bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic graphitization of ultra-nano-crystalline diamond and its effects on material resistivity
Authors: Nikhar Tanvi , Rechenberg Robert , Becker Michael F. , Baryshev Sergey V.
Published: December 2020

Detailed structural and electrical properties of ultra-nano-crystalline diamond (UNCD) films grown in H2/CH4/N2 plasma were systematically studied as a function of deposition temperature (Td) and nitrogen content (% N2) to thoroughly evaluate their effects on resistivity. It was found that even the films grown with no nitrogen in the synthetic gas mixture could be made as conductive as 10−2 Ω cm. The overall resistivity of all the films was tunable over 4 orders of magnitude through varying growth parameters. On a set of 27 samples, Raman spectroscopy and scanning electron microscopy show a progressive and highly reproducible material phase transformation from ultra-nano-crystalline diamond to nano-crystalline graphite as deposition temperature increases. The rate of this transformation is heavily dependent on the N2 content estimated by secondary ion mass spectroscopy. The addition of nitrogen greatly increases the amount of sp2 bonded carbon in the films, thus enhancing the physical connectivity in the grain boundary (GB) network that has high electronic density of states. However, the addition of nitrogen greatly slows down crystallization of the sp2 phase in the GBs compromising electron transport. Therefore, the proper balance between GB connectivity and crystallinity is the key in resistivity engineering of UNCD.
Phonon-boundary scattering and thermal transport in AlxGa1−xN: Effect of layer thickness
Authors: Tran Dat Q. , Delgado-Carrascon Rosalia , Muth John F. , Paskova Tania , Nawaz Muhammad , Darakchieva Vanya , Paskov Plamen P.
Published: December 2020

Thermal conductivity of AlxGa1−xN layers with 0≤x≤0.96 and variable thicknesses is systematically studied by combined thermoreflectance measurements and a modified Callaway model. We find a reduction in the thermal conductivity of AlxGa1−xN by more than one order of magnitude compared to that of GaN, which indicates a strong effect of phonon-alloy scattering. It is shown that the short-mean free path phonons are strongly scattered, which leads to a major contribution of the long-mean free path phonons to the thermal conductivity. In thin layers, the long-mean free path phonons become efficiently scattered by the boundaries, resulting in a further decrease in the thermal conductivity. Also, an asymmetry of thermal conductivity as a function of Al content is experimentally observed and attributed to the mass difference between Ga and Al host atoms.
Electric field modulated deformation dynamics of a compound drop in the presence of confined shear flow
Authors: Santra Somnath , Jana Anirban , Chakraborty Suman
Published: December 2020

Dynamics of compound drops is central in several emerging applications including emulsion-fueled direct injection, targeted drug delivery, and the development of mechano-sensitive artificial cells. These applications are commonly hallmarked by high shear rates in confined fluidic environments. In the present work, we depict the role of the transverse electric field in controlling the resulting morpho-dynamics, including non-monotonic topological evolution and pinch-off phenomenon. In a tightly confined domain, we further show that the critical value of the electric field for triggering the pinch-off phenomenon may be greatly reduced as compared to larger-sized conduits. Finally, we portray a non-trivial variation of the drop pinch-off time with the degree of domain confinement, as attributed to the complex electro-hydrodynamic coupling over small scales. These results may turn out to be critical in manipulating the shape evolution of bio-mimetic soft matter in physiologically relevant fluidic pathways and on-chip applications.
Synchronizing subgrid scale models of turbulence to data
Authors: Buzzicotti Michele , Clark Di Leoni Patricio
Published: December 2020

Large eddy simulations of turbulent flows are powerful tools used in many engineering and geophysical settings. Choosing the right value of the free parameters for their subgrid scale models is a crucial task for which the current methods present several shortcomings. Using a technique called nudging, we show that large eddy simulations can synchronize with data coming from a high-resolution direct numerical simulation of homogeneous and isotropic turbulence. Furthermore, we found that the degree of synchronization is dependent on the value of the parameters of the subgrid scale models utilized, suggesting that nudging can be used as a way to select the best parameters for a model. For example, we show that for the Smagorinsky model, synchronization is optimal when its constant takes the usual value of 0.16. Analyzing synchronization dynamics puts the focus on reconstructing trajectories in phase space, contrary to traditional a posteriori tests of large eddy simulations where the statistics of the flows are compared. These results open up the possibility of utilizing non-statistical analysis in a posteriori tests of large eddy simulations.
A redundant hydraulic function of root hairs in barley plants grown in hydroponics
Authors: Burke Shannon , Sadaune Emma , Rognon Lisa , Fontana Alexane , Jourdrin Marianne , Fricke Wieland
Published: December 2020

