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V. K. Ivanov

Publications and source records attributed to V. K. Ivanov.

At least 19 recordsLinked to original sources
arXiv2025

Sturmian basis set for the Dirac equation with finite nuclear size: Application to polarizability, Zeeman and hyperfine splitting, and vacuum polarization

We investigate the application of the Sturmian basis set in relativistic atomic structure calculations. We propose a simple implementation of this approach and demonstrate its ability to provide various quantities for hydrogen-like ions, including binding energies, static dipole polarizability, $g$ factor, hyperfine splitting, and nuclear magnetic shielding. Finally, we calculate the all-order (Wichmann-Kroll) vacuum polarization charge density, which was a challenge for the finite-basis-set approach until recently. Comparison of the obtained results with the previously published numerical and analytical calculations is presented. All calculations are performed with the finite size of the nucleus and can in principle be extended to arbitrary binding potentials.

physics.atom-ph↗
arXiv2024

Induced charge generated by a Coulomb impurity in transition metal dichalcogenides

We calculate analytically the charge density $ρ_{\text{ind}}(\boldsymbol{r})$ at small distances induced by a Coulomb impurity in two-dimensional transition metal dichalcogenides. The calculations were performed exactly in the coupling constant. We found the first three leading terms of the charge density asymptotics at small distances. Using this result, we demonstrate that the impurity with charge number $Z=1$ remains subcritical at any value of the coupling constant, whereas impurities with higher charge number could become supercritical at certain coupling constant values. Such a behavior is similar to that in graphene.

cond-mat.mes-hall↗
arXiv2024

Vacuum polarization and Wichmann-Kroll correction in the finite basis set approximation

The finite basis set method is commonly used to calculate atomic spectra, including QED contributions such as bound-electron self-energy. Still, it remains problematic and underexplored for vacuum-polarization calculations. We fill this gap by trying this approach in its application to the calculation of the vacuum-polarization charge density and the Wichmann-Kroll correction to the electron binding energy in a hydrogen-like ion. We study the convergence of the method with different types and sizes of basis sets. We cross-check our results for the Wichmann-Kroll correction by direct integration of the Green's function. As a relevant example, we consider several heavy hydrogen-like ions and evaluate the vacuum polarization correction for $S$ and $P$ electron orbitals.

physics.atom-ph↗
arXiv2024

Studying highly relativistic vortex-electron beams by atomic scattering

We explore the opportunities of using electron scattering by screened Coulomb potential as a tool to retrieve properties of the relativistic vortex beams of electrons, such as their transverse momentum and orbital angular momentum (OAM). We focus on relativistic and ultra-relativistic regimes of the electron energies of at least several MeV and higher, in which the transverse beam momentum is typically much smaller than its longitudinal momentum. Different scattering scenarios for the incident electron beam are considered. In particular, the scattering by a very wide target can be used to probe the electron transverse momentum when its values are larger than 10 keV. The scattering by a target of a width comparable to that of the incident beam allows one to obtain information about the electron OAM. Varying target sizes in the range from couple to hundreds of nanometers, one can in principle distinguish OAM values from several units of $\hbar$ up to thousands and more.

physics.atom-ph↗
arXiv2023

Atomistic modelling of electron propagation and radiation emission in oriented bent ultra-thin Si and Ge crystals

Computational modelling of passage of high-energy electrons through crystalline media is carried out by means of the relativistic molecular dynamics. The results obtained are compared with the experimental data for 855 MeV electron beam incident on oriented bent ultra-thin (15 microns) silicon and germanium crystals. The simulations have been performed for the geometries of the beam--crystal orientation that correspond (i) to the channeling regime and (ii) to the volume reflection. A comparison with the experiment is carried out in terms of angular distributions of the electrons deflected by the crystals bent with different curvature radii as well as of the spectra of the emitted radiation. For both crystals a good agreement between the simulated and experimentally measured data is reported. The origin of remaining minor discrepancies between theory and experiment is discussed.

physics.acc-ph↗
arXiv2021

Peculiarities of organization of data storage based on intelligent search agent and evolutionary model selection the target information

