bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arthropods and echinoderms.
Authors: Rees Paul A. 
Published: May 2021

Abstract

This chapter contains questions on the classification, anatomy and characteristics of the Arthropoda and Echinodermata. The questions are divided into three levels, i.e. foundation, intermediate, and advanced. Knowledge of basic facts are dealt with at the foundation level while the intermediate level and advanced levels contain questions involving more obscure facts and concepts.
Mimosa pigra (giant sensitive plant).
Authors: Rojas-Sandoval Julissa , Acevedo-Rodríguez Pedro 
Published: May 2021

Abstract

M. pigra is a small prickly shrub that infests wetlands and is also an agricultural weed in rice fields in many parts of the old world tropics. In natural wetlands the shrub alters open grasslands into dense thorny thickets and negatively impacts on native biodiversity. It is regarded as one of the worst alien invasive weeds of wetlands of tropical Africa, Asia and Australia, and the cost of control is often high.
The effect of laser irradiation on reducing the noise of solid-state nanopore
Authors: Liang Shengfa , Zhang Wenchang , Xiang Feibin 
Published: May 2021

Abstract
The performance of solid-state nanopore is affected by the noise level. This study aimed to investigate the effect of laser irradiation on the noise performance of solid-state nanopore in situ. Laser irradiation is applied to fresh and contaminated nanopores. The measurement results show that the noise of fresh and contaminated nanopores decreases with the laser power and there is a threshold of laser power in reducing the noise of contaminated nanopores. The possible reasons for reducing noise in the laser irradiation process are discussed. The laser treatment is proven to provide a convenient method for reducing the noise of solid-state nanopore.
Some properties of circle maps with zero topological entropy
Authors: Yang Yini 
Published: May 2021

Abstract
In this paper we introduce three pairs in ‘local entropy theory’. For a dynamical system (X, f), a pair

x
,
y

∈
X
×
X

is called an IN-pair (reps. an IT-pair) if for any neighborhoods U
1 and U
2 of x and y respectively,

U

1

,

U

2

has arbitrarily large finite independence sets (reps.

U

1

,

U

2

has an infinite independence set) where

I
⊂
N

is called an independence set of

A

1

,

A

2

,
…
,

A

k

if for any non-empty finite subset J of I and S ∈ {1, 2, …, k}
J
, ⋂
i∈J

f
−i

A

S(i) ≠ ∅. For a circle map or interval map (M, f), a pair ⟨x, y⟩ ∈ M × M with x ≠ y is called non-separable if there exists z ∈ M such that x, y ∈ ω(z, f) and ⟨x, y⟩ can not be separated. For a circle map

f
:
S
→
S

with zero topological entropy, we show that a non-diagonal pair

⟨

x
,
y

⟩

∈
S
×
S

is non-separable if and only if it is an IN-pair if and only if it is an IT-pair. We introduce the maximal pattern entropy and recall that a null system is a system with zero maximal pattern entropy. We also show that if a circle map is topological null then the maximal pattern entropy of every open cover is of polynomial order.
Sufficient conditions for local scaling laws for stationary martingale solutions to the 3D Navier–Stokes equations
Authors: Papathanasiou Stavros 
Published: May 2021

Abstract
The main goal of this paper is to obtain sufficient conditions that allow us to rigorously derive local versions of the 4/5 and 4/3 laws of hydrodynamic turbulence, by which we mean versions of these laws that hold in bounded domains. This is done in the context of stationary martingale solutions of the Navier–Stokes equations driven by an Ornstein–Uhlenbeck process. Specifically, we show that under an assumption of ‘on average’ precompactness in L
3, the local structure functions are expressed up to first order in the length scale as nonlinear fluxes, in the vanishing viscosity limit and within an appropriate range of scales. If in addition one assumes local energy equality, this is equivalent to expressing the structure functions in terms of the local dissipation. Our precompactness assumption is also shown to produce stationary martingale solutions of the Euler equations with the same type of forcing in the vanishing viscosity limit.
Stability and Hopf bifurcation analysis in a Lotka–Volterra competition–diffusion–advection model with time delay effect
*
Authors: Li Zhenzhen , Dai Binxiang 
Published: May 2021

