bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of turbulent drag reduction mechanisms of viscoelastic fluids based on the Fukagata-Iwamoto-Kasagi identity and the Renard-Deck identity
Authors: Zhang Wenhua , Zhang Hong-Na , Li Jingfa , Yu Bo , Li Fengchen
Published: January 2020

The friction coefficient decomposition was investigated in viscoelastic incompressible fluid turbulent channel flows based on two methods, i.e., the Fukagata-Iwamoto-Kasagi (FIK) identity [K. Fukagata, K. Iwamoto, and N. Kasagi, “Contribution of Reynolds stress distribution to the skin friction in wall-bounded flows,” Phys. Fluids 14(11), L73–L76 (2002)] and the Renard-Deck (RD) identity [N. Renard and S. Deck, “A theoretical decomposition of mean skin friction generation into physical phenomena across the boundary layer,” J. Fluid Mech. 790, 339–367 (2016)]. Direct numerical simulations of viscoelastic fluid turbulent and Newtonian fluid turbulent channel flows were carried out to provide a database for comparative investigations. By comparing the friction coefficient decomposition results based on the two identities, different understandings about the turbulent drag reduction (TDR) mechanism were comparatively analyzed. It was found that the reduction of the viscous contribution to the friction coefficient is also an important cause for TDR under the RD identity, and that the TDR effect in the near-wall region is more intense than that under the FIK identity. In addition, if the weight coefficient for the shear-stress contribution to the friction coefficient in the FIK identity is interpreted as the laminar shear strain rate, the TDR mechanisms obtained by the two identities can be unified; the difference in the understandings can be attributed to the difference in base flow selected to determine the weight coefficient.
Shock-induced consolidation of tungsten nanoparticles—A molecular dynamics approach
Authors: Feng Jianrui , Xie Jing , Zhang Mingjian , Liu Xiaowen , Zhou Qiang , Yang Rongjie , Chen Pengwan
Published: January 2020

Shock-induced consolidation of tungsten nanoparticles to form a bulk material was modeled using molecular dynamics simulation. By arranging the nanoparticles in a three-dimensional model of body-centered cubic super-lattice, the calculated shock velocity-particle velocity Hugoniot data are in good agreement with the experiments. Three states, including solid-undensified, solid-densified, and liquid-densified, can be sequentially obtained with the increase of the impact velocity. It is due to the flow deformation at the particle surface that densifies the cavity, and the high pressure and temperature that join the particles together. Melting is not a necessary factor for shock consolidation. Based on whether or not melting takes place, the consolidation mechanisms are liquid-diffusion welding or solid-pressure welding.
Interaction between shock wave and a movable sphere with cavitation effects in shallow water
Authors: Wu Wenbin , Zhang A-Man , Liu Yun-Long , Liu Moubin
Published: January 2020

In this paper, we establish a fluid-structure interaction (FSI) model to investigate the dynamic interactions between the underwater explosion (UNDEX) shock wave and a movable sphere near the free surface. We utilize the local discontinuous Galerkin (LDG) method to capture the propagation of the shock wave in the fluid domain and employ the pressure cutoff model to calculate cavitation effects. The fluid elements at the fluid-structure interface are directly coupled to the structural dynamic model, and the structural transient dynamic responses are coupled with fluid acoustic pressure at the fluid-structure interface in the governing equation. The validity of the present FSI model is verified by comparing with the continuous Galerkin method. Due to the advantage of the LDG method in capturing the discontinuous wave, the present model shows better properties than the traditional coupled acoustic-structural model. With the present FSI model, we investigate the interaction between the UNDEX shock wave and a submerged and floated sphere. Under the combined effects of the free surface and structure, the UNDEX shock and cavitation loading characteristics are analyzed, and the influences of complicated cavitation effects on dynamic responses of the sphere are discussed.
Picosecond pulses from a monolithic GaSb-based passive mode-locked laser
Authors: Becker S. , Scheuermann J. , Weih R. , Rößner K. , Kistner C. , Koeth J. , Hillbrand J. , Schwarz B. , Kamp M.
Published: January 2020

We present passive mode locking of a GaSb-based monolithic diode laser emitting at 2.2 μm with a fundamental repetition rate around 9.57 GHz. A pulse width of ∼2.4 ps is reconstructed by shifted wave intermode beat Fourier transform spectroscopy-measurements, yielding a time-bandwidth product of 1.8. Mode-locking is observed for a range of reverse bias voltages from 1.3 to 3.3 V and driving currents from 110 to 300 mA. The continuous wave output power is ∼17.5 mW with the absorber segment left floating and ∼4.5 mW at a reverse bias of 3.1 V in the mode-locked regime. The full-width-half-maximum of the radio frequency signal is measured for all operation conditions, with a minimum of 8.4 kHz.
Diagnostics of small plasma discharges using probing in wide range of microwave frequencies
Authors: Khomenko A. , Macheret S.
Published: January 2020

