, a reflection coefficient of -44 dB, and several resonant frequencies of 0.3–2.3 GHz. This is a seven-time wider bandwidth compared to earlier bowtie antennas while keeping a dimension of less than 100 mm². These properties allow for efficient PD detection in GIS and other insulating media. Experimental results indicate the sensor's capacity to reliably detect and analyze PD signals while responding appropriately to variations in voltage. Doi: 10.28991/ESJ-2024-08-05-03 Full Text: PDF

Linear-acoustic effects of asymmetrical undercutting of toneholes of woodwind instruments.

The influence of the presence and magnitude of asymmetrical undercutting of the toneholes of woodwind instruments on the change in their effective radius and the corresponding shift of the eigenfrequencies of the air duct is considered. Within the framework of the electro-acoustic analogy, a tonehole with an asymmetrical undercutting along the axis of the main bore is presented as a cascade connection of two holes with different radii (undercutting and not undercutting parts of the hole), and with a sideway undercutting-in the form of a parallel connection. Formulas for numerical calculations are given that make it possible to determine the effective radius of such holes for the open state in the low-frequency approximation. Based on the obtained dependencies, using the transmission-matrix method, the eigenfrequencies of an air duct with one hole were calculated and compared with the results of computer modeling in the COMSOL Multiphysics 5.6 program. It is shown that increasing the degree and angle of undercutting leads to an increase in the effective radius, a displacement of the "center of gravity" of the sound hole along the main bore axis, and has effect on the shift of resonant frequency.

Investigation of dual-mode cloaked cylindrical slot antennas with a pulsed radar signal processing

In this paper, the cloaked slot antennas (CSAs) in a circular conducting cylinder have been proposed, numerically studied, and fundamentally characterized with respect to the pulsed radar aspects. The two cylindrically slotted antennas have been introduced, namely the axially slotted cloaked antenna and the circumferentially slotted cloaked antenna (CSCA). These two cloaked slot antennas have been parametrically studied to explore the antenna’s resonant characteristics together with their cloaking performance. The resonant frequency of the antennas is controlled by the parameters of the aperture of the slot such as width and length, while independently cloaking the CSAs at the cloaking frequency controlled by the parameters of the coated metasurface. The characteristics of the dual-mode operation at resonant and cloaking frequencies have been intensively studied by pulsed radar signal processing. The modulated Gaussian pulse with the modulation frequency being either resonant or cloaking frequency is used as an excitation source. Several scenarios have been proposed and studied to characterize the cloaking performance and communication capacity of the cloaked slot antennas. The radiating pulse from the CSAs has been numerically characterized by a pulse radar signal processing with an interval of 22.5° in terms of the theta and phi polarizations. These two CSAs have directive and omnidirectional characteristics in the theta- and phi-polarization, respectively.

Full-Field Measurement of Lightweight Nonlinear Structures Using Three-Dimensional Scanning Laser Doppler Vibrometry

Modern noncontact measurement techniques such as the three-dimensional scanning laser Doppler vibrometry (3D SLDV) are advantageous in measuring vibrations of lightweight, thin-walled aerospace structures, which were conventionally deemed as difficult or not feasible to apply using attached transducers. Nevertheless, the full-field measurements using 3D SLDV are still limited to extracting modal properties of linear structures, while measurements of complex nonlinear structures are rarely reported. This paper aims to extend the full-field measurement capability of 3D SLDV and combines it with a multiple-input–single-output vibration controller to deal with nonlinear structures. An advanced test strategy is introduced, which is capable of obtaining amplitude-dependent resonant frequencies, modal damping ratios, and full-field, multiharmonic mode shapes of nonlinear normal modes (NNMs). Conflicting parameters such as the frequency resolution and measurement time are optimized by combining phase separation and phase resonance testing techniques in a coherent strategy. The capabilities of the proposed nonlinear modal testing strategy are demonstrated on a realistic, large-scale fan blade that exhibits softening behaviors. Two of its NNMs were investigated at larger vibration amplitudes. Its nonlinear modal parameters were successfully extracted and validated, highlighting the time efficiency and data accuracy of the proposed strategy for measuring industrial-scale, lightweight nonlinear structures.

Using 2-D Core and Origami Winding to Push the First Resonant Frequency of Nanocrystalline Common-Mode Inductors Beyond 10 MHz With Improved Performance

Using 2-D Core and Origami Winding to Push the First Resonant Frequency of Nanocrystalline Common-Mode Inductors Beyond 10 MHz With Improved Performance

Implant Stability After Graftless Motor-Driven Crestal Sinus Elevation: A Cohort Study.