The root hair-less brb of Hordeum vulgare L. (bald root barley) mutant was used to assess the significance that root hairs have for the hydraulic properties of roots and response to a limited supply of mineral nutrients in plants grown on hydroponics. The barley brb mutant and its parent wild-type (H. vulgare cv. Pallas) were grown under nutrient sufficient control conditions, and under conditions of low supply of P and N. Plants were analysed when they were 14–18 days old. Root hydraulic conductivity (Lp) was determined for excised root systems and intact transpiring plants, and cell Lp was determined through cell pressure probe measurements. The formation of Casparian bands and suberin lamellae was followed through staining of cross-sections. The presence or absence of root hairs had no effect on the overall hydraulic response of plants to nutritional treatments. Root and cell Lp did not differ between the two genotypes. The most apparent difference between brb and wild-type plants was the consistently reduced formation of apoplastic barriers in brb plants. Any hydraulic function of root hairs can be redundant in barley, at least under the hydroponic conditions tested.
Association between education level and HIV-associated neurocognitive disorder: a systematic review and meta-analysis
Authors: Liu Bozhi , Li Wei
Published: December 2020

In the era of antiretroviral treatment, human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) is common in HIV-positive (HIV+) patients, with an incidence of 30–50%. The relationship between education level and HAND has been evaluated in some studies, however, the results were inconsistent. The aim of this meta-analysis was to provide compelling evidence on the association between education level and the risk of HAND. Reports were searched for in the databases of Medline, Embase and PsyclNFO. Studies evaluating the relationship between education level and HAND in adult HIV+ patients were included. The pooled odds ratio/risk ratio was analysed by using the random-effects model. Two subgroup analyses were performed according to the adjustment of educational level in the neurocognitive impairment assessment and the income level. In total, 18 studies were included. Six studies and 12 studies reported education level as the continuous variable and categorical variable, respectively. The methods used for the assessment of neurocognitive impairment in included studies were neuropsychological battery tests (n = 10), HIV Dementia Scale (n = 1), the International HIV Dementia Scale (n = 6) and the Chinese version of the Montreal Cognitive Assessment (n = 1). The result showed that the risk of HAND in HIV+ patients who have lower education attainment was significantly higher than that in HIV+ patients who have higher education attainment. In conclusion, this meta-analysis demonstrated that HIV+ patients who have low education attainment carry higher risk of developing HAND compared with HIV+ patients who have high education attainment. This study highlighted the importance of early neurological screening for HIV+ patients who have low education level.
Nicotiana plumbaginifolia (Tex-Mex tobacco).
Authors: Vélez-Gavilán Jeanine
Published: December 2020

The Solanaceae family includes some genera of medicinal and agronomical importance. The genus Nicotiana is named after Jean Nicot, who brought tobacco seeds to France in the sixteenth century (Knapp et al., 2004). Species from the genus Nicotiana are primarily native to the Neotropics and Australia (Chase et al., 2003). N. plumbaginifolia belongs to the section Alatae, which is considered a monophyletic group (Kaczorowski et al., 2005). The species epithet 'plumbaginifolia' comes from the way in which the leaves resemble those of species in the genus Plumbago (Encyclopedia of Life, 2017). According to The Plant List (2013), N. cavanillesii and N. pusilla are no longer accepted synonyms of N. plumbaginifolia.
Corchorus hirtus (Orinoco jute).
Authors: Dube Shruti
Published: December 2020

C. hirtus is a herb or subshrub found to be infesting wetlands in Minas Gerias, Brazil due to its high frequency and density (Mascarenhas et al., 1995). In Brazil, it is widely distributed and grows either as a ruderal or as an invading weed infesting pastures. It was listed as a weed in a checklist of invasive plants in forestry plantations in the Lower Amazon (Pires, 1992), but the paper states that the term 'invasive' is equated with 'weed' defined as any plant growing where it is not wanted, so its status as a true invasive is dubious. It is listed as a weed in several countries by Sinha et al. (2011). It often grows as a weed in grain fields in Central America (Standley and Steyermark, 1949).
Reversing the null limit of the Szekeres metric
Authors: Hellaby Charles , Svítek Otakar
Published: December 2020

The null limits of the Lemaître–Tolman and Szekeres spacetimes are known to be the Vaidya and news-free Robinson–Trautman metrics. We generalise this result to the case of non-zero Λ, and then ask whether the reverse process is possible—is there a systematic procedure to retrieve the timelike-dust metric from the null-dust case? We present such an algorithm for re-constructing both the metric and matter tensor components of the timelike-dust manifold. This undertaking has elucidated the null limit process, highlighted which quantities approach unity or zero, and necessitated a careful discussion of how the functional dependencies are managed by the transformations and substitutions used.
Goos–Hänchen shift of a mid-infrared femtosecond filament visualized by the laser coloration method
Authors: Kompanets Victor , Melnikov Alexey , Chekalin Sergey
Published: December 2020

