Amplitude Density Research Articles

Systemic Hypothermia in the Acute Management of Traumatic Optic Neuropathy in a Murine Animal Model.

To examine the effects of systemic hypothermia on retinal ganglion cell survival and visual outcomes after optic nerve trauma in a sonication-inducted traumatic optic neuropathy murine animal model. Twenty mice underwent sonication-inducted traumatic optic neuropathy. Afterward, 10 mice were placed on a warming pad set to 36°C, and 10 mice were placed on a table. General anesthesia was maintained for 3 hours with subcutaneous injections of ketamine. The rectal temperature was measured every 15 minutes. Pattern electroretinograms were obtained at 2, 4, and 6 weeks. Mice were sacrificed at 6 weeks, and retinal ganglion cell counts were performed. The hypothermia group had an average rectal temperature of 23.1°C; the control group was 33.3°C. At 6 weeks, the hypothermia group had larger a-wave amplitudes (18.19 µV) than the control group (12.75 µV) (p < 0.05). At 6 weeks, retinal ganglion cell density over the entire retina was significantly higher in the hypothermia group versus the control (p < 0.0001). The hypothermia treatment group had significantly higher retinal ganglion cell density and pattern electroretinogram a-wave amplitudes 6 weeks after injury than the control group. Systemic hypothermia may have a neuroprotective effect when initiated immediately after sonication-inducted traumatic optic neuropathy.

Intrinsic versus extrinsic contribution to intraindividual sweat rate variability of individual eccrine glands

The purpose of the current study was twofold. First, to determine the intraindividual variability of sweat rate per gland for a given skin location during exercise in the heat. Second, to determine the relative importance of intrinsic vs. extrinsic factors as the source of the intraindividual variability in sweat rate per gland. Sweat rate of individual eccrine glands on the forearm was measured following pilocarpine iontophoresis and during exercise in the heat. In five participants during exercise in the heat the measured sweat rate for individual forearm eccrine glands (n = 500) ranged from 0.5 nL/gland/min to 16 nL/gland/min, or over a 30-fold difference. The mean (SD) intraindividual coefficient of variation in sweat rate per gland was 36 (5)% and 49 (10)% (p = 0.008) following pilocarpine iontophoresis and during exercise in the heat, respectively. Such results suggest that intrinsic factors (i.e., sweat gland size and cholinergic sensitivity) contribute approximately three times more than extrinsic factors (i.e., sweat gland nerve fiber density and threshold amplitude) towards explaining the large intra-person variability in sweat rate per gland seen during exercise in the heat.

Testing and simulation of the hysteresis characteristics of magnetostrictive materials under harmonic excitation

As various power electronic devices are widely used in the power grid, the current flowing through the drive winding of the magnetostrictive actuator inevitably contains harmonic components. The flux density within the hysteresis material is non-sinusoidal with harmonic components, which distorts the hysteresis characteristics of the material and affects the accurate calculation of losses. This paper builds a harmonic magnetic performance testing platform for magnetostrictive materials to test and analyze the magnetic properties under different excitation conditions (magnetic density amplitude, harmonic order, and harmonic content). To complete the mathematical description of the static hysteresis model containing closed minor hysteresis loops, two pinning coefficients k1(Bn,kTHD) and k2(Bn,kTHD), which are related to the degree of harmonic distortion, are used to express the rate of change of the irreversible magnetization components. Fractional order derivative and harmonic frequency-dependent terms are used to characterize the eddy losses and excess losses mathematically. Finally, the dynamic hysteresis model under harmonic excitation is developed. Comparative analysis of model calculation results and experimental test data shows that the model can not only accurately simulate the distorted hysteresis characteristics but also predict the loss of magnetostrictive materials. This research is of significance to the optimal design and temperature rise analysis of magnetostrictive devices.

