Cutoff Frequency Research Articles

Bias-dependent electron velocity and short-channel effect in scaling sub-100 nm InAlN/GaN HFETs

This work reports on the extraction and simulation of the electron velocity–gate voltages relationship for sub-100 nm InAlN/GaN heterojunction field-effect transistors (HFETs). A peak electron velocity (ve) at an electron density (ns) of 0.41 × 1013 cm−2 was observed at 1.06 × 107 cm/s in an InAlN/GaN HFET with 60 nm gate length (Lg) by delay time analysis. The ve at a high ns of 1.5 × 1013 cm−2 was observed at 0.6 × 107 cm/s. This peak ve behavior is explained by polarization Coulomb field (PCF) scattering and optical phonon scattering based on a Monte Carlo method. As Lg scaled from 350 to 60 nm, the current gain cutoff frequency (fT) and transconductance (gm) were improved. However, the thermal performance was degraded with a bad figure of merit P150 °C. Although a weakening of the control capability of Vgs on ns (Δns/ΔVgs) was observed in the shorter Lg device, which leads to a decrease in device gm, the larger electron velocity by the increased lateral electric field (E) and the larger Δve/ΔVgs by the increased PCF scattering still enhance the peak gm. Results indicate that the enhancement of Δve/ΔVgs is a vital method to strengthen the modulation of the gate on current and to suppress the short channel effect in GaN HFET. Our work supports a deeper understanding and analysis of sub-100 nm InAlN/GaN HFET device performance and physical mechanisms.

Survey on Power and Area efficient FIR Filter Architecture in Digital Encephalography System

In the process of Electroencephalogram (EEG) acquisition, the electrical signals from the brain are contaminated by numerous noise sources and artifacts. American Clinical Neurophysiology Society recommends digital filtering of acquired EEG signals with an upper cut-off frequency of 70 Hz before display in digital encephalography systems. We propose a linear symmetrical FIR filter architecture for filtering EEG signals using approximate computation techniques. Approximate computation techniques result in lower hardware resources and lower power consumption with some compromise in quality. Software tools used for this study include MATLAB (and its FDA tool) and Xilinx ISE 14.7. The chosen target platform is the Spartan-3e starter FPGA board. We propose the architecture for an Approximate Dadda Tree Multiplier. The proposed approximate multiplier consumes 25% lesser slices and 35.18% lower dynamic power than state-of-the-art approximate multipliers. The proposed FIR filter consumes 19.77% lesser LUTs and 34.97% lower power than state-of-the-art symmetric FIR filter architectures.

ZnPc based multifunctional devices designed as fast capacitors, rectifiers, infrared detectors and microwave resonators adequate for 6 G technology applications

Herein Zinc phthalocyanine (ZnPc) based multifunctional devices are fabricated and characterized. The device fabrication included formation of an Au nanosheets onto n-Si wafers and coating these nanosheets with 500 nm thick ZnPc layer. Silver and platinum were used to form a Schottky and an ohmic contacts with n-Si and ZnPc, respectively. The device hybrid structure (Ag/n-Si/Au/p-ZnPc/Pt; abbreviated as ASZ) is composed of Ag/n-Si Schottky arm and p- and n- layers forming pn junction separated by Au nanosheets. Electrical and photoelectrical measurements on the ASZ devices have shown their ability to perform as conventional metal-oxide-semiconductor capacitors (CMOS). These CMOS devices showed light and frequency controlled charge accumulation, depletion and inversion mechanisms within the range of 1.0–50 MHz. The flat band and threshold voltages of the ASZ capacitors are engineered by the imposed ac signal frequency and by infrared (IR) light. In addition, ASZ devices performed as biasing controlled IR photosensors and as current rectifiers. A rectification ratio of 103, IR light sensitivity of 39, specific detectivity of .96 ×109 Jones and current responsivity exceeding 9.0 mA W−1 are recorded at biasing voltage of 4.5 V. Moreover ASZ devices displayed microwave resonator characteristics presented by negative capacitance effect, resonance –antiresonance phenomena and high microwave cutoff frequency. The latter is larger than 10 GHz nominating the device for 6 G technology applications.