We present the results of investigation of total internal reflection of a femtosecond light filament in a LiF crystal in the regime of anomalous group velocity dispersion. We measure the Goos–Hänchen shift of the filament in the vicinity of the critical angle for a single femtosecond pulse using the laser coloration method. The obtained experimental values are compared to several existing theoretical models.
Dynamics of stochastic gradient descent for two-layer neural networks in the teacher–student setup*
Authors: Goldt Sebastian , Advani Madhu S , Saxe Andrew M , Krzakala Florent , Zdeborová Lenka
Published: December 2020

Deep neural networks achieve stellar generalisation even when they have enough parameters to easily fit all their training data. We study this phenomenon by analysing the dynamics and the performance of over-parameterised two-layer neural networks in the teacher–student setup, where one network, the student, is trained on data generated by another network, called the teacher. We show how the dynamics of stochastic gradient descent (SGD) is captured by a set of differential equations and prove that this description is asymptotically exact in the limit of large inputs. Using this framework, we calculate the final generalisation error of student networks that have more parameters than their teachers. We find that the final generalisation error of the student increases with network size when training only the first layer, but stays constant or even decreases with size when training both layers. We show that these different behaviours have their root in the different solutions SGD finds for different activation functions. Our results indicate that achieving good generalisation in neural networks goes beyond the properties of SGD alone and depends on the interplay of at least the algorithm, the model architecture, and the data set.
Generalized approximate survey propagation for high-dimensional estimation
*
Authors: Saglietti Luca , Lu Yue M , Lucibello Carlo
Published: December 2020

In generalized linear estimation (GLE) problems, we seek to estimate a signal that is observed through a linear transform followed by a component-wise, possibly nonlinear and noisy, channel. In the Bayesian optimal setting, generalized approximate message passing (GAMP) is known to achieve optimal performance for GLE. However, its performance can significantly degrade whenever there is a mismatch between the assumed and the true generative model, a situation frequently encountered in practice. In this paper, we propose a new algorithm, named generalized approximate survey propagation (GASP), for solving GLE in the presence of prior or model mis-specifications. As a prototypical example, we consider the phase retrieval problem, where we show that GASP outperforms the corresponding GAMP, reducing the reconstruction threshold and, for certain choices of its parameters, approaching Bayesian optimal performance. Furthermore, we present a set of state evolution equations that exactly characterize the dynamics of GASP in the high-dimensional limit.
Belief propagation: accurate marginals or accurate partition function—where is the difference?
Authors: Knoll Christian , Pernkopf Franz
Published: December 2020

We analyze belief propagation on patch potential models—attractive models with varying local potentials—obtain all of the potentially many fixed points, and gather novel insights into belief propagation properties. In particular, we observe and theoretically explain several regions in the parameter space that behave fundamentally differently. We specify and elaborate on one specific region that, despite the existence of multiple fixed points, is relatively well behaved and provides insights into the relationship between the accuracy of the marginals and the partition function. We demonstrate the inexistence of a principal relationship between both quantities and provide sufficient conditions for a fixed point to be optimal with respect to approximating both the marginals and the partition function.
A geometric interpretation of the multiplication of complex numbers
Authors: Ferro L A , Triana J G , Mendoza S M
Published: December 2020

In complex analysis courses, it is common to use physical interpretations as a didactic tool for teaching complex numbers. In the case of operations between complex numbers, the geometric interpretation of addition and subtraction is well known; however, many authors avoid the interpretation of the multiplication of complex numbers. In this paper, using the physical concepts of rotation and scaling, we will explain the multiplication of complex numbers through visualization in the Argand plane. In addition, we use visual representations in order to obtain proofs without words for some identities.
Contributing factors in academic performance and troubles associated with teaching in areas of physics in engineering students
Authors: Garzón-Agudelo P A , Palacios-Alvarado W , Medina-Delgado B
Published: December 2020

Learning processes are affected by a series of factors, both individual students and the institutional environment in which they develop. The present work is developed under the context of learning processes in areas of physics in engineering students, belonging to the academic program of technology in industrial processes, considering the socio-demographic and academic variables that affect students and that in turn affect student dropout. Data collection instruments were applied to a population group of 90 students, allowing to propose strategic scenarios that would contribute to improve the quality of academic processes and students’ skills in the study of mechanical and electromagnetic physics. It was determined that the role played by teachers and the methodology in which they teach their students, the physical conditions and teaching methods directly affect the effectiveness of learning and academic performance. It was also demonstrated that the lack of prior knowledge in the fundamentals of logic-mathematics and basic physics are determining aspects in the failure and repetition of the subjects.
Measurement of emotional variables through a brain-computer interface in the interaction with books with augmented reality in higher education
Authors: Rojas-Contreras M , Peña-Cortés C A , Cañas-Rodríguez S M
Published: December 2020

