bluuebunny/crossref_metadata_2025_split huggingface dataset:
Maximal relevance and optimal learning machines
Authors: Duranthon O , Marsili M , Xie R 
Published: March 2021

Abstract
We explore the hypothesis that learning machines extract representations of maximal relevance, where the relevance is defined as the entropy of the energy distribution of the internal representation. We show that the mutual information between the internal representation of a learning machine and the features that it extracts from the data is bounded from below by the relevance. This motivates our study of models with maximal relevance—that we call optimal learning machines—as candidates of maximally informative representations. We analyse how the maximisation of the relevance is constrained both by the architecture of the model used and by the available data, in practical cases. We find that sub-extensive features that do not affect the thermodynamics of the model, may affect significantly learning performance, and that criticality enhances learning performance, but the existence of a critical point is not a necessary condition. On specific learning tasks, we find that (i) the maximal values of the likelihood are achieved by models with maximal relevance, (ii) internal representations approach the maximal relevance that can be achieved in a finite dataset and (iii) learning is associated with a broadening of the spectrum of energy levels of the internal representation, in agreement with the maximum relevance hypothesis.
Molecular Dynamics Simulation of the Leidenfrost Effect
Authors: Biryukov D A , Gerasimov D N , Yurin E I 
Published: March 2021

Abstract
Results of the molecular dynamics simulation of the contact between an argon droplet and an overheated copper surface (with the temperature exceeding critical for argon) are presented. The direct contact of argon (supercritical fluid) and the overheated surface is observed in the numerical experiment. Dynamics of the droplet size change is described by a simple equation.
Experimental study of heat transfer, hydrodynamics and drying kinetics in a centrifugal fluidized bed apparatus
Authors: Nadeev A A , Barakov A V , Dubanin V Yu , Muravev A V , Khripunov K G , Solzhenikin P A 
Published: March 2021

Abstract
This paper presents the test results of a prototype installation for drying dispersed materials in a centrifugal fluidized bed. The prototype is a batch apparatus with a vertical supply of a drying agent. A diagram of a test bench designed to study the hydrodynamics of the apparatus and the heat and mass transfer process during drying in a centrifugal fluidized bed is given and described. Silica gel with a particle diameter of 3.8 mm was used as a dispersed material. Hydrodynamic experiments were carried out on a “cold” model. Based on their results, the relationship of the hydraulic resistance of the apparatus at various values of the air velocity and mass of material in the working chamber is constructed. Experimental data have been obtained on low-temperature drying of silica gel in a centrifugal fluidized bed for various modes. The data are presented as time relationships of the temperature and humidity of the material and the drying agent. Analysis of the data obtained showed that the heat and mass transfer process in a centrifugal fluidized bed has a high intensity. A positive conclusion is made about the possibility of using this apparatus for low-temperature drying of capillary-porous bodies.
An effective numerical method for simulating chemically and thermally nonequilibrium gas flows
Authors: Molchanov A M 
Published: March 2021

Abstract
A new efficient implicit numerical method has been developed for solving the equations of compressible viscous chemically and thermally nonequilibrium gas flow on structured grids. In this method, the problem of stiff is completely solved (the scheme is unconditionally stable), the number of matrix inversions is reduced, and the matrices themselves are factorized into smaller ones, and their inversion requires significantly less computer resources than for a fully implicit scheme. High convergence rate is achieved due to the fact that the algorithm can significantly reduce the decomposition errors of the approximate matrix in two ways. Test calculations were carried out, which showed a high efficiency of the proposed numerical schemes.
The Cavitation Process in Proximity to an Ultrasonic Waveguide
Authors: Biryukov D A , Gerasimov D N , Yurin E I 
Published: March 2021

Abstract
Ultrasonic cavitation may be accompanied by sonoluminescence – light emission from the cavitation area. The work discusses the connection between two-phase domains and light emission (sonoluminescence). Experimental evidences provide some proves to non-thermal theories of sonoluminescence.
Heat transfer between human and fluid under extreme conditions of partial body cryotherapy
Authors: Kolishkin L M , Shakurov A V 
Published: March 2021

