The boundary value problem of determining hydrogen concentration and the stress state in a titanium shell

Decreasing physical and mechanical properties of materials in contact with an aggressive environment is one of the factors determining the strength and service life of various structures. In this paper, the effect of a hydrogen-containing medium on the mechanical properties and stress state of a titanium alloy shell is shown. For this purpose, the diffusion boundary-value problem is solved and the distribution of hydrogen concentration over the shell wall thickness is determined. Then the boundary-value problem of statics is solved, and the stress state of the shell structure is determined before and after hydrogenation. The object of study is presented in the form of a shell of revolution loaded with internal pressure and working in a hydrogen-containing medium. © 2019 Author(s)

The orbits of outer planetary satellites using the Gaia data

Launch of the Gaia space observatory started a new era in astrometry when the accuracy of star coordinates increased by thousands of times. Significant improvement of accuracy was also expected for the coordinates of the Solar system bodies. Gaia DR3 provided us with the data which could be used to test our expectations. In this work, we refine the orbits of a number of outer planetary satellites using both ground-based and Gaia observations. From thirteen outer satellites observed by Gaia, we chose six to obtain their orbits. Some specific moments in using observations of outer satellites made by Gaia are demonstrated. These pecularities stem from scanning motion of Gaia, in particular from the fact that the accuracy of observations is significantly different along and across the scanning direction. As expected, Gaia observations proved to be more precise than those made from Earth, which results in more accurate satellite ephemerides. We estimate accuracy of the ephemerides of considered satellites for the interval between 1996 and 2030. As astrometric positions published in Gaia DR3 were not corrected for the relativistic light deflection by the Sun, we took into account this effect, which slightly diminished the rms residuals. In addition, relativistic light deflection by the giant planets was estimated, which, as it turned out, can be neglected with the given accuracy of Gaia observations.Comment: accepted in MNRAS 28.03.2023, 9 pages, 8 figure

Surface modification of titanium by pulsed laser radiation of femtosecond duration

The effect of an infrared pulse laser with femtosecond radiation (λ = 744 nm, τ ≈ 120 fs, E ≤ 8 mJ) on the surface of Ti of commercially purity in the submicrocrystalline state is investigated using scanning electron microscopy (SEM)yesBelgorod State Universit

Surface-enhanced optical third-harmonic generation in Ag island films

Surface-enhanced optical third-harmonic generation (THG) is observed in silver island films. The THG intensity from Ag nanoparticles is enhanced by more than two orders of magnitude with respect to the THG intensity from a smooth and homogeneous silver surface. This enhancement is attributed to local plasmon excitation and resonance of the local field at the third-harmonic wavelength. The diffuse and depolarized component of the enhanced THG is associated with the third-order hyper-Rayleigh scattering in a 2-D random array of silver nanoparticles.Comment: 4 pages, 2 figure

Cytomorphometric indicators of the gingiva epitheliocytes of patients with ischemic heart disease on the background of taking acetylsalicylic acid

The aim is to study the cytological and morphometric characteristics of gingiva epitheliocytes in patients with IHD who are constantly taking ASA drugs. To determine the dental status, 92 patients aged 40-60 years who are on outpatient treatment of IHD were examined. An in-depth scientific study was conducted and the results of cytomorphometric indicators of the gingiva epitheliocytes of patients with ischemic heart disease, constantly taking acetylsalicylic acid drugs, were presente

The application of plasma-electrolysis boronizing of parts

© Published under licence by IOP Publishing Ltd. The article deals with methods of increasing the working capacity of parts due to the improvement of structural condition of the surface. There were analyzed the characteristic features of the borating method and plasma-electrolysis processing, the necessity for joint use of these methods. On the basis of the review the author suggests the application of plasma-electrolysis boronizing of parts. By increasing the working capacity of parts due to the improvement of structural condition of the surface by means of borating method and plasma-electrolysis processing, it is possible to use more rational application of alloyed materials for manufacturing various parts that have high physical and mechanical, operational characteristics, which is certainly actual for modern machinery production

Possible solution to the main cosmological constant problem

A modified-gravity-type model of two hypothetical massless vector fields is presented. These vector fields are gravitationally coupled to standard matter and an effective cosmological constant. Considered in a cosmological context, the vector fields dynamically cancel an arbitrary cosmological constant, and flat Minkowski spacetime appears as the limit of attractor-type solutions of the field equations. Asymptotically, the field equations give rise to a standard Friedmann-Robertson-Walker universe and standard Newtonian gravitational dynamics of small systems.Comment: 28 pages, v5: published versio

Photon Filamentation in Resonant Media with High Fresnel Numbers

The phenomenon of turbulent photon filamentation occurs in lasers and other active optical media at high Fresnel numbers. A description of this phenomenon is suggested. The solutions to evolution equations are presented in the form of a bunch of filaments chaotically distributed in space and having different radii. The probability distribution of patterns is defined characterizing the probabilistic weight of different filaments. The most probable filament radius and filament number are found, being in good agreement with experiment.Comment: Revtex file, 5 pages. Reference to the English edition of the journal is give