non-Gaussian Pulse Research Articles

To the revision of the ISO 1999:2013 standard "Acoustics. Assessment of hearing loss due to noise exposure": an excessive correction for the "impulsiveness" of noise

Introduction. In connection with the development of measuring and computer technology, new opportunities and approaches are opening up to solve the problem of measurement, hygienic assessment, normalization and prediction of hearing impairment from exposure to unstable, in particular, pulse noise.
 The study aims to analyze the applicability of a model for assessing hearing loss based on the use of an excessive correction to the exposure of impacting noise, according to the draft ISO 1999:2023 standard.
 Materials and methods. The scientists have conducted an expert and analytical comparative analysis of ISO 1999 standards, which define the basis for assessing hearing loss due to noise exposure. The experts have carried out a literary review of domestic and foreign sources on the problem of using the index of the distribution of instantaneous values of sound pressure — excess to assess constant and non-constant noise, as well as its role in the formation of hearing loss under the action of non-Gaussian pulse noise, the applicability of the prediction model of the ISO 1999 standard to various types of noise exposure.
 Results. The scientists presented the results of the analysis of: indicators for assessing the adverse effects of non-constant, including pulse noise; the relationship between the effects of non-Gaussian noise and the constant shift in the hearing thresholds of workers; statistical indicator of excess — an indirect indicator of the temporal structure of noise, a significant risk factor in combination with noise exposure in the assessment of hearing loss.
 Conclusion. Revision of the ISO 1999:2013 standard with the introduction of a new indicator of the temporal structure of noise — kurtosis, will improve the accuracy of the method of predicting hearing loss when exposed to constant, non-constant noise, including impulsive.
 Ethics. In preparing the article, the authors were guided by the ethical principles of medical research set out in the Helsinki Declaration of the World Medical Association of the last revision.
 Limitation. Features of ISO 1999 standards dedicated to the assessment of the impact of industrial noise and the assessment of noise-induced hearing impairment.

Reflection and transmission of electromagnetic pulses at a planar dielectric interface: Theory and quantum lattice simulations

There is considerable interest in the application of quantum information science to advance computations in plasma physics. A particular point of curiosity is whether it is possible to take advantage of quantum computers to speed up numerical simulations relative to conventional computers. Many of the topics in fusion plasma physics are classical in nature. In order to implement them on quantum computers, it will require couching a classical problem in the language of quantum mechanics. Electromagnetic waves are routinely used in fusion experiments to heat a plasma or to generate currents in the plasma. The propagation of electromagnetic waves is described by Maxwell equations with an appropriate description of the plasma as a dielectric medium. Before advancing to the tensor dielectric of a magnetized plasma, this paper considers electromagnetic wave propagation in a one-dimensional inhomogeneous scalar dielectric. The classic theory of scattering of plane electromagnetic waves at a planar interface, separating two different dielectric media, leads to Fresnel equations for reflection and transmission coefficients. In contrast to plane waves, this paper is on the reflection and transmission of a spatially confined electromagnetic pulse. Following an analytical formulation for the scattering of a Gaussian pulse, it is deduced that the maximum transmission coefficient for a pulse is n2/n1 times that for a plane wave; the incident and transmitted pulses propagate in dielectric media with refractive indices n1 and n2, respectively. The analytical theory is complemented by numerical simulations using a quantum lattice algorithm for Maxwell equations. The algorithm, based on the Riemann–Silberstein–Weber representation of the electromagnetic fields and expressed in terms of qubits, is an interleaved sequence of entangling operators at each lattice site and unitary streaming operators, which transmit information from one site to an adjacent lattice site. Besides substantiating results from the theory for Gaussian pulses, numerical simulations show their validity for non-Gaussian pulses. Apart from their time-asymptotic forms, the simulations display an interplay between the incident, reflected, and transmitted pulses in the vicinity of the transition region between two dielectric media.

Analytical modeling of XPM in dispersion-managed coherent fiber-optic systems.

