bluuebunny/crossref_metadata_2025 huggingface dataset:
Searching for rare and secretive snakes: are camera-trap and box-trap methods interchangeable?
Authors: Neuharth Dalton B. , Ryberg Wade A. , Adams Connor S. , Hibbitts Toby J. , Walkup Danielle K. , Frizzell Shelby L. , Johnson Timothy E. , Pierce Brian L. , Pierce Josh B. , Rudolph D. Craig
Published: July 2020

Abstract
ContextAdvancements in camera-trap technology have provided wildlife researchers with a new technique to better understand their study species. This improved method may be especially useful for many conservation-reliant snake species that can be difficult to detect because of rarity and life histories with secretive behaviours.
AimsHere, we report the results of a 6-month camera-trapping study using time lapse-triggered camera traps to detect snakes, in particular the federally listed Louisiana pinesnake (Pituophis ruthveni) in eastern Texas upland forests in the USA.
MethodsSo as to evaluate the efficacy of this method of snake detection, we compared camera-trap data with traditional box-trapping data collected over the same time period across a similar habitat type, and with the same goal of detecting P. ruthveni.
Key resultsNo differences in focal snake species richness were detected across the trap methods, although the snake-detection rate was nearly three times higher with camera traps than with the box traps. Detection rates of individual snake species varied with the trapping method for all but two species, but temporal trends in detection rates were similar across the trap methods for all but two species. Neither trap method detected P. ruthveni in the present study, but the species has been detected with both trap methods at other sites.
ConclusionsThe higher snake-detection rate of the camera-trap method suggests that pairing this method with traditional box traps could increase the detection of P. ruthveni where it occurs. For future monitoring and research on P. ruthveni, and other similarly rare and secretive species of conservation concern, we believe these methods could be used interchangeably by saturating potentially occupied habitats with camera traps initially and then replacing cameras with box traps when the target species is detected.
ImplicationsThere are financial and logistical limits to monitoring and researching rare and secretive species with box traps, and those limits are far less restrictive with camera traps. The ability to use camera-trap technologies interchangeably with box-trap methods to collect similar data more efficiently and effectively will have a significant impact on snake conservation.
Generalised effective cosmology from group field theory
Authors: Gielen Steffen , Polaczek Axel
Published: July 2020

We extend various recent results regarding the derivation of effective cosmological Friedmann equations from the dynamics of group field theory (GFT). Restricting ourselves to a single GFT field mode (or fixed values of Peter–Weyl representation labels), we first consider dynamics given by a quadratic Hamiltonian, which takes the form of a squeezing operator, and then add a quartic interaction that can be seen as a toy model for interactions in full GFT. Our derivation of effective Friedmann equations does not require a mean-field approximation; we mostly follow a general approach in which these equations in fact hold for any state. The resulting cosmological equations exhibit corrections to classical Friedmann dynamics similar to those of loop quantum cosmology, leading to generic singularity resolution, but also involve further state-dependent terms. We then specify these equations to various types of coherent states, such as Fock coherent states or Perelomov–Gilmore states based on the su(1, 1) structure of harmonic quantum cosmology. We compute relative uncertainties of volume and energy in these states, clarifying whether they can be interpreted as semiclassical. In the interacting case, both analytical and numerical approximations are used to obtain modified cosmological dynamics. Our results clarify how effective cosmological equations derived from GFT can provide reliable approximations to the full dynamics.
On the discrepancy principle for stochastic gradient descent
Authors: Jahn Tim , Jin Bangti
Published: July 2020

Stochastic gradient descent (SGD) is a promising numerical method for solving large-scale inverse problems. However, its theoretical properties remain largely underexplored in the lens of classical regularization theory. In this note, we study the classical discrepancy principle, one of the most popular a posteriori choice rules, as the stopping criterion for SGD, and prove the finite-iteration termination property and the convergence of the iterate in probability as the noise level tends to zero. The theoretical results are complemented with extensive numerical experiments.
Bottomonium spectroscopy motivated by general features of pNRQCD
Authors: Chaturvedi Raghav , Rai A K , Soni N R , Pandya J N
Published: July 2020

The bottomonium mass spectra are computed in the framework of potential non-relativistic quantum chromodynamics. The potential consists of a static term incorporating the Coulomb plus confinement part along with a correction term added non-perturbatively from pNRQCD, which is classified in powers of the inverse of the heavy quark mass O(1/m). The masses of excited bottomonia are calculated by perturbatively adding spin–hyperfine, spin–orbit and tensor components of one-gluon exchange interactions in powers of O(1/m
2). Calculated masses are found to be consistent with other theoretical studies and experimental data. The Regge trajectories of the calculated mass spectra are also constructed. The values of the wave functions are extracted and employed to calculate the electromagnetic transition widths and γγ, e
+
e
−, light hadron and γγγ decay widths of several states at various leading orders, within the non-relativistic QCD formalism. Some of the experimentally reported states of bottomonium family like ϒ(10 860), ϒ(11 020) and X(10 610) are identified as mixed S–D wave and P wave states.
Quantum transport in Chern insulators on Möbius strips
Authors: Liu Yu , Ding Lu-Rong , He Ai-Lei , Wang Yi-Fei
Published: July 2020

