bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-temperature statistical mechanics of the Quantizer problem: Fast quenching and equilibrium cooling of the three-dimensional Voronoi liquid
Authors: Hain Tobias M. , Klatt Michael A. , Schröder-Turk Gerd E.
Published: December 2020

The quantizer problem is a tessellation optimization problem where point configurations are identified such that the Voronoi cells minimize the second moment of the volume distribution. While the ground state (optimal state) in 3D is almost certainly the body-centered cubic lattice, disordered and effectively hyperuniform states with energies very close to the ground state exist that result as stable states in an evolution through the geometric Lloyd’s algorithm [M. A. Klatt et al. Nat. Commun. 10, 811 (2019)]. When considered as a statistical mechanics problem at finite temperature, the same system has been termed the “Voronoi liquid” by Ruscher, Baschnagel, and Farago [Europhys. Lett. 112, 66003 (2015)]. Here, we investigate the cooling behavior of the Voronoi liquid with a particular view to the stability of the effectively hyperuniform disordered state. As a confirmation of the results by Ruscher et al., we observe, by both molecular dynamics and Monte Carlo simulations, that upon slow quasi-static equilibrium cooling, the Voronoi liquid crystallizes from a disordered configuration into the body-centered cubic configuration. By contrast, upon sufficiently fast non-equilibrium cooling (and not just in the limit of a maximally fast quench), the Voronoi liquid adopts similar states as the effectively hyperuniform inherent structures identified by Klatt et al. and prevents the ordering transition into a body-centered cubic ordered structure. This result is in line with the geometric intuition that the geometric Lloyd’s algorithm corresponds to a type of fast quench.
First integrals of holonomic systems without Noether symmetries
Authors: Tsamparlis Michael , Mitsopoulos Antonios
Published: December 2020

A theorem is proved that determines the first integrals of the form I=Kab(t,q)q̇aq̇b+Ka(t,q)q̇a+K(t,q) of autonomous holonomic systems using only the collineations of the kinetic metric that is defined by the kinetic energy or the Lagrangian of the system. It is shown how these first integrals can be associated via the inverse Noether theorem with a gauged weak Noether symmetry, which admits the given first integral as a Noether integral. It is shown also that the associated Noether symmetry is possible to satisfy the conditions for a Hojman or a form-invariance symmetry; therefore, the so-called non-Noetherian first integrals are gauged weak Noether integrals. The application of the theorem requires a certain algorithm due to the complexity of the special conditions involved. We demonstrate this algorithm by a number of solved examples. We choose examples from published works in order to show that our approach produces new first integrals not found before with the standard methods.
Delay-time analysis in radio-frequency
β
-Ga2O3 field effect transistors
Authors: Kamimura Takafumi , Nakata Yoshiaki , Higashiwaki Masataka
Published: December 2020

β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) with gate lengths (Lg) of 50–1000 nm were fabricated, employing a thin channel layer formed by a shallow Si-ion implantation doping to maintain a high aspect ratio between an Lg and a gate-to-channel distance. The MOSFETs with Lg = 200 nm had a maximum drain current density of about 250 mA/mm and a peak extrinsic transconductance of 17 mS/mm. The short-channel effect was well suppressed for the devices with Lg ≥200 nm, leading to excellent RF device characteristics represented by a record maximum oscillation frequency of 27 GHz at Lg = 200 nm. From simple delay-time analysis on the MOSFETs, the effective electron velocity passing through a region under the gate was estimated to be about 2 × 106 cm/s. Moreover, it was analyzed that the parasitic channel charging delay occupied a substantial proportion of the total delay due to a large sheet resistance of the Ga2O3 channel and thus limited their high-frequency device performance. These results suggest that both suppressing the short channel effect with a reduction in Lg to the sub-0.1-μm range and minimizing the access resistance are important to further improve RF device characteristics of Ga2O3 MOSFETs.
Confronting pitfalls of AI-augmented molecular dynamics using statistical physics
Authors: Pant Shashank , Smith Zachary , Wang Yihang , Tajkhorshid Emad , Tiwary Pratyush
Published: December 2020

Artificial intelligence (AI)-based approaches have had indubitable impact across the sciences through the ability to extract relevant information from raw data. Recently, AI has also found use in enhancing the efficiency of molecular simulations, wherein AI derived slow modes are used to accelerate the simulation in targeted ways. However, while typical fields where AI is used are characterized by a plethora of data, molecular simulations, per construction, suffer from limited sampling and thus limited data. As such, the use of AI in molecular simulations can suffer from a dangerous situation where the AI-optimization could get stuck in spurious regimes, leading to incorrect characterization of the reaction coordinate (RC) for the problem at hand. When such an incorrect RC is then used to perform additional simulations, one could start to deviate progressively from the ground truth. To deal with this problem of spurious AI-solutions, here, we report a novel and automated algorithm using ideas from statistical mechanics. It is based on the notion that a more reliable AI-solution will be one that maximizes the timescale separation between slow and fast processes. To learn this timescale separation even from limited data, we use a maximum caliber-based framework. We show the applicability of this automatic protocol for three classic benchmark problems, namely, the conformational dynamics of a model peptide, ligand-unbinding from a protein, and folding/unfolding energy landscape of the C-terminal domain of protein G. We believe that our work will lead to increased and robust use of trustworthy AI in molecular simulations of complex systems.
Intermittent dynamic bursting in vertically vibrated liquid drops
Authors: Pototsky Andrey , Maksymov Ivan S. , Suslov Sergey A. , Leontini Justin
Published: December 2020

