bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract

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

Abstract

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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

AbstractLinear 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.