A diagnostic method for small and microcavity plasma discharges is proposed. The method is based on applying a weak variable-frequency probing signal to the same electrodes that are used to create the plasma and measuring the reflected signal's amplitude and phase over a wide frequency range. Thus, the discharge impedance at multiple probing frequencies may be found, and the key plasma discharge parameters, such as the electron density and temperature and the sheath thickness, can be inferred. The method is dubbed SPRIGHT (Small Plasma Reflection Inter-rogation with GigaHertz Transmitter) and is demonstrated for a small (2 mm interelectrode gap) radio frequency capacitively coupled discharge in argon at pressures of 1–5 Torr.
Parameter-free coordination numbers for solutions and interfaces
Authors: Staub Ruben , Steinmann Stephan N.
Published: January 2020

Coordination numbers are among the central quantities to describe the local environment of atoms and are thus used in various applications such as structure analysis, fingerprints, and parameters. Yet, there is no consensus regarding a practical algorithm, and many proposed methods are designed for specific systems. In this work, we propose a scale-free and parameter-free algorithm for nearest neighbor identification. This algorithm extends the powerful Solid-Angle based Nearest-Neighbor (SANN) framework to explicitly include local anisotropy. As such, our Anisotropically corrected SANN (ASANN) algorithm provides with a fast, robust, and adaptive method for computing coordination numbers. The ASANN algorithm is applied to flat and corrugated metallic surfaces to demonstrate that the expected coordination numbers are retrieved without the need for any system-specific adjustments. The same applies to the description of the coordination numbers of metal atoms in AuCu nanoparticles, and we show that ASANN based coordination numbers are well adapted for automatically counting neighbors and the establishment of cluster expansions. Analysis of classical molecular dynamics simulations of an electrified graphite electrode reveals a strong link between the coordination number of Cs+ ions and their position within the double layer, a relation that is absent for Na+, which keeps its first solvation shell even close to the electrode.
The nuclear Overhauser Effect (NOE) as a tool to study macromolecular confinement: Elucidation and disentangling of crowding and encapsulation effects
Authors: Honegger Philipp , Steinhauser Othmar
Published: January 2020

We propose a methodology to capture short-lived but biophysically important contacts of biomacromolecules using the biomolecule-water nuclear Overhauser effect as an indirect microscope. Thus, instead of probing the direct correlation with the foreign biomolecule, we detect its presence by the disturbance it causes in the surrounding water. In addition, this information obtained is spatially resolved and can thus be attributed to specific sites. We extend this approach to the influence of more than one change in chemical environment and show a methodological way of resolution. This is achieved by taking double differences of corresponding σNOE/σROE ratios of the systems studied and separating specific, unspecific, and intermediate influence. While applied to crowding and encapsulation in this study, this method is generally suitable for any combination of changes in chemical environment.
Sexual practices of female sex workers in Melbourne, Australia: an anonymous cross-sectional questionnaire study in 2017–18
Authors: Zappulla Annalisa , Fairley Christopher K. , Donovan Basil , Guy Rebecca , Bradshaw Catriona S. , Chen Marcus Y. , Phillips Tiffany R. , Maddaford Kate , Chow Eric P. F.
Published: January 2020

Background
Sexually transmissible infections (STIs) are rising among female sex workers (FSW) in Australia. The rise might be explained by changes in sexual practices; however, there is limited behavioural data available. This study aimed to explore the current sexual practices among FSW in Melbourne. Methods: This cross-sectional study was conducted among FSW at Melbourne Sexual Health Centre between September 2017 and March 2018. Participants were asked about current sexual practices with male clients in an average working week. The frequency and proportion of each sexual practice was calculated. Results: There were 180 questionnaires included in the analysis. The median age of the FSW was 28 years (interquartile range [IQR]: 25–34). Most FSW (80.6%) worked in brothels. In an average working week, FSW had a median of 10 (IQR: 7–20) male clients. The most common sexual practices included: vaginal sex (98.3%), fellatio (97.2%), cunnilingus (92.2%) and tongue-kissing (83.7%). FSW had a median number of 10 (IQR: 6–18) vaginal, 10 (IQR: 5–18) fellatio, 7 (IQR: 2–10) cunnilingus and 6 (IQR: 2–10) tongue-kissing clients. Consistent condom use with all clients was highest for vaginal sex (97.1%), followed by anal sex (92.3%), then fellatio (78.9%). Only 3.1% used dental dams consistently for cunnilingus. Conclusion: Consistent condom use with all clients was high among FSWs, especially for vaginal and anal sex. However, one-fifth of FSW had condomless fellatio during an average working week. Tongue-kissing was more common than previously published. Peer-led sexual health education on safe sex practice for FSW is of high importance.
Forest stand and site characteristics influence fuel consumption in repeat prescribed burns
Authors: Levine Jacob I. , Collins Brandon M. , York Robert A. , Foster Daniel E. , Fry Danny L. , Stephens Scott L.
Published: January 2020

