bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance investigation of Ti
x
N
x−1O2 MXene (x = 2, 3, 4) as anode materials for Na-ion batteries by first-principles calculation
Authors: Zhang Wenshu , Qu Jianping , Wang Xudong , Huang Hao , Yao Man 
Published: September 2022

Abstract
The number of MXene layers plays a crucial role in their performance when they are used as anode materials for sodium-ion batteries. Herein, Ti-based nitride MXenes with different layers, Ti
x
N
x−1O2 MXene (x = 2, 3, 4) structures, were constructed to calculate the structural stability of their precursor, electronic properties after etching, and sodium storage behavior compared with the common Ti2CO2 and Ti3C2O2 MXene. First-principles calculations indicate that nitride MXenes possess a better rate capability than carbide MXenes of the same thickness. Moreover, the barrier for Na diffusion on the Ti2NO2 MXene surface (0.114 eV) is lowest. Meanwhile, comparing the properties of three nitride MXenes with different thicknesses, Ti2NO2 MXene performs relatively well with a high theoretical capacity with 756 mAh g−1 and a lower open circuit voltage of 1.1 V. In conclusion, the performance improvement of nitride MXene is not linear with thickness, because that of Ti3N2O2 MXene is relatively weaker. This work lays the foundation for the feasibility of Ti3N2T
x
experimental preparation and provides corresponding evidence on the choice of MXene thickness. More attention should be paid to the etching method for Ti2NT
x
MXene.
Excitonic properties in a double-layer graphene
Authors: Do Thi-Hong-Hai , Bui Duc-Tinh , Phan Van-Nham 
Published: September 2022

Abstract
This paper investigates theoretically the excitonic condensation state at zero temperature in a double-layer graphene structure. In the framework of the unrestricted Hartree–Fock approximation, the electron-hole system in the structure described in the two-band electronic model is analyzed and one finds a set of self-consistent equations determining the excitonic order parameter. The optical properties of the excitonic condensation state then are examined in the Kubo linear optical response theory. Our results indicate that in the case of sufficiently large Coulomb interaction, the BEC excitonic condensation state might occur at low electronic excitation density. By turning the external electric field, the superfluid state stabilizes in the BCS-type excitonic condensate. The optical conductivity spectrum also provides us more insight into the excitonic condensation states.
Vector dark radiation and gravitational-wave polarization
Authors: Miravet Alfredo D. , Maroto Antonio L. 
Published: September 2022

Abstract
We consider conformal vector models which could play the role of a cosmological dark
radiation component. We analyse the propagation of gravitational waves in the presence of this
vector background and find a suppression in the tensor transfer function at large scales. We also
find that although the cosmological background metric is isotropic, anisotropies are imprinted in
the tensor power spectrum. In addition, the presence of the background vector fields induces a net
polarization of the gravitational wave background and, for certain configurations of the vector
field, a linear to circular polarization conversion. We also show that this kind of effects are
also present for vector models with more general potential terms.
Inflation with two-form field: the production of primordial black holes and gravitational waves
Authors: Fujita Tomohiro , Nakatsuka Hiromasa , Obata Ippei , Young Sam 
Published: September 2022

AbstractAntisymmetric tensor field (two-form field) is a ubiquitous component in string theory and generally couples to the scalar sector through its kinetic term. In this paper, we propose a cosmological scenario that the particle production of two-form field, which is triggered by the background motion of the coupled inflaton field, occurs at the intermediate stage of inflation and generates the sizable amount of primordial black holes as dark matter after inflation. We also compute the secondary gravitational waves sourced by the curvature perturbation and show that the resultant power spectra are testable with the future space-based laser interferometers.
Dynamics of phase inclusion during rotational oscillations of simply connected annulus
Authors: Karpunin I E , Kozlov N V , Zimasova A R 
Published: September 2022

