bluuebunny/crossref_metadata_2025 huggingface dataset:
Gestures in patients’ presentation of medically unexplained symptoms (MUS)
Authors: Sowińska Agnieszka , Boruta-Żywiczyńska Monika
Published: February 2021

The aim of this paper is to explore speech-accompanying gesture use in presentation of medically unexplained
symptoms (MUS). The data are 19 video-filmed semi-structured interviews with patients presenting MUS. Four patterns of gestural
behaviors are established in symptom presentation: (1) No gesturing; (2) Overall low gesture rate; (3) Overall high gesture rate
with low rate for symptoms; (4) Overall high gesture rate with high rate for symptoms. The patients with overall low gesture rate
tend to perform deictic gestures, pointing to exact locations of the symptoms; those with overall high gesture rate and low
symptom rate produce metaphorics, and those who gesticulate at high rates – mainly iconics and metaphorics. Although exact factors
that lead to the four types of gesturing patterns are unclear, the findings encourage medical professionals to attend to the
information in gesture use in order to obtain a better understanding of the patient’s experience of MUS.
Spatial characterization of edge zonal flows in the TJ-II stellarator: the roles of plasma heating and isotope mass
Authors: Losada U , Kobayashi T , Ohshima S , Cappa A , Van Milligen B , Liniers M , López-Miranda B , Liu B , Pastor I , Silva C , Hidalgo C
Published: February 2021

In this article, we report the latest results for the impacts of the isotope mass and the plasma heating scenario on the spatiotemporal characteristics of the low-frequency zonal flow (ZF)-like electrostatic oscillation found in the plasma edge of the TJ-II stellarator. The radial profile of the toroidal cross-coherence in low-frequency floating potential fluctuations (1 < f < 25 kHz), known as long-range correlations (LRCs), was explored along the plasma boundary region by a dual Langmuir probe system. The study was performed using electron cyclotron resonance heating (ECRH)- and neutral beam injection (NBI)-heated plasmas with two different isotope concentrations: pure hydrogen plasmas and plasmas dominated by deuterium (

≈
70
%

D

). The highest toroidal coherence levels are detected for floating potential oscillations at less than 10 kHz in hydrogen and deuterium plasmas, in both the ECRH and NBI heating schemes. The radial extent of the LRC profile is clearly larger in the ECRH than in the NBI-heated plasma scenarios. While the maximum amplitude of the LRC does not show a significant dependence on isotope mass, the relation between the LRCs’ radial sizes in plasmas and different isotope masses increases with the isotope mass in NBI-heated scenarios. These results provide the first experimental observation of ZFs with a larger radial size in deuterium than in hydrogen plasmas.
EMI-GCN: a hybrid model for real-time monitoring of multiple bolt looseness using electromechanical impedance and graph convolutional networks
Authors: Zhou Lu , Chen Si-Xin , Ni Yi-Qing , Choy Alex Wai-Hing
Published: February 2021

Electro-mechanical impedance (EMI) has been proved as an effective non-destructive evaluation indicator in monitoring the looseness of bolted joints. Yet due to the complex electro-mechanical coupling mechanism, EMI-based methods in most cases are considered as qualitative approaches and are only applicable for single-bolt monitoring. These issues limit practical applications of EMI-based methods in industrial and transportation sectors where real-time and reliable monitoring of multiple bolted joints in a localized area is desired. Previous research efforts have integrated various machine learning (ML) algorithms in EMI-based monitoring to enable quantitative diagnosis, but only one-to-one (single sensor single bolt) case was considered, and the EMI–ML integrations are basically unnatural and ingenious by learning the EMI measurements from isolated sensors. This paper presents a novel EMI-based bolt looseness monitoring method incorporating both physical mechanism (acoustic attenuation) and data-driven analysis, by implementing a lead zirconate titanate (PZT) sensor network and a built-in graph convolutional network (GCN) model. The GCN model is constructed in such a way that the structure of the PZT network is fully represented, with the sensor-bolt distance and sweeping frequency encoded in the propagation function. The proposed method takes into account not only the EMI signature but also the relationship between the sensing nodes and the bolted joints and can quantitatively infer the torque loss of multiple bolts through node-level outputs. A proof-of-concept experiment was conducted on a twin-bolt plate, and results show that the proposed method outperforms other baseline models either without a graph network structure or does not consider sensor-bolt distance. The developed hybrid model provides new thinking in interpreting sensor networks which are widely adopted in structural health monitoring, and the approach is expected to be applicable in practical scenarios such as rail insulated joints and aircraft wings where bolt joints are clustered.
Speeding up generation of photon Fock state in a superconducting circuit via counterdiabatic driving*
Authors: Dong Xin-Ping , Lu Xiao-Jing , Li Ming , Zhao Zheng-Yin , Feng Zhi-Bo
Published: February 2021

