bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of the unusable liquid propellant residues evaporation processes parameters in the tanks of the launch vehicle expended stage in microgravity
Authors: Trushlyakov V I , Urbansky V A , Pustovoy N V
Published: January 2020

A method is proposed for studying the evaporation process of unusable rocket propellant (RP) residues in an expended stage (ES) under weightless conditions. Two options were considered as boundary conditions for liquid RP residues: a) liquid drop distribution in N identical drops, whose surface decreases during evaporation and b) the liquid distribution in the lower tank bottom and the mirror presence, whose area decreases during evaporation. A high-temperature stream of hydrogen peroxide decomposition products is used as a heat carrier (HC) fed to the fuel tank. The physical and mathematical model of the liquid evaporation process is based on the first thermodynamics law. Based on the analysis of the Frud and Grashof criteria, the assumption that there is no convection movement inside the drop (Rayleigh number is less than critical) for both boundary conditions variants, the heat transfer coefficient of the gas-vapor mixture (GVM) produced in the tank is determined due to the regression dependence obtained under ground conditions as a function of the Nusselt, Reynolds and Prandtl numbers. GVM parameters for the considered boundary conditions variants and the proposed physical mathematical model are compared with the results obtained earlier for the boundary conditions variant of uniform fluid distribution over the inner tank wall (third boundary conditions variant) and the boundary layer theory usage based on integral impulses, energy and diffusion ratios. The thermophysical GVM parameters and the GVM exhaust velocity for oxygen and kerosene are provided for two boundary conditions types, using the example of Soyuz-2.1.v type fuel tanks. The total mass of the RP residues evaporation system structure is less than 1.3% of the total “dry” ES design mass.
Possibilities for calculating rubber-cord shells in modern finite-element analyses packages
Authors: Tsyss V G , Strokov I M , Sergaeva M Yu
Published: January 2020

As flexible inserts of various designs, including pipeline systems, vibration-insulating pipes are used, which act as compensators to reduce the resulting deformations and vibration loads. The main element of the design of the pipe, perceiving the action of internal overpressure, is a rubber-cord sheath. To study the possibility of calculating rubber-cord shells in modern finite element analysis packages in the present work, the cylindrical shell of the vibration-insulating pipe has been simulated and its stress-strain state in the software package has been calculated. Since the RCS is a composite design, the simulation was carried out using the built into modules. The results obtained make it possible to analysis the composite material of the RCS and to determine the criteria for shell destruction.
A study of the contact of the wheel with the rail for various conditions of freight car
Authors: Vorobev A A , Konogray O A , Krutko A A , Malakhov I I
Published: January 2020

The paper presents the results of calculations of the parameters of contact interaction of the wheels of a freight car with R65 rails (wheel wear rate, areas of wheel contact spots with rails, friction power capacities in contact spots) for various operating conditions on the Russian Railways road network. The choice of groups of operating conditions was made on the basis of the methodology for ranking the characteristics of the main roads in the plan and profile. The quantitative values of the parameters of contact interaction were established, and their comparative analysis was carried out for the conditions under consideration.
Method for determining optimal parameters of vortex devices for drying compressed air to reduce operating costs of production processes
Authors: Yakovlev A B , Yakovleva E V
Published: January 2020

For most technological processes, low humidity air is used, obtained in various ways. The possibility of using the vortex effect for drying compressed air used in industrial plants and providing savings in operating costs is shown. A mathematical model of the process for reducing moisture content is developed. A method for calculating the optimal geometric dimensions of the drying device is established. The main goal is to develop an effective device for air drying and calculate its optimal parameters. The developed method of calculation allows one to determine the optimal geometric dimensions of the vortex device for drying compressed air, which is more cost-effective, based on the minimum moisture content under the condition of low hydraulic losses.
Analysis of complex product design problem using an L-partition approach
Authors: Adelshin A V
Published: January 2020

In this paper, we analyze the complex product design problem using the model of the partial maximum satisfiability problem. In previous papers, estimates of the cardinality of L-complexes of polyhedrons of the SAT and the MAX SAT problems were obtained. In this paper, a relation of the cardinality of the L-complexes of the partial MAX SAT problem and the corresponding SAT problem is obtained. Using this result, it is possible to obtain theoretical estimates of the cardinality of the L-complex of the polyhedron of the complex product design problem on the basis of similar estimates for the SAT and the MAX SAT problems.
On the properties of the solutions of the problem of cross-diffusion with the dual nonlinearity and the convective transfer
Authors: Aripov M M , Muhamediyeva D K
Published: January 2020