Abstract
The dynamics of a phase inclusion in a coaxial liquid layer divided with a radial partition is studied experimentally. The working volume of the container is filled with a viscous liquid, inside which an air bubble, immiscible with the main phase, is injected. This inclusion has a lower density than the surrounding liquid does. The container performs rotational oscillations as a whole with the zero average rotation. Such a motion brings to the generation of a harmonically oscillating azimuthal shear flow, which, as a consequence, excites the oscillations of the phase inclusion. During the bubble’s oscillations, the displacement of its geometric center follows the sinusoidal law. On the background of such a motion a periodic deformation of the bubble is observed, i.e. the phase boundary starts oscillating. A new and surprising result of the experiments is found, when the light bubble sinks and takes a quasi-steady position near the inner wall of the layer.
The influence of heat release on the dynamics of a porous material saturation in the course of gaseous silicon condensation
Authors: Demin V A , Maryshev B S , Menshikov A I 
Published: September 2022

Abstract
The results of a direct numerical simulation are presented which describe the specific process of a porous medium high-temperature siliconizing. The calculations were performed taking into account the diffusion, the weak pressure gradient across a workpiece and the heat release during the condensation of gaseous silicon in pores. Phenomenological formulas for the evaporation and condensation coefficients in dependence on temperature are offered. An evolutionary equation for the temperature distribution in a sample is derived, which takes into account these processes. Mathematical statement of the problem is based on the modified MIM-model with addition Darcy’s law. Numerical modeling has been fulfilled by the finite difference method using an explicit scheme. It is shown that the heating release in the sample slows down the process of particle settling. The results of numerical simulation are consistent qualitatively with known experimental data.
Liquid free boundary in vertical gap subject to modulated rotation
Authors: Kozlov V G , Petukhova M A 
Published: September 2022

Abstract
The effect of rotation velocity modulation on the equilibrium shape of the liquid-air interface in a vertical slot gap rotating around a horizontal axis is studied experimentally. The case is considered when the modulation frequency coincides with the rotation frequency. It is found that in this case, velocity modulation leads to a violation of the axial symmetry of the interface formed by the centrifugal force of inertia. The displacement of the center of symmetry of the interface increases linearly with the amplitude of the velocity modulation and decreases quadratically with the speed of rotation. It is shown that the detected phenomenon is explained by the averaged effect of an external gravitational field on a fluid in a rotating frame of reference.
Modelling of bone tissue adaptation in Ilyushin's spaces
Authors: Tverier V M , Chikova T N 
Published: September 2022

AbstractSome bones of the human skeleton are porous inside and resemble a sponge. The cancellous bone tissue forms the epiphyses of the long bones and practically the entire volume of the cancellous bones. It is known that the structural units of the spongy substance – trabeculae, are located along the lines of action of the greatest mechanical loads created by the muscles attached to the skeleton. If the load during life changes due to some reason, for example, injuries, the characteristics of the profession or lifestyle, then the cancellous bone rebuilds its structure in order to withstand this load. In the presented study, a model is proposed for describing the process of cancellous bone tissue adaptation in the geometric Ilyushin’s spaces
Application of the automatic code generation and symbolic computation techniques to numerical solution of PDE problems
Authors: Khlybov Oleg A 
Published: September 2022

Abstract
A software package for the numerical solution of systems of linear and nonlinear partial differential equations by grid methods is presented, which combines symbolic computations and automatic code generation techniques. Discretization of differential equations is carried out by the methods of finite volumes and finite differences on two-dimensional and three-dimensional regular rectangular grids. The solution of the systems of nonlinear algebraic equations obtained as a result of discretization is performed by Newton’s method with employment of third-party SLAE solvers. The generated code can exploit shared and distributed memory parallelisms and take advantage of heterogeneous computations. The results of the numerical solutions of two sample CFD problems of the fluid flow generation in a cylindrical cavity filled with electrically conductive liquid driven the by traveling and rotating magnetic fields are presented.
Stability of a system of circular rings reinforced with inextensible threads
Authors: Andryukova V. Yu. , Tarasov V. N. 
Published: September 2022