FRACTAL-BASED MODELING OF RAIL ROUGHNESS

This paper uses fractal modeling techniques to effectively depict the roughness characteristics of the rails examined in this study by means of both the structure function and the Weierstrass–Mandelbrot function to capture the intricate nature of the rail roughness. Experimental analysis of the roughness of the railway rails from Faurei Railway Testing Center (RTC Faurei) in Romania proves that the roughness height exhibits distinct mathematical fractal characteristics. The study evaluated and compared 41 classical statistical parameters derived from roughness measurements with simulated fractal parameters. The classical roughness parameters, including the Autocorrelation function, Amplitude Density Function, as well as Bearing Area Curves, and rail acoustic roughness, were determined from a profile obtained using the Weierstrass function and compared to the measured ones, revealing a noticeable congruence between the generated charts. The research findings indicate a strong convergence between experimental measurements and simulated profiles, with most parameters falling within a 10% relative error range. This aspect highlights the approach of fractal potent in assessing rail roughness behavior. Consequently, the simulated parameters could potentially analyze rail roughness quality to maintain and track grinding and mitigate the rolling noise.

Experimental measurement of track irregularities in EMS maglev systems using the mid-chord offset method and inverse filtering technology

Track irregularities are the main factors causing changes in suspension stability and vibrations in EMS (Electro-magnetic Suspension) maglev trains. Due to the scarcity of actual measurement data on EMS maglev track irregularities, this paper utilizes the principles of the mid-chord offset method to develop a track irregularity detector with a 1-m test chord length. Tests were conducted on the maglev line in Qingyuan, Guangdong. Based on the “using small to predict large” algorithm, data simulating a 3-m test chord length were output. The experimental data were processed to remove trend items and outliers, and an inverse filter was designed to counteract the amplitude gain error of the mid-chord offset method, obtaining accurate data on vertical and lateral track irregularities. The results show that the amplitude and power spectral density (PSD) fluctuations of track irregularities on the left and right rails of the measured line section are similar, with height irregularities of 2.5–3 mm and alignment irregularities of 1–1.5 mm. Periodic wavelength components related to the longitudinal spacing of sleepers, rail length, and beam span, such as 1.2 m, 6.5 m, 12.5 m, and 25 m, are evident, highlighting the need for enhanced inspection and maintenance of these structural components in engineering projects.

Dysfunction and Morphological Involvement of Inner Macular Layers in Glaucoma.

Objectives: This study aimed to study the inner retina functional and morphological impairment of retinal ganglion cells (RGCs) from specific macular rings and sectors to identify whether selective macular regions were more vulnerable than others within the 20 central degrees in patients with open-angle glaucoma (OAG). Methods: In total, 21 OAG patients [mean age 50.19 ± 7.86 years, Humphrey Field Analyzer (HFA) 24-2 mean deviation (MD) between -5.02 and -22.38 dB, HFA 10-2 MD between -3.07 and -17.38 dB], providing 21 eyes, were enrolled in this retrospective case-control study. And 20 age-similar healthy subjects, providing 20 eyes, served as controls. The multifocal photopic negative response (mfPhNR) response amplitude density (RAD) from concentric rings and macular sectors and ganglion cell layer thickness (GCL-T) assessed by Spectral Domain-Optical Coherence Tomography (SD-OCT) was measured. Mean RAD and GCL-T values were compared between OAG and control ones by ANOVA. In OAG eyes, the relationship between mfPhNR and SD-OCT data was examined by linear regression analysis, and Pearson's correlation coefficients were computed. Results: In considering all rings and sectors, compared to the controls, the OAG group showed a significant (p < 0.01) reduction in mean mfPhNR RAD and in GCL-T values with the greatest reduction in the central area. In OAG eyes, a significant (p < 0.01) correlation between all mfPhNR RAD and GCL-T values, with significant (p < 0.01) correlation coefficients, were found. Conclusions: In OAG eyes, RGC dysfunction was detectable by abnormal mfPhNR responses in localized macular areas, mainly in the central one. Localized macular RGC dysfunction was linearly correlated with the GCL morphological changes.