The article presents a systematic review of the results of the development of the theoretical basis and the pilot implementation of data storage technology with automatic replenishment of data from sources belonging to different thematic segments. It is expected that the repository will contain information about objects with significant innovative potential. The mechanism of selection of such information is based on the determination of its semantic relevance to the generated search queries. At the same time, a quantitative assessment of the innovation of objects, in particular their technological novelty and demand is given. The article describes the accepted indicators of innovation, discusses the application of the theory of evidence for the processing of incomplete and fuzzy information, identifies the main ideas of the method of processing the results of measurements for the calculation of the probabilistic value of the components of innovation, briefly describes the application of the evolutionary approach in the formation of the linguistic model of the archetype of the object, provides information about the experimental verification of the adequacy of the developed computational model. The research results that are described in the article can be used for business planning, forecasting of technological development, information support of investment projects expertise.

cs.DB↗
arXiv2021

Experimental check of model of object innovation evaluation

The article discusses the approach for evaluating the innovation index of the products and technologies. The evaluation results can be used to create a warehouse of the object descriptions with significant innovation potential. The model of innovation index computation is based on the concepts of novelty, relevance, and implementability of the object. Formal definitions of these indicators are given and a methodology for their calculation are described. The fuzzy methods to coprocess (incomplete) data from numerous sources and to obtain probabilistic innovation assessments are used. The experimental data of the model check including the calculations of local criteria and global additive evaluation criterion are presented. The cyclical nature of dynamic changes in indicators, their interdependence was established, some general features of the products promotion were found. The obtained experimental data are consistent with expert estimates of the products under study. The analysis of the local criteria used in the research gives grounds to assert the correct use of the additive n-dimensional utility function. The adequacy of assumptions and formal expressions that are used in computational algorithms for selection information for data warehouse is confirmed.

cs.DB↗
arXiv2021

Determination of weight coefficients for additive fitness function of genetic algorithm

The paper presents a solution for the problem of choosing a method for analytical determining of weight factors for a genetic algorithm additive fitness function. This algorithm is the basis for an evolutionary process, which forms a stable and effective query population in a search engine to obtain highly relevant results. The paper gives a formal description of an algorithm fitness function, which is a weighted sum of three heterogeneous criteria. The selected methods for analytical determining of weight factors are described in detail. It is noted that expert assessment methods are impossible to use. The authors present a research methodology using the experimental results from earlier in the discussed project "Data Warehouse Support on the Base Intellectual Web Crawler and Evolutionary Model for Target Information Selection". There is a description of an initial dataset with data ranges for calculating weights. The calculation order is illustrated by examples. The research results in graphical form demonstrate the fitness function behavior during the genetic algorithm operation using various weighting options.

cs.NE↗
arXiv2021

Some Results of Experimental Check of The Model of the Object Innovativeness Quantitative Evaluation

The paper presents the results of the experiments that were conducted to confirm the main ideas of the proposed approach to determining the objects innovativeness. This approach assumed that the product life cycle of whose descriptions are placed in different data warehouses is adequate. The proposed formal model allows us to calculate the quantitative value of the additive evaluation criterion of objects innovativeness. The obtained experimental data make it possible to evaluate the adopted approach correctness.

cs.DB↗
arXiv2021

Computational Model to Quantify Object Innovativeness

The article considers the quantitative assessment approach to the innovativeness of different objects. The proposed assessment model is based on the object data retrieval from various databases including the Internet. We present an object linguistic model, the processing technique for the measurement results including the results retrieved from the different search engines, and the evaluating technique of the source credibility. Empirical research of the computational model adequacy includes the acquisition and preprocessing of patent data from different databases and the computation of invention innovativeness values: their novelty and relevance. The experiment results, namely the comparative assessments of innovativeness values and major trends, show the models developed are sufficiently adequate and can be used in further research.

cs.DL↗
arXiv2021

Quantitative Assessment of Solution Innovation in Engineering Education

The article discusses the quantitative assessment approach to the innovation of engineering system components. The validity of the approach is based on the expert appraisal of the university's electronic information educational environment components and the measurement of engineering solution innovation in engineering education. The implementation of batch processing of object innovation assessments is justified and described.

cs.CY↗
arXiv2021

Current Trends and Applications of Dempster-Shafer Theory (Review)