A previously unreported regime of type III intermittency is observed in a vertically vibrated milliliter-sized liquid drop submerged in a more viscous and less dense immiscible fluid layer supported by a hydrophobic solid plate. As the vibration amplitude is gradually increased, subharmonic Faraday waves are excited at the upper surface of the drop. We find a narrow window of vibration amplitudes slightly above the Faraday threshold, where the drop exhibits an irregular sequence of large amplitude bursting events alternating with intervals of low amplitude activity. Our experimental results and the suggested phenomenological model directly link the onset of the intermittent bursting regime in an isolated liquid drop to the competition between two hydrodynamic modes: the surface Faraday waves and the shape deformation mode, responsible for the horizontal drop elongation.
A first-principles study on ferroelectric phase formation of Si-doped HfO2 through nucleation and phase transition in thermal process
Authors: Wu Jixuan , Mo Fei , Saraya Takuya , Hiramoto Toshiro , Kobayashi Masaharu
Published: December 2020

We have investigated ferroelectric phase formation of Si-doped HfO2 through nucleation and phase transition in the thermal process by first-principles simulation. For the nucleation process from amorphous HfO2 in the thin film during thermal annealing, the tetragonal phase can be thermodynamically preferred with the effects of dopant and surface energy and temperature for which entropy is directly calculated from phonon spectrum calculations. During cooling down, the diffusionless phase transition from the tetragonal to ferroelectric phase takes place by atomic displacement and the transition to the monoclinic phase is suppressed by the high kinetic activation barrier. The phase transition process from the tetragonal phase to the ferroelectric phase is directly confirmed by ab initio molecular-dynamics simulation.
Fish fins as a non-lethal alternative to muscle tissue in stable isotope studies of food webs in an Australian river
Authors: McIntosh Leah M. , Reid Michael A.
Published: December 2020

This study found a strong relationship between fin and muscle tissue in three Australian fish species, showing that non-lethally collected fin tissue can be used as a proxy for muscle tissue in isotopic trophic studies. We hypothesised that a strong linear relationship exists between fin and muscle δ13C and δ15N isotope ratios, and conversion equations can be developed where differences exist. We analysed fin and muscle tissues of three common species (Cyprinus carpio, Macquaria ambigua and Nematalosa erebi) from the Barwon–Darling River, New South Wales, Australia. There were significant differences between fin and muscle δ13C values for all species, and fin tissue was a good predictor of muscle tissue δ13C (r2=0.77 for all species). The relationship between δ15N values was less consistent, with a significant difference found in one species, but fin tissue was still a good predictor (r2=0.72 for all species). Developing species-specific tissue conversion models results in the least amount of error, but regional models result in similar error and are more accurate than general global models. These results are consistent with prior studies of different species. This study provides tissue conversion models for three species common to Australian lowland rivers, facilitating the inclusion of fish in food web studies with non-lethal collection methods.
Effects of a cathode fall region on deposition rate of copper atoms in Dc plasma sputtering source
Authors: Yahya Khalid A
Published: December 2020

A theoretical investigation was carried out to show the effect of the length of the cathode fall region on the deposition rate of copper atoms on a substrate using dc plasma sputtering source. The effects of the discharge voltage (−1 to −3 kV) and argon gas pressure (1 × 10–2 to 5 × 10–1 mbar) on the length of the cathode fall region of the proposed plasma source were investigated. The flux energies of gas ions, neutral’s gas atoms and electrons in one dimension were calculated to determine the length of the cathode fall region, total current density and the rate of deposition of copper atoms. The results show that the length of the cathode fall region increases when low gas pressure is used at high values of the discharge voltage for the plasma source. There is also a relationship between the length of the cathode fall region and the rate of deposition of copper atoms on the substrate, where the deposition rate increased by 76% when the cathode fall length increased by 120% at the discharge voltage −3 kV and the pressure of gas 1 × 10–2 mbar.
New Observations with Gemini and GTC of the VHE Blazar KUV 00311–1938: About Its Redshift and Environment
Authors: Pichel A. , Donzelli C. , Rosa-Gonzalez D. , Alonso M. Fernandez , Rovero A. C. , Muriel H. , Mayya Y. D. , Aretxaga I. , González J. Becerra , Carramiñana A. , Mendez-Abreu J. , Vega O. , Terlevich E. , Terlevich R. J.
Published: December 2020

