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As on land, oceans exhibit high temporal and spatial temperature variation. This ocean weather contributes to the physiological and ecological processes that ultimately determine the patterns of species distribution and abundance, yet is often unrecognized, especially in tropical oceans. Here, we tested the paradigm of temperature stability in shallow waters (

Continuous microseismic monitoring using three-component (3C) accelerometers deployed in multiple boreholes allows for tracking the detailed evaluation of mesoscale (∼10 m scale) fracture growth during the fracture stimulation experiments at the first Enhanced Geothermal Systems (EGS) Collab testbed. Building on a well-constrained microseismic event catalog, we invert for moment tensor of the events to better understand the fracture geometry and stress orientations. However, it is challenging because of the unknown orientation of 3C accelerometers and low signal-to-noise-ratio nature of high-frequency (several kHz) monitoring. To address these challenges, we first perform the hodogram analysis on the continuous active-source seismic monitoring (CASSM) data to determine the orientations of the 18 3C accelerometers. We then apply the principal component analysis (PCA) to the observed microseismic waveforms to improve the signal-to-noise ratios. We perform a grid search for the full moment tensor by fitting the PCA-denoised waveforms at a frequency range of 5 to 8 kHz. The moment tensor results show both the creation of hydraulic fractures and the reactivation of natural fractures during the hydraulic stimulations. Our stress inversion based on the inverted moment tensors reveals the alteration of stress regime caused by hydraulic fracture stimulations.

Large-scale inter-combustor thermoacoustic interactions occur frequently in modern can-annular gas turbine combustion systems due to the presence of an annular cross-talk section upstream of the first stage turbine stator vanes. Although the whole system's modal dynamics depend on the relative dominance of low-frequency planar or high-frequency transverse acoustic waves, the majority of prior studies have chiefly focused on longitudinal mode instabilities. Motivated by the paucity of detailed information, here we examine high-frequency transverse acoustic interactions between two adjacent lean-premixed hydrogen combustors connected via two different pathways, known as cross-fire (XF) and cross-talk (XT) sections. We observe that the dual-combustor system undergoes high-frequency spinning mode in the clockwise direction, manifested as well-defined limit cycles with peak-to-peak amplitude of around 10 kPa. The transverse pressure oscillations, in contrast to the well-established low-frequency mutual synchronization dynamics, are not fully synchronized even in the presence of cross-talk communication. This situation leads to the formation of two closely-spaced 1T modes at 4.76 and 4.86 kHz in the respective hydrogen combustors, accompanied by the beating of the pressure fluctuations solely in the XF tube section. Remarkably, the pressure waves induced near the XF tube section tend to lag behind the pressure waves spinning in the injector face, demonstrating the existence of the angular shift characteristically connected to the high-frequency transverse combustion dynamics. • High-frequency transverse instabilities are investigated in subscale dual-combustor test environments. • Distinctive features derived from high-frequency cross-talk interactions are experimentally identified. • Collective dynamics are characterized by weak coupling-induced beating in cross-fire section. • Angular shift in spinning modes is generated from two acoustically coupled hydrogen combustors. [ABSTRACT FROM AUTHOR]

To improve the dielectric strength in vacuum, spark conditioning through repetitive breakdowns by AC or impulse voltage is an effective method. AC conditioning at commercial power frequencies has been widely used due to its cost‐effectiveness, but the breakdown voltage after AC conditioning is generally lower compared to impulse conditioning. We have confirmed that multiple breakdowns occur successively in a half cycle of AC voltage application. It is considered that the multiple breakdowns are harmful for conditioning and triggered due to the previous breakdown in the same half cycle. In this paper, we discuss dielectric strength improvement by high frequency AC conditioning and how the multiple breakdowns are induced. We experimentally confirmed that the AC conditioning effect is improved by increasing the frequency of AC voltage for different applied AC conditioning voltages in a sphere‐plane electrode system. We focused on the breakdown position from the light emission images during AC conditioning to investigate whether the multiple breakdowns were induced or affected by the previous breakdown. We found that the multiple breakdowns occurred close to the previous breakdown position. The multiple breakdowns would be induced by the collision of metal particles due to the previous breakdown with the counter electrode. These breakdowns do not contribute to removing protrusion and would lead to damage to the electrode surface. The increasing frequency of AC conditioning would suppress the multiple breakdowns and improve the dielectric strength in vacuum. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Introduction. The presence of broad-spectrum and high-amplitude electromagnetic interference (EMI) within a single-phase induction motor (SPIM) drive poses a significant threat to both the system and other electronic equipment. High-frequency (HF) models of electrical motors play a critical role in overcoming these challenges, as they are essential for characterizing electromagnetic compatibility (EMC) in drives and designing effective EMI filters. The novelty of this study proposes an enhanced HF motor model based on transfer functions (TFs) to accurately represent the motor’s behavior at HFs for frequency-domain analyses in the range of 100 Hz to 30 MHz. Purpose. The equivalent HF model for a SPIM is discussed in this paper. The suggested equivalent circuit describes a motor’s common-mode (CM) properties. Methodology. HF model was developed by a frequency-domain analysis utilizing an experimental setup and MATLAB software. The motor impedance analysis is based on the measurement of variations in motor characteristics as a function of frequency in the CM setup. Originality. TF has been tuned using an asymptotic identification method of Bode to match the behavior of the real impedances of the motor parameters as a function of the frequency in the CM configuration. This tuned TFs are then synthesized into a comprehensive wideband EMC equivalent circuit model using the Foster network technique, which can be then simulated in any Spice-based simulator tools. Results. The proposed mathematical model was employed to conduct simulations, and the resulting predictions were validated against experimental data. CM response of the EMC equivalent circuit at low, medium, and HFs were compared between simulations and experimental measurements using Lt-Spice simulator software. Practical value. It is observed that results show satisfactory agreement with the measurements over a large frequency bandwidth [100 Hz–30 MHz], and the equivalent model of SPIM can be cascaded with other electronic and electrical modules to form a complete single-phase electric drive system model for fast analysis and prediction of system level EMI and electromagnetic sensitivity. [ABSTRACT FROM AUTHOR]

New Caledonian crickets of the tribe Lebinthini are renowned for their high endemicity and their use of high‐frequency calling songs. Although previous studies have found them to originate from New Guinea around 30 Ma, recent discoveries of new lineages of Lebinthini in New Caledonia and in Australia questioned this result. Here, we describe Kanakinthus koniambo Le Flanchec & Robillard gen. et sp.nov., a new genus and species endemic to New Caledonia. We also describe three new species of the endemic genus Agnothecous: A. anonymous Le Flanchec, Vendanger & Robillard sp.nov., A. borendyi Le Flanchec, Vendanger & Robillard sp.nov. and A. kwakwe Le Flanchec, Vendanger & Robillard sp.nov. We include these new taxa and the Australian Lebinthini in a molecular phylogeny of the subfamily Eneopterinae, estimate their divergence times and reconstruct their historical biogeography. Our results confirm the monophyly of the clade endemic to New Caledonia and its origin from a single colonization event from New Guinea, around 30 Ma, shortly after the archipelago completely re‐emerged in its current configuration, 34 Ma. We also infer an independent colonization of Australia by the genus Julverninthus from New Guinea, around 25 Ma. [ABSTRACT FROM AUTHOR]