Optimal creation of photon Fock states is of importance for quantum information processing and state engineering. Here an efficient strategy is presented for speeding up generation of photon Fock state in a superconducting circuit via counterdiabatic driving. A transmon qubit is dispersively coupled to a quantized electrical field. We address a Λ-configuration interaction between the composite system and classical drivings. Based on two Gaussian-shaped drivings, a single-photon Fock state can be generated adiabatically. Instead of adding an auxiliary counterdiabatic driving, our concern is to modify these two Rabi drivings in the framework of shortcut to adiabaticity. Thus an accelerated operation with high efficiency can be realized in a much shorter time. Compared with the adiabatic counterpart, the shortcut-based operation is significantly insusceptible to decoherence effects. The scheme could offer a promising way to deterministically prepare photon Fock states with superconducting quantum circuits.
Quantum annealing for semi-supervised learning
Authors: Zheng Yu-Lin , Zhang Wen , Zhou Cheng , Geng Wei
Published: February 2021

Recent advances in quantum technology have led to the development and the manufacturing of programmable quantum annealers that promise to solve certain combinatorial optimization problems faster than their classical counterparts. Semi-supervised learning is a machine learning technique that makes use of both labeled and unlabeled data for training, which enables a good classifier with only a small amount of labeled data. In this paper, we propose and theoretically analyze a graph-based semi-supervised learning method with the aid of the quantum annealing technique, which efficiently utilizes the quantum resources while maintaining good accuracy. We illustrate two classification examples, suggesting the feasibility of this method even with a small portion (30%) of labeled data involved.
Functional synergy recruitment index as a reliable biomarker of motor function and recovery in chronic stroke patients
Authors: Irastorza-Landa Nerea , García-Cossio Eliana , Sarasola-Sanz Andrea , Brötz Doris , Birbaumer Niels , Ramos-Murguialday Ander
Published: February 2021

Objective. Stroke affects the expression of muscle synergies underlying motor control, most notably in patients with poorer motor function. The majority of studies on muscle synergies have conventionally approached this analysis by assuming alterations in the inner structures of synergies after stroke. Although different synergy-based features based on this assumption have to some extent described pathological mechanisms in post-stroke neuromuscular control, a biomarker that reliably reflects motor function and recovery is still missing. Approach. Based on the theory of muscle synergies, we alternatively hypothesize that functional synergy structures are physically preserved and measure the temporal correlation between the recruitment profiles of healthy modules by paretic and healthy muscles, a feature hereafter reported as the FSRI. We measured clinical scores and extracted the muscle synergies of both ULs of 18 chronic stroke survivors from the electromyographic activity of 8 muscles during bilateral movements before and after 4 weeks of non-invasive BMI controlled robot therapy and physiotherapy. We computed the FSRI as well as features quantifying inter-limb structural differences and evaluated the correlation of these synergy-based measures with clinical scores. Main results. Correlation analysis revealed weak relationships between conventional features describing inter-limb synergy structural differences and motor function. In contrast, FSRI values during specific or combined movement data significantly correlated with UL motor function and recovery scores. Additionally, we observed that BMI-based training with contingent positive proprioceptive feedback led to improved FSRI values during the specific trained finger extension movement. Significance. We demonstrated that FSRI can be used as a reliable physiological biomarker of motor function and recovery in stroke, which can be targeted via BMI-based proprioceptive therapies and adjuvant physiotherapy to boost effective rehabilitation.
High-density mapping of primate digit representations with a 1152-channel µECoG array
Authors: Kaiju Taro , Inoue Masato , Hirata Masayuki , Suzuki Takafumi
Published: February 2021

Objective. Advances in brain–machine interfaces (BMIs) are expected to support patients with movement disorders. Electrocorticogram (ECoG) measures electrophysiological activities over a large area using a low-invasive flexible sheet placed on the cortex. ECoG has been considered as a feasible signal source of the clinical BMI device. To capture neural activities more precisely, the feasibility of higher-density arrays has been investigated. However, currently, the number of electrodes is limited to approximately 300 due to wiring difficulties, device size, and system costs. Approach. We developed a high-density recording system with a large coverage (14 × 7 mm2) and using 1152 electrodes by directly integrating dedicated flexible arrays with the neural-recording application-specific integrated circuits and their interposers. Main results. Comparative experiments with a 128-channel array demonstrated that the proposed device could delineate the entire digit representation of a nonhuman primate. Subsampling analysis revealed that higher-amplitude signals can be measured using higher-density arrays. Significance. We expect that the proposed system that simultaneously establishes large-scale sampling, high temporal-precision of electrophysiology, and high spatial resolution comparable to optical imaging will be suitable for next-generation brain-sensing technology.
Fatigue tests simulation of materials with a random endurance limit
Authors: Pervadchuk V P , Davydov A R
Published: February 2021