This article aims to describe the process of measuring mental state variables through a brain-computer interface in the interaction of humans with books with augmented reality; specifically, it seeks to analyze the variables commitment, stress, interest, relaxation, excitement, concentration in the interaction of students with a book with augmented reality compared with the measurement of the same variables when reading a traditional text. For the process of measuring emotional signals, two texts were designed for the data structure subject of the systems engineering program, the first in traditional format and the second with augmented reality applications. Subsequently, the mental state measures were taken through the brain-computer interface to the sample of students of the subject interacting with the traditional book and the book with augmented reality. Finally, through the interface software application, the results of the variables of each student interacting with the mentioned texts were downloaded and comparatively analyzed. Through comparative analysis, it is shown that the variable of mental state interest increases in the interaction of higher education students with books with augmented reality compared to reading a traditional text. Brain-computer interface systems have become an effective strategy for the measurement of emotional variables in the incorporation of emerging technologies such as augmented reality into teaching-learning processes in higher education.
Affective and interactive suitability indicators: an experience in physics from the onto-semiotic approach
Authors: Rincón Leal O L , Jaimes Fonseca L K , Fonseca Palacios R A
Published: December 2020

The purpose of this research was to propose theoretical elements for the description of the students’ attitudes in the teaching of differential calculus and its applications to physics from the onto-semiotic approach in the affective and interactional suitability. The design of this research with a complementary approach of qualitative and quantitative methods, with predominance of the first one, under the interpretative paradigm. The field modality and a quasi-experimental design to evaluate the applicability of the concepts of differential calculus. The collection techniques were: first, the semi-structured interview, in order to guarantee the depth and density of the information so that it converges in an emerging system of meanings and categories; second, the application of a questionnaire to evaluate the cognitive capacity of students under the onto-semiotic and traditional approach; third, observation through surveys. The findings lead to an instructional process through which mathematical concepts are taught efficiently, the student’s role is valued as being assertive, autonomous, and responsible, while the teacher contributes to the development of emotional support by increasing the student’s motivation, self-confidence, and interest in learning mathematics.
A method to solve the heat transfer problem for laminar flow of Phan-Tien-Tanner fluid in a flat channel
Authors: Kadyirov A I , Vachagina E K
Published: December 2020

The paper presents a solution to the heat transfer problem for a flow of a four-mode viscoelastic linear Phan-Tien Tanner fluid in flat channels at a constant wall temperature. A special feature of this solution is the parametric representation of dependence of an axial velocity and temperature on coordinates. To obtain a solution to the energy transfer equation, we used the method of separating variables and decomposing the sought-for function into series by parameter. For a specific liquid, the profiles of dimensionless velocity and distribution of dimensionless temperature, Nusselt numbers, and other heat transfer characteristics for various Weissenberg numbers are presented.
Tornado-like vortices behind a cylinder in a channel at moderate Reynolds numbers
Authors: Molochnikov V M , Mazo A B , Kalinin E I , Paereliy A A , Dushina O A , Kluev M A
Published: December 2020

Experiments and direct numerical simulation were employed to study the near wake of a circular cylinder in a cross flow in a rectangular channel. The gap between the cylinder and the channel wall was varied. Moderate Reynolds numbers were considered. The analysis of experimental results in combination with numerical simulation revealed the common patterns in the vortical structure of flow behind the cylinder, namely the tornado-like vortices formed in the region where the cylinder was attached to the sidewalls of the channel. The effect of the cylinder location on the onset of Karman vortex street was estimated. The formation mechanism of tornado-like vortices was described.
RANS and LES simulation of separated flow in a flat channel with a back-facing step
Authors: Terekhov V V , Barsukov A V , Terekhov V I
Published: December 2020

The results of numerical calculation by the RANS and LES methods of turbulent separated flow in a flat channel with a back-facing step are presented. The calculation was carried out for Reynolds number Re = 5000, determined by the average mass velocity and the step height. The effect of vortex generators in the form of a transverse rib on the heat transfer intensity has been studied, and the data obtained are compared with experiment.
Experimental comparative research of convective heat transfer enhancement in channels
Authors: Frantsuzov M S , Ilchenko M A , Koroleva A P
Published: December 2020

This article presents the results of a comparative-experimental research of various methods to intensify heat transfer in the channel. Four different methods of heat exchange enhancement are considered: twisted tape, wire spiral, joint intensifier made of wire tape and twisted spiral, and acoustic method of intensification. The thermal and hydraulic characteristics of various methods of heat exchange intensification are experimentally investigated, and the efficiency of heat exchange intensification is determined. The thermal and hydraulic characteristics of a smooth channel without intensification obtained experimentally under the same conditions were used as a reference. In the course of the comparative analysis of the considered methods of intensification, the most effective ones are found in the range of changes in the Reynolds number from 10000 to 60000. The presented data can be used in the design of heat exchangers.
Superheated metastable atomized water plume diagnostics peculiarities in confusor-diffuser nozzles; atomizaton process: dimensionless treatment
Authors: Zalkind V I , Zeigarnik Yu A , Nizovskiy V L , Nizovskiy L V , Schigel S S
Published: December 2020