Extragalactic very-high-energy (VHE; E > 100 GeV) sources are unique objects to study the most powerful particle accelerators in nature, as active galactic nuclei are likely sources of ultra-high-energy cosmic rays. BL Lacertae blazars are the most frequent extragalactic objects found in the VHE gamma-ray catalogs. It is very difficult to estimate their redshifts, considering they have no strong enough optical spectral features, hence ∼20% of them have unknown or poorly constrained redshifts. KUV 00311–1938 is a VHE BL Lacertae blazar, with an uncertain redshift in the range of 0.5 < z < 0.98. We have obtained deep spectroscopy using Gemini and the GTC telescopes of KUV 00311–1938 and its surroundings with high signal-to-noise ratio in 2016–2017. The lack of features did not allow us to determine the spectroscopic redshift of KUV 00311–1938; nevertheless, we obtain a lower limit of z ≳ 0.475. We determined the redshifts of 41 galaxies observed in the field-of-view of the blazar and through a population study, identified three pairs and four groups consisting of 3 or 4 members with redshifts in the range z = 0.1468–0.4756. Due to the absence of a large group of galaxies, we could not associate KUV 00311–1938 with any of the groups detected.
Shannon unicity distance, ε-secrecy criterion and Holevo information in quantum cryptography
Authors: Arbekov I M , Molotkov S N
Published: December 2020

In this paper, we consider the relationship between C Shannon’s unicity distance, which is determined by the number of symbols of the encrypted message required to uniquely find the encryption key of the cryptosystem in information-theoretical sense, ε-secrecy criterion in quantum cryptography and Holevo information. A lower bound for the unicity distance for ε-secret keys in quantum cryptography is obtained. The relationship between unicity distance, ε-secrecy criterion in quantum cryptography and Holevo information is demonstrated.
Asymptotic learning curves of kernel methods: empirical data versus teacher–student paradigm
Authors: Spigler Stefano , Geiger Mario , Wyart Matthieu
Published: December 2020

How many training data are needed to learn a supervised task? It is often observed that the generalization error decreases as n
−β
where n is the number of training examples and β is an exponent that depends on both data and algorithm. In this work we measure β when applying kernel methods to real datasets. For MNIST we find β ≈ 0.4 and for CIFAR10 β ≈ 0.1, for both regression and classification tasks, and for Gaussian or Laplace kernels. To rationalize the existence of non-trivial exponents that can be independent of the specific kernel used, we study the teacher–student framework for kernels. In this scheme, a teacher generates data according to a Gaussian random field, and a student learns them via kernel regression. With a simplifying assumption—namely that the data are sampled from a regular lattice—we derive analytically β for translation invariant kernels, using previous results from the kriging literature. Provided that the student is not too sensitive to high frequencies, β depends only on the smoothness and dimension of the training data. We confirm numerically that these predictions hold when the training points are sampled at random on a hypersphere. Overall, the test error is found to be controlled by the magnitude of the projection of the true function on the kernel eigenvectors whose rank is larger than n. Using this idea we predict the exponent β from real data by performing kernel PCA, leading to β ≈ 0.36 for MNIST and β ≈ 0.07 for CIFAR10, in good agreement with observations. We argue that these rather large exponents are possible due to the small effective dimension of the data.
Design and implementation of silicon photomultiplier characterization setup for plasma physics applications
Authors: Baquero P A , Castañeda L F , Hernandez W A , Fuentes F , Cruz-Cardozo J L
Published: December 2020

Silicon photomultipliers are devices widely used and have direct applications in multiple scientific fields. Currently, the Universidad Antonio Nariño, Colombia, finance the research project Characterization of the coherent structures in the edge region of the plasma column in the TCABR tokamak using Langmuir probes in collaboration with Universidade de Sao Paulo, Brazil. In this project, we research plasma, and recently, we proposed a silicon photomultiplier to measure X-ray emissions from the plasma column. In this application, we have to know specific characteristics of silicon photomultiplier in behavior controlled conditions to establish its possible changes during exposure to radiation of plasma; one of silicon photomultiplier characteristics more important is gain due to its temperature dependence that generates disturbances on its response. To characterize the silicon photomultiplier in controlled conditions, we developed an analog integral proportional temperature automatic control system for the control of a silicon photomultiplier characterization setup that lets temperature variations from room temperature to 50°C reaching reference temperature in 1 minute with a steady state error less than 2% and overshoot of 5.53%.
Fractal analysis for estimating electricity demand through the application of Hurst’s re-staging exponent
Authors: Mesa F , Devia D M , Ospina R
Published: December 2020

This article presents a methodology for fractal analysis using the Hurst re-staging exponent for the generation prediction of a hydroelectric power plant. Which is an innovative technique to address this problem since literature usually performs it through classical and lately Bayesian statistical processes. The importance of the work implies amalgamation of concepts from fractal theory, chaos, phase space, delay time and Hurst exponent, necessary in the analysis that will determine an estimate of the future behavior of a chaotic series. Thus, the problem is addressed from the qualitative analysis through the theory of chaos.
Calibration of physicochemical parameters in aquaculture. A case study of tilapia breeding in Mozambique
Authors: Mulema S A , Prada-Núñez R , Mendoza-Lizcano S M
Published: December 2020

