bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarity dependent DC resistance degradation and electrical breakdown in Nb doped PZT films
Authors: Akkopru-Akgun Betul , Zhu Wanlin , Randall Clive A. , Lanagan Michael T. , Trolier-McKinstry Susan
Published: December 2019

The role of interfacial defect chemistry in time dependent breakdown and associated charge transport mechanisms was investigated for Pb0.99(Zr0.52Ti0.48)0.98Nb0.02O3 (PNZT) films. Electrical degradation was strongly dependent on the sign of the electric field; a significant increase in the median time to failure from 4.8 ± 0.7 to 7.6 ± 0.4 h was observed when the top electrode was biased negatively compared to the bottom electrode. The improvement in the electrical reliability of Pt/PNZT/Pt films is attributed to (1) a VO•• distribution across the film due to PbO nonstoichiometry and (2) Ti/Zr segregation in PNZT films. Compositional mapping indicates that PbO loss is more severe near the bottom electrode, leading to a VO•• gradient across the film thickness. Upon degradation, VO•• migration toward the bottom Pt electrode is enhanced. The concentration of VO•• accumulated near the bottom Pt interface (6.2 × 1018/cm3) after degradation under an electric field of 350 kV/cm for 12 h was two times higher than that near the top Pt/PNZT interface (3.8 × 1018/cm3). The VO•• accumulation near the bottom Pt/PNZT interface causes severe band bending and a decrease in potential barrier height, which in turn accelerates the electron injection, followed by electron trapping by Ti4+. This causes a dramatic increase in the leakage current upon degradation. In contrast to the bottom Pt/PNZT interface, only a small decrease in potential barrier height for electron injection was observed at the top Pt/PNZT interface following degradation. It is also possible that a Zr-rich layer near the top interface reduces electron trapping by Ti4+.
Suppression of dynamic disorder in fullerenes at metal-organic interfaces
Authors: Pazoki Sara , Dougherty Daniel B.
Published: December 2019

Organic semiconductors are prone to strong disorder effects that often exhibit significant dynamic characteristics. In this study, static disorder and dynamic disorder of fullerene molecules at the interface of Au(111) are directly distinguished using Scanning Tunneling Microscopy (STM) and Scanning Tunneling Spectroscopy. We consider an STM image consisting of hundreds of different molecules, as an ensemble which exhibits conductance fluctuations due to both dynamic disorder and static disorder. On the other hand, local conductance measurement of single molecules over time reflects only dynamic disorder. We demonstrate that dynamic disorder is always smaller than static disorder at the C60/Au(111) interface due to structural constraints of molecules at the interface. Dynamic disorder in our experiment is due to small librations of individual molecules that are restricted by the metal surface, while static disorder is related to different bonding orientations of the C60 cage that are frozen-in at room temperature. Our experimental results can be modeled with direct simulations of differential tunneling conductance.
On-chip background dilution in droplets with high particle recovery using acoustophoresis
Authors: Liu Zhenhua , Fornell Anna , Barbe Laurent , Hjort Klas , Tenje Maria
Published: December 2019

Droplet microfluidics has shown great potential for on-chip biological and chemical assays. However, fluid exchange in droplet microfluidics with high particle recovery is still a major bottleneck. Here, using acoustophoresis, we present for the first time a label-free method to achieve continuous background dilution in droplets containing cells with high sample recovery. The system comprises droplet generation, acoustic focusing, droplet splitting, picoinjection, and serpentine mixing on the same chip. The capacities of the picoinjection and the droplet split to dilute the background fluorescent signal in the droplets have been characterized. The sample recovery at different droplet split ratios has also been characterized. The results show a maximum of 4.3-fold background dilution with 87.7% particle recovery. We also demonstrated that the system can be used to dilute background fluorescent signal in droplets containing either polystyrene particles or endothelial cells.
Extensive subclonal mutational diversity in human colorectal cancer and its significance
Authors: Loeb Lawrence A. , Kohrn Brendan F. , Loubet-Senear Kaitlyn J. , Dunn Yasmin J. , Ahn Eun Hyun , O’Sullivan Jacintha N. , Salk Jesse J. , Bronner Mary P. , Beckman Robert A.
Published: December 2019

Human colorectal cancers (CRCs) contain both clonal and subclonal mutations. Clonal driver mutations are positively selected, present in most cells, and drive malignant progression. Subclonal mutations are randomly dispersed throughout the genome, providing a vast reservoir of mutant cells that can expand, repopulate the tumor, and result in the rapid emergence of resistance, as well as being a major contributor to tumor heterogeneity. Here, we apply duplex sequencing (DS) methodology to quantify subclonal mutations in CRC tumor with unprecedented depth (10
4
) and accuracy (<10
−7
). We measured mutation frequencies in genes encoding replicative DNA polymerases and in genes frequently mutated in CRC, and found an unexpectedly high effective mutation rate, 7.1 × 10
−7
. The curve of subclonal mutation accumulation as a function of sequencing depth, using DNA obtained from 5 different tumors, is in accord with a neutral model of tumor evolution. We present a theoretical approach to model neutral evolution independent of the infinite-sites assumption (which states that a particular mutation arises only in one tumor cell at any given time). Our analysis indicates that the infinite-sites assumption is not applicable once the number of tumor cells exceeds the reciprocal of the mutation rate, a circumstance relevant to even the smallest clinically diagnosable tumor. Our methods allow accurate estimation of the total mutation burden in clinical cancers. Our results indicate that no DNA locus is wild type in every malignant cell within a tumor at the time of diagnosis (probability of all cells being wild type, 10
−308
).
Equilibrium structure and deformation response of 2D kinetoplast sheets
Authors: Klotz Alexander R. , Soh Beatrice W. , Doyle Patrick S.
Published: December 2019