Solar Chromospheric Heating by Magnetohydrodynamic Waves: Dependence on the Inclination of the Magnetic Field

A proposed mechanism for solar chromospheric heating is magnetohydrodynamic waves propagating upward along magnetic field lines and dissipating their energy in the chromosphere. In particular, compressible magnetoacoustic waves may contribute to the heating. Theoretically, the components below the cutoff frequency cannot propagate into the chromosphere; however, the cutoff frequency depends on the inclination of the magnetic field lines. In this study, using high-temporal cadence spectral data of IRIS and Hinode Solar Optical Telescope spectropolarimeter in plages, we investigated the dependence of the low-frequency waves on magnetic field properties and quantitatively estimated the amount of energy dissipation in the chromosphere. The following results were obtained: (a) The amount of energy dissipated by the low-frequency component (3–6 mHz) increases with the inclination of the field below 40°, whereas it decreases as a function of the inclination of the field above 40°. (b) The amount of the energy is enhanced toward 104 W m−2, which is the energy required for heating in the chromospheric plage regions when the magnetic field is higher than 600 G and inclined more than 40°. (c) In the photosphere, the low-frequency component has much more power in the magnetic field inclined more and weaker than 400 G. The results suggest that the observed low-frequency components can bring the energy along the magnetic field lines and that only a specific range of the inclination angles of the field and the strength of the field may allow the low-frequency component to bring a sufficient amount of the energy into the chromosphere.

Measurement and Analysis of In Vivo Gastroduodenal Slow Wave Patterns Using Anatomically-Specific Cradles and Electrodes.

Bioelectrical 'slow waves' regulate gastrointestinal contractions. We aimed to confirm whether the pyloric sphincter demarcates slow waves in the intact stomach and duodenum. We developed and validated novel anatomically-specific electrode cradles and analysis techniques which enable high-resolution slow wave mapping across the in vivo gastroduodenal junction. Cradles housed flexible-printed-circuit and custom cradle-specific electrode arrays during acute porcine experiments (N = 9; 44.92 kg ± 8.49 kg) and maintained electrode contact with the gastroduodenal serosa. Simultaneous gastric and duodenal slow waves were filtered independently after determining suitable organ-specific filters. Validated algorithms calculated slow wave propagation patterns and quantitative descriptions. Butterworth filters, with cut-off frequencies (0.0167 - 2) Hz and (0.167 - 3.33) Hz, were optimal filters for gastric and intestinal slow wave signals, respectively. Antral slow waves had a frequency of (2.76 ± 0.37) cpm, velocity of (4.83 ± 0.21) mm·s-1, and amplitude of (1.13 ± 0.24) mV, before terminating at the quiescent pylorus that was (46.54 ± 5.73) mm wide. Duodenal slow waves had a frequency of (18.13 ± 0.56) cpm, velocity of (11.66 ± 1.36) mm·s-1, amplitude of (0.32 ± 0.03) mV, and originated from a pacemaker region (7.24 ± 4.70) mm distal to the quiescent zone. Novel engineering methods enable measurement of in vivo electrical activity across the gastroduodenal junction and provide qualitative and quantitative definitions of slow wave activity. The pylorus is a clinical target for a range of gastrointestinal motility disorders and this work may inform diagnostic and treatment practices.