This paper discusses the adequacy of methods used in monitoring the aquatic environment in aquaculture. It is assumed that the strategy of controlling each of the environmental parameters by observing their compliance with the technical limits established in aquaculture is not sufficient to highlight all the aspects that may compromise the quality of the process. Therefore, the univariate methods that are usually used in water monitoring in aquaculture cannot show aspects of the process derived from the joint variability between the parameters. Thus, a multivariate method for monitoring the aquatic environment in aquaculture based on Hotelling’s T2 chart was proposed in this paper. Data on four physicochemical parameters (oxygen, temperature, pH and transparency) were collected from four aquatic species breeding ponds at the company Aquapesca in Mozambique, located in southeastern Africa. The correlation structure evidenced in the four physicochemical parameters analyzed showed a strong and positive relationship between temperature and pH, oxygen and transparency are inversely correlated. This correlation structure indicates that a possible reduction in water temperature also reduces the pH and vice versa, while a reduction in transparency implies an increase in dissolved oxygen. The multivariate method used shows the relationship between the parameters and the strategies to manage them, as well as the control strategy of the multivariate structure through Hotelling’s T2 chart, pointing out and correcting all the aspects that may compromise the quality of the breeding of the species in aquaculture.
Heat transfer in a tube with sudden expansion and additional miniturbulator
Authors: Terekhov V I , Bogatko T V
Published: December 2020

The process of interaction of two separated flows of various scales in a tube with a sudden expansion is investigated. It has been determined that an additional turbulizing element in the form of a small diaphragm leads to dramatic changes in the structure of the recirculation zone in the channel behind a step, shift in the flow attachment point, and, accordingly, redistribution of heat and mass transfer coefficients. The approach of a mini-turbulizer to the separation point increases the size of recirculation zone and heat transfer intensity. An increase in the height of a mini-turbulizer affects similarly the characteristics of a separated flow.
Promising dimple technologies of vortex heat and mass transfer enhancement in energy and microelectronics
Authors: Isaev S A , Popov I A , Mikheev N I , Guvernyuk S V , Nikushchenko D V , Sudakov A G
Published: December 2020

Turbulent separated air flow and heat transfer at the starting hydrodynamic length of the longitudinal section of the dimpled narrow channel (1 in height, 4 in width, and 84 in length) with inclined one-row oval-trench dimples (OTD) are calculated. Packages of 20 and 31 dimples are compared. Each dimple has a length of 4.5, a width of 1, a depth of 0.2, an edge rounding radius of 0.2, and an inclination angle of 45°. Re=6000 and is determined in terms of the flow velocity at the channel entrance. The effect of abnormal separated flow intensification and heat transfer enhancement in OTDs due to the dimple density is confirmed. (fx/fxpl)min=−4 and (Nu/Nupl)max=7.2. Relative heat transfer grows by a factor of 1.9 and relative hydraulic losses – by a factor of 1.6.
The flow of Giesekus fluid around a cylinder between two parallel plates
Authors: Kadyirov A I , Karaeva J V , Zaripov R R , Vachagina E K
Published: December 2020

This paper presents the numerical results of the flow of the viscoelastic Giesekus fluid around a cylinder between two plates. An aqueous solution of polyacrylamide (PAA) is taken as the working fluid. A method for determining the nonlinear parameter of the Giesekus model to approximate the viscosity curve is proposed. The developed method is tested on the approximation of experimental data presented in the literature. The parameters of the four-mode Giesekus model for describing the rheological properties of an aqueous solution of polyacrylamide with concentrations from 2,500 to 10,000 ppm are determined based on a set of experimental data.
Application of machine learning methods for investigating the heat transfer enhancement performance in a circular tube with artificial roughness
Authors: Koroleva A P , Kuzmenkov N V , Frantcuzov M S
Published: December 2020

This paper presents a hybrid approach for investigation of heat transfer enhancement performance using computational fluid dynamics and artificial neural network. More than 5,000 CFD simulations are carried out for turbulent flow in pipes provided with artificial roughness of transverse rectangular ribs to analyze heat transfer, pressure drop, and thermal hydraulic performance. The rib height and pitch are widely varied along with the flow Reynolds number, working fluid, and material of roughness elements. To accurately predict major parameters (Nusselt number, friction factor, and thermal hydraulic performance) a deep neural network is developed, trained, and tested by current CFD data. The ANN allowed finding optimal rib roughness parameters for the current problem and opened perspectives of industrial application due to low computational cost and prediction error of less than 1.5%.
Simulating gas-dynamic energy separation in laminar swirling flows
Authors: Naumkin V S , Terekhov V I
Published: December 2020

Using numerical methods it is shown that the process of gas-dynamic energy separation can be observed in the laminar flow inside a vortex tube. The magnitude of the observed energy separation is less than the energy separation under turbulent conditions.
Numerical investigation of heat transfer and friction factor characteristics for staggered double drop-shaped tubes bundle in cross-flow
Authors: Deeb R , Sidenkov D V
Published: December 2020

A numerical study has been conducted to clarify the flow and heat transfer characteristics of a cross-flow heat exchanger with drop-shaped tubes at zero angle of attack. A mathematical and numerical model in software package Ansys for numerical evaluation of heat transfer and flow field of a bundle of drop-shaped tubes, with taking into account the strain caused by different pressures inside and outside the tubes has been developed. The result of the numerical simulation indicates the superior thermal and hydrodynamics performance of the drop-shaped tube bundles over the circular tubes.
Implementation of heat pump systems for minimizing heat losses with ventilating steam supply
Authors: Vendland L.E , Gavrilova Yu.A. , Pugachuk A.S.
Published: December 2020