The considerable interest in two-dimensional (2D) materials and complex molecular topologies calls for a robust experimental system for single-molecule studies. In this work, we study the equilibrium properties and deformation response of a complex DNA structure called a kinetoplast, a 2D network of thousands of linked rings akin to molecular chainmail. Examined in good solvent conditions, kinetoplasts appear as a wrinkled hemispherical sheet. The conformation of each kinetoplast is dictated by its network topology, giving it a unique shape, which undergoes small-amplitude thermal fluctuations at subsecond timescales, with a wide separation between fluctuation and diffusion timescales. They deform elastically when weakly confined and swell to their equilibrium dimensions when the confinement is released. We hope that, in the same way that linear DNA became a canonical model system on the first investigations of its polymer-like behavior, kinetoplasts can serve that role for 2D and catenated polymer systems.
A noncanonical vacuolar sugar transferase required for biosynthesis of antimicrobial defense compounds in oat
Authors: Orme Anastasia , Louveau Thomas , Stephenson Michael J. , Appelhagen Ingo , Melton Rachel , Cheema Jitender , Li Yan , Zhao Qiang , Zhang Lei , Fan Danlin , Tian Qilin , Vickerstaff Robert J. , Langdon Tim , Han Bin , Osbourn Anne
Published: December 2019

Plants produce an array of natural products with important ecological functions. These compounds are often decorated with oligosaccharide groups that influence bioactivity, but the biosynthesis of such sugar chains is not well understood. Triterpene glycosides (saponins) are a large family of plant natural products that determine important agronomic traits, as exemplified by avenacins, antimicrobial defense compounds produced by oats. Avenacins have a branched trisaccharide moiety consisting of
l
-arabinose linked to 2
d
-glucose molecules that is critical for antifungal activity. Plant natural product glycosylation is usually performed by uridine diphosphate-dependent glycosyltransferases (UGTs). We previously characterized the arabinosyltransferase that initiates the avenacin sugar chain; however, the enzymes that add the 2 remaining
d
-glucose molecules have remained elusive. Here we characterize the enzymes that catalyze these last 2 glucosylation steps. AsUGT91G16 is a classical cytosolic UGT that adds a 1,2-linked
d
-glucose molecule to
l
-arabinose. Unexpectedly, the enzyme that adds the final 1,4-linked
d
-glucose (AsTG1) is not a UGT, but rather a sugar transferase belonging to Glycosyl Hydrolase family 1 (GH1). Unlike classical UGTs, AsTG1 is vacuolar. Analysis of oat mutants reveals that
AsTG1
corresponds to
Sad3
, a previously uncharacterized locus shown by mutation to be required for avenacin biosynthesis.
AsTG1
and
AsUGT91G16
form part of the avenacin biosynthetic gene cluster. Our demonstration that a vacuolar transglucosidase family member plays a critical role in triterpene biosynthesis highlights the importance of considering other classes of carbohydrate-active enzymes in addition to UGTs as candidates when elucidating pathways for the biosynthesis of glycosylated natural products in plants.
Evolution of resistance in vitro reveals mechanisms of artemisinin activity in
Toxoplasma gondii
Authors: Rosenberg Alex , Luth Madeline R. , Winzeler Elizabeth A. , Behnke Michael , Sibley L. David
Published: December 2019

Artemisinins are effective against a variety of parasites and provide the first line of treatment for malaria. Laboratory studies have identified several mechanisms for artemisinin resistance in
Plasmodium falciparum
, including mutations in Kelch13 that are associated with delayed clearance in some clinical isolates, although other mechanisms are likely involved. To explore other potential mechanisms of resistance in parasites, we took advantage of the genetic tractability of
Toxoplasma gondii
, a related parasite that shows moderate sensitivity to artemisinin. Resistant populations of
T. gondii
were selected by culture in increasing concentrations and whole-genome sequencing identified several nonconservative point mutations that emerged in the population and were fixed over time. Genome editing using CRISPR/Cas9 was used to introduce point mutations conferring amino acid changes in a serine protease homologous to DegP and a serine/threonine protein kinase of unknown function. Single and double mutations conferred a competitive advantage over wild-type parasites in the presence of drug, despite not changing EC
50
values. Additionally, the evolved resistant lines showed dramatic amplification of the mitochondria genome, including genes encoding cytochrome
b
and cytochrome
c
oxidase I. Prior studies in yeast and mammalian tumor cells implicate the mitochondrion as a target of artemisinins, and treatment of wild-type parasites with high concentrations of drug decreased mitochondrial membrane potential, a phenotype that was stably altered in the resistant parasites. These findings extend the repertoire of mutations associated with artemisinin resistance and suggest that the mitochondrion may be an important target of inhibition of resistance in
T. gondii
.
Bee colony health indicators: synthesis and future directions.
Authors: Requier F.
Published: December 2019