Prescribed fire is a vital tool for mitigating wildfire hazard and restoring ecosystems in many western North American forest types. However, there can be considerable variability in fuel consumption from prescribed burns, which affects both hazard mitigation and emissions. In the present study, data from replicated, repeat-entry burns following a period of 100+ years of fire exclusion were used to provide a detailed quantification of fuel consumption as it varies by fuel type, size class, stand and prescribed burn number (first, second or third). Using model selection on a series of linear mixed-effects models, it was determined that total fuel load, proportion of overstorey pine, slope, canopy cover, basal area of live trees, burn number and stand influenced fuel consumption at a 0.04-ha scale. Specifically, overstorey pine composition had a positive effect on fuel consumption. Overall fuel consumption across the three burns averaged 45% of pre-burn fuel loads. Overall consumption was highest for the first burn at 65%, decreasing by 15–20% with each successive burn number. Fuel consumption was highly variable by fuel type, stand and tree species composition. This variability may be advantageous for managers seeking to foster structural diversity and resilience in forest stands.
“What we do and don’t do”
Authors: Woodhams Jay M.
Published: January 2020

Academic language and learning advisers are employed by many Australasian universities to help students develop
their academic literacies, that is, the knowledge and skills needed to be successful at university both within and beyond
disciplinary contexts. At the Academic Skills and Learning Centre of the Australian National University, a team of Learning
Advisers spend a third of their time consulting students individually, often about a piece of writing to be submitted for
assessment. There is much concern in the literature about the pedagogical effectiveness of the one-to-one session, yet little that
examines it and its discourses as sites of identity genesis. This study examines Advisers’ post-consultation notes, and through a
community of practice approach to workplace discourse finds that discussion of “what we do and don’t do” is the nexus at which
Advisers negotiate the discourses of their organization, define boundaries around their work, and develop their professional
identities.
Writing for engineering
Authors: Simpson-Smith Claire
Published: January 2020

Professional engineers must move easily between concretization and abstraction in written communication, while
remaining rooted in the context of the particular engineering problem to be solved. Engineering programmes often seek to use a
replicated professional situation in order to prepare students for the workplace; however, there are questions as to how a
decontextualized task prepares students for the language and knowledge requirements of the field. This paper reports on the
findings of a Master’s research project, which investigated this issue through a comparison of two sets of engineering feasibility
studies: publicly available industry texts and English as an Additional Language (EAL) student texts from a Master’s engineering
program. The findings show that while the corpora have some similarities, there are differences that suggest that the student
texts are less bound to the concrete reality of their project, which has implications for those working in disciplinary and
professional literacies.
The distal radial physis: Exploring normal anatomy on MRI enables interpretation of stress related changes in young gymnasts
Authors: Kraan R. B. J. , Kox L. S. , Oostra R. J. , Kuijer P. P. F. M. , Maas M.
Published: January 2020

Rationale: Explore the MRI‐appearance of the healthy distal radial physis and the distribution of stress‐related changes in physeal thickness in young gymnasts to aid in the understanding of the pathophysiological process of stress‐related physeal injury.

Methods: Symptomatic gymnasts with clinically suspected overuse injury of the distal radial physis and age and gender‐matched asymptomatic gymnasts and healthy non‐gymnasts underwent an MRI‐scan of the wrist. A cartilage‐specific sequence was used to obtain three‐dimensional reconstructions of the distal radial physis. Heat maps and line charts of these reconstructions visualised distribution of physeal thickness per study group and were used to explore differences between study groups. Symptomatic gymnasts displaying the most profound physeal widening (n = 10) were analysed separately.

Results: Twenty‐seven symptomatic – (skeletal age 12.9 ± 1.5 years), 16 asymptomatic – (skeletal age 12.8 ± 1.9 years) and 23 non‐gymnasts (skeletal age 13.6 ± 1.9 years) were included for analysis. Physes of healthy non‐gymnasts had a thin centre and increased in thickness towards the borders. Gymnasts demonstrated an increase in thickness of the entire physeal surface. In symptomatic gymnasts increase in physeal thickness was most prominent at the volar side when compared to asymptomatic gymnasts and non‐gymnasts.

Conclusion: The healthy distal radial physis is characterised by a thin centre surrounded by thicker borders. Stress applied to the wrist during gymnastics causes an overall increase in physeal thickness. Profound thickness increase is present at the volar side of the physis mainly in symptomatic gymnasts. These results can help unravel the pathophysiological mechanism of stress‐related physeal injury in gymnasts and aid early injury identification.
Feeble projects and aspirations: the Caucasian and Transcaucasian federation/confederation in the geopolitics of 1918–1920
Authors: Kobakhidze Beka
Published: January 2020

The collapse of central power in the Russian Empire 1917 left the peoples of the Caucasus alone in the midst of the havoc of the Great War. While political elites were forced to detach the region from Soviet Russia, they simultaneously realized that Transcaucasia could survive only in unity, and thus formed first a Commissariat and then a Federation. Yet geopolitics, the shared imperial legacy, the economic prognoses, the complex ethnic demography, and the existing boundary disagreements ultimately made federation impossible. Nevertheless, the victorious Allies of the Great War saw their interests in the Caucasian “package”, advising that a Federation or a Confederation be created in the region. This article examines the geopolitical significance of the discourse surrounding this proposed Caucasian and Transcaucasian federation/confederation.
Ukraine and the Transcaucasus in 1917–1918: parallels, interactions, influences
Authors: Blauvelt Timothy K. , Tumis Stanislav
Published: January 2020