A Digital Proportional–Resonant Controller With Desired Tracking-Error Convergence

Proportional-resonant (PR) controllers were initially presented within a continuous-time control framework; hence, their digital implementations may be susceptible to resonant-frequency offset and modulation-signal computational delay. Consequently, engineers may need to tune the controller parameters by trial and error to design the control systems that achieve desired performance. In digital control, sinusoidal references of power converters are discrete-time sequences. Based on this, we present a digital design technique for the PR controllers and demonstrate the design process using a 13.2-kW grid-connected inverter prototype. The design ensures the sinusoidal reference's tracking-error sequence converges at the desired rate. The advised design technique's merits include: 1) The tracking-error convergence rate, phase margin, and cut-off frequency have clear mathematical relations, allowing engineers to uniquely determine the controller parameters by specifying any two indicators. 2) With the tuned controller parameters, the tracking-error sequence can converge at the desired rate. 3) The resultant controller can be partitioned into one proportional term and two resonant terms; the first two terms are construed as a standard PR controller digitally implemented via the zero-order-hold method, whereas the second resonant term guarantees the tracking-error sequence converging in the desired manner. A case study results confirm the digital PR controller's efficacy.

Automatic speaker and age identification of children from raw speech using sincNet over ERB scale

This paper presents the newly developed non-native children’s English speech (NNCES) corpus to reveal the findings of automatic speaker and age recognition from raw speech. Convolutional neural networks (CNN), which have the ability to learn low-level speech representations, can be fed directly with raw speech signals instead of using traditional hand-crafted features. Moreover, the filters that were learned using standard CNNs appeared to be noisy because they consider all elements of each filter. In contrast, sincNet can be able to generate more meaningful filters simply by replacing the first convolutional layer by a sinc-layer in standard CNNs. The low and high cutoff frequencies of the rectangular band-pass filter are the only parameters that can be learned in sincNet, which has the potential to extract significant speech cues from the speaker, such as pitch and formants. In this work, the sincNet model is significantly changed by switching from baseline Mel scale initializations to equivalent rectangular bandwidth (ERB) initializations, which has the added benefit of allocating additional filters in the lower region of the spectrum. Additionally, it needs to be highlighted that the novel sincNet model is well suited to identify the age of the children. The investigations on both read and spontaneous speech tasks in speaker identification, gender independent & dependent age-group identification of children outperform the baseline models with varying relative improvements in terms of accuracy.

Исследование отражения и прохождения волны через планарный слой кирального метаматериала, расположенного в прямоугольном волноводе с учетом материальной дисперсии

The work analyzes the diffraction of the fundamental wave of a rectangular waveguide on a planar layer of a chiral metamaterial located in a transverse plane. The mathematical model of the metamaterial takes into account its chirality and dispersion of material parameters. To connect the electromagnetic field vectors through the parameters of the chiral layer, two-sided approximate boundary conditions are used. Cross-polarization of the field is taken into account in the work. A system of linear algebraic equations for the reflection and transmission coefficients of the fundamental and cross-polarized waves was obtained in the work. It is shown that at the cutoff frequencies of the fundamental and cross-polarized waves are also excited in the waveguide. It is shown that at different levels of attenuation in the waveguide, situations arise when the degeneracy of resonant frequencies arises and disappears. It has been proven that the reflection and transmission of the fundamental wave at low attenuation values is of a frequency-selective resonant nature.

Ferroelectric Based Low Power MOSFET for DC/RF Applications: Machine Learning Assisted Statistical Variation Analysis

The analog/radio-frequency (RF) performance of a ferroelectric-based substrate metal oxide semiconductor field effect transistor (FE-MOSFET) with dielectric spacer was designed and proposed. The utilization of gate side wall spacers aims to mitigate short-channel effects (SCEs), and improve overall device performance. Simulation results demonstrate enhanced performance metrics, including improved transconductance (80%), reduced gate leakage (95.4%), and enhanced cutoff frequency (25%), making this design a promising candidate for next-generation high-performance analog and RF applications. Additionally, a novel machine learning (ML)-assisted approach is proposed for investigating the spacer-based FE-MOSFET to reduce the computational cost of numerical TCAD device simulations with the help of conventional- artificial neural network (C-ANN). This method is reported for the first-time ML-based C-ANN for Fe-based low-power MOSFET, matches the similar accuracy of physics-based TCAD with the fastest learning rate and fastest computational speed (in 95–100 s). An ML-based prediction replacement for physics-based TCAD is developed to save around 8–10 h of runtime for each iteration. Because ML predictions can never be 100% accurate, it is essential to ensure approximately zero mean-square error in the final results.