Graftless motor-driven crestal sinus elevation may be a preferable alternative to conventional methods due to the reduction of postsurgical complications and lower cost. This prospective cohort study evaluated the stability of implants installed using this technique. Twenty-nine Straumann BLT (bone level tapered) implants in 29 patients were included in the sample. Average implant stability quotients (ISQ) were measured immediately after surgery (mean: 73.5 ± 9.2) and after a period of healing (mean: 77.1 ± 4.5) using resonance frequency analysis (RFA). There was a significant increase in implant stability after healing (P = .035). The healing duration did not significantly influence how implant stability increased (P =.373). The mean ISQ after healing was significantly higher than the clinically acceptable stability value of 65 ISQ (P < .001). Implant length and width were not significantly correlated with ISQ increase (P = .764 and P = .085, respectively). In addition, there were no significant differences in average ISQ values measured immediately postsurgery (at baseline) or after healing between implants with and without registered perforations during surgery (P = .118 and P = .366, respectively). The posthealing stability of 4 implants that did not achieve primary stability was not significantly less stable after the healing period than those that had achieved primary stability (P = .086). Moreover, the level of insertion torque significantly impacted implant stability immediately postsurgery (P < .001), but the ISQ values measured after healing were not significantly different based on the initial insertion torque values (P = .131). This study suggests that implants installed using graftless motor-driven crestal sinus elevation may achieve clinically acceptable stability as measured by RFA.

Performance assessment of a Triple Coaxial-Cylinder Wave-Energy Converter (TCWEC)

We propose a novel Triple Coaxial-cylinder Wave-Energy Converter (TCWEC) system, as an evolution of the commonly deployed dual-coaxial cylinder WEC (DCWEC). TCWEC consists of one inner cylinder and two concentric outer cylinders, characterized by two coupled resonant frequencies, improving wave power absorption. A semi-analytical model, based on potential flow theory and matched eigenfunction expansions, is developed to analyze the 3-Degrees of Freedom (DOF) system. The viscous drag coefficients are determined by Computational Fluid Dynamics (CFD) simulations and employed as equivalent linear damping. Analysis of impact of the viscous flow-separation factor fvis on the capture width indicates that the higher energy-absorption capability of TCWEC is not merely attributed to a smaller fvis value, but rather a planned split of the outer cylinder in DCWEC design into two cylinders in TCWEC, so as to produce an effectively broader resonance property. Under identical sea conditions, it is found that, compared to DCWEC, the optimal capture width of TCWEC is increased by as much as 77% in regular waves. In irregular waves, the optimal capture width is increased up to 40% across the entire frequency range. These findings suggest that the energy absorption efficiency of TCWEC is promising and its potential for real-world applications.

Multi-resonance terahertz (THz) generation from magnetized cylindrical and spherical nanoclusters of AlAs and InP nanoparticles

We report a theoretical model for THz generation from the interaction of Gaussian laser beams with semiconductor nanoparticles suspended in argon gas in the presence of a DC magnetic field. Our investigations include two different shapes of nanoparticles [spherical (SNPs) and cylindrical (CNPs)]. The laser fields ionize nanoparticles converting them into plasma, which takes the form of spherical and cylindrical periodic nanoclusters with the electron density profile n=n0+nqeiqz, where q is the wave number of the density ripple and nq is the amplitude of density modulation. In our investigations, nanoparticles of AlAs and InP semiconductors are considered. Resonance condition is obtained when the laser beat frequency matches with the surface plasmon frequency of nanoparticles. We obtain resonances at two different frequencies when we apply a DC magnetic field. The resonance frequencies of THz fields shift with the nanoparticles' shape and orientation. THz field amplitude varies with material properties, spacing, size, and orientation of the nanoparticles. The applied magnetic field enhances the THz field and also helps in controlling the field profile. A THz field ∼0.1GV/cm with ∼2% efficiency is obtained for an optimized set of parameters for CNPs.

Development of cable-climbing robot with inspection function

Abstract The primary purpose of this study is to research and develop a crawler-type cable climbing robot to meet the demand of Sinotech Engineering Consultants, Ltd, using excellent structural design to meet the current practical requirements of the application of cable diameter varies greatly and simplify the operation process, improve the efficiency of the safety inspection of bridge cables and reduce the related risks, and through numerical analysis and the finite element method to optimize the design. The design is mainly divided into three parts: vibration measurement mechanism, robot control system, and cable climbing mechanism. The vibration measurement mechanism adopts the micro-vibration measurement method, in which a 3-axis piezoelectric accelerometer is tightly attached to the cable to measure the resonance frequency of the cable and detect the cable force. The robot control system adopts the fourth-generation Raspberry Pi as the central controller, with a ground remote control system and a backup system to prevent the robot from losing control due to the failure of the central system. The drive unit adopts a stepping motor with a planetary gearbox to drive the crawler. The cable-climbing mechanism uses a compression device to keep the robot’s track close to the cable to achieve a maximum speed of 0.04 m/s and to cross an obstacle limit of 9 mm over a 60-200 mm vertical or horizontal cable. The tracked cable-climbing robot is tested to be installed and operated by a single person and is adaptable to different cable environments with rapid deployment and operation.

