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Extremely fast spin relaxation of triplet oxygen molecules reduces the spin selectivity in reactions involving 3O2 to a much lesser extent than might be expected.

A novel computationally effective approach to multiscale thermoelastic modelling of composite structures and its application to a thermomechanical analysis of two ITER superconducting strands is presented. Homogenisation and recovering problems are solved by means of the “fundamental solutions” method, which was expanded to the case of thermoelastic analysis. We describe a general procedure of multiscale analysis on the basis of this method and apply it to recover stresses at the microscopic scale of a composite strands using a two-level procedure. The recovered micro-stresses are found to be in good correlation with the stresses obtained in the reference problem where the entire composite structure was modelled with a fine mesh.

An understanding of the interplay between the spin and electronic degrees of freedom of polarons migrating along conjugated polymer molecules is required to further the development of organic electronics and spintronics. In this study, a novel experimental approach is proposed for studying spin-correlated polaron pairs (PPs) on an isolated molecule of a conjugated polymer. The polymer molecule of interest is immobilized in a nonluminescent poly(vinyl chloride) matrix, which is irradiated with X-rays to rapidly form secondary PPs on the conjugated polymer. The migration, recombination, and evolution of the spin state of the PPs can be monitored at nanosecond resolution by observing the recombination fluorescence under different magnetic fields. Examples supporting this concept are presented.

The article presents a technique for process-induced residual strain modeling for thermoset composite material parts. The model takes into account the mechanical and thermal contact between the part and the mold. The technique is implemented in the ABAQUS software using user subroutines. Using the technique, it is possible to clarify the distribution of the heat transfer coefficient on the surface of the part and mold using the CFD method. Distribution of heat transfer coefficients are obtained in ANSYS CFX under the appropriate process conditions. The method is verified for the U-shaped sample. Also, the results of modeling the stringer-stiffened curved composite panel using the developed technique without taking into account the mold and heat transfer coefficient distribution are presented.

The paper presents results of CFD parametric study of centrifugal compressor stage vane diffusers in the Ansys CFX. The results obtained will be used to build a mathematical model of vane diffuser in optimization design system. Objects of research are vane diffusers with external relative diameter (relative to the diameter of the impeller) equal to 1.5; vane inlet angle of 20°; relative vane heights of 0.025, 0.034, 0.045, 0.06, and 0.08; and vane profile curvature angles of 10, 15, and 20 °. The characteristics of polytrophic efficiency, loss coefficient, recovery coefficient, ratio of inlet and outlet velocities, and flow deviation angle versus incidence angle are set. The analysis of the flow structure in the vane diffuser channels is presented. Unlike with a straight vane cascade, the deviation angle in the circular rows of vane diffusers tends to increase with increasing row density. This may be due to the complex nature of the interaction of the active part of the flow with separation zones. In rows with almost straight vanes at a lower density, the separation zone on the pressure side decreases and even shifts to the very end of the suction side.

This study presents a model for Ti6Al4V alloy produced by applying electron beam melting as continuum media with orthotropic elastic and plastic properties and its application in total hip replacement (THR). The model exhibits three Young’s moduli, three shear moduli, and three Poisson’s ratios as elastic properties and six coefficients describing the Hill yield criterion. Several uniaxial tension and torsion experiments and subsequent data processing were performed to evaluate the properties and coefficients. The typical values obtained for Young’s moduli, shear moduli, and Poisson’s ratio were 121–124 MPa, 37–42 MPa, and 0.25–0.26, respectively. A comparison of the experimental tension and torsion curves with those obtained by a finite element analysis revealed a good correlation with a maximum error of 9.5%. The finite element simulation of a personalised pelvic implant for THR manufactured from the obtained material proved the mechanical capability of the implant to successfully withstand the applied loads.