Computational hemodynamics and hemoacoustic study on carotid bifurcation: Effect of stenosis and branch angle

Investigation of sound-signal-based noninvasive diagnosis of arterial stenosis is an active area of research. This study focuses on computational investigation of hemodynamic and hemoacoustic parameters within the carotid bifurcation. The objective is to analyze the effect of 40 distinct geometric configurations on indicative sound signals, useful for understanding the feasibility of stethoscope-based diagnosis of stenosis. The study employs an in-house flow-solver based on the semi-implicit pressure-projection method on a curvilinear grid. Physiological condition-based pulsatile flow waveforms and three-element Windkessel model-based pressure are utilized at the inlet and outlets of the bifurcating carotid artery. The research involves assessment of parameters like wall shear stress (WSS) and integrated pressure force rate (IPFR) fast Fourier transform (FFT) spectrum. Geometric configurations are varied based on stenosis level S (0, 45%, 60%, and 70%), bifurcation angle BA (30°, 40°, 50°, and 65°), and length of stenosis L (1, 1.5, and 2). In the investigated geometries, WSS exhibits a distinct behavior, reaching a peak at stenosis and subsequently transitioning to a negative value. Furthermore, IPFR-spectrum analysis reveals distinguishable frequencies for S≥ 40%, hinting at the potential for stethoscope-based diagnosis. A novel correlation between the cutoff frequencies of IPFR FFT-spectrum and arterial geometry is established, which reflect the influence of artery geometry on sound signals. Computational fluid dynamics (CFD)-based flow-visualization approach is proposed to calculate characteristic frequencies, which are close to IPFR spectrum frequencies. Our study contributes to a framework for potential sound-based classification of plaque-induced constrictions.

Flywheel rotor cross-filter tracking feedback control

In light of the matter that the fixed-parameter cross-filter circuit cannot satisfy the phase compensation requirement in the full speed range, a cross-feedback tracking control method based on cross-filter feedback, in which the high-pass cutoff frequency varies with the nutation frequency, is proposed. The stability analysis of the designed control method is carried out by using the phase angle margin and the root trajectory diagram, and the results show that the cross-feedback tracking control can increase the phase angle margin and significantly enhance the stability of the system. Simulation results of the magnetic levitation rotor system show that the designed control method possesses the benefits of high stability, rapid response time, and strong anti-jamming ability.

On vehicle response under non-Gaussian road profile excitation

Gaussian road profile is widely used to study vehicle response and fatigue damage potential, while field measured road profile often is non-Gaussian. In this paper, a new amplitude modulation method which has full control of cutoff frequency (denoted as Wcut) and amplitude of the amplitude modulation signal is firstly presented to synthesize non-Gaussian road profile with different kurtosis. The forced response of a quarter vehicle under non-Gaussian road profile excitation is then calculated using the ramp invariant digital filter method. The relationship between the vehicle response characteristics and the kurtosis of input non-Gaussian road profile are developed. A case study is used to verify the proposed method. The results show that a small Wcut should be selected so that the high kurtosis of the non-Gaussian road profile is correctly transferred to the vehicle response. The FDS of the vehicle response increases over the entire frequency range as the kurtosis of the input road profile increases.

