Impulsive Source Research Articles

A Novel Calibration-Free Remote Antenna Impedance Measurement

Connecting the antenna under test (AUT) to a network analyzer through a feeding cable is a typical method for determining the input impedance. However, the induced current on the feeding cable obstructs precise measurement in the case of electrically small antennas (ESAs). A remote impedance measurement technique is proposed to address the drawbacks of network analyzer-based measurements. First, the AUT is connected to three standard loads, a short, an open, and a matched load consecutively. Then an electrostatic discharge (ESD) is used as an impulsive source to excite the AUT. Concurrently, a probe connected to an oscilloscope captures the impulse responses. Finally, the input impedance of the AUT is determined by extracting complex natural resonances (CNRs) from three impulse responses. Four different antennas are designed and prototyped. Then, using a full-wave simulator, their input impedances are computed and compared to those estimated using the proposed technique. The input impedances obtained by the proposed technique are very consistent with those from full-wave simulations.

Detecting Infrasonic Signals from Impulsive Sources on the Basis of Their Wavelet Spectrum Forms

Detecting Infrasonic Signals from Impulsive Sources on the Basis of Their Wavelet Spectrum Forms

Spurious oscillations reduction in transient diffusion and wave propagation problems discretized with the Finite Element Method

This work presents a new method, the SOR_FEM, spurious oscillation reduction-FEM, that uses analytical solutions of simple problems to find numerical solutions of more complex problems to reduce the spurious oscillations that occur due to solution discontinuity. With the proposed method it is possible to find numerical solutions without spurious oscillations of problems submitted to impulsive point sources without using any approximation for the Dirac delta function. To validate the proposed method, linear problems of heat diffusion and wave propagation in homogeneous and heterogeneous media are solved with the Finite Element Method (FEM).

Calculation of Step Discontinuities in Electric Circuits: A Time-Domain Analysis

Contribution: Two general rules for calculating, in the time domain, step discontinuities of voltages and currents in electric circuits, combining physical principles and basic mathematical treatment. The two general rules, resulting from a formal method of analysis, provide a straightforward way to update the states of a circuit, immediately after the occurrence of switching or impulsive excitation. Among its advantages, they can be used to simplify the numerical simulation of elaborate circuit topologies by avoiding approximate models of impulsive sources or switches. Background: In most engineering undergraduate textbooks, the effects of switching and impulsive sources on higher order electric circuits are usually studied for the particular case of linear time-invariant (LTI) circuits in the Laplace transform domain. This approach, however, can be time consuming and demands little reasoning on the physical principles of circuit operation. Moreover, it is not adequate for linear time-variant or nonlinear circuits. Intended Outcomes: Step discontinuities in electric circuits, caused by switching or impulsive sources, are identified and calculated through the method, allowing complete responses to be obtained afterward. Not only can the method be extended to linear time-variant and nonlinear circuits but it also has interesting consequences in numerical simulation of circuits. Application Design: An application exercise and a set of conceptual questions on the subject were proposed to electrical engineering students. Findings: The analysis of the educational experiment indicates that applying the method presented herein improves the students’ ability to obtain initial conditions of circuits, being a more straightforward and effective approach than using Laplace transform techniques.

Exploring surface source contributions to ocean ambient noise interferometry with airgun shots.

A seismic reflection survey conducted directly over two bottom-mounted hydrophones in the north-east Pacific Ocean is used to explore how surface source locations affect ambient noise interferometry for the two hydrophones. The airgun shots are used as an approximation of an impulsive sound source at a discrete location, which allows us to investigate spatial contributions to the cross correlation between the two hydrophones. Simulated and experimental results are presented. The contributions to the cross correlations are explained by different reflections off the surface or bottom of the ocean, and a discussion about what can and cannot be inferred about the emergence to the Green's function is presented.

Construction and study of instrument response functions for analysis of the National Ignition Facility (NIF) neutron time-of-flight detectors.