Fatigue tests of materials are characterized by long duration and high cost. In this regard, it is relevant to develop methods for modeling test results in the widest possible range of loads. Fatigue curve mathematical model includes the equation of the relationship between the amplitude of the stress and the durability of the samples, considering the random nature of the values of durability and the limit of unbounded endurance. At the first stage, the values of the model parameters are determined using the maximum likelihood function using real test data in a limited range of stress amplitudes. At the second stage, the problem solution is found considering the random value of the limit of unbounded endurance. Moreover, the mean estimate is obtained from the solution of the first part of the problem. The estimate of the unbounded endurance limit variance is obtained by calculation from the variance balance conditions. The results of modeling fatigue tests for aluminum alloy samples in a wide range of stress amplitude values are presented. Simulation results for determining the values of the fatigue curve left tolerance are considered.
Twist effects on quantum vortex defects
Authors: Foresti M
Published: February 2021

We demonstrate that on a quantum vortex in Bose-Einstein condensates can form a new, central phase singularity. We define the twist phase for isophase surfaces and show that if the injection of a twist phase is global this phenomenon is given by an analog of the Aharonov-Bohm effect. We show analytically that the injection of a twist phase makes the filament unstable, that is the GP equation is modified by a new term that makes the Hamiltonian non-Hermitian. Using Kleinert’s theory for multi-valued fields we show that this instability is compensated by the creation of the second vortex, possibly linked with the first one.
A Variational Approach to Dissipative Optical Solitons
Authors: Ferreira M F. , Latas S. C.
Published: February 2021

The trial function approach is a useful technique to modelling soliton solutions for equations that can not be solved exactly. We use the variational approach to find approximate solutions for the dissipative solitons described by the cubic-quintic complex Giinzburg-Landau equation. We find that the evolution equations for the soliton parameters are similar to those derived using the method of moments. The existence of both stationary and pulsating soliton solutions is indicated by both approaches and confirmed through some numerical examples
Multi-physics simulation of in-flight ice shedding
Authors: Rausa A. , Guardone A.
Published: February 2021

In-flight ice accretion may possibly jeopardise the safety of fixed-and rotary-wing aircraft. Icing can possibly occur if supercooled water droplets in clouds impinge on the aircraft surfaces and freeze upon impact. A major issue related to ice accretion is the possibility of ice shedding from the main body and impacting other parts of the aircraft or being ingested by the engines. A multi-physics framework is presented to simulate ice accretion and shedding from wings and engine nacelles due to aerodynamic forces. The aerodynamics is computed using the open-source tool-kit SU2. Cloud droplet trajectories are computed using the arbitrary-precision Lagrangian in-house solver PoliDrop. Then, the in-house ice accretion tool-kit PoliMIce is used to determine the ice layer. A FEM structural analysis is performed on the accreted ice shape by means of the open-source code MoFEM. Internal stresses within the ice geometry due to aerodynamic forces are computed. The possibility of the occurrence of cracks in the ice layer is assessed and its propagation is determined numerically. Two-dimensional ice accretion simulations are performed to check the validity of the present approach and compare fairly well with available results.
Theoretical and experimental investigation of spatial temperature distribution in active fiber under conditions of laser radiation generation
Authors: Kostrov A. , Kovalenko N. , Shaidullin R. , Ryabushkin O.
Published: February 2021

The longitudinal and transversal temperature distribution in active waveguide, doped with Yb/Er ions, under conditions of laser generation was calculated as the composition of two mathematical models: computation of longitudinal pump radiation distribution by solution of rate equations for Yb/Er doped active medium and computation of transversal temperature distribution by solution of heat equation for convectively cooled fiber using finite element method. The theoretical results were in a good agreement with experimental data, measured by the piezoelectric resonators used as temperature sensors, placed on the surface of the fiber. The pump radiation transferring length in active waveguide and the location of the most heated fiber area, as well as the maximum temperature value, were calculated using a created model of pump radiation transferring into GT-wave active fiber.
Molecular Dynamics Simulations of Polyethylene Bilayers
Authors: Romanos Nikolaos , Megariotis Grigorios , Theodorou Doros N.
Published: February 2021

By conducting molecular dynamics (MD) simulations of polyethylene (PE) melts consisting of two different films, each comprised of chains of different molar mass, in molecular contact with each other, we compare the structural and dynamical properties between these subsystems. Joining layers of the same chemical constitution but different molecular weights is explored as a route towards packaging materials that combine good mechanical and barrier properties with recyclability and therefore provide more sustainable solutions for contemporary industrial needs. Initially, we construct two independent PE thin films characterized by periodic boundary conditions in two directions, but of finite thickness in the third direction. An “amorphous builder” is used for this purpose, which constructs the chains bead by bead (united atom), using the TraPPE force field. A slab is made by joining the two films in the thickness direction and periodic boundaries are introduced in this direction. The slab is energy minimized and then subjected to NPT molecular dynamics (MD) simulation at 350 K and 1 bar, over times longer than the longest relaxation times of both films. Both structural and dynamical properties of the films are calculated, including the self-diffusion coefficient for the chain centers of mass.
Quasi-singular methods for determining the limiting properties of the spacecraft entry trajectories into the planet’s atmosphere
Authors: Grushevskii Alexey
Published: February 2021