In this work, special methods for studying nonlinear parabolic equations were developed that allow a fairly detailed study of nonlinear problems based on self-similar and approximately self-similar solutions and the construction of an analogue Zeldovych-Kompanees type solution for a cross system, since the study of self-similar equations is relatively simpler in comparison with equations in private derivatives. Studied the properties of solutions to the problem of a biological population of the Fisher-Kolmogorov type in the case of cross-diffusion with the dual nonlinearity and the convective transfer. An estimate of the solutions is obtained, and on the basis of it the problem of choosing the initial approximation for the numerical solution of the Cauchy problem is solved.
Development of digital twin for composite pressure vessel
Authors: Burov A E , Burova O G
Published: January 2020

The present study is devoted to developing a digital twin for a composite overwrapped pressure vessel (COPV) used in electric propulsion engines of spacecraft. The digital twin is used to predict the future behavior and performance of a real physical object based on the currently available information without carrying out expensive and time-consuming full-scale prototyping and testing. Multiscale approach is employed to link the macroscopic stiffness degradation and failure with a progressive damage evolution at the microlevel of composite. The computational models for the stress state and failure analysis at different scale levels are presented. Based on a comparative analysis of the traditional approach for assessing the load-bearing capacity of the COPV and its digital analogue, the advantages of the latter are shown as the predicted burst pressure is in good agreement with the experimental results.
Construction a functional for comparison images of objects
Authors: Chukanov S N
Published: January 2020

The problem of comparing two diffeomorphic images is presenting in the paper To solve the problem, a functional is formed that characterizes the evolution of image transformation from the initial to the terminal, and a penalty for deviating the trajectory from the required one. The problem of comparing two images using the construction of a functional with the optimal image metamorphosis is considered. The metamorphosis of images of objects from initial to terminal using functional forms is considered.
Two ways for numerical solution of the Kramers problem for spatial diffusion over an edge-shaped barrier
Authors: Chushnyakova M V , Gontchar I I , Zakharov A V , Khmyrova N A
Published: January 2020

Thermal decay rate over an edge-shaped barrier at high dissipation is studied numerically through the computer modeling. Two sorts of the stochastic Langevin type equations are applied: (i) the Langevin equations for the coordinate and conjugate momentum (LEqp, the phase space diffusion) and (ii) the reduced Langevin equation (RLE, the spatial diffusion, overdamped motion). The latter method is much faster and self-similar; however, one can doubt about its applicability in the case of an edge-shaped barrier with a discontinuous force. The reason is that a formal condition of the applicability of the RLE is not fulfilled since the curvature of the potential profile at the barrier is equal to infinity. The present numerical study demonstrates that, for large friction, the decay rate calculated using the RLE agrees with the rate resulting from the more exact LEqp. Moreover, it turns out that the influence of the position of the absorbing border is similar to the case of harmonic potential known in the literature.
Presentation of preferences in multi-criterional tasks of decision-making
Authors: Egamberdiev N , Mukhamedieva D , Khasanov U
Published: January 2020

Annotation. Fuzzy relationship preferences are widely used in multi-criteria decision-making problems. Although the fuzzy relationship of preference has been intensively researched, and they are very useful in making decisions, there are still problems that need to be investigated. The paper proposes conditions under which fuzzy relationship preferences improve the quality of decision-making.
Models of recognition algorithms based on linear threshold functions
Authors: Fazilov Sh , Khamdamov R , Mirzaeva G , Gulyamova D , Mirzaev N
Published: January 2020

The problem of constructing a model of recognition algorithms in the conditions of high dimensionality of feature space is considered. To solve this problem, a new approach suggests that it takes into account the interconnectedness of the given features. The main concern of this approach is to isolate representative traits and form preferred combinations of traits. A distinctive feature of the proposed model of algorithms is to determine a suitable set of elementary threshold rules within the framework of the preferred combinations of representative features and build a proximity function based on this set of feature combinations. Scientifically, the results of this work in the aggregate represent a new solution to a scientific problem related to improving the reliability of recognition algorithms based on radial functions. The practical significance of the results lies in the fact that the developed algorithms can be applied in medical and technical diagnostics, geological forecasting, biometric identification. To test the performance of the proposed model, experimental studies were performed.
Reducing the dimensionality of feature space in pattern recognition tasks
Authors: Fazilov Sh , Mamatov N , Samijonov A , Abdullaev Sh
Published: January 2020

The definition of an informative set of features is one of the important tasks in pattern recognition. Typically, the determination of informative features is carried out using two types of methods. The first type of methods is “direct methods”, they are directly aimed at identifying informative sets of attributes. And the second type is called "inverse methods", these methods serve to build informative sets of signs by eliminating uninformative signs from the attribute space. This article is devoted specifically to the development of the second type of method; it proposes an accelerated method and an algorithm for determining non-informative features based on the selected non-informative criterion.
The Nash optimal control of forest ecosystem at risk of fire ignition
Authors: Guts A K , Kabanov A N , Volodchenkova L A
Published: January 2020

We are exploring a mathematical model of a forest ecosystem that is at risk of fire ignition when the ambient temperature rises. We believe that the main characteristic in this case is the amount of carbon entering the atmosphere. Fire control measures are an external control factor that is at the disposal of the Forestry Administration. We were interested in finding the optimal behavior strategy, with which the Forestry Administration could take the necessary measures in a timely manner. We describe the forest ecosystem by a differential equation with two external control factors and apply the theory of differential games to the search for optimal control. By optimal control we mean the Nash equilibrium that we search for our model.