This article proposes the use of an aircraft compressor for a heat pump installation to potentially increase the thermal efficiency of a combined heat and power (CHP) plant by 5-6%, and save heat in the winter period of a cogeneration turbine. The principle of operation of such a heat pump installation, the scheme of the modernized turbine and the economic justification of the modernization of the steam turbine are presented in this paper. This allowed the confirmation of the feasibility of using a heat pump installation for utilizing the energy of the ventilating steam supply. The quick payback of the project was chosen as a decisive factor in achieving high economic efficiency of the heat pump installation.
Investigation of structured 2D arrays of microdroplets levitating above the surface of hot liquid
Authors: Zaitsev D V , Shatekova A I
Published: December 2020

This work presents new experimental data on the evolution of two-dimensional (2D) ordered arrays of microdroplets levitating over a heated liquid surface. It was found that the average distance between the centers of the droplets in the array increases with the droplet diameter, being practically independent of the number of droplets in the array and substrate temperature. Dimensionless correlation ratios for the distance between the droplets were obtained, which can be used to verify the theoretical models under development.
The effect of the heating rate on the rupture dynamics of the horizontal layer of silicone oil
Authors: Kochkin D Y , Zaitsev D V , Kabov O A
Published: December 2020

The experimental study of the rupture of a horizontal layer of silicone oil non-uniformly heated from below was conducted. The rupture occurred through the formation of a residual film on the heater. Residual film thickness was measured using a confocal sensor. It was found that with increasing heating rate, the thickness of the residual film increases.
The inversion temperature during evaporation of water solutions of ethanol and acetone into a turbulent boundary layer
Authors: Makarov M S , Makarova S N
Published: December 2020

The results of studies of heat and mass transfer during adiabatic evaporation of binary liquids of water/ethanol and water/acetone into a turbulent boundary layer of a vapor-air mixture from a flat wetted plate are presented. The dependences are obtained for the evaporation intensity of solutions of various compositions on the temperature of the air flow or the equilibrium superheated steam into which the liquids evaporate. The inversion temperature values for liquids with different concentration of the volatile component are determined. The effect of flow turbulence on the evaporation rate and inversion temperature is analyzed.
Thermodynamics of single crystals of lithium tungstate with low molybdenum content: heat capacities, enthalpies and lat-tice energies
Authors: Matskevich N I , Stankus S V , Chernov A A , Shlegel V N , Semerikova A N , Samoshkin D A , Zaitsev V P
Published: December 2020

The thermodynamic properties (enthalpy, heat capacity) of lithium tungstate single crystals with low molybdenum content were measured by reaction and differential scanning calorimetry. An equation for lattice energies in Li2WO4-Li2MoO4 system on compositions was established. No anomalies connected with phase transitions for lithium tungstate doped with 15% molybdenum were found up to 960 K. An equation to describe heat capacity was proposed.
The formation of a closed vapor film during boiling of helium II on a cylindrical heater inside the porous structure
Authors: Korolyov P V , Yachevsky I A , Puzina Yu Yu , Kryukov A P
Published: December 2020

The results of experimental studies superfluid helium (He-II) film boiling are presented. Experimental studies of the He-II boiling on the surfaces of the cylindrical heaters in a bulk of He-II and under constrained conditions are described. Visualization of helium-II film boiling was first performed when observed from the end of a cylindrical heater. The scheme of the experimental facility, work cell and heater are given. The data in the form of files with visualization obtained from the experiments allow us to determine the outlines and the characteristic sizes of the films formed during boiling for different initial conditions.
Study on the brewing industry waste combustion
Authors: Larionov K B , Slyusarskiy K V , Tsibulskiy S A , Kaltaev A J , Gubin V E
Published: December 2020

The combustion of the waste from the brewing industry was investigated. Using the elemental analyzer and standard techniques, the elemental composition and technical characteristics of the studied sample were determined. The ignition and combustion of samples were carried out in a combustion chamber at heating medium temperatures (Tg) withinthe range of 500-700 °C. Gas-phase combustion products were analyzed using an in-line gas analyzer. The minimum ignition temperature of the sample was 337 °C. With an increase in the temperature Tg, a significant decrease in the ignition delay time of the sample was observed (by 9.7 times). The combustion process was accompanied by the formation of an intense flame near the sample surface. It was also found that, with increasing temperature of heating medium, the concentration of CO emission decreased with an inverse increase in the extremum value of CO2 emission.
Numerical investigation of the operating process in an annular detonation chamber of low diameter
Authors: Sidorov R S
Published: December 2020