The analysis of the National Ignition Facility (NIF) neutron time-of-flight (nToF) detectors uses a forward-fit routine that depends critically on the instrument response functions (IRFs) of the diagnostics. The details of the IRFs used can have large impacts on measurements such as ion temperature and down-scattered ratio (DSR). Here, we report on the recent steps taken to construct and validate nToF IRFs at the NIF to an increased degree of accuracy, as well as remove the need for fixed DSR baseline offsets. The IRF is treated in two parts: a "core," measured experimentally with an x-ray impulse source, and a "tail" that occurs later in time and has limited experimental data. The tail region is calibrated with the data from indirect drive exploding pusher shots, which have little neutron scattering and are traditionally assumed to have zero DSR. Using analytic modeling estimates, the non-zero DSR for these shots is estimated. The impact of varying IRF tail components on DSR is investigated with a systematic parameter study, and good agreement is found with the non-zero DSR estimates. These approaches will be used to improve the precision and uncertainty of NIF nToF DSR measurements.

Locating impulsive sound sources in microscale urban spaces

In this work, techniques for localizing impulsive acoustic sources in an urban environment are presented. Of particular interest is the localization of sources in urban street canyons and enclosed urban areas. Sound propagation in an urban environment is strongly influenced by multiple reflections. In urban street canyons, multiple reflections tend to amplify with decreasing canyon width. A numerical investigation is performed to study the role multiple reflections on time difference of arrival (TDOA) and beamforming source localization techniques. Results of various urban street canyon and enclosed space geometries are investigated. The results and limitations of the TDOA and beamforming techniques for estimating source position in urban environments are discussed.

Proposed updates for ANSI/ASA S12.42 impulsive noise test methods

ANSI/ASA S12.42-2010 contains the first standardized test method for measuring the performance of hearing protection devices (HPDs) with high-level impulsive noise. This standard defines the impulsive peak insertion loss (IPIL) as a time-domain metric that quantifies the reduction in peak sound pressure level provided by an HPD for impulsive noises. However, IPIL as defined in S12.42-2010 is dependent on the spectrum of the impulsive noise source used for measurements of HPDs. Recent studies of HPDs with impulsive noise have led to the investigation of frequency-domain metrics and calculation methods. Using frequency-domain calculations allows IPIL to be computed for a wide range of impulsive noises, not only those used for the measurement. Consequently, significant revisions to S12.42 are under consideration. This presentation highlights select proposals including: definition and calculation of the frequency-dependent impulsive insertion loss, incorporation of frequency-domain aspects such as bone-conduction limits to attenuation, and redefinition of IPIL to be calculated from the impulsive insertion loss.

Virtual acoustic reconstruction of the Roman amphitheater of Avella in Italy

In ancient Rome, gladiator fights were very popular. The places where these shows took place were called amphitheaters, due to the particular shape of the elliptical building. Amphitheaters were widespread, and in each city, one or more of these buildings was present. This paper describes the virtual reconstruction of the acoustics of the amphitheater Avella, close to Naples, Italy. This amphitheater was discovered a few decades ago and was only partially rebuilt. Today, it is used for musical performances during the summer season mainly. The plan of the building is elliptical, and the dimensions of the arena are 35 m for the minor axis and 65 m for the major axis. Acoustic measurements were performed in the current state with an impulsive sound source and the acoustic parameters were obtained according to the ISO 3382 standard. Subsequently, from the dimensions of the current state and in analogy with the architecture of other amphitheaters existing today, a virtual reconstruction of the original shape was performed. The virtual model was developed with the architectural acoustics software Ramsete in order to obtain the acoustic characteristics of the amphitheater as it was in Roman times. In particular, the spatial distribution of the acoustic characteristics on the steps where the audience was seated is described and discussed.

Numerical modeling of infrasound propagation in a stratified atmosphere with small-scale inhomogeneities

A major focus in infrasound research is the inclusion of realistic atmospheric flows in numerical propagation models. This usually encompasses temperature gradients and horizontal wind components, which create atmospheric waveguides. Additionally, gravity waves lead to small-scale variations of the ambient wind in the middle atmosphere, between 10 and 100 km in altitude. Using an internal gravity wave model from the literature [Gardner, J. Atmos. Terr. Phys. (1996)], we parametrize random fluctuations of the wind profiles, where the initial background state is based on a published case study [Sabatini et al., J. Acoust. Soc. Am. (2016)]. Acoustic propagation from an impulsive point source located at the ground is then modelled with solvers of the PLetma package [Khodr et al., J. Acoust. Soc. Am. (2021)], namely, ray tracing, normal modes, one-way equation and FDTD, for frequencies higher than 0.01 Hz. Cases with and without wind are considered, and propagation effects are investigated by a sensitivity analysis on source parameters and characteristics of the gravity wave. [This work was conducted within the framework of LETMA, a Contractual Research Laboratory shared between CEA, CNRS, Ecole Centrale de Lyon, C-Innov, and Sorbonne Université.]