The western honey bee
Apis melifera
plays an important role in human well-being by producing honey, sustaining populations of wild plants and supporting human-dependant crop production. Unfortunately, abnormal high-mortality rates of colonies have been revealed all over the world. This paper reviews the stress factors that are likely involved in the cause of honey bee poor health, the mechanisms underlying bee health and survival and the different early warning indicators of bee colony mortality. Honey bee colonies can be assimilated to a complex system for which survival depends on its individual quality, its adaptive capacity and its threshold of resilience to pressures. Many stress factors are likely involved, by interaction, in the cause of honey bee colony mortality. Three main groups of stressors are highlighted to affect the colony survival, including (i) environmental pressures such as lack of flowers and pesticide exposure, (ii) biotic pressures such as parasites and pathogens and (iii) beekeeping management such as the use of chemical treatments. Routine monitoring of colonies provides robust approaches to assess the health status of honey bees. By tracking specific colony parameters such as queen performance, colony dynamics, in-hive products and the prevalence of pathogens, beekeepers can establish a health status of the colony. By comparing this field-based health status with model-based predictions, a new area is emerging towards the detection of early warning indicators of colony mortality.
A 1-kHz Single Frequency Nd:YAG Ring Laser by Injection Seeding*
Authors: Cao Xue-Zhe , Li Pei-Lin , Wang Zai-Yuan , Liu Qiang
Published: December 2019

We report on an injection seeded 1 kHz single frequency pulsed Nd:YAG ring laser with pulse energy of 5.2 mJ and pulse width of 9.9 ns. The ramp-fire technique is used to maintain single frequency operation and the cavity length is modulated by an intracavity RbTiOPO
4
(RTP) crystal. The frequency stability (rms) of the output pulse is 1.99 MHz over 1 min and the linewidth is 64 MHz.
Terahertz Lens Fabricated by Natural Dolomite*
Authors: Hao Si-Bo , Zhang Zi-Li , Ma Yuan-Yuan , Chen Meng-Yu , Liu Yang , Huang Hao-Chong , Zheng Zhi-Yuan
Published: December 2019

Optical operations have served as the basis of spectroscopy and imaging in terahertz regimes for a long time. Available lenses are practical tools for modulations. We fabricate a kind of biconvex lens from the natural dolomite cluster. The lens works well at 0.1 THz based on the relatively high refractive index and low absorption coefficients. Compared with the lens fabricated by a dolomite stone, such a lens can focus dispersive terahertz beam efficiently in terahertz imaging systems, which indicates that natural minerals hold promising applications in terahertz optics.
Generation of Femtosecond Laser Pulse at 1.43GHz from an Optical Parametric Oscillator Based on LBO Crystal*
Authors: Song Jia-Jun , Meng Xiang-Hao , Wang Zhao-Hua , Wang Xian-Zhi , Tian Wen-Long , Zhu Jiang-Feng , Fang Shao-Bo , Teng Hao , Wei Zhi-Yi
Published: December 2019

A femtosecond LBO optical parametric oscillator (OPO) with widely adjustable repetition rate by fractionally decrement of the cavity length is demonstrated. The repetition rate of 755MHz to 1.43 GHz at an interval of 75.5MHz is realized, which is 10 to 19 times that of the pump laser. The properties of output signal at 750nm at different repetition rates are studied. The power of signal decreases with increasing the repetition rate. The maximum power of 194mW at the repetition rate of 755MHz and the minimum power of 22mW at repetition rate of 1.43 GHz for the signal at 750nm are obtained for the pump power of 3 W.
High Resolution Microwave B-Field Imaging Using a Micrometer-Sized Diamond Sensor*
Authors: He Wen-Hao , Dong Ming-Ming , Hu Zhen-Zhong , Zhang Qi-Han , Yang Bo , Liu Ying , Fan Xiao-Long , Du Guan-Xiang
Published: December 2019

We propose a diamond-based micron-scale sensor and perform high-resolution B-field imaging of the near-field distribution of coplanar waveguides. The sensor consists of diamond crystals attached to the tip of a tapered fiber with a physical size on the order of submicron. The amplitude of the B-field component B is obtained by measuring the Rabi oscillation frequency. The result of Rabi sequence is fitted with a decayed sinusoidal. We apply the modulation-locking technique that demonstrates the vector-resolved field mapping of the micromachine coplanar waveguide structure (CPW). B-field line scan was performed on the CPW with a scan step size of 1.25 μm. To demonstrate vector resolved rf field sensing, a full field line scan acts (was performed) along four NV axes at a height of 50 μm above the device surface. The simulations are compared with the experimental results by vector-resolved measurement. This technique allows the measurement of weak microwave signals with a minimum resolvable modulation depth of 20 ppm. The sensor will have great interest in micron-scale resolved microwave B-field measurements, such as electromagnetic compatibility testing of microwave integrated circuits and characterization of integrated microwave components.
Darkness of two-mode squeezed light in Λ-type atomic system
Authors: Moiseev E S , Tashchilina Arina , Moiseev S A , Lvovsky A I
Published: December 2019

