Frequency Range Research Articles

Pyramidal microwave absorbers: leveraging ceramic materials for improved electromagnetic interference shielding

This study presents the development and optimization of pyramidal microwave absorbers designed for efficient electromagnetic interference (EMI) reduction in anechoic chambers. Based on prior research, this work transitions from conventional flat cement-carbon absorbers to a novel pyramidal design, incorporating silicon carbide (SiC) as ceramic materials. Introducing ceramic materials into the cement-carbon composite aims to enhance absorption across a broader frequency range while maintaining structural integrity. The study evaluates five sets of pyramidal absorbers with varying SiC content within the 1–12 GHz frequency range. Reflectivity performance was assessed using the naval research laboratory (NRL) Arch free space method at a 0° incidence angle. Among the tested absorbers, the set containing 10% SiC demonstrated superior performance, achieving minimum and maximum reflectivity values of -26.6215 and -55.2752 dB, respectively, particularly in the C-band. The findings highlight the significant impact of material composition and porosity on the absorber's effectiveness, providing valuable insights for the future design of high-performance EMI absorbers.

Chilean brush-tailed mouse (Octodon degus): a diurnal precocial rodent as a new model to study visual receptive field properties of superior colliculus neurons.

Lab rodent species commonly used to study the visual system and its development (hamsters, rats, and mice) are crepuscular/nocturnal, altricial, and possess simpler visual systems than carnivores and primates. To widen the spectra of studied species, here we introduce an alternative model, the Chilean degu (Octodon degus). This diurnal, precocial Caviomorph rodent has a cone-enriched, well-structured retina, and well-developed central visual projections. To assess degus' visual physiological properties, we characterized the visual responses and receptive field (RF) properties of isolated neurons in the superficial layers of the superior colliculus (sSC). To facilitate comparison with studies in other rodent species, we used four types of stimuli: 1) a moving white square, 2) sinusoidal gratings, 3) an expanding black circle (looming), and 4) a stationary black circle. We found that as in other mammalian species, RF size increases from superficial to deeper SC layers. Compared with other lab rodents, degus sSC neurons had smaller RF sizes and displayed a broader range of spatial frequency (SF) tunings, including neurons tuned to high SF (up to 0.24 cycles/deg). Also, unlike other rodents, approximately half of sSC neurons exhibited linear responses to contrast. In addition, sSC units showed transient ON-OFF responses to stationary stimuli but increased their firing rates as a looming object increased in size. Our results suggest that degus have higher visual acuity, higher SF tuning, and lower contrast sensitivity than commonly used nocturnal lab rodents, positioning degus as a well-suited species for studies of diurnal vision that are more relevant to humans.NEW & NOTEWORTHY Rodent species commonly used to study vision are crepuscular/nocturnal, altricial, and possess simpler visual systems than diurnal mammals. Here we introduce an alternative model, the diurnal, precocial, Octodon degus, a Caviomorph rodent with a well-developed visual system. In this study, we characterize the visual responses of the degus' superior colliculus. Our results suggest that degus have higher visual acuity than nocturnal rodents, positioning degus as a well-suited species for studies of human-like diurnal vision.

Microstructural study with enhanced dielectric and magnetic properties of M−type Nd doped Ba1-xNdxFe12O19 (x = 0–0.20) hexaferrites synthesized via sol–gel auto-combustion route

In the present study, we have examined the influence of Nd doping on the structural, morphological, magnetic, and dielectric properties of barium hexaferrite (Ba1-xNdxFe12O19; 0 ≤ x ≤ 0.20) samples synthesized via the sol–gel auto-combustion route. The XRD patterns confirm the formation of the hexagonal phase, in addition to minor traces of Fe2O3 impurity in the samples. Doping with Nd3+ ions produced strain in the crystal, and the samples retain their hexagonal phase with space group P63/mmc, as ensured by the Rietveld refinement method. FTIR spectroscopy were performed for microstructural analysis, which shows the corresponding stretching and bending bands of iron and oxygen in the samples. The Raman spectra confirmed the Raman fundamental modes at various wavenumbers, which also confirm the hexagonal structure of the samples. The electronic states of all metal ions state were confirmed through x-ray photoelectron (XPS) spectroscopy analysis, which show that iron is present in two oxidation states (Fe2+ and Fe3+) in all the prepared samples. XPS spectra also revealed that the Nd-doped sample is more defective as compared to pure sample. Scanning electron microscopy (SEM) micrographs shows that the non-uniform particle size in the nanometer range. Elemental composition is confirmed using energy dispersive x-ray spectroscopy (EDS) measurement. Additionally, magnetic measurements using a vibrating sample magnetometer (VSM) revealed that the hysteresis loops for 5 % Nd-doped sample shows the maximum value 44.3 emu/g of magnetization, and its values decrease for further increase in Nd doping concentration. The dielectric measurements were performed at room temperature in the frequency range of 1 Hz to 10 MHz, when Nd3+ is doped at the Ba site, it enhances the dielectric constant, dielectric loss, tangent loss, and ac conductivity of the synthesized samples.