The impact of dry eye disease on retinal image quality in children

Background and ObjectivesDry eye disease (DED) is increasingly prevalent, resultinginhigher morbidityamong children. This study evaluates the impact of DED severity on visual quality using double-pass technology, focusing on dynamic observation of the ocular light scatter in pediatric DED cases. MethodIn this non-interventional, cross-sectional study, a mild DED group (37 cases, 37 eyes), a moderate DED group (40 cases, 40 eyes), and a control group of healthy children (35 cases, 35 eyes) were examined. Measurements included the Schirmer I test, tear film break-up time (BUT), and vision-related quality of life assessments using the Modified Ocular Surface Disease Index (OSDI) questionnaires. Participants underwent visual quality analysis using double-pass technology, which measured the modulation transfer function cut-off frequency value (MTF cutoff), Strehl ratio (SR), objective scatter index (OSI), and OQAS-II value (OQAS-II value OV100%, OQAS-II value OV 20%, and OQAS-II value OV 9%) under natural conditions. Additionally, dynamic changes in OSI post-blinking, Tear film mean-OSI (TFM-OSI), and the corresponding standard deviation OSI (SD-OSI) were recorded. ResultsStatistically significant differences were observed among the groups in modulation transfer function cutoff, Strehl ratio, OSI, OQAS-II value OV 100 %, OQAs-II value OV 20 %, OQAs-II value OV 9 %, tear film mean OSI, and standard deviation OSI (P < 0.05). As DED severity increased, tear film mean OSI significantly rose, while modulation transfer function cutoff, strehl ratio, OQAS-II value OV 100 %, OQAS-II value OV 20 %, OQAS-II value OV 9 % notably declined. All optical quality parameters were correlated with BUT, with no association observed with age, sex, or Schirmer I test. ConclusionDual-channel technology objectively assesses visual quality in pediatric DED, demonstrating that tear film scattering significantly affects retinal imaging and visual quality in children with DED.

Impact of Overlapping Signals on Parameterized Post-Newtonian Coefficients in Tests of Gravity

Gravitational waves have been instrumental in providing deep insights into the nature of gravity. Next-generation detectors, such as the Einstein Telescope, are predicted to have a higher detection rate given the increased sensitivity and lower cutoff frequency. However, this increased sensitivity raises challenges concerning parameter estimation due to the foreseeable overlap of signals from multiple sources. Overlapping signals (OSs), if not properly identified, may introduce biases in estimating post-Newtonian (PN) coefficients in parameterized tests of general relativity (GR). We investigate how OSs affect −1PN to 2PN terms in parameterized GR tests, examining their potential to falsely suggest GR deviations. We estimate the prevalence of such misleading signals in next-generation detectors, and their collective influence on GR tests. We compare the effects of OSs on coefficients at different PN orders, concluding that overall the 1PN coefficient suffers the most. Our findings also reveal that while a nonnegligible portion of OSs exhibit biases in PN coefficients that might individually prefer to conclude deviations from GR, collectively, the direction to deviate is random and a statistical combination will still be in favor of GR.

Numerical study of the pulsatile flow and aeroacoustics of straight and curved pipes

From an engineering point of view pulsatile pipe flows, which include the hydrodynamic and acoustic fluctuations, can cause many problems such as vibration, noise and structural fatigue etc. Knowledge of the characteristics of hydrodynamic fluctuations (pseudo sound) and acoustic waves inside pipes particularly those with bends make is crucial to pipeline vibration and noise reduction. Numerical simulation of the pulsatile pipe flows shows challenges especially in curved pipes with different flow modes compounded, and predicting the acoustic fluctuations is even tougher. In this work, the unsteady flows of a straight and curved pipe with a 90° elbow induced by a pulsatile pressure inlet were calculated by Detached Eddy Simulations (DES). The pipe acoustic fields are solved through an acoustic perturbation equation, which takes the time derivative of hydrodynamic pressure as the aeroacoustic source. The characteristics of the flow and sound fields are discussed detailly, and special attention is paid to the influence of the 90° elbow on the curved pipe flow. The results show that the amplitude of hydrodynamic pressure fluctuations decrease almost linearly along the straight pipe, and the 90° elbow has obvious local influence on the flow pressure and velocity especially in the downstream side. The acoustic field is of 1-D standing wave pattern because of the fundamental pulsation frequency lower than the pipe cutoff frequency, and the 90° elbow has only negligible effect on the acoustic field in the flow frequency range.