We show that, under certain circumstances, an optical field in a two-mode squeezed vacuum (TMSV) state can propagate through a lossy atomic medium without degradation or evolution. Moreover, the losses give rise to that state when a different state is initially injected into the medium. Such a situation emerges in a Λ-type atomic system, in which both optical transitions are driven by strong laser fields that are two-photon resonant with the respective signal modes. Then the interactions of the two signal modes with the ground-state atomic coherence interfere destructively, thereby ensuring the preservation of the TMSV with a particular squeezing parameter. This mechanism permits unified interpretation of recent experimental results and predicts new phenomena.
An experimental study of the propagation of a shock wave in a granular medium
Authors: Alyanov A V , Kazanin I V , Zinoviev V N , Vereshchagin A S , Fomin V M
Published: December 2019

In this work, experimental study of propagation shock waves and pressure-waves in granular medium was performed. As a granular medium are used hollow glass microspheres and composite sorbent based on them. The special experimental setup was prepared, which uses the principle of a shock tube. The setup includes a high pressure section and low pressure section with stepwise change of its internal diameter. The pressure graphics were obtained for the various tube sections for different media. The tube filling time and pressure wave velocity in the medium were estimated.
Gas heat exchange at inhomogeneous combustion of solid porous media
Authors: Amosova E V , Kuznetsov K S
Published: December 2019

The authors suggest using a numerical method based upon the finite element analysis of the equations of continuous inhomogeneous media mechanics to describe thermophysical properties of transient motions of viscous gas through porous media with chemical changes and phase transitions in a solid phase. The model takes into account heat exchange between a solid frame and gas, changes in the phase volume and mass at interaction, the presence of oxidant diffusion. The software developed in FreeFem++ allows clear and vivid studying the process of gas combustion in solid porous medium with inhomogeneous combustion source at forced filtration in the course of time as well as modeling and analyzing a real experiment.
Droplet breakup in shock waves at moderate values of the Weber number
Authors: Boiko V M , Poplavski S V
Published: December 2019

The object of this study was the physical mechanisms of aerodynamic fragmentation of droplets of low-viscosity liquids in shock waves in the region of existence of the shear breakup modes. New experimental data were obtained on the time induction of the droplets breakup depending on the gas flow velocity in the poorly studied range of Weber numbers We = 100 ÷ 2200.
Model of deformation of a liquid drop of zirconium dioxide after its collision with a steel porous surface
Authors: Bublik V V , Cherepanov A N
Published: December 2019

Based on the integral laws of conservation of mass and energy, a mathematical numerical-analytical model of the deformation of a continuous liquid-metal drop after its collision with a flat porous surface is constructed. The model takes into account the capillary and adhesive properties of the melt, the processes of cooling a liquid drop until it solidifies. Numerical calculations are performed for the model case of collision of a continuous liquid drop of zirconia with a porous steel substrate.
Determining the law of ice deformation
Authors: Buznik Vyacheslav , Golushko Sergey , Amelina Evgeniya , Belyaev Vasily , Bryndin Luka , Gorynin Arseniy , Shapeev Vasily
Published: December 2019

A mathematical model of nonlinear deformation of ice samples from distilled water is implemented. An algorithm for numerical solution of corresponding boundary-value problem is proposed and realized. Results of the numerical modeling have been compared to experimental data on the three-point bending of ice beams.
Influence of surface active agent on the size of metal powder particles during their ball milling in a planetary mill
Authors: Chesnokov A E , Smirnov A V , Vidyuk T M
Published: December 2019

The paper presents the results of a study of the influence of surface active agent during the ball milling of metal powders in a planetary mill. It is shown that the mass fraction of the surface active agent in the powder mixture under study affects the size of the particles being treated, depending on the time of processing. The particle size distribution, the specific surface area were determined, and the surface morphology of the initial and ball milled particles was studied.
Impact of the rate of input of specific energy on the ball milling of aluminium in a planetary mill
Authors: Chesnokov A E , Smirnov A V , Vidyuk T M
Published: December 2019

In the present study, the effect of the rate of the input of comparable amounts of energy into the material being processed on the particle size and on the value of specific surface area of the particles was analysed. It was shown that, irrespective of the rate of the energy input into the material, the resultant particles have similar characteristics, including their size and shape, and the value of the specific surface area. A more intense action exerted by the grinding bodies on the particles in the material being processed is accompanied by a sharp increase of temperature throughout the entire system. The heated particles plasticize, thus undergoing to a rolling-type granulation process.
Modeling the process of river bed bottom erosion in the area of the underwater pipelines location
Authors: Degtyarev V V , Garmakova M E , Shumkova M N , Chebotnikov A V
Published: December 2019

This paper deals with the modeling of flows and transport of sand particles during erosion of pipelines. The results of an experimental study of velocity fields and numerical CFD modeling in a three-dimensional transient formulation on the basis of Reynolds averaged Navier-Stokes equations in the ANSYS software package are presented. Modeling was carried out with different arrangement of pipelines, simulating cylinders, on a sandy bottom. The influence of the number of cylinders on the process of bottom soil reformation is analyzed.
Direct numerical simulation of viscous incompressible flow with spherical particles in the flat channel
Authors: Esipov D V , Lapin V N , Kuranakov D S , Chirkov D V
Published: December 2019