We also complicate our model by introducing into consideration a differential equation with four control external factors describing the mosaic-layer phytocenosis.
Algorithmization control of complex systems based on functioning tables
Authors: Kabulov A V , Normatov I H , Karimov A
Published: January 2020

This paper is devoted to algorithmic models and methods of managing complex systems based on algebra over the functioning tables. To build a control system, a description of processes, both strictly sequential and parallel, is required. For this, a unified description of processes with specified operations is introduced in the form of functioning tables. Then, algorithmic support for the equipment and organizational structure under consideration is built on the basis of algebra over the tables of the functioning of a complex system.
Building a model of recognizing operators based on the definition of basic reference objects
Authors: Kamilov M , Fazilov Sh , Mirzaeva G , Gulyamova D , Mirzaev N
Published: January 2020

The paper considers issues related to the construction of a model of recognizing operators, focused on the classification of objects in conditions of high dimensionality of a feature space. A new approach to constructing a model of recognition operators based on the construction of multi-level proximity functions is proposed. In this case, the construction of the model was carried out within the framework of recognition algorithms based on the calculation of estimates.

The goal of this work is develop a model is to form independent subsets of interrelated objects, highlighting a set of representative pairs of features. A distinctive feature of the proposed operator model is the definition of a suitable set of threshold functions when constructing an extremal recognition operator.

The purpose of this article is to develop a model of recognizing operators based on the calculation of estimates using two-dimensional threshold rules. Scientifically, the results of this work in aggregate represent a new solution of a scientific problem related to the issues of increasing the reliability of recognizing operators based on the evaluation of estimates. The practical significance of the results lies in the fact that the developed operators and programs can be applied in medical and technical diagnostics, geological forecasting, biometric identification and other areas where it is possible to solve the problem of classifying objects defined in a space of large dimensionality.
An iterative method for solving nonlinear equations of real gas pipeline transport
Authors: Khujaev I , Mamadaliev Kh
Published: January 2020

The study is devoted to the development of a numerical method to solve the equations of pipeline transport of compressible gas, taking into account the forces of resistance, gravity, local and convective components of the gas inertia force in the isothermal mode of factors. The power of the unknowns in the momentum conservation equation is reduced with the introduction of the auxiliary function of natural logarithm of the reduced density. Autonomous equations of linear combinations of the hydrodynamic flow rate and a newly introduced function were compiled with the participation of the propagation velocity of small pressure disturbances. In this paper, an iterative method is developed to solve equations for the implementation of the input condition for pressure and output condition for mass flow; it allows determining the unknown boundary and internal values of gas-dynamic parameters. The results of a computational experiment on the route change in flow indices at various slopes of the gas pipeline route are analyzed.
Determination of non-informative features based on the analysis of their relationships
Authors: Mamatov N , Samijonov A , Niyozmatova N
Published: January 2020

In solving most of the practical problems associated with classification, a heuristic approach is widely used. Currently, many heuristic methods and algorithms based on various heuristic criteria have been developed. The most popular criteria are heuristic informational criteria. These criteria are related to the assessment of the separability of these classes and are based on the fundamental hypothesis of recognition compactness, i.e. with an increase in the relationship between classes, their separability improves. If traits maximize relationships, they are called "good." Such heuristic criteria are widely used and give good results in solving practical problems, but they are poorly studied in theoretical terms. At present, the method for choosing non-informative features, taking into account the relationship of features based on heuristic criteria, has not yet been developed. The article considers the problem of determining informative features by eliminating uninformative ones.
Study parabolic type diffusion equations with double nonlinearity
Authors: Muhamediyeva D K
Published: January 2020