Chern insulators (CIs) or quantum anomalous Hall (QAH) states have drawn more attention, with emergence of quantized Hall conductance but in absence of Landau levels. Here, we study the Haldane-type CI/QAH states on Möbius strips and focus on the quantum transport properties. The Möbius strips can be constructed from the twisted honeycomb-lattice strips with domain walls. Topological properties of the Möbius CI/QAH states can be identified by the local density of states, the real-space Chern numbers and the transport properties. Nearly perfect quantized conductance plateaus are observed in the numerical quantum-transport simulations. In addition, we found that adding magnetic flux in domain walls can induce alternating edge states. At last, we discussed in details the different lead connection schemes, and found that we can use multiple domain walls to obtain various higher quantized conductance plateaus.
Interior dense 3D reconstruction system with RGB-D camera for complex large scenes
Authors: Fu Xiaofan , Li Guangqiang , Yu Lei
Published: July 2020

At present, a 3D reconstruction system with simultaneous localization and mapping (SLAM) based on the feature point method presents critical difficulties when the texture is missing. In contrast, with the SLAM based on the direct method, unsatisfactory reconstruction results are achieved when the camera moves at a high speed due to the difficulty in pose estimation. In order to solve such problems, this paper presents a dense 3D scene reconstruction system with a depth camera (RGB-D camera) based on semi-direct SLAM. The system uses the feature point method to estimate the pose of the camera in the rich region of the texture, and then uses an efficient incremental bundle adjustment to optimize the pose of the camera. In areas where the texture is missing, the direct method is used to estimate the pose of the camera. Therefore, the photometric error can be reduced when optimizing the pose of the camera. Then, a 3D map is constructed using the optimized camera pose. The surfel model and the deformation map are used to estimate the pose of the point cloud and the fusion point cloud. The 3D reconstruction system presents the following characteristics: (1) A hand-held camera can be used to scan for 3D reconstruction with any gesture, where the system can reduce the error of reconstruction model caused by human operation; (2) high robustness, stability and strength to deal with the jitter of the missing area and the camera; (3) dense reconstruction of a large scene can be performed, and the reconstruction effect can be well obtained. Multiple experiments show that the proposed system can be applied to 3D reconstruction of various typologies, and can get the optimal 3D reconstruction model. The obtained results prove its applicability in robot navigation, virtual reality shopping malls and other fields.
Performance analysis of a 2.45 GHz microwave plasma torch for CO2 decomposition in gas swirl configuration
Authors: D’Isa F A , Carbone E A D , Hecimovic A , Fantz U
Published: July 2020

Microwave plasmas are a promising technology for energy-efficient CO2 valorization via conversion of CO2 into CO and O2 using renewable energies. A 2.45 GHz microwave plasma torch with swirling CO2 gas flow is studied in a large pressure (20–1000 mbar) and flow (1–100 L min−1) range. Two different modes of the plasma torch, depending on the operating pressure and microwave input power, are described: at pressures below 120 mbar the plasma fills most of the plasma torch volume whereas at pressures of about 120 mbar an abrupt contraction of the plasma in the center of the resonator is observed along with an increase of the gas temperature from 3000 K to 6000 K. The CO outflow is generally found to be proportional to the plasma effective power and exhibits no significant dependence on the actual CO2 flow injected into the reactor but only on the input power at certain pressure. Thermal dissociation calculations show that, even at the lowest pressures of this study, the observed conversion and energy efficiency are compatible with a thermal dissociation mechanism.
A novel source material engineered double gate tunnel field effect transistor for radio frequency integrated circuit applications
Authors: Dassi Minaxi , Madan Jaya , Pandey Rahul , Sharma Rajnish
Published: July 2020

Tunnel field effect transistors (TFETs) have proved their potential for many possible electronic circuit applications. However, with the variety of TFET structures being worked upon it has been an unresolved challenge to optimize them for the applications to which they are best suited. In this paper we present a detailed comparative analysis of the linearity distortion and the radiofrequency (RF) performance parameters of a proposed heterojunction Mg2Si source double gate TFET (HMSDG-TFET) and a conventional homojunction Si source DG-TFET (SSDG-TFET). A source material engineering scheme is utilized to implement a staggered type 2 heterojunction at the source–channel junction by replacing the source material with Mg2Si (a low band gap material) to enhance the ON current (2.5 × 10–4 A µm−1), reduce the threshold voltage (0.26 V) and achieve a steeper subthreshold swing (10.05 mV decade−1). For linearity and distortion analysis, the figure of merit (FOM)-like higher-order transconductances, second- and third-order voltage intercepts, third-order intercept point, third-order intermodulation distortion, zero crossover point, 1 dB compression point, second-order harmonic distortion, third order harmonic distortion and total harmonic distortion have been examined. To portray the possible application of devices under consideration for RF integrated circuit applications, both structures are investigated for RF FOMs such as power gains,
cutoff frequency (fT), maximum oscillation frequency (F
max) and admittance parameters. Investigations carried out using a Silvaco ATLAS device simulator tool revealed that with fT approximately three orders higher (0.49 THz) and F
max approximately two orders higher (0.9 THz) than that of a SSDG-TFET, the HMSDG-TFET is an appropriate candidate for use in high-frequency, high-linearity, low-distortion and low-power analog/RF applications.
Real-time monitoring of thermal history of thermoplastic automatic lamination with FBG sensors and process modelling validation
Authors: Saenz-Castillo D , Martín M I , Calvo S , Güemes A
Published: July 2020