Abstract
This paper is aimed to study the cooling gas, cryocabin and skin temperature distributions to clear the partial body cryotherapy dosing. First, an experiment was performed in an empty cabin. It showed the effect of heat flow from the cabin walls to the cooling gas, as well as the distribution of gas temperature in the cabin without the human heat load. Second, an experiment was conducted with a volunteer. It showed the influence of the human heat load on the gas temperature, as well as the relationship between the skin surface temperature and the cooling gas temperature. Also, after the cooling gas supply is stopped, the dynamics of gas in the cabin, the cabin walls and the patient’s skin rewarming are considered. Data on the actual temperatures during cryotherapy may help correct current empiricism of cryotherapy protocols.
Searching of the optimum tilt of the pipe at condensation by using gradient heatmetry
Authors: Sapozhnikov S Z , Mityakov V Yu , Mityakov A V , Babich A Yu , Zainullina E R , Pavlov A V 
Published: March 2021

Abstract
The aim of the study is to determine optimum tilt of the pipe at film condensation by using of gradient heatmetry. Dependence of heat flux per unit area on time and azimuthal angle are presented for vertical, horizontal and inclined pipe. Maximal heat transfer coefficients for experimental conditions are observed for the angle 20° from vertical. The gradient heatmetry gives high informational content, which opens up new possibilities for studies of heat transfer during condensation.
Comparative study of performance of heat exchangers used in hypersonic wind tunnels
Authors: Drozdov S M , Rtishcheva A S 
Published: March 2021

Abstract
During the modernization of the TsAGI hypersonic wind tunnel, which implied an increase in the limiting values of stagnation parameters, and, consequently, the heat load, the operation of the main air cooler structures was analyzed. Two qualitatively different options are considered: Option-1, in which the flow moves in a large number of longitudinal tubes placed in a common compartment with cooling water circulating in the intertube area, and Option-2, that is a bundle of tubes (tubes of circular or elliptical section were considered) containing a moving cooler (water), and the air flow transversely moves in the intertube gaps. In the study, a previously worked out and experimentally verified approach to numerical simulation was implemented, according to which a through calculation of the flow and heat transfer was carried out in all areas of the duct with cooled walls (prechamber, nozzle, test section, diffuser) and a cooling compartment for the mode p
0=12 atm; T
0=5000 K; M≈7. The ANSYS FLUENT software package solved axisymmetric Navier-Stokes equations for viscous and heat-conducting gas using the Spalart-Allmaras turbulence model. For the flow in the area of the cooling compartment, the simplified Darcy’s model and the model of the “schematized axisymmetric tube bundle” were considered.
Features of vortex formation and heat transfer during cross flow around two cylinders
Authors: Guzeev A S , Sapozhnikov S Z , Mitiakov V Yu , Seroshtanov V V , Suchok V V , Vlasov A S , Zhidkov N A 
Published: March 2021

Abstract
The creation of all heat exchangers supposes the establishment of a quantitative and qualitative relationship between the flow and heat flux distribution at heat transfer surfaces. The paper presents the study’s results of the vortex flow’s structure and heat transfer near two circular cylinders. The distance between the cylinders ranged from 0.5d to 4d during the experiments (here d is the diameter of the cylinders). The vortex flow’s patterns in hydro- and wind tunnels in the Reynolds numbers’ range from 4000 to 40,000 are compared. To study heat transfer near the cylinders, gradient heat flux measurement was used. In aerodynamic experiments, both cylinders were heated with saturated steam, ensuring a constant surface temperature of the cylinder. The results showed an agreement of the flow patterns. The effect of distance and flow velocity on the flow around the second cylinder is revealed: there may be cases when the second cylinder is at rest, in other cases it fluctuates. Gradient heatmetry revealed a decrease in the level of fluctuations near the second cylinder. However, the average Nusselt number for the second cylinder is expectedly lower than for the first.
Efficiency of burning sediments of waste water in a boiling layer
Authors: Lyubov V K , Vladimirov A M , Koroleva P V 
Published: March 2021