Micron mode mass fraction
ε
determination method was tested for dense superheated water atomization plumes based on measurement attenuation coefficients of primary laser radiation. The initial water temperature in experiments was 200 and 240°C. The mass fraction of micron mode
ε
was determined using Bugger-Lambert equation and Mi theory. The comparison with previous data, which were obtained by scattering indicatrix analysis, was done. In terms of development of dimensionless treatment of experimental data on superheated water spray, the parameter expression for the transition to predominating role of nucleation in superheated water atomization in confusor-diffuser nozzles was revised the base of critical bubble formation.
Research of mechanisms of interaction of melt and coolant by means of small-sized experiments with solid and liquid metal samples
Authors: Ivochkin Yu P , Ismailov A M , Kubrikov K G , Teplyakov I O
Published: December 2020

Several basic fragmentation hypotheses described in the literature for the case of fine-scale spontaneous vapor explosion, when single hot drops are falling in the coolant, are analyzed. It is shown that all of them, depending on the experimental conditions, describe the real physical phenomena. It is highlighted, that the process of fragmentation during the spontaneous vapor explosion is directly connected to the regime of the film boiling collapse of the underheated liquid, which is still underexplored. The experiments on the liquid drops fragmentation are complemented by those with surface boiling at the solid metal samples of semi-spherical form. The connection between the vapor explosion of water and the increase of the surface wettability is confirmed. The video material, indicating the possibility of formation of liquid jets that strike the hot surface during the collapse of the vapor shell, is obtained. The time interval (duration of the contact) between the first contact of the coolant with the hot surface and the explosion boiling of the liquid is experimentally determined. The dependence of the contact duration on the temperature of the overheated wall is determined and its comparison with the theoretical estimations is provided.
The Development of a Mathematical Model of an Evaporative System with Film Flows
Authors: Minakov A V , Lobasov A S , Zaitsev D V , Kabov O A
Published: December 2020

A spatial mathematical model of the evaporation system using film flows has been developed. A numerical study of several modes of film flow in an evaporation cell at a heater temperature below the boiling point has been carried out. The characteristics of the film flow and the features of the coupled heat and mass transfer processes in the gas-film-metal substrate system have been studied. Good agreement between the calculation and the experiment on the main parameters of the wave motion of the film and the heat transfer characteristics has been obtained.
Study of heat exchange and hydrodynamics on the model of fuel assembly with microfuels
Authors: Tupotilov I A , Varava A N , Dedov A V , Zaharenkov A V , Komov A T , Loktionov V D , Mirnov S V , Smorchkova Y V
Published: December 2020

The design of the working section was developed and the hydraulic circuit of the TVS-MPEI experimental bench was modernized to study hydrodynamics and heat transfer in a fuel assembly with microfuel. Experimental studies were carried out to determine the pressure loss and hydraulic resistance coefficient of a cylindrical ball filling with the following operating parameters of the coolant: p = (2 ÷ 7) MPa, G = (0.05 ÷ 0.5) kg/s. The technology of installation, output and sealing of thermocouples at the work site has been developed. The first experimental data on the temperature distribution inside the ball filling were obtained.
Heat transfer under powerful heat release in supercritical-pressure liquids
Authors: Rutin S B , Skripov P V
Published: December 2020

The aim of the present article is to summarize the results of pulse experiments performed under conditions of powerful heat release in supercritical-pressure liquids. The parameters of the discussion are the values of the speed of crossing the vicinity of the critical temperature and pressure reduced to the critical one. These results obtained for “heater-probe / supercritical fluid” system and based solely on comparison of the primary data indicate a threshold decrease in the intensity of heat transfer near the critical temperature. The purpose of this summary is to suggest a relatively simple approach to reconciling the pulse heating results with the peaks of thermophysical properties derived from experiments in stationary conditions. It is assumed that the action of gradient in temperature and the presence of heat-transfer surface can serve as factors that suppress large-scale fluctuations in pulse heated system, leading to a “smoothing” the critical enhancement of the properties.
Thermal analysis and ignition of HEM containing aluminum and titanium borides
Authors: Korotkikh A G , Sorokin I V , Selikhova E A , Arkhipov V A
Published: December 2020

This paper describes the data of oxidation kinetics for metal fuels and ignition characteristics for the high-energy material (HEM) samples based on ammonium perchlorate, ammonium nitrate and an energetic binder, containing the powders of Al, B, AlB2, AlB12 and TiB2. The thermal oxidation of metal fuels and the thermal decomposition of the HEM samples were determined using a combined Netzsch STA 449 F3 Jupiter analyzer. The ignition of the HEM samples was studied using the radiant heating setup based on continuous CO2 laser in the heat flux density range of 90–200 W/cm2. Experimentally it was found that the complete replacement of aluminum powder by amorphous boron in the HEM sample significantly reduces the ignition delay time (by 2.2–2.8 times) in the same heat flux density. The ignition delay time of the HEM sample containing titanium diboride powder decreases slightly (by 10–25%) relative to the ignition delay time of the Al-based HEM.
Decrease in carbon monoxide release and incomplete burning of fuel during activated combustion of coal
Authors: Larionov K B , Zenkov A V , Mishakov I V , Gromov A A
Published: December 2020