Quantifying information content of modal dispersion data in geoacoustic inversion

This paper illustrates the information content of ocean acoustic modal-dispersion data to constrain parameters and uncertainties of seabed geoacoustic models. In particular, time-frequency warping analysis is applied to extract dispersion data consisting of arrival times as a function of frequency for 18 of the first 21 propagating modes from recordings of an impulsive sound source on a vertical hydrophone array. To quantify the information content of these dispersion data to resolve seabed structure, a Bayesian inversion formulation is applied that includes rigorous approaches to model selection and data error modeling. Model selection considers both layered and gradient representations of seabed profiles using trans-dimensional inversion and Bernstein-polynomial basis functions, respectively. In both cases, model parameterizations are determined probabilistically from the data as part of the inversion. The error model assumes a multi-variate Gaussian distribution with unknown variance and covariance for each mode; covariance estimation is formulated in terms of trans-dimensional sampling of zeroth- and first-order autoregressive processes. The applicability of these assumptions/approaches is validated with qualitative (graphical) and quantitative residual analyses. Results are considered as marginal probability profiles for geoacoustic properties, which quantify the resolution of seabed structure versus sub-bottom depth. [Work supported by the Office of Naval Research.]

Posidonius’ Two Systems: Animals and Emotions in Middle Stoicism

Abstract This paper attempts to reconstruct the views of the Stoic Posidonius on the emotions, especially as presented by Galen’s On the Doctrines of Hippocrates and Plato. This is a well-studied area, and many views have been developed over the last few decades. It is also significant that the reliability of Galen’s account is openly at issue. Yet it is not clear that the interpretative possibilities have been fully demarcated. Here I develop Galen’s claim that Posidonius accepted a persistent, non-rational aspect of the soul that he connects with the merely animal part of humans. The aim is to begin from this testimony in answering two questions: (1) How might the possession of a non-rational element of the soul operate alongside the hêgemonikon (leading-part of the soul) as a source of impulse for Posidonius. (2) How does this persistent animal aspect conform to the Stoic ontological classification found in their scala naturae? I shall argue in response to these that (a) Posidonius distinguished the merely cognitive aspects of the soul from those that are rational, and (b) that the hêgemonikon itself is not to be identified with what is rational. Accepting a persistent non-rational source of emotional impulses allows Posidonius a richer framework for explaining human affective responses and behaviours. I also briefly address Galen’s motivation for the account he offers. It is in view of Posidonius’ approach to Plato’s Timaeus that Galen’s discussion finds its most plausible interpretation.

Analysis the dispersive nature of Love wave in fibre‐reinforced composite materials plate: A Green's function approach

The research article mainly focuses on investigating the dispersive behaviour of Love waves influenced by an impulsive point source in a fibre‐reinforced magnetoelastic (FRME) plate placed on functionally graded fibre‐reinforced visco‐elastic (FGFRVE) semi‐infinite stratum. The materials of the considered structure have been assumed under the influence of magnetic field and functionally graded. The functionally graded in the lower semi‐infinite space is caused by consideration of quadratic variation in the shear moduli and mass density. Maxwell's equation and generalised Ohm's law have been employed to calculate the Laurentz force in the fibre‐reinforced magnetoelastic (FRME) plate. For solving the coupled field equations, three‐dimensional Green's function and Fourier transform are applied; consequently, the closed‐form of the Love wave's dispersion relation is obtained. The obtained dispersion curve is plotted and compared in the numerical results and discussions by taking the different magnitude of materials quantities such as reinforcement parameter, magnetoelastic coupling parameter, functionally graded parameter, and visco‐elastic parameter. In some particular cases, the deduced dispersion equation is found to be identical to the classical Love wave equation for uniform homogeneous isotropic cases, indicating that the assumed structures are valid. The obtained results from the entire study can be utilised to better understand the dispersive nature of Love wave propagation in the considered systems containing fibre‐reinforced, magnetoelastic, viscoelastic, and point sources.