Automated fibre placement (AFP) of thermoplastic composites has been reaching a high efficient and technological level in the last years. In situ consolidation (ISC) process involves cost reduction since extra autoclave cycle is not required. A good control of the temperature and pressure during the lamination is mandatory to achieve a good consolidation without thermal degradation for the manufacturing of high quality parts. Due to the manufacturing set-up, temperature monitoring is limited to infrared thermographic cameras and superficial measurements. Within this context, Fibre Bragg grating (FBG) sensors emerged as a potential device for thermal history monitoring in real-time. An investigation was carried out by using different FBG sensors for process monitoring of thermoplastic ISC. In this study, the sensors were embedded inside CF/PEEK thermoplastic samples and the lamination process was subsequently monitored. Also, a thermal model was created in order to obtain a simulated thermal history of the process. The process was successfully monitored, and it has been demonstrated that FBG sensors are a useful tool for thermoplastic ISC process monitoring. The results provided by the sensors allowed to identify different phases of the process (heating, consolidation and cooling down). The thermal history of the process was monitored by encapsulated FBG sensors acting as temperature probes. A good correlation between the sensors and the thermal was found. In addition to that, First steps were taken for strain history monitoring by means of FBG sensors.
Broadband tunable lossy metasurface with independent amplitude and phase modulations for acoustic holography
Authors: Fan Shi-Wang , Zhu Yifan , Cao Liyun , Wang Yan-Feng , Li Chen A- , Merkel Aurélien , Wang Yue-Sheng , Assouar Badreddine
Published: July 2020

Metasurface-based acoustic hologram projectors fabricated with fixed microstructures can only generate the predesigned images at a single or few discrete frequencies. Here, a variety of acoustic holographic applications can be realized in broadband by a matched helical design of the tunable lossy acoustic metasurface (TLAM). The proposed TLAM unit is composed of a grating channel and an adjustable internal absorber to achieve the independent amplitude and phase modulations (APM) in a continuous frequency range. We demonstrate the excellent performance of the scattering-free anomalous refection by the APM method for tuning loss without foam materials. Then, the multi-plane acoustic holograms and the broadband holographic images are demonstrated by the flexible reconfigurations of one designed TLAM. Due to the compact design and the great flexibility, this proposal may be more practical to achieve the high-quality holograms with multi-scale fine manipulation and multiplexed acoustic communication with high information content.
Dynamical suppression of Coulomb interaction and sub-fs jitter correction in electron pulse compression
Authors: Qi Yingpeng , Yang Yan , Sun Haitao , Wang Xuan , Cao Jianming , Ernstorfer Ralph , Sun Zhenrong
Published: July 2020

Achieving a few-femtosecond (fs) temporal resolution in electron diffraction and electron microscopy is essential for directly tracking the electronic processes and the fastest atomic motions in molecule and condensed matter systems. The intrinsic Coulomb interaction among electrons broadens the pulse duration and restricts the temporal resolution. To tackle this issue, the electron pulse compression by the time-varying electric fields at optical, THz and RF wavelengths has been demonstrated recently. However, the Coulomb interaction still exists in the compression process and the impact of the Coulomb interaction to the compression remains largely unaccounted for. In this work, we quantify the impact of the Coulomb interaction and present three intrinsic characters of Coulomb interaction in the compression process: the Coulomb interaction is dynamically suppressed as the compression field strength rises; the electron pulse with arbitrary kinetic energy (eV to MeV) suffers the same amount of Coulomb interaction, i.e. the Coulomb interaction is independent on the kinetic energy in compression; the dynamical suppression of Coulomb interaction within a single pulse gives rise to a dispersion of the temporal focus and impedes the further compression to attosecond. Potential applications based on the revealed characters of the Coulomb interaction in the compression process are discussed. Based on the dynamical evolution of the Coulomb interaction, three stages are identified to describe the compression process, which is beyond the ballistic compression model. Additionally, a robust and noninvasive jitter correction approach matching well with the compression regime is presented and the proof-of-principle experiment demonstrates a sub-fs accuracy.
Superlattice-barrier magnetic tunnel junctions with half-metallic magnets
Authors: Tseng Peng , Chen Zheng-Yi , Hsueh Wen-Jeng
Published: July 2020