Improving near-field spatial uniformity of secondary sources for active noise control headrests

In an active noise control (ANC) headrest system, the near field uniformity of the secondary sound field affects the size of the generated quiet zone because the secondary sources are closer to the control zone than primary sources. In this study, a compound source with uniform near-field radiation is proposed to improve noise reduction performance of the ANC headrest system by using the sound pressure matching method. The compound source is driven with only one signal but consists of two loudspeaker units, whose amplitude ratio and phase difference are optimized with an ideal uniform target field and the secondary paths measured in the free field. In the paper, a numerical model in a diffuse sound field is developed first and the proposed compound source is demonstrated to be able to generate a larger quiet zone than a single loudspeaker. Then, the simulation results based on measured secondary paths and road noise data in a vehicle cabin are provided to show that the proposed compound source improves the average noise reduction of road noise by 2.0 dB in the 100–500 Hz frequency range compared to that with a single loudspeaker. Finally, it is shown that the proposed compound source is universally applicable and does not depend on specific application scenarios.

MFIEN: multi-scale feature interactive enhancement network for seismic data denoising in desert areas

Due to complex acquisition environments and geological conditions, in desert seismic data, the background noise is always intense and overlaps with the frequency range of the seismic signals. This severely blurs the seismic signals, bringing challenges to accurately extract desired reflection information. Effectively suppressing random noise and significantly optimizing the signal-to-noise ratio (SNR) is emerging as a key issue in seismic data processing. A Multi-scale Feature Interaction Enhancement Network (MFIEN) for intense background seismic noise attenuation in desert areas is proposed in this paper to address this problem. In general, MFIEN has a multi-scale feature interaction structure that combines feature information from different layers and captures distinct features through effective information integration. Furthermore, a fusion feature enhancement module (FFEM), incorporating dilated convolutions and convolutions with different kernel sizes, is proposed. This expands the receptive field without changing the size of the feature maps, thereby preserving the structural features of seismic records more effectively. Both synthetic and field desert data denoising results indicate that MFIEN can accurately suppress intense background noise and effectively recover weak signals, significantly enhancing the quality of seismic data.

Study on the change of the oil-paper insulation’s AC conductivity characteristics based on dielectric response in frequency domain

Oil-immersed power equipment (transformers and high voltage bushings) are key components of power systems. Oil-paper insulation has endured complex and harsh operating conditions when used as a primary insulation system, so it is essential to determine the insulation state of oil-paper insulation system to ensure a stable operation for the power grid. The oil-paper insulation’s conductivity behavior can effectively characterize the degree of insulation deterioration. However, the relationship between the alternating current (AC) and direct current (DC) conductivity behavior for oil-paper insulation systems is still unclear in current research, resulting in limitations in the traditional evaluation model’s application. Therefore, this paper uses oil-paper insulation materials under different aging to carry out relevant research about the changing features of the complex AC conductivity under different test temperature environments. The influence of oil-paper insulation aging, test temperature, and excitation frequency on the complex AC conductivity is verified. Considering the correlation between low-frequency AC conductivity and DC conductivity, the frequency range of AC conductivity is extended by means of frequency temperature and conductance double translation. The temperature dependence of the AC conductivity behavior is defined over a wide frequency test range. The relaxation polarization process dominated the AC conductivity variation law is obtained. The impact of experimental temperature and insulation aging on the cumulative characteristic parameters of AC ionic mobility is clarified. This study theoretically corrects the traditional calculation model for AC conductivity of oil-paper insulation. The bias in conductivity calculations caused by only considering a single relaxation polarization process is eliminated. The conductivity model that can characterize multiple relaxation polarization processes in the dielectric is established. This model provides theoretical support for the later assessment of oil-paper insulation state depending on conductance behavior.