Development and Evaluation of a Body-Worn Dosimeter for Continuous and Impulsive Noise.

Noise exposure is encountered nearly everyday in both recreational and occupational settings, and can lead to a number of health concerns including hearing-loss, tinnitus, social-isolation and possibly dementia. Although guidelines exist to protect workers from noise, it remains a challenge to accurately quantify the noise exposure experienced by an individual due to the complexity and non-stationarity of noise sources. This is especially true for impulsive noise sources, such as weapons fire and industrial impact noise which are difficult to quantify due to technical challenges relating to sensor design and size, weight and power requirements. Because of this, personal noise dosimeters are often limited to a maximum 140 dB SPL and are not sufficient to measure impulse noise. This work details the design of a body-worn noise dosimeter (mNOISE) that processes both impulse and continuous noise ranging in level from 40 dBA-185 dBP (i.e. a quiet whisper to a shoulder fired rocket). Also detailed is the capability of the device to log the kurtosis of the sound pressure waveform in real-time, which is thought to be useful in characterizing complex noise exposures. Finally, we demonstrate the use of mNOISE in a military-flight noise environment. Clinical Relevance- On-body noise exposure monitoring can be used by audiologists industrial hygiene personnel and others to determine threshold of injury adequate hearing protection requirements and ultimately reduce permanent noise-induced hearing loss.

A Novel Solution for Resonant Scattering Using Self-consistent Boundary Conditions

We present two novel additions to the semianalytic solution of Lyα radiative transfer in spherical geometry: (1) implementation of the correct boundary condition for a steady source, and (2) solution of the time-dependent problem for an impulsive source. For the steady-state problem, the solution can be represented as a sum of two terms: a previously known analytic solution of the equation with mean intensity J = 0 at the surface, and a novel, semianalytic solution which enforces the correct boundary condition of zero-ingoing intensity at the surface. This solution is compared to that of the Monte Carlo method, which is valid at arbitrary optical depth. It is shown that the size of the correction is of order unity when the spectral peaks approach the Doppler core and decreases slowly with line center optical depth, specifically as , which may explain discrepancies seen in previous studies. For the impulsive problem, the time, spatial, and frequency dependence of the solution are expressed using an eigenfunction expansion in order to characterize the escape time distribution and emergent spectra of photons. It is shown that the lowest-order eigenfrequency agrees well with the decay rate found in the Monte Carlo escape time distribution at sufficiently large line center optical depths. The characterization of the escape time distribution highlights the potential for a Monte Carlo acceleration method, which would sample photon escape properties from distributions rather than calculating every photon scattering, thereby reducing computational demand.

Analysis of Spontaneous and Implicit Internal Self-Excitation in Aircraft Variable Frequency AC Power System Based on Dual-Stator Winding Induction Generator

The dual-stator winding induction generator (DWIG) is an alternative main generator in a variable frequency ac power system. So far, the existing studies have not covered the issue of DWIGs excitation controllability, which is a matter of importance for airworthiness. In this article, we develop an impedance-based modeling and analysis technique to investigate DWIGs excitation controllability. Two related topics are presented: the spontaneous self-excitation analysis in uncontrolled system and the implicit internal self-excitation pattern analysis in actively controlled system. In the topic about spontaneous self-excitation, a virtual impulse source technique is developed to derive the impedance-based method properly in the analysis for uncontrolled DWIG. In the second topic, the analysis performed in the presence of a closed-loop controller figures out the same underlying mechanism in both the plant's open-loop stability and the spontaneous self-excitation. The experimental results verify the proposed analysis and techniques that benefit the comprehensive understanding and practical application of DWIG-based power system.

Love-type surface wave propagation due to interior impulsive point source in a homogeneous-coated anisotropic poroelastic layer over a non-homogeneous extended substance

