Novosibirsk State Technical University
Novosibirsk, Russia

Novosibirsk State Technical University , until 1992 the Novosibirsk Electrotechnical Institute , is one of the major research and educational centers of Russia as well as one of the top technical universities located in Novosibirsk, Russia. Wikipedia.

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Avdeenko T.,Novosibirsk State Technical University
ACM International Conference Proceeding Series | Year: 2017

In present paper we propose an approach to support knowledge transformation in the knowledge-based systems facilitating transition of knowledge from the tacit form to the explicit one and vice versa. The approach is based on the dynamic integration of case-based and rule-based knowledge representation model with use of artificial intelligence methods. Efficient algorithm is proposed for conversion of knowledge from the case-based to the rule-based fuzzy representation to solving classification problem.

We study a nonlinear equation which is equivalent to an equation of generalization of the Leith model of turbulence and to the equation of the model of nonlinear diffusion in an inhomogeneous media without absorption. Using this equation, all submodels admitting continuous Lie transformation groups, acting on the set of solutions of the equations of these submodels are obtained. For obtained submodels, all invariant submodels are found. All essentially distinct invariant solutions describing these invariant submodels are found explicitly, or their finding is reduced to solving nonlinear integral equations. The integral equations defining these solutions reveal new possibilities for analytical and numerical studies. The presence of arbitrary constants in these equations allows one to apply them to the study of different boundary value problems. We have proved the existence and uniqueness of the solution for some boundary value problems. We have investigated the following boundary value problems: (1) a distribution of front-density turbulent kinetic energy in a framework of the generalizion of the Leith model of wave turbulence for which either the spectrum and its wavenumber derivative or the spectrum and its time derivative are given at the initial moment of time at a fixed wavenumber; (2) a nonlinear diffusion process in an inhomogeneous media without absorption, for which either the concentration and its gradient or the concentration and its rate of change are given at the initial moment of time at a fixed point. Under certain additional conditions we have established the existence and uniqueness of the solutions to boundary value problems describing these processes. © 2015 IOP Publishing Ltd.

Chirkunov Y.A.,Novosibirsk State Technical University
Journal of Mathematical Physics | Year: 2015

We study the five-parameter model, describing the process of nonlinear diffusion in an inhomogeneous medium in the presence of absorption, for which the differential equation of the model admits a continuous Lie group of transformations, acting on the set of its solutions. We found six submodels of the original model of nonlinear diffusion, with different symmetry properties. Of these six submodels, the five submodels with transient absorption, for which the absorption coefficient depends on time according to a power law, represent the greatest interest with a mathematical point of view and with the point of view of physical applications. For each of these nonlinear submodels, we obtained formulas for producing new solutions that contain arbitrary constants, and we found all invariant submodels. All essentially distinct invariant solutions describing these invariant submodels are found in an explicit form or are reduced to finding the solution of nonlinear integral equations. The presence of the arbitrary constants in the integral equations that determine these solutions provide new opportunities for analytical and numerical study of boundary value problems for the received submodels and, thus, for the original model of nonlinear diffusion. For the received invariant submodels, we studied diffusion processes for which at the initial moment of the time at a fixed point is specified as a concentration and its gradient or as a concentration and its velocity. Solving of boundary value problems describing these processes is reduced to the solving of nonlinear integral equations. We established the existence and uniqueness of solutions of these boundary value problems under some additional conditions. The obtained results can be used to study the diffusion of substances, diffusion of conduction electrons and other particles, diffusion of physical fields and propagation of heat in inhomogeneous medium, and also to study a turbulence (Leith model, differential approximation to wave turbulence). © 2015 AIP Publishing LLC.

Kibis O.V.,Novosibirsk State Technical University
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

Exact stationary solutions of the electron-photon Dirac equation are obtained to describe the strong interaction between massless Dirac fermions in graphene and circularly polarized photons. It follows from them that this interaction forms bound electron-photon states which should be considered as a kind of charged quasiparticles. The energy spectrum of the quasiparticles is of dielectric type and characterized by an energy gap between the valence and conductivity bands. Therefore the electron-photon interaction results in metal-insulator transition in graphene. The stationary energy gap, induced by photons, and concomitant effects can be observed for graphene exposed to a laser-generated circularly polarized electromagnetic wave. © 2010 The American Physical Society.

Kibis O.V.,Novosibirsk State Technical University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

It is demonstrated that the strong coupling of an electron gas to photons in systems with broken time-reversal symmetry results in bound electron-photon states which cannot be backscattered elastically. As a consequence, the electron gas can flow without dissipation. This quantum macroscopic phenomenon leads to the unconventional superconductivity which is analyzed theoretically for a two-dimensional electron system in a semiconductor quantum well exposed to an in-plane magnetic field. © 2012 American Physical Society.