Burning in unsteady rotating detonation waves is one of the ways of operating process organization in future aircrafts engines. However, a minimum combustion chamber diameter in which the unsteady rotating detonation process can be actualized is a significant limitation of such engines. A possibility of hydrogen-air mixture burning in an annular chamber with a diameter of 78 mm is shown in this paper using methods of three-dimensional computational fluid dynamics. The geometry of the chamber and the modes of its operation were selected, and the influence of the total pressure of air at the inlet was studied. At the pressure of 32 bar, the mass flux in the critical section of the aerodynamic nozzle was 7349.2 kg/(s·m2). It is shown that in a rotating reference frame in which the detonation wave is at rest, streamlines come to the wavefront almost at right angles. This fact allows making simple estimates of the fresh mixture parameters in front of the wave. Comparison with the detonation parameters in a premixed hydrogen-air mixture in the tube showed that the velocity of the detonation wave in the chamber is 0.65-0.74 of the Chapman-Jouguet detonation velocity, and its height is approximately equal to the characteristic size of the cellular structure of the detonation.
The structure of the Black Sea mesoscale eddies from the numerical modeling with various spatial resolution
Authors: Puzina O S , Mizyuk A I
Published: December 2020

The paper is based on the numerical modeling results and investigates the dynamics of the Batumi vertical structure of anti-cyclonic eddy. In the autumn-winter period, the Batumi Eddy intensifies; in the spring-summer period, the eddy weakens. In the calculation with a higher resolution, the eddy dynamics is more pronounced in comparison with the calculation with a low spatial resolution. The vertical structure of the Batumi Eddy was determined for temperature fields, current velocity and salinity.
Phase triangulation method for measuring 3D geometry of complex profile objects under dynamic noise
Authors: Dvoynishnikov S V , Rakhmanov V V , Meledin V G , Sadbakov O Yu
Published: December 2020

The paper proposes a method of phase triangulation for measuring the three-dimensional geometry of complex objects under conditions of dynamic noise. The method is based on statistical analysis of experimental data, adaptive filtering and use of a controlled source of structured exposure. Theoretical and experimental estimates of the error by the proposed method are presented in the paper. The method allows a reduction in the measurement error of the three-dimensional surface geometry of complex objects using phase triangulation methods.
Approbation of the Laser Doppler Anemometer under Kinematic Flow Parameters Diagnostics during Spray Formation in a Laboratory Wind-Wave Interaction Modelling
Authors: Kabardin I K , Meledin V G , Dvoinishnikov S V , Troitskaya Yu I , Kandaurov A A , Sergeev D A
Published: December 2020

The sea spray, a typical feature of the marine atmospheric boundary layer, is one of the most uncertain factors among those controlling hurricanes and severe storms. To investigate how extremely strong winds tear off spray from wave crests, to classify such events, and to quantify the efficiency of the disclosed mechanisms, the high-speed wind-wave flume was constructed. For development of understanding of spray formation under hurricane wind condition the information about velocity distribution is required. The flow kinematics inside the wind-wave was studied using a laser Doppler anemometer (LDA) with an adaptive temporal selection of the velocity vector (LAD-08).
Heat capacity of liquid Cs80Bi20 alloy with a partly ionic character of interatomic interaction
Authors: Khairulin A R , Savchenko I V , Stankus S V
Published: December 2020

Enthalpy increment of CS80Bi20 liquid alloy in the temperature range of 857–1076 K was measured by mixing method on a massive calorimeter with an isothermal shell. The heat capacity of the melt was determined and it was found that for the studied temperature range it remains constant, and its absolute value exceeds significantly the calculation by the additivity rule. The estimated errors for enthalpy and heat capacity of the melt were 0.4 and 1%, respectively. An approximation equation was obtained for the dependence of the mass heat capacity of the solid alloys of the cesium-bismuth system at 298.15 K by the atomic concentration of bismuth.
Intensification of electrohydrodynamic flows using carbon nano-tubes
Authors: Korobeynikov S M , Ridel A V , Karpov D I , Prokopenko Ya G , Bychkov A L
Published: December 2020

Study of behaviour of floating up bubbles in the mixture of transformer oil with carbon nanotubes under the action of high electric field was carried out. The possibility of using carbon nanotubes to create hydrodynamic flows in a liquid dielectric at a very low concentration of nanotubes is shown. It is assumed that the mechanism of the formation of flows is the injection of charge from the surface of nanotubes.
Influence of wood biomass on physical and chemical transformations during its joint high-temperature pyrolysis with coals
Authors: Kuznetsov G V , Tolokolnikov A A , Cherednik I V , Yankovsky S A
Published: December 2020

The article deals with a comparative analysis of the influence of wood biomass on the pyrolysis processes of three grades of coal, namely, “lean” (T), “long-flame” (D), and “lignite” (3B). The composition of the ash residue of the main components of fuels and mixtures based on them was determined experimentally using X-Supreme 8000 element analysis device. Fuel mixture samples were used with a percentage of wood/coal equal to 0/100, 10/90, 25/75, 50/50 wt.%. The experiments were performed in an inert gas (argon) environment within the temperature range from 400 to 800 °C. It was established that during pyrolysis of two-component fuels based on three different coals (T, D, and 3B) in a mixture with dispersed wood biomass (sawmill waste), the effect of the growth of calcium and aluminum sulfates was achieved in the ash of the thermal decomposition products of such mixtures due to a complex of reactions between pyrolysis products of coals and wood where the concentration of the wood component in the mixture changed from 10 to 50%. The results of experimental studies allow substantiating the previously formulated hypothesis about the sequestering mechanism of sulfur oxides formed during the pyrolysis of coals, as a result of the interaction of water vapor with gaseous products of thermal decomposition of wood and solid products of pyrolysis of three coals of different grades.
Numerical analysis of the effects of intense energy flows on a cylindrical target in a magnetic field
Authors: Kuzenov V V , Dobrynina A O , Shumaev V V , Starostin A V
Published: December 2020