Density Fluctuations in the Intracluster Medium: An Attempt to Constrain Viscosity with Cosmological Simulations

The impact of viscosity in the intracluster medium (ICM) is still an open question in astrophysics. To address this problem, we have run a set of cosmological simulations of three galaxy clusters with a mass larger than M Vir > 1015 M ⊙ at z = 0 using the smoothed particle magnetohydrodynamics-code OpenGadget3. We aim to quantify the influence of viscosity and constrain its value in the ICM. Our results show significant morphological differences at small scales, temperature variations, and density fluctuations induced by viscosity. We observe a suppression of instabilities at small scales, resulting in a more filamentary structure and a larger amount of small structures due to the lack of mixing with the medium. The conversion of kinetic to internal energy leads to an increase of the virial temperature of the cluster of ∼5%–10%, while the denser regions remain cold. The amplitude of density and velocity fluctuations are found to increase with viscosity. However, comparison with observational data indicates that the simulations, regardless of the viscosity, match the observed slope of the amplitude of density fluctuations, challenging the direct constraint of viscosity solely through density fluctuations. Furthermore, the ratio of density to velocity fluctuations remains close to 1 regardless of the amount of viscosity, in agreement with the theoretical expectations. Our results show for the first time in a cosmological simulation of a galaxy cluster the effect of viscosity in the ICM, a study that is currently missing in the literature.

Boosting gravitational waves: a review of kinematic effects on amplitude, polarization, frequency and energy density

AbstractWe review the kinematic effects on a gravitational wave due to either a peculiar motion of the astrophysical source emitting it or a local motion of the observer. Working in the context of general relativity, we show at fully non-linear order in velocity, that the amplitude of the wave is amplified by the Doppler factor in the case in which the source moves with respect to a reference frame, while it is invariant if the observer moves (with respect to a reference observer). However, the observed specific intensity transforms in the same way under a boost of the source or of the observer. We also show at fully non-linear order that under a boost (of either source or observer), the polarization tensor is rotated in the same way the wave direction is rotated by aberration, such that the only net effect of a boost on polarization is to change the phase of the helicity components. We apply these results to a wave emitted by a binary system of compact objects in the cosmological context.

A perspective on conditional spectrum-based determination of response statistics of nonlinear systems

This work focuses on determining the stochastic response properties, in the frequency domain, of a general class of nonlinear systems with polynomial nonlinearities. Specifically, the results are presented in terms of the stationary power spectral densities of the system's displacement and velocity. This is pursued by revisiting the conditional power spectrum concept, with the assumption that the response process is both ergodic and pseudo-harmonic and characterized by an amplitude, and a phase. A theoretical elucidation of an existing formula for the conditional spectrum is attempted. In particular, this concept is interpreted in conjunction with the time averaging approximation made in the definition of the stationary probability density function of a response amplitude quantity, associated with the original nonlinear system. It is shown that a proper definition of the stationary probability density of the response amplitude, along with a reasonable treatment of the distribution over the frequency domain of the amplitude contribution, lead to an improved approximation of the stationary response power spectral density. The treatment involves the averaging of a population of surrogate spectral densities of stationary random responses conforming with the system responses associated with individual values of the amplitudes of the responses. The semi-analytical results have been quite favourably juxtaposed with a large suite of à propos Monte Carlo simulations, both in terms of the shape and of the range of the involved germane frequencies, even for strongly nonlinear systems.

