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INTRODUCTION: Spondyloarthritis (SpA) take one of the leading positions among rheumatic diseases, constituting chronic inflammatory diseases of spinal cord, joints and enthesis. All spondyloarthritis develop as inflammatory lesion of sacroiliac joints (SIJ) — sacroiliitis and proliferation of bone tissues in the joint area and enthesis. Timely and quality visualization of sacroiliitis signs in patients with ankylosing and axial spondyloarthritis by means of radiation diagnostics is one of the main criteria for diagnosis verification at an earlier stage.OBJECTIVE: Review and analysis of the existing foreign and domestic literature for defining the role and place of digital tomosynthesis in methods and techniques of radiation diagnostics regarding axial spondyloarthritis.MATERIALS AND METHODS: A search of scientifiс publications and clinic guidelines in information and analytical systems PudMed (elibrary for 2015–2021) was carries out dedicated to radiation diagnostics of axial spondyloarthritis, including digital tomosynthesis.RESULTS: The review demonstrated wide opportunities and prospects of applying digital tomosynthesis in diagnosis and evaluation of axial spondyloarthritis progression, including the results of applying tomosynthesis with patients, having structural change in sacroiliac joints (SIJ).CONCLUSION: The method opportunity in this direction hasn’t been fully studied and the algorithm of its applying and criteria of patient selection for the research have not been developed.

Features of the simulation of the thermodynamic and gasdynamic processes occurring in devices for reducing the noise level of a shot from a gun were considered. A simulation of large vortices in the nonstationary turbulent flow of powder gases in a muzzle noise reduction device with a silencer representing a shaped channel with several chambers, whose volumes decrease in the direction to the silencer outlet, has been performed. Results of qualitative and quantitative investigations of the initiation, development, and damping of the shock waves in the flow of powder gases, formed as a result of the firing of a shot made from a signal gun, are presented.

The impetus for this article was provided by Ing. I. M. Pautkin and Dr. D. N. Matveev (for which I am grateful to them) the following works

Possibilities for using general-purpose graphics processing units to simulate compressible gas flows are discussed. Consideration is given to different schemes of computation of flows through the faces of the flow control volume and to the features of their implementation on graphics processing units. A solution of a number of model problems of gas dynamics on graphics processing units is presented and consideration is given to approaches to optimization of the program code connected with the use of different types of memory. A comparison is made between the rates of counting on a graphics processing unit and a central processor using grids having different resolution capabilities and various difference schemes of computation of flows.

Background.The prevalence of various allergic diseases has increased worldwide in recent decades. Allergy diagnosis in children should be economically optimal and as sparing as possible, while ensuring the high quality of medical care.Objective.The aim of the study is to develop optimal algorithms for analysis of sensitization profile in children with allergy family history, or suspected allergy, or atopy phenotype.Methods.Complete examination of 153 children aged from 1 to 17 years 11 months was performed. Children were divided in 4 groups according to the presence and characteristics of complaints, the presence of allergic disease. Sensitization was determined via the “gold standard” of allergy diagnosis — the ImmunoCap method (Phadia, Sweden), and the results of skin testing.Results.97 (63.4%) children have shown sensitization to various allergens. We have revealed seasonal manifestation of allergy in children to various allergens: Fagales in 89-92% of cases, grasses in 68-72% of cases, weeds in 39-57% of cases. Complaints of all-year manifestations of allergic rhinitis were revealed in 24% of cases to cat dandruff, complaints of coughing and/or bronchospasm — in 100% of cases to birch pollen and in 35% of cases to house dust. The sensitization analysis has revealed strong correlations with confirmed statistical significance between pollen allergen sensitization classes in groups of different plants.Conclusion.Optimal algorithms for sensitization diagnosis in children living in Moscow agglomeration were developed according to the obtained results and revealed correlations.

A numerical simulation of a nonstationary flow of a gas containing inert particle in a shock tube has been perfumed on the basis of the model of mutually penetrating continua, in which the gaseous and dispersed phases are defined by sets of mass, momentum, and energy conservation equations and the equation for the evolution of the dispersed-phase volume fraction. The main equations are hyperbolic, and they are solved using the Godunov-type method of increased accuracy. The shock-wave structure of the gas flow in the working section of the shock tube and the space and time dependences of this flow were determined. The numerical-simulation results are compared with available experimental and calculation data.

A numerical simulation of the flow induced by rotation of the ducted fan blades of a quadcopter is carried out using the vortex-resolving approach that assumes solution of the full Navier–Stokes equations. Based on the numerical simulation results, the aerodynamic characteristics of the ducted fan are determined in various flight modes with asymmetric airflow over the surface swept by the propeller. In the problem formulation, various angles of the ducted fan rotation plane deviation from the vertical were considered for various flight modes of a multicopter type aircraft as well as characteristics of the non-perturbing incident air flow.