Combustion products and ash residue of bituminous coal modified with copper salts (Cu(NO3)2, Cu (CH3COO)2andCuSO4) in amount of 5 wt.% are studied. Application of additives to the coal samples is carried out by the method of incipient wetness impregnation with preliminary dissolution of the additive in aqueous-alcohol solution with a volume ratio of C2H5OH/H2O = 50/50. Combustion of coal samples is conducted in combustion chamber at temperatures of the heating medium of 500–700°C. Gas-phase combustion products are analyzed using a flow-through gas analyzer. Application of additives contributes to the reduction of incomplete fuel burning. The maximum change (7.1 times) has been recorded for the sample modified with Cu(NO3)2 at a heating medium temperature of 600°C. Analysis of gas-phase products has shown that activation of the combustion process with copper salts allows significantly reducing the volume of formed CO, providing more complete oxidation of combustible products to CO2.
Development of a simplified mathematical model for a foil gas bearing operation
Authors: Volkov-Muzylev V V , Borisov Yu A , Beschastnykh V N
Published: December 2020

A theoretical study of a gas flow process in a clearance, changing during operation between a compliant foil of a foil gas bearing and a rotor of a high-speed turbomachine, is presented. The approaches to mathematic simulation of the position of the compliant foil of the gas bearing, deforming under the influence of gas pressure on the outer surface and a system of distributed springs on the inner surface, are developed. An example of numerical simulation of the foil gas bearing in order to obtain an elastic line of the compliant foil under the influence of gas forces, acting in a wedge-shaped clearance, is considered.
Features of water circulation on the Black Sea northwestern shelf based on physical reanalysis results
Authors: Dorofeyev V L , Sukhikh L I
Published: December 2020

The paper studies the main features of water circulation on the northwestern shelf (NWS) of the Black Sea. The study is based on a physical reanalysis performed previously. The result of reanalysis is a set of hydrodynamic fields for a period of twenty years on a regular grid with a discreteness of one day. To analyze the general properties of the currents on the NWS, the fields were averaged over a monthly period, and further analysis used the monthly average values of them. Spreading of the rivers outflow and wind stress are basic mechanisms, which controls the flow structure in the upper layer of the NWS. Surface currents are directed mainly to the southwest. Along the western coast, a compensatory current is formed, directed to the south, with the exception of the summer months, when the effects of wind are significantly weakened. A characteristic feature of the waters near the western shore is the strong horizontal stratification caused by fresh water with rivers outflow, mainly the Danube. An interesting feature of the circulation on the NWS is presence of a subsurface coastal jet counter-flow directed to the north. The center of this counter-flow is located approximately on the horizon of 20 meters. Its depth may vary, but the counter-flow itself is observed throughout the year.
Dynamics of laser plasma convective plume in high pressure xenon
Authors: Kotov M A , Lavrentyev S Yu , Solovyov N G , Shemyakin A N , Yakimov M Yu
Published: December 2020

This paper presents the results of numerical simulation of convective plume pulsations from a concentrated heat source equivalent to a continuous optical discharge (COD) in high pressure xenon compared to originally obtained experimental results. Simulated dynamic distributions of temperature, density and velocity of the gas around small spheroidal heat release zone are obtained, showing the process of formation of toroidal vortices in the convection zone, leading to the appearance of pulsations. The simulation results are qualitatively and quantitatively consistent with previously obtained experimental data.
Viscous fluid flow in a microchannel with hydrodynamic traps
Authors: Solnyshkina O A , Fatkullina N B
Published: December 2020

Simulation of creeping flows in complex three-dimensional domains is crucial for microfluidics applications, creating multipurpose microfluidic devices, which are used, for example, to study multistage chemical reactions and as analytical devices in medicine.In this work we study the features of the incompressible viscous fluid flow in a flat microchannel with a nontrivial internal structure (the hydrodynamic traps of various configurations) under the constant pressure drop.The three-dimensional boundary element method, improved by utilization high-efficient fast multipole method and heterogeneous computational workstation, was used in numerical simulation.We studied the flow pattern around C-shaped hydrodynamic traps distributed in a flat microchannel and consisting of five cylindrical elements of the same size. Such geometry is widely used in microfluidic devices for fixing particles in the flow, for example, biological objects during tests in medicine. The influence of the distance between the rows of traps on the flow pattern and distribution of the longitudinal and transverse components of the flow velocity was considered.
Software and hardware system for diagnostics of deposits inside the vortex chamber
Authors: Semenov D O , Dvoynishnikov S V , Rakhmanov V V , Meledin V G
Published: December 2020