The paper deals with numerical simulation of 3D fluid flow with relatively large spherical particles in the flat channel. The simulation is performed using the previously developed SIMPLE based immersed boundary method. The collision model, describing particle-particle and particle-wall collisions, complements the numerical method. This model prevents particle overlapping and takes into account the complicated fluid flow in the space between the particles. The computed flow rates decrease significantly with increasing the particle concentration. It is shown that the value of the particle diameter has a small influence on the flow rate. The flow rate can be approximated using the value of effective viscosity computed by Maron – Peirce formula with the use of extremely high packing concentration. Particles are moving faster than the mixture, and the difference increases with increasing concentration.
Numerical investigation of wave propagation in high-permeable cylindrical waveguide in porous medium
Authors: Gubaidullin A A , Boldyreva O Yu , Dudko D N
Published: December 2019

The features of waves propagating in a highly permeable cylindrical waveguide in a porous medium are numerically investigated. The influence of the ratio of permeability inside the cavity and the surrounding porous medium, as well as the signal frequency on the evolution of the pressure wave inside the cavity is studied. On the basis of the calculated data, estimates of the velocity and attenuation of the signal during its propagation in the waveguide in a wide frequency range are obtained. It is shown that with the increase in the waveguide permeability, the propagation velocity increases and the attenuation of waves decreases, the depth of penetration of perturbations into the surrounding space decreases. Increasing the frequency of the initial signal leads to an increase in the velocity and attenuation of the pulse. A comparison is made with the case of wave propagation in a liquid-filled cylindrical cavity in a porous medium. The results of the study can be used in the interpretation of well logging data.
Calculation of rocks permeability based on periodic models of porous media
Authors: Igoshin D E , Legostaev D Yu
Published: December 2019

The paper proposes a method for calculating rock permeability based on periodic cubic models of porous media, taking into account the particle size distribution of the samples. Conditional permeability is calculated for each fraction. The permeability of the sample depends on the relative position of the fractions and can be calculated as the weighted average (arithmetic, geometric or harmonic). Next, an optimization problem is solved, which allows one to choose the “weight” of a particular method of averaging permeability over fractions inside the sample for all samples of the selected formation. Results were obtained for several formations from different fields.
Mathematical model of the submerged jet for the cases of man-made spills
Authors: Kildibaeva S R , Gimaltdinov I K , Kildibaeva G R
Published: December 2019

The paper considers a mathematical model of the spread of a multiphase submerged jet, the flow of which is associated with a well damage during the development of a field or pipeline during oil transport. The jet consists of oil droplets and gas bubbles, as well as water involved into the jet. The case is considered when the environmental conditions correspond to the conditions of a stable hydrate existence, because a hydrate shell begins to form and the gas bubble turns into a hydrate on the surface of the bubbles. The integral Lagrangian control volume method is used to describe the jet spread process. The thermo-physical characteristics of a multiphase submerged jet, depending on the vertical coordinate, as well as the trajectory of the jet, are obtained.
Numerical simulation of fluid flow in a saturated fractured porous media based on the linear poroelasticity model
Authors: Legostaev D Yu , Botalov A Yu , Rodionov S P
Published: December 2019

Field development processes change the stress-strain state of the formation, which can especially affect on the state of fractured reservoir. In this paper, the coupled flow and geomechanics model was used to simulate a fractured-porous reservoir. To describe fractures in the fluid flow problem the discrete fracture model was used; the fracture was considered as an internal boundary for the geomechanics problem. The control volume method, which is widely used in computational fluid dynamics, was used for both flow and mechanics problems. Based on the developed coupled flow and geomechanics model, simulations of an fractured poroelastic system was carried out.
Application of continuous symmetry groups for numerical solutions of two-phase filtration problems
Authors: Markov Pavel
Published: December 2019

The method of numerical solution calculations for difference schemes on the basis of continuous symmetry groups has been presented for the two-phase flow equation. This method gives an opportunity to calculate numerical solutions using transformations of a symmetry group and known particular numerical solutions what allows to achieve an acceleration of serial numerical calculations by several orders. The families of invariant difference schemes have been obtained for one of generalized Buckley-Leverett equations - the Rapoport-Leas equation. A particular nonlinear equation of multiphase flow in fractured porous media with certain coefficients from the mentioned families is analyzed numerically by the presented method.
Simulation of the deposition of aerosol droplets in a person’s bronchial tree
Authors: Medvedev A E , Gafurova P S
Published: December 2019

The work is devoted to the mathematical construction of the human bronchial tree, calculating the flow of gas in the lungs and modelling the deposition of drops of medicinal aerosols in the human bronchial tree. Analytically built a symmetrical human bronchial tree. To calculate the flow of gas in the lungs and the deposition of aerosols, the method of phasing out the flow in one branch of the bronchial tree is used. Three-dimensional numerical calculations of air flow and aerosol droplets in human lungs were carried out. It is shown that the number of past drops depends (except for the flow, size of drops) on the duration of inhalation.
Effect of the structure of skeleton models of cellular materials on the drag of a cylinder with a frontal gas-permeable insert in a supersonic flow
Authors: Mironov S G , Kirilovskiy S V , Militsina T S , Poplavskaya T V , Tsyryulnikov I S , Valiullin I R
Published: December 2019

