Home – Home – Jornals – Avtometriya 2007 number 6

The problem of image reconstruction is considered for the case when the right-hand side of the 2D integral equation and the point-spread function (the integral equation kernel) are given with random errors. A stable image reconstruction algorithm is proposed. It is a combination of a regularizing algorithm for solving an integral equation (frequency filtering) and a local nonlinear filter (spatial filtering). Characteristics of the 2D point-spread function of the regularizing algorithm are introduced. The regularization parameter is chosen according to the required regularizing algorithm resolution. For eliminating the random reconstruction error, the regularized solution is subjected to nonlinear local filtering that preserves high-frequency information components of the image.

Synthesis and analysis of maximum likelihood algorithms for estimating the velocity of a spatially extended object image under different contents of a priori information on the background and object image intensities are carried out. The efficiency of the algorithms and the scope of applicability of the found asymptotical expressions for the velocity estimate characteristics are determined by statistical computer modeling.

A method for microwave tomography with a synthetic aerial aperture and a monochrome probing signal is proposed. A mathematical description of aerial aperture synthesis with regard to wave propagation in two media is presented. The velocity of wave propagation inside the object is assumed to be six times smaller than in the open space. Results of practical microwave object tomography with an aerial aperture synthesized by the proposed approach are given.

The nonparametric estimates of a density and its derivatives are considered within the scope of the L₂-approach. New sets of weight functions with a bounded support are proposed for constructing admissible (unimprovable in the space metric L₂(-∞, ∞)) estimates of the density itself and its derivatives to the third order, inclusive.

A cellular automata model is proposed for investigating the process of formation and percolation of gas or fluid flows through interstices in solid media. The model is a cellular automata analogy of a convection-diffusion equation in partial derivatives. The advantage of the model is that it allows a simple representation of boundary conditions and, thus, makes it possible to investigate properties of media with a complex pore configuration. Moreover, using probabilistic transition rules makes it possible to adapt to the properties of the boundaries between liquid and solid phases. A formal representation of the model is given. Results of experimental investigation for a medium with hydrophobic, hydrophilic, and neutral pores are presented.

Numerical realization of the model of unstable 3D processes in gravitating gas systems with a self-consistent field in the Cartesian coordinates is considered. Evolution of the disk gas component is described by a system of equations of gas dynamics with regard to the equation for temperature, and Poisson-s equation for gravity potential. A modified rotation-invariant fluids-in-cell method for numerical realization of equations of gas dynamics is considered. Results of applying the numerical model in a spatial case are presented.

A problem of extracting and analyzing knowledge oriented to expert-s individual goals is discussed. The information is represented as texts in a natural language. The system architecture, the main modules and algorithms, and also program functionality and perspectives of the approach are described.

A numerical formulation of the incident wave source conditions for a two-dimensional domain enclosed in a nonuniform envelope within the scope of the TF/RF technique (a special case of the TF/SF technique) is proposed. Comparison with traditional approaches to defining the incident wave source conditions is presented. Benefits of the proposed approach are shown.

A multibeam interferometer with oscillating mirrors is theoretically investigated. Transfer functions are presented and analyzed for two extreme cases, namely, for an interferometer with stationary mirrors and an interferometer operating in the mode of -superslow- mirror oscillations.

Peculiarities of forming a temperature track in circular laser writing in chromium films on glass substrates are studied. The temperature field is calculated for a wide range of writing diameters (20-150 mm). Dynamics of heating a chromium film on a quartz substrate upon switching on the beam in the course of movement for cases with temperature-dependent and independent thermophysical coefficients of the film and substrate is considered. Calculation results show the difference in the form (asymmetry) of the temperature track for an on/off writing beam. A method for correcting the procedure of choosing the writing beam power for producing small (about several microns) grooves is proposed. Calculated and experimental data are compared. The difference between images of synthetic microstructures in transmitted and reflected light is discussed.

The width and spectral dependence of the complex refractive index of upper layers in thin-film MBE-grown GaAs structures can be measured by means of spectral ellipsometry, that is, a nondestructive noncontact optical method, using an oscillatory model of dielectric function.

Methods for evaluating readiness of mining technologies to robotization and expediency of mining robotization are proposed.