bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated segmentation of metal stent and bioresorbable vascular scaffold in intravascular optical coherence tomography images using deep learning architectures
Authors: Lau Yu Shi , Tan Li Kuo , Chan Chow Khuen , Chee Kok Han , Liew Yih Miin
Published: December 2021

Percutaneous coronary intervention (PCI) with stent placement is a treatment effective for coronary artery diseases. Intravascular optical coherence tomography (OCT) with high resolution is used clinically to visualize stent deployment and restenosis, facilitating PCI operation and for complication inspection. Automated stent struts segmentation in OCT images is necessary as each pullback of OCT images could contain thousands of stent struts. In this paper, a deep learning framework is proposed and demonstrated for the automated segmentation of two major clinical stent types: metal stents and bioresorbable vascular scaffolds (BVS). U-Net, the current most prominent deep learning network in biomedical segmentation, was implemented for segmentation with cropped input. The architectures of MobileNetV2 and DenseNet121 were also adapted into U-Net for improvement in speed and accuracy. The results suggested that the proposed automated algorithm’s segmentation performance approaches the level of independent human obsevers and is feasible for both types of stents despite their distinct appearance. U-Net with DenseNet121 encoder (U-Dense) performed best with Dice’s coefficient of 0.86 for BVS segmentation, and precision/recall of 0.92/0.92 for metal stent segmentation under optimal crop window size of 256.
Barrow Entropy Cosmology: an observational approach with a hint of stability analysis
Authors: Leon Genly , Magaña Juan , Hernández-Almada A. , García-Aspeitia Miguel A. , Verdugo Tomás , Motta V.
Published: December 2021

In this work, we use an observational approach and dynamical system analysis to study the cosmological model recently proposed by Saridakis (2020), which is based on the modification of the entropy-area black hole relation proposed by Barrow (2020). The Friedmann equations governing the dynamics of the Universe under this entropy modification can be calculated through the gravity-thermodynamics conjecture. We investigate two models, one considering only a matter component and the other including matter and radiation, which have new terms compared to the standard model sourcing the late cosmic acceleration. A Bayesian analysis is performed in which using five cosmological observations (observational Hubble data, type Ia supernovae, HII galaxies, strong lensing systems, and baryon acoustic oscillations) to constrain the free parameters of both models. From a joint analysis, we obtain constraints that are consistent with the standard cosmological paradigm within 2σ confidence level. In addition, a complementary dynamical system analysis using local and global variables is developed which allows obtaining a qualitative description of the cosmology. As expected, we found that the dynamical equations have a de Sitter solution at late times.
Effects of rotation errors on goniometric measurements
Authors: Molloy E , Saunders P , Koo A
Published: December 2021

Goniometric measurements are essential for the determination of many optical quantities, and quantifying the effects of errors in the rotation axes on these quantities is a complex task. In this paper, we show how a measurement model for a four-axis goniometric system can be developed to allow the effects of alignment and rotation errors to be included in the uncertainty of the measurement. We use three different computational methods to propagate the uncertainties due to several error sources through the model to the rotation angles and then to the measurement of bidirectional reflectance and integrated diffuse reflectance, a task that would otherwise be intractable. While all three methods give the same result, the GTC Python package is the simplest and intrinsically provides a full uncertainty budget, including all correlations between measurement parameters. We then demonstrate how the development of a measurement model and the use of GTC has improved our understanding of the system. As a consequence, taking advantage of negative correlations between measurements in different geometries allows us to minimise the total uncertainty in integrated diffuse reflectance, lowering the standard uncertainty from 0.0029 to 0.0015.
Temperature distribution in a subduction zone
Authors: Kirdyashkin A G , Kirdyashkin A A , Nepogodina Yu M
Published: December 2021

A model of the thermal and hydrodynamic structure of the subduction zone is proposed. This model includes free convection flows in the asthenospheric layer and layerC(mantle transition zone). Temperature profiles in the subducting lithospheric plate, as well as in the continental limb of the subduction zone, are presented. The heat flux due to friction at the contact between the subducting plate and the continental limb significantly affects the heat transfer and, consequently, the temperature field formation in the subduction zone. The temperature level in the crustal layer of the submerging plate implies that there is no melting in the crustal layer.
Flow control by distributed suction behind three-dimensional roughness element on the straight wing model
Authors: Kaprilevskaya V S , Pavlenko A M , Katasonov M M , Kozlov V V
Published: December 2021

The paper is devoted to the close investigation of the flow over perforated suction section in the presence of the three-dimensional roughness element. Measurements were conducted over the surface of the straight wing with and without suction. It was shown that distributed suction allows diminishing the intensity of longitudinal structure. Also the boundaries of the effective suction usage were found.
Effect of Local Turbulent Structures on the Hot Jet in Transitional Flow
Authors: Sakhnov A , Lukashov V V
Published: December 2021