Ultralow‐k materials with promising comprehensive performance to meet the increasing requirements of high‐frequency communication are highly desired. Here, a cross‐linked porous polymer SiCOH, synthesized via simple sol–gel method, was used as the filler to prepare SiCOH/PI composite films by physically blending, which demonstrates ultralow dielectric constant at high frequency. Notably, only 2.5% of SiCOH in the composite can significantly reduce the dielectric constant of PI from 3.0 to an ultralow value of 1.7 in the 9.5–12.4 GHz, together with a low dielectric loss of 0.029. Additionally, the SiCOH/PI composite maintains a high tensile strength of 82.4 MPa and a tensile modulus of 1.82 GPa, which is comparable to pure PI film. While the glass transition temperature (Tg) increases to 370°C and the linear expansion coefficient is reduced to 30.7 ppm/°C, both of which are superior to those of pure PI film. Moreover, by introducing the hydrophobic SiCOH into PI, the contact angle of the composite films increased to 92.0°–99.0°. This simple and low‐cost method not only effectively lowers the dielectric constant of PI but also improves the thermal stability, mechanical properties, and hydrophobic ability, greatly boosts the practical application of PI in high‐frequency communication in the future. [ABSTRACT FROM AUTHOR]

Fe-Si-B-Cu-Nb nanocrystalline alloys have been commercially applied at power electronics. However, few research works are focused on improving high-frequency magnetic properties in the alloys. In this paper, the effect of additional magnetic field annealing temperature on high frequency soft magnetic properties of Si-rich FeSiBCuNb nanocrystalline ribbon was investigated. The as-quenched FeSiBCuNb amorphous alloys were crystallized annealing at 550 °C × 60 min for precipitating nanocrystalline α-Fe(Si) phase. Then the crystallized annealed alloy cores carried out additional transverse magnetic field annealing, and the induced uniaxial anisotropy Ku gradually increases from 9.4 to 21.6 J/m3 with increasing the annealing temperatures from 360 to 520 °C. By comparison with the non-magnetic field annealing sample, the μe of nanocrystalline cores with extra field annealing reduces at about the range of 1–30 kHz but gets significant improvement at 50–200 kHz, the Q improves and Ps decrease at all frequencies of 1 ~ 200 kHz. After the magnetic field is annealed at 480 °C, the core achieves optimal high-frequency properties of μe = 37.9 k (f = 100 kHz), Q = 0.87, and Ps = 30.94 W/kg. The improvement of high-frequency properties in cores upon transverse magnetic field annealing can be attributed to the fact that the magnetic domains appear in a rectangular band arrangement and are perpendicular to the longitudinal direction of the ribbon. When the magnetic cores operate in a dynamic magnetization field, the periodic magnetization is mainly characterized by domain rotation. [ABSTRACT FROM AUTHOR]

In this work, we analyze data collected by an HF transmitter/receiver radio link, operating as an oblique ionosonde between the McMurdo Station (transmitter) and South Pole Station (receiver) at 4.1, 5.1, 6.0, 6.4, and 7.2 MHz between 28 February and 14 March 2019. To help contextualize the link's data we have performed numerical raytrace simulations to help understand the observations. By considering both the data and simulations, we have identified both single‐ and two‐hop E‐ and F‐region propagation modes in the data, where the multi‐hop modes were observed in the hours around sunrise and sunset in the 4.1 and 5.1 MHz channels. This is an unexpected result given the accepted wisdom that multi‐hop modes, which require a ground scatter component, cannot be supported in Antarctica because of the highly absorptive ice covering much of the continent. Our results show that multi‐hop propagation modes can be supported in the region under specific ionospheric conditions—around sunrise and sunset—if the mode's ground scatter component is collocated with the Transantarctic Mountains. The mountains are located along the great‐circle path between the link's transmitter and receiver. However, the combination of favorable ionospheric and ground scattering conditions makes the detection of the multi‐hop mode a rare occurrence in the data set analyzed here. These findings are critical to data analysis efforts of any current or future oblique ionosonde systems operating in Antarctica and other regions such as the Arctic. Plain Language Summary: The ionosphere is a region of plasma located above approximately 60 km in altitude that affects the propagation of High Frequency (HF; 3–30 MHz) radio waves. An HF radio transmitter and a receiver link is commonly used as a remote sensing tool for analyzing the characteristics of the ionosphere over vast and inaccessible regions such as Antarctica. In this work, we analyze data collected by an HF which operated from 28 February–14 March 2019 in Antarctica. The experiment consisted of an HF transmitter located at the McMurdo Station and a receiver located at the South Pole Station. An important finding of this work is the identification transmission pathways in the link that are supported by reflections between the Antarctic ground and the Earth's ionosphere, commonly referred to as a "multi‐hop mode." This is an unexpected result because conventional wisdom says that the Antarctic ice should absorb the radio transmissions when they interact with the ice on the ground, preventing a multi‐hop mode. Our analysis shows that in the hours around sunrise and sunset, the HF link's ground reflections points can be collocated with the Transantarctic Mountains which act as a good reflector because the mountains are exposed rock. Key Points: Raytracing simulation results are compared to transmitter/receiver link observations between the McMurdo and South Pole StationsEvidence of a two‐hop propagation mode between the stations is observed in the data and supported in the modelingMulti‐hop modes in Antarctica are rare but possible under specific ionospheric conditions [ABSTRACT FROM AUTHOR]

A novel piezoelectric-hydraulic hybrid actuation system with a half-wave resonator is proposed in this paper to generate high-frequency, high-pressure liquid flow and mechanical output through liquid resonance. The new hybrid actuator is similar to the traditional hybrid actuator, with the main difference being the pump chamber itself. The length of the specially designed pump chamber is greater than that of the traditional pump chamber, which facilitates resonance by virtue of the compliance and inertia of the liquid. Once the excitation frequency approaches the resonant frequency of the liquid in the pump chamber, the pressure in the pump chamber will be higher than that under quasi-static conditions, and the output of the hybrid actuator will benefit from it. The compositional structure and working principle of the new hybrid actuator are presented, and its output performance is experimentally studied. When the voltage is 400 Vp-p and the frequency is approximately 2.44 kHz, the actuator can output a maximum no-load velocity of 5.4 mm/s and a maximum blocking force of 181 N. This strategy verifies the feasibility of using liquid resonance for actuation and realizes high-frequency excitation of the hybrid actuator, which also provides a reference for future research on high-frequency hybrid actuators. [ABSTRACT FROM AUTHOR]

In order to solve the problem that small defects hidden behind pipeline support parts are difficult to detect effectively in small spaces, such as offshore oil platforms, a meander-coil-type dual magnetic group circumferential magnetostrictive guided wave transducer is developed in this paper. The transducer, which consists of a coil, two sets of permanent magnets, and a magnetostrictive patch, can excite a high-frequency circumferential shear horizontal (CSH) guided wave. The energy conversion efficiency of the MPT is optimized through magnetic field simulation and experiment, and the amplitude of the defect signal is enhanced 1.9 times. The experimental results show that the MPT developed in this paper can effectively excite and receive CSH2 mode guided waves with a center frequency of 1.6 MHz. Compared with the traditional PPM EMAT transducer, the excitation energy of the transducer is significantly enhanced, and the defects of the 2 mm round hole at the back of the support can be effectively detected. [ABSTRACT FROM AUTHOR]