In this paper, qualitative properties of the reaction-diffusion equation with double nonlinearity investigated. Research carried out based on a self-similar analysis of solutions. Population models of two competing populations with double nonlinear diffusion, which described by a nonlinear system of competing individuals, are proposed.
Particle swarm method for solving the global optimization problem using the equilibrium coefficient
Authors: Muhamediyeva D T
Published: January 2020

the paper deals with the case when particles are evenly distributed in ravines, using the equilibrium coefficient to update the particle velocity. the method of optimizing a swarm of particles in the case of a "ravine" is one of the most effective approaches for multi-extremal optimization. however, in the existing methods of optimizing the swarm of particles with the "ravine" methods, the number of particles around the ravine is very different from each other, which makes it difficult to find high-quality algorithms in all the ravines. thus, the computational resources are distributed in the ravines in a more balanced way.
Simulation and numerical study of two-phase flow in a centrifugal dust catcher
Authors: Nazarov F Kh , Malikov Z M , Rakhmanov N M
Published: January 2020

Numerical study of turbulent swirling air flow with solid particles in a centrifugal dust catcher is carried out in this paper. The Spalart-Allmaras modified turbulence model (SARC) has been used to construct a mathematical model with account of the interaction between solid particles and air mass. The Lagrange approach has been used to study the trajectory of solid particles. The numerical results obtained are compared with experimental data. The experiment has been conducted with zinc powder on a laboratory stand of a centrifugal dust catcher. …
On radicals of system of equations over linear strict posets
Authors: Nikitin A Yu , Shevlyakov A N
Published: January 2020

In this paper we consider equations over linear posets with strict order and for certain kind of a system S of equations we prove when its radical coincides with congruent and transitive closure [S].
Application of network analysis methods in the selection of information sources
Authors: Olgina I G
Published: January 2020

A possibility of applying network analysis for solving practical tasks related to the selection of information sources. It is proposed to consider the following algorithm of actions necessary for qualitative selection of sources of information based on the analysis of the citation network of scientific publications. A possibility of applying a information sources ranking on a list of "important" articles of a citation network, is reviewed. Existing algorithms of clustering graphs are reviewed and analyzed. A formal description of the network is given and parameters of centrality of citation network nodes are presented. A method of calculating a degree of centrality according to relevance of network nodes, with importance and weight of a series of parameters that are required for publications ranging articles of the citation network. A mathematical model of selecting documents for a library collection on a list of "important" articles of a citation network, is reviewed.
Numerical method of modeling of a current of viscous liquid with free borders
Authors: Panichkin A V
Published: January 2020

The final and differential method with application of the fixed regular grids with constant steps is developed for modeling of a current of a layer of viscous liquid with free and moving firm surfaces, the analysis of orders of accuracy from net steps and to iterative parameter is carried out at application of the scheme of the second and first orders in the corresponding sizes. When modeling two-dimensional currents of viscous incompressible liquid preservation of orders of accuracy of the considered differential scheme and preservation of volumes of liquid is shown.
DEVELOPMENT OF MEDICAL INFORMATION SYSTEMS
Authors: Primova H A , Sakiyev T R , Nabiyeva S S
Published: January 2020

Today, the effectiveness of the implementation of information systems for var-ious purposes in medical institutions (MCI) is one of the most important issues. The classification of medical information systems (MIS) using modern communications and local information networks is considered: basic medical information systems, medical information systems at the medical level.

The article analyzes and models factors that may influence the diagnosis. We also build mathematical models taking into account factors affecting system changes.
Dependence of the reliable graph failure probability on the topological indicators of its elements
Authors: Pronin I V
Published: January 2020

An analysis is made of the dependence of the probability of network failure, presented in the form of reliability graphs, on the topological indicators of its elements, in particular, the variety of centrality proposed in the article in mediation. In connection with the study of the reliability of large networks (networks containing millions of elements), it became necessary to find critical groups of elements that have the greatest impact on the reliability of the system. The article solves the problem of quickly finding such elements without laborious analytical calculation. Monte Carlo analytical and statistical methods are used as methods in the article. As a result of the study, a method is obtained that allows one to find such groups of elements with a certain accuracy. As a confirmation of the great influence on the reliability of the system of the found group of elements, a repeated calculation of reliability was made with an increased probability of failure of the most influential nodes. The results obtained can effectively distribute resources to the most significant system nodes, and, accordingly, increase the reliability of these systems. The absence of a laborious calculation in the method makes it effective when working with large networks.
Operator splitting method for numerical solving the atmospheric pollutant dispersion problem
Authors: Ravshanov N , Muradov F , Akhmedov D
Published: January 2020

The paper discusses the numerical modeling of transport and diffusion of air pollutants in the atmospheric boundary layer. There was developed a mathematical model of industrial emissions spread in the atmosphere taking into account the deposition velocity of fine particles. The model is described by multidimensional partial differential equations with appropriate initial and boundary conditions. The basic laws of hydrothermodynamics were used in deriving the model. In order to obtain the numerical solution of the problem, we used one of the splitting methods according to physical processes involved (transport, diffusion and absorption), as well as a second-order implicit finite-difference scheme in time. Analysis of numerical results showed that the developed computational algorithm provides sufficient accuracy of the problem solution compared with field measurement data and it has a certain advantage over other numerical methods. In the course of computational experiments, there was determined the degree of influence of such parameters as wind speed and direction, absorption coefficient and physicomechanical properties of particles on the process of atmospheric air pollutants dispersion.
Estimates of the accuracy of numerical solutions using regularization
Authors: Rogalev A N , Rogalev A A
Published: January 2020