Turbulent parts localized in flow direction may arise in a pipe with transitional regime of the stable laminar Poiseuille flow. A key condition for occurrence of such structures is a pipe with rather long length relative to its diameter. Our paper presents numerical modelling of the hot air jet flowing from the long pipe into the cold open volume at Re=2426. The modelling was performed in OpenFOAM software on the basis of the large eddy simulation (LES) method. The WALE (Wall-adapting local eddy-viscosity) model was used for closure of Navier-Stokes equations on subgrid scales. We demonstrated that local turbulent structures have a weak effect on the hot jet at flowing into the cold open volume.
Investigation of unsteady combustion of methane-air flame in a model combustion chamber with swirling flow
Authors: Lobasov A S
Published: December 2021

The present paper reports on the investigation of unsteady combustion of a methane-air mixture, including combustion at increased pressure in the combustion chamber and increased temperature of mixture heating for a model gas-turbine swirl burner based on a design by Turbomeca. To measure the velocity and OH fluorescence fields in the flows a combination of stereoscopic PIV and acetone PLIF systems is used. In all cases, the flow dynamics is associated with the movement of large-scale vortex structures in the inner and outer mixing layers and the flow structure corresponds to a swirling jet with a central recirculation zone containing combustion products. An increase in the heating temperature of the mixture and pressure in the combustion chamber leads to a periodic partial separation of the flame from the model swirl nozzle. However, the flow of fuel through the central channel will stabilize the flame.
Numerical simulation of flow dynamics and heat transfer in a rectangular channel with periodic ribs on one of the walls
Authors: Barsukov A V , Terekhov V V , Terekhov V I
Published: December 2021

The result of numerical simulation of a turbulent flow in a flat channel with a periodic transverse rib by the RANS and LES methods is presented. The Reynolds number, calculated from the rib height and the superficial velocity, is Re = 12600. The data obtained as a result of the study demonstrate the influence of the modeling method and the turbulence model on the quality of heat transfer prediction. The optimal model for this type of problems is presented.
Large-eddy simulation of a reacting swirling flow in a model combustion chamber
Authors: Hrebtov M Yu , Palkin E V , Slastnaya D A , Mullyadzhanov R I , Alekseenko S V
Published: December 2021

We perform Large-eddy simulations of a non-premixed swirling flame in a model of a combustion chamber with a swirling air bulk flow at Re = 15000 and a central pilot low-velocity jet with methane using the Flamelet-generated manifold model. The unsteady behaviour of this regime is well reproduced based on the flame dynamics. The distribution of turbulent kinetic energy suggests the presence of intensive vortical structures typical of high-swirl flows similar to the precessing vortex core.
The effect of Reynolds number on near-wall reverse flow in a turbulent duct flow
Authors: Ivashchenko V A , Zaripov D I , Mullyadzhanov R I
Published: December 2021

The influence of the Reynolds number on the statistics of a near-wall reverse flow phenomenon, taking place in a turbulent duct flow, is studied. An increase in the NWRF probability is found in both the core and corner regions of the duct walls for higher Reynolds number. The mechanism of the NWRF formation, described recently by Zaripov et al. [1, 2], is validated for higher Reynolds number flows.
Investigation of the swirled flow structure in the improved four-vortex furnace model
Authors: Shadrin E Yu , Anufriev I S , Alekseenko S V
Published: December 2021

The flow structure in a model of promising four-vortex furnace is investigated using three-dimensional laser Doppler anemometry method (3D-LDA). Using the “minimum total pressure” criterion, a vortex flow structure was visualized: the core looks like a deformed elliptical cylinder. Results has been compared with early PIV experiments and showed good agreement. The mathematical model for full-scale furnace numerical studies can be verified using these data.
Modern methods of direct numerical simulations of transfer processes in random media
Authors: Derevich I V , Klochkov A K
Published: December 2021

The paper considers the methods of direct numerical investigation of the behaviour of dynamical systems of explosive type under the influence of random noise. Dynamical systems are described by a system of nonstationary ordinary differential equations (ODE). The dynamics of the system, taking into account random noise, is described by a system of stochastic ordinary differential equations (SODE). The paper provides an overview of modern algorithms based on modifications of Runge – Kutta integration methods. The features of the analysis of weak and strong convergence of the SODE integration methods are described. Methods for generating random noise with complex temporal structure (color noise) are described. The method of numerical solution of the system of SODE is used to generate random color noise. Examples of the study of the influence of random noise on biological and mechanical systems of explosive type are presented. It is shown that random noises acting on such systems qualitatively change the character of their behaviour.
Multi-scale flow patterns during immiscible displacement of oil by water in a layer-inhomogeneous porous media
Authors: Kuznetsov V V , Safonov S A
Published: December 2021

This paper presents the results of numerical study of the relationship between micro-and macroscale flows during immiscible displacement in a two-layer porous medium. A feature of the proposed approach is the allowance for large-scale capillarity induced flow due to curvature of the displacement front in macro-inhomogeneous porous medium. The physical mechanisms determining the development of viscous instability in a layer-inhomogeneous porous medium are considered, the methods for suppressing viscous fingers formation based on the stabilization of the displacement front due the action of capillary forces are proposed.
Mathematical modeling of three-layer flows with evaporation based on exact solutions
Authors: Laskovets E V
Published: December 2021