The article provides a review of the publications on the current trends and developments in Dempster-Shafer theory and its different applications in science, engineering, and technologies. The review took account of the following provisions with a focus on some specific aspects of the theory. Firstly, the article considers the research directions whose results are known not only in scientific and academic community but understood by a wide circle of potential designers and developers of advanced engineering solutions and technologies. Secondly, the article shows the theory applications in some important areas of human activity such as manufacturing systems, diagnostics of technological processes, materials and products, building and construction, product quality control, economic and social systems. The particular attention is paid to the current state of research in the domains under consideration and, thus, the papers published, as a rule, in recent years and presenting the achievements of modern research on Dempster-Shafer theory and its application are selected and analyzed.

cs.AI↗
arXiv2021

Implementing an expert system to evaluate technical solutions innovativeness

The paper presents a possible solution to the problem of algorithmization for quantifying inno-vativeness indicators of technical products, inventions and technologies. The concepts of technological nov-elty, relevance and implementability as components of product innovation criterion are introduced. Authors propose a model and algorithm to calculate every of these indicators of innovativeness under conditions of incompleteness and inaccuracy, and sometimes inconsistency of the initial information. The paper describes the developed specialized software that is a promising methodological tool for using interval estimations in accordance with the theory of evidence. These estimations are used in the analysis of complex multicomponent systems, aggregations of large volumes of fuzzy and incomplete data of various structures. Composition and structure of a multi-agent expert system are presented. The purpose of such system is to process groups of measurement results and to estimate indicators values of objects innovativeness. The paper defines active elements of the system, their functionality, roles, interaction order, input and output inter-faces, as well as the general software functioning algorithm. It describes implementation of software modules and gives an example of solving a specific problem to determine the level of technical products innovation.

cs.AI↗
arXiv2020

Channeling of ultrarelativistic particles in a diamond crystal

The results of numerical simulation of the channeling of ultra-relativistic 270 MeV electrons and positrons in a diamond crystal are presented. Using the MBN Explorer package, the trajectories of the have been determined of the particles incident on a 20 microns thick crystal along (110) crystallographic plane. The channeling parameters and radiation spectra of electrons and positrons have been computed for the cases of straight and periodically bent diamond crystals.

physics.acc-ph↗
arXiv2018

First rare-earth phosphate aerogel: sol-gel synthesis of monolithic ceric hydrogen phosphate aerogel

Since the late 1960s, ceric hydrogen phosphates have attracted the attention of scientists due to remarkable ion exchange, sorption, proton-conduction and catalytic properties. In this work, through the application of various solvents, we, for the first time, have obtained monolithic aerogels based on ceric hydrogen phosphates with high porosity (~99%) and extremely low density (~10 microg/cm3). The composition and structure of aerogels were thoroughly studied with XRD, TEM, SEM, XPS, low temperature nitrogen adsorption methods, TGA/DSC, Fourier-transform infrared spectroscopy (FTIR) and small-angle neutron scattering (SANS). The aerogels were found to belong to the fibrous macroporous aerogels family.

cond-mat.mtrl-sci↗
arXiv2017

Combined SANS and SAXS study of the action of ultrasound on the structure of amorphous zirconia gels

In the present work, we have studied for the first time the combined effect of both sonication and precipitation pH on the structure of amorphous zirconia gels synthesized from zirconium(IV) propoxide. The techniques of small-angle neutron and X-ray scattering (SANS and SAXS) and low temperature nitrogen adsorption provided the integral data on the changes in the microstructure and mesostructure of these materials caused by ultrasonic (US) treatment. Amorphous ZrO2.xH2O synthesized under ultrasonic treatment was found to possess a very structured surface, characterized by the surface fractal dimension 2.9-3.0, compared to 2.3-2.5 for the non US-assisted synthesis, and it was also found to possess a higher specific surface area, while the sizes of the primary particles remain unchanged.

cond-mat.mtrl-sci↗
arXiv2015

Genetic algorithm implementation for effective document subject search

This paper describes the software implementation of genetic algorithm for identifying and selecting most relevant results received during sequentially executed subject search operations. Simulated evolutionary process generates sustainable and effective population of search queries, forms search pattern of documents or semantic core, creates relevant sets of required documents, allows automatic classification of search results. The paper discusses the features of subject search, justifies the use of a genetic algorithm, describes arguments of the fitness function and describes basic steps and parameters of the algorithm.

cs.IR↗