The influence of the geometric and regime parameters of a resonance infrared jet-edge generator on the formation, in its resonance tube, of a sound field with a predominant discrete tone at the fundamental frequency of the generator resonant cavity was investigated. A parametric investigation of the self-sustained oscillation processes arising in the resonance tube of the generator as a result of the interaction of a subsonic gas jet and a supersonic one with its resonant cavity has been performed. The nonstationary structure of the gas flow inside this cavity, characteristic of the self-sustained oscillation interaction of a gas jet with an obstacle, is discussed. Prominence is given to the study of the pattern of the gas flow inside the resonant cavity and the amplitude-frequency characteristics of the wave process in it. Recommendations for designing a resonance infrasound jet-edge generator with regard for its use in actual practice are given.

The choice of non-drug methods for the treatment of systemic scleroderma is currently very limited. Several studies show that extracorporeal photochemotherapy can improve kidney and lung function and reduce skin fibrosis in patients with systemic scleroderma. We studied the dynamics of clinical and laboratory parameters in patients with systemic scleroderma with an assessment before and after 12 months against the background of complex treatment, which included programmed extracorporeal photochemotherapy. Indications for inclusion in the study was the ineffectiveness of standard therapy with glucocorticoids and cytostatics or the impossibility of their use, as well as signs of an unfavorable prognosis of the disease: diffuse form, high skin count (14), rapid progression with a significant initial decrease in the glomerular filtration rate, forced vital capacity, high immunological activity (high titer of antinuclear factor and positivity for antibodies to Scl-70). When evaluating the results of complex treatment, a good clinical effect was observed in all patients: the induration of the skin decreased, the functionality of the lungs and kidneys increased. A significant decrease in the disease activity index was noted. These positive changes were the basis for a decrease in the daily dose of glucocorticoids. Significantly significant changes were observed in a decrease in the immunological activity of the disease: levels of C-reactive protein, erythrocyte sedimentation rate and immunoglobulin G, antinuclear factor titer and all types of circulating immune complexes. The results of our study confirm the data of other studies that demonstrated the positive effect of extracorporeal photochemotherapy as a component of the complex treatment of systemic scleroderma.

The results of complex treatment with the programmed procedures of extracorporeal photopheresis and methotrexate in patients with psoriatic arthritis for 12 months are presented. It has been established that program extracorporeal photopheresis in combination with basic therapy with methotrexate in patients with psoriatic arthritis have a significant effect on the relief of articular syndrome (reduction of morning stiffness, pain intensity, joint swelling). It was revealed that the inclusion of programmed extracorporeal photopheresis and methotrexate in the complex treatment of psoriatic arthritis reduces the level of circulating low molecular weight, medium molecular weight and high molecular weight immune complexes and in most cases leads to clinical and immunological remission. This is confirmed by a decrease in complaints of the severity of articular syndrome and a decrease in the clinical and laboratory activity of the disease (a significant decrease in the level of C-reactive protein, erythrocyte sedimentation rate). A scheme has been developed for the programmed use of extracorporeal photopheresis procedures in the complex treatment of psoriatic arthritis, which consists of 2 procedures every other day with an interval of 2,5-3 months for 12 months. Combined therapy with the programmed application of extracorporeal photopheresis procedures and methotrexate prolongs the period of disease remission and can be recommended for patients with psoriatic arthritis with high activity, insufficient effect of basic therapy and intolerance to higher doses of immunosuppressive drugs.

Problems on the development of mathematical models for control of the technological processes of producing powders of metals from their melts and for optimization of these processes were considered. A numerical simulation of the solidification of melt droplets in a turbulent cold-gas jet has been performed with the use of a complex mathematical model, and results of this simulation were used for estimating the influence of different factors on the flying of a melt droplet in a gas flow until it is solidified.

The design of a subsonic jet-edge rod generator of the Hartmann-type oscillator and a scheme of measuring its acoustic parameters are presented. In this generator, unlike the Hartmann oscillator, not a cylindrical gas jet but an annular gas jet, moving along the thin cylindrical rod positioned at the axis of the generator nozzle, is used. A parametric investigation of the gasdynamic and acoustic processes arising in the tubular cavity of such a generator as a result of the interaction of a subsonic gas jet with this cavity has been performed with consideration for the nonstationary structure of the gas flow in the generator cavity. Recommendations on the choice of the design of a jet-edge rod generator of acoustic radiation with regard for its practical application are given.

Supersonic jets are widely used in devices based on a self-oscillation process emerging during the interaction of a gas flow with tubular cavities (gas-jet acoustic emitters). We analyze the mechanisms for sustaining undamped pulsations of pressure and determine the flow field in a tubular cavity during the interaction of an underexpanded supersonic jet with it. We consider the physical pattern of the flow in the cavity of a gas-jet emitter, demonstrate the existence of odd longitudinal modes, and propose wave diagrams for describing the flow in odd longitudinal modes. Wave diagrams are constructed based on analysis of signals from piezoelectric sensors detecting pressure pulsations in a tubular cavity. The flow parameters in the tubular cavity in the longitudinal modes are calculated using the flow velocity–velocity of sound diagram.