The paper presents the results of the numerical simulation of the supersonic (M∞ = 7) flow around the cylinder with the front gas-permeable porous insert at different angles of attack. The numerical simulation involves the comparative analysis of a number of skeleton models of high-porous cellular materials of the front insert: from the set of coaxial rings of different diameters, and the set of hollow spheres with different spatial resolution. The calculated data of the drag coefficient have been compared with the wind tunnel experiment results.
On the issue of the solutions existence of the problem of gas hydrate dissociation in a porous medium with the formation of an extended region of phase transitions
Authors: Musakaev N G , Khasanov M K
Published: December 2019

Mathematical model of the gas hydrate dissociation in a porous medium with the formation of an extended region of phase transitions is proposed. In a rectilinear-parallel approximation self-similar solutions are constructed that describe the distribution of pressure, temperature, and hydrate saturation in a reservoir. Based on the obtained solutions analysis it was proved that for the problem of injecting warm gas into a hydrate saturated reservoir with piezoconductivity coefficient exceeds the thermal diffusivity coefficient, there are no solutions with an extended region of phase transitions. The existence of such solutions is possible during gas production from a gas hydrate reservoir due to a decrease in pressure at the extraction point.
Cutting transport simulation in a horizontal borehole near tool joints
Authors: Orlik E , Ignatenko Y , Bocharov O
Published: December 2019

In the presented study, we investigated the influence of cuttings transport in a channel with variable cross-section area to determine the pressure drop and obtain preliminary data on tool joint effect on solids deposition. The influence of boundary conditions at the channel’s inlet on flow regimes was analysed. The average particle concentration over the cross-section significantly reduced due to increasing the velocity in the narrowing area on the tool joint. Behind the tool joint, particles deposition appeared due to the reverse flow, which manifested itself as a local maximum in concentration distribution along the channel. The impact of a tool joint on the pressure drop in a single-phase flow has been more pronounced if compared to one in a two-phase flow at the given conditions.
Models of heterogeneous medium in medicine
Authors: Pen’kovskiy V I , Korsakova N K
Published: December 2019

A review of models of the blood circulation in the tissues of the human brain and lower extremities is presented. The models take into account the well-known laws of physiology and theoretical mechanics. Mathematical models are based on the representation of organ tissues as a heterogeneous continuous medium consisting of three interpenetrating continua: living cells, and circulating arterial and venous blood. The results of numerical calculations of boundary value problems of the pulse blood flow in the brain of a healthy person and cases of pathologies such as arteriovenous malformation and embolism are presented. The distribution of blood pressure in the lower extremities is studied under the action of gravity and other overloads.
Studying the process of powder transportation during laser cladding with a coaxial nozzle
Authors: Polyanskiy T A , Zaitsev A V , Ermolaev G V
Published: December 2019

Results of experiments and numerical modeling of gas-powder flow for laser cladding are presented. Numerical simulation is based on solving Navier-Stokes equations with Lagrange approach for particle. The main attention is paid to the process of interaction between powder particles and nozzle walls. Simple particle-wall interaction model was suggested and verified with experiments for gas-powder jet formed in the long tubes with different diameters. The model was used for simulation of powder transport in the coaxial nozzle for laser cladding.
On the near wake structure of a supersonic coaxial gas-liquid jet
Authors: Poplavski S V , Nesterov A Yu
Published: December 2019

The work is devoted to a complex experimental study of the near wake of supersonic coaxial gas-liquid jets with a high concentration of the dispersed phase. At the various liquid flow rates, wave structure of a gas phase was visualized, droplet velocity profiles were obtained by the LDA method, and the spray concentration was measured. The effect of the liquid phase on the supersonic underexpanded jet was studied, in particular, a change in the general wave structure, Mach disk transformation, etc. A gas velocity profile was obtained in a two-phase core of a gas-liquid jet by the method of droplet velocity profile correction taking into account their velocity relaxation.
Numerical simulation of nucleation and solid phase growth in a nanomodified binary alloy
Authors: Shchukin V G , Popov V N
Published: December 2019

A mathematical model of solidification of a binary alloy with eutectic-type phase diagram modified by refractory nanoscale particles as nucleation centers of the crystalline phase is proposed. Thermodynamic processes in the melt and solid phase, heterogeneous nucleation and growth of particles of the main (α) phase of the crystallizing material are described. The crystal phase origin occurs on the surface of nanoscale particles. The volume of the solid phase grown on separate crystallization centers determines the character of the grain structure in the solidified alloy. On the example of a binary alloy based on iron (Fe-C) numerical simulation of melt solidification in a cylindrical casting is carried out. The features of the kinetics of heterogeneous nucleation and crystallization in the melt were considered. It is determined that the undercooling magnitudes, the conditions of nucleation, the rate of crystallization and solidification time vary significantly inside the casting. It is established that as the melt cools, volume-sequential crystallization takes place. The area with the finest structure of the solidified metal is located near the wall of the mold.
Numerical simulation of mono-disperse gravity-driven granular flow around a wedge using two-fluid model
Authors: Shoev Georgy
Published: December 2019