The paper is concerned with the effect of an impulsive point source on the Love-type surface wave propagation in an anisotropic poroelastic medium coated with an isotropic homogeneous thin layer over an infinite extent anisotropic non-homogeneous substance. The material properties of both the layer and extended medium are restricted on linear elasticity. Also, the transmissions of waves are considered as usually incidental transient. Infinitely extended medium is considered highly non-homogeneity with rigidity and density, which varies exponentially with depth. The closed-form equation of motion is formulated in each layered media depending on the conditional property of the surface seismic wave. Due to the presence of an impulsive point source at the interface of the intermediate layer and infinitely extended layer, a force density distribution function in the form of the Dirac-delta function is performed with the equations of motion. Green's function approach is demonstrated to obtain the closed-form dispersion relation of the Love-type wave. Attenuation analysis and numerical error analysis of the dispersive wave are performed for the complex quantity of the wavenumber and error percentage of the main dispersion. The validity of the Love-type dispersive wave is examined with the help of some particular cases. The theoretical prediction of phase and group velocities are illustrated numerically using MATLAB software. A short movie (link) of group velocity is created to show the changes of wave amplitude with porosity. It is observed that the phase/group velocity is highly affected by porosity, non-homogeneity, anisotropy, thickness of the layer, coated layer and attenuation coefficient. The derivation and analysis of the structural model bear the promise of having important applications in the field of seismology and civil engineering, particularly in the studies related to earthquakes and mechanical explosions on the near-surface of the Earth.

무용에서 에로스의 예술적 충동에 관한 연구

Eros is an important element and means of completing ''mental eros'' as a spiritual communion between the creator (dancer) and the listener (audience). Plato''s eros is the beauty of the soul that transcends the beauty of the body. When we call the existence of a world of the soul that cannot be seen with our eyes as ''idea'', in the invisible world, the audience reaches the spiritual pleasure by feeling and understanding the abstract image of the creator from the inner world. You could call it a desire. We experience, feel, touch, and perceive objects through our bodies. The body (body) is an absolute being with sensory perception, but it is regarded as a worldly thing with respect to reason and truth. When we experience an object, the only way we can easily approach it is through our bodily sense organs. The moment we experience, sense, and perceive an object, we feel a sense of satisfaction for the soul. In works of art, the dancer is conscious of the movement of her body (body), senses the audience''s reaction through the senses of the body, and the process of aesthetic experience felt through the vividly expressed movement of the dancer is the source of artistic impulse. After all, the soul interacts with the body in the body, revealing certain qualities. Seen in this way, in a large sense, the audience is the spiritual aspect of the figure with the potential of the vitality of the soul (eros), and the dancer is an artistic pathway leading to perfection by combining the emotions that show their potential through movement into the soul and body. it''s sam.

A combined deep learning and physical modelling method for estimating air pollutants’ source location and emission profile in street canyons

Roadside air pollution monitoring stations have become frequently available for street canyons. To efficiently estimate source location and emission profile in street canyons, this study developed a combined deep learning and physical modelling method using the monitoring data as inputs. First, a deep neural network (DNN) was constructed for locating the source. The training datasets were generated from numerical simulations by the computational fluid dynamics (CFD)-Markov chain model. An inverse method based on Tikhonov regularization was then used to estimate the emission profile. Finally, the Markov chain model was used to calculate the air pollutant distribution in the whole street canyon. Case studies were conducted to demonstrate the performance of the proposed method. For the unit impulse source in the 2-D ventilated chamber of 27 m2, the source in 83% of the cases were accurately identified, and in another 13% of the cases, the identified source was within 0.4 m to the true location. For the continuous pollutant source with varying emission profile in the 3-D street canyon with an area of 25,600 m2, the source in 36% of the cases were accurately located, and in another 52% of the cases, it was within 10 m from the true location.

Diagnosis and treatment of ventricular arrhythmias in the practice of a family doctor

Ventricular arrhythmia (VA) is a disorder in the frequency, rhythm, and sequence of myocardial excitation-contraction caused by an impulse source that is localized below the bundle of His: in the region of the branches of the bundle of His, in the Purkinje fibers or directly in the muscular thickness of the heart ventricles (ectopic focus of excitation). Thus, at first the myocardium of that ventricle in the conducting system of which an ectopic focus of excitation has arisen is excited, then, the impulse passes to the other branch of the His bundle along the anastomoses and causes excitation of the other ventricle. Ventricular arrhythmia (VA) has many causes, and each of them is of significant importance. Often, ventricular arrhythmia (VA) occurs in healthy people, with an accidental ECG recording; as a rule, these are young and middle-aged people. The incidence of this pathology is increasing every year in the world, despite good drug support. Ventricular arrhythmia (VA) is predominantly observed in the developed countries of the world, where there are prerequisites for this (stress, overwork, high workload).