The problem of the limiting dynamic properties determining of the spacecraft (SC) trajectories with non-zero aerodynamic quality entered the atmosphere of a planet (Earth, Venus, Mars etc.) often has singularities. First of all, the singularity of the optimal control and of the SC’ dynamic characteristics is appeared after the interplanetary flight or after the SC maneuver in deep space. The target landing point is either the regular landing site on the Earth, or is the selected region with the specified geological characteristics on the surface of the planet (for example, Venus). The bulk and very laborious numerical experiments have shown that the optimal in terms of maximum coverage of the planet’s surface by virtual trajectories of the descending spacecraft often presented as the trajectory with non-monotonic altitude changes (up to secondary spacecraft departure from the atmosphere and secondary entrance) and with the compact atmospheric regions of the spacecraft velocity break points. As it turned out, at the same time, the reachability areas on the surface of the planet obtained by optimization methods, have non-trivial geometric details. One of the most interesting nuances is the non-smooth beake-like border of the reverse side of the reachable area. In the certain sense, we can talk about generalized SC ricochets on the planet’s atmosphere, which allow us to expand the reachability of the SC (both in terms of range and lateral range). The paper presents a phenomenological semi-analytical model for the phase beams constructing of the quasi-singular SC descent in the planet’s atmosphere, which allows us to synthesize the main nuances of the reachability areas, instead the long-time big data optimization. As the result, the time of the preliminary mission ballistic analysis can be significantly reduced
Several Classes of Plain Dynamic Systems Qualitative Investigation
Authors: Andreeva I A
Published: February 2021

Dynamic systems in applications are useful as mathematical models of those processes and phenomena, where statistical events, or fluctuations, may be disregarded. Dynamic systems may be divided into the two main categories – the systems with continuous time (the flows) and systems with discrete time (the cascades). During the investigations of flows normal autonomous systems of ordinary differential equations are used. The present work is devoted to the original rigorous research of some important family of dynamic systems having reciprocal polynomial right parts, which are the forms of theirs phase variables. The whole wide family under consideration is being split into numeric subfamilies belonging to different hierarchical levels, and is subjected to the first and second Poincare transformations, or mappings. As a result, the full qualitative pattern of trajectories is constructed – using the Poincare sphere – in the Poincare disk. A series of new special investigation methods developed, useful for further investigations of similar dynamic systems’ classes.
Extended log periodic approach in analysing local critical behaviour–case study for Covid -19 spread in Albania.
Authors: Kushta Elmira , Prenga Dode
Published: February 2021

Log-periodic (LP) functions of the general form y = y
0 + A(t − t

c
)
m
(1 + Bcos(ω ∗ log(t − t

c
) + ϕ
1)) have been demonstrated effective in the analysis of the processes characterized by the discrete scale of invariance (DSI) structure and also self-organization behaviour. If other self-organization processes opposing or supporting the principal activity would be present, a multilevel DSI structure is expected to develop and the resulting dynamics would depart from the log-periodic shape. When discussing the processes characterising the daily new positive records for the COVID-19 cases in the country (Albania) we have identified the elements that are responsible to generate modified LP behaviour. The new records that initially represented simply the findings of the state laboratories, are modified each successive days by the pressure for more tests form anxious individuals and other effects which produce a herding behaviour which emergence a LP dynamics. Meanwhile, the reactive behaviour aiming to oppose undesired occurrence would generate additional LP sub-processes that can be trapped by a modified LP function of the form y = y
0 + A(t − t

c
)
m
+ B(t − t

c
)
m
cos (ω ∗ log(t − t

c
) + ϕ
1) + C
cos( (ω − ω
1 ) log(t − t

c
) + ϕ
2)+D(t − t

c
)
m
cos ((ω + ω
1) log(t − t

c
) + ϕ
3). During the period of the self-organization behaviour the process is highly nonlinear and therefore the classical models (SIR) based on the mean field assumption and the corresponding ODE equations are not effective to represent the system dynamics. In our case the LP fit to the Covid-19 new cases data series, has challenged the ODE models for the time interval of initial appearance of the positive cases in the country (as of 2 March 2020) up to 3 month later. Also, the LP function has predicated the multiphase waving behaviour and we have forecasted two peak, each of them weeks before recurrence, respectively at 28 April and 10-12 June. Those peaks have been confirmed later within 2 days uncertainty. It resulted that the first regime have been succeeded by another new self-organization regime due to drastic condition changes as result of the socio-economic opening which started in the end of the May 2020. As result, the new regime is juxtaposed over the old one and the LP dynamics remained characteristic and another critical time has appeared. The new critical time has been reproduced with good certainty (1 August) and also the magnitude of the new cases. We observed that our empirical LP function is effective in the describing long term dynamics whereas local techniques involving neural networks approaches have reproduced very well the new cases after the first regime. We concluded that after identification of the LP regimes, we can adopt successfully short time forecasting for new occurrence when working away from the critical time identified by the first method.
Dimension reduction of preference profile for aggregation of energy audit data
Authors: Muravyov S V , Borisova M A
Published: February 2021