The kinetics of spin-selective reactions involving triplet molecules, such as triplet–triplet annihilation or electron transfer to dioxygen molecules in the ground triplet spin state, are strongly dependent on the dipole–dipole interaction (DDI) of electron spins in spin-1 particles. The effect of this interaction on the intersystem crossing in the reaction encounter complex of the paramagnetic particles was previously considered for some particular cases using oversimplified approaches. In this study, we consider a rigorous kinetic model of the irreversible reaction between the spin-1/2 and spin-1 particles in an encounter complex with the reactive doublet state. This model explicitly includes both isotropic exchange coupling of the reactants and spin dependence of the reaction rate in the form of the Haberkorn reaction term. For the time-independent DDI, an analytical expression for the reaction kinetics was derived. The effect of DDI fluctuations was analyzed using numerical simulations. It was found that increasing both the exchange coupling and the reaction rate constants can significantly slow down the quartet–doublet spin transitions and, as a consequence, the observed spin-selective reaction rate. Additionally, the presence of the irreversible reaction in the doublet states affects a coherent evolution in the non-reactive quartet subsystem.

The spin evolution of an ensemble of immobile radical ion pairs, assuming different rate constants of the pair recombination in the singlet (kS) and triplet (kT) spin states, was investigated for an arbitrary initial state in the absence of paramagnetic relaxation. An analytical solution was obtained for the density matrix of a radical pair at the constant frequency of singlet–triplet transitions. This solution was applied to study how the shape of the curves of the time-resolved magnetic field effect (TR MFE), defined as the ratio of the recombination rates of the pairs in different magnetic fields, depended on the value of k = kS − kT in the presence of hyperfine and Zeeman interactions. The former were taken into account using a semi-classical model. It was shown that the shape of TR MFE curves changed dramatically at k ≠ 0 as compared to the case of k = 0. Experimental schemes aimed to reveal the spin-dependent recombination using the TR MFE approach were proposed.

The paper describes an up-to-date approach to searching for an optimal blade shape for the airplane propeller while considering geometric and technological restrictions. This approach uses the advanced parametric optimization methods. The paper shows an application of the approach developed to obtain an optimal aerodynamic blade shape for different engine operation modes.

In the work, a review of scientific articles on the behavior of tissues and organs of the human body under local mechanical effects on it, as well as a description of the physico-mechanical properties of biological materials. The selection of mechanical behavior for each biological material as part of a mathematical model of the human torso was carried out, its finite element model was created, validation experiments were modeled using data presented in the literature. An original calculation model of a human torso with a tuned interaction of organs with each other was developed. Contact interaction parameters are determined. The developed computational model of a human torso was verified based on data from open sources for an experiment with mechanical action by a cylindrical impactor. An algorithm for processing pressure and acceleration graphs has been implemented in order to obtain tolerance curves. A specialized modular program has been created for the automated processing of calculation results and the output of the main results. 42 numerical tests were carried out simulating the entry of a steel ball into each of 21 zones for power engineers of 40 and 80 J. According to the results of the tests for each organ, pressure and acceleration tolerance curves were obtained, animations of the behavior of organs under shock were created, visualization of the pressure field propagation in organs was obtained torso.

The new coronavirus pandemic has had a major impact on worldwide economic development Many infection-countering measures have imposed restrictions on economic activities At the same time, economic sectors contribute unequally to both the disease's spread and to regional economic development This article proposes a method for assessing the consequences of partial regional isolation Simulation modelling and system dynamics are applied to assess both epidemiological and economic consequences The classic “Susceptible - Exposed - Infected - Recovered” disease spread model has been modified with the addition of a new group: Isolated Individuals This modified model allows the size of the receptive population and the frequency of their contact to be regulated based on scenarios of partial regional isolation in the context of economic sectors The model is tested in St Petersburg Changes in the region's infected population are forecasted as the result of the establishment and removal of partial isolation measures in the context of individual economic sectors © 2020 All Rights Reserved

The problem of microgeometry profiling of the lubricating layer of an irreversible plain bearing is considered with the assumption of the maximum lift force on the basis of a Rayleigh pocket in order to construct profiles easy to manufacture. To this end the lift force dependence on several selected parameters, which most accurately approximate the considered profile to the profile of the global extremum, is investigated. The formulated problem of parametric optimization is solved using the software packages IOSO and modeFrontier, whereas the pressure field in the bearing is determined by the Navier–Stokes equations using the ANSYS/CFX. The results may be used to construct optimal processable profiles of plain bearings applied in various power engineering and other machines and devices.