The stationary flow in the “liquid-liquid-gas” system in a horizontal channel with solid impermeable upper and lower walls is investigated. Mathematical modeling in each of the layers of the system is based on exact solutions of a special type of Navier-Stokes equations in the Boussinesq approximation. The processes of vapor evaporation or condensation at the liquid-gas interface are modeled using the boundary conditions of the problem. In the upper layer the thermal diffusion effect and the effect of diffusional thermal conductivity are taken into account. Examples of three-layer flows for the “silicone oil - water - air” system are given. The influence of the thermal regime at the boundaries of the system and the thickness of the upper layer on the longitudinal velocity and temperature distribution is considered.
Movement of gas slug in annular channels with different diameter ratios
Authors: Kashinsky O.N. , Kurdumov A.S.
Published: December 2021

The motion of gas slugs in annular channels was studied experimentally. The outer tube diameter was 32 mm. The inner tube diameter varied from 4 to 25 mm. The gas slugs were produced by injecting air through a capillary tube. The shapes of gas slugs were studied by high-speed videos. The paper presents data on the rise velocity of gas slugs in the channels, and wall shear stress measurements, performed by electrodiffusional technique. The probes were mounted on both walls of the channel. The evolution of wall shear stress during slug passage was recorded.
Experimental study of wavy-annular flow in a rectangular microchannel using LIF method
Authors: Bartkus G V , Kuznetsov V V
Published: December 2021

This article aims at studying gas-liquid flow in a rectangular microchannel with a high aspect ratio (200 × 2045 μm). Liquid and gas phases were 95% ethanol and nitrogen mixture. Experimental flow characteristics are obtained using high-speed visualization and laser-induced fluorescence (LIF) methods. Using the LIF method for wavy-annular flow, the average film thickness, liquid film distribution, and liquid film width were measured. The dependences of the liquid film width and the average film thickness on gas superficial velocity are presented in graphical form and analyzed. An increase in gas superficial velocity causes growth of the liquid film width and thickness of the liquid film, which indicates the process of liquid transfer from the menisci area to the liquid film. For different liquid velocities and the same gas superficial velocities, close values of averaged liquid film thickness were observed for flow with 2D waves and 3D waves on liquid film.
Application of microfluidic technologies for enhanced oil recovery
Authors: Pryazhnikov M I , Minakov A V , Pryazhnikov A I , Denisov I A , Yakimov A S , Nemtsev I V
Published: December 2021

This paper presents the results of testing microfluidic technology for oil displacement problems using cheap and quickly manufactured chips made of polymethylmethacrylate (PMMA) by milling. The oil displacement process from a microfluidic chip simulating a homogeneous porous medium is studied. The microfluidic chip was manufactured by milling of polymethylmethacrylate. The size of the microchannels was 200 microns. The paper presents the results of visualization and microscopy of the oil displacement process. The effect of water flow on the efficiency of oil displacement from the microfluidic chip was studied.
CNN-based visual analysis to study local boiling characteristics
Authors: Chernyavskiy A N , Malakhov I P
Published: December 2021

Visual analysis allows an estimate of different local boiling characteristics including bubble growth rate, departure diameters and frequencies of nucleation, nucleation site density and evolution of bubbles and dry spots in time. At the same time, visual determination of the presented characteristics in case of big amounts of data requires the development of the appropriate software which will allow not only determination of bubble location, but also an estimate of their sizes based on high-speed video. The presented problem can be solved by using the instance segmentation approach based on a convolutional neural network. In the presented work Mask R-CNN network architecture was used for estimation of the local boiling characteristics.
Experimental investigation of water-nitrogen flow in microchannel with high aspect ratio (with the 20 µm gap)
Authors: Dementyev Y A , Ronshin F V , Chinnov E A , Evstrapov A A , Karpich S S , Gusev V S , Kabov O A
Published: December 2021

This study is devoted to the experimental investigation of two-phase water-nitrogen flow in the slit microchannel with a gap of 20 µm and a width of 10 mm. The technology of microchannel fabrication has been developed and described in detail. Experiments were conducted in adiabatic conditions. Using a modified schlieren system, four flow patterns have been observed and described: jet, bubble, churn, and annular. Flow pattern map was plotted according to obtained patterns. Moreover, a two-phase pressure drop was measured. Dependencies between two-phase pressure drop and superficial liquid and gas velocities have been investigated.
A review of modern numerical and analytical models of heat transfer in a dielectric layer during melting due to microwave radiation
Authors: Karelin V A , Salomatov Vl V
Published: December 2021

In this work, numerical and analytical solutions of heat transfer in a dielectric layer during melting in the microwave field were considered. We considered solutions, where the source term was obtained based on the solution of Maxwell equation, as well as using the Lambert law. The conditions applicable for analytical solutions, allowing the parametric analysis, are determined. The areas of application of the technology of microwave melting of dielectrics, in particular with melting ice on water, defrosting products, etc., were also considered.
Numerical simulation of the flow around a circular cylinder at Reynolds number Re = 3900 by means of the PANS model
Authors: Shebelev A. , Gavrilov A. , Dekterev A. , Sentyabov A.
Published: December 2021