This paper proposes a novel large-dimensional positive definite covariance estimator for high-frequency data under a general factor model framework. We demonstrate an appealing connection between the proposed estimator and a weighted group least absolute shrinkage and selection operator (LASSO) penalized least-squares estimator. The proposed estimator improves on traditional principal component analysis by allowing for weak factors, whose signal strengths are weak relative to idiosyncratic components. Despite the presence of microstructure noises and asynchronous trading, the proposed estimator achieves guarded positive definiteness without sacrificing the convergence rate. To make our method fully operational, we provide an extended simultaneous alternating direction method of multipliers algorithm to solve the resultant constrained convex minimization problem efficiently. Empirically, we study the monthly high-frequency covariance structure of the stock constituents of the S&P 500 index from 2008 to 2016, using all traded stocks from the NYSE, AMEX, and NASDAQ stock markets to construct the high-frequency Fama-French four and extended eleven economic factors. We further examine the out-of-sample performance of the proposed method through vast portfolio allocations, which deliver significantly reduced out-of-sample portfolio risk and enhanced Sharpe ratios. The success of our method supports the usefulness of machine learning techniques in finance. This paper was accepted by Agostino Capponi, finance. Funding: This work was supported by the Research Grants Council, University Grants Committee [Grants 11500119, 11505522, 11505721, and 21504818] and the National Natural Science Foundation of China (NSFC) Basic Scientific Center Project [Grant 71988101], entitled as "Econometric Modelling and Economic Policy Studies", as well as NSFC [Grants 71803166 and 72173104]. Supplemental Material: The online appendix and data files are available at https://doi.org/10.1287/mnsc.2022.04138. [ABSTRACT FROM AUTHOR]

In high‐frequency applications such as 5G‐6G communication, internet of things, automotive radar, and automated driver‐assistance systems, substrate materials excel as insulating layers owing to their superior dielectric properties. However, traditional methods for material development are often laborious and costly. To overcome these limitations, we employed molecular dynamics (MD) simulations to predict the dielectric properties of these materials at frequencies exceeding 107 Hz. Specifically, we selected thermosetting polyphenylene oxide (m‐PPO) as the resin matrix and combined it with three crosslinking agents, respectively: triallyl cyanurate, triallyl isocyanurate, and trimethylallyl isocyanurate. Our overarching goal is to provide comprehensive insights into the development and enhancement of materials critical for high‐frequency electronic devices. We anticipate that this methodology will be widely adopted for the development of advanced substrate materials across various applications, with the objective of effectively screening crosslinkers. Highlights: Developed a simulation method to efficiently explore material scenarios for high‐frequency applications.Studied the dielectric properties of m‐PPO combined with three crosslinking agents at high frequencies.Successfully predicted dielectric properties using MD simulations. [ABSTRACT FROM AUTHOR]

The nitrate--nitrogen (NO3-N) concentration is a key variable affecting the ecosystem services supported by headwater streams. The availability of such data monitored continuously at a high frequency (in parallel to hydrometric and other water quality data) potentially permits a greater insight into the dynamics of this key variable. This study demonstrates how single-input single-output (SISO) system identification tools can make better use of these high-frequency data to identify a reduced number of numerical characteristics that support new explanatory hypotheses of rain-driven NO3-N dynamics. A second-order watershed managed for commercial forestry in upland Wales (United Kingdom) provided the illustrative data. Fifteen-minute rainfall time series were used to simulate NO3-N concentration dynamics and the potentially associated dynamics in dissolved organic carbon (DOC) and runoff, monitored at the same high resolution for two 30-day periods with a differing temperature regime. The approach identified robust, high-efficiency models needing few parameters. Comparison of only three derived dynamic response characteristics (DRCs) of δ, TC, and SSG for the three variables for the two different periods led to new hypotheses of rain-driven NO3-N dynamics for further exploratory field investigation. [ABSTRACT FROM AUTHOR]

Soft magnetic composites (SMCs) are key materials in electronic devices. Conventional SMCs incorporate too much insulating material in order to reduce eddy current loss at high frequency, resulting in severe magnetic dilution and demagnetization field, which leads to deterioration of the magnetic performance. In this paper, ZnO precursor is homogeneously deployed on the surface of FeSiAl, which in situ generates a thin and dense Al2O3 layer on the surface of FeSiAl through the interfacial solid phase reaction between Al and O atoms during annealing process. Meanwhile, ferromagnetic ZnO layer is simultaneously obtained due to the loss of O. The formed Al2O3/ZnO layers effectively reduce power loss and endow high frequency stability with less influence on effective permeability. Finally, FeSiAl/ZnO‐0.4% SMC exhibits low power loss of 83.2 mW cm−3 (50 mT/100 kHz), high effective permeability of 92, and cut‐off frequency as high as 40 MHz. This study provides an efficient route for high performance SMCs and broadens high frequency application of soft magnetic devices. [ABSTRACT FROM AUTHOR]

In this study, a novel NiCuZn (Ni 0.24 Cu 0.21 Zn 0.55 Bi x Fe 2- x O 4 (x = 0,0.025, 0.050, 0.075)) ferrite composition (Ni/Zn molar ratio is 24/55) was successfully prepared by the addition of Bi3+ ion for substitution. It is demonstrated that Bi 2 O 3 served as an effective doping agent to reduce the sintering temperature to 900 °C and enhanced the high-frequency magneto-dielectric properties. Notably, the maximum permeability is ∼118 (@ 13.56 MHz) when x = 0.050 with a cut-off frequency of 47 MHz, which is nearly four times higher than that of the unsubstituted sample. In addition, an NFC antenna employing optimized ferrite as an electromagnetic shield sheet was designed and simulated. The results indicated that the chaotic and weakened magnetic field was recovered, and the biased resonant frequency was restored from 31.87 MHz to 13.68 MHz. These findings hold significant scientific importance and practical value in achieving superior electromagnetic shielding performance and miniaturization in NFC system. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of chromium-substituted cadmium post-spinel ferrites CdCr x Fe 2-x O 4 (x = 0.0, 0.1, 0.3, 0.5) have been synthesized through the sol-gel auto-ignition method. The structural, vibrational, dielectric, magnetic, and microwave absorption properties of β -spinel ferrites through modern techniques which include X-ray diffraction, FTIR Spectroscopy, and Vector network analyzer. X-ray diffraction technique was used for structural investigation which confirmed the monophasic orthorhombic structure of prepared samples and a detailed study revealed that no impurity/additional phases were detected. Crystallite size and strain were extracted via the Williamson-Hall (W–H) method and Size strain plot (SSP). Vibrational spectroscopy (FTIR) successfully verified the spectral qualities of studied ferrites as measured wave number ranges between 400 and 600 cm−1. X-ray photoelectron spectroscopy verified that all metal ions exist and possess the corresponding electronic states. Electrical properties have been investigated at the microwave region (1 MHz – 6 GHz). The conduction mechanism has been studied via Johnscher power law. The Cole-Cole plot of all the samples consisting of two semicircles corresponding to grain and grain boundaries described the increasing conduction phenomena. In the present research, stable dielectric constant, dielectric loss, enhanced magnetic characteristics, and minimum reflection loss (−31.9 dB) make these CdCr x Fe 2-x O 4 nano-crystallites most suitable candidates for highly dense and high-frequency microwave devices for EMI shielding material. [ABSTRACT FROM AUTHOR]