Spin-transfer torque (STT) applications in magnetization switching such as magnetic tunnel junctions (MTJs) have been of popular interest in the development of novel memory technologies. However, the high switching power associated with these is a critical disadvantage in the operation of typical magnesium oxide (MgO)-based STT-MTJs. In this study, an ultra-low switching power, only 10% of the MgO-based MTJs, is achieved by high-purity spin polarization current using a superlattice-barrier MTJ with half-metallic magnets. The resistance-area product of the device is reduced to 0.2 Ω μm2, which is less than 10% of that in traditional MgO-based MTJs. The proposed MTJ has a higher performance, including STT and required switching current. A decrease in the switching power could avoid not only the disadvantages of power dissipation but also the device endurance due to lower Joule heating in the proposed MTJs.
Experimental progress of hybrid operational scenario on EAST tokamak
Authors: Gao X. , Zeng L. , Wu M.Q. , Zhang T. , Yang Y. , Ming T.F. , Zhu X. , Wang Y.M. , Liu H.Q. , Zang Q. , Li G.Q. , Huang J. , Gong X.Z. , Li Y.Y. , Li J.G. , Wan Y.X.
Published: July 2020

Extensive experiments of advanced scenario development, which contribute to the ITER hybrid operational scenario have been carried out on experimental advanced superconducting tokamak (EAST) tokamak recently with the ITER-like tungsten divertor. The

β
N

in this operational scenario is intermediate up to 2.1 (EAST#78987,

β
N

∼ 2.1, I
p ∼ 0.45 MA, q
95 = 3.7,

B
T

∼ 1.5 T, 3 MW neutron beam injection and 1 MW 4.6 GHz lower hybrid wave). In these hybrid H-mode plasmas, the internal transport barrier (ITB) has been frequently observed with central flat q profile and it is found that the fishbone mode (m/n = 1/1) can be beneficial to sustain the central flat (q(0) ∼ 1) q profile, thus a stable ITB can be obtained. In this case, better plasma performance is achieved. The formation of the ITB of the electron density is related to the fishbone activities. Energy transport analysis shows that the fishbone instabilities have a suppression on electron turbulent energy transport, while the ITB of ion temperature is due to the suppression of high-k modes (electron temperature gradient). The mechanism of turbulence suppression from fishbone instabilities in the EAST tokamak is not clear and needs more investigation. It is also observed that the power threshold for ITB formation is

≥

3.5 MW, which is consistent with the scaling law for other tokamaks. The dimensionless parameter

G

 

(

=

 

H

89

β
N

/

q

95

2

) obtained in the EAST reaches 0.3, but is still lower than the ITER hybrid scenario design (G ≥ 0.4) and needs more extension. Further investigation of extending the operational regimes, such as expanding the ITB foot outwards, would be important for the development of the hybrid and steady-state scenarios for next-step fusion devices like ITER and CFETR.
Mini-EUSO onboard of the ISS for UV terrestrial and cosmic emission detection: space qualification and calibration
Authors: Cambiè G
Published: July 2020

The Mini-EUSO (Multi-wavelenght Imaging New Instrument - Extreme Universe Space Observatory) telescope is designed to observe the UV emission of the Earth from the vantage point of the International Space Station (ISS) in low Earth orbit. Mini-EUSO will map the Earth in the UV range (300 - 400 nm) offering the opportunity to study a variety of atmospheric events such as Transient Luminous Events (TLEs) and meteors, as well as searching for Strange Quark Matter (SQM) and bioluminescence. The instrument comprises a compact telescope with a large field of view (44°), based on an optical system employing two Fresnel lenses for light collection, focused onto an array of 36 multi-anode photomultiplier tubes. The resulting signal is converted into digital, processed and stored via the electronics subsystems onboard. In addition to the main UV detector, Mini-EUSO contains two ancillary cameras for complementary measurements in the near infrared (1500 - 1600 nm) and visible (400 - 780 nm) range and also a SiPM (Silicon PhotoMultiplier) array which will increase the Technology Readiness Level (TRL) of this ultrafast imaging sensor.
Fragmentation and agglomeration of biomass in fluidised bed pyrolysis and combustion
Authors: Litun D S , Ryabov G A , Folomeev O M , Shorina E A , Smirnova O A
Published: July 2020

The results of experiments on primary fragmentation of wood biomass particles during fast pyrolysis in an inert medium at different temperatures are presented. Growth of temperature and initial size in the range t = 800 – 950°C increases the probability and intensity of fragmentation in the process of rapid pyrolysis of wood particles. Oblong particles are more prone to fragmentation than quasi-circular (cubic) particles with the same equivalent diameter. The critical diameter of fragmentation for spruce wood particles at a process temperature of 950 °C is dv0 =18-19 mm at the ratio of longitudinal and transverse size h/a =1 and is in the range of 7-9 mm at h/a =8. Study of microstructure and chemical composition of coke particles (fragmentes) by microscope with SEM analysis showed existence of thin outer layer (0-15 μm) on the particle faces, containing increased quantity of mineral components. Microspheres with a size of 13-23 μm and increased content of sulfur were detected on the particle faces, resulting at 950°C. Coinciding of maximum and minimum of chlorine, sodium and potassium content in the outer layer denotes on existence of sodium and potassium chlorides on the surface of coke particles. Results of experimental studies of physical and chemical processes occurring between the fuel ash and the bed materials under prolonged temperature exposure were obtained. The aim of these studies was to determine the time and proportion of agglomerated (sintered) particles of several types of biomass depending on the bed temperature. The experiments were carried out in a furnace on biomass ash, sand and mixture of sand and ash. First experiments showed a clear dependence of the temperature of agglomeration beginning on the potassium concentration in the bed and gave the boundary values of the concentrations and temperatures in the bed.
Physical and chemical processes simulation of organic wastes processing by the method of high-temperature oxidation in the melted slag
Authors: Markelov A Yu , Kudrinskiy A A , Anpilov S V , Shiryaevsky V L
Published: July 2020