While the state of communications technology, the vicpen issitudes of war and revolution, and vast distances created obstacles to communication and interaction on the territory of the former Russian Empire during 1917–1918, very often during these revolutionary years, events in one region of the periphery were profoundly shaped by similar things taking place in others. Through a cross-regional and comparative analysis, this article considers the parallels between the situations in the Ukrainian and Transcaucasian theatres, and also the interactions that took place between the independent Ukrainian governments and the Transcaucasian Seim and Federation during this period, and also the ways in which the similar experiences and challenges facing the actors in these spaces, particularly among the ultimately victorious Bolsheviks, influenced their longer-term perspectives towards issues of nationalism, national sentiments, autonomy and federation in the minority regions of the periphery.
The effect of metal-oxide incorporation on the morphology of carbon nanostructures
Authors: Tigges Sebastian , Wöhrl Nicolas , Hagemann Ulrich , Ney Marcel , Lorke Axel
Published: January 2020

Metal-organic, single-source, low-temperature, morphology-controlled growth of carbon nanostructures is achieved, using an inductively coupled plasma-enhanced chemical vapor deposition system. Three distinctive morphologies, namely nanoflakes, nanowalls (CNWs) and nanorods (and intermediates between these morphologies), can be reproducibly deposited, depending on the process parameters. The synthesized structures can be described as hybrid materials consisting of metal oxide incorporated in a carbon matrix material. Since the incorporation of metal oxide into the carbon structure significantly influences their growth, the synthesis cannot be described solely with the existing models for the growth of CNWs. Optical emission spectroscopy is used to measure the relative number density of suspected growth and etching species in the plasma, while physical and chemical surface analysis techniques (scanning electron microscopy, Raman spectroscopy, scanning Auger microscopy and x-ray photoelectron spectroscopy) were employed to characterize the properties of the different nanostructures. Therefore, by using methods for both plasma and surface characterization, the growth process can be understood. The precursor dissociation in the plasma can be directly linked to the deposited morphology, as the incorporation of Al2O3 into the nanostructures is found to be a major cause for the transition between morphologies, by changing the dominant type of defect within the carbon structure.
In-situ measurement of permittivity distributions in reactors by cavity perturbation
Authors: Peter Ronny , Fischerauer Gerhard
Published: January 2020

The microwave cavity perturbation method is widely used for material parameter measurements in connection with small homogeneous samples. Its applicability to larger and inhomogeneous samples is uncertain, but highly desirable in connection with the in-
situ condition monitoring of chemical reactors. We have investigated the problem of the reconstruction of axially inhomogeneous permittivity distributions in tubular reactors from measured cavity resonance frequencies of the reactor. It is shown that the use of a priori knowledge about the function class of the permittivity distribution, which in turn follows from assumptions about the chemical process inside the reactor, allows one to reconstruct the permittivity distribution based on a few resonances only. The resulting errors in the function parameters or in the permittivity values identified are on the order of 5%, as demonstrated by analytical and numerical calculations, by numerical experiments, and by laboratory experiments.
Cultivating electroactive microbes—from field to bench
Authors: Yee Mon Oo , Deutzmann Joerg , Spormann Alfred , Rotaru Amelia-Elena
Published: January 2020

Electromicrobiology is an emerging field investigating and exploiting the interaction of microorganisms with insoluble electron donors or acceptors. Some of the most recently categorized electroactive microorganisms became of interest to sustainable bioengineering practices. However, laboratories worldwide typically maintain electroactive microorganisms on soluble substrates, which often leads to a decrease or loss of the ability to effectively exchange electrons with solid electrode surfaces. In order to develop future sustainable technologies, we cannot rely solely on existing lab-isolates. Therefore, we must develop isolation strategies for environmental strains with electroactive properties superior to strains in culture collections. In this article, we provide an overview of the studies that isolated or enriched electroactive microorganisms from the environment using an anode as the sole electron acceptor (electricity-generating microorganisms) or a cathode as the sole electron donor (electricity-consuming microorganisms). Next, we recommend a selective strategy for the isolation of electroactive microorganisms. Furthermore, we provide a practical guide for setting up electrochemical reactors and highlight crucial electrochemical techniques to determine electroactivity and the mode of electron transfer in novel organisms.
Investigation of spectrally-dependent phonon relaxation mechanism in Yb:YAG gain media and its consequences for thin disk laser performance
Authors: Severová P , Nagisetty S S , Chyla M , Miura T , Endo A , Smrž M , Mocek T
Published: January 2020