The paper aims to improve a technique based on preference aggregation, which allows to process a big amount of data from instrumental examinations of energy losses by substations of electrical energy distribution networks. An approach to transformation of the initial preference profile into the hierarchical one is considered. The absence of the influence of such a transformation on the correctness of processing results is shown. The workability of the proposed method is demonstrated on the basis of real energy surveys using the example of the Khakass enterprise of the Backbone Electric Grids (BEGs), being a part of Siberian BEG of the Unified National Electric Network of Russia. The method makes it possible to identify sources of economically inefficient expenditure of energy resources and unjustified energy losses, and also to provide compression of large volumes of energy survey data without diminution of essential information. The proposed method allows obtaining and representing a great amount of data of instrumental survey of substation energy losses in a form of a compact integral estimate in the ordinal scale. It can be an appropriate and promising tool for organizations engaged in energy consulting.
The modified Bessel functions I3/4(x) and I−3/4(x) in certain fractional differential equations
Authors: Funes Jorge Olivares , Valero Kari Elvis R. , Martin Pablo
Published: February 2021

Linear fracctional equations has been considered with modified Bessel functionsI3/4(x) andI−3/4(x) as no-homogeneus part. The result have been found using Laplace transform. Dun results lead to generalized hypergeometric functions. Several Coincidences have found between the results for the modified Bessel functions of the some order by different sign. No limitations have been found for the fracctional derivative, with could be any real numbers. Some specific values of Alpha have been also consifered.
Multi-criteria optimization of wind power plant parameters
Authors: Melekhin AA
Published: February 2021

The use of renewable energy sources to generate electricity is a hot topic. The author has developed a mathematical model of the aerodynamic process of a wind power plant with the solution of a multi-criteria optimization problem. The optimal range of controlled parameters affecting the aerodynamic process with a minimum amount of blown surface and maximum electrical energy production is determined. Regularities of aerodynamic process are established. The convergence of the results of the study in the calculation on the basis of theoretical dependencies and the solution of the mathematical model is determined. To find the optimal controlled parameters of the aerodynamic installation, a complex research method developed by the author is applied, based on multi-criteria optimization of parameters with the introduction of empirically obtained data. The preliminary procedure of IOSO NM 3.8 consists in the formation of an initial plan of the experiment, which can be implemented both in a passive way (using information about various parameters, optimization criteria and constraints obtained earlier) and in an active way, when too much is generated in the initial search area in accordance with a given distribution law. For each vector of variable parameters, the values of optimization criteria and constraints are determined by direct reference to the mathematical model of the object under study. The number of points that make up the initial plan of the experiment depends on the dimension of the problem and the chosen approximation functions. The solution results in a Pareto (optimal) set of solutions.
Finite Elements and Finite Differences in some differential equations of second linear order with GeoGebra
Authors: Funes Jorge Olivares , Valero Kari Elvis R.
Published: February 2021

In this paper we will show the numerical solutions of some linear second order differential equations through the finite difference methods with Lagrange interpolation and finite elements, using GeoGebra software. These numerical solutions mediated by GeoGebra are visualized with dynamic applets, which were built to analyze the absolute error produced by the corresponding solution and the approximation and also as an interactive teaching support material for the course of Numerical Calculation for Engineering and Science students.
On instability of three-dimensional dynamic equilibrium states of self-gravitating Vlasov-Poisson gas
Authors: Gubarev Yu G , Sun S
Published: February 2021

The Vlasov-Poisson kinetic equations describe the dynamics of point masses in a self-consistent gravitational field. For example, these equations describe clusters of stars, galaxies or interstellar gas, large-scale processes in the Universe. For stationary solutions to the Vlasov-Poisson kinetic equations, a sufficient stability condition has already been obtained previously. However, it has not been conversed until now (neither for small perturbations, nor, especially, for finite ones). The Vlasov-Poisson kinetic equations are related to equations of hydrodynamic type, for which, in turn, there are methods for conversing sufficient stability conditions (at least, in the linear approximation). In this paper, absolute instability for spatial dynamic equilibrium states of Vlasov-Poisson gas with respect to small three-dimensional (3D) perturbations will be proved by the direct Lyapunov method.
GCOAST: Skill assessments of coupling wave and circulation models (NEMO-WAM)
Authors: Staneva Joanna , Grayek Sebastian , Behrens Arno , Günther Heinz
Published: February 2021