The improvement of device linearity in AlGaN/GaN HEMTs at millimeter-wave frequencies using dual-gate configuration

The linearity performance of the AlGaN/GaN high-electron-mobility-transistors (HEMTs) is critical for circuit applications especially at millimeter-wave frequencies. In this paper, we propose a new dual-gate (DG) configuration for linearity improvement at millimeter-wave frequencies. Using 2D simulation, we observed the improvement in device linearity by placing the additional DC gate in the source-gate access region. Adjusting the bias voltage of the DC gate modulates the horizontal electric field in the channel and controls the acceleration behavior of the channel electrons. Furthermore, such bias adjustment enhances the electron density in the channel to compensate for the transconductance (Gm) degradation. Both of these contribute to the flattening of the Gm profile for linearity improvement. The proposed DG configuration improves the C/I ratio by 10 dB compared to the conventional single gate (SG) device at 38 GHz. Additionally, a 60 % improvement in the cutoff frequency (fT) and maximum oscillation frequency (fmax) is obtained compared to the traditional DG configuration where the second gate is placed in the gate-drain drift region. This is mainly due to the reduction in gate capacitances from the redistribution of the electrons in the device. Such superior characteristics have shown great potential of the proposed device for high linearity applications at millimeter-wave frequencies.

Nature inspired algorithm based design of near ideal fractional order low pass Chebyshev filters and their realization using OTAs and CCII

Fractional order filters offer greater freedom of design and a precise control over stopband attenuation in electronic circuits and systems. This paper presents the design of a fractional order low pass Chebyshev filter (FOLCF) that achieves near-ideal response characteristics. The methodology introduced utilizes metaheuristic optimization methods, including particle swarm optimization, firefly algorithm, and grey wolf optimization. These techniques are employed to precisely adjust the filter coefficients for the orders (1+α), (2+α), and (3+α). The adjustment is carried out by comparing the desired behaviour of the FOLCF with generalized fractional order low pass transfer functions. Throughout these instances, the parameter α is varied within the range of (0, 1). The designed filters are then tested and compared on the basis of various factors. Simulation results demonstrate that the designed filters closely follow the behaviour of an ideal Chebyshev filter with maximum passband and stopband magnitude errors being −31.93 dB and −52.74 dB respectively for (1+α) order filters. These values for (2+α) and (3+α) order FOLCF have been observed to be −30.04 dB and −55.91 dB; −17.72 dB and −49.52 dB respectively. Furthermore, it has been observed that the proposed work outperforms existing state-of-the-art approaches in various aspects, including magnitude error, stopband attenuation, and cut-off frequency. The stability of the designed filters has been verified through stability analysis. Additionally, practical feasibility of the proposed FOLCF is demonstrated through SPICE simulations for α = [0.2,0.5,0.8] using second generation current conveyor (CCII) and operational transconductance amplifier (OTA) based topologies while approximating the constant phase element using fifth order continued fraction expansion. The SPICE implementations closely follow the behaviour of ideal filter with −48.67 dB and −62.8 dB as mean square errors for CCII and OTA circuits respectively, showcasing the proposed filters' superiority and practical applicability in advanced electronic design.

Investigation on electrical parameters between single and double material gate nanoribbon FETs including trap distributions