Recycling of municipal waste is associated with accumulation of significant amounts of sewage sludge. The paper proposes a technology for the thermal utilization of sewage sludge with vitrification of a non-combustible residue. The paper presents the results of numerical simulation of the physical and chemical processes that accompany the high-temperature oxidation of pre-dried and pre-pelleted sewage sludge on the surface of the slag melt in a pilot plant with the melter capacity of up to 100 kg/h pellet. The mathematical model of the melter has been created and numerical calculations of the flow of high-temperature gaseous medium supplied by burner devices in the working volume of the furnace have been made in a stationary approximation taking into account the thermophysical and chemical processes occurring in the raw material, fed in the form of dry pellets (sediment).
Simulation of thermal explosion on the base of solution of the equation for the probability density function of particle temperature fluctuations
Authors: Derevich I V , Klochkov A K
Published: July 2020

The influence of temperature fluctuations of gas on the thermal explosion of particles with internal exothermic reactions is considered. The dependence of the rate of a chemical reaction on the concentration of a gas reagent is taken into account. Based on a rigorous system of heat and mass transfer equations, equations for the average temperature and concentration of the reagent inside the particle are obtained. A study of the dynamics of changes in the concentration of reagents and temperature inside the particle in a random field of temperature is carried out on the basis of the probability density function. Based on the solution of the systems of stochastic ordinary differential equations, a method of direct numerical simulation of random temperatures and reagent concentration in a particle is developed. A method for solving the equation for the probability density function is created. The results of comparing the empirical probability density function obtained by direct numerical simulation and the results of solving the equation for the probability density function are presented.
Gradient heat flux measurement in study of heat transfer during steam condensation inside pipes
Authors: Babich A Y , Zainullina E R , Sapozhnikov S Z
Published: July 2020

The article is about the application of the gradient heat flux measurement in the study of heat transfer during steam condensation at the inner surface of the pipe during different directions of water and steam supply. The installed gradient heat flux sensors (GHFS) and thermocouples did not disturb the condensate film flow on the pipe surface. Heat flux per unit areas and temperatures were measured along the length of the pipe. The obtained results confirmed the high informative of gradient heat flux measurement, as well as the capability of GHFS operating under experimental conditions.
Combustion-driven gas-dynamic CO2-laser on the basis of modern aviation engines
Authors: Boreisho A S , Vovk M Yu , Edigarev A D , Kiselev I A , Kulalaev V V , Morozov A V , Orlov A E , Smirnov P G
Published: July 2020

Combination of combustion-driven gas-dynamic lasers with gas-turbine turbojet and turbo-shaft engines has been considered. Development of aviation technologies has been analyzed. Output performance of a laser taking air from modern helicopter and airplane engines taking into account ensuring exhaust of spent active medium into the ambient atmosphere has been determined. The application of penetration cooling of the laser nozzle bank blades has been evaluated.
Modeling the influence of the river on the wind pattern of Krasnoyarsk
Authors: Meshkova V D , Dekterev A A , Gavrilov A A , Filimonov S A , Litvintsev K Yu
Published: July 2020

The article analyzes the environmental situation in the city of Krasnoyarsk based on data of the Ministry of Natural Resources and the Ministry of Ecology and Environmental Management of the Krasnoyarsk Territory. The influence of the non-freezing Yenisei River on the movement of air masses over the city is considered based on numerical simulation. The obtained results demonstrate the ability to quickly simulate the wind pattern of the city, taking into account the heterogeneous nature of the terrain, heat transfer, wind load, and the influence of the river.
Improving the energy efficiency of ship tank heating systems
Authors: Bagaev D V , Syraleva M N , Kudinovich I V
Published: July 2020

One of the challenges for creating objects of marine equipment operating in arctic conditions is to prevent freezing of fluids in tanks at extremely low temperatures as it may cause damage to the ship and its systems. This problem can be solved with efficient heating systems for ship tanks. In the paper the ballast tank heating simulation and optimization of heating coil position is discussed. The considered heating coil is typical for icebreakers and ice-class vessels (Arc 5 and above). On the basis of the performed computations the recommendations for improving the energy efficiency of ship heating systems are formulated.
The unified approach to a definition of effective conductivity index of percolating cluster in macroscopically disordered environments
Authors: Kolesnikov B P
Published: July 2020