Optimal turning of a 2-DOF proportional-integral-derivative controller based on a chess algorithm for load frequency control

Load frequency control is necessary for power system management. The power system must maintain a frequency range to ensure power supply stability. System faults and demand fluctuations may cause frequencies to change quickly. System stability and integrity suffer. We are optimizing the two-degree-of-freedom (2-DOF) proportional-integral-derivative (PID) controllers chess algorithm. This article addresses electrical load frequency regulation. We employ classical control theory and current adjustment. It aims for electrical system efficiency and dependability. It checks for errors using integral absolute error (IAE), integral squared error (ISE), integral of time multiply absolute error (ITAE), and integral time squared error (ITSE). Particle swarm algorithm (PSO) compares performance. The IAE of 0.03364, nearly identical to it, shows that chess trumps other algorithms in many scenarios. The chess algorithm's ISE was 0.00035, like PSO's 0.03363. The ISE was 0.00036, indicating PSO's error-reduction capabilities. For the chess algorithm, PSO is 0.07929, and ITAE is 0.07647. This indicates the PSO responds faster to system breakdowns and load changes. Finally, the chess algorithm's ITSE is 0.00072, below the PSO 0.00076. The chess algorithm is better at managing long-term load frequency.

Improving the thermal stability and dielectric properties of epoxy/phenolic resin type (novolac) composites by incorporating carbon nanofibers (CNFs)

This study aims to enhance the thermal stability and dielectric properties of an epoxy/phenolic resin-type novolac blend by incorporating carbon nanofibers (CNFs). The EP/novolac-CNF composite was created by dispersing a 10% weight fraction of CNFs into the EP/novolac blend. Various analyses were conducted to assess the improvements brought by the addition of CNFs. Differential Thermal Analysis (DTA) and Dielectric Measurements (DM) were employed to determine the Tg values. Thermogravimetric Analysis (TG) and Differential Thermogravimetric Analysis (DTG) were used to evaluate the thermal stability. Results indicated that the inclusion of carbon nanofibers enhanced the thermal stability of the composite, as evidenced by the increased char yield at temperatures exceeding 700 oC, reaching 27.08% compared to 8.4% for the EP/novolac blend. Dielectric measurements were conducted across a frequency range of 102 -107 Hz and a temperature range of 293-463 K. The results revealed a wide dielectric dispersion in all samples, indicating the presence of Debye relaxation and a broad distribution of relaxation times. Eyring’s relaxation rate equation was applied to determine the thermodynamic parameters, such as the Gibbs free energy of activation (\Delta G) and entropy (\Delta S). The results indicated strong intermolecular interactions in all tested samples. The incorporation of carbon nanofibers into the EP/novolac blend led to improvements in thermal stability and dielectric properties. The analysis of various parameters suggests enhanced performance and potential applications of the EP/novolac-CNF composite in relevant fields.

Bioinspired Disordered Aerogel for Omnidirectional Terahertz Response.

The structural disorder of the black butterfly assists in capturing sunlight across a wider spectral and angular range, injecting infinite vitality for omnidirectional and stimuli-responsive wave-absorbing materials. Here, the disordered micro-pores responding to terahertz (THz) waves through electromagnetic simulations, and then prepared via ice templating technology are analyzed and optimized. The customized disordered aerogel makes possible perfect terahertz response property with incidence-angle-insensitive and ultra-broadband. Ti3C2Tx MXene/carboxymethyl cellulose aerogels realize excellent shielding effectiveness exceeding 70.32dB and reflection loss of more than 43.02dB over the frequency range of 0.3-1.5 THz. Tailoring the structural orientation of anisotropic aerogels functions as a versatile dynamic modulation approach along terahertz propagation direction. The porous structure with moderate conductivity gradually triggers the resonance effect of the cavity, approximating a resonance sphere (pore) and waveguide system (tube). Ultimately, gradient impedance aerogel is proposed integrating THz-infrared stealth, hydrophobicity, and mechanical strength. This inspired biomimetic structural strategy will also enable various terahertz applications such as terahertz imaging, line-of-sight telecommunication, information encryption, and space exploration.