The paper presents a study of various versions of PANS approach for turbulence simulation using a flow around a cylinder at Reynolds number Re = 3900 as an example. The considered models were implemented in the in-house CFD package. The influence of the method of determining the parameter f
k on the flow behind the cylinder was studied. The first method assumed a constant value of f
k. In the second method, the f
k value depended on the local computational mesh scale and the shear scale.
Calculation of heat transfer coefficients for explosive boiling of a liquid under conditions of low pressure
Authors: Brester A E , Zhukov V I , Shvetsov D A , Pavlenko A N
Published: December 2021

The paper discusses the problem of determining the temperature head for calculating the heat transfer coefficient during explosive boiling of a liquid on a smooth horizontal surface under conditions of low pressure. The task of the work is obtaining the method for determining the characteristic pressure for calculating the temperature of saturated vapors. As a result, it is found that the difference between the heat transfer coefficients calculated at the pressure specified at the beginning of the experiment and the pressure averaged over time differ on average by 5%.
Investigation of heat transfer during evaporation of droplets of Fe3O4 nanofluids from biphilic surfaces
Authors: Starinskaya E M , Miskiv N B , Lei M K , Terekhov V V
Published: December 2021

In this work, unique biphilic substrates were prepared with a sharp spatial gradient of the contact angle of wetting. Experimental studies of the process of evaporation of liquid droplets lying on the structured surfaces have been carried out. In the experiment, the dynamics of the temperature of an evaporating droplet was compared depending on its orientation in space. It was found that suspended droplets of 0.1 wt % Fe3O4 nanofluid have a higher evaporation temperature and a higher evaporation rate as compared to sessile droplets.
The heat supply object thermal regime under conditions of gas infrared emitter and air exchange system joint operation
Authors: Kuznetsov G V , Maksimov V I , Nagornova T A , Vyatkin A V
Published: December 2021

The paper presents the results of experimental studies on the formation of thermal comfort conditions in large premises with the joint operation of gas infrared emitters and air exchange ventilation system. The values of temperatures and heat fluxes on the clothing surface under natural and mixed convection conditions were obtained. It has been established that the air exchange system operation in the premises reduces the temperature drop of the person clothes surface, respectively, a more favorable temperature condition is achieved in the working area.
Numerical analysis of the equipment position influence on the premises thermal regime under gas infrared emitter operation and mixed convection conditions
Authors: Borisov B V , Kuznetsov G V , Maksimov V I , Nagornova T A , Vyatkin A V
Published: December 2021

The analysis of mathematical modeling results on premise heating by a gas infrared emitter (GIE) during supply and exhaust ventilation operation is presented in this article. The model is presented in a one-dimensional non-stationary setting for an incompressible medium with allowances for the radiant heat flux transfer between opaque solid surfaces in the air. The air is transparent to thermal radiation. The traditional k-ε model is used for turbulence modeling. The possibility for creating comfortable conditions in the area of a horizontal surface with different heights, imitating laboratory equipment, is analyzed.
Dual axis solar tracking system for a parabolic dish CPU water heater
Authors: Alwan Naseer T. , Milia H. M , Shcheklein S E , Matveev A V
Published: December 2021

The solar parabolic dish water heater is highly efficient but has limited hours of work only when sunlight is perpendicular to its surface. Therefore, this work aims to continue the work of the solar parabolic dish in the daytime using a dual tracking system, depending on the geographic location of the system (longitude and latitude angles) and using the C # programming language. To verify the effect of the dual-axis solar tracking system, the current study considered two types of solar parabolic dishes, the first was fixed, and the second was a rotating dish (by the dual tracking system). It was observed that the water temperature at the outlet of the tracking type solar water heater is 22% higher than that for the fixed dish type; this means that the proposed system has improved the temperature of water in the heat exchanger. Therefore, the highest water temperature value of about 51.4ffiC was at the outlet of the heat exchanger for the tracking type at 1:00 pm, while the temperature recorded for the fixed type was about 46.1ffiC. The highest energy gained from the solar heating system was at 1:00 pm for both types, which was about 76.9 W from the tracking type and 54.7 W from the fixed type. It was also observed that in the fixed dish type, most energy losses occurred during the daytime, while for the tracer of the dish type, useful energy was gained during most of the sunny working hours depending on the solar radiation intensity.
Numerical estimation of thermal ignition conditions for reactive medium with Gaussian distribution of activation energy
Authors: Donskoy I G
Published: December 2021

The article investigates the solutions of the one-dimensional stationary integro-differential heat equation. The source of heat release is determined through the Gaussian distribution function of the activation energy. In such a statement, the critical conditions for the existence of a bounded solution depend on the distribution variance. With the help of numerical methods, such dependences are obtained; for their explanation, the analytical approximations of the thermal explosion theory are used.
Study of the dependences of coal-wood composition, identification of combustion features of the obtained composite materials
Authors: Kuznetsov A V , Gorelikov E U
Published: December 2021