Nonlinear phonon relaxation in Yb:YAG gain media has previously been investigated, and a hypothesis correlating photo-induced free electrons and heat generation in crystals pumped at a wavelength of 940 nm was established (Brandt et al 2011 Appl. Phys. B 102 765–8). Later, we demonstrated efficient suppression of nonlinear phonon relaxation by zero-phonon line (ZPL) pumping of Yb:YAG (969 nm). However, no hypothesis has yet been tested that correlates the heat load and the free electrons in Yb:YAG media. We investigate, both theoretically and experimentally, the behaviour of an Yb:YAG slab pumped by a high-power laser diode at a conventional broadband line (absorption maximum at 941 nm) and a ZPL (absorption maximum at 969 nm), and we compare the generated photocurrent, temperature, and absorbed pump power for those two pump wavelengths. Although the hypothesis established by Brandt et al (2011 Appl. Phys. B 102 765–8) was not confirmed, and the measured photocurrent was identical for the two pump wavelengths, our measurement contributes to the knowledge of the inner processes in Yb:YAG active media. In the following steps we characterized an Yb:YAG thin disk laser, measured the spectrally-resolved absorption and disk surface temperature, and optimised our predictive model of thin disk behaviour. All the experimental and theoretical results are reported.
Surface traps-related nonvolatile resistive switching memory effect in a single SnO2:Sm nanowire
Authors: Zhou Huiying , Shi Haiping , Cheng Baochang
Published: January 2020

For nanostructure SnO2, it is very difficult for its electric properties to accurately control due to the presence of abundant surface states. The introduction of Sm can improve the traps in surface space charge region of SnO2 nanowires, resulting in a controllable storage charge effect. For the single nanowire-based two-terminal device, two surface state-related back-to-back diodes are formed. At a relatively large voltage, electrons can be injected into the traps in surface space charge region from negative electrode, resulting in a decrease of surface barrier connected with negative electrode, and contrarily electrons can be extracted from the traps in surface space charge region into positive electrode, resulting in an increase of surface barrier connected with positive electrode. The reversible injection and extraction induce a nonvolatile resistive switching memory effect.
Nano-sphere surface arrays based on GaAs solar cells
Authors: Peng Yinsheng , Gong Shufeng , Liu Kai , Yao Minghai
Published: January 2020

In this paper, we present our efforts on simulating and analyzing the effect of two-dimensional nano-sphere surface array on the characteristic of GaAs solar cells. Based on the scattering and diffraction theory of the photonic crystals, the simulation results show that the distance of adjacent nano-spheres (D) has the pronounced influence on the conversion efficiency and exhibits much poor tolerance, the absolutely conversion efficiency is reduced by exceeding of 2% as the D varies from 0 to 1 μm, in addition, the lower conversion efficiency (< 18%) is exhibited and almost remains unaltered when theD is of > 2 μm. The radius (R) of nano-spheres demonstrates much great tolerance. For D = 0, the solar cells exhibit high conversion efficiency (> 20%) and the efficiency is only varied by less than 1% whenR is varied in a very wide region of 0.3–1.2 μm. One can also find out that there is good tolerance for efficiency around the optimal value of refractive index and there is only about 0.2% decrease in final cell efficiency for around ±24% variation in the optimal values, which implys that it does not demand high precision processing equipment and the whole nano-sphere array could be fully complemented using self-assembled chemical methods.
Evaluation of an integrated wood-burning stove with water tank system for heating rural homes in the Andean highlands of Peru
Authors: Soria L S G , Cabana-Hancco W R , Montoya L A , Palo-Tejada E
Published: January 2020

In this work, we study an improved wood-burning stove with a water tank placed in the flue gas outlet for use as a heater. This system takes advantage of the waste heat of the gases that pass through the chimney to heat the water contained in the tank. The evaluations were carried out in a house located in the district of San Antonio de Chuca (Imata), province of Caylloma, department of Arequipa, Peru, located above 4500m above sea level, where temperatures decrease to -20 °C during winter.

A method is proposed to measure the power input of the integrated tank, which consists of finding the maximum power that the flue gas delivers to the water in the tank when the stove is turned on. Once this power has been identified, the wood-burning stove is replaced by an electric heating system that delivers the same power to heat the water. Once the electrical system has been calibrated, the water in the tank is heated to different temperatures, and the following are calculated: the accumulated energy, the time needed to reach the desired temperature and the amount of wood that would be used if the kitchen were used for heating. The power that the heater can deliver to the test house is thus determined.

If the water in the tank is heated to 70 °C, this heating system can deliver an average power value of 450 W from 20:00 to 5:00 the next day.
Solar energy and the Energy Institute of the National University of Engineering (1962-1969)
Authors: Amaya E
Published: January 2020

This article examines one of the first institutional initiatives that promoted the study of solar energy in Peru. For this purpose, the case of the Energy Institute, a unit attached to the Faculty of Mechanical and Electrical Engineering (FIME) of the National University of Engineering, is analyzed during the 1960s. The Institute concentrated its efforts on the location of the regions with the highest solar incidence and in the development of devices that could use successfully this kind of energy. Through the hermeneutic analysis of journals, bulletins, theses, interviews and the use of specialized bibliography, we build a historical account in which the role of the Institute and its exponents for the promotion and research of solar energy is highlighted. With this objective, the article is divided into three sections, the first one details the context in which there was a greater awareness of the role that energy played in national development. Secondly, the changes that FIME went through and that allowed for the creation of the Energy Institute are described. Finally, the works undertaken by the Institute in the field of solar energy and the profile they take over time are exposed.
Mathematical model of the polymeric composition melt flow in the middle layer extruder of the coextrusion equipment
Authors: Dyadichev V V , Kolesnikov A V , Dyadichev A V , Menyuk S G , Melnik A Yu , Dyadicheva E A , Chornobay S Ye , Dyadicheva I V
Published: January 2020