Abstract
In this paper, we consider a classical two-species Lotka–Volterra competition–diffusion–advection model with time delay effect. By utilizing the implicit function theorem, we obtain the existence of at least one spatially nonhomogeneous positive steady state under some conditions on parameters. By analyzing the corresponding characteristic equation, we show the local stability of this spatially nonhomogeneous positive steady state and the occurrence of Hopf bifurcation from it. When there is no time delay, we also study the global stability of the positive steady state. Based on the idea of Chen et al (2018 J. Differ. Equ.
264 5333–5359), the stability and direction of Hopf bifurcation are derived by introducing a weighted inner product associated with the advection rate. Finally, numerical simulations are carried out to verify the theoretical analysis results.
Linear response for the dynamic Laplacian and finite-time coherent sets
Authors: Antown Fadi , Froyland Gary , Junge Oliver 
Published: May 2021

Abstract
Finite-time coherent sets represent minimally mixing objects in general nonlinear dynamics, and are spatially mobile features that are the most predictable in the medium term. When the dynamical system is subjected to small parameter change, one can ask about the rate of change of (i) the location and shape of the coherent sets, and (ii) the mixing properties (how much more or less mixing), with respect to the parameter. We answer these questions by developing linear response theory for the eigenfunctions of the dynamic Laplace operator, from which one readily obtains the linear response of the corresponding coherent sets. We construct efficient numerical methods based on a recent finite-element approach and provide numerical examples.
Design of phoxonic filter using locally-resonant cavities
Authors: Aboutalebi Seyedeh Zahra , Bahrami Ali 
Published: May 2021

Abstract
A phoxonic crystal structure with a full phononic and photonic band gap is designed in this study, which is capable of conducting sound waves and also light waves with transverse magnetic (TM) polarization. Materials used in the structures are nylon and molybdenum, both of which have adequate difference in refractive index and elastic constants. It is worth of noting that the filling factor is considered to be 28% in all of the structures, in order to ease of fabrication. The final phoxonic filter structure is obtained by the comparison of several phoxonic filter structures in a similar condition. Since it is difficult to coordinate light and sound in phoxonic structures, the proposed structure has some advantages compared to other filters. This structure shows the optical and acoustical transmission linewidths equal 3.8 KHz in phononic and 0.06 nm in photonic modes, respectively. Also, the output quality factor is 23699 in phononic and 21201 in photonic modes. Finite element, plane wave expansion, and finite-difference time-domain methods are utilized for simulation.
Non-isothermal flow of Sisko fluid in a stenotic tube induced via pulsatile pressure gradient and periodic body acceleration
Authors: Fahim M , Sajid M , Ali N 
Published: May 2021

Abstract
A theoretical study for pulsatile unsteady blood flow and heat transfer effects via tapered stenotic artery is presented. This study is based upon a non-Newtonian Sisko-fluid model. The order of magnitude analysis is executed for the derivation of momentum and energy equations for the mild constriction model. The coordinate transformation is utilized to transform the computational domain. A finite difference scheme is utilized for the solution of modeled non-linear partial differential equations. The computed results are exhibited in form of graphs for velocity, wall shear stress (WSS), resistive impendence, flow rate, and temperature for appropriate ranges of important physical parameters governing the flow, including the Sisko fluid material parameter

0.1
≤
ϵ
≤
1.5

,

power-law index

0.7
≤
n
≤
1.5

,

stenosis height

0
≤
δ
≤
0.4

,

the amplitude of body acceleration

0
≤

B

2

≤
2

,

shape parameter

2
≤
m
≤
15

,

Prandtl number

10
≤
P
r
≤
20

,

and Brinkman number

2
≤
B
r
≤
6

.