Published data on flat grid purges allow to evaluate the efficiency of blade devices with different kinematic scheme of stages and design parameters. The authors present the main provisions of the calculation program algorithm and some results of numerical analysis of the efficiency of flat grids of axial stages with different combinations of design parameters. The content of the article and the computer program are addressed to people who are improving their knowledge of gas dynamics of axial compressors. Some of the results may be of interest to specialists working professionally in this field.

Published data on flat grid purges allow to evaluate the efficiency of blade devices with different kinematic scheme of stages and design parameters. The corresponding computer program ODOS-GP04 and examples of numerical analysis of the efficiency of flat grids and spatial blade devices of axial stages with different combinations of design parameters was provided. Further development of the ODOS-GP04 program is described below, which makes it possible to perform an estimated calculation of the gas-dynamic characteristics of the stages designed using this program. Analysis of the calculated characteristics of a number of typical stages allows to draw a conclusion about the influence of the main design parameters. This article is primarily addressed to people who are developing their knowledge of the gas dynamics of axial compressors. Some results of calculations do not correspond to the published experimental data. The authors expect that this may attract the attention of specialists working in the field of gas dynamics of axial compressors.

To search for and elucidate the nature of radical cations arising in irradiated liquid ethylene carbonate (EC), the effect of the external magnetic field on the radiation-induced fluorescence of fluorophore solutions in EC has been studied. Using quantum-chemical calculations, it has been shown for the first time that primary EC radical cations are rapidly transformed into ion–molecular complexes containing, in addition to the initial radical cation, one or more solvent molecules. In the complexes, two particles are oriented to each other by carbonyl groups, on which almost all of the spin density is localized. This result shows that the prevailing concepts describing the primary stages of liquid carbonate radiolysis should be revised, and the possibility of the formation of such ion–molecular complexes should be taken into account when studying the oxidative decomposition of carbonates used in organic electrolytes.

The work presents the main provisions underlying the program for axial compressors calculation anddesign. The calculation of head losses and grids deflection capacity is based on the formulas of A. Komarov. Themodel contains empirical coefficients, values of which are selected during verification of the program based onthe tests results of multistage compressors and compressor stages. The main equations and algorithm for pressuresand velocities calculation under the radial equilibrium condition are presented. The use of computer programsbased on these models in the design of a 4-stage gas turbine engine compressor of moderate power with a totalpressure ratio of 3.2 and a given velocity is shown. For the first compressor stage, two variants with differentflow coefficients were compared. Variant #1 is designed with the classic recommendation to approach the samemechanical gas energy at the exit of the stage along the radius. Variant #2 is designed for a smaller flowcoefficient, but in order to ensure radial equilibrium, it was necessary to introduce a significant unevenness ofmechanical energy supply along the radius. Due to the lower kinetic energy, variant 2 has a 1.9% higher stageefficiency. Despite the fact that the loss coefficients of the blade devices are lower for variant #1. The questionremains as to how much the unavoidable mixing losses of variant #2 will reduce its efficiency in the process ofgas mechanical energy equalizing.

According to picosecond radiolysis data, primary radical cations in irradiated carbonates are very rapidly deprotonated. At the same time, analysis of the radiation-induced fluorescence from carbonate solutions indicates the formation of solvent-related radical cationic species with a relatively long lifetime. We use quantum chemical methods to develop a model of carbonate ionization that reconciles these conflicting data. Using ethylene carbonate as an example and assuming that its molecules exist in solution as a collection of dimeric associates, we show that both processes are the result of the loss of an electron from such dimers. This demonstrates that the generally accepted conceptualization of a primary ionization event, based on the idea of the formation of a radical cation of an individual molecule of an irradiated substance, requires revision in the case of polar aprotic liquids that tend to form molecular associates.