In recent years, the use of permanent magnet synchronous motors has become popular. These engines are cheaper, lighter, and more durable. However, to control these motors, accurate information about the position of the rotor is necessary. For this reason, various methods have been used to improve the motor position estimation performance. One of these methods is estimation by injecting harmonic current into the stator winding. In this paper, using high-frequency currents injected into the stator, the rotor position in IPMSM motors is estimated. However, the response obtained has a DC offset due to the inaccuracy of the current measurement sensors, which causes an error in the estimation of the rotor position. The improved ePLL method was used to solve this problem. This method causes the convergence of the estimated position of the rotor to its real position by removing the noises of the current measurement circuit and the DC offset effect. The efficiency of this method has been proven first by simulation in MATLAB software, then in a Psim environment, and then implemented on the drive of a permanent magnet motor using a TMS320F28034 processor. [ABSTRACT FROM AUTHOR]

In the paper results of the operation and efficiency of a DC-DC resonant converter with a switched capacitor topology, equipped with GaN transistors and SiC diodes are presented. Investigated problems are related to the optimization of the DC-DC power electronic converter in order to achieve miniaturization, a simplified design, and high efficiency. The proposed system operates at a high frequency with low switching losses. The proposed design helps to achieve uniform heating of the transistors and diodes, as demonstrated by the results of the thermal imaging measurements. The GaN transistors are integrated into one package with dedicated gate drivers and used to simplify the circuitry of drivers and increase the power density factor of the proposed device. In the high-frequency design presented in the paper, the converter is implemented without electrolytic capacitors. The results included in the paper contain waveforms recorded in the power circuit at ZVS operation when switching on the transistors. It occurs when the system operates above the frequency of current oscillations in the resonant circuit of the switched capacitor. Efficiency characteristics and a voltage gain curve of the converter versus its output power are presented as well. The results of efficiency and quality of waveforms are important because they facilitate characterizing the tested system for implementation using WBG devices. The use of integrated GaN modules to minimize elements in the physical system is also unique to this model and it allows for very short dead-time use, and operation in ZVS mode at low reverse-conduction losses. [ABSTRACT FROM AUTHOR]

Low order networks are widely used for linear stability analysis of combustors in the low frequency limit. High frequency stability analysis, however, is limited to cost-intensive numerical or experimental methods, since derivation of analytical solutions is either cumbersome or impossible. The article at hand provides a quasi-two-port network model for the effective modal acoustic pressure and axial velocity normalised with the transverse acoustic field for cylindrical combustors. This network modelling approach includes transfer matrices of acoustic area jumps, ducts for longitudinal, standing and spinning transverse and mixed mode wave propagation. The purely acoustic transfer matrices are validated with a generic non-reactive experiment. On the basis of phase-locked OH * images of an engine-similar multi-jet combustor with a forced T1 mode, a locally distributed flame response model is derived, which is reduced to a global flame transfer matrix. A locally resolved convective flame response model is implemented in a numerical model in order to verify the provided theory by the comparison of the analytical and numerical flame transfer matrix for the high-frequency regime. [ABSTRACT FROM AUTHOR]

The phenomenon known as bipolar cancellation is observed when biphasic nanosecond electric field pulses are used, which results in reduced electroporation efficiency when compared to unipolar pulses of the same parameters. Basically, the negative phase of the bipolar pulse diminishes the effect of the positive phase. Our study aimed to investigate how bipolar cancellation affects Ca2+ electrochemotherapy and cellular response under varying electric field intensities and pulse durations (3–7 kV/cm, 100, 300, and 500 ns bipolar 1 MHz repetition frequency pulse bursts, n = 100). As a reference, standard microsecond range parametric protocols were used (100 µs × 8 pulses). We have shown that the cancellation effect is extremely strong when the pulses are closely spaced (1 MHz frequency), which results in a lack of cell membrane permeabilization and consequent failure of electrochemotherapy in vitro. To validate the observations, we have performed a pilot in vivo study where we compared the efficacy of monophasic (5 kV/cm × ↑500 ns × 100) and biphasic sequences (5 kV/cm × ↑500 ns + ↓500 ns × 100) delivered at 1 MHz frequency in the context of Ca2+ electrochemotherapy (B16-F10 cell line, C57BL/6 mice, n = 24). Mice treated with bipolar pulses did not exhibit prolonged survival when compared to the untreated control (tumor-bearing mice); therefore, the bipolar cancellation phenomenon was also occurrent in vivo, significantly impairing electrochemotherapy. At the same time, the efficacy of monophasic nanosecond pulses was comparable to 1.4 kV/cm × 100 µs × 8 pulses sequence, resulting in tumor reduction following the treatment and prolonged survival of the animals. [ABSTRACT FROM AUTHOR]

Background: Premature ejaculation (PE) is the most prevalent sexual dysfunction among men. Eejaculation involves a complex nervous mechanism in which the ejaculatory centers play a key role in modulating sperm emission. Although treatment possibilities span from psychotherapy to pharmacological approaches, results show inconsistent efficacy. In this context, the emergence of repetitive transcranial magnetic stimulation (rTMS) as a non‐invasive neuromodulatory approach represents a compelling avenue for potential therapeutic exploration. Objective: To investigate whether high‐frequency transcranial magnetic stimulation can modulate the ejaculatory behavior of rats with rapid ejaculation by altering neurotransmitter levels and neuroplasticity in the hippocampus. Methods: Rats have been screened for rapid ejaculation by observing behavioral indices of mating, and subsequently divided into two groups. The intervention group was administered with a 10 Hz rTMS stimulation, whereas the control group received a sham procedure. Upon the delivery of rTMS, we investigated ejaculation latency (EL), the hippocampal 5‐hydroxytryptamine (5‐HT) concentration, brain‐derived neurotrophic factor (BDNF), synaptophysin (SYN), and postsynaptic density protein 95 (PSD95) expressions, as well as BDNF‐receptor tyrosine kinase receptor B (TrkB) pathway upregulation. Results: After 14 days, EL was increased in the intervention group compared with the control group. 5‐HT concentration in the hippocampal region was increased, and high‐frequency rTMS activated the BDNF and TrkB pathways, including phosphorylation of cAMP response element‐binding protein (CREB), and upregulated the transcription and protein expression of SYN, and PSD95. Conclusion: RTMS upregulates BDNF, SYN, and PSD95 expression through activation of the BDNF–TrkB pathway and increases brain 5‐hydroxytryptamine thereby regulating neuroplasticity and improving ejaculation. [ABSTRACT FROM AUTHOR]

