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Том 61, № 5 (2016)
- Год: 2016
- Статей: 11
- URL: https://journals.rcsi.science/1028-3358/issue/view/12000
Physics
207-210
Low-frequency three-dimensional ultrasonic tomography
Аннотация
The possibility of making ultrasonic 3D tomographs for medical diagnostics of soft tissues was established. The choice of frequencies of ultrasonic pulses of 300–500 kHz was due to low absorption in soft tissues within this range. The reverse problems of ultrasonic tomography, which are three-dimensional and nonlinear, have been considered in a model that takes into account both wave effects and absorption. The effectiveness of algorithms to solve the reverse problems that were developed has been illustrated by model calculations. The velocity configuration has been shown to be recovered better than the function that describes absorption in soft tissues.
211-214
Technical Physics
Carbon distribution in the martensite structure of structural steel
Аннотация
The martensite structure of a hardened pseudosingle crystal of grade 37KhN3A medium-carbon structural steel (0.37 wt % C, 1.50 Cr, 3.0 Ni, 0.33 Mn) had the form of coarse packets with dimensions of to 1 cm in the cross section. Every packet was composed of six-orientation martensite crystals arising on one common austenite plane of type {111}. The position of three texture maximums was determined using an X-ray diffractometer for every orientation. In addition, the position of four maximums of retained austenite was found. The periods of martensite lattices and retained austenite as well as the carbon concentration in martensite lattices and near the boundaries are determined.
215-217
Mechanics
Equations of nonlinear dynamics of elastic shells in cylindrical Eulerian coordinates
Аннотация
The equations of dynamics of elastic shells subjected to large deformations are formulated. The Eulerian coordinates on a circular cylinder and time are accepted as independent variables, and one of the unknown functions is the distance from a point of the shell surface to the cylinder axis. The equations of dynamics of nonlinearly elastic shells in the Eulerian coordinates are convenient for exact formulation of the problem on the interaction of strongly deformable shells with moving fluids and gases. The equations obtained can be used for dynamic calculations of fluids and gases flowings in pipelines, blood vessels, hoses, and other nonlinearly deformable thin-walled tubular elements of constructions.
218-222
Heterogeneous physical and chemical processes in a rarefied-gas flow in channels
Аннотация
A flow with physical and chemical reactions on hot surfaces is investigated. On the basis of physical experiments, determining the hydrogen-dissociation degree in rarefied gas and calculation of the flow by the method of direct simulation Monte Carlo (DSMC), it is possible to specify certain unknown constants of interaction of molecules and atoms with a tungsten surface. By the example of the hydrogen flow in a hightemperature tungsten cylindrical channel, the role of dissociation, sorption, and recombination processes is shown in a wide range of flow regimes from free-molecular to continuum.
223-226
Stages of transformation of block elements
Аннотация
The property to have various representations is investigated for the block elements describing the solutions of boundary-value problems for sets of partial differential equations in the regions with a boundary. These representations have various destinations. One of the representations, which is called packed, is convenient for constructing solutions in block structures on the basis of solutions in separate blocks. Another representation, which is called unpacked, is convenient for a detailed investigation of the properties of solutions in an individual block of the block structure.
227-231
232-234
Magma degassing during eruption through water-saturated porous rocks
Аннотация
In the case of extrusive eruption, we consider the problem on magma degassing which rises in a volcano conduit crossing porous water-saturated rocks. We show that the intensity of outflow of volcanic gases into the rocks is comparable to the intensity of their transport with the rising magma. The magma degassing in the rocks substantially affects the eruption dynamics, in particular, the duration of the periods of eruptive activity.
235-238
Deformation and fracture processes in graphene nanoribbons with linear quadrupoles of disclinations
Аннотация
The deformation and fracture processes in graphene nanoribbons containing linear quadrupoles of disclinations are investigated by the method of molecular dynamics. Special attention is given to estimating the effect of the curvature formed by disclinations and free boundaries in graphene nanoribbons with linear quadrupoles of disclinations on their mechanical characteristics (the stress–strain curve, the strength at the single-axis tension, and the degree of plastic deformation).
239-242
Probabilistic model of Kordylewski clouds
Аннотация
The problem of determining the phase-space distribution function for the system of the noninteracting dust particles for the mathematical model of cosmic dust Kordylewski clouds—clusters of the non-interacting dust particles in the vicinity of the triangular libration points of the Earth–Moon–Particle system taking into account perturbations from the Sun was considered.
243-246
An odd-symmetric boundary-value problem for a semistrip with longitudinal rigidity ribs: Biorthogonal sets of functions and Lagrange expansions
Аннотация
This study is devoted to construction of biorthogonal functions and Lagrange expansions in the sets of Fadle–Papkovich functions arising from solution of the odd-symmetric boundary-value problem for a strip, the longitudinal sides of which are supported by the rigidity ribs responding only to the bend. Primary attention is devoted to constructing the biorthogonal functions with a zero subscript.
247-251