Universal Pulse Shape Scaling Function and Exponents: A Critical Test for Avalanche Models applied to Barkhausen Noise

In order to test if the universal aspects of Barkhausen noise in magnetic materials can be predicted from recent variants of the non-equilibrium zero temperature Random Field Ising Model (RFIM), we perform a quantitative study of the universal scaling function derived from the Barkhausen pulse shape in simulations and experiment. Through data collapses and scaling relations we determine the critical exponents $\tau$ and $1/\sigma\nu z$ in both simulation and experiment. Although we find agreement in the critical exponents, we find differences between theoretical and experimental pulse shape scaling functions as well as between different experiments.Comment: 19 pages (in preprint format), 5 figures, 1 tabl

Disorder-Induced Critical Phenomena in Hysteresis: Numerical Scaling in Three and Higher Dimensions

We present numerical simulations of avalanches and critical phenomena associated with hysteresis loops, modeled using the zero-temperature random-field Ising model. We study the transition between smooth hysteresis loops and loops with a sharp jump in the magnetization, as the disorder in our model is decreased. In a large region near the critical point, we find scaling and critical phenomena, which are well described by the results of an epsilon expansion about six dimensions. We present the results of simulations in 3, 4, and 5 dimensions, with systems with up to a billion spins (1000^3).Comment: Condensed and updated version of cond-mat/9609072,``Disorder-Induced Critical Phenomena in Hysteresis: A Numerical Scaling Analysis'

SOME RELEVANT ASPECTS OF FOOTBRIDGE VIBRATIONS UDC 624.073.33(045)

Abstract. Considering the contemporary structural materials that are becoming more resistant, having higher strength to weight ratio, and the fact that live load of footbridges is low, the design based on static analysis only, respecting ultimate limit states requirements, leads to slender bridge structures for pedestrian and cycle track use. As a consequence, stiffness and masses decrease, facing lively, easy to excite structures, with smaller natural frequencies. The excitation of a footbridge by a pedestrian passing over it can be unpleasant for a person walking or standing on the bridge, but usually not destructive for the structure itself. Recent experiences regarding dynamic behavior of slender footbridges have especially shown that vibration serviceability limit states are very important requirements in any structural design. We are presenting a general algorithm for analytical testing of dynamic parameters of structures, calculation of deflection, thus speed and acceleration of superstructure under human-induced excitation, as predicted by Eurocode, British and Canadian standards in use, since no Yugoslav code deals with the problem. The evaluated system is a footbridge in a system of a simply supported concrete girder. The presented model is used to show correspondence of results, obtained by the algorithm, with the results obtained using the simplified methods suggested by the Codes of Practice, since the latter exists only for certain structural systems. Key words: Footbridge, human-induced excitation, forced vibrations, serviceability limit states

Stark effect of Ar I lines for electric field strength diagnostics in the cathode sheath of glow discharge

We present a study of argon glow discharge which shows that measured wavenumber DC Stark shifts $\Delta \nu$ of two neutral argon lines, Ar I 518.75 nm and Ar I 522.127 nm, can be used for reliable determination of the electric field strength F distribution in the cathode sheath region of the discharge. In order to experimentally determine the coefficient c in quadratic correlation $\Delta \nu =cF^{2}$ , manifested in a low field range (up to 15 kV/cm), the discharge is seeded with a small admixture of hydrogen, and the values of F are measured via Stark polarization spectroscopy of the hydrogen Balmer beta line. Once known, this can be used for the determination of F by a simple and inexpensive spectroscopic Stark shift measurement in discharges with other argon admixtures or pure argon. Reported shift results are in good agreement with data extrapolated from measurements performed at high electric fields (over 100 kV/cm) by Windholz (Phys. Scr., 21 (1980) 67)

Effects of external noise on threshold-induced correlations in ferromagnetic systems

In the present paper we investigate the impact of the external noise and detection threshold level on the simulation data for the systems that evolve through metastable states. As a representative model of such systems we chose the nonequilibrium athermal random-field Ising model with two types of the external noise, uniform white noise and Gaussian white noise with various different standard deviations, imposed on the original response signal obtained in model simulations. We applied a wide range of detection threshold levels in analysis of the signal and show how these quantities affect the values of exponent γS/T (describing the scaling of the average avalanche size with duration), the shift of waiting time between the avalanches, and finally the collapses of the waiting time distributions. The results are obtained via extensive numerical simulations on the equilateral three-dimensional cubic lattices of various sizes and disorders.publishedVersionPeer reviewe

The variations in quality of maize biomass in different environments

Successful maize cropping in rein-fed conditions depends mainly on meteorological factors and in lesser extent on substrate (soil). The trial with 5 maize hybrids was set up during period of 2005-2010 on alluvium and hydromorphous black soil with aim to examine productive traits and silage quality from the energetic point of view. Biomass yield, stover and cob mass were measured, as well as total energy of biomass, as calculated parameter. Nutritive units, total energy and metabolic energy were determined from the silage. Positive correlation was observed between yield parameters and precipitation amount. In most of seasons, biomass yield, stover and cob mass, total energy of biomass and silage were higher on hydromorphous black soil, compared to alluvium, while the nutritive units and metabolic energy were lower on the same soil during unfavorable seasons. Achieved results indicated that unfavorable meteorological factors could be partly reduced by cropping on heavier soils, such hydromorphous black soil is. In contrast to yield parameters, energy status of produced maize and silage biomass are in lesser extent dependable on meteorological conditions and soil type, and what is more important biomass total energy increases with unevenness of growing conditions. Such situation gives advantage to lower yield crop as a source for energy production (bio-fuels), while high yielding crop have better potential for conversion as a feedstuff