Core Loss Analysis of Axial Modular Flux Switching Permanent Magnet Machine Considering the Impact of No‐Magnetic Ring

This paper investigates the relationship between the distributions of the core loss and the flux density harmonic amplitude along the axial direction in an axial‐modular flux‐switching permanent‐magnet (AM‐FSPM) machine. The flux leakage in the no‐magnetic ring leads to an uneven distribution of flux density in the core due to the modular cooperation structure. Subsequently, variations in the fundamental flux density amplitudes in the PM field and the armature reaction field are obtained with changes in the thickness of the no‐magnetic ring. In addition, the impact of no‐magnetic ring thickness on machine torque and core loss is analyzed to determine the optimal thickness for the no‐magnetic ring. Finally, the validity of the theoretical analysis is confirmed by experimental validation. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Quasi-invariant states

In this paper, we develop the theory of quasi-invariant (respectively, strongly quasi-invariant) states under the action of a group [Formula: see text] of normal ∗-automorphisms of a ∗-algebra (or von Neumann algebra) [Formula: see text]. We prove that these states are naturally associated to left-[Formula: see text]-[Formula: see text]-cocycles. If [Formula: see text] is compact, the structure of strongly [Formula: see text]-quasi-invariant states is determined. For any [Formula: see text]-strongly quasi-invariant state [Formula: see text], we construct a unitary representation associated to the triple [Formula: see text]. We prove, under some conditions, that any quantum Markov chain with commuting, invertible and Hermitian conditional density amplitudes on a countable tensor product of type I factors is strongly quasi-invariant with respect to the natural action of the group [Formula: see text] of local permutations and we give the explicit form of the associated cocycle. This provides a family of nontrivial examples of strongly quasi-invariant states for locally compact groups obtained as inductive limit of an increasing sequence of compact groups.

Multi-Objective Optimization Analysis of Electromagnetic Performance of Permanent Magnet Synchronous Motors Based on the PSO Algorithm

In order to optimize the electromagnetic performance of a permanent magnet synchronous motor (PMSM) during operation, this paper takes the size of the stator slot structure of the motor as the optimization variable and the peak cogging torque and no-load back electromotive force (EMF) amplitude of the motor as the optimization objectives. A multi-objective optimization method based on the particle swarm optimization (PSO) algorithm is adopted to obtain a structural parameter combination that minimizes the peak cogging torque and no-load back EMF amplitude while meeting the reasonable range requirements of magnetic flux density amplitude. The optimized motor structure design prototype is experimentally verified. The results show that through multi-objective optimization based on the PSO algorithm, the electromagnetic performance of the motor has been improved, with a reduction of 36.33% in peak cogging torque and 2.65% in peak no-load back EMF, indicating a reasonable magnetic flux density amplitude. The experimental results of the optimized prototype show that the difference between the theoretical simulation values and the experimental values is within a reasonable range, which verifies the effectiveness of the multi-objective optimization method.

Adaptation of an Eddy Current Model for Characterizing Subsurface Defects in CFRP Plates Using FEM Analysis Based on Energy Functional

In this work, a known Eddy Current (EC) model is adapted to characterize subsurface defects in carbon fiber-reinforced polymer (CFRP) plates intended for the civil aerospace industry. The considered defects include delaminations, microcracks, porosity, fiber breakage, and the simultaneous presence of these defects. Each defect is modeled as an additive variation in the material’s electrical conductivity tensor, allowing for a detailed mathematical representation of the defect’s influence on the CFRP’s electromagnetic behavior. The additivity of the variations in the conductivity tensor is justified by the assumption that the defects are not visible to the naked eye, implying that the material does not require non-destructive testing. The adapted EC model admits a unique and stable solution by verifying that all analytical steps are satisfied. To reconstruct 2D maps of the magnetic flux density amplitude, a FEM formulation is adopted, based on the energy functional because it ensures a stable and consistent numerical formulation given its coercivity. Moreover, the numerical approach allows precise and reliable numerical solutions, enhancing the capability to detect and quantify defects. The numerical results show that the obtained 2D maps are entirely superimposable on those highlighting the distribution of mechanical stress states known in the literature, offering a clear advantage in terms of detection costs. This approach provides an effective and economical solution for the non-destructive inspection of CFRP, ensuring accurate and timely defect diagnosis for maintaining structural integrity.