This paper is devoted to the development of software for the system of visualization of deposits inside vortex chambers and the creation of algorithms for improving the quality of visualization. As part of the work, software for the microcontroller, which manages the entire hardware part, was created. An application for PC for visualizing images from the camera to the experimenter has been developed. Algorithms for correcting the distortion and subtracting the background are implemented for better analysis of the geometry of deposits.
Thermodynamic modeling of carbon nanoparticle C32 heating in the nitrogen environment
Authors: Barbin N M , Yakupova L V , Terent’ev D I , Kuanyshev V T
Published: December 2020

Using computer thermodynamic modeling, the behavior of carbon nanoparticles was studied C32when heated in nitrogen atmosphere at pressure 105 Pa. Modeling was carried out using a software package TERRA. Experiment temperature range – from 273 to 3373 κ. A graph of the carbon balance in the system is constructed C32-N2, physical and chemical processes are described. The equilibrium constants of reactions with the allocation of temperature ranges are calculated and graphs of the dependence of the equilibrium constants of reactions on temperature are given.
Thermal analysis of mechanochemically activated humic acids of brown coal
Authors: Mamylov S G , Skripkina T S , Tikhova V D , Bychkov A L , Lomovsky O I
Published: December 2020

Humic acids of brown coal before and after mechanochemical treatment under various conditions were studied by TG and DSC (carried out both in air and in an inert atmosphere, with the temperature range of 300–800 K), and gel permeation chromatography. The obtained data were used to calculate the values of the energy of activation and the thermal effects for each stage of thermal decomposition. Influence of mechanochemical treatment upon humic acids thermolysis stages was shown. Hypothesis of thermal stages chemical interpretation was proposed. The staged decomposition of humic acids includes the stages of decarboxylation of acid groups of various types. A change in the staging of decomposition is observed upon mechanochemical introduction of alkali into humic acids, associated with the conversion of acid groups to the salt form.
Data sources on the thermophysical properties of metals and alloys, a sketchy overview
Authors: Savchenko I V
Published: December 2020

A brief review about data sources on the thermophysical properties of metals and alloys is presented. The basic advantages and disadvantages of popular information sources are shown. Approaches to the choice of the most reliable data are discussed in general. A simple algorithm for searching the most appropriate property information for specific cases is recommended.
Development and experimental researches of refrigerating unit with a radar station
Authors: Beschastnyh V N , Borisov Yu A , Kosoi A S , Nizovskiy L V
Published: December 2020

The antennas of modern radar devices need effective cooling, which is carried out by forced circulation of the coolant. A new pneumohydraulic diagram of a refrigerating unit, which allows achieving effective heat removal from an antenna of a radar station with minimal overall dimensions and weight, is considered in this paper. The paper presents the results of experimental research related to an operation of the refrigerating unit at ambient temperatures equal to +50 °C and -50 °C within the temperature range from −50 °C to 10 °C.
A method of air-blast atomization of foamed liquid fuels for advanced combustors of gas-turbine engines
Authors: Vasilyev A Yu , Chelebyan O G , Sviridenkov A A , Domrina E S , Loginova A A , Tarasenko A N
Published: December 2020

The design of the combined nozzle module with bubbling and pneumatic spraying for the low-emission combustion GTE chamber has been carried out. Based on pervious work and literature analyzie a prototype of new combined nozzle module with five places of bubbling air supplying were pre-designed. To pre-select the position of the emulsification holes and to determine the possibility of combining the emulsion and pneumatic spraying principles in one design a series of experiments was carried out. The first results obtained using even not optimized device, showed that in modes close to the ground start and idle, the quality of the fuel spraying was improved by 30 % using the method of low-flow fuel bubbling.
Simulating heat and mass transfer processes during water film evaporation in a horizontal channel
Authors: Gorbachev M , Terekhov V
Published: December 2020

This paper is devoted to the numerical study of heat and mass transfer at evaporative cooling of a stream of a moist air in the horizontal channel, taking into account the final thickness of a film of water. Heat and mass transfer simulation is based on solving a system of differential equations for the laminar flow regime of air flow in a two-dimensional setting in the boundary layer approximation. Numerical studies are performed in a wide range of input parameters changes: temperature T0=10÷50 °C, relative humidity φ0 = 0÷100 %, and Reynolds number Re = 50÷2000. The geometric dimensions of the channel are taken for height H = 6 mm and length L = 50H. Calculations are performed at atmospheric pressure.
Study of heat transfer during cooling of highly loaded structural elements with a two-component heat carrier flow
Authors: Demidov A S , Tupotilov I A , Zakharenkov A V , Loktionov V D
Published: December 2020