On the use of Ar I 517.753 nm spectral line for electric field measurements in the cathode sheath of a Grimm-type glow discharge source

We present the results of the optical emission spectroscopy study of the Ar I 517.753 nm spectral line, observed at different positions in the cathode sheath of an abnormal DC Grimm-type glow discharge source operated in argon. The line profiles were recorded parallel to the cathode surface (side-on view), along the discharge axis from the cathode towards the negative glow. The spectra show a red line shift, which diminishes with the distance from the cathode surface and decreasing electric field. This allows experimental determination of the coefficient C in quadratic relation, Δν = CE2, between the wavenumber Stark shifts, Δν, and electric field strength, E. The above relation is a low-field (up to 25 kV/cm) approximation of the quadratic dependence of the upper-level shift, measured for a large set of argon lines at high electric fields (up to 700 kV/cm) by Windholz (Phys Scr 21:67–74, 1980). One of these lines, Ar I 537.349 nm, is used here for independent measurement of the electric field E and correlated with the Ar I 517.753 nm upper-level wavenumber shift Δν to obtain a line-specific coefficient C. In this way, the Ar I 517.753 nm spectral line complements the set of argon lines suitable for Stark spectroscopy diagnostics of the electric field distribution and cathode sheath length, the knowledge of which allows for a better understanding and description of the glow discharge processes through various theoretical models. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature

Hydrogen dissociation degree in the Grimm-type glow discharge measured by optical emission spectroscopy

The hydrogen dissociation degree is measured by means of optical emission spectroscopy in the cathode sheath of cylindrical abnormal Grimm-type DC glow discharge operating in the hydrogen–argon mixture at low pressure. The degree of dissociation, ranging from 80% in the close vicinity of the cathode and decreasing to 60% towards the negative glow, is obtained from the intensity ratio of the hydrogen Balmer Hγ line and the diagonal Fulcher-α molecular bands. The cathode sheath thickness is extracted from the electric field strength distribution measured using Stark spectroscopy of the hydrogen Balmer Hα line. An electron temperature of 2.7 eV in the negative glow region is estimated by observing the intensity ratio of the diagonal Fulcher-α bands and the Hα line

Ne II spectral lines in the cathode sheath of an abnormal glow discharge

We report the results of an experimental study of Ne II 369.421 nm, 371.308 nm, and 372.711 nm spectral line shapes by means of the optical emission spectroscopy The spectral lines are recorded in the cathode sheath region of an abnormal glow discharge operated in pure neon and by using different cathode materials: copper (Cu), iron (Fe), and titanium (Ti). The studied lines have complex spectral profiles which enabled us to determine important discharge parameters. In this work we present the correlation between the width of pedestals of the side-on recorded Ne II spectral lines and the electric field strength distribution as well as the correlation between line pedestal width and the distance of the recording position from the cathode

Estimation of the maximum electric field strength in the cathode sheath of a Grimm-type glow discharge by end-on view optical emission spectroscopy in neon and argon

We present a series of optical emission spectroscopy (OES) measurements of the stable correlation in characteristic features of spectral line shapes of neutral neon and argon, recorded in the Grimm-type plane cathode DC glow discharge (GD) source from two positions: (1) perpendicular to the cathode surface from the end of the discharge, in line with the discharge axis (end-on view) and (2) side-on cathode view, parallel to the cathode surface and perpendicular to the discharge axis, at the position of the maximum external electric field Fmax in the cathode sheath (CS), close to the cathode surface. Side-on view recording enables spatially resolved OES in the CS, where the Stark effect decisively determines the splitting and shifting of line components relative to the unshifted zero-field line. On the other hand, commonly available end-on view spectra recording in standard analytical Grimm-type sources collects integral light emission from the different layers of the discharge, both CS and negative glow (NG). However, distinct Stark components of several Ne I and Ar I lines' splitting and shifting in the CS are preserved as characteristic excessive wings broadening features in the end-on recordings as well. Following spectral measurements of six Ne I and four Ar I lines in a broad range of discharge conditions (pressure, voltage, current) and cathode materials, we report on a sustained correlation coefficient of 1.083 in neon and 1.129 in argon between the side-on recorded components shift Δλs at the position of maximum field Fmax in the CS, and the end-on recorded wings broadening characteristic features shift Δλe. Individual Ne I and Ar I lines' correlation coefficients Δλs/Δλe are reported also. These coefficients can be used to estimate the maximum CS electric field Fmax and the CS thickness dc within reasonable margins of uncertainty in a standard analytical Grimm-type GD source with an end-on view available only