In this paper, a new version of the method for numerically solving the equations of radiation magneto-plasma dynamics is presented. The developed numerical technique was verified by solving a number of test (model) problems. The one-dimensional calculations of the plasma-dynamic parameters of a cylindrical target for the combined scheme of the effects of magnetic inertial fusion take into account a wide range of physical effects. A method is proposed for the transition from a tetrahedral to a hexagonal irregular computational grid. A variant of the elliptic “regularizer” of the grid is developed, which is based on the “mechanical analogy” and is based on the solution of linear equations of the theory of elasticity. The paper presents the initial results of the reconstruction and “regularization” of the computational grid, as well as the distribution of the “angular” criterion for assessing its quality.
Cost optimization for information security systems
Authors: Kryanev A V , Kudryashov N A , Sliva D E
Published: December 2020

Protecting information that is potentially accessible through external communication channels from external threats is one of the primary objectives of information security. Creating an information security system requires material investments, the cost of which increases along with the increasing degree of information protection. Therefore, the task of determining the level of investment in information security that provides the minimum total cost of the information protection system and losses from realized threats that remain after the implementation of the information protection system arises. In this paper, we present a scheme that allows us to solve the problem of optimizing the costs of an information security system, the implementation of which ensures a minimum of average total costs for the implementation of the information security system and losses due to the remaining threats realized after the establishment of information security system.
Strain localization in two-dimensional lattices
Authors: Porubov A.V. , Antonov I.D. , Sokolov A.A. , Müller W.H.
Published: December 2020

Two-dimensional localized strain wave solutions of the nonlinear equation for shear waves in two-dimensional lattices are studied. The corresponding equation does not possess an invariance in one of the spatial direction while its exact plane traveling wave solution does not reflect that. However, the numerical simulation of a two-dimensional localized wave reveals a non-symmetric evolution.
Numerical solution of two-dimensional (2D) nonlinear heat conductivity problem on moving grids
Authors: Shilnikov Kirill E. , Kochanov Mark B.
Published: December 2020

For the numerical solution of two-dimensional (2D) nonlinear heat conduction problem a transition to a moving coordinate system is used. A local speed of the latter is chosen in such a way that the considered process is close to stationary. Such coordinate system guarantees a concentration of grid nodes in a range of the solution features. This allows for a quality improvement of the obtained numerical solution with a small number of computational grid nodes. The developed numerical algorithm is tested on the heat wave propagation problem which has an exact solution.
Preparation of Mo-S-P electrocatalytic films by pulsed laser ablation of MoS2/P composite target for effective hydrogen production
Authors: Rubinkovskaya O V , Fominski D V , Romanov R I , Nevolin V N , Yu Fominski V
Published: December 2020

The results of structural and electrochemical studies of thin Mo-S-P films obtained by pulsed laser deposition at various conditions from a target made of mixture of MoS2 and P powders are presented. For variation of S/P ratio and modification structure of the catalytic films, the deposition of the laser plume was conducted in vacuum, in Ar and H2S gas. The highest electrocatalytic properties for activating the hydrogen evolution reaction in an acid solution were found for composite amorphous/nanocrystalline MoS6P/nc-Mo films. In the chemical stateof S 2p, the high binding energy dominated. The doping of the films with phosphorus increased the efficiency of the reaction compared with that of MoS
x
/nc-Mo films. The analysis of the synergistic effect of phosphorus on the performance of amorphous MoS
x
P
y
films in H2 evolution was carried out using the density functional theory.
Modeling of heat and hydrodynamic processes in the big uranium target “BURAN” under the action of high-energy ions
Authors: Efremov V. , Kiverin A. , Yakovenko I. , Baldina E. , Baldin A. , Bleko V.
Published: December 2020

This paper is devoted to the analysis of heat transfer, hydrodynamic and acoustic processes induced by high-energy particles irradiating the big uranium target “BURAN”. The generation of heat and acoustic waves by relativistic ion beams is studied numerically. Energy transfer between irradiated target and ambient atmosphere was analyzed with different models. The study provides a basis for development of the new acoustic method for analysis of ion beam energy deposition and its further redistribution in the bulk of a target.
The thermographic study of the surface discharge electrode systems with a fixed and moving dielectric barriers
Authors: Ivchenko A V
Published: December 2020

The paper presents the thermographic investigation results of temperature fields on electrode systems of surface discharges excited on a fixed and moving dielectric layers. It is shown that temperature in the electrode systems with stationary dielectric barrier is of 28-1350C while temperature of electrode systems with a movable dielectric layer doesn’t exceed 500C. The effect of near-wall gas flows on the surface temperature distribution of electrode systems is discussed.
Cumulative effect in foams and mechanism of detonation development
Authors: Kiverin A D , Yakovenko I S , Kichatov B V , Korshunov A M
Published: December 2020