An analytical model for the cross-phase modulation (XPM) variance in dispersion-managed coherent fiber-optic systems is developed based on the first order perturbation theory. The XPM variance is analytically calculated for arbitrary pulse shapes. For a non-Gaussian pulse, the summation of time-shifted Gaussian pulses is used to fit the target pulse shape, which not only provides a good approximation of the non-Gaussian pulse but also allows explicit derivation of the XPM variance. The analytically estimated XPM variance is found to be in good agreement with numerical simulations.

Analytical modeling of a single channel nonlinear fiber optic system based on QPSK

A first order perturbation theory is used to develop analytical expressions for the power spectral density (PSD) of the nonlinear distortions due to intra-channel four-wave mixing (IFWM). For non-Gaussian pulses, the PSD can not be calculated analytically. However, using the stationary phase approximations, we found that convolutions become simple multiplications and a simple analytical expression for the PSD of the nonlinear distortion is found. The PSD of the nonlinear distortion is combined with the amplified spontaneous emission (ASE) PSD to obtain the total variance and bit error ratio (BER). The analytically estimated BER is found to be in good agreement with numerical simulations.

Signal processing of Thomson scattering data in a noisy environment in ASDEX Upgrade

For the Thomson scattering diagnostic in the ASDEX Upgrade tokamak, new transient recorders for acquiring the time evolution of the scattering pulses are used. Instead of integrating over the scattering pulse, as performed by the usually applied charge-sensitive analogue-to-digital converters (ADCs), a non-Gaussian pulse shape is fitted to the measured scattering signal. Both in this fitting procedure and in determination of the electron density and temperature from the scattering signals, correlated noise is taken into account. The number of outliers due to perturbations of the scattering signal is substantially reduced and the resulting electron density and temperature values are of higher accuracy than those that were obtained with the evaluation method based on charge-sensitive ADCs. The minimum electron density, detectable with a signal-to-noise ratio of 1, is now at ne = 0.75 × 1018 m−3, which is a factor of 3 lower than that obtained with the evaluation based on the integration over the scattering pulse.

Non-Gaussian Pulse Propagation and Pulse Quality Factor Using Intensity Moment Method

The propagation of ultra-short light pulses with nonlinear chirp and arbitrary amplitude profile is treated by using first-order and second-order intensity moments in temporal domain. A generalized pulse complex parameter P-1 is introduced and its propagation law through dispersive systems is derived. The pulse quality factor Mτ2 is introduced. As an example, the propagation of pulses with sech-type amplitude profile through dispersive media is included. This method is proved to be a simple way to treat the propagation of non-Gaussian pulses through dispersive system compared with the temporal integral.

Nonclassical secretory dynamics of LH revealed by hypothalamo-hypophyseal portal sampling of sheep.

Continuous withdrawal of hypophyseal portal blood from unrestrained sheep has permitted detailed assessments of the pulsatile secretion of gonadotrophin-releasing hormone (GnRH). To determine if this blood can also be used to characterize the sensory dynamics of pituitary hormones, patterns of luteinizing hormone (LH) in the hypophyseal portal blood of ovariectomized ewes was compared with previous patterns of GnRH and peripheral LH. Hypophyseal portal blood and jugular vein blood were collected every 5 min from six ovariectomized ewes over 6-12 h. Hypophyseal portal blood contained GnRH-associated, sharply defined LH pulses that were much larger than in the periphery. Pulses of secreted LH (hypophyseal portal LH less peripheral LH) showed much faster rates of rise and fall than peripheral and followed pulses of GnRH by an average of 1.26 min. In contrast to pulses in jugular blood, secreted LH pulses often reached a relatively unchanging interpulse nadir-plateau and thereby approached closely algorithm-estimated, extrapolated baselines. The interpulse baseline concentrations of secreted LH (99.6 ng/mL) in hypophyseal portal blood were 31-fold higher than those for jugular LH (3.23 ng/mL). These elevated concentrations also exceeded mean jugular peak concentrations (11.1 ng/mL) and, thus, primarily must represent newly secreted LH. The non-Gaussian profiles of this secreted LH were substantially more complex than the inputs predicted from jugular LH measurements by deconvolution. Furthermore, regardless of the analytical approach, estimations of the mass of secreted LH in each pulse did not correlate well with inputs predicted by deconvolution or Kushler-Brown pulsefit analysis of corresponding pulses in jugular blood (r2 ranging 0.40-0.48). Among alternative explanations is the possibility of heterogeneity in concentrations of GnRH in the portal vessels and variable distribution within the hypophysis. In summary, assay of hypophyseal portal blood obtained directly from the pituitary provides a method for direct assessment of secretory responses to hypothalamic peptides, and thereby serves as an unmatched method for studying the dynamics of LH secretion in vivo. With this approach, LH is revealed to be secreted as complex, non-Gaussian pulses that are far more sharply defined that those in the periphery, include non-GnRH-dependent, secretory components that cannot be predicted by deconvolution and are followed by periods of relatively constant, basal secretion.