Abstract
The paper deals with the problems of stability for a system of circular rings interconnected in such a way that the displacements of these rings, and the rotation angles of their sections at some points, coincide. This has been reduced to a certain variational problem with restrictions on the functions in question in the form of linear equations, and Fourier series are used to obtain a finite-dimensional approximation. The paper also presents the stability problem for a system of circular rings reinforced by inextensible threads that cannot resist compressive forces. In this case, constraints in the form of inequalities arise, and after finite-dimensional approximation the problem reduces to finding the bifurcation points for a nonlinear programming problem in the presence of inequality constraints.
Influence of the shape on the hydraulic resistance of bypass channels inside a smart pig for low pressure gas pipeline inspection
Authors: Muginov R R , Pavlov D A , Peshcherenko M P , Peshcherenko S N , Perminov A V 
Published: September 2022

Abstract
The in-line smart pig for gas pipeline diagnostics is driven by the pumped gas and performs quality diagnostics only if its speed is constant, when the information reading is uniform along the length of the pipeline. In a low-pressure gas pipeline, if there are inhomogeneities on its walls, the condition of the pig speed constancy is easily broken, as the force of resistance to the pig movement on the stoppers is comparable with the difference of pressure forces acting on its ends. A central bypass channel of constant cross-section is usually used to control the pig velocity. The paper shows insufficiency of such method of regulation, leading to noticeable flow pulsations at the outlet of the channel. The use of variable cross-section of the bypass channel along its length in the form of a Laval nozzle to reduce flow pulsations is proposed. The numerical simulation of gas flow in Laval nozzles of different configuration is performed; it is shown that for all considered nozzles, the pressure pulsation at the channel outlet is 20-30 times less than that in the cylindrical channel, which simplifies the velocity control of such pig. However, it is not possible to completely avoid detachment of the flow from the walls of the expanding part of the nozzle, so in order to reduce the area of the detachment zone and reduce the flow resistance force, additional peripheral bypass channels connecting the inlet end of the pig with the diffuser section of the central bypass are added. Thus, a 40% reduction of gas flow resistance force through the bypass compared to the cylindrical bypass is obtained.
Vibroconvective heat transfer in cylindrical container with oscillating elastic boundaries
Authors: Saidakov V , Plouraboué F , Kozlov N 
Published: September 2022

Abstract
Heat transfer in a horizontal annular region filled with the viscous fluid is studied experimentally. The external boundary of the working volume is formed by an elastic silicone shell, while the internal one – by a cylindrical copper heater. The walls of the shell are brought into symmetric oscillatory motion by two linear servomotors. The temperature outside the external cylinder is maintained constant by pumping the thermally stabilized liquid. The experiments are conducted with the low heating power that corresponds to relatively low values of the Rayleigh number. This allows maintaining a regime, in which the forced, vibrational convection is the main mechanism of heat transfer. Theoretical analysis of the experimental results shows that the structure of the fluid flows is determined by the competition between the free, thermal convection and the forced one – the steady streaming generated by vibration. At sufficiently high intensity of oscillations, the forced convection dominates and leads to the increase of the heat transfer rate.
Experimental study of light sphere motion in liquid in rotating tilted cylinder
Authors: Zvyagintseva E A , Kudymova E M , Romanets V Ya , Kozlov V G 
Published: September 2022

Abstract
The motion of a light spherical body in a rotating tilted cylindrical cavity with liquid is studied experimentally. The rotation rate and angle of inclination of the cuvette, the viscosity of the liquid and the characteristics of the body vary. It is shown that with an increase in the rate of the cell rotation, the velocity of the body’s ascent decreases. An increase in the angle of inclination of the cylinder relative to the vertical also leads to a decrease in the ascent rate of the body. A paradoxical behaviour of the body is demonstrated: with an increase in the viscosity of the liquid, the velocity of the body’s ascent increases while maintaining other parameters (rotation rate, size, density of the body and the angle of inclination). The results of investigations at various angles of inclination, properties of liquid and the body are generalized on the plane of two control dimensionless parameters. Comparison with theory and with experimental results of other authors in the case of vertical orientation of the cavity demonstrates good agreement. It was found that during ascent, the body performs differential rotation relative to the cavity, the rate of which depends on the axial coordinate of the body.
On disturbances of the geostrophic flow influenced by volume sources of buoyancy and momentum
Authors: Ingel Lev Kh. 
Published: September 2022