The paper analyzes the urgency of using coextrusion technology while recycling the secondary polymeric raw material. The balance equation in the melt flow tensions is obtained. The connection between the tensor of tensions and tensor of deformation rates components is determined. The generalized power law is used as a rheological equation of state. The energy balance equation is worked out for the stable regime of the melt flow. The limiting conditions for the complete differential model of extrusion are determined. The equation for determining the effective output of the middle layer extruder is worked out based on the efficiency of the whole extrusion machinery which depends on the characteristics of the rest four extruders and the head’s characteristics.
Research of the effect of preliminary preparation on characteristics of powders for modification of nickel superalloys
Authors: Eremin E N , Filippov Yu O
Published: January 2020

To improve the mechanical and operational properties of nickel alloys, complex modification has become widespread, in which refractory compound powders are used as inoculants. However, industrial powders are distinguished by a significant scatter of the specific surface and particle dispersion values. The aim of the work was to study the effect of the preliminary preparation of powders on their dispersity and dimensional stability. A method is proposed for preparing ultradispersed powders of plasma chemical synthesis for introduction into a liquid metal, including high-temperature purification of particles using ultrasonic vibrations of 17·103 Hz with an input power of 20 W/cm3 in the melt of alkali metal halides. It is established that the preliminary preparation of powders provides activation of particles and increases their dispersion by five times, dimensional stability by seven times, and the number of particles of nano-sized level increases to eight times.
Corrosion properties of metal deposited by chromium flux-cored wire with boride-nitride-intrmetallic alloyng
Authors: Eremin E N , Losev A S , Borodikhin S A , Ponomarev I A
Published: January 2020

The corrosion properties of the metal deposited with chromium flux-cored wire with boride-nitride-intermetallic alloying are investigated. It was established that the metal deposited with wire PP-Kh15+0.5%BN+1.25%TiB2+0.5%ZrB2 at the initial stage of corrosion behavior, estimated by the time until the first signs of corrosion appear, exceeds the metal welded with standard wire Sv-20Kh13 in 3.6 times, and long-term corrosion resistance 2.22 times. In this case, only a slight degree of etching of the matrix is observed in such a deposited metal, there is practically no dissolution of the boundaries of the boride eutectic, and the hardening phases do not undergo any changes, which determines the lower corrosion rate of such a coating. The powder wire PPKh15+0.5% BN+1.25% TiB2+0.5% ZrB2 can be recommended for surfacing wear-resistant coatings on parts of petrochemical equipment operating in an aggressive environment under abrasive wear.
Long-range action effects in the formation of nanostructured topocomposites under the impact of combined ion-plasma flows
Authors: Korotaev D N , Poleschenko K N , Orlov P V , Vershinin G A , Tarasov E E , Ivanova E V
Published: January 2020

The article updates the long-range action effect in the formation of nanostructured topocomposites under the conditions of the ion-plasma impact. The authors study the features of the concentration dependences of the distribution of elements in the boundary layers in the formation of the two-layer system "film-base". They determine that under the conditions of the implementation of the cascade cross-effect at considerable depths in the material of the hard-alloy base, locally inhomogeneous areas are formed, resulting in an increase in the microhardness of the material. Within the framework of the worked out simulation model, the study of factors contributing to the manifestation of the long-range action effect is undertaken. The contribution to the change of concentration dependences of the temperature, different diffusion mechanisms and the pressure gradient is established and differentiated. Based on the synthesis and analysis of the dynamics of the competing processes of "deceleration - acceleration" of the diffusion, the explanation to the formation of the hardened sublayers in the hard-alloy base of topocomposites and their role in the manifestation of the long-range action effect is offered.
Calculation of Phase Trajectories for Microstructural Analysis in Liquidus Fields of Cristobalite and Tridymite for System FeO-SiO2-Fe2O3
Authors: Lutsyk V , Zelenaya A , Lamueva M
Published: January 2020

Two spatial models of the phase diagram (PD) of system FeO-SiO2-Fe2O3 have been developed based on the method of computer assembly from phase regions. The first variant presents the simplified phase diagram for system FeO-SiO2-Fe2O3 without taking into account the immiscibility surface and without separation of tridymite field on the liquidus of silicon dioxide. Such model includes five liquidus surfaces corresponding to the initial components and two binary compounds fayalite and magnetite. The second model is more accurate and takes into account the presence of a two-phase region of liquid immiscibility, which divides the cristobalite field into two parts. It includes eight liquidus surfaces: two parts of cristobalite, iron, hematite, tridymite, fayalite, wustite, magnetite. The liquidus field of Fe is hypothetical. The surfaces of solidus, solvus, ruled surfaces are constructed and the phase regions are formed. Based on the complete computer model, the possibility of microstructural composition analyzes for system FeO-SiO2-Fe2O3 in the crystallization fields of cristobalite and tridimite is demonstrated using the diagrams of vertical mass balance, calculated for a given mass center in all temperature range of crystallization. Two-, one-, and zero-dimensional concentration fields with coincided and individual sets of micro-constituents are shown.
Physico-chemical properties of V1-XFeX O2 and FeV2O6
Authors: Semenyuk N A , Kuznetsova Y V , Surikov Vad I , Surikov Val I , Prokudina N A , Yanchij S V
Published: January 2020