The numerical simulation of glass beads granular flow around a wedge located in a rectangular channel is performed by the Two-Fluid Model (i.e. the Euler-Euler approach) aiming to make a comparison between the numerical and the available experimental data. The channel is tilted against the horizon making the glass beads fall under the action of the gravity force. The numerical simulation shows the glass beads structure that resembles a bow shock wave around the wedge. The computed bow shock stand-off distance is compared to the data extracted from the experimental results. The details of the comparison between the numerical and the experimental data are discussed.
Formation of the internal structure of copper particles during their ball milling followed by spheroidization
Authors: Smirnov A V , Chesnokov A E , Vidyuk T M
Published: December 2019

The paper presents the results of a study of the influence of high-energy effects on surface morphology and the formation of the internal structure of copper particles. It is shown that the ball milling of copper powder in a planetary mill leads to the formation of layered agglomerates consisting of many deformed ultrafine particles. It is noted that defects in the form of microcracks and micropores are observed in the volume of the agglomerated particle. Their subsequent treatment in a plasma jet leads to the formation of spherical particles. It is established that during the interaction of the molten material of a particle with distributed gas inclusions throughout the particle’s volume during plasma treatment, local copper oxidation occurs. Copper oxide inclusions of predominantly rounded shape are formed, ranging in size from tens of nanometers to 7 microns, uniformly distributed over the particle volume.
Determination of relative concentrations in two-component mixtures with unknown composition by laser-induced fluorescence spectra
Authors: Tsibulskaya E O , Maslov N A
Published: December 2019

The paper is devoted to the development of a new methodology of statistical analysis of laser-induced fluorescence excitation-emission matrices. The method allows one to calculate the number of fluorescent components, their excitation and fluorescence spectra in samples under study without using any prior information about their nature. The algorithm is based on the principal component method and is modified for analysis of excitation-emission matrices. Its features were tested on two-component optical phantoms, namely, optically thin mixtures of fluorescent dyes (pyridoxine and fluorescein). The calculated excitation and fluorescence spectra of components coincided with the initial ones with good accuracy (deviation less than 5% in intensity). The weight coefficients proportional to concentrations were calculated by the new algorithm. The comparison of its ratios with those calculated from known concentrations also showed good agreement (deviation of 5%).
Numerical modelling of plasmachemistry induced by cold atmospheric plasma jet near surface
Authors: Vagapov S , Schweigert I V
Published: December 2019

Recently the cold plasma jets are widely used for the development of anticancer therapy. The main mechanism of atmospheric plasma jet action on cells is related to the production of nitrogen and oxygen radicals in plasma-stimulated chemical reactions, followed by the diffusion of radicals into the media with cells. The increase of the plasma jet treatment efficiency depends on a detailed study of the plasma-chemical processes that occur when the plasma jet interacts with the target. In this work, a numerical study of the plasma-chemical processes for dry air is carried out, the main ways of production and loss of RONS are detected and mixture composition near the surface during plasma jet processing is estimated.
Mathematical model of gas mixture adsorption by a composite adsorbent
Authors: Vereshchagin A S , Zinovyev V N , Kazanin I V , Pak A Yu , Lebiga V A , Fomin V M
Published: December 2019

Within a framework of mechanics of multiphase media a mathematical model of the dynamics of a helium and water vapor mixture flowing through a bed of composite adsorbent, based on microspheres and aluminum oxide, is derived. It is shown how to coincide the flow in porous media of adsorber and gas diffusion in a cylindrical granule of adsorbent taking into account helium adsorption by microspheres and water vapor by a porous surface of an adsorbent.
Influence of post-processing on the strength of heterogeneous materials produced by the laser welding
Authors: Vitoshkin I E , Malikov A G , Orishich A M , Karpov E V
Published: December 2019

The paper presents the investigation of the laser welding of the alloy Al-Cu-Li and titanium alloy Ti-Al-V, as well as the analysis of the post=processing on the strength properties of welded joints. Macro- and micro-structure of the joints have been studied. The resulting heterogeneous welded materials have been post-processed. The mechanical characteristics of the welded joints have been determined before and after the thermal processing.
Spherically symmetric stationary flows of a gas suspension
Authors: Voronin S M , Panov A V , Turov M M
Published: December 2019

The dynamics of an isothermal gas suspension is studied. A spherically symmetric stationary submodel is derived and partially integrated. In a barochronous case, this submodel is fully integrated and results are discussed. Different modes of motion are analytically described in the barochronous case. The interpretation of the solutions is proposed. We highlight three essentially different modes of motion. In the first mode, we have a dispersion of gas suspension from the origin with a relaxation of velocities and leading to the uniform motion. In the second mode, phases focus in the origin with finite nonzero velocities and infinitely increasing densities. In the third mode, phases are interpenetrating to each other and decelerating due to the friction force, that leads to an accumulation of particles and an unlimited increase of densities in different nonzero raduises with zero velocities.
Numerical simulation of the cellular detonation interaction with inert gas plugs
Authors: Bedarev I A
Published: December 2019