The prediction method of MUF (Maximum Usable Frequency) has been extensively deliberated as a pivotal technology in HF (High Frequency) communication. To verify the reliability of MUF prediction models commonly used in HF communications, we evaluated the prediction accuracy of seven typical prediction models based on maximum observed frequency (MOFs) and predicted MUFs. The oblique-sounding (OS) circuit was from Changchun to Jingyang, with the vertical-sounding (VS) station situated in Beijing which is, approximately at the midpoint of this oblique-sounding (OS) circuit. The RMSE (root mean square error) and RRMSE (relative root mean square error) between the MOFs and predicted MUFs by the model were used to evaluate the accuracy of the models. The results of statistical analysis show that: (a) the prediction results of the seven models are consistent with the observed results in trend, among which the prediction results of the Lockwood model (LWM), the nonuniform ionospheric conditions MUF calculation model (NYM), and the model proposed by Istituto Nazionale di Geofisica e Vulcanologia (INGV) are in good agreement with the observed results; (b) In the four seasons, the seasonal distribution of the seven models is significantly different, and the INGV model has a better prediction effect; (c) The INGV model is superior to other models in relatively high solar activity epochs and relatively low solar activity epochs, followed by the LWM model, with little difference between the two models and close prediction accuracy; (d) The INGV model has a better prediction result in four different periods of a day, and the improved simplified MUF calculation model (MSPM) has a great prediction result in the periods of nighttime. [ABSTRACT FROM AUTHOR]

Graphene, a promising carbon nanomaterial, has garnered significant attention owing to its chemical stability, exceptional mechanical properties, and remarkable electrical conductivity and is being used in various electrical engineering applications ranging from solar cells to touch screens. The inherent mechanical strength and electric charge capacity of graphene enable efficient designs of diaphragms used in electrostatic loudspeakers, specifically within the high-frequency domain. This study incorporated single-layer and multi-layer graphene sheets, synthesized via chemical vapor deposition, as electrically charged diaphragms in electrostatic loudspeakers paired with an indium tin oxide film electrode to produce Coulomb force. Subsequently, the sound pressure levels of these distinct graphene- based electrostatic loudspeakers were determined through frequency response measurements. Based on our findings, we propose an optimal graphene film configuration for future electrostatic loudspeaker applications. [ABSTRACT FROM AUTHOR]

The phenomenon of arc compression in TIG welding with high-frequency longitudinal magnetic field (HF-LMF) has been observed. However, its mechanism remains unclear, and there is a lack of numerical investigation. This work presents a two-dimension axisymmetrical model of arc plasma in high-frequency longitudinal magnetic field based on the magnetohydrodynamics (MHD). The distributions of temperature, velocity and pressure of arc plasma in HF-LMF are investigated at different applied LMF frequencies ranging from 0 to 5000 Hz. In order to make the simulation results more convincing, the induced current and the electric force were considered. The results show that the HF-LMF could generate a circumferential electric field, causing particles rotating. However, since HF-LMF is variable, the direction of the electric field also changes, which causes the arc to rotate back and forth. When the frequency of HF-LMF reaches 2000 Hz, the negative pressure zone above the center of the anode disappeared and the arc was compressed. Thus, as the frequency of LMF increases, the distribution of current density, anodic heat flux, and arc pressure changes from a bimodal distribution to a unimodal distribution, and the peak value increases. The theoretical predictions were in good agreement with the experimental results.

Introduction. The presence of broad-spectrum and high-amplitude electromagnetic interference (EMI) within a single-phase induction motor (SPIM) drive poses a significant threat to both the system and other electronic equipment. High-frequency (HF) models of electrical motors play a critical role in overcoming these challenges, as they are essential for characterizing electromagnetic compatibility (EMC) in drives and designing effective EMI filters. The novelty of this study proposes an enhanced HF motor model based on transfer functions (TFs) to accurately represent the motor’s behavior at HFs for frequency-domain analyses in the range of 100 Hz to 30 MHz. Purpose. The equivalent HF model for a SPIM is discussed in this paper. The suggested equivalent circuit describes a motor’s common-mode (CM) properties. Methodology. HF model was developed by a frequency-domain analysis utilizing an experimental setup and MATLAB software. The motor impedance analysis is based on the measurement of variations in motor characteristics as a function of frequency in the CM setup. Originality. TF has been tuned using an asymptotic identification method of Bode to match the behavior of the real impedances of the motor parameters as a function of the frequency in the CM configuration. This tuned TFs are then synthesized into a comprehensive wideband EMC equivalent circuit model using the Foster network technique, which can be then simulated in any Spice-based simulator tools. Results. The proposed mathematical model was employed to conduct simulations, and the resulting predictions were validated against experimental data. CM response of the EMC equivalent circuit at low, medium, and HFs were compared between simulations and experimental measurements using Lt-Spice simulator software. Practical value. It is observed that results show satisfactory agreement with the measurements over a large frequency bandwidth [100 Hz–30 MHz], and the equivalent model of SPIM can be cascaded with other electronic and electrical modules to form a complete single-phase electric drive system model for fast analysis and prediction of system level EMI and electromagnetic sensitivity. References 37, table 5, figures 13.

Abstract Millimeter wave (mmWave) technologies at 60 GHz and 100 GHz bands are currently gaining significant attention for its potential to meet the demanding needs of next-generation networks. These include ultra-high data rate, ultra-low latency, high spectral efficiency, and high end-to-end reliability. However, mmWave signals’ blockage remains a critical issue that affects the reliability of mmWave at 60 GHz and at 100 GHz bands due to the significant attenuations induced by the blockers (BLs). Not only blockers that have the size of a human body or even larger can affect the signal, but also smaller objects with much narrower dimensions, as narrow as 4 cm, can severely affect the signal strength and introduce an attenuation that reaches up to 12 dB at 100 GHz. In this paper we have conducted new measurements and presented results for three small copper sheets at each frequency band, aiming to investigate the blockage effect of small-sized metal objects on signal strength at these two frequency bands. Also, we have examined the performance of the knife-edge diffraction (KED) blockage model of the third-generation partnership project (3GPP) standards body and its evolved version named the mmMAGIC blockage model in such scenarios. Furthermore, we investigated the applicability of the two blockage models in capturing the attenuation characteristics of other materials-such as wood and glass. Experimental results supported by numerical models have shown that the induced peak attenuations are 5(12) dB, 10(23) dB, 23(23) dB for 4 $$\times $$ × 4 cm, 8 $$\times $$ × 8 cm, 16 $$\times $$ × 16 cm copper blockers, respectively, at 60(100) GHz mmWave bands. Also, we have shown that both the 3GPP and mmMAGIC simulation models fail to accurately capture the attenuation characteristics of materials other than copper. The findings of this work highlight the importance of considering the dimensions and types of blockages when deploying reliable mmWave and sub-THz communications.

Financial commodity markets have an impact on company values and cash flows, where price movements within frequent time intervals can be both significant and random. Understanding highly frequent price movements is both important and difficult. In this paper, I measured and forecasted volatility for high-frequency (mostly twelve hours per day) WTI Oil front month price movements from 2012 to 2024 (about 40,500 observations). I created a new stochastic volatility model for extracting latent volatility using the non-linear Kalman filter. Stable and strictly ergodic hourly price series, along with the BIC optimal non-linear (generic) general method of moments model coefficients, enabled this process. The latent volatility seemed to separate into two volatility factors. One factor that was very persistent suggested slow mean reversion, and one choppy strongly mean-reverting factor. The data dependence found in the factor volatility series suggested forecasting ability. I applied classical static forecasts and three machine learning regression techniques to predict one-step-ahead volatility. The two volatility factors and one summarizing exponential factor were reported, along with several fit measures, including the root mean square error and Theil's measure of covariance.