Abstract
It has been experimentally shown that the Metso HYBEX steam boiler installed at CHP-1 of JSC APPM and designed to burn a mixture of bark and wood waste and sewage sludge ensures their efficient utilization without highlighting fuel oil. At boiler loads close to the nominal efficiency, the gross value was 85.22–85.24%. The environmental indicators of the boiler unit fully and even with a margin meet the requirements established by directive 2010/75 / EC and GOST R 50831-95. The operation of the boiler ensured the complete utilization of sewage sludge generated at the sewage treatment plant. The annual savings of fossil fuels amounted to more than 80 thousand tons of fuel equivalent. The total content of heavy metals in fly ash emitted into the atmospheric air by a recycling and energy boiler with a bubbling fluidized bed when burning high-moisture biofuels is many times lower than when burning coal, even in low-emission furnaces.
Simulation of the electrovortex flow in a linear approximation under the action of the external magnetic field
Authors: Georgievskaya E P , Mikhailov E A , Teplyakov I O 
Published: March 2021

Abstract
Electrovortex flows appear in a liquid metal when a non-uniform current interacts with its own magnetic field. They are very important in different electrometallurgical processes connected with melting of metals. We describe the electrovortex flow in a hemispherical container which is connected with experiment which is carried in Joint Institute of High Temperature. Our main aim is to study the influence of the extermal magnetic field, because the experiment shows that even weak Earth magnetic field can change the characteristics of the flow.
To solve this problem we formulate a system of equations using Stokes approximation. They are solved with Thoms’ boundary conditions using the time marching method. Our numerical scheme gives us the opportunity to parallelize the computing process. For the calculations we use the CUDA technology. It allows us accelerate the calculation process, even if we use low-power user graphics cards. We hope that our experience can be used to solved another similar problems.
Subcooled liquid boiling: details of the mechanism and phenomenological description
Authors: Vasil’ev N V , Khodakov K A 
Published: March 2021

Abstract
Using high-speed filming (with a frame frequency up to 100 kHz) the important details of the subcooled liquid boiling mechanism are specified, which allow to conclude that Snyder-Bergles phenomenological model describes the process with the maximal likelihood. This model accounts for the main subprocesses of the subcooled liquid boiling (evaporation of the liquid microlayer located under the bubble near the dry spot boundary, vapor condensation at the bubble dome, liquid inflow to the microlayer). It corresponds to the modern ideas regarding to boiling mechanism and qualitatively well meets the experimental data. On the basis of the conducted experiments the description of several subprocesses of the model is defined more exactly: nucleation sites deactivation, het removal from the bubble dome by means of unsteady heat conduction, bubble size evolution as a result from the balance of masses of the evaporating and condensing vapors. It was shown that large vapor agglomerates appear in the flow due to small vapor bubbles coalescence with a heat flux density increase. Formation of dry patches under the agglomerates was studied. These dry patches are precursors of the boiling crisis. Superheating of the surface under dry patches immediately leads to the heating surface burnout.
Heat transfer in cryosurgical device with an extended applicator
Authors: Pushkarev A V 
Published: March 2021

Abstract
This paper is aimed to study the prototype of cryosurgical device with an extended applicator. Three experiments were conducted. First, an experiment without heat load showed temperature distribution on extended applicator and its cooldown time. Second, an experiment with a typical heat load (when the applicator contacts the biotissue phantom) showed the impact of heat load on the surface temperature and on its cooldown time in this case, as well as the temperature at the control points inside the biotissue phantom and the dynamics of growth, shape and size of the freezing region. The third experiment was equivalent to the second, but without temperature sensors on the applicator surface for better freezing region visualization. Also, after the liquid nitrogen supply is stopped, the dynamics of thawing are considered. Data on the actual temperature during cryoexposure should help give basic recommendations for developing a cryoexposure technique with increased dosing accuracy.
Superheated metastable water atomization: fine atomized water plumes diagnostics and disperse characteristics; summary of results, applications in power generation and new techniques.
Authors: Zalkind V I , Zeigarnik Yu A , Nizovskiy V L , Nizovskiy L V , Schigel S S 
Published: March 2021