Abstract
As is well known, flows in a free atmosphere outside a narrow equatorial zone are characterized by a geostrophic regime. For several applications, it is of interest to estimate the disturbances of the geostrophic wind caused by the action of sources of heat and/or momentum. One possible example is associated with manifestations of internal gravitational waves. A linear analytical model of the geostrophic flow disturbances of a stratified rotating medium caused by the action of stationary sources of momentum and/or buoyancy is considered. The model makes it possible to estimate explicitly the amplitudes of such disturbances depending on the parameters of the sources and the characteristics of the medium.
Investigation of the conditions for the development of waves at the interface of water masses of different densities
Authors: Lyubimova T P , Parshakova Ya N 
Published: September 2022

Abstract
The influence of differences in the hydrochemical characteristics of the waters of merging rivers on the formation of density currents and the behavior of the density jump layer is studied numerically. The problem is solved for the velocity regimes of the confluent Chusovaya and Sylva rivers (Russian Federation), which are characterized by significantly different salinity values. To study the specific features of layered structures, numerical simulation is performed in the framework of a two-dimensional approach. The calculations are carried out for a section of the Chusovaya River with a length of 300 m, located downstream from confluence of the Chusovaya and Sylva rivers. The Chusovskoy water intake of the city of Perm is located on this site. In the winter-spring season, in this area a regime is established in which a stable layer of density and velocity jumps is observed. With the confluence parameters typical of the winter low water season in the area of the Chusovskoy water intake, 8 km below the confluence point, field measurements detected fluctuations in the concentration and flow velocity in the density jump layer. The two-dimensional numerical simulations performed in the present work also showed the presence of velocity and concentration fluctuations in the jump layer. We found that vortex structures are formed in the jump layer, leading to fluctuations in the concentration in time at a given point and to the formation of a wave structure of the concentration field at different times.
Numerical study of skewness, kurtosis and variance of droplet-size distribution in air-assisted atomizer
Authors: Mingalev S , Khudyakov D 
Published: September 2022

Abstract
We study the approach to calculating the scale and shape parameters of the Weibull droplet-size distribution by means of the skewness, kurtosis and variance, obtained by simulation of atomization in an air-assisted atomizer with different viscosities, densities, flow rates and surface tensions of atomizing liquid. Such approach evades necessity to determine the shift parameter and to use the approximation of distribution obtained from the calculation by the Weibull distribution. The major obstacle to an application of it in processing the data about the atomization of droplets (obtained through the calculation) is the high level of fluctuations of skewness and kurtosis in case of small averaging time.
On the efficiency of convective mixing in a Y-shaped channel
Authors: Bratsun Dmitry , Pismen Len , Siraev Ramil 
Published: September 2022

AbstractContinuous-flow microfluidic devices are widely used in microbiology, fine organic synthesis, pharmaceuticals, biomedicine, etc. Most applications require rapid mixing of the fluids that pass through the microfluidic chip. The mechanism of natural diffusion is not always efficient due to limitations on the length of the channel. In this work, we numerically study the efficiency of using various mechanisms of natural convection for the mixing of fluids entering the microfluidic chip. Solutions typically differ in buoyancy and diffusion rates of dissolved components, making them sensitive to gravity-dependent instabilities such as Rayleigh-Taylor convection, double diffusion and diffusion layer convection. We consider a Y-shaped microchannel, which is, on the one hand, the simplest, and, on the other hand, a typical element of a microfluidic network. We assume that two miscible solutions independently flow into a common channel where they come into contact. For each type of instability, we numerically estimated the characteristic channel length, after which complete mixing of the solutions occurs. The simulations were performed in the framework of both 2D and 3D models. Finally, we compare the numerical results with the experimental data obtained recently.
Influence of substrate properties on a fluid drop’s free translational oscillations
Authors: Alabuzhev A A 
Published: September 2022