This article explores the accuracy of numerical solutions, and suggests methods for analyzing accuracy depending on the properties of the problem. Numerical studies of complex expensive objects of technology and physics require that the computational results be obtained with guaranteed accuracy. It also depends on the fact that in the work of technical objects there are large intervals of operation time not observed experimentally. Therefore, there is a need to describe the location of the observed and calculated values, as well as the accuracy with which they are calculated. The effect of strong growth in estimates of error bounds is manifested for a large number of methods used to estimate the error of a numerical solution. This means the lack of correctness of algorithms for evaluating the accuracy of numerical solutions due to the failure of the stability conditions with respect to perturbations of the right-hand side. For many problems, among all the algorithms, the backward analysis of errors turned out to be the most effective method for assessing the accuracy of numerical solutions. The backward analysis of errors consists in the fact that when assessing the accuracy (error) of a numerical solution, the numerical solution is considered as an exact solution to a problem close to the original problem. A backward error analysis was proposed and developed in the algorithms of J Wilkinson in the context of the numerical solution of problems of linear algebra, and in the algorithms of V V Voevodin, who widely distributed it to many areas of numerical analysis. In the framework of the backward error analysis, the regularization of the algorithm for estimating the error of a numerical solution is reasonably applied. This article explores methods for the backward analysis of errors of numerical solutions.
Quasiminimal pairs for c.e. degrees of generic and coarse reducibilities
Authors: Rybalov Alexander
Published: January 2020

Generic approach to algorithmic problems in combinatorial group theory was suggested in 2003 by Kapovich, Myasnikov, Schupp and Shpilrain. This approach deals with algorithms, which solves algorithmic problems on ”most” of the inputs (i.e., on a generic set) instead of the entire domain and output undefined answer (do not halt) on the rest of inputs (a negligible set). Generic analog of Turing reducibility was introduced by Jockusch and Schupp in 2012. Later Hirschfeldt, Jockusch, Kuyper and Schupp defined coarse reducibility. In this paper we prove that there exist quasiminimal pairs for generic and coarse reducibilities of computably enumerable (c.e.) degrees. The work was supported by Russian Science Foundation, grant number 18-71-10028.
Modeling of regulatory mechanisms of oncogenic viruses Micro-RNA action
Authors: Saidalieva M , Hidirova M
Published: January 2020

The article is devoted to investigate the dynamics of the regulatory mechanisms of viral miRNA during oncogenesis at Hepatitis B virus infection. Studies show that mutually conjugated molecular-genetic systems of hepatocytes and micro-RNA of oncogenic viruses have the following domains: a stable functional activity, the possibility of oscillatory modes of functioning, irregular oscillations (it may occur the chaotic behavior of oncoviruses micro-RNA and their regulatory network connections, which leads to chaotic uncontrolled cellular reproduction and cancer) and black hole effect (sharp reduction in the number of cells, which corresponds to the metastasis of cancer cells). The results of computational experiments show that depending on the parameters of the cell and the cellular external environment, some miRNAs can both activate and inhibit tumor growth.
Neurohumoral contour regulation of arterial pressure
Authors: Shovin V A , Goltyapin V V
Published: January 2020

The article is devoted to the contour regulation of human arterial blood pressure, as well as other interrelated parameters. A system of algebro-differential equations is proposed for contour modeling. The system of equations has an odd symmetry group which leads to self-regulation and maintaining the contour parameters within a normal values. To calculate the dynamics of the system, original author software was used to solve structural equations. The finite difference scheme of two states was used to bring the equation system to a structural form. As a result, the calculated graphs of the contour parameters dynamics of blood pressure regulation are given. The innovation of the work is in the numerical solution and modeling of the mechanism of blood pressure regulation on the basis of a new approach to solving basic structural equations. Also novelty in the new software is the solver of basic structural equations, including nonlinear or differential equations, tested on this model.
Universal graph powerset
Authors: Treier Alexander
Published: January 2020

In this paper we define a series of B-graphs. A powerset of the limit graph of this series is a universal object in the category of finite simple graphs. The constructed graph is countable and has several pleasant model theoretic properties as well as famous Rado graph.
Preferential attachment graphs as agent interaction structure
Authors: Yudina M N
Published: January 2020