This investigation deduces that the flow rate and blood velocity rise with the escalation in the amplitude of body acceleration and shape parameter whereas both decrease by varying material parameter, power-law index, and stenosis height. The wall shear stress (WSS) rises with increasing the power-law index, material parameter, and stenosis height, whereas it decreases with the escalation in the amplitude of body acceleration and shape parameter. The resistive impedance increases with the increase of the size of stenosis and power-law index. The temperature field appears to dominate for smaller values of Prandtl number and larger values of Brinkman number.
Significance of increasing Lorentz force and buoyancy force on the dynamics of water conveying SWCNT and MWCNT nanoparticles through a vertical microchannel
Authors: Ramesh G K , Manohar G R , Venkatesh P , Gireesha B J 
Published: May 2021

Abstract
Carbon nanotubes are used to achieve high heat transfer rates in a variety of engineering applications include thermal storage systems, electronic component cooling, high-performance building insulation, heat exchangers and drying technologies. Hence the aim of this article is to examine the addition of single walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) to water in a vertical microchannel to improve heat transfer. The effects of MHD, slip, convective boundary condition and heat source/sink are incorporated. The Brinkman-Forchheimer flow model and type II hybrid nanofluid model is adopted. Converted dimensionless differential equations are solved numerically via Dsolve command with the aid of Maple. The simulation assessment is worked out by graphs. One of the main tasks of the analysis is to compare MWCNT/water and SWCNT-MWCNT/water. It is shown that the improvement of the heat source/sink parameter improves the temperature and the rate of heat transfer in MWCNT/water is higher than SWCNT-MWCNT/water. Also larger values of Lorentz force and buoyancy force decreases the drag coefficient.
Multi-transonic spherical-type flows around massive black holes: galactic potential induced standing isothermal shocks
Authors: Raychaudhuri Sananda , Ghosh Shubhrangshu , Joarder Partha S. 
Published: May 2021

Abstract
Accretion on length-scales of interstellar or even intergalactic is particularly relevant, in the context of spherical or quasi-spherical hot mode accretion, supposedly powering low excitation radio galaxies in the maintenance-mode feedback paradigm. In the present study, we aim to analyze such a spherical-type flow around the host active nucleus in the backdrop of a five-component galactic system (SMBH, stellar, dark matter, diffuse hot gas, Λ), with the principal intent to address the issue of galactic potential induced shock formation in the flow, that may contain (dissipative) isothermal standing shocks. The present paper is an extension of Raychaudhuri et al. (2018) [83], who conducted a preliminary investigation of such a problem. The galactic potential, not only renders the flow to be multi-transonic in nature, the flow topology resembles `Xα' and `α X' type trajectories of advective flows in the vicinity of the BHs/compact objects. Owing to the influence of the galactic potential, the entire range of galactic mass-to-light ratio (ΥB) allows shock formation in central to the outer radial regions of our wind-type flows, with the strength of those galactic induced shocks found to be comparable to that of the shocks one would expect in the advective flows in the vicinity of a BH. We also observe that the shock parameters remain sensitive to ΥB. We discussed the possible implication of these shocks in the context of radio source dynamics as well as their potential association with flaring in radio jets. Our study also reveals that galactic potential could substantially augment the mass inflow rate.
Prospects of constraining reionization model parameters using Minkowski tensors and Betti numbers
Authors: Kapahtia Akanksha , Chingangbam Pravabati , Ghara Raghunath , Appleby Stephen , Choudhury Tirthankar Roy 
Published: May 2021

Abstract
We explore the possibility of constraining model parameters of the Epoch of Reionization (EoR) from 21cm brightness temperature maps, using a combination of morphological descriptors constructed from the eigenvalues of the Contour Minkowski Tensor (CMT), Betti numbers (count of connected regions ncon and holes nhole) and the area of structures in the excursion set of the field. We use a three parameter model of EoR simulated using 21cmFAST, namely the ionizing efficiency of sources ζ, the minimum virial temperature Tvir required for collapse into a halo and the maximum radius for ionizing radiation described by Rmfp. We performed a Bayesian analysis to recover model parameters for a mock 21cm image from SKA phase I at a redshift of z=7.4 corresponding to a mean neutral hydrogen fraction of x̅HI≃ 0.5. We find that in the absence of noise the average size of structures in the field with xHI≲ 0.5 is smaller than regions with xHI≳ 0.5 and the structures are equally isotropic when x̅HI=0.5 . We also find that in order to recover the input model to within 1-σ accuracy for a mock noisy image at a single frequency channel of 1 MHz, for an observation time t_obs<2000 hrs, the noisy δ Tb map needs to be smoothed at a scale R_s>9.5 Mpc. Finally we show that the systematic behaviour of the statistic as ionization progresses, enables us to obtain stringent constraints on x̅HI (with a coefficient of variation ∼ 0.05 as compared to ∼ 0.1–0.2 for model parameter constraints), thereby making these descriptors a promising statistic for constraining EoR model parameters and the ionization history of the universe.
Developing an inverter controlling electric motor for small air transport
Authors: Zagumennov F A , Varyukhin A N , Kazakov A V , Zhuravlev D I , Zakharchenko V S , Ivanov G.S. 
Published: May 2021