Advancements in electrohydraulic fatigue testing: Innovations in variable resonance frequency control and comprehensive characterization

This study addresses the challenge in electro-hydraulic fatigue testing machines where increasing excitation frequency leads to reduced output load amplitude, making it difficult to optimize both frequency and amplitude simultaneously. A new approach is introduced with the variable resonance fatigue testing machine controlled with 2D excitation valves. This technique involves adjusting the system’s intrinsic frequency by altering its mass, aligning the excitation frequency with the intrinsic frequency, and leveraging resonance energy to enhance excitation amplitude for broad-range resonance near the resonance point. The relationship between the system’s intrinsic frequency, the equivalent mass of the upper connector, and the upper fixture is explored, yielding analytical solutions. Experimental research validates these simulations, in the resonance condition, the fatigue testing machine energy efficiency can reach 94 %, to further verify the fatigue testing machine in the resonance condition to realize the High energy efficiency. Demonstrating that the system’s intrinsic frequency decreases with increasing mass, allowing for a broad frequency resonance between 200 and 300 Hz. Operating in a broadband resonance region, the output load force is increased by 60 %–95 % and the system flow is reduced by 20 %–30 %. This mass-adjustment technique effectively alters the system’s intrinsic frequency, expanding the electro-hydraulic fatigue testing machine’s application scope.

Sintering behavior, lattice vibrational characteristics and dielectric properties of B-site ion substituted BaWO4 ceramics for LTCC applications

The influences of Mo6+ substitution at the B-site of scheelite structure on the sintering character, microstructures, lattice vibrational characteristics, and dielectric properties of BaW1-xMoxO4 (x = 0.10-0.30) ceramics were studied in detail in this paper. The sintering temperature of BaW1-xMoxO4 ceramics was effectively reduced to less than 950oC through forming a scheelite solid solution. The densification and the quality factor (Q×f) of BaW1-xMoxO4 ceramics were also enhanced compared with pure BaWO4 ceramic. Raman spectroscopy confirmed that the dielectric constant (εr) was highly correlated with molecular polarizability, and the Q×f was strongly dependent on the symmetric stretching bond of [WO4] tetrahedron. Oxygen bond valence was one of crucial parameters for modulating the temperature coefficient of resonant frequency (τf). Interestingly, the BaW0.75Mo0.25O4 ceramic sintered at 910oC exhibited favorable microwave dielectric properties of εr = 9.44, Q×f = 46,820GHz (@12.5GHz), and τf = −69.2 ppm/oC. Meanwhile, the BaW0.75Mo0.25O4 ceramic had stupendous dielectric properties in low-frequency band: εr = 17.5 and dielectric loss (tanδ) = 2.2×10-4 (@10MHz). In addition, there was good chemical compatibility between BaW0.75Mo0.25O4 ceramic and silver electrodes. These findings evidence that BaW1-xMoxO4 ceramics are competitive candidates in LTCC technology.

High performance (K,Na)NbO3-based textured ceramics for piezoelectric energy harvesting

Piezoelectric energy harvesters (PEHs), which can provide sustainable green energy for low-power electronics have received extensive attention in the viewpoint of science and industrialization. In order to achieve large output power of PEHs, high-performance piezoelectric materials are extremely desired. Herein, excellent electromechanical conversion properties of d33 ∼ 447 pC/N, g33 ∼ 30 × 10-3 Vm/N, k33 ∼ 47% and Suni ∼ 0.18% were achieved in <001> grain aligned KNN-based lead-free ceramics with a favorable rhombohedral (R), orthorhombic (O) and tetragonal (T) multiphase structure. The superior electromechanical conversion properties can be attributed to grain orientation and crystal symmetry controlled anisotropy, and multiphase coexistence significantly decreased poling energy barrier, as well as the flexible response to external stimuli of the nanometer domains. The PEHs fabricated using the optimal performance KNN-based textured ceramics exhibit high output power of 0.46 mW and power density of 6.7 mW/cm3 at a resonant frequency of 41 Hz, which is associated with the large k33 (∼ 47%) and figure-of-merit (d33×g33 ∼ 13.4×10-12 m2/N) values. The output power can actually light up more than 145 commercial LEDs, demonstrating great potential of KNN-based PEHs to power wireless sensors.