The preferential attachment graphs are considered as the basis for constructing agent interaction structures. The choice of such a structure has a great influence on the results of network processes simulation. Calibration (adjusting generation parameters) of the preferential attachment graphs improves the accuracy of the simulated processes results. An increase in the quality of calibration leads to the construction of adequate graph models. It can be used in processes simulation of telecommunication networks, social networks, cell molecular networks and other large networks of the modern networked world.
Models and methods for One-Dimensional Space Allocation Problem with forbidden zones
Authors: Zabudsky G G , Veremchuk N S
Published: January 2020

We consider an extension of the well–known optimization placement problem. The problem is One–Dimensional Space Allocation Problem (ODSAP). The classical formulation of the problem is to place rectangular connected objects on a line with the minimum total cost of connections between them. The extension of the problem is that there are fixed objects (forbidden zones) on the line. The objects are impossible to place in forbidden zones. The placed objects are connected among themselves and with the zones. The configuration of connections between objects is defined by a network. A similar situation arises, for example, when designing the location of technological equipment of petrochemical enterprise. It is necessary to place units of equipment so that the total cost of the pipeline ties was minimal. In this article a review of the models and methods to solve of the classical ODSAP is given. The properties of the problem with the forbidden zones are noted. Models of combinatorial optimization and integer programming for the problem are constructed. Algorithms for finding an approximate solution and branch and bounds are described. Results of computational experiments are reported.
Reduction of a boundary value problem for a system of diffusion-reaction equations to problem for a finite interval
Authors: Zadorin A I
Published: January 2020

The boundary value problem on a semi-infinite interval for a system of ordinary differential equations of the diffusion-reaction type is considered. To apply a difference scheme for the numerical solution of such a problem, it is necessary to reduce it to a problem for a finite interval. For this perpose we offer to use well-known method of construction of the stable variety of solutions that satisfy the limit condition at infinity. The estimates of the error arising when the problem is reduced to a finite interval are obtained.
Non-polynomial interpolation of functions in the presence of a boundary layer
Authors: Zadorin N A
Published: January 2020

The question of interpolation of a function of one variable with large gradients in the boundary layer region is investigated. The problem is that applying of polynomial interpolation formulas on a uniform grid to functions with large gradients can lead to unacceptable errors. We study the interpolation formulas with an arbitrarily number of interpolation nodes which are exact on the singular component. This component is responsible for the main growth of the function in the boundary layer and can be found based on asymptotic expansions. It is proved that error estimates don’t depend on the singular component and its derivatives. In the case of an exponential boundary layer these estimates don’t depend on a small parameter.
Accuracy of the analytical escape rate for a cusp barrier in the overdamping regime
Authors: Zakharov A V , Chushnyakova M V , Gontchar I I
Published: January 2020

For the first time, the accuracy of the approximate analytical Kramers formula for the thermal decay rate over a cusp barrier, RK
, is checked numerically for the overdamping regime. The numerical quasistationary rate, RD
, which is believed to be exact within the statistical errors is evaluated by means of computer modeling of the stochastic Langevin-type dynamical equations. The agreement between RK
and RD
significantly depends upon the friction strength and the height of the barrier in comparison to the thermal energy. The difference between RK
and RD
decreases with the dimensionless damping parameter φ, however, does not become smaller than 10-20%. The unexpected growth of the difference between RK
and RD
with the governing parameter is observed.
Mathematical modeling of a hydraulic flume for carrying out numerical experiments on coastal waves and erosion of cohesive soil
Authors: Zakharov Y N , Zimin A I , Nudner I S , Yashin M E
Published: January 2020

Hydrowave flumes are applied in laboratory experiments in order to study coastal wave impact on shore facilities. The realization of such laboratory experiments is costly and time-consuming concerning its preparation. Thus, it is pressing to apply a mathematical model. The paper presents a material hydrowave flume mathematical model that significantly broadens the capability of the research on coastal wave propagation and its impact on sea floor cohesive soil. The paper considers a solitary wave climb to the shore in the areas of different configuration including sea floor irregularities and a layer of cohesive soil. The wave propagation on the surface and soil shift in the water are modelled by three-component viscous incompressible fluid where air, water and soil are considered as components of non-homogeneous medium. The solution is obtained through finite difference numerical algorithm based on splitting scheme by physical factors and prediction correction method. Results of numerical calculations are presented in the paper.
Development of knowledge testing systems based on discrete optimization models
Authors: Zaozerskaya L A , Plankova V A
Published: January 2020

We present an approach to creating computer testing systems and an overview of our results obtained based on it. Special attention is paid to the problem of forming the optimal test content. This problem consists of finding a subset of the test tasks allowing us to get an objective conclusion about the degree of assimilation by a student the training course. Several formulations are described for solving this problem and the problem of forming an optimal test kit. Corresponding mathematical models are constructed on the base of the set covering problem and its generalizations. A specialized computer testing system, developed by us based on this approach, is described. The experience of this system use and the prospects of the proposed approach for creating knowledge testing systems are discussed.
Application of the descriptor approach for clustering entities from education sector
Authors: Zykina Anna , Kaneva Olga , Sharun Ivan
Published: January 2020

The article proposes the algorithm to solve objects clustering problem for such subject areas as education and labour market. Such objects are competence, discipline, specialty, vacancy, etc. The main problem in clustering algorithm development proved to be the stage of attributes design since the named objects have descriptions in a natural language. Consequently, a descriptive model for the objects was designed at first. The model was based on the fact that all necessary concepts are characterised in the space of descriptors ”know”, ”can”, etc.