The paper proposes the unified approach to a definition of effective conductivity index of percolating cluster’s t fractal, quasi-fractal and n homogeneous parts. The approach is based on probabilistic-statistical nature of percolation cluster’s formation. Two functions t (ϑ) and n(ϑ) are presented. By the use of simple exponentiations they allow describing the behavior of maximum of critical macroscopically disordered environments’ effective conductivity in case of the given values of concentration ϑ elements of conductive component from percolation threshold ϑ = ϑc to their entire consolidation ϑ = 1.
Hydrodynamics of the developed pulsating laminar flow in a flat channel in the quasi-stationary region
Authors: Valueva E P , Zyukin V S
Published: July 2020

The hydrodynamic characteristics of the developed pulsating laminar flow in a flat channel – the longitudinal component of the velocity vector, the dimensionless pressure gradient, and the shear stress on the wall — were investigated. The calculations were carried out in a quasistationary region, i.e, under relatively low frequencies of oscillations of the cross-section averaged velocity. To obtain data in a quasistationary region, we analysed and used the results of the calculations of a stationary developed flow. The calculations of the system of the stationary motion equations and continuity equations were carried out by the finite difference method. The calculation results turned out to be consistent with the data obtained earlier by other authors. It has been found that at high amplitude of oscillations of velocity averaged over the cross section and exceeding one, coefficients of hydraulic resistance and friction resistance near the channel entrance averaged over the period are higher than these values for a steady flow.
The experimental investigation of the effect of nanoparticle material on the evaporation rate of nanofluids
Authors: Lobasov A S , Minakov A V , Pryazhnikov M I
Published: July 2020

It was experimentally investigated the nanofluids evaporation rate in this study. The nanofluids were prepared using the distilled water and different nanoparticles. The nanoparticles of aluminium oxide, silicium and zirconium dioxides, as well as the nanodiamonds were used. The average diameters of the particles were as follows: SiO2 – 25 nm, ZrO2 – 105 nm, Al2O3 particles – 43 nm and nanodiamonds – 5 nm. The Simultaneous Thermal Analyzer STA 449 C Jupiter (NETZSCH) was used to carried out the study of the evaporation rates of fluids. The dependence of the evaporation rate on the material of the nanoparticles was investigated. It was found in that study that the evaporation rate significantly depends on the nanoparticles material. Moreover, based on the obtained results it was shown, that the evaporation rate of nanofluids monotonically increases with an increase of nanoparticles volume concentration.
Eddy-resolving numerical simulation of silicon melt convection in a Czochralski crucible: effects of radiation from the free surface at various crucible rotation rates
Authors: Abramov A G , Smirnov E M , Smirnov S I
Published: July 2020

The contribution covers results of numerical study based on conjugate heat transfer formulation of turbulent silicon melt convection in an industrial system for CZ Si-crystal growth of 100 mm diameter crystals. The computations have been performed using an eddy-resolving method treated as Implicit LES for two values of the emissivity from the melt free surface (0.25 and 0.3) and the crucible rotation rate of 2 and 5 rpm. The effects of these parameters on melt convection and characteristics of heat transfer are analyzed.
Experimental studies of the influence of hydrodynamics on heat transfer at evaporation and boiling of a film irrigating a bundle of horizontal finned tubes
Authors: Gogonin I I
Published: July 2020

A feature of operation of some devices, such as heat pump steam generators, evaporators of refrigerating machine, steam generators of binary freon station, etc., is a low value of specific heat fluxes. Heat transfer regimes occur, when boiling in the film is just beginning and the heat transfer rate during evaporation is comparable to that during boiling. Tube finning is a well-proven way to intensify heat transfer, both during evaporation and boiling. However, there are insufficient data on the choice of finning parameters and methods for evaluating heat transfer during boiling of a film that irrigates a bundle of finned tubes. This paper presents an algorithm for calculating heat transfer during evaporation and boiling of a film that irrigates a bundle of finned tubes, and compares the calculated and experimental data. The calculated parameters turn out to coincide satisfactorily with the experimental data.
Improving the schemes for ash removal from hopper ash collectors based on modeling
Authors: Elsukov V K , Ogar P M
Published: July 2020

Various ash removal schemes from the hopper ash collector to such transportation devices as hydraulic ash disposal channels, are analyzed. The drawbacks of these schemes are: high flow rates of flush water, gas flows through common ash gutters between bunkers of different pressure, and clogging of ash flows. The paper considers the invention and its introduction, which will eliminate or reduce these drawbacks by increasing the reliability of the circuits and centralizing the discharge of ash. The high efficiency of the invention under consideration is illustrated by the example of its practical use in the Galachinsk boiler house situated in the territory of Bratsk. To determine the design and operational parameters of the above mentioned invention its mathematical model has been developed based on the balance of forces acting in it (on the continuous gate). With the help of the obtained model, the structural and operational parameters of the device are calculated in three possible variants of its implementation. In these cases, the number of sections of different pressure changes and the presence of a periodic action shutter is taken into account. The determined parameters are the maximum and minimum heights of the ash column, the mass and the position of the load of the continuous gate. Ash collector performance indicators affecting these parameters have been identified. An ash collector of the TsBR-150U-1280 type, which has ash bunkers with three different values of vacuum, is accepted as an example. On the basis of the developed model, an algorithm has been compiled for calculating the design and operational parameters of the device under consideration during its design.
Thermal ablation of biological tissue by high intensity ultrasound
Authors: Andreeva T A , Belyankin A B , Berkovich A E , Bykov N Y , Kozyrev S V , Ya Lukin A
Published: July 2020