The article presents the results of a study of the heat capacity of V1-XFeXO2, temperatures of phase transformations in the semiconductor phase have been determined. The phase transition diagram of the V1-XFeXO2 system is presented. Values of the change in the entropy of phase transformations for V1-XFeXO2 materials are determined. It was determined that the values of the change in the entropy of the metal-semiconductor phase transition decrease with iron concentration increasing. The results of differential thermal analysis, temperature dependences of electrical resistivity, magnetic susceptibility, and thermoelectric coefficient are presented for the FeV2O6 compound. It was determined that the FeV2O6 compound is a semiconductor in the temperature range from 100 К up to 400 К.
Growth of conjugated semiconductor monocrystals based on benzothienobenzothiophenes from solutions
Authors: Shubenkova E G
Published: January 2020

Organic semiconductors are actively used for numerous applications, their use in flexible electronics technologies is especially promising. The mobility of current carriers is a determining parameter whose value is strongly influenced by the crystallinity and arrangement of molecules in the crystal lattice of the synthesized semiconductor materials. The goal of this work was to obtain thin monocrystal films of conjugated oligothiophene-phenylenes (OTP) structures from solutions and their characterization. In this work, the solvent vapor annealing method was adapted to obtain conjugated structures based on dihexyl- and dioctylbenzothienobenzothiophene (C6-BTBT and C8-BTBT) from dichlorobenzene and toluene solutions with a concentration of 0.06 to 0.80 g / l. Solutions of various concentrations were applied to silicon substrates by centrifugation and droplet method. According to microscopic studies, C8-BTBT single crystals of the required geometry and size of about 1 mm were grown from solutions in toluene with a concentration of less than 0.06 g / l by centrifugation at a speed of 800 rpm. Electrophysical measurements showed that the obtained crystals have hole conductivity with a fairly high carrier mobility up to 0.047 cm2 / V · s (average 0.03 cm2 / V · s), which makes it possible to use these materials for the manufacture of field effect transistors and other electronic devices based on them.
Dynamics of apatite and calcium silicate hydrate composites resorption in Tris-buffer
Authors: Solonenko A P , Blesman A I , Polonyankin D A
Published: January 2020

Composites based on several biocompatible inorganic compounds present oneself a class of promising materials that can be used to repair damaged areas of hard tissue. Development of these composites and their bioactivity establishing is paid a significant attention. Investigation of processes occurring at composite powder materials soaking based on poorly crystallized carbonate substituted hydroxyapatite and calcium silicate hydrate in Tris-buffer was performed in this work. Chemical composition analysis of solutions contacted with composites with varying calcium phosphate and calcium silicate contents was carried out. Examination of undissolved solid phases was performed by SEM, FTIR and LDA. The obtained results indicate that materials components gradually dissolve in Tris-buffer. Moreover, the samples resorption rate increases with the growth of calcium silicate hydrate content in materials composition. Precipitation of the apatite was repeatedly detected in experimental conditions; it designates a potentially high bioactivity of investigated synthetic mixtures.
The effect of boron nitride on the properties of rubber compounds
Authors: Zhansakova K S , Eremin E N , Russkikh G S , Kropotin O V
Published: January 2020

The work is devoted to research of vulcanization characteristics of mixtures and revealing of features of change of technological, dynamic and physical-mechanical properties of elastomers on the basis of isoprene rubber filled with carbon black N330 and boron nitride (BN). It has been established that with a gradual increase in the concentration of the inert filler BN a decrease in the curing rate by 33% and the density of the polymer cross-linking by 26% is observed, as well as an increase in the curing start time by almost 300% and the optimal curing time by 200%. At the same time, there is a 26% decrease in the "Payne effect", a 50% increase in the relative elongation at rupture and a 30% decrease in the tensile strength.
Mathematical Description of Solution of the Three-Dimensional Boundary Value Problem for the Stationary Magnetic Field in the Cylindrical Coordinate System
Authors: Andreeva E G , Tatevosyan A A
Published: January 2020

The paper proposes a method of forming a numerical projection-grid algorithm on a regular triangulation network for the calculation of three-dimensional models of the magnetic field of synchronous magnetoelectric generators with excitation from permanent magnets, using recurrent expressions obtained for the "regular element". The use of the" regular element "allows to automate the process of formation of a global system of linear algebraic equations in the projection-grid Galerkin method in combination with the finite element method, bypassing the stage of construction of" element " systems of equations.
Heat-mass exchange processes dynamics forecasting in fires in typical multistorey apartment buildings
Authors: Bedrina E A , Rekin A S , Khrapsky S F , Bokarev A I , Denisova E S
Published: January 2020