Engineered ionic polymer metal composites (eIPMCs) under dynamic compression loading conditions: theory and experiments

Abstract Engineered Ionic Polymer Metal Composites (eIPMCs) represent the next generation of IPMCs, soft electro-chemo-mechanically coupled smart materials used as actuators and sensors. Recent studies indicate that eIPMC sensors, featuring unique microstructures at the interface between the ionic polymer membrane and the electrode, exhibit enhanced electrochemical behavior and sensitivity under compression, as compared to traditional IPMCs. However, a complete and experimentally-validated model of how eIPMCs behave under dynamic compression loads is currently missing. In this paper, we develop an analytical model for eIPMC sensors, elucidating the role of the engineered interface, modeled as a separate material layer with unique mechanical and electrochemical properties. Theoretical predictions focus on the mechanical-to-electrochemical transduction response under dynamic compressive loads. Experimental verification is conducted on conventional IPMC and novel eIPMC samples fabricated using the polymer abrading technique. Electrochemical impedance spectroscopy is performed to study the effect of the engineered interface on the electrochemical properties. Open-circuit voltage and short-circuit current are measured under external compressive loads in different loading scenarios to demonstrate sensing performance. Results show good qualitative agreement between experimental trends and model predictions. Experiments over the frequency range 1-18 Hz demonstrate an increase of 220-290% in open-circuit voltage and 17-166% in short-circuit current sensitivity for eIPMCs over IPMCs.

A thin, wideband transmissive cross polarization converter.

This study presents a very thin wideband linear polarization converter in transmission mode with near-unity conversion efficiency. The suggested converter consists of a periodic array on a single-layer substrate, two metallic layers and six vias. Metallic vias connect the upper and lower layers of the construction. The radiated electromagnetic wave with linear polarization can be transformed into its orthogonal component in the transmission mode by the proposed converter. The suggested polarization converter operates well in the 9.53-13.35 GHz frequency band (36%). Additionally, The structure provides a larger than 90% Polarization Conversion Ratio (PCR) through the frequency range of 8.89-14.21 GHz. The conversion mechanism has been explained and confirmed through both surface current distribution, electric charge distribution and experimental tests. Over the whole frequency range, there is good agreement between the simulated and measured results.

Ultrathin Terahertz-Wave Absorber Based on Inorganic Materials for 6G Wireless Communications.

Terahertz waves are gathering attention as carrier waves for next-generation wireless communications such as sixth-generation wireless communication networks and autonomous driving systems. Electromagnetic-wave absorbers for the terahertz-wave region are necessary to ensure information security and avoid interference issues. Herein we report a high-performance terahertz-wave absorber composed of a composite of metallic λ-Ti3O5 and insulating TiO2 nanocrystals (λ-Ti3O5@TiO2). This material exhibits a strong terahertz-wave absorption with high values for the real (permittivity, ε') and imaginary parts (dielectric loss, ε″) of the complex dielectric constant. Furthermore, the tan(δ) (≡ ε″/ε') values are significantly high, ranging from 0.50 to 0.76 in the frequency range between 0.1 and 1 THz. An ultrathin film with a thickness of 48 μm recorded a reflection loss of -28 dB (99.8% of the terahertz wave is absorbed by the film). A terahertz-wave absorber with such a small thickness has yet to be developed. Not only does the present material exhibit resistance to heat, light, water, and organic solvents, but it can also be economically fabricated to support various applications, including outdoor uses.

An Improved PIN Diode Model Design for a Tunable Frequency Selective Absorber

An enhanced PIN diode model designed for a tunable frequency absorber is proposed, enabling continuous and adjustable absorption across the X-band frequency range. This new structure consists of four primary components: a frequency selective surface (FSS) layer, a dielectric substrate, an air spacer layer, and a metal substrate. Unlike previous designs, the PIN diode model introduced here offers significant advancements. It not only allows for the switching between absorption and reflection states but also enables precise tuning within the absorption state itself, providing a higher degree of control over the system’s performance. The unique arrangement of the PIN diodes in this design involves placing them between adjacent units of the structure. This strategic placement eliminates the need for complex and bulky bias networks, which are commonly used in conventional designs. As a result, it also minimizes the electromagnetic interference that often arises from bias lines, thereby improving the overall system efficiency and reliability. The proposed model, therefore, reduces the complexity of the absorbing system while enhancing its performance and tunability. Experimental results obtained through free-space measurements were conducted to validate the proposed design. The results show an excellent agreement with the simulation data, confirming that the improved structure can achieve continuous, tunable absorption with high precision. These findings suggest that the new PIN diode-based model could be a promising solution for a wide range of applications in dynamic frequency management and electromagnetic wave absorption systems.