This allowed the object to be represented as a tuple based on the object name, descriptors (and their values) and keywords related to descriptors. To obtain such structures, the toolkit of context-relative text mining was used. The ability to represent the entities in question as a formal structure allowed the attribute space formation algorithm to be developed and complex metrics to be constructed to solve the stated clustering problem. The developed algorithm permits development of various services for a faster and more objective decision making process in educational and professional sectors.

As a result of the work, about two thousand vacancies were obtained and transformed into descriptor entities.

Based on the error matrix, it can be judged that the resulting descriptor entities have been clustered with a sufficient level of quality. This demonstrates the applicability of the model for presentation and analysis for elements from the subject area.
The influence of soil moisture and solar altitude on surface spectral albedo in arid area
Authors: Yang Jiaxi , Li Zhenchao , Zhai Panmao , Zhao Yanyan , Gao Xiaoqing
Published: January 2020

Using data collected from a specially designed experiment at the Dunhuang Station (40°10′N, 94°31′E, 1150 m) from September 2017 to September 2018, we have characterized the influences of soil moisture and solar altitude on surface spectral albedo in an arid area. The specific settings of our experiment allowed us to minimize the influences of underlying surface, cloud cover, aerosol and weather conditions, and thus highlight the influence of soil moisture and solar altitude. During the timespan of the experiment, we observed the annual mean surface albedo of global radiation (GR), ultraviolet radiation (UV), visible radiation (VIS) and near-infrared radiation (NIR) to be 0.24, 0.11, 0.24 and 0.25. A significantly negative linear correlation between surface albedo and soil moisture was identified, with the correlation coefficients between GR, UV, VIS, NIR and soil moisture being −0.68, −0.75, −0.70 and −0.61. In addition, we identified an exponential relationship between surface albedo and solar altitude. The exponential regression coefficients are −0.21, −0.077, −0.53 and −0.21, respectively. From these analyses, we derived a new two-factor parametric formula for depicting the influence of soil moisture and solar altitude on surface spectral albedo. Using observation data, we demonstrate that the formula recapitulates the real-world relationship between soil moisture, solar altitude and surface spectral albedo with little deviation. These findings may help us gain a deeper understanding of improving land surface parameterizations and have potential implications for solar energy research and applications.
The end of gunpoint conservation: forest disturbance after the Colombian peace agreement
Authors: Murillo-Sandoval Paulo J. , Van Dexter Kristina , Van Den Hoek Jamon , Wrathall David , Kennedy Robert
Published: January 2020

In November 2016, after 52 years of armed conflict, the Colombian government and the primary rebel group, the FARC (Fuerzas Armadas Revolucionarias de Colombia) reached a peace agreement. The agreement incorporated three changes to institutions governing forest land occupation and use: (a) the demobilization of FARC from forested places, (2) the future distribution of legal land titles and new road construction into forests, and (3) the eradication of illicit crops. However, we document unprecedented rates of forest disturbance in the months following the peace agreement in biodiversity hotspots across the country. Are the declaration of peace and the increased rates of forest disturbance related? Here, we present the first systematic assessment of the impact of the Colombian peace agreement on forest disturbance. Focusing on the Andes-Amazon Transition Belt (AATB), we used automated satellite image disturbance detection methods and ethnographic data to quantify and interpret forest cover change from 2010 to 2018 that span wartime, peace negotiation, and post-peace agreement stages. Our findings indicate that during the post-peace agreement period (2017–2018), the area of forest disturbance increased by 50% (about 238 000 ha) across the AATB in comparison with the four-year peace negotiation stage (2013–2016); these changes reflect the end of FARC-led gunpoint conservation in the region. Forest disturbance also spread deeper into the Amazon watershed and increased in area by 187% within the AATB’s protected areas. We find that following the peace agreement and the withdrawal of FARC, key actors (viz. drug cartels, large landowners, campesinos and dissidents) with expectations of favorable land tenure policies swept into the region; this led to increases in large-scale cattle ranching, coca cultivation dispersal, and speculative illegal land markets each of which contributed to the widespread forest disturbance that we mapped. The rapid increase in forest disturbance occurred despite the interest of the international community in promoting forest conservation initiatives in the AATB and Colombia’s existing conservation and land titling frameworks for public lands. Our findings underscore the need for conservation strategies sensitive to rapid institutional and demographic changes in the course of the peace agreement to prevent forests from becoming an unexpected casualty of premature and unstable peace.
Large deviation analysis of function sensitivity in random deep neural networks
Authors: Li Bo , Saad David
Published: January 2020