The paper discusses the effect of a series of focused high-intensity ultrasound pulses from a multi-element transducer on the biological tissue. The simulation of the ultrasound intensity field in a homogeneous medium uses the Rayleigh integral. The thermal problem modelling is based on the numerical solution of the heat equation. The advantages of processing a given volume of tissue with pulses, whose focal points over time consistently diverge from the geometric focus of the transducer, have been demonstrated. The effect of the time delay between pulses on the nature of tissue heating and the size of the thermal ablation region is analyzed. The issues of scaling for the problem of heat distribution are discussed.
Diffusion and convective mixing modes of binary gas mixtures dissolved in the third component
Authors: Kossov V N , Fedorenko O V , Mukamedenkyzy V , Tuken M
Published: July 2020

The numerical investigation of the mixing of an isothermal binary gas mixture dissolved in the third component has been carried out. The boundary relation that determines the change of “diffusion – concentration convection” modes is obtained in the framework of a linear stability analysis for a flat vertical channel with mass-impermeable walls. Diffusion and convection regimes were studied for a mixture of a pair of gases H2 and Ar, which was diluted first with a light and then with a heavier component. It is shown that the nature of the ballast gas has a significant effect on the diffusion and convective mixing regimes of the main diffusing components.
Thermal characteristics of the radioactive graphite -CuO-Na2CO3-K2CO3-NaCl-KCl system in argon atmosphere
Authors: Barbin N , Kobelev A , Terent’ev D , Alekseev S
Published: July 2020

The article considers thermal characteristics of the radioactive graphite–CuO-Na2CO3-K2CO3-NaCl-KCl system in argon atmosphere. Thermodynamic calculations were carried out in the Terra program. Four temperature ranges with changes of thermal characteristics of the radioactive graphite–CuO-Na2CO3-K2CO3-NaCl-KCl system in argon atmosphere have been determined.
Parametric identification of differential-difference models of heat transfers in the systems of bodies
Authors: Pilipenko N V , Zarichnyak Y P
Published: July 2020

The combined inverse heat conduction problem (IHCP) was solved to restore the boundary conditions of heat exchange, in particular, unsteady heat flux, while simultaneously refining the thermophysical properties of the object material by parametric identification of the differential - difference models (DDM) of heat transfer in the object of study. The differential-difference model is a system of first order ordinary differential equations with respect to the state vector. The type of feedback, control, and measurement matrices included in the DDM is established. A priori parametrization and parametric identification of the heat transfer model was performed. The parametrization involves approximation of the desired heat flux by B-splines of the first order for each piecewise-linear segment. With parametric identification, the discrepancy between the model and experimental values of the parameters is minimized using a recurrent linear Kalman filter. Taking into account the parametrization and parametric identification, the time-varying heat flux at the body boundary was restored and its thermal and physical properties, in particular, thermal conductivity, were simultaneously refined. The uncertainty of restoration of parameters based on the Gram matrix is estimated. The boundaries of confidence areas for determining the desired parameters based on the sensitivity functions, which are obtained by solving the heat transfer equations, are established. The results of model experiments, in which initial estimates of the desired parameters were set twice less than the true ones, are given.
On experimental determination of the catalycity coefficient of heat-proof thermal protection materials
Authors: Shkuratenko A A
Published: July 2020

This paper reviews the developed and tested algorithm of experimental determination of the catalycity coefficient of heat-proof thermal protection materials and determines the conditions which should be followed during the simulation process at high-temperature gas-dynamic testbeds within the experiment.
Renewable energy in the Russian Arctic: Environmental challenges, opportunities and risks
Authors: Morgunova M O , Solovyev D A , Nefedova L V , Gabderakhmanova T S
Published: July 2020

The Arctic is a specific geographical region with extreme climate conditions, vulnerable environment, but rather intensive ongoing industrialization. The Arctic requires alternative solutions to provide energy supply to the energy consumers due to the growing energy demand and small-scale decentralized character of energy supply. At the moment, the largest part of energy consumption in the region is covered by hydrocarbon energy resources delivered from the mainland. Renewable energy technologies may be efficiently implemented to cover the needs of small scale decentralized energy consumers in the Russian Arctic, but at the moment they are applied on a very modest scale. The current study analyses and discusses the main challenges and risks related to renewable energy resources use in the Russian Arctic. Further, the study elaborates on the issues related to the environmental challenges and climate change-related threats, their relationship and influence on the technological choices of the future energy supply in the region, addressing the perspectives of sustainable development of the Russian Arctic.
The experience of implementing the water chemistry treatment on the gas-turbine power plant using the AMINAT reagents
Authors: Guseva O V , Butakova M V , Gubin D V , Orlov K A
Published: July 2020