The paper is devoted to the analysis of non-steady combustion and detonation in aqueous solutions foamed with the hydrogen-oxygen gaseous mixture. The processes of flame acceleration and transition to detonation are studied experimentally and numerically. Based on complex analysis, the effect of cumulative compression of the reactive gaseous mixture inside collapsing bubbles is proposed to be the mechanism of detonation formation and its further self- sustained propagation. Flame propagation through the foam leads to the compression waves generation. Under the action of compression waves, the gas bubble collapses, and states with high energy densities are achieved inside the bubble. As a result, the ignition inside the bubble takes place that represents a basic mechanism of detonation formation and propagation.
Reduction of detailed kinetic mechanisms for pyrolysis, combustion, and detonation modeling
Authors: Tereza A M , Agafonov G L , Betev A S , Medvedev S P
Published: December 2020

The values of ignition delay predicted for stoichiometric C2H2/O2 and CH4/O2 mixtures by various detailed kinetic mechanisms presented in the literature are compared over the temperature range of 1000 < T <2100 K and the pressure range of 0.02 < P < 1.1 MPa. The number of species in detailed kinetic mechanisms is reduced by a trial-and-error method while keeping the response of ignition delay within a relative error range of 5 = 30%. The automatic computer code developed in this study has made it possible to reduce the number of species by a factor of more than 2 for the C2H2/O2 mixture and a factor of 3 for the CH4/O2 mixture, respectively. A comparison of predictions based on the reduced mechanisms with experimental data presented in the literature shows good agreement.
Analytical approximation of neutrino distribution function in core-collapse supernova
Authors: Dobrynina A , Koptyaeva E , Ognev I
Published: December 2020

Results of the numerical simulations of the neutrino angular distribution in core-collapse supernova were analyzed. As analysis shown, the neutrino angular distribution function can be approximated by a one-parametric Gaussian function. The proposed approximation describes about 90% of all neutrinos in the core-collapse supernova at times t ≳ 0.2 sec after a core bounce and relatively large distances from proto-neutron-star center. Therefore, it could be a good analytical approximation of the numerical data. At small values of time and distance an accuracy of this approximation significantly decreases.
Rigidity dependences of the main characteristics of Forbush decreases
Authors: Lagoida I A , Voronov S A , Mikhailov V V
Published: December 2020

Forbush decrease is an effect in the cosmic rays physics which manifests itself as a sudden depression of the intensity of cosmic rays. Active phase of Forbush decrease lasts for several days and is often accompanied by a geomagnetic storm. The reason for such sudden depressions originates from the Sun, and is connected with a phenomenon of solar physics known as coronal mass ejections. Nowadays Forbush decreases are mostly studied by ground based detectors such as neutron monitors and muon hodoscopes. These detectors are characterized by small statistical fluctuations but register secondary cosmic rays which are created in interactions of primary cosmic rays with Earth atmosphere. This work is based on the data obtained by the satellite experiment PAMELA. The main characteristics of Forbush decreases are calculated for a fluxes of cosmic rays protons in the rigidity range 0.8 – 9 GV.
Effect of a strongly magnetized plasma on the resonant photon scattering process
Authors: Chistyakov M V , Rumuyantsev D A , Yarkov A A
Published: December 2020

In this paper, the photons absorption rate in a relatively strong magnetic field in the Compton process taking into account the resonance on the virtual electron are calculated. A comparative analysis of the obtained result with the nonresonant case was carried out.
Search for 10He in the stopped pion absorption 14C(π−, p
3He)X
Authors: Chernyshev B A , Gurov Yu B , Lapushkin S V , Leonova T I , Sandukovsky V G , Schurenkova T D , Tel’kushev M V
Published: December 2020

The formation of the 10He states was studied in the reaction of stopped pion absorption 14C(π−, p
3He)X. Measurements were carried out using two-arm multilayer semiconductor spectrometer and “radioactive” target consisting of 76% 14C and 23% 12C. The contribution of uncontrolled impurities in the target was ≤ 1%. In order to determine the contribution of the 12C impurity measurements were performed on an isotope pure carbon 12C target. An indication on the excitation state with Ex
~ 6 MeV (Er
~ 7 MeV) was observed in missing mass spectrum of 14C(π−, p
3He)X reaction. Comparison with theoretical and experimental results obtained by other authors was performed.
Analysis of velocity distributions in projectile fragmentation reactions of 18O ions on 9Be and 181Ta targets at 35 A MeV
Authors: Erdemchimeg B , Artukh A G , Klygin S A , Kononenko G A , Sereda Yu M , Vorontsov A N , Mikhailova T I
Published: December 2020

Up to date analysis of velocity and isotope distributions of light fragments obtained in the projectile fragmentation reactions of 18O at 35 A MeV on 9Be and 181Ta targets measured at COMBAS fragment separator at the U400 M Research Facility in JINR are presented. The results of velocity spectra analytical parameterization and isotopic ratios are compared with the ones obtained in the experiments presented in the literature. The discussion of the different mechanisms involved in these types of the reactions is given.