The aim of this paper is to investigate and compare the stress distribution of a reconstructed pelvis under different screw forces in a typical walking pattern. Computer-aided design models of the pelvic bones and sacrum made based on computer tomography images and individually designed implants are the basis for creating finite element models, which are imported into ABAQUS software. The screws provide compression loading and bring the implant and pelvic bones together. The sacrum is fixed at the level of the L5 vertebrae. The variants of strength analyses are carried out with four different screw pretension forces. The loads equivalent to the hip joint reaction forces arising during moderate walking are applied to reference points based on the centres of the acetabulum. According to the results of the performed analyses, the optimal and critical values of screw forces are estimated for the current model. The highest stresses among all the models occurred in the screws and implant. As soon as the screw force increases up to the ultimate value, the bone tissue might be locally destroyed. The results prove that the developed implant design with optimal screw pretension forces should have good biomechanical characteristics.

Magnetic resonance characteristics of carriers of both electron spin and electric charge (polarons) in conjugated polymers are required for a deeper understanding of properties of these semiconduct...

The High Field Side Reflectometry (HFSR) is one of the ITER diagnostics which provides information about plasma state by measuring the electron density profile. Five various designs have been developed and studied since 2014 as a result of interaction of Peter the Great St. Petersburg Polytechnic University, NRC “Kurchatov Institute”, and Fusion Centre. Multiphysics engineering finite-element analysis has been performed for each of the HFSR designs. The study deals with thermal loads which were discovered to be the most significant from structural integrity point of view. On the basis of the obtained results the decisions on introducing structural changes into individual parts of the diagnostics were made by the designers of the Kurchatov Institute. Key features of the proposed mathematical model and results of numerical simulations, which demonstrate a stress state of the diagnostics, are given. The process of multistage diagnostic design development based on the finite element analysis results is presented.

The delayed radiation-induced fluorescence from polyethylene and its alkyl- and fluorine-substituted analogues doped with aromatic luminophores was studied in the time range of 1-1000 ns. Qualitative analysis of the effects of a magnetic field on the fluorescence decay indicated that, in all polyolefins studied, the main portion of the fluorescence observed arose from the recombination of geminate spin-correlated radical ion pairs (RIPs). In the case of polyethylene, this conclusion was supported by observing the effect of an external electric field on the fluorescence decay. It was shown by comparison with the computer simulation of intratrack recombination that the tunneling character of the RIP recombination, which had an asymptotic time dependence of the geminate recombination rate close to

A kinematic model of the gearbox and a simplified kinematic model of a tractor are developed. These models take account of the characteristics of the internal-combustion engine employed, corresponding to the customer requirements on gearbox performance. Virtual tests of the tractor establish the tractional and dynamic characteristics of the tractor and its tractional class according to State Standards GOST 27021–86 and GOST 30745–2001 (ISO 789-9–90).

The method of time resolved magnetic field effects in the recombination fluorescence of spin-correlated radical ion pairs is used to detect for the first time the perfluorobenzocyclobutene radical anion. The quantum chemical analysis of the potential energy surface testifies that the particle is structurally flexible with respect to the pseudo-rotation coordinate. The calculated values of hyperfine interaction constants averaged over global minima are close to those estimated from the experimental data of time resolved magnetic field effects.

Intelligent data analysis based on artificial intelligence and Big Data tools is widely used by the scientific community to overcome global challenges. One of these challenges is the worldwide coronavirus pandemic, which began in early 2020. Data science not only provides an opportunity to assess the impact caused by a pandemic, but also to predict the infection spread. In addition, the model expansion by economic, social, and infrastructural factors makes it possible to predict changes in all spheres of human activity in competitive epidemiological conditions. This article is devoted to the use of anonymized and personal data in predicting the coronavirus infection spread. The basic “Susceptible–Exposed–Infected–Recovered” model was extended by including a set of demographic, administrative, and social factors. The developed model is more predictive and applicable in assessing future pandemic impact. After a series of simulation experiment results, we concluded that personal data use in high-level modeling of the infection spread is excessive.