Effect of nozzles on disease control with spraying fungicides in soybean crops

ABSTRACT The productivity of the soybean crop (Glycine max) can be limited by several factors, including diseases. In the integrated management of diseases, one of the strategies used is chemical control. The aim of this experiment was to evaluate the influence of spray nozzle types on the chemical control of fungal diseases in soybean plants. The experimental design was randomised blocks, with six treatments and four replications. The treatments consisted of control (without fungicide application on soybean plants) and application of fungicides with different spray nozzles: hollow cone jet, double flat jet, extended range flat jet, wide angle flat jet and air induction flat jet. The sprayer used was the backpack pressurised by carbon dioxide CO2. The experiment was installed in the Campos Gerais region (Paraná, Brazil); during three cropping seasons. The evaluated variables were incidence and severity, spray quality (covered area, droplet density, and relative amplitude) and yield components. It was concluded that the chemical control of fungal diseases in soybean plants reduced the proliferation of pathogens and losses in crop yield. There were significant changes in spraying quality in all analysed variables. There were no differences among the spray nozzle types regarding the analysis of incidence, severity and soybean yield components.

Comparison of non-invasive magnetomyography to Brink score for assessment of pelvic floor muscle strength.

Objective.Levator ani muscles undergo significant stretching and micro-trauma at childbirth. The goal was to assess the neuromuscular integrity of this muscle group by means of magnetomyography (MMG) and correlate with Brink score-a commonly used digital assessment of pelvic floor muscle strength.Approach.Non-invasive MMG data was collected on 22 pregnant women during rest and voluntary contraction of the pelvic-floor muscles (Kegels). The mean amplitude and power spectral density (PSD) of the Kegels were correlated to Brink pressure score.Main Results.The modified Brink pressure score demonstrated medium correlations (⩾0.3) with MMG amplitude and PSD with the average Kegel of medium intensity and rest. Data showed that the 'resting state' of the pelvic floor is, in actuality, quite dynamic and may have implications for pelvic floor disorder propensity postpartum.Significance.These results confirm the ability of non-invasive MMG to reliably capture pelvic floor contraction as these signals correlate with clinical measure.

Constitutive modelling of a dry sand–structure interface under high-frequency vibration with a constant normal load

Sand–structure interfaces undergo strength loss and volume contraction under high-frequency vibration, potentially compromising the performance of underground structures in high-speed railway engineering. However, an appropriate method for quantitatively characterizing the behaviour of the sand–structure interface under high-frequency vibration is currently lacking, impeding the advancement of related design methods. In this work, the primary deformation and strength characteristics, such as the evolution of shear stress and volumetric strain, of the dry sand–structure interface under high-frequency vibration are summarized via a modified direct shear apparatus under a constant normal load. The concept of “vibro-induced virtual pore pressure” is subsequently introduced to modify the expressions of the critical state, yield, and bounding surfaces. The relationships between vibro-induced volume contraction and the vibration stress amplitude and state parameters are also established. Ultimately, a constitutive model describing the behaviour of the dry sand–structure interface under high-frequency vibration is formulated within the frameworks of critical state soil mechanics and bounding surface plasticity. The model comprises 14 parameters, all of which can be calibrated via laboratory experiments. Through comparison with experimental observations, the model is found to accurately simulate the key behaviours of the dry sand–structure interface under both static and high-frequency vibration conditions with a constant normal load, effectively reflecting the influence of the density, normal stress, and vibration stress amplitude of the sample.

Charge separation at liquid interfaces

We present a theory for phase-separated liquid coacervates with salt, taking into account spatial heterogeneities and interfacial profiles. We find that charged layers of alternating sign can form around the interface while the bulk phases remain approximately charge neutral. We show that the salt concentration regulates the number of layers and the amplitude of the layer's charge density and electrostatic potential. Such charged layers can either repel or attract single-charged molecules diffusing across the interface. Our theory could be relevant for artificial systems and biomolecular condensates in cells. Our work suggests that interfaces of biomolecular condensates could mediate charge-specific transport similar to membrane-bound compartments. Published by the American Physical Society 2024