Optimized measurement methods and systems for the dielectric properties of active biological tissues in the 10Hz-100 MHz frequency range

Optimized measurement methods and systems for the dielectric properties of active biological tissues in the 10Hz-100 MHz frequency range

Modulation-free laser frequency locking using Fano resonance in a crystalline whispering-gallery-mode cavity

A low-thermal-noise, small-sized, monolithic crystalline whispering-gallery-mode cavity can achieve a compact laser frequency locking system. In this study, we propose generating a Fano resonance spectrum within the crystalline cavity to achieve frequency locking without the need for traditional modulation techniques, aiming to further simplify the locking system. By coupling a prism with the crystalline cavity, we generate a Fano transmission spectrum to serve as the error signal for laser frequency locking. Experimental results show that our method achieves a level of noise suppression comparable to the classical Pound-Drever-Hall technique, reducing laser frequency noise to near the thermal noise limit of the crystalline cavity. It enables us to suppress the laser frequency noise to below 1 Hz2/Hz in the offset frequency range of 103–105 Hz and achieve a minimum noise of 0.2 Hz2/Hz. We also analyzed various unique optical noises in the Fano locking technique and found that the primary factor limiting laser frequency noise in this work is still the inherent thermal noise of the crystalline cavity. Our results indicate that the proposed Fano locking technique has significant potential to simplify laser locking systems, enhance stability, and reduce overall power consumption and cost.

Design strategies and performance evaluation of reconfigurable notch filtering in UWB Vivaldi Antennas

Abstract This paper presents a frequency reconfigurable notch band enabled Vivaldi Antenna for ultra-wideband (UWB) applications. The proposed antenna structure features a fork shaped patch embedded with a PIN diode. Patch is fed with a triangular tapered feed line and supported by a novel shaped Vivaldi ground plane consisting two exponentially tapered fins adjoining with a triangular slot. The antenna design shows a −10 dB impedance bandwidth ranging 2.17–10.97 GHz with a notch band between 4.94–5.11 GHz. With the help of BAR64 PIN diode reconfigurable notch band is achieved at 5.0 GHz frequency. Moreover, this notch frequency can be shifted to the desired frequency by adjusting the feed settings and location of the diode. The idea behind this design is to introduce a simple design, independently controlled notch parameters, simple switching operation, and high gain abilities. The developed antenna exhibits steady unidirectional radiation patterns and a peak gain of 9.3 dBi with noticeable decreases at the notched band. Almost stable gain is observed between UWB frequency range of 3.1–10.6 GHz, gain is varying from 7.05 dBi to 8.3 dBi and only 1.25 dBi gain variation is observed within this range of frequency. The simulated and fabricated results showcase a close agreement with each other. The proposed antenna improves wireless communication performance, meeting the growing demand for dependable and interference-resistant solutions.

Vibration signal characteristics of debris flow initiation and motion experiments by considering clay content

Micro accelerometers are crucial tools for monitoring and providing early warning of geological disasters. This study focuses on the potential debris flow in Wangjiayuan, Fang County, Hubei Province, aiming to explore the relationship between clay content and debris flow motion characteristics. Physical model experiments were designed with varying clay content to simulate debris flow motion, and micro accelerometers were employed to monitor and record vibration acceleration changes during debris flow initiation and motion. Frequency spectra were generated using Fourier transform to analyze the motion characteristics in the frequency domain. The results showed that the predominant period of debris flow initiation ranged from 15 Hz to 29 Hz, while the period during motion in the middle section of the flow area ranged from 36 Hz to 54 Hz. Higher clay particle content was associated with a decrease in both the frequency range and mean of the predominant period, as well as a reduction in the Fourier amplitude extremum. These findings provide a foundation for monitoring and predicting debris flows, and the vibration signal characteristics of debris flow initiation and motion can be used to infer the clay content, offering insights into early warning systems for such geological hazards.

P-1008. Congenital Cytomegalovirus Infection Screening in the Newborn Nursery: Areas for Improvement in the Absence of Standardized Guidelines