The enhancement detection method based on the Fabry–Pérot cavity using terahertz frequency-domain spectroscopy

This article demonstrates a simple, efficient, and low-cost gas detection method for gases with absorption peaks in the terahertz range. A modes-adjustable Fabry–Pérot cavity is designed. By adjusting the length of the cavity, the center resonant frequency of the cavity can be coupled to the gas absorption peak. This kind of coupling can greatly enhance gas detection. To detect gas absorption peaks, we choose terahertz frequency domain spectroscopy (THz-FDS), whose frequency resolution can be up to the MHz level. Vapor is selected to verify the coupling phenomenon. The resonant frequency of the cavity is modified to couple to 0.56 THz, the absorption peak of vapor. Experiments are conducted at different humidity levels, the humidity is controlled by the supersaturated salt solution. Results indicate that at a humidity level of 15%, the coupling effect can enhance the detectability of vapor by approximately 167%, and this enhancement effect diminishes as humidity increases. We analyze the effect of different modes on the coupling and find that the high modes can make the coupling easier, but have little effect on the enhancement. Furthermore, the method is used to detect biomolecule-α-tyrosine to ensure it has wide applicability. This method can be used to detect substances with absorption peaks in the THz regime, especially for low-concentration gas.

Novel Multi-Band SIW Antenna with Filtering Function

In this paper, the basic structure of a quad-band substrate-integrated waveguide (SIW) antenna with filtering characteristics is proposed. The proposed antenna consists of a four-slot SIW and a single-probe feed. Despite having a single feed, it was able to independently control the four resonant frequencies. However, since a basic quad-band SIW antenna has three radiation null frequencies, the left skirt characteristics of f1 and the right characteristics of f4 were not good. To improve this, four pairs of vias and a pair of U-slots were introduced to add two radiation null frequencies to the lower part of f1 and the upper part of f4, respectively. This time, the parameters of the basic structure did not change, except for those of the added structure. The fabricated antenna operated at 3.9, 4.03, 4.2, and 4.3 GHz, and exhibited a radiation null below -15.6 dBi at 3.6, 3.95, 4.09, 4.27, and 5.07 GHz.

Study of Systems of Active Vibration Protection of Navigation Instrument Equipment

Assessment of the influence of vibration isolator parameters on the distribution of the system’s natural frequencies is a significant task in the design of vibration isolation systems. The root method was used to determine the natural frequencies of the controlled vibration isolator. For a certain feedback structure of a controlled electrodynamic type vibration isolator, the need for a consistent selection of parameters has been justified. A mathematical solution has been proposed for the approximate determination of the roots of the characteristic equation of the controlled vibration isolator, which enables the analytical assessment of the influence of the vibration isolator parameters on the distribution of its natural frequencies. The research has been conducted in relative parameters, which makes it possible to generalize the results. The specificity of the inertial dynamic vibration isolator, which in some cases is associated with the implementation of anti-resonance conditions, can lead to the fact that resonant frequencies can occur on both sides of the tuning frequency of the vibration isolator. The use of an elastic suspension on flat springs to protect navigation equipment from vibration allows reduction in the intensity of translational vibration, while not changing the orientation of the device relative to the Earth. The implementation of an elastic suspension according to the scheme of the inverted pendulum allows an increase in the effectiveness of vibration isolation, under the conditions of a controlled change of the vibration isolator parameters and due to the use of feedback. The results of this research can be used in precision systems, such as vibration isolators, laser processing equipment, ultraprecision measurements or medical devices.

3D printed hernia mesh implant: a conformability study

Aim: This study aims to explore the sensing capabilities of polyvinylidene fluoride-hydroxyapatite-chitosan (PVDF-HAP-CS) composite-based hernia mesh implants (of conformal/planar design), followed by in-vitro analysis for better understanding of the bio-stability in the patient’s body. Methods: For analyzing the sensing capabilities, a microstrip patch antenna (MPA)-based implantable sensor [with 17-4 precipitate hardened (PH) stainless steel (SS) (bio-compatible) and Cu alloy (non-biocompatible) materials as conducting plane/patch with PVDF-HAP-CS as dielectric material] has been considered separately in this study. Primarily, in this study, the 3D models of the hernia mesh implant have been designed in the high-frequency structure simulator (HFSS) software, and the sensing behaviour of the same has been recorded. Results: The HFSS results represent that for the 17-4PH SS-based sensor, resonant frequency (fr) decreases from 2.3953 to 2.3800 GHz, whereas the gain increases from 0.54 to 4.02 dB with a SAR value of 1.077 W/kg. The fr for Cu alloy increases up to 30° conformal angle and, after that, starts decreasing, whereas the gain reaches 3.24 dB with a SAR value of 1.238 W/kg. The in-vitro study highlights that both materials (17-4PH SS and Cu alloy) possess a low corrosion rate. Conclusions: The simulation-based comparison of the biosensors with conducting elements 17-4PH SS and Cu alloy for different conformal angles indicates that the 17-4PH SS shows promising results over Cu in terms of higher gain (up to 4.02 dB) and low SAR value (1.077 W/kg) with the fr lying in the industry scientific and medical (ISM) band and therefore may be used for implantable sensor applications and possesses the capability to be used as 3D-printed hernia mesh implant. The in-vitro results with the low corrosion rate ≈ of 5.1 × 10–8 mm/year, 17-4PH SS may be a suitable material for the fabrication of hernia mesh implant.

