Current relaxation in nonlinear random media

We study the current relaxation of a wave packet in a nonlinear random sample coupled to the continuum and show that the survival probability decays as $P(t) \sim 1/t^{\alpha}$. For intermediate times $t<t^*$, the exponent $\alpha$ satisfies a scaling law $\alpha =f(\Lambda=\chi/l_{\infty})$ where $\chi$ is the nonlinearity strength and $l_{\infty}$ is the localization length of the corresponding random system with $\chi=0$. For $t\gg t^*$ and $\chi>\chi_{\rm cr}$ we find a universal decay with $\alpha=2/3$ which is a signature of the {\it nonlinearity-induced delocalization}. Experimental evidence should be observable in coupled nonlinear optical waveguides.Comment: revised version, PRL in press, 4 pages, 4 figs (fig 3 with reduced quality

Comparative analysis of the structure and internal stress in Ti-6Al-4V alloys manufactured by 3D printing and processing with screw extrusion

Study is based on the compare characterization of the structure and evaluation of the residual internal stresses in Ti-6Al-4V samples manufactured by the 3D printing (selective laser melting) and in the Ti-6Al-4V samples obtained with using of the severe plastic deformation by screw extrusion. The microstructure and residual stresses were examined by transmission electron microscope and X-ray diffractometer. High tensile internal residual stresses in the 3D printed sample were found. The high compressive residual internal stresses were found in the hot pressed and in the twisted samples. It was shown that arising of the high residual stresses in the studied samples under various technological processes occurred in various ways. The residual stresses in the severe plastic deformed samples arose due to non-uniform volumetric plastic deformation. In 3D printed sample, the residual tensile stresses arose from both phase (martensitic) transformation and thermal deformation. © Published under licence by IOP Publishing Ltd

Generalized Ladder Operators for Shape-invariant Potentials

A general form for ladder operators is used to construct a method to solve bound-state Schr\"odinger equations. The characteristics of supersymmetry and shape invariance of the system are the start point of the approach. To show the elegance and the utility of the method we use it to obtain energy spectra and eigenfunctions for the one-dimensional harmonic oscillator and Morse potentials and for the radial harmonic oscillator and Coulomb potentials.Comment: in Revte

RADIATION DEFECTS IN ZINC SULFIDE

Zinc sulfide shows the great potential as the perspective material in the power quantum optic, but the problem is the influence o f defects and admixtures on the different properties o f the material. There is the complex interaction between point defects in zinc sulfide which makes difficult the interpretation of a deffect's nature and an influence on the material's properties

Measurement invariance in the social sciences:Historical development, methodological challenges, state of the art, and future perspectives

This review summarizes the current state of the art of statistical and (survey) methodological research on measurement (non)invariance, which is considered a core challenge for the comparative social sciences. After outlining the historical roots, conceptual details, and standard procedures for measurement invariance testing, the paper focuses in particular on the statistical developments that have been achieved in the last 10 years. These include Bayesian approximate measurement invariance, the alignment method, measurement invariance testing within the multilevel modeling framework, mixture multigroup factor analysis, the measurement invariance explorer, and the response shift-true change decomposition approach. Furthermore, the contribution of survey methodological research to the construction of invariant measurement instruments is explicitly addressed and highlighted, including the issues of design decisions, pretesting, scale adoption, and translation. The paper ends with an outlook on future research perspectives.</p

New Lump-like Structures in Scalar-field Models

In this work we investigate lump-like solutions in models described by a single real scalar field. We start considering non-topological solutions with the usual lump-like form, and then we study other models, where the bell-shape profile may have varying amplitude and width, or develop a flat plateau at its top, or even induce a lump on top of another lump. We suggest possible applications where these exotic solutions might be used in several distinct branches of physics.Comment: REvTex4, twocolumn, 10 pages, 9 figures; new reference added, to appear in EPJ

Using a microheterogeneous model to assess the applicability of ion-exchange membranes in the process of reverse electrodialysis

Received: 30.03.2021. Revised: 28.04.2021. Accepted: 30.04.2021. Available online: 30.04.2021.This paper shows the possibility of using a microheterogeneous model to describe the properties of ion-exchange membranes and calculate the characteristics of a reverse electrodialyzer from the data obtained. We studied the properties of eight samples of heterogeneous cation exchange membranes (two samples of each type of membrane). The samples differed in the year of issue and storage conditions. It is shown that for heterogeneous ion-exchange membranes MK-40 and MA-41, the samples' properties can differ significantly. The counterions transport numbers calculated within the framework of the microheterogeneous model for Ralex membranes differ insignificantly. The counterion transport number in 1 mol/L sodium chloride solution is 0.96 for Ralex CM and 0.98 ± 0.01 for Ralex AMH. For the MK-40 membrane, the transport number in the same solution is 0.94 ± 0.04, and for the MA-41 membrane, it is 0.85 ± 0.1. The possibility of calculating the transport numbers and predicting the open-circuit voltage based on simple physicochemical measurements allows selecting the best membrane pairs for the reverse electrodialysis process. Comparison of the open-circuit potential value calculated using the obtained transfer numbers with experimental data showed that in the case of using Ralex membranes, the difference between the experimental and calculated values is 2%. The calculated value of the open circuit potential was 0.19 V/membrane pair or 1.69 V for the investigated reverse electrodialyzer with nine pair chambers.The research was carried out with the financial support of the Kuban science Foundation in the framework of the scientific project № IFR-20.1/110