The presence of multiple interface of gate-oxide and semiconductor in Nano-ribbon FET (NR-FET) causes several defects and leads to the degraded electrical parameters. In this regard, the electrical parameters in the existence of interface trap charges (ITCs) for single material gate (SMG) and double material gate (DMG) NR-FETs are extracted using Technology Computer Aided Design (TCAD) simulator. The effect of Uniform/Gaussian ITCs at the oxide and semiconductor interface on drain current, electrostatic potential, ON current, OFF current, and threshold voltage are reported for these devices. The RF/analog performance like transconductance (gm), gate capacitance (Cgg), and cut-off frequency (fc) are reported for these structures in presence of non-ideal trap distributions. Moreover, the linearity parameters like higher order harmonics in gm (gm2 and gm3), voltage intercept points (VIP2 and VIP3), input intercept power (IIP3), and intermodulation distortion (IMD3) are highlighted for these structures. It is seen that DC, RF/analog, and linearity performance of both the NRFETs are significantly affected by Uniform and Gaussian distribution of ITCs. However, the electrical parameters in DMG NRFET is more immune to ITCs than SMG NRFET. Moreover, both the devices have ON state current in the order of 10−3 A, fc of order THz, and improved linearity behaviour in the presence of ITCs, which indicates sustainability of these devices including ITCs.

Reduced contrast sensitivity function is correlated with changes to cone photoreceptors in simple high myopia.

To investigate the contrast sensitivity function (CSF) changes in simple high myopia (SHM) and evaluate the correlations between these changes with the early changes in the retinal microstructure. This prospective study comprised 81 subjects, 20 with emmetropia (EM), 26 with low myopia and moderate myopia (LM/MM), and 35 with SHM. The area under the log CSF curve (AULCSF) and the cut-off spatial frequency (Cut-off SF) were employed as measures of CSF. Adaptive optics (AO) was employed to quantify the cone density, spacing, and regularity. The thickness and blood flow of the retinal sublayers were determined from vertical and horizontal optical coherence tomography angiography (OCTA) A-scans. Swept-source optical coherence tomography (SS-OCT) was employed to analyze the choroidal thickness (CT) and choroidal vascularity using a custom algorithm. Differences in the retinal and choroidal parameters, cone distribution, AULCSF, and Cut-off SF were compared among the three groups. Multivariate linear mixed models were used to elucidate the associations between photoreceptor morphological alterations, retinal and choroidal parameters, and AULCSF. The AULCSF and Cut-off SF were significantly lower in the SHM group compared to the EM and LM groups (p < 0.05). The SHM group had less cone density, larger cone spacing, and lower cone regularity than the EM and LM/MM groups (p < 0.05). Moreover, the thickness of the inner segment of photoreceptors (IS), retinal pigment epithelium (RPE) layer and choroid were reduced, and the outer segment of photoreceptors (OS) was thicker in the SHM group compared to the EM and LM/MM groups (all p < 0.05). A longer axial length (AL) was correlated with decreased AULCSF, cone density, and cone spacing (r = -0.800 to 0.752, all p < 0.050). Additionally, decreased CSF was correlated with lower cone density (r = 0.338, p = 0.035). Decreased contrast sensitivity was observed in patients with SHM and cone density was significantly correlated with reduced AUCSF.

Topology Optimization Design Method for Acoustic Imaging Array of Power Equipment.

Acoustic imaging technology has the advantages of non-contact and intuitive positioning. It is suitable for the rapid positioning of defects such as the mechanical loosening, discharge, and DC bias of power equipment. However, the existing research lacks the optimization design of microphone array topology. The acoustic frequency domain characteristics of typical power equipment are elaborately sorted out. After that, the cut-off frequencies of acoustic imaging instruments are determined, to meet the needs of the full bandwidth test requirements. Through a simulation calculation, the circular array is demonstrated to be the optimal shape. And the design parameters affect the imaging performance of the array to varying degrees, indicating that it is difficult to obtain the optimal array topology by an exhaustive method. Aimed at the complex working conditions of power equipment, a topology optimization design method of an acoustic imaging array for power equipment is proposed, and the global optimal solution of microphone array topology is obtained. Compared with the original array, the imaging performance of the improved LF and HF array is promoted by 54% and 49%, respectively. Combined with the simulation analysis and laboratory test, it is verified that the improved array can not only accurately locate the single sound source but also accurately identify the main sound source from the interference of the contiguous sound source.