The mathematical modeling of the interaction of a cellular detonation wave propagating through a hydrogen-air mixture with inert gas plugs is performed. A technology for calculating two-dimensional detonation flows in a reacting gas mixture - non-reacting gas system has been developed. The modes of cellular detonation waves interaction with inert gas plugs were studied. The geometric limits of the clouds of carbon dioxide, argon and nitrogen lead to the cellular detonation failure and isolation of the combustion zone are determined.
Combustion of round hydrogen microjet in a concurrent flow
Authors: Kozlov V V , Grek G R , Litvinenko M V , Litvinenko Yu A , Tambovtsev A S , Shmakov A G
Published: December 2019

Experimental data on the diffusion combustion of round hydrogen microjet in concurrent coaxial flows are presented. The effects on combustion of the concurrent flow of air and that of air premixed with nanopowder of TiO2 are of interest. The hydrogen microjet is emanated from a round micronozzle which is surrounded by a coaxial slit to produce the concurrent flow. Combustion events found in the present conditions are similar to those observed in the previous studies on diffusion combustion of hydrogen microjets at subsonic and supersonic velocities. In a subsonic range, the so-called “bottleneck-flame region” is generated close to the nozzle exit, while in high-speed conditions the flame separates from the nozzle. At increasing velocity of both the hydrogen microjet and the concurrent flow, the “bottleneck-flame region” is still found and the combustion becomes more intense. The “bottleneck-flame region” is suppressed at the microjet velocity approaching transonic values.
Investigation of the heterogeneous detonation suppression by clouds of inert particles and droplet suspension
Authors: Lavruk S A , Tropin D A
Published: December 2019

Using the methods of mechanics of heterogeneous media, we studied the process of suppressing heterogeneous detonation by clouds of inert particles and using a droplet suspension. The main flow regimes obtained as a result of modeling are described.
Effect of a smooth temperature gradient on the combustion of a preliminary mixed methane-air mixture
Authors: Ponomareva A A , Mokrin S N , Uriupin G V , Minaev S S
Published: December 2019

In this work, the ranges of different combustion modes of a methane-air mixture were studied in dependence on the flow velocity under conditions of a smooth temperature gradient of the channel. To carry out the experiments, a laboratory setup was designed and constructed to obtain a smooth temperature gradient in a quartz tube, and experiments were performed to determine the temperature gradient. The boundaries of different combustion regimes were determined for the mixtures with different fuel-air ratio coefficients (0.8, 1, 1.2), moreover, transient modes between main regimes were found.
Three-dimensional numerical simulation of continuous spin detonation in hydrogen-oxygen and hydrogen-air mixtures using OpenFOAM package
Authors: Rybnikov A I , Simonov E V , Gurin A M , Trilis A V , Samsonov A N
Published: December 2019

A mathematical model of continuous spin detonation for hydrogen-oxygen and hydrogen-air mixtures is developed within the framework of a nonstationary gas-dynamic formulation. An OpenFOAM package is used to carry out numerical calculations in an annular cylindrical combustor in order to compare the main solution parameters with experimental data for geometric dimensions of combustors 40 mm and 306 mm in diameter corresponding to the experiments for hydrogen-oxygen and hydrogen-air mixtures. Regimes with a single continuously rotating transversal detonation wave are obtained for given fuel mixtures. It is shown that the solution significantly depends on the coordinate along the radius. The results for the hydrogen-oxygen mixture are in good agreement with an experiment in terms of a wave velocity and satisfactory agreement relative to a front height and the number of waves (a 1.5- to 2-fold difference). The results for the hydrogen-air mixture are in satisfactory agreement with an experiment for the wave velocity and front height and significantly differ from it on a minimal flow rate of the mixture, in which the existence of continuous spin detonation is possible in the combustor.
Experimental study of the low-melting hydrocarbons regression rate in the inert gas flow
Authors: Shiplyuk A N , Zvegintsev V I , Frolov S M , Vnuchkov D A , Lukashevich S V , Nalivaychenko D G
Published: December 2019

Gasification of organic and inorganic materials in a high-temperature gas flow is a promising technology for various industrial applications like chemical industry, waste processing, rocket and air-breathing propulsion, etc. However, the characteristics of the gasification process of low-melting hydrocarbon materials remain insufficiently studied so far. The present authors propose a methodology for investigating the gasification of combustible materials for ramjets. Experiments on the gasification of cylindrical polypropylene (PP) samples by the high-temperature inert carrier gas (nitrogen) passing through multiple longitudinal channels of 3 mm in diameter and 200 mm long are performed. The flow of the carrier gas is heated by combustion of hydrogen–oxygen mixture. The temperature, pressure, and velocity of the carrier gas in the experiments range from 900 to 1700 K, 0.35 to 1.0 MPa, and 80 to 130 m/s, respectively. The yield of PP gasification products is shown to increase linearly with the carrier gas temperature. At the temperature of 1700 K, the yield of PP gasification products in the test facility attains 8.0 g/s, whereas the ratio of the mass flow rates of the carrier gas and gasification products reaches the value of 4.5.