Vector operations in the precise indication of local objects in images
Vector operations in the precise indication of local objects in images
Е. Н. Терентьев$^1$, N. E. Shilin-Terentyev$^2$, I. N. Prikhodko$^1$, I. I. Farshakova$^1$
In this paper, the image is considered as a scalar field and is associated with a vector gradient field. This approach combined with the methods of analyzing the shape of the fields makes it possible to search for vortices in space images. And knowing that images with a pronounced geometric shape create false vortices in the image, you can search for their location based on the proposed method. At the same time, the advantages of this approach include accuracy and applicability in the low-frequency region.
Show AbstractDiffuse light scattering effect on third-harmonic generation and Raman scattering efficiency in silicon nanowire arrays
Diffuse light scattering effect on third-harmonic generation and Raman scattering efficiency in silicon nanowire arrays
S. V. Zabotnov$^1$, A. V. Kolchin$^1$, N. B. Tkachenko$^1$, L. A. Osminkina$^3$, D. E. Presnov$^{2,4}$, A. A. Eliseev$^5$, A. I. Efimova$^1$, L. A. Golovan$^1$, P. K. Kashkarov$^1$
An elastic light scattering effect on third-harmonic generation and Raman scattering in silicon nanowire arrays of different thicknesses was shown. The four- and twelvefold signal increase correspondingly for these processes in comparison with the response from monocrystalline silicon is reached. The observed growth is caused by photon lifetime increase in the medium due to multiple diffuse light scattering which take place from 2 um thickness of the silicon nanowire arrays. This assumption well agrees with spectrophotometric data and cross-correlation function measurements in the studied samples.
Show AbstractModeling of the interaction of the solar wind plasma with dipolization fronts in the tail of the Earth's magnetosphere
Modeling of the interaction of the solar wind plasma with dipolization fronts in the tail of the Earth's magnetosphere
E. I. Parkhomenko$^1$, H. V. Malova$^{1,2}$, V. Yu. Popov$^{1,3,4}$, E. E. Grigorenko$^1$, A. A. Petrukovich$^1$, L. M. Zeleny$^1$, E. A. Kronberg$^{5,6}$
The work is devoted to the investigation of different mechanisms of acceleration of charged particles during magnetic substorms in the tail of the Earth's magnetosphere. A numerical model is constructed that allows one to investigate the acceleration of particles of three types: electrons e-, protons H+ and oxygen ions O+ as a result of two different mechanisms: (a) a single magnetic dipole with a jump in the normal component of the magnetic field lasting several minutes; (b) multiple jumps of the normal component of the magnetic field (dipolization fronts) lasting less than a minute. It is shown that under the influence of a single magnetic dipolarization (a), a predominant acceleration of oxygen ions occurs, which increase their energies to 200 keV. In this case, protons and electrons are accelerated to a lesser extent. In comparison with the mechanism (a), the process (b) promotes a greater acceleration of protons and electrons to energies of 300 and 150 keV, respectively. Thus, the acceleration efficiency of different particle populations is resonantly related to the duration of the jump in the magnetic field. The closer the scale of the magnetic dipole field changes to the particle's gyroperiod, the more effective is their acceleration.
Show AbstractOn the dynamics of the academic performance of students at the Faculty of Physics of MSU during the fall of 2017 from the viewpoint of testing
On the dynamics of the academic performance of students at the Faculty of Physics of MSU during the fall of 2017 from the viewpoint of testing
M. A. Terentyev
We present data on the dynamics of the academic performance of the 1st and 2nd year students during the fall of 2017, and compare the progress of academic groups in some of the disciplines studied. The data were obtained on the basis of the results of computer tests, conducted at the Center for Education Quality Control at the Faculty of Physics.
Show AbstractOn the one model of the reaction-diffusion-advection type for the nonlinear equation of the heat and mass transfer №2
On the one model of the reaction-diffusion-advection type for the nonlinear equation of the heat and mass transfer №2
M. A. Davydova
The present paper is aimed to the investigating of the multidimensional thermal structures in nonlinear incompressible dissipative media with the application of the latest scientific achievements in the asymptotic analysis. The class of the singularly perturbed multidimensional problems of nonlinear heat conduction, to which the asymptotic methods are applicable, has been singled out. We propose the reasonable algorithms for constructing the zero-order asymptotic solutions of the boundary layer type and the zero-order asymptotic solutions of the contrast structures type that describe the thermal structures in nonlinear homogeneous dissipative media. The use of an effective algorithm allows us to select and describe the transition surface in the neighborhood of which the internal layer of the contrast structure is localized. This approach extends to a more complex, so-called, critical case. The results of the paper are interpreted and illustrated by the example of a two-dimensional boundary value problem. They can be used to create a numerical algorithm that uses asymptotic analysis to construct spatially inhomogeneous mashes when describing the internal layer of contrast structure, and also for the purpose of constructing the test examples.
