arXiv subjects

Yuriy Ostapov

Publications and source records attributed to Yuriy Ostapov.

9 recordsLinked to original sources

arXiv2020

Frequency spectrum of nonlinear oscillations and resonance phenomena for graphene plates

The paper studies oscillations of graphene plates under the hypothesis that deformations are much more than the thickness of plate. In this most realistic case the oscillations are described by the system of nonlinear partial differential equations (the Foppl-von Karman equations). This system is reduced to one nonlinear ordinary differential equation and investigated by means of the Bogoliubov-Mitropolsky asymptotic methods. As a result, we have the real frequency spectrum for rectangular graphene plates. Next we have examined the nonlinear resonance effects under forced oscillations. These outcomes can apply for variable strain-induced pseudomagnetic fields. Such fields permit better to understand the properties of flexural phonons connected with transport process. Resonance phenomena play a leading role in application of graphene plates in engineering constructions.

physics.class-ph↗

arXiv2020

Application of Boltzmann equation to investigate kinetic processes of meson and baryon production in the quark-gluon plasma

We consider the meson and baryon production in the quark-gluon plasma as applied to the early Universe and ultrarelativistic heavy ion collisions in collider. The essential feature of our investigation is to take into account a potential barrier for quarks under meson and baryon production. We have used the Boltzmann equation to describe kinetic processes of quark fusion. We have derived analytic expressions for solutions of kinetic equations. This permits to find the dependence of reaction rate on a time, temperature, mass and charge of quarks as well as on a string tension connected with the confining potential. Next we have considered in detail the meson and baryon production for some concrete kinetic processes in collisions of ultrarelativistic heavy ions. Exactly the same results will be as well true for processes in expanding Universe

nucl-th↗

arXiv2017

The generating functional for the electromagnetic interaction in the strong gravitational field

This article is devoted problems of electromagnetic interaction in curved spacetime. Such problems exist, in particular, when we investigate electromagnetic quantum processes near black holes. The generalization of reduction formalism permits to find formulas for scattering matrices. For the free Dirac and electromagnetic fields corresponding generating functionals are calculated. Next we have found the generating functional for the interaction of these fields. This result holds the central position in our investigation. By means of generating functionals and reduction formulas we have obtained the scattering amplitudes for elementary electrodynamic processes: Compton scattering and the annihilation of electron-positron pair (for the tree-level approximation). On the base of these results we have formulated the generalized Feynman rules for the electromagnetic interaction in curved spacetime. Another electrodynamic processes can be studied by means of these Feynman rules and crossing-symmetry. The generating functional can be used to study problems of quantum statistics in curved spacetime.

hep-th↗

arXiv2013

Logical analysis of natural language semantics to solve the problem of computer understanding

An object--oriented approach to create a natural language understanding system is considered. The understanding program is a formal system built on the base of predicative calculus. Horn's clauses are used as well--formed formulas. An inference is based on the principle of resolution. Sentences of natural language are represented in the view of typical predicate set. These predicates describe physical objects and processes, abstract objects, categories and semantic relations between objects. Predicates for concrete assertions are saved in a database. To describe the semantics of classes for physical objects, abstract concepts and processes, a knowledge base is applied. The proposed representation of natural language sentences is a semantic net. Nodes of such net are typical predicates. This approach is perspective as, firstly, such typification of nodes facilitates essentially forming of processing algorithms and object descriptions, secondly, the effectiveness of algorithms is increased (particularly for the great number of nodes), thirdly, to describe the semantics of words, encyclopedic knowledge is used, and this permits essentially to extend the class of solved problems.

cs.CL↗

arXiv2012

Adaptive Control of Enterprise

Modern progress in artificial intelligence permits to realize algorithms of adaptation for critical events (in addition to ERP). A production emergence, an appearance of new competitive goods, a major change in financial state of partners, a radical change in exchange rate, a change in custom and tax legislation, a political and energy crisis, an ecocatastrophe can lead up to a decrease of profit or bankruptcy of enterprise. Therefore it is necessary to assess a probability of threat and to take preventive actions. If a critical event took place, one must estimate restoration expenses and possible consequences as well as to prepare appropriate propositions. This is provided using modern methods of diagnostics, prediction, and decision making as well as an inference engine and semantic analysis. Mathematical methods in use are called in algorithms of adaptation automatically. Because the enterprise is a complex system, to overcome complexity of control it is necessary to apply semantic representations. Such representations are formed from descriptions of events, facts, persons, organizations, goods, operations, scripts on a natural language. Semantic representations permit as well to formulate actual problems and to find ways to resolve these problems.

cs.CE↗

arXiv2012

Intellectual Management of Enterprise

A new technology (in addition to ERP) is proposed to provide an increase of profit and normal cash flow. This technology involves the next functions: forming of intellectual interface on a natural language to communicate with a control system; joint planning of production and sales to get the maximal profit; an adaptation of control system to internal and external events. The use of the natural language permits to overcome a barrier between the control system and upper managers. To solve posed actual problems of management the selection of information from a database and call to mathematical methods are executed automatically. Optimal planning provides the maximal use of available resources and opportunities of market. Adaptive control implements the efficient reaction to critical events that lead up to a decrease of profit and increase of accounts receivable.

cs.CE↗

arXiv2012

Inference and Plausible Reasoning in a Natural Language Understanding System Based on Object-Oriented Semantics

Algorithms of inference in a computer system oriented to input and semantic processing of text information are presented. Such inference is necessary for logical questions when the direct comparison of objects from a question and database can not give a result. The following classes of problems are considered: a check of hypotheses for persons and non-typical actions, the determination of persons and circumstances for non-typical actions, planning actions, the determination of event cause and state of persons. To form an answer both deduction and plausible reasoning are used. As a knowledge domain under consideration is social behavior of persons, plausible reasoning is based on laws of social psychology. Proposed algorithms of inference and plausible reasoning can be realized in computer systems closely connected with text processing (criminology, operation of business, medicine, document systems).

cs.CL↗

arXiv2011

Question Answering in a Natural Language Understanding System Based on Object-Oriented Semantics

Algorithms of question answering in a computer system oriented on input and logical processing of text information are presented. A knowledge domain under consideration is social behavior of a person. A database of the system includes an internal representation of natural language sentences and supplemental information. The answer {\it Yes} or {\it No} is formed for a general question. A special question containing an interrogative word or group of interrogative words permits to find a subject, object, place, time, cause, purpose and way of action or event. Answer generation is based on identification algorithms of persons, organizations, machines, things, places, and times. Proposed algorithms of question answering can be realized in information systems closely connected with text processing (criminology, operation of business, medicine, document systems).

cs.CL↗

arXiv2011

Object-oriented semantics of English in natural language understanding system

A new approach to the problem of natural language understanding is proposed. The knowledge domain under consideration is the social behavior of people. English sentences are translated into set of predicates of a semantic database, which describe persons, occupations, organizations, projects, actions, events, messages, machines, things, animals, location and time of actions, relations between objects, thoughts, cause-and-effect relations, abstract objects. There is a knowledge base containing the description of semantics of objects (functions and structure), actions (motives and causes), and operations.

cs.CL↗