The coupling of models is a commonly used approach when addressing the complex interactions between different components of the Earth system. This study presents the development of a new, high -resolution, coupled ocean and wave model system for the North Sea and the Baltic Sea, which is part of the Geestacht COAstal model SysTem GCOAST. We focus on the nonlinear feedback between strong tidal currents and wind -waves, which can no longer be ignored, in particular in the coastal zone where its role seems to be dominant. The proposed coupling parameterisations account for the feedback between of the upper ocean on the atmospheric circulation by accounting for the effects of the sea level, and ocean temperature and salinity. A focus is given on the newly implemented parameterisations that consider the effect of non-liner contribution and the component transfer of the momentum and energy fluxes from the atmosphere to the ocean thought the waves interface. Sensitivity experiments are performed to estimate the role of different wave-ocean coupling components. The performance of the coupled modelling system is illustrated for the cases of several extreme events. For example, the inclusion of wave coupling changes sea surface temperature, the mixing and ocean circulation and the total sea level leading to better agreement with in -situ and satellite observations. The model comparisons with data from satellite altimeter and in-situ observations showed that the use of the fully coupled system reduces the errors, especially under severe storm conditions.
Visual reasoning and the perception of forms
Authors: Vesely S L , Vesely A A , Dolci C A , Dolci S R
Published: February 2021

Whenever a new device enables our senses to access an uncharted sensible world, our experience needs to be widened to be able to embrace it. Many animals don’t recognize themselves in mirrors. Thus, mirrors found in ancient Egyptian tombs bear witness to a device that involved a widening of human experience. While by then reflectors were commonly believed to hold the spirit of their beholder, they also provided the motivating force for use of geometry as a logical framework, rather than the form of the outer world. Euclid of Alexandria conceived of geometric constructions and their rules as the connecting link between visual world and hypothetical-deductive reasoning. Yet, he didn’t have a clue about receivers. In our view the problem of linking received information in an image format to a mathematical space cannot be solved once and for all, but rather needs to be posed and understood afresh once in a while. All the more so in an information and telecommunication era, when the techniques of acquisition and rendering of visual information have been extended well beyond the domain of optical instruments, and the language of mathematics has advanced to a different level of proficiency.
Optimal Control and Stability Analysis of Nonlinear Control-Affine Systems
Authors: Bagdasaryan Armen
Published: February 2021

In this paper we will discuss the problems of optimal control and stabilization for nonlinear control-affine systems of the form

x

˙

=
A
(
x
)
+
B
(
x
)
u

where

x
=
x
(
t
)
,
x
∈

R

n

,
u
∈
R
,

|

u

|

≤
1

and vector functions A(x), B(x) are assumed to be smooth in the domain D ⊂ ℝ
n
, 0 ∈
D, A(0) = 0. We give an in-depth analysis of optimal control problems for nonlinear dynamical systems and then consider for the above systems the problem of synthesis of continuous control u = u(x), u(0) = 0, that stabilizes the system at the equilibrium point (x, u) = (0, 0). The solution to the problem is based on the transformation of the system to canonical form, and on nonlinear stabilization of the system.
Remastering the imperfect home-made CT projections data for further reconstruction
Authors: Kussainov Arman S , Saduev Nurzhan O
Published: February 2021

We developed and implemented a few strategies to recover the faulty, randomly shifted, off-axis rotation sequence of projections images for the home-made computed tomography. Features detection, homography and other image transformation and processing tools from the open-source free and non-free OpenCV libraries in C++ were used. The developed methods, routines and implemented strategies could be collected into the standalone library for any home-made CT software packages.
Explanation of Light Deflection, Precession of Mercury’s Perihelion, Gravitational Red Shift and Rotation Curves in Galaxies, by using General Relativity or equivalent Generalized Scalar Gravitational Potential, according to Special Relativity and Newtonian Physics
Authors: Vossos Spyridon , Vossos Elias , Massouros Christos G.
Published: February 2021

The development of Geometric theories of gravitation and the application of the Dynamics of General Relativity (GR) is the mainstream approach of gravitational field. Besides, the Generalized Special Relativity (GSR) contains the fundamental parameter (ξ
I) of Theories of Physics (TPs). Thus, it expresses at the same time Newtonian Physics (NPs) for ξ
I→ 0 and Special Relativity (SR) for ξ
I=1. Moreover, the weak Equivalence Principle (EP) in the context of GSR, has the interpretation: m
G=m, where m
G and m are the gravitational mass and the inertial rest mass, respectively. In this paper, we bridge GR with GSR. This is achieved, by using a GSR-Lagrangian, which contains the corresponding GR-proper time. Thus, we obtain a new central scalar GSR-gravitational generalized potential V=V(k,l,r,r_dot,ϕ
_dot), where k=k(ξ
I), l=l(ξ
I), r is the distance from the center of gravity and r_dot, ϕ
_dot are the radial and angular velocity, respectively. The replacement k=1 and l=ξ
I
2 makes the above GSR-potential equivalent to the original Schwarzschild Metric (SM). Thus, it explains the Precession of Mercury’s Perihelion (PMP), Gravitational Deflection of Light (GDL), Gravitational Red Shift (GRS) etc, by using SR and/or NPs. The procedure described in this paper can be applied to any other GR-spacetime metric, in order to find out the corresponding GSR-gravitational potential. So, we also use the GR-proper time of the 3rd Generalized Schwarzschild Metric (3GSM) and we obtain the central scalar GSR-gravitational potential V=V(a,k,l,r_dot,ϕ
_dot), where a=a(r). The combination of the above with MOND interpolating functions, or distributions of Dark Matter (DM) in galaxies, provides the functions corresponding a=a(r). Thus, we obtain a new GSR-Gravitational field, which explains the PMP, GDL, GRS as well as the Rotation Curves in Galaxies, eliminating the corresponding DM.
On regular and irregular movement of cylinder colliding with a moving belt
Authors: Lampart M , Zapoměl J
Published: February 2021