The probability of formation of spin-correlated secondary radical ion pairs (RIPs) in diluted solutions of charge acceptors in irradiated haloalkanes is believed to be extremely low due to the dissociative attachment of excess electrons to solvent molecules. Contrary to this, it has been found that spin-correlated RIPs can be formed upon irradiation in some liquid chloroalkanes with yield sufficient to observe the recombination fluorescence of the RIP's partners. This allowed the study of primary radical cations (RCs) as well as radical ionic states of molecules dissolved in haloalkanes using the method of time-resolved magnetic field effect (TR MFE) in radiation-induced fluorescence. With this method, the magnetic resonance characteristics of the solvent RCs in a series of liquid haloalkanes were examined for the first time. For the 1,2-dichloroethane RC, the rate of scavenging by solute molecules and the dominant mechanisms of paramagnetic relaxation were determined. Polysulfone and poly(ethyl methacrylate) were used to demonstrate that due to their high dissolving ability, chloroalkanes can be exploited as solvents to study the magnetic resonance characteristics of radical ionic states of polymeric molecules in solutions with the TR MFE method.

New ways of numerical simulation of nonstraight laying of reinforcing fibers in panels of variable rigidity and variants of setting optimization problems for them are proposed. The problem of parametric optimization of the dimensions and stacking of carbon fiber reinforced plastic layers in the design of the bracket for the installation of a star tracker was solved.

The mass of a support for a stellar sensor in a spacecraft is minimized in the light of requirements on the first eigenfrequency and the reactive force in the connectors. Topological and parametric optimization is employed. The finite-element method is adopted, within the capabilities of the Altair Optistruct system

The High Field Side Reflectometry (HFS-R) is diagnostic equipment subjected to the conditions that are severe even for ITER and make development of the appropriate design challenging: magnetic field over 9T, highly non-uniform temperature field with temperatures up to 700 °C, long in-vessel waveguides. A special global electromagnetic finite element model for performing poloidal field variation, toroidal field variation and halo current analyses for HFS-R was developed. The most dangerous for the equipment loads were identified by performing electromagnetic, thermal and stress analyses. Results indicate that current design of the HFS-R in-vessel elements withstands the possible electromagnetic loads, but thermal stresses above the allowable indicate the necessity of further design modifications and elaboration of computational approach for thermal analysis.

The problem solution for the thrust sector bearing of a hydrogenerator with oil lubrication is considered. The value of the most important hydrodynamic characteristic of the thrust bearing, which is the lifting force, is defined. The pressure field is determined by the direct numerical integration of the Navier-Stokes equations for a lubricating oil layer. The case of the absence of heat exchange between the lubrication layer and solid-state components of the thrust bearing and the case when the heat exchange is taken into account are considered. The calculation results, which are compared with an experiment, are presented. The research results can serve as the basis to develop automation systems for designing hydrogenerator thrust bearings.

Resolved hyperfine structure is observed for the first time in the OD EPR spectra of charge pairs recombining in a solid polymer matrix at room temperature.

The method of time-resolved magnetic field effect (TR MFE) in recombination fluorescence of spin-correlated radical ion pairs has been used to detect and identify radical cations generated at early stages after the pulse irradiation of polyethylene and tricosane. From analysis of TR MFE curves, the widths of unresolved EPR spectra of radical cations have been determined, and their g factors have been evaluated. The results have demonstrated that, as distinct from n-alkanes, primary radical cations in polyethylene are localized on chemical defects of the polymer chain in a time of about 1 ns or less.

In disagreement with the common concept of primary radiation-induced events in liquid carbonates, an analysis of the fluorescence response of irradiated luminophore solutions in propylene carbonate to magnetic fields reveals the presence of radical cations formed from the solvent. On the basis of their magnetic resonance characteristics, the radical cations are proposed to be ionised dimeric complexes with the spin density delocalised over two antiparallel carbonyl groups. The finding suggests that the basic models underlying the application of radiolysis to study the mechanisms of the oxidative decomposition of carbonates should be reexamined.