In the study of the combustion of samples, it was found that, other things being equal, under the experimental conditions and with the fixed technical characteristics of the fuel, different parameters of the flame are observed, namely, the speed of reaching a stationary mode, the completeness of fuel combustion, the size and distribution of temperature zones strongly depend on the methods used to carry out the mechanical fuel processing. Comparison of the results showed that under the same experimental conditions, the temperature distribution along the length of the experimental stand, in a stationary mode of operation, is higher for the composite fuel. In the case of composite fuel, 70 percent of the fuel burned up was observed at a 1 m section, which is indicative of these fuel consumption and kindling processes at industrial thermal power plants.
Synthesis of methanol in microchnnel
Authors: Dimov S V
Published: December 2021

Systematic experimental data have been obtained on the results of catalytic chemical reactions in a microchannel reactor for the synthesis of methanol from synthesis gas. Synthesis gas contains hydrogen, carbon monoxide and dioxide, as well as nitrogen in the ratio 58/29/5/8. The experiments were carried out at different flow rates in the temperature range 190-260C. Experiments were also carried out for methanol synthesis in fixed bed reactor at different synthesis pressures.
Distributed ferromagnetic enhanced inductive plasma source for plasma processing
Authors: Isupov M V
Published: December 2021

New experimental data on the plasma density profiles have been obtained for a low-frequency (100 kHz) distributed ferromagnetic enhanced inductive plasma source at different locations of inductive discharges. An ability to control the plasma density profiles in a large gas discharge chamber in order to achieve a uniform treatment of a substrate is demonstrated. The differences between the obtained results and literature data for a distributed ferromagnetic enhanced inductive plasma source combined with a radio-frequency inductive discharge are discussed.
Influence of synthesis parameters and thermal annealing on grain size of polycrystalline aluminum thin film
Authors: Merkulova I E
Published: December 2021

The thin polycrystalline aluminium films were synthesized on monocrystalline silicon substrates by ion-plasma sputtering. The synthesis was carried out at temperatures of 80 and 160°C and deposition rate of 10 and 110 nm/min. As-deposited films were annealed for 15 h at 550°C. The morphology of aluminium films before and after annealing was obtained using SEM images. The surfaces of as-deposited Al thin films, synthesized at high temperature, were uneven, while for low temperature films they were smooth enough with Al hillocks on the top of the film. After thermal annealing, morphology of the films was changed slightly. XRD patterns were obtained to calculate the average Al grain size of as-deposited and annealed films. The XRD analysis showed that an increase in the synthesis temperature leads to an increase in the average grain size from 50 to 84 nm and that increase in the rate of Al film synthesis leads to an increase in the average grain size from 50 to 63 nm. As the result of annealing, the average grain size increased for all samples and the final meaning was from 78 to 140 nm.
Numerical simulation of domain wall motion in a surface discharge over a ferroelectric
Authors: Bobrov M S , Hrebtov M Y , Yudin P V
Published: December 2021

The article presents a simplified numerical simulation of a vacuum ferroelectric cathode operating in a low-current mode (without surface plasma formation). The field emission from the cathode was simulated for the range of applied electric field magnitudes. The polarization domain growth process during the charging of ferroelectric surface was simulated using Landau-Ginzburg-Devonshire model. Interaction of the electrons with a depolarization field of a domain wall led to an attraction of the electrons to the polarization domain boundaries. A close to the linear dependence of the equilibrium domain wall position from the applied electric field was found with the total emitted charge proportional to the domain size.
Investigation of the effect of air humidity on the condensation growth of levitating liquid microdroplets
Authors: Zaitsev D V , Shatekova A I
Published: December 2021

Two-dimensional structured arrays of liquid microdroplets levitated over a hot liquid surface have been investigated in several recent papers, but the nature of this phenomenon has not yet been fully understood. In this work we investigate the effect of air humidity on the condensation growth of levitating liquid microdroplets. It was found that the higher the relative humidity of the surrounding air, the lower the rate of the droplet growth.
Evaporation of levitating liquid microdroplets over a dry heated surface
Authors: Kunts K A , Zaitsev D V , Kabov O A
Published: December 2021

The present work is devoted to the study of the evaporation process of micro-sized water droplets levitating over a heated dry substrate. The study of this process is relevant in connection with the development of spray cooling systems. Due to the extreme complexity of this phenomenon the mechanism of spray cooling is still not fully understood. In this work we studied the evaporation of micro-sized water droplets levitating over a dry substrate heated from below. The working area was open to the atmosphere. Evaporation was studied in the temperature substrate range from 23 to 95°C. During the experiment local values of the substrate temperature and geometric characteristics of the drop were determined. In the experiment a shadow method with high spatial resolution was used, shooting was performed with a high-speed camera.
Experimental setup for studying two-phase flows in micro-and minichannels at ultra-high heat fluxes: methodology and first experimental results
Authors: Zaitsev D V , Belosludtsev V V
Published: December 2021