This paper presents basic properties and laboratory tests of a commercial integrated high-frequency MOSFET gate driver IXRFD631 operating in the frequency range up to 30 MHz. The MOSFET driver has been tested for two operating states: in the idle state (no load) and at the gate load of a DE275-501N16A series MOSFET transistors. The obtained laboratory results were compared with three other commercial integrated drivers: DEIC420, DEIC515 and IXRFD630 (which are the base structures), and two previous solutions from the author (4xUCC27516 and 8xUCC27526). Additionally, this paper presents the characteristics of power losses and efficiency, measurements of switching and propagation times of the tested gate drivers. Also, this paper presents the output voltage waveforms of the integrated driver IXRFD631 for two operating states. The integrated circuit IXRFD631 of the gate driver is characterized by an efficiency of up to 70% for the tested frequency range, the power losses for two operating states (at idle state—15 W, at gate MOSFET load—43 W) and switching times of 2 ns for an operating frequency of 30 MHz. [ABSTRACT FROM AUTHOR]

A split-stepped gate field plate design has been incorporated on a gallium oxide (Ga2O3) metal-oxide semiconductor field-effect transistor (MOSFET). The aim of the present work is to unfold the potential of Ga2O3 MOSFET by enhancing its breakdown limits and also to overcome the challenge of simultaneous improvement in power as well as radio frequency (RF) metrics. An extensive simulation study focusing on analog and RF metrics has been carried out using technology computer-aided design simulations of the proposed device in a calibrated environment, and a comparative analysis of split stepped gate field plate design, shorted stepped gate field plate design, and conventional Ga2O3 MOSFET design has also been performed. The results highlight the superiority of the proposed device, and a substantial enhancement in breakdown voltage (i.e., 106.36% relative increase) and power figure-of-merit (i.e., 282.70% relative increase) has been demonstrated. [ABSTRACT FROM AUTHOR]

Digital microfluidics is a novel technique for manipulating discrete droplets with the advantages of programmability, small device size, low cost, and easy integration. The development of droplet sensing methods advances the automation control of digital microfluidics. Impedance measurement emerges as a promising technique for droplet localization and characterization due to its non-invasive nature, high sensitivity, simplicity, and cost-effectiveness. However, traditional impedance measurement approaches in digital microfluidics based on the high-voltage actuating signal are limited in sensing accuracy in practical applications. In this paper, we propose a novel droplet impedance sensing system for digital microfluidics by introducing a low-voltage and addressable measurement circuit, which enables impedance measurement over a wide frequency range. The proposed measurement system has also been used for detecting the droplet composition, size, and position in a digital microfluidic chip. The improved impedance sensing method can also promote the applications of the digital microfluidic, which requires high accuracy, real-time, and contactless sensing with automatic sample pretreatment. [ABSTRACT FROM AUTHOR]

This research review article provides a detailed examination of SMA (SubMiniature version A) connectors, which are integral components in high-frequency electronic systems. Through extensive S-parameter and time-domain reflectometry (TDR) measurements conducted on various SMA connector constructions, this study aims to evaluate the performance and impact of SMA connectors on signal integrity. Results reveal insights into the comparative performance of different SMA connector types mounted on PCB land pads, highlighting their strengths and limitations. Additionally, this paper explores the application of reference plane cut-outs for discontinuity impedance compensation, aiming to enhance the frequency response of SMA connectors. By linking measured performance parameters with relative market prices, this study offers valuable insights into the economic viability of different SMA connector types. The best and worst performing SMA connector measurements reveal an S11 < −10 dB bandwidth of more than 8 GHz and 1.5 GHz and a transition impedance of 46.5 Ω and 21 Ω, respectively. Overall, this research contributes to advancing the understanding and selection of SMA connectors for RF applications in telecommunications, aerospace, medical devices, and beyond. [ABSTRACT FROM AUTHOR]

We consider the park of high-precision instruments for measuring alternating voltage playing the role of working standards of the first and second categories within the frequency range 0.1–30.0 MHz. It is indicated that thermoelectric voltage transducers developed more than 30 years ago are now used as working standards of the first category without alternative despite the fact that they exceeded their service life and do not meet contemporary operating requirements. As an alternative to the sets of thermoelectric converters within the frequency range 0.1–30.0 MHz, it is possible to use the calibrators of alternating voltage. However, in the indicated frequency range, there are no calibrators of alternating voltage that can be used as working standards of the first category. Thus, an N5-10 high-frequency calibrator of AC voltage whose characteristics exceed the requirements to the characteristics of working standards of the first category was developed for operation within the frequency range 0.1–30.0 MHz under voltages of 1·10−3–10V. We describe the concept of design, the characteristics, and operating capabilities of the H5-10 calibrator. In the design of the calibrator, we used the method of equating the amplitude of high-frequency voltage with the known amplitude of low-frequency sinusoidal voltage by the method of amplitude detection. The high-frequency sinusoidal voltage in the calibrator is formed by a frequency synthesizer with the help of the method of direct digital synthesis by using a system of band-pass filters. The accuracy and stability of the amplitude of high-frequency voltage at the output of the calibrator are maintained by an automatic regulation system based on the principle of mutually reciprocal transformations realized with the use of a two-diode integrated assembly of identical Schottky diodes. The low-frequency stable voltage for the base input of the automatic regulation system is formed by a low-frequency calibrator at a frequency of 10 kHz. This calibrator generates an AC voltage within the range 0.1–10.0 V with a harmonic coefficient smaller than 0.01% and an amplitude tuning discreteness of 0.001%. The low-frequency calibrator is constructed on multiplying digital-to-analog converters by the method of digital synthesis of sinusoidal voltage with a stable measure of constant voltage of 2.5 V. The nominal output voltages of the H5-10 calibrator within the range 0.1–10.0 V are reproduced by an automatic regulation system. At the same time, within the range 1–100 mV, they are reproduced by scaling with the use of a voltage divider. The main fields of usage of the developed H5-10 calibrator are the verification and calibration of electronic voltmeters, voltage calibrators, multimeters, and voltage transducers used as working standards of lower categories. [ABSTRACT FROM AUTHOR]

To strike a balance between modeling accuracy and computational efficiency for simulations of ultrasound waves in soft tissues, we derive a pseudodifferential factorization of the wave operator with fractional attenuation. This factorization allows us to approximately solve the Helmholtz equation via one-way (transmission) or two-way (transmission and reflection) sweeping schemes tailored to high-frequency wave fields. We provide explicitly the three highest order terms of the pseudodifferential expansion to incorporate the well-known square-root first order symbol for wave propagation, the zeroth order symbol for amplitude modulation due to changes in wave speed and damping, and the next symbol to model fractional attenuation. We also propose wide-angle Padé approximations for the pseudodifferential operators corresponding to these three highest order symbols. Our analysis provides insights regarding the role played by the frequency and the Padé approximations in the estimation of error bounds. We also provide a proof-of-concept numerical implementation of the proposed method and test the error estimates numerically. [ABSTRACT FROM AUTHOR]