In high-pressure gas–jet Hartmann generators, the source of acoustic energy is kinetic energy of a gas jet by the supercritical ratio between the operation and ambient pressure. Under certain conditions, onflow of a supersonic jet to a resonator is accompanied by powerful self-sustained oscillations with irradiation of acoustic waves into the environment and resonator cavity. A model of a self-oscillating process arising from the interaction of a nonisobaric jet with semi-closed cylindrical cavities is considered, which allows one to identify typical elements of the gas-dynamic structure of the forming flow. The physical pattern of the flow in the gas–jet generator has been discussed and the study of the dependence of the self-sustained oscillation characteristics on the key gas-dynamic and geometric parameters has been performed.

The gasdynamic processes accompanying the injection of a pulsed gas jet into the diffuser part of a nozzle are considered in relation to the formation of control forces in rocket engines. The gas flow through the injection nozzle is controlled by a rotary damper. The finite volume method and moving mesh technology are used to discretize the Reynolds-averaged Navier–Stokes equations and the equations of the SST turbulence model. The effect of the opening time of the damper on the dynamics of the formation of the control force, as well as the dependence of the traction and energy characteristics of the nozzle on the flow rate of the injected working fluid, are studied. The results of calculations within the non-steady-state and quasi-steady-state problem statement are compared. The formation of the shock wave and vortex structure of the flow is discussed. Conclusions are drawn about the effect of the input parameters of the problem on the coefficient of the traction change.

Numerical modeling of the underwater outflow of a supersonic gas jet in a three-dimensional non-stationary formulation is carried out using an eddy-resolving approach based on a combination of RANS-LES turbulence modeling methods. The calculation of the interaction of a gaseous medium with a liquid is carried out using the VOF multi-phase model, the forces of surface tension and the compressibility of the liquid are taken into account. As a result of calculations, an unsteady pattern of the formation of a supersonic jet and a gas cavity in a liquid is obtained, the shock-wave structure of the flow is visualized, and pressure fluctuations in the liquid are estimated. The results of calculations are compared with the data of experimental high-speed photography.

A simulation of a high-temperature air flow in a nozzle with a nonstationary local power supply has been performed. The thermodynamic processes in this flow were simulated using an approximate model of equilibrium air thermodynamics. Results of a numerical simulation of one-dimensional flows in nozzles with a moving powersupply zone, used in alternating-current plasma generators, are presented. On the basis of the numerical-simulation data obtained, the qualitative patterns of the gasdynamic and thermal processes proceeding in such a nozzle with a nonstationary power supply were analyzed. The results of calculations performed on the basis of the ideal-gas and real-gas models with regard for the physicochemical processes occurring in a real gas at a high temperature were compared.

Interest in the development of models and methods focused on the mechanisms of noise generation in jet flows is due to strict noise requirements produced by various industrial devices, as well as the possibilities of using sound in engineering and technological processes. The tools of physical and computational modeling of gas dynamics and aero-acoustics problems are considered, and noise sources and mechanisms of noise generation in supersonic jet flows are discussed. The physical pattern of the flow in free supersonic under-expanded jets is discussed on the basis of experimental and numerical data, as well as the flow structure arising from the interaction of a supersonic under-expanded jet with a cylindrical cavity. The influence of the nozzle pressure ratio and cavity depth on the sound pressure level, amplitude and frequency characteristics of the flow parameters is studied.

The numerical simulation of gas-dynamic processes accompanying the transverse injection of a gas jet into the supersonic part of a nozzle is considered in the context of creating steering forces in rocket engines. Numerical calculations are conducted based on various turbulence models at different mass flow rates of the injected gas. The calculation results obtained for the non-viscous, laminar, and turbulent formulation of the problem are compared with each other and with the physical experiment data. The formation of a shock wave and vortex flow pattern is discussed. Conclusions about the effect of problem input parameters on the thrust gain coefficient are made.

The interaction of solid particles with vortex structures was investigated, and the scattering of such particles by a combined vortex was numerically simulated using the Euler–Lagrange approach. The concentration distributions of particles in the region of a gas flow occupied by a vortex at different instants of time have been obtained. The dependence of the time for which these particles escape from the central zone of the vortex on their size was determined. The results obtained can be used for increasing the efficiency of measurement of the parameters of the disperse phase in a fluid flow by optical methods.

In this paper, the method is proposed for compensating for distortion of signals transmitted in a fiber-optic link, based on the inclusion of an analog optical in-verse nonlinear phase filter. The proposed implementation of the restoring analog optical nonlinear phase filter. The simulation results are presented, which demonstrate the ability to compensate for nonlinear distortions and restore pulse signals in a fiber-optic transmission line using the proposed filter. It is shown that the quality of the restoration largely depends on the admissibility of the linear approximation for the exponential characteristic of the nonlinear filter.