Chernyshev A.P.,Novosibirsk State Technical University
European Physical Journal B | Year: 2011

The Mie-Grüneisen equation is adapted for the description of the thermodynamic properties of nano-objects. It is shown that the Grüneisen parameter Γ depends on the ratio of the number of surface atoms to the number of interior atoms of the nano-objects. This ratio is determined by the characteristic size of nano-object and its form. It increases with decrease of the characteristic size. Reduction of the characteristic size of nano-objects that have a free surface, leads to a change in the Grüneisen parameter. If the nano-object is embedded in a matrix and has with it the coherent boundary, at the decrease of the nano-object size occurs either an increase or decrease of Γ. Compression or stretching of nano-objects may bring about a change of the ratio between numbers of the interior and surface atoms caused by changing the form of nano-objects. The change of the Grüneisen parameter at the characteristic size decreasing of a nano-object is treated as the change of a degree of the anharmonicity of lattice thermal vibrations. It is established that an appreciable change of Γ occurs if the characteristic radius of a nano-object is less than 5 nm. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Levyakov S.V.,Novosibirsk State Technical University
Acta Mechanica | Year: 2013

The problem of nonlinear thermal bending of a pinned slender beam fabricated of functionally graded material is considered. Based on the concept of physically neutral surface, the problem is reduced to a system of two coupled transcendental equations in terms of Legendre's elliptic integrals. Solutions of these equations are presented in graphical and tabular form. Specific features of the nonlinear response of the functionally graded beam under thermal loading are discussed. © 2013 Springer-Verlag Wien.

Kibis O.V.,Novosibirsk State Technical University
Physical Review Letters | Year: 2011

It is shown that the electron coupling to photons in field-dressed nanostructures can result in the ground electron-photon state with a nonzero electric current. Since the current is associated with the ground state, it flows without the Joule heating of the nanostructure and is nondissipative. Such a dissipationless electron transport can be realized in strongly coupled electron-photon systems with the broken time-reversal symmetry-particularly, in quantum rings and chiral nanostructures dressed by circularly polarized photons. © 2011 American Physical Society.

Kulikov I.,Novosibirsk State Technical University
Astrophysical Journal, Supplement Series | Year: 2014

In this paper, a new scalable hydrodynamic code, GPUPEGAS (GPU-accelerated Performance Gas Astrophysical Simulation), for the simulation of interacting galaxies is proposed. The details of a parallel numerical method co-design are described. A speed-up of 55 times was obtained within a single GPU accelerator. The use of 60 GPU accelerators resulted in 96% parallel efficiency. A collisionless hydrodynamic approach has been used for modeling of stars and dark matter. The scalability of the GPUPEGAS code is shown. © 2014. The American Astronomical Society. All rights reserved..

News Article | August 4, 2016

A group of Russians has witnessed a seldom-seen phenomenon that scientists do not yet fully understand. One of them was able to capture the rare phenomenon known as ball lightning on video. Roman Tregubov, a graduate of the Novosibirsk State Technical University, used the camera on his cell phone to capture the bright white ball gliding over a field near his country house outside of Novosibirsk, Siberia's largest city. Although the video was shaky, Tregubov accurately identified what the phenomenon is. When somebody asked him what it is he was filming, he said it was a fireball lightning and it is the first time he witnessed one in his life. "Fireball lightening is very rare, yet they can appear anywhere at all," Tregubov said. "I was astonished to see the fireball lightening of such size — and not just that, but to catch the whole process from the beginning when it appeared until the end." Tregubov explained that the footage he took was shaky because he had to stand on a brick so he can get a view of the ball over the fence and the bushes. Ball lightning is a little-understood atmospheric electrical phenomenon that involves a luminous sphere of electricity with varying sizes. It can be very small but it sometimes reaches up to several meters in diameter. People have reported seeing the phenomenon for hundreds of years, but because it is seldom witnessed, some have dismissed it as an urban legend. Scientists do not yet fully know what it is exactly and what causes it. Eyewitnesses have described seeing a floating and glowing ball that looks like a tennis ball or a beach ball and the sightings often accompany thunderstorms. The ball lightning appears to glide near the ground, sometimes bouncing off the ground and other objects. It does not also seem to obey the whims of the wind and is neither influenced by the laws of gravity. The glowing balls, however, eventually disappear with some eyewitnesses reporting seeing them melt through glass windows. The phenomenon lasts about 10 seconds before it fades away or dissipates with a small explosion. A typical ball glows with the power of a 100-watt bulb. The ball lightning is not inherently deadly, but there are reports of people getting killed by contact. Electricity researcher Georg Richmann is believed to have been electrocuted by a ball lightning while conducting a lightning-rod experiment in St. Petersburg, Russia in 1753. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.

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