Heat-mass exchange dynamics forecasting in fires in typical multistorey buildings allows to prove the need and determine organizational and technical solutions parameters aimed to increasing such buildings residents safe evacuation probability, which is an urgent problem according to statistics on the deceased persons number of this population category as a result of fires. On the numerical studies results basis, the characteristic time changes regularities of critically dangerous fire factors for humans are established; the most dangerous factor according to the people safe evacuation possibility from these buildings is the optical smoke concentration level. A method for determining the critical smoke time for safe evacuation has been proposed. It is proposed to equip mass construction 5–9 storey apartment buildings with early fire detection and warning systems.
About the election strength criteria in calculations for long-term strength for non-isothermal processes of loading
Authors: Belov A V , Polivanov A A , Neumoina N G
Published: January 2020

In the paper the research methods of axially symmetric elastic - plastic stress strain state of structures in the form of thin single and multiple layer shells of rotation with an account of material damage at creep is represented. The long-term strength criterion definition, on the basis of which the time to failure of the structure is calculated, is one of the important task. There are multiple long-term strength criteria, but very little detail recommendations on their usage and concretizing, which is what makes this problem so difficult to solve. The authors proposed a simple and easy-to-use method for concretizing the Pisarenko–Lebedev generalized long-term strength criterion. To verify the reliability of the proposed method of concretizing the long-term strength criterion, the calculations of time to failure a cylindrical shell under the action of internal pressure and a thin lamina with a round hole stretched by external radial forces are carried out. The calculation results obtained by the proposed method differ from the experimental ones by 1.8% and 3.1%. These results are the most reliable. Therefore, proposed method for calculating the long-term strength criterion enables more accurate damage and time-to-rupture predictions, compared with other calculation methods.
Electro Steam Thermal Complex Powered by Wind-Driven Generator for the Treatment of the Oil Formation’s Bottomhole Area
Authors: Belsky A A , Dobush V S , Malarev V I
Published: January 2020

In this article authors propose application of the wind-driven power units as power source of bottomhole electric steam generator for the thermal high-viscosity oil reservoir stimulation. The structure of the electro steam thermal complex is proposed. An analysis of the wind energy potential in the areas where the largest high-viscosity oil deposits in Russia are located is carried out. As part of the complex under consideration, the type of the dependence of the bottomhole electric steam generator’s power on the formation depth has been established. The calculation of the required installed capacity of wind power plants for placement as part of the electro steam thermal complex at the largest high-viscosity oil deposits in Russia has been performed.
Electrical Complex for Autonomous Power Supply of Oil Leakage Detection Systems in Pipelines
Authors: Dobush V S , Belsky A A , Skamyin A N
Published: January 2020

The authors proposed a scheme of autonomous power supply for oil leakage detection systems in pipelines by applying the photovoltaic modules and thermoelectric generators as a power source. Laboratory experimental studies were carried out, the operating energy characteristics of the complex were obtained. A sufficient number of generating units has been determined for uninterrupted power supply to the data collection point of the oil leakage detection system.
Analysis of the application for the magnetohydrodynamic effect in the hydrocarbon production
Authors: Logunov A V , Kopyrin V A , Portnyagin A L , Deneko M V
Published: January 2020

Nowadays the main share of oil fields is at a late stage of operation. It is characterized by high water cut of the extracted products. Salts in the formation fluid, under certain thermobaric conditions, settle on the process equipment and they cause its failure. Failure of technological equipment entails the well’s downtime and high material costs. Water-soluble salts in the formation fluid are subject to electrolysis. There, the molecules of the substance are decomposed into ions. The Lorentz force acts when a magnetic field is applied to the ions. The magnetohydrodynamic effect is manifested in the formation fluid. The purpose of the article is to analyze the applicability of the magnetohydrodynamic effect for hydrocarbon production. The chemical composition of formation waters for some deposits is given. On its basis the chemical model for electrolysis of the main salts in sodium chloride and potassium chloride contained in the formation liquid is constructed. The design and operation principle of the simplest magnetohydrodynamic pump is considered. The description of the developed laboratory sample of the magnetohydrodynamic pump is given. The main conclusions are reflected in this article.
The operating conditions of the internal combustion engine with high temperature cooling
Authors: Razuvaev A V , Slobodina E N
Published: January 2020

This paper presents the analysis of the experimental data on the cylinder bushing and 21/21 engine piston temperature level, as well as the possibility of converting the engine operation mode to the high-temperature cooling mode. The power plant bench tests results confirming the efficiency of the engine with high-temperature cooling mode are represented.
Furnace chamber heat exchange peculiarities in using different types of coal
Authors: Slobodina E N , Stepashkin I A , Mikhailov A G , Semenov B A , Kikhtenko V A , Shalay V V , Vdovin O V
Published: January 2020

The paper considers the types of heat transfer in the furnace chamber and ash residue values influence on the heat released and received in the furnace. The influence of different grades of coal (Kamyshanskij, Taldinskij and Ekibastuzkij deposits) with ash residue value from 16.4 to 43 % on the furnace combustion heat was analyzed. The ash residue value influence on the value of the heat received in the combustion chamber, which is the boiler efficiency defining characteristic, is considered. The graphical dependence of the heat amount received in the combustion chamber on the ash residue for the different types of solid fuel is shown.