Dispersion of chemical solutes in chromatographs and reactors

The dispersion of a chemically active solute in unidirectional laminar flow in a channel of constant cross-sectional area is considered. Adsorption/desorption of the solute at the wall or the presence of a bulk or surface chemical reaction introduce additional timescales, in addition to the diffusive and convective ones, such that, under certain conditions, the asymptotic evolution of the cross-sectional mean concentration cannot be described by a one-dimensional Taylor-Aris model. We use the centre and invariant manifold theories to establish the proper time and length scale separations necessary for the existence of an effective transport equation and to determine the dependence of the effective transport coefficients on the kinetics of adsorption/desorption and reaction. For the case of classical Taylor-Aris dispersion with no reaction, we derive the effective transport equation to infinite order in the parameter, p , representing the ratio of the characteristic time for radial molecular diffusion to that for axial convection. We show that the infinite series in the effective transport model is convergent provided p is smaller than some critical value, which depends on the initial concentration distribution. We also examine the spatial evolution of time dependent inlet conditions and show that the spatial and temporal evolutions differ at third and higher orders. It is shown that, except for slow reactions with a kinetic timescale of the same order as the transverse diffusion time, fast bulk reaction does not allow an asymptotic axial dispersion description. Slow bulk reactions do not affect dispersion but a correction to the apparent kinetics may arise due to nonlinear interaction among reaction, diffusion and convection. It is also shown that with a slow bulk reaction, steady-state dispersion due to a coupling of reaction and transverse velocity gradient can arise. Although this mechanism is distinct from the transient Taylor—Aris mechanism, the dispersion coefficient is identical to the classical unreactive Taylor—Aris coefficient. Surface reaction of any speed yields the proper asymptotic behaviour in time because the species still needs to diffuse slowly to the conduit wall. In the limit of fast surface reaction, the Taylor-Aris dispersion coefficient is reduced by a factor of 4.2, 7.1 and 4.0 for pipe, plane Poiseuille and Couette flows, respectively, as the slow-moving solutes near the wall are depleted. For the case of a linear surface reaction, we use the invariant manifold theory to derive the effective transport equation to infinite order. We also show that the radius of convergence of the invariant manifold expansion is approximately three times that of the no reaction case. We demonstrate that if adsorption/desorption is as slow as transverse diffusion an adsorption-induced dispersion, distinct from the Taylor-Aris shear dispersion, exists. While the total dispersion may increase because of the contribution of both, the Taylor-Aris component is reduced by a physical mechanism similar to surface reaction. The adsorption/desorption induced dispersion coefficient is shown to have a maximum when the adsorption equilibrium constant is exactly 2. Nonlinear Langmuir type adsorption at large concentration is shown to introduce a nonlinear drift term which causes non-Gaussian pulse responses with long tails These tails are detrimental to separation chromatography since they cause overlaps which increase with the length of the chromatograph