Abstract
Complex experimental investigation of superheated flow and dispersion characteristics of sprays in atomizing nozzles of various types is made. The comparative analysis of experimental and calculating investigations of thermo physic and hydro- gas-dynamic flow and disperse characteristics was carried out for various types of spray nozzles. It has shown that the main process, which determine peculiarities of superheated metastable water flow and phase transformation in spray nozzles, is quick (explosive) boiling up. And the optimal variant for superheated water atomization and achieving the most fine spray plumes, which contain mainly submicron droplet fraction, at initial temperature 240°C (and higher) is atomization by means of contracting-expanding nozzles. In such nozzles the explosive boiling is accomplished by quick transformation of foamed liquid into vapor-droplet flow. Diagnostic peculiarities are considered for these optically dense spray plumes; the auxiliary measurement methods were worked out for estimation superheated water high atomization level. The experimental and calculating data dimensionless treatment was made for achieving extremely fine (mainly submicron) superheated water spray. The dimensionless parameter, which determines necessary water (or some other liquids, for example – fuels) superheating level was derived. The possible technical applications of superheated water sprays are described, and up-to-date state of corresponding projects is given.
Simulation of the propagation of heat waves in a radiation-cooled dispersed stream of liquid droplet radiators
Authors: Safronov A A , Filatov N I , Grigoriev A L , Bondareva N V 
Published: March 2021

Abstract
The problem of radiation cooling of a moving dispers stream is solved taking into account the heat transfer along the movement of the stream due to the action of the radiation heat conduction mechanism. Taking this phenomenon into account leads to the formation of a heat wave region in the solution of model equations. The characteristic parameters of this heat wave are calculated, the influence of heat waves on the stability of the process of forming the equilibrium flow temperature profile is discussed.
Effect of interphase heat transfer on bulk condensation in dust-laden vapor-gas flow
Authors: Kortsenshteyn N M , Yastrebov A K 
Published: March 2021

Abstract
The model was proposed for homogeneous-heterogeneous bulk condensation in vapor-gas flow with dust particles. The feature of the model is taking into account temperature difference between gaseous phase and dust particles (with condensate on them). Calculations were carried out for mixture of D2O (vapor) and N2 (gas). The model was verified by comparison of results for the flow without dust with experimental data. Results were obtained for different values of mass fraction of dust, radius of dust particles and their initial subcooling. It was shown that there is minimal initial subcooling at which there is liquid on dust particles at nozzle outlet. This value depends on size of particles and mass fraction of dust.
Comparing the formation and propagation features of subcritical and supercritical thermal detonation waves
Authors: Melikhov V I , Melikhov O I , Saleh B , Shkel A A , Blinkov V N 
Published: March 2021

Abstract
During a severe accident in a nuclear reactor, an ex-vessel steam explosion may occur when the molten core come into contact with the liquid coolant, the crucial factor in the fuel-coolant interaction is the fragmentation of melt into small droplets, which rapidly increase the heat transfer to the coolant, and could lead to a steam explosion and formation of a pressure wave with a disastrous consequence for the surrounding components. In this research a numerical simulation of a steam explosion was performed using the VAPEX-D code which is being developed at the Department of NPP in “Moscow Power Engineering Institute” for the simulation of fuel-coolant interactions. Using the microinteractions concept, the propagation of thermal detonation waves was studied, and the characteristics of subcritical and supercritical waves were compared. A sharp increase in pressure is noted during the transition from subcritical mode to supercritical mode of propagation. A parametric study was performed where the volume fraction of corium was varied to determine the critical value at which the thermal detonation wave decayed. The study shows that increasing the melt volume fraction, will increase the maximum pressure and the velocity of the thermal detonation wave. While varying the initial void fraction showed that the thermal detonation wave can propagate in a very low melt volume fraction.
Investigation of the equalization capability of submerged perforated sheets forWWER-1500 horizontal steam generator
Authors: Le Thanh Tung , Melikhov V I , Melikhov O I , Nerovnov A A 
Published: March 2021