Conveyors and moving belts are frequently used in the field of mechanical engineering. In many operating regimes they are subjected to impact loading, which can induce irregular motion and undesirable behaviour of the working machine. This paper focuses on the impacts between an impact body (the cylinder in our case) and a moving belt. Results of the simulations show that different combinations of the system parameters produce a high complexity of device motion. The bifurcation analysis together with outputs of the 0-1 test for chaos and sample entropy indicates different movement regions. The performed analysis elucidated more about the properties and behaviour of mechanical systems with strong nonlinearities such as impacts and dry friction.
Computer simulation in proton therapy
Authors: Echkina E. , Guzminova N.
Published: February 2021

The ionising radiation as a method of cancer treatment has a long history. Any types of radiation have been employed to achieve control of tumour viability such as a’low’ linear energy transfer (LET) beam of photons, two’high’ LET unmodified and spread-out Bragg peak (SOBP) beams of protons. Per the end of 2018, about 190036 patients have been treated with protons [1), 93 facilities in clinical operation worldwide in April 2020 (2). The unattainable goal so far is the creation and implementation of such a treatment plan in which the target volume receives 100 % of the prescribed dose and healthy surrounding tissue 0%. The goal of modern science to find ways to ”optimised” treatment plan especially in childhood cancer, where the preservation of healthy tissue surrounding the tumour is especially important. In our work we presented the results of a calculated experiment of the interaction of a laser impulse with various targets and showed the dependence of energy distribution from the target types.
Estimation of Parameters for Non-Equilibrium Phase Transitions during the Flow of Oil and Gas Mixtures
Authors: Indrupskiy I M , Cherneva N Yu
Published: February 2021

Problems of unsteady gas-liquid flows in wellbores with phase transitions are common for hydrocarbon production and well drilling. Typically, flow in wellbores is sufficiently fast which requires taking into account the non-equilibrium nature of phase transitions. The set of equations describing conservation of mass for components and momentum conservation for the mixture is supplemented by the relaxation equation for concentration of gas dissolved in the liquid. It is known that the characteristic times of gas evolution from the liquid and gas dissolution in the liquid differ significantly and depend on fluid properties, thermobaric conditions, and the flow pattern. Therefore, obtaining estimates of relaxation times for real flows turns to be a difficult problem. In this study, we propose a method for estimating the characteristic relaxation times for gas evolution and dissolution during the gas-liquid flow in a well. The method combines the solution of the convective diffusion equation for the growth/collapse of a vapor bubble in a liquid with the current parameters of the gas-liquid flow. Estimates of the relaxation times for the bubbly flow (small bubbles, gas evolution predominates) and slug flow (large bubbles, dissolution predominates), as functions of time from the beginning of the process, are obtained for the parameters of a real flow in a wellbore. It is shown that the obtained dependencies are consistent with the typical scaling of the diffusion process with respect to the size of bubbles. The results are important for mathematical simulation of gas-liquid flows in wellbores during hydrocarbon production, as well as for calculation of the gas-kick process during well drilling with oil-based muds.
Numerical simulations of gaseous flames in combustion chamber applications
Authors: Katona C , Safta C , Frunzulica F , Goemasn M
Published: February 2021

Recent developments and assessments of combustion models, numerical schemes and high-power computing allow simulations to be applied to real industrial thermal oxidizers and burners. In this paper, two type concepts in a complex geometry of a burner and combustion chamber is reviewed by means of measurements data from on-site during operations compared with the numerical simulation’s analysis. The combustion models as Flamelet, Flamelet Generated Manifolds (FGM) and Hybrid BML/Flamelet are performed to assess modeling and fundamental flow aspects of combustion instabilities in a swirl concept in the context of the Reynolds-averaged Navier Stokes (RANS) equations for gaseous flames. Simulations in real thermal oxidizers illustrate the prospective of the approach but the combustion modeling and chemistry sub-grid models are limited cases in terms of validations due to the lack of available advanced set of measurements. Specific issues associated to real thermal oxidizer are presented: on-site measurements during operations, multi-perforation of heat in the combustor walls and flame instabilities. The examples are assigned as mean flow predictions (velocity, temperature and species) and transient phenomena (ignition and flame instabilities). Finally, the conceptual differences of the potential perspectives are discussed in detail from a theoretical and practical point of view.
Optimizing thermo-mechanical processing and material coupling parameters in numerical modeling for additive manufacturing
Authors: Antoine Lamanna , Beauchesne Erwan , Pierre-Richard Dahoo , Meis Constantin
Published: February 2021

Additive manufacturing (AM) is gaining increasing industrial interest. Initially conceived to facilitate the pre-production, to manufacture efficiently and cheaply unique parts such as prototypes, it is now able to deliver parts that meet industrial production needs. In addition, AM is an effective way to achieve parts designed using topological optimization. Laser beam melting is an AM technique able to produce specific parts with mechanical properties matching industrial expectations. However, efficient production remains complex because of distortion, cracking and other failures linked to the process and to the machine parameters. The prime material being generally expensive and in order to achieve the required manufacturing quality from the very first attempt while reducing the processing time to market necessary for low cost mass production, a high-quality digital simulation is mandatory. We thus study the relation between the process and the material parameters with the final mechanical state of the part using a numerical model, which is developed in parallel.