Abstract
The liquid drop’s natural translational oscillations are considered. The equilibrium form of this drop is a circular cylinder. Its axis of symmetry is perpendicular to two parallel solid substrates. The properties (wetting, roughness etc.) of these surfaces differ from each other. The drop is in another liquid. The contact angles’s changes are linearly proportional to the velocities of both contact lines. The Fourier series form by Laplace’s operator eigenfunctions are used for the problem solution. A system of complex equations of eigenvalue problem is solved numerically. The main frequency of the translational mode becomes zero after a critical Hocking’s parameter in situation of identical plates. The branching point of a decrement curve agrees with the zero point of a fundamental frequency. This frequency may not be vanishing on nonidentical surfaces of plates.
Gamma Heating Evaluation of Silicide RSG-GAS Multipurpose Reactor
Authors: Rohanda A , Waris A , Kurniadi R , Bakhri S 
Published: September 2022

Abstract
In research reactor, gamma heating deposited in the samples is an important issue because it is related to the samples and the reactor operational safety. Multi Purpose Reactor (MPR) 30 MWth or its called Reaktor Serba Guna G.A. Siwabessy (RSG-GAS) is a research reactor that play a role as a place to irradiate various target material type. RSG-GAS has been operating since 1987 and the last measurement of gamma heating in the core was conducted around twenty years ago in oxide core. In 1996, RSG-GAS core was converted from oxide fuel type to silicide fuel type. The purpose of the conversion are to improve the performance and efficiency of RSG-GAS. As part of RSG-GAS irradiation facilities safety analysis, the gamma heating measurement was re-conducted in order to obtain latest data as benchmark data in silicide core. This paper presents the results of gamma heating measurement of LEU silicide RSG-GAS core in Central Irradiation Position (CIP) at 15 MW and 30 MW power level using gamma calorimeter. There were four types of calorimeter used, which were calorimeter with graphite (C) sample, iron (Fe) sample, aluminum (Al) sample and zirconium (Zr) sample. Gamma heating calculations using GAMSET code were performed to verify the measurement results. The measurement results are lower than the GAMSET results and the gamma heating value increases in proportion to the increase of calorimeter sample atomic number. This results are corresponds to gamma heating benchmarking results of RSG-GAS oxide core. Several optimization efforts both measuring and modeling with GAMSET were conducted as an evaluation and justification of the results. The best optimization results are achieved using the maximum value of the measurement and adjusting the power peaking factor (PPF) distribution. The calculated gamma heating value optimization results at 15 MW power are 2.78 W/g (C sample), 2.74 W/g (Al sample), 3.36 W/g (Fe sample) and 4.60 W/g (Zr sample) while at 30 MW power level are 5.57 W/g (C sample), 5.49 W/g (Al sample), 6.75 W/g (Fe sample) and 9.23 W/g (Zr sample). The best optimization results serve as a benchmark data for developing new gamma heating calculation programs based on 18 gamma energy groups.
Simulation of Neutron and Gamma Dose Rate of The TRIGA 2000 Reactor Using Monte Carlo Method
Authors: Rakotovao L.O. , Permana Sidik , Oetami R.H. , Rasito  
Published: September 2022

Abstract
The neutron and gamma radiation doses were calculated from the operation of the 1 MW TRIGA 2000 Reactor in a simulation using the Monte Carlo method with MCNPX and PHITS program. Simulation is done by modelling the geometry of the reactor component materials and running it on a computer. The radiation source in the form of a fission reaction in the reactor core has been simulated using MCNPX to produce a dose of neutron and gamma radiation in the TRIGA 2000 core. Attenuation of neutron and gamma radiation by the reactor building is simulated using the PHITS code so that the neutron and gamma dose rates are obtained on the source, y, and z from reactor core. Interpolation of dose rate curves on large material thicknesses was carried out with the TVL neutron and gamma values of the simulation results for each reactor material. The simulation results shows that the gamma neutron dose rate outside the TRIGA 2000 reactor building is still below the dose limit value for radiation workers.