The study of phase-change phenomena under high and ultra-high heat fluxes is urgent because of fast development of electronics and microelectronics. We have developed a test section with power of 3.5 kW with a heater of 1x1 cm2 and adjustable geometry of the channel for achieving ultra-high heat fluxes in flow boiling and shear-driven liquid film experiments. The methodology of calculating heat losses in the test section is proposed and verified by flow boiling experiment versus another well studied test section. Observed trend of decrease of relative heat losses with increase in the heat flux makes it possible to assume that the heat flux as high as 2.5 kW/cm2 can be reached by this test section.
The low temperature heat capacity of Li2Mo0.05W0.95O4
Authors: Musikhin A E , Bespyatov M A , Kuzin T M , Grigorieva V D , Shlegel V N
Published: December 2021

The heat capacity of a lithium tungstate single crystal doped by 5% molybdenum Li2Mo0.05W0.95O4 in the range of 78.5–302.8 K was measured by the adiabatic method. No anomalous behavior of heat capacity was found. The heat capacity function was obtained in the range of 0–303 K by extrapolating to zero temperature and fitting experimental points. Thermodynamic functions of entropy, enthalpy increment and Gibbs free energy at 298.15 K were calculated using the obtained data.
Heat capacity of bismuth cobalt oxides doped by neodymium and holmium in the temperature range of 319-1000 K
Authors: Matskevich N I , Samoshkin D A , Stankus S V , Tkachev E N , Zaitsev V P , Trifonov V A , Semerikova A N , Anyfrieva O I
Published: December 2021

The heat capacity of bismuth cobalt oxides doped by neodymium and holmium was measured for the first time by differential scanning calorimetry in the temperature range of 319-1000 K.
The interdiffusion in liquid alloys of alkali metals with lead
Authors: Abdullaev R N , Khairulin R A , Stankus S V
Published: December 2021

The mutual diffusion in liquid cesium-lead alloys containing from 20 to 70 at.% Pb is investigated by a gamma-ray attenuation technique. The obtained data are compared with the results of similar studies for Li-Pb, Na-Pb, and K-Pb melts, carried out by us earlier. The concentration dependences of the interdiffusion coefficient for alkali-lead liquid systems demonstrate pronounced maxima in the vicinity of 20 or 50 at.% Pb. These phenomena confirm a tendency for chemical short-range ordering in liquid alloys.
Experimental study of R-32/R-125 (75/25 wt.%) thermal conductivity in the vapor phase
Authors: Raschektaeva E P , Stankus S V
Published: December 2021

The article presents the investigation of the thermal conductivity of binary mixture R-32/R-125 (75/25) in the gas state. Measurements were taken with a coaxial cylinders method in the temperature range of 305-426 K and the pressure range of 0.1-1.8 MPa. The dependence of thermal conductivity on pressure and temperature was discussed. The equations for thermal conductivity on the dew line and in the ideal gas state were obtained.
Thermal diffusivity of corrosion-resistant coating SDP-1
Authors: Agazhanov A Sh , Samoshkin D A , Stankus S V
Published: December 2021

In the present work, the thermal diffusivity of the SDP-1 grade nickel alloy was investigated in the wide temperature range of 300-1476 K. The SDP-1 alloy (Ni-Co-Cr-Al-Y) is the heat-resistant coating for blades of gas turbine plants, providing protection against sulfide-oxide corrosion in the temperature range of 1070-1220 K. The measurements were performed by laser flash method using LFA-427 apparatus. The estimated errors of the obtained data were 2-5% depending on temperature. The thermal diffusivity approximation equations and a table of reference values for various scientific and practical applications were obtained.
Experimental studies of in-line gasification of mechanically activated coal fuel
Authors: Bondarchuk E N , Pochtar A S , Vinogradov S V , Popov V I
Published: December 2021

The 1 MW experimental stand was modernized with a scroll swirler and a crushed fuel supply system. Comparative data on combustion and gasification of coal fuel crushed in high-stress mills - disintegrator, vibrocentrifugal and hammer mill - at a stand with a thermal power of 1 MW were obtained. The experiments used coal of the Kuznetsk Basin, grade D, with technical characteristics: Wr, % = 5.4; Ar, %=22.3; Vr, % = 32.3; Qsr, MJ/kg = 20.0. Elemental analysis showed that: Cr, %=54.6; Hr, % = 4.1; Nr, % = 1.3; Sr, % = 0.5; Or = 11.8. In experiments with grinding coal on a disintegrator mill, the value of H2 = 4.5 vol.% and CO = 9.4 vol.%, when grinding in a vibro-centrifugal mill, the values of H2 = 0.6 vol.% and CO = 5.8 vol.%, when grinding in a hammer mill, the values of H2 = 0.3 vol.% and CO = 2.8 vol.%. When studying the combustion of mechanochemically treated coal samples, it was found that, all other things being equal, the gasification parameters, namely, the gas concentration and the distribution of temperature zones, depend strongly on the type of equipment used for processing. In particular, processing to approximately the same degree of fineness in mechanical mills-activators with constrained impact and in free impact mills (disintegrators) resulted in different flame parameters.
Monitoring and control of polymer production line based on machine learning
Authors: Abdurakipov S
Published: December 2021