This work focuses on the macroscopic scale. In order to carry out the thermo-mechanical study we use a finite element resolution method on the whole domain defined by the part, its supports and the baseplate. At this scale, one can neglect the packing of the powder as well as the hydrodynamic behavior of the melt pool in the laser beam melting process. We consider a Gaussian energy distribution for the heat source, imposed on several layers of powders below the deposited layer. Starting from a previous study [11], which considers the temperature dependence of the Young modulus, we improve, in this work, the model by considering the temperature dependency of other physical parameters pertaining to material properties or to elastoplastic and thermal laws coefficients. The aim is to bridge the macroscopic scale study of AM to the mesoscopic scale from results of this study.

In a first step, simulations are carried out with simple models like walls, cubes, beams and the popular cantilever used for calibrations. The results show the gain in precision with the contribution of the temperature dependence of various parameters as well as by considering the phase-transition during the printing process. The computing time is compatible with laptops and can iterate the simulations easily. The accuracy of the model is validated by comparing the distortion to the experimental results
Computation of the masses of neutrinos from the Hadron and Boson masses via the Rotating Lepton model of elementary particles
Authors: Vayenas C G , Tsousis D , Grigoriou D
Published: February 2021

We use the Rotating Lepton Model (RLM) of elementary particles in conjunction with special relativity and the de Broglie equation to compute analytically the masses of neutrinos from the masses of composite particles, such as hadrons, in the structures of which neutrinos have been recently shown to participate. In this way, three distinct neutrino masses are computed which are in good agreement with the values obtained experimentally at Superkamiokande for the three neutrino flavors of the Normal Hierarchy.
Inflation model with viscous fluid
Authors: Myrzakul S R , Tsyba P Yu , Razina O V , Myrzakulov Y M
Published: February 2021

We investigated f(R) gravity with k-essence using the Starobinsky model as an example, given by the expression f(R) = R + α
R
2. Using the hybrid function of the scale factor, we found the scalar field function and its potential. For the model under consideration, the parameters of the slow roll-off satisfy the inflationary stage. Our model allows us to obtain an accelerated expansion of the Universe during an inflationary period. A non-uniform non-viscous fluid was investigated, and then the viscosity was introduced in the second example. Received fluid equations for the accelerated universe.
On the stability of exponential variational integrators for multibody systems with holonomic constraints
Authors: Kosmas Odysseas
Published: February 2021

In the present we test the stability of the high order exponential variational integrators when applied to mechanical systems with holonomic constraints. Those geometric integrator schemes are determined by a discretization of a variational principle for a discrete Lagrangian. That expression, which is defined using exponential expressions of interpolation functions, is then applied on the discrete Euler-Lagrangian equations with constraints. The resulting schemes are then tested on a typical dynamical multibody system with constraints, i.e the double pendulum, and show good long-time behavior when compared to other traditional methods.
Convergence Analysis of Whale Optimization Algorithm
Authors: Feng Wentao
Published: February 2021

The whale optimization algorithm (WOA) has been widely used in different applications. It has simple control parameters and novel population updating mechanism. However, there is few theoretical analysis of WOA and the convergence property of WOA is ambiguity. This paper analyzes the convergence property of WOA by using the Markov chain of the stochastic process theory. The Markov chain model of the WOA algorithm is established. The one step transition probabilities and convergence properties of different population updating mechanisms in WOA are given. It’s proved that the convergence property of WOA is determined by its shrinking encircling mechanism. Finally, three algorithms with different population updating mechanisms are tested with thirteen benchmark functions on accuracy and convergence speed. The simulation results on benchmark functions verify the validity of the theoretical analysis of WOA.
Research on the Optimization of Staff Allocation under the Strategy of “Strong Leads the Weak”
Authors: Chen Chanjuan , Li Hanxu , Sun Junyan , Zhang Yuanyuan
Published: February 2021

Based on the operator’s competency index matrix, a two-layer mathematical model with the goal of maximizing the total competency of employees’ workstations is designed. The upper layer uses the Hungarian Algorithm to achieve the configuration of “strong employees”, and the lower layer uses the Hybrid Genetic Simulated Annealing Algorithm to achieve the configuration of “weak employees”. The results show that: compared with the traditional undifferentiated overall configuration. The double-level configuration based on the double-level mathematical model increases the employee competency difference ratio by 5.71%, which effectively embodies the idea of “strong leads the weak”.