Abstract Background Cytomegalovirus (CMV) is the most common viral cause of congenital defects in the U.S. Early identification of congenital CMV (cCMV) infection allows for optimal antiviral treatment which reduces progression of sensorineural hearing loss and improves neurodevelopmental outcomes. There is varying guidance from expert consensus groups ranging from universal screening to selective screening based on clinical features. With conflicting data, many hospitals have no standardized protocol for cCMV screening. This study aims to detail clinical characteristics and outcomes of infants with cCMV in a tertiary medical center prior to implementation of standardized guidelines. Methods This was a retrospective case study of newborns who screened positive for CMV between June 2017-July 2022 at Rainbow Babies & Children’s Hospital in Cleveland, Ohio. 1900 newborns less than 21 days old were tested for CMV during this period, and newborns who screened positive for CMV were included (n=18). Clinical characteristics of the patients were described using median and interquartile range for continuous variables and frequency and percentages for categorical variables. Results The prevalence rate of cCMV at our center is 9.5 per 1000 live births. The most common associated clinical features were small for gestational age (SGA; n=12), microcephaly (n=9), abnormal neuroimaging findings (n=6), and failed newborn hearing screen (n=4). Two patients had isolated SGA, and neither received treatment nor had clinical sequelae. Saliva PCR tests were used for screening with no confirmatory urine testing. 11 patients received oral valganciclovir with documented side effects of transient neutropenia and transaminitis. 33% of newborns had no infectious disease or audiology follow-up. Conclusion Targeted screening practices for cCMV infection in our institution varies between providers. Our center has a prevalence rate slightly above the national average; however, the yield of screening isolated SGA is shown to be low. This study highlights gaps in current cCMV screening including lack of confirmatory urine CMV testing, and infants lost to follow up. System-level interventions including creation of standardized guidelines and provider education are necessary to improve follow-up and outcomes. Disclosures All Authors: No reported disclosures

Characterization of motor nerve stimulation using sinusoidal low frequency alternating currents and cuff electrodes.

Direct electrical neurostimulation using continuous sinusoidal low frequency alternating currents (LFAC) is an emerging modality for neuromodulation. As opposed to the traditional rectangular pulse stimulation, there is limited background on the characteristics of peripheral nerves responses to sinusoidal LFAC stimulation; especially within the low frequency range (<50Hz). In this study, we demonstrate LFAC activation as a means to activate motor nerves by direct bipolar nerve stimulation via cuff electrodes, and characterize the factors of activation. We study and quantify the effects of sinusoidal frequency and electrode geometry on the motor nerve activation threshold in-vivo and in computational models, in-silico. Acute in-vivo experiments (N=34) were conducted on isoflurane-anaesthetized rats. A pure tone continuous sinusoidal current was applied to the rat sciatic nerve in bipolar configurations via bipolar or tripolar nerve cuff electrodes (different contact separations). LFAC activation thresholds were quantified by measuring the electromyogram (EMG) response of the triceps surae muscles and the induced twitch force to LFAC stimulation at six frequencies (1, 2, 3, 4, 8, and 20Hz). Computationally, we utilized a volume conductor model of a bipolar cuff electrode around a single rat-size fascicle and projected the potentials to the McIntyre-Richardson-Grill (MRG) models of myelinated motor nerve fibers. We compared the in-silico responses of a range of fiber diameters (5.7 to 16μm) to LFAC stimulation and their activation thresholds to the in-vivo findings. Sinusoidal LFAC stimulation elicited motor nerve activity in-vivo and in-silico, with a remarkable convergence of the in-silico predictions to the in-vivo observations. The EMG activity showed that muscle responses to LFAC stimulation were phase-locked to the sinusoidal cycle but exhibited two distinct activation modes. These modes were classified as burst and unitary, indicating the presence of two distinct patterns of muscle activation during LFAC stimulation. The LFAC motor activation threshold was significantly dependent on frequency and influenced by the contact separation of the cuff electrode, with a greater extent of reduction at a higher frequency or wider separation. Moreover, the order of fiber recruitment was found to be normal-physiological (small-to-large caliber) given the nature of the induced EMG activity and in-silico predictions. These findings provide significant insights into the nature of sinusoidal LFAC stimulation, at the explored range of frequency, and the expected mammalian peripheral motor nerve responses to LFAC. The characteristics of sinusoidal LFAC stimulation would facilitate selectivity approaches in a broader range of therapeutic and rehabilitative neuromodulation applications.

Experimental and Simulation Study on Vibration Transmission Characteristics and Vibration Isolation Effect of a New Floating Raft Vibration Isolation System

To enhance the floating raft vibration isolation system’s effect, a new two-stiffness floating raft vibration isolation experimental was constructed. First, the system’s mathematical model was established. The vibration transfer function was deduced via substructure derivative synthesis and four-end parameter matrix methods, and the structural parameter impacts on it were analyzed. Then, a modal test was conducted, and a finite element model was built. Comparing finite element analysis with test results verified the model’s validity, followed by a study of the support structure’s vibration characteristics. Finally, by measuring acceleration responses at the isolator’s upper and lower ends and using the difference as an evaluation index, the isolator’s vibration isolation effect on land and underwater was investigated, along with its impact on the device’s underwater acoustic radiation. The results demonstrate that the two-stiffness vibration isolator can reduce vibration transmission within a specific frequency range both on land and underwater, guiding practical engineering vibration isolation research.