One of the promising directions for the development of energy in the 21st century is thermonuclear energy. To implement this method of generating energy, experimental thermonuclear reactors have been operating for decades, the largest of which is currently being built in Cadarache (France). At the moment, one of the unsolved problems of such reactors is the creation of systems that provide reliable heat removal of heat fluxes from intracameral objects, such as a limiter, blanket, and divertor. In addition to high energy density, these objects have quite significant dimensions. Today, cooling of such objects is carried out mainly by water under pressure. This paper considers the possibility of using a dispersed two-component coolant flow as an alternative method of cooling such objects. A description is given of an experimental bench simulating uniform heating along the perimeter of the test section and it’s main systems. The paper presents the design of a spray device for forming a two-component dispersed coolant flow with its technical characteristics and a working area for conducting research. Experimental data were obtained on the temperature of the wall of the working area at various operating parameters of the coolant and power input.
SigmaFlow CFD code as a tool for predicting the wind environment around a group of buildings
Authors: Meshkova V D , Dekterev A A , Gavrilov A A , Litvintsev K Yu
Published: December 2020

The paper reveals the capabilities of SigmaFlow CFD code to predict wind conditions in terms of pedestrian comfort as illustrated by a model problem. The proposed numerical model was verified by comparing with experimental data. A group of buildings consisting of low-rise buildings and a high-rise building was considered. A comparative analysis of five computational variants with different grid saturation was performed. The results of mathematical modeling allow observing the vortex flow structure that is generated when streamlining buildings.
A new approach to the development of zero-emission power generation system
Authors: Ryzhkov A F , Bogatova T F , Maslennikov G E , Osipov P V
Published: December 2020

The problems of tightening harmful emissions standards and meeting commitments to reduce greenhouse gas emissions require the development of environmentally and economically viable technologies to capture CO2 and its subsequent utilization. The integration characteristics of the generic technologies for CO2 emission utilization from energy industries with a short, medium- and long-term commercialization prospects are considered, depending on the level of technological maturity and market attractiveness. Potential CO2 consumers were classified according to the central most sensitive energy generation parameters: volumes, pressure, and purity, depending on the CO2 capture processes parameters and types of thermal power plants. The CO2 utilization unit principles designed for full CO2 capture by various industries under the Paris agreements are considered. The joint analysis of the operating and prospective power plants, leading industrial technologies based on CO2 consumption, has revealed three types of energy-industrial symbioses representing a cost-effective “Power Plant – CO2 Consumer” model. This model operates without CO2 capture and conditioning unit and has the efficiency close to the traditional power plant without emissions utilization. Critical technology solutions are being developed for one of these types.
Stimulated Raman scattering in suspension of submicron diamond particles
Authors: Baranov A N , Bi Dongxue , Gorelik V S , Kudryavtseva A D , Maresev A N , Shevchenko M A , Skrabatun A V , Tcherniega N V
Published: December 2020

We report on the first experimental observation of stimulated Raman scattering (SRS), stimulated low-frequency Raman scattering and multiphoton excited negatively-charged single nitrogen-vacancy (NV-) centers luminescence in ethanol suspension of submicron diamond particles obtained at high pressures and temperatures (HPHT). The Stokes and anti-Stokes SRS components with a frequency shift of 1332 cm−1, corresponding to the fundamental optical mode of diamond crystal were observed. The spectral characteristics and energy thresholds of the studied processes were determined.
Hybrid interferometer system for velocity measurements
Authors: Pirog V A , Gubskiy K L , Yu Tishenko I , Kazieva T V
Published: December 2020

The first result of the developed hybrid system for measuring the mass velocity of a matter is presented in the article. It combines two methods, VISAR and PDV, to compensate for their shortcomings. The scheme of the measuring system and the results of the laboratory experiment are shown.
Ceramic packages prototyping for electronic components by using laser micromilling technology
Authors: Samotaev Nikolay N. , Oblov Konstantin Yu , Gorshkova Anastasia V. , Ivanova Anastasia V. , Philipchuk Dmitriy V.
Published: December 2020

The use of adaptive laser micromilling technology for the fast prototyping ceramic package of electronic components in a miniature surface mount form factor (SMD) is describing. Current experimental results and practical evaluation of one show that using the developed software and hardware is possible successfully producing SMD packages starting from the SOT-723 form-factor in the direction of larger overall dimensions to SOT-475 form-factor. Also discussed are the limiting physical factors arising in the course of the application of laser micromilling technology, which affect the production speed and quality of the resulting product from monolithic ceramics.
Focusing aspherical optical components for next generation megajoule laser system
Authors: Gorshkov V A , Saveliev A S , Nevrov A S , Smirnova A V
Published: December 2020

The idea of creating a laser thermonuclear installation was considered back in 1960s by Basov N and Krokhin O. [1]. Facility for conducting research near DT-fuel ignition threshold is being commenced at the moment [2], assembly of the laser installation interaction chamber has already been completed. To focus laser sight on the target, off-axis aspherical lenses are used as part of the final optical module (FOM). These lenses are manufactured using the developed technology of forming off-axis aspherical surfaces of optical parts. Combined use of shaping technology and stand for monitoring angular deviations of the surfaces of FOM lenses, allowed us to achieve high quality off-axis aspheric optical elements both in terms of standard deviation of the surface shape, as well as the value of the scattering circle.