Implementation of the program of import substitution considered on the example of pilot tests (PT) of reagents produced by NPF Travers LLC. The existing water chemistry of steam boilers and heat recovery steam boilers of RN-Tuapsinsky Oil Refinery LLC gas-turbine power plant is organized with the use of complex reagent Helamin BWR-150H. Considering the advantages and disadvantages of complex reagents for the organization of water chemistry, it was proposed to conduct PT of reagents AMINAT KO-4 based on a mixture of polyphosphates to prevent scale formation on heat transfer surfaces and AMINAT PK-2 based on mixtures of neutralizing amines to prevent carbon dioxide corrosion. The article presents the results of the PT, which showed that the correctional water chemistry of boilers using reagents AMINAT ensured the maintenance of the regulatory requirements of the regime maps of the equipment, as well as minimizing the processes of corrosion, scale formation and sludge formation during the entire period of work. Based on the results obtained, conclusions were drawn on the technical and economic feasibility of using these reagents.
Comparative analysis of the possibility to reduce vibration transmission through a pipeline compensator by suppressing dynamic forces and pressure pulsations by active methods
Authors: Kiryukhin A V , Loshkareva E A , Kondratev A V , Korljakova M O , Miloserdov V O
Published: July 2020

The results of experimental studies of joint two-channel active suppression of pressure surges and vibrations of the working medium to reduce vibration transfer through pipeline compensators of power plants with liquid are considered. No data is available in academic periodicals on the use of active methods to solve this problem. The test bench design with excitation and active damping systems of vibrations and pressure surges is given. Efficiency of more than 15 dB from the use of broadband active systems for damping vibration forces transmitted through the compensator and pressure surges of the working medium inside it, both working separately and together in the frequency range from 10 to 275 Hz has been experimentally obtained. In the narrower frequency ranges from 10 to 350 Hz, active damping up to 25 dB has been obtained.
Investigation of the airflow conditions at the city residential areas
Authors: Meshkova V D , Dekterev A A , Filimonov S A
Published: July 2020

There are the computerised simulation results of the airflow around Krasnoyarsk residential areas (“Tikhiye Zori” and “Beliye Rosi”) and the impact assessment of these estates on particular areas of the city.
Development of Internet algorithms and some calculations of power plant COP
Authors: Ustjuzhanin E E , Ochkov V F , Znamensky V E , Tun A T Y , Shishakov V V
Published: July 2020

The authors have analyzed Internet resources containing information on some thermodynamic properties of technically important substances (water, air, etc.). Here, we consider the databases that possess such resources and are located in the following organizations: Joint Institute for High Temperatures (Russian Academy of Sciences), Standartinform (Russia), National Institute of Standards and Technology (USA), Institute of Thermophysics (Siberian Branch of the Russian Academy of Sciences), etc. Currently, a typical form is an Internet resource that includes a text file, for example, it is a file containing tabulated properties, R = (ρ, s, h...), here ρ is the density, s is the entropy, h is the enthalpy of a substance. A small number of Internet resources, which have the following characteristic, are known. Every resource allows a customer to realize a number of options, for example: i) to enter the input data, Y = (p, T), here p is the pressure, T is the temperature, ii) to calculate R property using “an exe-file” program, iii) to copy the result X = (p, T, ρ, h, s, …). Recently, some researchers (including the authors of this report) have requested a software (SW) that is designed for R property calculations and has a form of an open interactive (OS) Internet resource (“a client function”, “template”). A computing part of OS-resource is linked: 1) with a formula, which is applied to calculate R property, 2) with a Mathcad program, Code_1(R,Y). An interactive part of OS-resource is based on Informatics and Internet technologies. We have proposed some methods and tools those are related to this part and let us: a) to post OS-resource on a remote server, b) to link a client PC with the remote server, c) to implement a number of options to clients. Among these options, there are: i) to calculate R property at given Y arguments, ii) to copy mathematical formulas, iii) to copy Code_1(R,Y) as a whole. We have developed some OS-resources that are focused on sharing: a) SW that is used to design power plants, for an example,Code - GTP_1(Z,R,Y) and b) client functions, aimed at determination of the R properties of the working fluid at fixed points of the thermodynamic cycle. The program let us calculate energy criteria, Z, including the internal coefficient of performance (COP) for a power plant. We have discussed OS-resources, among them OS-resource that includes Code - GTP_1(Z,R,Y) and connected with a complex power plant included: i) several gas turbines, i) several compressors etc.
Numerical Investigations on Latent Heat Storage Unit using Phase Change Material
Authors: Amer A E , Lebedev V A
Published: July 2020

Many renewable energy sources are not available at any time in nature so the development of energy storage technologies is very important to conserve the available energy and improve its utilization. Thermal energy storage by using Phase Change Materials (PCM) is considered one of the promising technology to store thermal energy. The numerical study of the shell and tube storage unit is carried out. Paraffin wax was filled in the shell side and the Heat Transfer Fluid (HTF) flowed inside the tube. The validation among numerical and experimental results was conducted. It is found that the effect of natural convection is important and should be taken to perform the model of the heat storage unit.