Characterization of hysteretic stress-strain behavior using the integrated Preisach density

In this paper, we introduce the concept of Integrated Preisach-Mayergoyz (IPM) density to analyze static uniaxial compression tests at values well below the critical strength, and to characterize the elasticity of materials with hysteresis in their stress-strain relationship. The IPM density can be deduced from a particular force protocol following basic data treatment. The advantage of the IPM density over prior approaches is that no second order differentiation of the data is required which reduces the errors and uncertainties typical for past practice in the specific context of rock elasticity using scanning curves and PM density analysis. The characterization of the elasticity of the material is established in terms of a non-hysteretic strain contribution in the form of a non-linear but reversible equation of state, and a hysteretic contribution represented by the IPM density. The IPM inversion procedure is tested for simulated stress-strain data subjected to additive noise, and the results are compared to the traditional methodology. In addition, we analyze the hysteretic and non-hysteretic characteristics of five natural building stones, and show evidence for a classification based on the inferred properties.     

Polarization in the quasielastic scattering of 1-GeV/c protons on light nuclei

Polarization measurements in the A(p, 2p)B reactions on ⁶Li, ⁷Li, and ²⁸Si nuclei at a proton-beam energy of 1 GeV were performed in a kinematically complete experiment. By using a two-arm magnetic spectrometer, two secondary protons were recorded in coincidence at asymmetric scattering angles of θ₁=15°?26° and θ₂=58.6° for residual-nucleus momenta in the range K _B=0–150 MeV/c. Either arm of the spectrometer was equipped with polarimeters based on proportional chambers. The data coming from this experiment are analyzed within the distorted-wave impulse approximation. It is shown that the polarization of recoil protons formed at angle θ₂ in the interaction featuring a proton from the P shell of the ⁷Li nucleus can be described under the assumption of an effective intranuclear-proton polarization by using the single-particle shell-model wave function of the nucleus. Our data on the polarizations of the two protons from the reaction (p, 2p) on a ²⁸Si nucleus also suggest the effective polarization of the protons in the D shell of the ²⁸Si nucleus. It is found that, for high recoil-nucleus momenta of K _B≥90 MeV/c, the effective polarization of the protons in the P shell of the ⁶Li nucleus—this polarization was discovered in studying the polarization of recoil protons in the reaction ⁶Li(p, 2p)⁵He—cannot be described within the shell model assuming LS coupling. As might have been expected, the polarization of recoil protons knocked out from the S shells of the ⁶Li and ⁷Li nuclei comply well with the predictions obtained in the impulse approximation with allowance for the depolarization effect alone.     

A General Solution of the Problem of Elastic-Wave Scattering by a Plane Crack

Doklady Physics - The 3D problem of elastic-wave scattering by cracks in a homogeneous isotropic medium is considered. Using the method of Green’s function and specially introduced auxiliary...     

Mechanical and conducting properties of polypropylene fibers filled with carbon nanotubes with functionalized surface

A procedure for functionalization of the surface of multiwall carbon nanotubes, based on treatment of the nanofiller with a strong oxidant and 1-hexadecylamine and aimed to improve the compatibility of nanotubes with a polypropylene matrix, was examined. Variation of the mechanical and electrical properties of the composite fiber based on polypropylene in relation to the concentration of the modified nanotubes was studied.     

Switching effects in composite films based on the conjugated polymer polyfluorene and ZnO nanoparticles

The S- and N-shaped current—voltage characteristics have been studied for composite films of the conjugated polymer polyfluorene and ZnO nanoparticles deposited onto Al and In₂O₃/SnO₂ electrodes with and without an intermediate sublayer of the conducting polymer PEDT/PSS. The differences in the current— voltage characteristics of the systems (the N- and S-types, respectively) are interpreted using the electro-thermal switching model, which takes into account the structural and electric properties of PEDT/PSS. The switching provides both alignment of polymer molecules and tunneling of charge carriers, which leads to an increase in conductivity. The current flow in this structure causes an increase in temperature of conducting channels; when the temperature reaches certain levels, the conductivity of the channels decreases because the alignment of polymer molecules is upset, which creates an N-shaped form of the current—voltage characteristics.     

Experiment for search for sterile neutrino at SM-3 reactor

In connection with the question of possible existence of sterile neutrino the laboratory on the basis of SM-3 reactor was created to search for oscillations of reactor antineutrino. A prototype of a neutrino detector with scintillator volume of 400 l can be moved at the distance of 6–11 m from the reactor core. The measurements of background conditions have been made. It is shown that the main experimental problem is associated with cosmic radiation background. Test measurements of dependence of a reactor antineutrino flux on the distance from a reactor core have been made. The prospects of search for oscillations of reactor antineutrino at short distances are discussed.     

Peculiarities of cellulose nitrate combustion in ballasted systems

Russian Chemical Bulletin - The dependence of the combustion parameters of cellulose nitrate (nitrocellulose, NC) mixtures with magnesium oxide on the content of the energetic component was studied...     

Continued fraction method in inverse problem of photothermal diagnostics

Received: 1 July 1996/Accepted: 16 October 1996