The work is devoted to the development of an application for monitoring and controlling the state of equipment (extruder) for the petrochemical industry based on sensor readings using a machine learning model. The statistical relationships of the technological process parameters are analyzed, the most significant parameters influencing the occurrence of failures are determined using SHAP values. The hypotheses regarding the effectiveness of various machine learning algorithms in relation to the real problem of predicting the technical state of the extruder are tested. A gradient boosting model has been developed to predict the probability of extruder shutdown due to the formation of polypropylene agglomerates. The developed application allows interpreting the results of the model, which makes it possible to select the most important process parameters that have the greatest impact on the probability of extruder failure, and also proposing a prototype of an extruder monitoring system based on sensor readings using a machine learning model.
Conjugate heat transfer in the mode of thermal gravitational-capillary convection in the model of a fuel tank, after a sudden heating of the sidewall
Authors: Mitin K. A. , Berdnikov V. S. , Bodneva N. I. , Ryabov V. O.
Published: December 2021

The evolution of unsteady gravitational-capillary convection in a layer of ethyl alcohol with a free surface after sudden electric heating of one of the vertical walls of a rectangular cavity was investigated numerically. The effect of the incoming flow of hot liquid on the time evolution of the temperature field on the opposite thin metal wall of the cavity was investigated. The calculations were carried out by the finite element method in the conjugate two-dimensional formulation with the Prandtl number Pr = 16, and the range of Grashof numbers determined by the heat flux density, 33·103 ≤ Gr ≤ 28·106. It is shown that the maximum local temperature gradients occur on the wall near the liquid-gas interface.
Dynamics of bubble growth during boiling at microgravity
Authors: Ronshin F , Sielaff A , Tadrist L , Stephan P , Kabov O
Published: December 2021

The purpose of this investigation is to study the mechanisms of boiling heat transfer in microgravity conditions. The RUBI (Reference mUltiscale Boiling Investigation) is an experiment where the basic phenomena of boiling heat transfer processes on a heated surface are investigated on the ISS (International Space Station). The special focus is paid to the coupling of macroscopic bubble dynamics from nucleation, growth and detachment combined with the microscopic phenomena in the thin films and micro layers on the heater, underneath the boiling bubbles. The image treatment program has been developed in order to extract the bubble volume as well as the contact angle from the experimental images. The first data of the bubble growth dynamics have been obtained and analysed.
Spatiotemporal distribution of the temperature field inside the thin heated foil during impacting liquid spray
Authors: Cheverda V V , Gigola T G , Somwanshi P M
Published: December 2021

The spatiotemporal distribution of the temperature inside a constantan foil during impacting spray is resolved experimentally in the present work. The received infrared image sequence will be used to find the local and average heat transfer coefficient of the foil. In the future, the results obtained will be used to calculate the heat flux in the region of the contact line of each drop.
The study of spray impact on the heated sapphire plate
Authors: Gigola T G , Cheverda V V
Published: December 2021

The process of the liquid spray impact on the heated surface is studied experimentally using the IR-transparent sapphire plate method. The spatiotemporal distribution of the temperature field on the sapphire substrate surface during impacting spray is received. The obtained experimental data are an important step in a study of the local characteristics of heat transfer in the areas of the contact lines during liquid spray impact on the heated surface. Further, the local heat fluxes and heat transfer coefficients will be determined by solving the problem of thermal conductivity in the sapphire substrate.
Assessment of the technical condition of lift guides using a magnetic field
Authors: Lonkwic P , Krakowski T , Ruta H
Published: December 2021

The systems that monitor individual components of machines and devices are under constant development. The ability to detect damages at an early stage allows failures to be prevented, so any uncontrolled downtime can be predicted in a controlled manner. Continuous monitoring of technical condition is an activity that also helps to reduce the losses due to equipment failures. However, not all areas can be monitored continuously. Such areas include lift guides where wear and tear can occur naturally, i.e. through abrasion of the material layer due to interaction with moving guide shoes or after emergency braking. Emergency braking causes local damages to the guide through plastic deformation of its surface resulting from indentation of the knurled roller of the brake. Such places are cleaned mechanically, which results in local reduction of the cross-sectional area. In such a case, it is difficult to continuously assess the technical condition of guides due to the prevailing operating conditions. Therefore, a concept of a head enabling assessment of the technical condition of guides at every stage of their operation has been developed. This article presents the novel concept of a magnetic head used for assessing the technical condition of lift guide rails that are the running track of lifting equipment. The initial tests were performed on the original test setup. The concept of the developed measuring head was verified for correct operation on specially prepared flat bars with holes. The results obtained in the form of laboratory tests proved that the proposed measuring head concept can be applied to the measurements under real conditions.
Numerical analysis of undercut anchor effect on rock
Authors: Jonak J , Karpiński R , Wójcik A
Published: December 2021