Accurate calculation of power losses has always been important for the design and optimization of magnetic components consisting of windings and magnetic cores, such as inductors and transformers. Focusing on windings, litz wire outperforms its counterparts in terms of eddy current losses, making it particularly suitable for high-frequency (HF) applications. The power loss calculation of litz wire is however challenging due to its complex structure of thin strands twisted in multiple levels. This article therefore aims to review various kinds of litz wire power loss calculation methods from analytical methods, numerical methods to coupling ones. In addition to, the principles and applications of each method, their inherent correlation and differences are also highlighted in this article. On this basis, a comprehensive review and comparison of different calculation methods of litz-wire power loss are provided. Finally, future challenges and directions are then summarized, whose ultimate goal is to calculate the power loss of litz wire accurately and efficiently. [ABSTRACT FROM AUTHOR]

Background: High‐frequency repeated transcranial magnetic stimulation (rTMS) stimulating the primary motor cortex (M1) is an alternative, adjunctive therapy for improving the motor symptoms of Parkinson's disease (PD). However, whether the high frequency of rTMS positively correlates to the improvement of motor symptoms of PD is still undecided. By controlling for other parameters, a disease animal model may be useful to compare the neuroprotective effects of different high frequencies of rTMS. Objective: The current exploratory study was designed to compare the protective effects of four common high frequencies of rTMS (5, 10, 15, and 20 Hz) and iTBS (a special form of high‐frequency rTMS) and explore the optimal high‐frequency rTMS on an animal PD model. Methods: Following high frequencies of rTMS application (twice a week for 5 weeks) in a MPTP/probenecid‐induced chronic PD model, the effects of the five protocols on motor behavior as well as dopaminergic neuron degeneration levels were identified. The underlying molecular mechanisms were further explored. Results: We found that all the high frequencies of rTMS had protective effects on the motor functions of PD models to varying degrees. Among them, the 10, 15, and 20 Hz rTMS interventions induced comparable preservation of motor function through the protection of nigrostriatal dopamine neurons. The enhancement of brain‐derived neurotrophic factor (BDNF), dopamine transporter (DAT), and vesicular monoamine transporter 2 (VMAT‐2) and the suppression of TNF‐α and IL‐1β in the nigrostriatum were involved in the process. The efficacy of iTBS was inferior to that of the above three protocols. The effect of 5 Hz rTMS protocol was weakest. Conclusions: Combined with the results of the present study and the possible side effects induced by rTMS, we concluded that 10 Hz might be the optimal stimulation frequency for preserving the motor functions of PD models using rTMS treatment. [ABSTRACT FROM AUTHOR]

Financial commodity markets have an impact on company values and cash flows, where price movements within frequent time intervals can be both significant and random. Understanding highly frequent price movements is both important and difficult. In this paper, I measured and forecasted volatility for high-frequency (mostly twelve hours per day) WTI Oil front month price movements from 2012 to 2024 (about 40,500 observations). I created a new stochastic volatility model for extracting latent volatility using the non-linear Kalman filter. Stable and strictly ergodic hourly price series, along with the BIC optimal non-linear (generic) general method of moments model coefficients, enabled this process. The latent volatility seemed to separate into two volatility factors. One factor that was very persistent suggested slow mean reversion, and one choppy strongly mean-reverting factor. The data dependence found in the factor volatility series suggested forecasting ability. I applied classical static forecasts and three machine learning regression techniques to predict one-step-ahead volatility. The two volatility factors and one summarizing exponential factor were reported, along with several fit measures, including the root mean square error and Theil's measure of covariance. [ABSTRACT FROM AUTHOR]

The urban radio‐frequency (RF) noise generated by our cities continues to change with time. Although models exist to describe the RF noise as functions of frequency and urban land use types, very few models describe the spatial character or structure of the noise on the scales of city blocks (50–150 m). The goal of this work is to investigate the connection between urban morphology and the higher‐order spatial statistics of the noise field. To achieve this goal, a large measurement campaign was conducted in Boston, Massachusetts. Many spatial measurements allowed for calculation of spatial correlation functions of noise power in three different neighborhoods, which were used to quantify the spatial structure of the fields. A statistical point source model is then developed, with adjustable parameters relating to urban morphology. Good agreement between the model and the experimental correlation functions suggests the 25 MHz urban noise field is well described by a random network of fixed point sources, radiating with a 1/r power law behavior. Plain Language Summary: Our modern cities are filled with electronic devices. Each device can emit radiation and contribute to what is called the urban radio‐frequency noise field. The noise field is the combined effect from all these devices. If the noise field is strong enough it can negatively impact wireless communication, and the use of other electric devices. It is important to better understand the nature of the noise field in order to mitigate and plan for its negative effects. This paper describes in detail how the noise field is distributed in space, or its spatial structure. A theoretical model or tool is developed to help predict how the noise field looks spatially. Key Points: Radio‐frequency noise spatial correlation functions were calculated for three different neighborhoods in Boston, MassachusettsGood theoretical agreement suggests the noise field is well described by a random network of point sources radiating with a 1/r behavior [ABSTRACT FROM AUTHOR]

Purpose of Review: Since the advent of spinal cord stimulation (SCS), advances in technology have allowed for improvement and treatment of various conditions, especially chronic pain. Additionally, as the system has developed, the ability to provide different stimulation waveforms for patients to treat different conditions has improved. The purpose and objective of the paper is to discuss basics of waveforms and present the most up-to-date literature and research studies on the different types of waveforms that currently exist. During our literature search, we came across over sixty articles that discuss the various waveforms we intend to evaluate. Recent Findings: There are several publications on several waveforms used in clinical practice, but to our knowledge, this is the only educational document teaching on waveforms which provides essential knowledge. Summary: There is a gap of knowledge related to understanding wave forms and how they work. [ABSTRACT FROM AUTHOR]

We consider approximating the solution of the Helmholtz exterior Dirichlet problem for a nontrapping obstacle, with boundary data coming from plane-wave incidence, by the solution of the corresponding boundary value problem where the exterior domain is truncated and a local absorbing boundary condition coming from a Padé approximation (of arbitrary order) of the Dirichlet-to-Neumann map is imposed on the artificial boundary (recall that the simplest such boundary condition is the impedance boundary condition). We prove upper- and lower-bounds on the relative error incurred by this approximation, both in the whole domain and in a fixed neighbourhood of the obstacle (i.e. away from the artificial boundary). Our bounds are valid for arbitrarily-high frequency, with the artificial boundary fixed, and show that the relative error is bounded away from zero, independent of the frequency, and regardless of the geometry of the artificial boundary. [ABSTRACT FROM AUTHOR]

Skin architecture and its underlying vascular structure could be used to assess the health status of skin. A non‐invasive, high resolution and deep imaging modality able to visualize skin subcutaneous layers and vasculature structures could be useful for determining and characterizing skin disease and trauma. In this study, a multispectral high‐frequency, linear array‐based photoacoustic/ultrasound (PAUS) probe is developed and implemented for the imaging of rat skin in vivo. The study seeks to demonstrate the probe capabilities for visualizing the skin and its underlying structures, and for monitoring changes in skin structure and composition during a 5‐day course of a chemical burn. We analayze composition of lipids, water, oxy‐hemoglobin, and deoxy‐hemoglobin (for determination of oxygen saturation) in the skin tissue. The study successfully demonstrated the high‐frequency PAUS imaging probe was able to provide 3D images of the rat skin architecture, underlying vasculature structures, and oxygen saturation, water, lipids and total hemoglobin. [ABSTRACT FROM AUTHOR]