Spatial distribution of plasma density and magnetic field amplitude in the dayside magnetosheath as a function of the IMF orientation

The properties of the magnetosheath are of pivotal importance in determining the coupling between the magnetosphere and interplanetary medium. In particular, the magnetic flux pileup and plasma depletion layer (PDL) modify the boundary conditions of magnetopause reconnection. However, the spatial distribution of the magnetic field strength and plasma density in the magnetosheath and their functional dependence on the interplanetary magnetic field (IMF) orientation remain poorly understood. This study characterizes these aspects in detail through the statistical processing of decades of data from Cluster, Double Star, THEMIS, and Magnetospheric Multiscale (MMS) missions. The first part of this study focuses on the poorly known variations across the magnetosheath, from the shock to the magnetopause. The magnetic pileup and PDL are significantly correlated, with a strong dependence on the IMF cone angle. Their dependence on the IMF clock angle is found only near the magnetopause, consistent with the expected effect of magnetic reconnection. The second part of this study examines the asymmetry in the magnetic field amplitude and density between the quasi-parallel and quasi-perpendicular sides of the equatorial magnetosheath. These asymmetries are characterized for different relative distances to the magnetopause and bow shock boundaries and for different IMF orientation. The magnetic field amplitude, observed to be higher on the quasi-perpendicular side of the magnetosheath, becomes more symmetric as it approaches the magnetopause. The quasi-parallel magnetosheath exhibits a higher plasma density near the magnetopause. However, this asymmetry reverses at approximately the mid-magnetosheath with a decreasing IMF cone angle.

Sparse reconstruction methods for wideband source localization in spherical harmonics domain

Wideband acoustic source localization is a challenging task especially in the presence of noise. Generally wideband source localization is done by averaging the Direction of Arrival (DOA) estimates obtained over multiple frequencies or narrow subbands by the method of frequency smoothing. Localization of multiple wideband sources which are correlated is even more challenging. In this work acoustic source localization under these challenging conditions is addressed. A sparse reconstruction framework is developed for wideband source localization in the Spherical Harmonics (SH) domain. The proposed framework jointly computes both the azimuth and elevation. In contrast to earlier methods of source localization in the SH domain, this work utilizes the expression for the SH coefficients of the amplitude density of the plane wave, to develop the sparse reconstruction framework. An expression for Cramér Rao Lower Bound (CRLB) on the DOA using this framework is also derived for the wideband sources. This CRLB is shown to easily generalize for narrowband sources as well. The performance of the proposed method is compared with MUltiple Signal Classification in SH domain (MUSIC-SH), Steered Response Power in SH domain (SRP-SH), MUSIC with Direct Path Dominance test in SH domain (MUSIC-DPD-SH) and Pressure based Compressive Sensing in SH domain (PCS-SH). The performance is evaluated for correlated narrowband and wideband sources through simulations, conducting experiments in an anechoic chamber and under reverberant conditions. Using the proposed framework, it is shown that correlated narrowband and wideband sources can be resolved reasonably well when compared to conventional methods of acoustic source localization in SH domain.

Laser driven wake wave in pair-ion electron plasma with inclusion of ion dynamics

The generation of laser driven plasma wake wave has been investigated in hydrogen pair-ion electron plasma. The consideration of dynamics of the positive and negative ion pair have been adopted. Inclusion of the ion motion has the effect of modifying the electric field and density profiles of the wake wave. This has been demonstrated by observing the variation of the electron density and electric field profiles with the change in positive ion/negative ion concentration. High density spikes and sawtooth like electric field profiles (indication of wave breaking) are observed to transform into sinusoidal electric field profile and low amplitude density profile when the positive ion density in the plasma system is kept higher. Furthermore, we observe the variation of the electric field amplitude of the wake wave with the laser pulse width. This feature is the indication of the possibility of hybrid acceleration (Direct Laser Acceleration and wake field acceleration) of accelerated beam. The results are quite relevant in laser plasma interaction field in experimental physics and also in planetary environment.