자계 이방성 축 방향에 따른 안테나 공진 주파수 특성

The main theme of the 2024 Mobile World Congress (MWC), held annually in Barcelona, Spain, is ‘5G and Beyond.’ Extensive research and activity focus on 6G (IMT-2030) technology, which is expected to become the core infrastructure of the mobile industry by 2030, representing the future of wireless communications. This necessitates the support of more wireless frequency bands for terminals to be compatible with the upcoming Beyond 5G (B5G) and 6G technologies. The antenna mounting space for B5G wireless communication, with various form factors for hardware, such as smartphones, smartwatches, and smart rings, is limited, as these devices become increasingly slimmer and lighter. Several methods have been studied to reduce antenna size while maintaining performance in a limited space. Representative examples include integrated-structure, metamaterial, and magnetodielectric antennas. In this study, it is analyzed for the effect of the resonance frequency characteristics of antennas based on the arrangement direction of the anisotropic material in the limited antenna mounting space of communication terminals. Aiming to reduce antenna size in the B5G era, it is proposed for the necessity of optimal design that focuses on the axial direction of the magneto-dielectric materials when designing antennas using anisotropic materials for antenna miniaturization.

Enhanced Cherenkov radiation in twisted hyperbolic Van der Waals crystals

AbstractCherenkov radiation in artificial structures experiencing strong radiation enhancements promises important applications in free‐electron quantum emitters, broadband light sources, miniaturized particle detectors, etc. However, the momentum matching condition between swift electrons and emitted photons generally restricts the radiation enhancement to a particular momentum. Efficient Cherenkov radiation over a wide range of momenta is highly demanded for many applications but still remains a challenging task. To this end, we explored the interaction between swift electrons and twisted hyperbolic Van der Waals crystals and observed enhanced Cherenkov radiation at the flatband resonance frequency. We show that, at the photonic magic angle of the twisted crystals, the electron momentum, once matching with that of the flatband photon, gives rise to a maximum energy loss (corresponding to the surface phonon generation), one‐order of magnitude higher than that in conventional hyperbolic materials. Such a significant enhancement is attributed to the excitation of flatband surface phonon polaritons over a broad momentum range. Our findings provide a feasible route for highly directional free‐electron radiation and radiation shaping.

A Self‐Powered, Highly Sensitive, and Frequency‐Tunable Triboelectric Acoustic Sensor Inspired by the Human Cochlea

AbstractConventional acoustic sensors used in human–machine interfaces often face challenges such as power supply requirements, limited sensitivity, and inability to tune their frequency response. A self‐powered, highly sensitive, and frequency‐tunable triboelectric acoustic sensor inspired by the human cochlea is introduced. By mimicking hair cells in the organ of Corti, a tapered microhair‐structured ferroelectric poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) and barium titanate nanoparticle (BTNP) composite film is proposed, which demonstrates a 16‐fold increase in triboelectric output voltage (1.3 V) compared to a planar one at 2.8 Pa. Furthermore, inspired by the frequency selectivity of the basilar membrane with gradient structural variations, integrating a mass‐beam diaphragm is proposed with varying kirigami length and circular mass diameter that enables precise tuning of the resonance frequency of the sensor, resulting in a 32 times improvement in sensitivity (860 mV Pa−1) compared to a nonbiomimetic sensor (28 mV Pa−1) and an expanded dynamic range. The proposed sensor differentiates between human voices with different frequencies. A robotic hand integrated with the sensor responds to acoustic stimuli with programmed hand gestures, which highlights its potential in acoustic human–machine interfaces. The biomimetic approach to developing a self‐powered, highly sensitive, and frequency‐tunable acoustic sensor offers new possibilities for intuitive and immersive human–machine interfaces.