The paper presents the results of a numerical analysis using the Finite Element Method (FEM) of the friction issue in the contact between the undercut anchor head and rock during anchor pull-out. Formation of failure zone of rock medium was analysed assuming different Coulomb friction coefficients in the contact zone of conical anchor head with a rock. The problem is interesting as regards practical aspects of rock mass loosening during anchor pull-out. The analysis revealed a significant effect of the friction coefficient on the propagation and extent of the failure zone. Increasing the friction factor significantly decreases the extent of the failure zone measured on a free rock surface.
Composite plate analysis made in an unsymmetric configuartion
Authors: Falkowicz K
Published: December 2021

The work presents a thin-walled plate element with the central rectangular cut-out which can be use as an elastic or load-bearing element. Plates were made of carbon epoxy laminate and subjected to uniform compression. Plates were simply supported on shorter edges, and loaded axial load. The study included analysis of the critical and weakly post-critical behavior using experimental and numerical methods. Numerical analysis was performed with using linear analysis of eigenvalue problem to determination critical loads. The second step connected nonlinear analysis of structure with initiated geometrically imperfection corresponding to the flexural-torsional buckling mode of the plate. To the numerical calculations the commercial ABAQUS program was used.
Simulation research of the strength of an engine mount in an aircraft piston diesel engine
Authors: Magryta P , Pietrykowski K
Published: December 2021

The article presents strength simulations of a mount for mounting the test engine. Mounted on a stationary test stand, this mount consists of external fixings, fixings to stabilize the engine and tubular elements as a truss. These tubular elements are pipes made of seamless black steel. The material of the truss is S235JR steel. The article examines three different versions of the mount: mount no. 1 - initial mount, mount no. 2 - mount after a modification of pipe arrangement, mount no. 3 - mount after a modification of pipe wall thickness. For each version of the mount and subsequent calculation steps, the same boundary conditions and results legend were assumed. All calculations were made in Catia v5 in the Generative Structure Analysis module. To reflect the conditions prevailing during the engine operation on the test bench, the following conditions as mount load were adopted: gravity from the engine mass as 1000 N; engine thrust as 5000 N, and engine torque as 227 Nm. First, the model was pre-calculated to check the influence of mesh size on the obtained results. 2 mm parabolic tetrahedral elements were used in a computational grid. All subsequent steps of the mount modification showed a positive effect of reducing the maximum stress values or their mitigation as dispersion over a larger area. The changes made it possible to eliminate potentially dangerous areas of stress accumulation points. The material used has a strength several times greater than the stresses occurring in the tested elements. It was found that no further modifications to the mount are required and it is possible to use the created geometry on the test stand.
FEM analysis of manufacturing of a hollow product with an outer flange in a four-stage cold forming process
Authors: Wójcik Ł , Bulzak T , Winiarski G
Published: December 2021

The paper presents the results of a FEM computer simulation of the cold forming process of a hollow sleeve forgings with an outer flange. Numerical simulations were carried out in DEFORM 2D / 3D. For the numerical calculations of the forming process the axisymmetric calculation module was used. As the test object, a tubular workpiece with an outer diameter of Ø50 mm and a wall thickness of 10 mm made of 42CrMo4 steel was used. The process of forming the rotary sleeve was conducted in four stages consisting of two technologies. The first stage of the research was the analysis and selection of parameters of the extrusion process, which was used for the first stage of forming. The processes of free extrusion and the use of a container were analysed. Furthermore different die angles and different wall thickness reductions were used. The products obtained in the extrusion process were upset in three conical blanks. The aim of the study was to analyse the numerical accuracy of the designed process of forming the hollow shaft with flange. The analysis of the results was based on the deformation intensity distribution maps, the Cockroft-Latham criterion distribution and the progress of the forming forces. On the basis of the conducted research, it was concluded that the presented process of forging a hollow product with a flange in four stages is possible to carry out correctly.
Modeling and optimizations of mixing and aeration processes in bioreactors with activated sludge
Authors: Zaburko J , Łagód G , Widomski M K , Szulżyk-Cieplak J , Szeląg B , Babko R
Published: December 2021

Mixing aimed at homogenization of the volume of bioreactors with the activated sludge is of great importance for the proper course of the wastewater treatment process. It affects both the efficiency of pollutants removal and the properties of the activated sludge related to its sedimentation. The mixing process in bioreactors can be carried out in different ways. In batch bioreactors in the aeration phase or flow bioreactors in aerobic chambers, mixing is carried out through aeration systems. These systems should aerate the activated sludge flocs for efficient biological treating of wastewater, as well as effectively homogenize the volume of the bioreactor. Hence, it is important to choose such a design of the aeration system and its operation settings that provide the amount of air ensuring the exact amount of oxygen for the implementation of technological processes, counteract sedimentation of sludge at the bottom of the reactor, are reliable as well as economical in operation (demand of electric energy). The paper presents the model studies aimed at optimization of the design and settings of aeration and mixing systems used in active sludge bioreactors.