Abstract
This paper provides a concept for developing inverters for high power aircraft brushless motors. It should be noted that such devices have an increased number of safety solutions, stable rotor synchronization parameters, and an increased number of isolated hardware nodes. The main result of this study is an engine motor controller with a power of up to 60 kW with control through optical fiber, liquid cooling, completely isolated power and control circuits, overcurrent, inverter and motor temperature protection, synchronization by Hall sensors. This paper also contains the calculation of the cost of introducing such solutions into a typical inverter.
A review of electrified propulsion system concepts for advanced aircraft
Authors: Ovdienko M A , Varyukhin A N , Zakharchenko V S , Vlasov A V 
Published: May 2021

Abstract
The active development of electrical technology provided leeway to creating fundamentally new configurations of propulsion systems and novel aerodynamic layouts of aircraft. Currently, this area of science is in the initial stage of development, but thanks to its huge potential, the number of projects with new propulsion system configurations is growing annually at an exponential rate. A classification of new types of propulsion system configurations is presented in order to understand its wide variety. Beneficial and negative impacts of each configuration are presented.
Research of the flat end gap’s clearance size influence on mechanical power losses in a centrifugal pump by hydrodynamic modeling methods
Authors: Kalinkin S , Petrov A 
Published: May 2021

Abstract
This article highlights the problems associated with calculating disk losses in pumping units. The paper addresses the problems of a theoretical description of the process of fluid flow in narrow end clearances. By varying several parameters of the system, the authors made attempts to identify the dependence of mechanical losses on the flow rate, rotor rotation frequency, the value of the clearance and the direction of the flow. The results of the research are given in a dimensionless form, based on which the corresponding conclusions are drawn.
Interaction of ethane with singlet oxygen: A theoretical study of potential energy surfaces
Authors: Pelevkin Alexey V. , Sharipov Alexander S. 
Published: May 2021

Abstract
A study of the C2H6+O2 reaction system was carried out using ab initio quantum chemistry methods. The main reaction and quenching channels were identified, corresponding activation energies were calculated, and the pathways of the minimum reaction energy were constructed. It was found that the reaction channels of ethane molecule with singlet delta oxygen proceed with a lower barrier than with the oxygen molecule in the ground state. The reaction of ethane with singlet sigma oxygen, in turn, proceeds through the dissociation of the O2 molecule; however, the quenching channel is still possible because of the intersystem crossings. Based on the obtained data, the appropriate reactions rate constants can be estimated by using variational and nonadiabatic transition state theories.
Hydrodynamics of detachment, free falling and impact of drops
Authors: Chashechkin Yuli 
Published: May 2021

Abstract
The results of optical measurements of drop dynamics are presented. Oscillations and waves on its surface were traced. The pattern of the secondary droplets falls onto an immersed drop and the discrete distribution of the substance of a uniformly colored drop in the targeted liquid was visualized. The important role of energy transport processes, both fast – local atomic-molecular – and slow that are translational and dissipative, in the formation of flow patterns is highlighted. A system of fundamental equations of fluid mechanics with equations of state for the Gibbs potential and density is applied. Ligaments – thin trickles with scales from atomic-molecular and macroscopic sizes – are investigated. Their images in the family of intrinsic solutions of the fundamental system and drop impact phenomena are shown.
Relevance of mathematical modelling of textile fillers’ 3-D structures for composite materials reinforcement
Authors: Bazaev E M , Zaretskaya G P , Privalov A A , Lunina E V , Rudneva T V , Shanygin A N , Smotrova S A 
Published: May 2021