Recent distributed acoustic sensing (DAS) experiments in ocean areas throughout the world have accumulated records for various wavefields. However, there are few tsunami records because tsunami observation depends on the DAS experimental period and its location. From continuous DAS records, we found tsunami signals at a frequency band of 5–30 mHz, which correspond to high‐frequency components of tsunamis and their propagation velocities differ from low‐frequency tsunamis. We estimated time series of the tsunami excitations at the source using the DAS records, which are consistent with those using records of ocean‐bottom absolute pressure gauges. Our study suggests that DAS records can be used for detecting tsunami propagations in the regions where other geophysical instruments are not available, and contribute to elucidating their excitation mechanisms. Plain Language Summary: Using distributed acoustic sensing (DAS) techniques, various types of wavefields, such as earthquake and ocean waves, have been captured by submarine fiber optic cables. However, the recording of tsunamis has been limited, as their observation depends on the timing and location of the DAS experiments. On 8 October 2023, in southern Japan, changes in sea level attributable to tsunamis were detected by tide gauges. Continuous DAS records in southern Japan have enabled the capture of signals associated with these tsunamis. The observed signals exhibit frequency‐dependent propagation velocities, which correspond to infragravity waves. These are essentially deep water waves or ocean surface gravity waves, representing the high‐frequency components of tsunamis. Using the DAS records alone, we were able to estimate the time‐series of the tsunami generation at the source location. The features obtained from the time‐series were consistent with those from records of absolute pressure gauges on the seafloor deployed in southwestern Japan. Our findings demonstrate the utility of DAS records in detecting tsunami propagations and also elucidating excitation mechanisms of tsunamis. Key Points: The countinuous records of our distributed acoustic sensing measuresment capture tsunami‐related signalsThe phase velocity dispersion of the obtained signals matches that of infragravity waves (high‐frequency tsunamis)The time‐series of the tsunami generation obtained by the cable data are consistent with those from nearby absolute pressure gauges [ABSTRACT FROM AUTHOR]

Electrical power systems represent an immense source of electromagnetic radiation spanning a wide frequency range, encompassing low-frequency, transient states, and high-frequency emissions. The radiation poses a significant self-pollution challenge for electric and electronic devices situated in close proximity to these systems. The present article aims to address this research, and provides a comprehensive review of the electromagnetic effects and pollution at differences frequency's ranges encompassing power systems network. In the context of the low-frequency range, the computation of electric and magnetic fields is conducted using quasi-static principles. To validate the behavior at high frequencies due to power line currents, Schelkunoff's approach is employed. Additionally, transient electromagnetic fields are analyzed using an exact analytical method. The results of computer simulations are compared with previously published and measured data for low-frequency regime and transient overvoltage conditions, verifying their consistency. Additionally, high-frequency results are presented and corroborated through the utilization of a numerical electromagnetic code (NEC-4). These analyses underscore the valuable role of computer-based calculations in examining the electromagnetic environment of power system networks. [ABSTRACT FROM AUTHOR]

Objectives Nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3-associated autoinflammatory disease (NLRP3 -AID) is a rare autosomal dominant systemic autoinflammatory disease. We aimed to summarize the phenotypic and genotypic features of Chinese adult NLRP3 -AID patients with hearing loss. Methods A retrospective cohort study of twenty-one adult patients with NLRP3 -AID was conducted in Peking Union Medical College Hospital between July 2015 and March 2023. All patients underwent whole exome sequencing and otorhinolaryngologic assessments. Clinical features and therapeutic data were collected and analysed. Results We found that 13/21 (61.90%) of patients had hearing loss with high-frequency impairment in the majority, and most patients presented with vestibular dysfunction as a new finding. The NLRP3 -AID patients with early-onset, cold or stress triggered episodes, red eyes, fatigue, hypopsia and mutations located in the NACHT domain of the NLRP3 protein were more likely to suffer from hearing loss, especially sensorineural hearing loss, perhaps as a result of pathogenic variants of high penetrance. By a series of audiological evaluations, TNF-α inhibitors were confirmed to improve or reverse hearing loss. Conclusions We reported the first cohort of Chinese adult NLRP3 -AID patients with hearing loss and characterized vestibular dysfunction, highlighted the necessity for attention to high-frequency hearing and provided potential alternative treatment. [ABSTRACT FROM AUTHOR]

In this research, an oxidized starch/styrene–butadiene rubber system with high capability of absorbing electromagnetic energy was adopted as the main component, the effect of oxidized starch content on the bonding and mechanical properties of aqueous polymer isocyanate (API) after high-frequency curing was evaluated, and the effect mechanisms were explored by combining thermodynamic tests and material characterization methods. Our findings revealed that the addition of oxidized starch enhanced the mechanical properties of API after high-frequency curing and the increase in the amount of oxidized starch enhanced the improvement effect of high-frequency curing on API bonding and mechanical properties. At 5 wt% oxidized starch, high-frequency curing improved API bonding properties by 18.0% and 17.3% under ambient conditions and after boiling water aging, respectively. An increase in oxidized starch content to 25 wt% increased enhancement to 25.1% and 26.4% for the above conditions, respectively. The enhancement effects of tensile strength and Young's modulus of the API adhesive body were increased from 9.4% and 18.2% to 18.7% and 22.6%, respectively. The potential enhancement mechanism could be that oxidized starch could increase the dielectric loss of API, converting more electromagnetic energy into thermal energy creating more cross-linked structures. [ABSTRACT FROM AUTHOR]

Planar magnetic components are compact and less susceptible to skin effect due to their thin copper layers. However, the increase in parasitic capacitance has been a challenge in high-frequency operation of planar transformers (PTs). Parasitic capacitances resonate with inductance and may damage switch devices. Thicker printed circuit board (PCB) and reconfigured windings are suggested in this paper to mitigate the parasitic capacitances. A detailed analysis of the parasitic capacitances is performed with a prototype PT. The resonant frequency increased from 1.27 to 1.63 MHz with a 0.4 mm thicker PCB. The reconfigured PT was 1.38 MHz, 0.3 MHz higher than the original PT. [ABSTRACT FROM AUTHOR]

Goal neglect refers to when an aspect of task instructions is not utilised due to increased competition between goal representations, an attentional limit theoretically linked to working memory. In an attempt to alleviate goal neglect and to investigate the association between dorsolateral prefrontal cortex (DLPFC)-supported working memory and goal neglect, we used high-frequency repetitive transcranial magnetic stimulation to the left DLPFC whilst participants completed the letter-monitoring task, a measure of goal neglect, and an N3-back task, a working memory task known to be affected by rTMS of the left DLPFC, following 20 min of active and sham stimulation (run on separate days). We found increased accuracy on the N3-back task in addition to decreased goal neglect in the active compared to sham condition when controlling for age and fluid abilities (as assessed by matrix reasoning performance). Furthermore, analysis showed that active stimulation improvements on both the N3-back and letter-monitoring tasks were greater for those with higher fluid abilities. These findings provide support for the link between the DLPFC-support working memory and goal neglect. Increased performance on the N3-back task also supports the literature reporting a link between left DLPFC and verbal working memory. Results are evaluated in the context of potential use to alleviate symptoms of disorders related to goal neglect. [ABSTRACT FROM AUTHOR]