Show AbstractAutomated system for estimation of tsunami hazard of an earthquake
Automated system for estimation of tsunami hazard of an earthquake
M. A. Nosov$^{1,2}$, S. V. Kolesov$^1$, A. V. Bolshakova$^1$, G. N. Nurislamova$^1$, K. A. Sementsov$^1$, V. A. Karpov$^1$
The prototype of fully automated system for estimation of tsunami hazard of an earthquake is described. The system is initiated after receiving of earthquake parameters (coordinates, seismic moment, focal mechanism, depth). At the first stage, vector field of co-seismic bottom deformation is calculated making use the Okada formulae and empirical scaling relations. Then, the initial elevation of water surface in tsunami source and its potential energy are determined. At the second stage, the Soloviev-Imamura tsunami intensity is estimated from empirical relationship derived from the statistical analysis of historical tsunami-events. At the final stage, if event is considered significant, numerical simulation of propagation of tsunami wave is performed.
Show AbstractThe modeling of magnetoplasma structures in the solar wind
The modeling of magnetoplasma structures in the solar wind
E. V. Maiewski$^1$, R. A. Kislov$^{2,3}$, H. V. Malova$^{2,4}$, O. V. Khabarova$^3$, V. Yu. Popov$^{2,5,6}$, A. A. Petrukovich$^2$
Axisymmetric MHD model of the solar wind is constructed, which allows us to study the spatial distribution of the magnetic field and plasma characteristics at radial distances from 20 to 400 radii of the Sun in a wide range of heliolatitudes. Self-consistent solutions for the magnetic field, plasma and current densities in the solar wind depending on the phase of the solar cycle are obtained. It is shown that during the dominance of the dipole magnetic component in the solar wind, a heliospheric current sheet (HCS) is formed, being the part of a system of longitudinal and transverse currents symmetric in the Northern and Southern hemispheres. As the relative contribution of a quadrupole component to the total magnetic field of HTS increases, the last one becomes to be cone-shaped; at high latitudes of the opposite hemisphere, a second conical HTS appears, its opening angle increases. The model describes a smooth transition from the fast solar wind at high heliolatitudes to the slow solar wind at low heliolatitudes and the steepened profiles of main solar wind characteristics with the increased radial distance from the Sun
Show AbstractMechanisms of generation of free gravity waves in the ocean by surface seismic waves
Mechanisms of generation of free gravity waves in the ocean by surface seismic waves
K. A. Sementsov$^1$, M. A. Nosov$^{1,2}$, S. V. Kolesov$^1$, A. V. Bolshakova$^1$
The subject of this work is numerical simulation of the process of generation of gravity waves in the ocean of variable depth by surface seismic waves. Physical mechanisms of generation of gravity waves are discussed. Theoretical estimates of their amplitudes are compared with the results of numerical experiments. It is shown that the horizontal component of the seismic wave generates gravity waves much more effectively than the vertical one. Also it is shown, that the key parameter determining the amplitude of gravity waves is the steepness of the underwater slope.
Show AbstractAn iterative way for the approximate solution of perturbed equations
An iterative way for the approximate solution of perturbed equations
E. E. Bukzhalev$^1$
We propose an iterative approach to regularly perturbed differential equations. With this approach we construct a sequence that converges (with respect to the norm of the space of continuous functions) to the solution to the Cauchy problem for a perturbed by a small parameter first-order weakly nonlinear differential equation (weakly nonlinearity means the presence of a small factor in front of the nonlinear term). This sequence also converges to the solution to the problem in the asymptotic sense. The proof of convergence (both the ordinary and the asymptotic) of the sequence constructed and the estimate of the rate of convergence are based on the Banach fixed-point theorem for a contraction mapping of a complete metric space.
Show AbstractContribution of secondary particles to the depth distribution of absorbed dose by photon irradiation
Contribution of secondary particles to the depth distribution of absorbed dose by photon irradiation
A. V. Belousov$^1$, G. A. Krusanov$^2$, A. P. Chernyeav$^{1,2}$
In this paper, the computer simulation using the Geant4 software package examines the contribution of photonuclear reactions products to the absorbed dose. The absorbed dose is determined along the central axis of the beam in an aqueous phantom upon irradiation with both monochromatic photons with energy above the threshold of photonuclear reactions and bremsstrahlung. It is shown that in spite of the smaller cross section of photoproton and photoneutron reactions relatively to other channels, the main contribution among all products is produced by alpha particles. The lower estimate of the total contribution of all products is about 5% for bremsstrahlung photons with a maximum energy of 20-30 MeV.
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