Abstract
This paper discusses current and promising areas in the field of solving the fundamental problem of mathematical modelling in the design of bulk structures of textile fillers, which largely depend on the strength and weight characteristics of elements of aircraft made of polymer composite materials (PCM). Examples of mathematical modelling results of an aircraft engine blade’s textile filler for PCM are given. The study was funded by RFBR, project number 19-29-13044.
The dimension indicator of the vibration signal for diagnosing gas turbine engines support bearings
Authors: Tyapkin S A 
Published: May 2021

Abstract
This paper showcases the results of a study on the correlation dimension of the vibration signal in cases of the destruction of aviation engines support bearings. The relevance of the study is determined by the search for promising solutions to improve the maintenance of aircraft engines. It is established that the correlation dimension of the vibration signal of working and defective bearings are contrast with a significance level of 0.002. The scientific significance of the research lies in the statistical substantiation of the application of the vibration signal dimension in gas turbine engines diagnosis systems.
Influence of operating time on the strength reliability of the gas generator turbine disk of the aircraft drive for the GPA
Authors: Velikanova N P , Protasova N A , Velikanov P G , Kiselev A S , Salih Salih Indad Shareef 
Published: May 2021

Abstract
This paper contains the analysis of characteristics changes of mechanical properties of the EI698-VD alloy depending on the duration of operation of the NK family gas turbine disks working as part of a gas generator turbine for GPA. Their stress-strain state was determined using the finite element method. The strength reserves are defined as characteristics of the disks’ strength reliability at different levels of the operating time.
An automated measuring complex of electromagnetic parameters of materials in the field of superhigh frequencies
Authors: Golentsov D , Flanden V , Solntseva M 
Published: May 2021

Abstract
This work is dedicated to the features of measuring the electromagnetic parameters of materials. In the field of superhigh frequencies, there are practically no documents regulating the requirements for the properties of materials and means for measuring the electromagnetic parameters of materials. To solve the problems of metrological support for this frequency range and new materials, several steps are required. One of them is the development of a measuring complex. This work describes the composition of the developed model of such a complex and its distinctive features. The text contains models of materials. The extended frequency ranges from 200 MHz to 80 GHz. The range of external magnetic fields has been expanded from 4 kA/m to 70 kA/m.
A study of the effect of electron-beam processing on the surface of samples obtained by additive technologies from cobalt-chromium powder
Authors: Dzhafarov E E , Erikov K M , Bytsenko O A 
Published: May 2021

AbstractProducts made of cobalt-chromium made by additive manufacturing methods are widely used in many branches of modern industry (aviation, mechanical engineering, shipbuilding and instrumentation, energy, medicine, etc.). Surface treatment with high-current pulsed electron beams (HPEB) is a promising method for further expanding the scope of these alloys. The article presents studies of the structural and phase state of the surface layer of samples before and after treatment with high-current pulsed electron beams.
Designing gears with minimal effective transmission error by optimizing the parameters of tooth modification
Authors: Dorofeev D V , Kalinin D V , Kozarinov E V 
Published: May 2021

Abstract
This paper is dedicated to the development of a method for optimizing the parameters of modification of gears. An experimental study of the effectiveness of the modification, calculated according to the current standard, has been carried out. Within the framework of the project, a software has been developed that implements an algorithm for designing three-dimensional models of gears with a modified topology of contacting side surfaces, which are used for the subsequent modeling by the finite element method of the process of teeth meshing. The results obtained were used to solve the one-criterion optimization problem. As an example of using the method, the optimization of the parameters of the modification of the teeth was carried out in order to minimize the amplitude of the transmission error harmonics.
Monitoring the state of power plants’ friction pairs on the basis of single-coil eddy-current sensors
Authors: Blinov A , Borovik S , Luchsheva M , Muhutdinov F , Sekisov Yu 
Published: May 2021

Abstract
The tasks of “on-line” assessment of the state of friction pairs of high-power power plants are considered. They are based on the use of clusters (groups) of original single-coil eddy-current sensors. It is proposed to use the information about the presence of wear particles in the lubrication system of the power plant and the axial displacement of the shaft in a radial thrust bearing as the main monitored parameters. A brief description of the methods for obtaining the information about the desired parameters and the tools that implement them is provided.