Abstract
Non-uniform heat transfer occurs at the steam generator secondary side, thus inducing a non-uniform steam generation and a non-uniform steam flow rate along the evaporation surface. In order to equalize the steam flow rate, submerged perforated sheet is installed in the horizontal SGs An analysis of the equalization of the non-uniform steam load in the WWER-1500 horizontal steam generator is performed using the STEG calculation code. Variant calculations of various options for the perforation of sheets allowed us to determine the design of submerged perforated sheet, which very well equalizes the initially non-uniform steam load.
The method of comparative analysis of the effectiveness of vapor-liquid compression cooling system and conventional liquid cooling system by relative energy indicators
Authors: Karelin D L , Boldyrev A V , Gureev V M , Boldyrev S V , Kharchyk S I 
Published: March 2021

Abstract
The article presents a new method for the comparative analysis of the effectiveness of a vapor-liquid compression cooling system and traditional solutions based on single-phase liquid and air cooling, while taking into account the combination of cooling capacity factors, the power expended on this, depending on the ambient temperature. As a result of numerical simulation, it was proved that the total power consumption CS

∑

N

c
s

′

for ensuring the operability of the vapor-liquid compression cooling system with increasing ambient temperature decreases relative to the similar total power consumption ∑N
CS for a system using traditional cooling methods. With increasing mass flow rate and temperature of the cooling air, the relative power consumption

∑

N

C
O

′

/

∑

N

C
O

for the functioning of the cooling systems under consideration becomes less than the relative energy indicator of the quantities of heat removed Q
И/Q
CO from the cooled object.
The active external heat and mass transfer multifunctional “one-wall” model with “nullified” friction resistance parietal boundary layer for the high-speed aircraft
Authors: Prudnikov A G , Mamaev V K , Zakharov N N , Severinova V V , Tarasenko A N 
Published: March 2021

Abstract
In this paper, a new “single-wall” scheme of a high-speed wingless jet aircraft without compressor, which has the smallest, practically “zeroed” external friction and heat and mass transfer resistance with an active external near-wall boundary layer and tangential injection of the superheated steam from a cooling jacket SCC walls was proposed. Moreover, due to the limited flow rate of the combustible laminar sublayer vapor injection and the laminar “scaly” sublayer zeroed friction, the average Mach number of the vortex external near-wall boundary layer will be only 2% less than the Mach number of the flight speed. This circumstance allows not to merge the frontier layer of the hull (“fuselage”), as is done on the overwhelming majority of the aircrafts, but to use the energy and mass of the near-wall boundary layer as a normal incoming air flow.
Direct numerical simulation of methane-air mixture combustion with extended kinetics at moderate Reynolds numbers
Authors: Semenev P A , Toktaliev P D 
Published: March 2021

AbstractResults of direct numerical simulations of turbulent premixed combustion of methane-air mixture at model conditions in simple cubic computational domain at moderate Reynolds number Reλ∼50 and Karlovitz number Ka∼5 are presented. These conditions correspond to combustion regime with main oxidation reactions localized in thin area. Extended kinetic mechanism of methane oxidation is used for chemical reactions description. Laminar flame velocity values are obtained and compared with other results of 1D and 3D calculations. Thickness, form and local flame front structures are revealed based on computation results.
Modeling of Thermal-Hydraulic Processes in the Marine Power Installation Elements
Authors: Mitrofanova O V , Bayramukov A S , Ivlev O A , Urtenov D S , Fedorinov A V 
Published: March 2021

Abstract
The results of the current study presented the hydrodynamics and heat transfer features occur in the pipe systems of the thermal-hydraulic various elements of the ship nuclear power installations. A comparative analysis of the turbulent models choice, their approbation on typical elements of the curved pipelines, and comparison of the calculation results with experimental data were fulfilled. The conditions of the swirl flow crisis were determined on base of obtained results of theoretical studies and comparison with experimental data. The mechanism of occurrence of acoustic oscillations generated by large-scale vortex structures and causes of cyclic thermal loads were identified. The fundamental nature of the research, the use of the thermodynamic approach and the conclusions of the stability theory made it possible to predict the results of numerical calculations.