Mean field theory has been successfully used to analyze deep neural networks (DNN) in the infinite size limit. Given the finite size of realistic DNN, we utilize the large deviation theory and path integral analysis to study the deviation of functions represented by DNN from their typical mean field solutions. The parameter perturbations investigated include weight sparsification (dilution) and binarization, which are commonly used in model simplification, for both ReLU and sign activation functions. We find that random networks with ReLU activation are more robust to parameter perturbations with respect to their counterparts with sign activation, which arguably is reflected in the simplicity of the functions they generate.
Endothelial cells support osteogenesis in an in vitro vascularized bone model developed by 3D bioprinting
Authors: Chiesa Irene , De Maria Carmelo , Lapomarda Anna , Fortunato Gabriele Maria , Montemurro Francesca , Di Gesù Roberto , Tuan Rocky S , Vozzi Giovanni , Gottardi Riccardo
Published: January 2020

Bone is a highly vascularized tissue, in which vascularization and mineralization are concurrent processes during skeletal development. Indeed, both components should be included in any reliable and adherent in vitro model platform for the study of bone physiology and pathogenesis of skeletal disorders. To this end, we developed an in vitro vascularized bone model, using a gelatin-nanohydroxyapatite (gel-nHA) three-dimensional (3D) bioprinted scaffold. First, we seeded human mesenchymal stem cells (hMSCs) on the scaffold, which underwent osteogenic differentiation for 2 weeks. Then, we included lentiviral-GFP transfected human umbilical vein endothelial cells (HUVECs) within the 3D bioprinted scaffold macropores to form a capillary-like network during 2 more weeks of culture. We tested three experimental conditions: condition 1, bone constructs with HUVECs cultured in 1:1 osteogenic medium (OM): endothelial medium (EM); condition 2, bone constructs without HUVECs cultured in 1:1 OM:EM; condition 3: bone construct with HUVECs cultured in 1:1 growth medium:EM. All samples resulted in engineered bone matrix. In conditions 1 and 3, HUVECs formed tubular structures within the bone constructs, with the assembly of a complex capillary-like network visible by fluorescence microscopy in the live tissue and histology. CD31 immunostaining confirmed significant vascular lumen formation. Quantitative real-time PCR was used to quantify osteogenic differentiation and endothelial response. Alkaline phosphatase and runt-related transcription factor 2 upregulation confirmed early osteogenic commitment of hMSCs. Even when OM was removed under condition 3, we observed clear osteogenesis, which was notably accompanied by upregulation of osteopontin, vascular endothelial growth factor, and collagen type I. These findings indicate that we have successfully realized a bone model with robust vascularization in just 4 weeks of culture and we highlighted how the inclusion of endothelial cells more realistically supports osteogenesis. The approach reported here resulted in a biologically inspired in vitro model of bone vascularization, simulating de novo morphogenesis of capillary vessels occurring during tissue development.
Fluorophore photostability and saturation in the hotspot of DNA origami nanoantennas
Authors: Grabenhorst Lennart , Trofymchuk Kateryna , Steiner Florian , Glembockyte Viktorija , Tinnefeld Philip
Published: January 2020

Fluorescent dyes used for single-molecule spectroscopy can undergo millions of excitation-emission cycles before photobleaching. Due to the upconcentration of light in a plasmonic hotspot, the conditions for fluorescent dyes are even more demanding in DNA origami nanoantennas. Here, we briefly review the current state of fluorophore stabilization for single-molecule imaging and reveal additional factors relevant in the context of plasmonic fluorescence enhancement. We show that despite the improved photostability of single-molecule fluorophores by DNA origami nanoantennas, their performance in the intense electric fields in plasmonic hotspots is still limited by the underlying photophysical processes, such as formation of dim states and photoisomerization. These photophysical processes limit the photon count rates, increase heterogeneity and aggravate quantification of fluorescence enhancement factors. These factors also reduce the time resolution that can be achieved in biophysical single-molecule experiments. Finally, we show how the photophysics of a DNA hairpin assay with a fluorophore-quencher pair can be influenced by plasmonic DNA origami nanoantennas leading to implications for their use in fluorescence-based diagnostic assays. Especially, we show that such assays can produce false positive results by premature photobleaching of the dark quencher.